WorldWideScience

Sample records for stokes-shift fluorescent silica

  1. Benzothiadiazole oligoene fatty acids: fluorescent dyes with large Stokes shifts

    Directory of Open Access Journals (Sweden)

    Lukas J. Patalag

    2016-12-01

    Full Text Available Herein, we report on the synthesis and characterization of novel fluorescent fatty acids with large Stokes shifts. Three examples consisting of the same number of carbon atoms and thus of similar chain length are presented differing in their degree of unsaturation. As major fluorogenic contributor at the terminus benzo[c][1,2,5]thiadiazole was used. Respective syntheses based on Wittig reactions followed by iodine-mediated isomerization are presented. The absorption properties are modulated by the number of conjugated C=C double bonds of the oligoene chain ranging from one to three. Large Stokes shifts of about 4900–5700 cm−1 and fluorescence quantum yields of up to 0.44 were observed.

  2. Role of excited state solvent fluctuations on time-dependent fluorescence Stokes shift

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tanping, E-mail: tanping@lsu.edu, E-mail: revatik@lsu.edu; Kumar, Revati, E-mail: tanping@lsu.edu, E-mail: revatik@lsu.edu [Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

    2015-11-07

    We explore the connection between the solvation dynamics of a chromophore upon photon excitation and equilibrium fluctuations of the solvent. Using molecular dynamics simulations, fluorescence Stokes shift for the tryptophan in Staphylococcus nuclease was examined using both nonequilibrium calculations and linear response theory. When the perturbed and unperturbed surfaces exhibit different solvent equilibrium fluctuations, the linear response approach on the former surface shows agreement with the nonequilibrium process. This agreement is excellent when the perturbed surface exhibits Gaussian statistics and qualitative in the case of an isomerization induced non-Gaussian statistics. However, the linear response theory on the unperturbed surface breaks down even in the presence of Gaussian fluctuations. Experiments also provide evidence of the connection between the excited state solvent fluctuations and the total fluorescence shift. These observations indicate that the equilibrium statistics on the excited state surface characterize the relaxation dynamics of the fluorescence Stokes shift. Our studies specifically analyze the Gaussian fluctuations of the solvent in the complex protein environment and further confirm the role of solvent fluctuations on the excited state surface. The results are consistent with previous investigations, found in the literature, of solutes dissolved in liquids.

  3. Phospholyl(borane) Amino Acids and Peptides: Stereoselective Synthesis and Fluorescent Properties with Large Stokes Shift.

    Science.gov (United States)

    Arribat, Mathieu; Rémond, Emmanuelle; Clément, Sébastien; Lee, Arie Van Der; Cavelier, Florine

    2018-01-24

    The synthesis of phospholyl(borane) amino acids was stereoselectively achieved by reaction of phospholide anion with iodo α-amino ester derived from l-aspartic acid or l-serine, followed by in situ complexation with borane. Phospholyl(borane) amino acids are easy to store and can be subjected to direct transformation into the corresponding free phospholyl, gold complex, oxide or sulfur derivatives as well as phospholinium salts, thus offering a variety of side chains. After selective deprotection of carboxylic function or amine, C- or N- peptide coupling with an alanine moiety proved the possible incorporation into peptides. Such phospholyl amino acid and peptide derivatives exhibit fluorescent properties with a large Stokes shift (160 nm) and fluorescence up to 535 nm, depending on the phosphole aromaticity and the chemical environment. These phospholyl(borane) amino acids constitute a new class of unnatural amino acids useful for structure-activities relationship studies and appear to be promising fluorophores for the development of labeled peptides.

  4. Fluorescent dyes with large Stokes shifts for super-resolution optical microscopy of biological objects: a review

    International Nuclear Information System (INIS)

    Sednev, Maksim V; Belov, Vladimir N; Hell, Stefan W

    2015-01-01

    The review deals with commercially available organic dyes possessing large Stokes shifts and their applications as fluorescent labels in optical microscopy based on stimulated emission depletion (STED). STED microscopy breaks Abbe’s diffraction barrier and provides optical resolution beyond the diffraction limit. STED microscopy is non-invasive and requires photostable fluorescent markers attached to biomolecules or other objects of interest. Up to now, in most biology-related STED experiments, bright and photoresistant dyes with small Stokes shifts of 20–40 nm were used. The rapid progress in STED microscopy showed that organic fluorophores possessing large Stokes shifts are indispensable in multi-color super-resolution techniques. The ultimate result of the imaging relies on the optimal combination of a dye, the bio-conjugation procedure and the performance of the optical microscope. Modern bioconjugation methods, basics of STED microscopy, as well as structures and spectral properties of the presently available fluorescent markers are reviewed and discussed. In particular, the spectral properties of the commercial dyes are tabulated and correlated with the available depletion wavelengths found in STED microscopes produced by LEICA Microsytems, Abberior Instruments and Picoquant GmbH. (topical review)

  5. An organic dye with very large Stokes-shift and broad tunability of fluorescence: Potential two-photon probe for bioimaging and ultra-sensitive solid-state gas sensor

    Energy Technology Data Exchange (ETDEWEB)

    He, Tingchao; Tian, Xiaoqing; Lin, Xiaodong, E-mail: linxd@szu.edu.cn, E-mail: hdsun@ntu.edu.sg [College of Physics Science and Technology, Shenzhen University, Shenzhen 518060 (China); Wang, Yue; Zhao, Xin; Sun, Handong, E-mail: linxd@szu.edu.cn, E-mail: hdsun@ntu.edu.sg [Division of Physics and Applied Physics, and Centre for Disruptive Photonic Technologies (CDPT), School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); Gao, Yang; Grimsdale, Andrew C. [School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2016-01-04

    Light-emitting nonlinear optical molecules, especially those with large Stokes shifts and broad tunability of their emission wavelength, have attracted considerable attention for various applications including biomedical imaging and fluorescent sensors. However, most fluorescent chromophores have only limited potential for such applications due to small Stokes shifts, narrow tunability of fluorescence emissions, and small optical nonlinearity in highly polar solvents. In this work, we demonstrate that a two-photon absorbing stilbene chromophore exhibits a large two-photon absorption action cross-section (ηδ = 320 GM) in dimethylsulfoxide (DMSO) and shows broad fluorescence tunability (125 nm) by manipulating the polarity of the surrounding medium. Importantly, a very large Stokes shift of up to 227 nm is achieved in DMSO. Thanks to these features, this chromophore can be utilized as a two-photon probe for bioimaging applications and in an ultrasensitive solid-state gas detector.

  6. From Dark to Light to Fluorescence Resonance Energy Transfer (FRET): Polarity-Sensitive Aggregation-Induced Emission (AIE)-Active Tetraphenylethene-Fused BODIPY Dyes with a Very Large Pseudo-Stokes Shift.

    Science.gov (United States)

    Şen, Esra; Meral, Kadem; Atılgan, Serdar

    2016-01-11

    The work presented herein is devoted to the fabrication of large Stokes shift dyes in both organic and aqueous media by combining dark resonance energy transfer (DRET) and fluorescence resonance energy transfer (FRET) in one donor-acceptor system. In this respect, a series of donor-acceptor architectures of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes substituted by one, two, or three tetraphenylethene (TPE) luminogens were designed and synthesised. The photophysical properties of these three chromophore systems were studied to provide insight into the nature of donor-acceptor interactions in both THF and aqueous media. Because the generation of emissive TPE donor(s) is strongly polarity dependent, due to its aggregation-induced emission (AIE) feature, one might expect the formation of appreciable fluorescence emission intensity with a very large pseudo-Stokes shift in aqueous media when considering FRET process. Interestingly, similar results were also recorded in THF for the chromophore systems, although the TPE fragment(s) of the dyes are non-emissive. The explanation for this photophysical behaviour lies in the DRET. This is the first report on combining two energy-transfer processes, namely, FRET and DRET, in one polarity-sensitive donor-acceptor pair system. The accuracy of the dark-emissive donor property of the TPE luminogen is also presented for the first time as a new feature for AIE phenomena. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. A dual-emission and large Stokes shift fluorescence probe for real-time discrimination of ROS/RNS and imaging in live cells.

    Science.gov (United States)

    Guo, Ting; Cui, Lei; Shen, Jiaoning; Wang, Rui; Zhu, Weiping; Xu, Yufang; Qian, Xuhong

    2013-03-04

    A novel dual-emission fluorescence probe has been developed for specific and sensitive detection of hypochlorite (ClO(-)). Upon addition of ClO(-), significant changes in fluorescence emission intensity at two discrete wavelengths were observed. Meanwhile OONO(-) led to only a single-channel fluorescence enhancement. This feature makes it a clear advantage in distinguishing ClO(-), RNS from other ROS.

  8. Dual-Analyte Fluorescent Sensor Based on [5]Helicene Derivative with Super Large Stokes Shift for the Selective Determinations of Cu2+ or Zn2+ in Buffer Solutions and Its Application in a Living Cell.

    Science.gov (United States)

    Sakunkaewkasem, Siwakorn; Petdum, Anuwut; Panchan, Waraporn; Sirirak, Jitnapa; Charoenpanich, Adisri; Sooksimuang, Thanasat; Wanichacheva, Nantanit

    2018-05-10

    A new fluorescent sensor, M201-DPA, based on [5]helicene derivative was utilized as dual-analyte sensor for determination of Cu 2+ or Zn 2+ in different media and different emission wavelengths. The sensor could provide selective and bifunctional determination of Cu 2+ in HEPES buffer containing Triton-X100 and Zn 2+ in Tris buffer/methanol without interference from each other and other ions. In HEPES buffer, M201-DPA demonstrated the selective ON-OFF fluorescence quenching at 524 nm toward Cu 2+ . On the other hand, in Tris buffer/methanol, M201-DPA showed the selective OFF-ON fluorescence enhancement upon the addition of Zn 2+ , which was specified by the hypsochromic shift at 448 nm. Additionally, M201-DPA showed extremely large Stokes shifts up to ∼150 nm. By controlling the concentration of Zn 2+ and Cu 2+ in a living cell, the imaging of a HepG2 cellular system was performed, in which the fluorescence of M201-DPA in the blue channel was decreased upon addition of Cu 2+ and was enhanced in UV channel upon addition of Zn 2+ . The detection limits of M201-DPA for Cu 2+ and Zn 2+ in buffer solutions were 5.6 and 3.8 ppb, respectively. Importantly, the Cu 2+ and Zn 2+ detection limits of the developed sensors were significantly lower than permitted Cu 2+ and Zn 2+ concentrations in drinking water as established by the U.S. EPA and WHO.

  9. Stokes shift spectroscopy for breast cancer diagnosis

    Science.gov (United States)

    Jeyasingh, Ebenezar; Prakashrao, Aruna; Singaravelu, Ganesan

    2010-02-01

    The objective of this study is to assess the diagnostic potential of stokes shift (SS) spectroscopy (SSS) for normal and different pathological breast tissues such as fibroadenoma and infiltrating ductal carcinoma. The SS spectra is measured by simultaneously scanning both the excitation and emission wavelengths while keeping a fixed wavelength interval Δλ=20 nm between them. Characteristic, highly resolved peaks and significant spectral differences between normal and different pathological breast tissues were observed. The SS spectra of normal and different pathological breast tissues shows the distinct peaks around 300, 350, 450, 500 and 600 nm may be attributed to tryptophan, collagen, NADH, flavin and porphyrin respectively. Using SSS technique one can obtain all the key fluorophores in a single scan and hence they can be targeted as a tumor markers in this study. In order to quantify the altered spectral differences between normal and different pathological breast tissues are verified by different ratio parameters.

  10. Origins of Stokes shift in PbS nanocrystals

    KAUST Repository

    Voznyy, Oleksandr

    2017-10-27

    Stokes shift, an energy difference between the excitonic absorption and emission, is a property of colloidal quantum dots (CQDs) typically ascribed to splitting between dark and bright excitons. In some materials, e.g., PbS, CuInS2, CdHgTe, a Stokes shift of up to 200 meV is observed, substantially larger than the estimates of dark-bright state splitting or vibronic relaxations. The shift origin remains highly debated, as contradictory signatures of both surface and bulk character were reported for the Stokes-shifted electronic state. Here we show that the energy transfer among CQDs in a polydispersed ensemble in solution suffices to explain the excess Stokes shift. This energy transfer is primarily due to CQD aggregation, and can be substantially eliminated by extreme dilution, higher-viscosity solvent, or better-dispersed colloids. Our findings highlight that ensemble polydispersity remains the primary source of the Stokes shift in CQDs in solution, propagating into the Stokes shift in films and the open-circuit voltage deficit in CQD solar cells. Improved synthetic control can bring notable advancements in CQD photovoltaics, and the Stokes shift continues to provide a sensitive and significant metric to monitor ensemble size distribution.

  11. Fluorescence metrology of silica sol-gels

    Indian Academy of Sciences (India)

    We have developed a new method for measuring in-situ the growth of the nanometre-size silica particles which lead to the formation of sol-gel glasses. This technique is based on the decay of fluorescence polarisation anisotropy due to Brownian rotation of dye molecules bound to the particles. Results to date give near ...

  12. A new plastic scintillator with large Stokes shift

    International Nuclear Information System (INIS)

    Destruel, P.; Taufer, M.

    1989-01-01

    We have developed a new plastic scintillator with the novel characteristic of highly localized light emission; scintillation and wavelength shifting take place within a few tens of micrometers of the primary ionization. The new scintillator consists of a scintillating polymer base [polyvinyl toluene (PVT) or polystyrene (PS)] doped with a single wavelength shifter, 1-phenyl-3-mesityl-2-pyrazoline (PMP), which has an exceptionally large Stokes shift and therefore a comparatively small self-absorption of its emitted light. In other characteristics (e.g. scintillation efficiency and decay time) the performance of the new scintillator is similar to a good quality commercial plastic scintillator such as NE110. (orig.)

  13. Bis-pyridinium quadrupolar derivatives. High Stokes shift selective probes for bio-imaging

    Science.gov (United States)

    Salice, Patrizio; Versari, Silvia; Bradamante, Silvia; Meinardi, Francesco; Macchi, Giorgio; Pagani, Giorgio A.; Beverina, Luca

    2013-11-01

    We describe the design, synthesis and characterization of five high Stokes shift quadrupolar heteroaryl compounds suitable as fluorescent probes in bio-imaging. In particular, we characterize the photophysical properties and the intracellular localization in Human Umbilical Vein Endothelial Cells (HUVEC) and Human Mesenchymal Stem Cells (HMSCs) for each dye. We show that, amongst all of the investigated derivatives, the 2,5-bis[1-(4-N-methylpyridinium)ethen-2-yl)]- N-methylpyrrole salt is the best candidates as selective mitochondrial tracker. Finally, we recorded the full emission spectrum of the most performing - exclusively mitochondrial selective - fluorescent probe directly from HUVEC stained cells. The emission spectrum collected from the stained mitochondria shows a remarkably more pronounced vibronic structure with respect to the emission of the free fluorophore in solution.

  14. Noninvasive diagnosis of oral cancer by Stokes shift spectroscopy

    Science.gov (United States)

    Ebenezar, Jeyasingh; Ganesan, Singaravelu; Aruna, Prakasrao; Muralinaidu, Radhakrishnan

    2014-03-01

    The objective of this study is to evaluate the diagnostic potential of stokes shift (SS) spectroscopy (S3) for normal, precancer and cancerous oral lesions in vivo. The SS spectra were recorded in the 250 - 650 nm spectral range by simultaneously scanning both the excitation and emission wavelengths while keeping a fixed wavelength interval Δλ=20 nm between them. Characteristic, highly resolved peaks and significant spectral differences between normal and different pathological oral lesions observed around 300, 355, 395, and 420 nm which are attributed to tryptophan, collagen, and NADH respectively. Using S3 technique one can obtain the key fluorophores in a single scan and hence they can be targeted as a tumor markers in this study. In order to quantify the altered spectral differences between normal and different pathological oral lesions are verified by different ratio parameters.

  15. Uniform silica nanoparticles encapsulating two-photon absorbing fluorescent dye

    International Nuclear Information System (INIS)

    Wu Weibing; Liu Chang; Wang Mingliang; Huang Wei; Zhou Shengrui; Jiang Wei; Sun Yueming; Cui Yiping; Xu Chunxinag

    2009-01-01

    We have prepared uniform silica nanoparticles (NPs) doped with a two-photon absorbing zwitterionic hemicyanine dye by reverse microemulsion method. Obvious solvatochromism on the absorption spectra of dye-doped NPs indicates that solvents can partly penetrate into the silica matrix and then affect the ground and excited state of dye molecules. For dye-doped NP suspensions, both one-photon and two-photon excited fluorescence are much stronger and recorded at shorter wavelength compared to those of free dye solutions with comparative overall dye concentration. This behavior is possibly attributed to the restricted twisted intramolecular charge transfer (TICT), which reduces fluorescence quenching when dye molecules are trapped in the silica matrix. Images from two-photon laser scanning fluorescence microscopy demonstrate that the dye-doped silica NPs can be actively uptaken by Hela cells with low cytotoxicity. - Graphical abstract: Water-soluble silica NPs doped with a two-photon absorbing zwitterionic hemicyanine dye were prepared. They were found of enhanced one-photon and two-photon excited fluorescence compared to free dye solutions. Images from two-photon laser scanning fluorescence microscopy demonstrate that the dye-doped silica NPs can be actively uptaken by Hela cells.

  16. Synthesis and characterization of photoswitchable fluorescent silica nanoparticles.

    Science.gov (United States)

    Fölling, Jonas; Polyakova, Svetlana; Belov, Vladimir; van Blaaderen, Alfons; Bossi, Mariano L; Hell, Stefan W

    2008-01-01

    We have designed and synthesized a new functional (amino reactive) highly efficient fluorescent molecular switch (FMS) with a photochromic diarylethene and a rhodamine fluorescent dye. The reactive group in this FMS -N-hydroxysuccinimide ester- allows selective labeling of amino containing molecules or other materials. In ethanolic solutions, the compound displays a large fluorescent quantum yield of 52 % and a large fluorescence modulation ratio (94 %) between two states that may be interconverted with red and near-UV light. Silica nanoparticles incorporating the new FMS were prepared and characterized, and their spectroscopic and switching properties were also studied. The dye retained its properties after the incorporation into the silica, thereby allowing light-induced reversible high modulation of the fluorescence signal of a single particle for up to 60 cycles, before undergoing irreversible photobleaching. Some applications of these particles in fluorescence microscopy are also demonstrated. In particular, subdiffraction images of nanoparticles were obtained, in the focal plane of a confocal microscope.

