A polyacrylonitrile copolymer-silica template for three-dimensional hierarchical porous carbon as a Pt catalyst support for the oxygen reduction reaction.

Science.gov (United States)

Liu, Minmin; Li, Jian; Cai, Chao; Zhou, Ziwei; Ling, Yun; Liu, Rui

2017-08-01

Herein, we report a novel route to construct a hierarchical three-dimensional porous carbon (3DC) through a copolymer-silica assembly. In the synthesis, silica acts as a hard template and leads to the formation of an interconnected 3D macropore, whereas styrene-co-acrylonitrile polymer has been used as both a carbon source and a soft template for micro- and meso-pores. The obtained 3DC materials possess a large surface area (∼550.5 m 2 g -1 ), which facilitates high dispersion of Pt nanoparticles on the carbon support. The 3DC-supported Pt electrocatalyst shows excellent performance in the oxygen reduction reaction (ORR). The easy processing ability along with the characteristics of hierarchical porosity offers a new strategy for the preparation of carbon nanomaterials for energy application.

Meso-scale modelling of the heat conductivity effect on the shock response of a porous material

Science.gov (United States)

Resnyansky, A. D.

2017-06-01

Understanding of deformation mechanisms of porous materials under shock compression is important for tailoring material properties at the shock manufacturing of advanced materials from substrate powders and for studying the response of porous materials under shock loading. Numerical set-up of the present work considers a set of solid particles separated by air representing a volume of porous material. Condensed material in the meso-scale set-up is simulated with a viscoelastic rate sensitive material model with heat conduction formulated from the principles of irreversible thermodynamics. The model is implemented in the CTH shock physics code. The meso-scale CTH simulation of the shock loading of the representative volume reveals the mechanism of pore collapse and shows in detail the transition from a high porosity case typical for abnormal Hugoniot response to a moderate porosity case typical for conventional Hugoniot response. Results of the analysis agree with previous analytical considerations and support hypotheses used in the two-phase approach.

Synthesis and Characterization of Meso porous Material Functionalized with Different Silylating Agent and Their Capability to Remove Cu2+

International Nuclear Information System (INIS)

Zaini Hamzah; Norhidayu Narawi; Hamizah Mohd Rasid; Amira Nazirah Mohd Yusoff

2012-01-01

Meso porous material MCM-41 with uniform hexagonally ordered pores in range of 2-10 nm was synthesized through hydrothermal method. The synthesis started from highly pure silica source known as Ludox which act as an active source of silica in the presence of organic surfactant (CTABr) as structure-directing agent. MCM-41 has been functionalized with the organic group known as 3-aminopropyltriethoxysilane (APTES), 3-mercaptopropyltrimethoxysilane (MPTMS), and chloropropyl triethoxysilane (CPTES) by co-condensation method in order to enhance the surface hydrophobicity of MCM-41. The increasing hydrophobicity will lead to efficient reaction specifically for organic reaction in organic solvent. The resulting materials were characterized with various techniques which are PXRD, FTIR, NMR, Elemental Analysis and AAS. The formation of uniform hexagonal framework of synthesized materials was shown in PXRD result. The functionalized groups of modified MCM-41 can be characterized via FTIR and 13 C-NMR results. The Elemental Analysis shows the percentage of nitrogen, carbon, hydrogen and sulphur in MCM-41 and functionalized MCM-41. From AAS, MCM-41 MPTMS has high capability for removal of Cu (II) in aqueous solution compared with others. (author)

Impact of pore characteristics of silica materials on loading capacity and release behavior of ibuprofen.

Science.gov (United States)

Numpilai, Thanapha; Muenmee, Suthaporn; Witoon, Thongthai

2016-02-01

Impact of pore characteristics of porous silica supports on loading capacity and release behavior of ibuprofen was investigated. The porous silica materials and ibuprofen-loaded porous silica materials were thoroughly characterized by N2-sorption, thermal gravimetric and derivative weight analyses (TG-DTW), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) to determine the physical properties of materials, amount of ibuprofen adsorbed and position of ibuprofen. The detailed characterization reveals that the ibuprofen molecules adsorbed inside the mesopores. Increasing the mesopore size from 5nm to 10nm increased the ibuprofen loading from 0.74 to 0.85mmol/g, respectively. Incorporation of macropore into the structure of porous silica materials enhanced the ibuprofen loading capacity of 11.8-20.3%. The ibuprofen-loaded bimodal meso-macroporous silica materials exhibited the highest dissolution of 92wt.% within an hour. The ibuprofen particles deposited on the external surface of the porous silica materials showed a lower dissolution rate than the ibuprofen adsorbed inside the mesopores due to the formation of ibuprofen crystalline. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis of porous carbon/silica nanostructured microfiber with ultrahigh surface area

Science.gov (United States)

Zhou, Dan; Dong, Yan; Cui, Liru; Lin, Huiming; Qu, Fengyu

2014-12-01

Carbon/silica-nanostructured microfibers were synthesized via electrospinning method using phenol-formaldehyde resin and tetraethyl orthosilicate as carbon and silica precursor with triblock copolymer Pluronic P123 as soft template. The prepared samples show uniform microfiber structure with 1 μm in diameter and dozens of microns in length. Additionally, the mesopores in the material is about 2-6 nm. When the silica component was removed by HF, the porous carbon microfibers (PCMFs) were obtained. In addition, after the carbon/silica composites were calcined in air, the porous silica microfibers (PSiMFs) were obtained, revealing the converse porous nanostructure as PCMFs. It is a simple way to prepare PCMFs and PSiMFs with silica and carbon as the template to each other. Additionally, PCMFs possess an ultrahigh specific surface area (2,092 m2 g-1) and large pore volume. The electrochemical performance of the prepared PCMF material was investigated in 6.0 M KOH electrolyte. The PCMF electrode exhibits a high specific capacitance (252 F g-1 at 0.5 A g-1). Then, superior cycling stability (97 % retention after 4,000 cycles) mainly is due to its unique nanostructure.

Study of water radiolysis in porous media

International Nuclear Information System (INIS)

Rotureau, Patricia

2001-08-01

The understanding of the production of H 2 in the radiolysis of water confined into pores of concrete is important for the disposal of radioactive waste. In order to describe the mechanisms of water radiolysis in such heterogeneous porous systems we have studied the behaviour under gamma radiation of water confined in porous silica glasses with pores going from 8 to 300 nm of diameter and meso-porous molecular sieves (MCM-41). The radiolytic yields of hydroxyl radicals, hydrated electron and dihydrogen, have been determined with respect to the pore size of materials. The increase of these radiolytic yields compared to those of free water allowed us to show a charge transfer from silica to confined water. On the other hand the kinetics of hydrated electron reactions measured by pulse radiolysis are not modified. (author) [fr

One-step synthesis of dye-incorporated porous silica particles

Energy Technology Data Exchange (ETDEWEB)

Liu Qing; DeShong, Philip; Zachariah, Michael R., E-mail: mrz@umd.edu [University of Maryland, Department of Chemistry and Biochemistry (United States)

2012-07-15

Fluorescent nanoparticles have a variety of biomedical applications as diagnostics and traceable drug delivery agents. Highly fluorescent porous silica nanoparticles were synthesized in a water/oil phase by a microemulsion method. What is unique about the resulting porous silica nanoparticles is the combination of a single-step, efficient synthesis and the high stability of its fluorescence emission in the resulting materials. The key of the success of this approach is the choice of a lipid dye that functions as a surrogate surfactant in the preparation. The surfactant dye was incorporated at the interface of the inorganic silica matrix and organic environment (pore template), and thus insures the stability of the dye-silica hybrid structure. The resulting fluorescent silica materials have a number of properties that make them attractive for biomedical applications: the availability of various color of the resulting nanoparticle from among a broad spectrum of commercially dyes, the controllablity of pore size (diameters of {approx}5 nm) and particle size (diameters of {approx}40 nm) by adjusting template monomer concentration and the water/oil ratio, and the stability and durability of particle fluorescence because of the deep insertion of surfactant's tail into the silica matrix.

Effect of Nano Silica on the Physical Property of Porous Concrete Pavement

Science.gov (United States)

Yusak, Mohd Ibrahim Mohd; Ezree Abdullah, Mohd; Putra Jaya, Ramadhansyah; Rosli Hainin, Mohd; Ibrahim, Mohd Haziman Wan

2017-08-01

Rice husk can be categorized as an organic waste material from paddy industries. Silica is a major inorganic element of the rice husk. The aim of present study is to evaluate the effect of Nano silica on the physical properties of porous concrete pavement. Rice husk has been burned in the furnace (650°C for 6 hours) and ground for four different grinding times (33, 48, 63 and 81 hours). Five types of mixes were prepared to evaluate the different Nano silica grinding time. A Nano silica dosage of 10% by weight of binder was used throughout the experiments. The physical properties were examined through compressive strength, transmission electron microscopy and x-ray fluorescence. The experimental results indicate that the different Nano size gives a different effect to porous concrete strength. Based on the results obtained, Nano silica ground for 63 hours (65.84nm) gives the best result and performance to porous concrete pavement specimens.

The effect of NaOH and KOH on the characterization of meso porous AlOOH nano structures in the hydrothermal route

International Nuclear Information System (INIS)

Haghnazari, N.; Abdollahifar, M.; Jahani, F.

2014-01-01

Meso porous AlOOH was synthesized by hydrothermal treatment from aluminium nitrate and NaOH or KOH. The effect of NaOH and KOH as precipitating agents on the characterization of samples were investigated. XRD, Ftir, FESEM and N 2 adsorption-desorption analytical techniques were used to characterize the products. Our results showed that using KOH as precipitating agent was favour-able for the formation of meso porous and crystalline AlOOH with high Bet-specific surface area of 98 m 2 /g. (Author)

The effect of NaOH and KOH on the characterization of meso porous AlOOH nano structures in the hydrothermal route

Energy Technology Data Exchange (ETDEWEB)

Haghnazari, N.; Abdollahifar, M.; Jahani, F., E-mail: abdollahifar@gmail.com [Islamic Azad University, Kermanshah Branch, Department of Chemical Engineering, 67131 Kermanshah (Iran, Islamic Republic of)

2014-10-01

Meso porous AlOOH was synthesized by hydrothermal treatment from aluminium nitrate and NaOH or KOH. The effect of NaOH and KOH as precipitating agents on the characterization of samples were investigated. XRD, Ftir, FESEM and N{sub 2} adsorption-desorption analytical techniques were used to characterize the products. Our results showed that using KOH as precipitating agent was favour-able for the formation of meso porous and crystalline AlOOH with high Bet-specific surface area of 98 m{sup 2}/g. (Author)

Synthesis of porous carbon/silica nanostructured microfiber with ultrahigh surface area

Energy Technology Data Exchange (ETDEWEB)

Zhou, Dan; Dong, Yan; Cui, Liru; Lin, Huiming, E-mail: hiuminglin@gmail.com; Qu, Fengyu, E-mail: qufengyu2012@yahoo.cn, E-mail: qufengyu@hrbnu.edu.cn [Harbin Normal University, College of Chemistry and Chemical Engineering (China)

2014-12-15

Carbon/silica-nanostructured microfibers were synthesized via electrospinning method using phenol-formaldehyde resin and tetraethyl orthosilicate as carbon and silica precursor with triblock copolymer Pluronic P123 as soft template. The prepared samples show uniform microfiber structure with ∼1 μm in diameter and dozens of microns in length. Additionally, the mesopores in the material is about 2–6 nm. When the silica component was removed by HF, the porous carbon microfibers (PCMFs) were obtained. In addition, after the carbon/silica composites were calcined in air, the porous silica microfibers (PSiMFs) were obtained, revealing the converse porous nanostructure as PCMFs. It is a simple way to prepare PCMFs and PSiMFs with silica and carbon as the template to each other. Additionally, PCMFs possess an ultrahigh specific surface area (2,092 m{sup 2} g{sup −1}) and large pore volume. The electrochemical performance of the prepared PCMF material was investigated in 6.0 M KOH electrolyte. The PCMF electrode exhibits a high specific capacitance (252 F g{sup −1} at 0.5 A g{sup −1}). Then, superior cycling stability (97 % retention after 4,000 cycles) mainly is due to its unique nanostructure.

The retained templates as "helpers" for the spherical meso-silica in adsorption of heavy metals and impacts of solution chemistry.

Science.gov (United States)

Liang, Zhijie; Shi, Wenxin; Zhao, Zhiwei; Sun, Tianyi; Cui, Fuyi

2017-06-15

The spherical mesoporous silica (meso-silica) MCM-41 and those with different dosage of the retained templates were prepared and characterized. Particularly, effects of the retained template and its dosage on the adsorption of typical heavy metals (Cu 2+ and Cd 2+ ) in the synthesized materials were investigated. The results indicated that the retained templates acted as "helpers" for the adsorption of Cu 2+ and Cd 2+ in the spherical meso-silica MCM-41, and the maximum adsorption capacities (Q max ) increased with the increase of the retained template dosage. The interaction between the metal ions and the cationic heads of the templates contributed to the enhancement effect due to the anions (Cl - and OH - ) electronically adsorbed on the interface of the template micelles. Additionally, the presented results indicated that the adsorption of Cu 2+ and Cd 2+ depended on pH and high ion strength of the solution but not on the coexisted humic acid. Copyright © 2017 Elsevier Inc. All rights reserved.

Silica decorated on porous activated carbon nanofiber composites for high-performance supercapacitors

Science.gov (United States)

Kim, So Yeun; Kim, Bo-Hye

2016-10-01

A hybrid of silica decorated on porous activated carbon nanofibers (ACNFs) is fabricated in the form of a web via electrospinning and an activation process as an electrode material for electrochemical capacitors in an organic electrolyte. The introduction of PhSiH3 (PS) into the polyacrylonitrile (PAN) solution induces a porous ACNF structure containing silica nanoparticles (NPs) via the spontaneous sol-gel process of PS by steam in the subsequent physical activation process. These inorganic-organic hybrid composites of porous ACNF containing silica NPs show superior specific capacitance and energy density in electrochemical tests, along with good rate capability and excellent cycle life in an organic electrolyte, which is attributed to the combination of ACNF's high surface area and silica's hydrophilicity. The electrochemical performance decreases with increasing PS concentration, and this trend is consistent with the specific surface area results, which reveal the rapid formation of a double layer.

Study of the radiolysis of water in porous media

International Nuclear Information System (INIS)

Rotureau, P.

2004-01-01

The understanding of the production of H 2 in the radiolysis of water confined into pores of concrete is important for the disposal of radioactive waste. In order to describe the mechanisms of water radiolysis in such heterogeneous porous systems we have studied the behaviour under gamma radiation of water confined in porous silica glasses with pores going from 8 to 300 nm of diameter and meso-porous molecular sieves (MCM-41). The radiolytic yields of hydroxyl radicals, hydrated electron and dihydrogen, have been determined with respect to the pore size of materials. The increase of these radiolytic yields compared to those of free water allowed us to show a charge transfer from silica to confined water. On the other hand the kinetics of hydrated electron reactions measured by pulse radiolysis are not modified. (author) [fr

Impact of pore characteristics of silica materials on loading capacity and release behavior of ibuprofen

Energy Technology Data Exchange (ETDEWEB)

Numpilai, Thanapha [Department of Chemical Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900 (Thailand); Muenmee, Suthaporn [Department of Chemical Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900 (Thailand); Center for Advanced Studies in Nanotechnology and Its Applications in Chemical Food and Agricultural Industries, Kasetsart University, Bangkok 10900 (Thailand); Witoon, Thongthai, E-mail: fengttwi@ku.ac.th [Department of Chemical Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900 (Thailand); Center for Advanced Studies in Nanotechnology and Its Applications in Chemical Food and Agricultural Industries, Kasetsart University, Bangkok 10900 (Thailand); NANOTEC-KU-Center of Excellence on Nanoscale Materials Design for Green Nanotechnology, Kasetsart University, Bangkok 10900 (Thailand)

2016-02-01

Impact of pore characteristics of porous silica supports on loading capacity and release behavior of ibuprofen was investigated. The porous silica materials and ibuprofen-loaded porous silica materials were thoroughly characterized by N{sub 2}-sorption, thermal gravimetric and derivative weight analyses (TG-DTW), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) to determine the physical properties of materials, amount of ibuprofen adsorbed and position of ibuprofen. The detailed characterization reveals that the ibuprofen molecules adsorbed inside the mesopores. Increasing the mesopore size from 5 nm to 10 nm increased the ibuprofen loading from 0.74 to 0.85 mmol/g, respectively. Incorporation of macropore into the structure of porous silica materials enhanced the ibuprofen loading capacity of 11.8–20.3%. The ibuprofen-loaded bimodal meso-macroporous silica materials exhibited the highest dissolution of 92 wt.% within an hour. The ibuprofen particles deposited on the external surface of the porous silica materials showed a lower dissolution rate than the ibuprofen adsorbed inside the mesopores due to the formation of ibuprofen crystalline. - Highlights: • Impacts of pore characteristics of supports on adsorption and release of ibuprofen • Increasing mesopore size increased the ibuprofen loading and dissolution rate. • Macropores reduced the diffusion pathway of ibuprofen and dissolution medium.

Impact of pore characteristics of silica materials on loading capacity and release behavior of ibuprofen

International Nuclear Information System (INIS)

Numpilai, Thanapha; Muenmee, Suthaporn; Witoon, Thongthai

2016-01-01

Impact of pore characteristics of porous silica supports on loading capacity and release behavior of ibuprofen was investigated. The porous silica materials and ibuprofen-loaded porous silica materials were thoroughly characterized by N 2 -sorption, thermal gravimetric and derivative weight analyses (TG-DTW), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) to determine the physical properties of materials, amount of ibuprofen adsorbed and position of ibuprofen. The detailed characterization reveals that the ibuprofen molecules adsorbed inside the mesopores. Increasing the mesopore size from 5 nm to 10 nm increased the ibuprofen loading from 0.74 to 0.85 mmol/g, respectively. Incorporation of macropore into the structure of porous silica materials enhanced the ibuprofen loading capacity of 11.8–20.3%. The ibuprofen-loaded bimodal meso-macroporous silica materials exhibited the highest dissolution of 92 wt.% within an hour. The ibuprofen particles deposited on the external surface of the porous silica materials showed a lower dissolution rate than the ibuprofen adsorbed inside the mesopores due to the formation of ibuprofen crystalline. - Highlights: • Impacts of pore characteristics of supports on adsorption and release of ibuprofen • Increasing mesopore size increased the ibuprofen loading and dissolution rate. • Macropores reduced the diffusion pathway of ibuprofen and dissolution medium.

Sonochemical synthesis and photocatalytic activity of meso- and macro-porous TiO2 for oxidation of toluene

International Nuclear Information System (INIS)

Yang Liu; Yan Li; Wang Yuntao; Xie Lei; Zheng Jie; Li Xingguo

2008-01-01

Meso-and macro-porous TiO 2 were synthesized by ultrasonic induced solvothermal method. Octadecylamine as a soft template was used to direct the formation of porous structure. The as-prepared porous TiO 2 was characterized by low angle and wide angle X-ray diffraction, N 2 adsorption-desorption isotherms and BET surface area. The energy influence of ultrasound and heat and concentration of nitric acid for post extraction on formation of porous structure were investigated. The photocatalytic activities of TiO 2 were investigated by degrading toluene gas under UV light. The results revealed that proper energy facilitates the formation of porous structure and too low concentration of nitric acid cannot extract template from pores. The photocatalytic activities of TiO 2 with porous structure are higher than those of nonporous ones

Effect of Synthesis Time on Morphology of Hollow Porous Silica Microspheres

Directory of Open Access Journals (Sweden)

Qian CHEN

2012-03-01

Full Text Available Hollow porous silica microspheres may be applicable as containers for the controlled release in drug delivery systems (DDS, foods, cosmetics, agrochemical, textile industry, and in other technological encapsulation use. In order to control the surface morphological properties of the silica microspheres, the effect of synthesis time on their formation was studied by a method of water-in-oil (W/O emulsion mediated sol-gel techniques. An aqueous phase of water, ammonium hydroxide and a surfactant Tween 20 was emulsified in an oil phase of 1-octanol with a stabilizer, hydroxypropyl cellulose (HPC, and a surfactant, sorbitan monooleate (Span 80 with low hydrophile-lipophile balance (HLB value. Tetraethyl orthosilicate (TEOS as a silica precursor was added to the emulsion. The resulting silica particles at different synthesis time 24, 48, and 72 hours were air-dried at room temperature and calcinated at 773 K for 3 hours. The morphology of the particles was characterized by scanning electron microscopy and the particle size distribution was measured by laser diffraction. The specific surface areas were studied by 1-point BET method, and pore sizes were measured by Image Tool Software. Both dense and porous silica microspheres were observed after all three syntheses. Hollow porous silica microspheres were formed at 24 and 48 hours synthesis time. Under base catalyzed sol-gel solution, the size of silica particles was in the range of 5.4 μm to 8.2 μm, and the particles had surface area of 111 m2/g – 380 m2/g. The longer synthesis time produced denser silica spheres with decreased pore sizes.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1344

Preparation and characterization of monodisperse large-porous silica microspheres as the matrix for protein separation.

Science.gov (United States)

Xia, Hongjun; Wan, Guangping; Zhao, Junlong; Liu, Jiawei; Bai, Quan

2016-11-04

High performance liquid chromatography (HPLC) is a kind of efficient separation technology and has been used widely in many fields. Micro-sized porous silica microspheres as the most popular matrix have been used for fast separation and analysis in HPLC. In this paper, the monodisperse large-porous silica microspheres with controllable size and structure were successfully synthesized with polymer microspheres as the templates and characterized. First, the poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) microspheres (P GMA-EDMA ) were functionalized with tetraethylenepentamine (TEPA) to generate amino groups which act as a catalyst in hydrolysis of tetraethyl orthosilicate (TEOS) to form Si-containing low molecular weight species. Then the low molecular weight species diffused into the functionalized P GMA-EDMA microspheres by induction force of the amino groups to form polymer/silica hybrid microspheres. Finally, the organic polymer templates were removed by calcination, and the large-porous silica microspheres were obtained. The compositions, morphology, size distribution, specific surface area and pore size distribution of the porous silica microspheres were characterized by infrared analyzer, scanning-electron microscopy, dynamic laser scattering, the mercury intrusion method and thermal gravimetric analysis, respectively. The results show that the agglomeration of the hybrid microspheres can be overcome when the templates were functionalized with TEPA as amination reagent, and the yield of 95.7% of the monodisperse large-porous silica microspheres can be achieved with high concentration of polymer templates. The resulting large-porous silica microspheres were modified with octadecyltrichlorosilane (ODS) and the chromatographic evaluation was performed by separating the proteins and the digest of BSA. The baseline separation of seven kinds of protein standards was achieved, and the column delivered a better performance when separating BSA digests

The micro and meso-porous materials. Characterization; Les materiaux micro et mesoporeux. Caracterisation

Energy Technology Data Exchange (ETDEWEB)

Thibault-Starzyk, F.

2004-10-01

The micro and meso-porous materials, called zeolites, are very important in the modern chemical industry and in petrochemistry. This book deals in particular with the study and the characterization of zeolites. Its aim is to give to generalist chemists the tools for approaching experimentally these particular materials. The main methods of study and characterization are gathered in eight chapters, and the authors stress on the specificities due to the porous system: -structural analysis by the diffraction methods; -infrared spectroscopy; -NMR; -micro-calorimetry; -adsorption thermodynamics; -methods using the programed temperature; -modeling; -reactivity: kinetics and chemical engineering. This book appeals to students, engineers or searchers, without previous knowledge on these materials, but having a bachelor's degree or a master degree in general chemistry. (O.M.)

Two-Stage Crystallizer Design for High Loading of Poorly Water-Soluble Pharmaceuticals in Porous Silica Matrices

Directory of Open Access Journals (Sweden)

Leia Dwyer

2017-05-01

Full Text Available While porous silica supports have been previously studied as carriers for nanocrystalline forms of poorly water-soluble active pharmaceutical ingredients (APIs, increasing the loading of API in these matrices is of great importance if these carriers are to be used in drug formulations. A dual-stage mixed-suspension, mixed-product removal (MSMPR crystallizer was designed in which the poorly soluble API fenofibrate was loaded into the porous matrices of pore sizes 35 nm–300 nm in the first stage, and then fed to a second stage in which the crystals were further grown in the pores. This resulted in high loadings of over 50 wt % while still producing nanocrystals confined to the pores without the formation of bulk-sized crystals on the surface of the porous silica. The principle was extended to another highly insoluble API, griseofulvin, to improve its loading in porous silica in a benchtop procedure. This work demonstrates a multi-step crystallization principle API in porous silica matrices with loadings high enough to produce final dosage forms of these poorly water-soluble APIs.

Porous silica from rice husk ash for tundish lining

International Nuclear Information System (INIS)

Ahmed, Y.M.Z; Ewais, E.M.

2007-01-01

Type of materials as well as its compressive strength and degree of porosity are the determinal parameters for deciding the suitability of its usage as lining for tundish in continuous casting of steel. Silica is one of the materials suitable for such application. High porosity degree with high compressive strength of its compacts is special demands for increasing its efficiency. The suitability of producing porous silica compacts from the combustion of rice husk ash (RHA) appropriate for this application is the objective of the present work. Experimental design technique was used to evaluate the effect of different parameters (i.e. firing temperature, time and compaction pressure) controlling both porosity degree and compressive strength of rice husk ash compacts. The results revealed that while the porosity degree of the compacts decreased with increasing the entire studied parameters, its compressive strength exhibits another trend especially at lower soaking time. At lower soaking time, increasing firing temperature leads to a slight decrease in the compressive strength and then increased thereafter. Porous silica compacts having 30% porosity and > 25 kg/cm/sup 2/ compressive strength suitable for tundish lining could obtain from the combustion of rice husk ash compacts. (author)

Selective porous gates made from colloidal silica nanoparticles

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Roberto Nisticò

2015-11-01

Full Text Available Highly selective porous films were prepared by spin-coating deposition of colloidal silica nanoparticles on an appropriate macroporous substrate. Silica nanoparticles very homogenous in size were obtained by sol–gel reaction of a metal oxide silica precursor, tetraethyl orthosilicate (TEOS, and using polystyrene-block-poly(ethylene oxide (PS-b-PEO copolymers as soft-templating agents. Nanoparticles synthesis was carried out in a mixed solvent system. After spin-coating onto a macroporous silicon nitride support, silica nanoparticles were calcined under controlled conditions. An organized nanoporous layer was obtained characterized by a depth filter-like structure with internal porosity due to interparticle voids. Permeability and size-selectivity were studied by monitoring the diffusion of probe molecules under standard conditions and under the application of an external stimulus (i.e., electric field. Promising results were obtained, suggesting possible applications of these nanoporous films as selective gates for controlled transport of chemical species in solution.

Thermally induced structural modifications and O2 trapping in highly porous silica nanoparticles

International Nuclear Information System (INIS)

Alessi, A.; Agnello, S.; Iovino, G.; Buscarino, G.; Melodia, E.G.; Cannas, M.; Gelardi, F.M.

2014-01-01

In this work we investigate by Raman spectroscopy the effect of isochronal (2 h) thermal treatments in air in the temperature range 200–1000 °C of amorphous silicon dioxide porous nanoparticles with diameters ranging from 5 up to 15 nm and specific surface 590–690 m 2 /g. Our results indicate that the amorphous structure changes similarly to other porous systems previously investigated, in fact superficial SiOH groups are removed, Si–O–Si linkages are created and the ring statistic is modified, furthermore these data evidence that the three membered rings do not contribute significantly to the Raman signal detected at about 495 cm −1 . In addition, after annealing at 900 and 1000 °C we noted the appearance of the O 2 emission at 1272 nm, absent in the not treated samples. The measure of the O 2 emission has been combined with electron paramagnetic resonance measurements of the γ irradiation induced HO · 2 radicals to investigate the O 2 content per mass unit of thin layers of silica. Our data reveal that the porous nanoparticles have a much lower ability to trap O 2 molecules per mass units than nonporous silica supporting a model by which O 2 trapping inside a surface layer of about 1 nm of silica is always limited. - Highlights: • O 2 emission and HO · 2 electron paramagnetic resonance signals are investigated. • Silica surface ability to trap O 2 molecules is explored by thermal treatments. • Raman study of thermally induced structural changes in porous silica nanoparticles. • Raman signal attributable to the three membered rings in silica

TiO2-Impregnated Porous Silica Tube and Its Application for Compact Air- and Water-Purification Units

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Tsuyoshi Ochiai

2015-09-01

Full Text Available A simple, convenient, reusable, and inexpensive air- and water-purification unit including a one-end sealed porous amorphous-silica (a-silica tube coated with TiO2 photocatalyst layers has been developed. The porous a-silica layers were formed through outside vapor deposition (OVD. TiO2 photocatalyst layers were formed through impregnation and calcination onto a-silica layers. The resulting porous TiO2-impregnated a-silica tubes were evaluated for air-purification capacity using an acetaldehyde gas decomposition test. The tube (8.5 mm e.d. × 150 mm demonstrated a 93% removal rate for high concentrations (ca. 300 ppm of acetaldehyde gas at a single-pass condition with a 250 mL/min flow rate under UV irradiation. The tube also demonstrated a water purification capacity at a rate 2.0 times higher than a-silica tube without TiO2 impregnation. Therefore, the tubes have a great potential for developing compact and in-line VOC removal and water-purification units.

Thermally induced structural modifications and O{sub 2} trapping in highly porous silica nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Alessi, A., E-mail: antonino.alessi@unipa.it; Agnello, S.; Iovino, G.; Buscarino, G.; Melodia, E.G.; Cannas, M.; Gelardi, F.M.

2014-12-15

In this work we investigate by Raman spectroscopy the effect of isochronal (2 h) thermal treatments in air in the temperature range 200–1000 °C of amorphous silicon dioxide porous nanoparticles with diameters ranging from 5 up to 15 nm and specific surface 590–690 m{sup 2}/g. Our results indicate that the amorphous structure changes similarly to other porous systems previously investigated, in fact superficial SiOH groups are removed, Si–O–Si linkages are created and the ring statistic is modified, furthermore these data evidence that the three membered rings do not contribute significantly to the Raman signal detected at about 495 cm{sup −1}. In addition, after annealing at 900 and 1000 °C we noted the appearance of the O{sub 2} emission at 1272 nm, absent in the not treated samples. The measure of the O{sub 2} emission has been combined with electron paramagnetic resonance measurements of the γ irradiation induced HO{sup ·}{sub 2} radicals to investigate the O{sub 2} content per mass unit of thin layers of silica. Our data reveal that the porous nanoparticles have a much lower ability to trap O{sub 2} molecules per mass units than nonporous silica supporting a model by which O{sub 2} trapping inside a surface layer of about 1 nm of silica is always limited. - Highlights: • O{sub 2} emission and HO{sup ·}{sub 2} electron paramagnetic resonance signals are investigated. • Silica surface ability to trap O{sub 2} molecules is explored by thermal treatments. • Raman study of thermally induced structural changes in porous silica nanoparticles. • Raman signal attributable to the three membered rings in silica.

Moisture sensor based on evanescent wave light scattering by porous sol-gel silica coating

Science.gov (United States)

Tao, Shiquan; Singh, Jagdish P.; Winstead, Christopher B.

2006-05-02

An optical fiber moisture sensor that can be used to sense moisture present in gas phase in a wide range of concentrations is provided, as well techniques for making the same. The present invention includes a method that utilizes the light scattering phenomenon which occurs in a porous sol-gel silica by coating an optical fiber core with such silica. Thus, a porous sol-gel silica polymer coated on an optical fiber core forms the transducer of an optical fiber moisture sensor according to an embodiment. The resulting optical fiber sensor of the present invention can be used in various applications, including to sense moisture content in indoor/outdoor air, soil, concrete, and low/high temperature gas streams.

Syntheses of carbon porous materials with varied pore sizes and their performances as catalyst supports during methanol oxidation reaction

International Nuclear Information System (INIS)

Lo, An-Ya; Hung, Chin-Te; Yu, Ningya; Kuo, Cheng-Tzu; Liu, Shang-Bin

2012-01-01

Highlights: ► CPMs with varied pore sizes (1–400 nm) were replicated from various porous silicas by CVI method. ► MOR activities of Pt/CPM electrocatalysts increase with increasing pore size of CPM support. ► Microporous CPMs are favorable supports for Pt in terms of catalytic performance and CO-tolerance. -- Abstract: Carbon porous materials (CPMs) with extended ranges of pore size and morphology were replicated using various porous silicas, such as zeolites, mesoporous silicas, and photonic crystals, as templates by means of chemical vapor infiltration (CVI) method. The micro-, meso-, and macro-porous carbons so fabricated were adopted as supports for the metal (Pt) catalyst for direct methanol fuel cells (DMFCs), and the supported Pt/CPM electrocatalysts were characterized by a variety of different spectroscopic/analytical techniques, viz. transmission electron microscopy (TEM), Raman, X-ray photoelectron spectroscopy (XPS), gas physisorption/chemisorption analyses, and cyclic voltammetry (CV). That these Pt/CPMs were found to exhibit superior electrocatalytic activities compared to the commercial Pt/XC-72 with a comparable Pt loading during methanol oxidation reaction (MOR) is attributed to the presence of Pt nanoparticles (NPs; typically 1–3 nm in size) that are highly dispersed in the CPMs, facilitating an improved tolerance for CO poisoning. While the MOR activity observed for various Pt/CPMs tend to increase with increasing pore size of the carbon supports, Pt catalyst supported on carbon substrates possessing microporosities was found to have superior stability in terms of tolerance for CO poisoning than those with greater pore size or having meso- and macroporosities.

A new apparatus for the determination of adsorption isotherms and adsorption enthalpies on microporous and meso-porous media

International Nuclear Information System (INIS)

Mouahid, A.

2010-01-01

A specific thermostated experimental device comprising a differential heat flow calorimeter coupled with a home built manometric system has been built for the simultaneous determination of adsorption isotherms and adsorption enthalpies. The differential heat flow calorimeter is a Tian Calvet Setaram C80 model which measures the heat flux of a gas and can be operated isothermally, the manometric system is a stainless steel homemade apparatus. This coupled apparatus allows measurements for pressure up to 2.5 MPa and temperature up to 423.15 K. On the one hand, the apparatus and the experimental procedures are described. On the second hand the reliability and reproducibility were established by measuring adsorption isotherms on a benchmark (Filtrasorb F400) at 318.15 K. The gravimetric method has been used at higher pressure at various temperatures. These devices allowed us to study the adsorption of supercritical fluid (nitrogen N 2 , methane CH 4 , carbon dioxide CO 2 ) in activated carbons and microporous or meso-porous silica. The adsorption of methane on a rock of type (TGR) was also studied. These experimental results are used for the study of the interactions fluid / solid that must be taken into account in molecular simulations or DFT theory. (author)

Sedimentation behaviour and colloidal properties of porous, chemically modified silicas in non-aqueous solvents

NARCIS (Netherlands)

Vissers, J.P.C.; Laven, J.; Claessens, H.A.; Cramers, C.A.M.G.; Agterof, W.G.M.

1997-01-01

The sedimentation behaviour and colloidal properties of porous, chemically modified silicas dispersed in non-aqueous solvents have been studied. The free settling behaviour of non-aggregated silica suspensions could effectively be described with a modified Stokes equation that takes into account the

Impact of physicochemical properties of porous silica materials conjugated with dexamethasone via pH-responsive hydrazone bond on drug loading and release behavior

Science.gov (United States)

Numpilai, Thanapha; Witoon, Thongthai; Chareonpanich, Metta; Limtrakul, Jumras

2017-02-01

The conjugation of dexamethasone (DEX) onto modified-porous silica materials via a pH-responsive hydrazone bond has been reported to be highly efficient method to specifically deliver the DEX to diseased sites. However, the influence of physicochemical properties of porous silica materials has not yet been fully understood. In this paper, the impact of pore sizes, particle sizes and silanol contents on surface functionalization, drug loading and release behavior of porous silica materials conjugated with dexamethasone via pH-responsive hydrazone bond was investigated. The grafting density was found to relate to the number of silanol groups on the surface of porous silica materials. The particle size and macropores of the porous silica materials played an vital role on the drug loading and release behavior. Although the porous silica materials with larger particle sizes possessed a lower grafting density, a larger amount of drug loading could be achieved. Moreover, the porous silica materials with larger particle sizes showed a slower release rate of DEX due to a longer distance for cleaved DEX diffusion out of pores. DEX release rate exhibited pH-dependent, sustained release. At pH 4.5, the amount of DEX release within 10 days could be controlled in the range of 12.74-36.41%, depending on the host material. Meanwhile, less than 1.5% of DEX was released from each of type of the porous silica materials at pH 7.4. The results of silica dissolution suggested that the degradation of silica matrix did not significantly affect the release rate of DEX. In addition, the kinetic modeling studies revealed that the DEX releases followed Korsmeyer-Peppas model with a release exponent (n) ranged from 0.3 to 0.47, indicating a diffusion-controlled release mechanism.

Interphases, gelation, vitrification, porous glasses and the generalized Cauchy relation: epoxy/silica nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Philipp, M; Mueller, U; Jimenez Rioboo, R J; Baller, J; Sanctuary, R; Krueger, J K [Laboratoire de Physique des Materiaux, University of Luxembourg, 162A avenue de la Faiencerie, L-1511 Luxembourg (Luxembourg); Possart, W [Fachbereich Werkstoffwissenschaften, Universitaet des Saarlandes, D-66123 Saarbruecken (Germany)], E-mail: martine.philipp@uni.lu

2009-02-15

The generalized Cauchy relation (gCR) of epoxy/silica nano-composites does not show either the chemically induced sol-gel transition or the chemically induced glass transition in the course of polymerization. Astonishingly, by varying the silica nanoparticles' concentration between 0 and 25 vol% in the composites, the Cauchy parameter A of the gCR remains universal and can be determined from the pure epoxy's elastic moduli. Air-filled porous silica glasses are considered as models for percolated silica particles. A longitudinal modulus versus density representation evidences the aforementioned transition phenomena during polymerization of the epoxy/silica nanocomposites. The existence of optically and mechanically relevant interphases is discussed.

Interphases, gelation, vitrification, porous glasses and the generalized Cauchy relation: epoxy/silica nanocomposites

International Nuclear Information System (INIS)

Philipp, M; Mueller, U; Jimenez Rioboo, R J; Baller, J; Sanctuary, R; Krueger, J K; Possart, W

2009-01-01

The generalized Cauchy relation (gCR) of epoxy/silica nano-composites does not show either the chemically induced sol-gel transition or the chemically induced glass transition in the course of polymerization. Astonishingly, by varying the silica nanoparticles' concentration between 0 and 25 vol% in the composites, the Cauchy parameter A of the gCR remains universal and can be determined from the pure epoxy's elastic moduli. Air-filled porous silica glasses are considered as models for percolated silica particles. A longitudinal modulus versus density representation evidences the aforementioned transition phenomena during polymerization of the epoxy/silica nanocomposites. The existence of optically and mechanically relevant interphases is discussed.

A bio-inspired zinc finger analogue anchored in 2D hexagonal meso-porous silica for room temperature CO_2 activation via a hydrogeno-carbonate route

International Nuclear Information System (INIS)

Doghri, Hanene; Baranova, Elena A.; Albela, Belen; Bonneviot, Laurent; Mongia Said-Zina

2017-01-01

Bio-inspired diethylenetriamine-zinc(II) complexes were anchored into the nano-pores of hexagonal meso-porous MCM41-like silicas targeting a carbamate free and low temperature CO_2 recycling process. A step-by-step approach was adopted to perform an in situ synthesis in order to mimic the zinc finger of carbonic anhydrases, the fastest family of enzymes. In the presence of a surface-masking pattern of TMA"+ ions, some silanol groups were capped using grafted trimethylsilyl functions, TMSgr, (gr for grafted). After removing the masking ions, a tridentate diethylenetriamine ligand was anchored using diethylenetriamine propyl-trimethoxysilane. The so-called DETA_a_n ligands (an for anchored) were partially mono-protonated using either cyclohexane or isopropanol as a solvent. Nonetheless, up to two thirds of them were metallated by Zn(II) ions, leading to the targeted anchored zinc finger mimic [Zn(DETAan)L]+(L = Cl or OH). CO_2 is then adsorbed at room temperature and in humid ambient air by the formation of an intermediate hydrogeno-carbonate-zinc complex. Specific IR signatures at 1330 and 1400 cm"-"1 together with characteristic C 1s and Zn 2p3/2 XPS binding energies at 286.4 and 1024.6 eV advocate for a rather symmetrical bidentate [η"2-CO_3] structural unit in the anchored complex [Zn(DETA_a_n)(η"2-HCO_3"*)]"+, where the Zn(II) ion is most likely penta-coordinated. The internal pH value varied by less than 0.5 depending on the metal reacting with the DETA_a_n ligand and its ability to generate HCO_3"-, due to the buffering effect of surface silanol and amino groups according to the level of protonation of the DETA moieties measured from the N 1s XPS spectra. In contrast to nitrate ions, chloride ions were found to inhibit the formation of hydrogeno-carbonate. (authors)

Nanoscale assembly of lanthanum silica with dense and porous interfacial structures.

Science.gov (United States)

Ballinger, Benjamin; Motuzas, Julius; Miller, Christopher R; Smart, Simon; Diniz da Costa, João C

2015-02-03

This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate.

Construction and evaluation of controlled-release delivery system of Abamectin using porous silica nanoparticles as carriers.

Science.gov (United States)

Wang, Yan; Cui, Haixin; Sun, Changjiao; Zhao, Xiang; Cui, Bo

2014-12-01

Photolysis and poor solubility in water of Abamectin are key issues to be addressed, which causes low bioavailability and residual pollution. In this study, a novel hydrophilic delivery system through loading Abamectin with porous silica nanoparticles (Abam-PSNs) was developed in order to improve the chemical stability, dispersity, and the controlled release of Abamectin. These results suggest that Abam-PSNs can significantly improve the performance of controllable release, photostability, and water solubility of Abamectin by changing the porous structure of silica nanoparticles, which is favorable to improve the bioavailability and reduce the residues of pesticides.

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.

Fabrication of Meso-Porous Gamma-Alumina Films by Sol-Gel and Gel Casting Processes for Making Moisture Sensors

Directory of Open Access Journals (Sweden)

Kalyan Kumar Mistry

2007-04-01

Full Text Available Meso-porous g-Al2O3 film may be used as a highly sensitive trace moisture sensor. The crack-free alumina film was developed using a combination of sol-gel and tape casting processes, which produce high porosity, high surface area and small pore dimensions in the range of few nano-meter at uniform distribution. Sol-gel processes are well known in nano-technology and nano-material preparation, but it is difficult to make crack-free thick or thin films using this method. Tape cast methods are used for the fabrication of flexible crack-free thick ceramic sheets. Our objective was to develop nano-structured, crack-free, transparent Al2O3 film a few microns thick, has a highly porous and stable crystallographic nature. A metallic paste was printed by screen printing on both side of the film surface for electrodes to form a sensitive element. A silver wire (dia j=0.1mm lead was connected to a grid structure electrode using a silver paste spot for fine joining. Alumina is absorbs moisture molecules into its meso-porous layer and changes its electrical characteristics according to the moisture content, its dielectric constant increase as moisture increase. Moisture molecules can be conceived of as dipoles in random state before the application of an electric field. When the dipole orientation was changed from random to an equilibrium state under the application of external field, a large change in dielectric constant was observed. The number of water molecules absorbed determines the electrical impedance of the capacitor, which in turn is proportional to water vapor pressure.

Effect of Pore Size on the Carbon Dioxide Adsorption Behavior of Porous Liquids Based on Hollow Silica.

Science.gov (United States)

Shi, Ting; Zheng, Yaping; Wang, Tianyu; Li, Peipei; Wang, Yudeng; Yao, Dongdong

2018-01-05

Porous liquids are an expanding class of material that has huge potential in gas separation and gas adsorption. Pore size has a dramatic influence on the gas adsorption of porous liquids. In this article, we chose hollow silica nanoparticles as cores, 3-(trihydroxysilyl)-1-propanesulfonic acid (SIT) as corona, and inexpensive industrial reagent polyether amine (M2070) as canopy to obtain a new type of porous liquids. Hollow silica nanospheres with different pore sizes were chosen to investigate the influence of porosity size on CO 2 adsorption capacity of porous liquids. Their chemical structure, morphology, thermal behavior and possible adsorption mechanism are discussed in detail. It was proved that with similar grafting density, porous liquid that has bigger pore size possesses a better CO 2 adsorption capacity (2.182 mmol g -1 under 2.5 MPa at 298 K). More than that, this article demonstrates a more facile and low-cost method to obtain porous liquids with good CO 2 adsorption capacity, recyclability, and huge variability. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Porous Silica Sol-Gel Glasses Containing Reactive V2O5 Groups

Science.gov (United States)

Stiegman, Albert E.

1995-01-01

Porous silica sol-gel glasses into which reactive vanadium oxide functional groups incorporated exhibit number of unique characteristics. Because they bind molecules of some species both reversibly and selectively, useful as chemical sensors or indicators or as scrubbers to remove toxic or hazardous contaminants. Materials also oxidize methane gas photochemically: suggests they're useful as catalysts for conversion of methane to alcohol and for oxidation of hydrocarbons in general. By incorporating various amounts of other metals into silica sol-gel glasses, possible to synthesize new materials with broad range of new characteristics.

Development of pore interconnectivity/morphology in porous silica films investigated by cyclic voltammetry and slow positron annihilation spectroscopy

International Nuclear Information System (INIS)

Tang, Xiuqin; Xiong, Bangyun; Li, Qichao; Mao, Wenfeng; Xiao, Wei; Fang, Pengfei; He, Chunqing

2015-01-01

Highlights: •Porous silica films were studied by cyclic voltammetry and positron annihilation. •Highly interconnected pores were formed in the film fabricated with more CTAB. •Aligned nanochannels were observed in the porous flim prepared with 25 wt.% CTAB. •I − and Ps diffusion in the films was governed by pore interconnectivity/morphology. •Cyclic voltammetry is feasible to explore pore interconnectivity/morphology. -- Abstract: Cyclic voltammetry and positronium (Ps) 3γ-annihilation spectroscopy were applied to investigate pore interconnectivity/morphology of porous silica films fabricated with various loading of cetyltrimethyl ammonium bromide (CTAB). With increasing the ratio of CTAB up to 15 wt.%, the total charge Q, resulted from I − diffusion across the silica films, increased remarkably, indicative of formation of highly interconnected pores in the films prepared with more porogen. However, it decreased dramatically with further loading CTAB of 25 wt.%. Interestingly, 3γ-annihilation fraction I 3γ due to a triplet-state Ps (ortho-positronium, o-Ps) emission from the silica films showed a similar behavior as a function of CTAB loading. The abnormal decrement in Q and I 3γ in the film fabricated with 25 wt.% CTAB was well explained by formation of long nanochannels aligning parallel to the film surface. The results indicated that the total charge Q and Ps 3γ-annihilation fraction were closely associated with I − and Ps diffusion governed by the pore interconnectivity/morphology of the silica films, which made cyclic voltammetry possible to be a feasible tool to characterize pore interconnectivity/morphology of porous thin films

Fullerenol-Capped Porous Silica Nanoparticles for pH-Responsive Drug Delivery

Directory of Open Access Journals (Sweden)

Nikola Ž. Knežević

2015-01-01

Full Text Available Novel nanocomposite containing fullerenol nanoparticles (FNP and porous silica nanoparticles (PSNs was constructed and characterized. The capability of FNP to serve as a pore-capping agent and for entrapping 9-aminoacridine (9-AA inside the pores of the PSN material was also demonstrated. Nitrogen sorption measurements evidence the successful capping of the silica pores while thermogravimetric analysis of FNP loaded PSN indicates the existence of pore-loaded fullerenol molecules. Higher amount of the drug release was noted by exposing the material to weakly acidic conditions in comparison to physiological pH, which may find application in targeted treatment of weakly acidic tumor tissues.

Vapor phase epitaxy of silicon on meso porous silicon for deposition on economical substrate and low cost photovoltaic application

International Nuclear Information System (INIS)

Quoizola, S.

2003-01-01

The silicon is more and more used in the industry. Meanwhile the production cost is a problem to solve to develop the photovoltaic cells production. This thesis presents a new technology based on the use of a meso-porous silicon upper layer,to grow the active silicon layer of 50 μm width. The photovoltaic cell is then realized, the device is removed and placed on a low cost substrate. The silicon substrate of beginning can be used again after cleaning. The first chapter presents the operating and the characteristics of the silicon photovoltaic cell. The second chapter is devoted to the growth technique, the vapor phase epitaxy, and the third chapter to the epitaxy layer. The chapter four deals with the porous silicon and the structure chosen in this study. The chapter five is devoted to the characterization of the epitaxy layer on porous silicon. The photovoltaic cells realized on these layers are presented in the last chapter. (A.L.B.)

Development of new microporous silica membranes for gas separation

International Nuclear Information System (INIS)

Camelia Barboiu; Alejandro Mourgues; Beatrice Sala; Serge de Perthuis; Camelia Barboiu; Alejandro Mourgues; Beatrice Sala; Anne Julbe; Jose Sanchez

2006-01-01

This paper presents the synthesis and the application of molecular sieving ceramic membranes to purify hydrogen or helium from various gas mixtures. The membranes prepared in this work consist of an ultra-microporous silica-based separative layer produced via a sol-gel process. Ultra microporous silica containing boron is synthesized by the acid catalyzed hydrolysis and condensation of tetra-ethyl-ortho-silicate in ethanol. The layer is deposited inside a tubular asymmetric alumina support with a meso-porous y alumina inner layer. The thickness of the silica layers after treatment is about 200 nm, estimated from their cross-section SEM micrographs. Ultra-microporous membranes (with pore sizes less than 0.7 nm) are thus required to get high selectivity. Such membranes enable to carry out gas separation up to 500 deg C under a transmembrane pressure lower than 8 bars. He and H 2 permeance values close to 10 -7 mol.m -2 s -1 Pa -1 are obtained, associated with ideal selectivities α(He/CO 2 ) and α(H 2 /CO 2 ) between 10 and 20 at 300 deg C. (authors)

Transport of Silica Colloid through Saturated Porous Media under Different Hydrogeochemical and Hydrodynamic Conditions Considering Managed Aquifer Recharge

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Zhuo Wang

2016-11-01

Full Text Available Colloids may have an important role in regulating the structure and function of groundwater ecosystems, and may influence the migration of low solubility contaminants in groundwater. There is, however, a degree of uncertainty about how colloids behave under the variable hydrogeochemical and hydrodynamic conditions that occur during managed aquifer recharge. We used an online monitoring system to monitor the transport of silica colloid in saturated porous media under different hydrogeochemical conditions, including a range of pH values (5, 7, and 9, ionic strengths (<0.0005, 0.02, and 0.05 M, cation valences (Na+, Ca2+, flow rates (0.1, 0.2, and 0.4 mL/min. The results showed that silica colloid was more likely to deposit on the surface of porous media in acidic conditions (pH = 5 than in alkaline conditions (pH = 9, indicating that the risks of pollution from colloidal interactions would be higher when the pH of the recharge water was higher. Colloid deposition occurred when the ionic strength of the colloidal suspension increased, and bivalent cations had a greater effect than monovalent cations. This suggests that bivalent cation-rich recharge water might affect the porosity of the porous medium because of colloid deposition during the managed aquifer recharge process. As the flow rate increased, the migration ability of silica colloid increased. We simulated the migration of silica colloid in porous media with the COMSOL Multiphysics model.

Meso Mechanical Analysis of AC Mixture Response

NARCIS (Netherlands)

Woldekidan, M.F.; Huurman, M.; Vaccari, E.; Poot, M.

2012-01-01

Ongoing research into performance modeling of Asphalt Concrete (AC) mixtures using meso mechanics approaches is being undertaken at Delft University of Technology (TUD). The approach has already been successfully employed for evaluating the long term performance of porous asphalt concrete. The work

One-pot pseudomorphic crystallization of mesoporous porous silica to hierarchical porous zeolites

Energy Technology Data Exchange (ETDEWEB)

Xing, Jun-Ling; Jiang, Shu-Hua; Pang, Jun-Ling; Yuan, En-Hui; Ma, Xiao-Jing [Shanghai Key Laboratory of Green Chemistry and Chemical Processes, College of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhongshan North Road, 200062 Shanghai (China); Lam, Koon-Fung [Department of Chemical Engineering, University College London, Torrington Place, London (United Kingdom); Xue, Qing-Song, E-mail: qsxue@chem.ecnu.edu.cn [Shanghai Key Laboratory of Green Chemistry and Chemical Processes, College of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhongshan North Road, 200062 Shanghai (China); Zhang, Kun, E-mail: kzhang@chem.ecnu.edu.cn [Shanghai Key Laboratory of Green Chemistry and Chemical Processes, College of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhongshan North Road, 200062 Shanghai (China)

2015-09-15

Hierarchically porous silica with mesopore and zeolitic micropore was synthesized via pseudomorphic crystallization under high-temperature hydrothermal treatment in the presence of cetyltrimethylammonium tosylate and tetrapropylammonium ions. A combined characterization using small-angle X-ray diffraction (XRD), nitrogen adsorption, high-resolution transmission electron microscopy (TEM), thermogravimetric analysis (TG), and elemental analysis showed that dual templates, CTA{sup +} and TPA{sup +} molecules, can work in a cooperative manner to synthesize mesoporous zeolite in a one-pot system by precisely tuning the reaction conditions, such as reaction time and temperature, and type and amount of heterometal atoms. It is found that the presence of Ti precursor is critical to the successful synthesis of such nanostructure. It not only retards the nucleation and growth of crystalline MFI domains, but also acts as nano-binder or nano-glue to favor the assembly of zeolite nanoblocks. - Graphical abstract: Display Omitted - Highlights: • A facile method to synthesize mesoporous zeolites with hierarchical porosity was presented. • It gives a new insight into keeping the balance between mesoscopic and molecular ordering in hierarchical porous materials. • A new understanding on the solid–solid transformation mechanism for the synthesis of titanosilicate zeolites was proposed.

Biogenic porous silica and silicon sourced from Mexican Giant Horsetail (Equisetum myriochaetum) and their application as supports for enzyme immobilization.

Science.gov (United States)

Sola-Rabada, Anna; Sahare, Padma; Hickman, Graham J; Vasquez, Marco; Canham, Leigh T; Perry, Carole C; Agarwal, Vivechana

2018-06-01

Porous silica-based materials are attractive for biomedical applications due to their biocompatibility and biodegradable character. In addition, inorganic supports such as porous silicon are being developed due to integrated circuit chip compatibility and tunable properties leading to a wide range of multidisciplinary applications. In this contribution, biosilica extracted from a rarely studied plant material (Equisetum Myriochaetum), its conversion to silicon and the potential for both materials to be used as supports for enzyme immobilization are investigated. E. myriochaetum was subject to conventional acid digestion to extract biogenic silica with a% yield remarkably higher (up to 3 times) than for other Equisetum sp. (i.e. E. Arvense). The surface area of the isolated silica was ∼400 m 2 /g, suitable for biotechnological applications. Biogenic silicon was obtained by magnesiothermic reduction. The materials were characterized by SEM-EDX, XRD, FT-IR, ICP-OES, TGA and BET analysis and did not contain significant levels of class 1 heavy elements (such as Pb, Cd, Hg and As). Two commercial peroxidases, horseradish peroxidase (HRP) and Coprinus cinereus peroxidase (CiP) were immobilized onto the biogenic materials using three different functionalization routes: (A) carbodiimide, (B) amine + glutaraldehyde and (C) amine + carbodiimide. Although both biogenic silica and porous silicon could be used as supports differences in behaviour were observed for the two enzymes. For HRP, loading onto biogenic silica via the glutaraldehyde immobilization technique (route B) was most effective. The loading of CiP showed a much higher peroxidase activity onto porous silicon than silica functionalized by the carbodiimide method (route A). From the properties of the extracted materials obtained from Equisetum Myriochaetum and the immobilization results observed, these materials appear to be promising for industrial and biomedical applications. Copyright © 2018 Elsevier

Controlling porosity of porous carbon cathode for lithium oxygen batteries: Influence of micro and meso porosity

Science.gov (United States)

Kim, Minjae; Yoo, Eunjoo; Ahn, Wha-Seung; Shim, Sang Eun

2018-06-01

In rechargeable lithium-oxygen (Li-O2) batteries, the porosity of porous carbon materials plays a crucial role in the electrochemical performance serving as oxygen diffusion path and Li ion transfer passage. However, the influence of optimization of porous carbon as an air electrode on cell electrochemical performance remains unclear. To understand the role of carbon porosity in Li-O2 batteries, carbon materials featuring controlled pore sizes and porosity, including C-800 (nearly 96% microporous) and AC-950 (55:45 micro/meso porosity), are designed and synthesized by carbonization using a triazine-based covalent organic polymer (TCOP). We find that the microporous C-800 cathode allows 120 cycles with a limited capacity of 1000 mAh g-1, about 2 and 10 times higher than that of mixed-porosity AC-950 and mesoporous CMK-3, respectively. Meanwhile, the specific discharge capacity of the C-800 electrode at 200 mA g-1 is 6003 mAh g-1, which is lower than that of the 8433 and 9960 mAh g-1 when using AC-950 and CMK-3, respectively. This difference in the electrochemical performance of the porous carbon cathode with different porosity causes to the generation and decomposition of Li2O2 during the charge and discharge cycle, which affects oxygen diffusion and Li ion transfer.

Meso-/Nanoporous Semiconducting Metal Oxides for Gas Sensor Applications

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Nguyen Duc Hoa

2015-01-01

Full Text Available Development and/or design of new materials and/or structures for effective gas sensor applications with fast response and high sensitivity, selectivity, and stability are very important issues in the gas sensor technology. This critical review introduces our recent progress in the development of meso-/nanoporous semiconducting metal oxides and their applications to gas sensors. First, the basic concepts of resistive gas sensors and the recent synthesis of meso-/nanoporous metal oxides for gas sensor applications are introduced. The advantages of meso-/nanoporous metal oxides are also presented, taking into account the crystallinity and ordered/disordered porous structures. Second, the synthesis methods of meso-/nanoporous metal oxides including the soft-template, hard-template, and temple-free methods are introduced, in which the advantages and disadvantages of each synthetic method are figured out. Third, the applications of meso-/nanoporous metal oxides as gas sensors are presented. The gas nanosensors are designed based on meso-/nanoporous metal oxides for effective detection of toxic gases. The sensitivity, selectivity, and stability of the meso-/nanoporous gas nanosensors are also discussed. Finally, some conclusions and an outlook are presented.

A Hierarchically Micro-Meso-Macroporous Zeolite CaA for Methanol Conversion to Dimethyl Ether

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Yan Wang

2016-11-01

Full Text Available A hierarchical zeolite CaA with microporous, mesoporous and macroporous structure was hydrothermally synthesized by a ”Bond-Blocking” method using organo-functionalized mesoporous silica (MS as a silica source. The characterization by XRD, SEM/TEM and N2 adsorption/desorption techniques showed that the prepared material had well-crystalline zeolite Linde Type A (LTA topological structure, microspherical particle morphologies, and hierarchically intracrystalline micro-meso-macropores structure. With the Bond-Blocking principle, the external surface area and macro-mesoporosity of the hierarchical zeolite CaA can be adjusted by varying the organo-functionalized degree of the mesoporous silica surface. Similarly, the distribution of the micro-meso-macroporous structure in the zeolite CaA can be controlled purposely. Compared with the conventional microporous zeolite CaA, the hierarchical zeolite CaA as a catalyst in the conversion of methanol to dimethyl ether (DME, exhibited complete DME selectivity and stable catalytic activity with high methanol conversion. The catalytic performances of the hierarchical zeolite CaA results clearly from the micro-meso-macroporous structure, improving diffusion properties, favoring the access to the active surface and avoiding secondary reactions (no hydrocarbon products were detected after 3 h of reaction.

