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Sample records for mesostructured silica shell

  1. Titanate-silica mesostructured nanocables: synthesis, structural analysis and biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Su Yonghua; Sheng Jiayu; Ling Changquan [Department of Traditional Chinese Medicine, Changhai Hospital, The Second Military Medical University, 168 Changhai Road, Shanghai 200433 (China); Qiao Shizhang; Jin Yonggang; Stahr, Frances; Cheng Lina; Lu Gao Qing [ARC Centre of Excellence for Functional Nanomaterials, Australian Institute for Bioengineering and Nanotechnology, and School of Chemical Engineering, University of Queensland, QLD 4072 (Australia); Yang Huagui; Yang Chen, E-mail: s.qiao@uq.edu.au, E-mail: lingchangquan@smmu.edu.cn [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2010-02-10

    1D hierarchical composite mesostructures of titanate and silica were synthesized via an interfacial surfactant templating approach. Such mesostructures have complex core-shell architectures consisting of single-crystalline H{sub 2}Ti{sub 3}O{sub 7} nanobelts inside the ordered mesoporous SiO{sub 2} shell, which are nontoxic and highly biocompatible. The overall diameter of as-prepared 1D hierarchical composite mesostructures is only approx. 34.2 nm with a length over 500 nm on average. A model to explain the formation mechanism of these mesostructures has been proposed; the negatively charged surface of H{sub 2}Ti{sub 3}O{sub 7} nanobelts controls the formation of the octadecyltrimethylammonium bromide (C{sub 18}TAB) bilayer, which in turn regulates the cooperative self-assembly of silica and C{sub 18}TAB complex micelles on the interface to produce a mesoporous silica shell. More importantly, the application of synthesized mesostructured nanocables as anticancer drug reservoirs has also been explored, which indicates that the membranes containing these mesoporous nanocables have a great potential to be used as transdermal drug delivery systems.

  2. Titanate-silica mesostructured nanocables: synthesis, structural analysis and biomedical applications

    Science.gov (United States)

    Su, Yonghua; Qiao, Shizhang; Yang, Huagui; Yang, Chen; Jin, Yonggang; Stahr, Frances; Sheng, Jiayu; Cheng, Lina; Ling, Changquan; Qing Lu, Gao

    2010-02-01

    1D hierarchical composite mesostructures of titanate and silica were synthesized via an interfacial surfactant templating approach. Such mesostructures have complex core-shell architectures consisting of single-crystalline H2Ti3O7 nanobelts inside the ordered mesoporous SiO2 shell, which are nontoxic and highly biocompatible. The overall diameter of as-prepared 1D hierarchical composite mesostructures is only approx. 34.2 nm with a length over 500 nm on average. A model to explain the formation mechanism of these mesostructures has been proposed; the negatively charged surface of H2Ti3O7 nanobelts controls the formation of the octadecyltrimethylammonium bromide (C18TAB) bilayer, which in turn regulates the cooperative self-assembly of silica and C18TAB complex micelles on the interface to produce a mesoporous silica shell. More importantly, the application of synthesized mesostructured nanocables as anticancer drug reservoirs has also been explored, which indicates that the membranes containing these mesoporous nanocables have a great potential to be used as transdermal drug delivery systems.

  3. Titanate-silica mesostructured nanocables: synthesis, structural analysis and biomedical applications

    International Nuclear Information System (INIS)

    Su Yonghua; Sheng Jiayu; Ling Changquan; Qiao Shizhang; Jin Yonggang; Stahr, Frances; Cheng Lina; Lu Gao Qing; Yang Huagui; Yang Chen

    2010-01-01

    1D hierarchical composite mesostructures of titanate and silica were synthesized via an interfacial surfactant templating approach. Such mesostructures have complex core-shell architectures consisting of single-crystalline H 2 Ti 3 O 7 nanobelts inside the ordered mesoporous SiO 2 shell, which are nontoxic and highly biocompatible. The overall diameter of as-prepared 1D hierarchical composite mesostructures is only approx. 34.2 nm with a length over 500 nm on average. A model to explain the formation mechanism of these mesostructures has been proposed; the negatively charged surface of H 2 Ti 3 O 7 nanobelts controls the formation of the octadecyltrimethylammonium bromide (C 18 TAB) bilayer, which in turn regulates the cooperative self-assembly of silica and C 18 TAB complex micelles on the interface to produce a mesoporous silica shell. More importantly, the application of synthesized mesostructured nanocables as anticancer drug reservoirs has also been explored, which indicates that the membranes containing these mesoporous nanocables have a great potential to be used as transdermal drug delivery systems.

  4. Oxygen Sensing with Perfluorocarbon-Loaded Ultraporous Mesostructured Silica Nanoparticles.

    Science.gov (United States)

    Lee, Amani L; Gee, Clifford T; Weegman, Bradley P; Einstein, Samuel A; Juelfs, Adam R; Ring, Hattie L; Hurley, Katie R; Egger, Sam M; Swindlehurst, Garrett; Garwood, Michael; Pomerantz, William C K; Haynes, Christy L

    2017-06-27

    Oxygen homeostasis is important in the regulation of biological function. Disease progression can be monitored by measuring oxygen levels, thus producing information for the design of therapeutic treatments. Noninvasive measurements of tissue oxygenation require the development of tools with minimal adverse effects and facile detection of features of interest. Fluorine magnetic resonance imaging ( 19 F MRI) exploits the intrinsic properties of perfluorocarbon (PFC) liquids for anatomical imaging, cell tracking, and oxygen sensing. However, the highly hydrophobic and lipophobic properties of perfluorocarbons require the formation of emulsions for biological studies, though stabilizing these emulsions has been challenging. To enhance the stability and biological loading of perfluorocarbons, one option is to incorporate perfluorocarbon liquids into the internal space of biocompatible mesoporous silica nanoparticles. Here, we developed perfluorocarbon-loaded ultraporous mesostructured silica nanoparticles (PERFUMNs) as 19 F MRI detectable oxygen-sensing probes. Ultraporous mesostructured silica nanoparticles (UMNs) have large internal cavities (average = 1.8 cm 3 g -1 ), facilitating an average 17% loading efficiency of PFCs, meeting the threshold fluorine concentrations needed for imaging studies. Perfluoro-15-crown-5-ether PERFUMNs have the highest equivalent nuclei per PFC molecule and a spin-lattice (T 1 ) relaxation-based oxygen sensitivity of 0.0032 mmHg -1 s -1 at 16.4 T. The option of loading PFCs after synthesizing UMNs, rather than traditional in situ core-shell syntheses, allows for use of a broad range of PFC liquids from a single material. The biocompatible and tunable chemistry of UMNs combined with the intrinsic properties of PFCs makes PERFUMNs a MRI sensor with potential for anatomical imaging, cell tracking, and metabolic spectroscopy with improved stability.

  5. Growth of ordered silver nanoparticles in silica film mesostructured with a triblock copolymer PEO-PPO-PEO

    International Nuclear Information System (INIS)

    Bois, L.; Chassagneux, F.; Parola, S.; Bessueille, F.; Battie, Y.; Destouches, N.; Boukenter, A.; Moncoffre, N.; Toulhoat, N.

    2009-01-01

    Elaboration of mesostructured silica films with a triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide, (PEO-PPO-PEO) and controlled growth of silver nanoparticles in the mesostructure are described. The films are characterized using UV-visible optical absorption spectroscopy, TEM, AFM, SEM, X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). Organized arrays of spherical silver nanoparticles with diameter between 5 and 8 nm have been obtained by NaBH 4 reduction. The size and the repartition of silver nanoparticles are controlled by the film mesostructure. The localization of silver nanoparticles exclusively in the upper-side part of the silica-block copolymer film is evidenced by RBS experiment. On the other hand, by using a thermal method, 40 nm long silver sticks can be obtained, by diffusion and coalescence of spherical particles in the silica-block copolymer layer. In this case, migration of silver particles toward the glass substrate-film interface is shown by the RBS experiment. - Graphical abstract: Growth of silver nanoparticles in a mesostructured block copolymer F127-silica film is performed either by a chemical route involving NaBH 4 reduction or by a thermal method. An array of spherical silver nanoparticles with 10 nm diameter on the upper-side of the mesostructured film or silver sticks long of 40 nm with a preferential orientation are obtained according to the method used. a: TEM image of the Fag5SiNB sample illustrating the silver nanoparticles array obtained by the chemical process; b: HR-TEM image of the Fag20Sid2 sample illustrating the silver nanosticks obtained by the thermal process.

  6. Investigating the mesostructure of ordered porous silica nanocomposites by transmission electron microscopy techniques

    Energy Technology Data Exchange (ETDEWEB)

    Bullita, S.; Casula, M. F., E-mail: casulaf@unica.it [INSTM and Department of Chemical and Geological Science, University of Cagliari, Monserrato (Canada) (Italy); Piludu, M. [Department of Biomedical Sciences, University of Cagliari, Monserrato (Canada) (Italy); Falqui, A. [INSTM and Department of Chemical and Geological Science, University of Cagliari, Monserrato (Canada) Italy and KAUST-King Abdullah University of Science and Technology, Jeddah (Saudi Arabia); Carta, D. [INSTM and Department of Chemical and Geological Science, University of Cagliari, Monserrato (Canada), Italy and Faculty of Physical Sciences and Engineering, University of Southampton, Southampton (United Kingdom); Corrias, A. [INSTM and Department of Chemical and Geological Science, University of Cagliari, Monserrato (Canada) Italy and School of Physical Sciences, Ingram Building, University of Kent, Canterbury (United Kingdom)

    2014-10-21

    Nanocomposites made out of FeCo alloy nanocrystals supported onto pre-formed mesoporous ordered silica which features a cubic arrangement of pores (SBA-16) were investigated. Information on the effect of the nanocrystals on the mesostructure (i.e. pore arrangement symmetry, pore size, and shape) were deduced by a multitechnique approach including N2 physisorption, low angle X-ray diffraction, and Transmission electron microscopy. It is shown that advanced transmission electron microscopy techniques are required, however, to gain direct evidence on key compositional and textural features of the nanocomposites. In particular, electron tomography and microtomy techniques make clear that the FeCo nanocrystals are located within the pores of the SBA-16 silica, and that the ordered mesostructure of the nanocomposite is retained throughout the observed specimen.

  7. Synthesis and carbon dioxide sorption of layered double hydroxide/silica foam nanocomposites with hierarchical mesostructure

    KAUST Repository

    Fu, Liling; Qi, Genggeng; Shekhah, Osama; Belmabkhout, Youssef; Esté vez, Luis Antonio; Eddaoudi, Mohamed; Giannelis, Emmanuel P.

    2014-01-01

    Layered double hydroxides (LDHs) with a hierarchical mesostructure are successfully synthesized on mesoporous silica foams by simple impregnation and hydrothermal treatment. The as-synthesized LDH/silica foam nanocomposites show well-defined mesostructures with high surface areas, large pore volumes, and mesopores of 6-7 nm. The nanocomposites act as carbon dioxide (CO2) sorbents under simulated flue gas conditions. They also exhibit significantly enhanced CO2 capacities under high-pressure conditions and high CO2/N2 and CO2/CH4 selectivities. Respect the hierarchy: Hierarchical mesoporous layered double hydroxide (LDH) nanocomposites with high surface areas and large pore volumes are synthesized by controlled hydrothermal growth of LDH precursors on a mesoporous silica foam. The as-synthesized nanocomposites exhibit a significantly enhanced capacity and selectivity towards carbon dioxide, making them very promising candidates for carbon dioxide (CO2) separation applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Synthesis and carbon dioxide sorption of layered double hydroxide/silica foam nanocomposites with hierarchical mesostructure

    KAUST Repository

    Fu, Liling

    2014-03-05

    Layered double hydroxides (LDHs) with a hierarchical mesostructure are successfully synthesized on mesoporous silica foams by simple impregnation and hydrothermal treatment. The as-synthesized LDH/silica foam nanocomposites show well-defined mesostructures with high surface areas, large pore volumes, and mesopores of 6-7 nm. The nanocomposites act as carbon dioxide (CO2) sorbents under simulated flue gas conditions. They also exhibit significantly enhanced CO2 capacities under high-pressure conditions and high CO2/N2 and CO2/CH4 selectivities. Respect the hierarchy: Hierarchical mesoporous layered double hydroxide (LDH) nanocomposites with high surface areas and large pore volumes are synthesized by controlled hydrothermal growth of LDH precursors on a mesoporous silica foam. The as-synthesized nanocomposites exhibit a significantly enhanced capacity and selectivity towards carbon dioxide, making them very promising candidates for carbon dioxide (CO2) separation applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Mercury Binding Sites in Thiol-Functionalized Mesostructured Silica

    International Nuclear Information System (INIS)

    Billinge, Simon J.L.; McKimmey, Emily J.; Shatnawi, Mouath; Kim, HyunJeong; Petkov, Valeri; Wermeille, Didier; Pinnavaia, Thomas J.

    2005-01-01

    Thiol-functionalized mesostructured silica with anhydrous compositions of (SiO 2 ) 1-x (LSiO 1.5 ) x , where L is a mercaptopropyl group and x is the fraction of functionalized framework silicon centers, are effective trapping agents for the removal of mercuric(II) ions from water. In the present work, we investigate the mercury-binding mechanism for representative thiol-functionalized mesostructures by atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffraction data and by Raman spectroscopy. The mesostructures with wormhole framework structures and compositions corresponding to x = 0.30 and 0.50 were prepared by direct assembly methods in the presence of a structure-directing amine porogen. PDF analyses of five mercury-loaded compositions with Hg/S ratios of 0.50-1.30 provided evidence for the bridging of thiolate sulfur atoms to two metal ion centers and the formation of chain structures on the pore surfaces. We find no evidence for Hg-O bonds and can rule out oxygen coordination of the mercury at greater than the 10% level. The relative intensities of the PDF peaks corresponding to Hg-S and Hg-Hg atomic pairs indicate that the mercury centers cluster on the functionalized surfaces by virtue of thiolate bridging, regardless of the overall mercury loading. However, the Raman results indicate that the complexation of mercury centers by thiolate depends on the mercury loading. At low mercury loadings (Hg/S (le) 0.5), the dominant species is an electrically neutral complex in which mercury most likely is tetrahedrally coordinated to bridging thiolate ligands, as in Hg(SBu t ) 2 . At higher loadings (Hg/S 1.0-1.3), mercury complex cations predominate, as evidenced by the presence of charge-balancing anions (nitrate) on the surface. This cationic form of bound mercury is assigned a linear coordination to two bridging thiolate ligands.

  10. Ordered and disordered evolution of the pore mesostructure in hybrid silica anti-reflective films obtained by one-pot self-assembly method

    Energy Technology Data Exchange (ETDEWEB)

    Ghazzal, Mohamed N., E-mail: g_nawfel@yahoo.fr; Debecker, Damien P.; Gaigneaux, Eric M.

    2016-07-29

    Hybrid mesoporous silica films were prepared in acid-catalysed medium using a one-pot self-assembly method. A gradual content of methyl groups was introduced into the inorganic framework by co-condensation of tetraethyl orthosilicate and methyltriethoxysilane. To better understand how the ordered and disordered transition occurs in mesoporous hybrid organosilica sytem as function of the MTES molar ratio in the starting solution, textural, chemical and optical properties of the films were studied by transmission electronic microscopy (TEM), grazing-incident small angle X-ray scattering (GISAXS), transmission Fourier transformed infrared (FTIR) and UV–visible spectroscopy. Increasing the loading of the incorporated organic groups (up to 40% in the starting solution) led simultaneously to a disorganization of the pore mesostructure and a reduction in the pore diameter. Concomitantly, a disordered domain of the silica rings in the walls was observed, which created bond strains in the silica wall contributing also to the disorganization of the pore mesostructure. Furthermore, an optimal MTES content was identified in order to obtain antireflection coatings, exhibiting low reflection in the visible range. - Highlights: • Mesoporous hybrid silica films where prepared by one-pot co-condensation of MTES and TEOS. • Ordered and disordered mesostructures were studied as function as variable MTES molar ratio. • A rearrangement of the silica cyclic species occurred as the molar ratio of MTES increases. • Transmittance of the silica coatings is affected by the MTES molar ratio.

  11. Cyclodextrin-functionalized mesostructured silica nanoparticles for removal of polycyclic aromatic hydrocarbons.

    Science.gov (United States)

    Topuz, Fuat; Uyar, Tamer

    2017-07-01

    Polycyclic aromatic hydrocarbons (PAHs) are the byproducts of the incomplete combustion of carbon-based fuels, and have high affinity towards DNA strands, ultimately exerting their carcinogenic effects. They are ubiquitousenvironmental contaminants,and can accumulate on tissues due to their lipophilic nature. In this article, we describe a novel concept for PAH removal from aqueous solutions using cyclodextrin-functionalized mesostructured silica nanoparticles (CDMSNs) and pristine mesostructured silica nanoparticles (MSNs). The adsorption applications of MSNs are greatly restricted due to the absence of surface functional groups on such particles. In this regard, cyclodextrins can serve as ideal functional molecules with their toroidal, cone-type structure, capable of inclusion-complex formation with many hydrophobic molecules, including genotoxic PAHs. The CDMSNs were synthesized by the surfactant-templated, NaOH-catalyzed condensation reactions of tetraethyl orthosilicate (TEOS) in the presence of two different types of cyclodextrin (i.e. hydroxypropyl-β-cyclodextrin (HP-β-CD) and native β-cyclodextrin (β-CD)). The physical incorporation of CD moieties was supported by XPS, FT-IR, NMR, TGA and solid-state 13 C NMR. The CDMSNs were treated with aqueous solutions of five different PAHs (e.g. pyrene, anthracene, phenanthrene, fluorene and fluoranthene). The functionalization of MSNs with cyclodextrin moieties significantly boosted the sorption capacity (q) of the MSNs up to ∼2-fold, and the q ranged between 0.3 and 1.65mg per gram CDMSNs, of which the performance was comparable to that of the activated carbon. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Communication: Programmable self-assembly of thin-shell mesostructures

    Science.gov (United States)

    Halverson, Jonathan D.; Tkachenko, Alexei V.

    2017-10-01

    We study numerically the possibility of programmable self-assembly of various thin-shell architectures. They include clusters isomorphic to fullerenes C20 and C60, finite and infinite sheets, tube-shaped and toroidal mesostructures. Our approach is based on the recently introduced directionally functionalized nanoparticle platform, for which we employ a hybrid technique of Brownian dynamics with stochastic bond formation. By combining a number of strategies, we were able to achieve a near-perfect yield of the desired structures with a reduced "alphabet" of building blocks. Among those strategies are the following: the use of bending rigidity of the interparticle bond as a control parameter, programming the morphology with a seed architecture, use of chirality-preserving symmetries for reduction of the particle alphabet, and the hierarchic approach.

  13. Mesostructured metal germanium sulfides

    Energy Technology Data Exchange (ETDEWEB)

    MacLachlan, M.J.; Coombs, N.; Bedard, R.L.; White, S.; Thompson, L.K.; Ozin, G.A.

    1999-12-29

    A new class of mesostructured metal germanium sulfide materials has been prepared and characterized. The synthesis, via supramolecular assembly of well-defined germanium sulfide anionic cluster precursors and transition-metal cations in formamide, represents a new strategy for the formation of this class of solids. A variety of techniques were employed to examine the structure and composition of the materials. Structurally, the material is best described as a periodic mesostructured metal sulfide-based coordination framework akin to periodic hexagonal mesoporous silica, MCM-41. At the molecular scale, the materials strongly resemble microstructured metal germanium sulfides, in which the structure of the [Ge{sub 4}S{sub 10}]{sup 4{minus}} cluster building-blocks are intact and linked via {mu}-S-M-S bonds. Evidence for a metal-metal bond in mesostructured Cu/Ge{sub 4}S{sub 10} is also provided.

  14. Soft template synthesis of yolk/silica shell particles.

    Science.gov (United States)

    Wu, Xue-Jun; Xu, Dongsheng

    2010-04-06

    Yolk/shell particles possess a unique structure that is composed of hollow shells that encapsulate other particles but with an interstitial space between them. These structures are different from core/shell particles in that the core particles are freely movable in the shell. Yolk/shell particles combine the properties of each component, and can find potential applications in catalysis, lithium ion batteries, and biosensors. In this Research News article, a soft-template-assisted method for the preparation of yolk/silica shell particles is presented. The demonstrated method is simple and general, and can produce hollow silica spheres incorporated with different particles independent of their diameters, geometry, and composition. Furthermore, yolk/mesoporous silica shell particles and multishelled particles are also prepared through optimization of the experimental conditions. Finally, potential applications of these particles are discussed.

  15. Magnetic core-shell silica particles

    NARCIS (Netherlands)

    Claesson, E.M.

    2007-01-01

    This thesis deals with magnetic silica core-shell colloids and related functionalized silica structures. Synthesis routes have been developed and optimized. The physical properties of these colloids have been investigated, such as the magnetic dipole moment, dipolar structure formation and

  16. A multifunctional role of trialkylbenzenes for the preparation of aqueous colloidal mesostructured/mesoporous silica nanoparticles with controlled pore size, particle diameter, and morphology

    Science.gov (United States)

    Yamada, Hironori; Ujiie, Hiroto; Urata, Chihiro; Yamamoto, Eisuke; Yamauchi, Yusuke; Kuroda, Kazuyuki

    2015-11-01

    Both the pore size and particle diameter of aqueous colloidal mesostructured/mesoporous silica nanoparticles (CMSS/CMPS) derived from tetrapropoxysilane were effectively and easily controlled by the addition of trialkylbenzenes (TAB). Aqueous highly dispersed CMPS with large pores were successfully obtained through removal of surfactants and TAB by a dialysis process. The pore size (from 4 nm to 8 nm) and particle diameter (from 50 nm to 380 nm) were more effectively enlarged by the addition of 1,3,5-triisopropylbenzene (TIPB) than 1,3,5-trimethylbenzene (TMB), and the enlargement did not cause the variation of the mesostructure and particle morphology. The larger molecular size and higher hydrophobicity of TIPB than TMB induce the incorporation of TIPB into micelles without the structural change. When TMB was used as TAB, the pore size of CMSS was also enlarged while the mesostructure and particle morphology were varied. Interestingly, when tetramethoxysilane and TIPB were used, CMSS with a very small particle diameter (20 nm) with concave surfaces and large mesopores were obtained, which may strongly be related to the initial nucleation of CMSS. A judicious choice of TAB and Si sources is quite important to control the mesostructure, size of mesopores, particle diameter, and morphology.Both the pore size and particle diameter of aqueous colloidal mesostructured/mesoporous silica nanoparticles (CMSS/CMPS) derived from tetrapropoxysilane were effectively and easily controlled by the addition of trialkylbenzenes (TAB). Aqueous highly dispersed CMPS with large pores were successfully obtained through removal of surfactants and TAB by a dialysis process. The pore size (from 4 nm to 8 nm) and particle diameter (from 50 nm to 380 nm) were more effectively enlarged by the addition of 1,3,5-triisopropylbenzene (TIPB) than 1,3,5-trimethylbenzene (TMB), and the enlargement did not cause the variation of the mesostructure and particle morphology. The larger molecular size

  17. Synthesis and characterization of mesoporous silica core-shell particles

    Directory of Open Access Journals (Sweden)

    Milan Nikolić

    2010-06-01

    Full Text Available Core-shell particles were formed by deposition of primary silica particles synthesized from sodium silicate solution on functionalized silica core particles (having size of ~0.5 µm prepared by hydrolysis and condensation of tetraethylortosilicate. The obtained mesoporous shell has thickness of about 60 nm and consists of primary silica particles with average size of ~21 nm. Scanning electron microscopy and zeta potential measurements showed that continuous silica shell exists around functionalized core particles which was additionally proved by FTIR and TEM results.

  18. Measurement of Fluorescence in a Rhodamine-123 Doped Self-Assembled “Giant” Mesostructured Silica Sphere Using a Smartphone as Optical Hardware

    Directory of Open Access Journals (Sweden)

    Ingemar Petermann

    2011-07-01

    Full Text Available The blue OLED emission from a mobile phone was characterised, revealing a sharp emission band centred at λ = 445 nm with a 3dB bandwidth Δλ ~ 20 nm. It was used to excite Rhodamine 123 doped within a “giant” mesostructured silica sphere during fabrication through evaporative self-assembly of silica nanoparticles. Fluorescence was able to be detected using a standard optical microscope fitted with a green transmission pass filter and cooled CCD and with 1 ms exposure time demonstrating the potential of mobile platforms as the basis for portable diagnostics in the field.

  19. Fabrication of Magnetite/Silica/Titania Core-Shell Nanoparticles

    Directory of Open Access Journals (Sweden)

    Suh Cem Pang

    2012-01-01

    Full Text Available Fe3O4/SiO2/TiO2 core-shell nanoparticles were synthesized via a sol-gel method with the aid of sonication. Fe3O4 nanoparticles were being encapsulated within discrete silica nanospheres, and a layer of TiO2 shell was then coated directly onto each silica nanosphere. As-synthesized Fe3O4/SiO2/TiO2 core-shell nanoparticles showed enhanced photocatalytic properties as evidenced by the enhanced photodegradation of methylene blue under UV light irradiation.

  20. Synthesis of eccentric titania-silica core-shell and composite particles

    NARCIS (Netherlands)

    Demirors, A.F.; van Blaaderen, A.; Imhof, A.

    2009-01-01

    We describe a novel method to synthesize colloidal particles with an eccentric core-shell structure. Titania-silica core-shell particles were synthesized by silica coating of porous titania particles under Sto¨ber (Sto¨ber et al. J. Colloid Interface Sci. 1968, 26, 62) conditions. We can control

  1. Chemical and thermal stability of core-shelled magnetite nanoparticles and solid silica

    Science.gov (United States)

    Cendrowski, Krzysztof; Sikora, Pawel; Zielinska, Beata; Horszczaruk, Elzbieta; Mijowska, Ewa

    2017-06-01

    Pristine nanoparticles of magnetite were coated by solid silica shell forming core/shell structure. 20 nm thick silica coating significantly enhanced the chemical and thermal stability of the iron oxide. Chemical and thermal stability of this structure has been compared to the magnetite coated by mesoporous shell and pristine magnetite nanoparticles. It is assumed that six-membered silica rings in a solid silica shell limit the rate of oxygen diffusion during thermal treatment in air and prevent the access of HCl molecules to the core during chemical etching. Therefore, the core/shell structure with a solid shell requires a longer time to induce the oxidation of iron oxide to a higher oxidation state and, basically, even strong concentrated acid such as HCl is not able to dissolve it totally in one month. This leads to the desired performance of the material in potential applications such as catalysis and environmental protection.

  2. A novel thermal decomposition approach for the synthesis of silica-iron oxide core–shell nanoparticles

    International Nuclear Information System (INIS)

    Kishore, P.N.R.; Jeevanandam, P.

    2012-01-01

    Highlights: ► Silica-iron oxide core–shell nanoparticles have been synthesized by a novel thermal decomposition approach. ► The silica-iron oxide core–shell nanoparticles are superparamagnetic at room temperature. ► The silica-iron oxide core–shell nanoparticles serve as good photocatalyst for the degradation of Rhodamine B. - Abstract: A simple thermal decomposition approach for the synthesis of magnetic nanoparticles consisting of silica as core and iron oxide nanoparticles as shell has been reported. The iron oxide nanoparticles were deposited on the silica spheres (mean diameter = 244 ± 13 nm) by the thermal decomposition of iron (III) acetylacetonate, in diphenyl ether, in the presence of SiO 2 . The core–shell nanoparticles were characterized by X-ray diffraction, infrared spectroscopy, field emission-scanning electron microscopy coupled with energy dispersive X-ray analysis, transmission electron microscopy, diffuse reflectance spectroscopy, and magnetic measurements. The results confirm the presence of iron oxide nanoparticles on the silica core. The core–shell nanoparticles are superparamagnetic at room temperature indicating the presence of iron oxide nanoparticles on silica. The core–shell nanoparticles have been demonstrated as good photocatalyst for the degradation of Rhodamine B.

  3. Probe based manipulation and assembly of nanowires into organized mesostructures

    Science.gov (United States)

    Reynolds, K.; Komulainen, J.; Kivijakola, J.; Lovera, P.; Iacopino, D.; Pudas, M.; Vähäkangas, J.; Röning, J.; Redmond, G.

    2008-12-01

    A convenient approach to patterning inorganic and organic nanowires using a novel probe manipulator is presented. The system utilizes an electrochemically etched tungsten wire probe mounted onto a 3D actuator that is directed by a 3D controller. When it is engaged by the user, the movement of the probe and the forces experienced by the tip are simultaneously reported in real time. Platinum nanowires are manipulated into organized mesostructures on silicon chip substrates. In particular, individual nanowires are systematically removed from aggregates, transferred to a chosen location, and manipulated into complex structures in which selected wires occupy specific positions with defined orientations. Rapid prototyping of complex mesostructures, by pushing, rotating and bending conjugated polymer, i.e., polyfluorene, nanowires into various configurations, is also achieved. By exploiting the strong internal axial alignment of polymer chains within the polyfluorene nanowires, mesostructures tailored to exhibit distinctly anisotropic optical properties, such as birefringence and photoluminescence dichroism, are successfully assembled on fused silica substrates.

  4. Probe based manipulation and assembly of nanowires into organized mesostructures

    International Nuclear Information System (INIS)

    Reynolds, K; Lovera, P; Iacopino, D; Redmond, G; Komulainen, J; Pudas, M; Vaehaekangas, J; Kivijakola, J; Roening, J

    2008-01-01

    A convenient approach to patterning inorganic and organic nanowires using a novel probe manipulator is presented. The system utilizes an electrochemically etched tungsten wire probe mounted onto a 3D actuator that is directed by a 3D controller. When it is engaged by the user, the movement of the probe and the forces experienced by the tip are simultaneously reported in real time. Platinum nanowires are manipulated into organized mesostructures on silicon chip substrates. In particular, individual nanowires are systematically removed from aggregates, transferred to a chosen location, and manipulated into complex structures in which selected wires occupy specific positions with defined orientations. Rapid prototyping of complex mesostructures, by pushing, rotating and bending conjugated polymer, i.e., polyfluorene, nanowires into various configurations, is also achieved. By exploiting the strong internal axial alignment of polymer chains within the polyfluorene nanowires, mesostructures tailored to exhibit distinctly anisotropic optical properties, such as birefringence and photoluminescence dichroism, are successfully assembled on fused silica substrates.

  5. Heterogeneous silicon mesostructures for lipid-supported bioelectric interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yuanwen; Carvalho-de-Souza, João L.; Wong, Raymond C. S.; Luo, Zhiqiang; Isheim, Dieter; Zuo, Xiaobing; Nicholls, Alan W.; Jung, Il Woong; Yue, Jiping; Liu, Di-Jia; Wang, Yucai; De Andrade, Vincent; Xiao, Xianghui; Navrazhnykh, Luizetta; Weiss, Dara E.; Wu, Xiaoyang; Seidman, David N.; Bezanilla, Francisco; Tian, Bozhi

    2016-06-27

    Silicon-based materials have widespread application as biophysical tools and biomedical devices. Here we introduce a biocompatible and degradable mesostructured form of silicon with multi-scale structural and chemical heterogeneities. The material was synthesized using mesoporous silica as a template through a chemical vapour deposition process. It has an amorphous atomic structure, an ordered nanowire-based framework and random submicrometre voids, and shows an average Young’s modulus that is 2–3 orders of magnitude smaller than that of single-crystalline silicon. In addition, we used the heterogeneous silicon mesostructures to design a lipid-bilayer-supported bioelectric interface that is remotely controlled and temporally transient, and that permits non-genetic and subcellular optical modulation of the electrophysiology dynamics in single dorsal root ganglia neurons. Our findings suggest that the biomimetic expansion of silicon into heterogeneous and deformable forms can open up opportunities in extracellular biomaterial or bioelectric systems.

  6. Innovative preparation of Au/C by replication of gold-containing mesoporous silica catalysts

    KAUST Repository

    Kerdi, Fatmé

    2010-01-01

    A new strategy, based on the nanocasting concept, has been used to prepare gold nanoparticles (NPs) highly dispersed in meso-structured carbons. Gold is first introduced in various functionalized mesostructured silicas (MCM-48 and SBA-15) and particles are formed inside the porosity upon reduction of Au 3+ cations. Silica pores are then impregnated with a carbon precursor and the composite material is heated at 900°C under vacuum. Silica is then removed by acid leaching, leading to partially encapsulated gold particles in mesoporous carbon. Carbon prevents aggregation of gold particles at high temperature, both the mean size and distribution being similar to those observed in silica. However, while Au@SiO2 exhibit significant catalytic activity in the aerobic oxidation of trans-stilbene in the liquid phase, its Au@C mesostructured replica is quite inactive. © 2010 Elsevier B.V. All rights reserved.

  7. Innovative preparation of Au/C by replication of gold-containing mesoporous silica catalysts

    KAUST Repository

    Kerdi, Fatmé ; Caps, Valerie; Tuel, Alain

    2010-01-01

    A new strategy, based on the nanocasting concept, has been used to prepare gold nanoparticles (NPs) highly dispersed in meso-structured carbons. Gold is first introduced in various functionalized mesostructured silicas (MCM-48 and SBA-15

  8. Method to incorporate anisotropic semiconductor nanocrystals of all shapes in an ultrathin and uniform silica shell

    NARCIS (Netherlands)

    Hutter, Eline M.; Pietra, Francesca; Moes, Relinde; Mitoraj, Dariusz; Meeldijk, Johannes D.; De Mello Donegá, Celso; Vanmaekelbergh, Daniël

    2014-01-01

    In this work, we present a method for the incorporation of anisotropic colloidal nanocrystals of many different shapes in silica in a highly controlled way. This method yields a uniform silica shell, with thickness tunable from 3 to 17 nm. The silica shell perfectly adapts to the shape of the

  9. Synthesis of N-halamine-functionalized silica-polymer core-shell nanoparticles and their enhanced antibacterial activity

    International Nuclear Information System (INIS)

    Dong, Alideertu; Wang Tao; Xiao Linghan; Wang Weiwei; Zhao Tianyi; Zheng Xin; Liu Fengqi; Gao Ge; Huang Jinfeng; Chen Yuxin; Lan Shi

    2011-01-01

    N-halamine-functionalized silica-polymer core-shell nanoparticles with enhanced antibacterial activity were synthesized through the encapsulation of silica nanoparticles as support with polymeric N-halamine. The as-synthesized nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive x-ray spectrometry (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR). These N-halamine-functionalized silica-polymer core-shell nanoparticles displayed powerful antibacterial performance against both Gram-positive bacteria and Gram-negative bacteria, and their antibacterial activities have been greatly improved compared with their bulk counterparts. Therefore, these N-halamine-functionalized silica-polymer core-shell nanoparticles have the potential for various significant applications such as in medical devices, healthcare products, water purification systems, hospitals, dental office equipment, food packaging, food storage, household sanitation, etc.

  10. Synthesis of N-halamine-functionalized silica-polymer core-shell nanoparticles and their enhanced antibacterial activity

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Alideertu; Wang Tao; Xiao Linghan; Wang Weiwei; Zhao Tianyi; Zheng Xin; Liu Fengqi; Gao Ge [College of Chemistry, Jilin University and MacDiarmid Laboratory, Changchun 130021 (China); Huang Jinfeng; Chen Yuxin [Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, Jilin University, Changchun 130012 (China); Lan Shi, E-mail: gaoge@jlu.edu.cn [College of Chemistry and Chemical Engineering, Inner Mongolia University for the Nationalities, Tongliao 028000 (China)

    2011-07-22

    N-halamine-functionalized silica-polymer core-shell nanoparticles with enhanced antibacterial activity were synthesized through the encapsulation of silica nanoparticles as support with polymeric N-halamine. The as-synthesized nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive x-ray spectrometry (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR). These N-halamine-functionalized silica-polymer core-shell nanoparticles displayed powerful antibacterial performance against both Gram-positive bacteria and Gram-negative bacteria, and their antibacterial activities have been greatly improved compared with their bulk counterparts. Therefore, these N-halamine-functionalized silica-polymer core-shell nanoparticles have the potential for various significant applications such as in medical devices, healthcare products, water purification systems, hospitals, dental office equipment, food packaging, food storage, household sanitation, etc.

  11. Innovative Route to Prepare of Au/C Catalysts by Replication of Gold-containing Mesoporous Silicas

    KAUST Repository

    Kerdi, Fatmé

    2011-12-23

    Gold-catalyzed aerobic epoxidations in the liquid phase are generally performed in low-polarity solvents, in which conventional oxide-supported catalysts are poorly dispersed. To improve the wettability of the catalytic powder and, thus, the efficiency of the catalyst, gold nanoparticles (NPs) have been dispersed on meso-structured carbons. Gold is first introduced in functionalized mesostructured silica and particles are formed inside the porosity. Silica pores are then impregnated with a carbon precursor and the composite material is heated at 900 °C under vacuum or nitrogen. Silica is then removed by acid leaching, leading to partially encapsulated gold particles in mesoporous carbon. Carbon prevents aggregation of gold particles at high temperature, both the mean size and distribution being similar to those observed in silica. However, while Au@SiO2 exhibit significant catalytic activity in the aerobic oxidation of trans-stilbene in the liquid phase, its Au@C mesostructured replica is quite inactive.

  12. Formation of monodisperse mesoporous silica microparticles via spray-drying.

    Science.gov (United States)

    Waldron, Kathryn; Wu, Winston Duo; Wu, Zhangxiong; Liu, Wenjie; Selomulya, Cordelia; Zhao, Dongyuan; Chen, Xiao Dong

    2014-03-15

    In this work, a protocol to synthesize monodisperse mesoporous silica microparticles via a unique microfluidic jet spray-drying route is reported for the first time. The microparticles demonstrated highly ordered hexagonal mesostructures with surface areas ranging from ~900 up to 1500 m(2)/g and pore volumes from ~0.6 to 0.8 cm(3)/g. The particle size could be easily controlled from ~50 to 100 μm from the same diameter nozzle via changing the initial solute content, or changing the drying temperature. The ratio of the surfactant (CTAB) and silica (TEOS), and the amount of water in the precursor were found to affect the degree of ordering of mesopores by promoting either the self-assembly of the surfactant-silica micelles or the condensation of the silica as two competing processes in evaporation induced self-assembly. The drying rate and the curvature of particles also affected the self-assembly of the mesostructure. The particle mesostructure is not influenced by the inlet drying temperature in the range of 92-160 °C, with even a relatively low temperature of 92 °C producing highly ordered mesoporous microparticles. The spray-drying derived mesoporous silica microparticles, while of larger sizes and more rapidly synthesized, showed a comparable performance with the conventional mesoporous silica MCM-41 in controlled release of a dye, Rhodamine B, indicating that these spray dried microparticles could be used for the immobilisation and controlled release of small molecules. Copyright © 2013 Elsevier Inc. All rights reserved.

  13. Core-shell fluorescent silica nanoparticles for sensing near-neutral pH values

    International Nuclear Information System (INIS)

    Gao, F.; Chen, X.; Ye, Q.; Yao, Z.; Guo, X.; Wang, L.

    2011-01-01

    pH-responsive fluorescent core-shell silica nanoparticles (SiNPs) were prepared by encapsulating the pH-sensitive fluorophore 8-hydroxypyrene-1,3, 6-trisulfonate into their silica shell via a facile reverse microemulsion method. The resulting SiNPs were characterized by SEM, TEM, fluorescence lifetime spectroscopy, photobleaching experiments, and photoluminescence. The core-shell structure endows the SiNPs with reduced photobleaching, excellent photostability, minimized solvatachromic shift, and increased fluorescence efficiency compared to the free fluorophore in aqueous solution. The dynamic range for sensing pH ranges from 5. 5 to 9. 0. The nanosensors show excellent stability, are highly reproducible, and enable rapid detection of pH. The results obtained with the SiNPs are in good agreement with data obtained with a glass electrode. (author)

  14. Novel chiral core-shell silica microspheres with trans-(1R,2R)-diaminocyclohexane bridged in the mesoporous shell: synthesis, characterization and application in high performance liquid chromatography.

    Science.gov (United States)

    Wu, Xiabing; You, Linjun; Di, Bin; Hao, Weiqiang; Su, Mengxiang; Gu, Yu; Shen, Lingling

    2013-07-19

    Novel chiral core-shell silica microspheres with trans-(1R,2R)-diaminocyclohexane (DACH) moiety bridged in the mesoporous shell were synthesized using layer-by-layer method. The chiral mesoporous shell around the nonporous silica core was formed by the co-condensation of N,N'-bis-[(triethoxysilyl)propyl]-trans-(1R,2R)-bis-(ureido)-cyclohexane (DACH-BS) and tetraethoxysilane (TEOS) using octadecyltrimethylammonium chloride (C18TMACl) and triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymer (P123) as the templates. The functionalized core-shell silica microspheres were characterized and tested as chiral stationary phases for high performance liquid chromatography (HPLC). R/S-1,1'-bi-2,2'-naphthol, R/S-6,6'-dibromo-1,1'-bi-2-naphthol and R/S-1,1'-bi-2,2'-phenanthrol were enantioseparated rapidly on the column packed with the DACH core-shell silica particles. Moreover, the column packed with core-shell particles exhibited better performance than the column packed with the DACH functionalized periodic mesoporous organosilicas. Copyright © 2013 Elsevier B.V. All rights reserved.

  15. Nanocellulose Derivative/Silica Hybrid Core-Shell Chiral Stationary Phase: Preparation and Enantioseparation Performance

    Directory of Open Access Journals (Sweden)

    Xiaoli Zhang

    2016-05-01

    Full Text Available Core-shell silica microspheres with a nanocellulose derivative in the hybrid shell were successfully prepared as a chiral stationary phase by a layer-by-layer self-assembly method. The hybrid shell assembled on the silica core was formed using a surfactant as template by the copolymerization reaction of tetraethyl orthosilicate and the nanocellulose derivative bearing triethoxysilyl and 3,5-dimethylphenyl groups. The resulting nanocellulose hybrid core-shell chiral packing materials (CPMs were characterized and packed into columns, and their enantioseparation performance was evaluated by high performance liquid chromatography. The results showed that CPMs exhibited uniform surface morphology and core-shell structures. Various types of chiral compounds were efficiently separated under normal and reversed phase mode. Moreover, chloroform and tetrahydrofuran as mobile phase additives could obviously improve the resolution during the chiral separation processes. CPMs still have good chiral separation property when eluted with solvent systems with a high content of tetrahydrofuran and chloroform, which proved the high solvent resistance of this new material.

  16. Synthesis and characterization of multifunctional silica core-shell nanocomposites with magnetic and fluorescent functionalities

    International Nuclear Information System (INIS)

    Ma Zhiya; Dosev, Dosi; Nichkova, Mikaela; Dumas, Randy K.; Gee, Shirley J.; Hammock, Bruce D.; Liu Kai; Kennedy, Ian M.

    2009-01-01

    Multifunctional core-shell nanocomposites with a magnetic core and a silica shell doped with lanthanide chelate have been prepared by a simple method. First, citric acid-modified magnetite nanoparticles were synthesized by a chemical coprecipitation method. Then the magnetite nanoparticles were coated with silica shells doped with terbium (Tb 3+ ) complex by a modified Stoeber method based on hydrolyzing and condensation of tetraethyl orthosilicate (TEOS) and a silane precursor. These multifunctional nanocomposites are potentially useful in a variety of biological areas such as bio-imaging, bio-labeling and bioassays because they can be simultaneously manipulated with an external magnetic field and exhibit unique phosphorescence properties.

  17. Hierarchical Mesoporous Organosilica-Silica Core-Shell Nanoparticles Capable of Controlled Fungicide Release.

    Science.gov (United States)

    Luo, Leilei; Liang, Yucang; Erichsen, Egil Severin; Anwander, Reiner

    2018-05-17

    A new class of hierarchically structured mesoporous silica core-shell nanoparticles (HSMSCSNs) with a periodic mesoporous organosilica (PMO) core and a mesoporous silica (MS) shell is reported. The applied one-pot, two-step strategy allows rational control over the core/shell chemical composition, topology, and pore/particle size, simply by adjusting the reaction conditions in the presence of cetyltrimethylammonium bromide (CTAB) as structure-directing agent under basic conditions. The spherical, ethylene- or methylene-bridged PMO cores feature hexagonal (p6mm) or cage-like cubic symmetry (Pm3‾ n) depending on the organosilica precursor. The hexagonal MS shell was obtained by n-hexane-induced controlled hydrolysis of TEOS followed by directional co-assembly/condensation of silicate/CTAB composites at the PMO cores. The HSMSCSNs feature a hierarchical pore structure with pore diameters of about 2.7 and 5.6 nm in the core and shell domains, respectively. The core sizes and shell thicknesses are adjustable in the ranges of 90-275 and 15-50 nm, respectively, and the surface areas (max. 1300 m 2  g -1 ) and pore volumes (max. 1.83 cm 3  g -1 ) are among the highest reported for core-shell nanoparticles. The adsorption and controlled release of the fungicide propiconazole by the HSMSCSNs showed a three-stage release profile. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Hierarchical Ag mesostructures for single particle SERS substrate

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Minwei, E-mail: xuminwei@xjtu.edu.cn; Zhang, Yin

    2017-01-30

    Highlights: • Hierarchical Ag mesostructures with the size of 250, 360 and 500 nm are synthesized via a seed-mediated approach. • The Ag mesostructures present the tailorable size and highly roughened surfaces. • The average enhancement factors for individual Ag mesostructures were estimated to be as high as 10{sup 6}. - Abstract: Hierarchical Ag mesostructures with highly rough surface morphology have been synthesized at room temperature through a simple seed-mediated approach. Electron microscopy characterizations indicate that the obtained Ag mesostructures exhibit a textured surface morphology with the flower-like architecture. Moreover, the particle size can be tailored easily in the range of 250–500 nm. For the growth process of the hierarchical Ag mesostructures, it is believed that the self-assembly mechanism is more reasonable rather than the epitaxial overgrowth of Ag seed. The oriented attachment of nanoparticles is revealed during the formation of Ag mesostructures. Single particle surface enhanced Raman spectra (sp-SERS) of crystal violet adsorbed on the hierarchical Ag mesostructures were measured. Results reveal that the hierarchical Ag mesostructures can be highly sensitive sp-SERS substrates with good reproducibility. The average enhancement factors for individual Ag mesostructures are estimated to be about 10{sup 6}.

  19. Enhanced adsorption of trivalent arsenic from water by functionalized diatom silica shells.

    Directory of Open Access Journals (Sweden)

    Jianying Zhang

    Full Text Available The potential of porous diatom silica shells as a naturally abundant low-cost sorbent for the removal of arsenic in aqueous solutions was investigated in a batch study. The objective of this work was to chemically modify the silica shells of a diatom Melosira sp. with bifunctional (thiol and amino groups to effectively remove arsenic in its toxic As(III form (arsenite predominant in the aquatic environment. Sorption experiments with this novel sorbent were conducted under varying conditions of pH, time, dosage, and As(III concentration. A maximum adsorption capacity of 10.99 mg g-1 was achieved within 26 h for a solution containing 12 mg L-1 As(III at pH 4 and sorbent dosage of 2 g L-1. The functionalized diatom silica shells had a surface morphological change which was accompanied by increased pore size at the expense of reduced specific surface area and total pore volume. As(III adsorption was best fitted with the Langmuir-Freundlich model, and the adsorption kinetic data using pore surface diffusion model showed that both the external (film and internal (intraparticle diffusion can be rate-determining for As(III adsorption. Fourier transform infrared spectroscopy (FTIR indicated that the thiol and amino groups potentially responsible for As(III adsorption were grafted on the surface of diatom silica shells. X-ray photoelectron spectroscopy (XPS further verified that this unique sorbent proceeded via a chemisorption mechanism through the exchange between oxygen-containing groups of neutral As(III and thiol groups, and through the surface complexation between As(III and protonated nitrogen and hydroxyl groups. Results indicate that this functionalized bioadsorbent with a high As(III adsorption capacity holds promise for the treatment of As(III containing wastewater.

  20. Porous silica nanoparticles as carrier for curcumin delivery

    Science.gov (United States)

    Hartono, Sandy Budi; Hadisoewignyo, Lannie; Irawaty, Wenny; Trisna, Luciana; Wijaya, Robby

    2018-04-01

    Mesoporous silica nanoparticles (MSN) with large surface areas and pore volumes show great potential as drug and gene carriers. However, there are still some challenging issues hinders their clinical application. Many types of research in the use of mesoporous silica material for drug and gene delivery involving complex and rigorous procedures. A facile and reproducible procedure to prepare combined drug carrier is required. We investigated the effect of physiochemical parameters of mesoporous silica, including structural symmetry (cubic and hexagonal), particles size (micro size: 1-2 µm and nano size: 100 -300 nm), on the solubility and release profile of curcumin. Transmission Electron Microscopy, X-Ray Powder Diffraction, and Nitrogen sorption were used to confirm the synthesis of the mesoporous silica materials. Mesoporous silica materials with different mesostructures and size have been synthesized successfully. Curcumin has anti-oxidant, anti-inflammation and anti-virus properties which are beneficial to fight various diseases such as diabetic, cancer, allergic, arthritis and Alzheimer. Curcumin has low solubility which minimizes its therapeutic effect. The use of nanoporous material to carry and release the loaded molecules is expected to enhance curcumin solubility. Mesoporous silica materials with a cubic mesostructure had a higher release profile and curcumin solubility, while mesoporous silica materials with a particle size in the range of nano meter (100-300) nm also show better release profile and solubility.

  1. Determination of the shell growth direction during the formation of silica microcapsules by confocal fluorescence microscopy

    NARCIS (Netherlands)

    van Wijk, J.; Salari, J.W.O.; Meuldijk, J.; Klumperman, L.

    2015-01-01

    A novel procedure was developed to determine the direction of silica growth during the formation of a silica shell around aqueous microdroplets in water-in-oil Pickering emulsions. Two fluorescently labeled silica precursors were added consecutively and the resulting microcapsules were visualized

  2. Anisotropic silica mesostructures for DNA encapsulation

    Indian Academy of Sciences (India)

    The encapsulation of biomolecules in inert meso or nanostructures is an important step towards controlling drug delivery agents. Mesoporous silica nanoparticles (MSN) are of immense importance owing to their high surface area, large pore size, uniform particle size and chemical inertness. Reverse micellar method with ...

  3. Preparation of hierarchical micro-mesoporous aluminosilicate composites by simple Y zeolite/MCM-48 silica assembly

    Energy Technology Data Exchange (ETDEWEB)

    Enterría, Marina, E-mail: marina@incar.csic.es; Suárez-García, Fabián; Martínez-Alonso, Amelia; Tascón, Juan M.D.

    2014-01-15

    Highlights: • Hierarchical micro-mesoporous aluminosilicates were synthesized. • Y zeolite core/MCM-48 silica shell structures were obtained. • Y zeolite favors the formation of the mesostructure. • Porosity and structure can be varied by modifying the preparation variables. • Duration of the hydrothermal step has a great effect on the materials properties. -- Abstract: A simple procedure to obtain hierarchical micro-mesoporous aluminosilicate composites was developed by growing MCM-48 silica over commercial Y zeolite. The obtained hierarchical composites have a microporous core and a mesoporous shell. The process consists in assembling dispersed Y zeolite with a mesoporous silica phase that is formed “in situ” by “soft-templating” with cetryltrimethylammonium bromide (CTAB) as surfactant. The Y zeolite/MCM-48 silica ratio and aging time were varied to study their effects on the final porosity and structure of the hierarchical composites. The pore textural and structural characteristics of the composites did not match those of the corresponding Y zeolite/MCM-48 silica physical mixtures. This implies that the synthesized composites integrate micropores and mesopores in the same bulk. The obtained composites exhibited micropore and mesopore volumes ranging between 0.15–0.31 and 0.30–0.51 cm{sup 3}/g, respectively. X-ray diffraction and N{sub 2} adsorption results revealed that the presence of zeolite in the reaction medium favors the formation of mesopores in the obtained materials, especially for short hydrothermal treatments. TEM results showed that the obtained adsorbents are constituted by an integrated micro-mesoporous bimodal system in which Y zeolite is surrounded by a thin cover of MCM-48 silica.

  4. Preparation of hierarchical micro-mesoporous aluminosilicate composites by simple Y zeolite/MCM-48 silica assembly

    International Nuclear Information System (INIS)

    Enterría, Marina; Suárez-García, Fabián; Martínez-Alonso, Amelia; Tascón, Juan M.D.

    2014-01-01

    Highlights: • Hierarchical micro-mesoporous aluminosilicates were synthesized. • Y zeolite core/MCM-48 silica shell structures were obtained. • Y zeolite favors the formation of the mesostructure. • Porosity and structure can be varied by modifying the preparation variables. • Duration of the hydrothermal step has a great effect on the materials properties. -- Abstract: A simple procedure to obtain hierarchical micro-mesoporous aluminosilicate composites was developed by growing MCM-48 silica over commercial Y zeolite. The obtained hierarchical composites have a microporous core and a mesoporous shell. The process consists in assembling dispersed Y zeolite with a mesoporous silica phase that is formed “in situ” by “soft-templating” with cetryltrimethylammonium bromide (CTAB) as surfactant. The Y zeolite/MCM-48 silica ratio and aging time were varied to study their effects on the final porosity and structure of the hierarchical composites. The pore textural and structural characteristics of the composites did not match those of the corresponding Y zeolite/MCM-48 silica physical mixtures. This implies that the synthesized composites integrate micropores and mesopores in the same bulk. The obtained composites exhibited micropore and mesopore volumes ranging between 0.15–0.31 and 0.30–0.51 cm 3 /g, respectively. X-ray diffraction and N 2 adsorption results revealed that the presence of zeolite in the reaction medium favors the formation of mesopores in the obtained materials, especially for short hydrothermal treatments. TEM results showed that the obtained adsorbents are constituted by an integrated micro-mesoporous bimodal system in which Y zeolite is surrounded by a thin cover of MCM-48 silica

  5. Sulfonic-based precursors (SAPs for silica mesostructures: Advances in synthesis and applications

    Directory of Open Access Journals (Sweden)

    Sadegh Rostamnia*

    2016-01-01

    Full Text Available Sulfonic acid-based precursors (SAP play an important role in tailoring mesoporous silica’s and convert them to a solid acid catalyst with a Bronsted-type nature. These kinds of solid acids contribute to sustainable and green chemistry by their heterogeneous, recyclable, and high efficiency features. Therefore, knowing the properties and reactivity of SAPs can guide us to manufacture a sulfonated mesostructures compatible with reaction type and conditions. In the present review, some of the important SAPs, their reactivity and mechanism of functionalization are discussed.

  6. Enhanced Thermal Properties of Novel Latent Heat Thermal Storage Material Through Confinement of Stearic Acid in Meso-Structured Onion-Like Silica

    Science.gov (United States)

    Gao, Junkai; Lv, Mengjiao; Lu, Jinshu; Chen, Yan; Zhang, Zijun; Zhang, Xiongjie; Zhu, Yingying

    2017-12-01

    Meso-structured onion-like silica (MOS), which had a highly ordered, onion-like multilayer; large surface area and pore volume; and highly curved mesopores, were synthesized as a support for stearic acid (SA) to develop a novel shape-stabilized phase change material (SA/MOS). The characterizations of SA/MOS were studied by the analysis technique of scanning electron microscope, infrared spectroscopy, x-ray diffraction, differential scanning calorimeter (DSC), and thermal gravimetry analysis (TGA). The results showed that the interaction between the SA and the MOS was physical adsorption and that the MOS had no effect on the crystal structure of the SA. The DSC results suggested that the melting and solidifying temperature of the SA/MOS were 72.7°C and 63.9°C with a melting latent heat of 108.0 J/g and a solidifying latent heat of 126.0 J/g, respectively, and the TGA results indicated that the SA/MOS had a good thermal stability. All of the results demonstrated that the SA/MOS was a promising thermal energy storage material candidate for practical applications.

  7. Structural rearrangement of mesostructured silica nanoparticles incorporated with ZnO catalyst and its photoactivity: Effect of alkaline aqueous electrolyte concentration

    Science.gov (United States)

    Jusoh, N. W. C.; Jalil, A. A.; Triwahyono, S.; Karim, A. H.; Salleh, N. F.; Annuar, N. H. R.; Jaafar, N. F.; Firmansyah, M. L.; Mukti, R. R.; Ali, M. W.

    2015-03-01

    ZnO-incorporated mesostructured silica nanoparticles (MSN) catalysts (ZM) were prepared by the introduction of Zn ions into the framework of MSN via a simple electrochemical system in the presence of various concentrations of NH4OH aqueous solution. The physicochemical properties of the catalysts were studied by XRD, 29Si MAS NMR, nitrogen adsorption-desorption, FE-SEM, TEM, FTIR, and photoluminescence spectroscopy. Characterization results demonstrated that the alkaline aqueous electrolyte simply generated abundant silanol groups on the surface of the catalysts as a consequence of desilication to form the hierarchical-like structure of the MSN. Subsequent restructuring of the silica network by the creation of oxygen vacancies and formation of Si-O-Zn during the electrolysis, as well as formation of new Si-O-Si bonds during calcination seemed to be the main factors that enhanced the catalytic performance of photodecolorization of methyl orange. A ZM prepared in the presence of 1.0 M NH4OH (ZM-1.0) was determined to be the most effective catalyst. The catalyst displays a higher first-order kinetics rate of 3.87 × 10-1 h-1 than unsupported ZnO (1.13 × 10-1 h-1) that prepared under the same conditions in the absence of MSN. The experiment on effect of scavengers showed that hydroxyl radicals generated from the three main sources; reduced O2 at the conduction band, decomposed water at the valence band and irradiated H2O2 in the solution, are key factors that influenced the reaction. It is also noted that the recycled ZM-1.0 catalyst maintained its activity up to five runs without serious catalyst deactivation.

  8. Magnetoliposomes based on nickel/silica core/shell nanoparticles: Synthesis and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Ana Rita O.; Gomes, I.T.; Almeida, Bernardo G. [Centro de Física (CFUM), Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Araújo, J.P. [IFIMUP/IN – Instituto de Nanociência e Nanotecnologia, R. Campo Alegre, 4169-007 Porto (Portugal); Castanheira, Elisabete M.S. [Centro de Física (CFUM), Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Coutinho, Paulo J.G., E-mail: pcoutinho@fisica.uminho.pt [Centro de Física (CFUM), Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal)

    2014-12-15

    In the present work, nickel magnetic nanoparticles with diameters lower than 100 nm, with and without silica shell, were synthesized by microheterogeneous templating. The magnetic properties of the nanoparticles show a typical ferromagnetic behavior with a coercive field of 80 Oe. Dry magnetoliposomes (DMLs) with diameter between 58 nm and 76 nm were obtained from the synthesis of nanoparticles in the presence of a lipid or surfactant layer, and aqueous magnetoliposomes (AMLs) were obtained by encapsulation of the nanoparticles in liposomes. FRET (Förster resonance energy transfer) experiments were performed to study the non-specific interactions between aqueous magnetoliposomes and giant unilamellar vesicles (GUVs), as models of cell membranes. It was possible to detect membrane fusion between GUVs and AMLs containing both NBD-C{sub 6}-HPC (donor) and the dye Nile Red (acceptor). - Highlights: • Magnetic nickel nanoparticles were synthesized in microheterogeneous media. • The nanoparticles were covered with a silica shell to improve biocompatibility. • Aqueous and dry magnetoliposomes were prepared, the latter with diameter around 70 nm. • Membrane fusion between magnetoliposomes and models of cell membranes was detected by FRET.

  9. Magnetoliposomes based on nickel/silica core/shell nanoparticles: Synthesis and characterization

    International Nuclear Information System (INIS)

    Rodrigues, Ana Rita O.; Gomes, I.T.; Almeida, Bernardo G.; Araújo, J.P.; Castanheira, Elisabete M.S.; Coutinho, Paulo J.G.

    2014-01-01

    In the present work, nickel magnetic nanoparticles with diameters lower than 100 nm, with and without silica shell, were synthesized by microheterogeneous templating. The magnetic properties of the nanoparticles show a typical ferromagnetic behavior with a coercive field of 80 Oe. Dry magnetoliposomes (DMLs) with diameter between 58 nm and 76 nm were obtained from the synthesis of nanoparticles in the presence of a lipid or surfactant layer, and aqueous magnetoliposomes (AMLs) were obtained by encapsulation of the nanoparticles in liposomes. FRET (Förster resonance energy transfer) experiments were performed to study the non-specific interactions between aqueous magnetoliposomes and giant unilamellar vesicles (GUVs), as models of cell membranes. It was possible to detect membrane fusion between GUVs and AMLs containing both NBD-C 6 -HPC (donor) and the dye Nile Red (acceptor). - Highlights: • Magnetic nickel nanoparticles were synthesized in microheterogeneous media. • The nanoparticles were covered with a silica shell to improve biocompatibility. • Aqueous and dry magnetoliposomes were prepared, the latter with diameter around 70 nm. • Membrane fusion between magnetoliposomes and models of cell membranes was detected by FRET

  10. HPLC-CUPRAC post-column derivatization method for the determination of antioxidants: a performance comparison between porous silica and core-shell column packing.

    Science.gov (United States)

    Haque, Syed A; Cañete, Socrates Jose P

    2018-01-01

    An HPLC method employing a post-column derivatization strategy using the cupric reducing antioxidant capacity reagent (CUPRAC reagent) for the determining antioxidants in plant-based materials leverages the separation capability of regular HPLC approaches while allowing for detection specificity for antioxidants. Three different column types, namely core-shell and porous silica including two chemically different core-shell materials (namely phenyl-hexyl and C18), were evaluated to assess potential improvements that could be attained by changing from a porous silica matrix to a core-shell matrix. Tea extracts were used as sample matrices for the evaluation specifically looking at catechin and epigallocatechin gallate (EGCG). Both the C18 and phenyl-hexyl core-shell columns showed better performance compared to the C18 porous silica one in terms of separation, peak shape, and retention time. Among the two core-shell materials, the phenyl-hexyl column showed better resolving power compared to the C18 column. The CUPRAC post-column derivatization method can be improved using core-shell columns and suitable for quantifying antioxidants, exemplified by catechin and EGCG, in tea samples.

  11. Synthesis and characterization of fluorescence-labelled silica core-shell and noble metal-decorated ceria nanoparticles

    Directory of Open Access Journals (Sweden)

    Rudolf Herrmann

    2014-12-01

    Full Text Available The present review article covers work done in the cluster NPBIOMEM in the DFG priority programme SPP 1313 and focuses on synthesis and characterization of fluorescent silica and ceria nanoparticles. Synthetic methods for labelling of silica and polyorganosiloxane/silica core–shell nanoparticles with perylenediimide derivatives are described, as well as the modification of the shell with thiol groups. Photometric methods for the determination of the number of thiol groups and an estimate for the number of fluorescent molecules per nanoparticles, including a scattering correction, have been developed. Ceria nanoparticles decorated with noble metals (Pt, Pd, Rh are models for the decomposition products of automobile catalytic converters which appear in the exhaust gases and finally interact with biological systems including humans. The control of the degree of agglomeration of small ceria nanoparticles is the basis for their synthesis. Almost monodisperse agglomerates (40 ± 4–260 ± 40 nm diameter can be prepared and decorated with noble metal nanoparticles (2–5 nm diameter. Fluorescence labelling with ATTO 647N gave the model particles which are now under biophysical investigation.

  12. Fabrication of poly(o-anisidine) coated silica core-shell microspheres and their electrorheological response

    Science.gov (United States)

    Lee, Chul Joo; Choi, Hyoung Jin

    2017-11-01

    In this work, silica/poly(o-anisidine) (POA) core-shell structured microspheres were synthesized by coating the silica core surface with POA with a help of a chemical grafting agent, N-[(3-trimethoxylsilyl)-propyl] aniline. The synthesized silica microspheres were then applied as a polymer/inorganic composite particle-based electrorheological (ER) fluid. The morphology of the silica/POA microspheres was examined by using both transmission electron microscopy and scanning electron microscopy, while their thermal properties and chemical structure were checked by thermogravimetric analysis and Fourier-transform infrared spectroscopy, respectively. The ER properties of the silica/POA particle-based ER fluid were examined by using a Couette-type rotational rheometer equipped with a high-voltage power supplier and analyzed by the Bingham model and modified Mason number. In order to obtain additional information about the electrical polarization properties, the dielectric spectra were measured by an LCR meter and fitted by using the Cole-Cole equation. Furthermore, suspension stability of the ER fluid was tested using Turbiscan.

  13. Palladium nanoparticles encapsulated in core-shell silica: A structured hydrogenation catalyst with enhanced activity for reduction of oxyanion water pollutants

    KAUST Repository

    Wang, Yin; Liu, Jinyong; Wang, Peng; Werth, Charles; Strathmann, Timothy J.

    2014-01-01

    Noble metal nanoparticles have been applied to mediate catalytic removal of toxic oxyanions and halogenated hydrocarbons in contaminated water using H2 as a clean and sustainable reductant. However, activity loss by nanoparticle aggregation and difficulty of nanoparticle recovery are two major challenges to widespread technology adoption. Herein, we report the synthesis of a core-shell-structured catalyst with encapsulated Pd nanoparticles and its enhanced catalytic activity in reduction of bromate (BrO3-), a regulated carcinogenic oxyanion produced during drinking water disinfection process, using 1 atm H2 at room temperature. The catalyst material consists of a nonporous silica core decorated with preformed octahedral Pd nanoparticles that were further encapsulated within an ordered mesoporous silica shell (i.e., SiO2@Pd@mSiO2). Well-defined mesopores (2.3 nm) provide a physical barrier to prevent Pd nanoparticle (6 nm) movement, aggregation, and detachment from the support into water. Compared to freely suspended Pd nanoparticles and SiO2@Pd, encapsulation in the mesoporous silica shell significantly enhanced Pd catalytic activity (by a factor of 10) under circumneutral pH conditions that are most relevant to water purification applications. Mechanistic investigation of material surface properties combined with Langmuir-Hinshelwood modeling of kinetic data suggest that mesoporous silica shell enhances activity by promoting BrO3- adsorption near the Pd active sites. The dual function of the mesoporous shell, enhancing Pd catalyst activity and preventing aggregation of active nanoparticles, suggests a promising general strategy of using metal nanoparticle catalysts for water purification and related aqueous-phase applications.

  14. Palladium nanoparticles encapsulated in core-shell silica: A structured hydrogenation catalyst with enhanced activity for reduction of oxyanion water pollutants

    KAUST Repository

    Wang, Yin

    2014-10-03

    Noble metal nanoparticles have been applied to mediate catalytic removal of toxic oxyanions and halogenated hydrocarbons in contaminated water using H2 as a clean and sustainable reductant. However, activity loss by nanoparticle aggregation and difficulty of nanoparticle recovery are two major challenges to widespread technology adoption. Herein, we report the synthesis of a core-shell-structured catalyst with encapsulated Pd nanoparticles and its enhanced catalytic activity in reduction of bromate (BrO3-), a regulated carcinogenic oxyanion produced during drinking water disinfection process, using 1 atm H2 at room temperature. The catalyst material consists of a nonporous silica core decorated with preformed octahedral Pd nanoparticles that were further encapsulated within an ordered mesoporous silica shell (i.e., SiO2@Pd@mSiO2). Well-defined mesopores (2.3 nm) provide a physical barrier to prevent Pd nanoparticle (6 nm) movement, aggregation, and detachment from the support into water. Compared to freely suspended Pd nanoparticles and SiO2@Pd, encapsulation in the mesoporous silica shell significantly enhanced Pd catalytic activity (by a factor of 10) under circumneutral pH conditions that are most relevant to water purification applications. Mechanistic investigation of material surface properties combined with Langmuir-Hinshelwood modeling of kinetic data suggest that mesoporous silica shell enhances activity by promoting BrO3- adsorption near the Pd active sites. The dual function of the mesoporous shell, enhancing Pd catalyst activity and preventing aggregation of active nanoparticles, suggests a promising general strategy of using metal nanoparticle catalysts for water purification and related aqueous-phase applications.

  15. Fluorescence lifetime measurements to determine the core-shell nanostructure of FITC-doped silica nanoparticles: An optical approach to evaluate nanoparticle photostability

    International Nuclear Information System (INIS)

    Santra, Swadeshmukul; Liesenfeld, Bernd; Bertolino, Chiara; Dutta, Debamitra; Cao Zehui; Tan Weihong; Moudgil, Brij M.; Mericle, Robert A.

    2006-01-01

    In this paper, we described a novel fluorescence lifetime-based approach to determine the core-shell nanostructure of FITC-(fluorescein isothiocyanate, isomer I) doped fluorescent silica nanoparticles (FSNPs). Because of phase homogeneity between the core and the shell, electron microscopic technique could not be used to characterize such core-shell nanostructure. Our optical approach not only revealed the core-shell nanostructure of FSNPs but also evaluated photobleaching of FSNPs both in the solvated and non-solvated (dry) states. The FSNPs were produced via Stoeber's method by hydrolysis and co-condensation reaction of tetraethylorthosilicate (TEOS) and fluorescein linked (3-aminopropyl)triethoxysilane (FITC-APTS conjugate) in the presence of ammonium hydroxide catalyst. To obtain a pure silica surface coating, FSNPs were then post-coated with TEOS. The average particle size was 135 nm as determined by TEM (transmission electron microscope) measurements. Fluorescence excitation and emission spectral data demonstrated successful doping of FITC dye molecules in FSNPs. Fluorescence lifetime data revealed that approximately 62% of dye molecules remained in the solvated silica shell, while 38% of dye molecules remained in the non-solvated (dry) silica core. Photobleaching experiments of FSNPs were conducted both in DI water (solution state) and in air (dry state). Severe photobleaching of FSNPs was observed in air. However, FSNPs were moderately photostable in the solution state. Photostability of FSNPs in both solution and dry states was explained on the basis of fluorescence lifetime data

  16. Benefits of Silica Core-Shell Structures on the Temperature Sensing Properties of Er,Yb:GdVO4 Up-Conversion Nanoparticles.

    Science.gov (United States)

    Savchuk, Oleksandr A; Carvajal, Joan J; Cascales, C; Aguiló, M; Díaz, F

    2016-03-23

    We studied the temperature-dependent luminescence of GdVO4 nanoparticles co-doped with Er(3+) (1 mol %) and Yb(3+) (20 mol %) and determined their thermal sensing properties through the fluorescence intensity ratio (FIR) technique. We also analyzed how a silica coating, in a core-shell structure, affects the temperature sensing properties of this material. Spectra were recorded in the range of biological temperatures (298-343 K). The absolute sensitivity for temperature determination calculated for the core-shell nanoparticles is double the one calculated for bare nanoparticles, achieving a thermal resolution of 0.4 K. Moreover, silica-coated nanoparticles show good dispersibility in different solvents, such as water, DMSO, and methanol. Also, they show good luminescence stability without interactions with solvent molecules. Furthermore, we also observed that the silica coating shell prevents progressive heating of the nanoparticles during prolonged excitation periods with the 980 nm laser, preventing effects on their thermometric applications.

  17. Gradual growth of gold nanoseeds on silica for SiO2-gold homogeneous nano core/shell applications by the chemical reduction method

    International Nuclear Information System (INIS)

    Rezvani Nikabadi, H; Shahtahmasebi, N; Rezaee Rokn-Abadi, M; Bagheri Mohagheghi, M M; Goharshadi, E K

    2013-01-01

    In this paper, a facile method for the synthesis of gold nanoseeds on the functionalized surface of silica nanoparticles has been investigated. Mono-dispersed silica particles and gold nanoparticles were prepared by the chemical reduction method. The thickness of the Au shell was well controlled by repeating the reduction time of HAuCl 4 on silica/3-aminopropyltriethoxysilane (APTES)/initial gold nanoparticles. The prepared SiO 2 -gold core/shell nanoparticles were studied using x-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy and ultraviolet visible (UV-Vis) spectroscopy. The TEM images indicated that the silica nanoparticles were spherical in shape with 100 nm diameters and functionalizing silica nanoparticles with a layer of bi-functional APTES molecules and tetrakis hydroxy methyl phosphonium chloride. The gold nanoparticles show a narrow size of up to 5 nm and by growing gold nanoseeds over the silica cores a red shift in the maximum absorbance of UV-Vis spectroscopy from 524 to 637 nm was observed.

  18. Preparation and characterization of bimetallic catalysts supported on mesoporous silica films

    NARCIS (Netherlands)

    Muraza, O.; Rebrov, E.V.; Khimyak, T.; Johnson, B.F.G.; Kooyman, P.J.; Lafont, U.; Albouy, P.A.; Croon, de M.H.J.M.; Schouten, J.C.

    2006-01-01

    Thin (300–1000 nm) mesoporous silica coatings with hexagonal and cubic mesostructure have been prepared on Pyrex® 7740 borosilicate glass substrates by the evaporation induced self assembly assisted sol-gel route. Prior to the synthesis, a 50 nm TiO2 layer has been deposited on the substate by

  19. Exploration of the growth process of ultrathin silica shells on the surface of gold nanorods by the localized surface plasmon resonance

    International Nuclear Information System (INIS)

    Li, Chong; Li, Yujie; Ling, Yunyang; Lai, Yangwei; Wu, Chuanliu; Zhao, Yibing

    2014-01-01

    Ultrathin silica coating (UTSC) has emerged as an effective way to improve the compatibility and stability of nanoparticles without attenuating their intrinsic optical properties. Exploration strategies to probe the growth process of ultrathin silica shells on the surface of nanoparticles would represent a valuable innovation that would benefit the development of ultrathin silica coated nanoparticles and their relevant applications. In this work, we report a unique, very effective and straightforward strategy for probing the growth of ultrathin silica shells on the surface of gold nanorods (Au NRs), which exploits the localized surface plasmon resonance (LSPR) as a reporting signal. The thickness of the ultrathin silica shells on the surface of Au NRs can be quantitatively measured and predicted in the range of 0.5–3.5 nm. It is demonstrated that the LSPR shift accurately reflects the real-time change in the thickness of the ultrathin silica shells on Au NRs during the growth process. By using the developed strategy, we further analyze the growth of UTSC on the surface of Au NRs via feeding of Na 2 SiO 3 in a stepwise manner. The responsiveness analysis of LSPR also provides important insight into the shielding effect of UTSC on the surface of Au NRs that is not accessible with conventional strategies. This LSPR-based strategy permits exploration of the surface-mediated sol–gel reactions of silica from a new point of view. (paper)

  20. Micelle swelling agent derived cavities for increasing hydrophobic organic compound removal efficiency by mesoporous micelle@silica hybrid materials

    KAUST Repository

    Shi, Yifeng; Li, Bin; Wang, Peng; Dua, Rubal; Zhao, Dongyuan

    2012-01-01

    Mesoporous micelle@silica hybrid materials with 2D hexagonal mesostructures were synthesized as reusable sorbents for hydrophobic organic compounds (HOCs) removal by a facile one-step aqueous solution synthesis using 3-(trimethoxysily)propyl

  1. Hierarchical silica particles by dynamic multicomponent assembly

    DEFF Research Database (Denmark)

    Wu, Z. W.; Hu, Q. Y.; Pang, J. B.

    2005-01-01

    Abstract: Aerosol-assisted assembly of mesoporous silica particles with hierarchically controllable pore structure has been prepared using cetyltrimethylammonium bromide (CTAB) and poly(propylene oxide) (PPO, H[OCH(CH3)CH2],OH) as co-templates. Addition of the hydrophobic PPO significantly...... influences the delicate hydrophilic-hydrophobic balance in the well-studied CTAB-silicate co-assembling system, resulting in various mesostructures (such as hexagonal, lamellar, and hierarchical structure). The co-assembly of CTAB, silicate clusters, and a low-molecular-weight PPO (average M-n 425) results...... in a uniform lamellar structure, while the use of a high-molecular-weight PPO (average M-n 2000), which is more hydrophobic, leads to the formation of hierarchical pore structure that contains meso-meso or meso-macro pore structure. The role of PPO additives on the mesostructure evolution in the CTAB...

  2. Mesoporous silica films as catalyst support for microstructured reactors: preparation and characterization

    NARCIS (Netherlands)

    Muraza, O.; Kooyman, P.J.; Lafont, U.; Albouy, P.A.; Khimyak, T.; Rebrov, E.V.; Croon, de M.H.J.M.; Schouten, J.C.

    2008-01-01

    Mesoporous silica thin films with hexagonal and cubic mesostructure have been deposited by the evaporation induced self-assembly assisted sol–gel route on microchannels etched in a Pyrex® 7740 borosilicate glass substrate. Prior to the synthesis, a 50 nm TiO2 film has been deposited on the substrate

  3. Synthesis and characterization of mesostructured borosilica oxynitrides

    International Nuclear Information System (INIS)

    Xiu Tongping; Liu Qian; Wang Jiacheng

    2007-01-01

    Mesoporous borosilica oxynitrides were prepared by heat treatment of boron substituted MCM-41 in flowing ammonia at high-temperatures. Based on absorption-desorption isotherms, high-resolution transmission electron microscopy (HRTEM) and small-angle X-ray diffraction (SAXRD) measurement of the samples, it was found that the mesostructured ordering, high BET surface area and narrow pore size distribution of B-MCM-41 could be maintained after nitridation. Mesostructured borosilica oxynitrides may be potential acid-base solid catalysts in future

  4. Silica-modified luminescent LaPO4 :Eu@LaPO4 @SiO2 core/shell nanorods: Synthesis, structural and luminescent properties.

    Science.gov (United States)

    Ansari, Anees A

    2018-02-01

    Monoclinic-type tetragonal LaPO 4 :Eu (core) and LaPO 4 :Eu@LaPO 4 (core/shell) nanorods (NRs) were successfully prepared using a urea-based co-precipitation process under ambient conditions. An amorphous silica layer was coated around the luminescent core/shell NRs via the sol-gel process to improve their solubility and colloidal stability in aqueous and non-aqueous media. The prepared nano-products were systematically characterized by X-ray diffraction pattern, transmission electron microscopy, energy dispersive X-ray analysis, and FTIR, UV/Vis, and photoluminescence spectroscopy to examine their phase purity, crystal phase, surface chemistry, solubility and luminescence characteristics. The length and diameter of the nano-products were in the range 80-120 nm and 10-15 nm, respectively. High solubility of the silica-modified core/shell/Si NRs was found for the aqueous medium. The luminescent core NRs exhibited characteristic excitation and emission transitions in the visible region that were greatly affected by surface growth of insulating LaPO 4 and silica layers due to the multiphonon relaxation rate. Our luminescence spectral results clearly show a distinct difference in intensities for core, core/shell, and core/shell/Si NRs. Highly luminescent NRs with good solubility could be useful candidates for a variety of photonic-based biomedical applications. Copyright © 2017 John Wiley & Sons, Ltd.

  5. Synthesis and characterization of the superparamagnetic iron oxide nanoparticles modified with cationic chitosan and coated with silica shell

    Energy Technology Data Exchange (ETDEWEB)

    Lewandowska-Łańcucka, Joanna, E-mail: lewandow@chemia.uj.edu.pl [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland); Staszewska, Magdalena; Szuwarzyński, Michał; Kępczyński, Mariusz [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland); Romek, Marek [Department of Cytology and Histology, Institute of Zoology, Jagiellonian University, Gronostajowa 9, 30-387 Krakow (Poland); Tokarz, Waldemar [Department of Solid State Physics, AGH University of Science and Technology, al. A. Mickiewicza 30, 30-059 Krakow (Poland); Szpak, Agnieszka; Kania, Gabriela; Nowakowska, Maria [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland)

    2014-02-15

    Highlights: • The new, facile methodology for synthesis of silica covered SPIONs is proposed. • The SPIONs was modified with cationic chitosan and coated with silica shell. • Negatively charged, rounded in shape particles of ca. 330 nm were obtained. • The product exhibits the superparamagnetic properties. • The product properties imply its potential applications in biomedicine areas. -- Abstract: Novel method for synthesis of superparamagnetic iron oxide nanoparticles (SPION) modified with a cationic chitosan (CCh) and coated with a silica shell, SPION-CCh-SiO{sub 2} was developed. The process was carried out in two steps. In the first step the chitosan coated SPIONs were obtained by co-precipitation of Fe{sup 2+} and Fe{sup 3+} with ammonium hydroxide in aqueous solution of CCh. In the second one, the silica shell is formed on their surfaces. The formation of SPION-CCh-SiO{sub 2} was achieved by direct decomposition of tetraethoxysilane (TEOS) adsorbed on a surface of SPION-CCh dispersed in aqueous phase under sonication and mechanical stirring at room temperature. The chemical composition and physicochemical properties of the materials were determined using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS) and zeta potential measurements. The morphology of the particles was evaluated by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). Magnetic properties were confirmed using Atomic Force Microscopy/Magnetic Force Microscopy (AFM/MFM) and magnetization measurements. The resulting products are negatively charged, rounded in shape and exhibit the superparamagnetic properties what implies their potential applications in engineering and biomedicine areas.