  17. Origin of the Size-Dependent Stokes Shift in CsPbBr3 Perovskite Nanocrystals.

    Science.gov (United States)

    Brennan, Michael C; Herr, John E; Nguyen-Beck, Triet S; Zinna, Jessica; Draguta, Sergiu; Rouvimov, Sergei; Parkhill, John; Kuno, Masaru

    2017-09-06

    The origin of the size-dependent Stokes shift in CsPbBr 3 nanocrystals (NCs) is explained for the first time. Stokes shifts range from 82 to 20 meV for NCs with effective edge lengths varying from ∼4 to 13 nm. We show that the Stokes shift is intrinsic to the NC electronic structure and does not arise from extrinsic effects such as residual ensemble size distributions, impurities, or solvent-related effects. The origin of the Stokes shift is elucidated via first-principles calculations. Corresponding theoretical modeling of the CsPbBr 3 NC density of states and band structure reveals the existence of an intrinsic confined hole state 260 to 70 meV above the valence band edge state for NCs with edge lengths from ∼2 to 5 nm. A size-dependent Stokes shift is therefore predicted and is in quantitative agreement with the experimental data. Comparison between bulk and NC calculations shows that the confined hole state is exclusive to NCs. At a broader level, the distinction between absorbing and emitting states in CsPbBr 3 is likely a general feature of other halide perovskite NCs and can be tuned via NC size to enhance applications involving these materials.

  18. How to distinguish elastically scattered light from Stokes shifted light for solid-state lighting?

    NARCIS (Netherlands)

    Meretska, Maryna; Lagendijk, Aart; Thyrrestrup Nielsen, Henri; Mosk, Allard; IJzerman, W.L.; Vos, Willem L.

    2016-01-01

    We have studied the transport of light through phosphor diffuser plates that are used in commercial solid-state lighting modules (Fortimo). These polymer plates contain YAG:Ce+3phosphor particles that both elastically scatter and Stokes shift light in the visible wavelength range (400–700 nm). We

  19. Resolving the ambiguity in the relation between Stokes shift and Huang-Rhys parameter

    NARCIS (Netherlands)

    de Jong, Mathijs; Seijo, Luis; Meijerink, A; Rabouw, F.T.

    2015-01-01

    Electronic transitions in luminescent molecules or centers in crystals couple to vibrations. This results in broadening of absorption and emission bands, as well as in the occurence of a Stokes shift EStokes. In principle, one can derive from EStokes the Huang–Rhys parameter S, which describes the

  20. Liposome encapsulation of fluorescent nanoparticles: Quantum dots and silica nanoparticles

    International Nuclear Information System (INIS)

    Chen, C.-S.; Yao Jie; Durst, Richard A.

    2006-01-01

    Quantum dots (QDs) and silica nanoparticles (SNs) are relatively new classes of fluorescent probes that overcome the limitations encountered by organic fluorophores in bioassay and biological imaging applications. We encapsulated QDs and SNs in liposomes and separated nanoparticle-loaded liposomes from unencapsulated nanoparticles by size exclusion chromatography. Fluorescence correlation spectroscopy was used to measure the average number of nanoparticles inside each liposome. Results indicated that nanoparticle-loaded liposomes were formed and separated from unencapsulated nanoparticles by using a Sepharose gel. As expected, fluorescence self-quenching of nanoparticles inside liposomes was not observed. Each liposome encapsulated an average of three QDs. These studies demonstrated that nanoparticles could be successfully encapsulated into liposomes and provided a methodology to quantify the number of nanoparticles inside each liposome by fluorescence correlation spectroscopy

  1. Interferences of Silica Nanoparticles in Green Fluorescent Protein Folding Processes.

    Science.gov (United States)

    Klein, Géraldine; Devineau, Stéphanie; Aude, Jean Christophe; Boulard, Yves; Pasquier, Hélène; Labarre, Jean; Pin, Serge; Renault, Jean Philippe

    2016-01-12

    We investigated the relationship between unfolded proteins, silica nanoparticles and chaperonin to determine whether unfolded proteins could stick to silica surfaces and how this process could impair heat shock protein activity. The HSP60 catalyzed green fluorescent protein (GFP) folding was used as a model system. The adsorption isotherms and adsorption kinetics of denatured GFP were measured, showing that denaturation increases GFP affinity for silica surfaces. This affinity is maintained even if the surfaces are covered by a protein corona and allows silica NPs to interfere directly with GFP folding by trapping it in its unstructured state. We determined also the adsorption isotherms of HSP60 and its chaperonin activity once adsorbed, showing that SiO2 NP can interfere also indirectly with protein folding through chaperonin trapping and inhibition. This inhibition is specifically efficient when NPs are covered first with a layer of unfolded proteins. These results highlight for the first time the antichaperonin activity of silica NPs and ask new questions about the toxicity of such misfolded proteins/nanoparticles assembly toward cells.

  2. Stokes shift spectroscopy for the early diagnosis of epithelial precancers in DMBA treated mouse skin carcinogenesis

    Science.gov (United States)

    Jeyasingh, Ebenezar; Singaravelu, Ganesan; Prakasarao, Aruna

    2018-02-01

    In this study, we aim to characterize the tissue transformation in dimethylbenz(a)anthracene (DMBA) treated mouse skin tumor model using stokes shift spectroscopy (SSS) technique for early detection of the neoplastic changes. Stokes shift (SS) spectra measured by scanning both excitation and emission wavelength simultaneously with a fixed wavelength of interval (Δλ=20 nm) in vivo from 33 DMBA treated animals and 6 control animals. The SS spectra of normal (n=6), hyperplasia (n=10), dysplasia (n=10), and WDSCC (n=13) of mice skin shows the distinct peaks around 300, 350, and 386 nm may be attributed to tryptophan, collagen, and NADH respectively. From the observed spectral differences and the ratio variables that resulted in better classification between groups, it is concluded that tryptophan, collagen, and NADH are the key fluorophores that undergo changes during tissue transformation process and hence they can be targeted as tumor markers for early neoplastic changes.

  3. Reduction of reabsorption effects in scintillators by employing solutes with large Stokes shifts

    International Nuclear Information System (INIS)

    Harrah, L.A.; Renschler, C.L.

    1986-01-01

    A radiation or high energy particle responsive system is described useful as a scintillator, and comprising, a first component which interacts with the radiation or high energy particle to emit photons in a certain first wavelength range; and at least one additional solute component which absorbs the photons in the first wavelength range and thereupon emits photons in another wavelength range higher than the first range; the improvement wherein at least one of the components absorbs substantially no photons in the wavelength range in which it emits photons, due to large Stokes shift caused by an excited states intramolecular rearrangement, with the proviso that the component having a large Stokes shift is not methyl salicylate or salicyclic acid

  4. Optical transitions and nature of Stokes shift in spherical CdS quantum dots

    OpenAIRE

    Demchenko, D. O.; Wang, Lin-Wang

    2006-01-01

    We study the structure of the energy spectra along with the character of the states participating in optical transitions in colloidal CdS quantum dots (QDs) using the {\\sl ab initio} accuracy charge patching method combined with the %pseudopotential based folded spectrum calculations of electronic structure of thousand-atom nanostructures. In particular, attention is paid to the nature of the large resonant Stokes shift observed in CdS quantum dots. We find that the top of the valence band st...

  5. Fluorescent Functionalized Mesoporous Silica for Radioactive Material Extraction

    International Nuclear Information System (INIS)

    Li, Juan; Zhu, Kake; Shang, Jianying; Wang, Donghai; Nie, Zimin; Guo, Ruisong; Liu, Chongxuan; Wang, Zheming; Li, Xiaolin; Liu, Jun

    2012-01-01

    Mesoporous silica with covalently bound salicylic acid molecules incorporated in the structure was synthesized with a one-pot, co-condensation reaction at room temperature. The as-synthesized material has a large surface area, uniform particle size, and an ordered pore structure as determined by characterization with transmission electron microscopy, thermal gravimetric analysis, and infrared spectra, etc. Using the strong fluorescence and metal coordination capability of salicylic acid, functionalized mesoporous silica (FMS) was developed to track and extract radionuclide contaminants, such as uranyl (U(VI)) ions encountered in subsurface environments. Adsorption measurements showed a strong affinity of the FMS toward U(VI) with a Kd value of 105 mL/g, which is four orders of magnitude higher than the adsorption of U(VI) onto most of the sediments in natural environments. The new materials have a potential for synergistic environmental monitoring and remediation of the radionuclide U(VI) from contaminated subsurface environments.

  6. Fluorescent Silica Nanoparticles in the Detection and Control of the Growth of Pathogen

    International Nuclear Information System (INIS)

    Chitra, K.; Annadurai, G.

    2013-01-01

    In this present study the bio conjugated fluorescent silica nanoparticles give an efficient fluorescent-based immunoassay for the detection of pathogen. The synthesized silica nanoparticles were poly dispersed and the size of the silica nanoparticles was in the range of 114-164 nm. The energy dispersive X-ray spectrophotometer showed the presence of silica at 1.8 keV and the selected area diffractometer showed amorphous nature of silica nanoparticles. The FTIR spectrum confirmed the attachment of dye and carboxyl group onto the silica nanoparticles surface. The fluorescent silica nanoparticles showed highly efficient fluorescence and the fluorescent emission of silica nanoparticles occurred at 536 nm. The SEM image showed the aggregation of nanoparticles and bacteria. The growth of the pathogenic E. coli was controlled using silica nanoparticles; therefore silica nanoparticles could be used in food packaging material, biomedical material, and so forth. This work provides a rapid, simple, and accurate method for the detection of pathogen using fluorescent-based immunoassay.

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

    NARCIS (Netherlands)

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

    2015-01-01

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

  8. Preparation and flow cytometry of uniform silica-fluorescent dye microspheres.

    Science.gov (United States)

    Bele, Marjan; Siiman, Olavi; Matijević, Egon

    2002-10-15

    Uniform fluorescent silica-dye microspheres have been prepared by coating preformed monodispersed silica particles with silica layers containing rhodamine 6G or acridine orange. The resulting dispersions exhibit intense fluorescent emission between 500 and 600 nm, over a broad excitation wavelength range of 460 to 550 nm, even with exceedingly small amounts of dyes incorporated into the silica particles (10-30 ppm, expressed as weight of dye relative to weight of dry particles). The fluorescent particles can be prepared in micrometer diameters suitable for analyses using flow cytometry with 488-nm laser excitation.

  9. Microspectroscopic analysis of green fluorescent proteins infiltrated into mesoporous silica nanochannels

    NARCIS (Netherlands)

    Ma, Yujie; Rajendran, Prayanka; Blum, Christian; Cesa, Yanina; Gartmann, Nando; Brühwiler, Dominik; Subramaniam, Vinod

    2011-01-01

    The infiltration of enhanced green fluorescent protein (EGFP) into nanochannels of different diameters in mesoporous silica particles was studied in detail by fluorescence microspectroscopy at room temperature. Silica particles from the MCM-41, ASNCs and SBA-15 families possessing nanometer-sized

  10. Resolving the ambiguity in the relation between Stokes shift and Huang-Rhys parameter.

    Science.gov (United States)

    de Jong, Mathijs; Seijo, Luis; Meijerink, Andries; Rabouw, Freddy T

    2015-07-14

    Electronic transitions in luminescent molecules or centers in crystals couple to vibrations. This results in broadening of absorption and emission bands, as well as in the occurence of a Stokes shift EStokes. In principle, one can derive from EStokes the Huang-Rhys parameter S, which describes the microscopic details of the vibrational coupling and can be related to the equilibrium position offset ΔQe between the ground state and excited state. The commonly used textbook relations EStokes = (2S - 1)ℏω and EStokes = 2Sℏω are only approximately valid. In this paper we investigate how EStokes is related to S, taking into account the effects of a finite temperature. We show that in different ranges of temperature, different approximate relations between EStokes and S are appropriate. Moreover, we demonstrate that the difference between the barycenters of absorption and emission bands can be used to determine S in an unambiguous way. The position of the barycenter is, contrary to the Stokes shift, unaffected by temperature.

  11. Imaging subsurface damage of grinded fused silica optics by confocal fluorescence microscopy

    International Nuclear Information System (INIS)

    Neauport, J.; Cormont, P.; Destribats, J.; Legros, P.; Ambard, C.

    2009-01-01

    We report an experimental investigation of fluorescence confocal microscopy as a tool to measure subsurface damage on grinded fused silica optics. Confocal fluorescence microscopy was performed with an excitation at the wavelength of 405 nm on fixed abrasive diamond grinded fused silica samples. We detail the measured fluorescence spectrums and compare them to those of oil based coolants and grinding slurries. We evidence that oil based coolant used in diamond grinding induces a fluorescence that marks the subsurface damages and eases its observation. Such residual traces might also be involved in the laser damage process. (authors)

  12. Stokes shift and fine-structure splitting in CdSe / CdTe invert type-II ...

    Indian Academy of Sciences (India)

    Worasak Sukkabot

    2018-01-09

    Jan 9, 2018 ... optical properties can be easily manipulated. The entan- ... and shape on the Stokes shift and FSS in core/shell .... Figure 4. Ground-state wave function overlaps of. CdSe/CdTe and CdTe/CdSe core/shell nanocrystals as.

  13. Bioconjugated fluorescent silica nanoparticles for the rapid detection of Entamoeba histolytica.

    Science.gov (United States)

    Hemadi, Ahmad; Ekrami, Alireza; Oormazdi, Hormozd; Meamar, Ahmad Reza; Akhlaghi, Lame; Samarbaf-Zadeh, Ali Reza; Razmjou, Elham

    2015-05-01

    Rapid detection of Entamoeba histolytica based on fluorescent silica nanoparticle (FSNP) indirect immunofluorescence microscopy was evaluated. Silica nanoparticles were synthesized using Stöber's method, with their surface activated to covalently bind to, and immobilize, protein A. For biolabeling, FSNP was added to conjugated E. histolytica trophozoites with monoclonal anti-E. histolytica IgG1 for microscopic observation of fluorescence. Fluorescent silica nanoparticle sensitivity was determined with axenically cultured E. histolytica serially diluted to seven concentrations. Specificity was evaluated using other intestinal protozoa. Fluorescent silica nanoparticles detected E. histolytica at the lowest tested concentration with no cross-reaction with Entamoeba dispar, Entamoeba moshkovskii, Blastocystis sp., or Giardia lamblia. Visualization of E. histolytica trophozoites with anti-E. histolytica antibody labeled with fluorescein isothiocyanate (FITC) was compared with that using anti-E. histolytica antibody bioconjugated FSNP. Although FITC and FSNP produced similar results, the amount of specific antibody required for FITC to induce fluorescence of similar intensity was fivefold that for FSNP. Fluorescent silica nanoparticles delivered a rapid, simple, cost-effective, and highly sensitive and specific method of detecting E. histolytica. Further study is needed before introducing FSNP for laboratory diagnosis of amoebiasis. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Plasmonic properties and enhanced fluorescence of gold and dye-doped silica nanoparticle aggregates

    Science.gov (United States)

    Green, Nathaniel Scott

    The development of metal-enhanced fluorescence has prompted a great interest in augmenting the photophysical properties of fluorescent molecules with noble metal nanostructures. Our research efforts, outlined in this dissertation, focus on augmenting properties of fluorophores by conjugation with gold nanostructures. The project goals are split into two separate efforts; the enhancement in brightness of fluorophores and long distance non-radiative energy transfer between fluorophores. We believe that interacting dye-doped silica nanoparticles with gold nanoparticles can facilitate both of these phenomena. Our primary research interest is focused on optimizing brightness, as this goal should open a path to studying the second goal of non-radiative energy transfer. The two major challenges to this are constructing suitable nanomaterials and functionalizing them to promote plasmonically active complexes. The synthesis of dye-doped layered silica nanoparticles allows for control over the discrete location of the dye and a substrate that can be surface functionalized. Controlling the exact location of the dye is important to create a silica spacer, which promotes productive interactions with metal nanostructures. Furthermore, the synthesis of silica nanoparticles allows for various fluorophores to be studied in similar environments (removing solvent and other chemo-sensitive issues). Functionalizing the surface of silica nanoparticles allows control over the degree of silica and gold nanoparticle aggregation in solution. Heteroaggregation in solution is useful for producing well-aggregated clusters of many gold around a single silica nanoparticle. The dye-doped surface functionalized silica nanoparticles can than be mixed efficiently with gold nanomaterials. Aggregating multiple gold nanospheres around a single dye-doped silica nanoparticle can dramatically increase the fluorescent brightness of the sample via metal-enhanced fluorescence due to increase plasmonic

  15. Fine tuning the emission wavelengths of the 7-hydroxy-1-indanone based nano-structure dyes: Near-infrared (NIR) dual emission generation with large stokes shifts

    Science.gov (United States)

    Roohi, Hossein; Alizadeh, Parvaneh

    2018-05-01

    Near-infrared (NIR) fluorescent dyes have recently gained special attention due to their applications to use as molecular probes for imaging of biological targets and sensitive determination. In this study, photophysical properties of the 7-hydroxy-1-indanone based fluorophors A1, A2, A3, B1, B2 and 3R-B2 (R = CF3, NH2, NO2 and OMe) in the gas and three solution phases were probed using TD-DFT method at PBE0/6-311++G(d,p) and M06-2X/6-311++G(d,p) levels of theory. In addition to structural and photophysical properties as well as ESIPT mechanism of all mentioned molecules, the FC and relaxed potential energy surfaces of B2 and 3R-B2 (R = CF3 and NH2) molecules were explored in gas phase and acetonitrile, cyclohexane and water solvents. It is predicted that the A1, A3 and 3R-B2 chromophores afford normal (615-670 nm) and NIR fluorescence emissions (770-940 nm; biological window) with the large Stokes shifts of >160 and >300 nm, respectively. A good aggrement was found between theoretical and experimental results. In sum, these new types of dyes may render the new approaches for the development of the most efficient NIR fluorescent probes for enhanced image contrast and optimal apparent brightness in biological applications.

  16. Reduced reabsorption and enhanced propagation induced by large Stokes shift in quantum dot-filled optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Hua; Zhang, Yu, E-mail: yuzhang@jlu.edu.cn; Lu, Min; Liu, Wenyan [Jilin University, State Key Laboratory on Integrated Optoelectronics and College of Electronic Science and Engineering (China); Xu, Jian [The Pennsylvania State University, Department of Engineering Science and Mechanics (United States); Yu, William W., E-mail: wyu6000@gmail.com [Jilin University, State Key Laboratory on Integrated Optoelectronics and College of Electronic Science and Engineering (China)

    2016-07-15

    With tunable emission wavelength, high photoluminescence quantum yield, and broad absorption, colloidal quantum dots are attractive for the application in optical fiber as dopants. However, most of the quantum dots have a large overlap between their absorption and photoluminescence spectra, resulting in reabsorption loss which hinders the realization of long-distance waveguides. Therefore, ZnCuInS/ZnSe/ZnS quantum dots with large Stokes shift were proposed to fabricate a liquid-core optical fiber in this work. In this work, ZnCuInS/ZnSe/ZnS QDs with an average size of 3.3 nm were synthesized and the optical properties of the QD-filled fiber were also investigated as a function of fiber length and doping concentration. Compared to the control sample filled with CdSe/CdS/ZnS quantum dots, the ZnCuInS/ZnSe/ZnS quantum dot-based waveguides showed reduced reabsorption and enhanced signal propagation, which demonstrates great potential of large Stokes-shift quantum dots in optical waveguide devices.Graphical AbstractA reduced reabsorption and enhanced propagation of ZnCuInS/ZnSe/ZnS QDs-doped liquid-core optical fiber was achieved due to the large Stokes shift.