Nanoparticles of Pt and Ag supported in meso porous SiO{sub 2}: characterization and catalytic applications; Nanoparticulas de Pt y Ag soportadas en SiO{sub 2} mesoporosa: caracterizacion y aplicaciones cataliticas

Energy Technology Data Exchange (ETDEWEB)

Espinosa, M.E.; Perez H, R.; Perez A, M.; Mondragon G, G. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Arenas A, J. [IFUNAM, A.P. 20-364, 01000 Mexico D.F. (Mexico)

2004-07-01

The surface properties of catalysts of Pt and Ag supported in conventional SiO{sub 2} hey have been studied through reduction reactions of N{sub 2}O with H{sub 2} which is a sensitive reaction to the structure. In our case it was used a meso porous ceramic support of SiO{sub 2} of great surface area (1100 m{sup 2}/gr), where it is caused a high dispersion of the metallic nanoparticles of Pt and Ag, the total charge of the active phase in the meso porous support was of 3% in weight. The catalysts show a variation in the percentages of conversion of N{sub 2}O depending on the size and dispersion of the metallic phases. (Author)

NMR of mercury in porous coal and silica gel

International Nuclear Information System (INIS)

Kasperovich, V.S.; Charnaya, E.V.; Tien, C.; Wur, C.S.

2003-01-01

Temperature dependences of the integral intensity and NMR signals Knight shift in 199 Hg nuclei are measured for liquid and solid mercury introduced into the porous coal and silica gel. The decrease in the crystallization completion temperature and small temperature hysteresis (from 4 up to 9 K) between melting and crystallization are identified. Mercury melting temperature in pores coincided with melting temperature of the bulk mercury. NMR signal from crystalline mercury under conditions of limited geometry was observed for the first time. It is ascertained that Knight shift for mercury in the pores both in liquid and crystalline phases is lesser than for the bulk mercury [ru

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.

Influences of surface charge, size, and concentration of colloidal nanoparticles on fabrication of self-organized porous silica in film and particle forms.

Science.gov (United States)

Nandiyanto, Asep Bayu Dani; Suhendi, Asep; Arutanti, Osi; Ogi, Takashi; Okuyama, Kikuo

2013-05-28

Studies on preparation of porous material have attracted tremendous attention because existence of pores can provide material with excellent performances. However, current preparation reports described successful production of porous material with only partial information on charges, interactions, sizes, and compositions of the template and host materials. In this report, influences of self-assembly parameters (i.e., surface charge, size, and concentration of colloidal nanoparticles) on self-organized porous material fabrication were investigated. Silica nanoparticles (as a host material) and polystyrene (PS) spheres (as a template) were combined to produce self-assembly porous materials in film and particle forms. The experimental results showed that the porous structure and pore size were controllable and strongly depended on the self-assembly parameters. Materials containing highly ordered pores were effectively created only when process parameters fall within appropriate conditions (i.e., PS surface charge ≤ -30 mV; silica-to-PS size ratio ≤0.078; and silica-to-PS mass ratio of about 0.50). The investigation of the self-assembly parameter landscape was also completed using geometric considerations. Because optimization of these parameters provides significant information in regard to practical uses, results of this report could be relevant to other functional properties.

Two-Stage Crystallizer Design for High Loading of Poorly Water-Soluble Pharmaceuticals in Porous Silica Matrices

OpenAIRE

Leia Dwyer; Samir Kulkarni; Luzdary Ruelas; Allan Myerson

2017-01-01

While porous silica supports have been previously studied as carriers for nanocrystalline forms of poorly water-soluble active pharmaceutical ingredients (APIs), increasing the loading of API in these matrices is of great importance if these carriers are to be used in drug formulations. A dual-stage mixed-suspension, mixed-product removal (MSMPR) crystallizer was designed in which the poorly soluble API fenofibrate was loaded into the porous matrices of pore sizes 35 nm-300 nm in the first st...

One pot synthesized Li, Zr doped porous silica nanoparticle for low temperature CO2 adsorption

Directory of Open Access Journals (Sweden)

Mani Ganesh

2017-05-01

Full Text Available Li, Zr doped porous silica was synthesized in one pot and investigated for low temperature CO2 adsorption. The synthesized nanoparticle was characterized by X-ray diffraction (XRD, N2 adsorption–desorption measurement, thermogravimetric analysis (TGA and scanning electron microscopy (SEM. The specific surface area, average pore diameter and pore volume were determined to be 962 m2/g, 2.3 nm and 0.56 cm3/g respectively. ICP-AES analysis revealed a metal content of 4 wt.% (Zr and 3.42 wt.% (Li. Their CO2 adsorption capacity was tested at room temperature and atmospheric pressure. An uptake of about 5 wt.% was observed and regenerable at a low temperature of 200 °C. This adsorption and desorption temperature of the sorbent is lower than the reported lithium silicate. The CO2 adsorption–desorption cyclic performance studies illustrated that Li, Zr doped porous silica is a recyclable, selective and potential sorbent for CO2 adsorption.

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.

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.

Sol–gel hybrid membranes loaded with meso/macroporous SiO2, TiO2–P2O5 and SiO2–TiO2–P2O5 materials with high proton conductivity

International Nuclear Information System (INIS)

Castro, Yolanda; Mosa, Jadra; Aparicio, Mario; Pérez-Carrillo, Lourdes A.; Vílchez, Susana; Esquena, Jordi; Durán, Alicia

2015-01-01

In this work, highly conductive hybrid organic–inorganic membranes loaded with SiO 2 , TiO 2 –P 2 O 5 and SiO 2 –TiO 2 –P 2 O 5 meso/macroporous particles were prepared via a sol–gel process. Meso/macroporous particles were incorporated to hybrid membranes, for improving water retention and enhancing electrochemical performance. These particles with a polymodal pore size distribution were prepared by templating in highly concentrated emulsions, the particles showed a specific surface area between 50 m 2 /g (TiO 2 –P 2 O 5 ) and 300 m 2 /g (SiO 2 –TiO 2 –P 2 O 5 ). The particles were dispersed in a hybrid silica sol and further sprayed onto glass paper. The films were polymerized and sintered; those loaded with meso/macroporous particles had a homogenous distribution. High temperature proton conductivity measurements confirmed a high water retention. Conductivity of these materials is higher than that of Nafion ® at higher temperatures (120 °C) (2·10 −2  S/cm). This study provides processing guideline to achieve hybrid electrolytes for efficient conduction of protons due to their high surface area and porous structure. - Highlights: • Hybrid electrolyte with meso/macroporous particles were synthesized by sol–gel. • Depositions of hybrid solutions by spraying onto glass substrates were performed. • Proton conductivity was evaluated as a function of composition and porous structure

Pretreatments of porous silica for improving the activity of a nickel-loaded catalyst

Energy Technology Data Exchange (ETDEWEB)

Arai, M.; Ikushima, Y.; Nishiyama, Y.

1986-02-01

Nickel catalysts supported on porous silicas treated with water, ethanol, and 1-butanol were found to be more active than that supported on untreated silica for ethane hydrogenolysis and furan hydrogenation. To elucidate the reason for the activation, some surface properties of the treated silicas were examined. The treatments decreased the surface area and increased the volume of the macropores, the surface density of hydroxyl groups, and the heat of immersion in water per unit surface area. The state of nickel on the support was examined by temperature programed desorption (TPD) of hydrogen, X-ray diffraction (XRD), and scanning electron microscopy/X-ray microanalysis. The dispersion measured by XRD was not appreciably altered by the treatments, but the TPD showed more hydrogen desorbed above 150/sup 0/C from nickel on the treated supports. The activation of nickel by pretreatment of the support was ascribed to the increase of those nickel atoms which dispersed finely over the support by the increased number of surface hydroxyl groups. This was based on the number of hydroxyl groups per unit surface area. The nickel catalyst supported on the pretreated silicas showed greater thermal stability. 16 references, 5 figures, 1 table.

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.

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.

Granulation study of porous silica particles for MA recovery process

International Nuclear Information System (INIS)

Goto, Ichiro; Kofuji, Hirohide; Oriuchi, Akio; Watanabe, Sou; Takeuchi, Masayuki

2017-01-01

JAEA has been working on partition of MA from HLLW generated in the reprocessing by extraction chromatography technology. This technology utilizes 50 μm porous silica particles coated by styrene-divinylbenzene copolymer in which an extractant for MA recovery is impregnated as adsorbent. In this study, spray drying granulating experiments with various operating conditions and with different experimental apparatuses were carried out to find an appropriate condition to control the size of the particle and the pore. The target average sizes of the particle and pore are more than 50 μm and 600 nm respectively. Suspension containing fine silica particles were supplied to the spray drying devices, and small droplets generated through the spray nozzle were dried inside the drying chamber. In this study, viscosity of the feed solution and some granulation conditions were parametrically changed, and two different types of the spray nozzles were used. An air atomizing nozzle and a rotary disk nozzle were equipped at different chambers respectively. Then, performance of the product particle was evaluated by particle and pore size distributions and adsorption experiment after the polymer coating and an extractant impregnation. The particle size of the product depended on the atomizing pressure and viscosity of the feed solution, and the size increased with decrease in the pressure and in the viscosity. The maximum size obtained in this study was about 40 μm. Large viscosity of the feed solution lead poor recovery ratio and uniformity in the size distribution of the product powder. The pore size of the resultant particle was 550-800 nm as expected. As the type of the nozzle changed from the air atomizing nozzle to the rotary disk nozzle and size of the drying chamber became large, the average particle size and the particle size distribution became large and sharp, respectively. Rotation speed of the nozzle also influenced on the particle size, and targeted average size of the

Rhodamine 6G impregnated porous silica: A photoluminescence study

Energy Technology Data Exchange (ETDEWEB)

Anedda, A. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Canada) (Italy); Carbonaro, C.M. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Canada) (Italy)]. E-mail: cm.carbonaro@dsf.unica.it; Clemente, F. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Ca) (Italy); Corpino, R. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Ca) (Italy); Ricci, P.C. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Ca) (Italy); Rossini, S. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Ca) (Italy)

2005-12-15

The optical properties of rhodamine 6G dye confined in porous silica are reported. Photoluminescence properties of embedded chromophores in mesoporous hosts can be affected by the surrounding matrices: shifts in emission spectra and variations of photoluminescence quantum yield are found as compared to dye solutions. Host-guest interactions are studied here by varying both SiO{sub 2} xerogels porosity and the dye concentration. Comparing samples obtained by impregnating matrices with 5.4 and 18.2 nm pores with solutions having concentrations in the rhodamine 6G high laser gain, matrices with 5.4 nm pores impregnated with a dye concentration of 5 x 10{sup -4} M are found to be the most stable and efficient in the examined range.

Tailored Porous Materials

Energy Technology Data Exchange (ETDEWEB)

BARTON,THOMAS J.; BULL,LUCY M.; KLEMPERER,WALTER G.; LOY,DOUGLAS A.; MCENANEY,BRIAN; MISONO,MAKOTO; MONSON,PETER A.; PEZ,GUIDO; SCHERER,GEORGE W.; VARTULI,JAMES C.; YAGHI,OMAR M.

1999-11-09

Tailoring of porous materials involves not only chemical synthetic techniques for tailoring microscopic properties such as pore size, pore shape, pore connectivity, and pore surface reactivity, but also materials processing techniques for tailoring the meso- and the macroscopic properties of bulk materials in the form of fibers, thin films and monoliths. These issues are addressed in the context of five specific classes of porous materials: oxide molecular sieves, porous coordination solids, porous carbons, sol-gel derived oxides, and porous heteropolyanion salts. Reviews of these specific areas are preceded by a presentation of background material and review of current theoretical approaches to adsorption phenomena. A concluding section outlines current research needs and opportunities.

Enhanced microcontact printing of proteins on nanoporous silica surface

Energy Technology Data Exchange (ETDEWEB)

Blinka, Ellen; Hu Ye; Gopal, Ashwini; Hoshino, Kazunori; Lin, Kevin; Zhang, John X J [Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78758 (United States); Loeffler, Kathryn; Liu Xuewu; Ferrari, Mauro, E-mail: John.Zhang@engr.utexas.edu [Department of Nanomedicine and Biomedical Engineering, University of Texas Health Science Service, Houston, TX 77031 (United States)

2010-10-15

We demonstrate porous silica surface modification, combined with microcontact printing, as an effective method for enhanced protein patterning and adsorption on arbitrary surfaces. Compared to conventional chemical treatments, this approach offers scalability and long-term device stability without requiring complex chemical activation. Two chemical surface treatments using functionalization with the commonly used 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA) were compared with the nanoporous silica surface on the basis of protein adsorption. The deposited thickness and uniformity of porous silica films were evaluated for fluorescein isothiocyanate (FITC)-labeled rabbit immunoglobulin G (R-IgG) protein printed onto the substrates via patterned polydimethlysiloxane (PDMS) stamps. A more complete transfer of proteins was observed on porous silica substrates compared to chemically functionalized substrates. A comparison of different pore sizes (4-6 nm) and porous silica thicknesses (96-200 nm) indicates that porous silica with 4 nm diameter, 57% porosity and a thickness of 96 nm provided a suitable environment for complete transfer of R-IgG proteins. Both fluorescence microscopy and atomic force microscopy (AFM) were used for protein layer characterizations. A porous silica layer is biocompatible, providing a favorable transfer medium with minimal damage to the proteins. A patterned immunoassay microchip was developed to demonstrate the retained protein function after printing on nanoporous surfaces, which enables printable and robust immunoassay detection for point-of-care applications.

IR-spectroscopical investigations on the glass structure of porous and sintered compacts of colloidal silica gels

Science.gov (United States)

Clasen, Rolf; Hornfeck, M.; Theiss, Wolfgang

1991-08-01

The forming and sintering of fumed silica powders is an interesting route for the preparation of large, very pure or doped silica glasses with a precise geometry. The processing from the shaping of a porous compact to the sintering of transparent silica glass can be successfully investigated with optical spectroscopy. As only the dielectric function DF (a dielectric function is the square root of the complex refractive index) characterizes the material, the vibrational bands were calculated from reflectance measurements. In compacts of fine particles, the topology cannot be neglected. Therefore, the models describing topological effects are briefly reviewed. With these model calculations it could be proven that new bands in the compacts and the significant shifts in the reflectance spectra during sintering are mainly caused by topological effects and that changes in the glass structure play only a secondary role.

Control of Partial Coalescence of Self-Assembled Metal Nano-Particles across Lyotropic Liquid Crystals Templates towards Long Range Meso-Porous Metal Frameworks Design

Directory of Open Access Journals (Sweden)

Ludovic F. Dumée

2015-10-01

Full Text Available The formation of purely metallic meso-porous metal thin films by partial interface coalescence of self-assembled metal nano-particles across aqueous solutions of Pluronics triblock lyotropic liquid crystals is demonstrated for the first time. Small angle X-ray scattering was used to study the influence of the thin film composition and processing conditions on the ordered structures. The structural characteristics of the meso-structures formed demonstrated to primarily rely on the lyotropic liquid crystal properties while the nature of the metal nano-particles used as well as the their diameters were found to affect the ordered structure formation. The impact of the annealing temperature on the nano-particle coalescence and efficiency at removing the templating lyotropic liquid crystals was also analysed. It is demonstrated that the lyotropic liquid crystal is rendered slightly less thermally stable, upon mixing with metal nano-particles and that low annealing temperatures are sufficient to form purely metallic frameworks with average pore size distributions smaller than 500 nm and porosity around 45% with potential application in sensing, catalysis, nanoscale heat exchange, and molecular separation.

On the use of mesophase pitch for the preparation of hierarchical porous carbon monoliths by nanocasting

Directory of Open Access Journals (Sweden)

Philipp Adelhelm, Karin Cabrera and Bernd M Smarsly

2012-01-01

Full Text Available A detailed study is given on the synthesis of a hierarchical porous carbon, possessing both meso- and macropores, using a mesophase pitch (MP as the carbon precursor. This carbon material is prepared by the nanocasting approach involving the replication of a porous silica monolith (hard templating. While this carbon material has already been tested in energy storage applications, various detailed aspects of its formation and structure are addressed in this study. Scanning electron microscopy (SEM, Hg porosimetry and N2 physisorption are used to characterize the morphology and porosity of the carbon replica. A novel approach for the detailed analysis of wide-angle x-ray scattering (WAXS from non-graphitic carbons is applied to quantitatively compare the graphene microstructures of carbons prepared using MP and furfuryl alcohol (FA. This WAXS analysis underlines the importance of the carbon precursor in the synthesis of templated porous carbon materials via the nanocasting route. Our study demonstrates that a mesophase pitch is a superior precursor whenever a high-purity, low-micropore-content and well-developed graphene structure is desired.

Sol–gel hybrid membranes loaded with meso/macroporous SiO{sub 2}, TiO{sub 2}–P{sub 2}O{sub 5} and SiO{sub 2}–TiO{sub 2}–P{sub 2}O{sub 5} materials with high proton conductivity

Energy Technology Data Exchange (ETDEWEB)

Castro, Yolanda, E-mail: castro@icv.csic.es [Instituto de Cerámica y Vidrio, Consejo Superior de Investigaciones Científicas (ICV-CSIC), Campus de Cantoblanco, 28049 Madrid (Spain); Mosa, Jadra, E-mail: jmosa@icv.csic.es [Instituto de Cerámica y Vidrio, Consejo Superior de Investigaciones Científicas (ICV-CSIC), Campus de Cantoblanco, 28049 Madrid (Spain); Aparicio, Mario [Instituto de Cerámica y Vidrio, Consejo Superior de Investigaciones Científicas (ICV-CSIC), Campus de Cantoblanco, 28049 Madrid (Spain); Pérez-Carrillo, Lourdes A.; Vílchez, Susana; Esquena, Jordi [Instituto de Química Avanzada de Cataluña, Consejo Superior de Investigaciones Científicas (IQAC-CSIC), CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Jordi Girona 18-26, 08034 Barcelona (Spain); Durán, Alicia [Instituto de Cerámica y Vidrio, Consejo Superior de Investigaciones Científicas (ICV-CSIC), Campus de Cantoblanco, 28049 Madrid (Spain)

2015-01-15

In this work, highly conductive hybrid organic–inorganic membranes loaded with SiO{sub 2}, TiO{sub 2}–P{sub 2}O{sub 5} and SiO{sub 2}–TiO{sub 2}–P{sub 2}O{sub 5} meso/macroporous particles were prepared via a sol–gel process. Meso/macroporous particles were incorporated to hybrid membranes, for improving water retention and enhancing electrochemical performance. These particles with a polymodal pore size distribution were prepared by templating in highly concentrated emulsions, the particles showed a specific surface area between 50 m{sup 2}/g (TiO{sub 2}–P{sub 2}O{sub 5}) and 300 m{sup 2}/g (SiO{sub 2}–TiO{sub 2}–P{sub 2}O{sub 5}). The particles were dispersed in a hybrid silica sol and further sprayed onto glass paper. The films were polymerized and sintered; those loaded with meso/macroporous particles had a homogenous distribution. High temperature proton conductivity measurements confirmed a high water retention. Conductivity of these materials is higher than that of Nafion{sup ®} at higher temperatures (120 °C) (2·10{sup −2} S/cm). This study provides processing guideline to achieve hybrid electrolytes for efficient conduction of protons due to their high surface area and porous structure. - Highlights: • Hybrid electrolyte with meso/macroporous particles were synthesized by sol–gel. • Depositions of hybrid solutions by spraying onto glass substrates were performed. • Proton conductivity was evaluated as a function of composition and porous structure.

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.

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 ...

Molecular dynamics study of shock compression in porous silica glass

Science.gov (United States)

Jones, Keith; Lane, J. Matthew D.; Vogler, Tracy J.

2017-06-01

The shock response of porous amorphous silica is investigated using classical molecular dynamics, over a range of porosity ranging from fully dense (2.21 g/cc) down to 0.14 g/cc. We observe an enhanced densification in the Hugoniot response at initial porosities above 50 %, and the effect increases with increasing porosity. In the lowest initial densities, after an initial compression response, the systems expand with increased pressure. These results show good agreement with experiments. Mechanisms leading to enhanced densification will be explored, which appear to differ from mechanisms observed in similar studies in silicon. Sandia National Laboratories is a multi mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

TiO2 supported over porous silica photocatalysts for pesticide degradation using solar light: Part 2. Silica prepared using acrylic acid emulsion

International Nuclear Information System (INIS)

Phanikrishna Sharma, Mangalampalli V.; Durga Kumari, Valluri; Subrahmanyam, Machiraju

2010-01-01

An acrylic acid emulsion mixture is used for synthesis of novel porous silica (E-Si) material. The photocatalytic activity of TiO 2 under solar light irradiation for isoproturon (herbicide) degradation is drastically increased when dispersed over E-Si support using solid state dispersion (SSD) technique. The composite material is characterized by XRD, nitrogen adsorption-desorption isotherms, UV-vis DRS, SEM and TEM measurements. The photocatalytic activities of the composite catalysts are evaluated for different parameters. The 5 wt% TiO 2 /E-Si is found to be highly active for isoproturon degradation.

Response to Extreme Temperatures of Mesoporous Silica MCM-41: Porous Structure Transformation Simulation and Modification of Gas Adsorption Properties.

Science.gov (United States)

Zhang, Shenli; Perez-Page, Maria; Guan, Kelly; Yu, Erick; Tringe, Joseph; Castro, Ricardo H R; Faller, Roland; Stroeve, Pieter

2016-11-08

Molecular dynamics (MD) and Monte Carlo (MC) simulations were applied together for the first time to reveal the porous structure transformation mechanisms of mesoporous silica MCM-41 subjected to temperatures up to 2885 K. Silica was experimentally characterized to inform the models and enable prediction of changes in gas adsorption/separation properties. MD simulations suggest that the pore closure process is activated by a collective diffusion of matrix atoms into the porous region, accompanied by bond reformation at the surface. Degradation is kinetically limited, such that complete pore closure is postponed at high heating rates. We experimentally observe decreased gas adsorption with increasing temperature in mesoporous silica heated at fixed rates, due to pore closure and structural degradation consistent with simulation predictions. Applying the Kissinger equation, we find a strong correlation between the simulated pore collapse temperatures and the experimental values which implies an activation energy of 416 ± 17 kJ/mol for pore closure. MC simulations give the adsorption and selectivity for thermally treated MCM-41, for N 2 , Ar, Kr, and Xe at room temperature within the 1-10 000 kPa pressure range. Relative to pristine MCM-41, we observe that increased surface roughness due to decreasing pore size amplifies the difference of the absolute adsorption amount differently for different adsorbate molecules. In particular, we find that adsorption of strongly interacting molecules can be enhanced in the low-pressure region while adsorption of weakly interacting molecules is inhibited. This then results in higher selectivity in binary mixture adsorption in mesoporous silica.

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

Fabrication of hierarchical porous N-doping carbon membrane by using ;confined nanospace deposition; method for supercapacitor

Science.gov (United States)

Wang, Guoxu; Liu, Meng; Du, Juan; Liu, Lei; Yu, Yifeng; Sha, Jitong; Chen, Aibing

2018-03-01

The membrane carbon materials with hierarchical porous architecture are attractive because they can provide more channels for ion transport and shorten the ions transport path. Herein, we develop a facile way based on "confined nanospace deposition" to fabricate N-dopi-ng three dimensional hierarchical porous membrane carbon material (N-THPMC) via coating the nickel nitrate, silicate oligomers and triblock copolymer P123 on the branches of commercial polyamide membrane (PAM). During high temperature treatment, the mesoporous silica layer and Ni species serve as a "confined nanospace" and catalyst respectively, which are indispensable elements for formation of carbon framework, and the gas-phase carbon precursors which derive from the decomposition of PAM are deposited into the "confined nanospace" forming carbon framework. The N-THPMC with hierarchical macro/meso/microporous structure, N-doping (2.9%) and large specific surface area (994m2 g-1) well inherits the membrane morphology and hierarchical porous structure of PAM. The N-THPMC as electrode without binder exhibits a specific capacitance of 252 F g-1 at the current density of 1 A g-1 in 6 M KOH electrolyte and excellent cycling stability of 92.7% even after 5000 cycles.

Phase equilibria and thermodynamic modeling of ethane and propane hydrates in porous silica gels.

Science.gov (United States)

Seo, Yongwon; Lee, Seungmin; Cha, Inuk; Lee, Ju Dong; Lee, Huen

2009-04-23

In the present study, we examined the active role of porous silica gels when used as natural gas storage and transportation media. We adopted the dispersed water in silica gel pores to substantially enhance active surface for contacting and encaging gas molecules. We measured the three-phase hydrate (H)-water-rich liquid (L(W))-vapor (V) equilibria of C(2)H(6) and C(3)H(8) hydrates in 6.0, 15.0, 30.0, and 100.0 nm silica gel pores to investigate the effect of geometrical constraints on gas hydrate phase equilibria. At specified temperatures, the hydrate stability region is shifted to a higher pressure region depending on pore size when compared with those of bulk hydrates. Through application of the Gibbs-Thomson relationship to the experimental data, we determined the values for the C(2)H(6) hydrate-water and C(3)H(8) hydrate-water interfacial tensions to be 39 +/- 2 and 45 +/- 1 mJ/m(2), respectively. By using these values, the calculation values were in good agreement with the experimental ones. The overall results given in this study could also be quite useful in various fields, such as exploitation of natural gas hydrate in marine sediments and sequestration of carbon dioxide into the deep ocean.

Dynamic behavior of porous concretes under drop weight impact testing

NARCIS (Netherlands)

Agar Ozbek, A.S.; Weerheijm, J.; Schlangen, E.; Breugel, K. van

2013-01-01

Porous concrete is used as a construction material in various applications mainly as a permeable cementitious material. However, its response under impact loading is generally not considered. Due to the high percentage of its intentional meso-size air pores, porous concrete has a moderate static

Investigating porous concrete with improved strength: Testing at different scales

NARCIS (Netherlands)

Agar-Ozbek, A.S.; Weerheijm, J.; Schlangen, E.; Breugel, K. van

2013-01-01

Porous concrete incorporates a high percentage of meso-size air voids that makes its mechanical characteristics remarkably different from normal concrete. A research project was undertaken to design a special type of porous concrete, that fractures into small fragments when exposed to impact loading

TiO{sub 2} supported over porous silica photocatalysts for pesticide degradation using solar light: Part 2. Silica prepared using acrylic acid emulsion

Energy Technology Data Exchange (ETDEWEB)

Phanikrishna Sharma, Mangalampalli V.; Durga Kumari, Valluri [Inorganic and Physical Chemistry Division, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500607, Andhra Pradesh (India); Subrahmanyam, Machiraju, E-mail: subrahmanyam@iict.res.in [Inorganic and Physical Chemistry Division, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500607, Andhra Pradesh (India)

2010-03-15

An acrylic acid emulsion mixture is used for synthesis of novel porous silica (E-Si) material. The photocatalytic activity of TiO{sub 2} under solar light irradiation for isoproturon (herbicide) degradation is drastically increased when dispersed over E-Si support using solid state dispersion (SSD) technique. The composite material is characterized by XRD, nitrogen adsorption-desorption isotherms, UV-vis DRS, SEM and TEM measurements. The photocatalytic activities of the composite catalysts are evaluated for different parameters. The 5 wt% TiO{sub 2}/E-Si is found to be highly active for isoproturon degradation.

Porous Materials from Thermally Activated Kaolinite: Preparation, Characterization and Application

Directory of Open Access Journals (Sweden)

Jun Luo

2017-06-01

Full Text Available In the present study, porous alumina/silica materials were prepared by selective leaching of silicon/aluminum constituents from thermal-activated kaolinite in inorganic acid or alkali liquor. The correlations between the characteristics of the prepared porous materials and the dissolution properties of activated kaolinite were also investigated. The results show that the specific surface area (SSA of porous alumina/silica increases with silica/alumina dissolution, but without marked change of the BJH pore size. Furthermore, change in pore volume is more dependent on activation temperature. The porous alumina and silica obtained from alkali leaching of kaolinite activated at 1150 °C for 15 min and acid leaching of kaolinite activated at 850 °C for 15 min are mesoporous, with SSAs, BJH pore sizes and pore volumes of 55.8 m2/g and 280.3 m2/g, 6.06 nm and 3.06 nm, 0.1455 mL/g and 0.1945 mL/g, respectively. According to the adsorption tests, porous alumina has superior adsorption capacities for Cu2+, Pb2+ and Cd2+ compared with porous silica and activated carbon. The maximum capacities of porous alumina for Cu2+, Pb2+ and Cd2+ are 134 mg/g, 183 mg/g and 195 mg/g, respectively, at 30 °C.

Investigation of porous concrete through macro and meso-scale testing

NARCIS (Netherlands)

Agar Ozbek, A.S.; Weerheijm, J.; Schlangen, H.E.J.G.

2010-01-01

In designing a porous concrete, containing a high volume of air pores, the effects of its mesoscale phases on its macro level properties have to be known. For this purpose, porous concretes having different aggregate gradings and cement paste compositions were investigated through macro-scale

Methanol-Sensing Property Improvement of Meso structured Zinc Oxide Prepared by the Nano casting Strategy

International Nuclear Information System (INIS)

Gao, Q.; Zheng, W.T.; Wei, C.D.; Lin, H.M.

2013-01-01

The specific structure and morphology often play a critical role in governing the excellent intrinsic properties of the compound semiconductor. Herein, meso structured 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 meso pores and crystalline walls, and its structure is an ideal replication of CMK-3 template. Consequently, meso structured 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 non porous ZnO prepared through conventional coprecipitation approach, meso structured 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

Reactive silica transport in fractured porous media: Analytical solutions for a system of parallel fractures

Science.gov (United States)

Yang, Jianwen

2012-04-01

A general analytical solution is derived by using the Laplace transformation to describe transient reactive silica transport in a conceptualized 2-D system involving a set of parallel fractures embedded in an impermeable host rock matrix, taking into account of hydrodynamic dispersion and advection of silica transport along the fractures, molecular diffusion from each fracture to the intervening rock matrix, and dissolution of quartz. A special analytical solution is also developed by ignoring the longitudinal hydrodynamic dispersion term but remaining other conditions the same. The general and special solutions are in the form of a double infinite integral and a single infinite integral, respectively, and can be evaluated using Gauss-Legendre quadrature technique. A simple criterion is developed to determine under what conditions the general analytical solution can be approximated by the special analytical solution. It is proved analytically that the general solution always lags behind the special solution, unless a dimensionless parameter is less than a critical value. Several illustrative calculations are undertaken to demonstrate the effect of fracture spacing, fracture aperture and fluid flow rate on silica transport. The analytical solutions developed here can serve as a benchmark to validate numerical models that simulate reactive mass transport in fractured porous media.

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...

SiO2-TiO2-P2O5 meso porous coatings for proton exchange membranes fuel cells

International Nuclear Information System (INIS)

Castro, Y.; Mosa, J.; Duran, A.

2014-01-01

The article describes the preparation of meso porous SiO 2 -TiO 2 -P 2 O 5 coatings by Sol-Gel process combined to EISA method for using as proton exchange membranes fuel cells. Tetraethyl orthosilicate (TEOS), methyl triethoxysilane (MTES), titanium tetrachloride (TiCl 4 ) and phosphorus trichloride (PCl 3 ) have used as precursors and cetyl trimethylammonium bromide (CTAB) as porous generator agent. Films were deposited by immersion technique controlling the relative humidity at 40 and 20-70% and treated at 400 to 500 degree centigrade for 15, 30, 45 and 60 min. The variation of the refractive index and thickness have studied as a function of temperature and sintering time as well as the pore volume and density of the coatings by spectroscopic ellipsometry. Moreover, the hydrophobic/hydrophilic character of the coatings has been studied by Transform Infrared Spectroscopy (FTIR) and by contact angle measurements, following the loss of methyl groups with the temperature and sintering time. The results show that these parameters are crucial to obtain coatings with high porosity and low contact angle, important to obtain high proton conductivity conditions. The sintering conditions were fixed to 400 degree centigrade/60 min. Conductivity measurements at four points show high proton conductivity, 0,16 and 0,85 S/cm, up and down ramp, respectively, at 80 degree centigrade and 80 % of humidity. These coatings are good candidates for PEMFC membranes, if they are deposited onto electrodes. (Author)

Encapsulating Silica/Antimony into Porous Electrospun Carbon Nanofibers with Robust Structure Stability for High-Efficiency Lithium Storage.

Science.gov (United States)

Wang, Hongkang; Yang, Xuming; Wu, Qizhen; Zhang, Qiaobao; Chen, Huixin; Jing, Hongmei; Wang, Jinkai; Mi, Shao-Bo; Rogach, Andrey L; Niu, Chunming

2018-04-24

To address the volume-change-induced pulverization problems of electrode materials, we propose a "silica reinforcement" concept, following which silica-reinforced carbon nanofibers with encapsulated Sb nanoparticles (denoted as SiO 2 /Sb@CNFs) are fabricated via an electrospinning method. In this composite structure, insulating silica fillers not only reinforce the overall structure but also contribute to additional lithium storage capacity; encapsulation of Sb nanoparticles into the carbon-silica matrices efficiently buffers the volume changes during Li-Sb alloying-dealloying processes upon cycling and alleviates the mechanical stress; the porous carbon nanofiber framework allows for fast charge transfer and electrolyte diffusion. These advantageous characteristics synergistically contribute to the superior lithium storage performance of SiO 2 /Sb@CNF electrodes, which demonstrate excellent cycling stability and rate capability, delivering reversible discharge capacities of 700 mA h/g at 200 mA/g, 572 mA h/g at 500 mA/g, and 468 mA h/g at 1000 mA/g each after 400 cycles. Ex situ as well as in situ TEM measurements confirm that the structural integrity of silica-reinforced Sb@CNF electrodes can efficiently withstand the mechanical stress induced by the volume changes. Notably, the SiO 2 /Sb@CNF//LiCoO 2 full cell delivers high reversible capacities of ∼400 mA h/g after 800 cycles at 500 mA/g and ∼336 mA h/g after 500 cycles at 1000 mA/g.

Electric double layer capacitance on hierarchical porous carbons in an organic electrolyte

OpenAIRE

Yamada, Hirotoshi; Moriguchi, Isamu; Kudo, Tetsuichi

2008-01-01

Nanoporous carbons were prepared by using colloidal crystal as a template. Nitrogen adsorption/desorption isotherms and transmission electron microscope images revealed that the porous carbons exhibit hierarchical porous structures with meso/macropores and micropores. Electric double layer capacitor performance of the porous carbons was investigated in an organic electrolyte of 1 M LiClO4 in propylene carbonate and dimethoxy ethane. The hierarchical porous carbons exhibited large specific dou...

Porous glass with high silica content for nuclear waste storage : preparation, characterization and leaching

International Nuclear Information System (INIS)

Aegerter, M.A.; Santos, D.I. dos; Ventura, P.C.S.

1984-01-01

Aqueous solutions simulating radioactive nuclear wastes (like Savanah River Laboratory) were incorporated in porous glass matrix with high silica content prepared by decomposition of borosilicate glass like Na 2 O - B 2 O 3 - SiO 2 . After sintering, the samples were submitted, during 28 days, to standard leaching tests MCC1, MCC5 (Soxhlet) and stagnating. The total weight loss, ph, as well as the integral and differential leaching rates and the accumulated concentrations in the leach of Si, Na, B, Ca, Mn, Al, Fe and Ni. The results are compared with the results from reference borosilicate glass, made by fusion, ceramic, synroc, concrets, etc... (E.G.) [pt

Omega-3 PUFA concentration by a novel PVDF nano-composite membrane filled with nano-porous silica particles.

Science.gov (United States)

Ghasemian, Samaneh; Sahari, Mohammad Ali; Barzegar, Mohsen; Ahmadi Gavlighi, Hasan

2017-09-01

In this study, polyvinylidene fluoride (PVDF) and nano-porous silica particle were used to fabricate an asymmetric nano-composite membrane. Silica particles enhanced the thermal stability of PVDF/SiO 2 membranes; increasing the decomposition temperature from 371°C to 408°C. Cross sectional morphology showed that silica particles were dispersed in polymer matrix uniformly. However, particle agglomeration was found at higher loading of silica (i.e., 20 by weight%). The separation performance of nano-composite membranes was also evaluated using the omega-3 polyunsaturated fatty acids (PUFA) concentration at a temperature and pressure of 30°C and 4bar, respectively. Silica particle increased the omega-3PUFA concentration from 34.8 by weight% in neat PVDF to 53.9 by weight% in PVDF with 15 by weight% of silica. Moreover, PVDF/SiO 2 nano-composite membranes exhibited enhanced anti-fouling property compared to neat PVDF membrane. Fouling mechanism analysis revealed that complete pore blocking was the predominant mechanism occurring in oil filtration. The concentration of omega-3 polyunsaturated fatty acids (PUFA) is important in the oil industries. While the current methods demand high energy consumptions in concentrating the omega-3, membrane separation technology offers noticeable advantages in producing pure omega-3 PUFA. Moreover, concentrating omega-3 via membrane separation produces products in the triacylglycerol form which possess better oxidative stability. In this work, the detailed mechanisms of fouling which limits the performance of membrane separation were investigated. Incorporating silica particles to polymeric membrane resulted in the formation of mixed matrix membrane with improved anti-fouling behaviour compared to the neat polymeric membrane. Hence, the industrial potential of membrane processing to concentrate omega-3 fatty acids is enhanced. Copyright © 2017. Published by Elsevier Ltd.

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.

Acoustic properties of a porous glass (vycor) at hypersonic frequencies

International Nuclear Information System (INIS)

Levelut, C; Pelous, J

2007-01-01

Brillouin scattering experiments have been performed from 5 to 1600 K in vycor, a porous silica glass. The acoustic velocity and attenuation at hypersonic frequencies are compared to those of bulk silica and others porous silica samples. The experimental evidence for the influence of porosity on the scattering by acoustic waves is compared to calculations. The correlation between internal friction and thermal conductivity at low temperature is discussed

Fabrication and Properties of Silica Gel/Calcium Sulfate/Strontium-doped β-tricalcium Phosphate Composite Porous Scaffolds for Bone Tissue Engineering

Directory of Open Access Journals (Sweden)

QIN Xiao-su

2018-03-01

Full Text Available The calcium sulfate/strontium-doped β-tricalcium phosphate composite spherical pellets was fabricated, using the calcium sulfate/strontium-doped β-TCP as raw material, and through the stirring spray drying method, and then composite spherical pellets were combined with silica gel, porous silica gel/calcium sulfate/strontium-doped β-tricalcium phosphate scaffold was obtained by stacking aggregation method in the mould. The XRD, SEM and FT-IR, etc are employed to examine the chemical composition, composite morphology and structure characteristics, and the degradability, porosity, mechanical properties and cytotoxicity of the scaffolds materials were studied. The results reveal that the composite porous scaffolds have irregular pore structure with pore size between 0.2-1.0mm, and they have a large number of micropores on each of the composite spherical pellets, with the aperture between 50-200μm. Moreover, the porosity of the composite scaffolds is about 62%, which can meet the requirements of scaffolds for bone tissue engineering in porosity; the cytotoxicity tests show the composite scaffolds have no cytotoxic effect and it has good degradation. Therefore, it has good application prospect in bone tissue engineering of the bone defect repair of non-bearing site.

Fractal dimensions of silica gels generated using reactive molecular dynamics simulations

International Nuclear Information System (INIS)

Bhattacharya, Sudin; Kieffer, John

2005-01-01

We have used molecular dynamics simulations based on a three-body potential with charge transfer to generate nanoporous silica aerogels. Care was taken to reproduce the sol-gel condensation reaction that forms the gel backbone as realistically as possible and to thereby produce credible gel structures. The self-similarity of aerogel structures was investigated by evaluating their fractal dimension from geometric correlations. For comparison, we have also generated porous silica glasses by rupturing dense silica and computed their fractal dimension. The fractal dimension of the porous silica structures was found to be process dependent. Finally, we have determined that the effect of supercritical drying on the fractal nature of condensed silica gels is not appreciable

Synthesis of silica nanoparticles for the manufacture of porous carbon membrane and particle size analysis by sedimentation field-flow fractionation

Energy Technology Data Exchange (ETDEWEB)

Lee, Seung Ho; Eum, Chul; Hun; Choi, Seong Ho; Kim, Woon Jung [Dept. of Chemistry, Hannam University, Daejeon (Korea, Republic of)

2016-11-15

Silica nanoparticles were synthesized by emulsion polymerization by mixing ethanol, ammonium hydroxide, water, and tetraethyl orthosilicate. An apparatus was designed and assembled for a large-scale synthesis of silica nanospheres, which was aimed for uniform mixing of the reactants. Then sedimentation field-flow fractionation (SdFFF) was used to determine the size distribution of the silica nanoparticles. SdFFF provided mass-based separation where the retention time increased with the particle size, thus the size distribution of silica nanoparticles obtained from SdFFF appeared more accurate than that from dynamic light scattering, particularly for those having broad and multimodal size distributions. A disk-shaped porous carbon membrane (PCM) was manufactured for application as an adsorbent by pressurizing the silica particles, followed by calcination. Results showed that PCM manufactured in this study has relatively high surface area and temperature stability. The PCM surface was modified by attaching a carboxyl group (PCM-COOH) and then by incorporating silver (PCM-COOH-Ag). The amount of COOH group on PCM was measured electrochemically by cyclic voltammetry, and the surface area, pore size, pore volume of PCM-COOH-Ag by Brunauer–Emmet–Teller measurement. The surface area was 40.65 and reduced to 13.02 after loading a COOH group then increased up to 30.37 after incorporating Ag.

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.

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

Analazing the impact behavior of porous concrete

NARCIS (Netherlands)

Agar Ozbek, A.S.; Weerheijm, J.

2014-01-01

Porous concrete is a special type of cementitious material incorporating a high amount of meso-size air pores that makes its characteristics markedly different from normal concrete. Therefore, it is being investigated for various applications, aiming to benefit from the presence of the air voids in

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

Silica- and silylated europium-based luminescent hybrids: new analysis tools for biological environments

International Nuclear Information System (INIS)

Pereira Duarte, Adriana

2012-01-01

The association of the very interesting luminescence properties of the lanthanide chelates with the physicochemical properties of inorganic matrix such as silica is a promising way to obtain new probes or luminescent markers for biology analyses. In this idea, this work focuses on the preparation of new hybrid materials based on the grafting of new europium(III) complexes on silica nanoparticles. These europium complexes were developed in our group using bifunctional ligands containing both complexing and grafting sites. Intrinsic characteristic of the ligands gives us the ability to make a covalent bond between the material surface and the complex. Two different methodologies were used; the first one is the direct grafting reaction involving the complex and silica nanoparticles (i.e. dense or meso-porous particles). The second one is the Stoeber reaction, where the SiO 2 nanoparticles were prepared in presence of the europium complex. The last methodology has an additional difficult, because of the presence of silylated europium complex, it needs a closer control of the physicochemical conditions. The new organic-inorganic hybrid materials, obtained in this work, present an interesting luminescence behavior and this one is depending on the localization of the europium complex, i.e. on the surface or within the nanoparticles. In addition, the obtained hybrids present the nano-metric dimension and the complex is not leachable. Analyses were realized to describe the luminescence properties, beyond surface and structural characteristics. Initial results show that the new hybrids are promising candidates for luminescent bio-markers, particularly for the time-resolved analysis. (author) [fr

Effect of various structure directing agents on the physicochemical properties of the silica aerogels prepared at an ambient pressure

KAUST Repository

Sarawade, Pradip

2013-12-01

We studied the effects of various surfactants on the textural properties (BET surface area, pore size, and pore volume) of the silica aerogels prepared at an ambient pressure. A simple surface modification of silica gel prepared at an ambient pressure through hydrolysis and polycondensation of TEOS as asilica precursor was conducted using various structure directing agents. The treatment was found to induce a significant difference in the porosity of the silica aerogel. Highly porous silica aerogels with bimodal porous structures were prepared by modifying the surface of the silica wet-gel (alcogel) with trimethylchlorosilane (TMCS) in order to preserve its porosity. The samples were analyzed by small-angle X-ray scattering and nitrogen adsorption. In this work, a possible new type of highly porous hydrophobic silica aerogel with a bimodal porous structure is presented. A hydrophilic extremely porous (high surface area and large pore volume) silica aerogel was obtained by heating the as-synthesized hydrophobic silica aerogel at 400°C for 1 h. There was a significant effect of structure directing agent on the textural properties, such as specific surface area, pore size distribution and cumulative pore volume of the silicaaerogels. © 2013 Elsevier B.V. All rights reserved.

Effect of various structure directing agents on the physicochemical properties of the silica aerogels prepared at an ambient pressure

KAUST Repository

Sarawade, Pradip; Shao, Godlistennamwel; Quang, Dangviet; Kim, Heetaik

2013-01-01

We studied the effects of various surfactants on the textural properties (BET surface area, pore size, and pore volume) of the silica aerogels prepared at an ambient pressure. A simple surface modification of silica gel prepared at an ambient pressure through hydrolysis and polycondensation of TEOS as asilica precursor was conducted using various structure directing agents. The treatment was found to induce a significant difference in the porosity of the silica aerogel. Highly porous silica aerogels with bimodal porous structures were prepared by modifying the surface of the silica wet-gel (alcogel) with trimethylchlorosilane (TMCS) in order to preserve its porosity. The samples were analyzed by small-angle X-ray scattering and nitrogen adsorption. In this work, a possible new type of highly porous hydrophobic silica aerogel with a bimodal porous structure is presented. A hydrophilic extremely porous (high surface area and large pore volume) silica aerogel was obtained by heating the as-synthesized hydrophobic silica aerogel at 400°C for 1 h. There was a significant effect of structure directing agent on the textural properties, such as specific surface area, pore size distribution and cumulative pore volume of the silicaaerogels. © 2013 Elsevier B.V. All rights reserved.

Development of porous structure simulator for multi-scale simulation of irregular porous catalysts

International Nuclear Information System (INIS)

Koyama, Michihisa; Suzuki, Ai; Sahnoun, Riadh; Tsuboi, Hideyuki; Hatakeyama, Nozomu; Endou, Akira; Takaba, Hiromitsu; Kubo, Momoji; Del Carpio, Carlos A.; Miyamoto, Akira

2008-01-01

Efficient development of highly functional porous materials, used as catalysts in the automobile industry, demands a meticulous knowledge of the nano-scale interface at the electronic and atomistic scale. However, it is often difficult to correlate the microscopic interfacial interactions with macroscopic characteristics of the materials; for instance, the interaction between a precious metal and its support oxide with long-term sintering properties of the catalyst. Multi-scale computational chemistry approaches can contribute to bridge the gap between micro- and macroscopic characteristics of these materials; however this type of multi-scale simulations has been difficult to apply especially to porous materials. To overcome this problem, we have developed a novel mesoscopic approach based on a porous structure simulator. This simulator can construct automatically irregular porous structures on a computer, enabling simulations with complex meso-scale structures. Moreover, in this work we have developed a new method to simulate long-term sintering properties of metal particles on porous catalysts. Finally, we have applied the method to the simulation of sintering properties of Pt on alumina support. This newly developed method has enabled us to propose a multi-scale simulation approach for porous catalysts

Thiol-functionalized silica colloids, grains, and membranes for irreversible adsorption of metal(oxide) nanoparticles

NARCIS (Netherlands)

Claesson, E.M.; Philipse, A.P.

2007-01-01

Thiol-functionalization is described for silica surfaces from diverging origin, including commercial silica nanoparticles and St¨ober silica as well as silica structures provided by porous glasses and novel polymer-templated silica membranes. The functionalization allows in all cases for the

Supramolecular structures on silica surfaces and their adsorptive properties.

Science.gov (United States)

Belyakov, Vladimir N; Belyakova, Lyudmila A; Varvarin, Anatoly M; Khora, Olexandra V; Vasilyuk, Sergei L; Kazdobin, Konstantin A; Maltseva, Tetyana V; Kotvitskyy, Alexey G; Danil de Namor, Angela F

2005-05-01

The study of adsorptive and chemical immobilization of beta-cyclodextrin on a surface of hydroxylated silicas with various porous structure is described. Using IR spectroscopy, thermal gravimetrical analysis with a programmed heating, and chemical analysis of the silica surface, it is shown that the process of adsorption-desorption of beta-cyclodextrin depends on the porous structure of the silica. The reaction of esterification was used for chemical grafting of beta-cyclodextrin on the surface of hydroxylated silicas. Hydrolytic stability of silicas chemically modified by beta-cyclodextrin apparently is explained by simultaneous formation of chemical and hydrogen bonds between surface silanol groups and hydroxyl groups of beta-cyclodextrin. The uptake of the cations Cu(II), Cd(II), and Pb(II) and the anions Cr(VI) and As(V) by silicas modified with beta-cyclodextrin is investigated as a function of equilibrium ion concentrations. The increase of ion uptake and selectivity of ion extraction in comparison with starting silicas is established. It is due to the formation of surface inclusion complexes of the "host-guest" type in which one molecule of beta-cyclodextrin interacts simultaneously with several ions.

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.

Synthesis and characterization of a new material based on porous silica-Chemically immobilized C,N-pyridylpyrazole for heavy metals adsorption

Energy Technology Data Exchange (ETDEWEB)

Radi, Smaail [Laboratoire de Chimie Organique, Macromoleculaire et Produits Naturels, Departement de Chimie, Faculte des Sciences, Universite Mohamed 1er, BP 524, 60 000 Oujda (Morocco)], E-mail: radi_smaail@yahoo.fr; Attayibat, Ahmed [Laboratoire de Chimie Organique, Macromoleculaire et Produits Naturels, Departement de Chimie, Faculte des Sciences, Universite Mohamed 1er, BP 524, 60 000 Oujda (Morocco); Lekchiri, Yahya [Laboratoire de Biochimie, Departement de Biologie, Faculte des Sciences, Universite Mohamed 1er, BP 524, 60 000 Oujda (Morocco); Ramdani, Abdelkrim [Laboratoire de Chimie Organique, Macromoleculaire et Produits Naturels, Departement de Chimie, Faculte des Sciences, Universite Mohamed 1er, BP 524, 60 000 Oujda (Morocco); Bacquet, Maryse [Laboratoire de Chimie Macromoleculaire, Universite des Sciences et Technologies de Lille, 59655 Villeneuve d' Ascq (France)

2008-10-15

The immobilization of C,N-pyridylpyrazole on the surface of epoxy group containing silica gel phase for the formation of a newly synthesized material based on porous silica-bound C,N-pyridylpyrazole (SGPP) is described. The surface modification was characterized by {sup 13}C NMR of solid sample, elemental analysis and infrared spectra and was studied and evaluated by determination of the surface area using the BET equation, the adsorption and desorption capability using the isotherm of nitrogen and BJH pore sizes, respectively. The new material exhibits good thermal stability determined by thermogravimetry curves. The synthesized material was utilised in column and batch methods for separation and trace extraction of (Hg{sup 2+}, Cd{sup 2+}, Pb{sup 2+}, Cu{sup 2+}, Zn{sup 2+}, K{sup +}, Na{sup +} and Li{sup +}) and compared to results of classical liquid-liquid extraction with the unbound C,N-pyridylpyrazole compound. The grafting at the surface of silica does not affect complexing properties of the ligand and the material exhibits a high selectivity toward Hg(II)

Polymer-Silica Nanocomposites: A Versatile Platform for Multifunctional Materials

Science.gov (United States)

Chiu, Chi-Kai

Solution sol-gel synthesis is a versatile approach to create polymer-silica nanocomposite materials. The solution-to-solid transformation results in a solid consisting of interconnected nanoporous structure in 3D space, making it the ideal material for filtration, encapsulation, optics, electronics, drug release, and biomaterials, etc. Although the pore between nano and meso size may be tunable using different reaction conditions, the intrinsic properties such as limited diffusion within pore structure, complicated interfacial interactions at the pore surfaces, shrinkage and stress-induced cracking and brittleness have limited the applications of this material. To overcome these problems, diffusion, pore size, shrinkage and stress-induced defects need further investigation. Thus, the presented thesis will address these important questions such as whether these limitations can be utilized as the novel method to create new materials and lead to new applications. First, the behaviors of polymers such as poly(ethylene glycol) inside the silica pores are examined by studying the nucleation and growth of AgCl at the surface of the porous matrix. The pore structure and the pressure induced by the shrinkage affect have been found to induce the growth of AgCl nanocrystals. When the same process is carried out at 160 °C, silver metallization is possible. Due to the shrinkage-induced stresses, the polymer tends to move into open crack spaces and exterior surfaces, forming interconnected silver structure. This interconnected silver structure is very unique because its density is not related to the size scale of nanopore structures. These findings suggest that it is possible to utilize defect surface of silica material as the template to create interconnected silver structure. When the scale is small, polymer may no longer be needed if the diffusion length of Ag is more than the size of silica particles. To validate our assumption, monoliths of sol-gel sample containing AgNO3

SEM and Raman studies of CNT films on porous Si

Science.gov (United States)

Belka, R.; Keczkowska, J.; Suchańska, M.; Firek, P.; Wronka, H.; Kozłowski, M.; Radomska, J.; Czerwosz, E.; Craciunoiu, F.

2017-08-01

Carbon nanotube (CNT) films deposited on different porous silica substrates were studied by Scanning Electron Microscopy (SEM) and Raman Spectroscopy (RS). The films samples were prepared by a two-step method consisting of PVD and CVD processes. In the first step the nanocomposite Ni-C film was obtained by evaporation in dynamic vacuum from two separated sources of fullerenes and nickel acetate. Those films were deposited on porous silica and DLC/porous silica substrates. Analysis of SEM imaging showed that the obtained film are composed of carbon nanotubes, the distribution, size and quality of which depend on the type of substrate. The CNT films were studied by RS method to determine the influence of the substrate type on disordering of carbonaceous structure and quality of CNT in deposited films.

Poly(NIPAM-co-MPS-grafted multimodal porous silica nanoparticles as reverse thermoresponsive drug delivery system

Directory of Open Access Journals (Sweden)

Sushilkumar A. Jadhav

2017-05-01

Full Text Available Hybrid drug delivery systems (DDS have been prepared by grafting poly(NIPAM-co-MPS chains on multimodal porous silica nanoparticles having an inner mesoporous structure and an outer thin layer of micropores. The hybrid thermoresponsive DDS were fully characterized and loaded with a model drug. The in vitro drug release tests are carried out at below and above the lower critical solution temperature (LCST of the copolymer. The results have revealed that due to the presence of small diameter (~1.3 nm micropores at the periphery of the particles, the collapsed globules of the thermoresponsive copolymer above its LCST hinders the complete release of the drug which resulted in a reverse thermoresponsive drug release profile by the hybrid DDS.

Positron annihilation lifetime spectroscopy (PALS) application in metal barrier layer integrity for porous low- k materials

CERN Document Server

Simon, Lin; Gidley, D W; Wetzel, J T; Monnig, K A; Ryan, E T; Simon, Jang; Douglas, Yu; Liang, M S; En, W G; Jones, E C; Sturm, J C; Chan, M J; Tiwari, S C; Hirose, M

2002-01-01

Positron Annihilation Lifetime Spectroscopy (PALS) is a useful tool to pre-screen metal barrier integrity for Si-based porous low-k dielectrics. Pore size of low-k, thickness of metal barrier Ta, positronium (Ps) leakage from PALS, trench sidewall morphology, electrical test from one level metal (1LM) pattern wafer and Cu diffusion analysis were all correlated. Macro-porous low-k (pore size >=200 AA) and large scale meso-porous low-k (>50~200 AA) encounter both Ps leakage and Cu diffusion into low-k dielectric in the 0.25 mu mL/0.3 mu mS structures when using SEMATECH in-house PVD Ta 250 AA as barrier layer. For small scale meso-porous (>20~50 AA) and micro- porous (<=20 AA) low-k, no Ps leakage and no Cu diffusion into low-k were observed even with PVD Ta 50 AA, which is proved also owing to sidewall densification to seal all sidewall pores due to plasma etch and ash. For future technology, smaller pore size of porous Si-based low-k (=<50 AA) will be preferential for dense low-k like trench sidewall to...

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

Ordered mesoporous silica materials with complicated structures

KAUST Repository

Han, Yu; Zhang, Daliang

2012-01-01

Periodically ordered mesoporous silicas constitute one of the most important branches of porous materials that are extensively employed in various chemical engineering applications including adsorption, separation and catalysis. This short review

Fluid Flow Programming in Paper-Derived Silica-Polymer Hybrids.

Science.gov (United States)

Dubois, Christelle; Herzog, Nicole; Rüttiger, Christian; Geißler, Andreas; Grange, Eléonor; Kunz, Ulrike; Kleebe, Hans-Joachim; Biesalski, Markus; Meckel, Tobias; Gutmann, Torsten; Gallei, Markus; Andrieu-Brunsen, Annette

2017-01-10

In paper-based devices, capillary fluid flow is based on length-scale selective functional control within a hierarchical porous system. The fluid flow can be tuned by altering the paper preparation process, which controls parameters such as the paper grammage. Interestingly, the fiber morphology and nanoporosity are often neglected. In this work, porous voids are incorporated into paper by the combination of dense or mesoporous ceramic silica coatings with hierarchically porous cotton linter paper. Varying the silica coating leads to significant changes in the fluid flow characteristics, up to the complete water exclusion without any further fiber surface hydrophobization, providing new approaches to control fluid flow. Additionally, functionalization with redox-responsive polymers leads to reversible, dynamic gating of fluid flow in these hybrid paper materials, demonstrating the potential of length scale specific, dynamic, and external transport control.

Synthesis of Porous Carbon Monoliths Using Hard Templates.

Science.gov (United States)

Klepel, Olaf; Danneberg, Nina; Dräger, Matti; Erlitz, Marcel; Taubert, Michael

2016-03-21

The preparation of porous carbon monoliths with a defined shape via template-assisted routes is reported. Monoliths made from porous concrete and zeolite were each used as the template. The porous concrete-derived carbon monoliths exhibited high gravimetric specific surface areas up to 2000 m²·g -1 . The pore system comprised macro-, meso-, and micropores. These pores were hierarchically arranged. The pore system was created by the complex interplay of the actions of both the template and the activating agent as well. On the other hand, zeolite-made template shapes allowed for the preparation of microporous carbon monoliths with a high volumetric specific surface area. This feature could be beneficial if carbon monoliths must be integrated into technical systems under space-limited conditions.

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

Monitoring Phase Behavior of Sub- and Supercritical CO2 Confined in Porous Fractal Silica with 85% Porosity

International Nuclear Information System (INIS)

Melnichenko, Yuri B.; Mayama, Hiroyuki; Cheng, Gang; Cheng, Gang; Blach, Tomasz P.

2010-01-01

Phase behavior of CO 2 confined in porous fractal silica with volume fraction of SiO 2 φ 5 = 0.15 was investigated using small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) techniques. The range of fluid densities (0 CO2 ) bulk 3 ) and temperatures (T = 22 C, 35 and 60 C) corresponded to gaseous, liquid, near critical and supercritical conditions of the bulk fluid. The results revealed formation of a dense adsorbed phase in small pores with sizes D CO2 ) bulk 3 ) the average fluid density in pores may exceed the density of bulk fluid by a factor up to 6.5 at T = 22 C. This 'enrichment factor' gradually decreases with temperature, however significant fluid densification in small pores still exists at temperature T = 60 C, i.e., far above the liquid?gas critical temperature of bulk CO 2 (T c = 31.1 C). Larger pores are only partially filled with liquid-like adsorbed layer which coexists with unadsorbed fluid in the pore core. With increasing pressure, all pores become uniformly filled with the fluid, showing no measurable enrichment or depletion of the porous matrix with CO 2 .

Positronium chemistry in porous materials

International Nuclear Information System (INIS)

Kobayashi, Y.; Ito, K.; Oka, T.; Hirata, K.