  6. Synthesis and characterization of the superparamagnetic iron oxide nanoparticles modified with cationic chitosan and coated with silica shell

    International Nuclear Information System (INIS)

    Lewandowska-Łańcucka, Joanna; Staszewska, Magdalena; Szuwarzyński, Michał; Kępczyński, Mariusz; Romek, Marek; Tokarz, Waldemar; Szpak, Agnieszka; Kania, Gabriela; Nowakowska, Maria

    2014-01-01

    Highlights: • The new, facile methodology for synthesis of silica covered SPIONs is proposed. • The SPIONs was modified with cationic chitosan and coated with silica shell. • Negatively charged, rounded in shape particles of ca. 330 nm were obtained. • The product exhibits the superparamagnetic properties. • The product properties imply its potential applications in biomedicine areas. -- Abstract: Novel method for synthesis of superparamagnetic iron oxide nanoparticles (SPION) modified with a cationic chitosan (CCh) and coated with a silica shell, SPION-CCh-SiO 2 was developed. The process was carried out in two steps. In the first step the chitosan coated SPIONs were obtained by co-precipitation of Fe 2+ and Fe 3+ with ammonium hydroxide in aqueous solution of CCh. In the second one, the silica shell is formed on their surfaces. The formation of SPION-CCh-SiO 2 was achieved by direct decomposition of tetraethoxysilane (TEOS) adsorbed on a surface of SPION-CCh dispersed in aqueous phase under sonication and mechanical stirring at room temperature. The chemical composition and physicochemical properties of the materials were determined using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS) and zeta potential measurements. The morphology of the particles was evaluated by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). Magnetic properties were confirmed using Atomic Force Microscopy/Magnetic Force Microscopy (AFM/MFM) and magnetization measurements. The resulting products are negatively charged, rounded in shape and exhibit the superparamagnetic properties what implies their potential applications in engineering and biomedicine areas

  7. Encapsulation of dye molecules into mesoporous polymer resin and mesoporous polymer-silica films by an evaporation-induced self-assembly method

    Energy Technology Data Exchange (ETDEWEB)

    Chi Yue; Li Nan; Tu Jinchun; Zhang Yujie [School of Material Science and Engineering, Key Laboratory of Automobile Materials of Ministry of Education, Jilin University, Changchun 130012 (China); Li Xiaotian, E-mail: xiaotianli@jlu.edu.c [School of Material Science and Engineering, Key Laboratory of Automobile Materials of Ministry of Education, Jilin University, Changchun 130012 (China); Shao Changlu, E-mail: clshao@nenu.edu.c [Center for Advanced Optoelectronic Functional Materials Research, Northeast Normal University, Changchun 130024 (China)

    2010-03-15

    Polymer resin and polymer-silica films with highly ordered mesostructure have been used as host materials to encapsulate DCM (4-(dicyanomethylene) -2-methyl-6-(4-dimethylaminostyryl)-4h-pyran), a kind of fluorescent dye, through evaporation-induced self-assembly method (EISA). After encapsulation, the composites show significant blue-shift in photoluminescence (PL) spectra. Particularly, by changing the excitation wavelength, the samples show different emission bands. These phenomena are related to the mesostructure and the positions of DCM molecules in the host.

  8. Positron annihilation studies of mesoporous silica films using a slow positron beam

    International Nuclear Information System (INIS)

    He Chunqing; Muramatsu, Makoto; Ohdaira, Toshiyuki; Kinomura, Atsushi; Suzuki, Ryoichi; Ito, Kenji; Kabayashi, Yoshinori

    2006-01-01

    Positron annihilation lifetime spectra were measured for mesoporous silica films, which were synthesized using triblock copolymer (EO 106 PO 70 EO 106 ) as a structure-directing agent. Different positron lifetime spectra for the deposited and calcined films indicated the formation of meso-structure after calcination, which was confirmed by Fourier transform infrared (FTIR) spectra and field emission-scanning electron microscopy (FE-SEM) observation. Open porosity or pore interconnectivity of a silica film might be evaluated by a two-dimensional positron annihilation lifetime spectrum of an uncapped film. Pore sizes and their distributions in the silica films were found to be affected by thermal treatments

  9. Multifunctional magnetic core–shell dendritic mesoporous silica nanospheres decorated with tiny Ag nanoparticles as a highly active heterogeneous catalyst

    International Nuclear Information System (INIS)

    Sun, Zebin; Li, Haizhen; Cui, Guijia; Tian, Yaxi; Yan, Shiqiang

    2016-01-01

    Graphical abstract: - Highlights: • A multifunctional magnetic core–shell dendritic silica nanocatalyst was successfully fabricated by an oil–water biphase stratification coating strategy. • The magnetic core–shell dendritic silica nanomaterials Fe_3O_4@SiO_2@Dendritic-SiO_2 were chosen as the catalyst's support for the first time. • The as-synthesized nanocatalyst exhibited excellent catalytic activity and reusability due to easy accessibility of active sites and superparamagnetism. • The novel catalyst could be conveniently recovered by magnetic separation from the reaction system. - Abstract: In present work, a multifunctional magnetic core–shell dendritic silica nanocatalyst Fe_3O_4@SiO_2@Dendritic-SiO_2-NH_2-Ag with easy accessibility of active sites and convenient recovery was successfully fabricated by an oil–water biphase stratification coating strategy, and characterized by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N_2 adsorption–desorption, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The as-synthesized nanocatalyst Fe_3O_4@SiO_2@Dendritic-SiO_2-NH_2-Ag displayed excellent catalytic activity for the catalytic reduction of 4-nitrophenol and 2-nitroaniline using sodium borohydride in aqueous solution at room temperature due to easy accessibility of active sites. Interestingly, the novel catalyst could be conveniently recovered by magnetic separation from the reaction system and recycled for at least five times without significant loss in activity. These results indicate that the above mentioned approach based on magnetic core–shell dendritic silica Fe_3O_4@SiO_2@Dendritic-SiO_2 provided a useful platform for the preparation of noble metal nanocatalysts with easy accessibility, excellent catalytic activity and convenient recovery.

  10. Synthesis, characterization, and photocatalytic properties of core/shell mesoporous silica nanospheres supporting nanocrystalline titania

    International Nuclear Information System (INIS)

    Cendrowski, K.; Chen, X.; Zielinska, B.; Kalenczuk, R. J.; Rümmeli, M. H.; Büchner, B.; Klingeler, R.; Borowiak-Palen, E.

    2011-01-01

    The facile bulk synthesis of silica nanospheres makes them an attractive support for the transport of chemical compounds such as nanocrystalline titanium dioxide. In this contribution we present a promising route for the synthesis of mesoporous silica nanospheres (m-SiO 2 ) with diameter in range 200 nm, which are ideal supports for nanocrystalline titanium dioxide (TiO 2 ). The detailed microscopic and spectroscopic characterizations of core/shell structure (m-SiO 2 /TiO 2 ) were conducted. Moreover, the photocatalytic potential of the nanostructures was investigated via phenol decomposition and hydrogen generation. A clear enhancement of photoactivity in both reactions as compared to commercial TiO 2 -Degussa P25 catalyst is detected.

  11. Synthesis, characterization, and photocatalytic properties of core/shell mesoporous silica nanospheres supporting nanocrystalline titania

    Science.gov (United States)

    Cendrowski, K.; Chen, X.; Zielinska, B.; Kalenczuk, R. J.; Rümmeli, M. H.; Büchner, B.; Klingeler, R.; Borowiak-Palen, E.

    2011-11-01

    The facile bulk synthesis of silica nanospheres makes them an attractive support for the transport of chemical compounds such as nanocrystalline titanium dioxide. In this contribution we present a promising route for the synthesis of mesoporous silica nanospheres (m-SiO2) with diameter in range 200 nm, which are ideal supports for nanocrystalline titanium dioxide (TiO2). The detailed microscopic and spectroscopic characterizations of core/shell structure (m-SiO2/TiO2) were conducted. Moreover, the photocatalytic potential of the nanostructures was investigated via phenol decomposition and hydrogen generation. A clear enhancement of photoactivity in both reactions as compared to commercial TiO2-Degussa P25 catalyst is detected.

  12. Tailored Synthesis of Core-Shell Mesoporous Silica Particles—Optimization of Dye Sorption Properties

    Directory of Open Access Journals (Sweden)

    Andrzej Baliś

    2018-04-01

    Full Text Available Monodisperse spherical silica particles, with solid cores and mesoporous shells (SCMS, were synthesized at various temperatures using a one-pot method utilizing a cationic surfactant template. The temperature of the synthesis was found to significantly affect the diameters of both the cores (ca. 170–800 nm and shells (ca. 11–80 nm of the particles, which can be tailored for specific applications that require a high specific surface area of the nanocarriers (mesoporous shells and simultaneously their mechanical robustness for, e.g., facile isolation from suspensions (dense cores. The applied method enabled the formation of the relatively thick mesoporous shells at conditions below room temperature. Radially ordered pores with narrow distributions of their sizes in 3–4 nm range were found in the shells. The adsorption ability of the SCMS particles was studied using rhodamine 6G as a model dye. Decolorization of the dye solution in the presence of the SCMS particles was correlated with their structure and specific surface area and reached its maximum for the particles synthesized at 15 °C. The presented strategy may be applied for the fine-tuning of the structure of SCMS particles and the enhancement of their adsorption capabilities.

  13. Folic acid-functionalized magnetic ZnFe2O4 hollow microsphere core/mesoporous silica shell composite particles: synthesis and application in drug release.

    Science.gov (United States)

    Yang, Dandan; Wei, Kaiwei; Liu, Qi; Yang, Yong; Guo, Xue; Rong, Hongren; Cheng, Mei-Ling; Wang, Guoxiu

    2013-07-01

    A drug delivery system was designed by deliberately combining the useful functions into one entity, which was composed of magnetic ZnFe2O4 hollow microsphere as the core, and mesoporous silica with folic acid molecules as the outer shell. Amine groups coated magnetic ZnFe2O4 hollow microsphere core/mesoporous silica shell (MZHM-MSS-NH2) composite particles were first synthesized by a one-pot direct co-condensation method. Subsequently a novel kind of folic acid-functionalized magnetic ZnFe2O4 hollow microsphere core/mesoporous silica shell (MZHM-MSS-NHFA) composite particles were synthesized by conjugating folic acid as targeted molecule to MZHM-MSS-NH2. Ibuprofen, a well-known antiphlogistic drug, was used as a model drug to assess the loading and releasing behavior of the composite microspheres. The results show that the MZHM-MSS-NHFA system has the higher capacity of drug storage and good sustained drug-release property. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Protocol optimization for the mild detemplation of mesoporous silica nanoparticles resulting in enhanced texture and colloidal stability

    NARCIS (Netherlands)

    Zhang, Zheng; Mayoral, Alvaro; Melian-Cabrera, Ignacio

    2016-01-01

    Porosity development of mesostructured colloidal silica nanoparticles is related to the removal of the organic templates and co-templates which is often carried out by calcination at high temperatures, 500 -600 degrees C. In this study a mild detemplation method based on the oxidative Fenton

  15. Characterization of silica particles prepared via urease-catalyzed urea hydrolysis and activity of urease in sol–gel silica matrix

    International Nuclear Information System (INIS)

    Kato, Katsuya; Nishida, Masakazu; Ito, Kimiyasu; Tomita, Masahiro

    2012-01-01

    Highlights: ► Silica precipitation occurred via urease-catalytic reactions. ► Higher urease activity for silica synthesis enables mesostructure of silica–urease composites. ► Urease encapsulating in silica matrix retained high activity. - Abstract: Urease templated precipitation of silica synthesized by sol–gel chemistry produces a composite material allowing high urease activity. This study investigates the structural properties of the composite material that allow for the retention of the urease hydrolysis activity. Scanning (SEM) and transmission (TEM) electron microscopy reveal that the composite has a mesoporous structure composed of closely packed spherical structures ∼20–50 nm in diameter. Brunauer–Emmett–Teller (BET) analysis revealed that the surface area and pore volume of the composite prepared under the conditions of 50 mM urea and 25 °C is relatively high (324 m 2 /g and 1.0 cm 3 /g). These values are equivalent to those of usual mesoporous silica materials synthesized from the self-assembly of triblock copolymers as organic templates. In addition, after encapsulating in a sol–gel silica matrix, urease retained high activity (∼90% of the activity compared with native urease). Our results suggest a new method for synthesizing mesoporous silica materials with highly tunable pore sizes and shapes under mild conditions.

  16. Morphological classification of mesoporous silicas synthesized in a binary water-ether solvent system

    NARCIS (Netherlands)

    Cai, Qiang; Geng, Yi; Zhao, Xiang; Cui, Kai; Sun, Qianyao; Chen, Xihua; Feng, Qingling; Li, Hengde; Vrieling, Engel G.

    2008-01-01

    Using diethyl ether as a co-solvent, a non-stable interface of biphasic oil-water system (the so-called oil-water two-phase (OWTP) system) was employed in the preparation of mesostructured silicas with diversified particle morphologies. By adjusting the molar ratios of H2O:C2H5OC2H5:NH3 center dot

  17. Template removal via Boudouard equilibrium allows for synthesis of mesostructured molybdenum compounds

    Energy Technology Data Exchange (ETDEWEB)

    Schieder, Martin; Bojer, Carina; Koch, Sebastian; Martin, Thomas; Breu, Josef [Lehrstuhl fuer Anorganische Chemie I, Universitaet Bayreuth (Germany); Stein, Julia vom [Abteilung fuer Heterogene Katalyse, Max-Planck-Institut fuer Kohlenforschung, Muelheim a.d. Ruhr (Germany); Schmalz, Holger [Lehrstuhl fuer Makromolekulare Chemie II, Universitaet Bayreuth (Germany); Lunkenbein, Thomas [Abteilung fuer Anorganische Chemie, Fritz-Haber-Institut, Max-Planck-Gesellschaft, Berlin (Germany)

    2017-11-06

    Oxidative thermal removal of the polymeric templates is not trivial for molybdenum oxides and hampers mesostructuring of this material. At ambient oxygen fugacity, Mo{sup VI} is the thermodynamically stable oxidation state and sublimation of MoO{sub 3} leads to a quick loss of the mesostructure through Oswald ripening. Taking advantage of the Boudouard equilibrium allows to fix the oxygen fugacity at a level where non-volatile MoO{sub 2-x} is stable while carbonaceous material may be oxidized by CO{sub 2}. Mesostructured MoO{sub 2-x} can be chemically converted into MoO{sub 3} or MoN under retention of the mesostructure. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Use of specific polysaccharide-immobilized monodisperse poly(glycidyl methacrylate) core-silica shell microspheres for affinity purification of lectins

    Czech Academy of Sciences Publication Activity Database

    Antonyuk, V.; Grama, Silvia; Plichta, Zdeněk; Magorivska, I.; Horák, Daniel; Stoika, R.

    2015-01-01

    Roč. 29, č. 5 (2015), s. 783-787 ISSN 0269-3879 Institutional support: RVO:61389013 Keywords : polysaccharide-immobilized microspheres * core-silica shell with amino groups * yeast mannan Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.729, year: 2015

  19. Pecan drying with silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Ghate, S.R.; Chhinnan, M.S.

    1983-07-01

    High moisture in-shell pecans were dried by keeping them in direct and indirect contact with silica gel to investigate their drying characteristics. In-shell pecans were also dried with ambient air from a controlled environment chamber and with air dehumidified by silica gel. Direct contact and dehumidified air drying seemed feasible approaches.

  20. Enhanced pervaporative desulfurization by polydimethylsiloxane membranes embedded with silver/silica core-shell microspheres

    International Nuclear Information System (INIS)

    Cao Ruijian; Zhang Xiongfei; Wu Hong; Wang Jingtao; Liu Xiaofei; Jiang Zhongyi

    2011-01-01

    Pervaporative desulfurization based on membrane technology provides a promising alternative for removal of sulfur substances (as represented by thiophene) in fluid catalytic cracking (FCC) gasoline. The present study focused on the performance enhancement of polydimethylsiloxane (PDMS) membrane by incorporation of core-shell structured silver/silica microspheres. A silane coupling agent, N-[3-(trimethoxysily)propyl]-ethylenediamine (TSD), was used to chelate the Ag + via its amino groups and attach the silver seeds onto the silica surface via condensation of its methoxyl groups. The resultant microspheres were characterized by Zeta-positron annihilation lifetime spectroscopy (ZetaPALS), inductively coupled plasmaoptical emission spectrophotometer (ICP), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Ag + /SiO 2 -PDMS composite membranes were prepared by blending PDMS with the as-synthesized silver/silica microspheres. PALS analysis was used to correlate the apparent fractional free volume with permeation flux. The sorption selectivity towards thiophene was enhanced after incorporation of silver/silica microspheres due to the π-complexation between the silver on the microsphere surface and the thiophene molecules. The pervaporative desulfurization performance of the composite membrane was investigated using thiophene/n-octane mixture as a model gasoline. The composite membrane exhibited an optimum desulfurization performance with a permeation flux of 7.76 kg/(m 2 h) and an enrichment factor of 4.3 at the doping content of 5%.

  1. Structural rearrangement of mesostructured silica nanoparticles incorporated with ZnO catalyst and its photoactivity: Effect of alkaline aqueous electrolyte concentration

    International Nuclear Information System (INIS)

    Jusoh, N.W.C.; Jalil, A.A.; Triwahyono, S.; Karim, A.H.; Salleh, N.F.; Annuar, N.H.R.; Jaafar, N.F.; Firmansyah, M.L.; Mukti, R.R.; Ali, M.W.

    2015-01-01

    Graphical abstract: - Highlights: • Hierarchical-like structure of MSN was formed in alkaline aqueous electrolyte. • Desilication generated abundant silanol groups and oxygen vacancies. • Zn 2+ inserted to external –OH groups of the MSN to form Si–O–Zn bonds. • Oxygen vacancies trapped electrons to enhance electron–hole pair separation. • Hydroxyl radical generated from three main sources greatly influenced photoactivity. - Abstract: ZnO-incorporated mesostructured silica nanoparticles (MSN) catalysts (ZM) were prepared by the introduction of Zn ions into the framework of MSN via a simple electrochemical system in the presence of various concentrations of NH 4 OH aqueous solution. The physicochemical properties of the catalysts were studied by XRD, 29 Si MAS NMR, nitrogen adsorption–desorption, FE-SEM, TEM, FTIR, and photoluminescence spectroscopy. Characterization results demonstrated that the alkaline aqueous electrolyte simply generated abundant silanol groups on the surface of the catalysts as a consequence of desilication to form the hierarchical-like structure of the MSN. Subsequent restructuring of the silica network by the creation of oxygen vacancies and formation of Si–O–Zn during the electrolysis, as well as formation of new Si–O–Si bonds during calcination seemed to be the main factors that enhanced the catalytic performance of photodecolorization of methyl orange. A ZM prepared in the presence of 1.0 M NH 4 OH (ZM-1.0) was determined to be the most effective catalyst. The catalyst displays a higher first-order kinetics rate of 3.87 × 10 −1 h −1 than unsupported ZnO (1.13 × 10 −1 h −1 ) that prepared under the same conditions in the absence of MSN. The experiment on effect of scavengers showed that hydroxyl radicals generated from the three main sources; reduced O 2 at the conduction band, decomposed water at the valence band and irradiated H 2 O 2 in the solution, are key factors that influenced the reaction. It is

  2. Structural rearrangement of mesostructured silica nanoparticles incorporated with ZnO catalyst and its photoactivity: Effect of alkaline aqueous electrolyte concentration

    Energy Technology Data Exchange (ETDEWEB)

    Jusoh, N.W.C. [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Jalil, A.A., E-mail: aishah@cheme.utm.my [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Institute of Hydrogen Economy, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Triwahyono, S.; Karim, A.H. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Salleh, N.F. [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Annuar, N.H.R.; Jaafar, N.F.; Firmansyah, M.L. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Mukti, R.R. [Division of Inorganic and Physical Chemistry, Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, Jl Ganesha No 10, Bandung 40132 (Indonesia); Ali, M.W. [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Institute of Hydrogen Economy, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia)

    2015-03-01

    Graphical abstract: - Highlights: • Hierarchical-like structure of MSN was formed in alkaline aqueous electrolyte. • Desilication generated abundant silanol groups and oxygen vacancies. • Zn{sup 2+} inserted to external –OH groups of the MSN to form Si–O–Zn bonds. • Oxygen vacancies trapped electrons to enhance electron–hole pair separation. • Hydroxyl radical generated from three main sources greatly influenced photoactivity. - Abstract: ZnO-incorporated mesostructured silica nanoparticles (MSN) catalysts (ZM) were prepared by the introduction of Zn ions into the framework of MSN via a simple electrochemical system in the presence of various concentrations of NH{sub 4}OH aqueous solution. The physicochemical properties of the catalysts were studied by XRD, {sup 29}Si MAS NMR, nitrogen adsorption–desorption, FE-SEM, TEM, FTIR, and photoluminescence spectroscopy. Characterization results demonstrated that the alkaline aqueous electrolyte simply generated abundant silanol groups on the surface of the catalysts as a consequence of desilication to form the hierarchical-like structure of the MSN. Subsequent restructuring of the silica network by the creation of oxygen vacancies and formation of Si–O–Zn during the electrolysis, as well as formation of new Si–O–Si bonds during calcination seemed to be the main factors that enhanced the catalytic performance of photodecolorization of methyl orange. A ZM prepared in the presence of 1.0 M NH{sub 4}OH (ZM-1.0) was determined to be the most effective catalyst. The catalyst displays a higher first-order kinetics rate of 3.87 × 10{sup −1} h{sup −1} than unsupported ZnO (1.13 × 10{sup −1} h{sup −1}) that prepared under the same conditions in the absence of MSN. The experiment on effect of scavengers showed that hydroxyl radicals generated from the three main sources; reduced O{sub 2} at the conduction band, decomposed water at the valence band and irradiated H{sub 2}O{sub 2} in the solution

  3. Sol–gel one-pot synthesis in soft conditions of mesoporous silica materials ready for drug delivery system

    NARCIS (Netherlands)

    Tourne-Peteilh, C.; Begu, S.; Lerner, D.A.; Galarneau, A.; Lafont, U.; Devoiselle, J.M.

    2011-01-01

    The present work reveals a new and simple strategy, a one-step sol–gel procedure, to encapsulate a low water-soluble drug in silica mesostructured microparticles and to improve its release in physiological media. The synthesis of these new materials is based on the efficient solubilisation of a

  4. Controlled Release from Core-Shell Nanoporous Silica Particles for Corrosion Inhibition of Aluminum Alloys

    Directory of Open Access Journals (Sweden)

    Xingmao Jiang

    2011-01-01

    Full Text Available Cerium (Ce corrosion inhibitors were encapsulated into hexagonally ordered nanoporous silica particles via single-step aerosol-assisted self-assembly. The core/shell structured particles are effective for corrosion inhibition of aluminum alloy AA2024-T3. Numerical simulation proved that the core-shell nanostructure delays the release process. The effective diffusion coefficient elucidated from release data for monodisperse particles in water was 1.0×10−14 m2s for Ce3+ compared to 2.5×10−13 m2s for NaCl. The pore size, pore surface chemistry, and the inhibitor solubility are crucial factors for the application. Microporous hydrophobic particles encapsulating a less soluble corrosion inhibitor are desirable for long-term corrosion inhibition.

  5. Study the effect of calcination temperature on physical and magnetic properties of bare Cobalt nanoparticles and that coated with silica shell

    International Nuclear Information System (INIS)

    Arabi, H.; Pourarian, F.; Chahkandinejad, R.

    2012-01-01

    In this paper, in order to investigate the effect of calcination temperature on the structural and magnetic properties of cobalt nanoparticles, samples have been prepared by Co-precipitation method at different calcination temperature. Cobalt nanoparticles have been prepared by Co-precipitation method at room temperature using hydrazine as reducing in ethanol hydrazine alkaline environment. This agent reduces cobalt salts to Cobalt nanoparticles in FCC and HCP phases. Phase analysis and investigation of Structural properties of the samples using X-ray diffraction patterns (XRD) confirm the formation of hexagonal phases of Co nanoparticles. Transmission electron microscopy was used for determining the size and shape morphology of nanoparticles. Magnetic properties of these nanoparticles have been investigated using a Vibrating sample magnetometer. The results indicate that these nanoparticles are ferromagnetic at room temperature. In addition, in this paper Co nanoparticles coated with silica shell have been prepared by the wet chemical method. Transmission electron microscopy images showed the cobalt core with average diameter of 17-20 nm coated by a silica shell with thickness of 5-7 nm. Hysteresis Loop of these Co nanoparticles coated by silica shell illustrates 16.9 emu/gr for saturation magnetization at 10000 (Oe), which is much less than that of Cobalt nanoparticles

  6. Mesostructure of fibrillar protein gels

    NARCIS (Netherlands)

    Veerman, C.; Sagis, L.M.C.; Linden, van der E.

    2003-01-01

    We investigated the mesostructure of three different food proteins (ß-lactoglobulin (ß-lg), bovine serum albumin (BSA), and ovalbumin), after protein assembly at pH 2, using rheology and transmission electron microscopy (TEM). TEM micrographs showed fibrils with a contour length of about 2-7 µm for

  7. Controlled Release from Core-Shell Nano porous Silica Particles for Corrosion Inhibition of Aluminum Alloys

    International Nuclear Information System (INIS)

    Jiang, X.; Rathod, Sh.; Shah, P.; Brinker, C.J.; Jiang, X.; Jiang, Y.; Liu, N.; Xu, H.; Brinker, C.J.

    2011-01-01

    Cerium (Ce) corrosion inhibitors were encapsulated into hexagonally ordered nanoporous silica particles via single-step aerosol-assisted self-assembly. The core/shell structured particles are effective for corrosion inhibition of aluminum alloy AA2024-T3. Numerical simulation proved that the core-shell nanostructure delays the release process. The effective diffusion coefficient elucidated from release data for monodisperse particles in water was 1.0x10-14 m 2 s for Ce 3+ compared to 2.5x10-13 m 2 s for NaCl. The pore size, pore surface chemistry, and the inhibitor solubility are crucial factors for the application. Microporous hydrophobic particles encapsulating a less soluble corrosion inhibitor are desirable for long-term corrosion inhibition.

  8. Core-shell microspheres with porous nanostructured shells for liquid chromatography.

    Science.gov (United States)

    Ahmed, Adham; Skinley, Kevin; Herodotou, Stephanie; Zhang, Haifei

    2018-01-01

    The development of new stationary phases has been the key aspect for fast and efficient high-performance liquid chromatography separation with relatively low backpressure. Core-shell particles, with a solid core and porous shell, have been extensively investigated and commercially manufactured in the last decade. The excellent performance of core-shell particles columns has been recorded for a wide range of analytes, covering small and large molecules, neutral and ionic (acidic and basic), biomolecules and metabolites. In this review, we first introduce the advance and advantages of core-shell particles (or more widely known as superficially porous particles) against non-porous particles and fully porous particles. This is followed by the detailed description of various methods used to fabricate core-shell particles. We then discuss the applications of common silica core-shell particles (mostly commercially manufactured), spheres-on-sphere particles and core-shell particles with a non-silica shell. This review concludes with a summary and perspective on the development of stationary phase materials for high-performance liquid chromatography applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Synthesis of Various Silica Nanoparticles for Foam Stability

    International Nuclear Information System (INIS)

    Yoon, Suk Bon; Yoon, Inho; Jung, Chonghun; Kim, Chorong; Choi, Wangkyu; Moon, Jeikwon

    2013-01-01

    The synthesis of the non-porous silica nanoparticles with uniform sizes has been reported through the Sto ber method, the synthesis of meso porous silica nanoparticles with a specific morphology such as core-shell, rod-like, and hexagonal shapes is not so common. As a synthetic strategy for controlling the particle size, shape, and porosity, the synthesis of core-shell silicas with meso porous shells formed on silica particle cores through the self-assembly of silica precursor and organic templates or spherical meso porous silicas using modified Sto ber method was also reported. Recently, in an effort to reduce the amount of radioactive waste and enhance the decontamination efficiency during the decontamination process of nuclear facilities contaminated with radionuclides, a few research for the preparation of the decontamination foam containing solid nanoparticles has been reported. In this work, the silica nanoparticles with various sizes, shapes, and structures were synthesized based on the previous literatures. The resulting silica nanoparticles were used to investigate the effect of the nanoparticles on the foam stability. In a study on the foam stability using various silica nanoparticles, the results showed that the foam volume and liquid volume in foam was enhanced when using a smaller size and lower density of the silica nanoparticles. Silica nanoparticles with various sizes, shapes, and structures such as a non-porous, meso porous core-shell, and meso porous silica were synthesized to investigate the effect of the foam stability. The sizes and structural properties of the silica nanoparticles were easily controlled by varying the amount of silica precursor, surfactant, and ammonia solution as a basic catalyst. The foam prepared using various silica nanoparticles showed that foam the volume and liquid volume in the foam were enhanced when using a smaller size and lower density of the silica nanoparticles

  10. Highly selective coextraction of rhodamine B and dibenzyl phthalate based on high-density dual-template imprinted shells on silica microparticles.

    Science.gov (United States)

    Long, Zerong; Xu, Weiwei; Peng, Yumei; Lu, Yi; Luo, Qian; Qiu, Hongdeng

    2017-01-01

    A simple one-pot approach based on molecularly imprinted polymer shells dispersed on the surface of silica for simultaneous determination of rhodamine B and dibenzyl phthalate (DBzP) has been developed. Highly dense molecularly imprinted polymer shells were formed in the mixture of acetonitrile and toluene by the copolymerization of methacrylic acid and ethylene glycol dimethacrylate, as well as two templates, rhodamine B and dibenzyl phthalate, directed by the vinyl end groups functional monolayer at surface silica microspheres after 3-methacryloxypropyl trimethoxysilane modification. The obtained imprinted polymer shells showed large average pore diameter (102.5 nm) and about 100 nm shell thickness. The imprinted particles also showed high imprinting factor (α RhB = 3.52 and α DBzP = 3.94), rapid binding kinetics, and excellent selective affinity capacity for rhodamine B and dibenzyl phthalate containing another three competitors in mixed solution. Moreover, the imprinted particles coupled with ultra high performance liquid chromatography was successfully applied to simultaneous analysis of rhodamine B and dibenzyl phthalate in two spiked beverage samples with average recoveries in the range of 88.0-93.0% for rhodamine B and 84.0-92.0% for dibenzyl phthalate with the relative standard deviation lower than 5.1%. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Copper Ferrocyanide Functionalized Core-Shell Magnetic Silica Composites for the Selective Removal of Cesium Ions from Radioactive Liquid Waste.

    Science.gov (United States)

    Lee, Hyun Kyu; Yang, Da Som; Oh, Wonzin; Choi, Sang-June

    2016-06-01

    The copper ferrocyanide functionalized core-shell magnetic silica composite (mag@silica-CuFC) was prepared and was found to be easily separated from aqueous solutions by using magnetic field. The synthesized mag@silica-CuFC composite has a high sorption ability of Cs owing to its strong affinity for Cs as well as the high surface area of the supports. Cs sorption on the mag@silica-CuFC composite quickly reached the sorption equilibrium after 2 h of contact time. The effect of the presence of salts with a high concentration of up to 3.5 wt% on the efficiency of Cs sorption onto the composites was also studied. The maximum sorption ability was found to be maintained in the presence of up to 3.5 wt% of NaCl in the solution. Considering these results, the mag@silica-CuFC composite has great potential for use as an effective sorbent for the selective removal of radioactive Cs ions.

  12. Amperometric glucose sensor based on enhanced catalytic reduction of oxygen using glucose oxidase adsorbed onto core-shell Fe3O4-silica-Au magnetic nanoparticles

    International Nuclear Information System (INIS)

    Wang Aijun; Li Yongfang; Li Zhonghua; Feng Jiuju; Sun Yanli; Chen Jianrong

    2012-01-01

    Monodisperse Fe 3 O 4 magnetic nanoparticles (NPs) were prepared under facile solvothermal conditions and successively functionalized with silica and Au to form core/shell Fe 3 O 4 -silica-Au NPs. Furthermore, the samples were used as matrix to construct a glucose sensor based on glucose oxidase (GOD). The immobilized GOD retained its bioactivity with high protein load of 3.92 × 10 −9 mol·cm −2 , and exhibited a surface-controlled quasi-reversible redox reaction, with a fast heterogeneous electron transfer rate of 7.98 ± 0.6 s −1 . The glucose biosensor showed a broad linear range up to 3.97 mM with high sensitivity of 62.45 μA·mM −1 cm −2 and fast response (less than 5 s). - Graphical abstract: Core-shell structured Fe 3 O 4 -silica-Au nanoparticles were prepared and used as matrix to construct an amperometric glucose sensor based on glucose oxidase, which showed broad linear range, high sensitivity, and fast response. Highlights: ► Synthesis of monodispersed Fe 3 O 4 nanoparticles. ► Fabrication of core/shell Fe 3 O 4 -silica-Au nanoparticles. ► Construction of a novel glucose sensor with wide linear range, high sensitivity and fast response.

  13. Triconstituent co-assembly to ordered mesostructured polymer-silica and carbon-silica nanocomposites and large-pore mesoporous carbons with high surface areas.

    Science.gov (United States)

    Liu, Ruili; Shi, Yifeng; Wan, Ying; Meng, Yan; Zhang, Fuqiang; Gu, Dong; Chen, Zhenxia; Tu, Bo; Zhao, Dongyuan

    2006-09-06

    Highly ordered mesoporous polymer-silica and carbon-silica nanocomposites with interpenetrating networks have been successfully synthesized by the evaporation-induced triconstituent co-assembly method, wherein soluble resol polymer is used as an organic precursor, prehydrolyzed TEOS is used as an inorganic precursor, and triblock copolymer F127 is used as a template. It is proposed for the first time that ordered mesoporous nanocomposites have "reinforced concrete"-structured frameworks. By adjusting the initial mass ratios of TEOS to resol, we determined the obtained nanocomposites possess continuous composition with the ratios ranging from zero to infinity for the two constituents that are "homogeneously" dispersed inside the pore walls. The presence of silicates in nanocomposites dramatically inhibits framework shrinkage during the calcination, resulting in highly ordered large-pore mesoporous carbon-silica nanocomposites. Combustion in air or etching in HF solution can remove carbon or silica from the carbon-silica nanocomposites and yield ordered mesoporous pure silica or carbon frameworks. The process generates plenty of small pores in carbon or/and silica pore walls. Ordered mesoporous carbons can then be obtained with large pore sizes of approximately 6.7 nm, pore volumes of approximately 2.0 cm(3)/g, and high surface areas of approximately 2470 m(2)/g. The pore structures and textures can be controlled by varying the sizes and polymerization degrees of two constituent precursors. Accordingly, by simply tuning the aging time of TEOS, ordered mesoporous carbons with evident bimodal pores at 2.6 and 5.8 nm can be synthesized.

  14. Sugarcane bagasse lignin, and silica gel and magneto-silica as drug vehicles for development of innocuous methotrexate drug against rheumatoid arthritis disease in albino rats.

    Science.gov (United States)

    Wahba, Sanaa M R; Darwish, Atef S; Shehata, Iman H; Abd Elhalem, Sahar S

    2015-03-01

    The present study clarifies co-therapy action of deliveries from their textural changes point of view. Methotrexate (MTX) was immobilized onto biodegradable lignin, silica gel and iron/silica nanocomposite. Loaded-MTX was i.p. injected into albino rats at doses of 0.25 and 0.5mg/kg/week for 2.5months, after which spleen, liver, testes and knee joint tissues were collected for tests. IFN-γ and IL-17A mRNA gene expressions in spleen in all biological samples were determined by RT-PCR. Physicochemical features of drug carriers were monitored by XRD, BET-PSD, SEM and TEM. Drug inflammatory-site targeting was found to be closely related to the physico-features of deliverers. The interlayered lignin of micro- and meso-pore channels directed MTX toward concealed infected cells in liver and testes tissues, while meso-structured silica flacks satisfied by gathering MTX around knee joints. The magneto-silica nanocomposite targeted MTX toward spleen tissue, which is considered as a lively factory for the production of electron rich compounds. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Reinforcement of Natural Rubber with Core-Shell Structure Silica-Poly(Methyl Methacrylate Nanoparticles

    Directory of Open Access Journals (Sweden)

    Qinghuang Wang

    2012-01-01

    Full Text Available A highly performing natural rubber/silica (NR/SiO2 nanocomposite with a SiO2 loading of 2 wt% was prepared by combining similar dissolve mutually theory with latex compounding techniques. Before polymerization, double bonds were introduced onto the surface of the SiO2 particles with the silane-coupling agent. The core-shell structure silica-poly(methyl methacrylate, SiO2-PMMA, nanoparticles were formed by grafting polymerization of MMA on the surface of the modified SiO2 particles via in situ emulsion, and then NR/SiO2 nanocomposite was prepared by blending SiO2-PMMA and PMMA-modified NR (NR-PMMA. The Fourier transform infrared spectroscopy results show that PMMA has been successfully introduced onto the surface of SiO2, which can be well dispersed in NR matrix and present good interfacial adhesion with NR phase. Compared with those of pure NR, the thermal resistance and tensile properties of NR/SiO2 nanocomposite are significantly improved.

  16. Core/shell fluorescent magnetic silica-coated composite nanoparticles for bioconjugation

    Science.gov (United States)

    He, Rong; You, Xiaogang; Shao, Jun; Gao, Feng; Pan, Bifeng; Cui, Daxiang

    2007-08-01

    A new class of highly fluorescent, photostable, and magnetic core/shell nanoparticles has been synthesized from a reverse microemulsion method. The obtained bifunctional nanocomposites were characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectrometry, photoluminescence (PL) spectrometry, and fluorescence microscopy in a magnetic field. To further improve their biocompatibility, the silica-coated nanoparticles were functionalized with amino groups. The fluorescent magnetic composite nanoparticles (FMCNPs) had a typical diameter of 50 ± 5 nm and a saturation magnetization of 3.21 emu g-1 at room temperature, and exhibited strong excitonic photoluminescence. Through activation with glutaraldehyde, the FMCNPs were successfully conjugated with goat anti-mouse immunoglobin G (GM IgG), and the bioactivity and binding specificity of the as-prepared FMCNPs-GM IgG were confirmed via immunofluorescence assays, commonly used in bioanalysis. So they are potentially useful for many applications in biolabelling, imaging, drug targeting, bioseparation and bioassays.

  17. Core/shell fluorescent magnetic silica-coated composite nanoparticles for bioconjugation

    International Nuclear Information System (INIS)

    He Rong; You Xiaogang; Shao Jun; Gao Feng; Pan Bifeng; Cui Daxiang

    2007-01-01

    A new class of highly fluorescent, photostable, and magnetic core/shell nanoparticles has been synthesized from a reverse microemulsion method. The obtained bifunctional nanocomposites were characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectrometry, photoluminescence (PL) spectrometry, and fluorescence microscopy in a magnetic field. To further improve their biocompatibility, the silica-coated nanoparticles were functionalized with amino groups. The fluorescent magnetic composite nanoparticles (FMCNPs) had a typical diameter of 50 ± 5 nm and a saturation magnetization of 3.21 emu g -1 at room temperature, and exhibited strong excitonic photoluminescence. Through activation with glutaraldehyde, the FMCNPs were successfully conjugated with goat anti-mouse immunoglobin G (GM IgG), and the bioactivity and binding specificity of the as-prepared FMCNPs-GM IgG were confirmed via immunofluorescence assays, commonly used in bioanalysis. So they are potentially useful for many applications in biolabelling, imaging, drug targeting, bioseparation and bioassays

  18. Mesostructure-Induced Selectivity in CO2 Reduction Catalysis.

    Science.gov (United States)

    Hall, Anthony Shoji; Yoon, Youngmin; Wuttig, Anna; Surendranath, Yogesh

    2015-12-02

    Gold inverse opal (Au-IO) thin films are active for CO2 reduction to CO with high efficiency at modest overpotentials and high selectivity relative to hydrogen evolution. The specific activity for hydrogen evolution diminishes by 10-fold with increasing porous film thickness, while CO evolution activity is largely unchanged. We demonstrate that the origin of hydrogen suppression in Au-IO films stems from the generation of diffusional gradients within the pores of the mesostructured electrode rather than changes in surface faceting or Au grain size. For electrodes with optimal mesoporosity, 99% selectivity for CO evolution can be obtained at overpotentials as low as 0.4 V. These results establish electrode mesostructuring as a complementary method for tuning selectivity in CO2-to-fuels catalysis.

  19. A hybrid concept (segmented plus monolithic fused silica shells) for a high-throughput and high-angular resolution x-ray mission (Lynx/X-Ray Surveyor like)

    Science.gov (United States)

    Basso, Stefano; Civitani, Marta; Pareschi, Giovanni; Parodi, Giancarlo

    2017-09-01

    Lynx is a large area and high angular resolution X-ray mission being studied by NASA to be presented to the next Decadal Survey for the implementation in the next decade. It aims to realize an X-ray telescope with the effective area similar to Athena (2 m2 at 1 keV) but with the same angular resolution of Chandra and a much larger Field Of View (up 20 arcmin x 20 arcmin). The science of X-ray Surveyor requires a large-throughput mirror assembly with sub-arcsec angular resolution. These future X-ray mirrors have a set of requirements which, collectively, represents very substantial advances over any currently in operation or planned for missions other than X-ray Surveyor. Of particular importance is achieving low mass per unit collecting area, while maintaining Chandra like angular resolution. Among the possible solutions under study, the direct polishing of both thin monolithic pseudo-cylindrical shells and segments made of fused silica are being considered as viable solutions for the implementation of the mirrors. Fused silica has very good thermomechanical parameters (including a very low CTE), making the material particularly well suited for for the production of the Lynx mirrors. It should be noted that the use of close shells is also very attractive, since the operations for the integration of the shells will be greatly simplified and the area lost due to the vignetting from the interfacing structures minimized even if the management of such big (diameter of 3 m) and thin shells have to be demonstrated. In this paper we will discuss a possible basic layout for a full shell mirror and a hybrid concept (segmented plus monolithic shells made of fused silica) as a second solution, for the Lynx/XRS telescope, discussing preliminary results in terms of optical and mechanical performance.

  20. Interconnected mesopores and high accessibility in UVM-7-like silicas

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Cabero, Monica [Universitat de Valencia, Institut de Ciencia dels Materials (Spain); Hungria, Ana B. [Universidad de Cadiz, Departamento de Ciencia de Materiales, Ingenieria Metalurgica y Quimica Inorganica (Spain); Morales, Jose Manuel [Universitat de Valencia, Institut de Ciencia dels Materials (Spain); Tortajada, Marta; Ramon, Daniel [Biopolis S. L. (Spain); Moragues, Alaina; El Haskouri, Jamal; Beltran, Aurelio; Beltran, Daniel; Amoros, Pedro, E-mail: pedro.amoros@uv.es [Universitat de Valencia, Institut de Ciencia dels Materials (Spain)

    2012-08-15

    Nanoparticulated bimodal mesoporous silicas (NBS) have proved to constitute adequate supports in a variety of applications requiring enhanced accessibility to the active sites. Mass-transfer kinetics seems to be highly favoured in UVM-7-derived NBS materials. To understand the mass-diffusion phenomena throughout UVM-7-like supports requires well-grounded knowledge about their pore architecture. 3-D reconstructions of the UVM-7 mesostructure carried out by electron tomography reveal the existence of a true hierarchic connectivity involving both inter- and intra-nanoparticle pores. This connectivity makes self-supported nanoparticulated mesoporous bimodal carbon replicas of the supports feasible to obtaining by nanocasting. Both the temperature-induced mobility of gold nanodomains and the fast and efficient enzyme adsorption in UVM-7-like silicas are examples of non-constrained diffusion processes happening inside such an open network.

  1. Interconnected mesopores and high accessibility in UVM-7-like silicas

    International Nuclear Information System (INIS)

    Pérez-Cabero, Mónica; Hungría, Ana B.; Morales, José Manuel; Tortajada, Marta; Ramón, Daniel; Moragues, Alaina; El Haskouri, Jamal; Beltrán, Aurelio; Beltrán, Daniel; Amorós, Pedro

    2012-01-01

    Nanoparticulated bimodal mesoporous silicas (NBS) have proved to constitute adequate supports in a variety of applications requiring enhanced accessibility to the active sites. Mass-transfer kinetics seems to be highly favoured in UVM-7-derived NBS materials. To understand the mass-diffusion phenomena throughout UVM-7-like supports requires well-grounded knowledge about their pore architecture. 3-D reconstructions of the UVM-7 mesostructure carried out by electron tomography reveal the existence of a true hierarchic connectivity involving both inter- and intra-nanoparticle pores. This connectivity makes self-supported nanoparticulated mesoporous bimodal carbon replicas of the supports feasible to obtaining by nanocasting. Both the temperature-induced mobility of gold nanodomains and the fast and efficient enzyme adsorption in UVM-7-like silicas are examples of non-constrained diffusion processes happening inside such an open network.

  2. An in situ carbonization-replication method to synthesize mesostructured WO3/C composite as nonprecious-metal anode catalyst in PEMFC.

    Science.gov (United States)

    Cui, Xiangzhi; Hua, Zile; Wei, Chenyang; Shu, Zhu; Zhang, Liangxia; Chen, Hangrong; Shi, Jianlin

    2013-02-01

    A meostructured WO(3)/C composite with crystalline framework and high electric conductivity has been synthesized by a new in situ carbonization-replication route using the block copolymer (poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)) present in situ in the pore channels of mesoporous silica template as carbon source. X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, thermogravimetry differential thermal analysis, and N(2) adsorption techniques were adopted for the structural characterization. Cyclic voltammetry, chronoamperometry, and single-cell test for hydrogen electrochemical oxidation were adopted to characterize the electrochemical activities of the mesoporous WO(3)/C composite. The carbon content and consequent electric conductivity of these high-surface-area (108-130 m(2) g(-1)) mesostructured WO(3)/C composite materials can be tuned by variation of the duration of heat treatment, and the composites exhibited high and stable electrochemical catalytic activity. The single-cell test results indicated that the mesostructured WO(3)/C composites showed clear electrochemical catalytic activity toward hydrogen oxidation at 25 °C, which makes them potential non-precious-metal anode catalysts in proton exchange membrane fuel cell. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Anisotropic deformation of metallo-dielectric core-shell colloids under MeV ion irradiation

    International Nuclear Information System (INIS)

    Penninkhof, J.J.; Dillen, T. van; Roorda, S.; Graf, C.; Blaaderen, A. van; Vredenberg, A.M.; Polman, A.

    2006-01-01

    We have studied the deformation of metallo-dielectric core-shell colloids under 4 MeV Xe, 6 and 16 MeV Au, 30 MeV Si and 30 MeV Cu ion irradiation. Colloids of silica surrounded by a gold shell, with a typical diameter of 400 nm, show anisotropic plastic deformation under MeV ion irradiation, with the metal flowing conform the anisotropically deforming silica core. The 20 nm thick metal shell imposes a mechanical constraint on the deforming silica core, reducing the net deformation strain rate compared to that of pure silica. In colloids consisting of a Au core and a silica shell, the silica expands perpendicular to the ion beam, while the metal core shows a large elongation along the ion beam direction, provided the silica shell is thick enough (>40 nm). A minimum electronic energy loss of 3.3 keV/nm is required for shape transformation of the metal core. Silver cores embedded in a silica shell show no elongation, but rather disintegrate. Also in planar SiO 2 films, Au and Ag colloids show entirely different behavior under MeV irradiation. We conclude that the deformation model of core-shell colloids must include ion-induced particle disintegration in combination with thermodynamical effects, possibly in combination with mechanical effects driven by stresses around the ion tracks

  4. Anisotropic deformation of metallo-dielectric core shell colloids under MeV ion irradiation

    Science.gov (United States)

    Penninkhof, J. J.; van Dillen, T.; Roorda, S.; Graf, C.; van Blaaderen, A.; Vredenberg, A. M.; Polman, A.

    2006-01-01

    We have studied the deformation of metallo-dielectric core-shell colloids under 4 MeV Xe, 6 and 16 MeV Au, 30 MeV Si and 30 MeV Cu ion irradiation. Colloids of silica surrounded by a gold shell, with a typical diameter of 400 nm, show anisotropic plastic deformation under MeV ion irradiation, with the metal flowing conform the anisotropically deforming silica core. The 20 nm thick metal shell imposes a mechanical constraint on the deforming silica core, reducing the net deformation strain rate compared to that of pure silica. In colloids consisting of a Au core and a silica shell, the silica expands perpendicular to the ion beam, while the metal core shows a large elongation along the ion beam direction, provided the silica shell is thick enough (>40 nm). A minimum electronic energy loss of 3.3 keV/nm is required for shape transformation of the metal core. Silver cores embedded in a silica shell show no elongation, but rather disintegrate. Also in planar SiO2 films, Au and Ag colloids show entirely different behavior under MeV irradiation. We conclude that the deformation model of core-shell colloids must include ion-induced particle disintegration in combination with thermodynamical effects, possibly in combination with mechanical effects driven by stresses around the ion tracks.

  5. Amperometric glucose sensor based on enhanced catalytic reduction of oxygen using glucose oxidase adsorbed onto core-shell Fe{sub 3}O{sub 4}-silica-Au magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wang Aijun [College of Geography and Environmental Science, College of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004 (China); Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007 (China); Li Yongfang [College of Chemistry and Chemical Engineering, Henan Institute of Science and Technology, Xinxiang 453003 (China); Li Zhonghua [Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007 (China); Feng Jiuju, E-mail: jjfengnju@gmail.com [College of Geography and Environmental Science, College of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004 (China); Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007 (China); Sun Yanli [Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007 (China); Chen Jianrong [College of Geography and Environmental Science, College of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004 (China)

    2012-08-01

    Monodisperse Fe{sub 3}O{sub 4} magnetic nanoparticles (NPs) were prepared under facile solvothermal conditions and successively functionalized with silica and Au to form core/shell Fe{sub 3}O{sub 4}-silica-Au NPs. Furthermore, the samples were used as matrix to construct a glucose sensor based on glucose oxidase (GOD). The immobilized GOD retained its bioactivity with high protein load of 3.92 Multiplication-Sign 10{sup -9} mol{center_dot}cm{sup -2}, and exhibited a surface-controlled quasi-reversible redox reaction, with a fast heterogeneous electron transfer rate of 7.98 {+-} 0.6 s{sup -1}. The glucose biosensor showed a broad linear range up to 3.97 mM with high sensitivity of 62.45 {mu}A{center_dot}mM{sup -1} cm{sup -2} and fast response (less than 5 s). - Graphical abstract: Core-shell structured Fe{sub 3}O{sub 4}-silica-Au nanoparticles were prepared and used as matrix to construct an amperometric glucose sensor based on glucose oxidase, which showed broad linear range, high sensitivity, and fast response. Highlights: Black-Right-Pointing-Pointer Synthesis of monodispersed Fe{sub 3}O{sub 4} nanoparticles. Black-Right-Pointing-Pointer Fabrication of core/shell Fe{sub 3}O{sub 4}-silica-Au nanoparticles. Black-Right-Pointing-Pointer Construction of a novel glucose sensor with wide linear range, high sensitivity and fast response.

  6. Novel mesostructured inclusions in the epidermal lining of Artemia franciscana ovisacs show optical activity

    Directory of Open Access Journals (Sweden)

    Elena Hollergschwandtner

    2017-10-01

    Full Text Available Background Biomineralization, e.g., in sea urchins or mollusks, includes the assembly of mesoscopic superstructures from inorganic crystalline components and biopolymers. The resulting mesocrystals inspire biophysicists and material scientists alike, because of their extraordinary physical properties. Current efforts to replicate mesocrystal synthesis in vitro require understanding the principles of their self-assembly in vivo. One question, not addressed so far, is whether intracellular crystals of proteins can assemble with biopolymers into functional mesocrystal-like structures. During our electron microscopy studies into Artemia franciscana (Crustacea: Branchiopoda, we found initial evidence of such proteinaceous mesostructures. Results EM preparations with high-pressure freezing and accelerated freeze substitution revealed an extraordinary intracellular source of mesostructured inclusions in both the cyto-and nucleoplasm of the epidermal lining of ovisacs of A. franciscana. Confocal reflection microscopy not only confirmed our finding; it also revealed reflective, light dispersing activity of these flake-like structures, their positioning and orientation with respect to the ovisac inside. Both the striation of alternating electron dense and electron-lucent components and the sharp edges of the flakes indicate self-assembly of material of yet unknown origin under supposed participation of crystallization. However, selected area electron diffraction could not verify the status of crystallization. Energy dispersive X-ray analysis measured a marked increase in nitrogen within the flake-like inclusion, and the almost complete absence of elements that are typically involved in inorganic crystallization. This rise in nitrogen could possibility be related to higher package density of proteins, achieved by mesostructure assembly. Conclusions The ovisac lining of A. franciscana is endowed with numerous mesostructured inclusions that have not been

  7. CuO mesostructures as ammonia sensors

    Science.gov (United States)

    Bhuvaneshwari, S.; Gopalakrishnan, N.

    2018-04-01

    The emission threshold of NH3 in air is 1000 kg/yr which is now about 20 Tg/yr according to environmental protection agencies. Hence, there is a rapid increase in need of NH3 sensors to timely detect and control NH3 emissions. Metal oxide nanostructures such as CuO with special features are potential candidates for NH3 sensing. In the present study, morphology controlled 3-dimensional CuO mesostructures were synthesized by surfactant-free hydrothermal method. A modified approach using a mixture of water and ethylene glycol (EG) was used as solvent to control the growth process. Hierarchical mesostructures namely, hollow-sphere-like and urchin-like feature with particle dimensions ranging from 0.3-1 µm were obtained by varying water/EG ratio. The room temperature ammonia sensing behavior of all samples was studied using an indigenous gas sensing set-up. It was found that hollow-sphere like CuO nanostructures showed a maximum response of 2 towards 300 ppm ammonia with a response and recovery time of 5 and 15 min. The hydrothermal synthesis strategy reported here has the advantage of producing shape controlled hierarchical materials are highly suitable for various technological applications.

  8. Morphable 3D mesostructures and microelectronic devices by multistable buckling mechanics

    Science.gov (United States)

    Fu, Haoran; Nan, Kewang; Bai, Wubin; Huang, Wen; Bai, Ke; Lu, Luyao; Zhou, Chaoqun; Liu, Yunpeng; Liu, Fei; Wang, Juntong; Han, Mengdi; Yan, Zheng; Luan, Haiwen; Zhang, Yijie; Zhang, Yutong; Zhao, Jianing; Cheng, Xu; Li, Moyang; Lee, Jung Woo; Liu, Yuan; Fang, Daining; Li, Xiuling; Huang, Yonggang; Zhang, Yihui; Rogers, John A.

    2018-03-01

    Three-dimensional (3D) structures capable of reversible transformations in their geometrical layouts have important applications across a broad range of areas. Most morphable 3D systems rely on concepts inspired by origami/kirigami or techniques of 3D printing with responsive materials. The development of schemes that can simultaneously apply across a wide range of size scales and with classes of advanced materials found in state-of-the-art microsystem technologies remains challenging. Here, we introduce a set of concepts for morphable 3D mesostructures in diverse materials and fully formed planar devices spanning length scales from micrometres to millimetres. The approaches rely on elastomer platforms deformed in different time sequences to elastically alter the 3D geometries of supported mesostructures via nonlinear mechanical buckling. Over 20 examples have been experimentally and theoretically investigated, including mesostructures that can be reshaped between different geometries as well as those that can morph into three or more distinct states. An adaptive radiofrequency circuit and a concealable electromagnetic device provide examples of functionally reconfigurable microelectronic devices.

  9. Properties of CdSe quantum dots coated with silica fabricated in a facile way

    International Nuclear Information System (INIS)

    Liao Yufeng; Li Wenjiang; He Sailing

    2007-01-01

    High quality quantum dots (QDs) CdSe were prepared using a novel and non-TOP method. Quantum dots of different sizes ranging from 2 to 4 nm could be obtained by removing aliquots of the reaction solution at different time intervals or by adjusting some reaction conditions. The CdSe quantum dots (core) were directly coated with silica (shell) using a microemulsion method. The design and preparation of a model QD/silica was described and characterized using transmission electron microscopy (TEM), UV-vis absorption, photoluminescence and laser confocal scanning microscopy. TEM images confirmed the well-monodispersed QDs and the silica shell around the CdSe core, respectively; laser confocal microscope images, UV-vis absorption and photoluminescence spectra clearly indicated that both the original QDs and the silica-coated QDs had good fluorescence properties. The quantum dots coated with silica shells were stable, water-soluble and less toxic (due to the silica shells), and are anticipated to be used as fluorescent probes for biosensing and imaging applications

  10. Synthesis of Magnetic Rattle-Type Silica with Controllable Magnetite and Tunable Size by Pre-Shell-Post-Core Method.

    Science.gov (United States)

    Chen, Xue; Tan, Longfei; Meng, Xianwei

    2016-03-01

    In this study, we have developed the pre-shell-post-core route to synthesize the magnetic rattle-type silica. This method has not only simplified the precursor's process and reduced the reacting time, but also ameliorated the loss of magnetite and made the magnetite content and the inner core size controllable and tunable. The magnetite contents and inner core size can be easily controlled by changing the type and concentration of alkali, reaction system and addition of water. The results show that alkali aqueous solution promotes the escape of the precursor iron ions from the inner space of rattle-type silica and results in the loss of magnetite. In this case, NaOH ethanol solution is better for the formation of magnetite than ammonia because it not only offers an appropriate alkalinity to facilitate the synthesis of. magnetic particles, but also avoids the escape of the iron ions from the mesopores of rattle-type silica. The synthesis process is very simple and efficient, and it takes no more than 2 hours to complete the total preparation and handling of the magnetic rattle-type silica. The end-product Fe3O4@SiO2 nanocomposites also have good magnetic properties which will perform potential application in biomedical science.

  11. Core-shell designs of photoluminescent nanodiamonds with porous silica coatings for bioimaging and drug delivery II: application.

    Science.gov (United States)

    Prabhakar, Neeraj; Näreoja, Tuomas; von Haartman, Eva; Karaman, Didem Şen; Jiang, Hua; Koho, Sami; Dolenko, Tatiana A; Hänninen, Pekka E; Vlasov, Denis I; Ralchenko, Victor G; Hosomi, Satoru; Vlasov, Igor I; Sahlgren, Cecilia; Rosenholm, Jessica M

    2013-05-07

    Recent advances within materials science and its interdisciplinary applications in biomedicine have emphasized the potential of using a single multifunctional composite material for concurrent drug delivery and biomedical imaging. Here we present a novel composite material consisting of a photoluminescent nanodiamond (ND) core with a porous silica (SiO2) shell. This novel multifunctional probe serves as an alternative nanomaterial to address the existing problems with delivery and subsequent tracing of the particles. Whereas the unique optical properties of ND allows for long-term live cell imaging and tracking of cellular processes, mesoporous silica nanoparticles (MSNs) have proven to be efficient drug carriers. The advantages of both ND and MSNs were hereby integrated in the new composite material, ND@MSN. The optical properties provided by the ND core rendered the nanocomposite suitable for microscopy imaging in fluorescence and reflectance mode, as well as super-resolution microscopy as a STED label; whereas the porous silica coating provided efficient intracellular delivery capacity, especially in surface-functionalized form. This study serves as a demonstration how this novel nanomaterial can be exploited for both bioimaging and drug delivery for future theranostic applications.

  12. Synthesis of Novel Mesoporous Silica Materials with Hierarchical Pore Structures

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Suk Bon; Choi, Wang Kyu; Choi, Byung Seon; Moon, Jei Kwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    Porous materials with various pore sizes in the range of micropore (< 2 nm), mesopore (2-50 nm), and macropore (> 50 nm) are attractive due to their many emerging applications such as catalysts, separation systems, and low dielectric constant materials. The discovery of new M41S mesoporous silica families with pore sizes larger than 2 nm in diameter in 1992 extended the applications into much wider pore ranges, bringing in a new prosperous era in porous material research. The synthesis of these silica materials has been mainly accomplished through a self-assembly between surfactant molecules and inorganic species under various pH conditions. Recently, core-shell nanoparticles with a silica core and mesoporous shell under basic conditions were synthesized using the silica nanoparticles as a core, and a silica precursor (TEOS) and cationic surfactant (CTABr) as a material for the formation of the mesoporous shell. The resultant materials were very monodispersive in size and showed a narrow pore size distribution in the range of ca 2-3 nm in diameter, depending on the alkyl-chain length of the surfactants used. In this work, the mesoporous shell coated-fumed silicas (denoted as MS M-5s) were synthesized by using fumed silica instead of the silica nanoparticle as a core based on previous reports. Also, the structural properties of the MS M-5s such as the specific surface area and pore volume were easily controlled by varying the amount of the silica precursor and surfactant. The resultant materials exhibited a BET surface area of ca 279-446 m{sup 2}/g and total pore volume of ca 0.64-0.74 cm{sup 3}/g and showed a narrow pore size distribution (PSD) due to the removal of the organic surfactant molecules

  13. Synthesis of Pt-immobilized on silica and polystyrene-encapsulated silica and their applications as electrocatalysts in the proton exchange membrane fuel cell

    International Nuclear Information System (INIS)

    Yi, Sung-Chul; Kim, Chang Young; Jung, Chi Young; Jeong, Sung Hoon; Kim, Wha Jung

    2011-01-01

    Nano sized Pt particles were successfully immobilized onto SiO 2 and polystyrene-encapsulated silica core shell (SiO 2 @PS). To make the immobilization of Pt onto both silica and polystyrene-encapsulated silica core shell, SiO 2 was first functionalized with -NH 2 using 3-amino propyl trimethoxysilane (APTMS) while for core shell, the negatively charged surface of polystyrene (PS) was changed with positive charge by cationic surfactant such as cetyltrimethylammonium chloride (CTACl) to make the formation of SiO 2 shell on preformed PS sphere. Transmission electron micrograph (TEM) images shows that Pt nanoparticles immobilized onto SiO 2 and SiO 2 @PS were to be 3-4 nm without agglomeraiton. The energy dispersive spectroscope (EDS) shows that Pt contents on both SiO 2 and SiO 2 @PS were to be 21.45% and 20.28%, respectively. In case of Pt-SiO 2 @PS, it is believed that Pt should have been immobilized onto PS surface and pore within SiO 2 shell as well as SiO 2 surface. The MEA fabricated with Pt-SiO 2 @PS shows better cell performance than of Pt-SiO 2 .

  14. Solventless acid-free synthesis of mesostructured titania: Nanovessels for metal complexes and metal nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Dag, Oe.; Celik, Oe.; Ozin, G.A. [Department of Chemistry, Bilkent University, 06533 Ankara (Turkey); Soten, I.; Polarz, S.; Coombs, N. [Materials Chemistry Research Group, Chemistry Department, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada)

    2003-01-01

    A new and highly reproducible method to obtain mesostructured titania materials is introduced in this contribution. The mesostructured titania is obtained by employing self-assembled structures of non-ionic alkyl-poly(ethylene oxide) surfactants as templates. The materials are produced without additional solvents such as alcohols, or even water. Only the titanium(IV) ethoxide and the surfactant (C{sub 12}EO{sub 10}) are needed. Water, in the form of that attached to the surfactant and from the atmosphere, induces growth of titania nanoclusters in the synthesis sol. It is indicated that these nanoclusters interact with the surfactant EO-head groups to form a new titanotropic amphiphile. The new amphiphiles self-assemble into titanium nanocluster-surfactant hybrid lyotropic phases, which are transformed to the final mesostructured materials by further condensation of the titania network. The titania materials can be obtained also with noble-metal particles immobilized in the mesostructured framework. It is seen that when different metal salts are used as the metal precursors, different interactions with the titania walls are found. The materials are characterized by X-ray diffraction (XRD), polarization optical microscopy (POM), transmission electron microscopy (TEM), UV-vis spectroscopy, and micro-Raman analysis. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  15. Methanol-Sensing Property Improvement of Mesostructured Zinc Oxide Prepared by the Nanocasting Strategy

    Directory of Open Access Journals (Sweden)

    Qian Gao

    2013-01-01

    Full Text Available The specific structure and morphology often play a critical role in governing the excellent intrinsic properties of the compound semiconductor. Herein, mesostructured ZnO with excellent methanol-sensing properties was prepared by a structure replication procedure through the incipient wetness technique. The investigation on the crystal structure and morphology of the resultant material shows that the product consists of hexagonally arranged mesopores and crystalline walls, and its structure is an ideal replication of CMK-3 template. Consequently, mesostructured ZnO was fabricated as a gas sensor for methanol. The excellent methanol-sensing performance was achieved at a relatively low operating temperature of 120°C. In comparison with the nonporous ZnO prepared through conventional coprecipitation approach, mesostructured ZnO material shows the higher sensitivity and stability. Furthermore, it shows the discrimination between methanol and ethanol sensitivity, which makes it a good candidate in fabricating selective methanol sensor in practice.

  16. Face-specific Replacement of Calcite by Amorphous Silica Nanoparticles

    Science.gov (United States)

    Liesegang, M.; Milke, R.; Neusser, G.; Mizaikoff, B.

    2016-12-01

    Amorphous silica, composed of nanoscale spheres, is an important biomineral, alteration product of silicate rocks on the Earth's surface, and precursor material for stable silicate minerals. Despite constant progress in silica sphere synthesis, fundamental knowledge of natural silica particle interaction and ordering processes leading to colloidal crystals is absent so far. To understand the formation pathways of silica spheres in a geologic environment, we investigated silicified Cretaceous mollusk shell pseudomorphs from Coober Pedy (South Australia) using focused ion beam (FIB)-SEM tomography, petrographic microscopy, µ-XRD, and EMPA. The shells consist of replaced calcite crystals (ionic strength remain constant throughout the replacement process, permitting continuous silica nanoparticle formation and diffusion-limited colloid aggregation. Our study provides a natural example of the transformation of an atomic crystal to an amorphous, mesoscale ordered material; thus, links the research fields of natural colloidal crystal formation, carbonate-silica replacement, and crystallization by oriented particle aggregation (CPA).

  17. Synthesis of uniform carbon at silica nanocables and luminescent silica nanotubes with well controlled inner diameters

    International Nuclear Information System (INIS)

    Qian Haisheng; Yu Shuhong; Ren Lei; Yang Yipeng; Zhang Wei

    2006-01-01

    Uniform carbon at silica nanocables and silica nanotubes with well-controlled inner diameters can be synthesized in an easy way by a sacrificial templating method. This was performed using carbon nanofibres as hard templates that were synthesized previously by a hydrothermal carbonization process. Silica nanotubes with well-controlled inner diameters were synthesized from carbon at silica core-shell nanostructures by removal of the core carbon component. The inner diameters of the as-prepared silica nanotubes can be well controlled from several nanometres to hundreds of nanometres by adjusting the diameters of the carbon nanofibres. The silica nanotubes synthesized by this method display strong photoluminescence in ultraviolet at room temperature. Such uniform silica nanotubes might find potential applications in many fields such as encapsulation, catalysis, chemical/biological separation, and sensing

  18. Synthesis of hydrophobic zeolite X-SiO{sub 2} core-shell composites

    Energy Technology Data Exchange (ETDEWEB)

    Liu Liying [School of Material and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China); Cooperative Research Centre for Greenhouse Gas Technologies (CO-2CRC) (Australia); Singh, Ranjeet; Li Gang; Xiao Gongkui [Cooperative Research Centre for Greenhouse Gas Technologies (CO-2CRC) (Australia); Department of Chemical Engineering, Monash University, Clayton, Victoria 3800 (Australia); Webley, Paul A., E-mail: paul.webley@eng.monash.edu.au [Cooperative Research Centre for Greenhouse Gas Technologies (CO-2CRC) (Australia); Department of Chemical and Biomolecular Engineering, University of Melbourne, Victoria 3010 (Australia); Zhai Yuchun [School of Material and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Hydrophobic 13X zeolite composites with silicalite and mesoporous silica shells are designed. Black-Right-Pointing-Pointer These core-shell composites are silynated and their hydrophobicity is tested. Black-Right-Pointing-Pointer Addition of silica layer increases the density of surface hydroxyl groups which makes the improvement of the hydrophobicity possible by further silynation. - Abstract: Core-shell structures of zeolite X coated with silicalite as well as mesoporous (MCM-41) have been synthesized. Furthermore, the surfaces of the silicalite and mesoporous silica shells were silylated using organosilanes. The materials were characterized by X-ray diffraction, nitrogen adsorption/desorption, scanning and transmission electron microscopy. The results show that the properties of zeolite 13X-silicalite and zeolite 13X-mesoporous silica core-shells composite structures are well maintained even after the modification. As expected, the shell thickness increased with increase in synthesis time, however, the micropore volume decreased. Silylation with smaller organosilanes (trimethyl chlorosilane) resulted in decrease in surface area as they diffused through the pores; however, bulkier silane reacted with surface hydroxyl groups and maintained the pore structure. Contact angle measurements revealed that hydrophobicity of zeolite 13X was enhanced by the microporous and mesoporous shell coating and was further improved by silylation.

  19. Sensing behavior study of silica-coated Ag nanoparticles deposited on glassy carbon toward nitrobenzene

    Energy Technology Data Exchange (ETDEWEB)

    Devi, Pooja; Reddy, Pramod [CSIR, Sector-30C, Central Scientific Instruments Organization (India); Arora, Swati [Shri Mata Vaishno Devi University (India); Singh, Suman; Ghanshyam, C.; Singla, M. L., E-mail: singla_min@yahoo.co.in [CSIR, Sector-30C, Central Scientific Instruments Organization (India)

    2012-10-15

    In this study, we report the synthesis and characterization of silica-coated silver core/shell nanostructures (NSs) and their sensing behavior when deposited on glassy carbon (GC) electrode for nitrobenzene (NB) detection. Synthesized silica-coated silver core/shell NSs were characterized for their chemical, structural and morphological properties. TEM analysis confirmed that the silica-coated silver nanoparticles (size {approx}200 nm) are spherical in shape and the core diameter is {approx}38 nm. FT-IR spectra also confirmed the coating of silica on the surface of silver nanoparticles. Cyclic voltammetry studies of NB with silica-coated silver core-shell nanoparticles-modified GC electrodes revealed two cathodic peaks at -0.74 V (C{sub 1}) and -0.34 V (C{sub 2}) along with two anodic peaks at -0.64 V (A{sub 1}) and -0.2 V (A{sub 2}). Enhanced cathodic peak current (C{sub 1}, I{sub P}) of the core-shell NSs-modified electrode is observed relative to bare and silica-modified electrodes. Amperometric studies revealed a very high current sensitivity (114 nA/nM) and linearly dependent reduction current with NB amount in the low concentration range and a detection limit of 25 nM. Moreover, the core-shell NSs-modified electrode showed good reproducibility and selectivity toward NB in the presence of many cationic, anionic, and organic interferents.

  20. Sensing behavior study of silica-coated Ag nanoparticles deposited on glassy carbon toward nitrobenzene

    International Nuclear Information System (INIS)

    Devi, Pooja; Reddy, Pramod; Arora, Swati; Singh, Suman; Ghanshyam, C.; Singla, M. L.

    2012-01-01

    In this study, we report the synthesis and characterization of silica-coated silver core/shell nanostructures (NSs) and their sensing behavior when deposited on glassy carbon (GC) electrode for nitrobenzene (NB) detection. Synthesized silica-coated silver core/shell NSs were characterized for their chemical, structural and morphological properties. TEM analysis confirmed that the silica-coated silver nanoparticles (size ∼200 nm) are spherical in shape and the core diameter is ∼38 nm. FT-IR spectra also confirmed the coating of silica on the surface of silver nanoparticles. Cyclic voltammetry studies of NB with silica-coated silver core–shell nanoparticles-modified GC electrodes revealed two cathodic peaks at −0.74 V (C 1 ) and −0.34 V (C 2 ) along with two anodic peaks at −0.64 V (A 1 ) and −0.2 V (A 2 ). Enhanced cathodic peak current (C 1 , I P ) of the core–shell NSs-modified electrode is observed relative to bare and silica-modified electrodes. Amperometric studies revealed a very high current sensitivity (114 nA/nM) and linearly dependent reduction current with NB amount in the low concentration range and a detection limit of 25 nM. Moreover, the core–shell NSs-modified electrode showed good reproducibility and selectivity toward NB in the presence of many cationic, anionic, and organic interferents.

  1. Mesostructured Fullerene Electrodes for Highly Efficient n–i–p Perovskite Solar Cells

    KAUST Repository

    Zhong, Yufei

    2016-10-21

    Electron-transporting layers in today\\'s stateof-the-art n-i-p organohalide perovskite solar cells are almost exclusively made of metal oxides. Here, we demonstrate a novel mesostructured fullerene-based electron-transporting material (ETM) that is crystalline, hydrophobic, and cross-linked, rendering it solvent-and heat resistant for subsequent perovskite solar cell fabrication The fullerene ETM is shown to enhance the structural and electronic properties of the CH3NH3PbI3 layer grown atop, reducing its Urbach energy from similar to 26 to 21 meV, while also increasing crystallite size and improving texture. The resulting mesostructured n-i-p solar cells achieve reduced recombination, improved device-to-device variation, reduced hysteresis, and a power conversion efficiency above 15%, surpassing the performance of similar devices prepared using mesoporous TiO2 and well above the performance of planar heterojunction devices on amorphous or crystalline [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM). This work is the first demonstration of a viable, hydrophobic, and high-performance mesostructured electron-accepting contact to work effectively in n-i-p perovskite solar cells.

  2. Mesoporous hollow spheres from soap bubbling.

    Science.gov (United States)

    Yu, Xianglin; Liang, Fuxin; Liu, Jiguang; Lu, Yunfeng; Yang, Zhenzhong

    2012-02-01

    The smaller and more stable bubbles can be generated from the large parent bubbles by rupture. In the presence of a bubble blowing agent, hollow spheres can be prepared by bubbling a silica sol. Herein, the trapped gas inside the bubble acts as a template. When the porogen, i.e., other surfactant, is introduced, a mesostructured shell forms by the co-assembly with the silica sol during sol-gel process. Morphological evolution emphasizes the prerequisite of an intermediate interior gas flow rate and high exterior gas flow rate for hollow spheres. The method is valid for many compositions from inorganic, polymer to their composites. Copyright © 2011 Elsevier Inc. All rights reserved.

  3. Synthesis of highly monodisperse particles composed of a magnetic core and fluorescent shell.

    Science.gov (United States)

    Nagao, Daisuke; Yokoyama, Mikio; Yamauchi, Noriko; Matsumoto, Hideki; Kobayashi, Yoshio; Konno, Mikio

    2008-09-02

    Highly monodisperse particles composed of a magnetic silica core and fluorescent polymer shell were synthesized with a combined technique of heterocoagulation and soap-free emulsion polymerization. Prior to heterocoagulation, monodisperse, submicrometer-sized silica particles were prepared with the Stober method, and magnetic nanoparticles were prepared with a modified Massart method in which a cationic silane coupling agent of N-trimethoxysilylpropyl- N, N, N-trimethylammonium chloride was added just after coprecipitation of Fe (2+) and Fe (3+). The silica particles with negative surface potential were heterocoagulated with the magnetic nanoparticles with positive surface potential. The magnetic silica particles obtained with the heterocoagulation were treated with sodium silicate to modify their surfaces with silica. In the formation of a fluorescent polymer shell onto the silica-coated magnetic silica cores, an amphoteric initiator of 2,2'-azobis[ N-(2-carboxyethyl)-2-2-methylpropionamidine] (VA-057) was used to control the colloidal stability of the magnetic cores during the polymer coating. The polymerization of St in the presence of a hydrophobic fluorophore of pyrene could coat the cores with fluorescent polymer shells, resulting in monodisperse particles with a magnetic silica core and fluorescent polymer shell. Measurements of zeta potential for the composite particles in different pH values indicated that the composite particles had an amphoteric property originating from VA-057 initiator.

  4. Polystyrene Core-Silica Shell Particles with Defined Nanoarchitectures as a Versatile Platform for Suspension Array Technology.

    Science.gov (United States)

    Sarma, Dominik; Gawlitza, Kornelia; Rurack, Knut

    2016-04-19

    The need for rapid and high-throughput screening in analytical laboratories has led to significant growth in interest in suspension array technologies (SATs), especially with regard to cytometric assays targeting a low to medium number of analytes. Such SAT or bead-based assays rely on spherical objects that constitute the analytical platform. Usually, functionalized polymer or silica (SiO2) microbeads are used which each have distinct advantages and drawbacks. In this paper, we present a straightforward synthetic route to highly monodisperse SiO2-coated polystyrene core-shell (CS) beads for SAT with controllable architectures from smooth to raspberry- and multilayer-like shells by varying the molecular weight of poly(vinylpyrrolidone) (PVP), which was used as the stabilizer of the cores. The combination of both organic polymer core and a structurally controlled inorganic SiO2 shell in one hybrid particle holds great promises for flexible next-generation design of the spherical platform. The particles were characterized by electron microscopy (SEM, T-SEM, and TEM), thermogravimetry, flow cytometry, and nitrogen adsorption/desorption, offering comprehensive information on the composition, size, structure, and surface area. All particles show ideal cytometric detection patterns and facile handling due to the hybrid structure. The beads are endowed with straightforward modification possibilities through the defined SiO2 shells. We successfully implemented the particles in fluorometric SAT model assays, illustrating the benefits of tailored surface area which is readily available for small-molecule anchoring. Very promising assay performance was shown for DNA hybridization assays with quantification limits down to 8 fmol.

  5. Magnetothermal release of payload from iron oxide/silica drug delivery agents

    Energy Technology Data Exchange (ETDEWEB)

    Luong, T.T., E-mail: thientai.luong@chem.kuleuven.be [KU Leuven, Department of Chemistry, Celestijnenlaan 200D, Heverlee 3001 (Belgium); Hanoi National University of Education, Faculty of Chemistry, Xuan Thuy 136, Cau Giay, Hanoi (Viet Nam); Knoppe, S.; Bloemen, M.; Brullot, W.; Strobbe, R. [KU Leuven, Department of Chemistry, Celestijnenlaan 200D, Heverlee 3001 (Belgium); Locquet, J.-P. [KU Leuven, Department of Physics, Celestijnenlaan 200D, Heverlee 3001 (Belgium); Verbiest, T. [KU Leuven, Department of Chemistry, Celestijnenlaan 200D, Heverlee 3001 (Belgium)

    2016-10-15

    The release of covalently bound Rhodamine B from iron oxide/mesoporous silica core/shell nanoparticles under magnetically induced heating was studied. The system acts as a model to study drug delivery and payload release under magnetothermal heating. - Graphical abstract: The release of covalently bound Rhodamine B from iron oxide/mesoporous silica core/shell nanoparticles under magnetically induced heating was studied. - Highlights: • Iron oxide/mesoporous-SiO{sub 2} core-shell NPs were synthesized. • The dye was covalently bound to SiO{sub 2} shells. • The release of dye under magnetothermal heating was studied. • The results are relevant for controlled drug release.

  6. Polystyrene-Core, Silica-Shell Scintillant Nanoparticles for Low-Energy Radionuclide Quantification in Aqueous Media.

    Science.gov (United States)

    Janczak, Colleen M; Calderon, Isen A C; Mokhtari, Zeinab; Aspinwall, Craig A

    2018-02-07

    β-particle emitting radionuclides are useful molecular labels due to their abundance in biomolecules. Detection of β-emission from 3 H, 35 S, and 33 P, important biological isotopes, is challenging due to the low energies (E max ≤ 300 keV) and short penetration depths (≤0.6 mm) in aqueous media. The activity of biologically relevant β-emitters is usually measured in liquid scintillation cocktail (LSC), a mixture of energy-absorbing organic solvents, surfactants, and scintillant fluorophores, which places significant limitations on the ability to acquire time-resolved measurements directly in aqueous biological systems. As an alternative to LSC, we developed polystyrene-core, silica-shell nanoparticle scintillators (referred to as nanoSCINT) for quantification of low-energy β-particle emitting radionuclides directly in aqueous solutions. The polystyrene acts as an absorber for energy from emitted β-particles and can be loaded with a range of hydrophobic scintillant fluorophores, leading to photon emission at visible wavelengths. The silica shell serves as a hydrophilic shield for the polystyrene core, enabling dispersion in aqueous media and providing better compatibility with water-soluble analytes. While polymer and inorganic scintillating microparticles are commercially available, their large size and/or high density complicates effective dispersion throughout the sample volume. In this work, nanoSCINT nanoparticles were prepared and characterized. nanoSCINT responds to 3 H, 35 S, and 33 P directly in aqueous solutions, does not exhibit a change in scintillation response between pH 3.0 and 9.5 or with 100 mM NaCl, and can be recovered and reused for activity measurements in bulk aqueous samples, demonstrating the potential for reduced production of LSC waste and reduced total waste volume during radionuclide quantification. The limits of detection for 1 mg/mL nanoSCINT are 130 nCi/mL for 3 H, 8 nCi/mL for 35 S, and <1 nCi/mL for 33 P.