  17. Fabrication of fluorescent silica nanoparticles with aggregation-induced emission luminogens for cell imaging.

    Science.gov (United States)

    Chen, Sijie; Lam, Jacky W Y; Tang, Ben Zhong

    2013-01-01

    Fluorescence-based techniques have found wide applications in life science. Among various luminogenic materials, fluorescent nanoparticles have attracted much attention due to their fabulous emission properties and potential applications as sensors. Here, we describe the fabrication of fluorescent silica nanoparticles (FSNPs) containing aggregation-induced emission (AIE) luminogens. By employing surfactant-free sol-gel reaction, FSNPs with uniform size and high surface charge and colloidal stability are generated. The FSNPs emit strong light upon photoexcitation, due to the AIE characteristic of the silole -aggregates in the hybrid nanoparticles. The FSNPs are cytocompatible and can be utilized as fluorescent visualizer for intracellular imaging for HeLa cells.

  18. Fluorescent proteins as efficient tools for evaluating the surface PEGylation of silica nanoparticles

    Science.gov (United States)

    Zhang, Wei; Ma, Minyan; Zhang, Xiao-ai; Zhang, Ze-yu; Saleh, Sayed M.; Wang, Xu-dong

    2017-06-01

    Surface PEGylation is essential for preventing non-specific binding of biomolecules when silica nanoparticles are utilized for in vivo applications. Methods for installing poly(ethylene glycol) on a silica surface have been widely explored but varies from study to study. Because there is a lack of a satisfactory method for evaluating the properties of silica surface after PEGylation, the prepared nanoparticles are not fully characterized before use. In some cases, even non-PEGylated silica nanoparticles were produced, which is unfortunately not recognized by the end-user. In this work, a fluorescent protein was employed, which acts as a sensitive material for evaluating the surface protein adsorption properties of silica nanoparticles. Eleven different methods were systematically investigated for their reaction efficiency towards surface PEGylation. Results showed that both reaction conditions (including pH, catalyst) and surface functional groups of parent silica nanoparticles play critical roles in producing fully PEGylated silica nanoparticles. Great care needs to be taken in choosing the proper coupling chemistry for surface PEGylation. The data and method shown here will guarantee high-quality PEGylated silica nanoparticles to be produced and guide their applications in biology, chemistry, industry and medicine.

  19. Novel fluorescent poly(glycidyl methacrylate) - silica microspheres

    Czech Academy of Sciences Publication Activity Database

    Grama, Silvia; Boiko, N.; Bilyy, R.; Klyuchivska, O.; Antonyuk, V.; Stoika, R.; Horák, Daniel

    2014-01-01

    Roč. 56, July (2014), s. 92-104 ISSN 0014-3057 R&D Projects: GA MŠk EE2.3.30.0029; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:61389013 Keywords : microspheres * silica * poly(glycidyl methacrylate) Subject RIV: CE - Biochemistry Impact factor: 3.005, year: 2014

  20. Synthesis and characterization of photoswitchable fluorescent silica nanoparticles

    NARCIS (Netherlands)

    Fölling, J.; Polyakova, S.; Belov, V.; van Blaaderen, A.; Bossi, M.L.; Hell, S.W.

    2008-01-01

    We have designed and synthesized a new functional (amino reactive) highly efficient fluorescent molecular switch (FMS) with a photochromic diarylethene and a rhodamine fluorescent dye. The reactive group in this FMS -N-hydroxysuccinimide ester- allows selective labeling of amino containing molecules

  1. High-quality substrate for fluorescence enhancement using agarose-coated silica opal film.

    Science.gov (United States)

    Xu, Ming; Li, Juan; Sun, Liguo; Zhao, Yuanjin; Xie, Zhuoying; Lv, Linli; Zhao, Xiangwei; Xiao, Pengfeng; Hu, Jing; Lv, Mei; Gu, Zhongze

    2010-08-01

    To improve the sensitivity of fluorescence detection in biochip, a new kind of substrates was developed by agarose coating on silica opal film. In this study, silica opal film was fabricated on glass substrate using the vertical deposition technique. It can provide stronger fluorescence signals and thus improve the detection sensitivity. After coating with agarose, the hybrid film could provide a 3D support for immobilizing sample. Comparing with agarose-coated glass substrate, the agarose-coated opal substrates could selectively enhance particular fluorescence signals with high sensitivity when the stop band of the silica opal film in the agarose-coated opal substrate overlapped the fluorescence emission wavelength. A DNA hybridization experiment demonstrated that fluorescence intensity of special type of agarose-coated opal substrates was about four times that of agarose-coated glass substrate. These results indicate that the optimized agarose-coated opal substrate can be used for improving the sensitivity of fluorescence detection with high quality and selectivity.

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

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  3. Fluorescent single walled nanotube/silica composite materials

    Science.gov (United States)

    Dattelbaum, Andrew M.; Gupta, Gautam; Duque, Juan G.; Doorn, Stephen K.; Hamilton, Christopher E.; DeFriend Obrey, Kimberly A.

    2013-03-12

    Fluorescent composites of surfactant-wrapped single-walled carbon nanotubes (SWNTs) were prepared by exposing suspensions of surfactant-wrapped carbon nanotubes to tetramethylorthosilicate (TMOS) vapor. Sodium deoxycholate (DOC) and sodium dodecylsulphate (SDS) were the surfactants. No loss in emission intensity was observed when the suspension of DOC-wrapped SWNTs were exposed to the TMOS vapors, but about a 50% decrease in the emission signal was observed from the SDS-wrapped SWNTs nanotubes. The decrease in emission was minimal by buffering the SDS/SWNT suspension prior to forming the composite. Fluorescent xerogels were prepared by adding glycerol to the SWNT suspensions prior to TMOS vapor exposure, followed by drying the gels. Fluorescent aerogels were prepared by replacing water in the gels with methanol and then exposing them to supercritical fluid drying conditions. The aerogels can be used for gas sensing.

  4. Cytotoxicity and fluorescence studies of silica-coated CdSe quantum dots for bioimaging applications

    International Nuclear Information System (INIS)

    Vibin, Muthunayagam; Vinayakan, Ramachandran; John, Annie; Raji, Vijayamma; Rejiya, Chellappan S.; Vinesh, Naresh S.; Abraham, Annie

    2011-01-01

    The toxicological effects of silica-coated CdSe quantum dots (QDs) were investigated systematically on human cervical cancer cell line. Trioctylphosphine oxide capped CdSe QDs were synthesized and rendered water soluble by overcoating with silica, using aminopropyl silane as silica precursor. The cytotoxicity studies were conducted by exposing cells to freshly synthesized QDs as a function of time (0–72 h) and concentration up to micromolar level by Lactate dehydrogenase assay, MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] assay, Neutral red cell viability assay, Trypan blue dye exclusion method and morphological examination of cells using phase contrast microscope. The in vitro analysis results showed that the silica-coated CdSe QDs were nontoxic even at higher loadings. Subsequently the in vivo fluorescence was also demonstrated by intravenous administration of the QDs in Swiss albino mice. The fluorescence images in the cryosections of tissues depicted strong luminescence property of silica-coated QDs under biological conditions. These results confirmed the role of these luminescent materials in biological labeling and imaging applications.

  5. Cytotoxicity and fluorescence studies of silica-coated CdSe quantum dots for bioimaging applications

    Energy Technology Data Exchange (ETDEWEB)

    Vibin, Muthunayagam [University of Kerala, Department of Biochemistry (India); Vinayakan, Ramachandran [National Institute for Interdisciplinary Science and Technology (CSIR), Photosciences and Photonics (India); John, Annie [Sree Chitra Tirunal Institute of Medical Sciences and Technology, Biomedical Technology Wing (India); Raji, Vijayamma; Rejiya, Chellappan S.; Vinesh, Naresh S.; Abraham, Annie, E-mail: annieab2@yahoo.co.in [University of Kerala, Department of Biochemistry (India)

    2011-06-15

    The toxicological effects of silica-coated CdSe quantum dots (QDs) were investigated systematically on human cervical cancer cell line. Trioctylphosphine oxide capped CdSe QDs were synthesized and rendered water soluble by overcoating with silica, using aminopropyl silane as silica precursor. The cytotoxicity studies were conducted by exposing cells to freshly synthesized QDs as a function of time (0-72 h) and concentration up to micromolar level by Lactate dehydrogenase assay, MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] assay, Neutral red cell viability assay, Trypan blue dye exclusion method and morphological examination of cells using phase contrast microscope. The in vitro analysis results showed that the silica-coated CdSe QDs were nontoxic even at higher loadings. Subsequently the in vivo fluorescence was also demonstrated by intravenous administration of the QDs in Swiss albino mice. The fluorescence images in the cryosections of tissues depicted strong luminescence property of silica-coated QDs under biological conditions. These results confirmed the role of these luminescent materials in biological labeling and imaging applications.

  6. A new approach for white organic light-emitting diodes of single emitting layer using large stokes shift.

    Science.gov (United States)

    Kim, Beomjin; Park, Youngil; Kim, Seungho; Lee, Younggu; Park, Jongwook

    2014-08-01

    DPPZ showed UV-Vis. and PL maximum values of 412 and 638 nm, meaning the large stokes shift. Blue host compound, TAT was synthesized and used for co-mixed white emission. TAT exhibited UV-Vis. and PL maximum values of 403 nm and 445 nm in film state. Thus, when two compounds are used as co-mixed emitter in OLED device, there is no energy transfer from blue emission of TAT to DPPZ due to large stokes shift of DPPZ. Based on the PL result, it is available to realize two-colored white in PL and EL spectra. As a result of this, two-mixed compounds showed vivid their own PL emission peaks of 449 and 631 nm in film state. Also, white OLED device using two-mixed compounds system was fabricated. EL spectrum shows 457 and 634 nm peaks and two separate EL peaks, respectively. As the operation voltage is increased from 7 to 11 V, EL spectrum does not change the peak shape and maximum wavelength values. EL performance of white device showed 0.29 cd/A, 0.14 lm/W, and CIE (0.325, 0.195) at 7 V.

  7. A new approach way for white organic light-emitting diodes based on single emitting layer and large stokes shift.

    Science.gov (United States)

    Kim, Beomjin; Park, Youngil; Shin, Yunseop; Lee, Jiwon; Shin, Hwangyu; Park, Jongwook

    2014-07-01

    New red dopant, DPPZ based on porphyrin moiety was synthesized. DPPZ showed UV-Vis and PL maximum values of 412 and 638 nm, indicating the large stokes shift. New blue host compound, TATa was also synthesized and used for co-mixed white emission. TATa exhibited UV-Vis. and PL maximum values of 403 nm and 463 nm in film state. Thus, when two compounds are used as co-mixed emitter in OLED device, there is no energy transfer from blue emission of TATa to DPPZ due to large stokes shift of DPPZ. Based on the PL result, it is available to realize two-colored white in PL and EL spectra. As a result of this, two-mixed compounds showed vivid their own PL emission peaks of 466 and 638 nm in film state. Also, white OLED device using two-mixed compounds system was fabricated. EL spectrum shows 481 and 646 nm peaks and two separate EL peaks. As the operation voltage is increased from 8 to 11 V, EL spectrum does not change the peak shape and maximum wavelength values. EL performance of white device showed 0.041 cd/A, 0.018 Im/W, and CIE (0.457, 0.331) at 8 V.

  8. Preparation of fluorescent mesoporous hollow silica-fullerene nanoparticles via selective etching for combined chemotherapy and photodynamic therapy

    Science.gov (United States)

    Yang, Yannan; Yu, Meihua; Song, Hao; Wang, Yue; Yu, Chengzhong

    2015-07-01

    Well-dispersed mesoporous hollow silica-fullerene nanoparticles with particle sizes of ~50 nm have been successfully prepared by incorporating fullerene molecules into the silica framework followed by a selective etching method. The fabricated fluorescent silica-fullerene composite with high porosity demonstrates excellent performance in combined chemo/photodynamic therapy.Well-dispersed mesoporous hollow silica-fullerene nanoparticles with particle sizes of ~50 nm have been successfully prepared by incorporating fullerene molecules into the silica framework followed by a selective etching method. The fabricated fluorescent silica-fullerene composite with high porosity demonstrates excellent performance in combined chemo/photodynamic therapy. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02769a

  9. Silica encapsulation of fluorescent nanodiamonds for colloidal stability and facile surface functionalization.

    Science.gov (United States)

    Bumb, Ambika; Sarkar, Susanta K; Billington, Neil; Brechbiel, Martin W; Neuman, Keir C

    2013-05-29

    Fluorescent nanodiamonds (FNDs) emit in the near-IR and do not photobleach or photoblink. These properties make FNDs better suited for numerous imaging applications compared with commonly used fluorescence agents such as organic dyes and quantum dots. However, nanodiamonds do not form stable suspensions in aqueous buffer, are prone to aggregation, and are difficult to functionalize. Here we present a method for encapsulating nanodiamonds with silica using an innovative liposome-based encapsulation process that renders the particle surface biocompatible, stable, and readily functionalized through routine linking chemistries. Furthermore, the method selects for a desired particle size and produces a monodisperse agent. We attached biotin to the silica-coated FNDs and tracked the three-dimensional motion of a biotinylated FND tethered by a single DNA molecule with high spatial and temporal resolution.

  10. Mesoporous silica for drug delivery: Interactions with model fluorescent lipid vesicles and live cells.

    Science.gov (United States)

    Bardhan, Munmun; Majumdar, Anupa; Jana, Sayantan; Ghosh, Tapas; Pal, Uttam; Swarnakar, Snehasikta; Senapati, Dulal

    2018-01-01

    Formulated mesoporous silica nanoparticle (MSN) systems offer the best possible drug delivery system through the release of drug molecules from the accessible pores. In the present investigation, steady state and time resolved fluorescence techniques along with the fluorescence imaging were applied to investigate the interactions of dye loaded MSN with fluorescent unilamellar vesicles and live cells. Here 1,2-dimyristoyl-sn-glycero-3-phospocholine (DMPC) was used to prepare Small Unilamellar Vesicles (SUVs) as the model membrane with fluorescent 1,6-diphenyl-1,3,5-hexatriene (DPH) molecule incorporated inside the lipid bilayer. The interaction of DPH incorporated DMPC membrane with Fluorescein loaded MSN lead to the release of Fluorescein (Fl) dye from the interior pores of MSN systems. The extent of release of Fl and spatial distribution of the DPH molecule has been explored by monitoring steady-state fluorescence intensity and fluorescence lifetime at physiological condition. To investigate the fate of drug molecule released from MSN, fluorescence anisotropy has been used. The drug delivery efficiency of the MSN as a carrier for doxorubicin (DOX), a fluorescent chemotherapeutic drug, has also been investigated at physiological conditions. The study gives a definite confirmation for high uptake and steady release of DOX in primary oral mucosal non-keratinized squamous cells in comparison to naked DOX treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

    Yoo, Hyojong; Pak, Joonsung

    2013-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-05-15

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

  13. Folate receptor targeting silica nanoparticle probe for two-photon fluorescence bioimaging

    Science.gov (United States)

    Wang, Xuhua; Yao, Sheng; Ahn, Hyo-Yang; Zhang, Yuanwei; Bondar, Mykhailo V.; Torres, Joseph A.; Belfield, Kevin D.

    2010-01-01

    Narrow dispersity organically modified silica nanoparticles (SiNPs), diameter ~30 nm, entrapping a hydrophobic two-photon absorbing fluorenyl dye, were synthesized by hydrolysis of triethoxyvinylsilane and (3-aminopropyl)triethoxysilane in the nonpolar core of Aerosol-OT micelles. The surface of the SiNPs were functionalized with folic acid, to specifically deliver the probe to folate receptor (FR) over-expressing Hela cells, making these folate two-photon dye-doped SiNPs potential candidates as probes for two-photon fluorescence microscopy (2PFM) bioimaging. In vitro studies using FR over-expressing Hela cells and low FR expressing MG63 cells demonstrated specific cellular uptake of the functionalized nanoparticles. One-photon fluorescence microscopy (1PFM) imaging, 2PFM imaging, and two-photon fluorescence lifetime microscopy (2P-FLIM) imaging of Hela cells incubated with folate-modified two-photon dye-doped SiNPs were demonstrated. PMID:21258480

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

    Science.gov (United States)

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

    2007-08-01

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

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

    International Nuclear Information System (INIS)

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

    2007-01-01

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

  16. 2-Hydroxy-naphthyl functionalized mesoporous silica for fluorescence sensing and removal of aluminum ions.

    Science.gov (United States)

    Das, Trisha; Roy, Ankita; Uyama, Hiroshi; Roy, Partha; Nandi, Mahasweta

    2017-06-06

    Mesoporous silica functionalized with a 2-hydroxy-naphthyl moiety has been synthesized and characterized by standard techniques like powder X-ray diffraction, N 2 adsorption/desorption studies, transmission electron microscopy and spectral studies like FT-IR, UV-visible, fluorescence and 13 C and 29 Si solid state NMR. The functionalized silica material showed significant enhancement in its emission intensity in the presence of Al 3+ ions whereas other metal ions could not bring about any increase in its emission intensity. They either quench the emission or do not alter the intensity significantly making the functionalized material a fluorescence chemosensor for Al 3+ . The sensitivity of the probe towards Al 3+ has been determined to be high with a low limit of detection value. As functionalized silica is not soluble in common solvents, it has been effectively used to bind and remove Al 3+ from a solution. Theoretical calculations on a model system have been performed to investigate the electronic spectral transitions.

  17. Steady state and time resolved fluorescence studies of azadioxatriangulenium (ADOTA) fluorophore in silica and PVA thin films

    DEFF Research Database (Denmark)

    Chib, Rahul; Raut, Sangram; Shah, Sunil

    2015-01-01

    A cationic azadioxatriangulenium dye was entrapped in silica thin films obtained by the sol-gel process and in poly (vinyl) alcohol (PVA) thin films. Azadioxatriangulenium is a red emitting fluorophore with a long fluorescence lifetime of ∼20 ns. The fluorescent properties of azadioxatriangulenium...

  18. Fluorescent silica colloids for study and visualization of skin care products.

    Science.gov (United States)

    Iyer, Swaminathan; Kievsky, Yaroslav; Sokolov, Igor

    2007-08-01

    The efficacy of skin care products depends on the time and dynamics of their absorbance by the skin, and its spatial distribution on the skin. Regular scrape-based methods may depend on the operator and are destructive and invasive in nature. Here, we describe a novel method based on non-contact optical measurements to trace the location and dynamics of skin care products on the skin. We use fluorescent silica colloidal particles of micron sizes at a rather small concentration as non-invasive tracers. As an example of skin care products, we use two base materials: either glycerin or vaseline. A mixture of each product with fluorescent particles is applied on human skin. The amount of fluorescence is monitored by means of a fluorescent spectrometer. The scraping method is used to compare with the spectroscopic measurements. Fluorescent tracers make the skin care product visible under UV light. This allows obtaining an optical image of the spatial distribution of the product on the skin. The quantitative data of fluorescence are well correlated with the scrape data. Comparison of the difference in the spectral and scraped mass data reveals the details of accumulation of the skin products in skin cracks and crevices. We described an efficient non-invasive benign method to quantify dynamics and to perform mapping of emollients and humectants on the skin.