2007-01-01

Porous materials have fascinated positron and positronium chemists for over decades. In the early 1970s it was already known that ortho-positronium (o-Ps) exhibits characteristic long lifetimes in silica gels, porous glass and zeolites. Since then, our understanding of Ps formation, diffusion and annihilation has been drastically deepened. Ps is now well recognized as a powerful porosimetric and chemical probe to study the average pore size, pore size distribution, pore connectivity and surface properties of various porous materials including thin films. In this paper, developments of Ps chemistry in porous materials undertaken in the past some 40 yr are surveyed and problems to be addressed in future are briefly discussed

A novel approach for osteocalcin detection by competitive ELISA using porous silicon as a substrate.

Science.gov (United States)

Rahimi, Fereshteh; Mohammadnejad Arough, Javad; Yaghoobi, Mona; Davoodi, Hadi; Sepehri, Fatemeh; Amirabadizadeh, Masood

2017-11-01

In this study, porous silicon (PSi) was utilized instead of prevalent polystyrene platforms, and its capability in biomolecule screening was examined. Here, two types of porous structure, macroporous silicon (Macro-PSi) and mesoporous silicon (Meso-PSi), were produced on silicon wafers by electrochemical etching using different electrolytes. Moreover, both kinds of fresh and oxidized PSi samples were investigated. Next, osteocalcin as a biomarker of the bone formation process was used as a model biomarker, and the colorimetric detection was performed by competitive enzyme-linked immunosorbent assay (ELISA). Both Macro-PSi and Meso-PSi substrates in the oxidized state, specifically the Meso-porous structure, were reported to have higher surface area to volume ratio, more capacitance of surface-antigen interaction, and more ability to capture antigen in comparison with the prevalent platforms. Moreover, the optical density signal of osteocalcin detected by the ELISA technique was notably higher than the common platforms. Based on the findings of this study, PSi can potentially be used in the ELISA to achieve better results and consequently more sensitivity. A further asset of incorporating such a nanometer structure in the ELISA technique is that the system response to analyte concentration could be maintained by consuming lower monoclonal antibody (or antigen) and consequently reduces the cost of the experiment. © 2016 International Union of Biochemistry and Molecular Biology, Inc.

Self-diffusion of charged colloidal tracer spheres in transparent porous glass media: Effect of ionic strength and pore size

Science.gov (United States)

Kluijtmans, Sebastiaan G. J. M.; de Hoog, Els H. A.; Philipse, Albert P.

1998-05-01

The influence of charge on diffusion in porous media was studied for fluorescent colloidal silica spheres diffusing in a porous glass medium. The bicontinuous porous silica glasses were optically matched with an organic solvent mixture in which both glass and tracers are negatively charged. Using fluorescence recovery after photobleaching, the long-time self-diffusion coefficient DSL of the confined silica particles was monitored in situ as a function of the ionic strength and particle to pore size ratio. At high salt concentration DSL reaches a relatively high plateau value, which depends on the particle to pore size ratio. This plateau value is unexpectedly higher than the value found for uncharged silica spheres in these porous glasses, but still significantly smaller than the free particle bulk diffusion coefficient of the silica spheres. At low salt concentration DSL reduces markedly, up to the point where colloids are nearly immobilized. This peculiar retardation probably originates from potential traps and barriers at pore intersections due to deviations from cylinder symmetry in the double layer interactions between tracers and pore walls. This indicates that diffusion of charged particles in tortuous porous media may be very different from transport in long capillaries without such intersections.

Meso-optics for science and industry

International Nuclear Information System (INIS)

Soroko, L.M.

1996-01-01

The paper represents a concise overview of the meso-optical devices which provide very high selectivity and productivity. The source of these advantages is governed by the absence of the traditional 3D scanning operations. The information compression is accomplished on-line via conical wavefronts without any computer data processing. The factor of merits is of the order of 100:1. Meso-optical Fourier transition microscope for nuclear emulsion sees only straight line particle tracks and does not require depth scanning. Confocal meso-optical microscope accomplishes selective observation of the vertical particle tracks. In the meso-optical profilometer we use the phenomenon of the longitudinal interference of the conical waves. Meso-optical undulator as inserted device in the photon factories transforms conical waves into spherical ones and then into a point. Self-focusing undulator focuses side-going synchrotron radiation. Meso-optical conicometer accomplishes precise control of the conical surfaces both internal and external. Meso-optical interferometer with multipass transmission of the conical waves is used for on-line observation of the deviation of the surface of the industrial parts from the conical etalon without any scanning operations. 23 refs., 23 figs

Effect of Steam Activation on Development of Light Weight Biomorphic Porous SiC from Pine Wood Precursor

Science.gov (United States)

Manocha, Satish M.; Patel, Hemang; Manocha, L. M.

2013-02-01

Biomorphic SiC materials with tailor-made microstructure and properties similar to ceramic materials manufactured by conventional method are a new class of materials derived from natural biopolymeric cellulose templates (wood). Porous silicon carbide (SiC) ceramics with wood-like microstructure have been prepared by carbothermal reduction of charcoal/silica composites at 1300-1600 °C in inert Ar atmosphere. The C/SiO2 composites were fabricated by infiltrating silica sol into porous activated biocarbon template. Silica in the charcoal/silica composite, preferentially in the cellular pores, was found to get transformed in forms of fibers and rods due to shrinkage during drying. The changes in the morphology of resulting porous SiC ceramics after heat treatment to 1600 °C, as well as the conversion mechanism of wood to activated carbon and then to porous SiC ceramic have been investigated using scanning electron microscope, x-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. Activation of carbon prior to silica infiltration has been found to enhance conversion of charcoal to SiC. The pore structure is found to be uniform in these materials than in those made from as-such charcoal/silica composites. This provides a low-cost and eco-friendly route to advanced ceramic materials, with near-net shape potential.

Capillary pressure controlled methane hydrate and ice growth-melting patterns in porous media : synthetic silica versus natural sandstone

Energy Technology Data Exchange (ETDEWEB)

Anderson, R.; Tohidi, B.; Webber, B. [Heriot-Watt Univ., Centre for Gas Research, Edinburgh (United Kingdom). Inst. of Petroleum Engineering

2008-07-01

Although naturally-occurring gas hydrates (or clathrate hydrates) in marine sediments can pose a hazard to deepwater hydrocarbon production operations, they represent a potential strategic energy reserve. Gas hydrates can also provide a means for deep ocean carbon dioxide disposal through sequestration/storage. They have long-term importance with respect to ocean margin stability, methane release, and global climate change. However, fundamental knowledge is still lacking regarding the mechanisms of hydrate growth, accumulation and distribution within the subsurface. Marine sediments which host gas hydrates are commonly fine-grained silts, muds, and clays with narrow mean pore diameters, leading to speculation that capillary phenomena could play a significant role in controlling hydrate distribution in the seafloor, and may be partly responsible for discrepancies between observed and predicted hydrate stability zone thicknesses. A close relationship between hydrate inhibition and pore size has been confirmed through previous laboratory studies. Clathrate stability has been significantly reduced in narrow pores. However, the focus of investigations has generally been hydrate dissociation conditions in porous media, with capillary controls on the equally important process of hydrate growth being largely overlooked. This paper presented the results of an experimental investigation into methane hydrate growth and dissociation equilibria in natural medium grained sandstone. The study also compared data with that previously measured for mesoporous silica glasses. The paper discussed solid-liquid phase behaviour in confined geometries including hysteresis in porous media. It also discussed the experimental equipment and method. It was concluded that, as for synthetic silicas, hydrate growth and dissociation in the sandstone were characterised by a measurable hysteresis between opposing transitions, notably hydrate (or ice) formation occurring at temperatures lower than

Comparison of three labeled silica nanoparticles used as tracers in transport experiments in porous media. Part II: Transport experiments and modeling

International Nuclear Information System (INIS)

Vitorge, Elsa; Szenknect, Stéphanie; Martins, Jean M.-F.; Barthès, Véronique; Gaudet, Jean-Paul

2014-01-01

Three types of labeled silica nanoparticles were used in transport experiments in saturated sand. The goal of this study was to evaluate both the efficiency of labeling techniques (fluorescence (FITC), metal (Ag(0) core) and radioactivity ( 110m Ag(0) core)) in realistic transport conditions and the reactive transport of silica nanocolloids of variable size and concentration in porous media. Experimental results obtained under contrasted experimental conditions revealed that deposition in sand is controlled by nanoparticles size and ionic strength of the solution. A mathematical model is proposed to quantitatively describe colloid transport. Fluorescent labeling is widely used to study fate of colloids in soils but was the less sensitive one. Ag(0) labeling with ICP-MS detection was found to be very sensitive to measure deposition profiles. Radiolabeled ( 110m Ag(0)) nanoparticles permitted in situ detection. Results obtained with radiolabeled nanoparticles are wholly original and might be used for improving the modeling of deposition and release dynamics. -- Highlights: • Three kinds of labeled nanotracers were used in transport experiments in sand columns. • They were used as surrogates of silica nanoparticles or mineral colloid. • Deposition depending on colloid size and ionic strength was observed and modeled. • Fluorescence labeling had the worse detection limit but was the more convenient. • Radiolabeled nanotracers were detected in situ in a non destructive way. -- Follow the kinetics of transport, deposition and release of silica nanoparticles with suitably labeled nanoparticles

Ion-Exchange-Induced Selective Etching for the Synthesis of Amino-Functionalized Hollow Mesoporous Silica for Elevated-High-Temperature Fuel Cells.

Science.gov (United States)

Zhang, Jin; Liu, Jian; Lu, Shanfu; Zhu, Haijin; Aili, David; De Marco, Roland; Xiang, Yan; Forsyth, Maria; Li, Qingfeng; Jiang, San Ping

2017-09-20

As differentiated from conventional synthetic processes, amino-functionalized hollow mesoporous silica (NH 2 -HMS) has been synthesized using a new and facile strategy of ion-exchange-induced selective etching of amino-functionalized mesoporous silica (NH 2 -meso-silica) by an alkaline solution. Nuclear magnetic resonance (NMR) spectroscopy and in situ time-resolved small-angle X-ray scattering (SAXS) reveal that ion-exchange-induced selective etching arises from the gradient distribution of OH - in the NH 2 -meso-silica nanospheres. Moreover, the ion-exchange-induced selective etching mechanism is verified through a successful synthesis of hollow mesoporous silica. After infiltration with phosphotungstic acid (PWA), PWA-NH 2 -HMS nanoparticles are dispersed in the poly(ether sulfone)-polyvinylpyrrolidone (PES-PVP) matrix, forming a hybrid PWA-NH 2 -HMS/PES-PVP nanocomposite membrane. The resultant nanocomposite membrane with an optimum loading of 10 wt % of PWA-NH 2 -HMS showed an enhanced proton conductivity of 0.175 S cm -1 and peak power density of 420 mW cm -2 at 180 °C under anhydrous conditions. Excellent durability of the hybrid composite membrane fuel cell has been demonstrated at 200 °C. The results of this study demonstrated the potential of the facile synthetic strategy in the fabrication of NH 2 -HMS with controlled mesoporous structure for application in nanocomposite membranes as a technology platform for elevated-temperature proton exchange membrane fuel cells.

An efficient sodium citrate-promoted synthetic method for the preparation of AuNPs@mesoSiO2 for surface enhanced Raman spectroscopy in the detection of diluted blood

Directory of Open Access Journals (Sweden)

Yun Zou

2017-12-01

Full Text Available We report on a novel, green, and efficient organically synthetic method for the preparation of gold nanoparticles embedded in mesoporous silica (AuNPs@mesoSiO2. AuNPs@mesoSiO2 prepared by one-pot synthesis method using sodium citrate as the key reactant was applied for surface enhanced Raman spectroscopy (SERS application in the analysis of diluted blood traces. The synthesized nanoparticles are of high quality, as characterized by use of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. They exhibit high surface areas (170.18–883 m2/g and significant SERS enhancement. Detection of diluted blood (v/v, 1:50 traces through AuNPs@mesoSiO2 enhanced SERS is demonstrated, which has not been studied in previous literature. The combination of the SERS and AuNPs@mesoSiO2 would be a valuable tool for forensic investigation. Keywords: Gold nanoparticles, Mesoporous materials, Synthesis, SERS, Blood trace

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.

Strong visible-light emission of ZnS nanocrystals embedded in sol-gel silica xerogel

International Nuclear Information System (INIS)

Yang Ping; Lue, M.-K.; Song, C.-F.; Zhou, G.-J.; Ai, Z.-P.; Xu Dong; Yuan, D.-R.; Cheng, X.-F.

2003-01-01

ZnS nanoparticles embedded in novel porous phosphor silica xerogel have been synthesized by sol-gel processing. Their fluorescence properties have been evaluated and compared with those of the Na + -doped and un-doped silica xerogels. Stable and strong visible-light emission of the doped samples has been observed. The relative fluorescence intensities of the samples doped with ZnS nanoparticles (S 2- ions have been obtained by the water solution of NaS) are the highest among all of the doped samples. Its relative fluorescence intensity is about 7.5 times of that of the un-doped silica xerogel and about 300 times of that of pure ZnS nanoparticles. The emission wavelength of the ZnS-doped and Na + -doped samples is the same as that of the un-doped silica xerogel and ZnS nanoparticles (λ em =440-450 nm). This high efficiency luminescence of the doped silica xerogels has been assigned to the luminescence centers of ZnS nanoparticles and Na + in the porous phosphorescence silica xerogel

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.

Synthesis of Macroporous Silica Particles by Continuous Generation of Droplets for Insulating Materials.

Science.gov (United States)

Cho, Young-Sang; Lee, Dokyoung

2018-09-01

We report on the synthesis of porous silica particles by self-assembly routes in a continuous manner for application to thermal insulators. A continuous process was employed to produce tiny droplets containing precursor materials such as silica and organic templates for self-organization to fabricate particles with well defined pores. A rotating cylinder system or a spray drying process was adopted to form emulsions or aerosol droplets as micro-reactors for self-assembly, and the physical properties including the thermal conductivity of the resulting porous particles were compared between the two methods. The porous particles could be coated as a thick film by solution dripping, and the fluorination treatment using a silane coupling agent was performed to produce superhydrophobic surfaces of insulating layers by a lotus effect.

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

Preparation of porous bio-char and activated carbon from rice husk by leaching ash and chemical activation.

Science.gov (United States)

Ahiduzzaman, Md; Sadrul Islam, A K M

2016-01-01

Preparation porous bio-char and activated carbon from rice husk char study has been conducted in this study. Rice husk char contains high amount silica that retards the porousness of bio-char. Porousness of rice husk char could be enhanced by removing the silica from char and applying heat at high temperature. Furthermore, the char is activated by using chemical activation under high temperature. In this study no inert media is used. The study is conducted at low oxygen environment by applying biomass for consuming oxygen inside reactor and double crucible method (one crucible inside another) is applied to prevent intrusion of oxygen into the char. The study results shows that porous carbon is prepared successfully without using any inert media. The adsorption capacity of material increased due to removal of silica and due to the activation with zinc chloride compared to using raw rice husk char. The surface area of porous carbon and activated carbon are found to be 28, 331 and 645 m(2) g(-1) for raw rice husk char, silica removed rice husk char and zinc chloride activated rice husk char, respectively. It is concluded from this study that porous bio-char and activated carbon could be prepared in normal environmental conditions instead of inert media. This study shows a method and possibility of activated carbon from agro-waste, and it could be scaled up for commercial production.

Meso-Decorated Switching-Knot Gels

Science.gov (United States)

Gong, Jin; Sawamura, Kensuke; Makino, Masato; Kabir, M. H.; Furukawa, Hidemitsu

Gels are a new material having three-dimensional network structures of macromolecules. They possess excellent properties as swellability, high permeability and biocompatibility, and have been applied in various fields of daily life, food, medicine, architecture, and chemistry .In this study, we tried to prepare new multi-functional and high-strength gels by using Meso-Decoration (Meso-Deco), one new method of structure design at intermediate mesoscale. High-performance rigid-rod aromatic polymorphic crystals. The strengthening of gels can be realized by meso-decorating the gels' structure using high-performance polymorphic crystals. New gels with good mechanical properties, novel optical properties and thermal properties are expected to be developed.

A novel gel combustion procedure for the preparation of foam and porous pellets of UO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Sanjay Kumar, D. [Fuel Chemistry Division, Materials Chemistry and Metal Fuel Cycle Group, Homi Bhabha National Institute, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India); Ananthasivan, K., E-mail: asivan@igcar.gov.in [Fuel Chemistry Division, Materials Chemistry and Metal Fuel Cycle Group, Homi Bhabha National Institute, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India); Venkata Krishnan, R.; Maji, Dasarath [Fuel Chemistry Division, Materials Chemistry and Metal Fuel Cycle Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India); Dasgupta, Arup [Microscopy and Thermo-Physical Property Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Homi Bhabha National Institute, Kalpakkam, 603102, Tamil Nadu (India)

2017-01-15

In this study, it has been demonstrated for the first time how sucrose gel-combustion could be used for the preparation of UO{sub 2} foam. Further the citrate gel-combustion was gainfully used for preparing porous pellets of UO{sub 2}. The utility of two-step sintering (1073 K for 30 min and 1473 K for 4 h) for obtaining these porous bodies was demonstrated for the first time. The foams and pellets possessed meso and macro pores. A starting mixture with sucrose to nitrate ratio of 2.4 was found to yield urania foam with adequate crush strength. The porous pellets were found to possess better handling strength, lesser carbon residue and higher overall density than the foam. A citric acid to nitrate ratio 0.25 in the starting mixture, 180 MPa compaction pressure were optimal for obtaining a pellet with 40% porosity. - Highlights: • Urania foam was successfully prepared for the first time by using sucrose-gel precursor method. • Porous urania pellets were successfully prepared for the first time by using citrate gel-combustion method. • The foam comprised both meso and macro pores, possessed good crush strength and porosity. • Citric acid to nitrate ratio of 0.25 and a compaction pressure of 180 MPa were best suited for the preparation of porous pellets.

Toughening Mechanisms in Silica-Filled Epoxy Nanocomposites

Science.gov (United States)

Patel, Binay S.

and modeled fracture energy results. Furthermore, the contribution of microcracking was most prevalent at lower filler contents which suggests that the presence of microcracking may account for the previously unexplained improvements in fracture behavior attained in silica-filled epoxy nanocomposites at low filler contents. Secondly, surface modification through the application of three different propriety surface treatments ("A", "B" and "C") was found to greatly influence the processibility and fracture behavior of silica-filled epoxy nanocomposites. B-treated silica nanoparticles were found to readily form micron-scale agglomerates, settled during nanocomposite curing and showed no improvement in fracture toughness with increasing filler content. In contrast, the nanocomposites consisting of A-treated and C-treated silica nanoparticles yielded morphologies primarily containing well-dispersed nanoparticles. Therefore, fracture toughness improved with increasing filler content. Finally, particle porosity was found to have no significant effect on fracture behavior for the range of silica-filled epoxy nanocomposites investigated. Lower density porous silica nanoparticles were just as effective toughening agents as higher density non-porous silica nanoparticles. Consequently, the potential exists for the use of toughened-epoxies in lightweight structural applications.

Mass transport in thin supported silica membranes

NARCIS (Netherlands)

Benes, Nieck Edwin

2000-01-01

In this thesis multi-component mass transport in thin supported amorphous silica membranes is discussed. These membranes are micro-porous, with pore diameters smaller than 4Å and show high fluxes for small molecules (such as hydrogen) combined with high selectivities for these molecules with respect

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.

Citrus pectin derived porous carbons as a superior adsorbent toward removal of methylene blue

International Nuclear Information System (INIS)

Zhang, Wenlin; Zhang, Lian Ying; Zhao, Xi Juan; Zhou, Zhiqin

2016-01-01

An adsorbent, citrus pectin derived porous carbons with ultra-high adsorption capacity, rapid adsorption rate and good reusability toward removal of methylene blue, was synthesized by a facile zinc chloride activation approach in this study. The materials hold a great potential for treatment of dye wastewater. - Graphical abstract: Citrus pectin derived porous carbons with ultra-high adsorption capacity, rapid adsorption rate and good reusability toward methylene blue removal. - Highlights: • Citrus pectin derived porous carbons (CPPCs) were synthesized a facile zinc chloride activation approach. • CPPCs had abundant macro/meso/micropores for trapping MB molecules. • CPPCs exhibited ultrahigh adsorption capacity, rapid adsorption rate and good reusability toward removal of MB.

Citrus pectin derived porous carbons as a superior adsorbent toward removal of methylene blue

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wenlin [College of Horticulture and landscape Architecture, Southwest University, Chongqing 400716 (China); Zhang, Lian Ying [Institute for Clean Energy & Advanced Materials, Southwest University, Chongqing 400715 (China); Zhao, Xi Juan [College of Horticulture and landscape Architecture, Southwest University, Chongqing 400716 (China); Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, Chongqing 400715 (China); Zhou, Zhiqin, E-mail: zhouzhiqin@swu.edu.cn [College of Horticulture and landscape Architecture, Southwest University, Chongqing 400716 (China); Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, Chongqing 400715 (China)

2016-11-15

An adsorbent, citrus pectin derived porous carbons with ultra-high adsorption capacity, rapid adsorption rate and good reusability toward removal of methylene blue, was synthesized by a facile zinc chloride activation approach in this study. The materials hold a great potential for treatment of dye wastewater. - Graphical abstract: Citrus pectin derived porous carbons with ultra-high adsorption capacity, rapid adsorption rate and good reusability toward methylene blue removal. - Highlights: • Citrus pectin derived porous carbons (CPPCs) were synthesized a facile zinc chloride activation approach. • CPPCs had abundant macro/meso/micropores for trapping MB molecules. • CPPCs exhibited ultrahigh adsorption capacity, rapid adsorption rate and good reusability toward removal of MB.

Titanium dioxide encapsulation of supported Ag nanoparticles on the porous silica bead for increased photocatalytic activity

Science.gov (United States)

Liu, Hui; Deng, Lu; Sun, Chaochao; Li, Junqi; Zhu, Zhenfeng

2015-01-01

A new synthetic strategy has been developed to encapsulate Ag nanoparticles in heterogeneous catalysts to prevent their dropping and sintering. Ag nanoparticles with diameters about 5-10 nm were first supported on the porous silica bead. These were then covered with a fresh layer of titanium dioxide with the thickness about 5 nm. SEM and TEM images were used to confirm the success of each synthesis step, and the photocatalytic activity of the as-synthesized samples was evaluated by photocatalytic decolorization of Rhodamine B (Rh B) aqueous solution at ambient temperature under both UV and visible light irradiation. The resulting titanium dioxide encapsulated Ag nanoparticles exhibited an enhanced photocatalytic activity under both UV and visible light irradiation, this can be attributed to effective charge separation and light harvesting of the plasmonic silver nanoparticles decoration, even the reducing of the exciton recombination rate caused by the small grain size of anatase TiO2 nanocrystals.

Meso-porous α-Fe2O3 thin films synthesized via the sol-gel process for light-driven water oxidation

International Nuclear Information System (INIS)

Hamd, Wael; Laberty-Robert, Christel; Sanchez, Clement; Cobo, Saioa; Fize, Jennifer; Artero, Vincent; Baldinozzi, Gianguido; Schwartz, Wilfrid; Reymermier, Maryse; Pereira, Alexandre; Fontecave, Marc

2012-01-01

This work reports a facile and cost-effective method for synthesizing photoactive α-Fe 2 O 3 films as well as their performances when used as photoanodes for water oxidation. Transparent α-Fe 2 O 3 meso-porous films were fabricated by template-directed sol-gel chemistry coupled with the dip-coating approach, followed by annealing at various temperatures from 350 degrees C to 750 degrees C in air. α-Fe 2 O 3 films were characterized by X-ray diffraction, XPS, FE-SEM and electrochemical measurements. The photoelectrochemical performance of α-Fe 2 O 3 photoanodes was characterized and optimized through the deposition of Co-based co-catalysts via different methods (impregnation, electro-deposition and photo-electro-deposition). Interestingly, the resulting hematite films heat-treated at relatively low temperature (500 degrees C), and therefore devoid of any extrinsic dopant, achieve light-driven water oxidation under near-to-neutral (pH = 8) aqueous conditions after decoration with a Co catalyst. The onset potential is 0.75 V vs. the reversible hydrogen electrode (RHE), thus corresponding to 450 mV light-induced under potential, although modest photocurrent density values (40 μAcm -2 ) are obtained below 1.23 V vs. RHE. These new materials with a very large interfacial area in contact with the electrolyte and allowing for a high loading of water oxidation catalysts open new avenues for the optimization of photo-electrochemical water splitting. (authors)

In Situ Formed Phosphoric Acid/Phosphosilicate Nanoclusters in the Exceptional Enhancement of Durability of Polybenzimidazole Membrane Fuel Cells at Elevated High Temperatures

DEFF Research Database (Denmark)

Zhang, Jin; Aili, David; Bradley, John

2017-01-01

-meso-silica. The results indicate that the optimum limit of PWA-meso-silica loading in the PA/PBI membranes is 15 wt%. Detaled analysis indicates that the mesoporous structure of the PWA-meso-silica framework disintegrates, forming phosphosilicate phases within the PBI polymeric matrix during fuel cell operation at 200°C......Most recently, we developed a phosphotungstic acid impregnated mesoporous silica (PWA-meso-silica) and phosphoric acid doped polybenzimidazole (PA/PBI) composite membrane for use in high temperature fuel cells and achieved exceptional durability under a constant current load of 200 mA cm−2 at 200°C...... for over 2700 h. In this work, the fundamental role of PWA-meso-silica in enhancing the stability of the PA/PBI membrane has been investigated. The microstructure, the PA uptake, swelling ratio, mechanical property and conductivity of PA/PBI/PWA-meso-silica composite membranes depend on the loading of PWA...

A review on chemical methodologies for preparation of mesoporous silica and alumina based materials.

Science.gov (United States)

Naik, Bhanudas; Ghosh, Narendra Nath

2009-01-01

The discovery of novel family of molecular sieves called M41S aroused a worldwide resurgence in the field of porous materials. According to IUPAC definition inorganic solids that contain pores with diameter in the size range of 20-500 A are considered mesoporous materials. Mesoporous silica and alumina based materials find applications in catalysis, adsorption, host- guest encapsulation etc. This article reviews the current state of art and outline the recent patents in mesoporous materials research in three general areas: Synthesis, various mechanisms involved for porous structure formation and applications of silica and alumina based mesoporous materials.

Fabrication of keratin-silica hydrogel for biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Kakkar, Prachi; Madhan, Balaraman, E-mail: bmadhan76@yahoo.co.in

2016-09-01

In the recent past, keratin has been fabricated into different forms of biomaterials like scaffold, gel, sponge, film etc. In lieu of the myriad advantages of the hydrogels for biomedical applications, a keratin-silica hydrogel was fabricated using tetraethyl orthosilicate (TEOS). Textural analysis shed light on the physical properties of the fabricated hydrogel, inturn enabling the optimization of the hydrogel. The optimized keratin-silica hydrogel was found to exhibit instant springiness, optimum hardness, with ease of spreadability. Moreover, the hydrogel showed excellent swelling with highly porous microarchitecture. MTT assay and DAPI staining revealed that keratin-silica hydrogel was biocompatible with fibroblast cells. Collectively, these properties make the fabricated keratin-silica hydrogel, a suitable dressing material for biomedical applications. - Highlights: • Keratin-silica hydrogel has been fabricated using sol–gel technique. • The hydrogel shows appropriate textural properties. • The hydrogel promotes fibroblast cells proliferation. • The hydrogel has potential soft tissue engineering applications like wound healing.

Drug delivery via porous silicon: a focused patent review.

Science.gov (United States)

Kulyavtsev, Paulina A; Spencer, Roxanne P

2017-03-01

Although silicon is more commonly associated with computer chips than with drug delivery, with the discovery that porous silicon is a viable biocompatible material, mesoporous silicon with pores between 2 and 50 nm has been loaded with small molecule and biomolecule therapeutics and safely implanted for controlled release. As porous silicon is readily oxidized, porous silica must also be considered for drug delivery applications. Since 2010, only a limited number of US patents have been granted, primarily for ophthalmologic and immunotherapy applications, in contrast to the growing body of technical literature in this area.

Epoxy Crosslinked Silica Aerogels (X-Aerogels)

Science.gov (United States)

fabrizio, Eve; Ilhan, Faysal; Meador, Mary Ann; Johnston, Chris; Leventis, Nicholas

2004-01-01

NASA is interested in the development of strong lightweight materials for the dual role of thermal insulator and structural component for space vehicles; freeing more weight for useful payloads. Aerogels are very-low density materials (0.010 to 0.5 g/cc) that, due to high porosity (meso- and microporosity), can be, depending on the chemical nature of the network, ideal thermal insulators (thermal conductivity approx. 15 mW/mK). However, aerogels are extremely fragile. For practical application of aerogels, one must increase strength without compromising the physical properties attributed to low density. This has been achieved by templated growth of an epoxy polymer layer that crosslinks the "pearl necklace" network of nanoparticles: the framework of a typical silica aerogel. The requirement for conformal accumulation of the epoxy crosslinker is reaction both with the surface of silica and with itself. After cross-linking, the strength of a typical aerogel monolith increases by a factor of 200, in the expense of only a 2-fold increase in density. Strength is increased further by coupling residual unreacted epoxides with diamine.

Storage and sustained release of volatile substances from a hollow silica matrix

Energy Technology Data Exchange (ETDEWEB)

Wang Jiexin [Key Lab for Nanomaterials, Ministry of Education, Beijing 100029 (China); Ding Haomin [Research Center of the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, Beijing 100029 (China); Tao Xia [Key Lab for Nanomaterials, Ministry of Education, Beijing 100029 (China); Chen Jianfeng [Key Lab for Nanomaterials, Ministry of Education, Beijing 100029 (China)

2007-06-20

Porous hollow silica nanospheres (PHSNSs) prepared by adopting a nanosized CaCO{sub 3} template were utilized for the first time as a novel carrier for the storage and sustained release of volatile substances. Two types of volatile substances, Indian pipal from perfumes and peroxyacetic acid from disinfectants, were selected and then tested by one simple adsorption process with two separate comparative carriers, i.e. activated carbon and solid porous silica. It was demonstrated that a high storage capacity (9.6 ml{sub perfume}/mg{sub carrier}) of perfume could be achieved in a PHSNS matrix, which was almost 14 times as much as that of activated carbon. The perfume release profiles showed that PHSNSs exhibited sustained multi-stage release behaviour, while the constant release of activated carbon at a low level was discerned. Further, a Higuchi model study proved that the release process of perfume in both carriers followed a Fickian diffusion mechanism. For peroxyacetic acid as a disinfectant model, PHSNSs also displayed a much better delayed-delivery process than a solid porous silica system owing to the existence of unique hollow frameworks. Therefore, the aforementioned excellent sustained-release behaviours would make PHSNSs a promising carrier for storage and sustained delivery applications of volatile substances.

Ordered mesoporous silica materials with complicated structures

KAUST Repository

Han, Yu

2012-05-01

Periodically ordered mesoporous silicas constitute one of the most important branches of porous materials that are extensively employed in various chemical engineering applications including adsorption, separation and catalysis. This short review gives an introduction to recently developed mesoporous silicas with emphasis on their complicated structures and synthesis mechanisms. In addition, two powerful techniques for solving complex mesoporous structures, electron crystallography and electron tomography, are compared to elucidate their respective strength and limitations. Some critical issues and challenges regarding the development of novel mesoporous structures as well as their applications are also discussed. © 2011 Elsevier Ltd.

Porous silicon technology for integrated microsystems

Science.gov (United States)

Wallner, Jin Zheng

With the development of micro systems, there is an increasing demand for integrable porous materials. In addition to those conventional applications, such as filtration, wicking, and insulating, many new micro devices, including micro reactors, sensors, actuators, and optical components, can benefit from porous materials. Conventional porous materials, such as ceramics and polymers, however, cannot meet the challenges posed by micro systems, due to their incompatibility with standard micro-fabrication processes. In an effort to produce porous materials that can be used in micro systems, porous silicon (PS) generated by anodization of single crystalline silicon has been investigated. In this work, the PS formation process has been extensively studied and characterized as a function of substrate type, crystal orientation, doping concentration, current density and surfactant concentration and type. Anodization conditions have been optimized for producing very thick porous silicon layers with uniform pore size, and for obtaining ideal pore morphologies. Three different types of porous silicon materials: meso porous silicon, macro porous silicon with straight pores, and macro porous silicon with tortuous pores, have been successfully produced. Regular pore arrays with controllable pore size in the range of 2mum to 6mum have been demonstrated as well. Localized PS formation has been achieved by using oxide/nitride/polysilicon stack as masking materials, which can withstand anodization in hydrofluoric acid up to twenty hours. A special etching cell with electrolytic liquid backside contact along with two process flows has been developed to enable the fabrication of thick macro porous silicon membranes with though wafer pores. For device assembly, Si-Au and In-Au bonding technologies have been developed. Very low bonding temperature (˜200°C) and thick/soft bonding layers (˜6mum) have been achieved by In-Au bonding technology, which is able to compensate the potentially

Impact of Micro Silica Surface Hydroxyl Groups on the Properties of Calcium Silicate Products

DEFF Research Database (Denmark)

Haastrup, Sonja; Jørgensen, Bianca; Yu, Donghong

2017-01-01

Porous calcium silicates are widely used in insulating systems for high temperature applications. In the production of porous calcium silicates, quicklime and micro silica have been utilized as key raw materials. In the reaction between SiO2 and CaO, the dissolution of SiO2 has been proven...

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.

Pore fabrication in various silica-based nanoparticles by controlled etching

KAUST Repository

Zhao, Lan

2010-07-20

A novel method based on controlled etching was developed to fabricate nanopores on preformed silica nanoparticles (<100 nm in diameter). The obtained monodisperse nanoporous particles could form highly stable homogeneous colloidal solution. Fluorescent silica nanoparticles and magnetic silica-coated γ-Fe 2O 3 nanoparticles were investigated as examples to illustrate that this strategy could be generally applied to various silica-based functional nanoparticles. The results indicated that this method was effective for generating pores on these nanoparticles without altering their original functionalities. The obtained multifunctional nanoparticles would be useful for many biological and biomedical applications. These porous nanoparticles could also serve as building blocks to fabricate three-dimensionally periodic structures that have the potential to be used as photonic crystals. © 2010 American Chemical Society.

Electroless porous silicon formation applied to fabrication of boron-silica-glass cantilevers

DEFF Research Database (Denmark)

Teva, Jordi; Davis, Zachary James; Hansen, Ole

2010-01-01

This work describes the characterization and optimization of anisotropic formation of porous silicon in large volumes (0.5-1 mm3) of silicon by an electroless wet etching technique. The main goal is to use porous silicon as a sacrificial volume for bulk micromachining processes, especially in cases...... where etching of the full wafer thickness is needed. The porous silicon volume is formed by a metal-assisted etching in a wet chemical solution composed of hydrogen peroxide (30%), hydrofluoric acid (40%) and ethanol. This paper focuses on optimizing the etching conditions in terms of maximizing...... for bio-chemical sensors. The porous silicon volume is formed in an early step of the fabrication process, allowing easy handling of the wafer during all of the micromachining processes in the process flow. In the final process step, the porous silicon is quickly etched by immersing the wafer in a KOH...

Targeting of porous hybrid silica nanoparticles to cancer cells

NARCIS (Netherlands)

Rosenholm, J.M.; Meinander, A.; Peuhu, E.; Niemi, R.; Eriksson, J.E.; Sahlgren, C.; Lindén, M.

2009-01-01

Mesoporous silica nanoparticles functionalized by surface hyperbranching polymerization of polyethylene imine), PEI, were further modified by introducing both fluorescent and targeting moieties, with the aim of specifically targeting cancer cells. Owing to the high abundance of folate receptors in

Fabrication of polystyrene porous films with gradient pore structures

International Nuclear Information System (INIS)

Yan Hongwei; Zhang Lin; Li Bo; Yin Qiang

2010-01-01

Silica opals and multilayer heterostructures were fabricated by vertical deposition technique. Polystyrene inverse opals and gradient porous structures were obtained by colloidal templating, in order to control the pore microstructure of polymer porous materials. As shown in the scanning electron microscopy images, the polystyrene porous structures are precise replicas of inverse structures of the original templates. After being infiltrated with the polystyrene, the photonic stop-band position of the opal composite is redshifted compared with the original template, and it is blueshifted after the opal template being removed. The filling ratio of polystyrene was calculated according to the Bragg formula. (authors)

Three-dimensional printing of transparent fused silica glass

Science.gov (United States)

Kotz, Frederik; Arnold, Karl; Bauer, Werner; Schild, Dieter; Keller, Nico; Sachsenheimer, Kai; Nargang, Tobias M.; Richter, Christiane; Helmer, Dorothea; Rapp, Bastian E.

2017-04-01

Glass is one of the most important high-performance materials used for scientific research, in industry and in society, mainly owing to its unmatched optical transparency, outstanding mechanical, chemical and thermal resistance as well as its thermal and electrical insulating properties. However, glasses and especially high-purity glasses such as fused silica glass are notoriously difficult to shape, requiring high-temperature melting and casting processes for macroscopic objects or hazardous chemicals for microscopic features. These drawbacks have made glasses inaccessible to modern manufacturing technologies such as three-dimensional printing (3D printing). Using a casting nanocomposite, here we create transparent fused silica glass components using stereolithography 3D printers at resolutions of a few tens of micrometres. The process uses a photocurable silica nanocomposite that is 3D printed and converted to high-quality fused silica glass via heat treatment. The printed fused silica glass is non-porous, with the optical transparency of commercial fused silica glass, and has a smooth surface with a roughness of a few nanometres. By doping with metal salts, coloured glasses can be created. This work widens the choice of materials for 3D printing, enabling the creation of arbitrary macro- and microstructures in fused silica glass for many applications in both industry and academia.

Ordered silica particles made by nonionic surfactant for VOCs sorption

Energy Technology Data Exchange (ETDEWEB)

Difallah, Oumaima; Hamaizi, Hadj, E-mail: hamaizimizou@yahoo.fr [University of Oran, OranMenaouer (Algeria); Amate, Maria Dolores Urena; Socias-Viciana, Maria Del Mar [University of Almeria (Spain)

2017-07-15

Adsorption of light organic compounds such acetone, 1-propanol and carbon dioxide was tested by using mesoporous silica materials made from non ionic surfactant with long chain and silica sources as tetraethyl orthosilicate TEOS and modified Na-X and Li-A Zeolites. X-ray powder diffraction (XRD), nitrogen adsorption-desorption analysis and scanning electron microscopy (SEM) were applied to characterize the silica particles of a variety prepared samples. Acetone, 1-propanol and CO{sub 2} adsorption at 298K was evaluated by a volumetric method and indicate a high sorption capacity of organic compounds depending essentially on the porous texture of adsorbents. An adsorption kinetic model was proposed to describe the adsorption of VOCs over template-free mesoporous silica materials. A good agreement with experimental data was found. (author)

Experiences with the ALICE Mesos infrastructure

Science.gov (United States)

Berzano, D.; Eulisse, G.; Grigoraş, C.; Napoli, K.

2017-10-01

Apache Mesos is a resource management system for large data centres, initially developed by UC Berkeley, and now maintained under the Apache Foundation umbrella. It is widely used in the industry by companies like Apple, Twitter, and Airbnb and it is known to scale to 10 000s of nodes. Together with other tools of its ecosystem, such as Mesosphere Marathon or Metronome, it provides an end-to-end solution for datacenter operations and a unified way to exploit large distributed systems. We present the experience of the ALICE Experiment Offline & Computing in deploying and using in production the Apache Mesos ecosystem for a variety of tasks on a small 500 cores cluster, using hybrid OpenStack and bare metal resources. We will initially introduce the architecture of our setup and its operation, we will then describe the tasks which are performed by it, including release building and QA, release validation, and simple Monte Carlo production. We will show how we developed Mesos enabled components (called “Mesos Frameworks”) to carry out ALICE specific needs. In particular, we will illustrate our effort to integrate Work Queue, a lightweight batch processing engine developed by University of Notre Dame, which ALICE uses to orchestrate release validation. Finally, we will give an outlook on how to use Mesos as resource manager for DDS, a software deployment system developed by GSI which will be the foundation of the system deployment for ALICE next generation Online-Offline (O2).

Synthesis and Gas Transport Properties of Hyperbranched Polyimide–Silica Hybrid/Composite Membranes

Directory of Open Access Journals (Sweden)

Masako Miki

2013-12-01

Full Text Available Hyperbranched polyimide–silica hybrids (HBPI–silica HBDs and hyperbranched polyimide–silica composites (HBPI–silica CPTs were prepared, and their general and gas transport properties were investigated to clarify the effect of silica sources and preparation methods. HBPI–silica HBDs and HBPI–silica CPTs were synthesized by two-step polymerization of A2 + B3 monomer system via polyamic acid as precursor, followed by hybridizing or blending silica sources. Silica components were incorporated by the sol-gel reaction with tetramethoxysilane (TMOS or the addition of colloidal silica. In HBPI-silica HBDs, the aggregation of silica components is controlled because of the high affinity of HBPI and silica caused by the formation of covalent bonds between HBPI and silica. Consequently, HBPI-silica HBDs had good film formability, transparency, and mechanical properties compared with HBPI-silica CPTs. HBPI-silica HBD and CPT membranes prepared via the sol-gel reaction with TMOS showed specific gas permeabilities and permselectivities for CO2/CH4 separation, that is, both CO2 permeability and CO2/CH4 selectivity increased with increasing silica content. This result suggests that gas transport can occur through a molecular sieving effect of the porous silica network derived from the sol-gel reaction and/or through the narrow interfacial region between the silica networks and the organic matrix.

Mathematical model and calculation algorithm of micro and meso levels of separation process of gaseous mixtures in molecular sieves

International Nuclear Information System (INIS)

Umarova, Zhanat; Botayeva, Saule; Yegenova, Aliya; Usenova, Aisaule

2015-01-01

In the given article, the main thermodynamic aspects of the issue of modeling diffusion transfer in molecular sieves have been formulated. Dissipation function is used as a basic notion. The differential equation, connecting volume flow with the change of the concentration of catchable component has been derived. As a result, the expression for changing the concentration of the catchable component and the coefficient of membrane detecting has been received. As well, the system approach to describing the process of gases separation in ultra porous membranes has been realized and micro and meso-levels of mathematical modeling have been distinguished. The non-ideality of the shared system is primarily taken into consideration at the micro-level and the departure from the diffusion law of Fick has been taken into account. The calculation method of selectivity considering fractal structure of membranes has been developed at the meso level. The calculation algorithm and its software implementation have been suggested

Mathematical model and calculation algorithm of micro and meso levels of separation process of gaseous mixtures in molecular sieves

Energy Technology Data Exchange (ETDEWEB)

Umarova, Zhanat; Botayeva, Saule; Yegenova, Aliya; Usenova, Aisaule [South Kazakhstan State University, 5, Tauke Khan Avenue, 160012 Shymkent (Kazakhstan)

2015-05-15

In the given article, the main thermodynamic aspects of the issue of modeling diffusion transfer in molecular sieves have been formulated. Dissipation function is used as a basic notion. The differential equation, connecting volume flow with the change of the concentration of catchable component has been derived. As a result, the expression for changing the concentration of the catchable component and the coefficient of membrane detecting has been received. As well, the system approach to describing the process of gases separation in ultra porous membranes has been realized and micro and meso-levels of mathematical modeling have been distinguished. The non-ideality of the shared system is primarily taken into consideration at the micro-level and the departure from the diffusion law of Fick has been taken into account. The calculation method of selectivity considering fractal structure of membranes has been developed at the meso level. The calculation algorithm and its software implementation have been suggested.

Unifying Inference of Meso-Scale Structures in Networks.

Science.gov (United States)

Tunç, Birkan; Verma, Ragini

2015-01-01

Networks are among the most prevalent formal representations in scientific studies, employed to depict interactions between objects such as molecules, neuronal clusters, or social groups. Studies performed at meso-scale that involve grouping of objects based on their distinctive interaction patterns form one of the main lines of investigation in network science. In a social network, for instance, meso-scale structures can correspond to isolated social groupings or groups of individuals that serve as a communication core. Currently, the research on different meso-scale structures such as community and core-periphery structures has been conducted via independent approaches, which precludes the possibility of an algorithmic design that can handle multiple meso-scale structures and deciding which structure explains the observed data better. In this study, we propose a unified formulation for the algorithmic detection and analysis of different meso-scale structures. This facilitates the investigation of hybrid structures that capture the interplay between multiple meso-scale structures and statistical comparison of competing structures, all of which have been hitherto unavailable. We demonstrate the applicability of the methodology in analyzing the human brain network, by determining the dominant organizational structure (communities) of the brain, as well as its auxiliary characteristics (core-periphery).

Unifying Inference of Meso-Scale Structures in Networks.

Directory of Open Access Journals (Sweden)

Birkan Tunç

Full Text Available Networks are among the most prevalent formal representations in scientific studies, employed to depict interactions between objects such as molecules, neuronal clusters, or social groups. Studies performed at meso-scale that involve grouping of objects based on their distinctive interaction patterns form one of the main lines of investigation in network science. In a social network, for instance, meso-scale structures can correspond to isolated social groupings or groups of individuals that serve as a communication core. Currently, the research on different meso-scale structures such as community and core-periphery structures has been conducted via independent approaches, which precludes the possibility of an algorithmic design that can handle multiple meso-scale structures and deciding which structure explains the observed data better. In this study, we propose a unified formulation for the algorithmic detection and analysis of different meso-scale structures. This facilitates the investigation of hybrid structures that capture the interplay between multiple meso-scale structures and statistical comparison of competing structures, all of which have been hitherto unavailable. We demonstrate the applicability of the methodology in analyzing the human brain network, by determining the dominant organizational structure (communities of the brain, as well as its auxiliary characteristics (core-periphery.

Growth and physiological responses of maize (Zea mays L.) to porous silica nanoparticles in soil

Energy Technology Data Exchange (ETDEWEB)

Suriyaprabha, R.; Karunakaran, G.; Yuvakkumar, R.; Prabu, P.; Rajendran, V., E-mail: veerajendran@gmail.com [K. S. Rangasamy College of Technology, Centre for Nano Science and Technology (India); Kannan, N. [K. S. Rangasamy College of Arts and Science, Department of Biotechnology (India)

2012-12-15

The present study aims to explore the effect of high surface area (360.85 m{sup 2} g{sup -1}) silica nanoparticles (SNPs) (20-40 nm) extracted from rice husk on the physiological and anatomical changes during maize growth in sandy loam soil at four concentrations (5-20 kg ha{sup -1}) in comparison with bulk silica (15-20 kg ha{sup -1}). The plant responses to nano and bulk silica treatments were analyzed in terms of growth characteristics, phyto compounds such as total protein, chlorophyll, and other organic compounds (gas chromatography-mass spectroscopy), and silica accumulation (high-resolution scanning electron microscopy). Growth characteristics were much influenced with increasing concentration of SNPs up to 15 kg ha{sup -1} whereas at 20 kg ha{sup -1}, no significant increments were noticed. Silica accumulation in leaves was high at 10 and 15 kg ha{sup -1} (0.57 and 0.82 %) concentrations of SNPs. The observed physiological changes show that the expression of organic compounds such as proteins, chlorophyll, and phenols favored to maize treated with nanosilica especially at 15 kg ha{sup -1} compared with bulk silica and control. Nanoscale silica regimes at 15 kg ha{sup -1} has a positive response of maize than bulk silica which help to improve the sustainable farming of maize crop as an alternative source of silica fertilizer.

NMR 1D-imaging of water infiltration into meso-porous matrices

International Nuclear Information System (INIS)

Le Feunteun, St.; Diat, O.; Podor, R.; Le Feunteun, St.; Poulesquen, A.; Poulesquen, A.

2011-01-01

It is shown that coupling nuclear magnetic resonance (NMR) 1D-imaging with the measure of NMR relaxation times and self-diffusion coefficients can be a very powerful approach to investigate fluid infiltration into porous media. Such an experimental design was used to study the very slow seeping of pure water into hydrophobic materials. We consider here three model samples of nuclear waste conditioning matrices which consist in a dispersion of NaNO 3 (highly soluble) and/or BaSO 4 (poorly soluble) salt grains embedded in a bitumen matrix. Beyond studying the moisture progression according to the sample depth, we analyze the water NMR relaxation times and self-diffusion coefficients along its 1D-concentration profile to obtain spatially resolved information on the solution properties and on the porous structure at different scales. It is also shown that, when the relaxation or self-diffusion properties are multimodal, the 1D-profile of each water population is recovered. Three main levels of information were disclosed along the depth-profiles. They concern (i) the water uptake kinetics, (ii) the salinity and the molecular dynamics of the infiltrated solutions and (iii) the microstructure of the water-filled porosities: open networks coexisting with closed pores. All these findings were fully validated and enriched by NMR cryo-poro-metry experiments and by performing environmental scanning electronic microscopy observations. Surprisingly, results clearly show that insoluble salts enhance the water progression and thereby increase the capability of the material to uptake water. (authors)

Synthesis of nano grade hollow silica sphere via a soft template method.

Science.gov (United States)

Tsai, Ming-Shyong; Li, Miao Ju; Yen, Fu-Hsu

2008-06-01

The nano grade hollow silica sphere (HSS) was synthesized by a novel soft template method. We found that the precipitate of aluminate had a porous structure that could be the soft template for HSS. After mixing the colloidal silica with the aluminate precipitate, the bubble trapped in this porous structure could form the nano grade HSS. The aluminate precipitate was removed by adjusting the pH of the slurry to approximately 1. The outside diameter, the specific surface, and the mean pore size diameter of the forming HSS were 60-90 nm, 571 m2/g, and 3 nm, respectively. The formed HSS was collected by modifying the surface with Si(OCH3)3CHCH2 (VTMO) and then filtrating the precipitated gel in the n-butanol and ethanol solvent system.

A facile approach for the synthesis of monolithic hierarchical porous carbons – high performance materials for amine based CO2 capture and supercapacitor electrode

KAUST Repository

Estevez, Luis; Dua, Rubal; Bhandari, Nidhi; Ramanujapuram, Anirudh; Wang, Peng; Giannelis, Emmanuel P.

2013-01-01

An ice templating coupled with hard templating and physical activation approach is reported for the synthesis of hierarchically porous carbon monoliths with tunable porosities across all three length scales (macro- meso- and micro), with ultrahigh

Porous asymmetric SiO2-g-PMMA nanoparticles produced by phase inversion

KAUST Repository

Munirasu, Selvaraj

2014-07-22

A new kind of asymmetric organic-inorganic porous structure has been proposed. Asymmetric lattices of polymer grafted silica nanoparticles were manufactured by casting and phase inversion in water. Silica nanoparticles were first functionalized with 3-(dimethylethoxysilyl)propyl-2-bromoisobutyrate, followed by grafting of poly(methylmethacrylate) (PMMA) segments, performed by atom-transfer radical polymerization. Mechanically stable self-standing films were prepared by casting a dispersion of functionalized nanoparticles in different solvents and immersion in water. The resulting asymmetrically porous morphology and nanoparticle assembly was characterized by scanning electron and atomic force microscopy. The PMMA functionalized SiO2 hybrid material in acetone or acetone/dioxane led to the best-assembled structures. Porous asymmetric membranes were prepared by adding free PMMA and PMMA terminated with hydrophilic hydroxyl group. Nitrogen flow of 2800 L m-2 h -1 was measured at 1.3 bar demonstrating the porosity and potential application for membrane technology. © 2014 Springer Science+Business Media New York.

A study of the isobutane dehydrogenation in a porous membrane catalytic reactor: design, use and modelling

Energy Technology Data Exchange (ETDEWEB)

Casanave, D

1996-01-26

The aim of this study was to set up and model a catalytic fixed-bed membrane reactor for the isobutane dehydrogenation. The catalyst, developed at Catalysis Research Institute (IRC), was a silicalite-supported Pt-based catalyst. Their catalytic performances (activity, selectivity, stability) where found better adapted to the membrane reactor, when compared with commercial Pt or Cr based catalysts. The kinetic study of the reaction has been performed in a differential reactor and led to the determination of a kinetic law, suitable when the catalyst is used near thermodynamic equilibrium. The mass transfer mechanisms were determined in meso-porous and microporous membranes through both permeability and gas mixtures (iC{sub 4}/H{sub 2}/N{sub 2}) separation measurements. For the meso-porous {gamma}-alumina, the mass transfer is ensured by a Knudsen diffusion mechanism which can compete with surface diffusion for condensable gas like isobutane. The resulting permselectivity H{sub 2}/iC4 of this membrane is low ({approx} 4). For the microporous zeolite membrane, molecular sieving occurs due to steric hindrance, leading to higher permselectivity {approx}14. Catalyst/membrane associations were compared in terms of isobutane dehydrogenation performances, for both types of membranes (meso-porous and microporous) and for two different reactor configurations (co-current and counter-current sweep gas flow). The best experimental results were obtained with the zeolite membrane, when sweeping the outer compartment in a co-current flow. The equilibrium displacement observed with the {gamma}-alumina membrane was lower and mainly due to a dilution effect of the reaction mixture by the sweep gas. A mathematical model was developed, which correctly describes all the experimental results obtained with the zeolite membrane, when the co-current mode is used. (Abstract Truncated)

Synthesis And Characterization Of Pure-Silica- Zeolite-Beta Membrane

Directory of Open Access Journals (Sweden)

Yeong Yin Fong

2017-11-01

Full Text Available The semiconductor industry needs low dielectric constant (low k-value materials to more advance microprocessor and chips by reducing the size of the device features. In fabricate this context, a new material with lower k value than conventional silica ( k = 3.9 - 4.2 is needed in order to improve the circuit performance. As per the recent International Semiconductor Technology plan, a low-k material with a k = 1.6 will be needed by 2010. The choice of the inorganic zeolite membrane is an attractive option for low k material and suitable for microprocess application.  In the present study, a pure silica zeolite beta membrane coated on the non-porous stainless steel support was synthesized using in situ crystallization of a gel with the composition of  SiO2 : 0.6 TEAOH : 0.6 HF : 10.1 H2O. The crystallization was carried in the presence of tetraethylammonium hydroxide TEA(OH as structure directing agent, fumed silica, HF and deionized water at pH value of 9. The crystallization under hydrothermal conditions at 130oC was carried out for the time period of 14 days. The membrane was characterized by X-Ray Diffraction ( XRD ,  Thermogravimetric Analysis ( TGA , Nitrogen Adsorption and Scanning Electron Microscope ( SEM .   SEM micrographs show highly crystalline, truncated square bipyramidal morphology of pure silica zeolite beta was coated on the non-porous stainless steel support. The membrane dielectric constant, k-value was measured as 2.64 which makes it suitable for the microprocessor applications.

Kinetics Study of Gas Pollutant Adsorption and Thermal Desorption on Silica Gel

Directory of Open Access Journals (Sweden)

Rong A

2017-06-01

Full Text Available Silica gel is a typical porous desiccant material. Its adsorption performance for gaseous air pollutants was investigated to determine its potential contribution to reducing such pollutants. Three gaseous air pollutants, toluene, carbon dioxide, and methane, were investigated in this paper. A thermogravimetric analyzer was used to obtain the equilibrium adsorption capacity of gases on single silica gel particles. The silica gel adsorption capacity for toluene is much higher than that for carbon dioxide and methane. To understand gas pollutant thermal desorption from silica gel, the thermogravimetric analysis of toluene desorption was conducted with 609 ppm toluene vapor at 313 K, 323 K, and 333 K. The overall regeneration rate of silica gel was strongly dependent on temperature and the enthalpy of desorption. The gas pollutant adsorption performance and thermal desorption on silica gel material may be used to estimate the operating and design parameters for gas pollutant adsorption by desiccant wheels.

SiO{sub 2}-TiO{sub 2}-P{sub 2}O{sub 5} meso porous coatings for proton exchange membranes fuel cells; Recubrimientos meso-porosos de SiO{sub 2}-TiO{sub 2}-P{sub 2}O{sub 5} para aplicaciones en pilas de combustible de intercambio protonico

Energy Technology Data Exchange (ETDEWEB)

Castro, Y.; Mosa, J.; Duran, A.

2014-07-01

The article describes the preparation of meso porous SiO{sub 2}-TiO{sub 2}-P{sub 2}O{sub 5} coatings by Sol-Gel process combined to EISA method for using as proton exchange membranes fuel cells. Tetraethyl orthosilicate (TEOS), methyl triethoxysilane (MTES), titanium tetrachloride (TiCl{sub 4}) and phosphorus trichloride (PCl{sub 3}) have used as precursors and cetyl trimethylammonium bromide (CTAB) as porous generator agent. Films were deposited by immersion technique controlling the relative humidity at 40 and 20-70% and treated at 400 to 500 degree centigrade for 15, 30, 45 and 60 min. The variation of the refractive index and thickness have studied as a function of temperature and sintering time as well as the pore volume and density of the coatings by spectroscopic ellipsometry. Moreover, the hydrophobic/hydrophilic character of the coatings has been studied by Transform Infrared Spectroscopy (FTIR) and by contact angle measurements, following the loss of methyl groups with the temperature and sintering time. The results show that these parameters are crucial to obtain coatings with high porosity and low contact angle, important to obtain high proton conductivity conditions. The sintering conditions were fixed to 400 degree centigrade/60 min. Conductivity measurements at four points show high proton conductivity, 0,16 and 0,85 S/cm, up and down ramp, respectively, at 80 degree centigrade and 80 % of humidity. These coatings are good candidates for PEMFC membranes, if they are deposited onto electrodes. (Author)

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...

High-density oxidized porous silicon

International Nuclear Information System (INIS)

Gharbi, Ahmed; Souifi, Abdelkader; Remaki, Boudjemaa; Halimaoui, Aomar; Bensahel, Daniel

2012-01-01

We have studied oxidized porous silicon (OPS) properties using Fourier transform infraRed (FTIR) spectroscopy and capacitance–voltage C–V measurements. We report the first experimental determination of the optimum porosity allowing the elaboration of high-density OPS insulators. This is an important contribution to the research of thick integrated electrical insulators on porous silicon based on an optimized process ensuring dielectric quality (complete oxidation) and mechanical and chemical reliability (no residual pores or silicon crystallites). Through the measurement of the refractive indexes of the porous silicon (PS) layer before and after oxidation, one can determine the structural composition of the OPS material in silicon, air and silica. We have experimentally demonstrated that a porosity approaching 56% of the as-prepared PS layer is required to ensure a complete oxidation of PS without residual silicon crystallites and with minimum porosity. The effective dielectric constant values of OPS materials determined from capacitance–voltage C–V measurements are discussed and compared to FTIR results predictions. (paper)

Titanium dioxide encapsulation of supported Ag nanoparticles on the porous silica bead for increased photocatalytic activity

International Nuclear Information System (INIS)

Liu, Hui; Deng, Lu; Sun, Chaochao; Li, Junqi; Zhu, Zhenfeng

2015-01-01

Graphical abstract: - Highlights: • A novel Ag-loading and TiO 2 -coating technique was used to prepare samples. • The photocatalytic activity of the product was evaluated by removing of Rh B. • The as-synthesized samples showed an excellent photocatalytic activity. - Abstract: A new synthetic strategy has been developed to encapsulate Ag nanoparticles in heterogeneous catalysts to prevent their dropping and sintering. Ag nanoparticles with diameters about 5–10 nm were first supported on the porous silica bead. These were then covered with a fresh layer of titanium dioxide with the thickness about 5 nm. SEM and TEM images were used to confirm the success of each synthesis step, and the photocatalytic activity of the as-synthesized samples was evaluated by photocatalytic decolorization of Rhodamine B (Rh B) aqueous solution at ambient temperature under both UV and visible light irradiation. The resulting titanium dioxide encapsulated Ag nanoparticles exhibited an enhanced photocatalytic activity under both UV and visible light irradiation, this can be attributed to effective charge separation and light harvesting of the plasmonic silver nanoparticles decoration, even the reducing of the exciton recombination rate caused by the small grain size of anatase TiO 2 nanocrystals

In Situ Loading of Basic Fibroblast Growth Factor Within Porous Silica Nanoparticles for a Prolonged Release

Directory of Open Access Journals (Sweden)

Postovit Lynne-Marie

2009-01-01

Full Text Available Abstract Basic fibroblast growth factor (bFGF, a protein, plays a key role in wound healing and blood vessel regeneration. However, bFGF is easily degraded in biologic systems. Mesoporous silica nanoparticles (MSNs with well-tailored porous structure have been used for hosting guest molecules for drug delivery. Here, we report an in situ route to load bFGF in MSNs for a prolonged release. The average diameter (d of bFGF-loaded MSNs is 57 ± 8 nm produced by a water-in-oil microemulsion method. The in vitro releasing profile of bFGF from MSNs in phosphate buffer saline has been monitored for 20 days through a colorimetric enzyme linked immunosorbent assay. The loading efficiency of bFGF in MSNs is estimated at 72.5 ± 3%. In addition, the cytotoxicity test indicates that the MSNs are not toxic, even at a concentration of 50 μg/mL. It is expected that the in situ loading method makes the MSNs a new delivery system to deliver protein drugs, e.g. growth factors, to help blood vessel regeneration and potentiate greater angiogenesis.