  7. Preparation of thick silica coatings on carbon fibers with fine-structured silica nanotubes induced by a self-assembly process

    Directory of Open Access Journals (Sweden)

    Benjamin Baumgärtner

    2017-05-01

    Full Text Available A facile method to coat carbon fibers with a silica shell is presented in this work. By immobilizing linear polyamines on the carbon fiber surface, the high catalytic activity of polyamines in the sol–gel-processing of silica precursors is used to deposit a silica coating directly on the fiber’s surface. The surface localization of the catalyst is achieved either by attaching short-chain polyamines (e.g., tetraethylenepentamine via covalent bonds to the carbon fiber surface or by depositing long-chain polyamines (e.g., linear poly(ethylenimine on the carbon fiber by weak non-covalent bonding. The long-chain polyamine self-assembles onto the carbon fiber substrate in the form of nanoscopic crystallites, which serve as a template for the subsequent silica deposition. The silicification at close to neutral pH is spatially restricted to the localized polyamine and consequently to the fiber surface. In case of the linear poly(ethylenimine, silica shells of several micrometers in thickness can be obtained and their morphology is easily controlled by a considerable number of synthesis parameters. A unique feature is the hierarchical biomimetic structure of the silica coating which surrounds the embedded carbon fiber by fibrillar and interconnected silica fine-structures. The high surface area of the nanostructured composite fiber may be exploited for catalytic applications and adsorption purposes.

  8. Sugarcane bagasse lignin, and silica gel and magneto-silica as drug vehicles for development of innocuous methotrexate drug against rheumatoid arthritis disease in albino rats

    International Nuclear Information System (INIS)

    Wahba, Sanaa M.R.; Darwish, Atef S.; Shehata, Iman H.; Abd Elhalem, Sahar S.

    2015-01-01

    The present study clarifies co-therapy action of deliveries from their textural changes point of view. Methotrexate (MTX) was immobilized onto biodegradable lignin, silica gel and iron/silica nanocomposite. Loaded-MTX was i.p. injected into albino rats at doses of 0.25 and 0.5 mg/kg/week for 2.5 months, after which spleen, liver, testes and knee joint tissues were collected for tests. IFN-γ and IL-17A mRNA gene expressions in spleen in all biological samples were determined by RT-PCR. Physicochemical features of drug carriers were monitored by XRD, BET-PSD, SEM and TEM. Drug inflammatory-site targeting was found to be closely related to the physico-features of deliverers. The interlayered lignin of micro- and meso-pore channels directed MTX toward concealed infected cells in liver and testes tissues, while meso-structured silica flacks satisfied by gathering MTX around knee joints. The magneto-silica nanocomposite targeted MTX toward spleen tissue, which is considered as a lively factory for the production of electron rich compounds. - Highlights: • Opening the door to synthesize smart targeted drug deliveries against RA disease • Therapy action of MTX-laden lignin and Fe 3 O 4 /SiO 2 composite toward RA disease • Procure selective targeted drug deliveries of near 100% curing against RA disease • Revolutionary clinical therapies for RA disease by inventive MTX-delivery models

  9. Morphology conserving aminopropyl functionalization of hollow silica nanospheres in toluene

    Science.gov (United States)

    Dobó, Dorina G.; Berkesi, Dániel; Kukovecz, Ákos

    2017-07-01

    Inorganic nanostructures containing cavities of monodisperse diameter distribution find applications in e.g. catalysis, adsorption and drug delivery. One of their possible synthesis routes is the template assisted core-shell synthesis. We synthesized hollow silica spheres around polystyrene cores by the sol-gel method. The polystyrene template was removed by heat treatment leaving behind a hollow spherical shell structure. The surface of the spheres was then modified by adding aminopropyl groups. Here we present the first experimental evidence that toluene is a suitable alternative functionalization medium for the resulting thin shells, and report the comprehensive characterization of the amino-functionalized hollow silica spheres based on scanning electron microscopy, transmission electron microscopy, N2 adsorption, FT-IR spectroscopy, Raman spectroscopy and electrokinetic potential measurement. Both the presence of the amino groups and the preservation of the hollow spherical morphology were unambiguously proven. The introduction of the amine functionality adds amphoteric character to the shell as shown by the zeta potential vs. pH function. Unlike pristine silica particles, amino-functionalized nanosphere aqueous sols can be stable at both acidic and basic conditions.

  10. Mesostructured Au/C materials obtained by replication of functionalized SBA-15 silica containing highly dispersed gold nanoparticles

    KAUST Repository

    Kerdi, Fatmé

    2011-04-01

    The preparation and characterization of highly dispersed gold nanoparticles in ordered mesoporous carbons CMK-3 are reported. These carbons were obtained using gold-containing functionalized SBA-15 silicas as hard templates. Two series of Au/SiO2 templates were prepared, depending on the nature of the functionalization molecule. While ammonium-functionalized silicas gave gold particles with a size determined by the pores of the silica support, the use of mercaptopropyltrimethoxysilane as grafting molecule afforded the possibility to control the particle size inside the mesopores. Both series gave highly ordered mesoporous carbons with gold particles incorporated in the carbon nanorods. However, the gold particle size in mesoporous carbons was the same for both series and apparently did not depend on the nature of the silica template. Both Au/SiO2 templates and their corresponding Au/CMK-3 materials have been characterized by X-ray diffraction, nitrogen adsorption/desorption, chemical analysis, solid-state nuclear magnetic resonance and transmission electron microscopy. They were also used as catalysts in the aerobic oxidation of cyclohexene and trans-stilbene in the liquid phase. © 2010 Elsevier Inc. All rights reserved.

  11. Removal of lead(II ions from aqueous solutions using cashew nut shell liquid-templated thiol-silica materials

    Directory of Open Access Journals (Sweden)

    J. E. G. Mdoe

    2014-09-01

    Full Text Available A range of thiol-silica composites were prepared using cashew nut shell liquid (CNSL or one of its phenolic constituents, cardanol, as templates. The procedure involved formation of a CNSL or cardanol emulsion in a water-ethanol system into which (3-mercaptopropyl-trimethoxysilane and tetraethyl orthosilicate were simultaneously added at various ratios. The reaction mixture was aged at room temperature for 18 h followed by a Soxhlet extraction of the template and drying. The materials were characterized by diffuse reflectance Fourier transform infrared, nitrogen physisorption, scanning electron microscopy and acid titration. Results indicated that indeed the thiol-silica composites were successfully prepared, with thiol group loadings ranging from 1.6-2.5 mmol/g. The materials were tested for lead(II adsorption, and results showed that they had maximum adsorption capacities up to 66.7 mg/g, depending on the thiol group loading and type of template used in preparing the adsorbent. DOI: http://dx.doi.org/10.4314/bcse.v28i3.5

  12. Au/BiOCl heterojunction within mesoporous silica shell as stable plasmonic photocatalyst for efficient organic pollutants decomposition under visible light

    International Nuclear Information System (INIS)

    Yan, Xiaoqing; Zhu, Xiaohui; Li, Renhong; Chen, Wenxing

    2016-01-01

    Highlights: • A heterojunction of Au/BiOCl was fabricated within the mesoporous silica shell. • The compact contact between Au and BiOCl enables electrons back flow from Au to BiOCl. • Au/BiOCl@mSiO 2 plasmonic photocatalyst shows efficient visible light photoactivity. • Hydroxyl radicals are the main oxidants in formaldehyde and Rhodamine B decomposition. - Abstract: A new mesoporous silica protected plasmonic photocatalyst, Au/BiOCl@mSiO 2 , was prepared by a modified AcHE method and a subsequent UV light induced photodeposition process. The surfactant-free heterojunction allows the electrons spontaneously flow from Au to nearby BiOCl surface, leading to the accumulation of positive charges on Au surface, and negative charges on Bi species under visible light. Au/BiOCl@mSiO 2 exhibits high visible light photocatalytic efficiency in complete oxidation of aqueous formaldehyde and Rhodamin B. We showed that a positive relationship exists between the LSPR effect and rate enhancements, and leads to a hypothesis that the metallic Au LSPR enhances the photocatalytic rates on nearby semiconductors by transferring energetic electrons to BiOCl and increasing the steady-state concentration of active ·OH species by a multi-electron reduction of molecular oxygen. The ·OH species is the main oxidant in photocatalytic transformations, whose intensity is greatly enhanced in the dye-involving systems due to the synergetic effect between LSPR and dye sensitization processes. In addition, the mesoporous SiO 2 shell not only inhibits the over growth of BiOCl nanocrystals within the silica frameworks, but also protects the dissolution of chloride or Au species into aqueous solution, which ultimately makes the Au/BiOCl@mSiO 2 catalysts rather stable during photocatalysis.

  13. The role of curvature in silica mesoporous crystals

    KAUST Repository

    Miyasaka, Keiichi

    2012-02-08

    Silica mesoporous crystals (SMCs) offer a unique opportunity to study micellar mesophases. Replication of non-equilibrium mesophases into porous silica structures allows the characterization of surfactant phases under a variety of chemical and physical perturbations, through methods not typically accessible to liquid crystal chemists. A poignant example is the use of electron microscopy and crystallography, as discussed herein, for the purpose of determining the fundamental role of amphiphile curvature, namely mean curvature and Gaussian curvature, which have been extensively studied in various fields such as polymer, liquid crystal, biological membrane, etc. The present work aims to highlight some current studies devoted to the interface curvature on SMCs, in which electron microscopy and electron crystallography (EC) are used to understand the geometry of silica wall surface in bicontinuous and cage-type mesostructures through the investigation of electrostatic potential maps. Additionally, we show that by altering the synthesis conditions during the preparation of SMCs, it is possible to isolate particles during micellar mesophase transformations in the cubic bicontinuous system, allowing us to view and study epitaxial relations under the specific synthesis conditions. By studying the relationship between mesoporous structure, interface curvature and micellar mesophases using electron microscopy and EC, we hope to bring new insights into the formation mechanism of these unique materials but also contribute a new way of understanding periodic liquid crystal systems. © 2012 The Royal Society.

  14. The role of curvature in silica mesoporous crystals

    KAUST Repository

    Miyasaka, Keiichi; Bennett, Alfonso Garcia; Han, Lu; Han, Yu; Xiao, Changhong; Fujita, Nobuhisa; Castle, Toen; Sakamoto, Yasuhiro; Che, Shunai; Terasaki, Osamu

    2012-01-01

    Silica mesoporous crystals (SMCs) offer a unique opportunity to study micellar mesophases. Replication of non-equilibrium mesophases into porous silica structures allows the characterization of surfactant phases under a variety of chemical and physical perturbations, through methods not typically accessible to liquid crystal chemists. A poignant example is the use of electron microscopy and crystallography, as discussed herein, for the purpose of determining the fundamental role of amphiphile curvature, namely mean curvature and Gaussian curvature, which have been extensively studied in various fields such as polymer, liquid crystal, biological membrane, etc. The present work aims to highlight some current studies devoted to the interface curvature on SMCs, in which electron microscopy and electron crystallography (EC) are used to understand the geometry of silica wall surface in bicontinuous and cage-type mesostructures through the investigation of electrostatic potential maps. Additionally, we show that by altering the synthesis conditions during the preparation of SMCs, it is possible to isolate particles during micellar mesophase transformations in the cubic bicontinuous system, allowing us to view and study epitaxial relations under the specific synthesis conditions. By studying the relationship between mesoporous structure, interface curvature and micellar mesophases using electron microscopy and EC, we hope to bring new insights into the formation mechanism of these unique materials but also contribute a new way of understanding periodic liquid crystal systems. © 2012 The Royal Society.

  15. Preparation and CO{sub 2} adsorption properties of aminopropyl-functionalized mesoporous silica microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Araki, S.; Doi, H.; Sano, Y.; Tanaka, S.; Miyake, Y. [Hitachi Zosen Corp., Osaka (Japan). Technical Research Institute

    2009-11-15

    Aminopropyl-functionalized mesoporous silica microspheres (AF-MSM) were synthesized by a simple one-step modified Stober method. Dodecylamine (DDA) was used as the catalyst for the hydrolysis and condensation of the silica source and as the molecular template to prepare the ordered mesopores. The mesoporous silica surfaces were modified to aminopropyl groups by the co-condensation of tetraethoxysilane (TEOS) with 3-aminopropyltriethoxysilane (APTES), up to a maximum of 20 mol.% APTES content in the silica source. The particle size, Brunauer-Emmet-Teller (BET) specific surface area, and mesoporous regularity decreased with increasing APTES content. It is believed that this result is caused by a decreasing amount of DDA incorporated into AF-MSM with increasing APTES content. It was also confirmed that the spherical shape and the mesostructure were maintained even if 20 mol.% of APTES was added to the silica source. Moreover, AF-MSM was applied to the CO{sub 2} adsorbent. The breakthrough time of the CO{sub 2} and CO{sub 2} adsorption capacities increased with increasing APTES content. The adsorption capacity of CO{sub 2} for AF-MSM, prepared at 20 mol.% APTES, was 0.54 mmol g{sup -1}. Carbon dioxide adsorbed onto AF-MSM was completely desorbed by heating in a N{sub 2} purge at 423 K for 30 min.

  16. Adsorption of Pb(II) using silica gel composite from rice husk ash modified 3-aminopropyltriethoxysilane (APTES)-activated carbon from coconut shell

    Science.gov (United States)

    Yusmaniar, Purwanto, Agung; Putri, Elfriyana Awalita; Rosyidah, Dzakiyyatur

    2017-03-01

    Silica gel modified by 3-aminopropyltriethoxysilane (APTES) was synthesized from rice husk ash combined with activated carbon from coconut shell yielded the composite adsorbent. The composite was characterized by Fourier Transform Infra Red spectroscopy (FT-IR), Electron Dispersive X-Ray (EDX), Surface Area Analyzer (SAA) and adsorption test by Atomic Absorption Spectrometry (AAS). This composite adsorbent has been used moderately for the removal of lead ions from metal solutions and compared with silica gel modified APTES and activated carbon. The adsorption experiments of Pb -ions by adsorbents were performed at different pH and contact time with the same metal solutions concentration, volume solution, and adsorbent dosage. The optimum pH for the adsorption was found to be 5.0 and the equilibrium was achieved for Pb with 20 min of contact time. Pb ions adsorption by composite silica gel modified APTES-activated carbon followed by Langmuir isotherm model with qmax value of 46.9483 mg/g that proved an adsorbent mechanism consistent to the mechanism of monolayer formation.

  17. A tri-continuous mesoporous material with a silica pore wall following a hexagonal minimal surface

    KAUST Repository

    Han, Yu

    2009-04-06

    Ordered porous materials with unique pore structures and pore sizes in the mesoporous range (2-50nm) have many applications in catalysis, separation and drug delivery. Extensive research has resulted in mesoporous materials with one-dimensional, cage-like and bi-continuous pore structures. Three families of bi-continuous mesoporous materials have been made, with two interwoven but unconnected channels, corresponding to the liquid crystal phases used as templates. Here we report a three-dimensional hexagonal mesoporous silica, IBN-9, with a tri-continuous pore structure that is synthesized using a specially designed cationic surfactant template. IBN-9 consists of three identical continuous interpenetrating channels, which are separated by a silica wall that follows a hexagonal minimal surface. Such a tri-continuous mesostructure was predicted mathematically, but until now has not been observed in real materials. © 2009 Macmillan Publishers Limited. All rights reserved.

  18. A tri-continuous mesoporous material with a silica pore wall following a hexagonal minimal surface

    KAUST Repository

    Han, Yu; Zhang, Daliang; Chng, Leng Leng; Sun, Junliang; Zhao, L. J.; Zou, Xiaodong; Ying, Jackie

    2009-01-01

    Ordered porous materials with unique pore structures and pore sizes in the mesoporous range (2-50nm) have many applications in catalysis, separation and drug delivery. Extensive research has resulted in mesoporous materials with one-dimensional, cage-like and bi-continuous pore structures. Three families of bi-continuous mesoporous materials have been made, with two interwoven but unconnected channels, corresponding to the liquid crystal phases used as templates. Here we report a three-dimensional hexagonal mesoporous silica, IBN-9, with a tri-continuous pore structure that is synthesized using a specially designed cationic surfactant template. IBN-9 consists of three identical continuous interpenetrating channels, which are separated by a silica wall that follows a hexagonal minimal surface. Such a tri-continuous mesostructure was predicted mathematically, but until now has not been observed in real materials. © 2009 Macmillan Publishers Limited. All rights reserved.

  19. Synthesis and spectroscopic properties of silica-dye-semiconductor nanocrystal hybrid particles.

    Science.gov (United States)

    Ren, Ting; Erker, Wolfgang; Basché, Thomas; Schärtl, Wolfgang

    2010-12-07

    We prepared silica-dye-nanocrystal hybrid particles and studied the energy transfer from semiconductor nanocrystals (= donor) to organic dye molecules (= acceptor). Multishell CdSe/CdS/ZnS semiconductor nanocrystals were adsorbed onto monodisperse Stöber silica particles with an outer silica shell of thickness 2-23 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the energy transfer efficiency, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of nanocrystals with increasing dye amount. Our conclusions were underlined by comparison of the experimental results with numerically calculated FRET efficiencies and by control experiments confirming attractive interaction between the nanocrystals and Texas Red freely dissolved in solution.

  20. Patchy silica-coated silver nanowires as SERS substrates

    International Nuclear Information System (INIS)

    Hunyadi Murph, Simona E.; Murphy, Catherine J.

    2013-01-01

    We report a class of core–shell nanomaterials that can be used as efficient surface-enhancement Raman scattering (SERS) substrates. The core consists of silver nanowires, prepared through a chemical reduction process, that are used to capture 4-mercaptobenzoic acid (4-MBA), a model analyte. The shell was prepared through a modified Stöber method and consists of patchy or full silica coats. The formation of silica coats was monitored via transmission electron microscopy, UV–visible spectroscopy, and phase-analysis light-scattering for measuring effective surface charge. Surprisingly, the patchy silica-coated silver nanowires are better SERS substrate than silver nanowires; nanomolar concentration of 4-MBA can be detected. In addition, “nano-matryoshka” configurations were used to quantitate/explore the effect of the electromagnetic field at the tips of the nanowire (“hot spots”) in the Raman scattering experiment.

  1. Patchy silica-coated silver nanowires as SERS substrates

    Energy Technology Data Exchange (ETDEWEB)

    Hunyadi Murph, Simona E.; Murphy, Catherine J.

    2013-05-08

    We report a class of core-shell nanomaterials that can be used as efficient surface-enhancement Raman scattering (SERS) substrates. The core consists of silver nanowires, prepared through a chemical reduction process, that are used to capture 4- mercaptobenzoic acid (4-MBA), a model analyte. The shell was prepared through a modified Stöber method and consists of patchy or full silica coats. The formation of silica coats was monitored via transmission electron microscopy, UV-visible spectroscopy and phase-analysis light scattering for measuring effective surface charge. Surprisingly, the patchy silica coated silver nanowires are better SERS substrate than silver nanowires; nanomolar concentration of 4-MBA can be detected. In addition, “nano-matryoshka” configurations were used to quantitate/explore the effect of the electromagnetic field at the tips of the nanowire (“hot spots”) in the Raman scattering experiment.

  2. Preparation and Characterization of WS2@SiO2 and WS2@PANI Core-Shell Nanocomposites

    Directory of Open Access Journals (Sweden)

    Hagit Sade

    2018-03-01

    Full Text Available Two tungsten disulfide (WS2-based core-shell nanocomposites were fabricated using readily available reagents and simple procedures. The surface was pre-treated with a surfactant couple in a layer-by-layer approach, enabling good dispersion of the WS2 nanostructures in aqueous media and providing a template for the polymerization of a silica (SiO2 shell. After a Stöber-like reaction, a conformal silica coating was achieved. Inspired by the resulting nanocomposite, a second one was prepared by reacting the surfactant-modified WS2 nanostructures with aniline and an oxidizing agent in an aqueous medium. Here too, a conformal coating of polyaniline (PANI was obtained, giving a WS2@PANI nanocomposite. Both nanocomposites were analyzed by electron microscopy, energy dispersive X-ray spectroscopy (EDS and FTIR, verifying the core-shell structure and the character of shells. The silica shell was amorphous and mesoporous and the surface area of the composite increases with shell thickness. Polyaniline shells slightly differ in their morphologies dependent on the acid used in the polymerization process and are amorphous like the silica shell. Electron paramagnetic resonance (EPR spectroscopy of the WS2@PANI nanocomposite showed variation between bulk PANI and the PANI shell. These two nanocomposites have great potential to expand the use of transition metals dichalcogenides (TMDCs for new applications in different fields.

  3. Sugarcane bagasse lignin, and silica gel and magneto-silica as drug vehicles for development of innocuous methotrexate drug against rheumatoid arthritis disease in albino rats

    Energy Technology Data Exchange (ETDEWEB)

    Wahba, Sanaa M.R. [Zoology department, Women College, Ain-Shams University,11566 Cairo (Egypt); Darwish, Atef S., E-mail: atef_mouharam@sci.asu.edu.eg [Chemistry department, Faculty of Science, Ain Shams University, Cairo (Egypt); Shehata, Iman H. [Microbiology and Immunology Department, Faculty of Medicine, Ain-Shams University, Cairo (Egypt); Abd Elhalem, Sahar S. [Zoology department, Women College, Ain-Shams University,11566 Cairo (Egypt)

    2015-03-01

    The present study clarifies co-therapy action of deliveries from their textural changes point of view. Methotrexate (MTX) was immobilized onto biodegradable lignin, silica gel and iron/silica nanocomposite. Loaded-MTX was i.p. injected into albino rats at doses of 0.25 and 0.5 mg/kg/week for 2.5 months, after which spleen, liver, testes and knee joint tissues were collected for tests. IFN-γ and IL-17A mRNA gene expressions in spleen in all biological samples were determined by RT-PCR. Physicochemical features of drug carriers were monitored by XRD, BET-PSD, SEM and TEM. Drug inflammatory-site targeting was found to be closely related to the physico-features of deliverers. The interlayered lignin of micro- and meso-pore channels directed MTX toward concealed infected cells in liver and testes tissues, while meso-structured silica flacks satisfied by gathering MTX around knee joints. The magneto-silica nanocomposite targeted MTX toward spleen tissue, which is considered as a lively factory for the production of electron rich compounds. - Highlights: • Opening the door to synthesize smart targeted drug deliveries against RA disease • Therapy action of MTX-laden lignin and Fe{sub 3}O{sub 4}/SiO{sub 2} composite toward RA disease • Procure selective targeted drug deliveries of near 100% curing against RA disease • Revolutionary clinical therapies for RA disease by inventive MTX-delivery models.

  4. Laser oxidative pyrolysis synthesis and annealing of TiO{sub 2} nanoparticles embedded in carbon–silica shells/matrix

    Energy Technology Data Exchange (ETDEWEB)

    Fleaca, C.T. [National Institute for Plasma, Laser and Radiation Physics (NILPRP), Atomistilor 409, P.O. Box MG 36, R-077125 Magurele, Bucharest (Romania); “Politehnica” University of Bucharest, Physics Department, Independentei 313, Bucharest (Romania); Scarisoreanu, M., E-mail: monica.scarisoreanu@inflpr.ro [National Institute for Plasma, Laser and Radiation Physics (NILPRP), Atomistilor 409, P.O. Box MG 36, R-077125 Magurele, Bucharest (Romania); Morjan, I.; Luculescu, C.; Niculescu, A.-M.; Badoi, A. [National Institute for Plasma, Laser and Radiation Physics (NILPRP), Atomistilor 409, P.O. Box MG 36, R-077125 Magurele, Bucharest (Romania); Vasile, E. [“Politehnica” University of Bucharest, Faculty of Applied Chemistry and Materials Science, Department of Oxide Materials and Nanomaterials, Gh. Polizu 1-7, Bucharest (Romania); Kovacs, G. [“Babes-Boyai” University, Faculty of Chemistry and Chemical Engineering, Arany Janos 11, Cluj-Napoca (Romania)

    2015-05-01

    Highlights: • TiO{sub 2}-based nanocomposites were obtained by one-step laser oxidative pyrolysis. • Titania particles are surrounded by/embedded in carbon/silica shells/matrix. • They contain an anatase/rutile mixture with mean crystalline diameters up to 24 nm. • Their carbon content decreased with the increasing of introduced air coflow. • Their bandgap energy decreased due to the carbon incorporation. - Abstract: Titania nanoparticles containing a mixture of anatase and rutile phases (with mean crystalline sizes up to 24 nm) covered with/embedded in carbon/silica thin layers or matrix were obtained in a single step using laser oxidative pyrolysis. Titanium tetrachloride and hexamethyldisiloxane (HMDSO) vapors were separately introduced into the reaction zone – both together with the laser-absorbing agent (sensitizer) ethylene – which acts also as carbon source – and the oxidant (air) – through the inner and the concentric nozzle, respectively. By increasing the air flow through the annular nozzle, while keeping constant the TiC{sub 4}, inner air, HMDSO and C{sub 2}H{sub 4} flows, the atomic carbon concentration as well as the rutile to anatase ratio in the resulted nanopowders decrease. A much brighter and extended flame was observed for the experiment involving the greatest air flow. The Ti/Si atomic ratio in the resulted nanocomposites was higher than that from the introduced precursors (1.8), indicating a partial siloxane conversion to silica. The annealed powders (at 450 °C to further carbon content reducing) exhibit a lower bandgap energy than those of the reference sample without silica (and also lower than the commercial Degussa P25 nano-TiO{sub 2})

  5. Preparation of acridine orange-doped silica nanoparticles for pH measurement

    International Nuclear Information System (INIS)

    Liu, Jinshui; Zang, Lingjie; Wang, Yiru; Liu, Guoning

    2014-01-01

    Acridine orange was first encapsulated into silica shell via a facile reverse microemusion method to built core–shell fluorescent nanoparticles. The nanoparticles are all in spherical shape and have a narrow size distribution, and its application as a optical pH sensor has been demonstrated. This novel sensor is based on the pH-dependent fluorescence intensities of acridine orange in different pH value. The fluorescence intensity of acridine orange-doped silica nanoparticles was decreased by increasing pH value. Under optimum conditions, the changes of fluorescence intensity were proportional to the pH value in the range of 8.00–10.90. In addition, the sensor can be easily separated by centrifugation and adds no pollution to the environment compared to the free dyes. Furthermore, the effects of ionic strength and co-existing substances were proved to have little influence on the determination of pH. The sensor has been successfully applied to determine the pH of two artificial samples. Hence, the core–shell fluorescent nanoparticles show potential for practical application. -- Highlights: • Acridine orange was encapsulated into silica shell via a facile reverse microemusion method to built core–shell fluorescent nanoparticles. • The fluorescence intensity of acridine orange-doped silica nanoparticles was decreased by increasing pH value. • Its can be used as an optical pH sensor. • The sensor can be easily separated by centrifugation and adds no pollution to the environment compared to the free dyes. • The sensor has been successfully applied to determine the pH of artificial samples

  6. Silica nanoparticle stability in biological media revisited.

    Science.gov (United States)

    Yang, Seon-Ah; Choi, Sungmoon; Jeon, Seon Mi; Yu, Junhua

    2018-01-09

    The stability of silica nanostructure in the core-silica shell nanomaterials is critical to understanding the activity of these nanomaterials since the exposure of core materials due to the poor stability of silica may cause misinterpretation of experiments, but unfortunately reports on the stability of silica have been inconsistent. Here, we show that luminescent silver nanodots (AgNDs) can be used to monitor the stability of silica nanostructures. Though relatively stable in water and phosphate buffered saline, silica nanoparticles are eroded by biological media, leading to the exposure of AgNDs from AgND@SiO 2 nanoparticles and the quenching of nanodot luminescence. Our results reveal that a synergistic effect of organic compounds, particularly the amino groups, accelerates the erosion. Our work indicates that silica nanostructures are vulnerable to cellular medium and it may be possible to tune the release of drug molecules from silica-based drug delivery vehicles through controlled erosion.

  7. Thermally stable silica-coated hydrophobic gold nanoparticles.

    Science.gov (United States)

    Kanehara, Masayuki; Watanabe, Yuka; Teranishi, Toshiharu

    2009-01-01

    We have successfully developed a method for silica coating on hydrophobic dodecanethiol-protected Au nanoparticles with coating thickness ranging from 10 to 40 nm. The formation of silica-coated Au nanoparticles could be accomplished via the preparation of hydrophilic Au nanoparticle micelles by cationic surfactant encapsulation in aqueous phase, followed by hydrolysis of tetraethylorthosilicate on the hydrophilic surface of gold nanoparticle micelles. Silica-coated Au nanoparticles exhibited quite high thermal stability, that is, no agglomeration of the Au cores could be observed after annealing at 600 degrees C for 30 min. Silica-coated Au nanoparticles could serve as a template to derive hollow nanoparticles. An addition of NaCN solution to silica-coated Au nanoparticles led the formation of hollow silica nanoparticles, which were redispersible in deionized water. The formation of the hollow silica nanoparticles results from the mesoporous structures of the silica shell and such a mesoporous structure is applicable to both catalyst support and drug delivery.

  8. Supercritical carbon dioxide behavior in porous silica aerogel

    International Nuclear Information System (INIS)

    Ciccariello, Salvino; Melnichenko, Yuri B.; He, Lilin

    2011-01-01

    Analysis of the tails of the small-angle neutron scattering (SANS) intensities relevant to samples formed by porous silica and carbon dioxide at pressures ranging from 0 to 20 MPa and at temperatures of 308 and 353 K confirms that the CO2 fluid must be treated as a two-phase system. The first of these phases is formed by the fluid closer to the silica wall than a suitable distance (delta) and the second by the fluid external to this shell. The sample scattering-length densities and shell thicknesses are determined by the Porod invariants and the oscillations observed in the Porod plots of the SANS intensities. The resulting matter densities of the shell regions (thickness 15-35 (angstrom)) are approximately equal, while those of the outer regions increase with pressure and become equal to the bulk CO2 at the higher pressures only in the low-temperature case.

  9. Studying the loading effect of acidic type antioxidant on amorphous silica nanoparticle carriers

    Science.gov (United States)

    Ravinayagam, Vijaya; Rabindran Jermy, B.

    2017-06-01

    The study investigates the suitable nanosilica carriers to transport acidic type cargo molecules for potential targeted drug delivery application. Using phenolic acidic type antioxidant gallic acid (GA) as model compound, the present study investigates the loading effect of GA (0.3-15.9 mmol GA g-1 support) on textural characteristics of amorphous silica nanoparticles such as Q10 silica (1D), structured two-dimensional Si-MCM-41 (2D), and three-dimensional Si-SBA-16 (3D). The variation in the nature of textures after GA loading was analyzed using X-ray diffraction, N2 adsorption, FT-IR, scanning electron microscopy with energy dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy. Among the nanocarriers, high adsorption of GA was found in the following order: Si-SBA-16 (3D)˜Si-KIT-6 (3D) > Si-MCM-41 (2D) > ultralarge pore FDU-12 (ULPFDU-12; 3D) > Q10 (1D)˜mesostructured cellular silica foam (MSU-F). 3D-type silicas Si-SBA-16 and KIT-6 were shown to maintain structural integrity at acidic condition (pH ˜3) and accommodate GA in non-crystalline form. In the case of ULPFDU-12 and MSU-F cellular foam, only crystalline deposition of GA occurs with a significant variation in the surface area and pore volume. [Figure not available: see fulltext.

  10. Optical properties of spherical and oblate spheroidal gold shell colloids

    NARCIS (Netherlands)

    Penninkhof, J.J.; Moroz, A.; van Blaaderen, A.; Polman, A.

    2008-01-01

    The surface plasmon modes of spherical and oblate spheroidal core−shell colloids composed of a 312 nm diameter silica core and a 20 nm thick Au shell are investigated. Large arrays of uniaxially aligned core−shell colloids with size aspect ratios ranging from 1.0 to 1.7 are fabricated using a novel

  11. Design and development of a layer-based additive manufacturing process for the realization of metal parts of designed mesostructure

    Science.gov (United States)

    Williams, Christopher Bryant

    Low-density cellular materials, metallic bodies with gaseous voids, are a unique class of materials that are characterized by their high strength, low mass, good energy absorption characteristics, and good thermal and acoustic insulation properties. In an effort to take advantage of this entire suite of positive mechanical traits, designers are tailoring the cellular mesostructure for multiple design objectives. Unfortunately, existing cellular material manufacturing technologies limit the design space as they are limited to certain part mesostructure, material type, and macrostructure. The opportunity that exists to improve the design of existing products, and the ability to reap the benefits of cellular materials in new applications is the driving force behind this research. As such, the primary research goal of this work is to design, embody, and analyze a manufacturing process that provides a designer the ability to specify the material type, material composition, void morphology, and mesostructure topology for any conceivable part geometry. The accomplishment of this goal is achieved in three phases of research: (1) Design---Following a systematic design process and a rigorous selection exercise, a layer-based additive manufacturing process is designed that is capable of meeting the unique requirements of fabricating cellular material geometry. Specifically, metal parts of designed mesostructure are fabricated via three-dimensional printing of metal oxide ceramic powder followed by post-processing in a reducing atmosphere. (2) Embodiment ---The primary research hypothesis is verified through the use of the designed manufacturing process chain to successfully realize metal parts of designed mesostructure. (3) Modeling & Evaluation ---The designed manufacturing process is modeled in this final research phase so as to increase understanding of experimental results and to establish a foundation for future analytical modeling research. In addition to an analysis of

  12. Amine-functionalized magnetic mesoporous silica nanoparticles for DNA separation

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Wei; Wei, Wei; Li, Junjian; Qi, Xiaoliang; Zuo, Gancheng; Chen, Qi; Pan, Xihao; Dong, Wei, E-mail: weidong@njust.edu.cn

    2016-11-30

    Highlights: • Fe{sub 3}O{sub 4}@SiO{sub 2}@EDPS with uniform size and good dispersity is prepared. • We fabricated MMSN@EDPS with distinct core-shell–shell triple-layer composition. • DNA adsorption capacity of MMSN@EDPS is considerable. - Abstract: We report a modified approach for the functionalized magnetic mesoporous silica nanoparticles (MMSN) using polymer microspheres incorporated with magnetic nanoparticles in the presence of cetyltrimethylammonium bromide (CTAB) and the core-shell magnetic silica nanoparticles (MSN). These particles were functionalized with amino groups via the addition of aminosilane directly to the particle sol. We then evaluate their DNA separation abilities and find the capacity of DNA binding significantly increased (210.22 μg/mg) compared with normal magnetic silica spheres (138.44 μg/mg) by using an ultraviolet and visible spectrophotometer (UV). The morphologies, magnetic properties, particle size, pore size, core-shell structure and Zeta potential are characterized by Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), Transmission electron microscopy (TEM), Powder X-ray diffraction (XRD), and dynamic light scattering (DLS). This work demonstrates that our MMSN own an excellent potential application in bioseparation and drug delivery.

  13. Micelle swelling agent derived cavities for increasing hydrophobic organic compound removal efficiency by mesoporous micelle@silica hybrid materials

    KAUST Repository

    Shi, Yifeng

    2012-06-01

    Mesoporous micelle@silica hybrid materials with 2D hexagonal mesostructures were synthesized as reusable sorbents for hydrophobic organic compounds (HOCs) removal by a facile one-step aqueous solution synthesis using 3-(trimethoxysily)propyl-octadecyldimethyl-ammonium chloride (TPODAC) as a structure directing agent. The mesopores were generated by adding micelle swelling agent, 1,3,5-trimethyl benzene, during the synthesis and removing it afterward, which was demonstrated to greatly increase the HOC removal efficiency. In this material, TPODAC surfactant is directly anchored on the pore surface of mesoporous silica via SiOSi covalent bond after the synthesis due to its reactive Si(OCH 3) 3 head group, and thus makes the synthesized materials can be easily regenerated for reuse. The obtained materials show great potential in water treatment as pollutants sorbents. © 2011 Elsevier Inc. All rights reserved.

  14. Mesostructured platinum-free anode and carbon-free cathode catalysts for durable proton exchange membrane fuel cells.

    Science.gov (United States)

    Cui, Xiangzhi; Shi, Jianlin; Wang, Yongxia; Chen, Yu; Zhang, Lingxia; Hua, Zile

    2014-01-01

    As one of the most important clean energy sources, proton exchange membrane fuel cells (PEMFCs) have been a topic of extensive research focus for decades. Unfortunately, several critical technique obstacles, such as the high cost of platinum electrode catalysts, performance degradation due to the CO poisoning of the platinum anode, and carbon corrosion by oxygen in the cathode, have greatly impeded its commercial development. A prototype of a single PEMFC catalyzed by a mesostructured platinum-free WO3/C anode and a mesostructured carbon-free Pt/WC cathode catalysts is reported herein. The prototype cell exhibited 93% power output of a standard PEMFC using commercial Pt/C catalysts at 50 and 70 °C, and more importantly, CO poisoning-free and carbon corrosion-resistant characters of the anode and cathode, respectively. Consequently, the prototype cell demonstrated considerably enhanced cell operation durability. The mesostructured electrode catalysts are therefore highly promising in the future development and application of PEMFCs. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Radiolarians decreased silicification as an evolutionary response to reduced Cenozoic ocean silica availability.

    Science.gov (United States)

    Lazarus, David B; Kotrc, Benjamin; Wulf, Gerwin; Schmidt, Daniela N

    2009-06-09

    It has been hypothesized that increased water column stratification has been an abiotic "universal driver" affecting average cell size in Cenozoic marine plankton. Gradually decreasing Cenozoic radiolarian shell weight, by contrast, suggests that competition for dissolved silica, a shared nutrient, resulted in biologic coevolution between radiolaria and marine diatoms, which expanded dramatically in the Cenozoic. We present data on the 2 components of shell weight change--size and silicification--of Cenozoic radiolarians. In low latitudes, increasing Cenozoic export of silica to deep waters by diatoms and decreasing nutrient upwelling from increased water column stratification have created modern silica-poor surface waters. Here, radiolarian silicification decreases significantly (r = 0.91, P stratification and abundance of diatoms. In high southern latitudes, Southern Ocean circulation, present since the late Eocene, maintains significant surface water silica availability. Here, radiolarian silicification decreased insignificantly (r = 0.58, P = 0.1), from approximately 0.13 at 35 Ma to 0.11 today. Trends in shell size in both time series are statistically insignificant and are not correlated with each other. We conclude that there is no universal driver changing cell size in Cenozoic marine plankton. Furthermore, biologic and physical factors have, in concert, by reducing silica availability in surface waters, forced macroevolutionary changes in Cenozoic low-latitude radiolarians.

  16. Synthesis of novel core-shell structured dual-mesoporous silica nanospheres and their application for enhancing the dissolution rate of poorly water-soluble drugs

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chao, E-mail: wuchao27@126.com [Department of Pharmaceutics, Liaoning Medical University, 40 Songpo Road, Linghe District, Jinzhou, Liaoning Province 121001 (China); Sun, Xiaohu [Management Center for Experiments, Bohai University, 19 Keji Road, Songshan District, Jinzhou, Liaoning Province 121000 (China); Zhao, Zongzhe; Zhao, Ying; Hao, Yanna; Liu, Ying [Department of Pharmaceutics, Liaoning Medical University, 40 Songpo Road, Linghe District, Jinzhou, Liaoning Province 121001 (China); Gao, Yu, E-mail: gaoyu_1116@163.com [Department of Medical Oncology, First Affiliated Hospital of Liaoning Medical University, 40 Songpo Road, Linghe District, Jinzhou, Liaoning Province 121001 (China)

    2014-11-01

    Novel core-shell dual-mesoporous silica nanospheres (DMSS) with a tunable pore size were synthesized successfully using a styrene monomer as a channel template for the core and cetyltrimethyl ammonium bromide (CTAB) as a channel template for the shell in order to improve the dissolution rate of poorly water-soluble drugs. Simvastatin was used as a model drug and loaded into DMSS and the mesoporous core without the shell (MSC) by the solvent evaporation method. The drug loading efficiency of DMSS and MSC were determined by thermogravimetric analysis (TGA) and ultraviolet spectroscopy (UV). Characterization, using scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR) showed that simvastatin adsorbed in DMSS and MSC was in an amorphous state, and in vitro release test results demonstrated that both DMSS and MSC increased the water solubility and dissolution rate of simvastatin. The shell structure of DMSS was able to regulate the release of simvastatin compared with MSC. It is worth noting that DMSS has significant potential as a carrier for improving the dissolution of poorly water-soluble drugs and reducing the rapid release. - Highlights: • A novel core-shell DMSS is prepared for improving the dissolution rate of simvastatin. • The diffusional resistance of the mesoporous shell can delay and regulate drug release. • Simvastatin absorbed in DMSS exists in amorphous form due to spatial confinement.

  17. Synthesis of novel core-shell structured dual-mesoporous silica nanospheres and their application for enhancing the dissolution rate of poorly water-soluble drugs

    International Nuclear Information System (INIS)

    Wu, Chao; Sun, Xiaohu; Zhao, Zongzhe; Zhao, Ying; Hao, Yanna; Liu, Ying; Gao, Yu

    2014-01-01

    Novel core-shell dual-mesoporous silica nanospheres (DMSS) with a tunable pore size were synthesized successfully using a styrene monomer as a channel template for the core and cetyltrimethyl ammonium bromide (CTAB) as a channel template for the shell in order to improve the dissolution rate of poorly water-soluble drugs. Simvastatin was used as a model drug and loaded into DMSS and the mesoporous core without the shell (MSC) by the solvent evaporation method. The drug loading efficiency of DMSS and MSC were determined by thermogravimetric analysis (TGA) and ultraviolet spectroscopy (UV). Characterization, using scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR) showed that simvastatin adsorbed in DMSS and MSC was in an amorphous state, and in vitro release test results demonstrated that both DMSS and MSC increased the water solubility and dissolution rate of simvastatin. The shell structure of DMSS was able to regulate the release of simvastatin compared with MSC. It is worth noting that DMSS has significant potential as a carrier for improving the dissolution of poorly water-soluble drugs and reducing the rapid release. - Highlights: • A novel core-shell DMSS is prepared for improving the dissolution rate of simvastatin. • The diffusional resistance of the mesoporous shell can delay and regulate drug release. • Simvastatin absorbed in DMSS exists in amorphous form due to spatial confinement

  18. Organosulfonic acid-functionalized mesoporous composites based on natural rubber and hexagonal mesoporous silica

    Energy Technology Data Exchange (ETDEWEB)

    Nuntang, Sakdinun; Poompradub, Sirilux [Fuels Research Center, Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Butnark, Suchada [PTT Research and Technology Institute, PTT Public Company Limited, Wangnoi, Ayutthaya 13170 (Thailand); Yokoi, Toshiyuki; Tatsumi, Takashi [Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Ngamcharussrivichai, Chawalit, E-mail: Chawalit.Ng@Chula.ac.th [Fuels Research Center, Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand)

    2014-10-15

    This study is the first report on synthesis, characterization and catalytic application of propylsulfonic acid-functionalized mesoporous composites based on natural rubber (NR) and hexagonal mesoporous silica (HMS). In comparison with propylsulfonic acid-functionalized HMS (HMS-SO{sub 3}H), a series of NR/HMS-SO{sub 3}H composites were prepared via an in situ sol–gel process using tetrahydrofuran as the synthesis media. Tetraethylorthosilicate as the silica source, was simultaneously condensed with 3-mercaptopropyltrimethoxysilane in a solution of NR followed by oxidation with hydrogen peroxide to achieve the mesoporous composites containing propylsulfonic acid groups. Fourier-transform infrared spectroscopy and {sup 29}Si MAS nuclear magnetic resonance spectroscopy results verified that the silica surfaces of the NR/HMS-SO{sub 3}H composites were functionalized with propylsulfonic acid groups and covered with NR molecules. After the incorporation of NR and organo-functional group into HMS, the hexagonal mesostructure remained intact concomitantly with an increased framework wall thickness and unit cell size, as evidenced by the X-ray powder diffraction analysis. Scanning electron microscopy analysis indicated a high interparticle porosity of NR/HMS-SO{sub 3}H composites. The textural properties of NR/HMS-SO{sub 3}H were affected by the amount of MPTMS loading to a smaller extent than that of HMS-SO{sub 3}H. NR/HMS-SO{sub 3}H exhibited higher hydrophobicity than HMS-SO{sub 3}H, as revealed by H{sub 2}O adsorption–desorption measurements. Moreover, the NR/HMS-SO{sub 3}H catalysts possessed a superior specific activity to HMS-SO{sub 3}H in the esterification of lauric acid with ethanol, resulting in a higher conversion level. - Highlights: • Acidic NR/HMS-SO{sub 3}H composites were prepared by in situ sol–gel process. • Propylsulfonic acid was functionalized onto HMS surface by direct co-condensation. • NR/HMS-SO{sub 3}H exhibited a hexagonal

  19. Surface zwitterionicalization of poly(vinylidene fluoride) membranes from the entrapped reactive core-shell silica nanoparticles.

    Science.gov (United States)

    Zhu, Li-Jing; Zhu, Li-Ping; Zhang, Pei-Bin; Zhu, Bao-Ku; Xu, You-Yi

    2016-04-15

    We demonstrate the preparation and properties of poly(vinylidene fluoride) (PVDF) filtration membranes modified via surface zwitterionicalization mediated by reactive core-shell silica nanoparticles (SiO2 NPs). The organic/inorganic hybrid SiO2 NPs grafted with poly(methyl meth acrylate)-block-poly(2-dimethylaminoethyl methacrylate) copolymer (PMMA-b-PDMAEMA) shell were prepared by surface-initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization and then used as a membrane-making additive of PVDF membranes. The PDMAEMA exposed on membrane surface and pore walls were quaternized into zwitterionic poly(sulfobetaine methacrylate) (PSBMA) using 1,3-propane sultone (1,3-PS) as the quaternization agent. The membrane surface chemistry and morphology were analyzed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The hydrophilicity, permeability and antifouling ability of the investigated membranes were evaluated in detail. It was found that the PSBMA chains brought highly-hydrophilic and strong fouling resistant characteristics to PVDF membranes due to the powerful hydration of zwitterionic surface. The SiO2 cores and PMMA chains in the hybrid NPs play a role of anchors for the linking of PSBMA chains to membrane surface. Compared to the traditional strategies for membrane hydrophilic modification, the developed method in this work combined the advantages of both blending and surface reaction. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Facile synthesis of mesostructured ZSM-5 zeolite with enhanced mass transport and catalytic performances

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chao; Ren, Yanqun [School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Tianhe District, Guangzhou 510641 (China); Gou, Jinsheng [College Material Science and Technology, Beijing Forestry University, Key Laboratory of Wooden Material Science and Application, Ministry of Education, 35 Tsinghua East Road, Haidian District, Beijing 100083 (China); Liu, Baoyu [School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Tianhe District, Guangzhou 510641 (China); Xi, Hongxia, E-mail: cehxxi@scut.edu.cn [School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Tianhe District, Guangzhou 510641 (China)

    2017-01-15

    Highlights: • A mesostructured MFI zeolite was synthesized via dual-functional surfactant approach. • Mass transport was investigated by applying zero length column technique. • The catalyst exhibited excellent catalytic activity and long lifetime. • Gaussian DFT was employed to study the role of surfactant in crystallization process. - Abstract: A mesostructured ZSM-5 zeolite with multilamellar structure was successfully synthesized by employing a tetra-headgroup rigid bolaform quaternary ammonium surfactant. It was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherms, amines temperature programmed desorption (amines-TPD), and computer simulation. These results indicated that the dual-functional amphiphilic surfactants play a critical role for directing the multilamellar structure with high mesoporosity. The mass transport and catalytic performances of the zeolite were investigated by zero length column (ZLC) technique and aldol condensation reactions to evaluate the structure-property relationship. These results clearly indicated that the mass transport of selected molecules in hierarchical zeolite can be accelerated by introducing mesoporous structure with mesostructure with reduced diffusion length and an overall enhanced resistance against deactivation in reactions involving large molecules. Furthermore, the dual-functional surfactant approach of making hierarchical zeolite with MFI nanosheets framework would open up new opportunities for design and synthesis of hierarchical zeolites with controllable mesoporous structures.

  1. Facile synthesis of mesostructured ZSM-5 zeolite with enhanced mass transport and catalytic performances

    International Nuclear Information System (INIS)

    Li, Chao; Ren, Yanqun; Gou, Jinsheng; Liu, Baoyu; Xi, Hongxia

    2017-01-01

    Highlights: • A mesostructured MFI zeolite was synthesized via dual-functional surfactant approach. • Mass transport was investigated by applying zero length column technique. • The catalyst exhibited excellent catalytic activity and long lifetime. • Gaussian DFT was employed to study the role of surfactant in crystallization process. - Abstract: A mesostructured ZSM-5 zeolite with multilamellar structure was successfully synthesized by employing a tetra-headgroup rigid bolaform quaternary ammonium surfactant. It was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherms, amines temperature programmed desorption (amines-TPD), and computer simulation. These results indicated that the dual-functional amphiphilic surfactants play a critical role for directing the multilamellar structure with high mesoporosity. The mass transport and catalytic performances of the zeolite were investigated by zero length column (ZLC) technique and aldol condensation reactions to evaluate the structure-property relationship. These results clearly indicated that the mass transport of selected molecules in hierarchical zeolite can be accelerated by introducing mesoporous structure with mesostructure with reduced diffusion length and an overall enhanced resistance against deactivation in reactions involving large molecules. Furthermore, the dual-functional surfactant approach of making hierarchical zeolite with MFI nanosheets framework would open up new opportunities for design and synthesis of hierarchical zeolites with controllable mesoporous structures.

  2. Nanoengineering of methylene blue loaded silica encapsulated magnetite nanospheres and nanocapsules for photodynamic therapy

    Energy Technology Data Exchange (ETDEWEB)

    Andhariya, Nidhi [Bhavnagar University, Department of Physics (India); Chudasama, Bhupendra, E-mail: bnchudasama@gmail.com [Thapar University, School of Physics and Materials Science (India); Mehta, R. V. [Bhavnagar University, Department of Physics (India); Upadhyay, R. V. [Charotar University of Science and Technology, P.D. Patel Institute of Applied Sciences (India)

    2011-09-15

    Core-shell nanostructures have emerged as an important class of functional materials with potential applications in diverse fields, especially in health sciences. In this article, nanoengineering of novel magnetic colloidal dispersion containing surface modifiable silica with a core of single domain magnetite nanoparticles loaded with photosensitizer (PS) drug 'Methylene blue' (MB) has been described. Magnetite core is produced by the well-established chemical coprecipitation technique and silica shell is formed over it by the modified hydrolysis and condensation of TEOS (tetraethyl orthosilicate). Conditions for reaction kinetics have been established to tailor the core-shell structures in the form of nanospheres and nanocapsules. MB is loaded into the nanostructures by demethylation reaction. The major conclusion drawn from this study is that the synthesis route yields stable, non-aggregated MB loaded superparamagnetic magnetite-silica nanostructures with tailored morphology, tunable loading, and excellent magnetic properties.

  3. A rational repeating template method for synthesis of 2D hexagonally ordered mesoporous precious metals.

    Science.gov (United States)

    Takai, Azusa; Doi, Yoji; Yamauchi, Yusuke; Kuroda, Kazuyuki

    2011-03-01

    A repeating template method is presented for the synthesis of mesoporous metals with 2D hexagonal mesostructures. First, a silica replica (i.e., silica nanorods arranged periodically) is prepared by using 2D hexagonally ordered mesoporous carbon as the template. After that, the obtained silica replica is used as the second template for the preparation of mesoporous ruthenium. After the ruthenium species are introduced into the silica replica, the ruthenium species are then reduced by a vapor-infiltration method by using the reducing agent dimethylamine borane. After the ruthenium deposition, the silica is chemically removed. Analysis by transmission and scanning electron microscopies, a nitrogen-adsorption-desorption isotherm, and small-angle X-ray scattering revealed that the mesoporous ruthenium had a 2D hexagonal mesostructure, although the mesostructural ordering is decreased compared to that of the original mesoporous carbon template. This method is widely applicable to other metal systems. By changing the metal species introduced into the silica replica, several mesoporous metals (palladium and platinum) can be synthesized. Ordered mesoporous ruthenium and palladium, which are not easily attainable by the soft-templating methods, can be prepared. This study has overcome the composition variation limitations of the soft-templating method. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Sequential Vapor Infiltration Treatment Enhances the Ionic Current Rectification Performance of Composite Membranes Based on Mesoporous Silica Confined in Anodic Alumina.

    Science.gov (United States)

    Liang, Yanyan; Liu, Zhengping

    2016-12-20

    Ionic current rectification of nanofluidic diode membranes has been studied widely in recent years because it is analogous to the functionality of biological ion channels in principle. We report a new method to fabricate ionic current rectification membranes based on mesoporous silica confined in anodic aluminum oxide (AAO) membranes. Two types of mesostructured silica nanocomposites, hexagonal structure and nanoparticle stacked structure, were used to asymmetrically fill nanochannels of AAO membranes by a vapor-phase synthesis (VPS) method with aspiration approach and were further modified via sequence vapor infiltration (SVI) treatment. The ionic current measurements indicated that SVI treatment can modulate the asymmetric ionic transport in prepared membranes, which exhibited clear ionic current rectification phenomenon under optimal conditions. The ionic current rectifying behavior is derived from the asymmetry of surface conformations, silica species components, and hydrophobic wettability, which are created by the asymmetrical filling type, silica depositions on the heterogeneous membranes, and the condensation of silanol groups. This article provides a considerable strategy to fabricate composite membranes with obvious ionic current rectification performance via the cooperation of the VPS method and SVI treatment and opens up the potential of mesoporous silica confined in AAO membranes to mimic fluid transport in biological processes.

  5. Bone tissue engineering using silica-based mesoporous nanobiomaterials:Recent progress.

    Science.gov (United States)

    Shadjou, Nasrin; Hasanzadeh, Mohammad

    2015-10-01

    Bone disorders are of significant concern due to increase in the median age of our population. It is in this context that tissue engineering has been emerging as a valid approach to the current therapies for bone regeneration/substitution. Tissue-engineered bone constructs have the potential to alleviate the demand arising from the shortage of suitable autograft and allograft materials for augmenting bone healing. Silica based mesostructured nanomaterials possessing pore sizes in the range 2-50 nm and surface reactive functionalities have elicited immense interest due to their exciting prospects in bone tissue engineering. In this review we describe application of silica-based mesoporous nanomaterials for bone tissue engineering. We summarize the preparation methods, the effect of mesopore templates and composition on the mesopore-structure characteristics, and different forms of these materials, including particles, fibers, spheres, scaffolds and composites. Also, the effect of structural and textural properties of mesoporous materials on development of new biomaterials for production of bone implants and bone cements was discussed. Also, application of different mesoporous materials on construction of manufacture 3-dimensional scaffolds for bone tissue engineering was discussed. It begins by giving the reader a brief background on tissue engineering, followed by a comprehensive description of all the relevant components of silica-based mesoporous biomaterials on bone tissue engineering, going from materials to scaffolds and from cells to tissue engineering strategies that will lead to "engineered" bone. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Assembly of core–shell structured porous carbon–graphene composites as anode materials for lithium-ion batteries

    International Nuclear Information System (INIS)

    Guo, Rong; Zhao, Li; Yue, Wenbo

    2015-01-01

    As potential anode materials for lithium-ion batteries, mesoporous carbons such as CMK-3 and CMK-8 usually show stable cycling performances but only slightly higher reversible capacities than commercial graphite. Graphene has much higher theoretical capacity than that of graphite in theory. However, its electrochemical behavior is not as good as expected due to the aggregation of graphene nanosheets. Herein we describe a novel strategy for the preparation of core–shell structured porous carbon–graphene composites. Compared to pure porous carbons or pure graphene nanosheets, these novel composites exhibit superior electrochemical performances including higher reversible capacities and better cycle/rate performances. This core–shell structure can avoid the aggregation of graphene nanosheets as well as may stabilize the mesostructure of porous carbon, which is beneficial to improving the electrochemical performances of the composites

  7. Modeling of absorption and scattering properties of core -shell nanoparticles for application as nanoantenna in optical domain

    Science.gov (United States)

    Devi, Jutika; Saikia, Rashmi; Datta, Pranayee

    2016-10-01

    The present paper describes the study of core-shell nanoparticles for application as nanoantenna in the optical domain. To obtain the absorption and extinction efficiencies as well as the angular distribution of the far field radiation pattern and the resonance wavelengths for these metal-dielectric, dielectric-metal and metal-metal core-shell nanoparticles in optical domain, we have used Finite Element Method based COMSOL Multiphysics Software and Mie Theory. From the comparative study of the extinction efficiencies of core-shell nanoparticles of different materials, it is found that for silica - gold core - shell nanoparticles, the resonant wavelength is greater than that of the gold - silver, silver-gold and gold-silica core - shell nanoparticles and also the radiation pattern of the silica-gold core-shell nanoparticle is the most suitable one from the point of view of directivity. The dielectric functions of the core and shell material as well as of the embedded matrix are extremely important and plays a very major role to tune the directivity and resonance wavelength. Such highly controllable parameters of the dielectric - metal core - shell nanoparticles make them suitable for efficient coupling of optical radiation into nanoscale structures for a broad range of applications in the field of communications.

  8. Modeling of absorption and scattering properties of core -shell nanoparticles for application as nanoantenna in optical domain

    International Nuclear Information System (INIS)

    Devi, Jutika; Datta, Pranayee; Saikia, Rashmi

    2016-01-01

    The present paper describes the study of core-shell nanoparticles for application as nanoantenna in the optical domain. To obtain the absorption and extinction efficiencies as well as the angular distribution of the far field radiation pattern and the resonance wavelengths for these metal-dielectric, dielectric-metal and metal-metal core-shell nanoparticles in optical domain, we have used Finite Element Method based COMSOL Multiphysics Software and Mie Theory. From the comparative study of the extinction efficiencies of core-shell nanoparticles of different materials, it is found that for silica - gold core - shell nanoparticles, the resonant wavelength is greater than that of the gold - silver, silver-gold and gold-silica core - shell nanoparticles and also the radiation pattern of the silica-gold core-shell nanoparticle is the most suitable one from the point of view of directivity. The dielectric functions of the core and shell material as well as of the embedded matrix are extremely important and plays a very major role to tune the directivity and resonance wavelength. Such highly controllable parameters of the dielectric - metal core - shell nanoparticles make them suitable for efficient coupling of optical radiation into nanoscale structures for a broad range of applications in the field of communications. (paper)

  9. Nano-structured silica coated mesoporous carbon micro-granules for potential application in water filtration

    Science.gov (United States)

    Das, Avik; Sen, D.; Mazumder, S.; Ghosh, A. K.

    2017-05-01

    A novel nano-composite spherical micro-granule has been synthesized using a facile technique of solvent evaporation induced assembly of nanoparticles for potential application in water filtration. The spherical micro-granule is comprised of nano-structured shell of hydrophilic silica encapsulating a hydrophobic mesoporous carbon at the core. Hierarchical structure of such core-shell micro-granules has been rigorously characterized using small-angle neutron and X-ray scattering techniques and complemented with scanning electron microscopy. The hydrophilic silica envelope around the carbon core helps in incorporation of such granules into the hydrophilic polymeric ultra-filtration membrane. The interstitial micro-pores present in the silica shell can serve as water transport channels and the mesoporus carbon core enhances the separation performance due its well adsorption characteristics. It has been found that the incorporation of such granules inside the ultra-filtration membrane indeed enhances the water permeability as well as the separation performance in a significant way.

  10. Electrochemiluminescence immunosensor for ultrasensitive detection of biomarker using Ru(bpy)(3)(2+)-encapsulated silica nanosphere labels.

    Science.gov (United States)

    Qian, Jing; Zhou, Zhenxian; Cao, Xiaodong; Liu, Songqin

    2010-04-14

    Here, we describe a new approach for electrochemiluminescence (ECL) assay with Ru(bpy)(3)(2+)-encapsulated silica nanoparticle (SiO(2)@Ru) as labels. A water-in-oil (W/O) microemulsion method was employed for one-pot synthesis of SiO(2)@Ru nanoparticles. The as-synthesized SiO(2)@Ru nanoparticles have a narrow size distribution, which allows reproducible loading of Ru(bpy)(3)(2+) inside the silica shell and of alpha-fetoprotein antibody (anti-AFP), a model antibody, on the silica surface with glutaraldehyde as linkage. The silica shell effectively prevents leakage of Ru(bpy)(3)(2+) into the aqueous solution due to strong electrostatic interaction between the positively charged Ru(bpy)(3)(2+) and the negatively charged surface of silica. The porous structure of silica shell allowed the ion to move easily through the pore to exchange energy/electrons with the entrapped Ru(bpy)(3)(2+). The as-synthesized SiO(2)@Ru can be used as a label for ultrasensitive detection of biomarkers through a sandwiched immunoassay process. The calibration range of AFP concentration was 0.05-30 ng mL(-1) with linear relation from 0.05 to 20 ng mL(-1) and a detection limit of 0.035 ng mL(-1) at 3sigma. The resulting immunosensors possess high sensitivity and good analytical performance. Copyright 2010 Elsevier B.V. All rights reserved.

  11. Preparation of gluten-free bread using a meso-structured whey protein particle system

    NARCIS (Netherlands)

    Riemsdijk, van L.E.; Goot, van der A.J.; Hamer, R.J.; Boom, R.M.

    2011-01-01

    This article presents a novel method for making gluten-free bread using mesoscopically structured whey protein. The use of the meso-structured protein is based on the hypothesis that the gluten structure present in a developed wheat dough features a particle structure on a mesoscopic length scale

  12. Time-Resolved Small-Angle X-Ray Scattering

    NARCIS (Netherlands)

    ten Elshof, Johan E.; Besselink, R.; Stawski, Tomasz; Castricum, H.L.; Levy, D.; Zayat, M.

    2015-01-01

    This chapter focuses on time-resolved studies of nanostructure development in sol-gel liquids, that is, diluted sols, wet gels, and drying thin fffilms. The most commonly investigated classes of sol-gel materials are silica, organically modified silica, template-directed mesostructured silica,

  13. Mesostructured Au/C materials obtained by replication of functionalized SBA-15 silica containing highly dispersed gold nanoparticles

    KAUST Repository

    Kerdi, Fatmé ; Caps, Valerie; Tuel, Alain

    2011-01-01

    was the same for both series and apparently did not depend on the nature of the silica template. Both Au/SiO2 templates and their corresponding Au/CMK-3 materials have been characterized by X-ray diffraction, nitrogen adsorption/desorption, chemical analysis

  14. Meso-structures of dynamical chaos and E-infinity theory

    International Nuclear Information System (INIS)

    Mukhamedov, A.M.

    2009-01-01

    A novel proposal is made to develop a unified theory of dynamical chaos using an idea of extra-coordinates. It is supposed that chaos is capable to translate influences from quantum level of description to the classical macroscopic one and vise versa. The notion of macroscopically prepared microstates is proposed to determine a special case of extra-coordinates induced by cooperative effects at quantum resolution of dynamical events. Meso-structures mediating quantum and classical appearances of chaotic motion are studied in the light of E-infinity theory.

  15. A study of mesoporous silica-encapsulated gold nanorods as enhanced light scattering probes for cancer cell imaging

    Energy Technology Data Exchange (ETDEWEB)

    Zhan Qiuqiang; Qian Jun; Li Xin; He Sailing, E-mail: qianjun@coer.zju.edu.cn [Centre for Optical and Electromagnetic Research, State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310058 (China)

    2010-02-05

    Mesoporous encapsulation of gold nanorods (GNRs) in a silica shell of controllable thickness (4.5-25.5 nm) was realized through a single-step coating method without any intermediary coating. The dependence of localized surface plasmon resonance (LSPR) extinction spectra of the coated GNRs on the thickness of the silica shell was investigated with both simulation and experiments, which agreed well with each other. It was found that cetyltrimethyl ammonium bromide (CTAB) molecules, which act as surfactants for the GNRs and dissociate in the solution, greatly affect the silica coating. Mesoporous silica-encapsulated GNRs were also shown to be highly biocompatible and stable in bio-environments. Based on LSPR enhanced scattering, mesoporous silica-encapsulated GNRs were utilized for dark field scattering imaging of cancer cells. Biomolecule-conjugated mesoporous silica-encapsulated GNRs were specifically taken up by cancer cells in vitro, justifying their use as effective optical probes for early cancer diagnosis. Mesoporous silica can also be modified with functional groups and conjugated with certain biomolecules for specific labeling on mammalian cells as well as carrying drugs or biomolecules into biological cells.

  16. Preparation and unique electrical behaviors of monodispersed hybrid nanorattles of metal nanocores with hairy electroactive polymer shells.

    Science.gov (United States)

    Cai, Tao; Zhang, Bin; Chen, Yu; Wang, Cheng; Zhu, Chun Xiang; Neoh, Koon-Gee; Kang, En-Tang

    2014-03-03

    A versatile template-assisted strategy for the preparation of monodispersed rattle-type hybrid nanospheres, encapsulating a movable Au nanocore in the hollow cavity of a hairy electroactive polymer shell (Au@air@PTEMA-g-P3HT hybrid nanorattles; PTEMA: poly(2-(thiophen-3-yl)ethyl methacrylate; P3HT: poly(3-hexylthiophene), was reported. The Au@silica core-shell nanoparticles, prepared by the modified Stöber sol-gel process on Au nanoparticle seeds, were used as templates for the synthesis of Au@silica@PTEMA core-double shell nanospheres. Subsequent oxidative graft polymerization of 3-hexylthiophene from the exterior surface of the Au@silica@PTEMA core-double shell nanospheres allowed the tailoring of surface functionality with electroactive P3HT brushes (Au@silica@PTEMA-g-P3HT nanospheres). The Au@air@ PTEMA-g-P3HT hybrid nanorattles were obtained after etching of the silica interlayer by HF. The as-prepared nanorattles were dispersed into an electrically insulating polystyrene matrix and for the first time used to fabricate nonvolatile memory devices. As a result, unique electrical behaviors, including insulator behavior, write-once-read-many-times and rewritable memory effects, and conductor behavior as well, were observed in the Al/Au@air@PTEMA-g-P3HT+PS/ITO (ITO: indium-tin oxide) sandwich thin-film devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Advances in Multicompartment Mesoporous Silica Micro/Nanoparticles for Theranostic Applications.

    Science.gov (United States)

    Liu, Jian; Liu, Tingting; Pan, Jian; Liu, Shaomin; Lu, G Q Max

    2018-04-04

    Mesoporous silica nanoparticles (MSNs) are promising functional nanomaterials for a variety of biomedical applications, such as bioimaging, drug/gene delivery, and cancer therapy. This is due to their low density, low toxicity, high biocompatibility, large specific surface areas, and excellent thermal and mechanical stability. The past decade has seen rapid advances in the development of MSNs with multiple compartments. These include hierarchical porous structures and core-shell, yolk-shell, and Janus structured particles for efficient diagnosis and therapeutic applications. We review advances in this area, covering the categories of multicompartment MSNs and their synthesis methods, with an emphasis on hierarchical structures and the incorporation of multiple functions. We classify multicompartment mesoporous silica micro/nanostructures, ranging from core-shell and yolk-shell structures to Janus and raspberry-like nanoparticles, and discuss their synthesis methods. We review applications of these multicompartment MSNs, including bioimaging, targeted drug/gene delivery, chemotherapy, phototherapy, and in vitro diagnostics. We also highlight the latest trends and new opportunities. Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering Volume 9 is June 7, 2018. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

  18. Silica encapsulation of luminescent silicon nanoparticles: stable and biocompatible nanohybrids

    Energy Technology Data Exchange (ETDEWEB)

    Maurice, Vincent [CEA Saclay, DSM/IRAMIS/SPAM-LFP (France); Rivolta, Ilaria [University of Milano-Bicocca, Department of Experimental Medicine (DIMS) (Italy); Vincent, Julien [CEA Saclay, DSM/IRAMIS/SPAM-LFP (France); Raccurt, Olivier [CEA Grenoble, Department of Nano Materials, NanoChemistry and NanoSafety Laboratory (DRT/LITEN/DTNM/LCSN) (France); Rouzaud, Jean-Noel [Ecole Normale superieure de Paris, Laboratoire de Geologie (France); Miserrochi, Giuseppe [University of Milano-Bicocca, Department of Experimental Medicine (DIMS) (Italy); Doris, Eric [CEA, Service de Chimie Bioorganique et de Marquage, iBiTecS (France); Reynaud, Cecile; Herlin-Boime, Nathalie, E-mail: nathalie.herlin@cea.fr [CEA Saclay, DSM/IRAMIS/SPAM-LFP (France)

    2012-02-15

    This article presents a process for surface coating and functionalization of luminescent silicon nanoparticles. The particles were coated with silica using a microemulsion process that was adapted to the fragile silicon nanoparticles. The as-produced core-shell particles have a mean diameter of 35 nm and exhibit the intrinsic photoluminescence of the silicon core. The silica layer protects the core from aqueous oxidation for several days, thus allowing the use of the nanoparticles for biological applications. The nanoparticles were further coated with amines and functionalized with polyethylene glycol chains and the toxicity of the particles has been evaluated at the different stages of the process. The core-shell nanoparticles exhibit no acute toxicity towards lung cells, which is promising for further development.

  19. Silica coating of luminescent quantum dots prepared in aqueous media for cellular labeling

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yunfei; Li, Yan, E-mail: yli@ecust.edu.cn; Zhong, Xinhua, E-mail: zhongxh@ecust.edu.cn

    2014-12-15

    Graphical abstract: A facile route based on modified Stöber method was used for the synthesis of silica coated QDs (QD@SiO{sub 2}) starting from aqueously prepared CdTe/CdS QDs. The resultant QD@SiO{sub 2} exhibited a significant increase in emission efficiency compared with that of the initial QDs, along with a small size (∼5 nm in diameter), great stability and low cytotoxicity, which makes it a good candidate as robust biomarker. - Highlights: • We present a facile modified Stöber method to prepare highly luminescent QD@SiO{sub 2}. • The PL efficiency of QDs increases significantly after silica coating. • QD@SiO{sub 2} exhibits small size (∼5 nm) and great dispersibility in aqueous solution. • QD@SiO{sub 2} presents extraordinary photo and colloidal stability. • The silica shell eliminates QD cytotoxicity, providing the access of bioconjugation. - Abstract: Silica coating is an effective approach for rendering luminescent quantum dots (QDs) with water dispersibility and biocompatibility. However, it is still challenging to prepare silica-coated QDs (QD@SiO{sub 2}) with high emission efficiency, small size and great stability in favor for bioapplication. Herein, we reported a modified Stöber method for silica coating of aqueously-prepared CdTe/CdS QDs. With the coexistence of Cd{sup 2+} and thioglycolic acid (TGA), a thin silica shell was formed around QDs by the hydrolysis of tetraethyl orthosilicate (TEOS). The resultant QD@SiO{sub 2} with a small size (∼5 nm in diameter) exhibits significantly higher emission efficiencies than that of the initial QDs. Also, QD@SiO{sub 2} has extraordinary photo and colloidal stability (pH range of 5–13, 4.0 M NaCl solution). Protected by the silica shell, the cytotoxicity of QDs could be reduced. Moreover, the QD@SiO{sub 2} conjugated with folic acid (FA) presents high specific binding toward receptor-positive HeLa cells over receptor-negative A549 cells.

  20. Biomimetic silica encapsultation of living cells

    Science.gov (United States)

    Jaroch, David Benjamin

    Living cells perform complex chemical processes on size and time scales that artificial systems cannot match. Cells respond dynamically to their environment, acting as biological sensors, factories, and drug delivery devices. To facilitate the use of living systems in engineered constructs, we have developed several new approaches to create stable protective microenvironments by forming bioinspired cell-membrane-specific silica-based encapsulants. These include vapor phase deposition of silica gels, use of endogenous membrane proteins and polysaccharides as a site for silica nucleation and polycondensation in a saturated environment, and protein templated ordered silica shell formation. We demonstrate silica layer formation at the surface of pluripotent stem-like cells, bacterial biofilms, and primary murine and human pancreatic islets. Materials are characterized by AFM, SEM and EDS. Viability assays confirm cell survival, and metabolite flux measurements demonstrate normal function and no major diffusion limitations. Real time PCR mRNA analysis indicates encapsulated islets express normal levels of genetic markers for β-cells and insulin production. The silica glass encapsulant produces a secondary bone like calcium phosphate mineral layer upon exposure to media. Such bioactive materials can improve device integration with surrounding tissue upon implantation. Given the favorable insulin response, bioactivity, and long-term viability observed in silica-coated islets, we are currently testing the encapsulant's ability to prevent immune system recognition of foreign transplants for the treatment of diabetes. Such hybrid silica-cellular constructs have a wide range of industrial, environmental, and medical applications.

  1. Hierarchically structured transparent hybrid membranes by in situ growth of mesostructured organosilica in host polymer

    Science.gov (United States)

    Vallé, Karine; Belleville, Philippe; Pereira, Franck; Sanchez, Clément

    2006-02-01

    The elaborate performances characterizing natural materials result from functional hierarchical constructions at scales ranging from nanometres to millimetres, each construction allowing the material to fit the physical or chemical demands occurring at these different levels. Hierarchically structured materials start to demonstrate a high input in numerous promising applied domains such as sensors, catalysis, optics, fuel cells, smart biologic and cosmetic vectors. In particular, hierarchical hybrid materials permit the accommodation of a maximum of elementary functions in a small volume, thereby optimizing complementary possibilities and properties between inorganic and organic components. The reported strategies combine sol-gel chemistry, self-assembly routes using templates that tune the material's architecture and texture with the use of larger inorganic, organic or biological templates such as latex, organogelator-derived fibres, nanolithographic techniques or controlled phase separation. We propose an approach to forming transparent hierarchical hybrid functionalized membranes using in situ generation of mesostructured hybrid phases inside a non-porogenic hydrophobic polymeric host matrix. We demonstrate that the control of the multiple affinities existing between organic and inorganic components allows us to design the length-scale partitioning of hybrid nanomaterials with tuned functionalities and desirable size organization from ångström to centimetre. After functionalization of the mesoporous hybrid silica component, the resulting membranes have good ionic conductivity offering interesting perspectives for the design of solid electrolytes, fuel cells and other ion-transport microdevices.

  2. Synthesis and surface modification of hydrophobic magnetite to processible magnetite at silica-propylamine

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Kyoungja [Korea Institute of Science and Technology, Nanomaterials Research Center, P.O. Box 131, Cheongryang, Seoul 130-650 (Korea, Republic of)]. E-mail: kjwoo@kist.re.kr; Hong, Jangwon [Korea Institute of Science and Technology, Nanomaterials Research Center, P.O. Box 131, Cheongryang, Seoul 130-650 (Korea, Republic of); Ahn, Jae-Pyoung [Korea Institute of Science and Technology, Nanomaterials Research Center, P.O. Box 131, Cheongryang, Seoul 130-650 (Korea, Republic of)

    2005-05-15

    Hydrophobic magnetite nanoparticles with a narrow size distribution were prepared by thermal decomposition of Fe(CO){sub 5} in octyl ether solution of oleic acid and by consecutive aeration. The nanoparticles were converted into magnetite core/silica shell (magnetite at silica) structured particles with hydrophilic and processible aminopropyl groups on their surfaces.

  3. Controlled drug release from bifunctionalized mesoporous silica

    Science.gov (United States)

    Xu, Wujun; Gao, Qiang; Xu, Yao; Wu, Dong; Sun, Yuhan; Shen, Wanling; Deng, Feng

    2008-10-01

    Serial of trimethylsilyl-carboxyl bifunctionalized SBA-15 (TMS/COOH/SBA-15) have been studied as carriers for controlled release of drug famotidine (Famo). To load Famo with large capacity, SBA-15 with high content of carboxyl groups was successfully synthesized by one-pot synthesis under the assistance of KCl. The mesostructure of carboxyl functionalized SBA-15 (COOH/SBA-15) could still be kept even though the content of carboxyl groups was up to 57.2%. Increasing carboxyl content could effectively enhance the loading capacity of Famo. Compared with pure SBA-15, into which Famo could be hardly adsorbed, the largest drug loading capacity of COOH/SBA-15 could achieve 396.9 mg/g. The release of Famo from mesoporous silica was studied in simulated intestine fluid (SIF, pH=7.4). For COOH/SBA-15, the release rate of Famo decreased with narrowing pore size. After grafting TMS groups on the surface of COOH/SBA-15 with hexamethyldisilazane, the release of Famo was greatly delayed with the increasing content of TMS groups.

  4. Utilization of Snail (Achatina fulica Shell Waste for Synthesis of Calcium Tartrate Tetrahydrate (CaC4H4O6.4H2O Single Crystals in Silica Gel

    Directory of Open Access Journals (Sweden)

    Imam Sakdi

    2012-01-01

    Full Text Available Snail (Achatina fulica shell waste is massively produced by many home industries in Indonesia, especially in East Java. The snail shell is known for high calcium; therefore it is potential to be used as calcium source of supernatant in the synthesis of piezoeletric material, such as single crystal of calcium tartrate tetrahydrate (CaTT. The aim of this research is to study the synthesis and characterization of CaTT or CaC4H4O6.4H2O from snail shell waste in silica gel. Supernatant solution of CaCl2 was prepared from CaO, which previously made by calcinating the shell at 1000°C, and then reacted with HCl 1,5M. Synthesis of CaTT was conducted in a single-tube reaction at room temperature in which silica gel was used as growth medium with gelling time of 10 days and growth time of 2 weeks. The pH of gel and CaCl2 concentration were varied, 3.00; 3.50; 4.00; 4.50; 5.00; and 0.27; 0.36; 0.45; 0.54 M respectively, in order to obtain optimum condition of the synthesis, which is indicated from crystal yields. The synthesized crystals were characterized by atomic adsorption spectrophotometry (AAS, infrared spectroscopy (IR and powder X-ray diffraction (XRD. Experimental data shows that optimum condition was obtained at pH of 3.50 and [CaCl2] of 0.45M with yield of 69.37%. The obtained single crystal has clear color and octahedral-like shape with size ranged between 4 – 9 mm. Analysis data by FTIR and powder XRD confirmed that the obtained crystal was CaTT single crystals with crystal system of orthorhombic.

  5. Rare Earth-Activated Silica-Based Nanocomposites

    Directory of Open Access Journals (Sweden)

    C. Armellini

    2007-01-01

    Full Text Available Two different kinds of rare earth-activated glass-based nanocomposite photonic materials, which allow to tailor the spectroscopic properties of rare-earth ions: (i Er3+-activated SiO2-HfO2 waveguide glass ceramic, and (ii core-shell-like structures of Er3+-activated silica spheres obtained by a seed growth method, are presented.

  6. Hypersonic vibrations of Ag@SiO2 (cubic core)-shell nanospheres.

    Science.gov (United States)

    Sun, Jing Ya; Wang, Zhi Kui; Lim, Hock Siah; Ng, Ser Choon; Kuok, Meng Hau; Tran, Toan Trong; Lu, Xianmao

    2010-12-28

    The intriguing optical and catalytic properties of metal-silica core-shell nanoparticles, inherited from their plasmonic metallic cores together with the rich surface chemistry and increased stability offered by their silica shells, have enabled a wide variety of applications. In this work, we investigate the confined vibrational modes of a series of monodisperse Ag@SiO(2) (cubic core)-shell nanospheres synthesized using a modified Stöber sol-gel method. The particle-size dependence of their mode frequencies has been mapped by Brillouin light scattering, a powerful tool for probing hypersonic vibrations. Unlike the larger particles, the observed spheroidal-like mode frequencies of the smaller ones do not scale with inverse diameter. Interestingly, the onset of the deviation from this linearity occurs at a smaller particle size for higher-energy modes than for lower-energy ones. Finite element simulations show that the mode displacement profiles of the Ag@SiO(2) core-shells closely resemble those of a homogeneous SiO(2) sphere. Simulations have also been performed to ascertain the effects that the core shape and the relative hardness of the core and shell materials have on the vibrations of the core-shell as a whole. As the vibrational modes of a particle have a bearing on its thermal and mechanical properties, the findings would be of value in designing core-shell nanostructures with customized thermal and mechanical characteristics.