  19. Breast cancer cells synchronous labeling and separation based on aptamer and fluorescence-magnetic silica nanoparticles

    Science.gov (United States)

    Wang, Qiu-Yue; Huang, Wei; Jiang, Xing-Lin; Kang, Yan-Jun

    2018-01-01

    In this work, an efficient method based on biotin-labeled aptamer and streptavidin-conjugated fluorescence-magnetic silica nanoprobes (FITC@Fe3O4@SiNPs-SA) has been established for human breast carcinoma MCF-7 cells synchronous labeling and separation. Carboxyl-modified fluorescence-magnetic silica nanoparticles (FITC@Fe3O4@SiNPs-COOH) were first synthesized using the Stöber method. Streptavidin (SA) was then conjugated to the surface of FITC@Fe3O4@SiNPs-COOH. The MCF-7 cell suspension was incubated with biotin-labeled MUC-1 aptamer. After centrifugation and washing, the cells were then treated with FITC@Fe3O4@SiNPs-SA. Afterwards, the mixtures were separated by a magnet. The cell-probe conjugates were then imaged using fluorescent microscopy. The results show that the MUC-1 aptamer could recognize and bind to the targeted cells with high affinity and specificity, indicating the prepared FITC@Fe3O4@SiNPs-SA with great photostability and superparamagnetism could be applied effectively in labeling and separation for MCF-7 cell in suspension synchronously. In addition, the feasibility of MCF-7 cells detection in peripheral blood was assessed. The results indicate that the method above is also applicable for cancer cells synchronous labeling and separation in complex biological system.

  20. NIR-fluorescent dye doped silica nanoparticles for in vivo imaging, sensing and theranostic

    Science.gov (United States)

    Rampazzo, Enrico; Genovese, Damiano; Palomba, Francesco; Prodi, Luca; Zaccheroni, Nelsi

    2018-04-01

    The development of nanostructures devoted to in vivo imaging and theranostic applications is one of the frontier fields of research worldwide. In this context, silica nanoparticles (SiO2-NPs) offer unquestionable positive properties: silica is intrinsically non-toxic, several versatile and accessible synthetic methods are available and many variations are possible, both in terms of porosity and functionalization for delivery and targeting purposes, respectively. Moreover, the accumulation of several dyes within a single nanostructure offers remarkable possibilities to produce very bright and photostable luminescent nanosystems. Advancements in imaging technology, bioassay, fluorescent molecular probes have boosted the efforts to develop dye doped fluorescent SiO2-NPs, but despite this, only a quite limited set of systems are applicable in vivo. Herein we discuss selected examples that appeared in the literature between 2013-17, with imaging capabilities in vivo and characterized by a significant near infrared (NIR) fluorescence emission. We present here very promising strategies to develop SiO2-NPs for diagnostic and therapeutic applications—some of which are already in clinical trials—and the possibility to develop bio-erodable SiO2-NPs. We are convinced that all these findings will be the basis for the spread of SiO2-NPs into clinical use in the near future.

  1. A fluorescent and chemiluminescent difunctional mesoporous silica nanoparticle as a label for the ultrasensitive detection of cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Tao Liang [Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi' an 710062 (China); Song Chaojun; Sun Yuanjie [Department of Immunology, The Fourth Military Medical University, Xi' an 710032 (China); Li Xiaohua; Li Yunyun [Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi' an 710062 (China); Jin Boquan [Department of Immunology, The Fourth Military Medical University, Xi' an 710032 (China); Zhang Zhujun, E-mail: zhangzj@snnu.edu.cn [Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi' an 710062 (China); Yang Kun, E-mail: yangkunkun@fmmu.edu.cn [Department of Immunology, The Fourth Military Medical University, Xi' an 710032 (China)

    2013-01-25

    Highlights: Black-Right-Pointing-Pointer Difunctional amino mesoporous silica nanoparticles (FCMSN) were synthesized. Black-Right-Pointing-Pointer The fluorescence and chemiluminescence properties of the FCMSN were studied. Black-Right-Pointing-Pointer The NaIO{sub 4} oxidation method was used for modification of the FCMSN. Black-Right-Pointing-Pointer Liver cancer 7721 cell was detected. Black-Right-Pointing-Pointer The specificity affected by FCMSN's amino groups was studied. - Abstract: A new kind of ultrabright fluorescent and chemiluminescent difunctional mesoporous silica nanoparticle (FCMSN) is reported. A luminescent dye, Rhodamine 6G or tris(2,2 Prime -bipyridyl)dichlororuthenium(II) hexahydrate (Rubpy), is doped inside nanochannels of a silica matrix. The hydrophobic groups in the silica matrix avoid the leakage of dye from open channels. The amines groups on the surface of the FCMSN improve the modification performance of the nanoparticle. Because the nanochannels are isolated by a network skeleton of silica, fluorescence quenching based on the inner filter effect of the fluorescent dyes immobilized in nanochannels is weakened effectively. The Quantum Yield of obtained 90 nm silica particles was about 61%. Compared with the fluorescent core-shell nanoparticle, the chemiluminescence reagents can freely enter the nanoparticles to react with fluorescent dyes to create chemiluminescence. The results show that the FCMSN are both fluorescent labels and chemiluminescent labels. In biological applications, the NaIO{sub 4} oxidation method was proven to be superior to the glutaraldehyde method. The amount of amino could affect the specificity of the FCMSN. The fluorescence microscopy imaging demonstrated that the FCMSN is viable for biological applications.

  2. Fluorescent silica hybrid materials containing benzimidazole dyes obtained by sol-gel method and high pressure processing

    International Nuclear Information System (INIS)

    Hoffmann, Helena Sofia; Stefani, Valter; Benvenutti, Edilson Valmir; Costa, Tania Maria Haas; Gallas, Marcia Russman

    2011-01-01

    Research highlights: → Sol-gel technique was used to obtain silica based hybrid materials containing benzimidazole dyes. → The sol-gel catalysts, HF and NaF, produce xerogels with different optical and textural characteristics. → High pressure technique (6.0 GPa) was used to produce fluorescent and transparent silica compacts with the dyes entrapped in closed pores, maintaining their optical properties. → The excited state intramolecular proton transfer (ESIPT) mechanism of benzimidazole dyes was studied by steady-state fluorescence spectroscopy for the monoliths, powders, and compacts. - Abstract: New silica hybrid materials were obtained by incorporation of two benzimidazole dyes in the silica network by sol-gel technique, using tetraethylorthosilicate (TEOS) as inorganic precursor. Several syntheses were performed with two catalysts (HF and NaF) producing powders and monoliths with different characteristics. The dye 2-(2'-hydroxy-5'-aminophenyl)benzimidazole was dispersed and physically adsorbed in the matrix, and the dye 2'(5'-N-(3-triethoxysilyl)propylurea-2'-hydroxyphenyl)benzimidazole was silylated, becoming chemically bonded to the silica network. High pressure technique was used to produce fluorescent and transparent silica compacts with the silylated and incorporated dye, at 6.0 GPa and room temperature. The excited state intramolecular proton transfer (ESIPT) mechanism of benzimidazole dyes was studied by steady-state fluorescence spectroscopy for the monoliths, powders, and compacts. The influence of the syntheses conditions was investigated by textural analysis using nitrogen adsorption isotherms.

  3. Highly fluorescent silver nanoclusters in alumina-silica composite optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Halder, A.; Chattopadhyay, R.; Majumder, S.; Paul, M. C.; Das, S.; Bhadra, S. K., E-mail: skbhadra@cgcri.res.in [Fiber Optics and Photonics Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata 700032 (India); Bysakh, S.; Unnikrishnan, M. [Material Characterization Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata 700032 (India)

    2015-01-05

    An efficient visible fluorescent optical fiber embedded with silver nanoclusters (Ag-NCs) having size ∼1 nm, uniformly distributed in alumina-silica composite core glass, is reported. Fibers are fabricated in a repetitive controlled way through modified chemical vapour deposition process associated with solution doping technique. Fibers are drawn from the transparent preforms by conventional fiber drawing process. Structural characteristics of the doped fibers are studied using transmission electron microscopy and electron probe micro analysis. The oxidation state of Ag within Ag-NCs is investigated by X-ray photo electron spectroscopy. The observed significant fluorescence of the metal clusters in fabricated fibers is correlated with electronic model. The experimentally observed size dependent absorption of the metal clusters in fabricated fibers is explained with the help of reported results calculated by ab-initio density functional theory. These optical fibers may open up an opportunity of realizing tunable wavelength fiber laser without the help of rare earth elements.

  4. Carbon dots based dual-emission silica nanoparticles as ratiometric fluorescent probe for nitrite determination in food samples.

    Science.gov (United States)

    Xiang, Guoqiang; Wang, Yule; Zhang, Heng; Fan, Huanhuan; Fan, Lu; He, Lijun; Jiang, Xiuming; Zhao, Wenjie

    2018-09-15

    In this work, a simple and effective strategy for designing a ratiometric fluorescent nanosensor was described. A carbon dots (CDs) based dual-emission nanosensor for nitrite was prepared by coating the CDs on to dye-doped silica nanoparticles. Dual-emission silica nanoparticles fluorescence was quenched in sulfuric acid using potassium bromate (KBrO 3 ). The nitrite present catalyzed the KBrO 3 oxidation, resulting in ratiometric fluorescence response of the dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated. Under optimized conditions, the limit of detection was 1.0 ng mL -1 and the linear range 10-160 ng mL -1 . Furthermore, the sensor was suitable for nitrite determination in different food samples. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. Fluorescence properties of riboflavin-functionalized mesoporous silica SBA-15 and riboflavin solutions in presence of different metal and organic cations

    Science.gov (United States)

    Lewandowski, Dawid; Schroeder, Grzegorz; Sawczak, Mirosław; Ossowski, Tadeusz

    2015-10-01

    Riboflavin was covalently linked to mesoporous SBA-15 silica surface via grafting technique. Then fluorescence properties of the system obtained were analyzed in the presence of several metal and organic cations. Both quenching and strengthening of fluorescence as well as significant changes in the maximum fluorescence wavelength were observed. The results were compared with absorption and fluorescence data obtained for riboflavin water solutions.

  6. Quasi-self-trapped Frenkel-exciton near-UV luminescence with large Stokes shift in wide-bandgap Cs4PbCl6 nanocrystals

    Science.gov (United States)

    Zhang, Yumeng; Fan, Baolu; Liu, Yuzhen; Li, Hongxia; Deng, Kaiming; Fan, Jiyang

    2018-04-01

    Inorganic lead halide perovskite nanocrystals (NCs) have attracted great interest owing to their superior luminescence and optoelectronic properties. In comparison to cubic CsPbX3 (X = Cl, Br, or I) that has visible luminescence, trigonal Cs4PbX6 has a much larger bandgap and distinct optical properties. Little has been known about the luminescence properties of the Cs4PbX6 NCs. In this study, we synthesize the well-crystallized Cs4PbCl6 NCs with sizes of 2.2-11.8 nm, which exhibit stable and near-UV luminescence (with a lifetime of 19.7-24.2 ns) with a remarkable quantum confinement effect at room temperature. In comparison to the negligible Stokes shift in the CsPbCl3 NCs, the Stokes shift of the Cs4PbCl6 NCs is very large (0.91 eV). The experimental results in combination with the first-principles calculations reveal that the near-UV luminescence of the Cs4PbCl6 NCs stems from the Frenkel excitons self-trapped in the isolated PbCl64- octahedrons. This is different from the CsPbCl3 NCs whose luminescence originates from the free Wannier excitons. The theoretical model based on the lattice relaxation is proposed to account for the large Stokes shift and its abnormal decrease with the decreasing particle size.

  7. Microviscosity of supercooled water confined within aminopropyl-modified mesoporous silica as studied by time-resolved fluorescence spectroscopy.

    Science.gov (United States)

    Yamaguchi, Akira; Namekawa, Manato; Itoh, Tetsuji; Teramae, Norio

    2012-01-01

    The fluorescence dynamics of rhodamine B (RhB) immobilized on the pore surface of aminopropyl (AP)-modified mesoporous silica (diameter of the silica framework, 3.1 nm) was examined at temperatures between 293 and 193 K to study the microviscosity of supercooled water confined inside the pores. The mesoporous silica specimen with a dense AP layer (2.1 molecules nm(-2)) was prepared, and RhB isothiocyanate was covalently bound to part of the surface AP groups. The fluorescence lifetime of the surface RhB increased with decreasing temperature from 293 to 223 K, indicating that freezing of the confined water did not occur in this temperature range. The microviscosity of the supercooled confined water was evaluated from an analysis of the lifetime data based on a frequency-dependent friction model.

  8. Grazing angle X-ray fluorescence from periodic structures on silicon and silica surfaces

    International Nuclear Information System (INIS)

    Nowak, S.H.; Banaś, D.; Błchucki, W.; Cao, W.; Dousse, J.-Cl.; Hönicke, P.; Hoszowska, J.; Jabłoński, Ł.; Kayser, Y.; Kubala-Kukuś, A.; Pajek, M.; Reinhardt, F.; Savu, A.V.; Szlachetko, J.

    2014-01-01

    Various 3-dimensional nano-scaled periodic structures with different configurations and periods deposited on the surface of silicon and silica substrates were investigated by means of the grazing incidence and grazing emission X-ray fluorescence techniques. Apart from the characteristics which are typical for particle- and layer-like samples, the measured angular intensity profiles show additional periodicity-related features. The latter could be explained by a novel theoretical approach based on simple geometrical optics (GO) considerations. The new GO-based calculations were found to yield results in good agreement with experiment, also in cases where other theoretical approaches are not valid, e.g., periodic particle distributions with an increased surface coverage

  9. Novel acridone-modified MCM-41 type silica: Synthesis, characterization and fluorescence tuning

    Directory of Open Access Journals (Sweden)

    Maximilian Hemgesberg

    2011-06-01

    Full Text Available A Mobil Composition of Matter (MCM-41 type mesoporous silica material containing N-propylacridone groups has been successfully prepared by co-condensation of an appropriate organic precursor with tetraethyl orthosilicate (TEOS under alkaline sol–gel conditions. The resulting material was fully characterized by means of X-ray diffraction (XRD, N2-adsorption–desorption, transmission electron microscopy (TEM, IR and UV–vis spectroscopy, as well as 29Si and 13C CP-MAS NMR techniques. The material features a high inner surface area and a highly ordered two-dimensional hexagonal pore structure. The fluorescence properties of the organic chromophore can be tuned via complexation of its carbonyl group with scandium triflate, which makes the material a good candidate for solid state sensors and optics. The successful synthesis of highly ordered MCM materials through co-condensation was found to be dependent on the chemical interaction of the different precursors.

  10. Application of x-ray fluorescence (XRF) absolute analysis method for silica refractories

    International Nuclear Information System (INIS)

    Asakura, Hideo; Yamada, Yasujiro; Kansai, Kouhei; Tomatsu, Ichirou; Murata, Mamoru

    2015-01-01

    X-ray fluorescence (XRF) analysis is a rapid and precise quantitative analytical method for the determination of major and trace elements in many industries and academics. XRF analytical values are relative due to the use of the calibration curves calculated from measuring the reference standard materials such as Japanese Refractory Reference Materials (JRRM) series with certified values determined by wet chemical analysis. The development of the XRF analytical method from relative to absolute analysis will help much to determine the absolute values of samples from the fields where reference standard samples have not been prepared, and thus can be applied widely in many industries. The implement of the absolute XRF analysis for silica refractories requires high purity reagents and/or reference standard solution for the binary basic calibration curve, and theoretical matrix correction coefficients for the multi-components silica refractories analysis. The reproducibility and repeatability of this method for Al 2 O 3 5 mass% sample were 0.009 and 0.006 mass% in Al 2 O 3 and showed better values that those of ICP-AES recognized as an absolute method in JIS R 2212-2, which yielded 0.028 and 0.031 mass%, respectively. The XRF absolute analysis for JRRM 200 series, 201a and 205a does not show a bias but coincides with their certified values. (author)

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

    International Nuclear Information System (INIS)

    Chu Maoquan; Sun Ye; Xu Shi

    2008-01-01

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

  12. Antioxidant flavone analog functionalized fluorescent silica nanoparticles: Synthesis and exploration of their possible use as biomolecule sensor.

    Science.gov (United States)

    Das, Sreeparna; Batuta, Shaikh; Alam, Md Niharul; Fouzder, Chandrani; Kundu, Rakesh; Mandal, Debabrata; Begum, Naznin Ara

    2017-09-01

    For the first time, a synthetic fluorescent antioxidant flavone analog was successfully anchored onto the surface of the APTES-modified mesoporous silica nanoparticles (NPs) through sulfonamide linkage. The surface chemistry and morphology of the flavone modified fluorescent silica (FMFS) NPs were studied in detail. The flavone moiety when attached onto the FMFS NP surface, imparted its characteristic fluorescence and antioxidant activities to these NPs. Moreover, the NPs are highly biocompatible as evidenced from their cytotoxicity assay on normal lung cell (L132). The fluorescence activity of these biocompatible NPs was further utilized to study their interaction with a biomolecule, BSA (Bovine Serum Albumin). It was interesting to note that the fluorescence behavior of FMFS NPs completely changed on their binding with BSA. On the other hand, the intrinsic fluorescence activity of BSA was also significantly modified due to its interaction with FMFS NPs. Thus, the sensing and detection of biomolecules like BSA in presence of FMFS NPs can be accomplished by monitoring changes in the fluorescence behavior of either FMFS NPs or BSA. Furthermore, these FMFS NPs retained their intrinsic fluorescence behavior in the cellular medium which opens up their possible use as biocompatible cell imaging agents in future. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Goat anti-rabbit IgG conjugated fluorescent dye-doped silica nanoparticles for human breast carcinoma cell recognition.