Morphology and properties of silica/novolac hybrid xerogels synthesized using sol–gel polymerization at solvent vapor-saturated atmosphere

International Nuclear Information System (INIS)

Seraji, Mohamad Mehdi; Seifi, Azadeh; Bahramian, Ahmad Reza

2015-01-01

Highlights: • Sol–gel polymerization in vapor of solvent saturated atmosphere is developed. • Highly porous novolac–silica hybrid xerogels are successfully synthesized. • Novolac–silica hybrid gel was dried in ambient condition with low shrinkage. • Required time for preparation of gel reduced from 5 days to about 5 h. • By incorporation of silica into the novolac xerogel structure, the pore size decreases. - Abstract: Highly porous novolac–silica hybrid xerogels were successfully synthesized via the novel method of sol–gel polymerization in solvent vapor-saturated atmosphere. This method removes the need for supercritical drying and yields the hybrid xerogels with reduced shrinkage in comparison with conventional sol–gel process. Tetraethoxysilane (TEOS) was used as the precursor of silica-based inorganic phase. The chemical and structural characterization of the prepared hybrid xerogels were performed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis, respectively. Thermal and mechanical properties of the hybrid samples were investigated by differential scanning calorimetry (DSC), and compressive strength analysis. The resultant hybrid xerogels show a nanostructured colloidal hybrid network with high porosity (above 80%) and low density (below 0.25 g cm −3 ). Si mapping images shows the good distribution of silica phase throughout the hybrid structure

Fabrication of high-capacity polyelectrolyte brush-grafted porous AAO-silica composite membrane via RAFT polymerization.

Science.gov (United States)

Song, Cunfeng; Wang, Meijie; Liu, Xin; Wang, He; Chen, Xiaoling; Dai, Lizong

2017-09-01

Surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization has been utilized to fabricate high-capacity strong anion-exchange (AEX) membrane for the separation of protein. By means of RAFT polymerization, quaternized poly(3-(methacrylamidomethyl)-pyridine) brushes formed 3-dimensional nanolayers on the surface of porous anodic aluminum oxide (AAO)-silica composite membrane. The surface properties of the membranes were analyzed by SEM, water contact angle, ATR-FTIR, XPS and TGA. To investigate the adsorption performance, the new AEX membranes were applied to recover a model protein, ovalbumin (OVA). High adsorption capacities of 95.8mg/g membranes (static) and 65.3mg/g membranes (dynamic) were obtained at ambient temperature. In the further studies, up to 90% of the adsorbed OVA was efficiently eluted by using phosphate buffer-1M NaCl as elution medium. The successful separation of OVA with high purity from a mixture protein solution was also achieved by using the AEX membranes. The present study demonstrated that under mild reaction condition, RAFT polymerization can be used to fabricate ion-exchange membrane which has many remarkable features, such as high capacity and selectivity, easy elution and so on. Copyright © 2017. Published by Elsevier B.V.

Transport of oxidized multi-walled carbon nanotubes through silica based porous media: influences of aquatic chemistry, surface chemistry, and natural organic matter.

Science.gov (United States)

Yang, Jin; Bitter, Julie L; Smith, Billy A; Fairbrother, D Howard; Ball, William P

2013-12-17

This paper provides results from studies of the transport of oxidized multi-walled carbon nanotubes (O-MWCNTs) of varying surface oxygen concentrations under a range of aquatic conditions and through uniform silica glass bead media. In the presence of Na(+), the required ionic strength (IS) for maximum particle attachment efficiency (i.e., the critical deposition concentration, or CDC) increased as the surface oxygen concentration of the O-MWCNTs or pH increased, following qualitative tenets of theories based on electrostatic interactions. In the presence of Ca(2+), CDC values were lower than those with Na(+) present, but were no longer sensitive to surface oxygen content, suggesting that Ca(2+) impacts the interactions between O-MWCNTs and glass beads by mechanisms other than electrostatic alone. The presence of Suwannee River natural organic matter (SRNOM) decreased the attachment efficiency of O-MWCNTs in the presence of either Na(+) or Ca(2+), but with more pronounced effects when Na(+) was present. Nevertheless, low concentrations of SRNOM (organic carbon) were sufficient to mobilize all O-MWCNTs studied at CaCl2 concentrations as high as 10 mM. Overall, this study reveals that NOM content, pH, and cation type show more importance than surface chemistry in affecting O-MWCNTs deposition during transport through silica-based porous media.

On the improvement of mechanical properties of monolithic silica aerogels (for transparent insulating material); Silica aerogel (tomei dannetsu zairyo) kyodo no kaizen ni tsuite

Energy Technology Data Exchange (ETDEWEB)

Tajiri, K; Igarashi, K; Tanemura, S [National Industrial Research Institute of Nagoya, Nagoya (Japan)

1997-11-25

Study was made on improvement of the strength of silica aerogel as transparent insulating material. Silica aerogel is a low-density porous material with high heat insulation and transparency. To develop a insulating material with high transparency, monolithic silica aerogel was studied. For direct use of it for windows, its strength improvement was attempted. The aerogel was prepared by supercritical drying (alcohol or CO2) of silica wet gel obtained by hydrolysis and condensation of silicon alkoxide solution. To prepare the aerogel bonded on plate glass for strength improvement, the aerogel was bonded to alkoxide by exposing active silanol radical through F-etching of plate glass surface. However, to obtain the practical large-area bonded aerogel, shrinkage control of the aerogel in supercritical drying was necessary. Addition of Laponite into a silica network for strength improvement by polymer increased the bending strength by 50%. Although some reduction of its transparency was observed because of clouding, its heat insulation was stable. Further strength improvement is necessary for its practical use. 5 figs., 1 tab.

Lanthanide-doped luminescent ionogels

OpenAIRE

Lunstroot, Kyra; Driesen, Kris; Nockemann, Peter; Van Hecke, Kristof; Van Meervelt, Luc; Görller-Walrand, Christiane; Binnemans, Koen; Bellayer, Séverine; Viau, Lydie; Le Bideau, Jean; Vioux, André

2009-01-01

Ionogels are solid oxide host networks confining at a meso-scale ionic liquids, and retaining their liquid nature. Ionogels were obtained by dissolving anthanide(III) complexes in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C6mim][Tf2N], followed by confinement of the lanthanide-doped ionic liquid mixtures in the pores of a nano-porous silica network. [C6mim][Ln(tta)4], where tta is 2-thenoyltrifluoroacetonate and Ln = Nd, Sm, Eu, Ho, Er, Yb, and [choli...

Light and Strong Hierarchical Porous SiC Foam for Efficient Electromagnetic Interference Shielding and Thermal Insulation at Elevated Temperatures.

Science.gov (United States)

Liang, Caiyun; Wang, Zhenfeng; Wu, Lina; Zhang, Xiaochen; Wang, Huan; Wang, Zhijiang

2017-09-06

A novel light but strong SiC foam with hierarchical porous architecture was fabricated by using dough as raw material via carbonization followed by carbothermal reduction with silicon source. A significant synergistic effect is achieved by embedding meso- and nanopores in a microsized porous skeleton, which endows the SiC foam with high-performance electromagnetic interference (EMI) shielding, thermal insulation, and mechanical properties. The microsized skeleton withstands high stress. The meso- and nanosized pores enhance multiple reflection of the incident electromagnetic waves and elongate the path of heat transfer. For the hierarchical porous SiC foam with 72.8% porosity, EMI shielding can be higher than 20 dB, and specific EMI effectiveness exceeds 24.8 dB·cm 3 ·g -1 at a frequency of 11 GHz at 25-600 °C, which is 3 times higher than that of dense SiC ceramic. The thermal conductivity reaches as low as 0.02 W·m -1 ·K -1 , which is comparable to that of aerogel. The compressive strength is as high as 9.8 MPa. Given the chemical and high-temperature stability of SiC, the fabricated SiC foam is a promising candidate for modern aircraft and automobile applications.

Hexadecane trapped in nano-pores of silica-aerogel

International Nuclear Information System (INIS)

Slavikova, B.; Jesenak, K.; Iskrova, M.; Majernik, V.; Sausa, O.; Kristiak, J.

2009-01-01

Ways of filling of the high-porous silica-aerogel with hydrocarbon C 16 H 34 and its efficient removal from the pores by physical method of the Positron Annihilation Spectroscopy were studied. As the most effective way to fill the SiO 2 aerogel appears through the implementation of a liquid phase, while the most appropriate way of removing of hexadecane is firing at an elevated temperature. Molecular system of hexadecane closed in nano-pores of silica-aerogel behaves otherwise than volume system of the same molecules. In the case of pure hexadecane phase transition was observed at 291 K, while solidification process is gradual with decrease of temperature in cetane trapped in pores of silica-aerogel. The results of the periods of life of o-Ps indicate greater turbidity in the pores of the molecular system compared to the volume sample of hexadecane.

Investigations on the homogeneity of silica glass and on the order of X-amorphous silica by luminescence measurements

International Nuclear Information System (INIS)

Boden, G.

1982-08-01

Silica glasses melted from crystalline SiO 2 were exposed to ionizing radiation. At room temperature the spatial intensity distribution of the emitted luminescent radiation has been recorded by means of photographic or autoradiographic materials. Thereby schlieren and inhomogeneities are made visible and information is obtained on the melting process of the crystalline SiO 2 . Synthetic fused silica made from SiCl 4 shows no luminescent radiation. Depending on the penetration depth of the ionizing radiation the bulk or the surface of the sample can be studied. The decay curves of the integral luminescence intensity yield data on inhomogeneities in the silica glass leading to conclusions on order state and structure. The luminescence intensity and its half-life are a measure for the inhomogeneity of the silica glass and the existence of so-called 'preordered states'. This connection between luminescence intensity and the order state is found also with other X-amorphous SiO 2 modifications: silica gel, precipitated silicic acids, porous SiO 2 glasses, aerosil, thin SiO 2 layers, mechanically activated quartz: whereas no luminescence phenomena occur in disordered nearly ideally amorphous SiO 2 species, the luminescence increases with increasing order degree of the SiO 2 network and attains a high intensity in the case of the crystalline SiO 2 modifications quartz and cristobalite

Supercritical carbon dioxide versus toluene as reaction media in silica functionalisation: Synthesis and characterisation of bonded aminopropyl silica intermediate.

Science.gov (United States)

Ashu-Arrah, Benjamin A; Glennon, Jeremy D

2017-06-09

This research reports supercritical carbon dioxide versus toluene as reaction media in silica functionalisation for use in liquid chromatography. Bonded aminopropyl silica (APS) intermediates were prepared when porous silica particles (Exsil-pure, 3μm) were reacted with 3-aminopropyltriethoxysilane (3-APTES) or N,N-dimethylaminopropyltrimethoxysilane (DMAPTMS) using supercritical carbon dioxide (sc-CO 2 ) and toluene as reaction media. Covalent bonding to silica was confirmed using elemental microanalysis (CHN), thermogravimetric analysis (TGA), zeta potential (ξ), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, scanning electron microscopy (SEM) and solid-state nuclear magnetic resonance (CP/MAS NMR) spectroscopy. The results demonstrate that under sc-CO 2 conditions of 100°C/414bar in a substantial reduced time of 3h, the surface coverage of APS (evaluated from%C obtained from elemental analysis) prepared with APTES (%C: 8.03, 5.26μmol/m -2 ) or DMAPTES (%C: 5.12, 4.58μmol/m 2 ) is somewhat higher when compared to organic based reactions under reflux in toluene at a temperature of 110°C in 24h with APTES (%C: 7.33, 4.71μmol/m 2 ) and DMAPTMS (%C: 4.93, 4.38μmol/m 2 ). Zeta potential measurements revealed a change in electrostatic surface charge from negative values for bare Exsil-pure silica to positive for functionalised APS materials indicating successful immobilization of the aminosilane onto the surface of silica. Copyright © 2017 Elsevier B.V. All rights reserved.

Microstructure investigation on micropore formation in microporous silica materials prepared via a catalytic sol-gel process by small angle X-ray scattering.

Science.gov (United States)

Shimizu, Wataru; Hokka, Junsuke; Sato, Takaaki; Usami, Hisanao; Murakami, Yasushi

2011-08-04

The so-called sol-gel technique has been shown to be a template-free, efficient way to create functional porous silica materials having uniform micropores. This appears to be closely linked with a postulation that the formation of weakly branched polymer-like aggregates in a precursor solution is a key to the uniform micropore generation. However, how such a polymer-like structure can precisely be controlled, and further, how the generated low-fractal dimension solution structure is imprinted on the solid silica materials still remain elusive. Here we present fabrication of microporous silica from tetramethyl orthosilicate (TMOS) using a recently developed catalytic sol-gel process based on a nonionic hydroxyacetone (HA) catalyst. Small angle X-ray scattering (SAXS), nitrogen adsorption porosimetry, and transmission electron microscope (TEM) allowed us to observe the whole structural evolution, ranging from polymer-like aggregates in the precursor solution to agglomeration with heat treatment and microporous morphology of silica powders after drying and hydrolysis. Using the HA catalyst with short chain monohydric alcohols (methanol or ethanol) in the precursor solution, polymer-like aggregates having microscopic correlation length (or mesh-size) micropores with diameters 2 nm) in the solid product due to apertures between the particle-like aggregates. The data demonstrate that the extremely fine porous silica architecture comes essentially from a gaussian polymer-like nature of the silica aggregates in the precursor having the microscopic mesh-size and their successful imprint on the solid product. The result offers a general but significantly efficient route to creating precisely designed fine porous silica materials under mild condition that serve as low refractive index and efficient thermal insulation materials in their practical applications.

STUDY ON SILICA INFUSED RECYCLED AGGREGATE CONCRETE USING DESIGN OF EXPERIMENTS

Directory of Open Access Journals (Sweden)

P. M. MRUDUL

2017-04-01

Full Text Available Recycled Aggregate (RA generated from the construction industry is used as a material for sustainable construction. The old mortar attached to these aggregates makes it porous and are generally used for low-grade applications. However, by infusing with silica fumes, the properties of recycled aggregate concrete (RAC can be improved, as the silica fumes get infused into the pores of old mortar attached to it. In this study, the optimum percentage of recycled aggregate that can be used in fresh concrete for higher grade applications was found out. Design of experiments (DoE was used to optimize percentage of silica fumes and recycled aggregate to achieve optimum properties of concrete. Equations to predict the properties of concrete were also modelled using regression analysis.

Meso and microscopic characterization of deformation bands in porous sandstones: an example on the Paleozoic, Pre- and Sin-rift sequences of the Araripe Basin, Northeast of Brazil; Caracterizacao meso e microscopica de bandas de deformacao em arenitos porosos: um exemplo nas tectonossequencias Paleozoica, Pre- e Sin-rifte da Bacia do Araripe, Nordeste do Brasil

Energy Technology Data Exchange (ETDEWEB)

Araujo Neto, Joao Marculino de; Silva, Fernando Cesar Alves da; Sa, Emanuel Ferraz Jardim de [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Programa de Pos-Graduacao em Geodinamica e Geofisica], e-mails: jota_ex2@hotmail.com, fernando@geologia.ufrn.br, emanuel@ccet.ufrn.br

2012-04-15

Deformation bands are narrow tabular volumes developed in porous sandstones. Although these structures are a product of brittle deformation, they may have internally a continuous displacement gradient. When granular cataclasis is the dominant deformation mechanism, the initial properties of their host rocks (i.e., porosity and permeability) can change significantly. The deformation bands in sandstones from the pre- and syn-rift of the Araripe Basin were studied in meso and microscale in order to classify them and to understand the deformation mechanisms involved during their nucleation and development. Their geometric-spatial, kinematic, and rheological criteria allowed establishing relations between the origin of deformation bands and lithification of their host rocks. Additionally, some inferences on their influence to the fluid flow in the reservoir-scale were outlined. Moreover, the study of deformation bands contributed to the understanding of the tectonic evolution of the studied basin. Accordingly, the study of deformation bands can support research on local and regional aspects of the tectonosedimentary evolution of sedimentary basins. (author)

Preparation of tailored carbons with meso- and micro- porosity via template synthesis route

Directory of Open Access Journals (Sweden)

Howard. M. Williams

2009-02-01

Full Text Available A low cost templating approach to making non-ordered carbons with a tailored meso/micropore structure is described. A series of mesoporous carbons was prepared from polyfurfuryl alcohol and phenolic resin precursors by a templating route, using a variety of commercially available silica gels as the template material. Carbons were produced with mesopore volumes up to 1 cm3 g-1, mesopore sizes in the range of 4 nm to 8 nm and surface areas in the range of 300 to 700 m2 g-1. These mesoporous carbons were subsequently activated in CO2 to add controlled amounts of microporosity to produce carbons with both a micro and mesoporous structure. Significantly, the activation process did not appreciably change the mesopore size distribution of the carbons. By altering the activation time, it was possible to tailor the micropore: mesopore volume ratios within wide limits.

Synthesis of hierarchically meso-macroporous TiO2/CdS heterojunction photocatalysts with excellent visible-light photocatalytic activity.

Science.gov (United States)

Zhao, Haixin; Cui, Shu; Yang, Lan; Li, Guodong; Li, Nan; Li, Xiaotian

2018-02-15

Photocatalysts with a hierarchically porous structure have attracted considerable attention owing to their wide pore size distribution and high surface area, which enhance the efficiency of transporting species to active sites. In this study, hierarchically meso-macroporous TiO 2 photocatalysts decorated with highly dispersed CdS nanoparticles were synthesized via hydrolysis, followed by a hydrothermal treatment. The textural mesopores and interconnected pore framework provided more accessible active sites and efficient mass transport for the photocatalytic process. The light collection efficiency was enhanced because of multiple scattering of incident light in the macropores. Moreover, the formation of a heterojunction between the CdS and TiO 2 nanoparticles extended the photoresponse of TiO 2 to the visible-light range and enhanced the charge separation efficiency. Therefore, the hierarchically meso-macroporous TiO 2 /CdS photocatalysts exhibited excellent photocatalytic activity for the degradation of rhodaming B under visible-light irradiation. Trapping experiments demonstrated that superoxide radicals (O 2 - ) and hydroxyl radicals (OH) were the main active species in photocatalysis. A reasonable photocatalytic mechanism of TiO 2 /CdS heterojunction photocatalysts was also presented. Copyright © 2017 Elsevier Inc. All rights reserved.

Preparation of porous materials for radionuclides capture

International Nuclear Information System (INIS)

Bajzikova, Anna; Smrcek, Stanislav; Kozempel, Jan; Vlk, Martin; Barta, Jan

2015-01-01

Porous materials showing promise for radionuclide capture from water at contaminated sites were prepared. Nanoporous materials (size of pores 1-100 nm) and some polymers are well suited to this purpose owing their affinity for selected radionuclides. Nanoporous metal oxides and silica gel with styrene-divinylbenzene-TODGA-modified surface were prepared, characterized and tested for radionuclide ( 227 Ac, 227 Th, 223 Ra) capture efficiency. (orig.)

Tunable thick porous silica coating fabricated by multilayer-by-multilayer bonding of silica nanoparticles for open-tubular capillary chromatographic separation.

Science.gov (United States)

Qu, Qishu; Liu, Yuanyuan; Shi, Wenjun; Yan, Chao; Tang, Xiaoqing

2015-06-19

A simple coating procedure employing a multilayer-by-multilayer process to modify the inner surface of bare fused-silica capillaries with silica nanoparticles was established. The silica nanoparticles were adsorbed onto the capillary wall via a strong electrostatic interaction between amino functional groups and silica particles. The thickness of the coating could be tuned from 130 to 600 nm by increasing the coating cycles from one to three. Both the retention factor and the resolution were greatly increased with increasing coating cycles. The loading capacity determined by naphthalene in the column with three coating cycles is 152.1 pmol. The effects of buffer concentration and pH value on the stability of the coating were evaluated. The retention reproducibility of the separation of toluene was 0.8, 1.2, 2.3, and 4.5%, respectively, for run-to-run, day-to-day, column-to-column, and batch-to-batch, respectively. The chromatographic performance of these columns was evaluated by both capillary liquid chromatography and open-tubular capillary electrochromatography (OT-CEC). Separation of aromatic hydrocarbons in the column with three coating cycles provided high theoretical plate numbers (up to 269,280 plates m(-1) for toluene) and short separation time (<15 min) by using OT-CEC mode. The method was also used to separate egg white proteins. Both acidic and basic proteins as well as four glycoisoforms were separated in a single run. Copyright © 2015 Elsevier B.V. All rights reserved.

Impact of surface impurity on phase transitions in amorphous micro silica

DEFF Research Database (Denmark)

Haastrup, Sonja; Yu, Donghong; Yue, Yuanzheng

2016-01-01

In this work we study three types of spherically shaped micron and submicron sized amorphous micro silica (MS) as common raw material for production of porous calcium silicate products used for insulation, which are selected on basis of chemical composition and production method. Two of them have...... silica content of 96% (from silicon production) and one has that of 92% (from ferro-silicon production). In order to achieve high quality calcium silicate products, which strongly depends on the characteristics of the raw MS, it is crucial to study the chemical and physical properties of the raw MS...

Colloidal silica films for high-capacity DNA arrays

Science.gov (United States)

Glazer, Marc Irving

The human genome project has greatly expanded the amount of genetic information available to researchers, but before this vast new source of data can be fully utilized, techniques for rapid, large-scale analysis of DNA and RNA must continue to develop. DNA arrays have emerged as a powerful new technology for analyzing genomic samples in a highly parallel format. The detection sensitivity of these arrays is dependent on the quantity and density of immobilized probe molecules. We have investigated substrates with a porous, "three-dimensional" surface layer as a means of increasing the surface area available for the synthesis of oligonucleotide probes, thereby increasing the number of available probes and the amount of detectable bound target. Porous colloidal silica films were created by two techniques. In the first approach, films were deposited by spin-coating silica colloid suspensions onto flat glass substrates, with the pores being formed by the natural voids between the solid particles (typically 23nm pores, 35% porosity). In the second approach, latex particles were co-deposited with the silica and then pyrolyzed, creating films with larger pores (36 nm), higher porosity (65%), and higher surface area. For 0.3 mum films, enhancements of eight to ten-fold and 12- to 14-fold were achieved with the pure silica films and the films "templated" with polymer latex, respectively. In gene expression assays for up to 7,000 genes using complex biological samples, the high-capacity films provided enhanced signals and performed equivalently or better than planar glass on all other functional measures, confirming that colloidal silica films are a promising platform for high-capacity DNA arrays. We have also investigated the kinetics of hybridization on planar glass and high-capacity substrates. Adsorption on planar arrays is similar to ideal Langmuir-type adsorption, although with an "overshoot" at high solution concentration. Hybridization on high-capacity films is

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).

Experimental Study on Meso-Scale Milling Process Using Nanofluid Minimum Quantity Lubrication

International Nuclear Information System (INIS)

Lee, P. H.; Nam, T. S.; Li, Cheng Jun; Lee, S. W.

2010-01-01

This paper present the characteristics of micro- and meso-scale milling processes in which compressed cold air, minimum quantity lubrication (MQL) and MoS 2 nanofluid MQL are used. For process characterization, the micro and meso-scale milling experiments are conducted using desktop meso-scale machine tool system and the surface roughness is measured. The experimental results show that the use of compressed chilly air and nanofluid MQL in the micro- and meso-scale milling processes is effective in improving the surface finish

Caustic meso-optical confocal microscope for vertical particle tracks. Proposal

International Nuclear Information System (INIS)

Soroko, L.M.

1995-01-01

The principal of the proposed caustic meso-optical microscope for vertical particle tracks in the nuclear photoemulsion is explained. The results of the experiments performed to illustrate the main features of this new meso-optical microscope are given. The proposed caustic meso-optical microscope for vertical particle tracks in the nuclear photoemulsion can be effectively used in the experimental investigation of such rare processes as ν μ - ν τ oscillations and of the Pb-Pb interactions. 2 refs., 7 figs

Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction.

Science.gov (United States)

Ma, Hao; Zheng, Xiaoyang; Luo, Xuan; Yi, Yong; Yang, Fan

2018-01-30

Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM) method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress) of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future.

Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction

Directory of Open Access Journals (Sweden)

Hao Ma

2018-01-01

Full Text Available Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future.

Optimizing CMS build infrastructure via Apache Mesos

CERN Document Server

Abduracmanov, David; Degano, Alessandro; Elmer, Peter; Eulisse, Giulio; Mendez, David; Muzaffar, Shahzad

2015-12-23

The Offline Software of the CMS Experiment at the Large Hadron Collider (LHC) at CERN consists of 6M lines of in-house code, developed over a decade by nearly 1000 physicists, as well as a comparable amount of general use open-source code. A critical ingredient to the success of the construction and early operation of the WLCG was the convergence, around the year 2000, on the use of a homogeneous environment of commodity x86-64 processors and Linux. Apache Mesos is a cluster manager that provides efficient resource isolation and sharing across distributed applications, or frameworks. It can run Hadoop, Jenkins, Spark, Aurora, and other applications on a dynamically shared pool of nodes. We present how we migrated our continuos integration system to schedule jobs on a relatively small Apache Mesos enabled cluster and how this resulted in better resource usage, higher peak performance and lower latency thanks to the dynamic scheduling capabilities of Mesos.

Defect prevention in silica thin films synthesized using AP-PECVD for flexible electronic encapsulation

NARCIS (Netherlands)

Elam, F.M.; Starostin, S.A.; Meshkova, A.S.; Van Der Velden-Schuermans, B.C.A.M.; Van De Sanden, M.C.M.; De Vries, H.W.

2017-01-01

Industrially and commercially relevant roll-to-roll atmospheric pressure-plasma enhanced chemical vapour deposition was used to synthesize smooth, 80 nm silica-like bilayer thin films comprising a dense 'barrier layer' and comparatively porous 'buffer layer' onto a flexible polyethylene 2,6

Synthesis and separation properties of an α-alumina-supported high-silica MEL membrane

NARCIS (Netherlands)

Kosinov, N.; Hensen, E.J.M.

2013-01-01

A thin high-silica MEL membrane was synthesized on a porous a-alumina hollow fiber support by a secondary growth approach. The membrane quality was evaluated by permporometry, single-gas permeation and butane isomer separation. Comparison of the pervaporation performance of MEL membranes with a MFI

Faraday rotation measurements in maghemite-silica aerogels

International Nuclear Information System (INIS)

Taboada, E.; Real, R.P. del; Gich, M.; Roig, A.; Molins, E.

2006-01-01

Faraday rotation measurements have been performed on γ-Fe 2 O 3 /SiO 2 nanocomposite aerogels which are light, porous and transparent magnetic materials. The materials have been prepared by sol-gel polymerization of a silicon alkoxide, impregnation of the intermediate silica gel with a ferrous salt and supercritical drying of the gels. During supercritical evacuation of the solvent, spherical nanoparticles of iron oxide, with a mean particle diameter of 8.1±2.0 nm, are formed and are found to be homogenously distributed within the silica matrix. The specific Faraday rotation of the composite was measured at 0.6 T using polarized light of 810 nm, being 29.6 deg./cm. The changes in the plane of polarization of the transmitted light and the magnetization of the material present similar magnetic field dependencies and are characteristic of a superparamagnetic system

Quantitative study on crack of meso-damage and fracture concrete ...

Indian Academy of Sciences (India)

lysis of the meso-fracture process of concrete materials is performed. ... the result of the accumulation and development of damage and cracks at the meso-level. ... characteristics of concrete under uniaxial compression used fractal theory, and ...

Amperometric xanthine biosensors using glassy carbon electrodes modified with electrografted porous silica nanomaterials loaded with xanthine oxidase

International Nuclear Information System (INIS)

Saadaoui, Maroua; Sánchez, Alfredo; Díez, Paula; Raouafi, Noureddine; Pingarrón, José M.; Villalonga, Reynaldo

2016-01-01

Glassy carbon electrodes were modified with silica materials such as silica nanoparticles, mesoporous silica nanoparticles and mesoporous silica thin films with the aim to introduce scaffolds suitable for the immobilization of enzymes. Xanthine oxidase was selected as a model enzyme, and xanthine as the target analyte. A comparison of the modified electrodes showed the biosensor prepared with mesoporous silica nanoparticles to perform best. By using the respective biosensor, xanthine can be amperometrically determined (via measurement of enzymatically formed hydrogen peroxide) at a working voltage of 0.7 V (vs. Ag/AgCl) with a 0.28 μM detection limit. The biosensor was evaluated in terms of potential interferences, reproducibility and stability, and applied to the determination of fish freshness via sensing of xanthine. (author)

Organoclay hybrid materials as precursors of porous ZnO/silica-clay heterostructures for photocatalytic applications

Directory of Open Access Journals (Sweden)

Marwa Akkari

2016-12-01

Full Text Available In this study, ZnO/SiO2-clay heterostructures were successfully synthesized by a facile two-step process applied to two types of clays: montmorillonite layered silicate and sepiolite microfibrous clay mineral. In the first step, intermediate silica–organoclay hybrid heterostructures were prepared following a colloidal route based on the controlled hydrolysis of tetramethoxysilane in the presence of the starting organoclay. Later on, pre-formed ZnO nanoparticles (NP dispersed in 2-propanol were incorporated under ultrasound irradiation to the silica–organoclay hybrid heterostructures dispersed in 2-propanol, and finally, the resulting solids were calcinated to eliminate the organic matter and to produce ZnO nanoparticles (NP homogeneously assembled to the clay–SiO2 framework. In the case of montmorillonite the resulting materials were identified as delaminated clays of ZnO/SiO2-clay composition, whereas for sepiolite, the resulting heterostructure is constituted by the assembling of ZnO NP to the sepiolite–silica substrate only affecting the external surface of the clay. The structural and morphological features of the prepared heterostructures were characterized by diverse physico-chemical techniques (such as XRD, FTIR, TEM, FE-SEM. The efficiency of these new porous ZnO/SiO2-clay heterostructures as potential photocatalysts in the degradation of organic dyes and the removal of pharmaceutical drugs in water solution was tested using methylene blue and ibuprofen compounds, respectively, as model of pollutants.

Defect prevention in silica thin films synthesized using AP-PECVD for flexible electronic encapsulation

NARCIS (Netherlands)

Elam, F. M.; Starostin, S. A.; Meshkova, A. S.; van der Velden, B. C. A. M.; van de Sanden, M. C. M.; de Vries, H. W.

2017-01-01

Industrially and commercially relevant roll-to-roll atmospheric pressure-plasma enhanced chemical vapour deposition was used to synthesize smooth, 80 nm silica-like bilayer thin films comprising a dense ‘barrier layer’ and comparatively porous ‘buffer layer’ onto a flexible polyethylene 2,6

Atomic dynamics of tin nanoparticles embedded into porous glass

Energy Technology Data Exchange (ETDEWEB)

Parshin, P. P.; Zemlyanov, M. G., E-mail: zeml@isssph.kiae.ru; Panova, G. Kh.; Shikov, A. A. [Russian Research Centre Kurchatov Institute (Russian Federation); Kumzerov, Yu. A.; Naberezhnov, A. A. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Sergueev, I.; Crichton, W. [European Synchrotron Radiation Facility (France); Chumakov, A. I. [Russian Research Centre Kurchatov Institute (Russian Federation); Rueffer, R. [European Synchrotron Radiation Facility (France)

2012-03-15

The method of resonant nuclear inelastic absorption of synchrotron radiation has been used to study the phonon spectrum for tin nanoparticles (with a natural isotope mixture) embedded into a porous glassy (silica) matrix with an average pore diameter of 7 nm in comparison to the analogous spectrum of bulk tin enriched with {sup 119}Sn isotope. Differences between the spectra have been observed, which are related to both the dimensional effects and specific structural features of the porous glass-tin nanocomposite. Peculiarities in the dynamics of tin atoms embedded into nanopores of glass are interpreted in terms of a qualitative model of the nanocomposite structure.

Atomic dynamics of tin nanoparticles embedded into porous glass

International Nuclear Information System (INIS)

Parshin, P. P.; Zemlyanov, M. G.; Panova, G. Kh.; Shikov, A. A.; Kumzerov, Yu. A.; Naberezhnov, A. A.; Sergueev, I.; Crichton, W.; Chumakov, A. I.; Rüffer, R.

2012-01-01

The method of resonant nuclear inelastic absorption of synchrotron radiation has been used to study the phonon spectrum for tin nanoparticles (with a natural isotope mixture) embedded into a porous glassy (silica) matrix with an average pore diameter of 7 nm in comparison to the analogous spectrum of bulk tin enriched with 119 Sn isotope. Differences between the spectra have been observed, which are related to both the dimensional effects and specific structural features of the porous glass-tin nanocomposite. Peculiarities in the dynamics of tin atoms embedded into nanopores of glass are interpreted in terms of a qualitative model of the nanocomposite structure.

Optogenetic stimulation of a meso-scale human cortical model

Science.gov (United States)

Selvaraj, Prashanth; Szeri, Andrew; Sleigh, Jamie; Kirsch, Heidi

2015-03-01

Neurological phenomena like sleep and seizures depend not only on the activity of individual neurons, but on the dynamics of neuron populations as well. Meso-scale models of cortical activity provide a means to study neural dynamics at the level of neuron populations. Additionally, they offer a safe and economical way to test the effects and efficacy of stimulation techniques on the dynamics of the cortex. Here, we use a physiologically relevant meso-scale model of the cortex to study the hypersynchronous activity of neuron populations during epileptic seizures. The model consists of a set of stochastic, highly non-linear partial differential equations. Next, we use optogenetic stimulation to control seizures in a hyperexcited cortex, and to induce seizures in a normally functioning cortex. The high spatial and temporal resolution this method offers makes a strong case for the use of optogenetics in treating meso scale cortical disorders such as epileptic seizures. We use bifurcation analysis to investigate the effect of optogenetic stimulation in the meso scale model, and its efficacy in suppressing the non-linear dynamics of seizures.

Analysis of glyoxal, methylglyoxal and dimethylglyoxal in beverages and edible products by mekc using meso-stilbenediamine as derivatizing reagent

International Nuclear Information System (INIS)

Mirza, M.; Chaudhary, M.A.; Khuhawar, M.Y.; Arain, R.

2013-01-01

Summary: The reactive alpha-diketones; glyoxal (Go), methylglyoxal (MGo) and dimethyglyoxal (DMGo) were determined from wines, beers, whisky, coffee, tea, soy sauce, juices and yoghurt by micellar electrokinetic chromatography (MEKC) using meso-stilbenediamine (meso-SD) as derivatizing reagent. The separation was carried out from uncoated fused silica capillary with effective length 39 cm x 75 micro m internal diameter (id), applied voltage 20 kV and photodiode detection at 228 nm. SDS was used as micellar medium at pH 8, and sodium tetraborate (0.1M) as buffer. The amounts of Go, MGo, and DMGo in Pakistani wines and beers were found within 1.31-6.49 micro g /mL with RSD 1.2 -3.7 %. The amount of Go, MGo and DMGo in food products (Brewed Coffee, Instant Coffee, Instant Tea, Soy sauce, Orange juice , Apple juice and Yoghurt) found were within 0.043-3.42 micro g /mL or micro g /g with RSD 1.1-3.9 %. The analysis was repeatable and reproducible using MEKC. Samples of wine and apple juice were also analyzed by using standard addition method and recoveries were calculated within 96.3-98.5 % with RSD 1.8-2.6 %. (author)

Molecular imprinting at walls of silica nanotubes for TNT recognition.

Science.gov (United States)

Xie, Chenggen; Liu, Bianhua; Wang, Zhenyang; Gao, Daming; Guan, Guijian; Zhang, Zhongping

2008-01-15

This paper reports the molecular imprinting at the walls of highly uniform silica nanotubes for the recognition of 2,4,6-trinitrotoluene (TNT). It has been demonstrated that TNT templates were efficiently imprinted into the matrix of silica through the strong acid-base pairing interaction between TNT and 3-aminopropyltriethoxysilane (APTS). TNT-imprinted silica nanotubes were synthesized by the gelation reaction between APTS and tetraethylorthosilicate (TEOS), selectively occurring at the porous walls of APTS-modified alumina membranes. The removal of the original TNT templates leaves the imprinted cavities with covalently anchored amine groups at the cavity walls. A high density of recognition sites with molecular selectivity to the TNT analyte was created at the wall of silica nanotubes. Furthermore, most of these recognition sites are situated at the inside and outside surfaces of tubular walls and in the proximity of the two surfaces due to the ultrathin wall thickness of only 15 nm, providing a better site accessibility and lower mass-transfer resistance. Therefore, greater capacity and faster kinetics of uptaking target species were achieved. The silica nanotube reported herein is an ideal form of material for imprinting various organic or biological molecules toward applications in chemical/biological sensors and bioassay.

Preparation, characterization of electrospun meso-hydroxylapatite nanofibers and their sorptions on Co(II)

Energy Technology Data Exchange (ETDEWEB)

Wang, Hualin, E-mail: hlwang@hfut.edu.cn [School of Chemical Technology, Hefei University of Technology, Hefei, Anhui 230009 (China); Zhang, Peng; Ma, Xingkong; Jiang, Suwei; Huang, Yan; Zhai, Linfeng [School of Chemical Technology, Hefei University of Technology, Hefei, Anhui 230009 (China); Jiang, Shaotong [School of Biotechnology and Food Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China)

2014-01-30

Highlights: • PVA/HA nanofibers could change into meso-HA nanofibers by calcination process. • Sorption of Co(II) on meso-HA was strongly dependent on pH and ionic strength. • Sorption kinetic data were well fitted by the pseudo-second-order rate equation. • Sorption isotherms could be well described by the Langmuir model. • Sorption process of Co(II) on meso-HA nanofibers was spontaneous and endothermic. -- Abstract: In this work, mesoporous hydroxylapatite (meso-HA) nanofibers were prepared via calcination process with polyvinyl alcohol/HA (PVA/HA) hybrid nanofibers fabricated by electrospinning technique as precursors, and the removal efficiency of meso-HA nanofibers toward Co(II) was evaluated via sorption kinetics and sorption isotherms. Furthermore, the sorption behaviors of Co(II) on meso-HA nanofibers were explored as a function of pH, ionic strength, and thermodynamic parameters. There existed hydrogen bonds between HA and PVA matrix in precursor nanofibers which could change into meso-HA nanofibers with main pore diameter at 27 nm and specific surface area at 114.26 m{sup 2}/g by calcination process. The sorption of Co(II) on meso-HA was strongly dependent on pH and ionic strength. Outer-sphere surface complexation or ion exchange was the main mechanisms of Co(II) adsorption on meso-HA at low pH, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH. The sorption kinetic data were well fitted by the pseudo-second-order rate equation. The sorption isotherms could be well described by the Langmuir model. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) calculated from the temperature-dependent sorption isotherms suggested that the sorption process of Co(II) on meso-HA nanofibers was spontaneous and endothermic.

Study of silica sol-gel materials for sensor development

Science.gov (United States)

Lei, Qiong

Silica sol-gel is a transparent, highly porous silicon oxide glass made at room temperature by sol-gel process. The name of silica sol-gel comes from the observable physical phase transition from liquid sol to solid gel during its preparation. Silica sol-gel is chemically inert, thermally stable, and photostable, it can be fabricated into different desired shapes during or after gelation, and its porous structure allows encapsulation of guest molecules either before or after gelation while still retaining their functions and sensitivities to surrounding environments. All those distinctive features make silica sol-gel ideal for sensor development. Study of guest-host interactions in silica sol-gel is important for silica-based sensor development, because it helps to tailor local environments inside sol-gel matrix so that higher guest loading, longer shelf-life, higher sensitivity and faster response of silica gel based sensors could be achieved. We focused on pore surface modification of two different types of silica sol-gel by post-grafting method, and construction of stable silica hydrogel-like thin films for sensor development. By monitoring the mobility and photostability of rhodamine 6G (R6G) molecules in silica alcogel thin films through single molecule spectroscopy (SMS), the guest-host interactions altered by post-synthesis grafting were examined. While physical confinement remains the major factor that controls mobility in modified alcogels, both R6G mobility and photostability register discernable changes after surface charges are respectively reversed and neutralized by aminopropyltriethoxysilane (APTS) and methyltriethoxysilane (MTES) grafting. The change in R6G photostability was found to be more sensitive to surface grafting than that of mobility. In addition, silica film modification by 0.4% APTS is as efficient as that by pure MTES in lowering R6G photostability, which suggests that surface charge reversal is more effective than charge neutralization

Improving structural stability of water-dispersed MCM-41 silica nanoparticles through post-synthesis pH aging process

Energy Technology Data Exchange (ETDEWEB)

Varache, Mathieu; Bezverkhyy, Igor [UMR 6303 CNRS-Université Bourgogne Franche-Comté, Laboratoire Interdisciplinaire Carnot de Bourgogne (France); Bouyer, Florence [Inserm U866, Equipe Chimiothérapie, métabolisme des lipides et réponse immunitaire anti-tumorale (France); Chassagnon, Rémi; Baras, Florence; Bouyer, Frédéric, E-mail: frederic.bouyer@u-bourgogne.fr [UMR 6303 CNRS-Université Bourgogne Franche-Comté, Laboratoire Interdisciplinaire Carnot de Bourgogne (France)

2015-09-15

The colloidal and structural stabilities of MCM-41 mesoporous silica nanoparticles (MSNs) are of great importance in order to prepare optimal nanovectors. In this paper, MSNs (approximatively 160 nm in diameter) were synthesized using n-cetyltrimethylammonium bromide as a template and tetraethyl orthosilicate as a silica source under high N{sub 2} flow (MSN/N{sub 2}) to obtain stable dispersions in water. The degradation of the porous nanoparticles was investigated by immersion in water. The morphology and the porous structure were studied by TEM, XRD, N{sub 2} sorption, and {sup 29}Si MAS NMR and were compared to that of MSNs prepared in ambient air (MSN/air). The volumetric properties of the MSN/N{sub 2} after 1 day in water were drastically more decreased than MSN/air (a pore volume decrease of 85 % for MSN/N{sub 2} and 59 % for MSN/air) and the 2D-hexagonal porous structure was totally lost. Furthermore, synthesizing MSNs under a high N{sub 2} flow leads to a decrease in the synthesis yield (45 % MSN/N{sub 2} and 75 % for MSN/air). The lower structural stability of the MSN/N{sub 2} is explained by the lower polycondensation degree of the MSN/N{sub 2} observed by {sup 29}Si MAS NMR (Q{sup 4}/Q{sup 3} = 0.86 for MSN/N{sub 2} and 1.61 for MSN/air) and the lower silica molar ratio in the nanomaterials (SiO{sub 2}/CTA = 3.9 for MSN/N{sub 2} 7.1 for MSN/air). This allows for enhanced solubilization of silica in water. Four strategies were hence evaluated in order to reinforce the porous structure of the MSNs. Among them, the most efficient route was based on a pH adjustment of the colloidal suspension (pH 7.5) after 2 h of synthesis without any purification and while keeping a N{sub 2} static atmosphere (called MSN/N{sub 2}/7.5). After 1 day in water, the volumetric and structural properties of MSN/N{sub 2}/7.5 were similar to that obtained for MSN/air. The improvement of the stability arose as a result of the increase in the silica condensation (Q{sup 4

Mesoscopic analyses of porous concrete under static compression and drop weight impact tests

DEFF Research Database (Denmark)

Agar Ozbek, A.S.; Pedersen, R.R.; Weerheijm, J.

2008-01-01

was considered as a four-phase material incorporating aggregates, bulk cement paste, interfacial transition zones and meso-size air pores. The stress-displacement relations obtained from static compression tests, the stress values, and the corresponding damage levels provided by the drop weight impact tests were......The failure process in highly porous concrete was analyzed experimentally and numerically. A triaxial visco-plastic damage model and a mesoscale representation of the material composition were considered to reproduce static compression and drop weight impact tests. In the mesoscopic model, concrete...

Structure and thermal performance of poly(ethylene glycol) alkyl ether (Brij)/porous silica (MCM-41) composites as shape-stabilized phase change materials

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lingjian; Shi, Haifeng, E-mail: haifeng.shi@gmail.com; Li, Weiwei; Han, Xu; Zhang, Xingxiang, E-mail: zhangpolyu@gmail.com

2013-10-20

Graphical abstract: The maximum 50 wt% Brij58 is loaded into the porous MCM-41 networks, and a new peak at 18.8° in XRD patterns confirmed the changes of crystallization behavior of Brij58 against the bulk one. - Highlights: • Poly(ethylene glycol) hexadecyl ether and poly(ethylene glycol) octadecyl ether have the good thermal storage ability. • New peak at 18.8° proved the coexisted confined crystallization and nucleation-induced crystallization. • Poly(ethylene glycol) alkyl ether/MCM-41 PCMs exhibits the good thermal stability. - Abstract: A series of shape-stabilized phase change materials (PCMs), composed of poly(ethylene glycol) hexadecyl ether (Brij58) or poly(ethylene glycol) octadecyl ether (Brij76) and porous silica (MCM-41), were prepared by the physical mixing method. The structure, thermal stability, energy storage ability and crystallization behavior of these composites are deeply investigated and characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD) and thermogravimetric analysis (TGA). Obvious phase transition behavior and energy storage capability are observed for these Brij/MCM-41 composites, and the heat storage efficiency increased with the weight of Brij component. New peak at 18.8° demonstrated that the pore size and the surface adsorption ability of MCM-41 affect the crystallization behavior of Brij molecule. The crystalline structure and energy storage ability of these Brij/MCM-41 composites are discussed based on the crystallization process.

Transport and abatement of fluorescent silica nanoparticle (SiO_2 NP) in granular filtration: effect of porous media and ionic strength

International Nuclear Information System (INIS)

Zeng, Chao; Shadman, Farhang; Sierra-Alvarez, Reyes

2017-01-01

The extensive production and application of engineered silica nanoparticles (SiO_2 NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO_2 NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO_2 NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO_2 filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO_2 NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO_2 NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO_2 NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO_2 NP filtration.

Transport and abatement of fluorescent silica nanoparticle (SiO2 NP) in granular filtration: effect of porous media and ionic strength

Science.gov (United States)

Zeng, Chao; Shadman, Farhang; Sierra-Alvarez, Reyes

2017-03-01

The extensive production and application of engineered silica nanoparticles (SiO2 NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO2 NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO2 NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO2 filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO2 NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO2 NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO2 NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO2 NP filtration.

Multi-template synthesis of hierarchically porous carbon spheres with potential application in supercapacitors

NARCIS (Netherlands)

Zhou, Weizheng; Lin, Zhixing; Tong, Gangsheng; Stoyanov, Simeon D.; Yan, Deyue; Mai, Yiyong; Zhu, Xinyuan

2016-01-01

A new and simple multi-template approach towards hierarchical porous carbon (HPC) materials was reported. HPC spheres were prepared by using hierarchical silica capsules (HSCs) as the hard template and triblock copolymer Pluronic P123 as the soft template. Three types of pores were tunably

Thermal insulator made of ultra fine particles of silica. Chobiryushi silica kei dannetsuzai

Energy Technology Data Exchange (ETDEWEB)

Eguchi, T.

1991-05-30

An overview was presented of properties and applications of thermal insulator made of ultra fine powder of silica, MICROTHERM. The thermal conductivity of MICROTHERM is as low as (1/3) - (1/4) of that of conventional thermal insulator, because it is mainly composed of fumed silica or aero gel and formed into porous structure. In addition, metal oxide of special particle size is added to it in order to reject the radiative heat. The thermal insulation property and the mechanical strength of MICROTHERM is not affected by a sudden change in temperature and moisture. The standard type of MICROTHERM can be used at a temperature up to 950 {degree}C, while the high temperature type MICROTHERM can stand a high temperature up to 1025 {degree}C for long period of time. The thickness of insulator can be reduced markedly by using MICROTHERM as compared with the use of conventional insulating materials. Many new products in which MICROTHERM is used came into market. New type kilt, Semi-cylindrical block, Super high temperature MICROTHERM are just a few examples. Variety of application and energy saving effect are attracting public attention. 11 figs.

Exploring encapsulation mechanism of DNA and mononucleotides in sol-gel derived silica.

Science.gov (United States)

Kapusuz, Derya; Durucan, Caner

2017-07-01

The encapsulation mechanism of DNA in sol-gel derived silica has been explored in order to elucidate the effect of DNA conformation on encapsulation and to identify the nature of chemical/physical interaction of DNA with silica during and after sol-gel transition. In this respect, double stranded DNA and dAMP (2'-deoxyadenosine 5'-monophosphate) were encapsulated in silica using an alkoxide-based sol-gel route. Biomolecule-encapsulating gels have been characterized using UV-Vis, 29 Si NMR, FTIR spectroscopy and gas adsorption (BET) to investigate chemical interactions of biomolecules with the porous silica network and to examine the extent of sol-gel reactions upon encapsulation. Ethidium bromide intercalation and leach out tests showed that helix conformation of DNA was preserved after encapsulation. For both biomolecules, high water-to-alkoxide ratio promoted water-producing condensation and prevented alcoholic denaturation. NMR and FTIR analyses confirmed high hydraulic reactivity (water adsorption) for more silanol groups-containing DNA and dAMP encapsulated gels than plain silica gel. No chemical binding/interaction occurred between biomolecules and silica network. DNA and dAMP encapsulated silica gelled faster than plain silica due to basic nature of DNA or dAMP containing buffer solutions. DNA was not released from silica gels to aqueous environment up to 9 days. The chemical association between DNA/dAMP and silica host was through phosphate groups and molecular water attached to silanols, acting as a barrier around biomolecules. The helix morphology was found not to be essential for such interaction. BET analyses showed that interconnected, inkbottle-shaped mesoporous silica network was condensed around DNA and dAMP molecules.

An oral delivery system for indomethicin engineered from cationic lipid emulsions and silica nanoparticles

DEFF Research Database (Denmark)

Simovic, Spomenka; Hui, He; Song, Yunmei

2010-01-01

We report on a porous silica-lipid hybrid microcapsule (SLH) oral delivery system for indomethacin fabricated from Pickering emulsion templates, where the drug forms an electrostatic complex with cationic lipid present in the oil phase. Dry SLH microcapsules prepared either by spray drying...... (approximately 1-5 microm) or phase coacervation (20-50 microm) exhibit a specific internal porous matrix structure with pore diameters in the range of 20 to 100 nm. Dissolution studies under sink conditions and in the presence of electrolytes revealed a decreased extent of dissolution; this confirms...

Thermo-stabilized, porous polyimide microspheres prepared from nanosized SiO2 templating via in situ polymerization

Directory of Open Access Journals (Sweden)

M. Q. Liu

2015-01-01

Full Text Available In this article, we addressed a feasible and versatile method of the fabrication of porous polyimide microspheres presenting excellent heat resistance. The preparation process consisted of two steps. Firstly, a novel polyimide/nano-silica composite microsphere was prepared via the self-assembly structures of poly(amic acid (PAA, precursor of PI/nanosized SiO2 blends after in situ polymerization, following the two-steps imidization. Subsequently, the encapsulated nanoparticles were etched away by hydrofluoric acid treatment, giving rise to the pores. It is found the composite structure of PI/SiO2 is a precondition of the formation of nanoporous structures, furthermore, the morphology of the resultant pore could be relatively tuned by changing the content and initial morphology of silica nano-particles trapped into PI matrix. The thermal properties of the synthesized PI porous spheres were studied, indicating that the introduction of nanopores could not effectively influence the thermal stabilities of PI microspheres. Moreover, the fabrication technique described here may be extended to other porous polymer systems.

Rod-shaped silica particles derivatized with elongated silver nanoparticles immobilized within mesopores

Energy Technology Data Exchange (ETDEWEB)

Mnasri, Najib [Institut Charles Gerhardt de Montpellier, CNRS UMR 5253, Université Montpellier, Place Eugène Bataillon, 34095 Montpellier Cedex 5 (France); Materials, Environment and Energy Laboratory (UR14ES26), Faculty of Science, University of Gafsa, 2112 Gafsa (Tunisia); Charnay, Clarence; Ménorval, Louis-Charles de [Institut Charles Gerhardt de Montpellier, CNRS UMR 5253, Université Montpellier, Place Eugène Bataillon, 34095 Montpellier Cedex 5 (France); Elaloui, Elimame [Materials, Environment and Energy Laboratory (UR14ES26), Faculty of Science, University of Gafsa, 2112 Gafsa (Tunisia); Zajac, Jerzy, E-mail: jerzy.zajac@umontpellier.fr [Institut Charles Gerhardt de Montpellier, CNRS UMR 5253, Université Montpellier, Place Eugène Bataillon, 34095 Montpellier Cedex 5 (France)

2016-11-15

Silver-derivatized silica particles possessing a non-spherical morphology and surface plasmon resonance properties have been achieved. Nanometer-sized silica rods with uniformly sized mesopore channels were prepared first making use of alkyltrimethyl ammonium surfactants as porogens and the 1:0.10 tetraethyl orthosilicate (TEOS) : 3-aminopropyltriethoxysilane (APTES) mixture as a silicon source. Silica rods were subsequently functionalized by introducing elongated silver nanoparticles within the intra-particle mesopores thanks to the AgNO{sub 3} reduction procedure based on the action of hemiaminal groups previously located on the mesopore walls. The textural and structural features of the samples were inferred from the combined characterization studies including SEM and TEM microscopy, nitrogen adsorption-desorption at 77 K, powder XRD in the small- and wide-angle region, as well as UV–visible spectroscopy. {sup 129}Xe NMR spectroscopy appeared particularly useful to obtain a correct information about the porous structure of rod-shaped silica particles and the silver incorporation within their intra-particle mesopores. - Highlights: • Mesoporous monodisperse submicron-sized silica rods were achieved. • Silver nanoparticles were located lengthwise within the intra-particle mesopores. • Textural and plasmonic properties of particles studied by {sup 129}Xe NMR and UV–Vis.

Research on the Ordered Mesoporous Silica for Tobacco Harm Reduction

Science.gov (United States)

Wang, Y.; Y Li, Z.; Ding, J. X.; Hu, Z. J.; Liu, Z.; Zhou, G.; Huang, T. H.

2017-12-01

For reducting tobacco harm, this paper prepared an ordered mesoporous silica by using triblock copolymer Pluronic P123 as template. The property of this material was characterized by the X-ray scattering spectrum(XRD), Transmission electron microscopy(TEM), Scanning electron microscopy (SEM) and Nitrogen adsorption/desorption. Then this ordered mesoporous silica was added into the cigarette filter in order to researching its effect of cigarette harm index. The result shows that the feature of SBA-15 was grain morphology, ordered arrangement, tubular porous 2-D hexagonal structure. The application of SBA-15 in cigarette filter can selectively reduce harmful components in cigarette smoke such as crotonaldehyde, hydrogen cyanide, benzo pyrene and tar. The synthesized SBA-15 could properly reduce cigarette harm index.

[Distribution pattern of meso-micro soil fauna in Eucalyptus grandis plantation].

Science.gov (United States)

Huang, Yumei; Zhang, Jian; Yang, Wanqin

2006-12-01

In this paper, meso-micro soil fauna were extracted and collected by Baermann's and Tullgren' s method, and their distribution pattern in the Eucalyptus grandis plantation of Hongya County, Sichuan Province was studied. A total of 13 550 specimens were collected, belonging to 6 phyla, 13 classes, and 26 orders. Acarina, Nematoda, Collembola were the dominant groups, and Enchytraeidae was the frequent one. The group and individual numbers of meso-micro soil fauna varied with seasons, being the maximum in autumn or winter, fewer in summer, and the minimum in spring. The density of meso-micro soil fauna in soil profile decreased rapidly with increasing soil depth, but a converse distribution was observed from time to time in 5 - 10 cm and 10 - 15 cm soil layers. The meso-micro soil fauna collected by Baermann's and Tullgren's method had a density of 3. 333 x 10(3) - 2. 533 x 10(5) ind x m(-2) and 1.670 x 10(2) - 2.393 x 10(5) ind x m(-2), respectively, and the decreasing rate of the density with the increase of soil depth was higher for those collected by Tullgren's method. The density-group index of meso-micro soil fauna in the E. grandis plantation was the lowest in spring, but the highest in autumn or summer. There were no significant differences in the density of meso-micro soil fauna and in the density-group index between E. grandis plantation and Quercus acutissima secondary forest.

Meso-decorated self-healing gels: network structure and properties

Science.gov (United States)

Gong, Jin; Sawamura, Kensuke; Igarashi, Susumu; Furukawa, Hidemitsu

2013-04-01

Gels are a new material having three-dimensional network structures of macromolecules. They possess excellent properties as swellability, high permeability and biocompatibility, and have been applied in various fields of daily life, food, medicine, architecture, and chemistry. In this study, we tried to prepare new multi-functional and high-strength gels by using Meso-Decoration (Meso-Deco), one new method of structure design at intermediate mesoscale. High-performance rigid-rod aromatic polymorphic crystals, and the functional groups of thermoreversible Diels-Alder reaction were introduced into soft gels as crosslinkable pendent chains. The functionalization and strengthening of gels can be realized by meso-decorating the gels' structure using high-performance polymorphic crystals and thermoreversible pendent chains. New gels with good mechanical properties, novel optical properties and thermal properties are expected to be developed.

Bimetallic iron and cobalt incorporated MFI/MCM-41 composite and its catalytic properties

International Nuclear Information System (INIS)

Li, Baoshan; Xu, Junqing; Li, Xiao; Liu, Jianjun; Zuo, Shengli; Pan, Zhiyun; Wu, Ziyu

2012-01-01

Graphical abstract: The formation of FeCo-MFI/MCM-41 composite is based on two steps, the first step of synthesizing the MFI-type proto-zeolite unites under hydrothermal conditions. The second step of assembling these zeolite fragment together new silica and heteroatom source on the CTAB surfactant micelle to synthesize the mesoporous product with hexagonal structure. Highlights: ► Bimetallic iron and cobalt incorporated MFI/MCM-41 composite was prepared using templating method. ► FeCo-MFI/MCM-41 composite simultaneously possessed two kinds of meso- and micro-porous structures. ► Iron and cobalt ions incorporated into the silica framework with tetrahedral coordination. -- Abstract: The MFI/MCM-41 composite material with bimetallic Fe and Co incorporation was prepared using templating method via a two-step hydrothermal crystallization procedure. The obtained products were characterized by a series of techniques including powder X-ray diffraction, N 2 sorption, transmission electron microscopy, scanning electron microscope, H 2 temperature programmed reduction, thermal analyses, and X-ray absorption fine structure spectroscopy of the Fe and Co K-edge. The catalytic properties of the products were investigated by residual oil hydrocracking reactions. Characterization results showed that the FeCo-MFI/MCM-41 composite simultaneously possessed two kinds of stable meso- and micro-porous structures. Iron and cobalt ions were incorporated into the silicon framework, which was confirmed by H 2 temperature programmed reduction and X-ray absorption fine structure spectroscopy. This composite presented excellent activities in hydrocracking of residual oil, which was superior to the pure materials of silicate-1/MCM-41.