  7. A microemulsion preparation of nanoparticles of europium in silica with luminescence enhancement using silver

    International Nuclear Information System (INIS)

    Ma Zhiya; Dosev, Dosi; Kennedy, Ian M

    2009-01-01

    A facile one-pot microemulsion method has been developed for the synthesis of spherical silver core-silica shell (Ag-SiO 2 ) nanoparticles with europium chelates doped in the shell through a silane agent. The method is significantly more straightforward than other extant methods. Measurements of the luminescent emissions from the Ag-SiO 2 nanoparticles, in comparison with control silica nanoparticles without silver cores, showed that the presence of the silver cores can increase the fluorescence intensity approximately 24-fold and decrease the luminescence lifetime. This enhancement offers a potential increase in overall particle detectability with increased fluorophore photostability.

  8. An organosilane-directed growth-induced etching strategy for preparing hollow/yolk–shell mesoporous organosilica nanospheres with perpendicular mesochannels and amphiphilic frameworks

    KAUST Repository

    Zou, Houbing

    2014-06-27

    We have developed an organosilane-directed growth-induced etching strategy to prepare hollow periodic mesoporous organosilica (PMO) nanospheres with perpendicular mesoporous channels and a clear hollow interior as well as an amphiphilic framework. This facile strategy is simple, efficient, and highly controllable. Silica nanospheres were utilized as hard templates to obtain hollow PMO nanospheres through a one-step route, with the structure parameter highly controlled by adjusting the synthesis conditions. Different organosilanes were used to obtain bridged hollow PMO nanospheres of different organic groups and showed different directed capacities. The integrity of the bridged organic group was confirmed by Fourier-transform infrared (FT-IR) spectroscopy and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Transmission electron microscopy (TEM) observations showed that the growth of the PMO shell and the dissolution of the silica nanosphere core occurred simultaneously for each nanosphere, while 29Si NMR spectra revealed that the dissolved silica species from the silica nanospheres transformed into PMO shells by co-condensation with hydrolyzed organosilane oligomers. As a result, the obtained hollow nanospheres were amphiphilic, which can even be used as a particle emulsifier for O-W or W-O emulsion in various systems. These materials can also be served as an efficient sorbent for removal of hydrophobic contaminants in water. Using the proposed formation mechanism, this strategy can be extended to transform silica-coated composite materials into yolk-shell structures with a functional interior core and a perpendicular mesoporous amphiphilic shell. As a nanoreactor, the -Ph- bridged amphiphilic shell showed a faster diffusion rate for organic reactants in water than the hydrophilic silica shell, and thus better catalytic activity for reduction of 4-nitrophenol. This journal is © the Partner Organisations 2014.

  9. Development of SiO2@TiO2 core-shell nanospheres for catalytic applications

    Science.gov (United States)

    Kitsou, I.; Panagopoulos, P.; Maggos, Th.; Arkas, M.; Tsetsekou, A.

    2018-05-01

    Silica-titania core-shell nanospheres, CSNp, were prepared via a simple and environmentally friendly two step route. First, silica cores were prepared through the hydrolysis-condensation reaction of silicic acid in the presence of hyperbranched poly(ethylene)imine (HBPEI) followed by repeating washing, centrifugation and, finally, calcination steps. To create the core-shell structure, various amounts of titanium isopropoxide were added to the cores and after that a HBPEI-water solution was added to hydrolyze the titanium precursor. Washing with ethanol and heat treatment followed. The optimization of processing parameters led to well-developed core-shell structures bearing a homogeneous nanocrystalline anatase coating over each silica core. The photocatalytic activity for NO was examined in a continuous flux photocatalytic reactor under real environmental conditions. The results revealed a very potent photocatalyst as the degradation percentage reached 84.27% for the core-shell material compared to the 82% of pure titania with the photodecomposition rates measured at 0.62 and 0.55 μg·m-2·s-1, respectively. In addition, catalytic activities of the CSNp and pure titania were investigated by monitoring the reduction of 4-nitrophenol to 4-aminophenol by an excess of NaBH4. Both materials exhibited excellent catalytic activity (100%), making the core-shell material a promising alternative catalyst to pure titania for various applications.

  10. Synthesis of mesoporous hollow silica nanospheres using polymeric micelles as template and their application as a drug-delivery carrier.

    Science.gov (United States)

    Sasidharan, Manickam; Zenibana, Haruna; Nandi, Mahasweta; Bhaumik, Asim; Nakashima, Kenichi

    2013-10-07

    Mesoporous hollow silica nanospheres with uniform particle sizes of 31-33 nm have been successfully synthesized by cocondensation of tetramethoxysilane (TMOS) and alkyltrimethoxysilanes [RSi(OR)3], where the latter also acts as a porogen. ABC triblock copolymer micelles of poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) with a core-shell-corona architecture have been employed as a soft template at pH 4. The cationic shell block with 2-vinyl pyridine groups facilitates the condensation of silica precursors under the sol-gel reaction conditions. Phenyltrimethoxysilane, octyltriethoxysilane, and octadecyltriethoxysilanes were used as porogens for generating mesopores in the shell matrix of hollow silica and the octadecyl precursor produced the largest mesopore among the different porogens, of dimension ca. 4.1 nm. The mesoporous hollow particles were thoroughly characterized by small-angle X-ray diffraction (SXRD), thermal (TG/DTA) and nitrogen sorption analyses, infra-red (FTIR) and nuclear magnetic resonance ((13)C-CP MAS NMR and (29)Si MAS NMR) spectroscopies, and transmission electron microscopy (TEM). The mesoporous hollow silica nanospheres have been investigated for drug-delivery application by an in vitro method using ibuprofen as a model drug. The hollow silica nanospheres exhibited higher storage capacity than the well-known mesoporous silica MCM-41. Propylamine functionalized hollow particles show a more sustained release pattern than their unfunctionalized counterparts, suggesting a huge potential of hollow silica nanospheres in the controlled delivery of small drug molecules.

  11. Minute-made and low carbon fingerprint microwave synthesis of high quality templated mesoporous silica

    KAUST Repository

    Chaignon, J.; Bouizi, Y.; Davin, L.; Calin, N.; Albela, B.; Bonneviot, L.

    2015-01-01

    © The Royal Society of Chemistry 2015. Hexagonal mesostructured templated silicas were produced in less than 10 minutes using an ultra-fast microwave assisted hydrothermal synthesis. Typically, 10 g can be prepared at once in a commercial microwave device usually devoted to analytical digestion. Undesired alcohol side-products were avoided using inexpensive water colloidal silica instead of silicon alkoxides as the silicon source. In comparison with classical heating activation, the absence of pore expansion and pore wall thickening even for synthesis temperatures as high as 190 °C evidenced that heat transfer and diffusion of matter had no time to take place. Comparison between the chemically extracted and calcined samples shows that the structure was better stabilized for autoclaving above 150 °C. However, a fast temperature ramping and final temperatures above 180 °C were required to sear structures of the highest quality comparable to that of the best conventional methods. This is rationalized by assuming a sequential flake-by-flake assembly of the pore-wall at the micelle palisade. Notably, tosylate counterions yielded better structural characteristics than bromide counterions and allowed better opportunities for surfactant recycling.

  12. A novel synthesis of micrometer silica hollow sphere

    International Nuclear Information System (INIS)

    Pan Wen; Ye Junwei; Ning Guiling; Lin Yuan; Wang Jing

    2009-01-01

    Silica microcapsules (hollow spheres) were synthesized successfully by a novel CTAB-stabilized water/oil emulsion system mediated hydrothermal method. The addition of urea to a solution of aqueous phase was an essential step of the simple synthetic procedure of silica hollow spheres, which leads to the formation of silica hollow spheres with smooth shell during hydrothermal process. The intact hollow spheres were obtained by washing the as-synthesized solid products with distilled water to remove the organic components. A large amount of silanol groups were retained in the hollow spheres by this facile route without calcination. The morphologies and optical properties of the product were characterized by transmission electron microscopy, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Furthermore, on the basis of a series of SEM observations, phenomenological elucidation of a mechanism for the growth of the silica hollow spheres has been presented

  13. Silica-Assisted Nucleation of Polymer Foam Cells with Nanoscopic Dimensions : Impact of Particle Size, Line Tension, and Surface Functionality

    NARCIS (Netherlands)

    Liu, Shanqiu; Eijkelenkamp, Rik; Duvigneau, Joost; Vancso, G. Julius

    2017-01-01

    Core-shell nanoparticles consisting of silica as core and surface-grafted poly(dimethylsiloxane) (PDMS) as shell with different diameters were prepared and used as heterogeneous nucleation agents to obtain CO2-blown poly(methyl methacrylate) (PMMA) nanocomposite foams. PDMS was selected as the shell

  14. One-pot synthesis and characterization of rhodamine derivative-loaded magnetic core-shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Jin, E-mail: jzhang@eng.uwo.ca; Li Jiaxin [University of Western Ontario, Department of Chemical and Biochemical Engineering (Canada); Razavi, Fereidoon S. [Brock University, Department of Physics (Canada); Mumin, Abdul Md. [University of Western Ontario, Department of Chemical and Biochemical Engineering (Canada)

    2011-05-15

    A new method to produce elaborate nanostructure with magnetic and fluorescent properties in one entity is reported in this article. Magnetite (Fe{sub 3}O{sub 4}) coated with fluorescent silica (SiO{sub 2}) shell was produced through the one-pot reaction, in which one reactor was utilized to realize the synthesis of superparamagnetic core of Fe{sub 3}O{sub 4}, the formation of SiO{sub 2} coating through the condensation and polymerization of tetraethylorthosilicate (TEOS), and the encapsulation of tetramethyl rhodamine isothiocyanate-dextran (TRITC-dextran) within silica shell. Transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, and X-ray diffraction (XRD) were carried out to investigate the core-shell structure. The magnetic core of the core-shell nanoparticles is 60 {+-} 10 nm in diameter. The thickness of the fluorescent SiO{sub 2} shell is estimated at 15 {+-} 5 nm. In addition, the fluorescent signal of the SiO{sub 2} shell has been detected by the laser confocal scanning microscopy (LCSM) with emission wavelength ({lambda}{sub em}) at 566 nm. In addition, the magnetic properties of TRITC-dextran loaded silica-coating iron oxide nanoparticles (Fe{sub 3}O{sub 4}-SiO{sub 2} NPs) were studied. The hysteresis loop of the core-shell NPs measured at room temperature shows that the saturation magnetization (M{sub s}) is not reached even at the field of 70 kOe (7T). Meanwhile, the very low coercivity (H{sub c}) and remanent magnetization (M{sub r}) are 0.375 kOe and 6.6 emu/g, respectively, at room temperature. It indicates that the core-shell particles have the superparamagnetic properties. The measured blocking temperature (T{sub B}) of the TRITC-dextran loaded Fe{sub 3}O{sub 4}-SiO{sub 2} NPs is about 122.5 K. It is expected that the multifunctional core-shell nanoparticles can be used in bio-imaging.

  15. Electrochemiluminescence immunosensor for ultrasensitive detection of biomarker using Ru(bpy){sub 3}{sup 2+}-encapsulated silica nanosphere labels

    Energy Technology Data Exchange (ETDEWEB)

    Qian Jing [School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189 (China); Zhou Zhenxian [Nanjing Second Hospital, Nanjing, 210003 (China); Cao Xiaodong [School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189 (China); Liu Songqin, E-mail: liusq@seu.edu.cn [School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189 (China)

    2010-04-14

    Here, we describe a new approach for electrochemiluminescence (ECL) assay with Ru(bpy){sub 3}{sup 2+}-encapsulated silica nanoparticle (SiO{sub 2}-Ru) as labels. A water-in-oil (W/O) microemulsion method was employed for one-pot synthesis of SiO{sub 2}-Ru nanoparticles. The as-synthesized SiO{sub 2}-Ru nanoparticles have a narrow size distribution, which allows reproducible loading of Ru(bpy){sub 3}{sup 2+} inside the silica shell and of {alpha}-fetoprotein antibody (anti-AFP), a model antibody, on the silica surface with glutaraldehyde as linkage. The silica shell effectively prevents leakage of Ru(bpy){sub 3}{sup 2+} into the aqueous solution due to strong electrostatic interaction between the positively charged Ru(bpy){sub 3}{sup 2+} and the negatively charged surface of silica. The porous structure of silica shell allowed the ion to move easily through the pore to exchange energy/electrons with the entrapped Ru(bpy){sub 3}{sup 2+}. The as-synthesized SiO{sub 2}-Ru can be used as a label for ultrasensitive detection of biomarkers through a sandwiched immunoassay process. The calibration range of AFP concentration was 0.05-30 ng mL{sup -1} with linear relation from 0.05 to 20 ng mL{sup -1} and a detection limit of 0.035 ng mL{sup -1} at 3{sigma}. The resulting immunosensors possess high sensitivity and good analytical performance.

  16. A Highly Stable and Magnetically Recyclable Nanocatalyst System: Mesoporous Silica Spheres Embedded with FeCo/Graphitic Shell Magnetic Nanoparticles and Pt Nanocatalysts.

    Science.gov (United States)

    Kim, Da Jeong; Li, Yan; Kim, Yun Jin; Hur, Nam Hwi; Seo, Won Seok

    2015-12-01

    We have developed a highly stable and magnetically recyclable nanocatalyst system for alkene hydrogenation. The materials are composed of mesoporous silica spheres (MSS) embedded with FeCo/graphitic shell (FeCo/GC) magnetic nanoparticles and Pt nanocatalysts (Pt-FeCo/GC@MSS). The Pt-FeCo/GC@MSS have superparamagnetism at room temperature and show type IV isotherm typical for mesoporous silica, thereby ensuring a large enough inner space (surface area of 235.3 m(2)  g(-1), pore volume of 0.165 cm(3)  g(-1), and pore diameter of 2.8 nm) to undergo catalytic reactions. We have shown that the Pt-FeCo/GC@MSS system readily converts cyclohexene into cyclohexane, which is the only product isolated and Pt-FeCo/GC@MSS can be seperated very quickly by an external magnetic field after the catalytic reaction is finished. We have demonstrated that the recycled Pt-FeCo/GC@MSS can be reused further for the same hydrogenation reaction at least four times without loss in the initial catalytic activity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Thermal stability and surface acidity of mesoporous silica doubly doped by incorporation of sulfate and zirconium ions

    International Nuclear Information System (INIS)

    Salas, P.; Chen, L.F.; Wang, J.A.; Armendariz, H.; Guzman, M.L.; Montoya, J.A.; Acosta, D.R.

    2005-01-01

    A sulfated Si-Zr-MCM-41 solid with highly ordered mesostructure was synthesized through a templated synthesis route where the CTAB surfactant was used as template. During the synthesis procedure, various amounts of (NH 4 ) 2 SO 4 were added into the mixed solution of Zr and Si precursors to in situ sulfate the MCM-41 solids, aiming to enhance the acidity and thermal stability. The resultant materials showed a long-range ordered hexagonal arrangement with high surface area larger than 797 m 2 /g and an average pore size distributed at approximate 2.5-2.8 nm. The high-resolution TEM observations confirmed that the order of the mesostructure gained when the molar ratio of SO 4 2- /(ZrO 2 + SiO 2 ) increased from 0.1 to 0.3 but decreased as it reached 0.5, which is consistent with the results of 29 Si MAS-NMR and XRD analysis. Compared to Si-MCM-41, the (Q 2 + Q 3 )/Q 4 ratio derived from the NMR spectra of the Zr-doped sample was higher, indicating that zirconium atoms were incorporated into the silica framework. Unexpectedly, in situ sulfation does not enhance the surface Broensted acidity, most likely due to the sulfur retained within the bulk of the materials; however, it indeed improved the thermal stability of the solid and long-range order of the structure

  18. Fabrication of superhydrophobic fluorinated silica nanoparticles for multifunctional liquid marbles

    Science.gov (United States)

    Shang, Qianqian; Hu, Lihong; Hu, Yun; Liu, Chengguo; Zhou, Yonghong

    2018-01-01

    A facile one-pot method for the fabrication of superhydrophobic fluorinated silica nanoparticles is reported. Fluorinated aggregated silica (A-SiO2/FAS) nanoparticles were synthesized by controlling the nanoparticles assembly, in situ fixation and overgrowth of particle seeds with the assist of tetraethoxysilane (TEOS) in ethanol/water solution and then modification with fluoroalkylsilane (FAS) molecules. Such kind of A-SiO2/FAS nanoparticles showed superhydrophobicity and was not wetted by water, thus it could be served as the encapsulating shells to manipulate liquid droplets. Liquid marbles fabricated from A-SiO2/FAS nanoparticles were used for ammonia gas sensing or emitting by taking advantage of the porosity and superhydrophobicity of the liquid marble shells. In addition, the posibility of A-SiO2/FAS-based liquid marbles as microreactor for dopamine polymerization also was explored.

  19. Selective oxidation of cyclohexene through gold functionalized silica monolith microreactors

    Science.gov (United States)

    Alotaibi, Mohammed T.; Taylor, Martin J.; Liu, Dan; Beaumont, Simon K.; Kyriakou, Georgios

    2016-04-01

    Two simple, reproducible methods of preparing evenly distributed Au nanoparticle containing mesoporous silica monoliths are investigated. These Au nanoparticle containing monoliths are subsequently investigated as flow reactors for the selective oxidation of cyclohexene. In the first strategy, the silica monolith was directly impregnated with Au nanoparticles during the formation of the monolith. The second approach was to pre-functionalize the monolith with thiol groups tethered within the silica mesostructure. These can act as evenly distributed anchors for the Au nanoparticles to be incorporated by flowing a Au nanoparticle solution through the thiol functionalized monolith. Both methods led to successfully achieving even distribution of Au nanoparticles along the length of the monolith as demonstrated by ICP-OES. However, the impregnation method led to strong agglomeration of the Au nanoparticles during subsequent heating steps while the thiol anchoring procedure maintained the nanoparticles in the range of 6.8 ± 1.4 nm. Both Au nanoparticle containing monoliths as well as samples with no Au incorporated were tested for the selective oxidation of cyclohexene under constant flow at 30 °C. The Au free materials were found to be catalytically inactive with Au being the minimum necessary requirement for the reaction to proceed. The impregnated Au-containing monolith was found to be less active than the thiol functionalized Au-containing material, attributable to the low metal surface area of the Au nanoparticles. The reaction on the thiol functionalized Au-containing monolith was found to depend strongly on the type of oxidant used: tert-butyl hydroperoxide (TBHP) was more active than H2O2, likely due to the thiol induced hydrophobicity in the monolith.

  20. Spectroscopic and magnetic studies of highly dispersible superparamagnetic silica coated magnetite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Tadyszak, Krzysztof [NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań (Poland); Institute of Molecular Physics Polish Academy of Sciences, ul. Mariana Smo.luchowskiego 17, 60-179 Poznań (Poland); Kertmen, Ahmet, E-mail: ahmet.kertmen@pg.gda.pl [Department of Pharmaceutical Technology and Biochemistry, Faculty of Chemistry, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk (Poland); Coy, Emerson [NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań (Poland); Andruszkiewicz, Ryszard; Milewski, Sławomir [Department of Pharmaceutical Technology and Biochemistry, Faculty of Chemistry, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk (Poland); Kardava, Irakli; Scheibe, Błażej; Jurga, Stefan [NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań (Poland); Chybczyńska, Katarzyna, E-mail: katarzyna.chybczynska@ifmpan.poznan.pl [Institute of Molecular Physics Polish Academy of Sciences, ul. Mariana Smo.luchowskiego 17, 60-179 Poznań (Poland)

    2017-07-01

    Highlights: • Superparamagnetic core-shell nanoparticles of Fe{sub 2}O{sub 3}@Silica were obtained. • Magnetic response was studied by DC, AC magnetometry and EPR spectroscopy. • Nanoparticles show magnetite structure with a well-defined Verwey transition. • Samples show no inter particle magnetic interactions or agglomeration. - Abstract: Superparamagnetic behavior in aqueously well dispersible magnetite core-shell Fe{sub 3}O{sub 4}@SiO{sub 2} nanoparticles is presented. The magnetic properties of core-shell nanoparticles were measured with use of the DC, AC magnetometry and EPR spectroscopy. Particles where characterized by HR-TEM and Raman spectroscopy, showing a crystalline magnetic core of 11.5 ± 0.12 nm and an amorphous silica shell of 22 ± 1.5 nm in thickness. The DC, AC magnetic measurements confirmed the superparamagnetic nature of nanoparticles, additionally the EPR studies performed at much higher frequency than DC, AC magnetometry (9 GHz) have confirmed the paramagnetic nature of the nanoparticles. Our results show the excellent magnetic behavior of the particles with a clear magnetite structure, which are desirable properties for environmental remediation and biomedical applications.

  1. Cyclodextrin-Triazole Derivative Functionalized on Ag-SiO{sub 2} Core-Shell Nanoparticles via Click Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Park, Gun Bae; Singu, Bal Sydulu; Hong, Sang Eun; Yoon, Kuk Ro [Hannam Univ., Daejeon (Korea, Republic of)

    2016-09-15

    Click chemistry has provided a versatile strategy for functionalization in solution chemistry under mild reaction conditions with a high degree of functional group compatibility. Initially, silver (Ag) nanoparticles were prepared by the chemical reduction method, followed by the synthesis of silver–silica (Ag–SiO{sub 2}) core–shell nanoparticles by the Stöber method. The Ag–SiO2 core shell nanoparticles were functionalized with the alkyne derivative. The cycloaddition reaction between the azide-functionalized cyclodextrin and the alkyne-functionalized Ag–SiO{sub 2} core–shell nanoparticles was carried out via the copper-catalyzed click reaction, leading to the formation of the cyclodextrin-triazole derivative on the Ag–SiO{sub 2} core–shell nanoparticles. The presence of the resulting cyclodextrin-triazole derivative on the silver–silica core–shell nanoparticles was confirmed by Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA).

  2. Fixed-bed adsorption separation of xylene isomers over sio2/silicallite-1 core-shell adsorbents

    KAUST Repository

    Khan, Easir A.; Rajendran, Arvind; Lai, Zhiping

    2013-01-01

    SiO2/Silicalite-1 core-shell material has been demonstrated as potential shape selective adsorbent in gas phase separation of p-xylene from a mixture of p/o-xylene isomers. The core-shell composite comprised of large silica core and thin

  3. Agricultural waste as a source for the production of silica nanoparticles.

    Science.gov (United States)

    Vaibhav, Vineet; Vijayalakshmi, U; Roopan, S Mohana

    2015-03-15

    The major interest of the paper deals with the extraction of silica from four natural sources such as rice husk, bamboo leaves, sugarcane bagasse and groundnut shell. These waste materials in large quantities can create a serious environmental problem. Hence, there is a need to adopt proper strategy to reduce the waste. In the present investigation, all the waste materials are subjected to moisture removal in a hot plate and sintered at 900°C for 7 h. The sintered powder was treated with 1 M NaOH to form sodium silicate and then with 6M H2SO4 to precipitate silica. The prepared silica powders were characterized by FT-IR, XRD and SEM-EDAX analysis. The silica recovered from different sources was found to vary between 52% and 78%. Magnesium substituted silica was formed from the groundnut waste and further treatment is required to precipitate silica. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Constitutive relation of concrete containing meso-structural characteristics

    Directory of Open Access Journals (Sweden)

    Li Guo

    Full Text Available A constitutive model of concrete is proposed based on the mixture theory of porous media within thermodynamic framework. By treating concrete as a multi-phase multi-component mixture, we constructed the constitutive functions for elastic, interfacial, and plastic strain energy respectively. A constitutive law of concrete accommodating internal micro-cracks and interfacial boundaries was established. The peak stress predicted with the developed model depends primarily on the volume ratio of aggregate, and the results explain very well reported experimental phenomena. The strain-stress curve under uniaxial loading was found in a good agreement with experimental data for concrete with three different mixing proportions. Keywords: Constitutive model of concrete, Mixture theory of porous media, Meso-structure, Interfacial energy

  5. Non-Topotactic Transformation of Silicate Nanolayers into Mesostructured MFI Zeolite Frameworks During Crystallization.

    Science.gov (United States)

    Berkson, Zachariah J; Messinger, Robert J; Na, Kyungsu; Seo, Yongbeom; Ryoo, Ryong; Chmelka, Bradley F

    2017-05-02

    Mesostructured MFI zeolite nanosheets are established to crystallize non-topotactically through a nanolayered silicate intermediate during hydrothermal synthesis. Solid-state 2D NMR analyses, with sensitivity enhanced by dynamic nuclear polarization (DNP), provide direct evidence of shared covalent 29 Si-O- 29 Si bonds between intermediate nanolayered silicate moieties and the crystallizing MFI zeolite nanosheet framework. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Magnetic and fluorescent core-shell nanoparticles for ratiometric pH sensing

    International Nuclear Information System (INIS)

    Lapresta-Fernandez, Alejandro; Doussineau, Tristan; Moro, Artur J; Dutz, Silvio; Steiniger, Frank; Mohr, Gerhard J

    2011-01-01

    This paper describes the preparation of nanoparticles composed of a magnetic core surrounded by two successive silica shells embedding two fluorophores, showing uniform nanoparticle size (50-60 nm in diameter) and shape, which allow ratiometric pH measurements in the pH range 5-8. Uncoated iron oxide magnetic nanoparticles (∼10 nm in diameter) were formed by the coprecipitation reaction of ferrous and ferric salts. Then, they were added to a water-in-oil microemulsion where the hydrophilic silica shells were obtained through hydrolysis and condensation of tetraethoxyorthosilicate together with the corresponding silylated dye derivatives-a sulforhodamine was embedded in the inner silica shell and used as the reference dye while a pH-sensitive fluorescein was incorporated in the outer shell as the pH indicator. The magnetic nanoparticles were characterized using vibrating sample magnetometry, dynamic light scattering, transmission electron microscopy, x-ray diffraction and Fourier transform infrared spectroscopy. The relationship between the analytical parameter, that is, the ratio of fluorescence between the sensing and reference dyes versus the pH was adjusted to a sigmoidal fit using a Boltzmann type equation giving an apparent pK a value of 6.8. The fluorescence intensity of the reference dye did not change significantly (∼3.0%) on modifying the pH of the nanoparticle dispersion. Finally, the proposed method was statistically validated against a reference procedure using samples of water and physiological buffer with 2% of horse serum, indicating that there are no significant statistical differences at a 95% confidence level.

  7. Influence of Shell Thickness on the Colloidal Stability of Magnetic Core-Shell Particle Suspensions.

    Science.gov (United States)

    Neville, Frances; Moreno-Atanasio, Roberto

    2018-01-01

    We present a Discrete Element study of the behavior of magnetic core-shell particles in which the properties of the core and the shell are explicitly defined. Particle cores were considered to be made of pure iron and thus possessed ferromagnetic properties, while particle shells were considered to be made of silica. Core sizes ranged between 0.5 and 4.0 μm with the actual particle size of the core-shell particles in the range between 0.6 and 21 μm. The magnetic cores were considered to have a magnetization of one tenth of the saturation magnetization of iron. This study aimed to understand how the thickness of the shell hinders the formation of particle chains. Chain formation was studied with different shell thicknesses and particle sizes in the presence and absence of an electrical double layer force in order to investigate the effect of surface charge density on the magnetic core-shell particle interactions. For core sizes of 0.5 and 4.0 μm the relative shell thicknesses needed to hinder the aggregation process were approximately 0.4 and 0.6 respectively, indicating that larger core sizes are detrimental to be used in applications in which no flocculation is needed. In addition, the presence of an electrical double layer, for values of surface charge density of less than 20 mC/m 2 , could stop the contact between particles without hindering their vertical alignment. Only when the shell thickness was considerably larger, was the electrical double layer able to contribute to the full disruption of the magnetic flocculation process.

  8. A facile synthesis approach and impact of shell formation on morphological structure and luminescent properties of aqueous dispersible NaGdF{sub 4}:Yb/Er upconversion nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Ansari, Anees A., E-mail: aneesaansari@gmail.com [King Saud University, King Abdullah Institute for Nanotechnology (Saudi Arabia); Yadav, Ranvijay; Rai, S. B. [Banaras Hindu University, Department of Physics (India)

    2016-12-15

    A general facile synthesis approach was used for fabrication of highly emissive aqueous dispersible hexagonal phase upconversion luminescent NaGdF{sub 4}:Yb/Er nanorods (core NRs) through metal complex decomposition process. An inert NaGdF{sub 4} and porous silica layers were grafted surrounding the surface of each and every NRs to enhance their luminescence efficiency and colloidal dispersibility in aqueous environment. Optical properties in terms of band gap energy of core, core/shell, and silica-coated core/shell/SiO{sub 2} nanorods were observed to investigate the influence of surface coating, which was gradually decreased after surface coating because of increase crystalline size after growth of inert and silica shells. The inert shell formation before silica surface grafting, upconversion luminescence intensity was greatly improved by about 20 times, owing to the effective surface passivation of the seed core and, therefore, protection of Er{sup 3+} ion in the core from the nonradiative decay caused by surface defects. Moreover, after silica coating, core/shell nanorods shows strong upconversion luminescence property similar to the hexagonal upconversion core NRs. It is expected that these NaGdF{sub 4}:Yb/Er@NaGdF{sub 4}@SiO{sub 2} (core/shell/SiO{sub 2}) NRs including highly upconversion emissive and aqueous dispersible properties make them an ideal materials for various photonic-based potential applications such as in upconversion luminescent bioimaging, magnetic resonance imaging, and photodynamic therapy.

  9. Nanoengineered mesoporous silica nanoparticles for smart delivery of doxorubicin

    Science.gov (United States)

    Mishra, Akhilesh Kumar; Pandey, Himanshu; Agarwal, Vishnu; Ramteke, Pramod W.; Pandey, Avinash C.

    2014-08-01

    The motive of the at hand exploration was to contrive a proficient innovative pH-responsive nanocarrier designed for an anti-neoplastic agent that not only owns competent loading capacity but also talented to liberate the drug at the specific site. pH sensitive hollow mesoporous silica nanoparticles ( MSN) have been synthesized by sequence of chemical reconstruction with an average particle size of 120 nm. MSN reveal noteworthy biocompatibility and efficient drug loading magnitude. Active molecules such as Doxorubicin (DOX) can be stocked and set free from the pore vacuities of MSN by tuning the pH of the medium. The loading extent of MSN was found up to 81.4 wt% at pH 7.8. At mild acidic pH, DOX is steadily released from the pores of MSN. Both, the nitrogen adsorption-desorption isotherms and X-ray diffraction patterns reflects that this system holds remarkable stable mesostructure. Additionally, the outcomes of cytotoxicity assessment further establish the potential of MSN as a relevant drug transporter which can be thought over an appealing choice to a polymeric delivery system.

  10. An effective approach to synthesis of poly(methyl methacrylate)/silica nanocomposites

    International Nuclear Information System (INIS)

    Ding Xuefeng; Wang Zichen; Han Dongxue; Zhang Yuanjian; Shen Yanfei; Wang Zhijuan; Niu Li

    2006-01-01

    A novel synthetic route for nearly monodispersed poly(methyl methacrylate)/SiO 2 composite particles (PMSCP) is reported. Silica nanoparticles modified with oleic acid were used as 'seeds'. Methyl methacrylate (MMA) monomer was copolymerized with oleic acid via in situ emulsion polymerization, in the presence of an initiator; it resulted finally in the formation of composites with core-shell morphology. The composite particles were examined by transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The number of silica particles inside the composite particles increases with an increase in the silica concentration. The effect of grafted silica concentration on the morphology of PMSCP is also reported in detail. It was found by thermogravimetric analysis that PMSCP show a potential application for fire retardance

  11. Ultrafast Dynamics of Metallo-Dielectric Core-Shell Particles

    NARCIS (Netherlands)

    Shan, X.

    2008-01-01

    Optical properties of metallic nano-structures have attracted a lot of attention in the past decades. In this thesis, we focus on nano-sized silica-core gold-shell particles, study the linear, nonlinear and acoustic vibrations of the particles. The linear optical properties in the visible range of

  12. Quantitative analysis of silica aerogel-based thermal insulation coatings

    DEFF Research Database (Denmark)

    Kiil, Søren

    2015-01-01

    containing intact hollow glass or polymer spheres showed that silica aerogel particles are more efficient in an insulation coating than hollow spheres. In a practical (non-ideal) comparison, the ranking most likely cannot be generalized. A parameter study demonstrates how the model can be used, qualitatively......A mathematical heat transfer model for a silica aerogel-based thermal insulation coating was developed. The model can estimate the thermal conductivity of a two-component (binder-aerogel) coating with potential binder intrusion into the nano-porous aerogel structure. The latter is modelled using...... a so-called core–shell structure representation. Data from several previous experimental investigations with silica aerogels in various binder matrices were used for model validation. For some relevant cases with binder intrusion, it was possible to obtain a very good agreement between simulations...

  13. Plasma-assisted atomic layer deposition of TiO2 compact layers for flexible mesostructured perovskite solar cells

    NARCIS (Netherlands)

    Zardetto, V.; Di Giacomo, F.; Lucarelli, G.; Kessels, W.M.M.; Brown, T.M.; Creatore, M.

    2017-01-01

    In mesostructured perovskite solar cell devices, charge recombination processes at the interface between the transparent conductive oxide, perovskite and hole transport layer are suppressed by depositing an efficient compact TiO2 blocking layer. In this contribution we investigate the role of the

  14. Synthesis of Fe5C2@SiO2 core@shell nanoparticles as a potential candidate for biomedical application

    Science.gov (United States)

    Ahmadpoor, Fatemeh; Shojaosadati, Seyed Abbas; Delavari H, Hamid; Christiansen, Gunna; Saber, Reza

    2018-05-01

    A new strategy for water-dispersibility of hydrophobic carbide nanostructures was proposed. In this regard, hydrophobic Fe5C2 nanoparticles (NPs) with size ranging 25–40 nm were synthesized and coated with 12–15 nm silica shell for biomedical applications. X-ray diffraction (XRD) results revealed that Fe5C2 NPs with monoclinic structure were successfully prepared. The crystalline structure of Fe5C2 NPs was remained unchanged and saturation magnetization of core remained nearly constant after coating with silica shell. Moreover, Raman spectroscopy identified D-band of amorphous carbon shells which was also confirmed by transmission electron microscopy (TEM). Finally, Fe5C2@SiO2 core@shell NPs demonstrated no significant cytotoxicity and appropriate heat generating which makes them a promising candidate for magnetic fluid hyperthermia applications.

  15. High-temperature synthesis of highly hydrothermal stable mesoporous silica and Fe-SiO2 using ionic liquid as a template

    International Nuclear Information System (INIS)

    Liu, Hong; Wang, Mengyang; Hu, Hongjiu; Liang, Yuguang; Wang, Yong; Cao, Weiran; Wang, Xiaohong

    2011-01-01

    Mesoporous silicas and Fe-SiO 2 with worm-like structures have been synthesized using a room temperature ionic liquid, 1-hexadecane-3-methylimidazolium bromide, as a template at a high aging temperature (150-190 o C) with the assistance of NaF. The hydrothermal stability of mesoporous silica was effectively improved by increasing the aging temperature and adding NaF to the synthesis gel. High hydrothermally stable mesoporous silica was obtained after being aged at 190 o C in the presence of NaF, which endured the hydrothermal treatment in boiling water at least for 10 d or steam treatment at 600 o C for 6 h. The ultra hydrothermal stability could be attributed to its high degree of polymerization of silicate. Furthermore, highly hydrothermal stable mesoporous Fe-SiO 2 has been synthesized, which still remained its mesostructure after being hydrothermally treated at 100 o C for 12 d or steam-treated at 600 o C for 6 h. -- Graphical abstract: Worm-like mesoporous silica and Fe-SiO 2 with high hydrothermal stability have been synthesized using ionic liquid 1-hexadecane-3-methylimidazolium bromide as a template under the assistance of NaF at high temperature. Display Omitted Research highlights: → Increasing aging temperature improved the hydrothermal stability of materials. →Addition of NaF enhanced the polymerization degree of silicates. → Mesoporous SiO 2 and Fe-SiO 2 obtained have remarkable hydrothermal stability.

  16. Thermal stability and surface acidity of mesoporous silica doubly doped by incorporation of sulfate and zirconium ions

    Energy Technology Data Exchange (ETDEWEB)

    Salas, P. [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas No. 152, 07730 Mexico D.F. (Mexico)]. E-mail: psalas@imp.mx; Chen, L.F. [Departamento de Ingenieria Quimica, Universidad Autonoma Metropolitana-A, Av. San Pablo 180, Col. Reynosa-Tamaulipas, 02200 Mexico D.F. (Mexico); Wang, J.A. [Laboratorio de Catalisis y Materiales, ESIQIE, Instituto Politecnico Nacional, Col. Zacatenco, 07738 Mexico D.F. (Mexico); Armendariz, H. [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas No. 152, 07730 Mexico D.F. (Mexico); Guzman, M.L. [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas No. 152, 07730 Mexico D.F. (Mexico); Montoya, J.A. [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas No. 152, 07730 Mexico D.F. (Mexico); Acosta, D.R. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, A. P. 20-364, 01000 Mexico D.F. (Mexico)

    2005-11-15

    A sulfated Si-Zr-MCM-41 solid with highly ordered mesostructure was synthesized through a templated synthesis route where the CTAB surfactant was used as template. During the synthesis procedure, various amounts of (NH{sub 4}){sub 2}SO{sub 4} were added into the mixed solution of Zr and Si precursors to in situ sulfate the MCM-41 solids, aiming to enhance the acidity and thermal stability. The resultant materials showed a long-range ordered hexagonal arrangement with high surface area larger than 797 m{sup 2}/g and an average pore size distributed at approximate 2.5-2.8 nm. The high-resolution TEM observations confirmed that the order of the mesostructure gained when the molar ratio of SO{sub 4} {sup 2-}/(ZrO{sub 2} + SiO{sub 2}) increased from 0.1 to 0.3 but decreased as it reached 0.5, which is consistent with the results of {sup 29}Si MAS-NMR and XRD analysis. Compared to Si-MCM-41, the (Q{sup 2} + Q{sup 3})/Q{sup 4} ratio derived from the NMR spectra of the Zr-doped sample was higher, indicating that zirconium atoms were incorporated into the silica framework. Unexpectedly, in situ sulfation does not enhance the surface Broensted acidity, most likely due to the sulfur retained within the bulk of the materials; however, it indeed improved the thermal stability of the solid and long-range order of the structure.

  17. Colloidal titania-silica-iron oxide nanocomposites and the effect from silica thickness on the photocatalytic and bactericidal activities

    Energy Technology Data Exchange (ETDEWEB)

    Chanhom, Padtaraporn [Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Charoenlap, Nisanart [Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok 10210 (Thailand); Tomapatanaget, Boosayarat [Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Insin, Numpon, E-mail: Numpon.I@chula.ac.th [Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand)

    2017-04-01

    New types of colloidal multifunctional nanocomposites that combine superparamagnetic character and high photocatalytic activity were synthesized and investigated. The superparamagnetic nanocomposites composed of anatase titania, silica, and iron oxide nanoparticles (TSI) were synthesized using thermal decomposition method followed by microemulsion method, without calcination at high temperature. Different techniques including X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to characterize and confirm the structure of the nanocomposites. These nanocomposites showed high photocatalytic activity when used in the photodegradation of methylene blue under irradiation with a black light lamp. Moreover, the nanocomposites exhibited high antibacterial properties. From our study, the nanocomposites can be useful in various applications such as removal of pollutants with readily separation from the environment using an external magnetic field. These composites could effectively photo-degrade the dye at least three cycles without regeneration. The effects of silica shell thickness on the photocatalytic activity was investigated, and the thickness of 6 nm of the silica interlayer is enough for the inhibition of electron translocation between titania and iron oxide nanoparticles and maintaining the efficiency of photocatalytic activity of titania nanoparticles. - Highlights: • New colloidal nanocomposites of iron oxide-silica-titania were prepared. • The nanocomposites exhibited high photocatalytic activity with magnetic response. • The effects of silica thickness on photocatalytic activity were investigated. • Bactericidal activity of the nanocomposites was demonstrated.

  18. Biodistribution and stability of CdSe core quantum dots in mouse digestive tract following per os administration: Advantages of double polymer/silica coated nanocrystals

    International Nuclear Information System (INIS)

    Loginova, Y.F.; Dezhurov, S.V.; Zherdeva, V.V.; Kazachkina, N.I.; Wakstein, M.S.; Savitsky, A.P.

    2012-01-01

    Highlights: ► New QDs coated with combination of polythiol ligands and silica shell were synthesized. ► We examine the QDs stability in digestive tract of mice after per os administration. ► The polymer/silica shell prevents QDs degradation and fluorescence quenching in vivo. -- Abstract: CdSe-core, ZnS-capped semiconductor quantum dots (QDs) are of great potential for biomedical applications. However, applications in the gastrointestinal tract for in vivo imaging and therapeutic purposes are hampered by their sensitivity to acidic environments and potential toxicity. Here we report the use of coatings with a combination of polythiol ligands and silica shell (QDs PolyT–APS) to stabilize QDs fluorescence under acidic conditions. We demonstrated the stability of water-soluble QDs PolyT–APS both in vitro, in strong acidic solutions, and in vivo. The biodistribution, stability and photoluminescence properties of QDs in the gastrointestinal tract of mice after per os administration were assessed. We demonstrated that QDs coated with current traditional materials – mercapto compounds (QDs MPA) and pendant thiol group (QDs PolyT) – are not capable of protecting QDs from chemically induced degradation and surface modification. Polythiol ligands and silica shell quantum dots (QDs PolyT–APS) are suitable for biological and biomedical applications in the gastrointestinal tract.

  19. Synthesis of internally functionalized silica nanoparticles for theranostic applications

    Science.gov (United States)

    Walton, Nathan Isaac

    hydroboration, to make the nanoparticles into water-dispersible boron carriers that also have potential boron neutron capture therapy (BNCT) applications. Lastly, Chapter 4 provides a general description of NCT, specifically that involving boron-10 and gadolinium-157. It further describes the synthetic methodology used in producing fatty acid coated boron nanoparticles (BNPs). The BNPs are encapsulated with silica to add a hydrophilic shell so that they can potentially be used in biological systems as BNCT agents. The silica shell is also modified with a fluorophore, dansyl chloride, so that the particle hybrid could be imaged during cell studies.

  20. Controllable dielectric and electrical performance of polymer composites with novel core/shell-structured conductive particles through biomimetic method

    International Nuclear Information System (INIS)

    Yang, Dan; Tian, Ming; Wang, Wencai; Li, Dongdong; Li, Runyuan; Liu, Haoliang; Zhang, Liqun

    2013-01-01

    Highlights: ► Conductive core/shell-structured particles were synthesized by biomimetic method. ► These particles with silica/poly(dopamine)/silver core and poly(dopamine) shell. ► Dielectric composites were prepared with resulted particles and silicone elastomer. ► The dielectric properties of the composites can be controlled by shell thickness. ► This biomimetic method is simple, nontoxic, efficient and easy to control. - Abstract: Novel silica/poly(dopamine)/silver (from inner to outer) (denoted as SiO 2 /PDA/Ag) conductive micro-particles were first synthesized by biomimetic poly(dopamine) coating. These micro-particles were then coated with a poly(dopamine) layer to form core/shell-structured particles, with silica/poly(dopamine)/silver core and poly(dopamine) shell (denoted as SiO 2 /PDA/Ag/PDA). This multilayer core/shell micro-particles were confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscope. Polymer composites were then prepared by mechanical blending of poly(dimethyl siloxane) and the core/shell-structured particles. It was found that the silver layer and the poly(dopamine) shell had good adhesion with substrate and they kept intact even under violent shearing stress during mechanical mixing. The effect of the thickness of outermost poly(dopamine) shell as well as the loading amount of this filler on the dielectric and electrical properties of the composites was further studied. The results showed that the dielectric constant, dielectric loss, and conductivity of the composites decreased with increasing shell thickness (10–53 nm) at the same loading level. And the maximal dielectric constant of composites was achieved in the composites filled with SiO 2 /PDA/Ag/PDA (with 10–15 nm PDA shell) particles, which was much larger than that of the composite filled with SiO 2 /PDA/Ag particles without insulative PDA shell. At the same time, the composites can change

  1. Synthesis and Adsorption Property of SiO2@Co(OH2 Core-Shell Nanoparticles

    Directory of Open Access Journals (Sweden)

    Yongde Meng

    2015-04-01

    Full Text Available Silica nanoparticles were directly coated with cobalt hydroxide by homogeneous precipitation of slowly decomposing urea in cobalt nitrate solution. The cobalt hydroxide was amorphous, and its morphology was nanoflower-like. The BET (Brunauer-Emmett-Teller surface area of the core-shell composite was 221 m2/g. Moreover, the possible formation procedure is proposed: the electropositive cobalt ions were first adsorbed on the electronegative silica nanoparticles surface, which hydrolyzed to form cobalt hydroxide nanoparticles. Then, the cobalt hydroxide nanoparticles were aggregated to form nanoflakes. Finally, the nanoflakes self-assembled, forming cobalt hydroxide nanoflowers. Adsorption measurement showed that the core-shell composite exhibited excellent adsorption capability of Rhodamine B (RB.

  2. Enhanced linear photonic nanojet generated by core-shell optical microfibers

    Science.gov (United States)

    Liu, Cheng-Yang; Yen, Tzu-Ping; Chen, Chien-Wen

    2017-05-01

    The generation of linear photonic nanojet using core-shell optical microfiber is demonstrated numerically and experimentally in the visible light region. The power flow patterns for the core-shell optical microfiber are calculated by using the finite-difference time-domain method. The focusing properties of linear photonic nanojet are evaluated in terms of length and width along propagation and transversal directions. In experiment, the silica optical fiber is etched chemically down to 6 μm diameter and coated with metallic thin film by using glancing angle deposition. We show that the linear photonic nanojet is enhanced clearly by metallic shell due to surface plasmon polaritons. The large-area superresolution imaging can be performed by using a core-shell optical microfiber in the far-field system. The potential applications of this core-shell optical microfiber include micro-fluidics and nano-structure measurements.

  3. Intracellular pH-sensing using core/shell silica nanoparticles.

    Science.gov (United States)

    Korzeniowska, B; Woolley, R; DeCourcey, J; Wencel, D; Loscher, C E; McDonagh, C

    2014-07-01

    An in-depth understanding of biochemical processes occurring within biological systems is key for early diagnosis of disease and identification of appropriate treatments. Nanobiophotonics offers huge potential benefits for intracellular diagnostics and therapeutics. Intracellular sensing using fluorescent nanoparticles is a potentially useful tool for real-time, in vivo monitoring of important cellular analytes. This work is focused on synthesis of optical chemical nanosensors for the quantitative analysis of pH inside living cells. The structure of the nanosensor comprises a biofriendly silica matrix with co-encapsulated Texas Red, acting as a reference dye, and pH-sensitive fluorescein isothiocyanate enabling ratiometric quantitative environmental detection. In order to obtain silica-based nanoparticles -70 nm in size, a modified sol-gel-based Stöber method was employed. The potential of these nanosensors for intracellular pH monitoring is demonstrated inside a live human embryonic kidney cell line whereby a significant change in fluorescence is observed when the cell pH is switched from acidic to basic. High loading efficiencies of nanoparticles into the cells is seen, with little effect on cell morphology even following extended nanoparticle exposure (up to 72 h). Nanoparticle incubation time and the fast response of the nanosensor (-2 s) make it a very powerful tool in monitoring the processes occurring within the cytosol.

  4. Synthesis, characterization and biomedical application of multifunctional luminomagnetic core–shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Changqing [Key Laboratory of Biochip Technology, Biotech and Health Centre, Shenzhen Research Institutes of City University of Hong Kong, Shenzhen (China); Key Laboratory of Sensing Technology and Biomedical Instruments (Guangdong Province), School of Engineering, Sun Yat-Sen University, Guangzhou (China); Liu, Lei [Key Laboratory of Biochip Technology, Biotech and Health Centre, Shenzhen Research Institutes of City University of Hong Kong, Shenzhen (China); College of Chemistry and Environmental Science, Chemical Biology Key Laboratory of Hebei Province, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding (China); Li, Cheuk-Wing [Key Laboratory of Biochip Technology, Biotech and Health Centre, Shenzhen Research Institutes of City University of Hong Kong, Shenzhen (China); Zhang, Jinchao, E-mail: jczhang6970@163.com [Key Laboratory of Biochip Technology, Biotech and Health Centre, Shenzhen Research Institutes of City University of Hong Kong, Shenzhen (China); College of Chemistry and Environmental Science, Chemical Biology Key Laboratory of Hebei Province, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding (China); Yang, Mengsu, E-mail: bhmyang@cityu.edu.hk [Key Laboratory of Biochip Technology, Biotech and Health Centre, Shenzhen Research Institutes of City University of Hong Kong, Shenzhen (China)

    2015-01-01

    It has been well-established that nanomaterials provide a robust framework into which two or more functional moieties can be integrated to offer multifunctional and synergetic applications. We report here the facile synthesis and systematical investigation of the luminomagnetic core–shell nanoparticles (NPs) with the magnetic Fe{sub 3}O{sub 4} core coated with a silica shell incorporating fluorescent [Ru(bpy){sub 3}]{sup 2+}. The luminomagnetic NPs were monodisperse and spherical in shape with a diameter of 60 ± 10 nm. The luminomagnetic NPs possessed not only the desirable optical signature of Ru(bpy){sub 3}{sup 2+} but also the distinctive magnetic profile of Fe{sub 3}O{sub 4}, where a strong red-orange emission and the super-paramagnetic characteristics with the saturation magnetization values ca. 10 emu/g were observed for the luminomagnetic NPs. As revealed by Alamar blue assay and flow cytometry analysis, the Fe{sub 3}O{sub 4} NPs decrease the cell viability of HepG2 by ca. 10%, while an increase by ca. 10% on HepG2 cell proliferation was revealed after the silica shell was coated onto Fe{sub 3}O{sub 4} NPs, suggesting that the silica shell serves as a protective layer to increase the biocompatibility of the luminomagnetic NPs. Confocal laser scanning microscopy, transition electron microscopy and magnetic resonance (MR) images confirmed that the luminomagnetic NPs can enter into the interiors of HepG2 cells without damage, highlighting their capabilities for simultaneous optical fluorescence imaging and T2 MR imaging. Taking advantage of versatility of silica shell towards different surface modification protocols, the luminomagnetic NPs were successfully functionalized with epidermal growth factor receptor (EGFR) antibody for HepG2 cell recognition. All the results illustrated that the luminomagnetic NPs should be a potential candidate for future cancer diagnosis and therapy. - Highlights: • The luminomagnetic NPs were prepared by a water-in-oil reverse

  5. Design of Protein-Coated Carbon Nanotubes Loaded with Hydrophobic Drugs through Sacrificial Templating of Mesoporous Silica Shells.

    Science.gov (United States)

    Fiegel, Vincent; Harlepp, Sebastien; Begin-Colin, Sylvie; Begin, Dominique; Mertz, Damien

    2018-03-26

    One key challenge in the fields of nanomedicine and tissue engineering is the design of theranostic nanoplatforms able to monitor their therapeutic effect by imaging. Among current developed nano-objects, carbon nanotubes (CNTs) were found suitable to combine imaging, photothermal therapy, and to be loaded with hydrophobic drugs. However, a main problem is their resulting low hydrophilicity. To face this problem, an innovative method is developed here, which consists in loading the surface of carbon nanotubes (CNTs) with drugs followed by a protein coating around them. The originality of this method relies on first covering CNTs with a sacrificial template mesoporous silica (MS) shell grafted with isobutyramide (IBAM) binders on which a protein nanofilm is strongly adhered through IBAM-mediated physical cross-linking. This concept is first demonstrated without drugs, and is further improved with the suitable loading of hydrophobic drugs, curcumin (CUR) and camptothecin (CPT), which are retained between the CNTs and human serum albumin (HSA) layer. Such novel nanocomposites with favorable photothermal properties are very promising for theranostic systems, drug delivery, and phototherapy applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Silica-coated quantum dots fluorescent spheres synthesized using a quaternary 'water-in-oil' microemulsion system

    International Nuclear Information System (INIS)

    Chu Maoquan; Sun Ye; Xu Shi

    2008-01-01

    Nanoscale and microscale silica spheres embedded with multiple CdSe quantum dots (QDs, having average diameters of about 2.4 and 5.0 nm, respectively.) were synthesized by using a quaternary 'water-in-oil' microemulsion. Comparing the uncoated QDs, the quantum yields (QYs) of the silica-coated QD spheres were enhanced when the QD cores were synthesized using mercaptoacetic acid (MA) as a stabilizer, while the QYs were dramatically decreased when the cores were synthesized using citric acid (CA) as a stabilizer. The enhanced QYs could be further improved by heating the silica-coated QDs in aqueous solution. Although the QYs of the silica-coated QDs were not high, these spheres emitted bright fluorescence. The silica shells contained numerous micropores (∼0.58-0.91 nm), and small amounts of toxic ions (such as Cd 2+ ) could be released from the silica spheres. However, the release rate of toxic ions from the silica spheres was significantly reduced compared with that of the uncoated QDs

  7. Steam stable mesoporous silica MCM-41 stabilized by trace amounts of Al.

    Science.gov (United States)

    Tompkins, Jordan T; Mokaya, Robert

    2014-02-12

    Evaluation of low and ultralow Al content (Si/Al between 50 and 412) aluminosilicate Al-MCM-41 materials synthesized via three contrasting alumination routes, namely, direct mixed-gel synthesis, post-synthesis wet grafting, and post-synthesis dry grafting, indicates that trace amounts of Al introduced via dry grafting can stabilize mesoporous silica MCM-41 to steaming at 900 °C for 4 h. It was found that trace amounts of Al (Si/Al > 400) introduced via so-called dry grafting of Al stabilize the virtually purely siliceous MCM-41 to steaming, whereas Al incorporated via other methods that involve aqueous media such as direct mixed gel synthesis or wet grafting of Al offer only limited protection at low Al content. It is particularly remarkable that a post-synthesis dry grafted Al-MCM-41 material possessing trace amounts of Al (i.e., Si/Al ratio of 412) and surface area and pore volume of 1112 m(2)/g and 1.20 cm(3)/g, respectively, retains 90% (998 m(2)/g) of the surface area and 85% (1.03 cm(3)/g) of the pore volume after exposure to steaming at 900 °C for 4 h. Under similar steam treatment conditions, the mesostructure of pure silica Si-MCM-41 is virtually destroyed and undergoes a 93% reduction in surface area (958 m(2)/g to 69 m(2)/g) and 88% decrease in pore volume (0.97 cm(3)/g to 0.12 cm(3)/g). The steam stable ultralow (i.e., trace) Al containing MCM-41 materials is found to be virtually similar to mesoporous pure silica Si-MCM-41 with hardly any detectable acidity. The improvement in steam stability arises from not only the presence of trace amounts of Al, but also from an apparent increase in the level of silica condensation that is specific to dry grafted alluminosilicate MCM-41 materials. The more highly condensed framework has fewer silanol groups and therefore is more resistant to hydrolysis under steaming conditions.

  8. Synthesis of titania modified silica-pillared clay (SPC) with highly ordered interlayered mesoporous structure for removing toxic metal ion Cr(VI) from aqueous state

    International Nuclear Information System (INIS)

    Mao, Huihui; Zhu, Kongnan; Li, Baoshan; Yao, Chao; Kong, Yong

    2014-01-01

    Titanium-functionalized silica-pillared clays synthesized through post synthetic route was utilized as adsorbers for the removal of Cr(VI) ions from aqueous solutions under different temperatures and initial concentrations. The starting mesostructured silica-pillared clay is assembled by intragallery ammonia-catalyzed hydrolysis of tetraethoxysilane using cationic surfactant as gallery template, and subsequently, the formed interlayered pore walls were decorated with nano-sized TiO 2 particle through organic titanium functionalization process. The kind of structural transformation has been confirmed by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherms, Fourier transform infrared (FT-IR) analysis, UV–vis diffuse reflectance spectroscopy (DRS), elemental analysis (XRF), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Such results indicate that most of the grafted titanium species was combined with Si–OH on the surface of gallery pores. By changing the concentration of organic titanium source during synthesis, the porous structure system is effected. Under suitable conditions, these materials exhibit high adsorption capacity and efficiency. Qualitative estimates of the thermodynamic parameters showed that the overall adsorption process is spontaneous (ΔG° 0). The adsorption isotherms of Cr(VI) on titanium-functionalized silica-pillared clay were best fitted by Redlich–Peterson models. Detail results of thermodynamics and kinetics are also presented.

  9. Synthesis of titania modified silica-pillared clay (SPC) with highly ordered interlayered mesoporous structure for removing toxic metal ion Cr(VI) from aqueous state

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Huihui, E-mail: maohuihui_beijing@126.com [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou, Jiangsu Province 213164 (China); Zhu, Kongnan [Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou, Jiangsu Province 213164 (China); Li, Baoshan, E-mail: bsli@mail.buct.edu.cn [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Yao, Chao; Kong, Yong [Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou, Jiangsu Province 213164 (China)

    2014-02-15

    Titanium-functionalized silica-pillared clays synthesized through post synthetic route was utilized as adsorbers for the removal of Cr(VI) ions from aqueous solutions under different temperatures and initial concentrations. The starting mesostructured silica-pillared clay is assembled by intragallery ammonia-catalyzed hydrolysis of tetraethoxysilane using cationic surfactant as gallery template, and subsequently, the formed interlayered pore walls were decorated with nano-sized TiO{sub 2} particle through organic titanium functionalization process. The kind of structural transformation has been confirmed by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherms, Fourier transform infrared (FT-IR) analysis, UV–vis diffuse reflectance spectroscopy (DRS), elemental analysis (XRF), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Such results indicate that most of the grafted titanium species was combined with Si–OH on the surface of gallery pores. By changing the concentration of organic titanium source during synthesis, the porous structure system is effected. Under suitable conditions, these materials exhibit high adsorption capacity and efficiency. Qualitative estimates of the thermodynamic parameters showed that the overall adsorption process is spontaneous (ΔG° < 0) and endothermic (ΔH° > 0). The adsorption isotherms of Cr(VI) on titanium-functionalized silica-pillared clay were best fitted by Redlich–Peterson models. Detail results of thermodynamics and kinetics are also presented.

  10. Tuning dipolar magnetic interactions by controlling individual silica coating of iron oxide nanoparticles

    Science.gov (United States)

    Rivas Rojas, P. C.; Tancredi, P.; Moscoso Londoño, O.; Knobel, M.; Socolovsky, L. M.

    2018-04-01

    Single and fixed size core, core-shell nanoparticles of iron oxides coated with a silica layer of tunable thickness were prepared by chemical routes, aiming to generate a frame of study of magnetic nanoparticles with controlled dipolar interactions. The batch of iron oxides nanoparticles of 4.5 nm radii, were employed as cores for all the coated samples. The latter was obtained via thermal decomposition of organic precursors, resulting on nanoparticles covered with an organic layer that was subsequently used to promote the ligand exchange in the inverse microemulsion process, employed to coat each nanoparticle with silica. The amount of precursor and times of reaction was varied to obtain different silica shell thicknesses, ranging from 0.5 nm to 19 nm. The formation of the desired structures was corroborated by TEM and SAXS measurements, the core single-phase spinel structure was confirmed by XRD, and superparamagnetic features with gradual change related to dipolar interaction effects were obtained by the study of the applied field and temperature dependence of the magnetization. To illustrate that dipolar interactions are consistently controlled, the main magnetic properties are presented and analyzed as a function of center to center minimum distance between the magnetic cores.

  11. Synthesis and green up-conversion fluorescence of colloidal La0.78Yb0.20Er0.02F3/SiO2 core/shell nanocrystals

    International Nuclear Information System (INIS)

    Wang Yan; Qin Weiping; Zhang Jisen; Cao Chunyan; Zhang Jishuang; Jin Ye; Zhu Peifen; Wei Guodong; Wang Guofeng; Wang Lili

    2007-01-01

    Water-soluble PVP-stabilized hexagonal-phase La 0.78 Yb 0.20 Er 0.02 F 3 nanocrystals (NCs) were synthesized by hydrothermal method. The NCs were coated with a very thin silica shell, and amino groups were introduced to the surface of silica shells by copolymerization of 3-aminopropyl(triethoxy)silane. The core/shell NCs can be dispersed in ethanol and water to form stable colloidal solution. The transmission electron microscopy (TEM), selected area electron diffraction (SAED), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the core/shell materials. In addition, the green up-conversion fluorescence mechanism of La 0.78 Yb 0.20 Er 0.02 F 3 /SiO 2 NCs was studied with a 980-nm diode laser as excitation source. The water solubility, small core/shell particles size, and well colloidal stability mean the green up-conversion fluorescence NCs have potential applications in bioassay. - Graphical abstract: Colloidal La 0.78 Yb 0.20 Er 0.02 F 3 /SiO 2 Core/Shell nanocrystals (NCs) were synthesized and the free amino groups were introduced to the surface of silica shells by copolymerization 3-aminopropyl(triethoxy)silane. The NCs can be dispersed in ethanol and water to form stable colloidal solution. In addition, the NCs exhibit green up-conversion fluorescence under 980-nm excitation

  12. Silica-Polystyrene Nanocomposite Particles Synthesized by Nitroxide-Mediated Polymerization and Their Encapsulation through Miniemulsion Polymerization

    Directory of Open Access Journals (Sweden)

    Bérangère Bailly

    2006-01-01

    Full Text Available Polystyrene (PS chains with molecular weights comprised between 8000 and 64000 g⋅mol-1 and narrow polydispersities were grown from the surface of silica nanoparticles (Aerosil A200 fumed silica and Stöber silica, resp. through nitroxide-mediated polymerization (NMP. Alkoxyamine initiators based on N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide (DEPN and carrying a terminal functional group have been synthesized in situ and grafted to the silica surface. The resulting grafted alkoxyamines have been employed to initiate the growth of polystyrene chains from the inorganic surface. The maximum grafting density of the surface-tethered PS chains was estimated and seemed to be limited by initiator confinement at the interface. Then, the PS-grafted Stöber silica nanoparticles were entrapped inside latex particles via miniemulsion polymerization. Transmission electron microscopy indicated the successful formation of silica-polystyrene core-shell particles.

  13. Synthesis of magnetic CoPt/SiO{sub 2} core-shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Seto, Takafumi [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Koga, Kenji [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Takano, Fumiyoshi [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Akinaga, Hiroyuki [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Orii, Takaaki [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Hirasawa, Makoto [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Murayama, Mitsuhiro [National Institute for Material Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

    2007-04-15

    Core-shell nanoparticles composed of ferromagnetic cobalt platinum cores covered by non-magnetic silica shells were synthesized by laser ablating a composite target in a helium background gas. The average diameter of the CoPt core was controlled by adjusting the CoPt/SiO{sub 2} ratio of the ablation target. The particles were also classified in the gas phase using an electrical mobility classifier. The present method successfully synthesized nearly monodispersed nanoparticles with an average core diameter of 2.5nm. This article describes the synthesis of the core-shell nanoparticles and investigates their magnetic properties.

  14. Influence of the ammonium hydroxide concentration in morphological control of meso porous silica particles

    International Nuclear Information System (INIS)

    Yoon, Sukbon; Jung, Chonghun; Yoon, Inho; Kim, Changki; Choi, Wangkyu; Moon, Jeikwon

    2012-01-01

    The discovery of new M41S meso porous silica families in 1992 extended the applications into much wider pore ranges, bringing in a new prosperous era in porous material research. The synthesis of these meso porous silicas has been mainly accomplished through a self-assembly between surfactant molecules and inorganic species under various pH conditions. Meanwhile, many studies have been conducted on the application as catalysts, adsorbents, and packing materials for separation columns due to their unique properties such as high specific surface area, large pore volume, tuneable pore size, and narrow pore size distribution. The pore sizes of these materials can be easily controlled by changing the alkyl-chain length of the surfactant used. However, the control of the morphology and the pore structure is not so common. The morphological control of these materials in particular is one of the major challenges for their industrial application. Recently, the meso porous silica materials with various shapes such as fibers, films, polyhedral particles, and spheres have been reported. In our previous study, the core-shell nanoparticles with a silica core and a meso porous shell under basic conditions were synthesized using the silica nanoparticles as a core and tetraethyl orthosilicate (TEOS)-cetyltrimethylammonium bromide (CTABr)-NH 4 OH-H 2 O-C 2 H 5 OH system. In this work, we report the synthesis of the most well known hexagonal MCM-41 among three main mesophases in the M41S families using TEOS-CTABr-NH 4 OH-H 2 O system. Also, in the control of the morphology and pore structure of the meso porous silica materials, the influence of the NH 4 OH concentration was investigated

  15. In vivo magnetic resonance and fluorescence dual imaging of tumor sites by using dye-doped silica-coated iron oxide nanoparticles

    International Nuclear Information System (INIS)

    Jang, Haeyun; Lee, Chaedong; Nam, Gi-Eun; Quan, Bo; Choi, Hyuck Jae; Yoo, Jung Sun; Piao, Yuanzhe

    2016-01-01

    The difficulty in delineating tumor is a major obstacle for better outcomes in cancer treatment of patients. The use of single-imaging modality is often limited by inadequate sensitivity and resolution. Here, we present the synthesis and the use of monodisperse iron oxide nanoparticles coated with fluorescent silica nano-shells for fluorescence and magnetic resonance dual imaging of tumor. The as-synthesized core–shell nanoparticles were designed to improve the accuracy of diagnosis via simultaneous tumor imaging with dual imaging modalities by a single injection of contrast agent. The iron oxide nanocrystals (∼11 nm) were coated with Rhodamine B isothiocyanate-doped silica shells via reverse microemulsion method. Then, the core–shell nanoparticles (∼54 nm) were analyzed to confirm their size distribution by transmission electron microscopy and dynamic laser scattering. Photoluminescence spectroscopy was used to characterize the fluorescent property of the dye-doped silica shell-coated nanoparticles. The cellular compatibility of the as-prepared nanoparticles was confirmed by a trypan blue dye exclusion assay and the potential as a dual-imaging contrast agent was verified by in vivo fluorescence and magnetic resonance imaging. The experimental results show that the uniform-sized core–shell nanoparticles are highly water dispersible and the cellular toxicity of the nanoparticles is negligible. In vivo fluorescence imaging demonstrates the capability of the developed nanoparticles to selectively target tumors by the enhanced permeability and retention effects and ex vivo tissue analysis was corroborated this. Through in vitro phantom test, the core/shell nanoparticles showed a T2 relaxation time comparable to Feridex ® with smaller size, indicating that the as-made nanoparticles are suitable for imaging tumor. This new dual-modality-nanoparticle approach has promised for enabling more accurate tumor imaging.

  16. In vivo magnetic resonance and fluorescence dual imaging of tumor sites by using dye-doped silica-coated iron oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Haeyun; Lee, Chaedong [Seoul National University, Program in Nano Science and Technology, Graduate School of Convergence Science and Technology (Korea, Republic of); Nam, Gi-Eun [University of Ulsan College of Medicine, Department of Radiology, Asan Medical Center (Korea, Republic of); Quan, Bo [Seoul National University, Program in Nano Science and Technology, Graduate School of Convergence Science and Technology (Korea, Republic of); Choi, Hyuck Jae [University of Ulsan College of Medicine, Department of Radiology, Asan Medical Center (Korea, Republic of); Yoo, Jung Sun [Seoul National University, Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Smart Humanity Convergence Center (Korea, Republic of); Piao, Yuanzhe, E-mail: parkat9@snu.ac.kr [Seoul National University, Program in Nano Science and Technology, Graduate School of Convergence Science and Technology (Korea, Republic of)

    2016-02-15

    The difficulty in delineating tumor is a major obstacle for better outcomes in cancer treatment of patients. The use of single-imaging modality is often limited by inadequate sensitivity and resolution. Here, we present the synthesis and the use of monodisperse iron oxide nanoparticles coated with fluorescent silica nano-shells for fluorescence and magnetic resonance dual imaging of tumor. The as-synthesized core–shell nanoparticles were designed to improve the accuracy of diagnosis via simultaneous tumor imaging with dual imaging modalities by a single injection of contrast agent. The iron oxide nanocrystals (∼11 nm) were coated with Rhodamine B isothiocyanate-doped silica shells via reverse microemulsion method. Then, the core–shell nanoparticles (∼54 nm) were analyzed to confirm their size distribution by transmission electron microscopy and dynamic laser scattering. Photoluminescence spectroscopy was used to characterize the fluorescent property of the dye-doped silica shell-coated nanoparticles. The cellular compatibility of the as-prepared nanoparticles was confirmed by a trypan blue dye exclusion assay and the potential as a dual-imaging contrast agent was verified by in vivo fluorescence and magnetic resonance imaging. The experimental results show that the uniform-sized core–shell nanoparticles are highly water dispersible and the cellular toxicity of the nanoparticles is negligible. In vivo fluorescence imaging demonstrates the capability of the developed nanoparticles to selectively target tumors by the enhanced permeability and retention effects and ex vivo tissue analysis was corroborated this. Through in vitro phantom test, the core/shell nanoparticles showed a T2 relaxation time comparable to Feridex{sup ®} with smaller size, indicating that the as-made nanoparticles are suitable for imaging tumor. This new dual-modality-nanoparticle approach has promised for enabling more accurate tumor imaging.

  17. A novel core–shell nanocomposite Ni–Ca@mSiO_2 for benzophenone selective hydrogenation

    International Nuclear Information System (INIS)

    Han, Xue; Feng, Wenhui; Chu, Xiaoning; Chu, Hailong; Niu, Libo; Bai, Guoyi

    2017-01-01

    A novel core–shell nanocomposite Ni–Ca@mSiO_2 was first prepared by a modified Stöber method in this paper. It has a core–shell structure with Ni (about 8 nm in diameter) and Ca as the cores and mesoporous silica as the outer shell, as proven by the transmission electron microscopy. This nanocomposite exhibited good catalytic performance in the selective hydrogenation of benzophenone, with 96.1% conversion and 94.9% selectivity for benzhydrol under relatively mild reaction conditions. It was demonstrated that addition of small amounts of alkaline Ca can not only markedly improve the dispersion of the active species but also tune the acid–base property of this nanocomposite, resulting in the efficient suppression of benzhydrol dehydration to achieve a high selectivity. Furthermore, the core–shell nanocomposite Ni–Ca@mSiO_2 can be recycled four runs without appreciable loss of its initial activity, more stable than the traditional supported nanocatalyst Ni–Ca/mSiO_2. It was suggested that the outer mesoporous silica shell of Ni–Ca@mSiO_2 can prevent both the aggregation and the leaching of the active Ni species, accounting for its relatively good stability.

  18. Fixed-bed adsorption separation of xylene isomers over sio2/silicallite-1 core-shell adsorbents

    KAUST Repository

    Khan, Easir A.

    2013-12-29

    SiO2/Silicalite-1 core-shell material has been demonstrated as potential shape selective adsorbent in gas phase separation of p-xylene from a mixture of p/o-xylene isomers. The core-shell composite comprised of large silica core and thin polycrystalline silicalite-1 shell which was synthesized via a self-assembly of silicalite-1 nanocrystals on core silica surface followed by a secondary seeded growth method. The core materials, SiO2 used in this study has mesoporosity with an average pore diameter of 60Å and hence offers no shape selectivity for xylene isomers. However, the shell, silicalite-1 contains rigid pore structures and preferentially adsorbs p-xylene from their isomers mixtures. A series of adsorption fixed bed breakthrough adsorption/desorption experiment was performed to obtain the equilibrium isotherms and adsorption isotherm parameters of xylene isomers. The equilibrium isotherms of xylene isomers follow the Langmuir\\'s model. A chromatographic adsorption model has been used to describe the fixed-bed breakthrough profiles of xylene isomers. The model has successfully predicted the responses of the binary mixtures of p/o-xylene isomers. The SiO2/silicalite-1 core-shell adsorbents have shown para-selectivity as high as 15. © Bangladesh Uni. of Engg. & Tech.

  19. Preparation of thermally stable microcapsules with a chitosan-silica hybrid.

    Science.gov (United States)

    Kang, Hong-Yi; Chen, Hui-Huang

    2014-09-01

    Addition of microcapsules with a high dielectric constant and low specific heat capacity to a battered layer was designed to create a higher temperature in the crust than in the prefried fish nuggets to prevent the water vapor in the fish nuggets from migrating to the crust during microwave heating. Therefore, chitosan-silica hybrids and soybean oil were utilized to prepare the shell and core of the thermally stable microcapsules (MC(CS)), respectively. The MC(CS) were prepared by sol-gel coacervation from an oil-in-water emulsion. The sodium silicate was hydrolyzed and coacervated through polymerization for 24 h at pH 5. The zeta potential analysis indicated that chitosan with a positive charge and silica with a negative charge interacted through electrostatic attraction to form a hybrid shell. The volume mean particle size and encapsulation efficiency of the MC(CS) were 9.6 ± 0.2 μm and 75.6% ± 1.3%, respectively, when oil/chitosan = 0.2 and chitosan/silica = 0.5 (w/w). In addition to H-bonding and electrostatic attraction, Si-O-N bonds were formed between chitosan and silica. Dehydration of the bound water in the MC(CS) was observed in the range of 25 to 250 °C in the differential scanning calorimetry thermal analysis, with the lack of apparent thermal peaks indicating its high thermal stability. The decrease of force to cut the crust observed by texture analysis as well as the increase of hedonic score by consumer acceptance test revealed the addition of 1% MC(CS) significantly improved the crispness of the crust in the microwave-reheated nuggets. © 2014 Institute of Food Technologists®

  20. Fabrication of silica hollow particles using yeast cells as a template

    Science.gov (United States)

    Liao, Shenglan; Lin, Liqin; Chen, Xiaofang; Liu, Jingru; Zhang, Biao

    2018-04-01

    Inorganic hollow particles have attracted great interest in recent years. In this study, silica micro spheres were produced. Yeast cells were used as a biological template. The silica shell was synthesized by the hydrolysis of tetraethoxysilane (TEOS) in water-alcohol mixtures as solvent using ammonia as a catalyst according to the Stoeber process. Various approaches including X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transformed infrared (FT-IR) spectroscopy were used to characterize the products. The results showed that the thermally treated samples were SiO2 hollow microspheres with a diameter varying between 1-5μm.

  1. A novel approach to fabrication of superparamagnetite hollow silica/magnetic composite spheres

    Energy Technology Data Exchange (ETDEWEB)

    Yuan Junjie, E-mail: yuanjunjie@tongji.edu.c [School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China); Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200433 (China); Zhang Xiong; Qian He [School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China)

    2010-08-15

    We described a method for synthesizing hollow silica/magnetic composite spheres using sulfonic acid functionalized hollow silica spheres (SAFHSS) as templates. The Fe{sub 3}O{sub 4} nanoparticles were deposited on or imbedded in the hollow silica shell by a precipitation reaction. The morphologies, composition and properties of the hollow composite spheres were characterized by transmission electron microscopy, Fourier transform infrared analysis, X-ray diffraction measurement and vibrating-sample magnetometry measurement. The results indicated crystal sizes and amount of the Fe{sub 3}O{sub 4} nanoparticles on the SAFHSS. The magnetic properties of the hollow composite spheres were controlled by adjusting the proportion between Fe{sup 2+} and Fe{sup 3+} and iron ion total concentration. When appropriate loading species were added into the system, superparamagnetite hollow composite spheres were obtained. The method also could be applicable to prepare other superparamagnetite hollow silica/ferrite composite spheres.

  2. Multimodality Imaging with Silica-Based Targeted Nanoparticle Platforms

    International Nuclear Information System (INIS)

    Lewis, Jason S.

    2012-01-01

    Objectives: To synthesize and characterize a C-Dot silica-based nanoparticle containing 'clickable' groups for the subsequent attachment of targeting moieties (e.g., peptides) and multiple contrast agents (e.g., radionuclides with high specific activity) (1,2). These new constructs will be tested in suitable tumor models in vitro and in vivo to ensure maintenance of target-specificity and high specific activity. Methods: Cy5 dye molecules are cross-linked to a silica precursor which is reacted to form a dye-rich core particle. This core is then encapsulated in a layer of pure silica to create the core-shell C-Dot (Figure 1) (2). A 'click' chemistry approach has been used to functionalize the silica shell with radionuclides conferring high contrast and specific activity (e.g. 64Cu and 89Zr) and peptides for tumor targeting (e.g. cRGD and octreotate) (3). Based on the selective Diels-Alder reaction between tetrazine and norbornene, the reaction is bioorthogonal, highyielding, rapid, and water-compatible. This radiolabeling approach has already been employed successfully with both short peptides (e.g. octreotate) and antibodies (e.g. trastuzumab) as model systems for the ultimate labeling of the nanoparticles (1). Results: PEGylated C-Dots with a Cy5 core and labeled with tetrazine have been synthesized (d = 55 nm, zeta potential = -3 mV) reliably and reproducibly and have been shown to be stable under physiological conditions for up to 1 month. Characterization of the nanoparticles revealed that the immobilized Cy5 dye within the C-Dots exhibited fluorescence intensities over twice that of the fluorophore alone. The nanoparticles were successfully radiolabeled with Cu-64. Efforts toward the conjugation of targeting peptides (e.g. cRGD) are underway. In vitro stability, specificity, and uptake studies as well as in vivo imaging and biodistribution investigations will be presented. Conclusions: C-Dot silica-based nanoparticles offer a robust, versatile, and multi

  3. The impact of aminated surface ligands and silica shells on the stability, uptake, and toxicity of engineered silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Bonventre, Josephine A.; Pryor, Joseph B.; Harper, Bryan J.; Harper, Stacey L., E-mail: stacey.harper@oregonstate.edu [Oregon State University, Department of Environmental and Molecular Toxicology (United States)

    2014-12-15

    Inherent nanomaterial characteristics, composition, surface chemistry, and primary particle size, are known to impact particle stability, uptake, and toxicity. Nanocomposites challenge our ability to predict nanoparticle reactivity in biological systems if they are composed of materials with contrasting relative toxicities. We hypothesized that toxicity would be dominated by the nanoparticle surface (shell vs core), and that modulating the surface ligands would have a direct impact on uptake. We exposed developing zebrafish (Danio rerio) to a series of ∼70 nm amine-terminated silver nanoparticles with silica shells (AgSi NPs) to investigate the relative influence of surface amination, composition, and size on toxicity. Like-sized aminated AgSi and Si NPs were more toxic than paired hydroxyl-terminated nanoparticles; however, both AgSi NPs were more toxic than the Si NPs, indicating a significant contribution of the silver core to the toxicity. Incremental increases in surface amination did not linearly increase uptake and toxicity, but did have a marked impact on dispersion stability. Mass-based exposure metrics initially supported the hypothesis that smaller nanoparticles (20 nm) would be more toxic than larger particles (70 nm). However, surface area-based metrics revealed that toxicity was independent of size. Our studies suggest that nanoparticle surfaces play a critical role in the uptake and toxicity of AgSi NPs, while the impact of size may be a function of the exposure metric used. Overall, uptake and toxicity can be dramatically altered by small changes in surface functionalization or exposure media. Only after understanding the magnitude of these changes, can we begin to understand the biologically available dose following nanoparticle exposure.

  4. Effect of Mesostructured Layer upon Crystalline Properties and Device Performance on Perovskite Solar Cells.

    Science.gov (United States)

    Listorti, Andrea; Juarez-Perez, Emilio J; Frontera, Carlos; Roiati, Vittoria; Garcia-Andrade, Laura; Colella, Silvia; Rizzo, Aurora; Ortiz, Pablo; Mora-Sero, Ivan

    2015-05-07

    One of the most fascinating characteristics of perovskite solar cells (PSCs) is the retrieved obtainment of outstanding photovoltaic (PV) performances withstanding important device configuration variations. Here we have analyzed CH3NH3PbI3-xClx in planar or in mesostructured (MS) configurations, employing both titania and alumina scaffolds, fully infiltrated with perovskite material or presenting an overstanding layer. The use of the MS scaffold induces to the perovskite different structural properties, in terms of grain size, preferential orientation, and unit cell volume, in comparison to the ones of the material grown with no constraints, as we have found out by X-ray diffraction analyses. We have studied the effect of the PSC configuration on photoinduced absorption and time-resolved photoluminescence, complementary techniques that allow studying charge photogeneration and recombination. We have estimated electron diffusion length in the considered configurations observing a decrease when the material is confined in the MS scaffold with respect to a planar architecture. However, the presence of perovskite overlayer allows an overall recovering of long diffusion lengths explaining the record PV performances obtained with a device configuration bearing both the mesostructure and a perovskite overlayer. Our results suggest that performance in devices with perovskite overlayer is mainly ruled by the overlayer, whereas the mesoporous layer influences the contact properties.