    Science.gov (United States)

    Chen, Min-Yan; Chen, Ze-Zhong; Wu, Ling-Ling; Tang, Hong-Wu; Pang, Dai-Wen

    2013-11-12

    We report an indirect method for cancer cell recognition using photostable fluorescent silica nanoprobes as biological labels. The dye-doped fluorescent silica nanoparticles were synthesized using the water-in-oil (W/O) reverse microemulsion method. The silica matrix was produced by the controlled hydrolysis of tetraethylorthosilicate (TEOS) in water nanodroplets with the initiation of ammonia (NH3·H2O). Fluorescein isothiocyanate (FITC) or rhodamine B isothiocyanate conjugated with dextran (RBITC-Dextran) was doped in silica nanoparticles (NPs) with a size of 60 ± 5 nm as a fluorescent signal element by covalent bonding and steric hindrance, respectively. The secondary antibody, goat anti-rabbit IgG, was conjugated on the surface of the PEG-terminated modified FITC-doped or RBITC-Dextran-doped silica nanoparticles (PFSiNPs or PBSiNPs) by covalent binding to the PEG linkers using the cyanogen bromide method. The concentrations of goat anti-rabbit IgG covering the nanoprobes were quantified via the Bradford method. In the proof-of-concept experiment, an epithelial cell adhesion molecule (EpCAM) on the human breast cancer SK-Br-3 cell surface was used as the tumor marker, and the nanoparticle functionalized with rabbit anti-EpCAM antibody was employed as the nanoprobe for cancer cell recognition. Compared with fluorescent dye labeled IgG (FITC-IgG and RBITC-IgG), the designed nanoprobes display dramatically increased stability of fluorescence as well as photostability under continuous irradiation.

  14. A brilliant sandwich type fluorescent nanostructure incorporating a compact quantum dot layer and versatile silica substrates.

    Science.gov (United States)

    Huang, Liang; Wu, Qiong; Wang, Jing; Foda, Mohamed; Liu, Jiawei; Cai, Kai; Han, Heyou

    2014-03-18

    A "hydrophobic layer in silica" structure was designed to integrate a compact quantum dot (QD) layer with high quantum yield into scalable silica hosts containing desired functionality. This was based on metal affinity driven assembly of hydrophobic QDs with versatile silica substrates and homogeneous encapsulation of organosilica/silica layers.

  15. Two-photon induced fluorescence and other optical effects in irradiated and doped fused silica

    International Nuclear Information System (INIS)

    Kramer, S.D.

    1986-07-01

    The objective of this program was to assess and identify irradiation techniques which could be used to modify the optical charactistics of doped fused silica. Primary emphasis was placed on determining if gamma ray or neutron bombardment of the glass would enhance certain Raman and nonlinear optical effects. In particular, the effect of irradiation on optical two photon induced fluorescence was studied in detail. The maximum radiation exposures used were 10 6 rads (Si) of gamma rays and neutron fluences of 1 x 10 14 neutrons/cm 2 . The optical measurements were made at room temperature between one and four months after irradiation. The maximum input light intensity was 10 9 watts/cm 2 at a near infrared (1.06 μ) input wavelength which was chosen to lie in a transparent spectral region of the glass. Under these experimental conditions a careful search revealed no detectable two-photon induced fluorescence in the region from 550 to 900 nm. The upper limit for the photon efficiency of this process was determined to be less than 1 x 10 -10 %. 89 refs., 12 figs

  16. Fluorescent boronic acid terminated polymer grafted silica particles synthesized via click chemistry for affinity separation of saccharides

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Zhifeng, E-mail: 897061147@qq.com; Deng, Peihong; Tang, Siping; Li, Junhua

    2014-07-01

    Boronic acids are important for effective separation of biological active cis-diols. For the purpose of constructing a new type of saccharide-sensitive material which can not only provide convenient separation but also improve the access of boronic acid to guest molecules, the fluorogenic boronic acid terminated, thermo-sensitive polymers (BA-polyNIPAm) were grafted to an alkyne modified silica gel through the exploitation of click chemistry. The BA-polyNIPAm grafted silica gel (BA-polyNIPAm-SG) was characterized by FT-IR, fluorescence spectra, fluorescence microscopy, elemental analysis (EA), thermal gravimetric analysis (TGA), scanning electron microscope (SEM) and so on. BA-polyNIPAm-SG displayed affinity binding ability for saccharides under physiological pH value and allowed saccharides to be conveniently separated from solution. The maximum binding capacities for fructose and glucose are 83.2 μmol/g and 70.4 μmol/g polymer, respectively. The intensity of fluorescence emission of BA-polyNIPAm-SG increased with the increasing of fructose concentration. The present study provides a new kind of composite material which contains moveable and flexible grippers for recognizing and binding guest molecules. - Highlights: • Fluorogenic boronic acid terminated polymers were conjugated to silica particle. • The prepared material can conveniently separate saccharides from solution. • The prepared material displays increased fluorescence emission upon binding fructose.

  17. Fluorescent boronic acid terminated polymer grafted silica particles synthesized via click chemistry for affinity separation of saccharides

    International Nuclear Information System (INIS)

    Xu, Zhifeng; Deng, Peihong; Tang, Siping; Li, Junhua

    2014-01-01

    Boronic acids are important for effective separation of biological active cis-diols. For the purpose of constructing a new type of saccharide-sensitive material which can not only provide convenient separation but also improve the access of boronic acid to guest molecules, the fluorogenic boronic acid terminated, thermo-sensitive polymers (BA-polyNIPAm) were grafted to an alkyne modified silica gel through the exploitation of click chemistry. The BA-polyNIPAm grafted silica gel (BA-polyNIPAm-SG) was characterized by FT-IR, fluorescence spectra, fluorescence microscopy, elemental analysis (EA), thermal gravimetric analysis (TGA), scanning electron microscope (SEM) and so on. BA-polyNIPAm-SG displayed affinity binding ability for saccharides under physiological pH value and allowed saccharides to be conveniently separated from solution. The maximum binding capacities for fructose and glucose are 83.2 μmol/g and 70.4 μmol/g polymer, respectively. The intensity of fluorescence emission of BA-polyNIPAm-SG increased with the increasing of fructose concentration. The present study provides a new kind of composite material which contains moveable and flexible grippers for recognizing and binding guest molecules. - Highlights: • Fluorogenic boronic acid terminated polymers were conjugated to silica particle. • The prepared material can conveniently separate saccharides from solution. • The prepared material displays increased fluorescence emission upon binding fructose

  18. Fluorescence metrology of silica sol–gels – The effect of D2O and ...

    Indian Academy of Sciences (India)

    Administrator

    industrial quality control and helping fundamental research. ... Of all the possible syntheses, sodium silicate (i.e. water glass) production of silica gel, ... fine silica gel powders used in many applications (e.g. chromatography, toothpaste etc).

  19. Iodinated oil-loaded, fluorescent mesoporous silica-coated iron oxide nanoparticles for magnetic resonance imaging/computed tomography/fluorescence trimodal imaging

    Directory of Open Access Journals (Sweden)

    Xue S

    2014-05-01

    Full Text Available Sihan Xue,1 Yao Wang,1 Mengxing Wang,2 Lu Zhang,1 Xiaoxia Du,2 Hongchen Gu,1 Chunfu Zhang1,31School of Biomedical Engineering and Med-X Research Institute, Shanghai Jiao Tong University, 2Shanghai Key Laboratory of Magnetic Resonance, Department of Physics, East China Normal University, 3State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, People’s Republic of ChinaAbstract: In this study, a novel magnetic resonance imaging (MRI/computed tomography (CT/fluorescence trifunctional probe was prepared by loading iodinated oil into fluorescent mesoporous silica-coated superparamagnetic iron oxide nanoparticles (i-fmSiO4@SPIONs. Fluorescent mesoporous silica-coated superparamagnetic iron oxide nanoparticles (fmSiO4@SPIONs were prepared by growing fluorescent dye-doped silica onto superparamagnetic iron oxide nanoparticles (SPIONs directed by a cetyltrimethylammonium bromide template. As prepared, fmSiO4@SPIONs had a uniform size, a large surface area, and a large pore volume, which demonstrated high efficiency for iodinated oil loading. Iodinated oil loading did not change the sizes of fmSiO4@SPIONs, but they reduced the MRI T2 relaxivity (r2 markedly. I-fmSiO4@SPIONs were stable in their physical condition and did not demonstrate cytotoxic effects under the conditions investigated. In vitro studies indicated that the contrast enhancement of MRI and CT, and the fluorescence signal intensity of i-fmSiO4@SPION aqueous suspensions and macrophages, were intensified with increased i-fmSiO4@SPION concentrations in suspension and cell culture media. Moreover, for the in vivo study, the accumulation of i-fmSiO4@SPIONs in the liver could also be detected by MRI, CT, and fluorescence imaging. Our study demonstrated that i-fmSiO4@SPIONs had great potential for MRI/C/fluorescence trimodal imaging.Keywords: multifunctional probe, SPIONs, mesoporous silica

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

    Directory of Open Access Journals (Sweden)

    Rudolf Herrmann

    2014-12-01

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

  1. Time-dependent stokes shifts of fluorescent dyes in the hydrophobic backbone region of a phospholipid bilayer: Combination of fluorescence spectroscopy and ab initio calculations

    Czech Academy of Sciences Publication Activity Database

    Sýkora, Jan; Slavíček, Petr; Jungwirth, Pavel; Barucha-Kraszewska, Justyna; Hof, Martin

    2007-01-01

    Roč. 111, č. 21 (2007), s. 5869-5877 ISSN 1520-6106 R&D Projects: GA AV ČR IAA400400503; GA MŠk LC512; GA MŠk(CZ) LC06063 Grant - others:GA ČR GP203/07/P449 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z40550506 Keywords : solvation dynamics * solvent relaxation * 9-anthroid acid * preferential solvation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.086, year: 2007

  2. Synchronous fluorescence spectroscopic study of solvatochromic curcumin dye

    Science.gov (United States)

    Patra, Digambara; Barakat, Christelle

    2011-09-01

    Curcumin, the main yellow bioactive component of turmeric, has recently acquired attention by chemists due its wide range of potential biological applications as an antioxidant, an anti-inflammatory, and an anti-carcinogenic agent. This molecule fluoresces weakly and poorly soluble in water. In this detailed study of curcumin in thirteen different solvents, both the absorption and fluorescence spectra of curcumin was found to be broad, however, a narrower and simple synchronous fluorescence spectrum of curcumin was obtained at Δ λ = 10-20 nm. Lippert-Mataga plot of curcumin in different solvents illustrated two sets of linearity which is consistent with the plot of Stokes' shift vs. the ET30. When Stokes's shift in wavenumber scale was replaced by synchronous fluorescence maximum in nanometer scale, the solvent polarity dependency measured by λSFSmax vs. Lippert-Mataga plot or ET30 values offered similar trends as measured via Stokes' shift for protic and aprotic solvents for curcumin. Better linear correlation of λSFSmax vs. π* scale of solvent polarity was found compared to λabsmax or λemmax or Stokes' shift measurements. In Stokes' shift measurement both absorption/excitation as well as emission (fluorescence) spectra are required to compute the Stokes' shift in wavenumber scale, but measurement could be done in a very fast and simple way by taking a single scan of SFS avoiding calculation and obtain information about polarity of the solvent. Curcumin decay properties in all the solvents could be fitted well to a double-exponential decay function.

  3. Chlorophyll a Covalently Bonded to Organo-Modified Translucent Silica Xerogels: Optimizing Fluorescence and Maximum Loading

    Directory of Open Access Journals (Sweden)

    M. A. García-Sánchez

    2016-07-01

    Full Text Available Chlorophyll is a pyrrolic pigment with important optical properties, which is the reason it has been studied for many years. Recently, interest has been rising with respect to this molecule because of its outstanding physicochemical properties, particularly applicable to the design and development of luminescent materials, hybrid sensor systems, and photodynamic therapy devices for the treatment of cancer cells and bacteria. More recently, our research group has been finding evidence for the possibility of preserving these important properties of substrates containing chlorophyll covalently incorporated within solid pore matrices, such as SiO2, TiO2 or ZrO2 synthesized through the sol-gel process. In this work, we study the optical properties of silica xerogels organo-modified on their surface with allyl and phenyl groups and containing different concentrations of chlorophyll bonded to the pore walls, in order to optimize the fluorescence that these macrocyclic species displays in solution. The intention of this investigation was to determine the maximum chlorophyll a concentration at which this molecule can be trapped inside the pores of a given xerogel and to ascertain if this pigment remains trapped as a monomer, a dimer, or aggregate. Allyl and phenyl groups were deposited on the surface of xerogels in view of their important effects on the stability of the molecule, as well as over the fluorescence emission of chlorophyll; however, these organic groups allow the trapping of either chlorophyll a monomers or dimers. The determination of the above parameters allows finding the most adequate systems for subsequent in vitro or in vivo studies. The characterization of the obtained xerogels was performed through spectroscopic absorption, emission and excitation spectra. These hybrid systems can be employed as mimics of natural systems; the entrapment of chlorophyll inside pore matrices indicates that it is possible to exploit some of the most

  4. Chlorophyll a Covalently Bonded to Organo-Modified Translucent Silica Xerogels: Optimizing Fluorescence and Maximum Loading.

    Science.gov (United States)

    García-Sánchez, M A; Serratos, I N; Sosa, R; Tapia-Esquivel, T; González-García, F; Rojas-González, F; Tello-Solís, S R; Palacios-Enriquez, A Y; Esparza Schulz, J M; Arrieta, A

    2016-07-22

    Chlorophyll is a pyrrolic pigment with important optical properties, which is the reason it has been studied for many years. Recently, interest has been rising with respect to this molecule because of its outstanding physicochemical properties, particularly applicable to the design and development of luminescent materials, hybrid sensor systems, and photodynamic therapy devices for the treatment of cancer cells and bacteria. More recently, our research group has been finding evidence for the possibility of preserving these important properties of substrates containing chlorophyll covalently incorporated within solid pore matrices, such as SiO₂, TiO₂ or ZrO₂ synthesized through the sol-gel process. In this work, we study the optical properties of silica xerogels organo-modified on their surface with allyl and phenyl groups and containing different concentrations of chlorophyll bonded to the pore walls, in order to optimize the fluorescence that these macrocyclic species displays in solution. The intention of this investigation was to determine the maximum chlorophyll a concentration at which this molecule can be trapped inside the pores of a given xerogel and to ascertain if this pigment remains trapped as a monomer, a dimer, or aggregate. Allyl and phenyl groups were deposited on the surface of xerogels in view of their important effects on the stability of the molecule, as well as over the fluorescence emission of chlorophyll; however, these organic groups allow the trapping of either chlorophyll a monomers or dimers. The determination of the above parameters allows finding the most adequate systems for subsequent in vitro or in vivo studies. The characterization of the obtained xerogels was performed through spectroscopic absorption, emission and excitation spectra. These hybrid systems can be employed as mimics of natural systems; the entrapment of chlorophyll inside pore matrices indicates that it is possible to exploit some of the most physicochemical

  5. Stokes shift and fine structure splitting in composition-tunable Zn{sub x}Cd{sub 1−x}Se nanocrystals: Atomistic tight-binding theory

    Energy Technology Data Exchange (ETDEWEB)

    Sukkabot, Worasak, E-mail: w.sukkabot@gmail.com

    2017-02-01

    I report on the atomistic correlation of the structural properties and excitonic splitting of ternary alloy Zn{sub x}Cd{sub 1−x}Se wurtzite nanocrystals using the sp{sup 3}s* empirical tight-binding method with the description of the first nearest neighbouring interaction and bowing effect. Based on a successful model, the computations are presented under various Zn compositions (x) and diameters of alloy Zn{sub x}Cd{sub 1−x}Se nanocrystals with the experimentally synthesized compositions and sizes. With increasing Zn contents (x), the optical band gaps and electron-hole coulomb energies are improved, while ground electron-hole wave function overlaps, electron-hole exchange energies, stokes shift and fine structure splitting are reduced. A composition-tunable emission from blue to yellow wavelength is obviously demonstrated. The optical band gaps, ground electron-hole wave function overlaps, electron-hole interactions, stokes shift and fine structure splitting are progressively decreased with the increasing diameters. Alloy Zn{sub x}Cd{sub 1−x}Se nanocrystal with Zn rich and large diameter is the best candidate to optimistically be used as a source of entangled photon pairs. The agreement with the experimental data is remarkable. Finally, the present systematic study on the structural properties and excitonic splitting predominantly opens a new perspective to understand the size- and composition-dependent properties of Zn{sub x}Cd{sub 1−x}Se nanocrystals with a comprehensive strategy to design the optoelectronic devices.

  6. Hydration of poly( N-isopropylacrylamide) brushes on micro-silica beads measured by a fluorescent probe

    Science.gov (United States)

    Hattori, Yusuke; Nagase, Kenichi; Kobayashi, Jun; Kikuchi, Akihiko; Akiyama, Yoshikatsu; Kanazawa, Hideko; Okano, Teruo

    2010-05-01

    Hydration of poly( N-isopropylacrylamide) brushes on silica micro-beads was investigated using a fluorescent probe method. The free ends, the bottom, and the random of brushes were labeled with dansyl group. The emission spectra at the thin brushes were reduced with increasing temperature regardless of their labeling locations. At the free ends of thick brushes, the emission intensity was enhanced at 500 nm and reduced at 455 nm by heating, which was corresponding to the local micro-environmental change around the free ends. The spectral shift was speculated to be due to the enhancement of the flexibility and the hydration of thick brushes.

  7. Fluorescence lifetime studies of MeV erbium implanted silica glass

    International Nuclear Information System (INIS)

    Lidgard, A.; Polman, A.; Jacobsen, D.C.; Blonder, G.E.; Kistler, R.; Poate, J.M.; Becker, P.C.

    1991-01-01

    MeV erbium ion implantation into various SiO 2 glasses has been studied with the aim of incorporating the rare-earth dopant as an optically active ion in the silica network. The lifetime of the excited state ranges from 1.6 to 12.8 ms, depending on base material and implantation fluence. These results have positive implications for silica-based integrated optical technology. (Author)

  8. Fluorescence lifetime studies of MeV erbium implanted silica glass

    Energy Technology Data Exchange (ETDEWEB)

    Lidgard, A.; Polman, A.; Jacobsen, D.C.; Blonder, G.E.; Kistler, R.; Poate, J.M.; Becker, P.C. (AT and T Bell Labs., Murray Hill, NJ (USA))

    1991-05-23

    MeV erbium ion implantation into various SiO{sub 2} glasses has been studied with the aim of incorporating the rare-earth dopant as an optically active ion in the silica network. The lifetime of the excited state ranges from 1.6 to 12.8 ms, depending on base material and implantation fluence. These results have positive implications for silica-based integrated optical technology. (Author).

  9. Carbon-dot-based dual-emission silica nanoparticles as a ratiometric fluorescent probe for vanadium(V) detection in mineral water samples

    Science.gov (United States)

    He, Lijun; Zhang, Heng; Fan, Huanhuan; Jiang, Xiuming; Zhao, Wenjie; Xiang, Guo Qiang

    2018-01-01

    Herein, we propose a simple and effective strategy for designing a ratiometric fluorescent nanosensor. We designed and developed a carbon dots (CDs) based dual-emission nanosensor for vanadium(V) by coating the surface of dye-doped silica nanoparticles with CDs. The fluorescence of dual-emission silica nanoparticles was quenched in acetic acid through potassium bromate (KBrO3) oxidation. V(V) could catalyze KBrO3 oxidation reaction process, resulting in the ratiometric fluorescence quenching of dual-emission silica nanoparticles. We investigated several important parameters affecting the performance of the nanosensor. Under the optimized conditions, the detection limit of this nanosensor reached 1.1 ng mL- 1 and the linear range from 10 to 800 ng mL- 1. Furthermore, we found that the sensor was suitable for determination of V(V) in different mineral water samples with satisfactory results.