Impact of water mobility in some porous media on migration of radio isotopes to the geosphere

International Nuclear Information System (INIS)

AL-Hajji, E.

2011-07-01

The aim of this work is to study the behavior of the water state (bound /free water) in porous materials such as illite and bentonite. These materials are widely used in the storage of radioactive waste. The study was carried out using proton nuclear magnetic resonance technique (NMR). That permits to understand the mechanism of leakage of radioactive elements from these porous materials to the surrounding environment. Such a leakage may have very serious consequences like the contamination of groundwater. In addition, other porous materials like silica and alumina, the two main composite of bentonite, have been studied as well.(author)

Fabrication and excellent conductive performance of antimony-doped tin oxide-coated diatomite with porous structure

International Nuclear Information System (INIS)

Du Yucheng; Yan Jing; Meng Qi; Wang Jinshu; Dai Hongxing

2012-01-01

Graphical abstract: Antimony-doped tin oxide (ATO)-coated diatomite with porous structures are fabricated using the co-precipitation method. The porous ATO-coated diatomite material shows excellent conductive performance. Highlights: ► Sb-doped SnO 2 (ATO)-coated diatomite materials with porous structures are prepared. ► Sn/Sb ratio, ATO coating amount, pH value, and temperature influence resistivity. ► Porous ATO-coated diatomite materials show excellent conductive performance. ► The lowest resistivity of the porous ATO-coated diatomite sample is 10 Ω cm. - Abstract: Diatomite materials coated with antimony-doped tin oxide (ATO) were prepared by the co-precipitation method, and characterized by means of the techniques, such as X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, X-ray fluorescence spectroscopy, and N 2 adsorption–desorption measurement. It was shown that the coated ATO possessed a tetragonal rutile crystal structure, and the ATO-coated diatomite materials had a multi-pore (micro- meso-, and macropores) architecture. The porous ATO-coated diatomite materials exhibited excellent electrical conductive behaviors. The best conductive performance (volume resistivity = 10 Ω cm) was achieved for the sample that was prepared under the conditions of Sn/Sb molar ratio = 5.2, Sn/Sb coating amount = 45 wt%, pH = 1.0, and reaction temperature = 50 °C. Such a conductive porous material is useful for the applications in physical and chemical fields.

Preparation and characterization of micro-cell membrane chromatographic column with N-hydroxysuccinimide group-modified silica-based porous layer open tubular capillary.

Science.gov (United States)

Xu, Liang; Xu, Bei; Zhao, Zhi-Yu; Yang, Hui-Ping; Tang, Cheng; Dong, Lin-Yi; Liu, Kun; Fu, Li; Wang, Xian-Hua

2017-09-22

Cell membrane chromatography (CMC) is an effective tool in screening active compounds from natural products and studying membrane protein interactions. Nevertheless, it always consumes a large amount of cells (e.g. 10 7 -10 8 ) for column preparation. To overcome this, micro-CMC (mCMC), that employs a silica capillary as membrane carrier, was developed. However, both CMC and mCMC suffer from short column life span (e.g. 3days), mainly due to the falling-off of cellular membranes (CMs). This has greatly limited further application of CMC and mCMC, especially when the cells are hard to obtain. To solve this, N-hydroxysuccinimide (NHS)-modified silica-based porous layer open tubular capillary was first prepared for mCMC. The NHS groups can easily react with amino groups on CMs to form a stable covalent bond under a mild condition. So, CMs immobilized on the NHS-modified capillary are less likely to fall off. To verify this, SKBR3/mCMC (Her2 positive) and BALL1/mCMC (CD20 positive) columns were prepared. Two monoclonal antibody drugs, trastuzumab (anti-Her2) and rituximab (anti-CD20), were selected as analytes to characterize the columns. As a result, NHS-modified column for mCMC can afford higher chromatographic retention than non-modified column. Besides, the column life span was significantly improved to more than 16days for SKBR3/mCMC and 14days for BALL1/mCMC, while the compared column showed a sharp decline in retention factor in first 3days. Copyright © 2017 Elsevier B.V. All rights reserved.

A Holistic Approach with Special Reference to Heat Transfer in Multi-Component Porous Media Systems

Directory of Open Access Journals (Sweden)

A. K. Borah

2010-06-01

Full Text Available Problems involving multiphase flow, heat transfer and multi-component mass transport in porous media arise in a number of scientific engineering disciplines. Important technological applications include thermally enhanced oil recovery, subsurface contamination and remediation, capillary assisted thermal technologies, drying process, thermal insulation materials, multiphase trickle bed reactors, nuclear reactor safety analysis, high level radioactive waste repositories and geothermal energy exploitation. In this paper we demonstrate multiphase flows in porous media are driven by gravitational, capillary and viscous forces. But gravity causes phase migration in the direction of the gravitational field. Microscopic modelling efforts were made to accurately incorporate microscopic interfacial phenomena. Multi-scale modelling approaches were attempted in order to transmit information over various lengths scales, ranging from micro-scale, meso-scale, macro-scale and finally to the field scale.

Advanced three dimensional characterization of silica-based ultraporous materials

OpenAIRE

Foray , Genevieve; Roiban , L.; Rong , Q.; Perret , A.; Ihiawakrim , D.; Masenelli-Varlot , K.; Maire , E.; Yrieix , B.

2016-01-01

International audience; Whatever the field of application (building, transportation, packaging, etc.) energy losses must be reduced to meet the government target of a 40% cut in CO 2 emissions. This leads to a challenge for materials scientists: designing materials with thermal conductivities lower than 0.015 W m À1 K À1 under ambient conditions. Such a low value requires reducing air molecule mobility in highly porous materials, and silica-based superinsulation materials (SIM) made of packed...

Effect of DCCA on synthesis of inorganic mesoporous gels

International Nuclear Information System (INIS)

Nemancha, A.R.

2004-01-01

Full text.The porous texture of the monolith inorganic gels plays an important role in the utilization of porous material by control of several properties such as gas diffusion, thermal stability, mechanical strength. the sol gel process provides many possibilities to manufacture porous material with extremely low concentration of impurities at low sinter temperature. The serious problem in the production of the monolith gels is fracture and crack formation which may occur in the conversion of the wet gels to dry gels. This phenomenon is probably due to the capillary forces which appear during the drying steps. in order to reduce the effect of capillary forces a number of methods were applied (hyper critic drying, organic DCCAs). The purpose of the present work, is to understand the chemical changes that result from adding formamide as drying control chemical additives DCCA to the colloidal silica sols in the presence of acid catalyst. Fourier Transformed Infrared spectroscopy and Raman spectroscopy were used to investigate the influence of formamide on gel formation. The Nitrogen adsorption-desorption technique is used to investigate the effect of formamide on gel texture. The results show that the gels with formamide are monolith and obtained during a short time of gelling reaction, the silica particles link formation depend strongly on the formamide concentration. the BET and BJH results show that the presence of formamide promotes the creation of meso porous texture depending on formamide/silica molar ratio in the starting sol. The maximum average diameter of the obtained gel reaches a value close to 25 nm with a bulk density equal to 1.1 g/cm 3

Hierarchical self-assembly of heparin-PEG end-capped porous silica as a redox sensitive nanocarrier for doxorubicin delivery

Energy Technology Data Exchange (ETDEWEB)

Nguyen Thi, Thu Thao; Tran, Tuong Vi; Tran, Ngoc Quyen [Institute of Research and Development, Duy Tan University, Da Nang City 550000 (Viet Nam); Institute of Applied Materials Science, Vietnam Academy of Science and Technology, Ho Chi Minh City 70000 (Viet Nam); Nguyen, Cuu Khoa [Institute of Applied Materials Science, Vietnam Academy of Science and Technology, Ho Chi Minh City 70000 (Viet Nam); Nguyen, Dai Hai, E-mail: nguyendaihai0511@gmail.com [Institute of Applied Materials Science, Vietnam Academy of Science and Technology, Ho Chi Minh City 70000 (Viet Nam)

2017-01-01

Porous nanosilica (PNS) has been attracting a great attention in fabrication carriers for drug delivery system (DDS). However, unmodified PNS-based carriers exhibited the initial burst release of loaded bioactive molecules, which may limit their potential clinical application. In this study, the surface of PNS was conjugated with adamantylamine (A) via disulfide bonds (PNS-SS-A) which was functionalized with cyclodextrin-heparin-polyethylene glycol (CD-HPEG) for redox triggered doxorubicin (DOX) delivery. The modified PNS was successfully formed with spherical shape and diameter around 50 nm determined by transmission electron microscopy (TEM). DOX was efficiently trapped in the PNS-SS-A@CD-HPEG and slowly released in phosphate buffered saline (PBS) without any initial burst effect. Importantly, the release of DOX was triggered due to the cleavage of the disulfide bonds in the presence of dithiothreitol (DTT). In addition, the MTT assay data showed that PNS-SS-A@CD-HPEG was a biocompatible nanocarrier and reduced the toxicity of DOX. These results demonstrated that PNS-SS-A@CD-HPEG has great potential as a novel nanocarrier for anticancer drug in cancer therapy. - Graphic abstract: Hierarchical self-assembly of heparin-PEG end-capped mesoporous silica through host-guest interaction for trapping doxorubicin. The copolymer attached on PNS via disulfide bond which is rapidly cleaved in redox environment, and as a result a huge amount of doxorubicin will release. - Highlights: • Novel redox-responsive nanocarriers based on surface-modified porous nanosilica (PNS) were developed. • Spherical-shaped PNS nanoparticles with diameter around 50 nm were obtained. • Doxorubicin (DOX) was effectively loaded and released in a controlled manner without any initial burst release by surface modification of PNS. • The redox-responsive properties of the modified PNS were demonstrated due to reductive cleavage of disulfide bonds in dithiothreitol (DTT). • The

Structure and spectral properties of the silver-containing high-silica glasses

International Nuclear Information System (INIS)

Girsova, M A; Golovina, G F; Anfimova, I N; Antropova, T V; Arsent'ev, M Yu

2016-01-01

Silver-containing high-silica glasses were synthesized by an impregnation of the silica porous glasses (PGs) first with AgNO 3 aqueous solution (with or without the presence of the sensitizers, such as Cu(NO 3 ) 2 or Ce(NO 3 ) 3 ), next in the mixed halide salt (NH 4 Cl, KBr, KI) solution. Then some part of the samples was sintered at the temperatures from 850 to 900°C up to closing of the pores. The structure of glasses was studied by UV-VIS-NIR and IR spectroscopy and X-ray diffraction (XRD) techniques. According to XRD data the silver-containing high-silica glasses contain the AgBr, AgI, Ag 3 PO 4 , (CuBr) 0.75 (CuI) 0.25 phases. IR spectra confirmed B-O-B, Si- O-Si, P-O-P, O-P-O, O-B-O bonds, (PO 4 ) 3- and P-O - groups in glasses. (paper)

Meso-level analysis, the missing link in energy strategies

International Nuclear Information System (INIS)

Schenk, Niels J.; Moll, Henri C.; Schoot Uiterkamp, Anton J.M.

2007-01-01

Energy is essential for human societies. Energy systems, though, are also associated with several adverse environmental effects. So far societies have been unable to successfully change their energy systems in a way that addresses environmental and health concerns. Lack of policy consensus often resulted in so-called 'stop-go' policies, which were identified as some of the most important barriers regarding successful energy transitions. The lack of policy consensus and coherent long-term strategies may result from a lack of knowledge of energy systems' meso-level dynamics. The meso-level involves the dynamic behaviour of the individual system elements and the coupling of individual technologies, resulting in interdependencies and regimes. Energy systems are at the meso-level characterised by two typical aspects, i.e. dynamics driven by interactions between actors, and heterogeneous characteristics of actors. These aspects give rise to the ineffectiveness of traditional energy policies, which is illustrated with examples from the transport sector and household electricity consumption. We found that analysis of energy systems at the meso-level helps to better understand energy systems. To resolve persistent policy issues, the traditional 'one size fits all' energy policies are not sufficient. In order to tackle the difficult issues, 'redesign of system organisation', 'target group approach', or 'target group induced system re-orientation' are needed

Characteristics, distribution, origin, and significance of opaline silica observed by the Spirit rover in Gusev crater, Mars

Science.gov (United States)

Ruff, S.W.; Farmer, J.D.; Calvin, W.M.; Herkenhoff, K. E.; Johnson, J. R.; Morris, R.V.; Rice, M.S.; Arvidson, R. E.; Bell, J.F.; Christensen, P.R.; Squyres, S. W.

2011-01-01

The presence of outcrops and soil (regolith) rich in opaline silica (???65-92 wt % SiO2) in association with volcanic materials adjacent to the "Home Plate" feature in Gusev crater is evidence for hydrothermal conditions. The Spirit rover has supplied a diverse set of observations that are used here to better understand the formation of silica and the activity, abundance, and fate of water in the first hydrothermal system to be explored in situ on Mars. We apply spectral, chemical, morphological, textural, and stratigraphic observations to assess whether the silica was produced by acid sulfate leaching of precursor rocks, by precipitation from silica-rich solutions, or by some combination. The apparent lack of S enrichment and the relatively low oxidation state of the Home Plate silica-rich materials appear inconsistent with the originally proposed Hawaiian analog for fumarolic acid sulfate leaching. The stratiform distribution of the silica-rich outcrops and their porous and brecciated microtextures are consistent with sinter produced by silica precipitation. There is no evidence for crystalline quartz phases among the silica occurrences, an indication of the lack of diagenetic maturation following the production of the amorphous opaline phase. Copyright ?? 2011 by the American Geophysical Union.

Super-Hydrophobic/Icephobic Coatings Based on Silica Nanoparticles Modified by Self-Assembled Monolayers

Directory of Open Access Journals (Sweden)

Junpeng Liu

2016-12-01

Full Text Available A super-hydrophobic surface has been obtained from nanocomposite materials based on silica nanoparticles and self-assembled monolayers of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS using spin coating and chemical vapor deposition methods. Scanning electron microscope images reveal the porous structure of the silica nanoparticles, which can trap small-scale air pockets. An average water contact angle of 163° and bouncing off of incoming water droplets suggest that a super-hydrophobic surface has been obtained based on the silica nanoparticles and POTS coating. The monitored water droplet icing test results show that icing is significantly delayed by silica-based nano-coatings compared with bare substrates and commercial icephobic products. Ice adhesion test results show that the ice adhesion strength is reduced remarkably by silica-based nano-coatings. The bouncing phenomenon of water droplets, the icing delay performance and the lower ice adhesion strength suggest that the super-hydrophobic coatings based on a combination of silica and POTS also show icephobicity. An erosion test rig based on pressurized pneumatic water impinging impact was used to evaluate the durability of the super-hydrophobic/icephobic coatings. The results show that durable coatings have been obtained, although improvement will be needed in future work aiming for applications in aerospace.

Methane Hydrate Formation and Dissociation in the Presence of Silica Sand and Bentonite Clay

Directory of Open Access Journals (Sweden)

Kumar Saw V.

2015-11-01

Full Text Available The formation and dissociation of methane hydrates in a porous media containing silica sand of different sizes and bentonite clay were studied in the presence of synthetic seawater with 3.55 wt% salinity. The phase equilibrium of methane hydrate under different experimental conditions was investigated. The effects of the particle size of silica sand as well as a mixture of bentonite clay and silica sand on methane hydrate formation and its dissociation were studied. The kinetics of hydrate formation was studied under different subcooling conditions to observe its effects on the induction time of hydrate formation. The amount of methane gas encapsulated in hydrate was computed using a real gas equation. The Clausius-Clapeyron equation is used to estimate the enthalpy of hydrate dissociation with measured phase equilibrium data.

Positronium chemistry in porous adsorbents

International Nuclear Information System (INIS)

Foti, G.; Nagy, L.G.; Moravcsik, G.; Schay, G.

1981-01-01

Kinetic studies on the annihilation of orthopositronium in porous adsorbents have been performed using lifetime spectroscopy. The positron source applied was 22 Na with 0.2 MBq activity. The adsorbents investigated were silica gels of different particle size and pore structure. The appearance of the long-lived component in the lifetime spectra can be explained by the diffusion of the orthopositronium into the pores affected by the particle size and the pore size of the adsorbent, the coverage on it and the chemical nature of the adsorbate. The long-term aim of the work is to determine and to explain these effects. (author)

Transport and abatement of fluorescent silica nanoparticle (SiO{sub 2} NP) in granular filtration: effect of porous media and ionic strength

Energy Technology Data Exchange (ETDEWEB)

Zeng, Chao, E-mail: chaozeng@email.arizona.edu; Shadman, Farhang; Sierra-Alvarez, Reyes [University of Arizona, Department of Chemical and Environmental Engineering (United States)

2017-03-15

The extensive production and application of engineered silica nanoparticles (SiO{sub 2} NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO{sub 2} NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO{sub 2} NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO{sub 2} filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO{sub 2} NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO{sub 2} NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO{sub 2} NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO{sub 2} NP filtration.

One-step synthesis of highly efficient nanocatalysts on the supports with hierarchical pores using porous ionic liquid-water gel.

Science.gov (United States)

Kang, Xinchen; Zhang, Jianling; Shang, Wenting; Wu, Tianbin; Zhang, Peng; Han, Buxing; Wu, Zhonghua; Mo, Guang; Xing, Xueqing

2014-03-12

Stable porous ionic liquid-water gel induced by inorganic salts was created for the first time. The porous gel was used to develop a one-step method to synthesize supported metal nanocatalysts. Au/SiO2, Ru/SiO2, Pd/Cu(2-pymo)2 metal-organic framework (Cu-MOF), and Au/polyacrylamide (PAM) were synthesized, in which the supports had hierarchical meso- and macropores, the size of the metal nanocatalysts could be very small (esterification of benzyl alcohol to methyl benzoate, benzene hydrogenation to cyclohexane, and oxidation of benzyl alcohol to benzaldehyde because they combined the advantages of the nanocatalysts of small size and hierarchical porosity of the supports. In addition, this method is very simple.

Hydrothermal assisted synthesis of iron oxide-based magnetic silica spheres and their performance in magnetophoretic water purification

Energy Technology Data Exchange (ETDEWEB)

Caparros, C., E-mail: ccaparros@fisica.uminho.pt [Centro de Fisica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Benelmekki, M.; Martins, P.M. [Centro de Fisica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Xuriguera, E. [Facultat de Quimica, Universitat de Barcelona, 08028 Barcelona (Spain); Silva, C.J.R. [Departamento de Quimica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Martinez, Ll.M. [Sepmag Technologies, Parc Tecnologic del Valles, 08290 Barcelona (Spain); Lanceros-Mendez, S. [Centro de Fisica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal)

2012-08-15

Porous Magnetic Silica (PMS) spheres of about 400 nm diameter were synthesised by one-pot process using the classical Stber method combined with hydrothermal treatment. Maghemite nanoparticles ({gamma}-Fe{sub 2}O{sub 3}) were used as fillers and cetyltrimethylammonium bromide (CTAB) was used as templating agent. The application of the hydrothermal process (120 Degree-Sign C during 48 h) before the calcination leads to the formation of homogeneous and narrow size distribution PMS spheres. X-ray diffraction patterns (XRD), Infrared measurements (FTIR) and Transmission Electron microscopy (TEM) methods were used to determine the composition and morphology of the obtained PMS spheres. The results show a homogeneous distribution of the {gamma}-Fe{sub 2}O{sub 3} nanoparticles in the silica matrix with a 'hollow-like' morphology. Magnetophoresis measurements at 60 T m{sup -1} show a total separation time of the PMS spheres suspension of about 16 min. By using this synthesis method, the limitation of the formation of silica spheres without incorporation of magnetic nanoparticles is overcome. These achievements make this procedure interesting for industrial up scaling. The obtained PMS spheres were evaluated as adsorbents for Ni{sup 2+} in aqueous solution. Their adsorption capacity was compared with the adsorption capacity of magnetic silica spheres obtained without hydrothermal treatment before calcination process. PMS spheres show an increase of the adsorption capacity of about 15% of the initial dissolution of Ni{sup 2+} without the need to functionalize the silica surface. Highlights: Black-Right-Pointing-Pointer Homogeneous and controlled size porous magnetic silica spheres were obtained. Black-Right-Pointing-Pointer Magnetophoretic removing of Ni{sup 2+} processes was successfully preformed at HLGMF. Black-Right-Pointing-Pointer PMS show higher Ni{sup 2+} removing capacity than spheres without hydrothermal treatment. Black-Right-Pointing-Pointer PMS can be

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.

Adsorption of uranyl in SiO2 porous glass

International Nuclear Information System (INIS)

Benedetto, F. E.; Prado, M. O.

2013-01-01

Vitreous SiO 2 porous matrices can be used in many applications involving the uptake of chemical species on its solid surface. In this work, vitreous silica sponges were prepared from a sodium borosilicate glass manufactured in our laboratory. The product obtained was then separated into phases with subsequent leaching of the soluble phase rich in B and Na. The resulting porous matrices have a specific surface of 35 m2/gr. Adsorption of uranyl ions onto the SiO 2 porous surface was studied to evaluate the use of this material as a filter for treatment of uranium containing water. The effects of contact time, adsorbent mass and equilibrium concentration of solution were studied. The porous adsorbent exhibits a pseudo-second-order kinetic behavior. The sponges with adsorbed uranium were thermally sealed as a way of U immobilization. Retention of uranium was confirmed during the matrix sealing by TGA. Uranium concentration before and after adsorption tests were made by means of ICP-OES. For uranium concentration of 800 ppm, 72 hours contact time and pH of 3.5, the amount of uranium adsorbed was 21.06 ± 0.02 mg U per gram of vitreous porous SiO 2 . (author)

Developmentally Regulated Production of meso-Zeaxanthin in Chicken Retinal Pigment Epithelium/Choroid and Retina.

Science.gov (United States)

Gorusupudi, Aruna; Shyam, Rajalekshmy; Li, Binxing; Vachali, Preejith; Subhani, Yumna K; Nelson, Kelly; Bernstein, Paul S

2016-04-01

meso-Zeaxanthin is a carotenoid that is rarely encountered in nature outside of the vertebrate eye. It is not a constituent of a normal human diet, yet this carotenoid comprises one-third of the primate macular pigment. In the current study, we undertook a systematic approach to biochemically characterize the production of meso-zeaxanthin in the vertebrate eye. Fertilized White Leghorn chicken eggs were analyzed for the presence of carotenoids during development. Yolk, liver, brain, serum, retina, and RPE/choroid were isolated, and carotenoids were extracted. The samples were analyzed on C-30 or chiral HPLC columns to determine the carotenoid composition. Lutein and zeaxanthin were found in all studied nonocular tissues, but no meso-zeaxanthin was ever detected. Among the ocular tissues, the presence of meso-zeaxanthin was consistently observed starting at embryonic day 17 (E17) in the RPE/choroid, several days before its consistent detection in the retina. If RPE/choroid of an embryo was devoid of meso-zeaxanthin, the corresponding retina was always negative as well. This is the first report of developmentally regulated synthesis of meso-zeaxanthin in a vertebrate system. Our observations suggest that the RPE/choroid is the primary site of meso-zeaxanthin synthesis. Identification of meso-zeaxanthin isomerase enzyme in the developing chicken embryo will facilitate our ability to determine the biochemical mechanisms responsible for production of this unique carotenoid in other higher vertebrates, such as humans.

Lyophilized silica lipid hybrid (SLH) carriers for poorly water-soluble drugs: physicochemical and in vitro pharmaceutical investigations.

Science.gov (United States)

Yasmin, Rokhsana; Tan, Angel; Bremmell, Kristen E; Prestidge, Clive A

2014-09-01

Lyophilization was investigated to produce a powdery silica-lipid hybrid (SLH) carrier for oral delivery of poorly water-soluble drugs. The silica to lipid ratio, incorporation of cryoprotectant, and lipid loading level were investigated as performance indicators for lyophilized SLH carriers. Celecoxib, a nonsteroidal anti-inflammatory drug, was used as the model poorly soluble moiety to attain desirable physicochemical and in vitro drug solubilization properties. Scanning electron microscopy and confocal fluorescence imaging verified a nanoporous, homogenous internal matrix structures of the lyophilized SLH particles, prepared from submicron triglyceride emulsions and stabilized by porous silica nanoparticles (Aerosil 380), similar to spray-dried SLH. 20-50 wt % of silica in the formulation have shown to produce nonoily SLH agglomerates with complete lipid encapsulation. The incorporation of a cryoprotectant prevented irreversible aggregation of the silica-stabilized droplets during lyophilization, thereby readily redispersing in water to form micrometre-sized particles (water-soluble therapeutics is confirmed. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

A facile approach for the synthesis of monolithic hierarchical porous carbons – high performance materials for amine based CO2 capture and supercapacitor electrode

KAUST Repository

Estevez, Luis

2013-05-03

An ice templating coupled with hard templating and physical activation approach is reported for the synthesis of hierarchically porous carbon monoliths with tunable porosities across all three length scales (macro- meso- and micro), with ultrahigh specific pore volumes [similar]11.4 cm3 g−1. The materials function well as amine impregnated supports for CO2 capture and as supercapacitor electrodes.

High-silica glass matrix process for high-level waste solidification

International Nuclear Information System (INIS)

Simmons, J.H.; Macedo, P.B.

1981-01-01

In the search for an optimum glass matrix composition, we have determined that chemical durability and thermal stability are maximized, and that stress development is minimized for glass compositions containing large concentrations of glass-forming oxides, of which silica is the major component (80 mol%). These properties and characteristics were recently demonstrated to belong to very old geological glasses known as tektites (ages of 750,000 to 34 million years.) The barrier to simulating tektite compositions for the waste glasses was the high melting temperature (1600 to 1800 0 C) needed for these glasses. Such temperatures greatly complicate furnace design and maintenance and lead to an intolerable vaporization of many of the radioisotopes into the off-gas system. Research conducted at our laboratory led to the development of a porous high-silica waste glass material with approximately 80% SiO 2 by mole and 30% waste loading by weight. The process can handle a wide variety of compositions, and yields long, elliptical, monolithic samples, which consist of a loaded high-silica core completely enveloped in a high-silica glass tube, which has collapsed upon the core and sealed it from the outside. The outer glass layer is totally free of waste isotopes and provides an integral multibarrier protection system

Nano-porous inorganic-organic hybrid solids: some new materials for hydrogen storage?

International Nuclear Information System (INIS)

Serre, Ch.; Loiseau, Th.; Devic, T.; Ferey, G.; Latroche, M.; Llewellyn, Ph.; Chang, J.S.

2007-01-01

Recently have been studied chromium and aluminium carboxylates MIL-53(Cr, Al), formed from an assembly of octahedrons chains and for hybrid solids formed with octahedrons trimers (MIL-100 and MIL-101). The compounds MIL-53(Cr, Al) are microporous (φ ∼ 8 Angstroms, while the solids MIL-100 and MIL-101 have very large porous volumes (V ∼ 380-700000 (Angstroms) 3 ), meso-pores (φ ∼ 25-34 Angstroms) and a zeolitic architecture. The resulting specific surface areas are important (between 1000 m 2 .g -1 for the MIL-53 solids, until 4000 m 2 .g -1 for the MIL-101 compound. Here is presented their hydrogen adsorption properties, at 77 K and 298 K. The hydrogen adsorption kinetics has been tested on the MIL-53(Cr) solid at 77 K. Hydrogen adsorption micro-calorimetry experiments have been carried out on these solids between 0 and 1 bar in order to obtain data on the strongest interactions between hydrogen and the porous basic structure. (O.M.)

Hierarchically porous MgCo2O4 nanochain networks: template-free synthesis and catalytic application

Science.gov (United States)

Guan, Xiangfeng; Yu, Yunlong; Li, Xiaoyan; Chen, Dagui; Luo, Peihui; Zhang, Yu; Guo, Shanxin

2018-01-01

In this work, hierarchically porous MgCo2O4 nanochain networks were successfully synthesized by a novel template-free method realized via a facile solvothermal synthesis followed by a heat treatment. The morphologies of MgCo2O4 precursor could be adjusted from nanosheets to nanobelts and finally to interwoven nanowires, depending on the volume ratio of diethylene glycol to deionized water in the solution. After calcination, the interwoven precursor nanowires were transformed to hierarchical MgCo2O4 nanochain networks with marco-/meso-porosity, which are composed of 10-20 nm nanoparticles connected one by one. Moreover, the relative formation mechanism of the MgCo2O4 nanochain networks was discussed. More importantly, when evaluated as catalytic additive for AP thermal decomposition, the MgCo2O4 nanochain networks show excellent accelerating effect. It is benefited from the unique hierarchically porous network structure and multicomponent effect, which effectively accelerates ammonia oxidation and {{{{ClO}}}4}- species dissociation. This approach opens the way to design other hierarchically porous multicomponent metal oxides.

Power Generation from Concentration Gradient by Reverse Electrodialysis in Dense Silica Membranes for Microfluidic and Nanofluidic Systems

Directory of Open Access Journals (Sweden)

Sang Woo Lee

2016-01-01

Full Text Available In this study, we investigate power generation by reverse electrodialysis in a dense silica membrane that is between two NaCl solutions with various combinations of concentrations. Each silica membrane is fabricated by depositing a silica layer on a porous alumina substrate via chemical vapor deposition. The measured potential-current (V-I characteristics of the silica membrane are used to obtain the transference number, diffusion potential, and electrical resistance. We develop empirical correlations for the transference number and the area-specific resistance, and present the results of power generation by reverse electrodialysis using the fabricated silica membranes. The highest measured power density is 0.98 mW/m2. In addition, we develop a contour map of the power density as a function of NaCl concentrations on the basis of the empirical correlations. The contour map shows that a power output density of 1.2 mW/m2 is achievable with the use of silica membranes and is sufficient to drive nanofluidic and microfluidic systems. The dense silica membrane has the potential for use in micro power generators in nanofluidic and microfluidic systems.

Porous SiO_2 nanofiber grafted novel bioactive glass–ceramic coating: A structural scaffold for uniform apatite precipitation and oriented cell proliferation on inert implant

International Nuclear Information System (INIS)

Das, Indranee; De, Goutam; Hupa, Leena; Vallittu, Pekka K.

2016-01-01

A composite bioactive glass–ceramic coating grafted with porous silica nanofibers was fabricated on inert glass to provide a structural scaffold favoring uniform apatite precipitation and oriented cell proliferation. The coating surfaces were investigated thoroughly before and after immersion in simulated body fluid. In addition, the proliferation behavior of fibroblast cells on the surface was observed for several culture times. The nanofibrous exterior of this composite bioactive coating facilitated homogeneous growth of flake-like carbonated hydroxyapatite layer within a short period of immersion. Moreover, the embedded porous silica nanofibers enhanced hydrophilicity which is required for proper cell adhesion on the surface. The cells proliferated well following a particular orientation on the entire coating by the assistance of nanofibrous scaffold-like structural matrix. This newly engineered composite coating was effective in creating a biological structural matrix favorable for homogeneous precipitation of calcium phosphate, and organized cell growth on the inert glass surface. - Highlights: • Fabricated porous SiO_2 nanofibers grafted composite bioactive glass–ceramic coating on inert glass. • The newly engineered coating facilitates uniformly dense apatite precipitation. • Embedded porous silica nanofibers enhance hydrophilicity of the coated surface. • Cells proliferate well on the entire coating following a particular orientation by the assistance of nanofibers. • The coatings have potential to be used as biological scaffold on the surface of implants.

AuRu/meso-Mn2O3: A Highly Active and Stable Catalyst for Methane Combustion

Science.gov (United States)

Han, Z.; Fang, J. Y.; Xie, S. H.; Deng, J. G.; Liu, Y. X.; Dai, H. X.

2018-05-01

Three-dimensionally ordered mesoporous Mn2O3 (meso-Mn2O3) and its supported Au, Ru, and AuRu alloy (0.49 wt% Au/meso-Mn2O3, 0.48 wt% Ru/meso-Mn2O3, and 0.97 wt% AuRu/meso-Mn2O3 (Au/Ru molar ratio = 0.98)) nanocatalysts were prepared using the KIT-6-templating and polyvinyl alcohol-protected reduction methods, respectively. Physicochemical properties of the samples were characterized by means of numerous techniques, and their catalytic activities were evaluated for the combustion of methane. It is found that among all of the samples, 0.48 wt% Ru/meso-Mn 2O3 and 0.97 wt% AuRu/meso-Mn2O3 performed the best (the reaction temperature (T90% ) at 90% methane conversion was 530-540°C), but the latter showed a better thermal stability than the former. The partial deactivation of 0.97 wt% AuRu/meso-Mn2O3 due to H2O or CO2 introduction was reversible. It is concluded that the good catalytic activity and thermal stability of 0.97 wt% AuRu/meso-Mn2O3 was associated with the high dispersion of AuRu alloy NPs (2-5 nm) on the surface of meso-Mn2O3 and good low-temperature reducibility.

Fabrication and excellent conductive performance of antimony-doped tin oxide-coated diatomite with porous structure

Energy Technology Data Exchange (ETDEWEB)

Du Yucheng, E-mail: ychengdu@bjut.edu.cn [Key Lab of Advanced Functional Materials, Ministry of Education, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Yan Jing; Meng Qi; Wang Jinshu [Key Lab of Advanced Functional Materials, Ministry of Education, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Dai Hongxing, E-mail: hxdai@bjut.edu.cn [Laboratory of Catalysis Chemistry and Nanoscience, Department of Chemistry and Chemical Engineering, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124 (China)

2012-04-16

Graphical abstract: Antimony-doped tin oxide (ATO)-coated diatomite with porous structures are fabricated using the co-precipitation method. The porous ATO-coated diatomite material shows excellent conductive performance. Highlights: Black-Right-Pointing-Pointer Sb-doped SnO{sub 2} (ATO)-coated diatomite materials with porous structures are prepared. Black-Right-Pointing-Pointer Sn/Sb ratio, ATO coating amount, pH value, and temperature influence resistivity. Black-Right-Pointing-Pointer Porous ATO-coated diatomite materials show excellent conductive performance. Black-Right-Pointing-Pointer The lowest resistivity of the porous ATO-coated diatomite sample is 10 {Omega} cm. - Abstract: Diatomite materials coated with antimony-doped tin oxide (ATO) were prepared by the co-precipitation method, and characterized by means of the techniques, such as X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, X-ray fluorescence spectroscopy, and N{sub 2} adsorption-desorption measurement. It was shown that the coated ATO possessed a tetragonal rutile crystal structure, and the ATO-coated diatomite materials had a multi-pore (micro- meso-, and macropores) architecture. The porous ATO-coated diatomite materials exhibited excellent electrical conductive behaviors. The best conductive performance (volume resistivity = 10 {Omega} cm) was achieved for the sample that was prepared under the conditions of Sn/Sb molar ratio = 5.2, Sn/Sb coating amount = 45 wt%, pH = 1.0, and reaction temperature = 50 Degree-Sign C. Such a conductive porous material is useful for the applications in physical and chemical fields.

complexes based on meso-substituted dipyrrins

Indian Academy of Sciences (India)

Keywords. Coordination polymers; meso-substituted dipyrrins; heteroleptic; acetylacetonato; ... Room temperature magnetic susceptibility measurements were ... After cooling to ambient tem- perature it ... crystals of 1 were obtained from CH2Cl2/ hexane (1. : 1) solution. .... are air-stable, crystalline solids, soluble in common.

Fractionation and solubility of cadmium in paddy soils amended with porous hydrated calcium silicate.

Science.gov (United States)

Zhao, Xiu-Lan; Masaihiko, Saigusa

2007-01-01

Previous studies have shown that porous hydrated calcium silicate (PS) is very effective in decreasing cadmium (Cd) content in brown rice. However, it is unclear whether the PS influences cadmium transformation in soil. The present study examined the effect of PS on pH, cadmium transformation and cadmium solubility in Andosol and Alluvial soil, and also compared its effects with CaCO3, acidic porous hydrated calcium silicate (APS) and silica gel. Soil cadmium was operationally fractionationed into exchangeable (Exch), bound to carbonates (Carb), bound to iron and manganese oxides (FeMnO(x)), bound to organic matters (OM) and residual (Res) fraction. Application of PS and CaCO3 at hig rates enhanced soil pH, while APS and silica gel did not obviously change soil pH. PS and CaCO3 also increased the FeMnO(x)-Cd in Andosol and Carb-Cd in Alluvial soil, thus reducing the Exch-Cd in the tested soils. However, PS was less effective than CaCO3 at the same application rate. Cadmium fractions in the two soils were not changed by the treatments of APS and silica gel. There were no obvious differences in the solubility of cadmium in soils treated with PS, APS, silica gel and CaCO3 except Andosol treated 2.0% CaCO3 at the same pH of soil-CaCl2 suspensions. These findings suggested that the decrease of cadmium availability in soil was mainly attributed to the increase of soil pH caused by PS.

Preparation of mesoporous silica microparticles by sol-gel/emulsion route for protein release.

Science.gov (United States)

Vlasenkova, Mariya I; Dolinina, Ekaterina S; Parfenyuk, Elena V

2018-04-06

Encapsulation of therapeutic proteins into particles from appropriate material can improve both stability and delivery of the drugs, and the obtained particles can serve as a platform for development of their new oral formulations. The main goal of this work was development of sol-gel/emulsion method for preparation of silica microcapsules capable of controlled release of encapsulated protein without loss of its native structure. For this purpose, the reported in literature direct sol-gel/W/O/W emulsion method of protein encapsulation was used with some modifications, because the original method did not allow to prepare silica microcapsules capable for protein release. The particles were synthesized using sodium silicate and tetraethoxysilane as silica precursors and different compositions of oil phase. In vitro kinetics of bovine serum albumin (BSA) release in buffer (pH 7.4) was studied by Fourier transform infrared (FTIR) and fluorescence spectrometry, respectively. Structural state of encapsulated BSA and after release was evaluated. It was found that the synthesis conditions influenced substantially the porous structure of the unloaded silica particles, release properties of the BSA-loaded silica particles and structural state of the encapsulated and released protein. The modified synthesis conditions made it possible to obtain the silica particles capable of controlled release of the protein during a week without loss of the protein native structure.

Polymer-silica hybrids for separation of CO2 and catalysis of organic reactions

Science.gov (United States)

Silva Mojica, Ernesto

Porous materials comprising polymeric and inorganic segments have attracted interest from the scientific community due to their unique properties and functionalities. The physical and chemical characteristics of these materials can be effectively exploited for adsorption applications. This dissertation covers the experimental techniques for fabrication of poly(vinyl alcohol) (PVA) and silica (SiO2) porous supports, and their functionalization with polyamines for developing adsorbents with potential applications in separation of CO2 and catalysis of organic reactions. The supports were synthesized by processes involving (i) covalent cross-linking of PVA, (ii) hydrolysis and poly-condensation of silica precursors (i,e,. sol-gel synthesis), and formation of porous structures via (iii) direct templating and (iv) phase inversion techniques. Their physical structure was controlled by the proper combination of the preparation procedures, which resulted in micro-structured porous materials in the form of micro-particles, membranes, and pellets. Their adsorption characteristics were tailored by functionalization with polyethyleneimine (PEI), and their physicochemical properties were characterized by vibrational spectroscopy (FTIR, UV-vis), microscopy (SEM), calorimetry (TGA, DSC), and adsorption techniques (BET, step-switch adsorption). Spectroscopic investigations of the interfacial cross-linking reactions of PEI and PVA with glutaraldehyde (GA) revealed that PEI catalyzes the cross-linking reactions of PVA in absence of external acid catalysts. In-situ IR spectroscopy coupled with a focal plane array (FPA) image detector allowed the characterization of a gradient interface on a PEI/PVA composite membrane and the investigation of the cross-linking reactions as a function of time and position. The results served as a basis to postulate possible intermediates, and propose the reaction mechanisms. The formulation of amine-functionalized CO2 capture sorbents was based on the

Porous SiO{sub 2} nanofiber grafted novel bioactive glass–ceramic coating: A structural scaffold for uniform apatite precipitation and oriented cell proliferation on inert implant

Energy Technology Data Exchange (ETDEWEB)

Das, Indranee [Nano-Structured Materials Division, CSIR-Central Glass and Ceramic Research Institute, Kolkata 700032 (India); De, Goutam, E-mail: gde@cgcri.res.in [Nano-Structured Materials Division, CSIR-Central Glass and Ceramic Research Institute, Kolkata 700032 (India); Hupa, Leena [Johan Gadolin Process Chemistry Centre, Åbo Akademi University, FI-20500 Åbo (Finland); Vallittu, Pekka K. [Turku Clinical Biomaterials Centre—TCBC, University of Turku, FI-20520 Turku (Finland); Institute of Dentistry, University of Turku, Department of Biomaterials Science and City of Turku, Welfare Division, Turku (Finland)

2016-05-01

A composite bioactive glass–ceramic coating grafted with porous silica nanofibers was fabricated on inert glass to provide a structural scaffold favoring uniform apatite precipitation and oriented cell proliferation. The coating surfaces were investigated thoroughly before and after immersion in simulated body fluid. In addition, the proliferation behavior of fibroblast cells on the surface was observed for several culture times. The nanofibrous exterior of this composite bioactive coating facilitated homogeneous growth of flake-like carbonated hydroxyapatite layer within a short period of immersion. Moreover, the embedded porous silica nanofibers enhanced hydrophilicity which is required for proper cell adhesion on the surface. The cells proliferated well following a particular orientation on the entire coating by the assistance of nanofibrous scaffold-like structural matrix. This newly engineered composite coating was effective in creating a biological structural matrix favorable for homogeneous precipitation of calcium phosphate, and organized cell growth on the inert glass surface. - Highlights: • Fabricated porous SiO{sub 2} nanofibers grafted composite bioactive glass–ceramic coating on inert glass. • The newly engineered coating facilitates uniformly dense apatite precipitation. • Embedded porous silica nanofibers enhance hydrophilicity of the coated surface. • Cells proliferate well on the entire coating following a particular orientation by the assistance of nanofibers. • The coatings have potential to be used as biological scaffold on the surface of implants.

Highly porous flame-retardant and sustainable biofoams based on wheat gluten and in situ polymerized silica

DEFF Research Database (Denmark)

Wu, Qiong; Andersson, Richard L.; Holgate, Tim

2014-01-01

This article presents a novel type of flame-retardant biohybrid foam with good insulation properties based on wheat gluten and silica, the latter polymerized in situ from hydrolysed tetraethyl orthosilicate (TEOS). This led to the formation of intimately mixed wheat gluten and silica phases, wher...... with a vacuum treatment to remove the largest air bubbles. X-ray photoelectron and infrared spectroscopy showed that silicon was present mainly as SiO2....

Design of a superhydrophobic and superoleophilic film using cured fluoropolymer@silica hybrid

International Nuclear Information System (INIS)

Yang, Hao; Pi, Pihui; Yang, Zhuo-ru; Lu, Zhong; Chen, Rong

2016-01-01

Graphical abstract: - Highlights: • Cured fluoropolymer@silica hybrid was coated on stainless steel mesh. • The hybrid film showed superhydrophobicity and superoleophilicity by adjusting silica dosage. • The hybrid film exhibited good thermal stability and excellent oil/water separation efficiency. - Abstract: Recently, considerable efforts have been made on superhydrophobic–superoleophilic filter to satisfy the requirements of the applications to oil/water separation. In this work, we obtained a superhydrophobic and superoleophilic film by coating cured fluoropolymer@silica hybrid on stainless steel mesh. Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric-differential scanning calorimetry (TG-DSC) were used to determine the chemical composition and thermal stability of the sample. The effect of silica nanoparticles (NPs) concentration on the surface property of the hybrid film was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle analyzer. The results indicate that silica NPs not only enhance the thermal stability, but also strengthen the hydrophobicity and oleophilicity of the film. When 20 wt% silica NPs was added into the thermosetting fluoropolymer, the hybrid film shows both superhydrophobicity and superoleophilicity owing to the large surface roughness factor (RMS) and porous structure. Moreover, the hybrid film could be used to separate water from different oils effectively. When the pore size of the mesh is less than 300 μm, the oil/water separation efficiency of the film reaches above 99%, which shows a great potential application to dehydrate fuel oils.

Design of a superhydrophobic and superoleophilic film using cured fluoropolymer@silica hybrid

Energy Technology Data Exchange (ETDEWEB)

Yang, Hao [Key Laboratory for Green Chemical Process of Ministry of Education and School of Chemistry and Environmental Engineering, Wuhan Institute of Technology, Xiongchu Street, Wuhan, 430073 (China); Pi, Pihui; Yang, Zhuo-ru [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510640 (China); Lu, Zhong [Key Laboratory for Green Chemical Process of Ministry of Education and School of Chemistry and Environmental Engineering, Wuhan Institute of Technology, Xiongchu Street, Wuhan, 430073 (China); Chen, Rong, E-mail: rchenhku@hotmail.com [Key Laboratory for Green Chemical Process of Ministry of Education and School of Chemistry and Environmental Engineering, Wuhan Institute of Technology, Xiongchu Street, Wuhan, 430073 (China)

2016-12-01

Graphical abstract: - Highlights: • Cured fluoropolymer@silica hybrid was coated on stainless steel mesh. • The hybrid film showed superhydrophobicity and superoleophilicity by adjusting silica dosage. • The hybrid film exhibited good thermal stability and excellent oil/water separation efficiency. - Abstract: Recently, considerable efforts have been made on superhydrophobic–superoleophilic filter to satisfy the requirements of the applications to oil/water separation. In this work, we obtained a superhydrophobic and superoleophilic film by coating cured fluoropolymer@silica hybrid on stainless steel mesh. Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric-differential scanning calorimetry (TG-DSC) were used to determine the chemical composition and thermal stability of the sample. The effect of silica nanoparticles (NPs) concentration on the surface property of the hybrid film was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle analyzer. The results indicate that silica NPs not only enhance the thermal stability, but also strengthen the hydrophobicity and oleophilicity of the film. When 20 wt% silica NPs was added into the thermosetting fluoropolymer, the hybrid film shows both superhydrophobicity and superoleophilicity owing to the large surface roughness factor (RMS) and porous structure. Moreover, the hybrid film could be used to separate water from different oils effectively. When the pore size of the mesh is less than 300 μm, the oil/water separation efficiency of the film reaches above 99%, which shows a great potential application to dehydrate fuel oils.

Comparison of the surface ion density of silica gel evaluated via spectral induced polarization versus acid-base titration

Science.gov (United States)

Hao, Na; Moysey, Stephen M. J.; Powell, Brian A.; Ntarlagiannis, Dimitrios

2016-12-01

Surface complexation models are widely used with batch adsorption experiments to characterize and predict surface geochemical processes in porous media. In contrast, the spectral induced polarization (SIP) method has recently been used to non-invasively monitor in situ subsurface chemical reactions in porous media, such as ion adsorption processes on mineral surfaces. Here we compare these tools for investigating surface site density changes during pH-dependent sodium adsorption on a silica gel. Continuous SIP measurements were conducted using a lab scale column packed with silica gel. A constant inflow of 0.05 M NaCl solution was introduced to the column while the influent pH was changed from 7.0 to 10.0 over the course of the experiment. The SIP measurements indicate that the pH change caused a 38.49 ± 0.30 μS cm- 1 increase in the imaginary conductivity of the silica gel. This increase is thought to result from deprotonation of silanol groups on the silica gel surface caused by the rise in pH, followed by sorption of Na+ cations. Fitting the SIP data using the mechanistic model of Leroy et al. (Leroyet al., 2008), which is based on the triple layer model of a mineral surface, we estimated an increase in the silica gel surface site density of 26.9 × 1016 sites m- 2. We independently used a potentiometric acid-base titration data for the silica gel to calibrate the triple layer model using the software FITEQL and observed a total increase in the surface site density for sodium sorption of 11.2 × 1016 sites m- 2, which is approximately 2.4 times smaller than the value estimated using the SIP model. By simulating the SIP response based on the calibrated surface complexation model, we found a moderate association between the measured and estimated imaginary conductivity (R2 = 0.65). These results suggest that the surface complexation model used here does not capture all mechanisms contributing to polarization of the silica gel captured by the SIP data.

Silica nanoparticles as vehicles for therapy delivery in neurological injury

Science.gov (United States)

Schenk, Desiree

Acrolein, a very reactive aldehyde, is a culprit in the biochemical cascade after primary, mechanical spinal cord injury (SCI), which leads to the destruction of tissue initially unharmed, referred to as "secondary injury". Additionally, in models of multiple sclerosis (MS) and some clinical research, acrolein levels are significantly increased. This aldehyde overwhelms the natural anti-oxidant system, reacts freely with proteins, and releases during lipid peroxidation (LPO), effectively regenerating its self. Due to its ability to make more copies of itself in the presence of tissue via lipid peroxidation, researchers believe that acrolein plays a role in the increased destruction of the central nervous system in both SCI and MS. Hydralazine, an FDA-approved hypertension drug, has been shown to scavenge acrolein, but its side effects and short half life at the appropriate dose for acrolein scavenging must be improved for beneficial clinical translation. Due to the inefficient delivery of therapeutic drugs, nanoparticles have become a major field of exploration for medical applications. Based on their material properties, they can help treat disease by delivering drugs to specific tissues, enhancing detection methods, or a mixture of both. Nanoparticles made from silica provide distinct advantages. They form porous networks that can carry therapeutic molecules throughout the body. Therefore, a nanomedical approach has been designed using silica nanoparticles as a porous delivery vehicle hydralazine. The silica nanoparticles are formed in a one-step method that incorporates poly(ethylene) glycol (PEG), a stealth molecule, directly onto the nanoparticles. As an additional avenue for study, a natural product in green tea, epigallocatechin gallate (EGCG), has been explored for its ability to react with acrolein, disabling its reactive capabilities. Upon demonstration of attenuating acrolein, EGCG's delivery may also be improved using the nanomedical approach. The

Silica nanoparticles containing 159-Gadolinium as potential system for cancer treatment

International Nuclear Information System (INIS)

Oliveira, Andre Felipe de; Ferreira, Tiago Hilario; Sousa, Edesia Martins Barros de; Lacerda, Marco Aurelio

2013-01-01

Ordered silica nanoparticles are compounds highly organized which have very interesting textural characteristics, such as high thermal stability, well defined pore size, narrow size distribution and high area surface. Among the various types of nano materials ordered, the SBA-16 have a meso structure that can be considered very interesting due to the fact of the arrangement of mesoporous (tri dimensional as a cage) and spherical morphology, which make it in a promising material for a range of bioapplications such as incorporation of drugs and radioisotopes. In this study Gadodiamide® (Omniscan-General Electric Healthcare Company), a frequently non-ionic gadolinium complex contrasting used in MRI's was incorporated in the silica matrix SBA-16 as a carrier. From this gadolinium it is possible to obtain the isotope 159 Gd by neutron irradiation, wherein the isotope 158 Gd captures a neutron and becomes 159 Gd [ 15 '8Gd(n,c) 1 '5 9 Gd]. The 159 Gd is a beta (endpoint energy of 970.6 keV) and gamma (main energy: 363.54 keV) emitter with a half-life of 18.59 hours. These characteristics are similar to that of other isotopes already used in nuclear medicine such as 90 Y. In this work, the 158 Gd incorporated in the Gd-silica was activated by the neutron flux generated by the cyclotron located in the Centro de Desenvolvimento da Tecnologia Nuclear (CDTN) during the production of the 18 FDG. Atomic emission spectroscopy (ICP-AES) and infrared spectroscopy (FTIR) were used to confirm the presence of the gadolinium complex in the silica matrix. The antitumor activity of the complex after the irradiation was evaluated through cytotoxicity assay with T98 cell lines derived from a human glioblastoma multiform tumor. (author)

STUDY OF SUBCELLULAR DISTRIBUTION OF CRYSTALLINE MESO-TETRA(3-PYRIDYLBACTERIOCHLORIN NANOPARTICLES

Directory of Open Access Journals (Sweden)

Yu. S. Maklygina

2016-01-01

Full Text Available The results of the study of subcellular distribution of molecular meso-tetra(3-pyridylbacteriochlorin nanocrystals proposed as therapeutic agents for photodynamic therapy are represented in the article. Investigations and measurement of spectroscopic properties of molecular crystals of near-infrared photosensitizer were conducted using special device complex based on fiber-optic spectrometer. Investigation and analysis of the pattern of subcellular accumulation of meso-tetra(3-pyridylbacteriochlorin in molecular (dimethyl sulfoxide (DMSO as solvent and nanocrystalline forms on different cell lines: human monocytes (THP-1, human cervical cancer cells (HeLa and mouse malignant brain tumor cells (glioma C6. The dynamics of subcellylar accumulation of the agent at concentration of 5 and 10 mg/l was assessed with laser microscope-spectrum analyzer and by confocal microscopy. The study showed that in the course of interaction with cell lines molecular nanocrystals of the agent developed ability to fluorescence. Hence, in the cellular environment meso-tetra(3-pyridyl bacteriochlorin nanoparticles became phototoxic giving opportunities for their use for fluorescence diagnosis and photodynamic therapy. Specific role of meso-tetra(3-pyridylbacteriochlorin in the range of photosensitizers is determined by its spectral characteristics, i.e. absorption and fluorescence in near-infrared band, which allows measuring and affecting on deeper layers of biotissue. Thus, the use of meso-tetra(3-pyridylbacteriochlorin nanoparticles as nanophotosensitizers may improve the efficacy of diagnosis and treatment of deep-seated tumors.

Hyperpolarized Porous Silicon Nanoparticles: Potential Theragnostic Material for ²⁹Si Magnetic Resonance Imaging.

Science.gov (United States)

Seo, Hyeonglim; Choi, Ikjang; Whiting, Nicholas; Hu, Jingzhe; Luu, Quy Son; Pudakalakatti, Shivanand; McCowan, Caitlin; Kim, Yaewon; Zacharias, Niki; Lee, Seunghyun; Bhattacharya, Pratip; Lee, Youngbok

2018-05-20

Porous silicon nanoparticles have recently garnered attention as potentially-promising biomedical platforms for drug delivery and medical diagnostics. Here, we demonstrate porous silicon nanoparticles as contrast agents for ²⁹Si magnetic resonance imaging. Size-controlled porous silicon nanoparticles were synthesized by magnesiothermic reduction of silica nanoparticles and were surface activated for further functionalization. Particles were hyperpolarized via dynamic nuclear polarization to enhance their ²⁹Si MR signals; the particles demonstrated long ²⁹Si spin-lattice relaxation (T₁) times (~ 25 mins), which suggests potential applicability for medical imaging. Furthermore, ²⁹Si hyperpolarization levels were sufficient to allow ²⁹Si MRI in phantoms. These results underscore the potential of porous silicon nanoparticles that, when combined with hyperpolarized magnetic resonance imaging, can be a powerful theragnostic deep tissue imaging platform to interrogate various biomolecular processes in vivo. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanical properties of dental resin composites by co-filling diatomite and nanosized silica particles

International Nuclear Information System (INIS)

Wang Hua; Zhu Meifang; Li Yaogang; Zhang Qinghong; Wang Hongzhi

2011-01-01

The aim of this study was to investigate the mechanical property effects of co-filling dental resin composites with porous diatomite and nanosized silica particles (OX-50). The purification of raw diatomite by acid-leaching was conducted in a hot 5 M HCl solution at 80 deg. C for 12 h. Both diatomite and nanosized SiO 2 were silanized with 3-methacryloxypropyltrimethoxysilane. The silanized inorganic particles were mixed into a dimethacrylate resin. Purified diatomite was characterized by X-ray diffraction, UV-vis diffuse reflectance spectroscopy and an N 2 adsorption-desorption isotherm. Silanized inorganic particles were characterized using Fourier transform infrared spectroscopy and a thermogravimetric analysis. The mechanical properties of the composites were tested by three-point bending, compression and Vicker's microhardness. Scanning electron microscopy was used to show the cross-section morphologies of the composites. Silanization of diatomite and nanosized silica positively reinforced interactions between the resin matrix and the inorganic particles. The mechanical properties of the resin composites gradually increased with the addition of modified diatomite (m-diatomite). The fracture surfaces of the composites exhibited large fracture steps with the addition of m-diatomite. However, when the mass fraction of m-diatomite was greater than 21 wt.% with respect to modified nanosized silica (mOX-50) and constituted 70% of the resin composite by weight, the mechanical properties of the resin composites started to decline. Thus, the porous structure of diatomite appears to be a crucial factor to improve mechanical properties of resin composites.

A novel and facile synthesis approach for a porous carbon/graphene composite for high-performance supercapacitors.

Science.gov (United States)

Liu, Ting; Zhang, Xuesha; Liu, Kang; Liu, Yanyan; Liu, Mengjie; Wu, Wenyu; Gu, Yu; Zhang, Ruijun

2018-03-02

We propose a novel and facile synthesis approach to a porous carbon/graphene composite. Graphene is obtained from room-temperature expanded graphite (RTEG), not involving the use of graphite oxide (GO). Porous carbon is acquired by carbonization and KOH-activation of polyvinylpyrrolidone (PVP), which is used to exfoliate RTEG into graphene and inhibit the restacking of the resultant graphene in the present work. The prepared porous carbon/graphene composite has a high specific surface area (SSA) (3008 m 2 g -1 ) and a hierarchical micro- and meso- pore structure (dominant pores in the range of 1-5 nm). Electrochemical measurement demonstrates that the as-prepared porous carbon/graphene composite can deliver an outstanding specific capacitance of up to 340 F g -1 at 5 mV s -1 in 6 M KOH electrolyte. This specific capacitance is among the highest reported so far for porous carbon/graphene materials. Moreover, the prepared composite as an electrode material also exhibits excellent cycling stability (94.4% capacitance retention over 10 000 cycles). The as-fabricated symmetrical supercapacitor exhibits a high energy density of 10.9 W h kg -1 (based on total mass of electrode materials) and an outstanding energy density retention, even at high power density. Compared with conventional preparation routes for porous carbon/graphene composites, the present approach is significantly simple, convenient and cost-effective, which will make it more competent in the development of electrode materials for high-performance supercapacitors.

Synthesis and structural evaluation of freeze-cast porous alumina

Energy Technology Data Exchange (ETDEWEB)

Souza, Douglas F., E-mail: souzadf@outlook.com [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Nunes, Eduardo H.M., E-mail: eduardohmn@gmail.com [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Pimenta, Daiana S.; Vasconcelos, Daniela C.L. [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Nascimento, Jailton F.; Grava, Wilson [Petrobras/CENPES, Avenida Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ CEP:21941-915 (Brazil); Houmard, Manuel [Department of Materials Engineering and Civil Construction, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 1, sala 3304 (Brazil); Vasconcelos, Wander L., E-mail: wlv@demet.ufmg.br [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil)

2014-10-15

In this work we fabricated alumina samples by the freeze-casting technique using tert-butanol as the solvent. The prepared materials were examined by scanning electron microscopy and X-ray microtomography. Next, they were coated with sol–gel silica films by dip-coating. Permeability tests were carried out in order to assess the permeation behavior of the materials processed in this study. We observed that the sintering time and alumina loading showed a remarkable effect on both the structural properties and flexural strength of the freeze-cast samples. Nitrogen adsorption tests revealed that the silica prepared in this study exhibited a microporous structure. It was observed that the presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance by about one order of magnitude. Because of the similar kinetic diameters of nitrogen and carbon dioxide, the CO{sub 2}/N{sub 2} system showed a separation efficiency that was lower than that observed for the He/CO{sub 2} and He/N{sub 2} systems. We noticed that increasing the feed pressure improved the separation capacity of the obtained materials. - Highlights: • Porous alumina samples obtained by the freeze-casting technique • Microporous silica coating prepared by a simple sol–gel dip-coating methodology • Samples examined by SEM, μ-CT, and nitrogen sorption tests • Mechanical tests were carried out in the freeze-cast samples. • The presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance.