  5. A novel core–shell nanocomposite Ni–Ca@mSiO{sub 2} for benzophenone selective hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Han, Xue; Feng, Wenhui; Chu, Xiaoning; Chu, Hailong; Niu, Libo; Bai, Guoyi, E-mail: baiguoyi@hotmail.com [Hebei University, Key Laboratory of Chemical Biology of Hebei Province, College of Chemistry and Environmental Science (China)

    2017-02-15

    A novel core–shell nanocomposite Ni–Ca@mSiO{sub 2} was first prepared by a modified Stöber method in this paper. It has a core–shell structure with Ni (about 8 nm in diameter) and Ca as the cores and mesoporous silica as the outer shell, as proven by the transmission electron microscopy. This nanocomposite exhibited good catalytic performance in the selective hydrogenation of benzophenone, with 96.1% conversion and 94.9% selectivity for benzhydrol under relatively mild reaction conditions. It was demonstrated that addition of small amounts of alkaline Ca can not only markedly improve the dispersion of the active species but also tune the acid–base property of this nanocomposite, resulting in the efficient suppression of benzhydrol dehydration to achieve a high selectivity. Furthermore, the core–shell nanocomposite Ni–Ca@mSiO{sub 2} can be recycled four runs without appreciable loss of its initial activity, more stable than the traditional supported nanocatalyst Ni–Ca/mSiO{sub 2}. It was suggested that the outer mesoporous silica shell of Ni–Ca@mSiO{sub 2} can prevent both the aggregation and the leaching of the active Ni species, accounting for its relatively good stability.

  6. Biological Fate of Fe3O4 Core-Shell Mesoporous Silica Nanoparticles Depending on Particle Surface Chemistry

    Science.gov (United States)

    Rascol, Estelle; Daurat, Morgane; Da Silva, Afitz; Maynadier, Marie; Dorandeu, Christophe; Charnay, Clarence; Garcia, Marcel; Lai-Kee-Him, Joséphine; Bron, Patrick; Auffan, Mélanie; Angeletti, Bernard; Devoisselle, Jean-Marie; Guari, Yannick; Gary-Bobo, Magali; Chopineau, Joël

    2017-01-01

    The biological fate of nanoparticles (NPs) for biomedical applications is highly dependent of their size and charge, their aggregation state and their surface chemistry. The chemical composition of the NPs surface influences their stability in biological fluids, their interaction with proteins, and their attraction to the cell membranes. In this work, core-shell magnetic mesoporous silica nanoparticles (Fe3O4@MSN), that are considered as potential theranostic candidates, are coated with polyethylene glycol (PEG) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayer. Their biological fate is studied in comparison to the native NPs. The physicochemical properties of these three types of NPs and their suspension behavior in different media are investigated. The attraction to a membrane model is also evaluated using a supported lipid bilayer. The surface composition of NPs strongly influences their dispersion in biological fluids mimics, protein binding and their interaction with cell membrane. While none of these types of NPs is found to be toxic on mice four days after intravenous injection of a dose of 40 mg kg−1 of NPs, their surface coating nature influences the in vivo biodistribution. Importantly, NP coated with DMPC exhibit a strong accumulation in liver and a very low accumulation in lung in comparison with nude or PEG ones. PMID:28665317

  7. Sol-gel precursors and products thereof

    Science.gov (United States)

    Warren, Scott C.; DiSalvo, Jr., Francis J.; Weisner, Ulrich B.

    2017-02-14

    The present invention provides a generalizable single-source sol-gel precursor capable of introducing a wide range of functionalities to metal oxides such as silica. The sol-gel precursor facilitates a one-molecule, one-step approach to the synthesis of metal-silica hybrids with combinations of biological, catalytic, magnetic, and optical functionalities. The single-source precursor also provides a flexible route for simultaneously incorporating functional species of many different types. The ligands employed for functionalizing the metal oxides are derived from a library of amino acids, hydroxy acids, or peptides and a silicon alkoxide, allowing many biological functionalities to be built into silica hybrids. The ligands can coordinate with a wide range of metals via a carboxylic acid, thereby allowing direct incorporation of inorganic functionalities from across the periodic table. Using the single-source precursor a wide range of functionalized nanostructures such as monolith structures, mesostructures, multiple metal gradient mesostructures and Stober-type nanoparticles can be synthesized. ##STR00001##

  8. Multifunctional EuYVO4 nanoparticles coated with mesoporous silica

    International Nuclear Information System (INIS)

    Justino, Larissa G.; Nigoghossian, Karina; Capote, Ticiana S.O.; Scarel-Caminaga, Raquel M.; Ribeiro, Sidney J.L.; Caiut, José Maurício A.

    2016-01-01

    Mesoporous structures are interesting materials for the incorporation of dyes, drugs, and luminescent systems, leading to materials with important multifunctionalities. In a very unique way, these guest/host materials combine the high stability of inorganic systems, new guest-structuring features, and adsorption mechanisms in their well-defined pores. This work evaluates the luminescent properties of rare earth-doped YVO 4 nanoparticles coated with a mesoporous silica shell. The use of two different synthesis methodologies allowed for particle size control. The crystalline phase emerged without further heat treatment. The mesoporous shell decreased undesirable quenching effects on YVO 4 :Eu 3+ nanoparticles and rendered them biocompatible. The materials prepared herein could have interesting applications as luminescent markers or drug release systems.

  9. Evolution of Morphology and Crystallinity of Silica Minerals Under Hydrothermal Conditions

    Science.gov (United States)

    Isobe, H.

    2011-12-01

    Silica minerals are quite common mineral species in surface environment of the terrestrial planets. They are good indicator of terrestrial processes including hydrothermal alteration, diagenesis and soil formation. Hydrothermal quartz, metastable low temperature cristobalite and amorphous silica show characteristic morphology and crystallinity depending on their formation processes and kinetics under wide range of temperature, pressure, acidity and thermal history. In this study, silica minerals produced by acidic hydrothermal alteration related to volcanic activities and hydrothermal crystallization experiments from diatom sediment are examined with crystallographic analysis and morphologic observations. Low temperature form of cistobalite is a metastable phase and a common alteration product occured in highly acidic hydrothermal environment around fumaroles in geothermal / volcanic areas. XRD analysis revealed that the alteration degree of whole rock is represented by abundance of cristobalite. Detailed powder XRD analysis show that the primary diffraction peak of cristobalite composed with two or three phases with different d-spacing and FWHM by peak profile fitting analysis. Shorter d-spacing and narrower FWHM cristobalite crystallize from precursor materials with less-crystallized, longer d-spacing and wider FWHM cristobalite. Textures of hydrothermal cristobalite in altered rock shows remnant of porphylitic texture of the host rock, pyroxene-amphibole andesite. Diatom has amorphous silica shell and makes diatomite sediment. Diatomite found in less diagenetic Quarternary formation keeps amorphous silica diatom shells. Hydrothermal alteration experiments of amorphous silica diatomite sediment are carried out from 300 °C to 550 °C. Mineral composition of run products shows crystallization of cristobalite and quartz progress depending on temperature and run durations. Initial crystallization product, cristobalite grains occur as characteristic lepispheres and

  10. Synthesis of ordered mesoporous uranium dioxide by a nanocasting route

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Ran; Wang Lin; Shi, Wei-Qun [Chinese Academy of Sciences, Beijing (China). Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety; Chai, Zhi-Fang [Chinese Academy of Sciences, Beijing (China). Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety; Soochow Univ., Suzhou (China). School of Radiological and Interdisciplinary Sciences and Collaborative Innovation Center

    2016-11-01

    Ordered mesoporous UO{sub 2} with 3-D structure (for UO{sub 2}-KIT-6) and nanowire bundles (for UO{sub 2}-SBA-15) was synthesized for the first time by a nanocasting route using different ordered mesoporous silica (KIT-6 and SBA-15, respectively) as templates and uranyl nitrate hexahydrate as the metal precursor. The uranyl nitrate was impregnated into the mesopore of the silica template and was converted to U{sub 3}O{sub 8} after the first step. The synthesis of ordered UO{sub 2} mesostructure was achieved by reducing the mesoporous U{sub 3}O{sub 8} with silica composites under 5% H{sub 2}/Ar atmosphere at 700 C, followed by a template removal process. The as-prepared UO{sub 2}-KIT-6 had a particle size of several millimeters, and was constructed with uncoupled subframework mesostructure and crystalline walls, while UO{sub 2}-SBA-15 possessed a rope-like morphology and consisted of nanowire arrays. The surface area and pore volume of ordered UO{sub 2} mesostructure are 47.2 m{sup 2} g{sup -1} and 0.23 cm{sup 3} g{sup -1} for the UO{sub 2}-KIT-6, and 54.4 m{sup 2} g{sup -1} and 0.28 cm{sup 3} g{sup -1} for the UO{sub 2}-SBA-15, respectively.

  11. Magnetic properties of Ni nanoparticles on microporous silica spheres

    International Nuclear Information System (INIS)

    Godsell, Jeffrey F.; Donegan, Keith P.; Tobin, Joseph M.; Copley, Mark P.; Rhen, Fernando M.F.; Otway, David J.; Morris, Michael A.; O'Donnell, Terence; Holmes, Justin D.; Roy, Saibal

    2010-01-01

    Ni nanoparticles (∼32 nm particle diameter) have been synthesized on the walls of microporous (∼1 nm pore diameter) silica spheres (∼2.6 μm sphere diameter) and characterised magnetically to potentially produce a new class of core (silica micro-spheres)-shell (nanometallic)-type nanocomposite material. These magnetic nanocomposite materials display a characteristic increase in coercivity with reducing temperature. The average particle size has been used to calculate the anisotropy constant for the system, K. The discussion postulates the potential mechanisms contributing to the difference between the calculated K value and the magnetocrystalline anisotropy constant of bulk Ni. Various factors such as surface anisotropy and interparticle interactions are discussed as possible contributing factors to the anisotropy values calculated in the paper.

  12. A flexible, bolaamphiphilic template for mesoporous silicas.

    Science.gov (United States)

    Yuen, Alexander K L; Heinroth, Falk; Ward, Antony J; Masters, Anthony F; Maschmeyer, Thomas

    2013-08-28

    A novel symmetrical bolaamphiphile, containing two N-methylimidazolium head-groups bridged by a 32-methylene linker, was synthesized and characterized. A variety of mesoporous silicas was prepared using the bolaamphiphile as a "soft template". The effects of absolute surfactant concentration and synthesis conditions upon the morphologies of these silicas were investigated. For a given surfactant concentration, particle morphology; pore size; and pore ordering were modified through control of the template to silica-precursor ratio and synthesis conditions. Observed morphologies included: lenticular core-shell nanoparticles and decorticated globules, truncated hexagonal plates, and sheets. In all cases the mesopores are aligned along the shortest axis of the nanomaterial. Decorticated materials displayed surface areas of up to 1200 m(2) g(-1) and pore diameters (D(BJH)) of 24-28 Å. Small-angle X-ray diffraction and transmission electron microscopy measurements revealed that the majority of the materials has elliptical pores arranged in rectangular lattices (c2mm). Adoption of this symmetry group is a result of the template aggregate deformation from a regular hexagonal phase of cylindrical rods to a ribbon phase under the synthetic conditions.

  13. A novel enzyme-mimic nanosensor based on quantum dot-Au nanoparticle@silica mesoporous microsphere for the detection of glucose

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yang; Ma, Qiang; Liu, Ziping [Department of Analytical Chemistry, College of Chemistry, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Wang, Xinyan [Changchun Institute of Applied Chemistry Chinese Academy of Sciences, Changchun 130022 (China); Su, Xingguang, E-mail: suxg@jlu.edu.cn [Department of Analytical Chemistry, College of Chemistry, Jilin University, Qianjin Street 2699, Changchun 130012 (China)

    2014-08-20

    Highlights: • Design QD-Au NP@silica mesoporous microspheres as a novel enzyme-mimic nanosensor. • Composition of two kinds of nanoparticle can be controlled through silica layers coating. • Our nanosensor for glucose detection has high sensitivity and selectivity. - Abstract: QD-Au NP@silica mesoporous microspheres have been fabricated as a novel enzyme-mimic nanosensor. CdTe quantum dots (QDs) were loaded into the core, and Au nanoparticles (NPs) were encapsulated in the outer mesoporous shell. QDs and Au NPs were separated in the different space of the nanosensor, which prevent the potential energy or electron transfer process between QDs and Au NPs. As biomimetic catalyst, Au NPs in the mesoporous silica shell can catalytically oxidize glucose as glucose oxidase (GOx)-mimicking. The resultant hydrogen peroxide can quench the photoluminescence (PL) signal of QDs in the microsphere core. Therefore the nanosensor based on the decrease of the PL intensity of QDs was established for the glucose detection. The linear range for glucose was in the range of 5–200 μM with a detection limit (3σ) of 1.32 μM.

  14. Synthesis of highly fluorescent silica nanoparticles in a reverse microemulsion through double-layered doping of organic fluorophores

    International Nuclear Information System (INIS)

    Yoo, Hyojong; Pak, Joonsung

    2013-01-01

    Water-soluble, highly fluorescent double-layered silica nanoparticles (FL-DLSN) have been successfully synthesized through a reverse (water-in-oil) microemulsion method. The microemulsion was prepared by mixing a surfactant (Brij35), co-surfactant, organic solvent, water, and fluorescein as an organic fluorophore. The sizes of the silica nanoparticles were successfully controlled in the reverse microemulsion using Brij35 by changing the water-to-Brij35 ratio and by adding HCl. Initially, tetraethylorthosilicate was hydrolyzed by adding NH 4 OH as a catalyst and then polymerized to generate core fluorescent silica nanoparticles with fluorescein. 3-(Aminopropyl)triethoxysilane (APTS) was sequentially added into the reaction mixture, and reacted on the surface of pre-generated core silica nanoparticles to form the second layer in the form of a shell. The second silica layer that was derived from the condensation of APTS effectively protected the fluorescein dye within the silica matrix. This is a novel and simple synthetic approach to generate highly fluorescent, monodispersed silica nanoparticles by doping organic molecules into a silica matrix.Graphical Abstract

  15. Synthesis of highly fluorescent silica nanoparticles in a reverse microemulsion through double-layered doping of organic fluorophores

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Hyojong, E-mail: hyojong@hallym.ac.kr; Pak, Joonsung [Hallym University, Department of Chemistry (Korea, Republic of)

    2013-05-15

    Water-soluble, highly fluorescent double-layered silica nanoparticles (FL-DLSN) have been successfully synthesized through a reverse (water-in-oil) microemulsion method. The microemulsion was prepared by mixing a surfactant (Brij35), co-surfactant, organic solvent, water, and fluorescein as an organic fluorophore. The sizes of the silica nanoparticles were successfully controlled in the reverse microemulsion using Brij35 by changing the water-to-Brij35 ratio and by adding HCl. Initially, tetraethylorthosilicate was hydrolyzed by adding NH{sub 4}OH as a catalyst and then polymerized to generate core fluorescent silica nanoparticles with fluorescein. 3-(Aminopropyl)triethoxysilane (APTS) was sequentially added into the reaction mixture, and reacted on the surface of pre-generated core silica nanoparticles to form the second layer in the form of a shell. The second silica layer that was derived from the condensation of APTS effectively protected the fluorescein dye within the silica matrix. This is a novel and simple synthetic approach to generate highly fluorescent, monodispersed silica nanoparticles by doping organic molecules into a silica matrix.Graphical Abstract.

  16. Controlled epitaxial growth of mesoporous silica/gold nanorod nanolollipops and nanodumb-bells

    International Nuclear Information System (INIS)

    Huang, Ching-Mao; Chung, Ming-Fang; Lo, Leu-Wei; Souris, Jeffrey S.

    2014-01-01

    In this work, we describe the controlled synthesis of novel heterogeneous nanostructures comprised of mesoporous silica-coated gold nanorods (MSGNRs) in the form of core–shell nanolollipops and nanodumb-bells, using a seed-mediated sol–gel method. Although MSGNR core–shell (θ-MSGNR) structures have been reported previously by us and others, we herein discuss the first ever fabrication of MSGNR nanolollipops (φ-MSGNR) and nanodumb-bells (β-MSGNR), achieved by simply controlling the aging time of gold nanorods (GNRs), the residual cetyltrimethylammonium bromide (CTAB) coating of GNRs, and the addition of dimethyl formamide during incubation, centrifugation, and sonication, respectively. Transmission electron microscopy revealed two bare GNR isoforms, with aspect ratios of approximately 4 and 6, while scanning electron microscopy was used to further elucidate the morphology of φ-MSGNR and β-MSGNR heterostructures. In agreement with the smaller dielectric constants afforded by incomplete silica encasement, spectroscopic studies of φ-MSGNR and β-MSGNR, surface plasmon resonance (SPR) bands revealed 20-40 nm blue shifts relative to the SPR of θ-MSGNR. On the basis of the attributes and applications of more conventional θ-MSGNRs, φ-MSGNRs and β-MSGNRs are anticipated to provide most of the utility of θ-MSGNRs, but with the additional functionalities that accompany their incorporation of both bare gold and mesoporous silica encased tips; with significant/unique implications for biomedical and catalytic applications

  17. Thick-shelled, grazer-protected diatoms decouple ocean carbon and silicon cycles in the iron-limited Antarctic Circumpolar Current

    Science.gov (United States)

    Assmy, Philipp; Smetacek, Victor; Montresor, Marina; Klaas, Christine; Henjes, Joachim; Strass, Volker H.; Arrieta, Jesús M.; Bathmann, Ulrich; Berg, Gry M.; Breitbarth, Eike; Cisewski, Boris; Friedrichs, Lars; Fuchs, Nike; Herndl, Gerhard J.; Jansen, Sandra; Krägefsky, Sören; Latasa, Mikel; Peeken, Ilka; Röttgers, Rüdiger; Scharek, Renate; Schüller, Susanne E.; Steigenberger, Sebastian; Webb, Adrian; Wolf-Gladrow, Dieter

    2013-01-01

    Diatoms of the iron-replete continental margins and North Atlantic are key exporters of organic carbon. In contrast, diatoms of the iron-limited Antarctic Circumpolar Current sequester silicon, but comparatively little carbon, in the underlying deep ocean and sediments. Because the Southern Ocean is the major hub of oceanic nutrient distribution, selective silicon sequestration there limits diatom blooms elsewhere and consequently the biotic carbon sequestration potential of the entire ocean. We investigated this paradox in an in situ iron fertilization experiment by comparing accumulation and sinking of diatom populations inside and outside the iron-fertilized patch over 5 wk. A bloom comprising various thin- and thick-shelled diatom species developed inside the patch despite the presence of large grazer populations. After the third week, most of the thinner-shelled diatom species underwent mass mortality, formed large, mucous aggregates, and sank out en masse (carbon sinkers). In contrast, thicker-shelled species, in particular Fragilariopsis kerguelensis, persisted in the surface layers, sank mainly empty shells continuously, and reduced silicate concentrations to similar levels both inside and outside the patch (silica sinkers). These patterns imply that thick-shelled, hence grazer-protected, diatom species evolved in response to heavy copepod grazing pressure in the presence of an abundant silicate supply. The ecology of these silica-sinking species decouples silicon and carbon cycles in the iron-limited Southern Ocean, whereas carbon-sinking species, when stimulated by iron fertilization, export more carbon per silicon. Our results suggest that large-scale iron fertilization of the silicate-rich Southern Ocean will not change silicon sequestration but will add carbon to the sinking silica flux. PMID:24248337

  18. The Synthesis and Characterization of Gold-Core/LDH-Shell Nanoparticles

    Science.gov (United States)

    Rearick, Colton

    In recent years, the field of nanomedicine has progressed at an astonishing rate, particularly with respect to applications in cancer treatment and molecular imaging. Although organic systems have been the frontrunners, inorganic systems have also begun to show promise, especially those based upon silica and magnetic nanoparticles (NPs). Many of these systems are being designed for simultaneous therapeutic and diagnostic capabilities, thus coining the term, theranostics. A unique class of inorganic systems that shows great promise as theranostics is that of layered double hydroxides (LDH). By synthesis of a core/shell structures, e.g. a gold nanoparticle (NP) core and LDH shell, the multifunctional theranostic may be developed without a drastic increase in the structural complexity. To demonstrate initial proof-of-concept of a potential (inorganic) theranostic platform, a Au-core/LDH-shell nanovector has been synthesized and characterized. The LDH shell was heterogeneously nucleated and grown on the surface of silica coated gold NPs via a coprecipitation method. Polyethylene glycol (PEG) was introduced in the initial synthesis steps to improve crystallinity and colloidal stability. Additionally, during synthesis, fluorescein isothiocyanate (FITC) was intercalated into the interlayer spacing of the LDH. In contrast to the PEG stabilization, a post synthesis citric acid treatment was used as a method to control the size and short-term stability. The heterogeneous core-shell system was characterized with scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), dynamic light scattering (DLS), and powder x-ray diffraction (PXRD). A preliminary in vitro study carried out with the assistance of Dr. Kaushal Rege's group at Arizona State University was to demonstrate the endocytosis capability of homogeneously-grown LDH NPs. The DLS measurements of the core-shell NPs indicated an average particle size of 212nm. The PXRD analysis showed that PEG

  19. Effect of SiO2 concentration in silica sol on interface reaction during titanium alloy investment casting

    Directory of Open Access Journals (Sweden)

    Ya-meng Wei

    2018-01-01

    Full Text Available Using silica sol as a binder for titanium investment casting is very attractive due to its good stability and reasonable cost as compared with yttrium sol and zirconium sol. However, the mechanism of interface reaction in the related system remains unclear. In this investigation, the interface reaction between Y2O3-SiO2 (Y-Si shell mold and titanium alloys was studied. A group of shell molds were prepared by using Y2O3 sand and silica sol with different contents of SiO2. Ti-6Al-4V alloy was cast under vacuum by gravity casting through cold crucible induction melting (CCIM method. Scanning electron microscopy (SEM and energy dispersive x-ray spectroscopy (EDS were employed to characterize the micromorphology and composition of the reaction area, respectively. X-ray photoelectron spectroscopy (XPS was used to confirm the valence state of relevant elements. White light interferometer (WLI was used to obtain the surface topography of Y-Si shells. The results show that the thickness of reaction layers is below 3 μm when the SiO2 content of silica sol is below 20wt.%. Whereas, when the SiO2 content increases to 25wt.%, the thickness of the reaction layer increases sharply to about 15 μm. There is a good balance between chemical inertness and mechanical performance when the SiO2 content is between 15 and 20wt.%. Moreover, it was found that the distribution of SiO2 and the roughness at the surface of the shell are the key factors that determine the level of reaction.

  20. Synthesis and characterization of pharmaceutical surfactant templated mesoporous silica: Its application to controlled delivery of duloxetine

    Energy Technology Data Exchange (ETDEWEB)

    Mani, Ganesh; Pushparaj, Hemalatha; Peng, Mei Mei; Muthiahpillai, Palanichamy [Department of Chemical Engineering, Hanseo University, Seosan-si 356 706 (Korea, Republic of); Udhumansha, Ubaidulla [Department of Chemical Engineering, Hanseo University, Seosan-si 356 706 (Korea, Republic of); Department of Pharmaceutics, C.L. Baid Metha College of Pharmacy, Chennai (India); Jang, Hyun Tae, E-mail: htjang@hanseo.ac.kr [Department of Chemical Engineering, Hanseo University, Seosan-si 356 706 (Korea, Republic of)

    2014-03-01

    Graphical abstract: - Highlights: • Usefulness of dual pharmaceutical surfactants in silica synthesis was evaluated. • Effects of concentration of secondary template (Tween-40) were studied. • Effects of fixed solvothermal condition on mesostructure formation were studied. • Duloxetine drug loading capability was studied. • Sustained release of duloxetine was evaluated. - Abstract: A new group of mesoporous silica nanoparticles (MSNs) were synthesized using combination pharmaceutical surfactants, Triton X-100 and Tween-40 as template and loaded with duloxetine hydrochloride (DX), for improving the sustained release of DX and patterns with high drug loading. Agglomerated spherical silica MSNs were synthesized by sol–gel and solvothermal methods. The calcined and drug loaded MSNs were characterized using X-ray diffraction (XRD), Braunner–Emmett–Teller (BET), thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), diffuse reflectance ultraviolet–visible (DRS-UV–vis) spectroscopy. MSNs with high surface area and pore volume were selected and studied for their DX loading and release. The selected MSNs can accommodate a maximum of 34% DX within it. About 90% was released at 200 h and hence, the synthesized MSNs were capable of engulfing DX and sustain its release. Further form the Ritger and Peppas, Higuchi model for mechanism drug release from all the MSN matrices follows anomalous transport or Non-Fickian diffusion with the ‘r’ and ‘n’ value 0.9 and 0.45 < n < 1, respectively. So, from this study it could be concluded that the MSNs synthesized using pharmaceutical templates were better choice of reservoir for the controlled delivery of drug which requires sustained release.

  1. Mannose-functionalized porous silica-coated magnetic nanoparticles for two-photon imaging or PDT of cancer cells

    International Nuclear Information System (INIS)

    Perrier, Marine; Gary-Bobo, Magali; Lartigue, Lenaïc; Brevet, David; Morère, Alain; Garcia, Marcel; Maillard, Philippe; Raehm, Laurence; Guari, Yannick; Larionova, Joulia; Durand, Jean-Olivier; Mongin, Olivier; Blanchard-Desce, Mireille

    2013-01-01

    An original fluorophore engineered for two-photon excitation or a porphyrin derivative were entrapped in the silica shell of magnetic porous silica nanoparticles during the synthesis of the silica moiety without damaging the structure of the organic part. The mild conditions involved allowed obtaining microporous or mesoporous silica magnetic nanoparticles, respectively. Mannose was grafted on the surface of the nanoparticles to target MCF-7 breast cancer cells. The studies of magnetic properties of these hybrid nanoparticles show that they present a blocking temperature at 190 K. The nano-objects designed with the two-photon fluorophore were efficient for two-photon imaging of MCF-7 cancer cells, whereas the nano-objects with the photosensitizer efficiently killed cancer cells. The presence of the mannose moiety was demonstrated to improve both imaging and therapy properties.

  2. Mannose-functionalized porous silica-coated magnetic nanoparticles for two-photon imaging or PDT of cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Perrier, Marine [UMR 5253 CNRS-UM2-ENSCM-UM1, Institut Charles Gerhardt Montpellier (France); Gary-Bobo, Magali [Faculte de Pharmacie, Universite Montpellier 1, Universite Montpellier 2, Institut des Biomolecules Max Mousseron UMR 5247 CNRS (France); Lartigue, Lenaiec; Brevet, David [UMR 5253 CNRS-UM2-ENSCM-UM1, Institut Charles Gerhardt Montpellier (France); Morere, Alain; Garcia, Marcel [Faculte de Pharmacie, Universite Montpellier 1, Universite Montpellier 2, Institut des Biomolecules Max Mousseron UMR 5247 CNRS (France); Maillard, Philippe [Universite Paris-Sud, UMR 176 CNRS, Institut Curie (France); Raehm, Laurence; Guari, Yannick, E-mail: yannick.guari@um2.fr; Larionova, Joulia; Durand, Jean-Olivier, E-mail: durand@univ-montp2.fr [UMR 5253 CNRS-UM2-ENSCM-UM1, Institut Charles Gerhardt Montpellier (France); Mongin, Olivier [Universite de Rennes 1, Institut des Sciences Chimiques de Rennes, CNRS UMR 6226 (France); Blanchard-Desce, Mireille [Universite Bordeaux, Institut des Sciences Moleculaires, UMR CNRS 5255 (France)

    2013-05-15

    An original fluorophore engineered for two-photon excitation or a porphyrin derivative were entrapped in the silica shell of magnetic porous silica nanoparticles during the synthesis of the silica moiety without damaging the structure of the organic part. The mild conditions involved allowed obtaining microporous or mesoporous silica magnetic nanoparticles, respectively. Mannose was grafted on the surface of the nanoparticles to target MCF-7 breast cancer cells. The studies of magnetic properties of these hybrid nanoparticles show that they present a blocking temperature at 190 K. The nano-objects designed with the two-photon fluorophore were efficient for two-photon imaging of MCF-7 cancer cells, whereas the nano-objects with the photosensitizer efficiently killed cancer cells. The presence of the mannose moiety was demonstrated to improve both imaging and therapy properties.

  3. Simple Synthesis and Growth Mechanism of Core/Shell CdSe/SiOx Nanowires

    Directory of Open Access Journals (Sweden)

    Guozhang Dai

    2010-01-01

    Full Text Available Core-shell-structured CdSe/SiOx nanowires were synthesized on an equilateral triangle Si (111 substrate through a simple one-step thermal evaporation process. SEM, TEM, and XRD investigations confirmed the core-shell structure; that is, the core zone is single crystalline CdSe and the shell zone is SiOx amorphous layer and CdSe core was grown along (001 direction. Two-stage growth process was present to explain the growth mechanism of the core/shell nanwires. The silicon substrate of designed equilateral triangle providing the silicon source is the key factor to form the core-shell nanowires, which is significant for fabrication of nanowire-core sheathed with a silica system. The PL of the product studied at room temperature showed two emission bands around 715 and 560 nm, which originate from the band-band transition of CdSe cores and the amorphous SiOx shells, respectively.

  4. Multimodality Imaging with Silica-Based Targeted Nanoparticle Platforms

    Energy Technology Data Exchange (ETDEWEB)

    Jason S. Lewis

    2012-04-09

    Objectives: To synthesize and characterize a C-Dot silica-based nanoparticle containing 'clickable' groups for the subsequent attachment of targeting moieties (e.g., peptides) and multiple contrast agents (e.g., radionuclides with high specific activity) [1,2]. These new constructs will be tested in suitable tumor models in vitro and in vivo to ensure maintenance of target-specificity and high specific activity. Methods: Cy5 dye molecules are cross-linked to a silica precursor which is reacted to form a dye-rich core particle. This core is then encapsulated in a layer of pure silica to create the core-shell C-Dot (Figure 1) [2]. A 'click' chemistry approach has been used to functionalize the silica shell with radionuclides conferring high contrast and specific activity (e.g. 64Cu and 89Zr) and peptides for tumor targeting (e.g. cRGD and octreotate) [3]. Based on the selective Diels-Alder reaction between tetrazine and norbornene, the reaction is bioorthogonal, highyielding, rapid, and water-compatible. This radiolabeling approach has already been employed successfully with both short peptides (e.g. octreotate) and antibodies (e.g. trastuzumab) as model systems for the ultimate labeling of the nanoparticles [1]. Results: PEGylated C-Dots with a Cy5 core and labeled with tetrazine have been synthesized (d = 55 nm, zeta potential = -3 mV) reliably and reproducibly and have been shown to be stable under physiological conditions for up to 1 month. Characterization of the nanoparticles revealed that the immobilized Cy5 dye within the C-Dots exhibited fluorescence intensities over twice that of the fluorophore alone. The nanoparticles were successfully radiolabeled with Cu-64. Efforts toward the conjugation of targeting peptides (e.g. cRGD) are underway. In vitro stability, specificity, and uptake studies as well as in vivo imaging and biodistribution investigations will be presented. Conclusions: C-Dot silica-based nanoparticles offer a robust

  5. Investigation of the Mesostructure of Transition-Metal Monogermanides Synthesized under Pressure

    Science.gov (United States)

    Safiulina, I. A.; Altynbaev, E. V.; Iashina, E. G.; Heinemann, A.; Fomicheva, L. N.; Tsvyashchenko, A. V.; Grigoriev, S. V.

    2018-04-01

    The mesostructure of transition-metal monogermanides Mn1 - x Co x Ge is studied by small-angle neutron scattering in a wide range of concentrations x = 0-0.95. These compounds were synthesized under high pressure and are metastable under normal conditions. The experimental dependences I( Q) obtained for the whole series of samples in the range of transferred momenta (6 × 10-2 nm-1 interesting to note that such defects are absent in the isostructural FeGe compound, i.e., the experimental dependences of the intensity are described well by the expression Q - n with an exponent n = 4.1 ± 0.1, which demonstrates the presence of crystallites with a uniform density distribution inside and a sharp boundary characterizing the surface.

  6. Quantum dots/silica/polymer nanocomposite films with high visible light transmission and UV shielding properties.

    Science.gov (United States)

    Mumin, Md Abdul; Xu, William Z; Charpentier, Paul A

    2015-08-07

    The dispersion of light-absorbing inorganic nanomaterials in transparent plastics such as poly(ethylene-co-vinyl acetate) (PEVA) is of enormous current interest in emerging solar materials, including photovoltaic (PV) modules and commercial greenhouse films. Nanocrystalline semiconductor or quantum dots (QDs) have the potential to absorb UV light and selectively emit visible light, which can control plant growth in greenhouses or enhance PV panel efficiencies. This work provides a new and simple approach for loading mesoporous silica-encapsulated QDs into PEVA. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm size were synthesized using a modified facile approach based on pyrolysis of the single-molecule precursors and capping the CdS QDs with a thin layer of ZnS. To make both the bare and core-shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown on the QDs through a reverse microemulsion technique based on hydrophobic interactions. By careful experimental tuning, this encapsulation technique enhanced the quantum yield (∼65%) and photostability compared to the bare QDs. Both the encapsulated bare and core-shell QDs were then melt-mixed with EVA pellets using a mini twin-screw extruder and pressed into thin films with controlled thickness. The results demonstrated for the first time that mesoporous silica not only enhanced the quantum yield and photostability of the QDs but also improved the compatibility and dispersibility of QDs throughout the PEVA films. The novel light selective films show high visible light transmission (∼90%) and decreased UV transmission (∼75%).

  7. New method to evaluate optical properties of core-shell nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Renteria-Tapia, V. [Universidad de Guadalajara, Ameca, Departamento de Ciencias Naturales y Exactas, Centro Universitario de Los Valles (Mexico); Franco, A., E-mail: alfredofranco@fisica.unam.mx; Garcia-Macedo, J. [Universidad Nacional Autonoma de Mexico, Departamento de Estado Solido, Instituto de Fisica (Mexico)

    2012-06-15

    A new method is presented to calculate, for metallic core-dielectric shell nanostructures, the local refractive index, resonance condition, maximum spectral shift, plasma wavelength, and the sensitivity of the wavelength maximum to variations in the refractive index of the environment. The equations that describe these properties are directly related to the surface plasmon peak position, refractive index of the shell, and to the surrounding medium. The method is based on the approach that a layered core dispersed in a dielectric environment (core-shell model) can be figured out as an uncoated sphere dispersed in a medium with a local refractive index (local refractive index model). Thus, in the Mie theory, the same spectral position of the surface plasmon resonance peak can be obtained by varying the volume fraction of the shell or by varying the local refractive index. The assumed equivalence between plasmon resonance wavelengths enable us to show that the local refractive index depends geometrically on the shell volume fraction. Hence, simple relationships between optical and geometrical properties of these core-shell nanostructures are obtained. Furthermore, good agreement is observed between the new relationships and experimental data corresponding to gold nanoparticles (radius = 7.5 nm) covered with silica shells (with thicknesses up to 29.19 nm), which insured that the equivalence hypothesis is correct.

  8. New method to evaluate optical properties of core–shell nanostructures

    International Nuclear Information System (INIS)

    Rentería-Tapia, V.; Franco, A.; García-Macedo, J.

    2012-01-01

    A new method is presented to calculate, for metallic core–dielectric shell nanostructures, the local refractive index, resonance condition, maximum spectral shift, plasma wavelength, and the sensitivity of the wavelength maximum to variations in the refractive index of the environment. The equations that describe these properties are directly related to the surface plasmon peak position, refractive index of the shell, and to the surrounding medium. The method is based on the approach that a layered core dispersed in a dielectric environment (core–shell model) can be figured out as an uncoated sphere dispersed in a medium with a local refractive index (local refractive index model). Thus, in the Mie theory, the same spectral position of the surface plasmon resonance peak can be obtained by varying the volume fraction of the shell or by varying the local refractive index. The assumed equivalence between plasmon resonance wavelengths enable us to show that the local refractive index depends geometrically on the shell volume fraction. Hence, simple relationships between optical and geometrical properties of these core–shell nanostructures are obtained. Furthermore, good agreement is observed between the new relationships and experimental data corresponding to gold nanoparticles (radius = 7.5 nm) covered with silica shells (with thicknesses up to 29.19 nm), which insured that the equivalence hypothesis is correct.

  9. Core/shell magnetic mesoporous silica nanoparticles with radially oriented wide mesopores

    Directory of Open Access Journals (Sweden)

    Nikola Ž. Knežević

    2014-06-01

    Full Text Available Core/shell nanoparticles, containing magnetic iron-oxide (maghemite core and mesoporous shell with radial porous structure, were prepared by dispersing magnetite nanoparticles and adding tetraethylorthosilicate to a basic aqueous solution containing structure-templating cetyltrimethylammonium bromide and a pore-swelling mesithylene. The material is characterized by SEM and TEM imaging, nitrogen sorption and powder X-ray diffraction. Distinctive features of the prepared material are its high surface area (959 m2/g, wide average pore diameter (12.4 nm and large pore volume (2.3 cm3/g. The material exhibits radial pore structure and the high angle XRD pattern characteristic for maghemite nanoparticles, which are obtained upon calcination of the magnetite-containing material. The observed properties of the prepared material may render the material applicable in separation, drug delivery, sensing and heterogeneous catalysis.

  10. Exploiting the interactions between the ruthenium Hoveyda–Grubbs catalyst and Al-modified mesoporous silica: the case of SBA15 vs. KCC-1

    KAUST Repository

    Werghi, Baraa; Pump, Eva; Tretiakov, Mykyta; Abou-Hamad, Edy; Gurinov, Andrei; Doggali, Pradeep; Anjum, Dalaver H.; Cavallo, Luigi; Bendjeriou-Sedjerari, Anissa; Basset, Jean-Marie

    2018-01-01

    Immobilization of the 2 generation Hoveyda-Grubbs catalyst HG-II onto well-ordered 2D hexagonal (SBA15) and 3D fibrous (KCC-1) mesostructured silica, which contained tetra-coordinated Al, has been investigated through the Surface Organometallic Chemistry (SOMC) methodology. The main interest of this study lies in the peculiarity of the silica supports, which display a well-defined tetrahedral aluminum hydride site displaying a strong Lewis acid character, [(Si-O-Si)(Si-O-)Al-H]. The resulting supported Hoveyda-Grubbs catalysts have been fully characterized by advanced solid state characterization techniques (FT-IR, H and C solid state NMR, DNP-SENS, EF-TEM...). Together with DFT calculations, the immobilization of HG-II does not occur through the formation of a covalent bond between the complex and the Al-modified mesoporous silica as expected, but through an Al⋯Cl-[Ru]-coordination. It is not surprising that in functionalized olefin metathesis of diethyldiallyl malonate, DEDAM (liquid phase), leaching of the catalyst is observed which is not the case in non-functionalized olefin metathesis of propene (gas phase). Besides, the results obtained in propene metathesis with HG-II immobilized either on SBA15 (d = 6 nm) or KCC-1 (d = 4 or 8 nm) highlight the importance of the accessibility of the catalytic site. Therefore, we demonstrate that KCC-1 is a promising and suitable 3D mesoporous support to overcome the diffusion of reactants into the porous network of heterogeneous catalysts.

  11. Exploiting the interactions between the ruthenium Hoveyda–Grubbs catalyst and Al-modified mesoporous silica: the case of SBA15 vs. KCC-1

    KAUST Repository

    Werghi, Baraa

    2018-03-05

    Immobilization of the 2 generation Hoveyda-Grubbs catalyst HG-II onto well-ordered 2D hexagonal (SBA15) and 3D fibrous (KCC-1) mesostructured silica, which contained tetra-coordinated Al, has been investigated through the Surface Organometallic Chemistry (SOMC) methodology. The main interest of this study lies in the peculiarity of the silica supports, which display a well-defined tetrahedral aluminum hydride site displaying a strong Lewis acid character, [(Si-O-Si)(Si-O-)Al-H]. The resulting supported Hoveyda-Grubbs catalysts have been fully characterized by advanced solid state characterization techniques (FT-IR, H and C solid state NMR, DNP-SENS, EF-TEM...). Together with DFT calculations, the immobilization of HG-II does not occur through the formation of a covalent bond between the complex and the Al-modified mesoporous silica as expected, but through an Al⋯Cl-[Ru]-coordination. It is not surprising that in functionalized olefin metathesis of diethyldiallyl malonate, DEDAM (liquid phase), leaching of the catalyst is observed which is not the case in non-functionalized olefin metathesis of propene (gas phase). Besides, the results obtained in propene metathesis with HG-II immobilized either on SBA15 (d = 6 nm) or KCC-1 (d = 4 or 8 nm) highlight the importance of the accessibility of the catalytic site. Therefore, we demonstrate that KCC-1 is a promising and suitable 3D mesoporous support to overcome the diffusion of reactants into the porous network of heterogeneous catalysts.

  12. Mesostructure, contemporary training model of the Cuban boxing school

    Directory of Open Access Journals (Sweden)

    Juan Hernández Sierra

    2018-01-01

    Full Text Available The present work aims to convey the experiences on the development and application of a meso-structure of 3-4 microcycles that allowed maintaining a long state of the sport form (5-6 months on a scientific-technical and methodological basis in the planning of the Sports training of the national boxing team, who participated in the 4th World Boxing Series (WSB. The investigated sample consisted of 21 boxers, representing 58%, of a population made up of 36 athletes / students belonging to the National School of Boxing. The importance of the research is that it exposes the use of new planning concepts and the current modifications in the training structure, as well as the contribution of science to the adaptation of training loads, which allows to obtain positive results during a long period of time. state of the sport form, factors on which it is necessary to reflect for an effective planning of modern sports training.

  13. Bulletin of Materials Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Deposition and characterization of diamond-like nanocomposite coatings .... Chemical composition of deposited films has been analysed by FTIR which ... Modification of polysulfone with pendant carboxylic acid functionality for ultrafiltration membrane applications .... Anisotropic silica mesostructures for DNA encapsulation.

  14. Drug delivery from hydrophobic-modified mesoporous silicas: Control via modification level and site-selective modification

    International Nuclear Information System (INIS)

    Tang Qunli; Chen Yuxi; Chen Jianghua; Li Jin; Xu Yao; Wu Dong; Sun Yuhan

    2010-01-01

    Dimethylsilyl (DMS) modified mesoporous silicas were successfully prepared via co-condensation and post-grafting modification methods. The post-grafting modification was carried out by the reaction of the as-synthesized MCM-41 material (before CTAB removal) with diethoxydimethylsinale (DEDMS). N 2 adsorption-desorption and 29 Si MAS NMR characterization demonstrated that different amount of DMS groups were successfully incorporated into the co-condensation modified samples, and the functional DMS groups were placed selectively on the pore openings and external pore surfaces in the post-grafting modified samples. Subsequently, the controlled drug delivery properties from the resulting DMS-modified mesoporous silicas were investigated in detail. The drug adsorption experiments showed that the adsorption capacities were mainly depended on the content of silanol group (CSG) in the corresponding carriers. The in vitro tests exhibited that the incorporation of DMS groups greatly retarded the ibuprofen release rate. Moreover, the ibuprofen release profiles could be well modulated by varying DMS modification levels and site-selective distribution of functional groups in mesoporous carriers. - The distribution of DMS groups on the pore surfaces of the mesostructures strongly affects the drug release rate. The P-M41-1 and the P-M41-2 possess the close DMS modification levels as the C-M41-10, but the ibuprofen release rates from the P-M41-1 and P-M41-2 are much slower than that from the C-M41-10.

  15. Multifunctional EuYVO{sub 4} nanoparticles coated with mesoporous silica

    Energy Technology Data Exchange (ETDEWEB)

    Justino, Larissa G. [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14040-901 Ribeirão Preto, SP (Brazil); Nigoghossian, Karina [Inst. of Chemistry – São Paulo State University- UNESP, 14801-970 Araraquara, SP (Brazil); Capote, Ticiana S.O.; Scarel-Caminaga, Raquel M. [Department of Morphology, Dental School at Araraquara, Univ. Estadual Paulista – UNESP, Araraquara, SP (Brazil); Ribeiro, Sidney J.L. [Inst. of Chemistry – São Paulo State University- UNESP, 14801-970 Araraquara, SP (Brazil); Caiut, José Maurício A., E-mail: caiut@ffclrp.usp.br [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14040-901 Ribeirão Preto, SP (Brazil)

    2016-11-15

    Mesoporous structures are interesting materials for the incorporation of dyes, drugs, and luminescent systems, leading to materials with important multifunctionalities. In a very unique way, these guest/host materials combine the high stability of inorganic systems, new guest-structuring features, and adsorption mechanisms in their well-defined pores. This work evaluates the luminescent properties of rare earth-doped YVO{sub 4} nanoparticles coated with a mesoporous silica shell. The use of two different synthesis methodologies allowed for particle size control. The crystalline phase emerged without further heat treatment. The mesoporous shell decreased undesirable quenching effects on YVO{sub 4}:Eu{sup 3+} nanoparticles and rendered them biocompatible. The materials prepared herein could have interesting applications as luminescent markers or drug release systems.

  16. Electrostatically assisted fabrication of silver-dielectric core/shell nanoparticles thin film capacitor with uniform metal nanoparticle distribution and controlled spacing.

    Science.gov (United States)

    Li, Xue; Niitsoo, Olivia; Couzis, Alexander

    2016-03-01

    An electrostatically-assisted strategy for fabrication of thin film composite capacitors with controllable dielectric constant (k) has been developed. The capacitor is composed of metal-dielectric core/shell nanoparticle (silver/silica, Ag@SiO2) multilayer films, and a backfilling polymer. Compared with the simple metal particle-polymer mixtures where the metal nanoparticles (NP) are randomly dispersed in the polymer matrix, the metal volume fraction in our capacitor was significantly increased, owing to the densely packed NP multilayers formed by the electrostatically assisted assembly process. Moreover, the insulating layer of silica shell provides a potential barrier that reduces the tunneling current between neighboring Ag cores, endowing the core/shell nanocomposites with a stable and relatively high dielectric constant (k) and low dielectric loss (D). Our work also shows that the thickness of the SiO2 shell plays a dominant role in controlling the dielectric properties of the nanocomposites. Control over metal NP separation distance was realized not only by variation the shell thickness of the core/shell NPs but also by introducing a high k nanoparticle, barium strontium titanate (BST) of relatively smaller size (∼8nm) compared to 80-160nm of the core/shell Ag@SiO2 NPs. The BST assemble between the Ag@SiO2 and fill the void space between the closely packed core/shell NPs leading to significant enhancement of the dielectric constant. This electrostatically assisted assembly method is promising for generating multilayer films of a large variety of NPs over large areas at low cost. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Bending strength and fracture surface topography of natural fiber-reinforced shell for investment casting process

    Directory of Open Access Journals (Sweden)

    Kai Lu

    2016-05-01

    Full Text Available In order to improve the properties of silica sol shell for investment casting process, various contents of cattail fibers were added into the slurry to prepare a fiber-reinforced shell in the present study. The bending strength of fiber-reinforced shell was investigated and the fracture surfaces of shell specimens were observed using SEM. It is found that the bending strength increases with the increase of fiber content, and the bending strength of a green shell with 1.0 wt.% fiber addition increases by 44% compared to the fiber-free shell. The failure of specimens of the fiber-reinforced green shell results from fiber rupture and debonding between the interface of fibers and adhesive under the bending load. The micro-crack propagation in the matrix is inhibited by the micro-holes for ablation of fibers in specimens of the fiber-reinforced shell during the stage of being fired. As a result, the bending strength of specimens of the fired shell had no significant drop. Particularly, the bending strength of specimens of the fired shell reinforced with 0.6wt.% fiber reached the maximum value of 4.6 MPa.

  18. Nucleation of polystyrene latex particles in the presence of gamma-methacryloxypropyltrimethoxysilane: functionalized silica particles.

    Science.gov (United States)

    Bourgeat-Lami, Elodie; Insulaire, Mickaelle; Reculusa, Stéphane; Perro, Adeline; Ravaine, Serge; Duguet, Etienne

    2006-02-01

    Silica/polystyrene nanocomposite particles with different morphologies were synthesized through emulsion polymerization of styrene in the presence of silica particles previously modified by gamma-methacryloxypropyltrimethoxysilane (MPS). Grafting of the silane molecule was performed by direct addition of MPS to the aqueous silica suspension in the presence of an anionic surfactant under basic conditions. The MPS grafting density on the silica surface was determined using the depletion method and plotted against the initial MPS concentration. The influence of the MPS grafting density, the silica particles size and concentration and the nature of the surfactant on the polymerization kinetics and the particles morphology was investigated. When the polymerization was performed in the presence of an anionic surfactant, transmission electron microscopy images showed the formation of polymer spheres around silica for MPS grafting densities lower than typically 1 micromole x m(-2) while the conversion versus time curves indicated a strong acceleration effect under such conditions. In contrast, polymerizations performed in the presence of a larger amount of MPS moieties or in the presence of a non ionic emulsifier resulted in the formation of "excentered" core-shell morphologies and lower polymerization rates. The paper identifies the parameters that allow to control particles morphology and polymerization kinetics and describes the mechanism of formation of the nanocomposite colloids.

  19. Cell-in-Shell Hybrids: Chemical Nanoencapsulation of Individual Cells.

    Science.gov (United States)

    Park, Ji Hun; Hong, Daewha; Lee, Juno; Choi, Insung S

    2016-05-17

    Nature has developed a fascinating strategy of cryptobiosis ("secret life") for counteracting the stressful, and often lethal, environmental conditions that fluctuate sporadically over time. For example, certain bacteria sporulate to transform from a metabolically active, vegetative state to an ametabolic endospore state. The bacterial endospores, encased within tough biomolecular shells, withstand the extremes of harmful stressors, such as radiation, desiccation, and malnutrition, for extended periods of time and return to a vegetative state by breaking their protective shells apart when their environment becomes hospitable for living. Certain ciliates and even higher organisms, for example, tardigrades, and others are also found to adopt a cryptobiotic strategy for survival. A common feature of cryptobiosis is the structural presence of tough sheaths on cellular structures. However, most cells and cellular assemblies are not "spore-forming" and are vulnerable to the outside threats. In particular, mammalian cells, enclosed with labile lipid bilayers, are highly susceptible to in vitro conditions in the laboratory and daily life settings, making manipulation and preservation difficult outside of specialized conditions. The instability of living cells has been a main bottleneck to the advanced development of cell-based applications, such as cell therapy and cell-based sensors. A judicious question arises: can cellular tolerance against harmful stresses be enhanced by simply forming cell-in-shell hybrid structures? Experimental results suggest that the answer is yes. A micrometer-sized "Iron Man" can be generated by chemically forming an ultrathin (cell. Since the report on silica nanoencapsulation of yeast cells, in which cytoprotective yeast-in-silica hybrids were formed, several synthetic strategies have been developed to encapsulate individual cells in a cytocompatible fashion, mimicking the cryptobiotic cell-in-shell structures found in nature, for example

  20. Synthesis of Ni-SiO2/silicalite-1 core-shell micromembrane reactors and their reaction/diffusion performance

    KAUST Repository

    Khan, Easir A.

    2010-12-15

    Core-shell micromembrane reactors are a novel class of materials where a catalyst and a shape-selective membrane are synergistically housed in a single particle. In this work, we report the synthesis of micrometer -sized core-shell particles containing a catalyst core and a thin permselective zeolite shell and their application as a micromembrane reactor for the selective hydrogenation of the 1-hexene and 3,3-dimethyl-1-butene isomers. The bare catalyst, which is made from porous silica loaded with catalytically active nickel, showed no reactant selectivity between hexene isomers, but the core-shell particles showed high selectivities up to 300 for a 1-hexene conversion of 90%. © 2010 American Chemical Society.

  1. Dual soft-template system based on colloidal chemistry for the synthesis of hollow mesoporous silica nanoparticles.

    Science.gov (United States)

    Li, Yunqi; Bastakoti, Bishnu Prasad; Imura, Masataka; Tang, Jing; Aldalbahi, Ali; Torad, Nagy L; Yamauchi, Yusuke

    2015-04-20

    A new dual soft-template system comprising the asymmetric triblock copolymer poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) is used to synthesize hollow mesoporous silica (HMS) nanoparticles with a center void of around 17 nm. The stable PS-b-P2VP-b-PEO polymeric micelle serves as a template to form the hollow interior, while the CTAB surfactant serves as a template to form mesopores in the shells. The P2VP blocks on the polymeric micelles can interact with positively charged CTA(+) ions via negatively charged hydrolyzed silica species. Thus, dual soft-templates clearly have different roles for the preparation of the HMS nanoparticles. Interestingly, the thicknesses of the mesoporous shell are tunable by varying the amounts of TEOS and CTAB. This study provides new insight on the preparation of mesoporous materials based on colloidal chemistry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. The Phanerozoic diversification of silica-cycling testate amoebae and its possible links to changes in terrestrial ecosystems

    Science.gov (United States)

    Bosak, Tanja; Lara, Enrique; Mitchell, Edward A.D.

    2015-01-01

    The terrestrial cycling of Si is thought to have a large influence on the terrestrial and marine primary production, as well as the coupled biogeochemical cycles of Si and C. Biomineralization of silica is widespread among terrestrial eukaryotes such as plants, soil diatoms, freshwater sponges, silicifying flagellates and testate amoebae. Two major groups of testate (shelled) amoebae, arcellinids and euglyphids, produce their own silica particles to construct shells. The two are unrelated phylogenetically and acquired biomineralizing capabilities independently. Hyalosphenids, a group within arcellinids, are predators of euglyphids. We demonstrate that hyalosphenids can construct shells using silica scales mineralized by the euglyphids. Parsimony analyses of the current hyalosphenid phylogeny indicate that the ability to “steal” euglyphid scales is most likely ancestral in hyalosphenids, implying that euglyphids should be older than hyalosphenids. However, exactly when euglyphids arose is uncertain. Current fossil record contains unambiguous euglyphid fossils that are as old as 50 million years, but older fossils are scarce and difficult to interpret. Poor taxon sampling of euglyphids has also prevented the development of molecular clocks. Here, we present a novel molecular clock reconstruction for arcellinids and consider the uncertainties due to various previously used calibration points. The new molecular clock puts the origin of hyalosphenids in the early Carboniferous (∼370 mya). Notably, this estimate coincides with the widespread colonization of land by Si-accumulating plants, suggesting possible links between the evolution of Arcellinid testate amoebae and the expansion of terrestrial habitats rich in organic matter and bioavailable Si. PMID:26734499

  3. Preparation of non-spherical particles by shell-shield etching for near-field nanopatterning

    International Nuclear Information System (INIS)

    Ye, Jian; Liesbet, Lagae

    2014-01-01

    The shape of polymer particles plays an important role in determining their function. In this paper, we describe a simple and unconventional method called shell-shield etching (SSE) that allows us to prepare freestanding submicrometer- or micrometer-sized polymer particles with various shapes. By precisely varying the time of ultraviolet ozone treatment under the partial shielding effect of the silica shell, we controllably reshape polymer spheres into symmetry-reduced polymer peaches, mushrooms, bowls, and plates. Finite difference time domain simulations indicate that the non-spherical particles obtained from the SSE method might have potential for near-field nanopatterning applications. (papers)

  4. Hydrothermal stability of silica, hybrid silica and Zr-doped hybrid silica membranes

    NARCIS (Netherlands)

    ten Hove, Marcel; Luiten-Olieman, Mieke W.J.; Huiskes, Cindy; Nijmeijer, Arian; Winnubst, Louis

    2017-01-01

    Hybrid silica membranes have demonstrated to possess a remarkable hydrothermal stability in pervaporation and gas separation processes allowing them to be used in industrial applications. In several publications the hydrothermal stability of pure silica or that of hybrid silica membranes are

  5. Fumed silica. Fumed silica

    Energy Technology Data Exchange (ETDEWEB)

    Sukawa, T.; Shirono, H. (Nippon Aerosil Co. Ltd., Tokyo (Japan))

    1991-10-18

    The fumed silica is explained in particulate superfineness, high purity, high dispersiveness and other remarkable characteristics, and wide application. The fumed silica, being presently produced, is 7 to 40nm in average primary particulate diameter and 50 to 380m{sup 2}/g in specific surface area. On the surface, there coexist hydrophilic silanol group (Si-OH) and hydrophobic siloxane group (Si-O-Si). There are many characteristics, mutually different between the fumed silica, made hydrophobic by the surface treatment, and untreated hydrophilic silica. The treated silica, if added to the liquid product, serves as agent to heighten the viscosity, prevent the sedimentation and disperse the particles. The highest effect is given to heighten the viscosity in a region of 4 to 9 in pH in water and alcohol. As filling agent to strengthen the elastomer and polymer, and powder product, it gives an effect to prevent the consolidation and improve the fluidity. As for its other applications, utilization is made of particulate superfineness, high purity, thermal insulation properties and adsorption characteristics. 2 to 3 patents are published for it as raw material of quartz glass. 38 refs., 16 figs., 4 tabs.

  6. Titania-coated manganite nanoparticles: Synthesis of the shell, characterization and MRI properties

    Energy Technology Data Exchange (ETDEWEB)

    Jirák, Zdeněk; Kuličková, Jarmila [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic); Herynek, Vít [Institute for Clinical and Experimental Medicine, Vídeňská 1958/9, 140 21 Praha 4 (Czech Republic); Maryško, Miroslav [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic); Koktan, Jakub [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic); University of Chemistry and Technology, Prague, Technická 5, 166 28 Praha 6 (Czech Republic); Kaman, Ondřej, E-mail: kamano@seznam.cz [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic)

    2017-04-01

    Novel procedure for coating of oxide nanoparticles with titania, employing hydrolysis and polycondensation of titanium alkoxides under high-dilution conditions and cationic surfactants, is developed and applied to magnetic cores of perovskite manganite. Bare particles of the ferromagnetic La{sub 0.65}Sr{sub 0.35}MnO{sub 3} phase, possessing high magnetization, M{sub 10} {sub kOe}(4.5 K) = 63.5 emu g{sup −1}, and Curie temperature, T{sub C} = 355 K, are synthesized by sol-gel procedure and subsequently coated with titania. Further, a comparative silica-coated product is prepared. In order to analyse the morphology, colloidal stability, and surface properties of these two types of coated particles, a detailed study by means of transmission electron microscopy, dynamic light scattering, zeta-potential measurements, and IR spectroscopy is carried out. The experiments on the titania-coated sample reveal a continuous though porous character of the TiO{sub 2} shell, the nature of which is amorphous but can be transformed to anatase at higher temperatures. Finally, the relaxometric study at the magnetic field of 0.5 T, performed to quantity the transverse relaxivity and its temperature dependence, reveals important differences between the titania-coated and silica-coated nanoparticles. - Highlights: • Magnetic nanoparticles of perovskite La{sub 0.65}Sr{sub 0.35}MnO{sub 3} phase are coated with TiO{sub 2}. • The titania forms a continuous and amorphous shell and provides colloidal stability. • Morphology and surface properties are compared to a silica-coated product. • MRI properties of both the titania- and silica-coated particles are studied at 0.5 T. • The temperature dependence of r{sub 2} is strongly affected by the type of coating.

  7. Core–shell-typed Ag-SiO2 nanoparticles as solar selective coating materials

    International Nuclear Information System (INIS)

    Gao, Tao; Jelle, Bjørn Petter; Gustavsen, Arild

    2013-01-01

    Silver (Ag) nanoparticles with typical diameter of about 50 nm have been prepared via a polyol process. The as-prepared Ag nanoparticles are well crystallized and exhibit a characteristic surface plasmon resonance (SPR) band centered at ∼423 nm. The SPR band shows a strong dependence on the sizes of Ag nanoparticles and the types of the dielectric medium. Core–shell-typed Ag-SiO 2 nanoparticles have also been prepared by depositing a thin layer (∼25 nm) of silica on Ag nanoparticles. The core–shell-typed Ag-SiO 2 nanoparticles show similar optical behaviors (absorption, transmission, and reflection) but enhanced stability compared to those of the Ag nanoparticles, indicating that the core–shell-typed Ag-SiO 2 nanoparticles may be used as solar selective coating materials for architectural window applications.

  8. Multifunctional Amine Mesoporous Silica Spheres Modified with Multiple Amine as Carriers for Drug Release

    Directory of Open Access Journals (Sweden)

    Yan Li

    2018-01-01

    Full Text Available Mesoporous silica spheres were synthesized by using Stöber theory (MSN-40. Calcination of the mesostructured phase resulted in the starting solid. Organic modification with aminopropyl groups resulted in two MSN-40 materials: named MSN-NH2 and MSN-DQ-40, respectively. These two kinds of samples with different pore sizes (obtained from 3-[2-(2-aminoethylaminoethylamino]propyl-trimethox-ysilane (NQ-62 and modified NQ-62 showed control of the delivery rate of ibuprofen (IBU from the siliceous matrix. The obtained sample from modified NQ-62 has an increased loading rate and shows better control of the delivery rate of IBU than the obtained sample from NQ-62. These three solids were characterized using standard solid state procedures. During tests of in vitro drug release, an interesting phenomenon was observed: at high pH (pH 7.45, IBU in all carriers was released slowly; at low pH (pH 4.5, only a part of the IBU was slowly released from this carrier within 25 hours; most IBU was effectively confined in mesoporous material, but the remaining IBU was released rapidly and completely after 25 hours.

  9. Synthesis of Pt-Sn core-shell nanoparticles deposited on SBA-15 modified

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez-Contreras, L.; Alonso-Lemus, I. [Centro de Investigacion en Materiales Avanzados S.C., Laboratorio Nacional de Nanotecnologia (Mexico); Botte, G. G. [Ohio University, Center for Electrochemical Engineering Research, Department of Chemical and Biomolecular Engineering (United States); Verde-Gomez, Y., E-mail: ysmaelverde@yahoo.com [Instituto Tecnologico de Cancun (Mexico)

    2013-07-15

    A novel one-step synthesis method to prepare Pt-Sn bimetallic nanoparticles supported on mesoporous silica with high surface area (SBA-15, 700 m{sup 2}/g) and narrow pore size distribution (around 9.5 nm) was developed. Tin incorporation plays an important dual role, to create active sites into the silica walls that serve as particles anchors center, and to grow Pt-Sn core-shell nanoparticles. High-resolution transmission and scanning electron microscopy, and X-ray diffraction pattern confirm the formation of the Pt-Sn core-shell type nanoparticles ( Almost-Equal-To 1-10 nm). The metal loading was 2.2 and 2.3 wt% for Pt and Sn, respectively. Electron microscopy results show that the metal nanoparticles were deposited not only on the matrix, but also inside of it. Structural, textural, and morphological features of the SBA-15 were slightly affected after the nanoparticles deposition, maintaining its high surface area. The results obtained suggest that Pt-Sn on SBA-15 could be attractive material for several catalytic applications, due to the narrow particle size distribution achieved (from 1 to 10 nm) the high dispersion on the support, as well as the Pt-Sn alloy developed.Graphical Abstract.

  10. Development of magnetic luminescent core/shell nanocomplex particles with fluorescence using Rhodamine 6G

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hee Uk; Song, Yoon Seok [Department of Chemical and Biological Engineering, Korea University, 5 Ga, Anam-Dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of); Park, Chulhwan [Department of Chemical Engineering, Kwangwoon University, 447-1 Wolgye-Dong, Nowon-Gu, Seoul 139-701 (Korea, Republic of); Kim, Seung Wook, E-mail: kimsw@korea.ac.kr [Department of Chemical and Biological Engineering, Korea University, 5 Ga, Anam-Dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of)

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► A simple method was developed to synthesize Co-B/SiO{sub 2}/dye/SiO{sub 2} composite particles. ► The magnetic particle shows that highly luminescent and core/shell particles are formed. ► Such core/shell particles can be easily suspended in water. ► The magnetic particles could detect fluorescence for the application of biosensor. -- Abstract: A simple and reproducible method was developed to synthesize a novel class of Co-B/SiO{sub 2}/dye/SiO{sub 2} composite core/shell particles. Using a single cobalt core, Rhodamine 6G of organic dye molecules was entrapped in a silica shell, resulting in core/shell particles of ∼200 nm diameter. Analyses using a variety of techniques such as transmission electron microscopy, X-ray photoelectron spectroscopy, vibration sample magnetometry, confocal laser scanning microscopy, and fluorescence intensity demonstrated that dye molecules were trapped inside the core/shell particles. A photoluminescence investigation showed that highly luminescent and photostable core/shell particles were formed. Such core/shell particles can be easily suspended in water. The synthesized magnetic particles could be used to detect fluorescence on glass substrate arrays for bioassay and biosensor applications.

  11. A comprehensive study of soft magnetic materials based on FeSi spheres and polymeric resin modified by silica nanorods

    International Nuclear Information System (INIS)

    Strečková, M.; Füzer, J.; Kobera, L.; Brus, J.; Fáberová, M.; Bureš, R.; Kollár, P.; Lauda, M.; Medvecký, Ĺ.; Girman, V.; Hadraba, H.; Bat'ková, M.; Bat'ko, I.

    2014-01-01

    A novel soft magnetic composite (SMC) based on spherical FeSi particles precisely covered by hybrid phenolic resin was designed. The hybrid resin including silica nano-rods chemically incorporated into the phenolic polymer matrix was prepared by the modified sol–gel method. A chemical bridge connecting silica nano-rods with the base polymeric net was verified by FTIR, 13 C and 29 Si NMR spectroscopy, whereas the shape and size of silica nano-rods were determined by TEM. It is shown that the modification of polymeric resin by silica nano-rods generally leads to the improved thermal and mechanical properties of the final samples. The hybrid resin serves as a perfect insulating coating deposited on FeSi particles and the core–shell particles can be further compacted by standard powder metallurgy methods in order to prepare final samples for mechanical, electric and magnetic testing. SEM images evidence negligible porosity, uniform distribution of the hybrid resin around FeSi particles, as well as, dimensional shape stability of the final samples after thermal treatment. The hardness, flexural strength and density of the final samples are comparable to the sintered SMCs, but they simultaneously exhibit much higher specific resistivity along with only slightly lower coercivity and permeability. - Highlights: • Soft magnetic composites are designed for electrotechnical applications. • Electroinsulating layer consists of phenolic resin modified with silica nano-rods. • NMR, FTIR and DSC analysis is used to characterize hybrid resin. • Spherical Fe–Si particles covered by hybrid resin form a core–shell composite. • Mechanical, electrical and magnetic properties are described in detail

  12. Role of N-methyl-2-pyrrolidone for preparation of Fe{sub 3}O{sub 4}@SiO{sub 2} controlled the shell thickness

    Energy Technology Data Exchange (ETDEWEB)

    Wee, Sung-Bok [Hanyang University, Division of Materials Science and Engineering (Korea, Republic of); Oh, Hyeon-Cheol [Korea Nano Plus, Inc. (Korea, Republic of); Kim, Tae-Gyun; An, Gye-Seok; Choi, Sung-Churl, E-mail: choi0505@hanyang.ac.kr [Hanyang University, Division of Materials Science and Engineering (Korea, Republic of)

    2017-04-15

    We developed a simple and novel approach for the synthesis of Fe{sub 3}O{sub 4}@SiO{sub 2} nanoparticles with controlled shell thickness, and studied the mechanism. The introduction of N-methyl-2-pyrrolidone (NMP) led to trapping of monomer nuclei in single shell and controlled the shell thickness. Fe{sub 3}O{sub 4}@SiO{sub 2} controlled the shell thickness, showing a high magnetization value (64.47 emu/g). Our results reveal the role and change in the chemical structure of NMP during the core-shell synthesis process. NMP decomposed to 4-aminobutanoic acid in alkaline condition and decreased the hydrolysis rate of the silica coating process.

  13. Enhanced bio-compatibility of ferrofluids of self-assembled superparamagnetic iron oxide-silica core-shell nanoparticles

    Digital Repository Service at National Institute of Oceanography (India)

    Narayanan, T.N.; Mary, A.P.R.; Swalih, P.K.A.; Kumar, D.S.; Makarov, D.; Albrecht, M.; Puthumana, J.; Anas, A.; Anantharaman, A.

    -interacting, monodispersed and hence the synthesis of such nanostructures has great relevance in the realm of nanoscience. Silica-coated superparamagnetic iron oxide nanoparticles based ferrofluids were prepared using polyethylene glycol as carrier fluid by employing a...

  14. Fabrication of the tricontinuous mesoporous IBN-9 structure with surfactant CTAB

    KAUST Repository

    Zhao, Yunfeng

    2011-12-13

    IBN-9 is the first tricontinuous mesoporous material, consisting of three identical interpenetrating channels that are separated by a single continuous silica wall. It was originally synthesized using a specially designed surfactant as template. The need of special surfactant in the synthesis inhibits extensive investigation of this novel structure and its applications. We demonstrate in this study that such a complicated tricontinuous mesostructure can also be fabricated from the most common and commercially available surfactant cetyltrimethylammonium bromide (CTAB) with the help of polar organic additives, e.g., n-butanol. The role of n-butanol is to finely tune the surface curvature of the organic/inorganic interface during the cooperative self-assembly process. Electron microscopic techniques are employed to identify different mesostructures from the mixture. This study reveals the possibility of discovering unprecedented mesostructures from conventional surfactant-water- silicates systems. © 2011 American Chemical Society.

  15. Fluorescent nanodiamonds embedded in biocompatible translucent shells.

    Science.gov (United States)

    Rehor, Ivan; Slegerova, Jitka; Kucka, Jan; Proks, Vladimir; Petrakova, Vladimira; Adam, Marie-Pierre; Treussart, François; Turner, Stuart; Bals, Sara; Sacha, Pavel; Ledvina, Miroslav; Wen, Amy M; Steinmetz, Nicole F; Cigler, Petr

    2014-03-26

    High pressure high temperature (HPHT) nanodiamonds (NDs) represent extremely promising materials for construction of fluorescent nanoprobes and nanosensors. However, some properties of bare NDs limit their direct use in these applications: they precipitate in biological solutions, only a limited set of bio-orthogonal conjugation techniques is available and the accessible material is greatly polydisperse in shape. In this work, we encapsulate bright 30-nm fluorescent nanodiamonds (FNDs) in 10-20-nm thick translucent (i.e., not altering FND fluorescence) silica shells, yielding monodisperse near-spherical particles of mean diameter 66 nm. High yield modification of the shells with PEG chains stabilizes the particles in ionic solutions, making them applicable in biological environments. We further modify the opposite ends of PEG chains with fluorescent dyes or vectoring peptide using click chemistry. High conversion of this bio-orthogonal coupling yielded circa 2000 dye or peptide molecules on a single FND. We demonstrate the superior properties of these particles by in vitro interaction with human prostate cancer cells: while bare nanodiamonds strongly aggregate in the buffer and adsorb onto the cell membrane, the shell encapsulated NDs do not adsorb nonspecifically and they penetrate inside the cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Hydrothermal stability investigation of micro- and mesoporous silica containing long-range ordered cobalt oxide clusters by XAS.

    Science.gov (United States)

    Liu, Liang; Wang, David K; Kappen, Peter; Martens, Dana L; Smart, Simon; Diniz da Costa, João C

    2015-07-15

    This work investigates the hydrothermal stability of cobalt doped silica materials with different Co/Si molar ratios (0, 0.05, 0.10, and 0.25). The resultant materials were characterized by N2 sorption and chemical structures by Raman and X-ray absorption spectroscopy before and after a harsh hydrothermal exposure (550 °C, 75 mol% vapour and 40 h). The cobalt silica materials showed a lower surface area loss from 48% to 12% with increasing Co/Si molar ratio from 0.05 to 0.25 and relatively maintaining their pore size distribution, while pure silica exhibited significant surface area reduction (80%) and pore size broadening. For low cobalt loading sample (Co/Si = 0.05), the cobalt was highly dispersed in the silica network in a tetrahedral coordination with oxygen and a small proportion of Co-Co interaction in the second shell. Long range order Co3O4 was observed when Co/Si molar ratio increased to 0.10 and 0.25. The hydrothermal exposure did not affect the local cobalt environments and no cobalt-silicon interaction was observed by X-ray absorption spectroscopy. The hydrothermal stability of the silica matrix was attributed to the physical barrier of cobalt oxide in opposing densification and silica mobility under harsh hydrothermal conditions.

  17. Hydrophobic polymers modification of mesoporous silica with large pore size for drug release

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Shenmin, E-mail: smzhu@sjtu.edu.c [Shanghai Jiao Tong University, State Key Lab of Metal Matrix Composites (China); Zhang Di; Yang Na [Fudan University, Ministry of Education, Key Lab of Molecular Engineering of Polymers (China)

    2009-04-15

    Mesostructure cellular foam (MCF) materials were modified with hydrophobic polyisoprene (PI) through free radical polymerization in the pores network, and the resulting materials (MCF-PI) were investigated as matrices for drug storage. The successful synthesis of PI inside MCF was characterized by Fourier transform infrared (FT-IR), hydrogen nuclear magnetic resonance ({sup 1}H NMR), X-ray diffraction patterns (XRD) and nitrogen adsorption/desorption measurements. It was interesting to find the resultant system held a relatively large pore size (19.5 nm) and pore volume (1.02 cm{sup 3} g{sup -1}), which would benefit for drug storage. Ibuprofen (IBU) and vancomycin were selected as model drugs and loaded onto unmodified MCF and modified MCF (MCF-PI). The adsorption capacities of these model drugs on MCF-PI were observed increase as compared to that of on pure MCF, due to the trap effects induced by polyisoprene chains inside the pores. The delivery system of MCF-PI was found to be more favorable for the adsorption of IBU (31 wt%, IBU/silica), possibly attributing to the hydrophobic interaction between IBU and PI formed on the internal surface of MCF matrix. The release of drug through the porous network was investigated by measuring uptake and release of IBU.

  18. EXPERIMENTAL INVESTIGATION ON RICH MINERAL SILICA AND COCONUT SHELL IN CONCRETE

    OpenAIRE

    C. V. Saranya; V. Anusuya; T. Sreeshma Baburaj

    2017-01-01

    Concrete plays a vital role in the design and construction of the nation’s infrastructure. Almost three quarters of the volume of concrete is composed of aggregates. The current studies involved in the replacement of fine aggregate with Ecosand. In this study an attempt is made to use Ecosand which is a commercial by-product of cement manufacturing process introduced by ACC Cements, as fine aggregate replacement and crushed coconut shell as coarse aggregate. M20 grade of concrete is used. Dif...

  19. Coating of calcia-doped ceria with amorphous silica shell by seeded polymerization technique

    International Nuclear Information System (INIS)

    El-Toni, Ahmed Mohamed; Yin, Shu; Yabe, Shinryo; Sato, Tsugio

    2005-01-01

    Calcia-doped ceria is of potential interest as an ultraviolet (UV) radiation blocking material in personal care products. However, its high catalytic ability for oxidation of organic materials makes it difficult to use as a sunscreen material. Therefore, calcia-doped ceria was coated with amorphous silica by means of seeded polymerization technique in order to depress its oxidation catalytic ability. The catalytic ability as well as UV-shielding ability was investigated for coated particles

  20. Covalent immobilization of penicillin G acylase on aminopropyl-functionalized mesostructured cellular foams.

    Science.gov (United States)

    Zhao, Junqi; Wang, Yujun; Luo, Guangsheng; Zhu, Shenlin

    2010-10-01

    Mesostructured cellular foams (MCFs) are suitable for biomolecular immobilization because of their relatively large-pore diameter and pore volume. Penicillin G acylase (PGA) was immobilized on aminopropyl-functionalized MCFs through Schiff base reaction. It is shown that PGA could be fixed more firmly through the covalent immobilization on aminopropyl-functionalized MCFs support than through the adsorption immobilization on blank MCFs. The PGA loading amount on the aminopropyl-functionalized MCFs could reach 443 mg/g (dry support), and the apparent activity could achieve up to 4138 U/g (dry support). The influence of the amount of grafted aminopropyl group was studied, and it is found that the optimal molar ratio of MCFs to APTS was 15/1; in addition, the suitable enzyme distribution density for the specific activity of the immobilized PGA was 0.7 mg enzyme per m(2) of specific area of MCFs. Copyright 2010 Elsevier Ltd. All rights reserved.

  1. Polarized neutron study of the magnetic mesostructure in (Pd{sub 1-x}Fe{sub x}){sub 1-y}Mn{sub y}

    Energy Technology Data Exchange (ETDEWEB)

    Gordeev, G.P.; Axelrod, L.A.; Lazebnik, I.M.; Zabenkin, V.N. [Petersburg Nuclear Physics Institute, 188300, Gatchina (Russian Federation); Wagner, V. [Physikalisch-Technische Bundesanstalt, 38116, Braunschweig (Germany)

    2002-07-01

    In PdFeMn alloys with different Fe-atom concentrations, the behaviour of both mean magnetization and neutron depolarization in the magnetization/demagnetization process was observed by three-dimensional analysis of neutron-beam polarization. Both magnetization and depolarization have a hysteresis loop for the same values of an applied field. Depolarization loops are sharply distinguished for different alloys. This gives evidence of different magnetic mesostructures in these alloys. (orig.)

  2. Two emissive-magnetic composite platforms for Hg(II) sensing and removal: The combination of magnetic core, silica molecular sieve and rhodamine chemosensors

    Science.gov (United States)

    Mao, Hanping; Liu, Zhongshou

    2018-01-01

    In this paper, a composite sensing platform for Hg(II) optical sensing and removal was designed and reported. A core-shell structure was adopted, using magnetic Fe3O4 nanoparticles as the core, silica molecular sieve MCM-41 as the shell, respectively. Two rhodamine derivatives were synthesized as chemosensor and covalently immobilized into MCM-41 tunnels. Corresponding composite samples were characterized with SEM/TEM images, XRD analysis, IR spectra, thermogravimetry and N2 adsorption/desorption analysis, which confirmed their core-shell structure. Their emission was increased by Hg(II), showing emission turn on effect. High selectivity, linear working curves and recyclability were obtained from these composite samples.

  3. Magnetic silica hybrids modified with guanidine containing co-polymers for drug delivery applications

    Energy Technology Data Exchange (ETDEWEB)

    Timin, Alexander S., E-mail: a_timin@mail.ru [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000 Ivanovo (Russian Federation); RASA Center in Tomsk, Tomsk Polytechnic University, 30, Lenin Avenue, 634500 Tomsk (Russian Federation); Khashirova, Svetlana Yu. [Kabardino-Balkar State University, ul. Chernyshevskogo 173, Nal' chik, 360004 Kabardino-Balkaria (Russian Federation); Rumyantsev, Evgeniy V.; Goncharenko, Alexander A. [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000 Ivanovo (Russian Federation)

    2016-07-01

    Guanidine containing co-polymers grafted onto silica nanoparticles to form core-shell structure were prepared by sol-gel method in the presence of γ-Fe{sub 2}O{sub 3} nanoparticles. The morphological features for uncoated and coated silica particles have been characterized with scanning electron microscopy. The results show that the polymer coated silicas exhibit spherical morphology with rough polymeric surface covered by γ-Fe{sub 2}O{sub 3} nanoparticles. The grafting amount of guanidine containing co-polymers evaluated by thermogravimetric analysis was in the range from 17 to 30%. Then, the drug loading properties and cumulative release of silica hybrids modified with guanidine containing co-polymers were evaluated using molsidomine as a model drug. It was shown that after polymer grafting the loading content of molsidomine could reach up to 3.42 ± 0.21 and 2.34 ± 0.14 mg/g respectively. The maximum drug release of molsidomine is achieved at pH 1.6 (approximately 71–75% release at 37 °C), whereas at pH 7.4 drug release is lower (50.4–59.6% release at 37 °C). These results have an important implication that our magneto-controlled silica hybrids modified with guanidine containing co-polymers are promising as drug carriers with controlled behaviour under influence of magnetic field. - Highlights: • Polymer coated silica hybrids containing γ-Fe{sub 2}O{sub 3} were prepared via sol–gel method. • Polymer grafting influences pH-response and surface properties of final products. • Molsidomine as a model drug was effectively loaded into polymer coated silicas. • The drug loading depends on the nature of grafted polymer and its content.

  4. Fe3O4@polyaniline yolk–shell micro/nanospheres as bifunctional materials for lithium storage and electromagnetic wave absorption

    DEFF Research Database (Denmark)

    Wang, Xiaoliang; Zhang, Minwei; Zhao, Jianming

    2017-01-01

    Unique Fe3O4/polyaniline (PANI) composite with yolk-shell micro/nanostructure (FPys) has been successfully synthesized by a facile silica-assisted in-situ polymerization and subsequent etching strategy. The structural and compositional studies of the FPys composites are performed by employing X......-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The yolk-shell morphology of the products is confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. When evaluated as anode material for lithium-ion batteries, the as-prepared FPys electrodes...