  10. Efficient fluorescence energy transfer system between CdTe-doped silica nanoparticles and gold nanoparticles for turn-on fluorescence detection of melamine.

    Science.gov (United States)

    Gao, Feng; Ye, Qingqing; Cui, Peng; Zhang, Lu

    2012-05-09

    We here report an efficient and enhanced fluorescence energy transfer system between confined quantum dots (QDs) by entrapping CdTe into the mesoporous silica shell (CdTe@SiO₂) as donors and gold nanoparticles (AuNPs) as acceptors. At pH 6.50, the CdTe@SiO₂-AuNPs assemblies coalesce to form larger clusters due to charge neutralization, leading to the fluorescence quenching of CdTe@SiO₂ as a result of energy transfer. As compared with the energy transfer system between unconfined CdTe and AuNPs, the maximum fluorescence quenching efficiency of the proposed system is improved by about 27.0%, and the quenching constant, K(sv), is increased by about 2.4-fold. The enhanced quenching effect largely turns off the fluorescence of CdTe@SiO₂ and provides an optimal "off-state" for sensitive "turn-on" assay. In the present study, upon addition of melamine, the weak fluorescence system of CdTe@SiO₂-AuNPs is enhanced due to the strong interactions between the amino group of melamine and the gold nanoparticles via covalent bond, leading to the release of AuNPs from the surfaces of CdTe@SiO₂; thus, its fluorescence is restored. A "turn-on" fluorimetric method for the detection of melamine is proposed based on the restored fluorescence of the system. Under the optimal conditions, the fluorescence enhanced efficiency shows a linear function against the melamine concentrations ranging from 7.5 × 10⁻⁹ to 3.5 × 10⁻⁷ M (i.e., 1.0-44 ppb). The analytical sensitivity is improved by about 50%, and the detection limit is decreased by 5.0-fold, as compared with the analytical results using the CdTe-AuNPs system. Moreover, the proposed method was successfully applied to the determination of melamine in real samples with excellent recoveries in the range from 97.4 to 104.1%. Such a fluorescence energy transfer system between confined QDs and AuNPs may pave a new way for designing chemo/biosensing.

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

    International Nuclear Information System (INIS)

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

    2009-01-01

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

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  13. A Zero-Dimensional Organic Seesaw-Shaped Tin Bromide with Highly Efficient Strongly Stokes-Shifted Deep-Red Emission

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Chenkun [College of Engineering, Tallahassee, FL (United States). Dept. of Chemical and Biomedical Engineering; Lin, Haoran [College of Engineering, Tallahassee, FL (United States). Dept. of Chemical and Biomedical Engineering; Shi, Hongliang [Beihang Univ., Beijing (China). Dept. of Physics; Tian, Yu [Materials Science and Engineering Program, Florida State University, Tallahassee FL 32306 USA; Pak, Chongin [Florida State Univ., Tallahassee, FL (United States). Dept. of Chemistry and Biochemistry; Shatruk, Michael [Florida State Univ., Tallahassee, FL (United States). Dept. of Chemistry and Biochemistry; Zhou, Yan [Florida State Univ., Tallahassee, FL (United States). Dept. of Chemistry and Biochemistry; Djurovich, Peter [Univ. of Southern California, Los Angeles, CA (United States). Dept. of Chemistry; Du, Mao-Hua [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division, Center for Radiation Detection Materials and Systems; Ma, Biwu [College of Engineering, Tallahassee, FL (United States). Dept. of Chemical and Biomedical Engineering; Beihang Univ., Beijing (China). Dept. of Physics; Florida State Univ., Tallahassee, FL (United States). Dept. of Chemistry and Biochemistry

    2017-12-21

    The synthesis and characterization is reported of (C9NH20)2SnBr4, a novel organic metal halide hybrid with a zero-dimensional (0D) structure, in which individual seesaw-shaped tin (II) bromide anions (SnBr42-) are co-crystallized with 1-butyl-1-methylpyrrolidinium cations (C9NH20+). Upon photoexcitation, the bulk crystals exhibit a highly efficient broadband deep-red emission peaked at 695 nm, with a large Stokes shift of 332 nm and a high quantum efficiency of around 46 %. Furthermore, the unique photophysical properties of this hybrid material are attributed to two major factors: 1) the 0D structure allowing the bulk crystals to exhibit the intrinsic properties of individual SnBr42- species, and 2) the seesaw structure then enables a pronounced excited state structural deformation as confirmed by density functional theory (DFT) calculations.

  14. Free-radical sensing by using naphthalimide based mesoporous silica (MCM-41) nanoparticles: A combined fluorescence and cellular imaging study

    Science.gov (United States)

    Jha, Gaurav; Roy, Subhasis; Sahu, Prabhat Kumar; Banerjee, Somnath; Anoop, N.; Rahaman, Abdur; Sarkar, Moloy

    2018-01-01

    Keeping in mind the advantages of material-based systems over simple molecule-based systems, we have designed and developed three inorganic-organic hybrid systems by anchoring 1,8-naphthalimide derivatives to mesoporous silica nanoparticles for detection of free radicals. Prior to photophysical study, systems are characterized by spectroscopic, microscopic and thermo-gravimetric techniques. Steady state and time-resolved fluorescence studies demonstrate that the hydrazine based system is senstive towards detection of various free radicals. Cellular imaging study reveals cell permeability and toxicity study demonstrates the non-toxic nature of the material. These studies have suggested that present system has the potential to be used in various biological applications.

  15. Aptamer-fluorescent silica nanoparticles bioconjugates based dual-color flow cytometry for specific detection of Staphylococcus aureus.

    Science.gov (United States)

    He, Xiaoxiao; Li, Yuhong; He, Dinggen; Wang, Kemin; Shangguan, Jingfang; Shi, Hui

    2014-07-01

    This paper describes a sensitive and specific determination strategy for Staphylococcus aureus (S. aureus) detection using aptamer recognition and fluorescent silica nanoparticles (FSiNPs) label based dual-color flow cytometry assay (Aptamer/FSiNPs-DCFCM). In the protocol, an aptamer, having high affinity to S. aureus, was first covalently immobilized onto chloropropyl functionalized FSiNPs through a click chemistry approach to generate aptamer-nanoparticles bioconjugates (Aptamer/FSiNPs). Next, S. aureus was incubated with Aptamer/FSiNPs, and then stained with SYBR Green I (a special staining material for the duplex DNA). Upon target binding and nucleic acid staining with SYBR Green I, the S. aureus was determined using two-color flow cytometry. The method took advantage of the specificity of aptamer, signal amplification of FSiNPs label and decreased false positives of two-color flow cytometry assay. It was demonstrated that these Aptamer/FSiNPs could efficiently recognize and fluorescently label target S. aureus. Through multiparameter determination with flow cytometry, this assay allowed for detection of as low as 1.5 x 10(2) and 7.6 x 10(2) cells mL(-1) S. aureus in buffer and spiked milk, respectively, with higher sensitivity than the Aptamer/FITC based flow cytometry.

  16. Nanoscale Confinement and Fluorescence Effects of Bacterial Light Harvesting Complex LH2 in Mesoporous Silicas

    DEFF Research Database (Denmark)

    Ikemoto, Hideki; Tubasum, Sumera; Pullerits, Tonu

    2013-01-01

    Many key chemical and biochemical reactions, particularly in living cells, take place in confined space at the mesoscopic scale. Towards understanding of physicochemical nature of biomacromolecules confined in nanoscale space, in this work we have elucidated fluorescent effects of a light harvest...

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

    Directory of Open Access Journals (Sweden)

    Ingemar Petermann

    2011-07-01

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

  18. Evidence for the molecular-scale origin of the suppression of physical ageing in confined polymer: fluorescence and dielectric spectroscopy studies of polymer-silica nanocomposites

    International Nuclear Information System (INIS)

    Priestley, Rodney D; Rittigstein, Perla; Broadbelt, Linda J; Fukao, Koji; Torkelson, John M

    2007-01-01

    Fluorescence spectroscopy was used to characterize the rate of physical ageing at room temperature in nanocomposites of silica (10-15 nm diameter) nanoparticles in poly(methyl methacrylate) (PMMA). The physical ageing rate was reduced by more than a factor of 20 in 0.4 vol% silica-PMMA nanocomposites relative to neat PMMA. The molecular-scale origin of this nearly complete arresting of physical ageing was investigated with dielectric spectroscopy. The strength of the β relaxation process was reduced by nearly 50% in the nanocomposite relative to neat PMMA. This reduced strength of the β process results from dipoles (ester groups) having hindered motions or being virtually immobile on the timescale being probed at a frequency of 100 Hz. This hindered mobility results from hydrogen bonding between PMMA ester side groups and hydroxyl units on the surface of the silica nanoparticles. In contrast, no reduction in physical ageing rate was observed upon addition of silica to polystyrene, which cannot form hydrogen bonds with the silica surfaces. Thus, the molecular origin of the suppressed physical ageing in silica-PMMA nanocomposites is the interfacial hydrogen bonding, which leads to a major reduction in the strength of the β process, i.e., the β process is largely responsible for the observed physical ageing

  19. Detecting plant silica fibres in animal tissue by confocal fluorescence microscopy.

    Science.gov (United States)

    Hodson, M J; Smith, R J; van Blaaderen, A; Crafton, T; O'Neill, C H

    1994-04-01

    Silica fibres from the inflorescence bracts of the grass Phalaris canariensis L. cause dermatitis, and have been implicated in the aetiology of oesophageal cancer in northeastern Iran. Here we describe a method for labelling these fibres so that they can be located in mammalian tissue. Fluorescein was covalently linked to isolated, purified fibres with the silane coupling agent 3-aminopropyl triethoxysilane. The labelled hairs were then rubbed into the backs of mice. These were later killed and their skin fixed, stained and sliced at a thickness of 250 microns. A confocal laser scanning microscope gave brilliant images of the fibres at any depth up to 100 microns or more beneath the surface of the slice. Fibres penetrated deeply into the dermis. Several cubic millimetres of tissue could be surveyed in 1 h. The number of fibres present was approximately 2 mm-3 initially, falling to 0.1 mm-3 after 7 days.

  20. Fungus-Mediated Preferential Bioleaching of Waste Material Such as Fly - Ash as a Means of Producing Extracellular, Protein Capped, Fluorescent and Water Soluble Silica Nanoparticles

    Science.gov (United States)

    Khan, Shadab Ali; Uddin, Imran; Moeez, Sana; Ahmad, Absar

    2014-01-01

    In this paper, we for the first time show the ability of the mesophilic fungus Fusarium oxysporum in the bioleaching of waste material such as Fly-ash for the extracellular production of highly crystalline and highly stable, protein capped, fluorescent and water soluble silica nanoparticles at ambient conditions. When the fungus Fusarium oxysporum is exposed to Fly-ash, it is capable of selectively leaching out silica nanoparticles of quasi-spherical morphology within 24 h of reaction. These silica nanoparticles have been completely characterized by UV-vis spectroscopy, Photoluminescence (PL), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Energy dispersive analysis of X-rays (EDAX). PMID:25244567

  1. Fungus-mediated preferential bioleaching of waste material such as fly - ash as a means of producing extracellular, protein capped, fluorescent and water soluble silica nanoparticles.

    Directory of Open Access Journals (Sweden)

    Shadab Ali Khan

    Full Text Available In this paper, we for the first time show the ability of the mesophilic fungus Fusarium oxysporum in the bioleaching of waste material such as Fly-ash for the extracellular production of highly crystalline and highly stable, protein capped, fluorescent and water soluble silica nanoparticles at ambient conditions. When the fungus Fusarium oxysporum is exposed to Fly-ash, it is capable of selectively leaching out silica nanoparticles of quasi-spherical morphology within 24 h of reaction. These silica nanoparticles have been completely characterized by UV-vis spectroscopy, Photoluminescence (PL, Transmission electron microscopy (TEM, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR and Energy dispersive analysis of X-rays (EDAX.

  2. A near-infrared fluorescent sensor for H+ in aqueous solution and living cells

    OpenAIRE

    WU, Aibin; DUAN, Liping

    2014-01-01

    A heptamethine cyanine-based sensor (1) was designed and synthesized by incorporating heptamethine cyanine fluorophore and methylpiperazine. Sensor 1 exhibited good response to the change of pH levels, and a large Stokes shift (>100 nm) was obtained. Fluorescent image experiments in living cells further demonstrated its potential applications in biological systems.

  3. External and Intraparticle Diffusion of Coumarin 102 with Surfactant in the ODS-silica Gel/water System by Single Microparticle Injection and Confocal Fluorescence Microspectroscopy

    OpenAIRE

    NAKATANI, Kiyoharu; MATSUTA, Emi

    2015-01-01

    The release mechanism of coumarin 102 from a single ODS-silica gel microparticle into the water phase in the presence of Triton X-100 was investigated by confocal fluorescence microspectroscopy combined with the single microparticle injection technique. The release rate significantly depended on the Triton X-100 concentration in the water phase and was not limited by diffusion in the pores of the microparticle. The release rate constant was inversely proportional to the microparticle radius s...

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-02-15

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

  6. A facile method to prepare "green" nano-phosphors with a large Stokes-shift and solid-state enhanced photophysical properties based on surface-modified gold nanoclusters.

    Science.gov (United States)

    Cheng, C H; Huang, H Y; Talite, M J; Chou, W C; Yeh, J M; Yuan, C T

    2017-12-15

    Colloidal nano-materials, such as quantum dots (QDs) have been applied to light-conversion nano-phosphors due to their unique tunable emission. However, most of the QDs involve toxic elements and are synthesized in a hazardous solvent. In addition, conventional QD nano-phosphors with a small Stokes shift suffered from reabsorption losses and aggregation-induced quenching in the solid state. Here, we demonstrate a facile, matrix-free method to prepare eco-friendly nano-phosphors with a large Stokes shift based on aqueous thiolate-stabilized gold nanoclusters (GSH-AuNCs) with simple surface modifications. Our method is just to drop GSH-AuNCs solution on the aluminum foil and then surface-modified AuNCs (Al-GSH-AuNCs) can be spontaneously precipitated out of the aqueous solution. Compared with pristine GSH-AuNCs in solution, the Al-GSH-AuNCs exhibit enhanced solid-state PL quantum yields, lengthened PL lifetime, and spectral blue shift, which can be attributed to the aggregation-induced emission enhancement facilitated by surface modifications. Such surface-treatment induced aggregation of AuNCs can restrict the surface-ligand motion, leading to the enhancement of PL properties in the solid state. In addition, the Al-GSH-AuNCs nano-phosphors with a large Stokes shift can mitigate the aggregation-induced PL quenching and reabsorption losses, which would be potential candidates for "green" nano-phosphors. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. External and Intraparticle Diffusion of Coumarin 102 with Surfactant in the ODS-silica Gel/water System by Single Microparticle Injection and Confocal Fluorescence Microspectroscopy.

    Science.gov (United States)

    Nakatani, Kiyoharu; Matsuta, Emi

    2015-01-01

    The release mechanism of coumarin 102 from a single ODS-silica gel microparticle into the water phase in the presence of Triton X-100 was investigated by confocal fluorescence microspectroscopy combined with the single microparticle injection technique. The release rate significantly depended on the Triton X-100 concentration in the water phase and was not limited by diffusion in the pores of the microparticle. The release rate constant was inversely proportional to the microparticle radius squared, indicating that the rate-determining step is the external diffusion between the microparticle and the water phase.

  8. External and intraparticle diffusion of coumarin 102 with surfactant in the ODS-silica gel/water system by single microparticle injection and confocal fluorescence microspectroscopy

    International Nuclear Information System (INIS)

    Nakatani, Kiyoharu; Matsuta, Emi

    2015-01-01

    The release mechanism of coumarin 102 from a single ODS-silica gel microparticle into the water phase in the presence of Triton X-100 was investigated by confocal fluorescence microspectroscopy combined with the single microparticle injection technique. The release rate significantly depended on the Triton X-100 concentration in the water phase and was not limited by diffusion in the pores of the microparticle. The release rate constant was inversely proportional to the microparticle radius squared, indicating that the rate-determining step is the external diffusion between the microparticle and the water phase. (author)

  9. Magnetic, Fluorescence and Transition Metal Ion Response Properties of 2,6-Diaminopyridine Modified Silica-Coated Fe3O4 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Yunhui Zhai

    2016-08-01

    Full Text Available Multi-functional nanoparticles possessing magnetic, fluorescence and transition metal ion response properties were prepared and characterized. The particles have a core/shell structure that consists of silica-coated magnetic Fe3O4 and 2,6-diaminopyridine anchored on the silica surface via organic linker molecules. The resultant nanoparticles were found by transmission electron microscopy to be well-dispersed spherical particles with an average diameter of 10–12 nm. X-ray diffraction analysis suggested the existence of Fe3O4 and silica in/on the particle. Fourier transform infrared spectra revealed that 2,6-diaminopyridine molecules were successfully covalently bonded to the surface of magnetic composite nanoparticles. The prepared particles possessed an emission peak at 364 nm with an excitation wavelength of 307 nm and have a strong reversible response property for some transition metal ions such as Cu2+ and Zn2+. This new material holds considerable promise in selective magneto separation and optical determination applications.

  10. A new approach to dual-color two-photon microscopy with fluorescent proteins

    Directory of Open Access Journals (Sweden)

    Rebane Aleks

    2010-02-01

    Full Text Available Abstract Background Two-photon dual-color imaging of tissues and cells labeled with fluorescent proteins (FPs is challenging because most two-photon microscopes only provide one laser excitation wavelength at a time. At present, methods for two-photon dual-color imaging are limited due to the requirement of large differences in Stokes shifts between the FPs used and their low two-photon absorption (2PA efficiency. Results Here we present a new method of dual-color two-photon microscopy that uses the simultaneous excitation of the lowest-energy electronic transition of a blue fluorescent protein and a higher-energy electronic transition of a red fluorescent protein. Conclusion Our method does not require large differences in Stokes shifts and can be extended to a variety of FP pairs with larger 2PA efficiency and more optimal imaging properties.

  11. Development of dual-emission ratiometric probe-based on fluorescent silica nanoparticle and CdTe quantum dots for determination of glucose in beverages and human body fluids.