Mesoporous Carbon Produced from Tri-constituent Mesoporous Carbon-silica Composite for Water Purification

KAUST Repository

Yu, Yanjie

2012-01-01

Highly ordered mesoporous carbon-silica nanocomposites with interpenetrating carbon and silica networks were synthesized by the evaporation-induced tri-constituent co- assembly approach. The removal of silica by concentrated NaOH solution produced mesoporous carbons, which contained not only the primary large pores, but also the secondary mesopores in the carbon walls. The thus synthesized mesoporous carbon was further activated by using ZnCl2. The activated mesoporous carbon showed an improved surface area and pore volume. The synthesized mesoporous carbon was tested for diuron removal from water and the results showed that the carbon gave a fast diuron adsorption kinetics and a high diuron removal capacity, which was attributable to the primary mesopore channels being the highway for mass transfer, which led to short diffusion path length and easy accessibility of the interpenetrated secondary mesopores. The optimal adsorption capacity of the porous carbon was determined to be 390 mg/g, the highest values ever reported for diuron adsorption on carbon-based materials.

Mesoporous Carbon Produced from Tri-constituent Mesoporous Carbon-silica Composite for Water Purification

KAUST Repository

Yu, Yanjie

2012-05-01

Highly ordered mesoporous carbon-silica nanocomposites with interpenetrating carbon and silica networks were synthesized by the evaporation-induced tri-constituent co- assembly approach. The removal of silica by concentrated NaOH solution produced mesoporous carbons, which contained not only the primary large pores, but also the secondary mesopores in the carbon walls. The thus synthesized mesoporous carbon was further activated by using ZnCl2. The activated mesoporous carbon showed an improved surface area and pore volume. The synthesized mesoporous carbon was tested for diuron removal from water and the results showed that the carbon gave a fast diuron adsorption kinetics and a high diuron removal capacity, which was attributable to the primary mesopore channels being the highway for mass transfer, which led to short diffusion path length and easy accessibility of the interpenetrated secondary mesopores. The optimal adsorption capacity of the porous carbon was determined to be 390 mg/g, the highest values ever reported for diuron adsorption on carbon-based materials.

Preparation and characterization of nanostructured ZrO2 coatings on dense and porous substrates

International Nuclear Information System (INIS)

Shi Jingyu; Verweij, Henk

2008-01-01

Nanostructured ZrO 2 coatings are prepared on both dense and porous substrates by wet-chemical deposition of non-agglomerated 5 nm precursor particle dispersions, followed by thermal processing. The precursor particle dispersions are made by modified emulsion precipitation and a purification treatment to remove reaction products and additives. The coatings are formed by depositing the precursor nanoparticle dispersion directly onto the substrate, followed by drying and heating at 600 deg. C. Scanning electron microscopy and cross-sectional transmission electron microscopy observations of the heat-treated coatings indicate that the ZrO 2 coating on dense Si wafer substrate has a homogeneous, dense particle packing structure with shallow meniscus-shaped depressions in the surface, and microcracks below the meniscus surface. On the other hand, coatings formed on a meso-porous γ-alumina membrane substrate are free of defects, but with a lower packing density. The mechanism of the substrate effect on the particle packing behavior and defect formation during coating deposition is discussed. It is expected that by using a thin porous substrate with reduced capillary force, a defect-free, homogenously dense-packed coating structure can be achieved

Positron annihilation in vitreous silica glasses

International Nuclear Information System (INIS)

Uedono, Akira; Tanigawa, Shoichiro

1993-01-01

The annihilation characteristics of positrons in vitreous silica glasses (v-SiO 2 ) were studied by measurements of two-dimensional angular correlation of positron annihilation radiations and positron lifetime spectra. From the measurements, it was found that positrons and positronium (Ps) atoms mainly annihilate from trapped states by vacancy-type defects in v-SiO 2 . For v-SiO 2 specimens with cylindrical porous structures, annihilations of Ps with anisotropic momentum distributions were observed. This fact was attributed to the momentum uncertainty due to localization of Ps in a finite dimension of pores. This investigation showed possibilities for the detection of microstructures in v-SiO 2 by the positron annihilation technique. (author)

Structure and dynamics of spin-labeled insulin entrapped in a silica matrix by the sol-gel method.

Science.gov (United States)

Vanea, E; Gruian, C; Rickert, C; Steinhoff, H-J; Simon, V

2013-08-12

The structure and conformational dynamics of insulin entrapped into a silica matrix was monitored during the sol to maturated-gel transition by electron paramagnetic resonance (EPR) spectroscopy. Insulin was successfully spin-labeled with iodoacetamide and the bifunctional nitroxide reagent HO-1944. Room temperature continuous wave (cw) EPR spectra of insulin were recorded to assess the mobility of the attached spin labels. Insulin conformation and its distribution within the silica matrix were studied using double electron-electron resonance (DEER) and low-temperature cw-EPR. A porous oxide matrix seems to form around insulin molecules with pore diameters in the order of a few nanometers. Secondary structure of the encapsulated insulin investigated by Fourier transform infrared spectroscopy proved a high structural integrity of insulin even in the dried silica matrix. The results show that silica encapsulation can be used as a powerful tool to effectively isolate and functionally preserve biomolecules during preparation, storage, and release.

Porous glass matrix method for encapsulating high-level nuclear wastes

International Nuclear Information System (INIS)

Macedo, P.B.; Tran, D.C.; Simmons, J.H.; Saleh, M.; Barkatt, A.; Simmons, C.J.; Lagakos, N.; DeWitt, E.

1979-01-01

A novel process which uses solidified porous high-silica glass powder to fixate radioactive high-level wastes is described. The process yields cylinders consisting of a core of high-silica glass containing the waste elements in its structure and a protective layer also of high-silica glass completely free of waste elements. The process can be applied to waste streams containing 0 to 100% solids. The core region exhibits a higher coefficient of thermal expansion and a lower glass transition temperature than the outer protective layer. This leads to mechanical strengthening of the glass and good resistance to stress corrosion by the development of a high residual compressive stress on the surface of the sample. Both the core and the protective layer exhibit extremely high chemical durability and offer an effective fixation of the radioactive waste elements, including 239 Pu and 99 Tc which have long half-lives, for calculated periods of more than 1 million years, when temperatures are not allowed to rise above 100 0 C

In-situ ellipsometric characterization of the growth of porous anisotropic nanocrystalline ZnO layers

Energy Technology Data Exchange (ETDEWEB)

Laha, P., E-mail: plaha@vub.ac.be; Terryn, H.; Ustarroz, J., E-mail: justarro@vub.ac.be [Research Group Electrochemical and Surface Engineering (SURF), Vrije Universiteit Brussel, Pleinlaan 2, 1050 Elsene, Brussels (Belgium); Nazarkin, M. Y., E-mail: mikleo@mail.ru; Gavrilov, S. A. [Department of Materials of Functional Electronics (MFE), National Research University of Electronic Technology, Bld. 5, Pas. 4806, Zelenograd, Moscow 124498 (Russian Federation); Volkova, A. V.; Simunin, M. M. [Department of Quantum Physics and Nanoelectronics (QPN), National Research University of Electronic Technology, Bld. 5, Pas. 4806, Zelenograd, Moscow 124498 (Russian Federation)

2015-03-09

ZnO films have increasingly been in the spotlight due to their largely varied electro-physical and optical properties. For several applications, porous anisotropic nanocrystalline layers are especially interesting. To study the growth kinetics of such films during different fabrication processes, a powerful non-destructive in-situ technique is required. In this work, both ex-situ and in-situ spectroscopic ellipsometry are used along with advanced modelling techniques that are able to take both the anisotropy and the porosity of the films into account. Scanning electron microscopy, along with nitrogen absorption methods for measuring porosity, validated the ellipsometric data and proposed model. The film, grown by chemical bath deposition, was monitored from around 700 to 1800 nm in thickness. This same principle can now be used to monitor any other porous and/or anisotropic structure in an effective in-situ manner, e.g., growth of porous anodic aluminium oxides, nano-porous silica films, etc.

Synthesis and Textural Characterization of Mesoporous and Meso-/Macroporous Silica Monoliths Obtained by Spinodal Decomposition

Directory of Open Access Journals (Sweden)

Anne Galarneau

2016-04-01

Full Text Available Silica monoliths featuring either mesopores or flow-through macropores and mesopores in their skeleton are prepared by combining spinodal phase separation and sol-gel condensation. The macroporous network is first generated by phase separation in acidic medium in the presence of polyethyleneoxides while mesoporosity is engineered in a second step in alkaline medium, possibly in the presence of alkylammonium cations as surfactants. The mesoporous monoliths, also referred as aerogels, are obtained in the presence of alkylpolyethylene oxides in acidic medium without the use of supercritical drying. The impact of the experimental conditions on pore architecture of the monoliths regarding the shape, the ordering, the size and the connectivity of the mesopores is comprehensively discussed based on a critical appraisal of the different models used for textural analysis.

Luminescence of Tb.sup.3+./sup.-doped high silica glass under UV and X-ray excitation

Czech Academy of Sciences Publication Activity Database

Chewpraditkul, W.; Shen, Y.; Chen, D.; Beitlerová, Alena; Nikl, Martin

2013-01-01

Roč. 35, č. 3 (2013), s. 426-430 ISSN 0925-3467 R&D Projects: GA MŠk LH12185 Institutional support: RVO:68378271 Keywords : Tb 3+ * luminescence * luminescence decays * porous silica glass * scintillation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.075, year: 2013 http://dx.doi.org/10.1016/j.optmat.2012.09.012

Synthesis, characterization, and evaluation of a superficially porous particle with unique, elongated pore channels normal to the surface.

Science.gov (United States)

Wei, Ta-Chen; Mack, Anne; Chen, Wu; Liu, Jia; Dittmann, Monika; Wang, Xiaoli; Barber, William E

2016-04-01

In recent years, superficially porous particles (SPPs) have drawn great interest because of their special particle characteristics and improvement in separation efficiency. Superficially porous particles are currently manufactured by adding silica nanoparticles onto solid cores using either a multistep multilayer process or one-step coacervation process. The pore size is mainly controlled by the size of the silica nanoparticles and the tortuous pore channel geometry is determined by how those nanoparticles randomly aggregate. Such tortuous pore structure is also similar to that of all totally porous particles used in HPLC today. In this article, we report on the development of a next generation superficially porous particle with a unique pore structure that includes a thinner shell thickness and ordered pore channels oriented normal to the particle surface. The method of making the new superficially porous particles is a process called pseudomorphic transformation (PMT), which is a form of micelle templating. Porosity is no longer controlled by randomly aggregated nanoparticles but rather by micelles that have an ordered liquid crystal structure. The new particle possesses many advantages such as a narrower particle size distribution, thinner porous layer with high surface area and, most importantly, highly ordered, non-tortuous pore channels oriented normal to the particle surface. This PMT process has been applied to make 1.8-5.1μm SPPs with pore size controlled around 75Å and surface area around 100m(2)/g. All particles with different sizes show the same unique pore structure with tunable pore size and shell thickness. The impact of the novel pore structure on the performance of these particles is characterized by measuring van Deemter curves and constructing kinetic plots. Reduced plate heights as low as 1.0 have been achieved on conventional LC instruments. This indicates higher efficiency of such particles compared to conventional totally porous and

Silica Sol-Gel Entrapment of the Enzyme Chloro peroxidase

International Nuclear Information System (INIS)

Le, T.; Chan, S.; Ebaid, B.; Sommerhalter, M.

2015-01-01

The enzyme chloro peroxidase (CPO) was immobilized in silica sol-gel beads prepared from tetramethoxysilane. The average pore diameter of the silica host structure (∼3 nm) was smaller than the globular CPO diameter (∼6 nm) and the enzyme remained entrapped after sol-gel maturation. The catalytic performance of the entrapped enzyme was assessed via the pyrogallol peroxidation reaction. Sol-gel beads loaded with 4 μg CPO per mL sol solution reached 9-12% relative activity compared to free CPO in solution. Enzyme kinetic analysis revealed a decrease in K_cat but no changes in K_M or K_I . Product release or enzyme damage might thus limit catalytic performance. Yet circular dichroism and visible absorption spectra of transparent CPO sol-gel sheets did not indicate enzyme damage. Activity decline due to methanol exposure was shown to be reversible in solution. To improve catalytic performance the sol-gel protocol was modified. The incorporation of 5, 20, or 40% methyltrimethoxysilane resulted in more brittle sol-gel beads but the catalytic performance increased to 14% relative to free CPO in solution. The use of more acidic casting buffers (ph 4.5 or 5.5 instead of 6.5) resulted in a more porous silica host reaching up to 18% relative activity

Fabrication of Mesoporous Silica/Alumina Hybrid Membrane Film Nanocomposites using Template Sol-Gel Synthesis of Amphiphilic Triphenylene

Science.gov (United States)

Lintang, H. O.; Jalani, M. A.; Yuliati, L.; Salleh, M. M.

2017-05-01

Herein we reported that by introducing a one-dimensional (1D) substrate with a porous structure such as anodic aluminum oxide (AAO) membrane, mesoporous silica/alumina hybrid nanocomposites were successfully fabricated by using amphiphilic triphenylene (TPC10TEG) as a template in sol-gel synthesis (TPC10TEG/silicahex). For the optical study of the nanocomposites, TPC10TEG/silicahex showed absorption peak at 264 nm due to the ordered and long-range π-π stacking of the disc-like aromatic triphenylene core. Moreover, the hexagonal arrangement of TPC10TEG/silicahex was proven based on their diffraction peaks of d 100 and d 200 at 2θ = 2.52° and 5.04° and images of transmission electron microscopy (TEM), respectively. For fabrication of mesoporous silica/alumina hybrid membrane, TPC10TEG/silicahex was drop-casted onto AAO membrane for penetration into the porous structure via gravity. X-ray diffraction (XRD) analysis on the resulted hybrid nanocomposites showed that the diffraction peaks of d 100 and d 200 of TPC10TEG/silicahex were still preserved, indicating that the hexagonal arrangements of mesoporous silica were maintained even on AAO substrate. The morphology study on the hybrid nanocomposites using TEM, scanning electron microscope (SEM) and field emission scanning electron microscope (FE-SEM) showed the successful filling of most AAO channels with the TPC10TEG/silicahex nanocomposites.

Synthesis and characterization of novel mesocomposites Co3O4 and CuO@OMS (ordered mesoporous silica) as active catalysts for hydrocarbon oxidation

Science.gov (United States)

Comănescu, Cezar

2014-03-01

Novel metal nanoporous transition metal oxides M x O y (Co3O4, CuO) have been synthesized by thermal decomposition of inorganic salts precursors (acetates, nitrates) impregnated into hexagonal mesoporous silica (OMS, ordered mesoporous silica) of SBA-15 type (prepared in-house) at different precursor loadings, the mesocomposites thus obtained being monitored after each impregnation-calcination step by small and wide angle powder XRD. The pore size for the ordered silica host range from 5.08 to 7.06 nm. Retention of the hexagonal silica framework has been observed in spite of the temperatures up to 500 °C. Mesoporous Co3O4 has been obtained by leaching the silica through overnight HF dissolution, which partially preserved the small-range ordering found in the parent Co3O4@OMS composite prior to leaching. Both Co3O4 ( meso) and Co3O4@SBA-15 have been tested in methane oxidation and were found to be superior to the bulk Co3O4 performance, with mesoporous Co3O4 being able to fully oxidize methane to CO2 and H2O at 350 °C, while Co3O4@OMS exhibits a lower activity with 20 % conversion at 350 °C. CuO@OMS shows the lowest activity, with only 13 % conversion at 500 °C.

Isolation of two tissue-specific Drosophila paired box genes, Pox meso and Pox neuro.

OpenAIRE

Bopp, D; Jamet, E; Baumgartner, S; Burri, M; Noll, M

1989-01-01

Two new paired domain genes of Drosophila, Pox meso and Pox neuro, are described. In contrast to the previously isolated paired domain genes, paired and gooseberry, which contain both a paired and a homeo-domain (PHox genes), Pox meso and Pox neuro possess no homeodomain. Evidence suggesting that the new genes encode tissue-specific transcriptional factors and belong to the same regulatory cascade as the other paired domain genes includes (i) tissue-specific expression of Pox meso in the soma...

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

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.

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.

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.

Las comunidades locales como estructuras meso.

Directory of Open Access Journals (Sweden)

Ferrand, Alexis

2002-09-01

Full Text Available Entre el nivel micro y el nivel macro: meso. Si el nivel macro está definido por la regulación nacional, estatal o del mercado y el nivel micro por la regulación interpersonal, una agencia de regulación intermediaria de mayor importancia ha sido definida como “comunidad local” (Wellman, Fischer. Aparte de las dimensiones organizacionales (organizaciones locales, clubes, tiendas... e institucionales (poder local, partidos... locales, es posible definir algunas propiedades estructurales pertinentes de los sistemas de relaciones interpersonales privadas: uno es el grado de “cerrado” (closure local (Barnes: redes locales vs. transversales, o la “dualidad” de estos sistemas. Apoyándose en la idea de que la eficiencia de los “puentes” reside en el tipo de cliques que conectan (Lin, es posible definir tipos variados de micro-estructuras, cuyas distribuciones en diferentes localidades son indicadores sucedáneos o aproximaciones de las diferentes meso estructuras de sistemas relacionales como combinaciones de redes “locales” y “no locales”.

The measurement of pore size in porous and microporous materials using resonant ion beam backscattering

International Nuclear Information System (INIS)

Armitage, B.H.; Ramsay, J.D.F.; Brady, F.P.

1978-01-01

Established methods for measuring the size of pores in porous materials include those of mercury porosimetry and gas adsorption. A disadvantage of these methods is that only one determination can be made for each prepared specimen. A property of the ion beam backscattering method is that each specimen can be probed over the surface and also as a function of depth. Furthermore for microporous samples (pore width less than 2 nm) mercury penetration methods cannot be used because the high pressures involved make unreasonable demands in terms of mechanical strength. At the same time gas adsoption techniques are considerably restricted because capillary condensation is no longer possible because of the small size of the pores. A description is given of the methods of calculation of pore size from resonant ion beam backscattering data, with various assumptions for the pore and interpore path length distributions. Examples are shown of results obtained with highly porous silica gels where good agreement with gas adsoption has been achieved. Finally, some results obtained by scanning silica gels of lower porosity are also given. (Auth.)

Meso-Helical Ag(I) Coordination Polymer Based on a Pyridylimidazole Ligand

International Nuclear Information System (INIS)

Kang, Youngjin; Kim, Jinho; Lee, Eunji; Park, Ki-Min; Moon, Suk-Hee

2016-01-01

In the fields of material science and metallosupramolecular chemistry, coordination polymers with various helical types have been extensively explored because of their charming structures, and their potential applications in material chemistry. Among them, meso-helical coordination polymers consisting of achiral 1D strands, which are generally constructed by a crystallographic inversion symmetry, are relatively rare. The coordination polymer 1 exhibits a rare one-dimensional meso-helical chain topology constructed by its internal inversion symmetry. The skeleton of this meso-helical chain is preserved up to 300°C. The complexation of silver(I) ion to the free pyim ligand give rise to the enhanced photoluminescence intensity and slightly blue-shifted emission maximum, originated from intraligand (IL) π[BOND]π* transition and rigidochromic effect. Further exploration of complexation of this ligand with other transition metal ions is currently in progress

Meso-ester and carboxylic acid substituted BODIPYs with far-red and near-infrared emission for bioimaging applications

KAUST Repository

Ni, Yong

2014-01-21

A series of meso-ester-substituted BODIPY derivatives 1-6 are synthesized and characterized. In particular, dyes functionalized with oligo(ethylene glycol) ether styryl or naphthalene vinylene groups at the α positions of the BODIPY core (3-6) become partially soluble in water, and their absorptions and emissions are located in the far-red or near-infrared region. Three synthetic approaches are attempted to access the meso-carboxylic acid (COOH)-substituted BODIPYs 7 and 8 from the meso-ester-substituted BODIPYs. Two feasible synthetic routes are developed successfully, including one short route with only three steps. The meso-COOH-substituted BODIPY 7 is completely soluble in pure water, and its fluorescence maximum reaches around 650 nm with a fluorescence quantum yield of up to 15 %. Time-dependent density functional theory calculations are conducted to understand the structure-optical properties relationship, and it is revealed that the Stokes shift is dependent mainly on the geometric change from the ground state to the first excited singlet state. Furthermore, cell staining tests demonstrate that the meso-ester-substituted BODIPYs (1 and 3-6) and one of the meso-COOH-substituted BODIPYs (8) are very membrane-permeable. These features make these meso-ester- and meso-COOH-substituted BODIPY dyes attractive for bioimaging and biolabeling applications in living cells. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanical properties of dental resin composites by co-filling diatomite and nanosized silica particles

Energy Technology Data Exchange (ETDEWEB)

Wang Hua; Zhu Meifang [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620 (China); Li Yaogang [Engineering Research Center of Advanced Glasses Manufacturing Technology, MOE, Donghua University, Shanghai 201620 (China); Zhang Qinghong, E-mail: zhangqh@dhu.edu.cn [Engineering Research Center of Advanced Glasses Manufacturing Technology, MOE, Donghua University, Shanghai 201620 (China); Wang Hongzhi, E-mail: wanghz@dhu.edu.cn [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620 (China)

2011-04-08

The aim of this study was to investigate the mechanical property effects of co-filling dental resin composites with porous diatomite and nanosized silica particles (OX-50). The purification of raw diatomite by acid-leaching was conducted in a hot 5 M HCl solution at 80 deg. C for 12 h. Both diatomite and nanosized SiO{sub 2} were silanized with 3-methacryloxypropyltrimethoxysilane. The silanized inorganic particles were mixed into a dimethacrylate resin. Purified diatomite was characterized by X-ray diffraction, UV-vis diffuse reflectance spectroscopy and an N{sub 2} adsorption-desorption isotherm. Silanized inorganic particles were characterized using Fourier transform infrared spectroscopy and a thermogravimetric analysis. The mechanical properties of the composites were tested by three-point bending, compression and Vicker's microhardness. Scanning electron microscopy was used to show the cross-section morphologies of the composites. Silanization of diatomite and nanosized silica positively reinforced interactions between the resin matrix and the inorganic particles. The mechanical properties of the resin composites gradually increased with the addition of modified diatomite (m-diatomite). The fracture surfaces of the composites exhibited large fracture steps with the addition of m-diatomite. However, when the mass fraction of m-diatomite was greater than 21 wt.% with respect to modified nanosized silica (mOX-50) and constituted 70% of the resin composite by weight, the mechanical properties of the resin composites started to decline. Thus, the porous structure of diatomite appears to be a crucial factor to improve mechanical properties of resin composites.

Effect of hydrofluoric acid concentration on the evolution of photoluminescence characteristics in porous silicon nanowires prepared by Ag-assisted electroless etching method

KAUST Repository

Najar, Adel; Anjum, Dalaver H.; Hedhili, Mohamed N.; Ng, Tien Khee; Ooi, Boon S.; Ben Slimane, Ahmed; Sougrat, Rachid

2012-01-01

We report on the structural and optical properties of porous silicon nanowires (PSiNWs) fabricated using silver (Ag) ions assisted electroless etching method. Silicon nanocrystallites with sizes <5 nm embedded in amorphous silica have been

Random laser emission from a Rhodamine B-doped GPTS/TEOS-derived organic/silica monolithic xerogel

Science.gov (United States)

Abegão, Luis M. G.; Manoel, D. S.; Otuka, A. J. G.; Ferreira, P. H. D.; Vollet, D. R.; Donatti, D. A.; De Boni, L.; Mendonça, C. R.; De Vicente, F. S.; Rodrigues, J. J., Jr.; Alencar, M. A. R. C.

2017-06-01

A Rhodamine B-doped 3-glycidoxypropyltrimethoxysilane (GPTS)/tetraethyl orthosilicate (TEOS)-derived organic/silica monolithic xerogel with excellent optical properties was prepared and its potential as a random laser host investigated. This hybrid material has a non-porous organic/inorganic morphology with silica-rich nanoparticles of less than 10 nm in diameter homogeneously dispersed within the matrix. Random laser emission with incoherent feedback, centered at 618 nm, was observed from Rhodamine B incorporated into the monolithic xerogel when excited by a 532 nm pulsed laser. This hybrid system is shown to be very promising for the development of a new class of random laser-based integrated devices, with applications ranging from optical bio-imaging to sensing.

Genotoxicity of meso-2,3-dimercapto succinic acid-coated silver sulfide quantum dot

Directory of Open Access Journals (Sweden)

Deniz Özkan Vardar

2015-06-01

Full Text Available Nanotecnology products have been used in wide applications in chemistry, electronics, energy generation, and medicine. Despite significant interest in developing quantum dots (QDs for biomedical applications, many researchers are convinced that QDs will never be used for the treatment of patients because of their potential toxicity. In various in vitro cell culture studies, the cytotoxic properties of some QD have been demonstrated and they have been suggested to be toxic in humans. In this study, the cytotoxic properties of Ag2S-(Meso-2,3-Dimercapto Succinic acid nanomaterials in V79 cells (Chinese lung fibroblast cell line were determined by MTT assay. The genotoxic effects of Ag2S-(Meso-2,3-Dimercapto Succinic acid were evaluated by the alkaline single cell gel electrophoresis. The cells were treated with Ag2S-(Meso-2,3-Dimercapto Succinic acid at the concentrations of 5- 2000 µg/ml. No cytotoxic effect of Ag2S-(Meso-2,3-Dimercapto Succinic acid at all concentrations studied was observed. No significant increases in DNA damage were found at the studied concentrations when compared to negative control in V79 cells. In conclusion, further in vitro and in vivo studies are required to determine the safety doses of Ag2S-(Meso-2,3-Dimercapto Succinic acid.

Mesoporous silica materials modified with alumina polycations as catalysts for the synthesis of dimethyl ether from methanol

Energy Technology Data Exchange (ETDEWEB)

Macina, Daniel; Piwowarska, Zofia; Tarach, Karolina; Góra-Marek, Kinga [Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Kraków (Poland); Ryczkowski, Janusz [Maria Curie Skłodowska University, Faculty of Chemistry, Maria Curie-Skłodowska 2, 20-031 Lublin (Poland); Chmielarz, Lucjan, E-mail: chmielar@chemia.uj.edu.pl [Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Kraków (Poland)

2016-02-15

Highlights: • Deposition of alumina ologoctaions on mesoporous silicas modified with surface −SO{sub 3}H groups. • Alumina aggregates generated acid properties in the silica supports. • Alumina modified SBA-15 and MCF were active and selective catalysts in DME synthesis. - Abstract: Mesoporous silica materials (SBA-15 and MCF) were used as catalytic supports for the deposition of aggregated alumina species using the method consisting of the following steps: (i) anchoring 3-(mercaptopropyl)trimethoxysilane (MPTMS) on the silica surface followed by (ii) oxidation of −SH to−SO{sub 3}H groups and then (iii) deposition of aluminum Keggin oligocations by ion-exchange method and (iv) calcination. The obtained samples were tested as catalysts for synthesis of dimethyl ether from methanol. The modified silicas were characterized with respect to the ordering of their porous structure (XRD), textural properties (BET), chemical composition (EDS, CHNS), structure ({sup 27}Al NMR, FTIR) and location of alumina species (EDX-TEM), surface acidity (NH{sub 3}-TPD, Py-FTIR) and thermal stability (TGA). The obtained materials were found to be active and selective catalysts for methanol dehydration to dimethyl ether (DME) in the MTD process (methanol-to-dimethyl ether).

Meso-optical Fourier transform microscope with double focusing

International Nuclear Information System (INIS)

Batusov, Yu.A.; Soroko, L.M.; Tereshchenko, V.V.

1992-01-01

The meso-optical Fourier transform microscope (MFTM) with double focusing for particle tracks of low ionization level in the nuclear emulsion is described. It is shown experimentally that this device enables one to get high concentration of information about the position of the particle track in the nuclear emulsion and thus to increase the signal-to-noise ratio. It is shown that spreading of the meso-optical image of the particle track in the sagittal section of the MFTM can be eliminated completely in the frame of the diffraction limit. The number of the additional degrees of freedom in this new MFTM system along depth coordinate is equal to 20 in comparison to single degree of freedom in the Fourier transform microscope of the direct observation. 10 refs.; 15 figs

Mesoscopic objects, porous layers and nanocomposites-Possibilities of sol-gel chemistry

International Nuclear Information System (INIS)

Piwonski, Ireneusz

2009-01-01

The goal of this study was to prepare mesoscopic objects, thin porous films and nanocomposite coatings with the use of sol-gel technique. Silica nanotubes, titania nanoparticles, porous titania and zirconia coatings as well as titania nanocomposites were successfully synthesized by changing the type of sol-gel precursor, sol composition and applying dip-coating deposition procedure in order to obtain thin films or coatings. All materials were visualized and characterized by the Atomic Force Microcscopy (AFM) technique. Moreover, characterization of titania nanocomposites was extended to the tribological tests performed by means of microtribometer operating in normal loads range of 30-100 mN. The AFM analysis of mesoscopic objects and nanoparticles showed that the diameter of synthesized silica nanotubes was 60-70 nm and the size of titania nanoparticles was 43 nm. In case of porous layers the pore size in titania and zirconia coatings oscillated between 100 and 240 nm, however their shape and distribution were irregular. Microtribological studies of nanocomposites revealed the moderate decrease of the coefficient of friction for samples containing 5, 15 and 5 wt.% of zirconia nanoparticles in titania coatings annealed at 100, 500 and 1000 deg. C respectively. An enhancement of antiwear properties was already observed for 1 wt.% of nanophase content, except the sample annealed at 500 deg. C. It was also found that the annealing at high temperatures is a primary factor which affects the reduction of friction and wear of titania coatings while the presence of nanoparticles has secondary effect. Investigations in this study carried out with the use of the AFM technique highlighted the potential and flexibility of sol-gel approach in designing of various types of advanced materials in a form of mesoscopic objects, porous coatings and composite layers. Results collected in this study clearly demonstrated that sol-gel technique can be applied effectively in preparation of

Preparation and surface properties of mesoporous silica particles modified with poly(N-vinyl-2-pyrrolidone) as a potential adsorbent for bilirubin removal

Energy Technology Data Exchange (ETDEWEB)

Timin, Alexander, E-mail: a_timin@mail.ru [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000 Ivanovo (Russian Federation); Rumyantsev, Evgeniy, E-mail: evr@isuct.ru [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000 Ivanovo (Russian Federation); Lanin, Sergey N., E-mail: SNLanin@phys.chem.msu.ru [Chemistry Department, Physical Chemistry Division, Lomonosov Moscow State University, 1-3 Leninskie Gory, 119991 Moscow (Russian Federation); Rychkova, Sveta A. [Chemistry Department, Physical Chemistry Division, Lomonosov Moscow State University, 1-3 Leninskie Gory, 119991 Moscow (Russian Federation); Guseynov, Sabir S. [Krestov Institute of Solution Chemistry of Russian Academy of Sciences, 153000 Ivanovo (Russian Federation); Solomonov, Alexey V. [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000 Ivanovo (Russian Federation); Antina, Elena V. [Krestov Institute of Solution Chemistry of Russian Academy of Sciences, 153000 Ivanovo (Russian Federation)

2014-10-15

The surface of silica particles was modified with polyvinyl pyrrolidone (PVP) through sol–gel process. The different experimental techniques, i.e., thermogravimetric analysis (TGA and DTG), nitrogen adsorption, scanning electron microscopy (SEM), laser diffraction analysis (LDA), fourier transform spectroscopy (FTIR) are used to characterize the pure non-functionalized and functionalized silicas containing different amount of PVP. It was shown that PVP-modified silica samples have well developed porous structure; the values of specific surface area for PVP-modified silicas are in the range of 140–264 m{sup 2} g{sup −1}. While the non-functionalized silica shows the low surface area (S{sub BET} = 40 m{sup 2} g{sup −1}). The BJH analysis showed that PVP can be used as an effective agent to increase an average pore size and total pore volume. The results indicate that PVP functionalized silicas show a potential as effective adsorbents for bilirubin removal compared to other available adsorbents. - Highlights: • PVP functionalized silicas were synthesized via sol–gel method. • Modification of silica by PVP leads to the formation of mesoporous structure. • PVP functionalized mesoporous silicas demonstrate good adsorption properties for bilirubin removal.

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.

Comparative efficiency of racemic- and meso-2,3-dimercaptosuccinic acid to mobilize mercury in rats

International Nuclear Information System (INIS)

Prester, Lj.; Restek Samarzija, N.; Blanusa, M.; Piasek, M.; Kostial, K.; Jones, M.M.; Singh, P.K.

1996-01-01

Two stereoisomeric forms of chelating agent 2,3-dimercaptosuccinic acid (DMSA), meso- and racemic (rac-) DMSA, were compared for mercury mobilization in rats (Experiment 1). Acute oral toxicity of both chelators (LD 50 ) was also tested (Experiment 2). Experiments were carried out on 6-7 weeks old albino Wistar female rats. In Experiment 1 three groups of 9-10 animals were given intraperitoneally 0.5 mg HgCl 2 /kg b.w. and 2.5 mCi (92.5 kBq) of radioactive mercury in the form of 203 Hg(NO 3 ) 2 .Five days after mercury, therapy with 1.0 mmol/kg/day of either meso- or rac-DMSA was started and continued for four days. Whole body radioactivity was measured during the four-day therapy, i.e. 24 hours after each chelator application. In Experiment 2, chelators were given by gastric tube. They were dissolved in 8% NaHCOP 3 with addition of NaOH in equivalent quantities to obtain soluble sodium salts. Meso-DMSA was given at doses of 6, 8 or 12 mmol/kg and rac-DMSA at doses of 12 or 18.7 mmol/kg (3 rats at each dose level). Rat mortality was recorded during 8 days. Results of Experiment 1 showed that the efficiency of rac-DMSA in reducing body retention of mercury-203 was significantly higher than of meso-DMSA. At the end of experiment, reduction of mercury -203 whole body retention was 62% of control in meso-DMSA compared to 29% of control in rac D MSA group. In Experiment 2, the approximate oral LD 50 value were estimated to be >18.7 mmol/kg for meso-DMSA and between 8 and 12 mmol/kg for rac-DMSA. In conclusion, rac-DMSA reduces more efficiently mercury body load than its meso-form. However, more studies are needed to evaluate advantage of rac-DMSA application in spite of its higher toxicity compared to meso-DMSA. (author)

Nanotexture Optimization by Oxygen Plasma of Mesoporous Silica Thin Film for Enrichment of Low Molecular Weight Peptides Captured from Human Serum

Science.gov (United States)

Hu, Ye; Peng, Yang; Brousseau, Louis; Bouamrani, Ali; Liu, Xuewu; Ferrari, Mauro

2010-01-01

This study investigated the optimization of mesoporous silica thin films by nanotexturing using oxygen plasma versus thermal oxidation. Calcination in oxygen plasma provides superior control over pore formation with regard to the pore surface and higher fidelity to the structure of the polymer template. The resulting porous film offers an ideal substrate for the selective partitioning of peptides from complex mixtures. The improved chemico-physical characteristics of porous thin films (pore size distribution, nanostructure, surface properties and pore connectivity) were systematically characterized with XRD, Ellipsometry, FTIR, TEM and N2 adsorption/desorption. The enrichment of low molecular weight proteins captured from human serum on mesoporous silica thin films fabricated by both methodologies were investigated by comparison of their MALDI-TOF MS profiles. This novel on-chip fractionation technology offers advantages in recovering the low molecular weight peptides from human serum, which has been recognized as an informative resource for early diagnosis of cancer and other diseases. PMID:21179395

Guanidine-catalyzed enantioselective desymmetrization of meso-aziridines

KAUST Repository

Zhang, Yan

2011-01-01

An amino-indanol derived chiral guanidine was developed as an efficient Brønsted base catalyst for the desymmetrization of meso-aziridines with both thiols and carbamodithioic acids as nucleophiles, which provided 1,2-difunctionalized ring-opened products in high yields and enantioselectivities. © The Royal Society of Chemistry.

In vitro⿿in vivo performance of bare and drug loaded silica gel synthesized via optimized process parameters

Science.gov (United States)

Chakraborty, Suparna; Biswas, Supratim

2016-01-01

Silica xerogel as a potential drug carrier system for the in vivo as well as in vitro delivery of andrographolide was tested. The present study aims to optimize the effective experimental parameters; volume of ethanol, volume of water and drying temperature by applying response surface methodology coupled with Box⿿Behnken experimental design. The in vitro drug release in simulated body fluid at 37 οC from the selected formulation was significantly highest (44.83 ± 0.9%) among rest of the formulations. Results indicate that sol⿿gel method is useful for entrapping andrographolide in the silica gel and for releasing the same via diffusion through the porous matrix under the in vitro/in vivo conditions. Silica gel exhibited slow matrix degradation as well as sustained release of andrographolide within the experimental time frame of 168 h. In vivo study was performed with three increasing doses [2 mg (S1), 8 mg (S2), and 16 mg (S3)] of silica. Histological fates of different organs were executed with those doses.

Size Control of Porous Silicon-Based Nanoparticles via Pore-Wall Thinning.

Science.gov (United States)

Secret, Emilie; Leonard, Camille; Kelly, Stefan J; Uhl, Amanda; Cozzan, Clayton; Andrew, Jennifer S

2016-02-02

Photoluminescent silicon nanocrystals are very attractive for biomedical and electronic applications. Here a new process is presented to synthesize photoluminescent silicon nanocrystals with diameters smaller than 6 nm from a porous silicon template. These nanoparticles are formed using a pore-wall thinning approach, where the as-etched porous silicon layer is partially oxidized to silica, which is dissolved by a hydrofluoric acid solution, decreasing the pore-wall thickness. This decrease in pore-wall thickness leads to a corresponding decrease in the size of the nanocrystals that make up the pore walls, resulting in the formation of smaller nanoparticles during sonication of the porous silicon. Particle diameters were measured using dynamic light scattering, and these values were compared with the nanocrystallite size within the pore wall as determined from X-ray diffraction. Additionally, an increase in the quantum confinement effect is observed for these particles through an increase in the photoluminescence intensity of the nanoparticles compared with the as-etched nanoparticles, without the need for a further activation step by oxidation after synthesis.

Immobilization of plutonium from solutions on porous matrices by the method of high temperature sorption

Energy Technology Data Exchange (ETDEWEB)

Nardova, A.K.; Filippov, E.A. [All Research Institute of Chemical Technologies, Moscow (Russian Federation); Glagolenko, Y.B. [and others

1996-05-01

This report presents the results of investigations of plutonium immobilization from solutions on inorganic matrices with the purpose of producing a solid waste form. High-temperature sorption is described which entails the adsorption of radionuclides from solutions on porous, inorganic matrices, as for example silica gel. The solution is brought to a boil with additional thermal process (calcination) of the saturated granules.

Controlled in meso phase crystallization--a method for the structural investigation of membrane proteins.

Directory of Open Access Journals (Sweden)

Jan Kubicek

Full Text Available We investigated in meso crystallization of membrane proteins to develop a fast screening technology which combines features of the well established classical vapor diffusion experiment with the batch meso phase crystallization, but without premixing of protein and monoolein. It inherits the advantages of both methods, namely (i the stabilization of membrane proteins in the meso phase, (ii the control of hydration level and additive concentration by vapor diffusion. The new technology (iii significantly simplifies in meso crystallization experiments and allows the use of standard liquid handling robots suitable for 96 well formats. CIMP crystallization furthermore allows (iv direct monitoring of phase transformation and crystallization events. Bacteriorhodopsin (BR crystals of high quality and diffraction up to 1.3 Å resolution have been obtained in this approach. CIMP and the developed consumables and protocols have been successfully applied to obtain crystals of sensory rhodopsin II (SRII from Halobacterium salinarum for the first time.

In vivo immuno-reactivity analysis of the porous three-dimensional chitosan/SiO2 and chitosan/SiO2 /hydroxyapatite hybrids.

Science.gov (United States)

Guo, Mengxia; Dong, Yifan; Xiao, Jiangwei; Gu, Ruicai; Ding, Maochao; Huang, Tao; Li, Junhua; Zhao, Naru; Liao, Hua

2018-05-01

Inorganic/organic hybrid silica-chitosan (CS) scaffolds have promising potential for bone defect repair, due to the controllable mechanical properties, degradation behavior, and scaffold morphology. However, the precise in vivo immuno-reactivity of silica-CS hybrids with various compositions is still poorly defined. In this study, we fabricated the three-dimensional (3D) interconnected porous chitosan-silica (CS/SiO 2 ) and chitosan-silica-hydroxyapatite (CS/SiO 2 /HA) hybrids, through sol-gel process and 3D plotting skill, followed by the naturally or freeze drying separately. Scanning electron microscopy demonstrated the hybrids possessed the uniform geometric structure, while, transmission electron microscopy displayed nanoscale silica, or HA nanoparticles dispersed homogeneously in the CS matrix, or CS/silica hybrids. After intramuscular implantation, CS/SiO 2 and CS/SiO 2 /HA hybrids triggered a local and limited monocyte/macrophage infiltration and myofiber degeneration. Naturally dried CS/SiO 2 hybrid provoked a more severe inflammation than the freeze-dried ones. Dendritic cells were attracted to invade into the implants embedded-muscle, but not be activated to prime the adaptive immunity, because the absence of cytotoxic T cells and B cells in muscle received the implants. Fluorescence-activated cell sorting (FACS) analysis indicated the implanted hybrids were incapable to initiate splenocytes activation. Plasma complement C3 enzyme linked immunosorbent assay (ELISA) assay showed the hybrids induced C3 levels increase in early implanting phase, and the subsequent striking decrease. Thus, the present results suggest that, in vivo, 3D plotted porous CS/SiO 2 and CS/SiO 2 /HA hybrids are relatively biocompatible in vivo, which initiate a localized inflammatory procedure, instead of a systematic immune response. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1223-1235, 2018. © 2018 Wiley Periodicals, Inc.

On micro-meso relations homogenizing electrical properties of transversely cracked laminated composites

KAUST Repository

Lubineau, Gilles

2013-11-01

A practical way to track the development of transverse cracking in a laminated composite is to monitor the change of its electrical resistance. Yet, the relations between transverse cracking and the global modification of resistivity is still unclear that makes difficult to interpret these non-destructive-testing results. Here, we introduce the homogenization process that defines at the meso scale an equivalent homogeneous ply that is energetically equivalent to the cracked one. It is shown that this equivalent ply mainly depends on the cracking level while it can be considered independent on the rest of the laminated structure. The direct consequence is that the meso scale is a pertinent one to perform the homogenization. Then, non-destructive electrical measurements can be considered as a reliable technique to access meso scale damage indicators. © 2013 Elsevier Ltd.

Pore-Confined Carriers and Biomolecules in Mesoporous Silica for Biomimetic Separation and Targeting

Science.gov (United States)

Zhou, Shanshan

Selectively permeable biological membranes composed of lipophilic barriers inspire the design of biomimetic carrier-mediated membranes for aqueous solute separation. This work imparts selective permeability to lipid-filled pores of silica thin film composite membranes using carrier molecules that reside in the lipophilic self-assemblies. The lipids confined inside the pores of silica are proven to be a more effective barrier than bilayers formed on the porous surface through vesicle fusion, which is critical for quantifying the function of an immobilized carrier. The ability of a lipophilic carrier embedded in the lipid bilayer to reversibly bind the target solute and transport it through the membrane is demonstrated. Through the functionalization of the silica surface with enzymes, enzymatic catalysis and biomimetic separations can be combined on this nanostructured composite platform. The successful development of biomimetic nanocomposite membrane can provide for efficient dilute aqueous solute upgrading or separations using engineered carrier/catalyst/support systems. While the carrier-mediated biomimetic membranes hold great potential, fully understanding of the transport processes in composite synthetic membranes is essential for improve the membrane performance. Electrochemical impedance spectroscopy (EIS) technique is demonstrated to be a useful tool for characterizing the thin film pore accessibility. Furthermore, the effect of lipid bilayer preparation methods on the silica thin film (in the form of pore enveloping, pore filling) on ion transport is explored, as a lipid bilayer with high electrically insulation is essential for detecting activity of proteins or biomimetic carriers in the bilayer. This study provides insights for making better barriers on mesoporous support for carrier-mediated membrane separation process. Porous silica nanoparticles (pSNPs) with pore sizes appropriate for biomolecule loading are potential for encapsulating dsRNA within the

Plasma-deposited hybrid silica membranes with a controlled retention of organic bridges

Energy Technology Data Exchange (ETDEWEB)

Ngamou, P.H.T.; Creatore, M. [Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Overbeek, J.P.; Kreiter, R.; Van Veen, H.M.; Vente, J.F. [ECN, Energy research Centre of the Netherlands, Petten (Netherlands); Wienk, I.M.; Cuperus, P.F. [SolSep BV, Apeldoorn (Netherlands)

2013-03-05

Hybrid organically bridged silica membranes are suitable for energy-efficient molecular separations under harsh industrial conditions. Such membranes can be useful in organic solvent nanofiltration if they can be deposited on flexible, porous and large area supports. Here, we report the proof of concept for applying an expanding thermal plasma to the synthesis of perm-selective hybrid silica films from an organically bridged monomer, 1,2-bis(triethoxysilyl)ethane. This membrane is the first in its class to be produced by plasma enhanced chemical vapor deposition. By tuning the plasma and process parameters, the organic bridging groups could be retained in the separating layer. This way, a defect free film could be made with pervaporation performances of an n-butanol-water mixture comparable with those of conventional ceramic supported membranes made by sol-gel technology (i.e. a water flux of [similar]1.8 kg m'-{sup 2} h{sup -1}, a water concentration in the permeate higher than 98% and a separation factor of >1100). The obtained results show the suitability of expanding thermal plasma as a technology for the deposition of hybrid silica membranes for molecular separations.

Hierarchical mesoporous/microporous carbon with graphitized frameworks for high-performance lithium-ion batteries

Directory of Open Access Journals (Sweden)

Yingying Lv

2014-11-01

Full Text Available A hierarchical meso-/micro-porous graphitized carbon with uniform mesopores and ordered micropores, graphitized frameworks, and extra-high surface area of ∼2200 m2/g, was successfully synthesized through a simple one-step chemical vapor deposition process. The commercial mesoporous zeolite Y was utilized as a meso-/ micro-porous template, and the small-molecule methane was employed as a carbon precursor. The as-prepared hierarchical meso-/micro-porous carbons have homogeneously distributed mesopores as a host for electrolyte, which facilitate Li+ ions transport to the large-area micropores, resulting a high reversible lithium ion storage of 1000 mA h/g and a high columbic efficiency of 65% at the first cycle.

Bacterial-cellulose-derived interconnected meso-microporous carbon nanofiber networks as binder-free electrodes for high-performance supercapacitors

Science.gov (United States)

Hao, Xiaodong; Wang, Jie; Ding, Bing; Wang, Ya; Chang, Zhi; Dou, Hui; Zhang, Xiaogang

2017-06-01

Bacterial cellulose (BC), a typical biomass prepared from the microbial fermentation process, has been proved that it can be an ideal platform for design of three-dimensional (3D) multifunctional nanomaterials in energy storage and conversion field. Here we developed a simple and general silica-assisted strategy for fabrication of interconnected 3D meso-microporous carbon nanofiber networks by confine nanospace pyrolysis of sustainable BC, which can be used as binder-free electrodes for high-performance supercapacitors. The synthesized carbon nanofibers exhibited the features of interconnected 3D networks architecture, large surface area (624 m2 g-1), mesopores-dominated hierarchical porosity, and high graphitization degree. The as-prepared electrode (CN-BC) displayed a maximum specific capacitance of 302 F g-1 at a current density of 0.5 A g-1, high-rate capability and good cyclicity in 6 M KOH electrolyte. This work, together with cost-effective preparation strategy to make high-value utilization of cheap biomass, should have significant implications in the green and mass-producible energy storage.

Onset of meso-scale turbulence in active nematics

NARCIS (Netherlands)

Doostmohammadi, A.; Shendruk, T.N.; Thijssen, K.; Yeomans, J.M.

2017-01-01

Meso-scale turbulence is an innate phenomenon, distinct from inertial turbulence, that spontaneously occurs at low Reynolds number in fluidized biological systems. This spatiotemporal disordered flow radically changes nutrient and molecular transport in living fluids and can strongly affect the

NaCl as a solid solvent to assist the mechanochemical synthesis and post-synthesis of hierarchical porous MOFs with high I2 vapour uptake.

Science.gov (United States)

Yang, Junyi; Feng, Xiao; Lu, Guangnong; Li, Yulin; Mao, Chaochao; Wen, Zhongliang; Yuan, Wenbing

2018-04-03

The use of salts as grinding media to assist the mechanosynthesis, and the following one-pot mechanochemical post-synthesis, of hierarchically porous MOFs was carried out efficiently by ball milling. NaCl or KCl were used as a solid solvent to initially pre-grind with 1,3,5-benzenetricarboxylic acid (H3BTC) and copper acetate monhydrate, respectively, for 1 minute, then both mixtures were combined together for a further 20 minutes of grinding, and the resultant mixture was finally washed with ethanol and water to obtain the hierarchically micro-, meso- and macroporous HKUST-1 with a high yield. Moreover, the post-synthesis of these as-obtained hierarchically porous HKUST-1 was easily performed via grinding triethylenediamine (TED) with the above unwashed crude-products for 20 minutes. By adjusting the amount of NaCl and TED added, we simply fabricated the pore- and function-adjustable hierarchically porous HKUST-1. Furthermore, these as-obtained HKUST-1 products showed high performance in the capture of volatile iodine.

Synthesis and characterization of new meso-substituted ...

Indian Academy of Sciences (India)

WINTEC

tems. 10. Their ability to carry out the reactions rather unusual in organic chemistry has been the object of intensive investigations aiming to utilize them as a model compounds for biological systems and as catalysts. 11. Therefore, the synthesis of well defined meso-substituted unsymmetrical porphyrin deriva- tives (A3B) is ...

Flexible, cathodoluminescent and free standing mesoporous silica films with entrapped quasi-2D perovskites

Science.gov (United States)

Vassilakopoulou, Anastasia; Papadatos, Dionysios; Koutselas, Ioannis

2017-04-01

The effective entrapment of hybrid organic-inorganic semiconductors (HOIS) into mesoporous polymer-silica hybrid matrices, formed as free standing flexible films, is presented for the first time. A blend of quasi-2D HOIS, simply synthesized by mixing two-dimensional (2D) and three dimensional (3D) HOIS, exhibiting strong photoluminescence, is embedded into porous silica matrices during the sol-gel synthesis, using tetraethylorthosilicate as precursor and Pluronic F-127 triblock copolymer as structure directing agent, under acidic conditions. The final nanostructure hybrid forms flexible, free standing films, presenting high cathodoluminescence and long stable excitonic luminescence, indicating the protective character of the hybrid matrix towards the entrapped perovskite. A significant result is that the photoluminescence of the entrapped HOIS is not affected even after films' prolonged exposure to water.

Potassium vapor assisted preparation of highly graphitized hierarchical porous carbon for high rate performance supercapacitors

Science.gov (United States)

Liu, Zheng; Zeng, Ying; Tang, Qunli; Hu, Aiping; Xiao, Kuikui; Zhang, Shiying; Deng, Weina; Fan, Binbin; Zhu, Yanfei; Chen, Xiaohua

2017-09-01

Ultrahigh graphitized carbon microspheres with rich hierarchical pores (AGHPCM-1) have been successfully synthesized through the one-step activation-carbonization strategy (OACS) with porous sulfonated poly-divinylbenzene as the carbon precursor, iron as the hard template and catalyst, and potassium hydroxide (KOH) as activation agent. Through the XRD, TEM, Raman and BET analysis, AGHPCM-1 shows very high graphitization degree and rich micro-, meso- and macro-pores. More importantly, the mechanism for KOH to improve the graphitization degree of carbon materials in OACS has been illustrated by the thermodynamical theory. The tremendous heat releasing from the reaction between the catalyst precursor of Fe2O3 and potassium vapor plays a key role in the formation of graphitized carbon. It may provide a general direction to prepare highly graphitized porous carbon at a moderate temperature. Integrating the advantages of high graphitization degree and rich hierarchical porous structure, the AGHPCM-1 exhibits an excellent rate performance with a response to up to the high current density of 150 A g-1 and high scan rate of 2000 mV s-1. No obvious capacitance decay can be observed after 10000 charge/discharge cycles even at the high current density of 20 A g-1.

Tadalafil inclusion in microporous silica as effective dissolution enhancer: optimization of loading procedure and molecular state characterization.

Science.gov (United States)

Mehanna, Mohammed M; Motawaa, Adel M; Samaha, Magda W

2011-05-01

Tadalafil is an efficient drug used to treat erectile dysfunction characterized by poor water solubility, which has a negative influence on its bioavailability. Utilization of microporous silica represents an effective and facile technology to increase the dissolution rate of poorly soluble drugs. Our strategy involved directly introducing tadalafil as guest molecule into microporous silica as host material by incipient wetness impregnation method. To optimize tadalafil inclusion, response surface methodology (RSM) using 3(3) factorial design was utilized. Furthermore, to investigate the molecular state of tadalafil, Fourier-transform infrared spectroscopy, differential scanning calorimetery, thermal gravimetrical analysis, nitrogen adsorption, and powder X-ray diffraction (PXRD) were carried out. The results obtained pointed out that the quantity of microporous silica was the predominant factor that increased the loading efficiency. For the optimized formula, the loading efficiency was 42.50 wt %. Adsorption-desorption experiments indicated that tadalafil has been introduced into the micropores. Powder XRD and differential scanning calorimetry analyses revealed that tadalafil is arranged in amorphous form. In addition, the dissolution rate of tadalafil from the microporous silica was faster than that of free drug. Amorphous tadalafil occluded in microporous silica did not crystallize over 3 months. These findings contributed in opening a new strategy concerning the utilization of porous silica for the dissolution rate enhancement. Copyright © 2010 Wiley-Liss, Inc.

Porous Silicates Modified with Zirconium Oxide and Sulfate Ions for Alcohol Dehydration Reactions

Directory of Open Access Journals (Sweden)

Heriberto Esteban Benito

2015-01-01

Full Text Available Porous silicates were synthesized by a nonhydrothermal method, using sodium silicate as a source of silica and cetyltrimethylammonium bromide as a template agent. Catalysts were characterized using thermogravimetric analysis, N2 physisorption, X-ray diffraction, FTIR spectroscopy, pyridine adsorption, potentiometric titration with n-butylamine, scanning electronic microscopy, and transmission electronic microscopy. The surface area of the materials synthesized was greater than 800 m2/g. The introduction of zirconium atoms within the porous silicates increased their acid strength from −42 to 115 mV, while the addition of sulfate ions raised this value to 470 mV. The catalytic activity for the dehydration of alcohols yields conversions of up to 70% for ethanol and 30% for methanol.

MS-2 and poliovirus transport in porous media: Hydrophobic effects and chemical perturbations

Science.gov (United States)

Bales, Roger C.; Li, Shimin; Maguire, Kimberly M.; Yahya, Moyasar T.; Gerba, Charles P.

1993-04-01

In a series of pH 7 continuous-flow column experiments, removal of the bacteriophage MS-2 by attachment to silica beads had a strong, systematic dependence on the amount of hydrophobic surface present on the beads. With no hydrophobic surface, removal of phage at pH 5 was much greater than at pH 7. Release of attached phage at both pH values did occur, but was slow; breakthrough curves exhibited tailing. Poliovirus attached to silica beads at pH 5.5 much more than at pH 7.0, and attachment was also slowly reversible. Time scales for phage and poliovinis attachment were of the order of hours. The sticking efficiency factor (α), reflecting microscaie physicochemical influences on virus attachment, was in the range of 0.0007-0.02. Phage release was small but measurable under steady state conditions. Release was enhanced by lowering ionic strength and by introducing beef extract, a high-ionic-strength protein solution. Results show that viruses experience reversible attachment/detachment (sometimes termed sorption), that large chemical perturbations are needed to induce rapid virus detachment, and that viruses should be quite mobile in sandy porous media. Even small amounts of hydrophobic organic material in the porous media (≥0.001%) can retard virus transport.

Activity Tests of Macro-Meso Porous Catalysts over Metal Foam Plate for Steam Reforming of Bio-Ethanol.

Science.gov (United States)

Park, No-Kuk; Jeong, Yong Han; Kang, Misook; Lee, Tae Jin

2018-09-01

The catalytic activity of a macro-mesoporous catalyst coated on a metal foam plate in the reforming of bio-ethanol to synthesis gas was investigated. The catalysts were prepared by coating a support with a noble metal and transition metal. The catalytic activity for the production of synthetic gas by the reforming of bio-ethanol was compared according to the support material, reaction temperature, and steam/carbon ratio. The catalysts coated on the metal foams were prepared using a template method, in which macro-pores and meso-pores were formed by mixing polymer beads. In particular, the thermodynamic equilibrium composition of bio-ethanol reforming with the reaction temperature and steam/carbon ratio to produce synthetic gas was examined using the HSC (Enthalpy-Entropy-Heat capacity) chemistry program in this study. The composition of hydrogen and carbon monoxide in the reformate gas produced by steam reforming over the Rh/Ni-Ce-Zr/Al2O3-based pellet type catalysts and metal foam catalysts that had been coated with the Rh/Al-Ce-Zr-based catalysts was investigated by experimental activity tests. The activity of the metal foam catalyst was higher than that of the pellet type catalyst.

Micro- and meso-scale effects of forested terrain

DEFF Research Database (Denmark)

Dellwik, Ebba; Mann, Jakob; Sogachev, Andrey

2011-01-01

scales are the height of the planetary boundary layer and the Monin-Obukhov length, which both are related to the energy balance of the surface. Examples of important micro- and meso-scale effects of forested terrain are shown using data and model results from recent and ongoing experiments. For micro......The height and rotor diameter of modern wind turbines are so extensive, that the wind conditions they encounter often are well above the surface layer, where traditionally it is assumed that wind direction and turbulent fluxes are constant with respect to height, if the surface is homogenous....... Deviations from the requirement of homogeneity are often the focus of micro-scale studies in forested areas. Yet, to explain the wind climate in the relevant height range for turbines, it is necessary to also account for the length scales that are important parameters for the meso-scale flow. These length...

Preparation of reduced graphene oxide/meso-TiO_2/AuNPs ternary composites and their visible-light-induced photocatalytic degradation n of methylene blue

International Nuclear Information System (INIS)

Yang, Yongfang; Ma, Zheng; Xu, Lidong; Wang, Hefang; Fu, Nian

2016-01-01

Graphical abstract: Reduced graphene oxide/meso-TiO_2/AuNPs (RGO/meso-TiO_2/AuNPs) ternary composites were prepared via the addition of graphene oxide to the dispersion of meso-TiO_2/AuNPs under a hydrothermal condition. The RGO/meso-TiO_2/AuNPs ternary composites show high photocatalytic activity toward MB. - Highlights: • RGO/meso-TiO_2/AuNPs were obtained by addition of graphene oxide to meso-TiO_2/AuNPs. • Au NPs in the mesopores of meso-TiO_2 reduce the recombination of charge carriers. • RGO covered with the surface of the meso-TiO_2 enhance the adsorption of MB. • RGO/meso-TiO_2/AuNPs composites show high photocatalytic performance toward MB. - Abstract: Reduced graphene oxide/meso-TiO_2/AuNPs (RGO/meso-TiO_2/AuNPs) ternary composites were prepared via the addition of graphene oxide to the dispersion of meso-TiO_2/AuNPs under hydrothermal conditions. The structure and the morphology of the RGO/meso-TiO_2/AuNPs materials were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The photocatalytic activity of RGO/meso-TiO_2/AuNPs was evaluated by degradation of methyl blue (MB) under visible-light illumination. The ternary composites present an extended light absorption range, efficient charge separation properties, high adsorption ability for MB and high photocatalytic degradation activity of MB compared to the meso-TiO_2 and meso-TiO_2/AuNPs.