  5. Facile and Scalable Synthesis of Monodispersed Spherical Capsules with a Mesoporous Shell

    KAUST Repository

    Qi, Genggeng

    2010-05-11

    Monodispersed HMSs with tunable particle size and shell thickness were successfully synthesized using relatively concentrated polystyrene latex templates and a silica precursor in a weakly basic ethanol/water mixture. The particle size of the capsules can vary from 100 nm to micrometers. These highly engineered monodispersed capsules synthesized by a facile and scalable process may find applications in drug delivery, catalysis, separationm or as biological and chemical microreactors. © 2010 American Chemical Society.

  6. Mineral contents and their solubility on calcium carbonat calcite nanocrystals from cockle shell powder (Anadara granosa Linn)

    Science.gov (United States)

    Widyastuti, S.; Pramushinta, I. A.

    2018-03-01

    Prepared and characterized calcium carbonat calcite nanocrystals improves solubility. Calcium carbonat calcite nanocrystals were synthesized using precipitation method from the waste of blood clam cockle shells (Anadara granosa Linn). This study was conducted to analyze mineral composition of nanocrystals calcium carbonat calcite cockle (Anadara granosa) shell for calcium fortification of food applications and to evaluate the solubilities of Calsium and Phospor. The sample of nanocrystals from cockle shells was evaluated to determine the content of 11 macro-and micro-elements. These elements are Calcium (Ca), Magnesium (Mg), Sodium (Na), Phosphorus (P), Potassium (K), Ferrum (Fe), Copper (Cu), Nickel (Ni), Zink (Zn), Boron (B) and Silica (Si)). Cockleshell powders were found to contain toxic elements below detectable levels. The solubilities of Calcium and Phospor were p<0.05.

  7. Thin silica shell coated Ag assembled nanostructures for expanding generality of SERS analytes.

    Directory of Open Access Journals (Sweden)

    Myeong Geun Cha

    Full Text Available Surface-enhanced Raman scattering (SERS provides a unique non-destructive spectroscopic fingerprint for chemical detection. However, intrinsic differences in affinity of analyte molecules to metal surface hinder SERS as a universal quantitative detection tool for various analyte molecules simultaneously. This must be overcome while keeping close proximity of analyte molecules to the metal surface. Moreover, assembled metal nanoparticles (NPs structures might be beneficial for sensitive and reliable detection of chemicals than single NP structures. For this purpose, here we introduce thin silica-coated and assembled Ag NPs (SiO2@Ag@SiO2 NPs for simultaneous and quantitative detection of chemicals that have different intrinsic affinities to silver metal. These SiO2@Ag@SiO2 NPs could detect each SERS peak of aniline or 4-aminothiophenol (4-ATP from the mixture with limits of detection (LOD of 93 ppm and 54 ppb, respectively. E-field distribution based on interparticle distance was simulated using discrete dipole approximation (DDA calculation to gain insight into enhanced scattering of these thin silica coated Ag NP assemblies. These NPs were successfully applied to detect aniline in river water and tap water. Results suggest that SiO2@Ag@SiO2 NP-based SERS detection systems can be used as a simple and universal detection tool for environment pollutants and food safety.

  8. Monomer functionalized silica coated with Ag nanoparticles for enhanced SERS hotspots

    Science.gov (United States)

    Newmai, M. Boazbou; Verma, Manoj; Kumar, P. Senthil

    2018-05-01

    Mesoporous silica (SiO2) spheres are well-known for their excellent chromatographic properties such as the relatively high specific surface, large pore volume, uniform particle size, narrow pore size distribution with favorable pore connectivity; whereas the noble metal Ag nanoparticles have unique size/shape dependant surface plasmon resonance with wide ranging applications. Thus, the desire to synchronize both their properties for specific applications has naturally prompted research in the design and synthesis of core-shell type novel nanoAg@mesoSiO2 nanocomposites, which display potential utility in applications such as photothermal therapy, photocatalysis, molecular sensing, and photovoltaics. In the present work, SiO2 spheres were carefully functionalized with the monomer, N-vinyl pyrrolidone (NVP), which cohesively controls the uniform mass transfer of Ag+ metal ions, thereby enabling its sequential reduction to zerovalent Ag (in the presence of slightly excess NaOH) by electron transfer from nucleophilic attack of the NVP vinyl group by the water molecules even under ambient conditions. Complete metal nanoshell coverage of the silica surface was obtained after multiple Ag deposition cycles, as systematically confirmed from the BET, TEM, optical and FTIR characterization. Our present Ag-coated silica spheres were directly utilized as viable SERS substrates with high sensitivity in contrast with other long chain polymer/surfactant coated silica spheres, owing to the presence of significant number of nanogaps enhanced SERS 'hotspots', which were methodically analyzed utilizing two example analytes, such as crystal violet (CV) and calendula officinalis (CaF).

  9. The selected models of the mesostructure of composites percolation, clusters, and force fields

    CERN Document Server

    Herega, Alexander

    2018-01-01

    This book presents the role of mesostructure on the properties of composite materials. A complex percolation model is developed for the material structure containing percolation clusters of phases and interior boundaries. Modeling of technological cracks and the percolation in the Sierpinski carpet are described. The interaction of mesoscopic interior boundaries of the material, including the fractal nature of interior boundaries, the oscillatory nature of it interaction and also the stochastic model of the interior boundaries’ interaction, the genesis, structure, and properties are discussed. One of part of the book introduces the percolation model of the long-range effect which is based on the notion on the multifractal clusters with transforming elements, and the theorem on the field interaction of multifractals is described. In addition small clusters, their characteristic properties and the criterion of stability are presented.

  10. Pickering emulsion: A novel template for microencapsulated phase change materials with polymer–silica hybrid shell

    International Nuclear Information System (INIS)

    Yin, Dezhong; Ma, Li; Liu, Jinjie; Zhang, Qiuyu

    2014-01-01

    MePCMs (microencapsulated phase change materials) with covalently bonded SiO 2 /polymer hybrid as shell were fabricated via Pickering emulsion polymerization stabilized solely by organically-modified SiO 2 particles. Morphology and core–shell structure of these microcapsules were observed by scanning electron microscopy (SEM). Thermal properties of microencapsulated 1-dodecanol were determined using DSC (differential scanning calorimetry) and TGA (thermal gravimetric analysis). The results indicate that mass ratio of St (styrene)/DVB (divinylbenzene)/dodecanol has great effect on the morphology, inner structure, microencapsulation efficiency and durability of resultant MePCMs. When ratio of St/DVB/dodecanol was 5/1/12, dodecanol content of as much as 62.8% is obtained and the utility efficiency of dodecanol reaches 94.2%. The prepared MePCMs present good durability and thermal reliability. 2.2% of core material leached away the microcapsule after suspended in water for 10 days and 5.8% of core material leached after 2000 accelerated thermal cycling. Our study demonstrated that Pickering emulsion polymerization is a simple and robust method for the preparation of MePCMs with polymer–inorganic hybrids as shell. - Highlights: • We fabricated MePCM via surfactant-free Pickering emulsion polymerization. • The shell of MePCM was composed of PS/SiO 2 organic–inorganic hybrids. • The phase change enthalpy of MePCM is 125.0 J g −1 and the utility efficiency of 1-dodecanol reached 94.2%. • Only 2.2% and 5.8% of core material lost after durability test and 2000 accelerated thermal cycling respectively

  11. Silica diatom shells tailored with Au nanoparticles enable sensitive analysis of molecules for biological, safety and environment applications

    KAUST Repository

    Onesto, V.; Villani, M.; Coluccio, M. L.; Majewska, R.; Alabastri, A.; Battista, E.; Schirato, A.; Calestani, D.; Coppedé , N.; Cesarelli, M.; Amato, F.; Di Fabrizio, Enzo M.; Gentile, F.

    2018-01-01

    Diatom shells are a natural, theoretically unlimited material composed of silicon dioxide, with regular patterns of pores penetrating through their surface. For their characteristics, diatom shells show promise to be used as low cost, highly efficient drug carriers, sensor devices or other micro-devices. Here, we demonstrate diatom shells functionalized with gold nanoparticles for the harvesting and detection of biological analytes (bovine serum albumin—BSA) and chemical pollutants (mineral oil) in low abundance ranges, for applications in bioengineering, medicine, safety, and pollution monitoring.

  12. Silica diatom shells tailored with Au nanoparticles enable sensitive analysis of molecules for biological, safety and environment applications

    KAUST Repository

    Onesto, V.

    2018-04-19

    Diatom shells are a natural, theoretically unlimited material composed of silicon dioxide, with regular patterns of pores penetrating through their surface. For their characteristics, diatom shells show promise to be used as low cost, highly efficient drug carriers, sensor devices or other micro-devices. Here, we demonstrate diatom shells functionalized with gold nanoparticles for the harvesting and detection of biological analytes (bovine serum albumin—BSA) and chemical pollutants (mineral oil) in low abundance ranges, for applications in bioengineering, medicine, safety, and pollution monitoring.

  13. Silica Nephropathy

    Directory of Open Access Journals (Sweden)

    N Ghahramani

    2010-06-01

    Full Text Available Occupational exposure to heavy metals, organic solvents and silica is associated with a variety of renal manifestations. Improved understanding of occupational renal disease provides insight into environmental renal disease, improving knowledge of disease pathogenesis. Silica (SiO2 is an abundant mineral found in sand, rock, and soil. Workers exposed to silica include sandblasters, miners, quarry workers, masons, ceramic workers and glass manufacturers. New cases of silicosis per year have been estimated in the US to be 3600–7300. Exposure to silica has been associated with tubulointerstitial disease, immune-mediated multisystem disease, chronic kidney disease and end-stage renal disease. A rare syndrome of painful, nodular skin lesions has been described in dialysis patients with excessive levels of silicon. Balkan endemic nephropathy is postulated to be due to chronic intoxication with drinking water polluted by silicates released during soil erosion. The mechanism of silica nephrotoxicity is thought to be through direct nephrotoxicity, as well as silica-induced autoimmune diseases such as scleroderma and systemic lupus erythematosus. The renal histopathology varies from focal to crescentic and necrotizing glomerulonephritis with aneurysm formation suggestive of polyarteritis nodosa. The treatment for silica nephrotoxicity is non-specific and depends on the mechanism and stage of the disease. It is quite clear that further research is needed, particularly to elucidate the pathogenesis of silica nephropathy. Considering the importance of diagnosing exposure-related renal disease at early stages, it is imperative to obtain a thorough occupational history in all patients with renal disease, with particular emphasis on exposure to silica, heavy metals, and solvents.

  14. Enhanced near-infrared photoacoustic imaging of silica-coated rare-earth doped nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Yang [Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372 (Singapore); School of Materials Science and Engineering, Changzhou University, Changzhou, Jiangsu 213164 (China); Liao, Lun-De [Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, 35 Keyan Rd., Zhunan Town, Miaoli County 35053, Taiwan, ROC (China); Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456 (Singapore); Bandla, Aishwarya [Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456 (Singapore); Department of Biomedical Engineering, National University of Singapore, 21 Lower Kent Ridge Rd, Singapore 119077 (Singapore); Liu, Yu-Hang [Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 21 Lower Kent Ridge Rd, Singapore 119077 (Singapore); Yuan, Jun [Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456 (Singapore); Thakor, Nitish [Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456 (Singapore); Department of Biomedical Engineering, National University of Singapore, 21 Lower Kent Ridge Rd, Singapore 119077 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 21 Lower Kent Ridge Rd, Singapore 119077 (Singapore); Tan, Mei Chee, E-mail: meichee.tan@sutd.edu.sg [Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372 (Singapore)

    2017-01-01

    Near-infrared photoacoustic (PA) imaging is an emerging diagnostic technology that utilizes the tissue transparent window to achieve improved contrast and spatial resolution for deep tissue imaging. In this study, we investigated the enhancement effect of the SiO{sub 2} shell on the PA property of our core/shell rare-earth nanoparticles (REs) consisting of an active rare-earth doped core of NaYF{sub 4}:Yb,Er (REDNPs) and an undoped NaYF{sub 4} shell. We observed that the PA signal amplitude increased with SiO{sub 2} shell thickness. Although the SiO{sub 2} shell caused an observed decrease in the integrated fluorescence intensity due to the dilution effect, fluorescence quenching of the rare earth emitting ions within the REDNPs cores was successfully prevented by the undoped NaYF{sub 4} shell. Therefore, our multilayer structure consisting of an active core with successive functional layers was demonstrated to be an effective design for dual-modal fluorescence and PA imaging probes with improved PA property. The result from this work addresses a critical need for the development of dual-modal contrast agent that advances deep tissue imaging with high resolution and signal-to-noise ratio. - Graphical abstract: Illustration of multilayer structured imaging probe with REDNPs as active core, undoped NaYF{sub 4} as intermediate layer and SiO{sub 2} as outer shell. The PA signal amplitude of REs/SiO{sub 2} was increased with the SiO{sub 2} shell thickness. - Highlights: • Silica coating was demonstrated to be much more effective in enhancing the PA signal amplitude comparing to soft polymer. • PA enhancement was attributed to the increased phonon modes and phonon energy with the introduction of the SiO{sub 2} coating. • Multilayer structure was an effective design for dual-modal fluorescence and PA imaging probes with improved PA property.

  15. Novel mesoporous composites based on natural rubber and hexagonal mesoporous silica: Synthesis and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Nuntang, Sakdinun; Poompradub, Sirilux [Fuels Research Center, Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Butnark, Suchada [PTT Research and Technology Institute, PTT Public Company Limited, Wangnoi, Ayutthaya 13170 (Thailand); Yokoi, Toshiyuki; Tatsumi, Takashi [Division of Catalytic Chemistry, Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Ngamcharussrivichai, Chawalit, E-mail: Chawalit.Ng@Chula.ac.th [Fuels Research Center, Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand)

    2014-02-14

    The present study is the first report on the synthesis and characterization of mesoporous composites based on natural rubber (NR) and hexagonal mesoporous silica (HMS). A series of NR/HMS composites were prepared in tetrahydrofuran via an in situ sol–gel process using tetraethylorthosilicate as the silica precursor. The physicochemical properties of the composites were characterized by various techniques. The effects of the gel composition on the structural and textural properties of the NR/HMS composites were investigated. The Fourier-transform infrared spectroscopy (FTIR) and {sup 29}Si magic angle spinning nuclear magnetic resonance ({sup 29}Si MAS NMR) results revealed that the surface silanol groups of NR/HMS composites were covered with NR molecules. The powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) data indicated an expansion of the hexagonal unit cell and channel wall thickness due to the incorporation of NR molecules into the mesoporous structure. NR/HMS composites also possessed nanosized particles (∼79.4 nm) as confirmed by scanning electron microscopy (SEM) and particle size distribution analysis. From N{sub 2} adsorption–desorption measurement, the NR/HMS composites possessed a high BET surface area, large pore volume and narrow pore size distribution. Further, they were enhanced hydrophobicity confirmed by H{sub 2}O adsorption–desorption measurement. In addition, the mechanistic pathway of the NR/HMS composite formation was proposed. - Highlights: • NR molecules were incorporated into hexagonal meso-structure of HMS. • NR/HMS composites exhibited an expanded unit cell and channel wall thickness. • Nanosized NR/HMS composites with a lower particle size range were obtained. • NR/HMS had high surface area, large pore volume and narrow pore size distribution. • NR/HMS composites displayed an enhanced hydrophobicity.

  16. Synthesis Characterization and Photocatalytic Studies of Cobalt Ferrite-Silica-Titania Nanocomposites

    Directory of Open Access Journals (Sweden)

    David Greene

    2014-04-01

    Full Text Available In this work, CoFe2O4@SiO2@TiO2 core-shell magnetic nanostructures have been prepared by coating of cobalt ferrite nanoparticles with the double SiO2/TiO2 layer using metallorganic precursors. The Transmission Electron Microscopy (TEM, Energy Dispersive X-Ray Analysis (EDX, Vibrational Sample Magnetometer (VSM measurements and Raman spectroscopy results confirm the presence both of the silica and very thin TiO2 layers. The core-shell nanoparticles have been sintered at 600 °C and used as a catalyst in photo-oxidation reactions of methylene blue under UV light. Despite the additional non-magnetic coatings result in a lower value of the magnetic moment, the particles can still easily be retrieved from reaction mixtures by magnetic separation. This retention of magnetism was of particular importance allowing magnetic recovery and re-use of the catalyst.

  17. Silica-Assisted Nucleation of Polymer Foam Cells with Nanoscopic Dimensions: Impact of Particle Size, Line Tension, and Surface Functionality.

    Science.gov (United States)

    Liu, Shanqiu; Eijkelenkamp, Rik; Duvigneau, Joost; Vancso, G Julius

    2017-11-01

    Core-shell nanoparticles consisting of silica as core and surface-grafted poly(dimethylsiloxane) (PDMS) as shell with different diameters were prepared and used as heterogeneous nucleation agents to obtain CO 2 -blown poly(methyl methacrylate) (PMMA) nanocomposite foams. PDMS was selected as the shell material as it possesses a low surface energy and high CO 2 -philicity. The successful synthesis of core-shell nanoparticles was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy. The cell size and cell density of the PMMA micro- and nanocellular materials were determined by scanning electron microscopy. The cell nucleation efficiency using core-shell nanoparticles was significantly enhanced when compared to that of unmodified silica. The highest nucleation efficiency observed had a value of ∼0.5 for nanoparticles with a core diameter of 80 nm. The particle size dependence of cell nucleation efficiency is discussed taking into account line tension effects. Complete engulfment by the polymer matrix of particles with a core diameter below 40 nm at the cell wall interface was observed corresponding to line tension values of approximately 0.42 nN. This line tension significantly increases the energy barrier of heterogeneous nucleation and thus reduces the nucleation efficiency. The increase of the CO 2 saturation pressure to 300 bar prior to batch foaming resulted in an increased line tension length. We observed a decrease of the heterogeneous nucleation efficiency for foaming after saturation with CO 2 at 300 bar, which we attribute to homogenous nucleation becoming more favorable at the expense of heterogeneous nucleation in this case. Overall, it is shown that the contribution of line tension to the free energy barrier of heterogeneous foam cell nucleation must be considered to understand foaming of viscoelastic materials. This finding emphasizes the need for new strategies including the use of

  18. Synthesis of magnetic hollow silica using polystyrene bead as a template

    International Nuclear Information System (INIS)

    Wu, W.; Caruntu, D.; Martin, A.; Yu, M.H.; O'Connor, C.J.; Zhou, W.L.; Chen, J.-F.

    2007-01-01

    In this paper, we report a new route to synthesize novel magnetic hollow silica nanospheres (MHSNs) using polystyrene particles as sacrificial templates, and TEOS and Fe 3 O 4 as precursors. TEM, EDS, XRD, and SQUID were applied to characterize MHSNs. TEM and EDS results show that the MHSNs consist of about 200 nm of hollow cores and ∼35 nm shells with ∼10 nm of Fe 3 O 4 nanoparticles embedded. The polystyrene beads were successfully removed by immersing the as-prepared silica nanocomposite in a toluene solution. XRD results demonstrate that the Fe 3 O 4 magnetic nanoparticles still keep spinel structure even heated at low temperature. The surface status of the polystyrene beads and Fe 3 O 4 nanoparticles has an important effect on the formation of the MHSNs. The MHSNs present a superparamagnetism at room temperature by SQUID measurement. The MHSNs have potential applications in biosystem and nanomedicine

  19. Optimization and photomodification of extremely broadband optical response of plasmonic core-shell obscurants.

    Science.gov (United States)

    de Silva, Vashista C; Nyga, Piotr; Drachev, Vladimir P

    2016-12-15

    Plasmonic resonances of the metallic shells depend on their nanostructure and geometry of the core, which can be optimized for the broadband extinction normalized by mass. The fractal nanostructures can provide a broadband extinction. It allows as well for a laser photoburning of holes in the extinction spectra and consequently windows of transparency in a controlled manner. The studied core-shell microparticles synthesized using colloidal chemistry consist of gold fractal nanostructures grown on precipitated calcium carbonate (PCC) microparticles or silica (SiO 2 ) microspheres. The optimization includes different core sizes and shapes, and shell nanostructures. It shows that the rich surface of the PCC flakes is the best core for the fractal shells providing the highest mass normalized extinction over the extremely broad spectral range. The mass normalized extinction cross section up to 3m 2 /g has been demonstrated in the broad spectral range from the visible to mid-infrared. Essentially, the broadband response is a characteristic feature of each core-shell microparticle in contrast to a combination of several structures resonant at different wavelengths, for example nanorods with different aspect ratios. The photomodification at an IR wavelength makes the window of transparency at the longer wavelength side. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Photo-physical properties enhancement of bare and core-shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Mumin, Md Abdul, E-mail: pcharpentier@eng.uwo.ca; Akhter, Kazi Farida, E-mail: pcharpentier@eng.uwo.ca; Charpentier, Paul A., E-mail: pcharpentier@eng.uwo.ca [Chemical and Biochemical Engineering, Western University, London Ontario (Canada)

    2014-03-31

    Semiconductor nanocrystals (NCs) (also known as quantum dots, QDs) have attracted immense attention for their size-tunable optical properties that makes them impressive candidates for solar cells, light emitting devices, lasers, as well as biomedical imaging. However monodispersity, high and consistent photoluminescence, photostability, and biocompatibility are still major challenges. This work focuses on optimizing the photophysical properties and biocompatibility of QDs by forming core-shell nanostructures and their encapsulation by a carrier. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm sizes were synthesized using a facile approach based on pyrolysis of the single molecule precursors. After capping the CdS QDs with a thin layer of ZnS to reduce toxicity, the photoluminescence and photostability of the core-shell QDs was significantly enhanced. To make both the bare and core/shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown on the QDs through a reverse microemulsion technique based on hydrophobic interaction. This encapsulation enhanced the quantum yield and photostability compared to the bare QDs by providing much stronger resistance to oxidation and Oswald ripening of QDs. Encapsulation also improved biocompatibility of QDs that was evaluated with human umbilical vein endothelial cell lines (HUVEC)

  1. Some Durability Characteristics of Micro Silica and Nano Silica Contained Concrete

    Directory of Open Access Journals (Sweden)

    Mohammed Salah Nasr

    2016-12-01

    Full Text Available This paper aims to investigate the influence of replacement of cement with nano and micro silica admixtures on some durability properties of concrete such as water absorption, chloride content and pH tests. Three replacement ratios (5%,10%,15% of micro silica and four replacement proportions (0.5%,1.5%,3%,5% for nano silica were used in this study. Two exposure conditions were considered for chloride content test: wetting-drying and full immersing exposure in 6% of chloride ions solution, NaCl type. Results showed that mixes of %5 micro silica and 5% nano silica had lower content of chloride (about 0.19% and 0.18% for wetting-drying and full immersing exposure respectively. For water absorption test, all mixes incorporated micro and nano silica, except for %5 micro silica mix, showed lower absorption than control mixes. For pH test, results indicated that the adding of nano and micro silica didn’t affect adversely the alkalinity of concrete.

  2. Synthesis of partially graphitic ordered mesoporous carbons with high surface areas

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Wenjun; Wan, Ying [Department of Chemistry, Key Laboratory of Resource Chemistry of Ministry of Education, Shanghai Normal University, Shanghai 200234 (China); Dou, Yuqian; Zhao, Dongyuan [Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433 (China)

    2011-01-01

    Graphitic carbons with ordered mesostructure and high surface areas (of great interest in applications such as energy storage) have been synthesized by a direct triblock-copolymer-templating method. Pluronic F127 is used as a structure-directing agent, with a low-molecular-weight phenolic resol as a carbon source, ferric oxide as a catalyst, and silica as an additive. Inorganic oxides can be completely eliminated from the carbon. Small-angle XRD and N{sub 2} sorption analysis show that the resultant carbon materials possess an ordered 2D hexagonal mesostructure, uniform bimodal mesopores (about 1.5 and 6 nm), high surface area ({proportional_to}1300 m{sup 2}/g), and large pore volumes ({proportional_to}1.50 cm{sup 3}/g) after low-temperature pyrolysis (900 C). All surface areas come from mesopores. Wide-angle XRD patterns demonstrate that the presence of the ferric oxide catalyst and the silica additive lead to a marked enhancement of graphitic ordering in the framework. Raman spectra provide evidence of the increased content of graphitic sp{sup 2} carbon structures. Transmission electron microscopy images confirm that numerous domains in the ordered mesostructures are composed of characteristic graphitic carbon nanostructures. The evolution of the graphitic structure is dependent on the temperature and the concentrations of the silica additive, and ferric oxide catalyst. Electrochemical measurements performed on this graphitic mesoporous carbon when used as an electrode material for an electrochemical double layer capacitor shows rectangular-shaped cyclic voltammetry curves over a wide range of scan rates, even up to 200 mV/s, with a large capacitance of 155 F/g in KOH electrolyte. This method can be widely applied to the synthesis of graphitized carbon nanostructures. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Porous silicon and diatoms micro-shells: an example of inverse biomimetic

    Science.gov (United States)

    De Tommasi, Edoardo; Rea, Ilaria; Rendina, Ivo; De Stefano, Luca

    2011-05-01

    Porous silicon (PSi) is by far a very useful technological platform for optical monitoring of chemical and biological substances and due to its peculiar physical and morphological properties it is worldwide used in sensing experiments. On the other hand, we have discovered a natural material, the micro-shells of marine diatoms, ubiquitous unicellular algae, which are made of hydrated amorphous silica, but, most of all, show geometrical structures made of complex patterns of pores which are surprisingly similar to those of porous silicon. Moreover, under laser irradiation, this material is photoluminescent and the photoluminescence is very sensitive to the surrounding atmosphere, which means that the material can act as a transducer. Starting from our experience on PSi devices, we explore the optical and photonic properties of marine diatoms micro-shells in a sort of inverse biomimicry.

  4. Design of Magnetic Gelatine/Silica Nanocomposites by Nanoemulsification: Encapsulation versus in Situ Growth of Iron Oxide Colloids

    Directory of Open Access Journals (Sweden)

    Joachim Allouche

    2014-07-01

    Full Text Available The design of magnetic nanoparticles by incorporation of iron oxide colloids within gelatine/silica hybrid nanoparticles has been performed for the first time through a nanoemulsion route using the encapsulation of pre-formed magnetite nanocrystals and the in situ precipitation of ferrous/ferric ions. The first method leads to bi-continuous hybrid nanocomposites containing a limited amount of well-dispersed magnetite colloids. In contrast, the second approach allows the formation of gelatine-silica core-shell nanostructures incorporating larger amounts of agglomerated iron oxide colloids. Both magnetic nanocomposites exhibit similar superparamagnetic behaviors. Whereas nanocomposites obtained via an in situ approach show a strong tendency to aggregate in solution, the encapsulation route allows further surface modification of the magnetic nanocomposites, leading to quaternary gold/iron oxide/silica/gelatine nanoparticles. Hence, such a first-time rational combination of nano-emulsion, nanocrystallization and sol-gel chemistry allows the elaboration of multi-component functional nanomaterials. This constitutes a step forward in the design of more complex bio-nanoplatforms.

  5. Surface-engineered core-shell nano-size ferrites and their antimicrobial activity

    International Nuclear Information System (INIS)

    Baraliya, Jagdish D.; Joshi, Hiren H.

    2014-01-01

    We report the results of biological study on core-shell structured MFe 2 O 4 (where M = Co, Mn, Ni) nanoparticles and influence of silica- DEG dual coating on their antimicrobial activity. Spherical MFe 2 O 4 nanoparticles were prepared via a Co-precipitation method. The microstructures and morphologies of these nanoparticles were studied by x-ray diffraction and FTIR. The antimicrobial activity study carried out in nutrient agar medium with addition of antimicrobial synthesis compound which is tested for its activity against different types of bacteria

  6. Microporous silica membranes

    DEFF Research Database (Denmark)

    Boffa, Vittorio; Yue, Yuanzheng

    2012-01-01

    Hydrothermal stability is a crucial factor for the application of microporous silica-based membranes in industrial processes. Indeed, it is well established that steam exposure may cause densification and defect formation in microporous silica membranes, which are detrimental to both membrane...... permeability and selectivity. Numerous previous studies show that microporous transition metal doped-silica membranes are hydrothermally more stable than pure silica membranes, but less permeable. Here we present a quantitative study on the impact of type and concentration of transition metal ions...... on the microporous structure, stability and permeability of amorphous silica-based membranes, providing information on how to design chemical compositions and synthetic paths for the fabrication of silica-based membranes with a well accessible and highly stabile microporous structure....

  7. Surfactant adsorption and aggregate structure of silica nanoparticles: a versatile stratagem for the regulation of particle size and surface modification

    International Nuclear Information System (INIS)

    Chaudhary, Savita; Rohilla, Deepak; Mehta, S K

    2014-01-01

    The area of silica nanoparticles is incredibly polygonal. Silica particles have aroused exceptional deliberation in bio-analysis due to great progress in particular arenas, for instance, biocompatibility, unique properties of modifiable pore size and organization, huge facade areas and pore volumes, manageable morphology and amendable surfaces, elevated chemical and thermal stability. Currently, silica nanoparticles participate in crucial utilities in daily trade rationales such as power storage, chemical and genetic sensors, groceries dispensation and catalysis. Herein, the size-dependent interfacial relation of anionic silica nanoparticles with twelve altered categories of cationic surfactants has been carried out in terms of the physical chemical facets of colloid and interface science. The current analysis endeavours to investigate the virtual consequences of different surfactants through the development of the objective composite materials. The nanoparticle size controls, the surface-to-volume ratio and surface bend relating to its interaction with surfactant will also be addressed in this work. More importantly, the simulated stratagem developed in this work can be lengthened to formulate core–shell nanostructures with functional nanoparticles encapsulated in silica particles, making this approach valuable and extensively pertinent for employing sophisticated materials for catalysis and drug delivery. (papers)

  8. Preparation of silica coated and 90Y-radiolabeled β-NaYF4 upconverting nanophosphors for multimodal tracing

    Science.gov (United States)

    Najmr, Stan; Lu, Tianfeng; Keller, Austin W.; Zhang, Mingyue; Lee, Jennifer D.; Makvandi, Mehran; Pryma, Daniel A.; Kagan, Cherie R.; Murray, Christopher B.

    2018-06-01

    Rare-earth (RE) compounds have been actively pursued for therapeutic and diagnostic applications due to their ability to upconvert near infrared light into the UV–vis range. Through nanoengineering and bottom-up synthesis, additional functionality can be added to these upconverting systems. Herein, we report the synthesis of 90Y-doped β-NaYF4:Er, Yb upconverting nanophosphors (UCNPs) to enable β-particle emission and upconversion by the same UCNP. To homogenously incorporate the radionuclides, we employ a hydroxide metathesis method to produce the RE precursor required for the solvothermal synthesis of monodisperse UCNPs. Once incorporated, we find that the β-emitting 90Y dopants do not influence the energy pathways required for upconversion, enabling simultaneous radio- and optical-tracing. The resulting large (>100 nm in height and width), anisotropic, 90Y-radiolabeled β-NaYF4 UCNPs are then coated with silica using a modified, micelle-driven Stöber process to enable their dispersion in polar solvents. Doing so highlights the importance of surfactant (Igepal CO-520) and silica source (tetraethyl orthosilicate) interactions to the continuity of the silica shell and makes the vast library of silica surface chemistry and functionality accessible to upconverting radiotracers.

  9. Glass transition of poly (methyl methacrylate) filled with nanosilica and core-shell structured silica

    DEFF Research Database (Denmark)

    Song, Yihu; Bu, Jing; Zuo, Min

    2017-01-01

    transition and segmental dynamics of PMMA in the nanocomposites prepared via solution casting was compared. The remarkable depression (≥10 °C) of glass transition temperature (Tg) induced by the incorporation of SiO2 and CS was both observed at low loadings. Here, different mechanisms were responsible...... for the effect of SiO2 and CS on the segmental acceleration of PMMA matrix. The formation of rigid amorphous fraction (RAF) layer around SiO2 with the thickness of 16.4 nm led to the adjacent molecular packing frustration, while the “lubrication” effect of nonwetting interface between the grafted crosslinked......Core-shell (CS) nanocomposite particles with 53.4 wt% cross-linked poly (methyl methacrylate) (PMMA) shell of 11.6 nm in thickness were fabricated via miniemulsion polymerization of methyl methacrylate in the presence of modified nanosilica. The influence of nanosilica and CS nanoparticles on glass...

  10. Synthesis and Characterization of Ti-Phenyl at SiO2 Core-Shell Nanoparticles Catalyst

    International Nuclear Information System (INIS)

    Syamsi Aini; Jon Efendi; Syamsi Aini; Jon Efendi

    2012-01-01

    This study highlights the potential use of Ti-Phenyl at SiO 2 core-shell nanoparticles as heterogeneous catalysis in oxidation reaction. The Ti-Phenyl at SiO 2 was synthesized by reduction of TiCl 4 and diazonium salt with sodium borohydride to produce phenyl titanium nanoparticles (Ti-Phenyl), followed by the silica shell coating using tetraethyl orthosilicate (TEOS). The Ti-Phenyl at SiO 2 nanoparticles were characterized by Fourier transform infrared (FTIR) spectrometer, diffuse reflectance (DR) UV-visible spectrometer, thermogravimetric analyzer (TGA), X-ray diffraction (XRD) spectrometer, field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The core-shell size of Ti-Phenyl at SiO 2 was in the range of 40 to 100 nm with its core composed with an agglomeration of Ti-Phenyl. The Ti-Phenyl at SiO 2 was active as a catalyst in the liquid phase epoxidation of 1-octene with aqueous hydrogen peroxide as an oxidant. (author)

  11. Optical encoding of microbeads based on silica particle encapsulated quantum dots and its applications

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Xiaoxia; Cao Yuancheng; Jin Xin; Yang Jie; Hua Xiaofeng; Wang Haiqiao; Liu Bo; Wang Zhan; Wang Jianhao; Yang Liang; Zhao Yuandi [Key Laboratory of Biomedical Photonics of Ministry of Education-Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, HuBei 430074 (China); Hubei Bioinformatics and Molecular Imaging Key Laboratory, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, HuBei, 430074 (China)

    2008-01-16

    A novel method concerning the coding technology of polystyrene beads with Si encapsulated quantum dot (QD) particles (Si - QDs particles) is studied in this paper. In the reverse microemulsion system containing tetraethoxysilane (TEOS), water-soluble QDs (emission peak at 600 nm) were enveloped within the silica shell, forming Si - QDs particles. The Si - QDs particles were characterized by TEM, showing good uniform size, with an average diameter of about 167.0 nm. In comparison with the pure water-soluble QDs, the encapsulation of water-soluble QDs in the silica shell led to an enhancement in anti-photobleaching by providing inert barriers for the QDs. Images presented by SEM and confocal laser scanning microscopy demonstrated that the Si - QDs particles were equably coated on the surface of carboxyl functionalized polystyrene (PS) beads. Then, with the assistance of ethyl-3-(dimethyl aminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS), human IgG could be successfully crosslinked to Si - QDs particle coated PS-COOH beads. Furthermore, the Si - QDs coated PS-COOH beads with human IgG were examined in immunoassay experiments, and the results indicated that these beads could be applied in the specific recognition of goat-anti-human IgG in solution. This investigation is expected to provide a new route to bead coding in the field of suspension microarrays, based on the use of QDs.

  12. Morphology and orientational behavior of silica-coated spindle-type hematite particles in a magnetic field probed by small-angle X-ray scattering.

    Science.gov (United States)

    Reufer, Mathias; Dietsch, Hervé; Gasser, Urs; Hirt, Ann; Menzel, Andreas; Schurtenberger, Peter

    2010-04-15

    Form factor and magnetic properties of silica-coated spindle-type hematite nanoparticles are determined from SAXS measurements with applied magnetic field and magnetometry measurements. The particle size, polydispersity and porosity are determined using a core-shell model for the form factor. The particles are found to align with their long axis perpendicular to the applied field. The orientational order is determined from the SAXS data and compared to the orientational order obtained from magnetometry. The direct access to both, the orientational order of the particles, and the magnetic moments allow one to determine the magnetic properties of the individual spindle-type hematite particles. We study the influence of the silica coating on the magnetic properties and find a fundamentally different behavior of silica-coated particles. The silica coating reduces the effective magnetic moment of the particles. This effect is enhanced with field strength and can be explained by superparamagnetic relaxation in the highly porous particles.

  13. Encapsulation of antigen-loaded silica nanoparticles into microparticles for intradermal powder injection.

    Science.gov (United States)

    Deng, Yibin; Mathaes, Roman; Winter, Gerhard; Engert, Julia

    2014-10-15

    Epidermal powder immunisation (EPI) is being investigated as a promising needle-free delivery methods for vaccination. The objective of this work was to prepare a nanoparticles-in-microparticles (nano-in-micro) system, integrating the advantages of nanoparticles and microparticles into one vaccine delivery system for epidermal powder immunisation. Cationic mesoporous silica nanoparticles (MSNP-NH2) were prepared and loaded with ovalbumin as a model antigen. Loading was driven by electrostatic interactions. Ovalbumin-loaded silica nanoparticles were subsequently formulated into sugar-based microparticles by spray-freeze-drying. The obtained microparticles meet the size requirement for EPI. Confocal microscopy was used to demonstrate that the nanoparticles are homogeneously distributed in the microparticles. Furthermore, the silica nanoparticles in the dry microparticles can be re-dispersed in aqueous solution showing no aggregation. The recovered ovalbumin shows integrity compared to native ovalbumin. The present nano-in-micro system allows (1) nanoparticles to be immobilized and finely distributed in microparticles, (2) microparticle formation and (3) re-dispersion of nanoparticles without subsequent aggregation. The nanoparticles inside microparticles can (1) adsorb proteins to cationic shell/surface voids in spray-dried products without detriment to ovalbumin stability, (2) deliver antigens in nano-sized modes to allow recognition by the immune system. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Biosilica from Living Diatoms: Investigations on Biocompatibility of Bare and Chemically Modified Thalassiosira weissflogii Silica Shells

    Directory of Open Access Journals (Sweden)

    Stefania Roberta Cicco

    2016-12-01

    Full Text Available In the past decade, mesoporous silica nanoparticles (MSNs with a large surface area and pore volume have attracted considerable attention for their application in drug delivery and biomedicine. Here we propose biosilica from diatoms as an alternative source of mesoporous materials in the field of multifunctional supports for cell growth: the biosilica surfaces were chemically modified by traditional silanization methods resulting in diatom silica microparticles functionalized with 3-mercaptopropyl-trimethoxysilane (MPTMS and 3-aminopropyl-triethoxysilane (APTES. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that the –SH or –NH2 were successfully grafted onto the biosilica surface. The relationship among the type of functional groups and the cell viability was established as well as the interaction of the cells with the nanoporosity of frustules. These results show that diatom microparticles are promising natural biomaterials suitable for cell growth, and that the surfaces, owing to the mercapto groups, exhibit good biocompatibility.

  15. Cu₂-xSe@mSiO₂-PEG core-shell nanoparticles: a low-toxic and efficient difunctional nanoplatform for chemo-photothermal therapy under near infrared light radiation with a safe power density.

    Science.gov (United States)

    Liu, Xijian; Wang, Qian; Li, Chun; Zou, Rujia; Li, Bo; Song, Guosheng; Xu, Kaibing; Zheng, Yun; Hu, Junqing

    2014-04-21

    A low-toxic difunctional nanoplatform integrating both photothermal therapy and chemotherapy for killing cancer cells using Cu₂-xSe@mSiO₂-PEG core-shell nanoparticles is reported. Silica coating and further PEG modification improve the hydrophilicity and biocompatibility of copper selenide nanoparticles. As-prepared Cu₂-xSe@mSiO₂-PEG nanoparticles not only display strong near infrared (NIR) region absorption and good photothermal effect, but also exhibit excellent biocompatibility. The mesoporous silica shell is provided as the carrier for loading the anticancer drug, doxorubicin (DOX). Moreover, the release of DOX from Cu₂-xSe@mSiO₂-PEG core-shell nanoparticles can be triggered by pH and NIR light, resulting in a synergistic effect for killing cancer cells. Importantly, the combination of photothermal therapy and chemotherapy driven by NIR radiation with safe power density significantly improves the therapeutic efficacy, and demonstrates better therapeutic effects for cancer treatment than individual therapy.

  16. One-by-one imprinting in two eccentric layers of hollow core-shells: Sequential electroanalysis of anti-HIV drugs.

    Science.gov (United States)

    Singh, Kislay; Jaiswal, Swadha; Singh, Richa; Fatma, Sana; Prasad, Bhim Bali

    2018-07-15

    Double layered one-by-one imprinted hollow core-shells@ pencil graphite electrode was fabricated for sequential sensing of anti-HIV drugs. For this, two eccentric layers were developed on the surface of vinylated silica nanospheres to obtain double layered one-by-one imprinted solid core-shells. This yielded hollow core-shells on treatment with hydrofluoric acid. The modified hollow core-shells (single layered dual imprinted) evolved competitive diffusion of probe/analyte molecules. However, the corresponding double layered one-by-one imprinted hollow core-shells (outer layer imprinted with Zidovudine, and inner layer with Lamivudine) were found relatively better owing to their bilateral diffusions into molecular cavities, without any competition. The entire work is based on differential pulse anodic stripping voltammetry at double layered one-by-one imprinted hollow core-shells. This resulted in indirect detection of electro inactive targets with limits of detection as low as 0.91 and 0.12 (aqueous sample), 0.94 and 0.13 (blood serum), and 0.99 and 0.20 ng mL -1 (pharmaceutics) for lamivudine and zidovudine, respectively in anti-HIV drug combination. Copyright © 2018 Elsevier B.V. All rights reserved.

  17. Crystalline Silica Primer

    Science.gov (United States)

    ,

    1992-01-01

    Crystalline silica is the scientific name for a group of minerals composed of silicon and oxygen. The term crystalline refers to the fact that the oxygen and silicon atoms are arranged in a threedimensional repeating pattern. This group of minerals has shaped human history since the beginning of civilization. From the sand used for making glass to the piezoelectric quartz crystals used in advanced communication systems, crystalline silica has been a part of our technological development. Crystalline silica's pervasiveness in our technology is matched only by its abundance in nature. It's found in samples from every geologic era and from every location around the globe. Scientists have known for decades that prolonged and excessive exposure to crystalline silica dust in mining environments can cause silicosis, a noncancerous lung disease. During the 1980's, studies were conducted that suggested that crystalline silica also was a carcinogen. As a result of these findings, crystalline silica has been regulated under the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard (HCS). Under HCS, OSHAregulated businesses that use materials containing 0.1% or more crystalline silica must follow Federal guidelines concerning hazard communication and worker training. Although the HCS does not require that samples be analyzed for crystalline silica, mineral suppliers or OSHAregulated

  18. Silica-coated flexible liposomes as a nanohybrid delivery system for enhanced oral bioavailability of curcumin

    Directory of Open Access Journals (Sweden)

    Li C

    2012-12-01

    Full Text Available Chong Li, Yan Zhang, Tingting Su, Lianlian Feng, Yingying Long, Zhangbao ChenKey Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Pharmaceutical Sciences, Southwest University, Chongqing, ChinaAbstract: We investigated flexible liposomes as a potential oral drug delivery system. However, enhanced membrane fluidity and structural deformability may necessitate liposomal surface modification when facing the harsh environment of the gastrointestinal tract. In the present study, silica-coated flexible liposomes loaded with curcumin (CUR-SLs having poor water solubility as a model drug were prepared by a thin-film method with homogenization, followed by the formation of a silica shell by the sol-gel process. We systematically investigated the physical properties, drug release behavior, pharmacodynamics, and bioavailability of CUR-SLs. CUR-SLs had a mean diameter of 157 nm and a polydispersity index of 0.14, while the apparent entrapment efficiency was 90.62%. Compared with curcumin-loaded flexible liposomes (CUR-FLs without silica-coatings, CUR-SLs had significantly higher stability against artificial gastric fluid and showed more sustained drug release in artificial intestinal fluid as determined by in vitro release assays. The bioavailability of CUR-SLs and CUR-FLs was 7.76- and 2.35-fold higher, respectively, than that of curcumin suspensions. Silica coating markedly improved the stability of flexible liposomes, and CUR-SLs exhibited a 3.31-fold increase in bioavailability compared with CUR-FLs, indicating that silica-coated flexible liposomes may be employed as a potential carrier to deliver drugs with poor water solubility via the oral route with improved bioavailability.Keywords: silica, flexible liposome, oral bioavailability, curcumin

  19. Biocompatible and highly luminescent near-infrared CuInS₂/ZnS quantum dots embedded silica beads for cancer cell imaging.

    Science.gov (United States)

    Foda, Mohamed F; Huang, Liang; Shao, Feng; Han, He-You

    2014-02-12

    Bright and stable CuInS2/ZnS@SiO2 nanoparticles with near-infrared (NIR) emission were competently prepared by incorporating the as-prepared hydrophobic CuInS2/ZnS quantum dots (QDs) directly into lipophilic silane micelles and subsequently an exterior silica shell was formed. The obtained CuInS2/ZnS@SiO2 nanoparticles homogeneously comprised both single-core and multicore remarkable CuInS2/ZnS QDs, while the silica shell thickness could be controlled to within 5-10 nm and their overall size was 17-25 nm. Also, the functionalized CuInS2/ZnS QDs encapsulated in the silica spheres, expedited their bioconjugation with holo-Transferrin (Tf) for further cancer cell imaging. The CuInS2/ZnS@SiO2 nanoparticles not only showed a dominant NIR band-edge luminescence at 650-720 nm with a quantum yield (QY) between 30 and 50%, without a recognized photoluminescence (PL) red shift, but also exhibited excellent PL and colloidal stability in aqueous media. Impressively, the cytotoxicity studies revealed minor suppression on cell viability under both CuInS2/ZnS@SiO2 and CuInS2/ZnS@SiO2@Tf concentrations up to 1 mg/mL. The application in live-cell imaging revealed that the potential of CuInS2/ZnS QDs as biocompatible, robust, cadmium-free, and brilliant NIR emitters is considered promising for fluorescent labels.

  20. Oral rehabilitation with an implant-supported mesostructure on a microvascularized mandibular graft: A 12-year follow-up study

    Directory of Open Access Journals (Sweden)

    José Manuel Mendes

    2017-06-01

    Full Text Available Due to the increased survival of the population, treatment of oral cavity tumour patients is increasingly common. In this context, oral rehabilitation construction methods have been developed to contribute to improving the patient's quality of life. Developments in the areas of oral implantology and rehabilitation, along with microvascularized grafts, have increased the possibility of rehabilitating patients undergoing hemimandibulectomy with more effective and lasting treatment. This article aims to demonstrate an aesthetic and functional oral rehabilitation method, both in terms of the oral cavity and the lower face, in a young patient submitted to a left lateral hemimandibulectomy, using a mesostructure fixed onto implants.

  1. Decomposition of formic acid over silica encapsulated and amine functionalised gold nanoparticles

    DEFF Research Database (Denmark)

    Mielby, Jerrik Jørgen; Kunov-Kruse, Andreas Jonas; Kegnæs, Søren

    2017-01-01

    Formic acid has recently attracted considerable attention as a safe and convenient source of hydrogen for sustainable chemical synthesis and renewable energy storage. Here, we show that silica encapsulated and amine functionalised gold nanoparticles are highly active catalysts for the production...... of hydrogen by vapour phase decomposition of formic acid. The core-shell catalysts are prepared in a reverse micelle system that makes it possible to control the size of the Au nanoparticles and the thickness of the SiO2 shells, which has a large impact on the catalytic activity. The smallest gold...... nanoparticles are 2.2 ± 0.3 nm in diameter and have a turnover frequency (TOF) of up to 958 h−1 at a temperature of 130 °C. Based on detailed in situ ATR-FTIR studies and results from kinetic isotope labelling experiments we propose that the active site is a low-coordinated and amine functionalised Au atom...

  2. Synthesis of SiOx@CdS core–shell nanoparticles by simple thermal decomposition approach and studies on their optical properties

    International Nuclear Information System (INIS)

    Kandula, Syam; Jeevanandam, P.

    2014-01-01

    Highlights: • SiO x @CdS nanoparticles have been synthesized by a novel thermal decomposition approach. • The method is easy and there is no need for surface functionalization of silica core. • SiO x @CdS nanoparticles show different optical properties compared to pure CdS. - Abstract: SiO x @CdS core–shell nanoparticles have been synthesized by a simple thermal decomposition approach. The synthesis involves two steps. In the first step, SiO x spheres were synthesized using StÖber’s process. Then, cadmium sulfide nanoparticles were deposited on the SiO x spheres by the thermal decomposition of cadmium acetate and thiourea in ethylene glycol at 180 °C. Electron microscopy results show uniform deposition of cadmium sulfide nanoparticles on the surface of SiO x spheres. Electron diffraction patterns confirm crystalline nature of the cadmium sulfide nanoparticles on silica and high resolution transmission electron microscopy images clearly show the lattice fringes due to cubic cadmium sulfide. Diffuse reflectance spectroscopy results show blue shift of band gap absorption of SiO x @CdS core–shell nanoparticles with respect to bulk cadmium sulfide and this is attributed to quantum size effect. Photoluminescence results show enhancement in intensity of band edge emission and weaker emission due to surface defects in SiO x @CdS core–shell nanoparticles compared to pure cadmium sulfide nanoparticles

  3. Silica coated ionic liquid templated mesoporous silica nanoparticles ...

    African Journals Online (AJOL)

    A series of long chain pyridinium based ionic liquids 1-tetradecylpyridinium bromide, 1-hexadecylpyridinium bromide and 1-1-octadecylpyridinium bromide were used as templates to prepare silica coated mesoporous silica nanoparticles via condensation method under basic condition. The effects of alkyl chain length on ...

  4. Role of surface functionality on the formation of raspberry-like polymer/silica composite particles: Weak acid–base interaction and steric effect

    International Nuclear Information System (INIS)

    Wang, Lan; Song, LinYong; Chao, ZhiYin; Chen, PengPeng; Nie, WangYan; Zhou, YiFeng

    2015-01-01

    Graphical abstract: - Highlights: • Core–shell structured polymer/SiO 2 was obtained with carboxylic-functionalized templates. • Raspberry-like structure was observed with carboxylic and poly(ethylene glycol) hybrid-functionalized polymer microspheres. • Carboxylic groups contributed to the nucleation and the poly(ethylene glycol) chains was used to control the growth of silica particles. • Super-hydrophobic surface was obtained and the contact angle of water on the dual-sized structured surface was up to 160°. - Abstract: The surface functionality of polymer microspheres is the crucial factor to determine the nucleation and growth of silica particles and to construct the organic/inorganic hierarchical structures. The objective of this work was to evaluate the surface functionality and hierarchical morphology relationship via in situ sol–gel reaction. Carboxylic-functionalized poly (styrene-co-maleic anhydride) [P(S-co-MA)], poly(ethylene glycol)-functionalized poly(styrene-co-poly(ethylene glycol) methacrylate) [P(S-co-PEGMA)], and hybrid functionalized poly(styrene-co-maleic anhydride-co-poly(ethylene glycol) methacrylate) [P(S-co-MA-co-PEGMA)] microspheres were synthesized by emulsifier-free polymerization and used as templates. The morphologies of the composite particles were observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results showed that core–shell structure was obtained with P(S-co-MA) as templates; raspberry-like structure was observed by using P(S-co-MA-co-PEGMA) as templates; and no silica particles were attached onto the surface of P(S-co-PEGMA) microspheres. These results indicated that the carboxylic groups on the surface formed by hydrolysis of anhydride groups were the determinate factor to control the nucleation of silica nanoparticles, and the PEG chains on the surface can affect the growth of silica particles. In addition, the particulate films were constructed by assembling these

  5. Plasmonic nanodiamonds: targeted core-shell type nanoparticles for cancer cell thermoablation.

    Science.gov (United States)

    Rehor, Ivan; Lee, Karin L; Chen, Kevin; Hajek, Miroslav; Havlik, Jan; Lokajova, Jana; Masat, Milan; Slegerova, Jitka; Shukla, Sourabh; Heidari, Hamed; Bals, Sara; Steinmetz, Nicole F; Cigler, Petr

    2015-02-18

    Targeted biocompatible nanostructures with controlled plasmonic and morphological parameters are promising materials for cancer treatment based on selective thermal ablation of cells. Here, core-shell plasmonic nanodiamonds consisting of a silica-encapsulated diamond nanocrystal coated in a gold shell are designed and synthesized. The architecture of particles is analyzed and confirmed in detail using electron tomography. The particles are biocompatibilized using a PEG polymer terminated with bioorthogonally reactive alkyne groups. Azide-modified transferrin is attached to these particles, and their high colloidal stability and successful targeting to cancer cells overexpressing the transferrin receptor are demonstrated. The particles are nontoxic to the cells and they are readily internalized upon binding to the transferrin receptor. The high plasmonic cross section of the particles in the near-infrared region is utilized to quantitatively ablate the cancer cells with a short, one-minute irradiation by a pulse 750-nm laser. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. l-Cysteine-modified silver-functionalized silica-based material as an efficient solid-phase extraction adsorbent for the determination of bisphenol A.

    Science.gov (United States)

    Li, Yuanyuan; Zhu, Nan; Li, Bingxiang; Chen, Tong; Ma, Yulong; Li, Qiang

    2018-02-01

    A new silver-functionalized silica-based material with a core-shell structure based on silver nanoparticle-coated silica spheres was synthesized, and silver nanoparticles were modified using strongly bound l-cysteine. l-Cysteine-silver@silica was characterized by scanning electron microscopy and FTIR spectroscopy. Then, a solid-phase extraction method based on l-cysteine-silver@silica was developed and successfully used for bisphenol A determination prior to HPLC analysis. The results showed that the l-cysteine-silver@silica as an adsorbent exhibited good enrichment capability for bisphenol A, and the maximum adsorption saturation was 20.93 mg/g. Moreover, a short adsorption equilibrium time was obtained due to the presence of silver nanoparticles on the surface of the silica. The extraction efficiencies were then optimized by varying the eluents and pH. Under the optimized conditions, good linearity for bisphenol A was obtained in the range from 0.4 to 4.0 μM (R 2  > 0.99) with a low limit of detection (1.15 ng/mL). The spiked recoveries from tap water and milk samples were satisfactory (85-102%) with relative standard deviations below 5.2% (n = 3), which indicated that the method was suitable for the analysis of bisphenol A in complex samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Polarized neutron study of the magnetic mesostructure in (Pd sub 1 sub - sub x Fe sub x) sub 1 sub - sub y Mn sub y

    CERN Document Server

    Gordeev, G P; Lazebnik, I M; Zabenkin, V N; Wagner, V

    2002-01-01

    In PdFeMn alloys with different Fe-atom concentrations, the behaviour of both mean magnetization and neutron depolarization in the magnetization/demagnetization process was observed by three-dimensional analysis of neutron-beam polarization. Both magnetization and depolarization have a hysteresis loop for the same values of an applied field. Depolarization loops are sharply distinguished for different alloys. This gives evidence of different magnetic mesostructures in these alloys. (orig.)

  8. Magnetic, Fluorescence and Transition Metal Ion Response Properties of 2,6-Diaminopyridine Modified Silica-Coated Fe3O4 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Yunhui Zhai

    2016-08-01

    Full Text Available Multi-functional nanoparticles possessing magnetic, fluorescence and transition metal ion response properties were prepared and characterized. The particles have a core/shell structure that consists of silica-coated magnetic Fe3O4 and 2,6-diaminopyridine anchored on the silica surface via organic linker molecules. The resultant nanoparticles were found by transmission electron microscopy to be well-dispersed spherical particles with an average diameter of 10–12 nm. X-ray diffraction analysis suggested the existence of Fe3O4 and silica in/on the particle. Fourier transform infrared spectra revealed that 2,6-diaminopyridine molecules were successfully covalently bonded to the surface of magnetic composite nanoparticles. The prepared particles possessed an emission peak at 364 nm with an excitation wavelength of 307 nm and have a strong reversible response property for some transition metal ions such as Cu2+ and Zn2+. This new material holds considerable promise in selective magneto separation and optical determination applications.

  9. A fluorescent and chemiluminescent difunctional mesoporous silica nanoparticle as a label for the ultrasensitive detection of cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Tao Liang [Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi' an 710062 (China); Song Chaojun; Sun Yuanjie [Department of Immunology, The Fourth Military Medical University, Xi' an 710032 (China); Li Xiaohua; Li Yunyun [Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi' an 710062 (China); Jin Boquan [Department of Immunology, The Fourth Military Medical University, Xi' an 710032 (China); Zhang Zhujun, E-mail: zhangzj@snnu.edu.cn [Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi' an 710062 (China); Yang Kun, E-mail: yangkunkun@fmmu.edu.cn [Department of Immunology, The Fourth Military Medical University, Xi' an 710032 (China)

    2013-01-25

    Highlights: Black-Right-Pointing-Pointer Difunctional amino mesoporous silica nanoparticles (FCMSN) were synthesized. Black-Right-Pointing-Pointer The fluorescence and chemiluminescence properties of the FCMSN were studied. Black-Right-Pointing-Pointer The NaIO{sub 4} oxidation method was used for modification of the FCMSN. Black-Right-Pointing-Pointer Liver cancer 7721 cell was detected. Black-Right-Pointing-Pointer The specificity affected by FCMSN's amino groups was studied. - Abstract: A new kind of ultrabright fluorescent and chemiluminescent difunctional mesoporous silica nanoparticle (FCMSN) is reported. A luminescent dye, Rhodamine 6G or tris(2,2 Prime -bipyridyl)dichlororuthenium(II) hexahydrate (Rubpy), is doped inside nanochannels of a silica matrix. The hydrophobic groups in the silica matrix avoid the leakage of dye from open channels. The amines groups on the surface of the FCMSN improve the modification performance of the nanoparticle. Because the nanochannels are isolated by a network skeleton of silica, fluorescence quenching based on the inner filter effect of the fluorescent dyes immobilized in nanochannels is weakened effectively. The Quantum Yield of obtained 90 nm silica particles was about 61%. Compared with the fluorescent core-shell nanoparticle, the chemiluminescence reagents can freely enter the nanoparticles to react with fluorescent dyes to create chemiluminescence. The results show that the FCMSN are both fluorescent labels and chemiluminescent labels. In biological applications, the NaIO{sub 4} oxidation method was proven to be superior to the glutaraldehyde method. The amount of amino could affect the specificity of the FCMSN. The fluorescence microscopy imaging demonstrated that the FCMSN is viable for biological applications.

  10. Properties and mesostructural characteristics of linen fiber reinforced self-compacting concrete in slender columns

    Directory of Open Access Journals (Sweden)

    Sabry A. Ahmed

    2013-06-01

    Full Text Available In this study the linen fibers were used to reinforce self-compacting concrete (SCC with 2 and 4 kg/m3 contents; then their effects on the fresh and hardened properties of SCC were investigated. Furthermore, three circular slender columns were cast using both plain and linen fiber reinforced (LFR SCC in order to study the variations of hardened properties and mesostructural characteristics along the columns height. The addition of linen fibers to SCC reduced its workability and affected its self-compacting characteristics in a manner depending on the fiber content. Also, noticeable improvement in mechanical properties and slight reduction in unit weight and UPV were recorded. The hardened properties did not vary significantly along the height of columns, however, lower values were observed at the upper end of columns. The aggregate distribution was slightly more homogenous in case of LFRSCC, and the variation of fiber density along the height of columns was relatively high.

  11. Chitosan(PEO)/silica hybrid nanofibers as a potential biomaterial for bone regeneration.

    Science.gov (United States)

    Toskas, Georgios; Cherif, Chokri; Hund, Rolf-Dieter; Laourine, Ezzeddine; Mahltig, Boris; Fahmi, Amir; Heinemann, Christiane; Hanke, Thomas

    2013-05-15

    New hybrid nanofibers prepared with chitosan (CTS), containing a total amount of polyethylene oxide (PEO) down to 3.6wt.%, and silica precursors were produced by electrospinning. The solution of modified sol-gel particles contained tetraethoxysilane (TEOS) and the organosilane 3-glycidyloxypropyltriethoxysilane (GPTEOS). This is rending stable solution toward gelation and contributing in covalent bonding with chitosan. The fibers encompass advantages of biocompatible polymer template silicate components to form self-assembled core-shell structure of the polymer CTS/PEO encapsulated by the silica. Potential applicability of this hybrid material to bone tissue engineering was studied examining its cellular compatibility and bioactivity. The nanofiber matrices were proved cytocompatible when seeded with bone-forming 7F2-cells, promoting attachment and proliferation over 7 days. These found to enhance a fast apatite formation by incorporation of Ca(2+) ions and subsequent immersion in modified simulated body fluid (m-SBF). The tunable properties of these hybrid nanofibers can find applications as active biomaterials in bone repair and regeneration. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. NIF Double Shell outer/inner shell collision experiments

    Science.gov (United States)

    Merritt, E. C.; Loomis, E. N.; Wilson, D. C.; Cardenas, T.; Montgomery, D. S.; Daughton, W. S.; Dodd, E. S.; Desjardins, T.; Renner, D. B.; Palaniyappan, S.; Batha, S. H.; Khan, S. F.; Smalyuk, V.; Ping, Y.; Amendt, P.; Schoff, M.; Hoppe, M.

    2017-10-01

    Double shell capsules are a potential low convergence path to substantial alpha-heating and ignition on NIF, since they are predicted to ignite and burn at relatively low temperatures via volume ignition. Current LANL NIF double shell designs consist of a low-Z ablator, low-density foam cushion, and high-Z inner shell with liquid DT fill. Central to the Double Shell concept is kinetic energy transfer from the outer to inner shell via collision. The collision determines maximum energy available for compression and implosion shape of the fuel. We present results of a NIF shape-transfer study: two experiments comparing shape and trajectory of the outer and inner shells at post-collision times. An outer-shell-only target shot measured the no-impact shell conditions, while an `imaging' double shell shot measured shell conditions with impact. The `imaging' target uses a low-Z inner shell and is designed to perform in similar collision physics space to a high-Z double shell but can be radiographed at 16keV, near the viable 2DConA BL energy limit. Work conducted under the auspices of the U.S. DOE by LANL under contract DE-AC52-06NA25396.

  13. Silica-Immobilized Enzyme Reactors

    Science.gov (United States)

    2007-08-01

    Silica-IMERs 14 implicated in neurological disorders such as Schizophrenia and Parkinson’s disease.[86] Drug discovery for targets that can alter the...primarily the activation of prodrugs and proantibiotics for cancer treatments or antibiotic therapy , respectively.[87] Nitrobenzene nitroreductase was...BuChE) Monolith disks* Packed Silica Biosilica Epoxide- Silica Silica-gel Enzyme Human AChE Human AChE Human AChE Equine BuChE Human

  14. The effect of oxide shell thickness on the structural, electronic, and optical properties of Si-SiO{sub 2} core-shell nano-crystals: A (time dependent)density functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Nazemi, Sanaz, E-mail: s.nazemi@ut.ac.ir, E-mail: pourfath@ut.ac.ir; Soleimani, Ebrahim Asl [School of Electrical and Computer Engineering, University of Tehran, Tehran 14395-515 (Iran, Islamic Republic of); Pourfath, Mahdi, E-mail: s.nazemi@ut.ac.ir, E-mail: pourfath@ut.ac.ir [School of Electrical and Computer Engineering, University of Tehran, Tehran 14395-515 (Iran, Islamic Republic of); Institute for Microelectronics, Technische Universität Wien, Wien A-1040 (Austria); Kosina, Hans [Institute for Microelectronics, Technische Universität Wien, Wien A-1040 (Austria)

    2016-04-14

    Due to their tunable properties, silicon nano-crystals (NC) are currently being investigated. Quantum confinement can generally be employed for size-dependent band-gap tuning at dimensions smaller than the Bohr radius (∼5 nm for silicon). At the nano-meter scale, however, increased surface-to-volume ratio makes the surface effects dominant. Specifically, in Si-SiO{sub 2} core-shell semiconductor NCs the interfacial transition layer causes peculiar electronic and optical properties, because of the co-existence of intermediate oxidation states of silicon (Si{sup n+}, n = 0–4). Due to the presence of the many factors involved, a comprehensive understanding of the optical properties of these NCs has not yet been achieved. In this work, Si-SiO{sub 2} NCs with a diameter of 1.1 nm and covered by amorphous oxide shells with thicknesses between 2.5 and 4.75 Å are comprehensively studied, employing density functional theory calculations. It is shown that with increased oxide shell thickness, the low-energy part of the optical transition spectrum of the NC is red shifted and attenuated. Moreover, the absorption coefficient is increased in the high-energy part of the spectrum which corresponds to SiO{sub 2} transitions. Structural examinations indicate a larger compressive stress on the central silicon cluster with a thicker oxide shell. Examination of the local density of states reveals the migration of frontier molecular orbitals from the oxide shell into the silicon core with the increase of silica shell thickness. The optical and electrical properties are explained through the analysis of the density of states and the spatial distribution of silicon sub-oxide species.

  15. MASS BALANCE OF SILICA IN STRAW FROM THE PERSPECTIVE OF SILICA REDUCTION IN STRAW PULP

    Directory of Open Access Journals (Sweden)

    Celil Atik,

    2012-06-01

    Full Text Available The high silica content of wheat straw is an important limiting factor for straw pulping. High silica content complicates processing and black liquor recovery, wears out factory installations, and lowers paper quality. Each section of wheat straw has different cells and chemical compositions and thus different silica content. In this work, the silica content of balled straw samples were examined according to their physical components, including internodes, nodes, leaves (sheath and blade, rachis, grain, other plant bodies, and other plant spikes. Mass distribution of silica was determined by a dry ashing method. Half (50.90% of the silica comes from leaves, and its mechanical separation will reduce the silica content in wheat straw pulp significantly. Destroying silica bodies by sonication will increase the strength properties of straw pulp.

  16. Liquid Phase Deposition of Silica on the Hexagonally Close-Packed Monolayer of Silica Spheres

    Directory of Open Access Journals (Sweden)

    Seo Young Yoon

    2013-01-01

    Full Text Available Liquid phase deposition is a method used for the nonelectrochemical production of polycrystalline ceramic films at low temperatures, most commonly silicon dioxide films. Herein, we report that silica spheres are organized in a hexagonal close-packed array using a patterned substrate. On this monolayer of silica spheres, we could fabricate new nanostructures in which deposition and etching compete through a modified LPD reaction. In the early stage, silica spheres began to undergo etching, and then, silica bridges between the silica spheres appeared by the local deposition reaction. Finally, the silica spheres and bridges disappeared completely. We propose the mechanism for the formation of nanostructure.

  17. Zirconium(IV) oxide: New coating material for nanoresonators for shell-isolated nanoparticle-enhanced Raman spectroscopy

    Science.gov (United States)

    Krajczewski, Jan; Abdulrahman, Heman Burhanalden; Kołątaj, Karol; Kudelski, Andrzej

    2018-03-01

    One tool that can be used for determining the structure and composition of surfaces of various materials (even in in situ conditions) is shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). In SHINERS measurements, the surface under investigation is covered with a layer of surface-protected plasmonic nanoparticles, and then the Raman spectrum of the surface analysed is recorded. The plasmonic cores of the used core-shell structures act as electromagnetic nanoresonators, significantly locally enhancing the intensity of the electric field of the incident radiation, leading to a large increase in the efficiency of the generation of the Raman signal from molecules in the close proximity to the deposited SHINERS nanoresonators. A protective layer (from transparent dielectrics such as SiO2, Al2O3 or TiO2) prevents direct interaction between the plasmonic metal and the analysed surface (such interactions may lead to changes in the structure of the surface) and, in the case of plasmonic cores other than gold cores, the dielectric layer increases the chemical stability of the metal core. In this contribution, we show for the first time that core-shell nanoparticles having a silver core (both a solid and hollow one) and a shell of zirconium(IV) oxide are very efficient SHINERS nanoresonators that are significantly more stable in acidic and alkaline media than the silver-silica core-shell structures typically used for SHINERS experiments.

  18. Core-shell nanophosphor architecture: toward efficient energy transport in inorganic/organic hybrid solar cells.

    Science.gov (United States)

    Li, Qinghua; Yuan, Yongbiao; Chen, Zihan; Jin, Xiao; Wei, Tai-huei; Li, Yue; Qin, Yuancheng; Sun, Weifu

    2014-08-13

    In this work, a core-shell nanostructure of samarium phosphates encapsulated into a Eu(3+)-doped silica shell has been successfully fabricated, which has been confirmed by X-ray diffraction, transmission electron microscopy (TEM), and high-resolution TEM. Moreover, we report the energy transfer process from the Sm(3+) to emitters Eu(3+) that widens the light absorption range of the hybrid solar cells (HSCs) and the strong enhancement of the electron-transport of TiO2/poly(3-hexylthiophene) (P3HT) bulk heterojunction (BHJ) HSCs by introducing the unique core-shell nanoarchitecture. Furthermore, by applying femtosecond transient absorption spectroscopy, we successfully obtain the electron transport lifetimes of BHJ systems with or without incorporating the core-shell nanophosphors (NPs). Concrete evidence has been provided that the doping of core-shell NPs improves the efficiency of electron transfers from donor to acceptor, but the hole transport almost remains unchanged. In particular, the hot electron transfer lifetime was shortened from 30.2 to 16.7 ps, i.e., more than 44% faster than pure TiO2 acceptor. Consequently, a notable power conversion efficiency of 3.30% for SmPO4@Eu(3+):SiO2 blended TiO2/P3HT HSCs is achieved at 5 wt % as compared to 1.98% of pure TiO2/P3HT HSCs. This work indicates that the core-shell NPs can efficiently broaden the absorption region, facilitate electron-transport of BHJ, and enhance photovoltaic performance of inorganic/organic HSCs.

  19. Monodisperse metal nanoparticle catalysts on silica mesoporous supports: synthesis, characterizations, and catalytic reactions

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai, G.A.

    2009-09-14

    addition, Pt-mesoporous silica core-shell structured NPs (Pt{at}mSiO{sub 2}) were prepared, where the individual Pt NP is encapsulated by the mesoporous silica layer. The Pt{at}mSiO{sub 2} catalysts showed promising catalytic activity in high temperature CO oxidation. The design of catalytic structures with tunable parameters by rational synthetic methods presents a major advance in the field of catalyst synthesis, which would lead to uncover the structure-function relationships in heterogeneous catalytic reactions.

  20. High ink absorption performance of inkjet printing based on SiO2@Al13 core-shell composites

    Science.gov (United States)

    Chen, YiFan; Jiang, Bo; Liu, Li; Du, Yunzhe; Zhang, Tong; Zhao, LiWei; Huang, YuDong

    2018-04-01

    The increasing growth of the inkjet market makes the inkjet printing more necessary. A composite material based on core-shell structure has been developed and applied to prepare inkjet printing layer. In this contribution, the ink printing record layers based on SiO2@Al13 core-shell composite was elaborated. The prepared core-shell composite materials were characterized by X-ray photoelectron spectroscopy (XPS), zeta potential, X-ray diffraction (XRD), scanning electron microscopy (SEM). The results proved the presence of electrostatic adsorption between SiO2 molecules and Al13 molecules with the formation of the well-dispersed system. In addition, based on the adsorption and the liquid permeability analysis, SiO2@Al13 ink printing record layer achieved a relatively high ink uptake (2.5 gmm-1) and permeability (87%), respectively. The smoothness and glossiness of SiO2@Al13 record layers were higher than SiO2 record layers. The core-shell structure facilitated the dispersion of the silica, thereby improved its ink absorption performance and made the clear printed image. Thus, the proposed procedure based on SiO2@Al13 core-shell structure of dye particles could be applied as a promising strategy for inkjet printing.

  1. Fluorescent pH sensor based on Ag@SiO2 core-shell nanoparticle.

    Science.gov (United States)

    Bai, Zhenhua; Chen, Rui; Si, Peng; Huang, Youju; Sun, Handong; Kim, Dong-Hwan

    2013-06-26

    We have demonstrated a novel method for the preparation of a fluorescence-based pH sensor by combining the plasmon resonance band of Ag core and pH sensitive dye (HPTS). A thickness-variable silica shell is placed between Ag core and HPTS dye to achieve the maximum fluorescence enhancement. At the shell thickness of 8 nm, the fluorescence intensity increases 4 and 9 times when the sensor is excited at 405 and 455 nm, respectively. At the same time, the fluorescence intensity shows a good sensitivity toward pH value in the range of 5-9, and the ratio of emission intensity at 513 nm excited at 455 nm to that excited at 405 nm versus the pH value in the range of 5-9 is determined. It is believed that the present pH sensor has the potential for determining pH real time in the biological sample.

  2. Plasmonic Nanodiamonds – Targeted Core-shell Type Nanoparticles for Cancer Cell Thermoablation

    Science.gov (United States)

    Rehor, Ivan; Lee, Karin L.; Chen, Kevin; Hajek, Miroslav; Havlik, Jan; Lokajova, Jana; Masat, Milan; Slegerova, Jitka; Shukla, Sourabh; Heidari, Hamed; Bals, Sara

    2015-01-01

    Targeted biocompatible nanostructures with controlled plasmonic and morphological parameters are promising materials for cancer treatment based on selective thermal ablation of cells. Here, core-shell plasmonic nanodiamonds consisting of a silica-encapsulated diamond nanocrystal coated in a gold shell is designed and synthesized. The architecture of particles is analyzed and confirmed in detail using 3-dimensional transmission electron microscope tomography. The particles are biocompatibilized using a PEG polymer terminated with bioorthogonally reactive alkyne groups. Azide-modified transferrin is attached to these particles, and their high colloidal stability and successful targeting to cancer cells overexpressing the transferrin receptor is demonstrated. The particles are nontoxic to the cells and they are readily internalized upon binding to the transferrin receptor. The high plasmonic cross section of the particles in the near-infrared region is utilized to quantitatively ablate the cancer cells with a short, one-minute irradiation by a pulse 750-nm laser. PMID:25336437

  3. Nitrite sensing composite systems based on a core-shell emissive-superamagnetic structure: Construction, characterization and sensing behavior

    Science.gov (United States)

    Yang, Yan; Liu, Liang; Zha, Jianhua; Yuan, Ningyi

    2017-04-01

    Two recyclable nitrite sensing composite samples were designed and constructed through a core-shell structure, with Fe3O4 nanoparticles as core, silica molecular sieve MCM-41 as shell and two rhodamine derivatives as chemosensors, respectively. These samples and their structure were identified with their electron microscopy images, N2 adsorption/desorption isotherms, magnetic response, IR spectra and thermogravimetric analysis. Their nitrite sensing behavior was discussed based on emission intensity quenching, their limit of detection was found as low as 1.2 μM. Further analysis suggested a static sensing mechanism between nitrite and chemosensors through an additive reaction between NO+ and chemosensors. After finishing their nitrite sensing, these composite samples and their emission could be recycled and recovered by sulphamic acid.

  4. Grafting of polymer onto silica surface in the presence of γ-ray irradiated silica

    International Nuclear Information System (INIS)

    Tsuchida, A.; Yokoyama, R.; Takami, M.; Chen, J.; Ohta, M.; Tsubokawa, N.

    2002-01-01

    Complete text of publication follows. We have reported the graft polymerization of vinyl monomers initiated by surface radicals formed by the decomposition of azo and peroxide groups previously introduced onto the surface. In addition, the grafting of polymers onto carbon black has been reported by the reaction of polymer radicals with the surface. On the other hand, it is well known that the relatively stable radicals are generated on the surface by the γ-ray irradiation. In this paper, the grafting of polystyrene onto silica surface during the thermal polymerization of styrene in the presence of γ-ray irradiated silica, grafting mechanism and thermal stability of grafted polymer will be discussed. The grafting of polymers onto silica surface by irradiation of polymer-adsorbed silica was also investigated. Silica obtained from Mitsubishi Chemical Co., Japan was used after pulverization: the particle size was 0.037-0.088 mm. Irradiation was performed in Cs-137 source at room temperature. The silica was irradiated at 50 Gy with dose rate of 3.463 Gy/min. Into a polymerization tube, styrene and irradiated silica was charged and the polymerization was carried out under argon under stirring. The percentage of polystyrene grafting was determined from weight loss when polystyrene-grafted silica was heated at 600 deg C by a thermal analyzer. Untreated silica did not affect the thermal polymerization of styrene. On the contrary, the thermal polymerization of styrene was remarkably retarded in the presence of the irradiated silica at 60 deg C. Similar tendency was reported during the polymerization of vinyl monomers in the presence of carbon black. In the initial stage of the polymerization in the presence of the irradiated silica below 50 deg C, the polymerization was accelerated. During the polymerization in the presence of irradiated silica, polystyrene was grafted onto the surface: the percentage of grafting was 5-11%. The amount of polystyrene grafted onto silica

  5. Micromagnetic study of single-domain FePt nanocrystals overcoated with silica

    International Nuclear Information System (INIS)

    Hyun, Changbae; Lee, Doh C; Korgel, Brian A; Lozanne, Alex de

    2007-01-01

    Chemically-synthesized FePt nanocrystals must be annealed at a high temperature (>550 deg. C) to induce the hard ferromagnetic L 1 0 phase. Unfortunately, the organic stabilizer covering these nanocrystals degrades at these temperatures and the nanocrystals sinter, resulting in the loss of control over nanocrystal size and separation in the film. We have developed a silica overcoating strategy to prevent nanocrystal sintering. In this study, 6 nm diameter FePt nanocrystals were coated with 17 nm thick shells of silica using an inverse micelle process. Magnetization measurements of the annealed FePt-SiO 2 nanocrystals indicate ferromagnetism with a high coercivity at room temperature. Magnetic force microscopy (MFM) results show that the film composed of nanocrystals behaves as a dipole after magnetization by an 8 T external field. The individual nanocrystals are modelled as single-domain particles with random crystallographic orientations. We propose that the interparticle magnetic dipole interaction is weaker than the magnetocrystalline energy in the remanent state, leading to an unusual material with no magnetic anisotropy and no domains. Films of these nanoparticles are promising candidates for magnetic media with a data storage density of ∼Tb/in 2

  6. Hydrothermal stability of microporous silica and niobia-silica membranes

    NARCIS (Netherlands)

    Boffa, V.; Blank, David H.A.; ten Elshof, Johan E.

    2008-01-01

    The hydrothermal stability of microporous niobia–silica membranes was investigated and compared with silica membranes. The membranes were exposed to hydrothermal conditions at 150 and 200 °C for 70 h. The change of pore structure before and after exposure to steam was probed by single-gas permeation

  7. Serpentinization processes: Influence of silica

    Science.gov (United States)

    Huang, R.; Sun, W.; Ding, X.; Song, M.; Zhan, W.

    2016-12-01

    Serpentinization systems are highly enriched in molecular hydrogen (H2) and hydrocarbons (e.g. methane, ethane and propane). The production of hydrocarbons results from reactions between H2 and oxidized carbon (carbon dioxide and carbon monoxide), which possibly contribute to climate changes during early history of the Earth. However, the influence of silica on the production of H2 and hydrocarbons was poorly constrained. We performed experiments at 311-500 °C and 3.0 kbar using mechanical mixtures of silica and olivine in ratios ranging from 0 to 40%. Molecular hydrogen (H2), methane, ethane and propane were formed, which were analyzed by gas chromatography. It was found that silica largely decreased H2 production. Without any silica, olivine serpentinization produced 94.5 mmol/kg H2 after 20 days of reaction time. By contrast, with the presence of 20% silica, H2 concentrations decreased largely, 8.5 mmol/kg. However, the influence of silica on the production of hydrocarbons is negligible. Moreover, with the addition of 20%-40% silica, the major hydrous minerals are talc, which was quantified according to an established standard curve calibrated by infrared spectroscopy analyses. It shows that silica greatly enhances olivine hydration, especially at 500 °C. Without any addition of silica, reaction extents were serpentinization at 500 °C and 3.0 kbar. By contrast, with the presence of 50% silica, olivine was completely transformed to talc within 9 days. This study indicates that silica impedes the oxidation of ferrous iron into ferric iron, and that rates of olivine hydration in natural geological settings are much faster with silica supply.

  8. Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

    Science.gov (United States)

    Xu, Tiwen; Jia, Zhixin; Luo, Yuanfang; Jia, Demin; Peng, Zheng

    2015-02-01

    The epoxidized natural rubber (ENR) as an interfacial modifier was used to improve the mechanical and dynamical mechanical properties of NR/silica composites. In order to reveal the interaction mechanism between ENR and silica, the ENR/Silica model compound was prepared by using an open mill and the interfacial interaction of ENR with silica was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and stress-strain testing. The results indicated that the ring-opening reaction occurs between the epoxy groups of ENR chains and Si-OH groups on the silica surfaces and the covalent bonds are formed between two phases, which can improve the dispersion of silica in the rubber matrix and enhance the interfacial combination between rubber and silica. The ring-opening reaction occurs not only in vulcanization process but also in mixing process, meanwhile, the latter seems to be more important due to the simultaneous effects of mechanical force and temperature.