    Science.gov (United States)

    Zhai, Hong; Feng, Ting; Dong, Lingyu; Wang, Liyun; Wang, Xiangfeng; Liu, Hailing; Liu, Yuan; Chen, Luan; Xie, MengXia

    2016-08-01

    A novel dual emission ratiometric fluorescence probe for determination of glucose has been developed. The reference dye fluorescence isothiocyanate (FITC) has been encapsulated in the silica nanoparticles and then the red emission CdTe QDs were grafted on the surface of the silica particles to obtain the fluorescence probe. With glucose and dopamine as substrates, the glucose level was proportional to the fluorescence ratio change of above probe caused by dopamine oxidation, which was produced via bienzyme catalysis (glucose oxidase and horseradish peroxidase). The established approach was sensitive and selective, and has been applied to determine the glucose in beverage, urine and serum samples. The average recoveries of the glucose at various spiking levels ranged from 95.5% to 108.9% with relative standard deviations from 1.5% to 4.3%. The results provided a clue to develop sensors for rapid determination of the target analytes from complex matrices. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Preparation of strongly fluorescent silica nanoparticles of polyelectrolyte-protected cadmium telluride quantum dots and their application to cell toxicity and imaging

    International Nuclear Information System (INIS)

    Tang Jianhua; Xie Lian; Zhang Bin; Qiu Ting; Qi Bin; Xie Hongping

    2012-01-01

    Graphical abstract: The staining effect of the control group (a), QDs-SiO 2 (b) and QDs-PDADMAC-SiO 2 (c). Highlights: ► The fluorescence intensity of QDs-PDADMAC-SiO 2 is stronger than that of QDs-SiO 2 . ► The fluorescence stability of QDs-PDADMAC-SiO 2 is better than that of QDs-SiO 2 . ► The cytotoxicity of QDs-PDADMAC-SiO 2 was lower than that of QDs-SiO 2 ► The staining effect of QDs-PDADMAC-SiO 2 was much better than that of QDs-SiO 2 . - Abstract: Based on the polyelectrolyte-protected CdTe quantum dots (QDs), which were prepared by self-assembling of QDs and poly-diallyldimethylammonium chloride (PDADMAC) in the help of electrostatic attraction, the strong fluorescence silica nanoparticles (QDs-PDADMAC-SiO 2 ) have been prepared via a water-in-oil reverse microemulsion method. Transmission electron microscopy and Zeta potential analysis were used to characterize the as-prepared nanoparticles. All of the particles were almost spherical and there is a uniform distribution of the particle size with the average diameter about 25 nm. There is a large Zeta potential of −35.07 mV which is necessary for good monodispersity of nanoparticles solution. As compared with the QDs coated by SiO 2 (QDs-SiO 2 ), the QDs-PDADMAC-SiO 2 nanoparticles have much stronger fluorescence, and their fluorescence stability could be obviously improved. Moreover, QDs-PDADMAC-SiO 2 exhibits good biological compatibility which promotes their application in cellular imaging.

  13. Fluorescent magnetic nanoparticles for cell labeling: flux synthesis of manganite particles and novel functionalization of silica shell

    Czech Academy of Sciences Publication Activity Database

    Kačenka, Michal; Kaman, Ondřej; Kikerlová, S.; Pavlů, B.; Jirák, Zdeněk; Jirák, D.; Herynek, Vít; Černý, J.; Chaput, F.; Laurent, S.; Lukeš, I.

    2015-01-01

    Roč. 47, Jun (2015), s. 97-106 ISSN 0021-9797 R&D Projects: GA ČR(CZ) GAP108/11/0807; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:68378271 ; RVO:68378041 Keywords : manganites * magnetic nanoparticles * molten salt synthesis * silica coating * dual probes * MRI * cell labeling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.782, year: 2015

  14. A silica nanoparticle-based sensor for selective fluorescent detection of homocysteine via interaction differences between thiols and particle-surface-bound polymers

    International Nuclear Information System (INIS)

    Yu Changmin; Zeng Fang; Luo Ming; Wu Shuizhu

    2012-01-01

    Biothiols play crucial roles in maintaining biological systems; among them, homocysteine (Hcy) has received increasing attention since elevated levels of Hcy have been implicated as an independent risk factor for cardiovascular disease. Hence, the selective detection of this specific biothiol, which is a disease-associated biomarker, is very important. In this paper, we demonstrate a new mesoporous silica nanoparticle-based sensor for selective detection of homocysteine from biothiols and other common amino acids. In this fluorescent sensing system, an anthracene nitroolefin compound was placed inside the mesopores of mesoporous silica nanoparticles (MSNs) and used as a probe for thiols. The hydrophilic polyethylene glycol (PEG 5000) molecules were covalently bound to the MSN surface and used as a selective barrier for Hcy detection via different interactions between biothiols and the PEG polymer chains. The sensor can discriminate Hcy from the two low-molecular mass biothiols (GSH and Cys) and other common amino acids in totally aqueous media as well as in serum, with a detection limit of 0.1 μM. This strategy may offer an approach for designing other MSN-based sensing systems by using polymers as diffusion regulators in sensing assays for other analytes. (paper)

  15. A combination of positive dielectrophoresis driven on-line enrichment and aptamer-fluorescent silica nanoparticle label for rapid and sensitive detection of Staphylococcus aureus.

    Science.gov (United States)

    Shangguan, Jingfang; Li, Yuhong; He, Dinggeng; He, Xiaoxiao; Wang, Kemin; Zou, Zhen; Shi, Hui

    2015-07-07

    Staphylococcus aureus (S. aureus) is an important human pathogen that causes several diseases ranging from superficial skin infections to life-threatening diseases. Here, a method combining positive dielectrophoresis (pDEP) driven on-line enrichment and aptamer-fluorescent silica nanoparticle label has been developed for the rapid and sensitive detection of S. aureus in microfluidic channels. An aptamer, having high affinity to S. aureus, is used as the molecular recognition tool and immobilized onto chloropropyl functionalized fluorescent silica nanoparticles through a click chemistry approach to obtain S. aureus aptamer-nanoparticle bioconjugates (Apt(S.aureus)/FNPs). The pDEP driven on-line enrichment technology was used for accumulating the Apt(S.aureus)/FNP labeled S. aureus. After incubating with S. aureus, the mixture of Apt(S.aureus)/FNP labeled S. aureus and Apt(S.aureus)/FNPs was directly introduced into the pDEP-based microfluidic system. By applying an AC voltage in a pDEP frequency region, the Apt(S.aureus)/FNP labelled S. aureus moved to the electrodes and accumulated in the electrode gap, while the free Apt(S.aureus)/FNPs flowed away. The signal that came from the Apt(S.aureus)/FNP labelled S. aureus in the focused detection areas was then detected. Profiting from the specificity of aptamer, signal amplification of FNP label and pDEP on-line enrichment, this assay can detect as low as 93 and 270 cfu mL(-1)S. aureus in deionized water and spiked water samples, respectively, with higher sensitivities than our previously reported Apt(S.aureus)/FNP based flow cytometry. Moreover, without the need for separation and washing steps usually required for FNP label involved bioassays, the total assay time including sample pretreatment was within 2 h.

  16. Detection of trace tetracycline in fish via synchronous fluorescence quenching with carbon quantum dots coated with molecularly imprinted silica

    Science.gov (United States)

    Yang, Ji; Lin, Zheng-Zhong; Nur, A.-Zha; Lu, Yan; Wu, Ming-Hui; Zeng, Jun; Chen, Xiao-Mei; Huang, Zhi-Yong

    2018-02-01

    A novel fluorescence-based sensor combining synchronous fluorescence spectroscopy (SFS) with molecularly imprinted polymers (MIPs) was fabricated with reverse microemulsion method. Tetracycline (TC), (3-aminopropyl) triethoxysilane (APTES), tetraethyl orthosilicate (TEOS) and carbon quantum dots (CDs) were used as template, functional monomer, cross-linker and signal sources respectively in the probe preparation. A synchronous fluorescence emission (λem) at 355 nm was observed for the prepared MIP-coated CDs (MIP@CDs) particles when the wavelength interval (Δλ) was set as 70 nm, and the synchronous fluorescence intensity could be rapidly and efficiently quenched by TC based on inner filter effect (IFE). The quenching efficiencies of synchronous fluorescence intensity was linearly fitted with tetracycline (TC) concentrations ranging from 0.1 to 50 μmol L- 1 with a detection limit (DL) of 9 nmol L- 1 (3σ, n = 9). The MIP@CDs was used as a probe to detect TC in fish samples with the recoveries ranging from 98.4% to 103.1% and the relative standard deviation less than 6.0%. The results illustrated that the as-prepared MIP@CDs could be applied to the detection of trace TC in fish samples with rapidity, high sensitivity and accuracy.

  17. Volume labeling with Alexa Fluor dyes and surface functionalization of highly sensitive fluorescent silica (SiO2) nanoparticles

    Science.gov (United States)

    Wang, Wei; Nallathamby, Prakash D.; Foster, Carmen M.; Morrell-Falvey, Jennifer L.; Mortensen, Ninell P.; Doktycz, Mitchel J.; Gu, Baohua; Retterer, Scott T.

    2013-10-01

    A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems.A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in

  18. Magnetic Bead and Fluorescent Silica Nanoparticles Based Optical Immunodetection of Staphylococcal Enterotoxin B (SEB in Bottled Water

    Directory of Open Access Journals (Sweden)

    Shiva K. RASTOGI

    2009-10-01

    Full Text Available Staphylococcal enterotoxins (SEs are a major cause of food-borne diseases, most commonly SEs assayed immunologically with ELISA. An immunoassay based on fluorescein dye doped silica dioxide nanoparticles (F-SiNPs and magnetic bead (MB is described here for the detection of staphylococcal enterotoxin B (SEB. F-SiNPs have unique optical properties which make them attractive for biosensing. The water-in-oil (W/O reverse microemulsion method was used for the synthesis of F-SiNPs (~ 95 nm of diameter. The F-SiNPs were characterized using SEM, TEM and FTIR spectroscopy. The detection of SEB is preformed in PBS buffer, and bottled drinking water using sandwich immunoassay format. Target analytes were captured using MBs modified with the antigen-specific “capture” antibody, and detected using F-SiNP labeled secondary antigen-specific antibody. We report a limit of detection down to 1 ng/mL SEB spiked sample in less than 2 hr assay time using fluorocount method. This study demonstrates the bio warfare agent SEB capture by magnetic beads and detection using F-SiNPs.

  19. Two colorimetric and ratiometric fluorescence probes for hydrogen sulfide based on AIE strategy of α-cyanostilbenes

    Science.gov (United States)

    Zhao, Baoying; Yang, Binsheng; Hu, Xiangquan; Liu, Bin

    2018-06-01

    Aggregation-induced emission (AIE) active fluorescent probes have attracted great potential in biological sensors. In this paper two cyanostilbene based fluorescence chemoprobe Cya-NO2 (1) and Cya-N3 (2) were developed and evaluated for the selective and sensitive detection of hydrogen sulfide (H2S). Both of these probes behave aggression-induced emission (AIE) activity which fluoresces in the red region with a large Stokes shift. They exhibit rapid response to H2S with enormous colorimetric and ratiometric fluorescent changes. They are readily employed for assessing intracellular H2S levels.

  20. A dansyl-rhodamine ratiometric fluorescent probe for Hg2+ based on FRET mechanism.

    Science.gov (United States)

    Xie, Puhui; Guo, Fengqi; Wang, Lingyu; Yang, Sen; Yao, Denghui; Yang, Guoyu

    2015-03-01

    Based on resonance energy transfer (FRET) from dansyl to rhodamine 101, a new fluorescent probe (compound 1) containing rhodamine 101 and a dansyl unit was synthesized for detecting Hg(2+) through ratiometric sensing in DMSO aqueous solutions. This probe shows a fast, reversible and selective response toward Hg(2+) in a wide pH range. Hg(2+) induced ring-opening reactions of the spirolactam rhodamine moiety of 1, leading to the formation of fluorescent derivatives that can serve as the FRET acceptors. Very large stokes shift (220 nm) was observed in this case. About 97-fold increase in fluorescence intensity ratio was observed upon its binding with Hg(2+).

  1. Bis(pyridylvinyl)diaminobenzenes: synthesis, acidochromism and solvatochromism of the fluorescence

    International Nuclear Information System (INIS)

    Detert, H.; Sugiono, E.

    2005-01-01

    C 2 -symmetrical 1,4-distyrylbenzenes with 4-dimethylaminobenzene or pyridine as terminal rings, and propyloxy or dipropylamino groups in the central 2,5-positions were prepared. Solvatochromism of the absorption is small, but more pronounced in the fluorescence spectra. Some compounds exhibit huge Stokes shifts. Acid strongly alters the fluorescence: red shifts and decreasing quantum yields is the general result, but depending on the position and character of the basic sites, a strong recovery of fluorescence efficiency combined with large hypsochromic shifts may result in highly acidic solutions

  2. 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.

  3. Fluorescent carbon dot-gated multifunctional mesoporous silica nanocarriers for redox/enzyme dual-responsive targeted and controlled drug delivery and real-time bioimaging.

    Science.gov (United States)

    Wang, Ying; Cui, Yu; Zhao, Yating; He, Bing; Shi, Xiaoli; Di, Donghua; Zhang, Qiang; Wang, Siling

    2017-08-01

    A distinctive and personalized nanocarrier is described here for controlled and targeted antitumor drug delivery and real-time bioimaging by combining a redox/enzyme dual-responsive disulfide-conjugated carbon dot with mesoporous silica nanoparticles (MSN-SS-CD HA ). The carbon dot with controlling and targeting abilities was prepared through a polymerizing reaction by applying citric acid and HA as starting materials (named CD HA ). The as-prepared MSN-SS-CD HA exhibited not only superior photostability and excellent biocompatibility, but also the ability to target A549 cells with overexpression of CD44 receptors. Upon loading the antitumor drug, doxorubicin (DOX), into the mesoporous channels of MSN nanoparticles, CD HA with a diameter size of 3nm completely blocked the pore entrance of DOX-encapsulated MSN nanoparticles with a pore size of about 3nm, thus preventing the premature leakage of DOX and increasing the antitumor activity until being triggered by specific stimuli in the tumor environment. The results of the cell imaging and cytotoxicity studies demonstrated that the redox/enzyme dual-responsive DOX-encapsulated MSN-SS-CD HA nanoparticles can selectively deliver and control the release of DOX into tumor cells. Ex vivo fluorescence images showed a much stronger fluorescence of MSN-SS-CD HA -DOX in the tumor site than in normal tissues, greatly facilitating the accumulation of DOX in the target tissue. However, its counterpart, MSN-SH-DOX exhibited no or much lower tumor cytotoxicity and drug accumulation in tumor tissue. In addition, MSN-SS-CD was also used as a control to investigate the ability of MSN-SS-CD HA to target A549 cells. The results obtained indicated that MSN-SS-CD HA possessed a higher cellular uptake through the CD44 receptor-mediated endocytosis compared with MSN-SS-CD in the A549 cells. Such specific redox/enzyme dual-responsive targeted nanocarriers are a useful strategy achieving selective controlled and targeted delivery of

  4. 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.

  5. 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.

  6. 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.

  7. A benzothiazole-based fluorescent probe for hypochlorous acid detection and imaging in living cells

    Science.gov (United States)

    Nguyen, Khac Hong; Hao, Yuanqiang; Zeng, Ke; Fan, Shengnan; Li, Fen; Yuan, Suke; Ding, Xuejing; Xu, Maotian; Liu, You-Nian

    2018-06-01

    A benzothiazole-based turn-on fluorescent probe with a large Stokes shift (190 nm) has been developed for hypochlorous acid detection. The probe displays prompt fluorescence response for HClO with excellent selectivity over other reactive oxygen species as well as a low detection limit of 0.08 μM. The sensing mechanism involves the HClO-induced specific oxidation of oxime moiety of the probe to nitrile oxide, which was confirmed by HPLC-MS technique. Furthermore, imaging studies demonstrated that the probe is cell permeable and can be applied to detect HClO in living cells.

  8. A Low-Cost, High-Performance System for Fluorescence Lateral Flow Assays

    Directory of Open Access Journals (Sweden)

    Linda G. Lee

    2013-10-01

    Full Text Available We demonstrate a fluorescence lateral flow system that has excellent sensitivity and wide dynamic range. The illumination system utilizes an LED, plastic lenses and plastic and colored glass filters for the excitation and emission light. Images are collected on an iPhone 4. Several fluorescent dyes with long Stokes shifts were evaluated for their signal and nonspecific binding in lateral flow. A wide range of values for the ratio of signal to nonspecific binding was found, from 50 for R-phycoerythrin (R-PE to 0.15 for Brilliant Violet 605. The long Stokes shift of R-PE allowed the use of inexpensive plastic filters rather than costly interference filters to block the LED light. Fluorescence detection with R-PE and absorbance detection with colloidal gold were directly compared in lateral flow using biotinylated bovine serum albumen (BSA as the analyte. Fluorescence provided linear data over a range of 0.4–4,000 ng/mL with a 1,000-fold signal change while colloidal gold provided non-linear data over a range of 16–4,000 ng/mL with a 10-fold signal change. A comparison using human chorionic gonadotropin (hCG as the analyte showed a similar advantage in the fluorescent system. We believe our inexpensive yet high-performance platform will be useful for providing quantitative and sensitive detection in a point-of-care setting.

  9. 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.

  10. Synthesis of molecularly imprinted dye-silica nanocomposites with high selectivity and sensitivity: Fluorescent imprinted sensor for rapid and efficient detection of τ-fluvalinate in vodka.

    Science.gov (United States)

    Wang, Yunyun; Wang, Jixiang; Cheng, Rujia; Sun, Lin; Dai, Xiaohui; Yan, Yongsheng

    2018-04-01

    An imprinted fluorescent sensor was fabricated based on SiO 2 nanoparticles encapsulated with a molecularly imprinted polymer containing allyl fluorescein. High fluorine cypermethirin as template molecules, methyl methacrylate as functional monomer, and allyl fluorescein as optical materials synthesized a core-shell fluorescent molecular imprinted sensor, which showed a high and rapid sensitivity and selectivity for the detection of τ-fluvalinate. The sensor presented appreciable sensitivity with a limit of 13.251 nM, rapid detection that reached to equilibrium within 3 min, great linear relationship in the relevant concentration range from 0 to 150 nM, and excellent selectivity over structural analogues. In addition, the fluorescent sensor demonstrated desirable regeneration ability (eight cycling operations). The molecularly imprinted polymers ensured specificity, while the fluorescent dyes provided the stabile sensitivity. Finally, an effective application of the sensor was implemented by the detection of τ-fluvalinate in real samples from vodka. The molecularly imprinted fluorescent sensor showed a promising potential in environmental monitoring and food safety. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Thermally activated delayed fluorescence of fluorescein derivative for time-resolved and confocal fluorescence imaging.

    Science.gov (United States)

    Xiong, Xiaoqing; Song, Fengling; Wang, Jingyun; Zhang, Yukang; Xue, Yingying; Sun, Liangliang; Jiang, Na; Gao, Pan; Tian, Lu; Peng, Xiaojun

    2014-07-09

    Compared with fluorescence imaging utilizing fluorophores whose lifetimes are in the order of nanoseconds, time-resolved fluorescence microscopy has more advantages in monitoring target fluorescence. In this work, compound DCF-MPYM, which is based on a fluorescein derivative, showed long-lived luminescence (22.11 μs in deaerated ethanol) and was used in time-resolved fluorescence imaging in living cells. Both nanosecond time-resolved transient difference absorption spectra and time-correlated single-photon counting (TCSPC) were employed to explain the long lifetime of the compound, which is rare in pure organic fluorophores without rare earth metals and heavy atoms. A mechanism of thermally activated delayed fluorescence (TADF) that considers the long wavelength fluorescence, large Stokes shift, and long-lived triplet state of DCF-MPYM was proposed. The energy gap (ΔEST) of DCF-MPYM between the singlet and triplet state was determined to be 28.36 meV by the decay rate of DF as a function of temperature. The ΔE(ST) was small enough to allow efficient intersystem crossing (ISC) and reverse ISC, leading to efficient TADF at room temperature. The straightforward synthesis of DCF-MPYM and wide availability of its starting materials contribute to the excellent potential of the compound to replace luminescent lanthanide complexes in future time-resolved imaging technologies.