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.

Impact of the De-Alloying Kinetics and Alloy Microstructure on the Final Morphology of De-Alloyed Meso-Porous Metal Films

Directory of Open Access Journals (Sweden)

Bao Lin

2014-10-01

Full Text Available Nano-textured porous metal materials present unique surface properties due to their enhanced surface energy with potential applications in sensing, molecular separation and catalysis. In this paper, commercial alloy foils, including brass (Cu85Zn15 and Cu70Zn30 and white gold (Au50Ag50 foils have been chemically de-alloyed to form nano-porous thin films. The impact of the initial alloy micro-structure and number of phases, as well as chemical de-alloying (DA parameters, including etchant concentration, time and solution temperature on the final nano-porous thin film morphology and properties were investigated by electron microscopy (EM. Furthermore, the penetration depth of the pores across the alloys were evaluated through the preparation of cross sections by focus ion beam (FIB milling. It is demonstrated that ordered pores ranging between 100 nm and 600 nm in diameter and 2–5 μm in depth can be successfully formed for the range of materials tested. The microstructure of the foils were obtained by electron back-scattered diffraction (EBSD and linked to development of pits across the material thickness and surface during DA. The role of selective etching of both noble and sacrificial metal phases of the alloy were discussed in light of the competitive surface etching across the range of microstructures and materials tested.

Controlled release of ibuprofen by meso–macroporous silica

Energy Technology Data Exchange (ETDEWEB)

Santamaría, E., E-mail: esthersantamaria@ub.edu; Maestro, A.; Porras, M.; Gutiérrez, J.M.; González, C.

2014-02-15

Structured meso–macroporous silica was successfully synthesized from an O/W emulsion using decane as a dispersed phase. Sodium silicate solution, which acts as a silica source and a poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (EO{sub 19}PO{sub 39}EO{sub 19}) denoted as P84 was used in order to stabilize the emulsion and as a mesopore template. The materials obtained were characterized through transmission electron microscopy (TEM), scanning electron microscopy (SEM), small-angle X-ray diffraction scattering (SAXS) and nitrogen adsorption–desorption isotherms. Ibuprofen (IBU) was selected as the model drug and loaded into ordered meso–macroporous materials. The effect of the materials’ properties on IBU drug loading and release was studied. The results showed that the loading of IBU increases as the macropore presence in the material is increased. The IBU adsorption process followed the Langmuir adsorption isotherm. A two-step release process, consisting of an initial fast release and then a slower release was observed. Macropores enhanced the adsorption capacity of the material; this was probably due to the fact that they allowed the drug to access internal pores. When only mesopores were present, ibuprofen was probably adsorbed on the mesopores close to the surface. Moreover, the more macropore present in the material, the slower the release behaviour observed, as the ibuprofen adsorbed in the internal pores had to diffuse along the macropore channels up to the surface of the material. The material obtained from a highly concentrated emulsion was functionalized with amino groups using two methods, the post-grafting mechanism and the co-condensation mechanism. Both routes improve IBU adsorption in the material and show good behaviour as a controlled drug delivery system. - Graphical abstract: Ibuprofen release profiles for the materials obtained from samples P84{sub m}eso (black diamonds), P84{sub 2}0% (white squares), P84{sub 5

Nanoporous Silica Templated HeteroEpitaxy: Final LDRD Report.

Energy Technology Data Exchange (ETDEWEB)

Burckel, David Bruce; Koleske, Daniel; Rowen, Adam M.; Williams, John Dalton; Fan, Hongyou; Arrington, Christian Lew

2006-11-01

This one-year out-of-the-box LDRD was focused on exploring the use of porous growth masks as a method for defect reduction during heteroepitaxial crystal growth. Initially our goal was to investigate porous silica as a growth mask, however, we expanded the scope of the research to include several other porous growth masks on various size scales, including mesoporous carbon, and the UV curable epoxy, SU-8. Use of SU-8 as a growth mask represents a new direction, unique in the extensive literature of patterned epitaxial growth, and presents the possibility of providing a single step growth mask. Additional research included investigation of pore viability via electrochemical deposition into high aspect ratio photoresist patterns and pilot work on using SU-8 as a DUV negative resist, another significant potential result. While the late start nature of this project pushed some of the initial research goals out of the time table, significant progress was made. 3 Acknowledgements This work was performed in part at the Nanoscience @ UNM facility, a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation (Grant ECS 03-35765). Sandia is multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United Stated Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000. This work was supported under the Sandia LDRD program (Project 99405). 4

The role of positron annihilation lifetime studies and nuclear sensors for characterising porous materials

International Nuclear Information System (INIS)

Mume, E; Smith, S V; Uedono, A; Mizunaga, G; Lynch, D E

2011-01-01

A series of nuclear sensors were designed to assess the chemistry within the nanopores of a porous material. The nuclear sensors of varying size, charge, and hydrophobicity were exposed to hollow silica shells (HSS) at varying pH. Uptake and release kinetics were studied over a 24 h period at room temperature. Preliminary study indicate positively charged nuclear sensors were selectively and rapidly (within 10 min) absorbed by the HSS at pH 7 to 9. PALS showed there were two types of pores (1.7 and 0.7 nm) present. The data suggest the nuclear sensors sit within the larger pore of the HSS. Both PALS and nuclear sensors are required to obtain an accurate insight into the nanoporosity of the hollow silica shells.

Synthesis, Characterization and Application of Multiscale Porous Materials

Energy Technology Data Exchange (ETDEWEB)

Hussami, Linda

2010-07-01

This thesis work brings fresh insights and improved understanding of nano scale materials through introducing new hybrid composites, 2D hexagonal in MCM-41 and 3D random interconnected structures of different materials, and application relevance for developing fields of science, such as fuel cells and solar cells. New types of porous materials and organometallic crystals have been prepared and characterized in detail. The porous materials have been used in several studies: as hosts to encapsulate metal-organic complexes; as catalyst supports and electrode materials in devices for alternative energy production. The utility of the new porous materials arises from their unique structural and surface chemical characteristics as demonstrated here using various experimental and theoretical approaches. New single crystal structures and arene-ligand exchange properties of f-block elements coordinated to ligand arene and halogallates are described in Paper I. These compounds have been incorporated into ordered 2D-hexagonal MCM-41 and polyhedral silica nano foam (PNF-SiO{sub 2}) matrices without significant change to the original porous architectures as described in Paper II and III. The resulting inorganic/organic hybrids exhibited enhanced luminescence activity relative to the pure crystalline complexes. A series of novel polyhedral carbon nano foams (PNF-C's) and inverse foams were prepared by nano casting from PNF-SiO{sub 2}'s. These are discussed in Paper IV. The synthesis conditions of PNF-C's were systematically varied as a function of the filling ratio of carbon precursor and their structures compared using various characterization methods. The carbonaceous porous materials were further tested in Paper V and VI as possible catalysts and catalyst supports in counter- and working electrodes for solar- and fuel cell applications

Facile control of silica nanoparticles using a novel solvent varying method for the fabrication of artificial opal photonic crystals

International Nuclear Information System (INIS)

Gao, Weihong; Rigout, Muriel; Owens, Huw

2016-01-01

In this work, the Stöber process was applied to produce uniform silica nanoparticles (SNPs) in the meso-scale size range. The novel aspect of this work was to control the produced silica particle size by only varying the volume of the solvent ethanol used, whilst fixing the other reaction conditions. Using this one-step Stöber-based solvent varying (SV) method, seven batches of SNPs with target diameters ranging from 70 to 400 nm were repeatedly reproduced, and the size distribution in terms of the polydispersity index (PDI) was well maintained (within 0.1). An exponential equation was used to fit the relationship between the particle diameter and ethanol volume. This equation allows the prediction of the amount of ethanol required in order to produce particles of any target diameter within this size range. In addition, it was found that the reaction was completed in approximately 2 h for all batches regardless of the volume of ethanol. Structurally coloured artificial opal photonic crystals (PCs) were fabricated from the prepared SNPs by self-assembly under gravity sedimentation.

Facile control of silica nanoparticles using a novel solvent varying method for the fabrication of artificial opal photonic crystals

Science.gov (United States)

Gao, Weihong; Rigout, Muriel; Owens, Huw

2016-12-01

In this work, the Stöber process was applied to produce uniform silica nanoparticles (SNPs) in the meso-scale size range. The novel aspect of this work was to control the produced silica particle size by only varying the volume of the solvent ethanol used, whilst fixing the other reaction conditions. Using this one-step Stöber-based solvent varying (SV) method, seven batches of SNPs with target diameters ranging from 70 to 400 nm were repeatedly reproduced, and the size distribution in terms of the polydispersity index (PDI) was well maintained (within 0.1). An exponential equation was used to fit the relationship between the particle diameter and ethanol volume. This equation allows the prediction of the amount of ethanol required in order to produce particles of any target diameter within this size range. In addition, it was found that the reaction was completed in approximately 2 h for all batches regardless of the volume of ethanol. Structurally coloured artificial opal photonic crystals (PCs) were fabricated from the prepared SNPs by self-assembly under gravity sedimentation.

Facile control of silica nanoparticles using a novel solvent varying method for the fabrication of artificial opal photonic crystals

Energy Technology Data Exchange (ETDEWEB)

Gao, Weihong [The University of Manchester, School of Materials (United Kingdom); Rigout, Muriel [University of Leeds, School of Design (United Kingdom); Owens, Huw, E-mail: Huw.Owens@manchester.ac.uk [The University of Manchester, School of Materials (United Kingdom)

2016-12-15

In this work, the Stöber process was applied to produce uniform silica nanoparticles (SNPs) in the meso-scale size range. The novel aspect of this work was to control the produced silica particle size by only varying the volume of the solvent ethanol used, whilst fixing the other reaction conditions. Using this one-step Stöber-based solvent varying (SV) method, seven batches of SNPs with target diameters ranging from 70 to 400 nm were repeatedly reproduced, and the size distribution in terms of the polydispersity index (PDI) was well maintained (within 0.1). An exponential equation was used to fit the relationship between the particle diameter and ethanol volume. This equation allows the prediction of the amount of ethanol required in order to produce particles of any target diameter within this size range. In addition, it was found that the reaction was completed in approximately 2 h for all batches regardless of the volume of ethanol. Structurally coloured artificial opal photonic crystals (PCs) were fabricated from the prepared SNPs by self-assembly under gravity sedimentation.

Studies on hydrogen separation membrane for IS process. Membrane preparation with porous α-alumina tube

International Nuclear Information System (INIS)

Hwang, Gab-Jin; Onuki, Kaoru; Shimizu, Saburo

1998-01-01

It was investigated the preparation technique of hydrogen separation membrane to enhance the decomposition ratio of hydrogen iodide in the thermochemical IS process. Hydrogen separation membranes based on porous α-alumina tubes having pore size of 100 nm and 10 nm were prepared by chemical vapor deposition using tetraethylorthosilicate (TEOS) as the Si source. In the hydrogen separation membrane, its pore was closed by the deposited silica and then the permeation of gas was affected by the hindrance diffusion. At 600degC, the selectivity ratios (H 2 /N 2 ) were 5.2 and 160 for the membranes based on porous α-alumina tube having pore size of 100 nm and 10 nm, respectively. (author)

Scaling of water vapor in the meso-gamma (2-20km) and lower meso-beta (20-50km) scales from tall tower time series

Science.gov (United States)

Pressel, K. G.; Collins, W.; Desai, A. R.

2011-12-01

Deficiencies in the parameterization of boundary layer clouds in global climate models (GCMs) remains one of the greatest sources of uncertainty in climate change predictions. Many GCM cloud parameterizations, which seek to include some representation of subgrid-scale cloud variability, do so by making assumptions regarding the subgrid-scale spatial probability density function (PDF) of total water content. Properly specifying the form and parameters of the total water PDF is an essential step in the formulation of PDF based cloud parameterizations. In the cloud free boundary layer, the PDF of total water mixing ratio is equivalent to the PDF of water vapor mixing ratio. Understanding the PDF of water vapor mixing ratio in the cloud free atmosphere is a necessary step towards understanding the PDF of water vapor in the cloudy atmosphere. A primary challenge in empirically constraining the PDF of water vapor mixing ratio is a distinct lack of a spatially distributed observational dataset at or near cloud scale. However, at meso-beta (20-50km) and larger scales, there is a wealth of information on the spatial distribution of water vapor contained in the physically retrieved water vapor profiles from the Atmospheric Infrared Sounder onboard NASA`s Aqua satellite. The scaling (scale-invariance) of the observed water vapor field has been suggested as means of using observations at satellite observed (meso-beta) scales to derive information about cloud scale PDFs. However, doing so requires the derivation of a robust climatology of water vapor scaling from in-situ observations across the meso- gamma (2-20km) and meso-beta scales. In this work, we present the results of the scaling of high frequency (10Hz) time series of water vapor mixing ratio as observed from the 447m WLEF tower located near Park Falls, Wisconsin. Observations from a tall tower offer an ideal set of observations with which to investigate scaling at meso-gamma and meso-beta scales requiring only the

Modeling Time-Dependent Behavior of Concrete Affected by Alkali Silica Reaction in Variable Environmental Conditions.

Science.gov (United States)

Alnaggar, Mohammed; Di Luzio, Giovanni; Cusatis, Gianluca

2017-04-28

Alkali Silica Reaction (ASR) is known to be a serious problem for concrete worldwide, especially in high humidity and high temperature regions. ASR is a slow process that develops over years to decades and it is influenced by changes in environmental and loading conditions of the structure. The problem becomes even more complicated if one recognizes that other phenomena like creep and shrinkage are coupled with ASR. This results in synergistic mechanisms that can not be easily understood without a comprehensive computational model. In this paper, coupling between creep, shrinkage and ASR is modeled within the Lattice Discrete Particle Model (LDPM) framework. In order to achieve this, a multi-physics formulation is used to compute the evolution of temperature, humidity, cement hydration, and ASR in both space and time, which is then used within physics-based formulations of cracking, creep and shrinkage. The overall model is calibrated and validated on the basis of experimental data available in the literature. Results show that even during free expansions (zero macroscopic stress), a significant degree of coupling exists because ASR induced expansions are relaxed by meso-scale creep driven by self-equilibriated stresses at the meso-scale. This explains and highlights the importance of considering ASR and other time dependent aging and deterioration phenomena at an appropriate length scale in coupled modeling approaches.

Investigating the binding properties of porous drug delivery systems using nuclear sensors (radiotracers) and positron annihilation lifetime spectroscopy--predicting conditions for optimum performance.

Science.gov (United States)

Mume, Eskender; Lynch, Daniel E; Uedono, Akira; Smith, Suzanne V

2011-06-21

Understanding how the size, charge and number of available pores in porous material influences the uptake and release properties is important for optimising their design and ultimately their application. Unfortunately there are no standard methods for screening porous materials in solution and therefore formulations must be developed for each encapsulated agent. This study investigates the potential of a library of radiotracers (nuclear sensors) for assessing the binding properties of hollow silica shell materials. Uptake and release of Cu(2+) and Co(2+) and their respective complexes with polyazacarboxylate macrocycles (dota and teta) and a series of hexa aza cages (diamsar, sarar and bis-(p-aminobenzyl)-diamsar) from the hollow silica shells was monitored using their radioisotopic analogues. Coordination chemistry of the metal (M) species, subtle alterations in the molecular architecture of ligands (Ligand) and their resultant complexes (M-Ligand) were found to significantly influence their uptake over pH 3 to 9 at room temperature. Positively charged species were selectively and rapidly (within 10 min) absorbed at pH 7 to 9. Negatively charged species were preferentially absorbed at low pH (3 to 5). Rates of release varied for each nuclear sensor, and time to establish equilibrium varied from minutes to days. The subtle changes in design of the nuclear sensors proved to be a valuable tool for determining the binding properties of porous materials. The data support the development of a library of nuclear sensors for screening porous materials for use in optimising the design of porous materials and the potential of nuclear sensors for high through-put screening of materials.

Scalable 2D Hierarchical Porous Carbon Nanosheets for Flexible Supercapacitors with Ultrahigh Energy Density.

Science.gov (United States)

Yao, Lei; Wu, Qin; Zhang, Peixin; Zhang, Junmin; Wang, Dongrui; Li, Yongliang; Ren, Xiangzhong; Mi, Hongwei; Deng, Libo; Zheng, Zijian

2018-03-01

2D carbon nanomaterials such as graphene and its derivatives, have gained tremendous research interests in energy storage because of their high capacitance and chemical stability. However, scalable synthesis of ultrathin carbon nanosheets with well-defined pore architectures remains a great challenge. Herein, the first synthesis of 2D hierarchical porous carbon nanosheets (2D-HPCs) with rich nitrogen dopants is reported, which is prepared with high scalability through a rapid polymerization of a nitrogen-containing thermoset and a subsequent one-step pyrolysis and activation into 2D porous nanosheets. 2D-HPCs, which are typically 1.5 nm thick and 1-3 µm wide, show a high surface area (2406 m 2 g -1 ) and with hierarchical micro-, meso-, and macropores. This 2D and hierarchical porous structure leads to robust flexibility and good energy-storage capability, being 139 Wh kg -1 for a symmetric supercapacitor. Flexible supercapacitor devices fabricated by these 2D-HPCs also present an ultrahigh volumetric energy density of 8.4 mWh cm -3 at a power density of 24.9 mW cm -3 , which is retained at 80% even when the power density is increased by 20-fold. The devices show very high electrochemical life (96% retention after 10000 charge/discharge cycles) and excellent mechanical flexibility. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Positronium formation in porous materials for antihydrogen production

International Nuclear Information System (INIS)

Ferragut, R; Calloni, A; Dupasquier, A; Consolati, G; Giammarchi, M G; Quasso, F; Trezzi, D; Egger, W; Ravelli, L; Petkov, M P; Jones, S M; Wang, B; Yaghi, O M; Jasinska, B; Chiodini, N; Paleari, A

2010-01-01

Positronium (Ps) formation measurements in several porous materials as: Vycor, germanate Xerogel, Metal-Organic Frameworks MOF-177 and Aerogel with two densities (20 and 150 mg/cm 3 ), were performed by means of a variable energy positron beam provided with a Ge detector and a positron lifetime spectrometer. An efficient formation of cooled Ps atoms is a requisite for the production of antihydrogen, with the aim of a direct measurement of the Earth gravitational acceleration g of antimatter, which is a primary scientific goal of AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy). Porous materials are necessary to form a high yield of Ps atoms as well as to cool Ps through collisions with the inner walls of the pores. The different materials were characterized and produce Ps into the pores. Lifetime measurements give an estimation of the typical pores dimension of the substances. A comparative study of the positron lifetime and the Ps fraction values in the above mentioned materials indicates that silica Aerogel, with the appropriate density, is an excellent candidate for an efficient formation of cold Ps atoms for the AEGIS project.

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.

Polyoxotungstate nanoclusters supported on silica as an efficient solid-phase microextraction fiber of polycyclic aromatic hydrocarbons

International Nuclear Information System (INIS)

Abolghasemi, Mir Mahdi; Yousefi, Vahid; Rafiee, Ezzat

2014-01-01

A highly porous silica-supported tungstophosphoric acid (PW) nanocluster was prepared for use in solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The PWs represent a class of discrete transition metal-oxide nanoclusters and their structures resemble discrete fragments of metal-oxide structures of definite size and shape. Transition metal-oxide nanoclusters display large structural diversity, and their monodisperse sizes can be tuned from several Ångstroms up to 10 nm. The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The nanomaterial was immobilized on a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS. Analytical merits include limits of detection that range from 0.02 to 0.1 pg mL −1 and a dynamic range as wide as from 0.001 to 100 ng mL −1 . Under optimum conditions, the repeatability for one fiber (n = 3), expressed as the relative standard deviation, is between 4.3 % and 8.6 %. The method is simple, rapid, and inexpensive. The thermal stability of the fiber and the high relative recovery make this method superior to conventional methods of extraction. (author)

Fabrication of 3D heteroatom-doped porous carbons from self-assembly of chelate foams via a solid state method

KAUST Repository

Wang, Yu; Pan, Ying; Zhu, Liangkui; Guo, Ningning; Wang, Runwei; Zhang, Zongtao; Qiu, Shilun

2018-01-01

A novel 3D foam-like porous carbon architectures with homogeneous N doping and unique mesopore-in-macropore structures have been fabricated from metal-organic complex via a facile template-free solid state method, which show high specific surface area (2732 m2 g-1), large pore volume (3.31 cm3 g-1), interconnected hierarchical pore structures with macro/meso/micro multimodal distribution and abundant surface functionality N doping (5.36 wt%). These characteristics afford high catalytic performance for oxygen reduction with an onset potential of 0.98 V (vs RHE) and a half-wave potential of 0.83 V (vs RHE) in alkaline media, which are comparable with those of the commercial 20 wt% Pt/C catalyst and many state-of-the-art noble-metal-free catalysts. These results demonstrate the significant advantages of the unique mesopore-in-macropore porous structures with efficient heteroatom doping, which provides abundant of accessible active sites for highly mass and charge transports. The present work pave a new facile and environmentally benign synthesis strategy for the preparation of 3D porous carbon architectures as efficient electrochemical energy devices and give deep insights into fabricating advanced nanostructured materials.

Fabrication of 3D heteroatom-doped porous carbons from self-assembly of chelate foams via a solid state method

KAUST Repository

Wang, Yu

2018-01-09

A novel 3D foam-like porous carbon architectures with homogeneous N doping and unique mesopore-in-macropore structures have been fabricated from metal-organic complex via a facile template-free solid state method, which show high specific surface area (2732 m2 g-1), large pore volume (3.31 cm3 g-1), interconnected hierarchical pore structures with macro/meso/micro multimodal distribution and abundant surface functionality N doping (5.36 wt%). These characteristics afford high catalytic performance for oxygen reduction with an onset potential of 0.98 V (vs RHE) and a half-wave potential of 0.83 V (vs RHE) in alkaline media, which are comparable with those of the commercial 20 wt% Pt/C catalyst and many state-of-the-art noble-metal-free catalysts. These results demonstrate the significant advantages of the unique mesopore-in-macropore porous structures with efficient heteroatom doping, which provides abundant of accessible active sites for highly mass and charge transports. The present work pave a new facile and environmentally benign synthesis strategy for the preparation of 3D porous carbon architectures as efficient electrochemical energy devices and give deep insights into fabricating advanced nanostructured materials.

Biochar as porous media for thermally-induced non-catalytic transesterification to synthesize fatty acid ethyl esters from coconut oil

International Nuclear Information System (INIS)

Jung, Jong-Min; Lee, Jechan; Choi, Dongho; Oh, Jeong-Ik; Lee, Sang-Ryong; Kim, Jae-Kon; Kwon, Eilhann E.

2017-01-01

Highlights: • Biodiesel production using renewable resources. • Thermally-induced non-catalytic transesterification. • Synthesis of fatty acid ethyl esters without conventional catalysts. • Using biochar as porous medium in the non-catalytic transesterification. - Abstract: This study put great emphasis on evaluating biochar as porous media for the thermally-induced non-catalytic transesterification reaction to synthesize fatty acid ethyl esters (FAEE) from coconut oil. Thermogravimetric analysis (TGA) of coconut oil experimentally justified that the bond dissociation of fatty acid from the backbone of triglycerides (TGs) could be achieved, which finding could be applied to the non-catalytic transesterification reaction. To use biochar as porous medium, the surficial morphology of maize residue biochar (MRB) was characterized, revealing that biochar possessed the wider pore size distribution ranging from meso- to macro-pores than SiO 2 . The highest yield of FAEE from non-catalytic transesterification of coconut oil in the presence of MRB was 87% at 380 °C. To further enhance the FAEE yield, further studies associated with the production of FAEE with biochar made from different biomasses and various pyrolytic conditions should be performed.

Electroactive Properties of 1-propyl-3-methylimidazolium Ionic Liquid Covalently Bonded on Mesoporous Silica Surface: Development of an Electrochemical Sensor Probed for NADH, Dopamine and Uric Acid Detection

International Nuclear Information System (INIS)

Maroneze, Camila M.; Rahim, Abdur; Fattori, Natália; Costa, Luiz P. da; Sigoli, Fernando A.; Mazali, Italo O.; Custodio, Rogério; Gushikem, Yoshitaka

2014-01-01

Graphical abstract: - Abstract: A hybrid organic-inorganic porous material was successfully prepared through chemical modification of a non-ordered mesoporous silica, obtained by the sol-gel process, with 1-propyl-3-methylimidazolium groups. The porous material was evaluated as a platform for the development of electrochemical sensors, here probed toward the electrooxidation of NADH (β-nicotinamide adenine dinucleotide), uric acid (UA) and dopamine (DA). The presence of cationic imidazolium groups on the surface of the hybrid silica-based material allowed the electrochemical detection of these biomolecules without any other electron mediator or biomolecular recognition component. Such behavior highlights the potentiality of this material to be applied in the development of new electrochemical sensing devices. Theoretical calculations based on density functional theory emphasizes that the cationic character of imidazolium group provides better oxidation conditions if the solvent effect is minimized

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.

Preparation of reduced graphene oxide/meso-TiO{sub 2}/AuNPs ternary composites and their visible-light-induced photocatalytic degradation n of methylene blue

Energy Technology Data Exchange (ETDEWEB)

Yang, Yongfang; Ma, Zheng; Xu, Lidong [School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130 (China); Wang, Hefang, E-mail: whf0618@163.com [School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130 (China); Fu, Nian, E-mail: funian3678@163.com [School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130 (China); College of Physics Science and Technology of Hebei University, Baoding 071002 (China)

2016-04-30

Graphical abstract: Reduced graphene oxide/meso-TiO{sub 2}/AuNPs (RGO/meso-TiO{sub 2}/AuNPs) ternary composites were prepared via the addition of graphene oxide to the dispersion of meso-TiO{sub 2}/AuNPs under a hydrothermal condition. The RGO/meso-TiO{sub 2}/AuNPs ternary composites show high photocatalytic activity toward MB. - Highlights: • RGO/meso-TiO{sub 2}/AuNPs were obtained by addition of graphene oxide to meso-TiO{sub 2}/AuNPs. • Au NPs in the mesopores of meso-TiO{sub 2} reduce the recombination of charge carriers. • RGO covered with the surface of the meso-TiO{sub 2} enhance the adsorption of MB. • RGO/meso-TiO{sub 2}/AuNPs composites show high photocatalytic performance toward MB. - Abstract: Reduced graphene oxide/meso-TiO{sub 2}/AuNPs (RGO/meso-TiO{sub 2}/AuNPs) ternary composites were prepared via the addition of graphene oxide to the dispersion of meso-TiO{sub 2}/AuNPs under hydrothermal conditions. The structure and the morphology of the RGO/meso-TiO{sub 2}/AuNPs materials were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The photocatalytic activity of RGO/meso-TiO{sub 2}/AuNPs was evaluated by degradation of methyl blue (MB) under visible-light illumination. The ternary composites present an extended light absorption range, efficient charge separation properties, high adsorption ability for MB and high photocatalytic degradation activity of MB compared to the meso-TiO{sub 2} and meso-TiO{sub 2}/AuNPs.

Pore radius fine tuning of a silica matrix (MCM-41) based on the synthesis of alumina nanolayers with different thicknesses by atomic layer deposition

International Nuclear Information System (INIS)

Zemtsova, Elena G.; Arbenin, Andrei Yu.; Plotnikov, Alexander F.; Smirnov, Vladimir M.

2015-01-01

The authors investigated a new approach to modify the surface of the mesoporous silica matrix MCM-41. This approach is based on manipulating the chemical composition of the porous surface layer and also on fine tuning the pore radius by applying the atomic layer deposition (ALD) technique. The synthesis of alumina nanolayers was performed on the planar and the porous matrix (MCM-41) by the ALD technique using aluminum tri-sec-butoxide and water as precursors. The authors show that one cycle on silicon, using aluminum tri-sec-butoxide and water as precursors, results in a 1–1.2 Å increase in alumina nanolayer thickness. This is comparable to the increase in thickness per cycle for other precursors such as trimethylaluminum and aluminum chloride. The authors show that the synthesis of an Al 2 O 3 nanolayer on the pore surface of the mesoporous silica matrix MCM-41 by the ALD technique results in a regular change in the porous structure of the samples. The specific porosity (ml/g) of the MCM-41 was 0.95 and that of MCM-41 after 5 ALD cycles was 0.39. The pore diameter (nm) of MCM-41 was 3.3 and that of MCM-41 after 5 ALD cycles was 2.3

X-ray excited optical luminescence (XEOL) and its application to porous silicon

International Nuclear Information System (INIS)

Hill, D.A.

1998-09-01

X-ray Excited Optical Luminescence (XEOL) is investigated as a local structural probe of the light-emitting sites in porous silicon. A detailed microscopic model of the XEOL process in porous silicon is proposed. A central aspect of the technique is an assessment of the spatial separation between the primary photoionisation event and subsequent optical radiative recombination. By constructing a Monte Carlo simulation of hot electron propagation in silicon using both elastic and inelastic scattering cross-sections, the mean minimum range of luminescence excitation can be calculated. This range is estimated as 546±1A for the silicon K-edge (∼ 1839eV), but is reduced to 8.9±0.1A for the silicon L 2,3 -edge (∼ 99eV). From known porous silicon properties, it is concluded that this mean minimum range is comparable to the actual range of excitation. Hence, more localised structural information may be obtained from L 2,3 -edge XEOL measurements. This important difference between the two spectra has been neglected in previous studies. Simultaneous measurements of the XEOL and total electron yield (TEY) x-ray absorption spectra (XAS) have been conducted at both the silicon K-edge and L 2,3 -edge for various porous silicon samples and related materials. Measurements have been conducted at the Si K-edge on a rapid thermally oxidised (RTO) porous silicon sample. XEOL spectra yield two distinct luminescence bands in the visible region. From multi-bunch wavelength-selective XEOL measurements, it is concluded that there are blue luminescent defective silica sites together with a red luminescent site originating from silicon-like material. The spectral time decay curve under pulsed x-ray excitation gives two distinct decay components; one fast in the range of a few nanoseconds and the other slow in the range of microseconds. Time-resolved XEOL measurements in single-bunch mode show that the fast band mirrors the blue wavelength XEOL whereas the slow band correlates with the

Spatio-temporal distributions of meso convective systems in NE China and its vicinity

Science.gov (United States)

Yuan, Meiying; Li, Zechun; Zhang, Xiaoling; Li, Xun

2008-08-01

Based on the IR cloud imagery from the Chinese FY-2C satellite for June ~ August, 2005 - 2007, statistics is undertaken of meso convective systems (MCS) over NE China and its neighborhood, obtaining the space - time distributions of MCS. MCS include elliptical type( MCC's) , persistent elongated type (PECS's), in shape. Dividing the total MCS into MαMCS, MβMCS and MCC (PECS) . Results show that the number of meso-α MCS (dominantly PECS's) is considerably more than that of meso-β MCS (largely MCCss), which are observed mainly in the NE China plain and Daxing'an Mountains, especially in the entrance to the plain as well as its central ~ northern portion; the MCS occur mainly in June ~ August, particularly in June; the extratropical MCS show two peak phases, one being in 1500-2200 BST the other being 0000-0700 BST as the secondary peaking interval.

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.

Immobilization of Styrene-acrylamide Co-polymer on Either Silica Particles or Inner Surface of Silica Capillary for the Separation of D-Glucose Anomers

International Nuclear Information System (INIS)

Ali, Faiz; Kim, Yune Sung; Cheong, Won Jo

2014-01-01

Styrene-acrylamide co-polymer was immobilized on porous partially sub-2 μm silica monolith particles and inner surface of fused silica capillary (50 μm ID and 28 cm length) to result in μLC and CEC stationary phases, respectively, for separation of anomeric D-glucose derivatives. Reversed addition-fragmentation transfer (RAFT) polymerization was incorporated to induce surface polymerization. Acrylamide was employed to incorporate amide-functionality in the stationary phase. The resultant μLC and CEC stationary phases were able to separate isomers of D-glucose derivatives with high selectivity and efficiency. The mobile phase of 75/ 25 (v/v) acetonitrile (ACN)/water with 0.1% TFA, was used for HPLC with a packed column (1 mm ID, 300 mm length). The effects of pH and ACN composition on anomeric separation of D-glucose in CEC have been examined. A mobile phase of 85/15 (v/v) ACN/30 mM sodium acetate pH 6.7 was found the optimized mobile phase for CEC. The CEC stationary phase also gave good separation of other saccharides such as maltotriose and Dextran 1500 (MW∼1500) with good separation efficiency (number of theoretical plates ∼300,000/m)

Immobilization of Styrene-acrylamide Co-polymer on Either Silica Particles or Inner Surface of Silica Capillary for the Separation of D-Glucose Anomers

Energy Technology Data Exchange (ETDEWEB)

Ali, Faiz; Kim, Yune Sung; Cheong, Won Jo [Inha Univ., Incheon (Korea, Republic of)

2014-02-15

Styrene-acrylamide co-polymer was immobilized on porous partially sub-2 μm silica monolith particles and inner surface of fused silica capillary (50 μm ID and 28 cm length) to result in μLC and CEC stationary phases, respectively, for separation of anomeric D-glucose derivatives. Reversed addition-fragmentation transfer (RAFT) polymerization was incorporated to induce surface polymerization. Acrylamide was employed to incorporate amide-functionality in the stationary phase. The resultant μLC and CEC stationary phases were able to separate isomers of D-glucose derivatives with high selectivity and efficiency. The mobile phase of 75/ 25 (v/v) acetonitrile (ACN)/water with 0.1% TFA, was used for HPLC with a packed column (1 mm ID, 300 mm length). The effects of pH and ACN composition on anomeric separation of D-glucose in CEC have been examined. A mobile phase of 85/15 (v/v) ACN/30 mM sodium acetate pH 6.7 was found the optimized mobile phase for CEC. The CEC stationary phase also gave good separation of other saccharides such as maltotriose and Dextran 1500 (MW∼1500) with good separation efficiency (number of theoretical plates ∼300,000/m)

A Novel Environmental Route to Ambient Pressure Dried Thermal Insulating Silica Aerogel via Recycled Coal Gangue

Directory of Open Access Journals (Sweden)

Pinghua Zhu

2016-01-01

Full Text Available Coal gangue, one of the main hazardous emissions of purifying coal from coalmine industry, is rich in silica and alumina. However, the recycling of the waste is normally restricted by less efficient techniques and low attractive output; the utilization of such waste is still staying lower than 15%. In this work, the silica aerogel materials were synthesized by using a precursor extracted from recycled silicon-rich coal gangue, followed by a single-step surface silylation and ambient pressure drying. A low density (~0.19 g/cm3 nanostructured aerogel with a 3D open porous microstructure and high surface area (~690 m2/g was synthesized, which presents a superior thermal insulation performance (~26.5 mW·m−1·K−1 of a plane packed of 4-5 mm granules which was confirmed by transient hot-wire method. This study offers a new facile route to the synthesis of insulating aerogel material by recycling solid waste coal gangue and presents a potential cost reduction of industrial production of silica aerogels.

Preparation of monodisperse porous silica particles using poly(glycidyl methacrylate) microspheres as a template

Czech Academy of Sciences Publication Activity Database

Grama, Silvia; Horák, Daniel

2015-01-01

Roč. 64, Suppl. 1 (2015), S11-S17 ISSN 0862-8408 R&D Projects: GA MŠk(CZ) EE2.3.30.0029; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:61389013 Keywords : microspheres * monodisperse * silica Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.643, year: 2015 http://www.biomed.cas.cz/physiolres/pdf/64%20Suppl%201/64_S11.pdf

Arrays of Hollow Silica Half-Nanospheres Via the Breath Figure Approach

KAUST Repository

Gao, Yangqin; Hou, Yuanfang; Beaujuge, Pierre

2015-01-01

Breath figures (BFs) are patterns of liquid droplets that usually form upon condensation on a cold surface. Earlier work has shown that BFs can be used to produce continuous films of porous honeycomb-structured patterns on various types of materials, paving the path to a number of important applications such as the manufacturing of highly ordered nano- and micron-sized templates, micro lenses, and superhydrophobic coatings. It is worth noting, however, that few new findings have been reported in this area in recent years, limiting pursuits of novel architectures and key applications. In this report, an alternative method is described by which arrays of hollow silica half-nanospheres can be produced via BF templates. In the present method, a chemical vapor deposition (CVD) protocol performed while the BF is formed on a glass substrate yields a nanostructured pattern of silica half-spheres, which size (100-700 nm) and density across the glass surface vary with substrate modification and with the relative rates of water condensation and hydrolysis from silica precursors (a process carried out at room temperature). This method of forming arrays of hollow half-nanospheres via the BF approach may be applicable to various other oxides and a broad range of substrates including large-area flexible plastics. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Arrays of Hollow Silica Half-Nanospheres Via the Breath Figure Approach

KAUST Repository

Gao, Yangqin

2015-04-21

Breath figures (BFs) are patterns of liquid droplets that usually form upon condensation on a cold surface. Earlier work has shown that BFs can be used to produce continuous films of porous honeycomb-structured patterns on various types of materials, paving the path to a number of important applications such as the manufacturing of highly ordered nano- and micron-sized templates, micro lenses, and superhydrophobic coatings. It is worth noting, however, that few new findings have been reported in this area in recent years, limiting pursuits of novel architectures and key applications. In this report, an alternative method is described by which arrays of hollow silica half-nanospheres can be produced via BF templates. In the present method, a chemical vapor deposition (CVD) protocol performed while the BF is formed on a glass substrate yields a nanostructured pattern of silica half-spheres, which size (100-700 nm) and density across the glass surface vary with substrate modification and with the relative rates of water condensation and hydrolysis from silica precursors (a process carried out at room temperature). This method of forming arrays of hollow half-nanospheres via the BF approach may be applicable to various other oxides and a broad range of substrates including large-area flexible plastics. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Overview of the Meso-NH model version 5.4 and its applications

Directory of Open Access Journals (Sweden)

C. Lac

2018-05-01

Full Text Available This paper presents the Meso-NH model version 5.4. Meso-NH is an atmospheric non hydrostatic research model that is applied to a broad range of resolutions, from synoptic to turbulent scales, and is designed for studies of physics and chemistry. It is a limited-area model employing advanced numerical techniques, including monotonic advection schemes for scalar transport and fourth-order centered or odd-order WENO advection schemes for momentum. The model includes state-of-the-art physics parameterization schemes that are important to represent convective-scale phenomena and turbulent eddies, as well as flows at larger scales. In addition, Meso-NH has been expanded to provide capabilities for a range of Earth system prediction applications such as chemistry and aerosols, electricity and lightning, hydrology, wildland fires, volcanic eruptions, and cyclones with ocean coupling. Here, we present the main innovations to the dynamics and physics of the code since the pioneer paper of Lafore et al. (1998 and provide an overview of recent applications and couplings.

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.

A study of luminescence from silicon-rich silica fabricated by plasma enhanced chemical vapour deposition

International Nuclear Information System (INIS)

Trwoga, P.F.

1998-01-01

Silicon is the most studied electronic material known to man and dominates the electronics industry in its use as a semiconductors for nearly all integrated electronics. However, optoelectronics is almost entirely based on III-V materials. This technology is used because silicon is a very inefficient light source, whereas the III-V band structure can lend itself to efficient light emission by electron injection. However, due to the overwhelming dominance of silicon based electronics it is still a highly desirable goal to generate light efficiently from silicon based materials. Recently, studies have demonstrated that efficient visible luminescence can be obtained from certain novel forms of silicon. These materials include porous silicon, hydrogenated amorphous silicon, and silicon-rich silica (SiO x x x is studied in detail; in addition, electroluminescence and rare-earth doping of silicon-rich silica is also addressed. (author)

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.

A Mathematical Model of Repeated Impregnation of Porous Bodies with Solutions of Polymers

Directory of Open Access Journals (Sweden)

I. V. Glebov

2015-01-01

Full Text Available The paper describes basic methods of impregnating porous bodies with solutions of polymers and their use to manufacture prepregs. It also describes the existing methods of manufacturing multilayer prepregs to produce aerospace coating of the spacecraft "Soyuz". It is shown that these prepregs have to meet high requirements for the content of the polymer, as compared with other composite materials, about 35 - 40% of the mass. Methods used for their manufacturing are long-term and non-controllable. The assumption is made that using the vacuum impregnation technology of a woven material will allow to accelerate the manufacturing process of these prepregs and improve their quality.In reviewing the technical literature have been found works on modeling the processes of impregnation, but they are aimed only at studying the speed of the woven material impregnation by various fluids and determining the time of impregnation. There were no models found to define prepreg parameters during the process of multiple impregnations. The aim of this work is to develop the simple mathematical model, which enables us to predict the polymer content of volatile products in the prepreg after each cycle of multiple impregnation of woven material with a solution of the polymer.To consider the vacuum impregnation method are used the prepregs based on silica and silica-nylon stitch-bonding fabric and bakelite varnish LBS-4 containing 50 - 60% of phenol resin and the solvent with minor impurities of pure phenol and water, as an example. To describe the process of vacuum impregnation of the porous work-piece is developed a mathematical description of the process of filling the porous space of the material with a varnish. It is assumed that the varnish components fill the porous space of the material in the same proportion as they are contained in the varnish.It is shown that a single impregnation cannot ensure the content of phenol resin in the prepreg over 32%, which does

Densification of zirconia films by coevaporation with silica

International Nuclear Information System (INIS)

Feldman, A.; Farabaugh, E.N.

1985-04-01

Optical films of zirconia have been receiving considerable attention because of their potential use as the high-index layer in multilayer optical coatings for the ultraviolet portion of the spectrum. Several problems are associated with electron-beam deposited zirconia films, including index instability and index inhomogeneity. The index instability is caused by the adsorption and the desorption of water in the porous columnar structure of the zirconia films. Index inhomogeneity is due to the inhomogeneous structure in the films. Recent work has shown that the first several tens of nanometers of a film possess a cubic structure, whereas the outmost layers possess a monoclinic structure. One approach for producing bulk-like zirzonia films that is receiving considerable attention at present is ion-assisted electron-beam deposition. This is because the method has successfully produced zirconia films having bulk-like densities and refractive indices that show insignificant sensitivity to water adsorption. In this paper a similar effect is demonstrated when mixed zirconia:silica films are produced by coevaporation from independent electron-beam sources, and, in particular, it is shown that the admixture of a small amount of silica with the zirconia produces a film possessing a higher refractive index than a pure zirconia film

The Meso-level Structure of F/OSS Collaboration Network

DEFF Research Database (Denmark)

Conald, Guido; Rullani, Francesco

2010-01-01

Social networks in Free/Open Source Software (F/OSS) have been usually analyzed at the level of the single project e.g., [6], or at the level of a whole ecology of projects, e.g., [33]. In this paper, we also investigate the social network generated by developers who collaborate to one or multiple...... F/OSS projects, but we focus on the less-studied meso-level structure emerging when applying to this network a community-detection technique. The network of ‘communities’ emerging from this analysis links sub-groups of densely connected developers, sub-groups that are smaller than the components...... of the network but larger than the teams working on single projects. Our results reveal the complexity of this meso-level structure, where several dense sub-groups of developers are connected by sparse collaboration among different sub-groups. We discuss the theoretical implications of our findings...

Mesoporous silicas with covalently immobilized β-cyclodextrin moieties: synthesis, structure, and sorption properties

Science.gov (United States)

Roik, Nadiia V.; Belyakova, Lyudmila A.; Trofymchuk, Iryna M.; Dziazko, Marina O.; Oranska, Olena I.

2017-09-01

Mesoporous silicas with chemically attached macrocyclic moieties were successfully prepared by sol-gel condensation of tetraethyl orthosilicate and β-cyclodextrin-silane in the presence of a structure-directing agent. Introduction of β-cyclodextrin groups into the silica framework was confirmed by the results of IR spectral, thermogravimetric, and quantitative chemical analysis of surface compounds. The porous structure of the obtained materials was characterized by nitrogen adsorption-desorption measurements, powder X-ray diffraction, transmission electron microscopy, and dynamic light scattering. It was found that the composition of the reaction mixture used in β-cyclodextrin-silane synthesis significantly affects the structural parameters of the resulting silicas. The increase in (3-aminopropyl)triethoxysilane as well as the coupling agent content in relation to β-cyclodextrin leads ultimately to the lowering or complete loss of hexagonal arrangement of pore channels in the synthesized materials. Formation of hexagonally ordered mesoporous structure was observed at molar composition of the mixture 0.049 TEOS:0.001 β-CD-silane:0.007 CTMAB:0.27 NH4OH:7.2 H2O and equimolar ratio of components in β-CD-silane synthesis. The sorption of alizarin yellow on starting silica and synthesized materials with chemically attached β-cyclodextrin moieties was studied in phosphate buffer solutions with pH 7.0. Experimental results of the dye equilibrium sorption were analyzed using Langmuir, Freundlich, and Redlich-Peterson isotherm models. It was proved that the Redlich-Peterson isotherm model is the most appropriate for fitting the equilibrium sorption of alizarin yellow on parent silica with hexagonally arranged mesoporous structure as well as on modified one with chemically immobilized β-cyclodextrin groups. [Figure not available: see fulltext.

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.

Stellate macroporous silica nanospheres in bio-macromolecules encapsulation and delivery

Science.gov (United States)

Chi, Hao-Hsin

This project focused on using mesoporous silica as a solid support to encapsulate enzymes for operating a highly economic, and recyclable biomass processing system. The main objective is to turn non-food biomass sources into food products. Enzymes are macromolecules with the structural backbone of proteins or ribonucleic acid sequences (RNAs) which work as catalysts in living organisms. Enzymes have the advantage of being the least contaminating catalyst due to normal catalyst might generate toxic by-product, and preferable to organic and inorganic catalysts, especially when used for product related to human used, which require biocompatibility of final product. However, there are several disadvantages in enzyme utilization. Their fabrication is time-consuming and requires elaborated molecular biology processes. Most of the enzymes need well-defined reaction conditions to be functional and operate at high yield. Unfortunately, although they are reusable as normal catalysts, it proves difficult to extract or reuse the enzymes from a reaction. Also, enzyme molecules are easily degradable and demand proper storage. To overcome some of the disadvantages, especially regarding stability to degradation, recovery, and reusability, immobilization of enzyme on solid support has become a thriving methodology. In recent years, mesoporous silica nanomaterials(MSN) have been at the forefront of enzyme immobilization given their extensive surface area, which provides capability to increase enzyme loading and for their demonstrate ability to protect enzyme from degradation, thus enabling high recyclability. Mesoporous silica is biocompatible and has already been used for several applications included. Catalysis, drug delivery, and Bio-imaging. Previously published research utilized mesoporous silica to deliver drugs, DNAs, RNAs or encapsulate single enzyme. The objective of this research is completed to develop a new porous silica platform that is unique in its porosity structure

Heavy metals adsorption by novel EDTA-modified chitosan-silica hybrid materials.

Science.gov (United States)

Repo, Eveliina; Warchoł, Jolanta K; Bhatnagar, Amit; Sillanpää, Mika

2011-06-01

Novel adsorbents were synthesized by functionalizing chitosan-silica hybrid materials with (ethylenediaminetetraacetic acid) EDTA ligands. The synthesized adsorbents were found to combine the advantages of both silica gel (high surface area, porosity, rigid structure) and chitosan (surface functionality). The Adsorption potential of hybrid materials was investigated using Co(II), Ni(II), Cd(II), and Pb(II) as target metals by varying experimental conditions such as pH, contact time, and initial metal concentration. The kinetic results revealed that the pore diffusion process played a key role in adsorption kinetics, which might be attributed to the porous structure of synthesized adsorbents. The obtained maximum adsorption capacities of the hybrid materials for the metal ions ranged from 0.25 to 0.63 mmol/g under the studied experimental conditions. The adsorbent with the highest chitosan content showed the best adsorption efficiency. Bi-Langmuir and Sips isotherm model fitting to experimental data suggested the surface heterogeneity of the prepared adsorbents. In multimetal solutions, the hybrid adsorbents showed the highest affinity toward Pb(II). Copyright © 2011 Elsevier Inc. All rights reserved.

On Selective Derivatization of meso-Tetraarylporphyrins (A Microreview)

International Nuclear Information System (INIS)

Ostrowski, S.

2003-01-01

The studies on selective derivatization in one or two aromatic rings of meso-tetraarylporphyrin systems (and their zinc and copper complexes) using (a) selective nitration, (b) Vicarious Nucleophilic Substitution of Hydrogen(VNS), and (c) alkylation of the above intermediates with alkyl halides, are reported. The stepwise selective nitration of meso-aryl substituted porphyrins with fuming yellow nitric acid (d= 1.53) at the tempreture 0 deg to 20 deg results in the formation of 5-(4-nitroaryl)- 10, 15, 20-triarylporphyrins, 5,10-bis(4-nitroaryl)-15,20-diarylporphrins or trinitro- and tetranitro-derivatives, respectively, in good or reasonable yield. The above intermediates, after simple transformation to their copper or zinc complexes react with carbanions bearing leaving groups at the carbanionic center, according to VNS scheme. This reaction can be also realized at low temperature (-30 deg- 40 deg) without complexation of the parent nitroporphyrins. Alkylation of the products obtained with alkyl halides or alkyl halides bearing multiple bonds in the carbon chain led to useful compounds for further functionalization . (Author) 53 refs., 7sches., 4 figs

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....

Properties of BaTiO.sub.3./sub. confined in nanoporous Vycor and artificial opal silica

Czech Academy of Sciences Publication Activity Database

Nuzhnyy, Dmitry; Vaněk, Přemysl; Petzelt, Jan; Bovtun, Viktor; Kempa, Martin; Gregora, Ivan; Savinov, Maxim; Krupková, Radmila; Studnička, Václav; Buršík, Josef; Samoylovich, M.I.; Schranz, W.

2010-01-01

Roč. 4, č. 3 (2010), s. 215-223 ISSN 1820-6131 R&D Projects: GA AV ČR KAN301370701 Grant - others:FWF(AT) P19284-N20 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40320502 Keywords : nanocomposite * confined BaTiO 3 * porous silica * stiffened soft mode * effective dielectric properties Subject RIV: BM - Solid Matter Physics ; Magnetism http://www.tf.uns.ac.rs/publikacije/PAC/pdf/PAC%2009%2013.pdf

Molecular dynamics in porous media studied by nuclear magnetic resonance techniques

International Nuclear Information System (INIS)

Mattea, C.

2006-01-01

Field cycling NMR relaxometry was used to study dynamics of fluids under confinement in different scenarios: fluids flowing through porous media, fluids partially filling porous media and polymer melts in nanoscopic pores. Diffusion in partially filled porous media was also studied with the aid of an NMR diffusometry technique. It is shown that hydrodynamic flow influences the spin-lattice relaxation rate of water confined in mesoscopic porous media under certain conditions. The effect is predicted by an analytical theory and Monte Carlo simulations, and confirmed experimentally by field-cycling NMR relaxometry. Field-cycling NMR relaxometry has been applied to polar and non polar adsorbates in partially filled silica porous glasses. The dependence of the spin-lattice relaxation rate on the filling degree shows that limits for slow and fast exchange between different phases can be distinguished and identified depending on the pore size and polarity of the solvents. Diffusion in the same unsaturated systems was studied with the aid of NMR diffusometry technique. The effective diffusion coefficient of solvents with different polarities displays opposite tendencies as a function of the liquid content. A two-phase fast exchange model including Knudsen and ordinary diffusion and different effective tortuosities is presented accounting for these phenomena. In the case of polymer melts confined in narrow artificial tubes of a porous solid matrix with variable diameter (9 to 57 nm), the characteristics of reptation were experimentally verified using proton field cycling NMR relaxometry technique. This observation is independent of the molecular mass and pore size. In bulk, the same polymer melts show either Rouse or renormalized Rouse dynamics, depending on the molecular mass. The polymers under confinement show features specific for reptation even with a pore diameter 15 times larger than the Flory radius while bulk melts of the same polymers do not. (orig.)

Meso-ester and carboxylic acid substituted BODIPYs with far-red and near-infrared emission for bioimaging applications

KAUST Repository

Ni, Yong; Zeng, Lintao; Kang, Namyoung; Huang, Kuo-Wei; Wang, Liang; Zeng, Zebing; Chang, Young-Tae; Wu, Jishan

2014-01-01

-6) become partially soluble in water, and their absorptions and emissions are located in the far-red or near-infrared region. Three synthetic approaches are attempted to access the meso-carboxylic acid (COOH)-substituted BODIPYs 7 and 8 from the meso

A three-dimensional meso-scale modeling for helium bubble growth in metals

International Nuclear Information System (INIS)

Suzudo, T.; Kaburaki, H.; Wakai, E.

2007-01-01

A three-dimensional meso-scale computer model using a Monte-Carlo simulation method has been proposed to simulate the helium bubble growth in metals. The primary merit of this model is that it enables the visual comparison between the microstructure observed by the TEM imaging and those by calculations. The modeling is so simple that one can control easily the calculation by tuning parameters. The simulation results are confirmed by the ideal gas law and the capillary relation. helium bubble growth, meso-scale modeling, Monte-Carlo simulation, the ideal gas law and the capillary relation. (authors)

Inclusion of gold nanoparticles in meso-porous silicon for the SERS analysis of cell adhesion on nano-structured surfaces

KAUST Repository

Coluccio, M.L.

2016-03-25

The study and the comprehension of the mechanism of cell adhesion and cell interaction with a substrate is a key point when biology and medicine meet engineering. This is the case of several biomedical applications, from regenerative medicine and tissue engineering to lab on chip and many others, in which the realization of the appropriate artificial surface allows the control of cell adhesion and proliferation. In this context, we aimed to design and develop a fabrication method of mesoporous (MeP) silicon substrates, doped with gold nanoparticles, in which we combine the capability of porous surfaces to support cell adhesion with the SERS capabilities of gold nanoparticles, to understand the chemical mechanisms of cell/surface interaction. MeP Si surfaces were realized by anodization of a Si wafer, creating the device for cell adhesion and growth. Gold nanoparticles were deposited on porous silicon by an electroless technique. We thus obtained devices with superior SERS capabilities, whereby cell activity may be controlled using Raman spectroscopy. MCF-7 breast cancer cells were cultured on the described substrates and SERS maps revealing the different expression and distribution of adhesion molecules were obtained by Raman spectroscopic analyses.

Charge Transfer Mechanism in Titanium-Doped Microporous Silica for Photocatalytic Water-Splitting Applications

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Wendi Sapp

2016-02-01

Full Text Available Solar energy conversion into chemical form is possible using artificial means. One example of a highly-efficient fuel is solar energy used to split water into oxygen and hydrogen. Efficient photocatalytic water-splitting remains an open challenge for researchers across the globe. Despite significant progress, several aspects of the reaction, including the charge transfer mechanism, are not fully clear. Density functional theory combined with density matrix equations of motion were used to identify and characterize the charge transfer mechanism involved in the dissociation of water. A simulated porous silica substrate, using periodic boundary conditions, with Ti4+ ions embedded on the inner pore wall was found to contain electron and hole trap states that could facilitate a chemical reaction. A trap state was located within the silica substrate that lengthened relaxation time, which may favor a chemical reaction. A chemical reaction would have to occur within the window of photoexcitation; therefore, the existence of a trapping state may encourage a chemical reaction. This provides evidence that the silica substrate plays an integral part in the electron/hole dynamics of the system, leading to the conclusion that both components (photoactive materials and support of heterogeneous catalytic systems are important in optimization of catalytic efficiency.

LSP Studies As a Quest For Meso-Level Regularities

DEFF Research Database (Denmark)

Engberg, Jan

2015-01-01

the suggested type of analysis. I proceed to present Knowledge Communication as theoretical-methodological framework of such analyses, followed by a presentation of the differences between a micro, a macro and a meso level approach to studying specialized communication. In the last part of the paper, I...

Structure study of the tri-continuous mesoporous silica IBN-9 by electron crystallography

KAUST Repository

Zhang, Daliang

2011-12-01

High resolution electron microscopy (HRTEM) has unique advantages for structural determination of nano-sized porous materials compared to X-ray diffraction, because it provides the important structure factor phase information which is lost in diffraction. Here we demonstrate the structure determination of the first tri-continuous mesoporous silica IBN-9 by electron crystallography. IBN-9 has a hexagonal unit cell with the space group P6 3/mcm and a = 88.4 , c = 84.3 . HRTEM images taken along three main directions, [0 0 1], [11̄0] and [1 0 0] were combined to reconstruct the 3D electrostatic potential map, from which the tri-continuous pore structure of IBN-9 was discovered. The different steps of structure determination of unknown mesoporous structures by electron crystallography are described in details. Similar procedures can also be applied for structure determination of other porous and nonporous crystalline materials. © 2011 Elsevier Inc. All rights reserved.

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

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.

Silica-grafted ionic liquids for revealing the respective charging behaviors of cations and anions in supercapacitors.

Science.gov (United States)

Dou, Qingyun; Liu, Lingyang; Yang, Bingjun; Lang, Junwei; Yan, Xingbin

2017-12-19

Supercapacitors based on activated carbon electrodes and ionic liquids as electrolytes are capable of storing charge through the electrosorption of ions on porous carbons and represent important energy storage devices with high power delivery/uptake. Various computational and instrumental methods have been developed to understand the ion storage behavior, however, techniques that can probe various cations and anions of ionic liquids separately remain lacking. Here, we report an approach to monitoring cations and anions independently by using silica nanoparticle-grafted ionic liquids, in which ions attaching to silica nanoparticle cannot access activated carbon pores upon charging, whereas free counter-ions can. Aided by this strategy, conventional electrochemical characterizations allow the direct measurement of the respective capacitance contributions and acting potential windows of different ions. Moreover, coupled with electrochemical quartz crystal microbalance, this method can provide unprecedented insight into the underlying electrochemistry.

Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment.

Science.gov (United States)

Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

2015-01-01

Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits.

Highly porous layers of silica nanospheres sintered by drying: scaling up of the elastic properties of the beads to the macroscopic mechanical properties.

Science.gov (United States)

Lesaine, Arnaud; Bonamy, Daniel; Gauthier, Georges; Rountree, Cindy L; Lazarus, Véronique

2018-05-16

Layers obtained by drying a colloidal dispersion of silica spheres are found to be a good benchmark to test the elastic behaviour of porous media, in the challenging case of high porosities and nano-sized microstructures. Classically used for these systems, Kendall's approach explicitly considers the effect of surface adhesive forces onto the contact area between the particles. This approach provides the Young's modulus using a single adjustable parameter (the adhesion energy) but provides no further information on the tensorial nature and possible anisotropy of elasticity. On the other hand, homogenization approaches (e.g. rule of mixtures, and Eshelby, Mori-Tanaka and self-consistent schemes), based on continuum mechanics and asymptotic analysis, provide the stiffness tensor from the knowledge of the porosity and the elastic constants of the beads. Herein, the self-consistent scheme accurately predicts both bulk and shear moduli, with no adjustable parameter, provided the porosity is less than 35%, for layers composed of particles as small as 15 nm in diameter. Conversely, Kendall's approach is found to predict the Young's modulus over the full porosity range. Moreover, the adhesion energy in Kendall's model has to be adjusted to a value of the order of the fracture energy of the particle material. This suggests that sintering during drying leads to the formation of covalent siloxane bonds between the particles.

Noble Metal Immersion Spectroscopy of Silica Alcogels and Aerogels

Science.gov (United States)

Smith, David D.; Sibille, Laurent; Cronise, Raymond J.; Noever, David A.