  9. Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tiwen [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Jia, Zhixin, E-mail: zxjia@scut.edu.cn [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Luo, Yuanfang; Jia, Demin [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Peng, Zheng [Agricultural Product Processing Research Institute, Chinese Academy of Tropical Agriculture Sciences, Zhanjiang 524001 (China)

    2015-02-15

    Highlights: • Substantiate the ring open reaction between Si-OH of silica and epoxy groups of ENR. • ENR can act as a bridge between NR and silica to enhance the interfacial interaction. • As a modifier, ENR gets the potential to be used in the tread of green tire for improving the wet skid resistance apparently. - Abstract: The epoxidized natural rubber (ENR) as an interfacial modifier was used to improve the mechanical and dynamical mechanical properties of NR/silica composites. In order to reveal the interaction mechanism between ENR and silica, the ENR/Silica model compound was prepared by using an open mill and the interfacial interaction of ENR with silica was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and stress–strain testing. The results indicated that the ring-opening reaction occurs between the epoxy groups of ENR chains and Si-OH groups on the silica surfaces and the covalent bonds are formed between two phases, which can improve the dispersion of silica in the rubber matrix and enhance the interfacial combination between rubber and silica. The ring-opening reaction occurs not only in vulcanization process but also in mixing process, meanwhile, the latter seems to be more important due to the simultaneous effects of mechanical force and temperature.

  10. Synthesis of fly ash based core-shell composites for use as functional pigment in paints

    Science.gov (United States)

    Sharma, Richa; Tiwari, Sangeeta

    2016-04-01

    Fly ash is a combustion residue, mainly composed of silica, alumina and iron oxides. It is produced by the power industries in very large amounts and usually disposed in landfills, which have represented an environmental problem in recent years1. The need to generate a market for fly ash consumption is the main reason why alternative applications have been studied. It has been applied as an additive in construction materials like cement and pavements2. The present work describes the synthesis of Flyash-Titania core-shell particles by precipitation technique using Titanium tetra isopropoxide (TTIP) which can be used for variety of applications such as NIR reflecting materials for cool coatings, Photocatalysis etc. In this work, Fly ash is used in core and Nano -TiO2 is coated as shell on it. Surfactants are used to improve the adhesion of Nano Titania shell on fly ash core. Effect on adhesion of TiO2 on Fly ash is studied by using different types of surfactant. The preparation of core shells was carried out in absence of surfactant as well as using anionic and non-ionic surfactants. The percentage of surfactant was varied to study the effect of amount of surfactant on the uniformity and size of particles in the shell using Kubelka-Munk transformed reflectance spectra. The morphology of core shell structures was studied using SEM technique. Use of anionic surfactant results in more uniform coating with reduced particle size of the shell material. The composite particles prepared by using anionic surfactant are having good pigment properties and also shows good reflectance in Near Infrared region and hence can be used as a pigment in cool coatings.

  11. Transfer of pharmacopoeial liquid chromatography reversedphase methods for determination of related compounds in diclofenac sodium and metamizole sodium from conventional to core-shell column

    Directory of Open Access Journals (Sweden)

    Katerina Brezovska

    2015-04-01

    Full Text Available Core-shell silica particles were developed as a new material for chromatographic stationary phases in order to provide fast and high efficiency separations of small and large molecules and complex samples, at pressures compatible with conventional HPLC equipment. The aim of our work was to show the applicability of the HPLC columns based on a core-shell technology for determination of related substances in diclofenac sodium and in metamizole sodium using the methods described in the corresponding monographs of the European pharmacopoeia. The obtained results have shown that the proposed methods can be successfully transferred on core shell column, with suitable adjustment of injection volume and flow rate. The advantage of using core-shell column is fast and highly efficient separation on conventional HPLC equipment with increased sensitivity of the method and high throughput of the analysis, providing enhanced lab productivity and reduced costs.

  12. Functionalized porous silica&maghemite core-shell nanoparticles for applications in medicine: design, synthesis and immunotoxicity

    Czech Academy of Sciences Publication Activity Database

    Zasońska, Beata Anna; Líšková, A.; Kuricová, M.; Tulinská, J.; Pop-Georgievski, Ognen; Čiampor, F.; Vávra, I.; Dušinská, M.; Ilavská, S.; Horváthová, M.; Horák, Daniel

    2016-01-01

    Roč. 57, č. 2 (2016), s. 165-178 ISSN 0353-9504 R&D Projects: GA ČR(CZ) GC16-01128J Institutional support: RVO:61389013 Keywords : core-shell maghemite nanoparticles * proliferative activity of lymphocytes * phagocytic activity Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.619, year: 2016 http://www.cmj.hr/2016/57/2/27106358.htm

  13. Synthesis of SiCN@TiO2 core-shell ceramic microspheres via PDCs method

    Science.gov (United States)

    Liu, Hongli; Wei, Ning; Li, Jing; Zhang, Haiyuan; Chu, Peng

    2018-02-01

    A facile and effective polymer-derived ceramics (PDCs) emulsification-crosslinking-pyrolysis method was developed to fabricate SiCN@TiO2 core-shell ceramic microspheres with polyvinylsilazane (PVSZ) and tetrabutyl titanate (TBT) as precursors. The TBT: PVSZ mass ratios, emulsifier concentrations and the pyrolysis temperature were examined as control parameters to tune the size and morphology of microspheres. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the synthesized SiCN@TiO2 microspheres to be comprised of SiCN core coated with TiO2 crystals, with an average size of 0.88 μm when pyrolyzed at 1400 °C. The analysis of Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) ensured that SiCN@TiO2 core-shell ceramic microspheres composed of rutile TiO2, β-SiC and Si3N4 crystalline phases, The thermal properties were characterized by thermogravimetric analysis (TGA). The obtained SiCN@TiO2 core-shell ceramic microspheres were the promising candidate of the infrared opacifier in silica aerogels and this technique can be extended to other preceramic polymers.

  14. Gas Separation through Bilayer Silica, the Thinnest Possible Silica Membrane.

    Science.gov (United States)

    Yao, Bowen; Mandrà, Salvatore; Curry, John O; Shaikhutdinov, Shamil; Freund, Hans-Joachim; Schrier, Joshua

    2017-12-13

    Membrane-based gas separation processes can address key challenges in energy and environment, but for many applications the permeance and selectivity of bulk membranes is insufficient for economical use. Theory and experiment indicate that permeance and selectivity can be increased by using two-dimensional materials with subnanometer pores as membranes. Motivated by experiments showing selective permeation of H 2 /CO mixtures through amorphous silica bilayers, here we perform a theoretical study of gas separation through silica bilayers. Using density functional theory calculations, we obtain geometries of crystalline free-standing silica bilayers (comprised of six-membered rings), as well as the seven-, eight-, and nine-membered rings that are observed in glassy silica bilayers, which arise due to Stone-Wales defects and vacancies. We then compute the potential energy barriers for gas passage through these various pore types for He, Ne, Ar, Kr, H 2 , N 2 , CO, and CO 2 gases, and use the data to assess their capability for selective gas separation. Our calculations indicate that crystalline bilayer silica, which is less than a nanometer thick, can be a high-selectivity and high-permeance membrane material for 3 He/ 4 He, He/natural gas, and H 2 /CO separations.

  15. Shell Venster

    International Nuclear Information System (INIS)

    De Wit, P.; Looijesteijn, B.; Regeer, B.; Stip, B.

    1995-03-01

    In the bi-monthly issues of 'Shell Venster' (window on Shell) attention is paid to the activities of the multinational petroleum company Shell Nederland and the Koninklijke/Shell Groep by means of non-specialist articles

  16. EXAFS study of Tb-doped silica xerogels

    International Nuclear Information System (INIS)

    Rocca, F.; Monti, F.; Kuzmin, A.; Dalmaso, A.; Pasqualini, D.

    1999-01-01

    The modification of the local environment of Tb 3+ ions in optically active silica xerogels as a function of concentration (from 400 ppm to 40000 ppm) and thermal treatment (which induces densification) was studied by x-ray absorption spectroscopy at the Tb L 3 edge. Quantitative analysis of the first Tb-O coordination shell was performed using the experimental signal from Tb 3+ ions in water solution as a reference. The radial distribution functions (RDF) of the non-thermally treated (NT) gels are characterised by a nearly gaussian shape, as for the reference sample. On the contrary, the RDF of the densified gels (T) are asymmetric having the main peak at a shorter distance, with a reduced coordination number (N=4-5) and a secondary peak, with N=1-2, at a longer distance. The local environment of Tb in the low concentration sample (400 ppm) is different from that at higher concentrations, both in the NT- and in the T-gels. (au)

  17. EXAFS study of Tb-doped silica xerogels

    CERN Document Server

    Rocca, F; Kuzmin, A; Dalmaso, A; Pasqualini, D

    1999-01-01

    The modification of the local environment of Tb/sup 3+/ ions in optically active silica xerogels as a function of concentration (from 400 ppm to 40000 ppm) and thermal treatment (which induces densification) was studied by X-ray absorption spectroscopy at the Tb L/sub 3/ edge. Quantitative analysis of the first Tb-O coordination shell was performed using the experimental signal from Tb/sup 3+/ ions in water solution as a reference. The radial distribution functions (RDF) of the non-thermally treated (NT) gels are characterized by a nearly Gaussian shape, as for the reference sample. On the contrary, the RDF of the densified gels (T) are asymmetric having the main peak at a shorter distance, with a reduced coordination number (N=4-5) and a secondary peak, with N=1-2, at a longer distance. The local environment of Tb in the low concentration sample (400 ppm) is different from that at higher concentrations, both in the NT- and in the T-gels. (15 refs).

  18. Silica/Perfluoropolymer nanocomposites fabricated by direct melt-compounding: a novel method without surface modification on nano-silica.

    Science.gov (United States)

    Tanahashi, Mitsuru; Hirose, Masaki; Watanabe, Yusuke; Lee, Jeong-Chang; Takeda, Kunihiko

    2007-07-01

    A novel method for the fabrication of silica/perfluoropolymer nanocomposites was investigated, whereby nano-sized silica particles without surface modification were dispersed uniformly through mechanical breakdown of loosely packed agglomerates of silica nanoparticles with low fracture strength in a polymer melt during direct melt-compounding. The method consists of two stages. The first stage involves preparation of the loose silica agglomerate, and the second stage involves melt-compounding of a completely hydrophobic perfluoropolymer, poly(tetrafluoroethyleneco-perfluoropropylvinylether), with the loose silica agglomerates prepared in the first stage. In the first stage, the packing structure and the fracture strength of the silica agglomerate were controlled by destabilizing an aqueous colloidal silica solution with a mean primary diameter of 190 nm via pH control and salt addition. In the next stage, the silica/perfluoropolymer nanocomposite was fabricated by breaking down the prepared loose silica agglomerates with low fracture strength by means of a shear force inside the polymer melt during melt-compounding.

  19. Fluorescent magnetic nanoparticles for cell labeling: flux synthesis of manganite particles and novel functionalization of silica shell

    Czech Academy of Sciences Publication Activity Database

    Kačenka, Michal; Kaman, Ondřej; Kikerlová, S.; Pavlů, B.; Jirák, Zdeněk; Jirák, D.; Herynek, Vít; Černý, J.; Chaput, F.; Laurent, S.; Lukeš, I.

    2015-01-01

    Roč. 47, Jun (2015), s. 97-106 ISSN 0021-9797 R&D Projects: GA ČR(CZ) GAP108/11/0807; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:68378271 ; RVO:68378041 Keywords : manganites * magnetic nanoparticles * molten salt synthesis * silica coating * dual probes * MRI * cell labeling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.782, year: 2015

  20. Assembling photoluminescent tri(8-quinolinolato)aluminum into periodic mesoporous organosilicas.

    Science.gov (United States)

    Yang, Ying; Zhang, Xin; Kan, Qiubin

    2013-12-01

    Mesostructured and mesoporous materials are emerging as a new class of optical materials. However, their synthesis is nontrivial. In this work, periodic mesostructured metal complex-containing silicas of MCM- and SBA-type bearing homogeneously distributed photoluminescent tri(8-quinolinolato)aluminum inside the channel walls (denoted as Alq3@PMO-MCM and Alq3@PMO-SBA, respectively) have been achieved via one-pot co-assembling of inorganic/surfactant/optically active species. A comprehensive multianalytical characterization of the structural and optical properties demonstrates that both Alq3@PMO-MCM and Alq3@PMO-SBA series gainfully combine the photoluminescent properties of Alq3 with the porous features of PMOs. Regularly arranged pores provide high surface area to disperse optically active components well and render Alq3-containing PMOs promising materials for optoelectronic applications. Copyright © 2013. Published by Elsevier Inc.

  1. Gel-like TPGS-Based Microemulsions for Imiquimod Dermal Delivery: Role of Mesostructure on the Uptake and Distribution into the Skin.

    Science.gov (United States)

    Telò, Isabella; Favero, Elena Del; Cantù, Laura; Frattini, Noemi; Pescina, Silvia; Padula, Cristina; Santi, Patrizia; Sonvico, Fabio; Nicoli, Sara

    2017-10-02

    The aim of this work was to develop an innovative microemulsion with gel-like properties for the cutaneous delivery of imiquimod, an immunostimulant drug employed for the treatment of cutaneous infections and neoplastic conditions. A pseudoternary phase diagram was built using a 1/1 TPGS (d-α-tocopheryl polyethylene glycol 1000 succinate)/Transcutol mixture as surfactant system, and oleic acid as oil phase. Eight microemulsions-selected from the 1.25/8.75 oil/surfactants ratio, along the water dilution line (from 20 to 56% w/w)-were characterized in terms of rheological behavior, optical properties via polarized microscopy, and supramolecular structure using X-ray scattering. Then, these formulations were loaded with imiquimod and the uptake and distribution into the skin was evaluated on full-thickness porcine skin. X-ray scattering experiments revealed the presence of disconnected drops in the case of microemulsion with 20% water content. Diluting the system up to 48% water content, the structure turned into an interconnected lamellar microemulsion, reaching a proper disconnected lamellar structure for the highest water percentages (52-56%). Upon water addition, also the rheological properties changed from nearly Newtonian fluids to gel-like structures, displaying the maximum of viscosity for the 48% water content. Skin uptake experiments demonstrated that formulation viscosity, drug loading, and surfactant concentration did not play an important role on imiquimod uptake into the skin, while the skin penetration was related instead to the microemulsion mesostructure. In fact, drug uptake became enhanced by locally lamellar interconnected structures, while it was reduced in the presence of disconnected structures, either drops or proper lamellae. Finally, the data demonstrated that mesostructure also affects the drug distribution between the epidermis and dermis. In particular, a significantly higher dermal accumulation was found when disconnected lamellar

  2. Importance-truncated shell model for multi-shell valence spaces

    Energy Technology Data Exchange (ETDEWEB)

    Stumpf, Christina; Vobig, Klaus; Roth, Robert [Institut fuer Kernphysik, TU Darmstadt (Germany)

    2016-07-01

    The valence-space shell model is one of the work horses in nuclear structure theory. In traditional applications, shell-model calculations are carried out using effective interactions constructed in a phenomenological framework for rather small valence spaces, typically spanned by one major shell. We improve on this traditional approach addressing two main aspects. First, we use new effective interactions derived in an ab initio approach and, thus, establish a connection to the underlying nuclear interaction providing access to single- and multi-shell valence spaces. Second, we extend the shell model to larger valence spaces by applying an importance-truncation scheme based on a perturbative importance measure. In this way, we reduce the model space to the relevant basis states for the description of a few target eigenstates and solve the eigenvalue problem in this physics-driven truncated model space. In particular multi-shell valence spaces are not tractable otherwise. We combine the importance-truncated shell model with refined extrapolation schemes to approximately recover the exact result. We present first results obtained in the importance-truncated shell model with the newly derived ab initio effective interactions for multi-shell valence spaces, e.g., the sdpf shell.

  3. Efficient one-pot sonochemical synthesis of thickness-controlled silica-coated superparamagnetic iron oxide (Fe3O4/SiO2) nanospheres

    Science.gov (United States)

    Abbas, Mohamed; Abdel-Hamed, M. O.; Chen, Jiangang

    2017-12-01

    A facile and eco-friendly efficient sonochemical approach was designed for the synthesis of highly crystalline Fe3O4 and Fe3O4/SiO2 core/shell nanospheres in single reaction. The generated physical properties (shock waves, microjets, and turbulent flows) from ultrasonication as a consequence of the collapse of microbubbles and polyvinylpyrrolidone (PVP) as a chemical linker were found to play a crucial role in the successful formation of the core/shell NPs within short time than the previously reported methods. Transmission electron microscopy revealed that a uniform SiO2 shell is successfully coated over Fe3O4 nanospheres, and the thickness of the silica shell could be easily controlled in the range from 5 to 15 nm by adjusting the reaction parameters. X-ray diffraction data were employed to confirm the formation of highly crystalline and pure phase of a cubic inverse spinel structure for magnetite (Fe3O4) nanospheres. The magnetic properties of the as-synthesized Fe3O4 and Fe3O4/SiO2 core/shell nanospheres were measured at room temperature using vibrating sample magnetometer, and the results demonstrated a high magnetic moment values with superparamagnetic properties.

  4. Fabrication of Au-Pd Core-shell Nanoparticles using Au Thin-Film Dewetting at High Temperature and Chemical Synthesis Methods

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Gyu; Lee, Hye-Jung; Oh, Yong-Jun [Hanbat National Univ., Daejeon (Korea, Republic of)

    2016-07-15

    Au-Pd bimetallic nanoparticles (NPs) have received a lot of attention in the fields of catalysts and hydrogen sensors. In this study, Au-Pd core-shell NP arrays were successfully fabricated using two steps: formation of the ordered array of Au NPs cores via solid-state dewetting of a Au thin film on a topographic silica substrate, and Pd shell formation via chemical synthesis using two different surfactants (CTAB and CTAC). Using the CTAB surfactant in particular, a 2-D composite structure comprised of an ordered array of Au-Pd NPs, with smaller Pd NPs on the nanoscopic gaps between the Au-Pd NPs, could be formed. This structure is expected to have potential application in resistance-base hydrogen sensors.

  5. Sonochemical coating of magnetite nanoparticles with silica.

    Science.gov (United States)

    Dang, Feng; Enomoto, Naoya; Hojo, Junichi; Enpuku, Keiji

    2010-01-01

    Magnetite nanoparticles were coated with silica through the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under ultrasonic irradiation. The ultrasonic irradiation was used to prevent the agglomeration of the magnetite particles and accelerate the hydrolysis and condensation of TEOS. TEM, DLS, XRF, VSM, TG and sedimentation test were used to characterize the silica-coated magnetite particles. The dispersibility of silica-coated magnetite particles in aqueous solution was improved significantly and the agglomerate particle size was decreased to 110 nm. It was found that the agglomerate particle size of silica-coated magnetite particles was mainly decided by the coating temperature and the pH value in the silica-coating process. The weight ratio of silica in silica-coated magnetite particles was mainly decided by the pH value in the silica-coating process. The dispersibility of silica-coated magnetite particles was mainly decided by the agglomerate particle size of the suspension. The oxidation of magnetite particles in air was limited through the coated silica. The magnetism of silica-coated magnetite particles decreased slightly after silica-coating.

  6. Blocked-micropores, surface functionalized, bio-compatible and silica-coated iron oxide nanocomposites as advanced MRI contrast agent

    International Nuclear Information System (INIS)

    Darbandi, Masih; Laurent, Sophie; Busch, Martin; Li Zian; Yuan Ying; Krüger, Michael; Farle, Michael; Winterer, Markus; Vander Elst, Luce; Muller, Robert N.; Wende, Heiko

    2013-01-01

    Biocompatible magnetic nanoparticles have been found promising in several biomedical applications for tagging, imaging, sensing and separation in recent years. In this article, a systematic study of the design and development of surface-modification schemes for silica-coated iron oxide nanoparticles (IONP) via a one-pot, in situ method at room temperature is presented. Silica-coated IONP were prepared in a water-in-oil microemulsion, and subsequently the surface was modified via addition of organosilane reagents to the microemulsion system. The structure and the morphology of the as synthesized nanoparticles have been investigated by means of transmission electron microscopy (TEM) and measurement of N 2 adsorption–desorption. Electron diffraction and high-resolution transmission electron microscopic (TEM) images of the nanoparticles showed the highly crystalline nature of the IONP structures. Nitrogen adsorption indicates microporous and blocked-microporous structures for the silica-coated and amine functionalized silica-coated IONP, respectively which could prove less cytotoxicity of the functionalized final product. Besides, the colloidal stability of the final product and the presence of the modified functional groups on top of surface layer have been proven by zeta-potential measurements. Owing to the benefit from the inner IONP core and the hydrophilic silica shell, the as-synthesized nanocomposites were exploited as an MRI contrast enhancement agent. Relaxometric results prove that the surface functionalized IONP have also signal enhancement properties. These surface functionalized nanocomposites are not only potential candidates for highly efficient contrast agents for MRI, but could also be used as ultrasensitive biological-magnetic labels, because they are in nanoscale size, having magnetic properties, blocked-microporous and are well dispersible in biological environment.

  7. Facile synthesis of novel magnetic silica nanoparticles functionalized with layer-by-layer detonation nanodiamonds for secretome study.

    Science.gov (United States)

    Li, Hong; Wang, Yi; Zhang, Lei; Lu, Haojie; Zhou, Zhongjun; Wei, Liming; Yang, Pengyuan

    2015-12-07

    Novel magnetic silica nanoparticles functionalized with layer-by-layer detonation nanodiamonds (dNDs) were prepared by coating single submicron-size magnetite particles with silica and subsequently modified with dNDs. The resulting layer-by-layer dND functionalized magnetic silica microspheres (Fe3O4@SiO2@[dND]n) exhibit a well-defined magnetite-core-silica-shell structure and possess a high content of magnetite, which endow them with high dispersibility and excellent magnetic responsibility. Meanwhile, dNDs are known for their high affinity and biocompatibility towards peptides or proteins. Thus, a novel convenient, fast and efficient pretreatment approach of low-abundance peptides or proteins was successfully established with Fe3O4@SiO2@[dND]n microspheres. The signal intensity of low-abundance peptides was improved by at least two to three orders of magnitude in mass spectrometry analysis. The novel microsphere also showed good tolerance to salt. Even with a high concentration of salt, peptides or proteins could be isolated effectively from samples. Therefore, the convenient and efficient enrichment process of this novel layer-by-layer dND-functionalized microsphere makes it a promising candidate for isolation of protein in a large volume of culture supernatant for secretome analysis. In the application of Fe3O4@SiO2@[dND]n in the secretome of hepatoma cells, 1473 proteins were identified and covered a broad range of pI and molecular weight, including 377 low molecular weight proteins.

  8. Immobilization of Thiadiazole Derivatives on Magnetite Mesoporous Silica Shell Nanoparticles in Application to Heavy Metal Removal from Biological Samples

    International Nuclear Information System (INIS)

    Emadi, Masoomeh; Shams, Esmaeil

    2010-01-01

    In this report magnetite was synthesized by a coprecipitation method, then coated with a layer of silica. Another layer of mesoporous silica was added by a sol-gel method, then 5-amino-1,3,4-thiadiazole-thiol (ATT) was immobilized onto the synthesized nanoparticles with a simple procedure. This was followed by a series of characterizations, including transmission electron microscopy (TEM), FT-IR spectrum, elemental analysis and XRD. Heavy metal uptake of the modified nanoparticles was examined by atomic absorption spectroscopy. For further investigation we chose Cu 2+ as the preferred heavy metal to evaluate the amount of adsorption, as well as the kinetics and mechanism of adsorption. Finally, the capacity of our nanoparticles for the heavy metal removal from blood was shown. We found that the kinetic rate of Cu 2+ adsorption was 0.05 g/mg/min, and the best binding model was the Freundlich isotherm.

  9. Assembly and luminescence properties of lanthanide-polyoxometalates/polyethyleneimine/SiO{sub 2} particles with core–shell structure

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun, E-mail: junwang924@yahoo.com.cn; Fan, Shaohua; Zhao, Weiqian; Zhang, Hongyan

    2013-01-01

    In this paper, two lanthanide-polyoxometalate (LnW{sub 10}) complexes were bonded on the surface of the polyethyleneimine (PEI)-modified silica nanoparticles with different sizes, resulting in the formation of LnW{sub 10}/PEI/SiO{sub 2} particles. The hybrid core–shell particles were characterized by infrared, luminescent spectra, scanning electronic microscope, and transmission electronic microscope. The particles obtained exhibit the fine spherical core–shell structure and the excellent luminescence properties. The luminescence spectra studies revealed that the formation of LnW{sub 10}/PEI/SiO{sub 2} particles and the size of particle have an influence on the luminescence properties of lanthanide ions. - Highlights: ► SiO{sub 2}/polyethyleneimine (PEI) shows the chemisorption for Ln-polyoxometalates (LnW{sub 10}). ► The core-shell LnW{sub 10}/PEI/SiO{sub 2} nanoparticles with different sizes were fabricated. ► The hybrid particles exhibit the excellent luminescence properties. ► The sizes of particles affect the luminescence properties of lanthanide ions.

  10. High-frequency dielectric spectroscopy of BaTiO3 core - silica shell nanocomposites: problem of interdiffusion

    Czech Academy of Sciences Publication Activity Database

    Nuzhnyy, Dmitry; Petzelt, Jan; Bovtun, Viktor; Kempa, Martin; Savinov, Maxim; Elissalde, C.; Chung, U.-C.; Michau, D.; Estournes, C.; Maglione, M.

    2011-01-01

    Roč. 1, č. 3 (2011), 309-317 ISSN 2010-135X R&D Projects: GA ČR GA202/09/0430 Institutional research plan: CEZ:AV0Z10100520 Keywords : core-shell nanocomposites * infrared and THz spectroscopy * barium titanate * effective medium approximation Subject RIV: BM - Solid Matter Physics ; Magnetism

  11. MicroShell Minimalist Shell for Xilinx Microprocessors

    Science.gov (United States)

    Werne, Thomas A.

    2011-01-01

    MicroShell is a lightweight shell environment for engineers and software developers working with embedded microprocessors in Xilinx FPGAs. (MicroShell has also been successfully ported to run on ARM Cortex-M1 microprocessors in Actel ProASIC3 FPGAs, but without project-integration support.) Micro Shell decreases the time spent performing initial tests of field-programmable gate array (FPGA) designs, simplifies running customizable one-time-only experiments, and provides a familiar-feeling command-line interface. The program comes with a collection of useful functions and enables the designer to add an unlimited number of custom commands, which are callable from the command-line. The commands are parameterizable (using the C-based command-line parameter idiom), so the designer can use one function to exercise hardware with different values. Also, since many hardware peripherals instantiated in FPGAs have reasonably simple register-mapped I/O interfaces, the engineer can edit and view hardware parameter settings at any time without stopping the processor. MicroShell comes with a set of support scripts that interface seamlessly with Xilinx's EDK tool. Adding an instance of MicroShell to a project is as simple as marking a check box in a library configuration dialog box and specifying a software project directory. The support scripts then examine the hardware design, build design-specific functions, conditionally include processor-specific functions, and complete the compilation process. For code-size constrained designs, most of the stock functionality can be excluded from the compiled library. When all of the configurable options are removed from the binary, MicroShell has an unoptimized memory footprint of about 4.8 kB and a size-optimized footprint of about 2.3 kB. Since MicroShell allows unfettered access to all processor-accessible memory locations, it is possible to perform live patching on a running system. This can be useful, for instance, if a bug is

  12. Silica reinforced triblock copolymer gels

    DEFF Research Database (Denmark)

    Theunissen, E.; Overbergh, N.; Reynaers, H.

    2004-01-01

    The effect of silica and polymer coated silica particles as reinforcing agents on the structural and mechanical properties of polystyrene-poly(ethylene/butylene)-polystyrene (PS-PEB-PS) triblock gel has been investigated. Different types of chemically modified silica have been compared in order...

  13. Effect of silica concentration on electrical conductivity of epoxy resin-carbon black-silica nanocomposites

    International Nuclear Information System (INIS)

    Zhang Wei; Blackburn, Richard S.; Dehghani-Sanij, Abbas A.

    2007-01-01

    Electrical properties of nanocomposites are determined by the conductive paths of carbon black and influenced by a 'network' of silica. With increasing content of silica, carbon black (CB) particles are optimally dispersed, contributing to the generation of a conductive network between CB particles via direct particle contact and a tunneling effect; maximum conductivity for the epoxy resin-CB-silica nanocomposite described herein occurs at a ratio of 0.6:1.0 (SiO 2 :CB). As a non-conductive component, excessive silica will prevent electron flow, giving rise to low conductivity

  14. Selective degradation of model pollutants in the presence of core@shell TiO{sub 2}@SiO{sub 2} photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Nadrah, Peter, E-mail: peter.nadrah@zag.si [Slovenian National Building and Civil Engineering Institute, Dimičeva ul. 12, SI-1000 Ljubljana (Slovenia); Gaberšček, Miran [National Institute of Chemistry, Hajdrihova ul. 19, SI-1000 Ljubljana (Slovenia); Sever Škapin, Andrijana [Slovenian National Building and Civil Engineering Institute, Dimičeva ul. 12, SI-1000 Ljubljana (Slovenia)

    2017-05-31

    Highlights: • TiO{sub 2} encapsulated in mesoporous silica exhibits selective photocatalytic degradation of low-molecular-weight molecules. • Core@shell photocatalyst degrades rhodamine B in presence of fivefold mass concentration of starch, while pure TiO{sub 2} does not. • Potential use for removing water pollutants, while retaining non-harmful and beneficial macromolecules. - Abstract: Photocatalytic TiO{sub 2} degrades organic matter unselectively. However, in certain applications, such as degradation of pollutants, selectivity towards pollutants is beneficial. We synthesized core@shell TiO{sub 2}@SiO{sub 2} nanoparticles with photocatalytic activity featuring a significantly faster preferential degradation of model pollutant (rhodamine B) in presence of abundant concentration of natural organic matter compared to pure TiO{sub 2} (P25). The material’s photocatalytic activity was tested in aqueous medium. The selectivity of prepared effect of core@shell materials is explained based on transmission electron microscopy, nitrogen adsorption, X-ray powder diffraction and zeta potential measurements.

  15. Fabrication of high specificity hollow mesoporous silica nanoparticles assisted by Eudragit for targeted drug delivery.

    Science.gov (United States)

    She, Xiaodong; Chen, Lijue; Velleman, Leonora; Li, Chengpeng; Zhu, Haijin; He, Canzhong; Wang, Tao; Shigdar, Sarah; Duan, Wei; Kong, Lingxue

    2015-05-01

    Hollow mesoporous silica nanoparticles (HMSNs) are one of the most promising carriers for effective drug delivery due to their large surface area, high volume for drug loading and excellent biocompatibility. However, the non-ionic surfactant templated HMSNs often have a broad size distribution and a defective mesoporous structure because of the difficulties involved in controlling the formation and organization of micelles for the growth of silica framework. In this paper, a novel "Eudragit assisted" strategy has been developed to fabricate HMSNs by utilising the Eudragit nanoparticles as cores and to assist in the self-assembly of micelle organisation. Highly dispersed mesoporous silica spheres with intact hollow interiors and through pores on the shell were fabricated. The HMSNs have a high surface area (670 m(2)/g), small diameter (120 nm) and uniform pore size (2.5 nm) that facilitated the effective encapsulation of 5-fluorouracil within HMSNs, achieving a high loading capacity of 194.5 mg(5-FU)/g(HMSNs). The HMSNs were non-cytotoxic to colorectal cancer cells SW480 and can be bioconjugated with Epidermal Growth Factor (EGF) for efficient and specific cell internalization. The high specificity and excellent targeting performance of EGF grafted HMSNs have demonstrated that they can become potential intracellular drug delivery vehicles for colorectal cancers via EGF-EGFR interaction. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Silica particles and method of preparation thereof

    NARCIS (Netherlands)

    2015-01-01

    The invention is in the field of silica products. More in particular, the invention is in the field of amorphous silica particles. The invention is directed to amorphous silica particles and related products including clusters of said silica particles, a suspension of said silica particles, and an

  17. In situ growth of hollow gold-silver nanoshells within porous silica offers tunable plasmonic extinctions and enhanced colloidal stability.

    Science.gov (United States)

    Li, Chien-Hung; Jamison, Andrew C; Rittikulsittichai, Supparesk; Lee, Tai-Chou; Lee, T Randall

    2014-11-26

    Porous silica-coated hollow gold-silver nanoshells were successfully synthesized utilizing a procedure where the porous silica shell was produced prior to the transformation of the metallic core, providing enhanced control over the structure/composition of the bimetallic hollow core. By varying the reaction time and the precise amount of gold salt solution added to a porous silica-coated silver-core template solution, composite nanoparticles were tailored to reveal a readily tunable surface plasmon resonance that could be centered across the visible and near-IR spectral regions (∼445-800 nm). Characterization by X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed that the synthetic methodology afforded particles having uniform composition, size, and shape. The optical properties were evaluated by absorption/extinction spectroscopy. The stability of colloidal solutions of our composite nanoparticles as a function of pH was also investigated, revealing that the nanoshells remain intact over a wide range of conditions (i.e., pH 2-10). The facile tunability, enhanced stability, and relatively small diameter of these composite particles (∼110 nm) makes them promising candidates for use in tumor ablation or as photothermal drug-delivery agents.

  18. Optical properties of core-shell and multi-shell nanorods

    Science.gov (United States)

    Mokkath, Junais Habeeb; Shehata, Nader

    2018-05-01

    We report a first-principles time dependent density functional theory study of the optical response modulations in bimetallic core-shell (Na@Al and Al@Na) and multi-shell (Al@Na@Al@Na and Na@Al@Na@Al: concentric shells of Al and Na alternate) nanorods. All of the core-shell and multi-shell configurations display highly enhanced absorption intensity with respect to the pure Al and Na nanorods, showing sensitivity to both composition and chemical ordering. Remarkably large spectral intensity enhancements were found in a couple of core-shell configurations, indicative that optical response averaging based on the individual components can not be considered as true as always in the case of bimetallic core-shell nanorods. We believe that our theoretical results would be useful in promising applications depending on Aluminum-based plasmonic materials such as solar cells and sensors.

  19. COOH-functionalisation of silica particles

    Energy Technology Data Exchange (ETDEWEB)

    Majewski, Peter, E-mail: peter.majewski@unisa.edu.au [School of Advanced Manufacturing and Mechanical Engineering, Mawson Institute, University of South Australia, Adelaide (Australia); Albrecht, Trent [Ian Wark Research Institute, University of South Australia, Adelaide (Australia); Weber, Siegfried [Department of Biotechnology, University of Applied Sciences, Mannheim (Germany)

    2011-09-01

    In this study COOH-functionalised silica is synthesised using phosphonateN-(phosphonomethyl)iminodiacetic acid (PMIDA) in an aqueous solution. The presence of PMIDA on the silica particles was verified using Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy and titration. Experimentally, surface concentrations of COOH functional groups of up to about 3 mmol/g{sub silica} were achieved, whereas theoretical calculation of the maximum COOH functional group concentration gave about 1 mmol/g{sub silica}. The discrepancy may be caused by PMIDA multilayer formation on the particle.

  20. Hybrid shell engineering of animal cells for immune protections and regulation of drug delivery: towards the design of "artificial organs".

    Science.gov (United States)

    Dandoy, Philippe; Meunier, Christophe F; Michiels, Carine; Su, Bao-Lian

    2011-01-01

    With the progress in medicine, the average human life expectancy is continuously increasing. At the same time, the number of patients who require full organ transplantations is augmenting. Consequently, new strategies for cell transplantation are the subject of great interest. This work reports the design, the synthesis and the characterisation of robust and biocompatible mineralised beads composed of two layers: an alginate-silica composite core and a Ca-alginate layer. The adequate choice of materials was achieved through cytotoxicity LDH release measurement and in vitro inflammatory assay (IL-8) to meet the biocompatibility requirements for medical purpose. The results obtained following this strategy provide a direct proof of the total innocuity of silica and alginate networks for human cells as underscored by the non-activation of immune defenders (THP-1 monocytes). The accessible pore size diameter of the mineralised beads synthesized was estimated between 22 and 30 nm, as required for efficient immuno-isolation without preventing the diffusion of nutrients and metabolites. The model human cells, HepG2, entrapped within these hybrid beads display a high survival rate over more than six weeks according to the measurements of intracellular enzymatic activity, respiration rate, as well as the "de novo" biosynthesis and secretion of albumin out of the beads. The current study shows that active mammalian cells can be protected by a silica-alginate hybrid shell-like system. The functionality of the cell strain can be maintained. Consequently, cells coated with an artificial and a biocompatible mineral shell could respond physiologically within the human body in order to deliver therapeutic agents in a controlled fashion (i.e. insulin), substituting the declining organ functions of the patient.

  1. Facile and low energy consumption synthesis of microencapsulated phase change materials with hybrid shell for thermal energy storage

    Science.gov (United States)

    Wang, Hao; Zhao, Liang; Chen, Lijie; Song, Guolin; Tang, Guoyi

    2017-12-01

    We designed a photocurable pickering emulsion polymerization to create microencapsulated phase change materials (MicroPCM) with polymer-silica hybrid shell. The emulsion was stabilized by modified SiO2 particles without any surfactant or dispersant. The polymerization process can be carried out at ambient temperature only for 5 min ultraviolet radiation, which is a low-energy procedure. The resultant capsules were shown a good core-shell structure and uniform in size. The surface of the microcapsules was covered by SiO2 particles. According to the DSC and TGA examinations, the microcapsules has good thermal energy storage-release performance, enhanced thermal reliability and thermal stability. When ratio of MMA/n-octadecane was 1.5/1.5. The encapsulation efficiency of the microcapsules reached 62.55%, accompanied with 122.31 J/g melting enthalpy. The work is virtually applicable to the construction of a wide variety of organic-inorganic hybrid shell MicroPCM. Furthermore, with the application of this method, exciting opportunities may arise for realizing rapid, continuous and large-scale industrial preparation of MicroPCM.

  2. Metal-silica sol-gel materials

    Science.gov (United States)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  3. Light-stimulated cargo release from a core–shell structured nanocomposite for site-specific delivery

    International Nuclear Information System (INIS)

    Cai, Yun; Ling, Li; Li, Xiaofang; Chen, Meng; Su, Likai

    2015-01-01

    This paper reported a core–shell structured site-specific delivery system with a light switch triggered by low energy light (λ=510 nm). Its core was composed of supermagnetic Fe 3 O 4 nanoparticles for magnetic guiding and targeting. Its outer shell consisted of mesoporous silica molecular sieve MCM-41 which offered highly ordered hexagonal tunnels for cargo capacity. A light switch N1-(4aH-cyclopenta[1,2-b:5,4-b′]dipyridin-5(5aH)-ylidene)benzene-1, 4-diamine (CBD) was covalently grafted into these hexagonal tunnels, serving as light stimuli acceptor with loading content of 1.1 μM/g. This composite was fully characterized and confirmed by SEM, TEM, XRD patterns, N 2 adsorption/desorption, thermogravimetric analysis, IR, UV–vis absorption and emission spectra. Experimental data suggested that this composite had a core as wide as 150 nm and could be magnetically guided to specific sites. Its hexagonal tunnels were as long as 180 nm. Upon light stimuli of “on” and “off” states, controllable release was observed with short release time of ~900 s (90% capacity). - Graphical abstract: A core–shell structured site-specific delivery system with a light switch triggered by yellow light was constructed. Controllable release was observed with short release time of ~900 s (90% capacity). - Highlights: • A core–shell structured site-specific delivery system was constructed. • It consisted of Fe 3 O 4 core and MCM-41 shell grafted with light switch. • This delivery system was triggered by low energy light. • Controllable release was observed with short release time of ~900 s

  4. Light-stimulated cargo release from a core–shell structured nanocomposite for site-specific delivery

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Yun; Ling, Li; Li, Xiaofang [Department of Neurology, Affiliated Hospital of Hebei University, Baoding 071000 (China); Chen, Meng [Department of Rheumatology, Affiliated Hospital of Hebei University, Baoding 071000 (China); Su, Likai, E-mail: zhangdong19992003@163.com [Department of Neurology, Affiliated Hospital of Hebei University, Baoding 071000 (China)

    2015-03-15

    This paper reported a core–shell structured site-specific delivery system with a light switch triggered by low energy light (λ=510 nm). Its core was composed of supermagnetic Fe{sub 3}O{sub 4} nanoparticles for magnetic guiding and targeting. Its outer shell consisted of mesoporous silica molecular sieve MCM-41 which offered highly ordered hexagonal tunnels for cargo capacity. A light switch N1-(4aH-cyclopenta[1,2-b:5,4-b′]dipyridin-5(5aH)-ylidene)benzene-1, 4-diamine (CBD) was covalently grafted into these hexagonal tunnels, serving as light stimuli acceptor with loading content of 1.1 μM/g. This composite was fully characterized and confirmed by SEM, TEM, XRD patterns, N{sub 2} adsorption/desorption, thermogravimetric analysis, IR, UV–vis absorption and emission spectra. Experimental data suggested that this composite had a core as wide as 150 nm and could be magnetically guided to specific sites. Its hexagonal tunnels were as long as 180 nm. Upon light stimuli of “on” and “off” states, controllable release was observed with short release time of ~900 s (90% capacity). - Graphical abstract: A core–shell structured site-specific delivery system with a light switch triggered by yellow light was constructed. Controllable release was observed with short release time of ~900 s (90% capacity). - Highlights: • A core–shell structured site-specific delivery system was constructed. • It consisted of Fe{sub 3}O{sub 4} core and MCM-41 shell grafted with light switch. • This delivery system was triggered by low energy light. • Controllable release was observed with short release time of ~900 s.

  5. Preparation and Application of Hollow Silica/magnetic Nanocomposite Particle

    Science.gov (United States)

    Wang, Cheng-Chien; Lin, Jing-Mo; Lin, Chun-Rong; Wang, Sheng-Chang

    The hollow silica/cobalt ferrite (CoFe2O4) magnetic microsphere with amino-groups were successfully prepared via several steps, including preparing the chelating copolymer microparticles as template by soap-free emulsion polymerization, manufacturing the hollow cobalt ferrite magnetic microsphere by in-situ chemical co-precipitation following calcinations, and surface modifying of the hollow magnetic microsphere by 3-aminopropyltrime- thoxysilane via the sol-gel method. The average diameter of polymer microspheres was ca. 200 nm from transmission electron microscope (TEM) measurement. The structure of the hollow magnetic microsphere was characterized by using TEM and scanning electron microscope (SEM). The spinel-type lattice of CoFe2O4 shell layer was identified by using XRD measurement. The diameter of CoFe2O4 crystalline grains ranged from 54.1 nm to 8.5 nm which was estimated by Scherrer's equation. Additionally, the hollow silica/cobalt ferrite microsphere possesses superparamagnetic property after VSM measurement. The result of BET measurement reveals the hollow magnetic microsphere which has large surface areas (123.4m2/g). After glutaraldehyde modified, the maximum value of BSA immobilization capacity of the hollow magnetic microsphere was 33.8 mg/g at pH 5.0 buffer solution. For microwave absorption, when the hollow magnetic microsphere was compounded within epoxy resin, the maximum reflection loss of epoxy resins could reach -35dB at 5.4 GHz with 1.9 mm thickness.

  6. Silica aerogel Cerenkov counter

    International Nuclear Information System (INIS)

    Yasumi, S.; Masaike, A.; Yamamoto, A.; Yoshimura, Y.; Kawai, H.

    1984-03-01

    In order to obtain silica aerogel radiators of good quality, the prescription used by Saclay group has been developed. We have done several experiments using beams from KEK.PS to test the performance of a Cerenkov counter with aerogel modules produced in KEK. It turned out that these modules had excellent quality. The production rate of silica aerogel in KEK is 15 -- 20 litres a week. Silica aerogel modules of 20 x 10 x 3 cm 3 having the refractive index of 1.058 are successfully being used by Kyoto University group in the KEK experiment E92 (Σ). Methodes to produce silica aerogel with higher refractive index than 1.06 has been investigated both by heating an module with the refractive index of 1.06 and by hydrolyzing tetraethyl silicate. (author)

  7. Melt flow and mechanical properties of silica/perfluoropolymer nanocomposites Fabricated by direct melt-compounding without surface modification on nano-silica.

    Science.gov (United States)

    Tanahashi, Mitsuru; Watanabe, Yusuke; Lee, Jeong-Chang; Takeda, Kunihiko; Fujisawa, Toshiharu

    2009-01-01

    The authors have previously developed a novel method for the fabrication of silica/perfluoropolymer nanocomposites, wherein nano-sized silica particles without surface modification were dispersed uniformly through breakdown of loosely packed agglomerates of silica nanoparticles with low fracture strength in a polymer melt during direct melt-compounding. The method consists of two stages; the first stage involves preparation of the loose silica agglomerate, and the second stage involves melt-compounding of a completely hydrophobic perfluoropolymer, PFA (poly(tetrafluoroethylene-co-perfluoropropylvinylether)), with the loose silica agglomerates. By using this simple method without any lipophilic treatment of the silica surfaces, silica nanoparticles with a primary diameter of 190 nm could be dispersed uniformly into the PFA matrix. The main purpose of the present study is to evaluate the melt flow and tensile properties of silica/PFA nanocomposites fabricated by the above method. In order to elucidate the effects of the size of the dispersed silica in the PFA matrix on the properties of the composites, silica/PFA composite samples exhibiting the dispersion of larger-sized silica particle-clusters were fabricated as negative controls of the silica dispersion state. The results obtained under the present experimental conditions showed that the size of the dispersed silica in the PFA matrix exerts a strong influence on the ultimate tensile properties, such as tensile strength and elongation at break, and the melt flow rate (MFR) of the composite materials. The MFR of the silica/PFA nanocomposite became higher than that of the pure PFA without silica addition, although the MFR of the PFA composites containing larger silica particle-clusters became much lower than that of the pure PFA. Furthermore, uniform dispersion of isolated silica nanoparticles was found to improve not only the Young's modulus but also the ultimate tensile properties of the composite.

  8. Multifunctional nanomedicine with silica: Role of silica in nanoparticles for theranostic, imaging, and drug monitoring.

    Science.gov (United States)

    Chen, Fang; Hableel, Ghanim; Zhao, Eric Ruike; Jokerst, Jesse V

    2018-07-01

    The idea of multifunctional nanomedicine that enters the human body to diagnose and treat disease without major surgery is a long-standing dream of nanomaterials scientists. Nanomaterials show incredible properties that are not found in bulk materials, but achieving multi-functionality on a single material remains challenging. Integrating several types of materials at the nano-scale is critical to the success of multifunctional nanomedicine device. Here, we describe the advantages of silica nanoparticles as a tool for multifunctional nano-devices. Silica nanoparticles have been intensively studied in drug delivery due to their biocompatibility, degradability, tunable morphology, and ease of modification. Moreover, silica nanoparticles can be integrated with other materials to obtain more features and achieve theranostic capabilities and multimodality for imaging applications. In this review, we will first compare the properties of silica nanoparticles with other well-known nanomaterials for bio-applications and describe typical routes to synthesize and integrate silica nanoparticles. We will then highlight theranostic and multimodal imaging application that use silica-based nanoparticles with a particular interest in real-time monitoring of therapeutic molecules. Finally, we will present the challenges and perspective on future work with silica-based nanoparticles in medicine. Copyright © 2018 Elsevier Inc. All rights reserved.

  9. Exchange biased Co{sub 3}O{sub 4} nanowires: A new insight into its magnetic core–shell nature

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, S., E-mail: senoythomas@gmail.com [Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram 695019 (India); Jose, A.; Thanveer, T. [Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram 695019 (India); Anantharaman, M.R. [Department of Physics, Cochin University of Science and Technology, Cochin 682022 (India)

    2017-06-15

    Highlights: • Co{sub 3}O{sub 4} nanowires were synthesised within the channels of mesoporous silica, SBA 15. • Magnetometry measurements indicated a magnetic core-shell structure for Co{sub 3}O{sub 4} nanowires. • The core has characteristics of a 2D-DAFF and uncompensated surface spins constitutes the shell. • Exchange coupling between the core-shell magnetic phases results in exchange bias effect. - Abstract: We investigated interfacial exchange coupling effect in nano casted Co{sub 3}O{sub 4} nanowires. Magnetometry measurements indicated that the magnetic response of the wires has two contributions. First one from the core of the wire which has characteristics of a 2D-DAFF(two-dimensional diluted antiferromagnet in a field). The second one is from uncompensated surface spins which get magnetically ordered towards the field direction once field cooled below 25 K. Below 25 K, the net magnetization of the core of the wire gets exchange coupled with the uncompensated surface spins giving rise to exchange bias effect. The unique 2D-DAFF/spin-glass core/shell heterostructure showed a pronounced training effect in the first field cycling itself. The magnitude of exchange bias field showed a maximum at intermediate cooling fields and for the higher cooling field, exchange bias got reduced.

  10. Printing, folding and assembly methods for forming 3D mesostructures in advanced materials

    Science.gov (United States)

    Zhang, Yihui; Zhang, Fan; Yan, Zheng; Ma, Qiang; Li, Xiuling; Huang, Yonggang; Rogers, John A.

    2017-03-01

    A rapidly expanding area of research in materials science involves the development of routes to complex 3D structures with feature sizes in the mesoscopic range (that is, between tens of nanometres and hundreds of micrometres). A goal is to establish methods for controlling the properties of materials systems and the function of devices constructed with them, not only through chemistry and morphology, but also through 3D architectures. The resulting systems, sometimes referred to as metamaterials, offer engineered behaviours with optical, thermal, acoustic, mechanical and electronic properties that do not occur in the natural world. Impressive advances in 3D printing techniques represent some of the most broadly recognized developments in this field, but recent successes with strategies based on concepts in origami, kirigami and deterministic assembly provide additional, unique options in 3D design and high-performance materials. In this Review, we highlight the latest progress and trends in methods for fabricating 3D mesostructures, beginning with the development of advanced material inks for nozzle-based approaches to 3D printing and new schemes for 3D optical patterning. In subsequent sections, we summarize more recent methods based on folding, rolling and mechanical assembly, including their application with materials such as designer hydrogels, monocrystalline inorganic semiconductors and graphene.

  11. Continuous, size and shape-control synthesis of hollow silica nanoparticles enabled by a microreactor-assisted rapid mixing process

    Science.gov (United States)

    He, Yujuan; Kim, Ki-Joong; Chang, Chih-Hung

    2017-06-01

    Hollow silica nanoparticles (HSNPs) were synthesized using a microreactor-assisted system with a hydrodynamic focusing micromixer. Due to the fast mixing of each precursor in the system, the poly(acrylic acid) (PAA) thermodynamic-locked (TML) conformations were protected from their random aggregations by the immediately initiated growth of silica shells. When altering the mixing time through varying flow rates and flow rate ratios, the different degrees of the aggregation of PAA TML conformations were observed. The globular and necklace-like TML conformations were successfully captured by modifying the PAA concentration at the optimized mixing condition. Uniform HSNPs with an average diameter ∼30 nm were produced from this system. COMSOL numerical models was established to investigate the flow and concentration profiles, and their effects on the formation of PAA templates. Finally, the quality and utility of these uniform HSNPs were demonstrated by the fabrication of antireflective thin films on monocrystalline photovoltaic cells which showed a 3.8% increase in power conversion efficiency.

  12. Study of the pluronic-silica interaction in synthesis of mesoporous silica under mild acidic conditions.

    Science.gov (United States)

    Sundblom, Andreas; Palmqvist, Anders E C; Holmberg, Krister

    2010-02-02

    The interaction between silica and poly(ethylene oxide) (PEO) in water may appear trivial and it is generally stated that hydrogen bonding is responsible for the attraction. However, a literature search shows that there is not a consensus with respect to the mechanism behind the attractive interaction. Several papers claim that only hydrogen bonding is not sufficient to explain the binding. The silica-PEO interaction is interesting from an academic perspective and it is also exploited in the preparation of mesoporous silica, a material of considerable current interest. This study concerns the very early stage of synthesis of mesoporous silica under mild acidic conditions, pH 2-5, and the aim is to shed light on the interaction between silica and the PEO-containing structure directing agent. The synthesis comprises two steps. An organic silica source, tetraethylorthosilicate (TEOS), is first hydrolyzed and Pluronic P123, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymer, is subsequently added at different time periods following the hydrolysis of TEOS. It is shown that the interaction between the silica and the Pluronic is dependent both on the temperature and on the time between onset of TEOS hydrolysis and addition of the copolymer. The results show that the interaction is mainly driven by entropy. The effect of the synthesis temperature and of the time between hydrolysis and addition of the copolymer on the final material is also studied. The material with the highest degree of mesoorder was obtained when the reaction was performed at 20 degrees C and the copolymer was added 40 h after the start of TEOS hydrolysis. It is claimed that the reason for the good ordering of the silica is that whereas particle formation under these conditions is fast, the rate of silica condensation is relatively low.

  13. Silica coatings on clarithromycin.

    Science.gov (United States)

    Bele, Marjan; Dmitrasinovic, Dorde; Planinsek, Odon; Salobir, Mateja; Srcic, Stane; Gaberscek, Miran; Jamnik, Janko

    2005-03-03

    Pre-crystallized clarithromycin (6-O-methylerythromycin A) particles were coated with silica from the tetraethyl orthosilicate (TEOS)-ethanol-aqueous ammonia system. The coatings had a typical thickness of 100-150 nm and presented about 15 wt.% of the silica-drug composite material. The properties of the coatings depended on reactant concentration, temperature and mixing rate and, in particular, on the presence of a cationic surfactant (cetylpyridinium chloride). In the presence of cetylpyridinium chloride the silica coatings slightly decreased the rate of pure clarithromycin dissolution.

  14. Oxygen configurations in silica

    International Nuclear Information System (INIS)

    Chelikowsky, James R.; Chadi, D. J.; Binggeli, N.

    2000-01-01

    We propose a transition state for oxygen in silica. This state is produced by the insertion of an oxygen molecule into the Si-O-Si bond, i.e., it consists of producing a Si-O-O-O-Si bond. This state allows molecular oxygen diffusion in silica without breaking the molecular O 2 bond and it is energetically more stable than a peroxy configuration. This configuration may allow for exchange of molecular oxygen with the oxygen in the silica framework. (c) 2000 The American Physical Society

  15. The Effect of Various Acids to the Gelation Process to the Silica Gel Characteristic Using Organic Silica

    Science.gov (United States)

    Rahman, NA; Widiyastuti, W.; Sigit, D.; Ajiza, M.; Sujana, W.

    2018-01-01

    Bagasse ash is solid waste of cane sugar industry which contain of silica more than 51%. Some previous study of silica gel from bagasse ash have been conducted often and been applied. This study concerns about the effect of various acid used in the process of gelation to the characteristic of silica gel produced. Then, this silica gel will be used as adsorbent. As that, the silica gel must fulfill the requirements of adsorbent, as have good pores characteristics, fit in mesoporous size so that adsorbent diffusion process is not disturbed. A fitted pores size of silica gel can be prepared by managing acid concentration used. The effect of acid, organic acid (tartaric acid) and inorganic acid (hydrochloric acid), is investigated in detail. The acid is added into sodium silicate solution in that the gel is formed, the pores structures can be investigated with BET, the crystal form is analyzed with XRD and the pore structure is analyzed visually with SEM. By managing the acid concentration added, it gets the effect of acid to the pore structure of silica gel. The bigger concentration is, the bigger the pore’s size of silica gel produced.

  16. Synthesis of Siloxanes Directly from Amorphous Silica

    International Nuclear Information System (INIS)

    Myint Sandar Win

    2011-12-01

    A direct synthesis of oligomeric-siloxanes from amorphous silica has been achieved. The compound prepared was caedonal-siloxane. Cardonal is a mono hydroxyphenolic compound with a bulky group in the meta position. It was derived as a by-product from the renewable resources cashew nut shell liquid (CNSL). In the synthesis, one pot synthesis was carried out by using ethylene glycol (EG) as solvent. In the reaction ethylene glycol served as a primary precursor chelating ligand in the synthesised product. The one pot synthesis was enhanced by the strong base, triethylenetetramine (TETA) which served as the promoter catalyst. In the synthesis, optimal conditions were established on the basic of the yield percent of organo-siloxane compounds with respect to the variation of the weight fraction of TETA and to the variation of reaction time. Experimental runs were carried out at (ca 210 2c) which was nearly above the boiling point of the solvent. The substituted organo-silicon compounds obtained were characterized by FT- ir, Thermal analysis, XRD and SEM.

  17. EXAFS study of Tb-doped silica xerogels

    Energy Technology Data Exchange (ETDEWEB)

    Rocca, F. [CeFsa - Centro CNR-ITC de Fisica degli Stati Aggregati, Povo (Italy); Monti, F. [Univ. de Verona, Facolta di Scienze (Italy); Kuzmin, A. [Inst. of Solid State Physics, Riga (Latvia); Dalmaso, A.; Pasqualini, D. [Univ. di Trento, INFM - Dipartimento di Fisica (Italy)

    1999-11-01

    The modification of the local environment of Tb{sup 3+} ions in optically active silica xerogels as a function of concentration (from 400 ppm to 40000 ppm) and thermal treatment (which induces densification) was studied by x-ray absorption spectroscopy at the Tb L{sub 3} edge. Quantitative analysis of the first Tb-O coordination shell was performed using the experimental signal from Tb{sup 3+} ions in water solution as a reference. The radial distribution functions (RDF) of the non-thermally treated (NT) gels are characterised by a nearly gaussian shape, as for the reference sample. On the contrary, the RDF of the densified gels (T) are asymmetric having the main peak at a shorter distance, with a reduced coordination number (N=4-5) and a secondary peak, with N=1-2, at a longer distance. The local environment of Tb in the low concentration sample (400 ppm) is different from that at higher concentrations, both in the NT- and in the T-gels. (au) 15 refs.

  18. Preparation and characterization of hybrid Nafion/silica and Nafion/silica/PTA membranes for redox flow batteries

    Energy Technology Data Exchange (ETDEWEB)

    Glibin, V.; Pupkevich, V.; Svirko, L.; Karamanev, D. [Western Ontario Univ., London, ON (Canada). Dept. of Biochemical and Chemical Engineering

    2008-07-01

    Redox flow batteries are both efficient and cost-effective. However, the long-term stability of most ion-exchange membranes is limited as a result of the high oxidation rates of ions with high redox potentials. A method of synthesizing multi-component Nafion-silica and Nafion-silica-PTA membranes was presented in this study, which also investigated the electrochemical and ion transport properties of the membranes. Membranes were cast from dimethylformamide (DMFA) solution. The iron ion diffusion kinetics of the Nafion-silica and Nafion-silica PTA membranes were studied by dialysis. Results of the investigation demonstrated that the introduction of silica and phosphotungstic acid (PTA) into the Nafion membrane composition resulted in a significant decrease of ion transfer through the membrane. The addition of PTA also increased membrane permeability to ferric ions. The low iron diffusion coefficient and high ionic conductivity of the Nafion-silica membrane makes it a promising material for use in redox flow batteries. 4 refs., 1 tab., 1 fig.

  19. Surface-enhanced Raman scattering of amorphous silica gel adsorbed on gold substrates for optical fiber sensors

    Science.gov (United States)

    Degioanni, S.; Jurdyc, A. M.; Cheap, A.; Champagnon, B.; Bessueille, F.; Coulm, J.; Bois, L.; Vouagner, D.

    2015-10-01

    Two kinds of gold substrates are used to produce surface-enhanced Raman scattering (SERS) of amorphous silica obtained via the sol-gel route using tetraethoxysilane Si(OC2H5)4 (TEOS) solution. The first substrate consists of a gold nanometric film elaborated on a glass slide by sputter deposition, controlling the desired gold thickness and sputtering current intensity. The second substrate consists of an array of micrometer-sized gold inverted pyramidal pits able to confine surface plasmon (SP) enhancing electric field, which results in a distribution of electromagnetic energy inside the cavities. These substrates are optically characterized to observe SPR with, respectively, extinction and reflectance spectrometries. Once coated with thin layers of amorphous silica (SiO2) gel, these samples show Raman amplification of amorphous SiO2 bands. This enhancement can occur in SERS sensors using amorphous SiO2 gel as shells, spacers, protective coatings, or waveguides, and represents particularly a potential interest in the field of Raman distributed sensors, which use the amorphous SiO2 core of optical fibers as a transducer to make temperature measurements.

  20. Silica-Coated Liposomes for Insulin Delivery

    Directory of Open Access Journals (Sweden)

    Neelam Dwivedi

    2010-01-01

    Full Text Available Liposomes coated with silica were explored as protein delivery vehicles for their enhanced stability and improved encapsulation efficiency. Insulin was encapsulated within the fluidic phosphatidylcholine lipid vesicles by thin film hydration at pH 2.5, and layer of silica was formed above lipid bilayer by acid catalysis. The presence of silica coating and encapsulated insulin was identified using confocal and electron microscopy. The native state of insulin present in the formulation was evident from Confocal Micro-Raman spectroscopy. Silica coat enhances the stability of insulin-loaded delivery vehicles. In vivo study shows that these silica coated formulations were biologically active in reducing glucose levels.

  1. Hi shells, supershells, shell-like objects, and ''worms''

    International Nuclear Information System (INIS)

    Heiles, C.

    1984-01-01

    We present photographic representations of the combination of two Hi surveys, so as to eliminate the survey boundaries at Vertical BarbVertical Bar = 10 0 . We also present high-contrast photographs for particular velocities to exhibit weak Hi features. All of these photographs were used to prepare a new list of Hi shells, supershells, and shell-like objects. We discuss the structure of three shell-like objects that are associated with high-velocity gas, and with gas at all velocities that is associated with radio continuum loops I, II, and III. We use spatial filtering to find wiggly gas filaments: ''worms'': crawling away from the galactic plane in the inner Galaxy. The ''worms'' are probably parts of shells that are open at the top; such shells should be good sources of hot gas for the galactic halo

  2. Silica artificial opal incorporated with silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Li Wenjiang, E-mail: wjli@zju.edu.cn [Center for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang University, Joint Research Center of Photonics of the Royal Institute of Technology and Zhejiang University, Zijingang Campus, Room 210, East Building 5, Hangzhou 310058 (China); Sun Tan [Center for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang University, Joint Research Center of Photonics of the Royal Institute of Technology and Zhejiang University, Zijingang Campus, Room 210, East Building 5, Hangzhou 310058 (China)

    2009-07-15

    The silica artificial opal with a three-dimensional (3D) periodic structure was prepared using highly monodispersed silica microspheres by a force packing method in ITO glass cell. The silica artificial opal incorporated with silver nanoparticles was fabricated by the electroplating technique. The optical microscope images of the synthetic sample and the corresponding optical properties were measured after each treatment of electroplating-washing-drying circle. The transmission and reflection spectra presented a red shift, showing that the effective refractive index of the complex silver/silica opal increased after each electroplating. Combining the SEM images, it was seen that the silver nanoparticles could be directly deposited on the surface of silica spheres in the opaline structure. The silver/silica complex opal film could provide a simple way to tune the opal properties by controlling silver nanoparticles in the silica opal. The silver/silica opal crystal structures could be used for nano-photonic circuits, white-light LEDs or as photocatalysts.

  3. Silica artificial opal incorporated with silver nanoparticles

    International Nuclear Information System (INIS)

    Li Wenjiang; Sun Tan

    2009-01-01

    The silica artificial opal with a three-dimensional (3D) periodic structure was prepared using highly monodispersed silica microspheres by a force packing method in ITO glass cell. The silica artificial opal incorporated with silver nanoparticles was fabricated by the electroplating technique. The optical microscope images of the synthetic sample and the corresponding optical properties were measured after each treatment of electroplating-washing-drying circle. The transmission and reflection spectra presented a red shift, showing that the effective refractive index of the complex silver/silica opal increased after each electroplating. Combining the SEM images, it was seen that the silver nanoparticles could be directly deposited on the surface of silica spheres in the opaline structure. The silver/silica complex opal film could provide a simple way to tune the opal properties by controlling silver nanoparticles in the silica opal. The silver/silica opal crystal structures could be used for nano-photonic circuits, white-light LEDs or as photocatalysts.

  4. Lipid bilayer-coated mesoporous silica nanoparticles carrying bovine hemoglobin towards an erythrocyte mimic.

    Science.gov (United States)

    Tu, Jing; Bussmann, Jeroen; Du, Guangsheng; Gao, Yue; Bouwstra, Joke A; Kros, Alexander

    2018-05-30

    Hemoglobin (Hb)-loaded mesoporous silica nanoparticles (MSNs) coated with a lipid bilayer (LB-MSNs) were investigated as an erythrocyte mimic. MSNs with a large average pore size (10 nm) act as a rigid core and provide a protective environment for Hb encapsulated inside the pores. The colloidal stability of Hb-loaded MSNs was enhanced upon the application of a lipid bilayer, through fusion of PEGylated liposomes onto the exterior surface of Hb-loaded MSNs. The morphology and mesostructure of the MSNs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and surface area analysis. The Hb loading capacity (mg/g) in MSNs was studied by thermogravimetric analysis (TGA). UV-Vis absorption spectroscopy revealed that Hb inside MSNs had an identical, but slightly broadened peak in the Soret region compared to free Hb. Furthermore the encapsulated Hb exhibits similar peroxidase-like activity in catalyzing the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) with hydrogen peroxide. The introduction of a supported lipid bilayer (LB) demonstrated the potential to prevent premature Hb release (the burst release decreased from 25.50 ± 0.33% to 6.73 ± 0.83%) and increased the colloidal stability of the Hb-loaded MSNs (hydrodynamic diameter remained ∼250 nm for at least one week). The in vivo systemic circulation and biodistribution of LB-MSNs were studied in optically transparent zebrafish embryos, revealing that LB-MSNs have the potential to act as an erythrocyte mimic in transfusion therapy. Copyright © 2018 Elsevier B.V. All rights reserved.

  5. Chitosan-silica complex membranes from sulfonic acid functionalized silica nanoparticles for pervaporation dehydration of ethanol-water solutions.

    Science.gov (United States)

    Liu, Ying-Ling; Hsu, Chih-Yuan; Su, Yu-Huei; Lai, Juin-Yih

    2005-01-01

    Nanosized silica particles with sulfonic acid groups (ST-GPE-S) were utilized as a cross-linker for chitosan to form a chitosan-silica complex membranes, which were applied to pervaporation dehydration of ethanol-water solutions. ST-GPE-S was obtained from reacting nanoscale silica particles with glycidyl phenyl ether, and subsequent sulfonation onto the attached phenyl groups. The chemical structure of the functionalized silica was characterized with FTIR, (1)H NMR, and energy-dispersive X-ray. Homogeneous dispersion of the silica particles in chitosan was observed with electronic microscopies, and the membranes obtained were considered as nanocomposites. The silica nanoparticles in the membranes served as spacers for polymer chains to provide extra space for water permeation, so as to bring high permeation rates to the complex membranes. With addition of 5 parts per hundred of functionalized silica into chitosan, the resulting membrane exhibited a separation factor of 919 and permeation flux of 410 g/(m(2) h) in pervaporation dehydration of 90 wt % ethanol aqueous solution at 70 degrees C.

  6. Electron beam irradiation effect on nanostructured molecular sieve catalysts

    International Nuclear Information System (INIS)

    Yuan Zhongyong; Zhou Wuzong; Parvulescu, Viorica; Su Baolian

    2003-01-01

    Electron impact can induce chemical changes on particle surfaces of zeolites and molecular sieve catalysts. Some experimental observations of electron irradiation effect on molecular sieve catalysts are presented, e.g., electron-beam-induced growth of bare silver nanowires from zeolite crystallites, formation of vesicles in calcium phosphate, migration of microdomains in iron-oxide doped mesoporous silicas, structural transformation from mesostructured MCM-41 to microporous ZSM-5, etc. The formation mechanisms of the surface structures are discussed

  7. Embedding of Hollow Polymer Microspheres with Hydrophilic Shell in Nafion Matrix as Proton and Water Micro-Reservoir

    Directory of Open Access Journals (Sweden)

    Zhaolin Liu

    2012-08-01

    Full Text Available Assimilating hydrophilic hollow polymer spheres (HPS into Nafion matrix by a loading of 0.5 wt % led to a restructured hydrophilic channel, composed of the pendant sulfonic acid groups (–SO3H and the imbedded hydrophilic hollow spheres. The tiny hydrophilic hollow chamber was critical to retaining moisture and facilitating proton transfer in the composite membranes. To obtain such a tiny cavity structure, the synthesis included selective generation of a hydrophilic polymer shell on silica microsphere template and the subsequent removal of the template by etching. The hydrophilic HPS (100–200 nm possessed two different spherical shells, the styrenic network with pendant sulfonic acid groups and with methacrylic acid groups, respectively. By behaving as microreservoirs of water, the hydrophilic HPS promoted the Grotthus mechanism and, hence, enhanced proton transport efficiency through the inter-sphere path. In addition, the HPS with the –SO3H borne shell played a more effective role than those with the –CO2H borne shell in augmenting proton transport, in particular under low humidity or at medium temperatures. Single H2-PEMFC test at 70 °C using dry H2/O2 further verified the impactful role of hydrophilic HPS in sustaining higher proton flux as compared to pristine Nafion membrane.

  8. Amorphous silica from rice husk at various temperatures

    International Nuclear Information System (INIS)

    Javed, S.J.; Feroze, N.; Tajwar, S.

    2008-01-01

    Rice husk is being used as a source of energy in many heat generating system because of its high calorific value and its availability in many rice producing areas. Rice husk contains approximately 20% silica which is presented in hydrated form. This hydrated silica can be retrieved as amorphous silica under controlled thermal conditions. Uncontrolled burning of rice husk produces crystalline silica which is not reactive silica but can be used as filler in many applications. Amorphous silica is reactive silica which has better market value due to its reactive nature in process industry. The present study deals with the production of amorphous silica at various temperatures from rice husk. Various ashes were prepared in tube furnace by changing the burning temperatures for fixed time intervals and analyzed by XRD. It has been observed that for two hours calculation's of rice husk renders mostly amorphous silica at 650 degree C where as at higher temperatures crystalline silica was obtained. (author)

  9. Cellular membrane trafficking of mesoporous silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Fang, I-Ju [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    This dissertation mainly focuses on the investigation of the cellular membrane trafficking of mesoporous silica nanoparticles. We are interested in the study of endocytosis and exocytosis behaviors of mesoporous silica nanoparticles with desired surface functionality. The relationship between mesoporous silica nanoparticles and membrane trafficking of cells, either cancerous cells or normal cells was examined. Since mesoporous silica nanoparticles were applied in many drug delivery cases, the endocytotic efficiency of mesoporous silica nanoparticles needs to be investigated in more details in order to design the cellular drug delivery system in the controlled way. It is well known that cells can engulf some molecules outside of the cells through a receptor-ligand associated endocytosis. We are interested to determine if those biomolecules binding to cell surface receptors can be utilized on mesoporous silica nanoparticle materials to improve the uptake efficiency or govern the mechanism of endocytosis of mesoporous silica nanoparticles. Arginine-glycine-aspartate (RGD) is a small peptide recognized by cell integrin receptors and it was reported that avidin internalization was highly promoted by tumor lectin. Both RGD and avidin were linked to the surface of mesoporous silica nanoparticle materials to investigate the effect of receptor-associated biomolecule on cellular endocytosis efficiency. The effect of ligand types, ligand conformation and ligand density were discussed in Chapter 2 and 3. Furthermore, the exocytosis of mesoporous silica nanoparticles is very attractive for biological applications. The cellular protein sequestration study of mesoporous silica nanoparticles was examined for further information of the intracellular pathway of endocytosed mesoporous silica nanoparticle materials. The surface functionality of mesoporous silica nanoparticle materials demonstrated selectivity among the materials and cancer and normal cell lines. We aimed to determine

  10. Silica removal in industrial effluents with high silica content and low hardness.

    Science.gov (United States)

    Latour, Isabel; Miranda, Ruben; Blanco, Angeles

    2014-01-01

    High silica content of de-inked paper mill effluents is limiting their regeneration and reuse after membrane treatments such as reverse osmosis (RO). Silica removal during softening processes is a common treatment; however, the effluent from the paper mill studied has a low hardness content, which makes the addition of magnesium compounds necessary to increase silica removal. Two soluble magnesium compounds (MgCl₂∙6H₂O and MgSO₄∙7H₂O) were tested at five dosages (250-1,500 mg/L) and different initial pH values. High removal rates (80-90%) were obtained with both products at the highest pH tested (11.5). With these removal efficiencies, it is possible to work at high RO recoveries (75-85%) without silica scaling. Although pH regulation significantly increased the conductivity of the waters (at pH 11.5 from 2.1 to 3.7-4.0 mS/cm), this could be partially solved by using Ca(OH)₂ instead of NaOH as pH regulator (final conductivity around 3.0 mS/cm). Maximum chemical oxygen demand (COD) removal obtained with caustic soda was lower than with lime (15 vs. 30%). Additionally, the combined use of a polyaluminum coagulant during the softening process was studied; the coagulant, however, did not significantly improve silica removal, obtaining a maximum increase of only 10%.

  11. Hybrid shell engineering of animal cells for immune protections and regulation of drug delivery: towards the design of "artificial organs".

    Directory of Open Access Journals (Sweden)

    Philippe Dandoy

    Full Text Available BACKGROUND: With the progress in medicine, the average human life expectancy is continuously increasing. At the same time, the number of patients who require full organ transplantations is augmenting. Consequently, new strategies for cell transplantation are the subject of great interest. METHODOLOGY/PRINCIPAL FINDINGS: This work reports the design, the synthesis and the characterisation of robust and biocompatible mineralised beads composed of two layers: an alginate-silica composite core and a Ca-alginate layer. The adequate choice of materials was achieved through cytotoxicity LDH release measurement and in vitro inflammatory assay (IL-8 to meet the biocompatibility requirements for medical purpose. The results obtained following this strategy provide a direct proof of the total innocuity of silica and alginate networks for human cells as underscored by the non-activation of immune defenders (THP-1 monocytes. The accessible pore size diameter of the mineralised beads synthesized was estimated between 22 and 30 nm, as required for efficient immuno-isolation without preventing the diffusion of nutrients and metabolites. The model human cells, HepG2, entrapped within these hybrid beads display a high survival rate over more than six weeks according to the measurements of intracellular enzymatic activity, respiration rate, as well as the "de novo" biosynthesis and secretion of albumin out of the beads. CONCLUSIONS/SIGNIFICANCE: The current study shows that active mammalian cells can be protected by a silica-alginate hybrid shell-like system. The functionality of the cell strain can be maintained. Consequently, cells coated with an artificial and a biocompatible mineral shell could respond physiologically within the human body in order to deliver therapeutic agents in a controlled fashion (i.e. insulin, substituting the declining organ functions of the patient.

  12. Synthesis, characterization and nitrite ion sensing performance of reclaimable composite samples through a core-shell structure

    Science.gov (United States)

    Cui, Xiao; Yuqing, Zhao; Cui, Jiantao; Zheng, Qian; Bo, Wang

    2018-02-01

    The following paper reported and discussed a nitrite ion optical sensing platform based on a core-shell structure, using superamagnetic nanoparticles as the core, a silica molecular sieve MCM-41 as the shell and two rhodamine derivatives as probe, respectively. This superamagnetic core made this sensing platform reclaimable after finishing nitrite ion sensing procedure. This sensing platform was carefully characterized by means of electron microscopy images, porous structure analysis, magnetic response, IR spectra and thermal stability analysis. Detailed analysis suggested that the emission of these composite samples was quenchable by nitrite ion, showing emission turn off effect. A static sensing mechanism based on an additive reaction between chemosensors and nitrite ion was proposed. These composite samples followed Demas quenching equation against different nitrite ion concentrations. Limit of detection value was obtained as low as 0.4 μM. It was found that, after being quenched by nitrite ion, these composite samples could be reclaimed and recovered by sulphamic acid, confirming their recyclability.

  13. Enhancement and prediction of modulus of elasticity of palm kernel shell concrete

    International Nuclear Information System (INIS)

    Alengaram, U. Johnson; Mahmud, Hilmi; Jumaat, Mohd Zamin

    2011-01-01

    Research highlights: → Micro-pores of size 16-24 μm were found on the outer surface of palm kernel shell. → Infilling of pores by mineral admixtures was evident. → Sand content influenced both modulus of elasticity and compressive strength. → Proposed equation predicts modulus of elasticity within ±1.5 kN/mm 2 of test results. -- Abstract: This paper presents results of an investigation conducted to enhance and predict the modulus of elasticity (MOE) of palm kernel shell concrete (PKSC). Scanning electron microscopic (SEM) analysis on palm kernel shell (PKS) was conducted. Further, the effect of varying sand and PKS contents and mineral admixtures (silica fume and fly ash) on compressive strength and MOE was investigated. The variables include water-to-binder (w/b) and sand-to-cement (s/c) ratios. Nine concrete mixes were prepared, and tests on static and dynamic moduli of elasticity and compressive strength were conducted. The SEM result showed presence of large number of micro-pores on PKS. The mineral admixtures uniformly filled the micro-pores on the outer surface of PKS. Further, the increase in sand content coupled with reduction in PKS content enhanced the compressive strength and static MOE: The highest MOE recorded in this investigation, 11 kN/mm 2 , was twice that previously published. Moreover, the proposed equation based on CEB/FIP code formula appears to predict the MOE close to the experimental values.

  14. Silica-covered star-shaped Au-Ag nanoparticles as new electromagnetic nanoresonators for Raman characterisation of surfaces

    Science.gov (United States)

    Krajczewski, Jan; Kołątaj, Karol; Pietrasik, Sylwia; Kudelski, Andrzej

    2018-03-01

    One of the tools used for determining the composition of surfaces of various materials is shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). SHINERS is a modification of "standard" surface-enhanced Raman spectroscopy (SERS), in which, before Raman spectra are recorded, the surfaces analysed are covered with a layer of plasmonic nanoparticles protected by a very thin layer of a transparent dielectric. The plasmonic cores of the core-shell nanoparticles used in SHINERS measurements generate a local enhancement of the electric field of the incident electromagnetic radiation, whereas the transparent coatings prevent the metal cores from coming into direct contact with the material being analysed. In this contribution, we propose a new type of SHINERS nanoresonators that contain spiky, star-shaped metal cores (produced from a gold/silver alloy). These spiky, star-shaped Au-Ag nanoparticles have been covered by a layer of silica. The small radii of the ends of the tips of the spikes of these plasmonic nanostructures make it possible to generate a very large enhancement of the electromagnetic field there, with the result that such SHINERS nanoresonators are significantly more efficient than the standard semi-spherical nanostructures. The Au-Ag alloy nanoparticles were synthesised by the reduction of a solution containing silver nitrate and chloroauric acid by ascorbic acid. The final geometry of the nanostructures thus formed was controlled by changing the ratio between the concentrations of AuCl4- and Ag+ ions. The shape of the synthesised star-shaped Au-Ag nanoparticles does not change significantly during the two standard procedures for depositing a layer of silica (by the decomposition of sodium silicate or the decomposition of tetraethyl orthosilicate).

  15. Synthesis of a colloid solution of silica-coated gold nanoparticles for X-ray imaging applications

    Science.gov (United States)

    Kobayashi, Yoshio; Nagasu, Ryoko; Shibuya, Kyosuke; Nakagawa, Tomohiko; Kubota, Yohsuke; Gonda, Kohsuke; Ohuchi, Noriaki

    2014-08-01

    This work proposes a method for fabricating silica-coated gold (Au) nanoparticles, surface modified with poly(ethylene glycol) (PEG) (Au/SiO2/PEG), with a particle size of 54.8 nm. X-ray imaging of a mouse is performed with the colloid solution. A colloid solution of 17.9 nm Au nanoparticles was prepared by reducing Au ions (III) with sodium citrate in water at 80 °C. The method used for silica-coating the Au nanoparticles was composed of surface-modification of the Au nanoparticles with (3-aminopropyl)-trimethoxysilane (APMS) and a sol-gel process. The sol-gel process was performed in the presence of the surface-modified Au nanoparticles using tetraethylorthosilicate, APMS, water, and sodium hydroxide, in which the formation of silica shells and the introduction of amino groups to the silica-coated particles took place simultaneously (Au/SiO2-NH2). Surface modification of the Au/SiO2-NH2 particles with PEG, or PEGylation of the particle surface, was performed by adding PEG with a functional group that reacted with an amino group in the Au/SiO2-NH2 particle colloid solution. A computed tomography (CT) value of the aqueous colloid solution of Au/SiO2/PEG particles with an actual Au concentration of 0.112 M was as high as 922 ± 12 Hounsfield units, which was higher than that of a commercial X-ray contrast agent with the same iodine concentration. Injecting the aqueous colloid solution of Au/SiO2/PEG particles into a mouse increased the light contrast of tissues. A CT value of the heart rose immediately after the injection, and this rise was confirmed for up to 6 h.