1998-01-01

We have fabricated aerogels containing gold and silver nanoparticles for gas catalysis applications. By applying the concept of an average or effective dielectric constant to the heterogeneous interlayer surrounding each particle, we extend the technique of immersion spectroscopy to porous or heterogeneous media. Specifically, we apply the predominant effective medium theories for the determination of the average fractional composition of each component in this inhomogeneous layer. Hence, the surface area of metal available for catalytic gas reaction is determined. The technique is satisfactory for statistically random metal particle distributions but needs further modification for aggregated or surfactant modified systems. Additionally, the kinetics suggest that collective particle interactions in coagulated clusters are perturbed during silica gelation resulting in a change in the aggregate geometry.

Synthesis and crystallographic analysis of meso-2,3-difluoro-1,4-butanediol and meso-1,4-dibenzyloxy-2,3-difluorobutane

Directory of Open Access Journals (Sweden)

Bruno Linclau

2010-06-01

Full Text Available A large-scale synthesis of meso-2,3-difluoro-1,4-butanediol in 5 steps from (Z-but-2-enediol is described. Crystallographic analysis of the diol and the corresponding benzyl ether reveals an anti conformation of the vicinal difluoride moiety. Monosilylation of the diol is high-yielding but all attempts to achieve chain extension through addition of alkyl Grignard and acetylide nucleophiles failed.

Meso-scale effects of tropical deforestation in Amazonia: preparatory LBA modelling studies

Directory of Open Access Journals (Sweden)

A. J. Dolman

1999-08-01

Full Text Available As part of the preparation for the Large-Scale Biosphere Atmosphere Experiment in Amazonia, a meso-scale modelling study was executed to highlight deficiencies in the current understanding of land surface atmosphere interaction at local to sub-continental scales in the dry season. Meso-scale models were run in 1-D and 3-D mode for the area of Rondonia State, Brazil. The important conclusions are that without calibration it is difficult to model the energy partitioning of pasture; modelling that of forest is easier due to the absence of a strong moisture deficit signal. The simulation of the boundary layer above forest is good, above deforested areas (pasture poor. The models' underestimate of the temperature of the boundary layer is likely to be caused by the neglect of the radiative effects of aerosols caused by biomass burning, but other factors such as lack of sufficient entrainment in the model at the mixed layer top may also contribute. The Andes generate patterns of subsidence and gravity waves, the effects of which are felt far into the Rondonian area The results show that the picture presented by GCM modelling studies may need to be balanced by an increased understanding of what happens at the meso-scale. The results are used to identify key measurements for the LBA atmospheric meso-scale campaign needed to improve the model simulations. Similar modelling studies are proposed for the wet season in Rondonia, when convection plays a major role.Key words. Atmospheric composition and structure (aerosols and particles; biosphere-atmosphere interactions · Meterology and atmospheric dynamics (mesoscale meterology

Meso-scale effects of tropical deforestation in Amazonia: preparatory LBA modelling studies

Directory of Open Access Journals (Sweden)

A. J. Dolman

Full Text Available As part of the preparation for the Large-Scale Biosphere Atmosphere Experiment in Amazonia, a meso-scale modelling study was executed to highlight deficiencies in the current understanding of land surface atmosphere interaction at local to sub-continental scales in the dry season. Meso-scale models were run in 1-D and 3-D mode for the area of Rondonia State, Brazil. The important conclusions are that without calibration it is difficult to model the energy partitioning of pasture; modelling that of forest is easier due to the absence of a strong moisture deficit signal. The simulation of the boundary layer above forest is good, above deforested areas (pasture poor. The models' underestimate of the temperature of the boundary layer is likely to be caused by the neglect of the radiative effects of aerosols caused by biomass burning, but other factors such as lack of sufficient entrainment in the model at the mixed layer top may also contribute. The Andes generate patterns of subsidence and gravity waves, the effects of which are felt far into the Rondonian area The results show that the picture presented by GCM modelling studies may need to be balanced by an increased understanding of what happens at the meso-scale. The results are used to identify key measurements for the LBA atmospheric meso-scale campaign needed to improve the model simulations. Similar modelling studies are proposed for the wet season in Rondonia, when convection plays a major role.

Key words. Atmospheric composition and structure (aerosols and particles; biosphere-atmosphere interactions · Meterology and atmospheric dynamics (mesoscale meterology

Porous SiO2 nanofiber grafted novel bioactive glass-ceramic coating: A structural scaffold for uniform apatite precipitation and oriented cell proliferation on inert implant.

Science.gov (United States)

Das, Indranee; De, Goutam; Hupa, Leena; Vallittu, Pekka K

2016-05-01

A composite bioactive glass-ceramic coating grafted with porous silica nanofibers was fabricated on inert glass to provide a structural scaffold favoring uniform apatite precipitation and oriented cell proliferation. The coating surfaces were investigated thoroughly before and after immersion in simulated body fluid. In addition, the proliferation behavior of fibroblast cells on the surface was observed for several culture times. The nanofibrous exterior of this composite bioactive coating facilitated homogeneous growth of flake-like carbonated hydroxyapatite layer within a short period of immersion. Moreover, the embedded porous silica nanofibers enhanced hydrophilicity which is required for proper cell adhesion on the surface. The cells proliferated well following a particular orientation on the entire coating by the assistance of nanofibrous scaffold-like structural matrix. This newly engineered composite coating was effective in creating a biological structural matrix favorable for homogeneous precipitation of calcium phosphate, and organized cell growth on the inert glass surface. Copyright © 2016 Elsevier B.V. All rights reserved.

Hierarchical meso/macro-porous carbon fabricated from dual MgO templates for direct electron transfer enzymatic electrodes

Science.gov (United States)

Funabashi, Hiroto; Takeuchi, Satoshi; Tsujimura, Seiya

2017-03-01

We designed a three-dimensional (3D) hierarchical pore structure to improve the current production efficiency and stability of direct electron transfer-type biocathodes. The 3D hierarchical electrode structure was fabricated using a MgO-templated porous carbon framework produced from two MgO templates with sizes of 40 and 150 nm. The results revealed that the optimal pore composition for a bilirubin oxidase-catalysed oxygen reduction cathode was a mixture of 33% macropores and 67% mesopores (MgOC33). The macropores improve mass transfer inside the carbon material, and the mesopores improve the electron transfer efficiency of the enzyme by surrounding the enzyme with carbon.

Innovative synthesis of meso-structured YSZ using V2O5 complex fluids as a template

International Nuclear Information System (INIS)

Guiot, Camille; Grandjean, Stephane; Batail, Patrick

2008-01-01

Full text of publication follows: Within the framework of generation IV nuclear reactors, the prospect of a closed fuel cycle generate a need for new advanced materials integrating the actinides jointly. Researches are conducted on fuel material precursors synthesized by soft chemistry processes, which allow a fine control of the homogeneity and ordering at a nano-scale[1]. In a view to meso-structure an inorganic matrix, recent studies[2,3] have highlighted the potential of mineral liquid crystals as templates in new soft chemistry synthesis routes. The studies presently exposed relate to an original synthesis of an inorganic-inorganic hybrid material consisting in a main zirconia matrix tem plated by ribbon-like vanadium pentoxide. After eliminating the V 2 O 5 template, the obtained solid is to be a meso-porous material with ordered pores, and becomes a prime choice material, for example to immobilize actinides. The zirconia matrix has been chosen for its ability to host actinides, which are surrogated by neodymium. It is also a preliminary material for the study of the synthesis of uranium oxide based materials, thus preventing from the drawbacks of working with radioactive materials. The vanadium pentoxide is used as a template since it structure itself as ribbon-like mineral liquid crystals that can be aligned in weak magnetic field; consequently, the final material may be structured at a nano-scale over a macroscopic range. Since the shape of vanadium oxide in solution is very sensitive to the ionic strength of the medium and the pH, the real challenge is to establish a synthesis protocol which is compatible with the presence of vanadium pentoxide, remaining in its ribbon-like liquid crystal form. References: [1] Masson, M.; Grandjean, S.; Lacquement, J.; Bourg, S.; Delauzun, J. M.; Lacombe, J.; Nuclear Engineering and Design, 236 (5-6),516 (2006). [2] Camerel, F.; Gabriel, J.-C.P.; Batail, P.; Adv. Funct. Mater., 13 (5), 377 (2003). [3] Gabriel, J

Speciation of copper diffused in a bi-porous molecular sieve

International Nuclear Information System (INIS)

Huang, C.-H.; Paul Wang, H.; Wei, Y.-L.; Chang, J.-E.

2010-01-01

To better understand diffusion of copper in the micro- and mesopores, speciation of copper in a bi-porous molecular sieve (BPMS) possessing inter-connecting 3-D micropores (0.50-0.55 nm) and 2-D mesopores (4.1 nm) has been studied by X-ray absorption near edge structure (XANES) spectroscopy. It is found that about 77% (16% of CuO nanoparticles and 61% of CuO clusters) and 23% (CuO ads ) of copper can be diffused into the meso- and micropores, respectively, in the BPMS. At least two diffusion steps in the BPMS may be involved: (i) free diffusion of copper in the mesopores and (ii) diffusion-controlled copper migrating into the micropores of the BPMS. The XANES data also indicate that diffusion rate of copper in the BPMS (4.68x10 -5 g/s) is greater than that in the ZSM-5 (1.11x10 -6 g/s) or MCM-41 (1.17x10 -5 g/s).

Speciation of copper diffused in a bi-porous molecular sieve

Science.gov (United States)

Huang, C.-H.; Paul Wang, H.; Wei, Y.-L.; Chang, J.-E.

2010-07-01

To better understand diffusion of copper in the micro- and mesopores, speciation of copper in a bi-porous molecular sieve (BPMS) possessing inter-connecting 3-D micropores (0.50-0.55 nm) and 2-D mesopores (4.1 nm) has been studied by X-ray absorption near edge structure (XANES) spectroscopy. It is found that about 77% (16% of CuO nanoparticles and 61% of CuO clusters) and 23% (CuO ads) of copper can be diffused into the meso- and micropores, respectively, in the BPMS. At least two diffusion steps in the BPMS may be involved: (i) free diffusion of copper in the mesopores and (ii) diffusion-controlled copper migrating into the micropores of the BPMS. The XANES data also indicate that diffusion rate of copper in the BPMS (4.68×10 -5 g/s) is greater than that in the ZSM-5 (1.11×10 -6 g/s) or MCM-41 (1.17×10 -5 g/s).

Enantioselectively controlled release of chiral drug (metoprolol) using chiral mesoporous silica materials

Energy Technology Data Exchange (ETDEWEB)

Guo Zhen; Liu Xianbin; Ng, Siu-Choon; Chen Yuan; Yang Yanhui [School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637459 (Singapore); Du Yu, E-mail: du_yu@jlu.edu.cn, E-mail: yhyang@ntu.edu.sg [College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China)

2010-04-23

Chiral porous materials have attracted burgeoning attention on account of their potential applications in many areas, such as enantioseparation, chiral catalysis, chemical sensors and drug delivery. In this report, chiral mesoporous silica (CMS) materials with various pore sizes and structures were prepared using conventional achiral templates (other than chiral surfactant) and a chiral cobalt complex as co-template. The synthesized CMS materials were characterized by x-ray diffraction, nitrogen physisorption, scanning electron microscope and transmission electron microscope. These CMS materials, as carriers, were demonstrated to be able to control the enantioselective release of a representative chiral drug (metoprolol). The release kinetics, as modeled by the power law equation, suggested that the release profiles of metoprolol were remarkably dependent on the pore diameter and pore structure of CMS materials. More importantly, R- and S-enantiomers of metoprolol exhibited different release kinetics on CMS compared to the corresponding achiral mesoporous silica (ACMS), attributable to the existence of local chirality on the pore wall surface of CMS materials. The chirality of CMS materials on a molecular level was further substantiated by vibrational circular dichroism measurements.

Enantioselectively controlled release of chiral drug (metoprolol) using chiral mesoporous silica materials

International Nuclear Information System (INIS)

Guo Zhen; Liu Xianbin; Ng, Siu-Choon; Chen Yuan; Yang Yanhui; Du Yu

2010-01-01

Chiral porous materials have attracted burgeoning attention on account of their potential applications in many areas, such as enantioseparation, chiral catalysis, chemical sensors and drug delivery. In this report, chiral mesoporous silica (CMS) materials with various pore sizes and structures were prepared using conventional achiral templates (other than chiral surfactant) and a chiral cobalt complex as co-template. The synthesized CMS materials were characterized by x-ray diffraction, nitrogen physisorption, scanning electron microscope and transmission electron microscope. These CMS materials, as carriers, were demonstrated to be able to control the enantioselective release of a representative chiral drug (metoprolol). The release kinetics, as modeled by the power law equation, suggested that the release profiles of metoprolol were remarkably dependent on the pore diameter and pore structure of CMS materials. More importantly, R- and S-enantiomers of metoprolol exhibited different release kinetics on CMS compared to the corresponding achiral mesoporous silica (ACMS), attributable to the existence of local chirality on the pore wall surface of CMS materials. The chirality of CMS materials on a molecular level was further substantiated by vibrational circular dichroism measurements.

Adsorption Characteristics of Water and Silica Gel System for Desalination Cycle

KAUST Repository

Cevallos, Oscar R.

2012-07-01

An adsorbent suitable for adsorption desalination cycles is essentially characterized by a hydrophilic and porous structure with high surface area where water molecules are adsorbed via hydrogen bonding mechanism. Silica gel type A++ possesses the highest surface area and exhibits the highest equilibrium uptake from all the silica gels available in the market, therefore being suitable for water desalination cycles; where adsorbent’s adsorption characteristics and water vapor uptake capacity are key parameters in the compactness of the system; translated as feasibility of water desalination through adsorption technologies. The adsorption characteristics of water vapor onto silica gel type A++ over a temperature range of 30 oC to 60 oC are investigated in this research. This is done using water vapor adsorption analyzer utilizing a constant volume and variable pressure method, namely the Hydrosorb-1000 instrument by Quantachrome. The experimental uptake data is studied using numerous isotherm models, i. e. the Langmuir, Tóth, generalized Dubinin-Astakhov (D-A), Dubinin-Astakhov based on pore size distribution (PSD) and Dubinin-Serpinski (D-Se) isotherm for the whole pressure range, and for a pressure range below 10 kPa, proper for desalination cycles; isotherms type V of the International Union of Pure and Applied Chemistry (IUPAC) classification were exhibited. It is observed that the D-A based on PSD and the D-Se isotherm models describe the best fitting of the experimental uptake data for desalination cycles within a regression error of 2% and 6% respectively. All isotherm models, except the D-A based on PSD, have failed to describe the obtained experimental uptake data; an empirical isotherm model is proposed by observing the behavior of Tóth and D-A isotherm models. The new empirical model describes the water adsorption onto silica gel type A++ within a regression error of 3%. This will aid to describe the advantages of silica gel type A++ for the design of

CH of masonry materials via meshless meso-modeling

Directory of Open Access Journals (Sweden)

Giuseppe Giambanco

2014-07-01

Full Text Available In the present study a multi-scale computational strategy for the analysis of masonry structures is presented. The structural macroscopic behaviour is obtained making use of the Computational Homogenization (CH technique based on the solution of the boundary value problem (BVP of a detailed Unit Cell (UC chosen at the meso-scale and representative of the heterogeneous material. The smallest UC is composed by a brick and half of its surrounding joints, the former assumed to behave elastically while the latter considered with an elastoplastic softening response. The governing equations at the macroscopic level are formulated in the framework of finite element method while the Meshless Method (MM is adopted to solve the BVP at the mesoscopic level. The work focuses on the BVP solution. The consistent tangent stiffness matrix at a macroscopic quadrature point is evaluated on the base of BVP results for the UC together with a localisation procedure. Validation of the MM procedure at the meso-scale level is demonstrated by numerical examples that show the results of the BVP for the simple cases of normal and shear loading of the UC.

Temperature variations of average o-Ps lifetime in porous media

CERN Document Server

Goworek, T; Jasinska, B; Wawryszczuk, J

2000-01-01

Modification of the Tao-Eldrup model is proposed in order to extend its usefulness to the case of porous media. The modification consists in the transition from spherical to capillary geometry and in inclusion of pick-off annihilation from the excited states of a particle in the well. Approximated equations for pick-off constant in these states are given. The model was tested by observing the temperature dependences of o-Ps lifetime in various media. In the case of silica gels and Vycor glass with narrow pores, the model seems to work well, while for larger pores in Vycor unexpectedly long lifetimes appear in the range of lowest temperatures.

1.9 μm superficially porous packing material with radially oriented pores and tailored pore size for ultra-fast separation of small molecules and biomolecules.

Science.gov (United States)

Min, Yi; Jiang, Bo; Wu, Ci; Xia, Simin; Zhang, Xiaodan; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

2014-08-22

In this work, 1.9 μm reversed-phase packing materials with superficially porous structure were prepared to achieve the rapid and high efficient separation of peptides and proteins. The silica particles were synthesized via three steps, nonporous silica particle preparation by a modified seeded growth method, mesoporous shell formation by a one pot templated dissolution and redeposition strategy, and pore size expansion via acid-refluxing. By such a method, 1.9 μm superficially porous materials with 0.18 μm shell thickness and tailored pore diameter (10 nm, 15 nm) were obtained. After pore enlargement, the formerly dense arrays of mesoporous structure changed, the radially oriented pores dominated the superficially porous structure. The chromatographic performance of such particles was investigated after C18 derivatization. For packing materials with 1.9 μm diameter and 10 nm pore size, the column efficiency could reach 211,300 plates per m for naphthalene. To achieve the high resolution separation of peptides and proteins, particles with pore diameter of 15 nm were tailored, by which the baseline separation of 5 peptides and 5 intact proteins could be respectively achieved within 1 min, demonstrating the superiority in the high efficiency and high throughput analysis of biomolecules. Furthermore, BSA digests were well separated with peak capacity of 120 in 30 min on a 15 cm-long column. Finally, we compared our columns with a 1.7 μm Kinetex C18 column under the same conditions, our particles with 10nm pore size demonstrated similar performance for separation of the large intact proteins. Moreover, the particles with 15 nm pore size showed more symmetrical peaks for the separation of large proteins (BSA, OVA and IgG) and provided rapid separation of protein extracts from Escherichia coli in 5 min. All these results indicated that the synthesized 1.9 μm superficially porous silica packing materials would be promising in the ultra-fast and high

A Novel FCC Catalyst Based on a Porous Composite Material Synthesized via an In Situ Technique

Directory of Open Access Journals (Sweden)

Shu-Qin Zheng

2015-11-01

Full Text Available To overcome diffusion limitations and improve transport in microporous zeolite, the materials with a wide-pore structure have been developed. In this paper, composite microspheres with hierarchical porous structure were synthesized by an in situ technique using sepiolite, kaolin and pseudoboehmite as raw material. A novel fluid catalytic cracking (FCC catalyst for maximizing light oil yield was prepared based on the composite materials. The catalyst was characterized by XRD, FT-IR, SEM, nitrogen adsorption-desorption techniques and tested in a bench FCC unit. The results indicated that the catalyst had more meso- and macropores and more acid sites than the reference catalyst, and thus can increase light oil yield by 1.31 %, while exhibiting better gasoline and coke selectivity.

Influence of alkali-silica reaction on the physical, mechanical, and structural behaviour of reinforced concrete

DEFF Research Database (Denmark)

Barbosa, Ricardo Antonio

Alkali-silica reaction (ASR) is one of the major concrete deterioration mechanisms in the world. Cracking in concrete structures due to ASR has been observed worldwide. In Denmark numerous concrete structures have been built with a critical amount of ASR-reactive aggregate, mostly as porous opaline...... and porous calcareous opaline flint in the fine aggregate fraction. During the last few decades, an increasing number of bridges in Denmark have been severely damaged due to ASR. In the most severe cases, the ASR-damaged bridges have been demolished and reconstructed due to uncertainty about their residual...... following features in common: (a) significant amount of ASR cracks were observed on and inside the slabs, (b) the ASR cracks were oriented parallel to the plane of the slabs, and (c) ASR occurred in the fine aggregate fraction. In this PhD study, both the compressive strength and tensile strength of drilled...

Effects of using silica fume and polycarboxylate-type superplasticizer on physical properties of cementitious grout mixtures for semiflexible pavement surfacing.

Science.gov (United States)

Koting, Suhana; Karim, Mohamed Rehan; Mahmud, Hilmi; Mashaan, Nuha S; Ibrahim, Mohd Rasdan; Katman, Herdayati; Husain, Nadiah Md

2014-01-01

Semi-flexible pavement surfacing is a composite pavement that utilizes the porous pavement structure of the flexible bituminous pavement, which is subsequently grouted with appropriate cementitious materials. This study aims to investigate the compressive strength, flexural strength, and workability performance of cementitious grout. The grout mixtures are designed to achieve high strength and maintain flow properties in order to allow the cement slurries to infiltrate easily through unfilled compacted skeletons. A paired-sample t-test was carried out to find out whether water/cement ratio, SP percentages, and use of silica fume influence the cementitious grout performance. The findings showed that the replacement of 5% silica fume with an adequate amount of superplasticizer and water/cement ratio was beneficial in improving the properties of the cementitious grout.

Temperature dependence of positron lifetime in ordered porous silica (SBA-3)

International Nuclear Information System (INIS)

Kunishige, S.; Koshimizu, M.; Asai, K.

2009-01-01

The temperature dependence of positron lifetime in uniform mesopores was analyzed. We used SBA-3 as the sample material, which possesses an ordered porous structure with uniform cylindrical mesopores. The positron lifetime corresponding to the annihilation in the mesopores increased gradually with a decrease in temperature down to 100 K, and its relative intensity also increased concomitantly. This result was attributed to the lower probability of the escape of the ortho-positronium (o-Ps) from the mesopores into the intergrain space at lower temperatures. An anomalous and sudden increase in the lifetime was observed at around 100 K; this result was in agreement with an increase in the positron lifetime reported in a previous study. It was revealed that the increase in the lifetime is very steep in cases of uniform mesopores, suggesting that the temperature dependence is influenced by the pore size.

Characterization of geo-polymer porosity: temporal evolution and study of the confined water

International Nuclear Information System (INIS)

Benavent, Virginie

2016-01-01

In this study, we have investigated the porous network of geo-polymers. The first step consisted in characterizing the structure of the porous network by the means of both intrusive experimental techniques (water porosimetry, gas sorption and mercury intrusion) and non-intrusive techniques (small-angle X-ray and neutron scattering). By the same time, the evolutions of the porous structure as well as the mechanical properties were followed over time. The second step was to determine the structure, the thermodynamics and the dynamics of water confined in the porosity by differential scanning calorimetry, quasi-elastic neutron scattering and migration tests. Geo-polymer pore structure is a complex multi-scale porosity, a meso- and macroporous network, essentially open and connected. It consists in a vermicular meso-porous network which connects the macro-pores. The meso-pore characteristic size depends on the formulation of the geo-polymer paste and is ranged between about 4 and 10 nm. Geo-polymer have a total pore volume comprised between 40 and 50 %, the meso-porous volume represents between 7 and 15 % of the material global volume. The majority of the pore volume is then attributed to macro-pores. a slight closure of porosity was observed with time and was attributed to a dissolution-precipitation mechanism occurring at pore wall interfaces. The mechanical properties reach a maximum within 10 days, and then are stable over time when the samples were kept from drying and carbonation and at the temperature of 20 C. Besides, three kinds of water were highlighted inside the porosity: (i) an interfacial water linked at the pore surfaces, (ii) free water inside the meso-pores and (iii) free water inside macro-pores. at local time scale, the mobility of water was found close to the one of free water, and at the macroscopic scale, a decrease in diffusion coefficient of one order of magnitude was observed, together with an effect of meso-pore size. (author) [fr

Discrete meso-element simulation of the failure behavior of short-fiber composites under dynamic loading

International Nuclear Information System (INIS)

Liu Wenyan; Tang, Z.P.; Liu Yunxin

2000-01-01

In recent years, more attention has been paid to a better understanding of the failure behavior and mechanism of heterogeneous materials at the meso-scale level. In this paper, the crack initiation and development in epoxy composites reinforced with short steel fibers under dynamic loading were simulated and analyzed with the 2D Discrete Meso-Element Dynamic Method. Results show that the damage process depends greatly on the binding property between matrix and fibers

Isoporphyrin intermediate in heme oxygenase catalysis. Oxidation of alpha-meso-phenylheme.

Science.gov (United States)

Evans, John P; Niemevz, Fernando; Buldain, Graciela; de Montellano, Paul Ortiz

2008-07-11

Human heme oxygenase-1 (hHO-1) catalyzes the O2- and NADPH-dependent oxidation of heme to biliverdin, CO, and free iron. The first step involves regiospecific insertion of an oxygen atom at the alpha-meso carbon by a ferric hydroperoxide and is predicted to proceed via an isoporphyrin pi-cation intermediate. Here we report spectroscopic detection of a transient intermediate during oxidation by hHO-1 of alpha-meso-phenylheme-IX, alpha-meso-(p-methylphenyl)-mesoheme-III, and alpha-meso-(p-trifluoromethylphenyl)-mesoheme-III. In agreement with previous experiments (Wang, J., Niemevz, F., Lad, L., Huang, L., Alvarez, D. E., Buldain, G., Poulos, T. L., and Ortiz de Montellano, P. R. (2004) J. Biol. Chem. 279, 42593-42604), only the alpha-biliverdin isomer is produced with concomitant formation of the corresponding benzoic acid. The transient intermediate observed in the NADPH-P450 reductase-catalyzed reaction accumulated when the reaction was supported by H2O2 and exhibited the absorption maxima at 435 and 930 nm characteristic of an isoporphyrin. Product analysis by reversed phase high performance liquid chromatography and liquid chromatography electrospray ionization mass spectrometry of the product generated with H2O2 identified it as an isoporphyrin that, on quenching, decayed to benzoylbiliverdin. In the presence of H218O2, one labeled oxygen atom was incorporated into these products. The hHO-1-isoporphyrin complexes were found to have half-lives of 1.7 and 2.4 h for the p-trifluoromethyl- and p-methyl-substituted phenylhemes, respectively. The addition of NADPH-P450 reductase to the H2O2-generated hHO-1-isoporphyrin complex produced alpha-biliverdin, confirming its role as a reaction intermediate. Identification of an isoporphyrin intermediate in the catalytic sequence of hHO-1, the first such intermediate observed in hemoprotein catalysis, completes our understanding of the critical first step of heme oxidation.

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 ...

An Approach to Preparation of trans-DHQs via Ring-Opening of meso-N-Sulfonylaziridines

DEFF Research Database (Denmark)

Nolsøe, Jens Mortansson Jelstrup; Riegert, David; Müller, Paul

2011-01-01

As an approach to the enantioselective synthesis of trans-decahydroquinolines (DHQs), desymmetrization of meso-aziridine (5) with various carbon nucleophiles under catalytic conditions was investigated. By applying TMSCN in the presence of YbCl3 and chiral nonracemic ligands, nitrile 13 was obtai......As an approach to the enantioselective synthesis of trans-decahydroquinolines (DHQs), desymmetrization of meso-aziridine (5) with various carbon nucleophiles under catalytic conditions was investigated. By applying TMSCN in the presence of YbCl3 and chiral nonracemic ligands, nitrile 13...

Mesoporous silica nanoparticles for treating spinal cord injury

Science.gov (United States)

White-Schenk, Désirée.; Shi, Riyi; Leary, James F.

2013-02-01

An estimated 12,000 new cases of spinal cord injury (SCI) occur every year in the United States. A small oxidative molecule responsible for secondary injury, acrolein, is an important target in SCI. Acrolein attacks essential proteins and lipids, creating a feed-forward loop of oxidative stress in both the primary injury area and the surrounding areas. A small molecule used and FDA-approved for hypertension, hydralazine, has been found to "scavenge" acrolein after injury, but its delivery and short half-life, as well as its hypertension effects, hinder its application for SCI. Nanomedical systems broaden the range of therapeutic availability and efficacy over conventional medicine. They allow for targeted delivery of therapeutic molecules to tissues of interest, reducing side effects of untargeted therapies in unwanted areas. Nanoparticles made from silica form porous networks that can carry therapeutic molecules throughout the body. To attenuate the acrolein cascade and improve therapeutic availability, we have used a one-step, modified Stober method to synthesize two types of silica nanoparticles. Both particles are "stealth-coated" with poly(ethylene) glycol (PEG) (to minimize interactions with the immune system and to increase circulation time), which is also a therapeutic agent for SCI by facilitating membrane repair. One nanoparticle type contains an amine-terminal PEG (SiNP-mPEG-Am) and the other possesses a terminal hydrazide group (SiNP-mPEG-Hz). The former allows for exploration of hydralazine delivery, loading, and controlled release. The latter group has the ability to react with acrolein, allowing the nanoparticle to scavenge directly. The nanoparticles have been characterized and are being explored using neuronal PC-12 cells in vitro, demonstrating the potential of novel silica nanoparticles for use in attenuating secondary injury after SCI.

Positron and positronium annihilation in silica-based thin films studied by a pulsed positron beam

International Nuclear Information System (INIS)

Suzuki, R.; Ohdaira, T.; Kobayashi, Y.; Ito, K.; Shioya, Y.; Ishimaru, T.

2003-01-01

Positron and positronium annihilation in silica-based thin films has been investigated by means of measurement techniques with a monoenergetic pulsed positron beam. The age-momentum correlation study revealed that positron annihilation in thermally grown SiO 2 is basically the same as that in bulk amorphous SiO 2 while o-Ps in the PECVD grown SiCOH film predominantly annihilate with electrons of C and H at the microvoid surfaces. We also discuss time-dependent three-gamma annihilation in porous low-k films by two-dimensional positron annihilation lifetime spectroscopy

Validation of Micro-Meso Electrical Relations for Laminates with Varying Anisotropy

KAUST Repository

Selvakumaran, Lakshmi; Lubineau, Gilles

2015-01-01

For electrical impedance tomography (EIT) to be useful in monitoring transverse cracks in composites, it is imperative to establish the relation between conductivity and cracking density. Micro to meso scale homogenization has been developed

Inclusion of gold nanoparticles in meso-porous silicon for the SERS analysis of cell adhesion on nano-structured surfaces

KAUST Repository

Coluccio, M.L.; De Vitis, S.; Strumbo, G.; Candeloro, P.; Perozziello, G.; Di Fabrizio, Enzo M.; Gentile, F.

2016-01-01

MeP Si surfaces were realized by anodization of a Si wafer, creating the device for cell adhesion and growth. Gold nanoparticles were deposited on porous silicon by an electroless technique. We thus obtained devices with superior SERS capabilities, whereby cell activity may be controlled using Raman spectroscopy. MCF-7 breast cancer cells were cultured on the described substrates and SERS maps revealing the different expression and distribution of adhesion molecules were obtained by Raman spectroscopic analyses.

Facile preparation of organic-silica hybrid monolith for capillary hydrophilic liquid chromatography based on "thiol-ene" click chemistry.

Science.gov (United States)

Chen, Ming-Luan; Zhang, Jun; Zhang, Zheng; Yuan, Bi-Feng; Yu, Qiong-Wei; Feng, Yu-Qi

2013-04-05

In this work, a one-step approach to facile preparation of organic-inorganic hybrid monoliths was successfully developed. After vinyl-end organic monomers and azobisisobutyronitrile (AIBN) were mixed with hydrolyzed tetramethoxysilane (TMOS) and 3-mercaptopropyltrimethoxysilane (MPTMS), the homogeneous mixture was introduced into a fused-silica capillary for simultaneous polycondensation and "thiol-ene" click reaction to form the organic-silica hybrid monoliths. By employing this strategy, two types of organic-silica hybrid monoliths with positively charged quaternary ammonium and amide groups were prepared, respectively. The functional groups were successfully introduced onto the monoliths during the sol-gel process with "thiol-ene" click reaction, which was demonstrated by ζ-potential assessment, energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FT-IR) spectroscopy. The porous structure of the prepared monolithic columns was examined by scanning electron microscopy (SEM), nitrogen adsorption-desorption measurement, and mercury intrusion porosimetry. These results indicate the prepared organic-silica hybrid monoliths possess homogeneous column bed, large specific surface area, good mechanical stability, and excellent permeability. The prepared monolithic columns were then applied for anion-exchange/hydrophilic interaction liquid chromatography. Different types of analytes, including benzoic acids, inorganic ions, nucleosides, and nucleotides, were well separated with high column efficiency around 80,000-130,000 plates/m. Taken together, we present a facile and universal strategy to prepare organic-silica hybrid monoliths with a variety of organic monomers using one-step approach. Copyright © 2013 Elsevier B.V. All rights reserved.

Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment

Science.gov (United States)

Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

2015-01-01

Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits. PMID:26322304

Effectiveness of silica based Sol-gel microencapsulation Method for odorants and flavours leading to sustainable Environment

Directory of Open Access Journals (Sweden)

Muhammad Aqeel eAshraf

2015-08-01

Full Text Available Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol–gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol–gel SiO2 is non-toxic and safe, whereas the sol–gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped actives, thereby broadening the practical utilization of chemically unstable essential oils. Reviewing progress in the fabrication of diverse odorant and flavoured sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits.

Dendritic silica particles with center-radial pore channels: promising platforms for catalysis and biomedical applications.

Science.gov (United States)

Du, Xin; Qiao, Shi Zhang

2015-01-27

Dendritic silica micro-/nanoparticles with center-radial pore structures, a kind of newly created porous material, have attracted considerable attention owing to their unique open three-dimensional dendritic superstructures with large pore channels and highly accessible internal surface areas compared with conventional mesoporous silica nanoparticles (MSNs). They are very promising platforms for a variety of applications in catalysis and nanomedicine. In this review, their unique structural characteristics and properties are first analyzed, then novel and interesting synthesis methods associated with the possible formation mechanisms are summarized to provide material scientists some inspiration for the preparation of this kind of dendritic particles. Subsequently, a few examples of interesting applications are presented, mainly in catalysis, biomedicine, and other important fields such as for sacrificial templates and functional coatings. The review is concluded with an outlook on the prospects and challenges in terms of their controlled synthesis and potential applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectroscopy of nanosized composites silicon-organic polymer/nanoporous silicas

International Nuclear Information System (INIS)

Ostapenko, N.; Kozlova, N.; Suto, S.; Watanabe, A.

2006-01-01

Fluorescence and excitation spectra (T=5-290 K) of nanosized silicon-organic polymers poly(di-n-hexylsilane) and poly(methyl(phenyl)silane) incorporated into porous silica materials MCM-41 and SBA-15 have been studied with varying pore diameter from 2.8 to 10 nm. The controlled variation of the pore diameter in a wide range (2.8-10 nm) permitted us, for the first time, to investigate the optical properties of the polymers on their transition from isolated macromolecules to a film. It is found that this transition depends on polymer type and occurs via the formation of new spatially independent structures of the polymers not observed in the spectra of the film, namely, via the formation of disordered and (or) ordered conformations of polymer chains and clusters

Application of diazene-directed fragment assembly to the total synthesis and stereochemical assignment of (+)-desmethyl-meso-chimonanthine and related heterodimeric alkaloids

OpenAIRE

Lathrop, Stephen; Movassaghi, Mohammad

2013-01-01

We describe the first application of our methodology for heterodimerization via diazene fragmentation towards the total synthesis of (−)-calycanthidine, meso-chimonanthine, and (+)-desmethyl-meso-chimonanthine. Our syntheses of these alkaloids feature an improved route to C3a-aminocyclotryptamines, an enhanced method for sulfamide synthesis and oxidation, in addition to a late-stage diversification leading to the first enantioselective total synthesis of (+)-desmethyl-meso-chimonanthine and i...

Creating 3D Hierarchical Carbon Architectures with Micro-, Meso-, and Macropores via a Simple Self-Blowing Strategy for a Flow-through Deionization Capacitor.

Science.gov (United States)

Zhao, Shanshan; Yan, Tingting; Wang, Hui; Zhang, Jianping; Shi, Liyi; Zhang, Dengsong

2016-07-20

In this work, 3D hierarchical carbon architectures (3DHCAs) with micro-, meso-, and macropores were prepared via a simple self-blowing strategy as highly efficient electrodes for a flow-through deionization capacitor (FTDC). The obtained 3DHCAs have a hierarchically porous structure, large accessible specific surface area (2061 m(2) g(-1)), and good wettability. The electrochemical tests show that the 3DHCA electrode has a high specific capacitance and good electric conductivity. The deionization experiments demonstrate that the 3DHCA electrodes possess a high deionization capacity of 17.83 mg g(-1) in a 500 mg L(-1) NaCl solution at 1.2 V. Moreover, the 3DHCA electrodes present a fast deionization rate in 100-500 mg L(-1) NaCl solutions at 0.8-1.4 V. The 3DHCA electrodes also present a good regeneration behavior in the reiterative regeneration test. These above factors render the 3DHCAs a promising FTDC electrode material.

Evaluating healthcare priority setting at the meso level: A thematic review of empirical literature

Science.gov (United States)

Waithaka, Dennis; Tsofa, Benjamin; Barasa, Edwine

2018-01-01

Background: Decentralization of health systems has made sub-national/regional healthcare systems the backbone of healthcare delivery. These regions are tasked with the difficult responsibility of determining healthcare priorities and resource allocation amidst scarce resources. We aimed to review empirical literature that evaluated priority setting practice at the meso (sub-national) level of health systems. Methods: We systematically searched PubMed, ScienceDirect and Google scholar databases and supplemented these with manual searching for relevant studies, based on the reference list of selected papers. We only included empirical studies that described and evaluated, or those that only evaluated priority setting practice at the meso-level. A total of 16 papers were identified from LMICs and HICs. We analyzed data from the selected papers by thematic review. Results: Few studies used systematic priority setting processes, and all but one were from HICs. Both formal and informal criteria are used in priority-setting, however, informal criteria appear to be more perverse in LMICs compared to HICs. The priority setting process at the meso-level is a top-down approach with minimal involvement of the community. Accountability for reasonableness was the most common evaluative framework as it was used in 12 of the 16 studies. Efficiency, reallocation of resources and options for service delivery redesign were the most common outcome measures used to evaluate priority setting. Limitations: Our study was limited by the fact that there are very few empirical studies that have evaluated priority setting at the meso-level and there is likelihood that we did not capture all the studies. Conclusions: Improving priority setting practices at the meso level is crucial to strengthening health systems. This can be achieved through incorporating and adapting systematic priority setting processes and frameworks to the context where used, and making considerations of both process

Irreversible membrane fouling abatement through pre-deposited layer of hierarchical porous carbons

KAUST Repository

Hamad, Juma

2014-11-01

In this work, dual-templated hierarchical porous carbons (HPCs), produced from a coupled ice-hard templating approach, are shown to be a highly effective solution to the commonly occurring problem of irreversible fouling of low-pressure membranes used for pre-treatment in wastewater reuse. For the first time, dual-templated HPCs, along with their respective counterparts - single-templated meso-porous carbon (MPCs) (without macropores) - are tested in terms of their fouling reduction capacity and ability to remove different effluent organic matter fractions present in wastewater and compared with a commercially available powdered activated carbon (PAC). The synthesized HPCs provided exceptional fouling abatement, a 4-fold higher fouling reduction as compared to the previously reported best performing commercial PAC and ~2.5-fold better fouling reduction than their respective mesoporous counterpart. Thus, it is shown that not only mesoporosity, but macroporosity is also necessary to achieve high fouling reduction, thus emphasizing the need for dual templating. In the case of HPCs, the pre-deposition technique is also found to outperform the traditional sorbent-feed mixing approach, mainly in terms of removal of fouling components. Based on their superior performance, a high permeability (ultra-low-pressure) membrane consisting of the synthesized HPC pre-deposited on a large pore size membrane support (0.45μm membrane), is shown to give excellent pre-treatment performance for wastewater reuse application. © 2014 Elsevier Ltd.

Enhanced ferro-actuator with a porosity-controlled membrane using the sol-gel process and the HF etching method

International Nuclear Information System (INIS)

Kim, KiSu; Ko, Seong Young; Park, Jong-Oh; Park, Sukho

2016-01-01

In this paper, we propose a ferro-actuator using a porous polyvinylidene difluoride (PVDF) membrane. In detail, we fabricated the silica-embedded PVDF membrane using a sol-gel process with PVDF solution and tetraethyl orthosilicate (TEOS) solution, where the size of the silica was determined by the ratio of the PVDF and TEOS solutions. Using hydrofluoric acid (HF) etching, the silica were removed from the silica-embedded PVDF membrane, and porous PVDF membranes with different porosities were obtained. Finally, through absorption of a ferrofluid on the porous PVDF membrane, the proposed ferro-actuator using porous PVDF membranes with different porosities was fabricated. We executed the characterization and actuation test as follows. First, the silica size of the silica-embedded PVDF membrane and the pore size of the porous PVDF membrane were analyzed using scanning electron microscopy (SEM) imaging. Second, energy-dispersive x-ray spectroscopy analysis showed that the silica had clearly been removed from the silica-embedded PVDF membrane by HF etching. Third, through x-ray photoelectron spectroscopy and vibrating sample magnetometer (VSM) of the ferro-actuators, we found that more ferrofluids were absorbed by the porous PVDF membrane when the pore of the membrane was smaller and uniformly distributed. Finally, we executed tip displacement and a blocking force test of the proposed ferro-actuator using the porous PVDF membrane. Similar to the VSM result, the ferro-actuator that used a porous PVDF membrane with smaller pores exhibited better actuation performance. The ferro-actuator that used a porous PVDF membrane displayed a tip displacement that was about 7.2-fold better and a blocking force that was about 6.5-fold better than the ferro-actuator that used a pure PVDF membrane. Thus, we controlled the pore size of the porous PVDF membrane and enhanced the actuation performance of the ferro-actuator using a porous PVDF membrane. (technical note)

Environmentally-Friendly Dense and Porous Geopolymers Using Fly Ash and Rice Husk Ash as Raw Materials

Directory of Open Access Journals (Sweden)

Daniele Ziegler

2016-06-01

Full Text Available This paper assesses the feasibility of two industrial wastes, fly ash (FA and rice husk ash (RHA, as raw materials for the production of geopolymeric pastes. Three typologies of samples were thus produced: (i halloysite activated with potassium hydroxide and nanosilica, used as the reference sample (HL-S; (ii halloysite activated with rice husk ash dissolved into KOH solution (HL-R; (iii FA activated with the alkaline solution realized with the rice husk ash (FA-R. Dense and porous samples were produced and characterized in terms of mechanical properties and environmental impact. The flexural and compressive strength of HL-R reached about 9 and 43 MPa, respectively. On the contrary, the compressive strength of FA-R is significantly lower than the HL-R one, in spite of a comparable flexural strength being reached. However, when porous samples are concerned, FA-R shows comparable or even higher strength than HL-R. Thus, the current results show that RHA is a valuable alternative to silica nanopowder to prepare the activator solution, to be used either with calcined clay and fly ash feedstock materials. Finally, a preliminary evaluation of the global warming potential (GWP was performed for the three investigated formulations. With the mix containing FA and RHA-based silica solution, a reduction of about 90% of GWP was achieved with respect to the values obtained for the reference formulation.

Deletion of meso-2,3-butanediol dehydrogenase gene budC for enhanced D-2,3-butanediol production in Bacillus licheniformis

Science.gov (United States)

2014-01-01

Background D-2,3-butanediol has many industrial applications such as chiral reagents, solvents, anti-freeze agents, and low freezing point fuels. Traditional D-2,3-butanediol producing microorganisms, such as Klebsiella pneumonia and K. xoytoca, are pathogenic and not capable of producing D-2,3-butanediol at high optical purity. Bacillus licheniformis is a potential 2,3-butanediol producer but the wild type strain (WX-02) produces a mix of D- and meso-type isomers. BudC in B. licheniformis is annotated as 2,3-butanediol dehydrogenase or acetoin reductase, but no pervious experiment was performed to verify this hypothesis. Results We developed a genetically modified strain of B. licheniformis (WX-02 ΔbudC) as a D-2,3-butanediol producer with high optimal purity. A marker-less gene deletion protocol based on a temperature sensitive knock-out plasmid T2-Ori was used to knock out the budC gene in B. licheniformis WX-02. The budC knock-out strain successfully abolished meso-2,3-butanediol production with enhanced D-2,3-butanediol production. No meso-BDH activity was detectable in cells of this strain. On the other hand, the complementary strain restored the characteristics of wild strain, and produced meso-2,3-butanediol and possessed meso-BDH activity. All of these data suggested that budC encoded the major meso-BDH catalyzing the reversible reaction from acetoin to meso-2,3-butanediol in B. licheniformis. The budC knock-out strain produced D-2,3-butanediol isomer only with a high yield of 30.76 g/L and a productivity of 1.28 g/L-h. Conclusions We confirmed the hypothesis that budC gene is responsible to reversibly transfer acetoin to meso-2,3-butanediol in B. licheniformis. A mutant strain of B. licheniformis with depleted budC gene was successfully developed and produced high level of the D-2,3-butanediol with high optimal purity. PMID:24475980

Recent advances in porous nanoparticles for drug delivery in antitumoral applications: inorganic nanoparticles and nanoscale metal-organic frameworks.

Science.gov (United States)

Baeza, Alejandro; Ruiz-Molina, Daniel; Vallet-Regí, María

2017-06-01

Nanotechnology has provided new tools for addressing unmet clinical situations, especially in the oncology field. The development of smart nanocarriers able to deliver chemotherapeutic agents specifically to the diseased cells and to release them in a controlled way has offered a paramount advantage over conventional therapy. Areas covered: Among the different types of nanoparticle that can be employed for this purpose, inorganic porous materials have received significant attention in the last decade due to their unique properties such as high loading capacity, chemical and physical robustness, low toxicity and easy and cheap production in the laboratory. This review discuss the recent advances performed in the application of porous inorganic and metal-organic materials for antitumoral therapy, paying special attention to the application of mesoporous silica, porous silicon and metal-organic nanoparticles. Expert opinion: The use of porous inorganic nanoparticles as drug carriers for cancer therapy has the potential to improve the life expectancy of the patients affected by this disease. However, much work is needed to overcome their drawbacks, which are aggravated by their hard nature, exploiting the advantages offered by highly the ordered pore network of these materials.

A Review of the Appropriateness of Existing Micro- and Meso-level Models of Athlete Development within Equestrian Sport

NARCIS (Netherlands)

de Haan, D.M.

2017-01-01

The aim of this paper was to use a case study approach to review the appropriateness of existing micro- and meso-level models of athlete development within the sport specific context of equestrianism. At a micro-level the Long Term Athlete Development (LTAD) model was chosen. At a meso-level, the

Nano-Tomography of Porous Geological Materials Using Focused Ion Beam-Scanning Electron Microscopy

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Yang Liu

2016-10-01

Full Text Available Tomographic analysis using focused ion beam-scanning electron microscopy (FIB-SEM provides three-dimensional information about solid materials with a resolution of a few nanometres and thus bridges the gap between X-ray and transmission electron microscopic tomography techniques. This contribution serves as an introduction and overview of FIB-SEM tomography applied to porous materials. Using two different porous Earth materials, a diatomite specimen, and an experimentally produced amorphous silica layer on olivine, we discuss the experimental setup of FIB-SEM tomography. We then focus on image processing procedures, including image alignment, correction, and segmentation to finally result in a three-dimensional, quantified pore network representation of the two example materials. To each image processing step we consider potential issues, such as imaging the back of pore walls, and the generation of image artefacts through the application of processing algorithms. We conclude that there is no single image processing recipe; processing steps need to be decided on a case-by-case study.

Synthesis and Characterization of Fibre Reinforced Silica Aerogel Blankets for Thermal Protection

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S. Chakraborty

2016-01-01

Full Text Available Using tetraethoxysilane (TEOS as the source of silica, fibre reinforced silica aerogels were synthesized via fast ambient pressure drying using methanol (MeOH, trimethylchlorosilane (TMCS, ammonium fluoride (NH4F, and hexane. The molar ratio of TEOS/MeOH/(COOH2/NH4F was kept constant at 1 : 38 : 3.73 × 10−5 : 0.023 and the gel was allowed to form inside the highly porous meta-aramid fibrous batting. The wet gel surface was chemically modified (silylation process using various concentrations of TMCS in hexane in the range of 1 to 20% by volume. The fibre reinforced silica aerogel blanket was obtained subsequently through atmospheric pressure drying. The aerogel blanket samples were characterized by density, thermal conductivity, hydrophobicity (contact angle, and Scanning Electron Microscopy. The radiant heat resistance of the aerogel blankets was examined and compared with nonaerogel blankets. It has been observed that, compared to the ordinary nonaerogel blankets, the aerogel blankets showed a 58% increase in the estimated burn injury time and thus ensure a much better protection from heat and fire hazards. The effect of varying the concentration of TMCS on the estimated protection time has been examined. The improved thermal stability and the superior thermal insulation of the flexible aerogel blankets lead to applications being used for occupations that involve exposure to hazards of thermal radiation.

[Community structure of soil meso- and micro-fauna in different habitats of urbanized region].

Science.gov (United States)

Qin, Zhong; Zhang, Jia-en; Li, Qing-fang

2009-12-01

Investigations were made in May, June, and November 2007 and January 2008 to study the structural characteristics and their seasonal variations of soil meso- and micro-fauna communities in six habitats of three land use types (forest land, constructed grassland and farmland) in Tianhe District of Guangzhou City. The horizontal spatial distribution of soil fauna differed with habitat. During the investigation periods, the Botanical Garden of South China Agricultural University had the highest individual number (1286) of soil mesa- and micro-fauna, while the farmland, especially in the Fenghuang Street area, had the lowest number of individuals and groups. The seasonal variation of the individual number was in order of autumn (1815) > spring (1623) > winter (1365) > summer (1276). Hierarchical clustering and detrended correspondence analysis also showed that the community composition of soil meso- and micro-fauna in different habitats exhibited distinct seasonal variation. In the same seasons, the community structure and composition of soil meso- and micro-fauna in different habitats were correlated to the degrees of human interferences and the properties of soil environment.

Influence of structure of carrier (silica gel) on texture and catalytic properties of vanadium catalysts for sulfur dioxide oxidation

International Nuclear Information System (INIS)

Simonova, L.G.; Fenelonov, V.B.; Dzis'ko, V.A.; Noskova, S.P.; Kryukova, G.N.; Litvak, G.S.

1982-01-01

The influence of initial porous structure of a carrier-silica gel on texture and catalytic properties of vanadium catalysts is considered. It is shown that low thermal stability of the carrier results not only in considerable decrease of the catalyst surface during heat treatment but also in blocking part of active component in locked pores which accounts for the activity decrease in kinetic region and formation of active component forms that can not be extracted by acid

Energy intensities in Mato Grosso state and in meso-regions; Intensidades energeticas nas mesorregioes de Mato Grosso

Energy Technology Data Exchange (ETDEWEB)

Canavarros, Otacilio Borges; Melo, Moises Candido de; Dorileo, Ivo Leandro [Universidade Federal de Mato Grosso (UFMT), Cuiaba, MT (Brazil). Nucleo Interdisciplinar de Estudos em Planejamento Energetico (NIEPE)

2004-07-01

This work presents some energetic intensities in Mato Grosso state and in each of its five meso-regions that are in the document produced in 2002 by the NIPE/UFMT (Nucleo Interdisciplinar de Estudos em Planejamento Energetico of the Universidade Federal do Mato Grosso) entitled: 'Energetic Balance of the Mato Grosso and meso-regions: period 1995-2001'. (author)

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

Adsorption-Induced Deformation of Hierarchically Structured Mesoporous Silica-Effect of Pore-Level Anisotropy.

Science.gov (United States)

Balzer, Christian; Waag, Anna M; Gehret, Stefan; Reichenauer, Gudrun; Putz, Florian; Hüsing, Nicola; Paris, Oskar; Bernstein, Noam; Gor, Gennady Y; Neimark, Alexander V

2017-06-06

The goal of this work is to understand adsorption-induced deformation of hierarchically structured porous silica exhibiting well-defined cylindrical mesopores. For this purpose, we performed an in situ dilatometry measurement on a calcined and sintered monolithic silica sample during the adsorption of N 2 at 77 K. To analyze the experimental data, we extended the adsorption stress model to account for the anisotropy of cylindrical mesopores, i.e., we explicitly derived the adsorption stress tensor components in the axial and radial direction of the pore. For quantitative predictions of stresses and strains, we applied the theoretical framework of Derjaguin, Broekhoff, and de Boer for adsorption in mesopores and two mechanical models of silica rods with axially aligned pore channels: an idealized cylindrical tube model, which can be described analytically, and an ordered hexagonal array of cylindrical mesopores, whose mechanical response to adsorption stress was evaluated by 3D finite element calculations. The adsorption-induced strains predicted by both mechanical models are in good quantitative agreement making the cylindrical tube the preferable model for adsorption-induced strains due to its simple analytical nature. The theoretical results are compared with the in situ dilatometry data on a hierarchically structured silica monolith composed by a network of mesoporous struts of MCM-41 type morphology. Analyzing the experimental adsorption and strain data with the proposed theoretical framework, we find the adsorption-induced deformation of the monolithic sample being reasonably described by a superposition of axial and radial strains calculated on the mesopore level. The structural and mechanical parameters obtained from the model are in good agreement with expectations from independent measurements and literature, respectively.

MASS BALANCE OF SILICA IN STRAW FROM THE PERSPECTIVE OF SILICA REDUCTION IN STRAW PULP

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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.

Liquid Phase Deposition of Silica on the Hexagonally Close-Packed Monolayer of Silica Spheres

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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.

Effects of Using Silica Fume and Polycarboxylate-Type Superplasticizer on Physical Properties of Cementitious Grout Mixtures for Semiflexible Pavement Surfacing

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Suhana Koting

2014-01-01

Full Text Available Semi-flexible pavement surfacing is a composite pavement that utilizes the porous pavement structure of the flexible bituminous pavement, which is subsequently grouted with appropriate cementitious materials. This study aims to investigate the compressive strength, flexural strength, and workability performance of cementitious grout. The grout mixtures are designed to achieve high strength and maintain flow properties in order to allow the cement slurries to infiltrate easily through unfilled compacted skeletons. A paired-sample t-test was carried out to find out whether water/cement ratio, SP percentages, and use of silica fume influence the cementitious grout performance. The findings showed that the replacement of 5% silica fume with an adequate amount of superplasticizer and water/cement ratio was beneficial in improving the properties of the cementitious grout.

Hysteresis critical point of nitrogen in porous glass: occurrence of sample spanning transition in capillary condensation.

Science.gov (United States)

Morishige, Kunimitsu

2009-06-02

To examine the mechanisms for capillary condensation and for capillary evaporation in porous glass, we measured the hysteresis critical points and desorption scanning curves of nitrogen in four kinds of porous glasses with different pore sizes (Vycor, CPG75A, CPG120A, and CPG170A). The shapes of the hysteresis loop in the adsorption isotherm of nitrogen for the Vycor and the CPG75A changed with temperature, whereas those for the CPG120A and the CPG170A remained almost unchanged with temperature. The hysteresis critical points for the Vycor and the CPG75A fell on the common line observed previously for ordered mesoporous silicas. On the other hand, the hysteresis critical points for the CPG120A and the CPG170A deviated appreciably from the common line. This strongly suggests that capillary evaporation of nitrogen in the interconnected and disordered pores of both the Vycor and the CPG75A follows a cavitation process at least in the vicinity of their hysteresis critical temperatures in the same way as that in the cagelike pores of the ordered silicas, whereas the hysteresis critical points in the CPG120A and the CPG170A have origin different from that in the cagelike pores. The desorption scanning curves for the CPG75A indicated the nonindependence of the porous domains. On the other hand, for both the CPG120A and the CPG170A, we obtained the scanning curves that are expected from the independent domain theory. All these results suggest that sample spanning transitions in capillary condensation and evaporation take place inside the interconnected pores of both the CPG120A and the CPG170A.

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

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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.

An interview with James Wilbur, Ph.D. General Manager, Life Sciences, Meso Scale Discovery.

Science.gov (United States)

Wilbur, James

2004-06-01

James L. Wilbur, Ph.D. received a Bachelor's degree from the University of California, San Diego and a Ph.D. in Chemistry from Stanford University. After completing an NIH Postdoctoral Fellowship with Professor George M. Whitesides in the Department of Chemistry at Harvard University, he joined IGEN International, Inc., where he held a variety of positions in Research and Development. During that time, he was part of the team that developed the core technology and products for Meso Scale Discovery. He assumed his current position in 2001 when Meso Scale Discovery launched the products discussed here.

Book Review [Surfaces of Nanoparticles and Porous Materials. Edited by James A. Schwarz and Cristian I. Contescu. 1 999. Marcel Dekker, New York, USA. ISBN: 0824719336

International Nuclear Information System (INIS)

Gonzalez, Richard D

1999-01-01

The volume is organized into three sections. The first section deals with the preparation, characterization and transport properties of this unique class of materials. A total of twelve contributions are included in this section, ten of which are full reviews and two are essentially short papers. The topics include: the synthesis of polysilazane coatings on the surface of silica gel; preparation of molecular sieves by the pillaring of synthetic clays; the acid/base behavior of surfaces of porous materials; electro-optical spectroscopy of colloid systems; NMR studies of colloidal oxides; polymer surface dynamics via contact angle measurements; collagen fibers; the role of diffusion on adsorption on oxide surfaces; transport processes in microemulsions; electrokinetic phenomena in porous media, and structural effects on diffusivity within colloidal zirconia. The remaining two sections deal with the fundamental and practical utilization of nanostructured materials in gaseous and liquid environments. The second section addresses the former case. A total of seven well documented contributions are included in this section. The papers address studies in diverse areas: energetically heterogeneous surfaces as studied using experimental adsorption isotherms; computer simulations of adsorbed surface layers; the effect of surface heterogeneity on adsorption equilibria and kinetics; single and multicomponent adsorption; surface properties of modified porous silicas; heats of adsorption of pure gases; and nanodimensional magnetic assembly of confined oxygen. The final section includes a total of ten reviews that address adsorption from the liquid phase. The following topics are covered: surface chemistry of activated carbon; charge regulation at the surface of porous solids; surface ionization and complexation; ionic adsorbates on hydrophobic surfaces; adsorption of metals on humic acid surfaces; hydrated metal oxides as adsorbents for heavy metals; adsorption of ions on alumina

Dependence of O{sub 2} diffusion dynamics on pressure and temperature in silica nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Iovino, G., E-mail: giuseppe.iovino@unipa.it; Agnello, S., E-mail: simonpietro.agnello@unipa.it; Gelardi, F. M., E-mail: franco.gelardi@unipa.it [University of Palermo, Department of Physics and Chemistry (Italy)

2013-10-15

An experimental study of the molecular O{sub 2} diffusion process in high purity non-porous silica nanoparticles having 50 m{sup 2}/g BET specific surface and 20 nm average radius was carried out in the temperature range from 127 to 177 Degree-Sign C at O{sub 2} pressure in the range from 0.2 to 66 bar. The study was performed by measuring the volume average interstitial O{sub 2} concentration by a Raman and photoluminescence technique using a 1,064 nm excitation laser to detect the singlet to triplet emission at 1,272 nm of the molecular oxygen in silica. A dependence of the diffusion kinetics on the O{sub 2} absolute pressure, in addition to temperature dependence, was found. The kinetics can be fit by the solution of Fick's diffusion equation using an effective diffusion coefficient related to temperature and O{sub 2} external pressure. The fit results have evidenced that the temperature and pressure dependencies can be disentangled and that the pressure effects are more pronounced at lower temperatures. An Arrhenius temperature law is determined for the effective diffusion coefficient and the activation energy and pre-exponential factor are found in the explored experimental range. The reported findings have not been evidenced previously in the studies in bulk silica and could probably be originated by the reduced spatial extension of the considered system.