  16. Development of nanosilica bonded monetite cement from egg shells

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Huan, E-mail: huanzhou@cczu.edu.cn [Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, Jiangsu (China); Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Luchini, Timothy J.F.; Boroujeni, Nariman Mansouri [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Agarwal, Anand K.; Goel, Vijay K. [Department of Bioengineering, The University of Toledo, Toledo, OH (United States); Bhaduri, Sarit B. [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Division of Dentistry, The University of Toledo, Toledo, OH (United States)

    2015-05-01

    This work represents further effort from our group in developing monetite based calcium phosphate cements (CPC). These cements start with a calcium phosphate powder (MW-CPC) that is manufactured using microwave irradiation. Due to the robustness of the cement production process, we report that the starting materials can be derived from egg shells, a waste product from the poultry industry. The CPC were prepared with MW-CPC and aqueous setting solution. Results showed that the CPC hardened after mixing powdered cement with water for about 12.5 ± 1 min. The compressive strength after 24 h of incubation was approximately 8.45 ± 1.29 MPa. In addition, adding colloidal nanosilica to CPC can accelerate the cement hardening (10 ± 1 min) process by about 2.5 min and improve compressive strength (20.16 ± 4.39 MPa), which is more than double the original strength. The interaction between nanosilica and CPC was monitored using an environmental scanning electron microscope (ESEM). While hardening, nanosilica can bond to the CPC crystal network for stabilization. The physical and biological studies performed on both cements suggest that they can potentially be used in orthopedics. - Highlights: • Cement raw powder is derived from egg shells. • A microwave assisted system is used for preparing monetite bone cement. • Colloidal silica is used to reinforce cement.

  17. Development of nanosilica bonded monetite cement from egg shells

    International Nuclear Information System (INIS)

    Zhou, Huan; Luchini, Timothy J.F.; Boroujeni, Nariman Mansouri; Agarwal, Anand K.; Goel, Vijay K.; Bhaduri, Sarit B.

    2015-01-01

    This work represents further effort from our group in developing monetite based calcium phosphate cements (CPC). These cements start with a calcium phosphate powder (MW-CPC) that is manufactured using microwave irradiation. Due to the robustness of the cement production process, we report that the starting materials can be derived from egg shells, a waste product from the poultry industry. The CPC were prepared with MW-CPC and aqueous setting solution. Results showed that the CPC hardened after mixing powdered cement with water for about 12.5 ± 1 min. The compressive strength after 24 h of incubation was approximately 8.45 ± 1.29 MPa. In addition, adding colloidal nanosilica to CPC can accelerate the cement hardening (10 ± 1 min) process by about 2.5 min and improve compressive strength (20.16 ± 4.39 MPa), which is more than double the original strength. The interaction between nanosilica and CPC was monitored using an environmental scanning electron microscope (ESEM). While hardening, nanosilica can bond to the CPC crystal network for stabilization. The physical and biological studies performed on both cements suggest that they can potentially be used in orthopedics. - Highlights: • Cement raw powder is derived from egg shells. • A microwave assisted system is used for preparing monetite bone cement. • Colloidal silica is used to reinforce cement

  18. Size-dependent cytotoxicity and inflammatory responses of PEGylated silica-iron oxide nanocomposite size series

    Science.gov (United States)

    Injumpa, Wishulada; Ritprajak, Patcharee; Insin, Numpon

    2017-04-01

    Iron oxides nanoparticles have been utilized in biological systems and biomedical applications for many years because they are relatively safe and stable comparing to other magnetic nanomaterials. In some applications, iron oxide nanoparticles were modified with silica in order to be more stable in biological systems and able to be functionalized with various functional groups. Moreover, poly(ethylene glycol) (PEG) was one on the most used polymer to graft onto the nanoparticles in order to increase their biocompatibility, dispersibility and stability in aqueous solutions. Therefore, the nanocomposites comprising iron oxide nanoparticles, silica, and PEG could become multifunctional carriers combining superparamagnetic character, multi-functionality and high stability in biological environments. Herein, we reported the preparation of the nanocomposites and effects of their sizes on cytotoxicity and inflammatory responses. The PEGylated silica-iron oxide nanocomposites were prepared by coating of poly(poly(ethylene glycol) monomethyl ether methacrylate) (PPEGMA) on magnetic nanoparticle-silica nanocomposites via Atom Transfer Radical Polymerization (ATRP). The iron oxide nanoparticles were synthesized using a thermal decomposition method. The silica shells were then coated on iron oxides nanoparticles using reverse microemulsion and sol-gel methods. The size series of the nanocomposites with the diameter of 24.86±4.38, 45.24±5.00, 98.10±8.88 and 202.22±6.70 nm as measured using TEM were obtained. Thermogravimetric analysis (TGA) was used for the determination of % weight of PPEGMA on the nanocomposites showing the weight loss of ranging from 65% for smallest particles to 30% for largest particles. The various sizes (20, 40, 100, 200 nm) and concentrations (10, 100, 1000 μg/mL) of the nanocomposites were tested for their cytotoxicity in fibroblast and macrophage cell lines using MTT assay. The different sizes did not affect cell viability of fibroblast, albeit

  19. Y2O3:Yb,Er@mSiO2-CuxS double-shelled hollow spheres for enhanced chemo-/photothermal anti-cancer therapy and dual-modal imaging

    Science.gov (United States)

    Yang, Dan; Yang, Guixin; Wang, Xingmei; Lv, Ruichan; Gai, Shili; He, Fei; Gulzar, Arif; Yang, Piaoping

    2015-07-01

    Multifunctional composites have gained significant interest due to their unique properties which show potential in biological imaging and therapeutics. However, the design of an efficient combination of multiple diagnostic and therapeutic modes is still a challenge. In this contribution, Y2O3:Yb,Er@mSiO2 double-shelled hollow spheres (DSHSs) with up-conversion fluorescence have been successfully prepared through a facile integrated sacrifice template method, followed by a calcination process. It is found that the double-shelled structure with large specific surface area and uniform shape is composed of an inner shell of luminescent Y2O3:Yb,Er and an outer mesoporous silica shell. Ultra small CuxS nanoparticles (about 2.5 nm) served as photothermal agents, and a chemotherapeutic agent (doxorubicin, DOX) was then attached onto the surface of mesoporous silica, forming a DOX-DSHS-CuxS composite. The composite exhibits high anti-cancer efficacy due to the synergistic photothermal therapy (PTT) induced by the attached CuxS nanoparticles and the enhanced chemotherapy promoted by the heat from the CuxS-based PTT when irradiated by 980 nm near-infrared (NIR) light. Moreover, the composite shows excellent in vitro and in vivo X-ray computed tomography (CT) and up-conversion fluorescence (UCL) imaging properties owing to the doped rare earth ions, thus making it possible to achieve the target of imaging-guided synergistic therapy.Multifunctional composites have gained significant interest due to their unique properties which show potential in biological imaging and therapeutics. However, the design of an efficient combination of multiple diagnostic and therapeutic modes is still a challenge. In this contribution, Y2O3:Yb,Er@mSiO2 double-shelled hollow spheres (DSHSs) with up-conversion fluorescence have been successfully prepared through a facile integrated sacrifice template method, followed by a calcination process. It is found that the double-shelled structure with large

  20. The Pozzolanic reaction of silica fume

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    2012-01-01

    Silica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone. In the ......Silica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone....... In the present paper different aspects of the pozzolanic reaction of silica fume are investigated. These include chemical shrinkage, isothermal heat development and strength development. Key data for these are given and compared with theoretical calculations, and based on presented measurements the energy...

  1. Modified composites based on mesostructured iron oxyhydroxide and synthetic minerals: a potential material for the treatment of various toxic heavy metals and its toxicity.

    Science.gov (United States)

    Chung, Seung-Gun; Ryu, Jae-Chun; Song, Mi-Kyung; An, Byungryul; Kim, Song-Bae; Lee, Sang-Hyup; Choi, Jae-Woo

    2014-02-28

    The composites of mesostructured iron oxyhydroxide and/or commercial synthetic zeolite were investigated for use in the removal of toxic heavy metals, such as cadmium, copper, lead and arsenic, from aqueous solution. Four types of adsorbents, dried alginate beads (DABs), synthetic-zeolite impregnated beads (SZIBs), meso-iron-oxyhydroxide impregnated beads (MIOIBs) and synthetic-zeolite/meso-iron-oxyhydroxide composite beads (SZMIOIBs), were prepared for heavy metal adsorption tests. Laboratory experiments were conducted to investigate the removal efficiencies of cations and anions of heavy metals and the possibility of regenerating the adsorbents. Among these adsorbents, the MIOIBs can simultaneously remove cations and anions of heavy metals; they have high adsorption capacities for lead (60.1mgg(-1)) and arsenic (71.9mgg(-1)) compared with other adsorbents, such as DABs (158.1 and 0.0mgg(-1)), SZIB (42.9 and 0.0mgg(-1)) and SZMIOIB (54.0 and 5.9mgg(-1)) for lead and arsenic, respectively. Additionally, the removal efficiency was consistent at approximately 90%, notwithstanding repetitive regeneration. The characteristics of meso-iron-oxyhydroxide powder were confirmed by X-ray diffraction, Brunauer-Emmett-Teller and transmission electron microscopy. We also performed a comparative toxicity study that indicated that much lower concentrations of the powdered form of mesostructured iron oxyhydroxide had stronger cytotoxicity than the granular form. These results suggest that the granular form of meso iron oxyhydroxide is a more useful and safer adsorbent for heavy metal treatment than the powdered form. This research provides promising results for the application of MIOIBs as an adsorbent for various heavy metals from wastewater and sewage. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Determination of Organophosphorous Pesticides in Environmental Water Samples Using Surface-Engineered C18 Functionalized Silica-Coated Core-Shell Magnetic Nanoparticles-Based Extraction Coupled with GC-MS/MS Analysis.

    Science.gov (United States)

    Srivastava, Neha; Kumari, Supriya; Nair, Kishore; Alam, Samsul; Raza, Syed K

    2017-05-01

    The present paper depicts a novel method based on magnetic SPE (MSPE) for the determination of organophosphorus pesticides (OPs) such as phorate, malathion, and chlorpyrifos in environmental water samples. In this study, C18 functionalized silica-coated core-shell iron oxide magnetic nanoparticles (MNPs) were used as a surface-engineered magnetic sorbent for the selective extraction of pesticides from aqueous samples, followed by GC-MS and GC-tandem MS analysis for confirmative determination of the analytes. Various important method parameters, including quantity of MNP adsorbent, volume of sample, effective time for extraction, nature of the desorbing solvent, and pH of the aqueous sample, were investigated and optimized to obtain maximum method performance. Under the optimized instrumental analysis conditions, good linearity (r2 value ≥0.994) was achieved at the concentration range of 0.5-500 μg/L. Recoveries were in the range of 79.2-96.3 and 80.4-97.5% in selective-ion monitoring and multiple reaction monitoring (MRM) modes, respectively, at the spiking concentrations of 1, 5, and 10 μg/L. MRM mode showed better sensitivity, selectivity, and low-level detection (0.5 μg/L) of analytes. The novel MSPE method is a simple, cheap, rapid, and eco-friendly method for the determination of OPs in environmental water samples.

  3. 21 CFR 584.700 - Hydrophobic silicas.

    Science.gov (United States)

    2010-04-01

    ...) Product. Amorphous fumed hydrophobic silica or precipitated hydrophobic silica (CAS Reg. No. 68611-0944... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Hydrophobic silicas. 584.700 Section 584.700 Food... DRUGS, FEEDS, AND RELATED PRODUCTS FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE IN FEED AND...

  4. Free vibration analysis of delaminated composite shells using different shell theories

    International Nuclear Information System (INIS)

    Nanda, Namita; Sahu, S.K.

    2012-01-01

    Free vibration response of laminated composite shells with delamination is presented using the finite element method based on first order shear deformation theory. The shell theory used is the extension of dynamic, shear deformable theory according to the Sanders' first approximation for doubly curved shells, which can be reduced to Love's and Donnell's theories by means of tracers. An eight-noded C 0 continuity, isoparametric quadrilateral element with five degrees of freedom per node is used in the formulation. For modeling the delamination, multipoint constraint algorithm is incorporated in the finite element code. The natural frequencies of the delaminated cylindrical (CYL), spherical (SPH) and hyperbolic paraboloid (HYP) shells are determined by using the above mentioned shell theories, namely Sanders', Love's, and Donnell's. The validity of the present approach is established by comparing the authors' results with those available in the literature. Additional studies on free vibration response of CYL, SPH and HYP shells are conducted to assess the effects of delamination size and number of layers considering all three shell theories. It is shown that shell theories according to Sanders and Love always predict practically identical frequencies. Donnell's theory gives reliable results only for shallow shells. Moreover, the natural frequency is found to be very sensitive to delamination size and number of layers in the shell.

  5. A new parameter-free soft-core potential for silica and its application to simulation of silica anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Izvekov, Sergei, E-mail: sergiy.izvyekov.civ@mail.mil; Rice, Betsy M. [Weapons and Materials Research Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States)

    2015-12-28

    A core-softening of the effective interaction between oxygen atoms in water and silica systems and its role in developing anomalous thermodynamic, transport, and structural properties have been extensively debated. For silica, the progress with addressing these issues has been hampered by a lack of effective interaction models with explicit core-softening. In this work, we present an extension of a two-body soft-core interatomic force field for silica recently reported by us [S. Izvekov and B. M. Rice, J. Chem. Phys. 136(13), 134508 (2012)] to include three-body forces. Similar to two-body interaction terms, the three-body terms are derived using parameter-free force-matching of the interactions from ab initio MD simulations of liquid silica. The derived shape of the O–Si–O three-body potential term affirms the existence of repulsion softening between oxygen atoms at short separations. The new model shows a good performance in simulating liquid, amorphous, and crystalline silica. By comparing the soft-core model and a similar model with the soft-core suppressed, we demonstrate that the topology reorganization within the local tetrahedral network and the O–O core-softening are two competitive mechanisms responsible for anomalous thermodynamic and kinetic behaviors observed in liquid and amorphous silica. The studied anomalies include the temperature of density maximum locus and anomalous diffusivity in liquid silica, and irreversible densification of amorphous silica. We show that the O–O core-softened interaction enhances the observed anomalies primarily through two mechanisms: facilitating the defect driven structural rearrangements of the silica tetrahedral network and modifying the tetrahedral ordering induced interactions toward multiple characteristic scales, the feature which underlies the thermodynamic anomalies.

  6. One-pot synthesis of redox-responsive polymers-coated mesoporous silica nanoparticles and their controlled drug release.

    Science.gov (United States)

    Sun, Jiao-Tong; Piao, Ji-Gang; Wang, Long-Hai; Javed, Mohsin; Hong, Chun-Yan; Pan, Cai-Yuan

    2013-09-01

    A versatile one-pot strategy for the preparation of reversibly cross-linked polymer-coated mesoporous silica nanoparticles (MSNs) via surface reversible addition-fragmentation chain transfer (RAFT) polymerization is presented for the first time in this paper. The less reactive monomer oligo(ethylene glycol) acrylate (OEGA) and the more reactive cross-linker N,N'-cystaminebismethacrylamide (CBMA) are chosen to be copolymerized on the external surfaces of RAFT agent-functionalized MSNs to form the cross-linked polymer shells. Owing to the reversible cleavage and restoration of disulfide bonds via reduction/oxidation reactions, the polymer shells can control the on/off switching of the nanopores and regulate the drug loading and release. The redox-responsive release of doxorubicin (DOX) from this drug carrier is realized. The protein adsorption, in vitro cytotoxicity assays, and endocytosis studies demonstrate that this biocompatible vehicle is a potential candidate for delivering drugs. It is expected that this versatile grafting strategy may help fabricate satisfying MSN-based drug delivery systems for clinical application. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Microporous Silica Based Membranes for Desalination

    Directory of Open Access Journals (Sweden)

    João C. Diniz da Costa

    2012-09-01

    Full Text Available This review provides a global overview of microporous silica based membranes for desalination via pervaporation with a focus on membrane synthesis and processing, transport mechanisms and current state of the art membrane performance. Most importantly, the recent development and novel concepts for improving the hydro-stability and separating performance of silica membranes for desalination are critically examined. Research into silica based membranes for desalination has focussed on three primary methods for improving the hydro-stability. These include incorporating carbon templates into the microporous silica both as surfactants and hybrid organic-inorganic structures and incorporation of metal oxide nanoparticles into the silica matrix. The literature examined identified that only metal oxide silica membranes have demonstrated high salt rejections under a variety of feed concentrations, reasonable fluxes and unaltered performance over long-term operation. As this is an embryonic field of research several target areas for researchers were discussed including further improvement of the membrane materials, but also regarding the necessity of integrating waste or solar heat sources into the final process design to ensure cost competitiveness with conventional reverse osmosis processes.

  8. Composted oyster shell as lime fertilizer is more effective than fresh oyster shell.

    Science.gov (United States)

    Lee, Young Han; Islam, Shah Md Asraful; Hong, Sun Joo; Cho, Kye Man; Math, Renukaradhya K; Heo, Jae Young; Kim, Hoon; Yun, Han Dae

    2010-01-01

    Physio-chemical changes in oyster shell were examined, and fresh and composted oyster shell meals were compared as lime fertilizers in soybean cultivation. Structural changes in oyster shell were observed by AFM and FE-SEM. We found that grains of the oyster shell surface became smoother and smaller over time. FT-IR analysis indicated the degradation of a chitin-like compound of oyster shell. In chemical analysis, pH (12.3+/-0.24), electrical conductivity (4.1+/-0.24 dS m(-1)), and alkaline powder (53.3+/-1.12%) were highest in commercial lime. Besides, pH was higher in composted oyster shell meal (9.9+/-0.53) than in fresh oyster shell meal (8.4+/-0.32). The highest organic matter (1.1+/-0.08%), NaCl (0.54+/-0.03%), and moisture (15.1+/-1.95%) contents were found in fresh oyster shell meal. A significant higher yield of soybean (1.33 t ha(-1)) was obtained by applying composted oyster shell meal (a 21% higher yield than with fresh oyster shell meal). Thus composting of oyster shell increases the utility of oyster shell as a liming material for crop cultivation.

  9. On the core-mass-shell-luminosity relation for shell-burning stars

    International Nuclear Information System (INIS)

    Jeffery, C.S.; Saint Andrews Univ.

    1988-01-01

    Core-mass-shell-luminosity relations for several types of shell-burning star have been calculated using simultaneous differential equations derived from simple homology approximations. The principal objective of obtaining a mass-luminosity relation for helium giants was achieved. This relation gives substantially higher luminosities than the equivalent relation for H-shell stars with core masses greater than 1 solar mass. The algorithm for calculating mass-luminosity relations in this fashion was investigated in detail. Most of the assumptions regarding the physics in the shell do not play a critical role in determining the core-mass-shell-luminosity relation. The behaviour of the core-mass-core-radius relation for a growing degenerate core as a single unique function of mass and growth rate needs to be defined before a single core-mass-shell-luminosity relation for all H-shell stars can be obtained directly from the homology approximations. (author)

  10. Synthesis and application of silica gel modified with alkoxyalcohols. Alkoxyalcohol shushoku silica gel no gosei to riyo

    Energy Technology Data Exchange (ETDEWEB)

    Moriguchi, T.; Ishiguro, H.; Matsubara, Y.; Yoshihara, M.; Maeshima, T.; Ito, S. (Kinki University, Osaka (Japan). Faculty of Science and Engineering)

    1991-08-20

    Several kinds of silica gel modified by alkoxyalcohols were synthesized by refluxing and dehyration and the organic reactions were studied when these silica gels were used as the catalyst. It could be confirmed by FT-IR spectra, DTA and elementary analysis that alkoxylalcohols adhere to the surface of silica gels without any decomposition. The acetate was produced by using alkyl halides. It was found that the modified silica gels had clearly the catalytic action for the reaction with n-hexyl bromide and dibromoethane although unmodified silica gels did not show the catalytic action. The reducing reaction of carbonyl compounds was carried out. The reaction proceeded at 25 centigrade for acetophenone, cyclohexanone, 1-indanone and 2-octanone to produce the corresponding reduction products. 11 refs., 5 figs., 4 tabs.

  11. Variation in Orthologous Shell-Forming Proteins Contribute to Molluscan Shell Diversity.

    Science.gov (United States)

    Jackson, Daniel J; Reim, Laurin; Randow, Clemens; Cerveau, Nicolas; Degnan, Bernard M; Fleck, Claudia

    2017-11-01

    Despite the evolutionary success and ancient heritage of the molluscan shell, little is known about the molecular details of its formation, evolutionary origins, or the interactions between the material properties of the shell and its organic constituents. In contrast to this dearth of information, a growing collection of molluscan shell-forming proteomes and transcriptomes suggest they are comprised of both deeply conserved, and lineage specific elements. Analyses of these sequence data sets have suggested that mechanisms such as exon shuffling, gene co-option, and gene family expansion facilitated the rapid evolution of shell-forming proteomes and supported the diversification of this phylum specific structure. In order to further investigate and test these ideas we have examined the molecular features and spatial expression patterns of two shell-forming genes (Lustrin and ML1A2) and coupled these observations with materials properties measurements of shells from a group of closely related gastropods (abalone). We find that the prominent "GS" domain of Lustrin, a domain believed to confer elastomeric properties to the shell, varies significantly in length between the species we investigated. Furthermore, the spatial expression patterns of Lustrin and ML1A2 also vary significantly between species, suggesting that both protein architecture, and the regulation of spatial gene expression patterns, are important drivers of molluscan shell evolution. Variation in these molecular features might relate to certain materials properties of the shells of these species. These insights reveal an important and underappreciated source of variation within shell-forming proteomes that must contribute to the diversity of molluscan shell phenotypes. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  12. Off-shell CHY amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Lam, C.S., E-mail: Lam@physics.mcgill.ca [Department of Physics, McGill University, Montreal, Q.C., H3A 2T8 (Canada); Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Yao, York-Peng, E-mail: yyao@umich.edu [Department of Physics, The University of Michigan Ann Arbor, MI 48109 (United States)

    2016-06-15

    The Cachazo–He–Yuan (CHY) formula for on-shell scattering amplitudes is extended off-shell. The off-shell amplitudes (amputated Green's functions) are Möbius invariant, and have the same momentum poles as the on-shell amplitudes. The working principles which drive the modifications to the scattering equations are mainly Möbius covariance and energy momentum conservation in off-shell kinematics. The same technique is also used to obtain off-shell massive scalars. A simple off-shell extension of the CHY gauge formula which is Möbius invariant is proposed, but its true nature awaits further study.

  13. Fe3O4@mesoporous SBA-15: A magnetically recoverable catalyst for photodegradation of malachite green

    International Nuclear Information System (INIS)

    Aliyan, Hamid; Fazaeli, Razieh; Jalilian, Rahil

    2013-01-01

    Surface of mesostructured silica (SBA-15) was modified by immobilizing Fe 3 O 4 . This modified-nanosized mesoporous silica Fe 3 O 4 @SBA-15 was characterized by FTIR, XRD, BET and SEM. A comparison of the photoefficiency of Fe 3 O 4 @SBA-15 toward photodegradation of malachite green (MG) was investigated in a photocatalytic reactor using UV lamp as a light source. The effect of various experimental parameters on the degradation performance of the process was evaluated by examining catalyst dosage, initial dye concentration and pH of the dye solution in the presence of Fe 3 O 4 @SBA-15 as photocatalyst. It was found that the photocatalyst exhibited significantly high catalytic stability, and the activity loss is negligible after five MG degradation cycles.

  14. SCC modification by use of amorphous nano-silica

    NARCIS (Netherlands)

    Quercia Bianchi, G.; Spiesz, P.R.; Hüsken, G.; Brouwers, H.J.H.

    2014-01-01

    In this study two different types of nano-silica (nS) were applied in self-compacting concrete (SCC), both having similar particle size distributions (PSD), but produced through two different processes: fumed powder silica and precipitated silica in colloidal suspension. The influence of nano-silica

  15. Agmatine attenuates silica-induced pulmonary fibrosis.

    Science.gov (United States)

    El-Agamy, D S; Sharawy, M H; Ammar, E M

    2014-06-01

    There is a large body of evidence that nitric oxide (NO) formation is implicated in mediating silica-induced pulmonary fibrosis. As a reactive free radical, NO may not only contribute to lung parenchymal tissue injury but also has the ability to combine with superoxide and form a highly reactive toxic species peroxynitrite that can induce extensive cellular toxicity in the lung tissues. This study aimed to explore the effect of agmatine, a known NO synthase inhibitor, on silica-induced pulmonary fibrosis in rats. Male Sprague Dawley rats were treated with agmatine for 60 days following a single intranasal instillation of silica suspension (50 mg in 0.1 ml saline/rat). The results revealed that agmatine attenuated silica-induced lung inflammation as it decreased the lung wet/dry weight ratio, protein concentration, and the accumulation of the inflammatory cells in the bronchoalveolar lavage fluid. Agmatine showed antifibrotic activity as it decreased total hydroxyproline content of the lung and reduced silica-mediated lung inflammation and fibrosis in lung histopathological specimen. In addition, agmatine significantly increased superoxide dismutase (p Agmatine also reduced silica-induced overproduction of pulmonary nitrite/nitrate as well as tumor necrosis factor α. Collectively, these results demonstrate the protective effects of agmatine against the silica-induced lung fibrosis that may be attributed to its ability to counteract the NO production, lipid peroxidation, and regulate cytokine effects. © The Author(s) 2014.

  16. Synthesis of Cu/SiO2 Core-Shell Particles Using Hyperbranched Polyester as Template and Dispersant

    Science.gov (United States)

    Han, Wensong

    2017-07-01

    Third-generation hyperbranched polyester (HBPE3) was synthesized by stepwise polymerization with N, N-diethylol-3-amine methylpropionate as AB2 monomer and pentaerythritol as core molecule. Then, Cu particles were prepared by reduction of copper nitrate with ascorbic acid in aqueous solution using HBPE3 as template. Finally, Cu/SiO2 particles were prepared by coating silica on the surface of Cu particles. The structure and morphology of the samples were characterized by Fourier-transform infrared (FT-IR) spectrometry, x-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results confirmed the formation of the silica coating on the surface of Cu and that the Cu/SiO2 particles had spherical shape with particle size in the range of 0.8 μm to 2 μm. Compared with pure Cu, the synthesized Cu/SiO2 core-shell particles exhibited better oxidation resistance at high temperature. Moreover, the oxidation resistance of the Cu/SiO2 particles increased significantly with increasing tetraethyl orthosilicate (TEOS) concentration.

  17. All-silica nanofluidic devices for DNA-analysis fabricated by imprint of sol-gel silica with silicon stamp

    DEFF Research Database (Denmark)

    Mikkelsen, Morten Bo Lindholm; Letailleur, Alban A; Søndergård, Elin

    2011-01-01

    We present a simple and cheap method for fabrication of silica nanofluidic devices for single-molecule studies. By imprinting sol-gel materials with a multi-level stamp comprising micro- and nanofeatures, channels of different depth are produced in a single process step. Calcination of the imprin......We present a simple and cheap method for fabrication of silica nanofluidic devices for single-molecule studies. By imprinting sol-gel materials with a multi-level stamp comprising micro- and nanofeatures, channels of different depth are produced in a single process step. Calcination...... of the imprinted hybrid sol-gel material produces purely inorganic silica, which has very low autofluorescence and can be fusion bonded to a glass lid. Compared to top-down processing of fused silica or silicon substrates, imprint of sol-gel silica enables fabrication of high-quality nanofluidic devices without...

  18. Degradability and Clearance of Silicon, Organosilica, Silsesquioxane, Silica Mixed Oxide, and Mesoporous Silica Nanoparticles

    KAUST Repository

    Croissant, Jonas G.

    2017-01-13

    The biorelated degradability and clearance of siliceous nanomaterials have been questioned worldwide, since they are crucial prerequisites for the successful translation in clinics. Typically, the degradability and biocompatibility of mesoporous silica nanoparticles (MSNs) have been an ongoing discussion in research circles. The reason for such a concern is that approved pharmaceutical products must not accumulate in the human body, to prevent severe and unpredictable side-effects. Here, the biorelated degradability and clearance of silicon and silica nanoparticles (NPs) are comprehensively summarized. The influence of the size, morphology, surface area, pore size, and surface functional groups, to name a few, on the degradability of silicon and silica NPs is described. The noncovalent organic doping of silica and the covalent incorporation of either hydrolytically stable or redox- and enzymatically cleavable silsesquioxanes is then described for organosilica, bridged silsesquioxane (BS), and periodic mesoporous organosilica (PMO) NPs. Inorganically doped silica particles such as calcium-, iron-, manganese-, and zirconium-doped NPs, also have radically different hydrolytic stabilities. To conclude, the degradability and clearance timelines of various siliceous nanomaterials are compared and it is highlighted that researchers can select a specific nanomaterial in this large family according to the targeted applications and the required clearance kinetics.

  19. Functionalization of silica nanoparticles for polypropylene nanocomposites applications

    International Nuclear Information System (INIS)

    Bracho, Diego; Palza, Humberto; Quijada, Raul; Dougnac, Vivianne

    2011-01-01

    Synthetic silica nanospheres of different diameters produced via the sol-gel method were used in order to enhance the barrier properties of the polypropylene-silica nanocomposites. Modification of the silica surface by reaction with organic chlorosilanes was performed in order to improve the particles interaction with the polypropylene matrix and its dispersion. Unmodified and modified silica nanoparticles were characterized using electronic microscopy (TEM), elemental analysis, thermo gravimetric analysis (TGA), and solid state nuclear magnetic resonance (NMR) spectroscopy. Preliminary permeability tests of the polymer-silica nanocomposite films showed no significant change at low particles load (3 wt%) regardless its size or surface functionality, mainly because of the low aspect ratio of the silica nanospheres. However, it is expected that at a higher concentration of silica particles differences will be observed. (author)

  20. Fe3O4@polyaniline yolk-shell micro/nanospheres as bifunctional materials for lithium storage and electromagnetic wave absorption

    Science.gov (United States)

    Wang, Xiaoliang; Zhang, Minwei; Zhao, Jianming; Huang, Guoyong; Sun, Hongyu

    2018-01-01

    Unique Fe3O4/polyaniline (PANI) composite with yolk-shell micro/nanostructure (FPys) has been successfully synthesized by a facile silica-assisted in-situ polymerization and subsequent etching strategy. The structural and compositional studies of the FPys composites are performed by employing X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The yolk-shell morphology of the products is confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. When evaluated as anode material for lithium-ion batteries, the as-prepared FPys electrodes deliver superior capacity, better cycling stability and rate capability than those of bare Fe3O4 micro/nanospheres and Fe3O4/PANI core-shell (FPcs) electrodes. Moreover, FPys also exhibits excellent electromagnetic wave absorption performance when comparing to the synthesized Fe3O4-based electromagnetic wave absorbers, in which strong reflection loss and extensive response bandwidth can be achieved simultaneously. The excellent bifunctional properties of FPys material are associated with the specially designed hierarchical micro/nanostructures. The current strategy that application directed structural design can be applied to the synthesis of other multifunctional materials.

  1. Proper design of silica nanoparticles combines high brightness, lack of cytotoxicity and efficient cell endocytosis

    Science.gov (United States)

    Rampazzo, Enrico; Voltan, Rebecca; Petrizza, Luca; Zaccheroni, Nelsi; Prodi, Luca; Casciano, Fabio; Zauli, Giorgio; Secchiero, Paola

    2013-08-01

    Silica-based luminescent nanoparticles (SiNPs) show promising prospects in nanomedicine in light of their chemical properties and versatility. In this study, we have characterized silica core-PEG shell SiNPs derivatized with PEG moieties (NP-PEG), with external amino- (NP-PEG-amino) or carboxy-groups (NP-PEG-carbo), both in cell cultures as well as in animal models. By using different techniques, we could demonstrate that these SiNPs were safe and did not exhibit appreciable cytotoxicity in different relevant cell models, of normal or cancer cell types, growing either in suspension (JVM-2 leukemic cell line and primary normal peripheral blood mononuclear cells) or in adherence (human hepatocarcinoma Huh7 and umbilical vein endothelial cells). Moreover, by multiparametric flow cytometry, we could demonstrate that the highest efficiency of cell uptake and entry was observed with NP-PEG-amino, with a stable persistence of the fluorescence signal associated with SiNPs in the loaded cell populations both in vitro and in vivo settings suggesting this as an innovative method for cell traceability and detection in whole organisms. Finally, experiments performed with the endocytosis inhibitor Genistein clearly suggested the involvement of a caveolae-mediated pathway in SiNP endocytosis. Overall, these data support the safe use of these SiNPs for diagnostic and therapeutic applications.Silica-based luminescent nanoparticles (SiNPs) show promising prospects in nanomedicine in light of their chemical properties and versatility. In this study, we have characterized silica core-PEG shell SiNPs derivatized with PEG moieties (NP-PEG), with external amino- (NP-PEG-amino) or carboxy-groups (NP-PEG-carbo), both in cell cultures as well as in animal models. By using different techniques, we could demonstrate that these SiNPs were safe and did not exhibit appreciable cytotoxicity in different relevant cell models, of normal or cancer cell types, growing either in suspension (JVM-2

  2. Toughening Mechanisms in Silica-Filled Epoxy Nanocomposites

    Science.gov (United States)

    Patel, Binay S.

    Epoxies are widely used as underfill resins throughout the microelectronics industry to mechanically couple and protect various components of flip-chip assemblies. Generally rigid materials largely surround underfill resins. Improving the mechanical and thermal properties of epoxy resins to better match those of their rigid counterparts can help extend the service lifetime of flip-chip assemblies. Recently, researchers have demonstrated that silica nanoparticles are effective toughening agents for lightly-crosslinked epoxies. Improvements in the fracture toughness of silica-filled epoxy nanocomposites have primarily been attributed to two toughening mechanisms: particle debonding with subsequent void growth and matrix shear banding. Various attempts have been made to model the contribution of these toughening mechanisms to the overall fracture energy observed in silica-filled epoxy nanocomposites. However, disparities still exist between experimental and modeled fracture energy results. In this dissertation, the thermal, rheological and mechanical behavior of eight different types of silica-filled epoxy nanocomposites was investigated. Each nanocomposite consisted of up to 10 vol% of silica nanoparticles with particle sizes ranging from 20 nm to 200 nm, with a variety of surface treatments and particle structures. Fractographical analysis was conducted with new experimental approaches in order to accurately identify morphological evidence for each proposed toughening mechanism. Overall, three major insights into the fracture behavior of real world silica-filled epoxy nanocomposites were established. First, microcracking was observed as an essential toughening mechanism in silica-filled epoxy nanocomposites. Microcracking was observed on the surface and subsurface of fractured samples in each type of silica-filled epoxy nanocomposite. The additional toughening contribution of microcracking to overall fracture energy yielded excellent agreement between experimental

  3. Polar silica-based stationary phases. Part II- Neutral silica stationary phases with surface bound maltose and sorbitol for hydrophilic interaction liquid chromatography.

    Science.gov (United States)

    Rathnasekara, Renuka; El Rassi, Ziad

    2017-07-28

    Two neutral polyhydroxylated silica bonded stationary phases, namely maltose-silica (MALT-silica) and sorbitol-silica (SOR-silica), have been introduced and chromatographically characterized in hydrophilic interaction liquid chromatography (HILIC) for a wide range of polar compounds. The bonding of the maltose and sorbitol to the silica surface was brought about by first converting bare silica to an epoxy-activated silica surface via reaction with γ-glycidoxypropyltrimethoxysilane (GPTMS) followed by attaching maltose and sorbitol to the epoxy surface in the presence of the Lewis acid catalyst BF 3 .ethereate. Both silica based columns offered the expected retention characteristics usually encountered for neutral polar surface. The retention mechanism is majorly based on solute' differential partitioning between an organic rich hydro-organic mobile phase (e.g., ACN rich mobile phase) and an adsorbed water layer on the surface of the stationary phase although additional hydrogen bonding was also responsible in some cases for solute retention. The MALT-silica column proved to be more hydrophilic and offered higher retention, separation efficiency and resolution than the SOR-silica column among the tested polar solutes such as derivatized mono- and oligosaccharides, weak phenolic acids, cyclic nucleotide monophosphate and nucleotide-5'-monophosphates, and weak bases, e.g., nucleobases and nucleosides. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Silica-covered star-shaped Au-Ag nanoparticles as new electromagnetic nanoresonators for Raman characterisation of surfaces.

    Science.gov (United States)

    Krajczewski, Jan; Kołątaj, Karol; Pietrasik, Sylwia; Kudelski, Andrzej

    2018-03-15

    One of the tools used for determining the composition of surfaces of various materials is shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). SHINERS is a modification of "standard" surface-enhanced Raman spectroscopy (SERS), in which, before Raman spectra are recorded, the surfaces analysed are covered with a layer of plasmonic nanoparticles protected by a very thin layer of a transparent dielectric. The plasmonic cores of the core-shell nanoparticles used in SHINERS measurements generate a local enhancement of the electric field of the incident electromagnetic radiation, whereas the transparent coatings prevent the metal cores from coming into direct contact with the material being analysed. In this contribution, we propose a new type of SHINERS nanoresonators that contain spiky, star-shaped metal cores (produced from a gold/silver alloy). These spiky, star-shaped Au-Ag nanoparticles have been covered by a layer of silica. The small radii of the ends of the tips of the spikes of these plasmonic nanostructures make it possible to generate a very large enhancement of the electromagnetic field there, with the result that such SHINERS nanoresonators are significantly more efficient than the standard semi-spherical nanostructures. The Au-Ag alloy nanoparticles were synthesised by the reduction of a solution containing silver nitrate and chloroauric acid by ascorbic acid. The final geometry of the nanostructures thus formed was controlled by changing the ratio between the concentrations of AuCl 4 - and Ag + ions. The shape of the synthesised star-shaped Au-Ag nanoparticles does not change significantly during the two standard procedures for depositing a layer of silica (by the decomposition of sodium silicate or the decomposition of tetraethyl orthosilicate). Copyright © 2017 Elsevier B.V. All rights reserved.

  5. In Situ Loading of Drugs into Mesoporous Silica SBA-15.

    Science.gov (United States)

    Wan, Mi Mi; Li, Yan Yan; Yang, Tian; Zhang, Tao; Sun, Xiao Dan; Zhu, Jian Hua

    2016-04-25

    In a new strategy for loading drugs into mesoporous silica, a hydrophilic (heparin) or hydrophobic drug (ibuprofen) is encapsulated directly in a one-pot synthesis by evaporation-induced self-assembly. In situ drug loading significantly cuts down the preparation time and dramatically increases the loaded amount and released fraction of the drug, and appropriate drug additives favor a mesoporous structure of the vessels. Drug loading was verified by FTIR spectroscopy and release tests, which revealed much longer release with a larger amount of heparin or ibuprofen compared to postloaded SBA-15. Besides, the in vitro anticoagulation properties of the released heparin and the biocompatibility of the vessels were carefully assessed, including activated partial thromboplastin time, thrombin time, hemolysis, platelet adhesion experiments, and the morphologies of red blood cells. A concept of new drug-release agents with soft core and hard shell is proposed and offers guidance for the design of novel drug-delivery systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. The effect of SiO2/Au core-shell nanoparticles on breast cancer cell's radiotherapy.

    Science.gov (United States)

    Darfarin, Ghazal; Salehi, Roya; Alizadeh, Effat; Nasiri Motlagh, Behnam; Akbarzadeh, Abolfazl; Farajollahi, Alireza

    2018-05-09

    Recently it has been shown that radiation dose enhancement could be achievable in radiotherapy using nanoparticles (NPs). In this study, evaluation was made to determine efficiency of gold-silica shell-core NP in megavoltage irradiation of MCF7 breath cancer cells. Gold-silicon oxide shell-core NPs were obtained by conjugation of gold NP with amine or thiol functionalized silica NPs (AuN@SiO 2 and AuS@SiO 2 ). Cellular uptake and cytotoxicity of NPs were examined by fluorescent microscopy and MTT assay, respectively. MCF-7 breast cancer cells were treated with both NPs and irradiation was made with X-ray energies of 6 and 18 MV to the absorbed dose of 2, 4 and 8 Gy using Simense linear accelerator. The efficiency of radiation therapy was then evaluated by MTT and Brdu assay, DAPI staining and cell cycle analysis. TEM images indicated that synthesized NPs had average diameter of 25 nm. Cellular uptake demonstrated that the internalization of AuS@SiO 2 and AuN@SiO 2 NPs amounted to 18% and 34%, 3 h post treatment, respectively. Nontoxicity of prepared NPs on MCF-7 cells was proved by MTT and Brdu assays as well as DAPI staining and cell cycle studies. The highest enhancement in radiation dose was observed in the cells that irradiated with radiation energy of 18 MV and absorbed of 8 Gy at NPs concentration of 200 ppm. The Brdu findings revealed that the cytotoxicity and apoptosis on MCF-7 cells are dose dependent with a significantly more death in AuN@SiO 2 (amine) exposed cells (p < .05). Analysis also revealed interruption in cell cycle by demonstrating lack of cells, in S phase in amine treated cells (AuN@SiO 2 ) at given dose of 8 Gy using 18 MV X-ray in comparison to thiol treated cells. Based on the results of the study it can be concluded that the gold-silicon oxide shell-core NPs could play an effective role in radiotherapy of MCF-7 breast cancer cells.

  7. Dossier Shell Eco-Marathon; Dossier Shell Eco-Marathon

    Energy Technology Data Exchange (ETDEWEB)

    Matla, P.

    2012-05-15

    Three articles address subjects concerning the annual race with highly energy efficient cars: the Shell Eco-Marathon. [Dutch] In 3 artikelen wordt aandacht besteed aan de ontwerpen voor de jaarlijkse race met superzuinige auto's, de Shell Eco-Marathon.

  8. Size-dependent cytotoxicity and inflammatory responses of PEGylated silica-iron oxide nanocomposite size series

    Energy Technology Data Exchange (ETDEWEB)

    Injumpa, Wishulada [Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Ritprajak, Patcharee [Department of Microbiology, and RU in Oral Microbiology and Immunology, Faculty of Dentistry, Chulalongkorn University, Bangkok 10330 (Thailand); Insin, Numpon, E-mail: Numpon.I@chula.ac.th [Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand)

    2017-04-01

    Iron oxides nanoparticles have been utilized in biological systems and biomedical applications for many years because they are relatively safe and stable comparing to other magnetic nanomaterials. In some applications, iron oxide nanoparticles were modified with silica in order to be more stable in biological systems and able to be functionalized with various functional groups. Moreover, poly(ethylene glycol) (PEG) was one on the most used polymer to graft onto the nanoparticles in order to increase their biocompatibility, dispersibility and stability in aqueous solutions. Therefore, the nanocomposites comprising iron oxide nanoparticles, silica, and PEG could become multifunctional carriers combining superparamagnetic character, multi-functionality and high stability in biological environments. Herein, we reported the preparation of the nanocomposites and effects of their sizes on cytotoxicity and inflammatory responses. The PEGylated silica-iron oxide nanocomposites were prepared by coating of poly(poly(ethylene glycol) monomethyl ether methacrylate) (PPEGMA) on magnetic nanoparticle-silica nanocomposites via Atom Transfer Radical Polymerization (ATRP). The iron oxide nanoparticles were synthesized using a thermal decomposition method. The silica shells were then coated on iron oxides nanoparticles using reverse microemulsion and sol-gel methods. The size series of the nanocomposites with the diameter of 24.86±4.38, 45.24±5.00, 98.10±8.88 and 202.22±6.70 nm as measured using TEM were obtained. Thermogravimetric analysis (TGA) was used for the determination of % weight of PPEGMA on the nanocomposites showing the weight loss of ranging from 65% for smallest particles to 30% for largest particles. The various sizes (20, 40, 100, 200 nm) and concentrations (10, 100, 1000 μg/mL) of the nanocomposites were tested for their cytotoxicity in fibroblast and macrophage cell lines using MTT assay. The different sizes did not affect cell viability of fibroblast, albeit

  9. Dominant thermogravimetric signatures of lignin in cashew shell as compared to cashew shell cake.

    Science.gov (United States)

    Gangil, Sandip

    2014-03-01

    Dominant thermogravimetric signatures related to lignin were observed in cashew shell as compared to these signatures in cashew shell cake. The phenomenon of weakening of lignin from cashew shell to cashew shell cake was explained on the basis of changes in the activation energies. The pertinent temperature regimes responsible for the release of different constituents of both the bio-materials were identified and compared. The activation energies of cashew shell and cashew shell cake were compared using Kissinger-Akahira-Sunose method. Thermogravimetric profiling of cashew shell and cashew shell cake indicated that these were different kinds of bio-materials. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Anomalous enthalpy relaxation in vitreous silica

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    2015-01-01

    scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here, we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy...... relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hyperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas...... the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica....

  11. Mesoporous Silica from Rice Husk Ash

    Directory of Open Access Journals (Sweden)

    S.A. Mandavgane

    2010-12-01

    Full Text Available Mesoporous silica is used as a raw material in several areas: in preparation of catalysts, in inks, as aconcrete hardening accelerator, as a component of detergents and soaps, as a refractory constituent etc.Sodium silicate is produced by reacting rice hull ash (RHA with aqueous NaOH and silica is precipitatedfrom the sodium silicate by acidification. In the present work, conversion of about 90% of silica containedin RHA into sodium silicate was achieved in an open system at temperatures of about 100 °C. The resultsshowed that silica obtained from RHA is mesoporous, has a large surface area and small particle size.Rice Husk is usually mixed with coal and this mixture is used for firing boilers. The RHA therefore, usuallycontains carbon particles. Activated carbon embedded on silica has been prepared using the carbon alreadypresent in RHA. This carbon shows good adsorption capacity. ©2010 BCREC UNDIP. All rights reserved(Received: 25th April 2010, Revised: 17th June 2010, Accepted: 24th June 2010[How to Cite: V.R. Shelke, S.S. Bhagade, S.A. Mandavgane. (2010. Mesoporous Silica from Rice Husk Ash. Bulletin of Chemical Reaction Engineering and Catalysis, 5 (2: 63-67. doi:10.9767/bcrec.5.2.793.63-67

  12. Practical Hydrogen Loading of Air Silica Fibres

    DEFF Research Database (Denmark)

    Sørensen, Henrik Rokkjær; Jensen, Jesper Bevensee; Jensen, Jesper Bo Damm

    2005-01-01

    A method for hydrogen-loading air-silica optical fibres has been developed allowing out-diffusion times comparable to standard step-index fibres. Examples of the first grating written in Ge-doped air-silica fibres using a 266nm UV-laser are shown.......A method for hydrogen-loading air-silica optical fibres has been developed allowing out-diffusion times comparable to standard step-index fibres. Examples of the first grating written in Ge-doped air-silica fibres using a 266nm UV-laser are shown....

  13. Shell-like structures

    CERN Document Server

    Altenbach, Holm

    2011-01-01

    In this volume, scientists and researchers from industry discuss the new trends in simulation and computing shell-like structures. The focus is put on the following problems: new theories (based on two-dimensional field equations but describing non-classical effects), new constitutive equations (for materials like sandwiches, foams, etc. and which can be combined with the two-dimensional shell equations), complex structures (folded, branching and/or self intersecting shell structures, etc.) and shell-like structures on different scales (for example: nano-tubes) or very thin structures (similar

  14. Effect of support on hydro-metathesis of propene: A comparative study of W(CH 3 ) 6 anchored to silica vs. silica-alumina

    KAUST Repository

    Tretiakov, Mykyta; Samantaray, Manoja; Saidi, Aya; Basset, Jean-Marie

    2018-01-01

    Hydro-metathesis of propene was carried out by using well-defined W(CH3)6 supported on silica and silica-alumina. It was observed that W(CH3)6 supported silica-alumina catalyst is much better (TON 4577) than the silica supported catalyst (TON 2104

  15. Altering the concentration of silica tunes the functional properties of collagen-silica composite scaffolds to suit various clinical requirements.

    Science.gov (United States)

    Perumal, Sathiamurthi; Ramadass, Satiesh Kumar; Gopinath, Arun; Madhan, Balaraman; Shanmugam, Ganesh; Rajadas, Jayakumar; Mandal, Asit Baran

    2015-12-01

    The success of a tissue engineering scaffold depends on a fine balance being achieved between the physicochemical and biological properties. This study attempts to understand the influence of silica concentration on the functional properties of collagen-silica (CS) composite scaffolds for soft tissue engineering applications. Increasing the ratio of silica to collagen (0.25, 0.5, 0.75, 1.0, 1.25, 1.5 and 2.0 w/w) gave a marked advantage in terms of improving the water uptake and compressive modulus of the CS scaffolds, while also enhancing the biological stability and the turnover time. With increase in silica concentration the water uptake and compressive modulus increased concurrently, whereas it was not so for surface porous architecture and biocompatibility which are crucial for cell adhesion and infiltration. Silica:collagen ratio of ≤1 exhibits favourable surface biocompatibility, and any further increase in silica concentration has a detrimental effect. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Gold nanoflowers with mesoporous silica as "nanocarriers" for drug release and photothermal therapy in the treatment of oral cancer using near-infrared (NIR) laser light

    Science.gov (United States)

    Song, Wenzhi; Gong, Junxia; Wang, Yuqian; Zhang, Yan; Zhang, Hongmei; Zhang, Weihang; Zhang, Hu; Liu, Xin; Zhang, Tianfu; Yin, Wanzhong; Yang, Wensheng

    2016-04-01

    In this experiment, we successfully developed nanocarriers in the form of gold nanoflowers coated with two layers of silica for the purposes of drug loading and NIR (near-infrared) photothermal therapy for the treatment of oral cancer. The gold nanoflowers converted NIR laser energy into heat energy. The cores were coated with a thin silica layer (AuNFs@SiO2) to protect the gold nanoflowers from intraparticle ripening. The second layer was mesoporous silica (AuNFs@SiO2@mSiO2), which acted as a nanocarrier for anticancer drug (DOX) loads. The mean effective diameter of the nanoparticles was approximately 150-200 nm, whereas the peak absorption of the AuNFs was 684 nm. After the AuNFs were encapsulated by the silica shells, the plasmonic absorption peak of AuNFs@SiO2 and AuNFs@SiO2@mSiO2 exhibited a red shift to 718 nm. When exposed to an 808 nm NIR laser, these crystals showed an obvious photothermal conversion in the NIR region and a highly efficient release of DOX. Biocompatibility was assessed in vitro using Cell Counting Kit-8 assays, and the results showed that the nanocarriers induced no obvious cytotoxicity. This nanomaterial could be considered a new type of material that shows promising potential for photothermal-chemotherapy against malignant tumours, including those of oral cancers.

  17. Silica-Coated Liposomes for Insulin Delivery

    OpenAIRE

    Neelam Dwivedi; M. A. Arunagirinathan; Somesh Sharma; Jayesh Bellare

    2010-01-01

    Liposomes coated with silica were explored as protein delivery vehicles for their enhanced stability and improved encapsulation efficiency. Insulin was encapsulated within the fluidic phosphatidylcholine lipid vesicles by thin film hydration at pH 2.5, and layer of silica was formed above lipid bilayer by acid catalysis. The presence of silica coating and encapsulated insulin was identified using confocal and electron microscopy. The native state of insulin present in the formulation was evid...

  18. Progammed synthesis of magnetic mesoporous silica coated carbon nanotubes for organic pollutant adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Tong, Yue; Zhang, Min, E-mail: congmingyang123@163.com; Xia, Peixiong; Wang, Linlin; Zheng, Jing; Li, Weizhen; Xu, Jingli, E-mail: xujingli@sues.edu.cn

    2016-05-15

    Magnetic mesoporous silica coated carbon nanotubes were produced from hydrophilic monodisperse magnetic nanoparticles decorated carbon nanotubes using well controlled programmed synthesis method and were characterized by TEM, XRD, FTIR, TGA, N{sub 2} adsorption–desorption and VSM. The well-designed mesoporous magnetic nanotubes had a large specific area, a highly open mesoporous structure and high magnetization. Firstly, SiO{sub 2}-coated maghemite/CNTs nanoparticles (CNTs/Fe{sub 3}O{sub 4}@SiO{sub 2} composites) were synthesized by the combination of high temperature decomposition process and an sol–gel method, in which the iron acetylacetonate as well as TEOS acted as the precursor for maghemite and SiO{sub 2}, respectively. The CNTs/Fe{sub 3}O{sub 4}@SiO{sub 2} composites revealed a core–shell structure, Then, CNTs/Fe{sub 3}O{sub 4}@mSiO{sub 2} was obtained by extracting cetyltrimethylammonium bromide (CTAB) via an ion-exchange procedure. The resulting composites show not only a magnetic response to an externally applied magnetic field, but also can be a good adsorbent for the organic pollutant in the ambient temperature. - Graphical abstract: Magnetic mesoporous silica coated carbon nanotubes were produced from hydrophilic monodisperse magnetic nanoparticles decorated carbon nanotubes using well controlled programmed synthesis, which can be a good adsorbent for the organic pollutant in the ambient temperature. - Highlights: • The surface of CNTs/Fe{sub 3}O{sub 4} is hydrophilic, which facilitates the silica coating. • The CNTs/Fe{sub 3}O{sub 4}@mSiO{sub 2} was synthesized by a facile method. • The CNTs/Fe{sub 3}O{sub 4}@mSiO{sub 2} can be a good adsorbent for the organic pollutant.

  19. Shape-Controlled Synthesis of Magnetic Iron Oxide@SiO₂-Au@C Particles with Core-Shell Nanostructures.

    Science.gov (United States)

    Li, Mo; Li, Xiangcun; Qi, Xinhong; Luo, Fan; He, Gaohong

    2015-05-12

    The preparation of nonspherical magnetic core-shell nanostructures with uniform sizes still remains a challenge. In this study, magnetic iron oxide@SiO2-Au@C particles with different shapes, such as pseduocube, ellipsoid, and peanut, were synthesized using hematite as templates and precursors of magnetic iron oxide. The as-obtained magnetic particles demonstrated uniform sizes, shapes, and well-designed core-shell nanostructures. Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) analysis showed that the Au nanoparticles (AuNPs) of ∼6 nm were uniformly distributed between the silica and carbon layers. The embedding of the metal nanocrystals into the two different layers prevented the aggregation and reduced the loss of the metal nanocrystals during recycling. Catalytic performance of the peanut-like particles kept almost unchanged without a noticeable decrease in the reduction of 4-nitrophenol (4-NP) in 8 min even after 7 cycles, indicating excellent reusability of the particles. Moreover, the catalyst could be readily recycled magnetically after each reduction by an external magnetic field.

  20. Kinetics of silica-phase transitions

    International Nuclear Information System (INIS)

    Duffy, C.J.

    1993-07-01

    In addition to the stable silica polymorph quartz, several metastable silica phases are present in Yucca Mountain. The conversion of these phases to quartz is accompanied by volume reduction and a decrease in the aqueous silica activity, which may destabilize clinoptilolite and mordenite. The primary reaction sequence for the silica phases is from opal or glass to disordered opal-CT, followed by ordering of the opal-CT and finally by the crystallization of quartz. The ordering of opal-CT takes place in the solid state, whereas the conversion of opal-CT takes place through dissolution-reprecipitation involving the aqueous phase. It is proposed that the rate of conversion of opal-CT to quartz is controlled by diffusion of defects out of a disordered surface layer formed on the crystallizing quartz. The reaction rates are observed to be dependent on temperature, pressure, degree of supersaturation, and pH. Rate equations selected from the literature appear to be consistent with observations at Yucca Mountain

  1. Extensions to a nonlinear finite-element axisymmetric shell model based on Reissner's shell theory

    International Nuclear Information System (INIS)

    Cook, W.A.

    1981-01-01

    Extensions to shell analysis not usually associated with shell theory are described in this paper. These extensions involve thick shells, nonlinear materials, a linear normal stress approximation, and a changing shell thickness. A finite element shell-of-revolution model has been developed to analyze nuclear material shipping containers under severe impact conditions. To establish the limits for this shell model, the basic assumptions used in its development were studied; these are listed in this paper. Several extensions were evident from the study of these limits: a thick shell, a plastic hinge, and a linear normal stress

  2. Biocolloids with ordered urease multilayer shells as enzymatic reactors.

    Science.gov (United States)

    Lvov, Y; Caruso, F

    2001-09-01

    The preparation of biocolloids with organized enzyme-containing multilayer shells for exploitation as colloidal enzymatic nanoreactors is described. Urease multilayers were assembled onto submicrometer-sized polystyrene spheres by the sequential adsorption of urease and polyelectrolyte, in a predetermined order, utilizing electrostatic interactions for layer growth. The catalytic activity of the biocolloids increased proportionally with the number of urease layers deposited on the particles, demonstrating that biocolloid particles with tailored enzymatic activities can be produced. It was further found that precoating the latex spheres with nanoparticles (40-nm silica or 12-nm magnetite) enhanced both the stability (with respect to adsorption) and enzymatic activity of the urease multilayers. The presence of the magnetite nanoparticle coating also provided a magnetic function that allowed the biocolloids to be easily and rapidly separated with a permanent magnet. The fabrication of such colloids opens new avenues for the application of bioparticles and represents a promising route for the creation of complex catalytic particles.

  3. Health hazards due to the inhalation of amorphous silica

    Energy Technology Data Exchange (ETDEWEB)

    Merget, R.; Bruening, T. [Research Institute for Occupational Medicine (BGFA), Bochum (Germany); Bauer, T. [Bergmannsheil, University Hospital, Department of Internal Medicine, Division of Pneumonology, Allergology and Sleep Medicine, Bochum (Germany); Kuepper, H.U.; Breitstadt, R. [Degussa-Huels Corp., Wesseling (Germany); Philippou, S. [Department of Pathology, Augusta Krankenanstalten, Bochum (Germany); Bauer, H.D. [Research Institute for Hazardous Substances (IGF), Bochum (Germany)

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic (''thermal'' or ''fumed'') silica, and (3) chemically or physically modified silica. According to the different physico-chemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or

  4. Health hazards due to the inhalation of amorphous silica

    International Nuclear Information System (INIS)

    Merget, R.; Bruening, T.; Bauer, T.; Kuepper, H.U.; Breitstadt, R.; Philippou, S.; Bauer, H.D.

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic (''thermal'' or ''fumed'') silica, and (3) chemically or physically modified silica. According to the different physico-chemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or emphysema cannot be excluded. There is no

  5. Grassy Silica Nanoribbons and Strong Blue Luminescence

    Science.gov (United States)

    Wang, Shengping; Xie, Shuang; Huang, Guowei; Guo, Hongxuan; Cho, Yujin; Chen, Jun; Fujita, Daisuke; Xu, Mingsheng

    2016-09-01

    Silicon dioxide (SiO2) is one of the key materials in many modern technological applications such as in metal oxide semiconductor transistors, photovoltaic solar cells, pollution removal, and biomedicine. We report the accidental discovery of free-standing grassy silica nanoribbons directly grown on SiO2/Si platform which is commonly used for field-effect transistors fabrication without other precursor. We investigate the formation mechanism of this novel silica nanostructure that has not been previously documented. The silica nanoribbons are flexible and can be manipulated by electron-beam. The silica nanoribbons exhibit strong blue emission at about 467 nm, together with UV and red emissions as investigated by cathodoluminescence technique. The origins of the luminescence are attributed to various defects in the silica nanoribbons; and the intensity change of the blue emission and green emission at about 550 nm is discussed in the frame of the defect density. Our study may lead to rational design of the new silica-based materials for a wide range of applications.

  6. Investigation on raspberry-like magnetic-hollow silica nanospheres and its preliminary application for drug delivery

    International Nuclear Information System (INIS)

    Wang, Chunlei; Yan, Juntao; Li, Zhanfeng; Wang, Hongyan; Cui, Xuejun

    2013-01-01

    A series of raspberry-like magnetic-hollow silica nanospheres were successfully synthesized via the sol–gel process, which was based on the principle of the electrostatic interaction between negatively charged silica and positively charged polystyrene. The Fe 3 O 4 @SiO 2 particles as the outer shell were compactly assembled on the surface of PS, and then magnetic-hollow nanospheres were obtained by calcination. Different synthesis conditions including the amount of NH 4 OH, TEOS, Fe 3 O 4 , and the adding time of PS were systematically investigated to discuss the influence of these conditions on the morphology and structure. The prepared magnetic-hollow nanospheres were systematically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectrometry, energy-dispersive X-ray analysis, thermogravimetric analysis and nitrogen adsorption–desorption measurement. SEM and TEM images exhibited that the obtained samples with the perfect spherical profile and large cavities structure were well monodisperse and uniform under the optimized condition. Zeta-potential analysis was employed to make clear the formation mechanism of raspberry-like PS@Fe 3 O 4 @SiO 2 composite nanosphere. Moreover, the drug release of ibuprofen experiment results demonstrated that the magnetic-hollow nanospheres could be used as a drug carrier to slowly release and deliver drugs

  7. Winter climate change and fine root biogenic silica in sugar maple trees (Acer saccharum): Implications for silica in the Anthropocene

    Science.gov (United States)

    Maguire, Timothy J.; Templer, Pamela H.; Battles, John J.; Fulweiler, Robinson W.

    2017-03-01

    Winter temperatures are projected to increase over the next century, leading to reductions in winter snowpack and increased frequency of soil freezing in many northern forest ecosystems. Here we examine biogenic silica (BSi) concentrations in sugar maple (Acer saccharum) fine roots collected from a snow manipulation experiment at Hubbard Brook Experimental Forest (New Hampshire, USA). Increased soil freezing significantly lowered the BSi content of sugar maple fine roots potentially decreasing their capacity to take up water and dissolved nutrients. The reduced silica uptake (8 ± 1 kmol silica km-2) by sugar maple fine roots is comparable to silica export from temperate forest watersheds. We estimate that fine roots account for 29% of sugar maple BSi, despite accounting for only 4% of their biomass. These results suggest that increased frequency of soil freezing will reduce silica uptake by temperate tree roots, thereby changing silica availability in downstream receiving waters.

  8. Mesoporous Silica from Rice Husk Ash

    Directory of Open Access Journals (Sweden)

    V.R. Shelke

    2011-01-01

    Full Text Available Mesoporous silica is used as a raw material in several areas: in preparation of catalysts, in inks, as a concrete hardening accelerator, as a component of detergents and soaps, as a refractory constituent etc. Sodium silicate is produced by reacting rice hull ash (RHA with aqueous NaOH and silica is precipitated from the sodium silicate by acidification. In the present work, conversion of about 90% of silica contained in RHA into sodium silicate was achieved in an open system at temperatures of about 100 °C. The results showed that silica obtained from RHA is mesoporous, has a large surface area and small particle size. Rice Husk is usually mixed with coal and this mixture is used for firing boilers. The RHA therefore, usually contains carbon particles. Activated carbon embedded on silica has been prepared using the carbon already present in RHA. This carbon shows good adsorption capacity. ©2010 BCREC UNDIP. All rights reserved(Received: 25th April 2010, Revised: 17th June 2010, Accepted: 24th June 2010[How to Cite: V.R. Shelke, S.S. Bhagade, S.A. Mandavgane. (2010. Mesoporous Silica from Rice Husk Ash. Bulletin of Chemical Reaction Engineering and Catalysis, 5 (2: 63-67. doi:10.9767/bcrec.5.2.793.63-67][DOI: http://dx.doi.org/10.9767/bcrec.5.2.793.63-67

  9. Production and Application of Olivine Nano-Silica in Concrete

    Science.gov (United States)

    Mardiana, Oesman; Haryadi

    2017-05-01

    The aim of this research was to produce nano silica by synthesis of nano silica through extraction and dissolution of ground olivine rock, and applied the nano silica in the design concrete mix. The producing process of amorphous silica used sulfuric acid as the dissolution reagent. The separation of ground olivine rock occurred when the rock was heated in a batch reactor containing sulfuric acid. The results showed that the optimum mole ratio of olivine- acid was 1: 8 wherein the weight ratio of the highest nano silica generated. The heating temperature and acid concentration influenced the mass of silica produced, that was at temperature of 90 °C and 3 M acid giving the highest yield of 44.90%. Characterization using Fourier Transform Infrared (FTIR ) concluded that amorphous silica at a wavenumber of 1089 cm-1 indicated the presence of siloxane, Si-O-Si, stretching bond. Characterization using Scanning Electron Microscope - Energy Dispersive Spectroscopy (SEM-EDS) showed the surface and the size of the silica particles. The average size of silica particles was between 1-10 μm due to the rapid aggregation of the growing particles of nano silica into microparticles, caused of the pH control was not fully achieved.

  10. Pumping Iron and Silica Bodybuilding

    Science.gov (United States)

    Mcnair, H.; Brzezinski, M. A.; Krause, J. W.; Parker, C.; Brown, M.; Coale, T.; Bruland, K. W.

    2016-02-01

    The availability of dissolved iron influences the stoichiometry of nutrient uptake by diatoms. Under nutrient replete conditions diatoms consume silicic acid and nitrate in a 1:1 ratio, this ratio increases under iron stress. Using the tracers 32Si and PDMPO, the total community and group-specific silica production rates were measured along a gradient of dissolved iron in an upwelling plume off the California coast. At each station, a control (ambient silicic acid) and +20 µM silicic acid treatment were conducted with each tracer to determine whether silicic acid limitation controlled the rate of silica production. Dissolved iron was 1.3 nmol kg-1 nearshore and decreased to 0.15 nmol kg-1 offshore. Silicic acid decreased more rapidly than nitrate, it was nearly 9 µM higher in the nearshore and 7 µM lower than nitrate in the middle of the transect where the iron concentration had decreased. The rate of diatom silica production decreased in tandem with silicic acid concentration, and silica production limitation by low silicic acid was most pronounced when iron concentrations were >0.4 nmol kg-1. The composition of the diatom assemblage shifted from Chaetoceros spp. dominated nearshore to a more sparse pennate-dominated assemblage offshore. Changes in taxa-specific silica production rates will be reported based on examination of PDMPO labeled cells using confocal microscopy.

  11. Isogeometric shell formulation based on a classical shell model

    KAUST Repository

    Niemi, Antti

    2012-09-04

    This paper constitutes the first steps in our work concerning isogeometric shell analysis. An isogeometric shell model of the Reissner-Mindlin type is introduced and a study of its accuracy in the classical pinched cylinder benchmark problem presented. In contrast to earlier works [1,2,3,4], the formulation is based on a shell model where the displacement, strain and stress fields are defined in terms of a curvilinear coordinate system arising from the NURBS description of the shell middle surface. The isogeometric shell formulation is implemented using the PetIGA and igakit software packages developed by the authors. The igakit package is a Python package used to generate NURBS representations of geometries that can be utilised by the PetIGA finite element framework. The latter utilises data structures and routines of the portable, extensible toolkit for scientific computation (PETSc), [5,6]. The current shell implementation is valid for static, linear problems only, but the software package is well suited for future extensions to geometrically and materially nonlinear regime as well as to dynamic problems. The accuracy of the approach in the pinched cylinder benchmark problem and present comparisons against the h-version of the finite element method with bilinear elements. Quadratic, cubic and quartic NURBS discretizations are compared against the isoparametric bilinear discretization introduced in [7]. The results show that the quadratic and cubic NURBS approximations exhibit notably slower convergence under uniform mesh refinement as the thickness decreases but the quartic approximation converges relatively quickly within the standard variational framework. The authors future work is concerned with building an isogeometric finite element method for modelling nonlinear structural response of thin-walled shells undergoing large rigid-body motions. The aim is to use the model in a aeroelastic framework for the simulation of flapping wings.

  12. Simulation study of 3–5 keV x-ray conversion efficiency from Ar K-shell vs. Ag L-shell targets on the National Ignition Facility laser

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, G. E., E-mail: kemp10@llnl.gov; Colvin, J. D.; Fournier, K. B.; May, M. J.; Barrios, M. A.; Patel, M. V.; Scott, H. A.; Marinak, M. M. [Lawrence Livermore National Laboratory, Livermore, California 94550-9698 (United States)

    2015-05-15

    Tailored, high-flux, multi-keV x-ray sources are desirable for studying x-ray interactions with matter for various civilian, space and military applications. For this study, we focus on designing an efficient laser-driven non-local thermodynamic equilibrium 3–5 keV x-ray source from photon-energy-matched Ar K-shell and Ag L-shell targets at sub-critical densities (∼n{sub c}/10) to ensure supersonic, volumetric laser heating with minimal losses to kinetic energy, thermal x rays and laser-plasma instabilities. Using HYDRA, a multi-dimensional, arbitrary Lagrangian-Eulerian, radiation-hydrodynamics code, we performed a parameter study by varying initial target density and laser parameters for each material using conditions readily achievable on the National Ignition Facility (NIF) laser. We employ a model, benchmarked against Kr data collected on the NIF, that uses flux-limited Lee-More thermal conductivity and multi-group implicit Monte-Carlo photonics with non-local thermodynamic equilibrium, detailed super-configuration accounting opacities from CRETIN, an atomic-kinetics code. While the highest power laser configurations produced the largest x-ray yields, we report that the peak simulated laser to 3–5 keV x-ray conversion efficiencies of 17.7% and 36.4% for Ar and Ag, respectively, occurred at lower powers between ∼100–150 TW. For identical initial target densities and laser illumination, the Ag L-shell is observed to have ≳10× higher emissivity per ion per deposited laser energy than the Ar K-shell. Although such low-density Ag targets have not yet been demonstrated, simulations of targets fabricated using atomic layer deposition of Ag on silica aerogels (∼20% by atomic fraction) suggest similar performance to atomically pure metal foams and that either fabrication technique may be worth pursuing for an efficient 3–5 keV x-ray source on NIF.

  13. Effect of silica particle size on macrophage inflammatory responses.

    Directory of Open Access Journals (Sweden)

    Toshimasa Kusaka

    Full Text Available Amorphous silica particles, such as nanoparticles (<100 nm diameter particles, are used in a wide variety of products, including pharmaceuticals, paints, cosmetics, and food. Nevertheless, the immunotoxicity of these particles and the relationship between silica particle size and pro-inflammatory activity are not fully understood. In this study, we addressed the relationship between the size of amorphous silica (particle dose, diameter, number, and surface area and the inflammatory activity (macrophage phagocytosis, inflammasome activation, IL-1β secretion, cell death and lung inflammation. Irrespective of diameter size, silica particles were efficiently internalized by mouse bone marrow-derived macrophages via an actin cytoskeleton-dependent pathway, and induced caspase-1, but not caspase-11, activation. Of note, 30 nm-1000 nm diameter silica particles induced lysosomal destabilization, cell death, and IL-1β secretion at markedly higher levels than did 3000 nm-10000 nm silica particles. Consistent with in vitro results, intra-tracheal administration of 30 nm silica particles into mice caused more severe lung inflammation than that of 3000 nm silica particles, as assessed by measurement of pro-inflammatory cytokines and neutrophil infiltration in bronchoalveolar lavage fluid of mice, and by the micro-computed tomography analysis. Taken together, these results suggest that silica particle size impacts immune responses, with submicron amorphous silica particles inducing higher inflammatory responses than silica particles over 1000 nm in size, which is ascribed not only to their ability to induce caspase-1 activation but also to their cytotoxicity.

  14. Influence of organic solvents on interfacial water at surfaces of silica gel and partially silylated fumed silica

    International Nuclear Information System (INIS)

    Turov, V.V.; Gun'ko, V.M.; Tsapko, M.D.; Bogatyrev, V.M.; Skubiszewska-Zieba, J.; Leboda, R.; Ryczkowski, J.

    2004-01-01

    The effects of organic solvents (dimethylsulfoxide-d 6 (DMSO-d 6 ), chloroform-d, acetone-d 6 , and acetonitrile-d 3 ) on the properties of interfacial water at surfaces of silica gel Si-40 and partially silylated fumed silica A-380 were studied by means of the 1 H NMR spectroscopy with freezing-out of adsorbed water at 180 1 H NMR investigations were also analysed on the basis of the structural characteristics of silicas and quantum chemical calculations of the chemical shifts δ H and solvent effects. DMSO-d 6 and acetonitrile-d 3 are poorly miscible with water in silica gel pores in contrast to the bulk liquids. DMSO-d 6 and chloroform-d affect the structure of the interfacial water weaker than acetone-d 6 and acetonitrile-d 3 at amounts of liquids greater than the pore volume. Acetone-d 6 and acetonitrile-d 3 can displace water from pores under this condition. The chemical shift of protons in water adsorbed on silica gel is 3.5-6.5 ppm, which corresponds to the formation of two to four hydrogen bonds per molecule. Water adsorbed on partially silylated fumed silica has two 1 H NMR signals at 5 and 1.1-1.7 ppm related to different structures (droplets and small clusters) of the interfacial water

  15. Silica and lung cancer: a controversial issue.

    Science.gov (United States)

    Pairon, J C; Brochard, P; Jaurand, M C; Bignon, J

    1991-06-01

    The role of crystalline silica in lung cancer has long been the subject of controversy. In this article, we review the main experimental and epidemiological studies dealing with this problem. Some evidence for a genotoxic potential of crystalline silica has been obtained in the rare in vitro studies published to date. In vivo studies have shown that crystalline silica is carcinogenic in the rat; the tumour types appear to vary according to the route of administration. In addition, an association between carcinogenic and fibrogenic potency has been observed in various animal species exposed to crystalline silica. An excess of lung cancer related to occupational exposure to crystalline silica is reported in many epidemiological studies, regardless of the presence of silicosis. However, most of these studies are difficult to interpret because they do not correctly take into account associated carcinogens such as tobacco smoke and other occupational carcinogens. An excess of lung cancer is generally reported in studies based on silicosis registers. Overall, experimental and human studies suggest an association between exposure to crystalline silica and an excess of pulmonary malignancies. Although the data available are not sufficient to establish a clear-cut causal relationship in humans, an association between the onset of pneumoconiosis and pulmonary malignancies is probable. In contrast, experimental observations have given rise to a pathophysiological mechanism that might account for a putative carcinogenic potency of crystalline silica.

  16. New Silica Magnetite Sorbent: The Influence of Variations of Sodium Silicate Concentrations on Silica Magnetite Character

    Science.gov (United States)

    Azmiyawati, C.; Pratiwi, P. I.; Darmawan, A.

    2018-04-01

    The adsorption capacity of an adsorbent is determined by the adsorbent and the adsorbate properties. The character of the adsorbent will play a major role in its ability to adsorb the corresponding adsorbate. Therefore, in this study we looked at the effects of variations of sodium silicate concentrations on the resulting magnetite silica adsorbent properties. The application of silica coating on the magnetite was carried out through a sol-gel process with sodium silicate and HCl precursors. Based on the characterization data obtained, it was found that the silica coating on magnetite can increase the resistance to acid leaching, increase the particle size, but decrease the magnetic properties of the magnetite. Based on Gas Sorption Analyzer (GSA) and X-ray Difraction (XRD) data it can successively be determined that increase in concentration of sodium silicate will increase the surface area and amorphous structure of the Silica Magnetie.

  17. Dispersibility of silica fume in mortar and its effect on properties of mortar. Silica fume no bunsan to mortar no shotokusei

    Energy Technology Data Exchange (ETDEWEB)

    Oga, H; Uomoto, T [The University of Tokyo, Tokyo (Japan). Institute of Industrial Science

    1992-08-01

    Effect of silica fume dispersibility on concrete characteristics was discussed. Properties of mortar mixed with silica fume to exhibit compression strength varied with displacement rates, patterns, and mixing time of silica fume. In submerged curing age of 28 days, the compression strength in a mortar mixed with silica fume at 10% was affected only very little by the mixing time for both pelletizing and non-pelletizing types for up to 180 seconds. The strength increased thereafter with the mixing time. The compression strength at 1020 seconds showed higher value by about 150 kgf/cm [sup 2] than when no silica fume is added, with a difference because of patterns disappearing. In the case of a mixing time of 1020 seconds, neutralization depth receives very little effect from a pattern difference, and decreases with increasing displacement rate. Neutralization coefficient of the mortar mixed with silica fume at 10% decreased with the mixing time, and it was possible to suppress the neutralization coefficient to 25% of the case without silica fume addition in a 1020-second mixing. 7 refs., 8 figs., 1 tab.

  18. Synthesis of Silica Nanoparticles by Sol-Gel: Size-Dependent Properties, Surface Modification, and Applications in Silica-Polymer Nano composites-A Review

    International Nuclear Information System (INIS)

    Ismail, A.R.; Vejayakumaran, P.

    2012-01-01

    Application of silica nanoparticles as fillers in the preparation of nano composite of polymers has drawn much attention, due to the increased demand for new materials with improved thermal, mechanical, physical, and chemical properties. Recent developments in the synthesis of monodispersed, narrow-size distribution of nanoparticles by sol-gel method provide significant boost to development of silica-polymer nano composites. This paper is written by emphasizing on the synthesis of silica nanoparticles, characterization on size-dependent properties, and surface modification for the preparation of homogeneous nano composites, generally by sol-gel technique. The effect of nano silica on the properties of various types of silica-polymer composites is also summarized.

  19. Silica sol as grouting material: a physio-chemical analysis.

    Science.gov (United States)

    Sögaard, Christian; Funehag, Johan; Abbas, Zareen

    2018-01-01

    At present there is a pressing need to find an environmentally friendly grouting material for the construction of tunnels. Silica nanoparticles hold great potential of replacing the organic molecule based grouting materials currently used for this purpose. Chemically, silica nanoparticles are similar to natural silicates which are essential components of rocks and soil. Moreover, suspensions of silica nanoparticles of different sizes and desired reactivity are commercially available. However, the use of silica nanoparticles as grouting material is at an early stage of its technological development. There are some critical parameters such as long term stability and functionality of grouted silica that need to be investigated in detail before silica nanoparticles can be considered as a reliable grouting material. In this review article we present the state of the art regarding the chemical properties of silica nanoparticles commercially available, as well as experience gained from the use of silica as grouting material. We give a detailed description of the mechanisms underlying the gelling of silica by different salt solutions such as NaCl and KCl and how factors such as particle size, pH, and temperature affect the gelling and gel strength development. Our focus in this review is on linking the chemical properties of silica nanoparticles to the mechanical properties to better understand their functionality and stability as grouting material. Along the way we point out areas which need further research.

  20. Ordered nanoporous silica as carriers for improved delivery of water insoluble drugs: a comparative study between three dimensional and two dimensional macroporous silica

    Directory of Open Access Journals (Sweden)

    Wang Y

    2013-10-01

    Full Text Available Ying Wang, Qinfu Zhao, Yanchen Hu, Lizhang Sun, Ling Bai, Tongying Jiang, Siling WangDepartment of Pharmaceutics, Shenyang Pharmaceutical University, Liaoning Province, People’s Republic of ChinaAbstract: The goal of the present study was to compare the drug release properties and stability of the nanoporous silica with different pore architectures as a matrix for improved delivery of poorly soluble drugs. For this purpose, three dimensional ordered macroporous (3DOM silica with 3D continuous and interconnected macropores of different sizes (200 nm and 500 nm and classic mesoporous silica (ie, Mobil Composition of Matter [MCM]-41 and Santa Barbara Amorphous [SBA]-15 with well-ordered two dimensional (2D cylindrical mesopores were successfully fabricated and then loaded with the model drug indomethacin (IMC via the solvent deposition method. Scanning electron microscopy (SEM, N2 adsorption, differential scanning calorimetry (DSC, and X-ray diffraction (XRD were applied to systematically characterize all IMC-loaded nanoporous silica formulations, evidencing the successful inclusion of IMC into nanopores, the reduced crystallinity, and finally accelerated dissolution of IMC. It was worth mentioning that, in comparison to 2D mesoporous silica, 3DOM silica displayed a more rapid release profile, which may be ascribed to the 3D interconnected pore networks and the highly accessible surface areas. The results obtained from the stability test indicated that the amorphous state of IMC entrapped in the 2D mesoporous silica (SBA-15 and MCM-41 has a better physical stability than in that of 3DOM silica. Moreover, the dissolution rate and stability of IMC loaded in 3DOM silica was closely related to the pore size of macroporous silica. The colorimetric 3-(4,5-Dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT and Cell Counting Kit (CCK-8 assays in combination with direct morphology observations demonstrated the good biocompatibility of nanoporous