  12. Fluorenyl benzothiadiazole and benzoselenadiazole near-IR fluorescent probes for two-photon fluorescence imaging (Conference Presentation)

    Science.gov (United States)

    Belfield, Kevin D.; Yao, Sheng; Kim, Bosung; Yue, Xiling

    2016-03-01

    Imaging biological samples with two-photon fluorescence (2PF) microscopy has the unique advantage of resulting high contrast 3D resolution subcellular image that can reach up to several millimeters depth. 2PF probes that absorb and emit at near IR region need to be developed. Two-photon excitation (2PE) wavelengths are less concerned as 2PE uses wavelengths doubles the absorption wavelength of the probe, which means 2PE wavelengths for probes even with absorption at visible wavelength will fall into NIR region. Therefore, probes that fluoresce at near IR region with high quantum yields are needed. A series of dyes based on 5-thienyl-2, 1, 3-benzothiadiazole and 5-thienyl-2, 1, 3-benzoselenadiazole core were synthesized as near infrared two-photon fluorophores. Fluorescence maxima wavelengths as long as 714 nm and fluorescence quantum yields as high as 0.67 were achieved. The fluorescence quantum yields of the dyes were nearly constant, regardless of solvents polarity. These diazoles exhibited large Stokes shift (GM), and high two-photon fluorescence figure of merit (FM , 1.04×10-2 GM). Cells incubated on a 3D scaffold with one of the new probes (encapsulated in Pluronic micelles) exhibited bright fluorescence, enabling 3D two-photon fluorescence imaging to a depth of 100 µm.

  13. Comparison of Au and Ag nanoshells' metal-enhanced fluorescence

    International Nuclear Information System (INIS)

    Liaw, Jiunn-Woei; Chen, Huang-Chih; Kuo, Mao-Kuen

    2014-01-01

    The average enhancement factors of Au and Ag nanoshells (NSs) were analyzed theoretically to compare their overall performances on metal-enhanced fluorescence. We used the Mie theory and dyadic Green's functions to calculate the excitation rate and apparent quantum yield of NS interacting with a plane wave and a dipole, respectively, and then to obtain the enhancement factor. Moreover, the average enhancement factor (AEF) of NS on the fluorescence of a nearby molecule was obtained by averaging all possible orientations and locations of the molecule with a constant distance from NS. Our results show that the maximum AEF of Au NS occurs at the wavelength of the dipole mode, which is broadband. In contrast, the maximum AEF of Ag NS is at the narrowband quadrupole mode. In addition, the Stokes shift effect on AEF was studied for Au and Ag NSs. - Highlights: • The average enhancement factors of Au and Ag nanoshells were analyzed theoretically. • The maximum AEF of Au NS occurs at the wavelength of the dipole mode. • The maximum AEF of Ag NS is at the narrowband quadrupole mode. • The Stokes shift effect on AEF is discussed for Au and Ag NSs

  14. A highly sensitive, single selective, fluorescent sensor for Al3+ detection and its application in living cell imaging

    International Nuclear Information System (INIS)

    Ye, Xing-Pei; Sun, Shao-bo; Li, Ying-dong; Zhi, Li-hua; Wu, Wei-na; Wang, Yuan

    2014-01-01

    A new o-aminophenol-based fluorogenic chemosensor methyl 3,5-bis((E)-(2-hydroxyphenylimino)methyl)-4-hydroxybenzoate 1 have been synthesized by Schiff base condensation of methyl 3,5-diformyl-4-hydroxybenzoate with o-aminophenol, which exhibits high selectivity and sensitivity toward Al 3+ . Fluorescence titration studies of receptors 1 with different metal cations in CH 3 OH medium showed highly selective and sensitive towards Al 3+ ions even in the presence of other commonly coexisting metal ions. The detection limit of Al 3+ ions is at the parts per billion level. Interestingly, the Al(III) complex of 1 offered a large Stokes shift (>120 nm), which can miximize the selfquenching effect. In addition, possible utilization of this receptor as bio-imaging fluorescent probe to detect Al 3+ in human cervical HeLa cancer cell lines was also investigated by confocal fluorescence microscopy. - Highlights: • A new Schiff base chemosensor is reported. • The sensor for Al 3+ offers large Stokes shift. • The detection limit of Al 3+ in CH 3 OH solution is at the parts per billion level. • The utilization of sensor for the monitoring of Al 3+ levels in living cells was examined

  15. A highly sensitive, single selective, fluorescent sensor for Al{sup 3+} detection and its application in living cell imaging

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Xing-Pei [Department of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China); Sun, Shao-bo; Li, Ying-dong [Institute of Integrated Traditional and Western Medicine, Gansu University of Traditional Chinese Medicine, Lanzhou 730000 (China); Zhi, Li-hua [Department of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China); Wu, Wei-na, E-mail: wuwn08@hpu.edu.cn [Department of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China); Wang, Yuan, E-mail: wangyuan08@hpu.edu.cn [Department of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China)

    2014-11-15

    A new o-aminophenol-based fluorogenic chemosensor methyl 3,5-bis((E)-(2-hydroxyphenylimino)methyl)-4-hydroxybenzoate 1 have been synthesized by Schiff base condensation of methyl 3,5-diformyl-4-hydroxybenzoate with o-aminophenol, which exhibits high selectivity and sensitivity toward Al{sup 3+}. Fluorescence titration studies of receptors 1 with different metal cations in CH{sub 3}OH medium showed highly selective and sensitive towards Al{sup 3+} ions even in the presence of other commonly coexisting metal ions. The detection limit of Al{sup 3+} ions is at the parts per billion level. Interestingly, the Al(III) complex of 1 offered a large Stokes shift (>120 nm), which can miximize the selfquenching effect. In addition, possible utilization of this receptor as bio-imaging fluorescent probe to detect Al{sup 3+} in human cervical HeLa cancer cell lines was also investigated by confocal fluorescence microscopy. - Highlights: • A new Schiff base chemosensor is reported. • The sensor for Al{sup 3+} offers large Stokes shift. • The detection limit of Al{sup 3+} in CH{sub 3}OH solution is at the parts per billion level. • The utilization of sensor for the monitoring of Al{sup 3+} levels in living cells was examined.

  16. Diphenylacrylonitrile-connected BODIPY dyes: fluorescence enhancement based on dark and AIE resonance energy transfer.

    Science.gov (United States)

    Lin, Liangbin; Lin, Xiaoru; Guo, Hongyu; Yang, Fafu

    2017-07-19

    This study focuses on the construction of novel diphenylacrylonitrile-connected BODIPY dyes with high fluorescence in both solution and an aggregated state by combining DRET and FRET processes in a single donor-acceptor system. The first BODIPY derivatives with one, two, or three AIE-active diphenylacrylonitrile groups were designed and synthesized in moderate yields. Strong fluorescence emissions were observed in the THF solution under excitation at the absorption wavelength of non-emissive diphenylacrylonitrile chromophores, implying the existence of the DRET process between the dark diphenylacrylonitrile donor and the emissive BODIPY acceptor. In the THF/H 2 O solution, the fluorescence intensity of the novel BODIPY derivatives gradually increased under excitation at the absorption wavelength of diphenylacrylonitrile chromophores, suggesting a FRET process between diphenylacrylonitrile and BODIPY moieties. A greater number of diphenylacrylonitrile units led to higher energy-transfer efficiencies. The pseudo-Stokes shift for both DRET and FRET processes was as large as 190 nm.

  17. Characterization for Post-treatment Effect of Bagasse Ash for Silica Extraction

    OpenAIRE

    Patcharin Worathanakul; Wisaroot Payubnop; Akhapon Muangpet

    2009-01-01

    Utilization of bagasse ash for silica sources is one of the most common application for agricultural wastes and valuable biomass byproducts in sugar milling. The high percentage silica content from bagasse ash was used as silica source for sodium silicate solution. Different heating temperature, time and acid treatment were studies for silica extraction. The silica was characterized using various techniques including X-ray fluorescence, X-ray diffraction, Scanning electro...

  18. A new simple phthalimide-based fluorescent probe for highly selective cysteine and bioimaging for living cells

    Science.gov (United States)

    Shen, Youming; Zhang, Xiangyang; Zhang, Youyu; Zhang, Chunxiang; Jin, Junling; Li, Haitao

    2017-10-01

    A new turn-on phthalimide fluorescent probe has designed and synthesized for sensing cysteine (Cys) based on excited state intramolecular proton transfer (ESIPT) process. It is consisted of a 3-hydroxyphthalimide derivative moiety as the fluorophore and an acrylic ester group as a recognition receptor. The acrylic ester acts as an ESIPT blocking agent. Upon addition of cystein, intermolecular nucleophilic attack of cysteine on acrylic ester releases the fluorescent 3-hydroxyphthalimide derivative, thereby enabling the ESIPT process and leading to enhancement of fluorescence. The probe displays high sensitivity, excellent selectivity and with large Stokes shift toward cysteine. The linear interval range of the fluorescence titration ranged from 0 to 1.0 × 10- 5 M and detection limit is low (6 × 10- 8 M). In addition, the probe could be used for bio-imaging in living cells.

  19. Obtaining high purity silica from rice hulls

    Directory of Open Access Journals (Sweden)

    José da Silva Júnior

    2010-01-01

    Full Text Available Many routes for extracting silica from rice hulls are based on direct calcining. These methods, though, often produce silica contaminated with inorganic impurities. This work presents the study of a strategy for obtaining silica from rice hulls with a purity level adequate for applications in electronics. The technique is based on two leaching steps, using respectively aqua regia and Piranha solutions, which extract the organic matrix and inorganic impurities. The material was characterized by Fourier-transform infrared spectroscopy (FTIR, powder x-ray diffraction (XRD, x-ray fluorescence (XRF, scanning electron microscopy (SEM, particle size analysis by laser diffraction (LPSA and thermal analysis.

  20. Structural characterization of rondorfite, calcium silica chlorine mineral containing magnesium in tetrahedral position [MgO4]6-, with the aid of the vibrational spectroscopies and fluorescence.

    Science.gov (United States)

    Dulski, M; Bulou, A; Marzec, K M; Galuskin, E V; Wrzalik, R

    2013-01-15

    Raman and infrared spectra of rondorfite Ca8Mg(SiO4)4Cl2, a calcium chlorosilica mineral containing magnesium in tetrahedral position, has been studied in terms of spectra-structure relations. Raman spectra have been measured at different excited laser lines: 780 nm, 532 nm, 488 nm and 457 nm. This mineral is characterized by a single sharp intense Raman band at 863 cm(-1) assigned to the ν1 [SiO4]4- (Ag) symmetric stretching mode in the magnesiosilicate pentamer. Due to symmetry restriction the other Raman bands have a small intensity. Two Raman bands observed at 564 cm(-1) and 526 cm(-1) are associated simultaneously with ν4 [MgO4]6- and ν4 [SiO4]4- symmetric and antisymmetric modes where magnesium occurs in the tetrahedral configuration. The weak bands at 422 cm(-1) and 386 cm(-1) are associated with the ν2 bending mode of CaO6 in octahedral configuration, respectively. Moreover the infrared spectrum shows very weak bands associated with the hydroxyl group and/or water molecule. Additionally, the strong fluorescence phenomenon was observed and related to the presence of chlorine atoms, magnesium Mg2+ ions in atypical configuration or point defects. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. 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

  2. Origins of Stokes shift in PbS nanocrystals

    KAUST Repository

    Voznyy, Oleksandr; Levina, Larissa; Fan, Feng-Jia; Walters, Grant; Fan, James Z.; Kiani, Amirreza; Ip, Alexander H.; Thon, Susanna M.; Proppe, Andrew; Liu, Mengxia; Sargent, Edward H.

    2017-01-01

    shift of up to 200 meV is observed, substantially larger than the estimates of dark-bright state splitting or vibronic relaxations. The shift origin remains highly debated, as contradictory signatures of both surface and bulk character were reported

  3. Synthesis and characterization of novel 2, 2'-bipyrimidine fluorescent derivative for protein binding

    Directory of Open Access Journals (Sweden)

    Padalkar Vikas S

    2011-11-01

    Full Text Available Abstract Background Fluorescent dyes with biocompatible functional group and good fluorescence behavior are used as biosensor for monitoring different biological processes as well as detection of protein assay. All reported fluorophore used as sensors are having high selectivity and sensitivity but till there is more demand to synthesized new fluorophore which have improved fluorescence properties and good biocompatibility. Results Novel 4, 4'-(1, 1'-(5-(2-methoxyphenoxy-[2, 2'-bipyrimidine]-4, 6-diylbis(1H-pyrazol-3, 1-diyl dianiline fluorescent dye was synthesized by multistep synthesis from 2-phenylacetonitrile, 2-chloropyrimidine and 2-methoxyphenol. This dye has absorption at 379 nm with intense single emission at 497 nm having fairly good quantum yield (0.375 and Stokes shift. The intermediates and dye were characterized by FT-IR, 1H NMR, 13C NMR and Mass spectral analysis. The pyrazole bipyrimidine based fluorescent dye possessing two amino groups suitable for binding with protein is reported. Its utility as a biocompatible conjugate was explained by conjugation with bovine serum albumin. The method is based on direct fluorescence detection of fluorophore-labelled protein before and after conjugation. Purified fluorescent conjugate was subsequently analyzed by fluorimetry. The analysis showed that the tested conjugation reaction yielded fluorescent conjugates of the dye through carbodiimide chemistry. Conclusion In summery synthesized fluorophore pyrazole-bipyrimidine has very good interaction towards protein bovine serum albumin and it acts as good candidate for protein assay.

  4. Ultrafast proton shuttling in Psammocora cyan fluorescent protein.

    Science.gov (United States)

    Kennis, John T M; van Stokkum, Ivo H M; Peterson, Dayna S; Pandit, Anjali; Wachter, Rebekka M

    2013-09-26

    Cyan, green, yellow, and red fluorescent proteins (FPs) homologous to green fluorescent protein (GFP) are used extensively as model systems to study fundamental processes in photobiology, such as the capture of light energy by protein-embedded chromophores, color tuning by the protein matrix, energy conversion by Förster resonance energy transfer (FRET), and excited-state proton transfer (ESPT) reactions. Recently, a novel cyan fluorescent protein (CFP) termed psamFP488 was isolated from the genus Psammocora of reef building corals. Within the cyan color class, psamFP488 is unusual because it exhibits a significantly extended Stokes shift. Here, we applied ultrafast transient absorption and pump-dump-probe spectroscopy to investigate the mechanistic basis of psamFP488 fluorescence, complemented with fluorescence quantum yield and dynamic light scattering measurements. Transient absorption spectroscopy indicated that, upon excitation at 410 nm, the stimulated cyan emission rises in 170 fs. With pump-dump-probe spectroscopy, we observe a very short-lived (110 fs) ground-state intermediate that we assign to the deprotonated, anionic chromophore. In addition, a minor fraction (14%) decays with 3.5 ps to the ground state. Structural analysis of homologous proteins indicates that Glu-167 is likely positioned in sufficiently close vicinity to the chromophore to act as a proton acceptor. Our findings support a model where unusually fast ESPT from the neutral chromophore to Glu-167 with a time constant of 170 fs and resulting emission from the anionic chromophore forms the basis of the large psamFP488 Stokes shift. When dumped to the ground state, the proton on neutral Glu is very rapidly shuttled back to the anionic chromophore in 110 fs. Proton shuttling in excited and ground states is a factor of 20-4000 faster than in GFP, which probably results from a favorable hydrogen-bonding geometry between the chromophore phenolic oxygen and the glutamate acceptor, possibly

  5. A novel method to characterize silica bodies in grasses.

    Science.gov (United States)

    Dabney, Clemon; Ostergaard, Jason; Watkins, Eric; Chen, Changbin

    2016-01-01

    The deposition of silicon into epidermal cells of grass species is thought to be an important mechanism that plants use as a defense against pests and environmental stresses. There are a number of techniques available to study the size, density and distribution pattern of silica bodies in grass leaves. However, none of those techniques can provide a high-throughput analysis, especially for a great number of samples. We developed a method utilizing the autofluorescence of silica bodies to investigate their size and distribution, along with the number of carbon inclusions within the silica bodies of perennial grass species Koeleria macrantha. Fluorescence images were analyzed by image software Adobe Photoshop CS5 or ImageJ that remarkably facilitated the quantification of silica bodies in the dry ash. We observed three types of silica bodies or silica body related mineral structures. Silica bodies were detected on both abaxial and adaxial epidermis of K. macrantha leaves, although their sizes, density, and distribution patterns were different. No auto-fluorescence was detected from carbon inclusions. The combination of fluorescence microscopy and image processing software displayed efficient utilization in the identification and quantification of silica bodies in K. macrantha leaf tissues, which should applicable to biological, ecological and geological studies of grasses including forage, turf grasses and cereal crops.

  6. Molecular Organization Induced Anisotropic Properties of Perylene - Silica Hybrid Nanoparticles.

    Science.gov (United States)

    Sriramulu, Deepa; Turaga, Shuvan Prashant; Bettiol, Andrew Anthony; Valiyaveettil, Suresh

    2017-08-10

    Optically active silica nanoparticles are interesting owing to high stability and easy accessibility. Unlike previous reports on dye loaded silica particles, here we address an important question on how optical properties are dependent on the aggregation-induced segregation of perylene molecules inside and outside the silica nanoparticles. Three differentially functionalized fluorescent perylene - silica hybrid nanoparticles are prepared from appropriate ratios of perylene derivatives and tetraethyl orthosilicate (TEOS) and investigated the structure property correlation (P-ST, P-NP and P-SF). The particles differ from each other on the distribution, organization and intermolecular interaction of perylene inside or outside the silica matrix. Structure and morphology of all hybrid nanoparticles were characterized using a range of techniques such as electron microscope, optical spectroscopic measurements and thermal analysis. The organizations of perylene in three different silica nanoparticles were explored using steady-state fluorescence, fluorescence anisotropy, lifetime measurements and solid state polarized spectroscopic studies. The interactions and changes in optical properties of the silica nanoparticles in presence of different amines were tested and quantified both in solution and in vapor phase using fluorescence quenching studies. The synthesized materials can be regenerated after washing with water and reused for sensing of amines.

  7. Dimeric fluorescent energy transfer dyes comprising asymmetric cyanine azole-indolenine chromophores

    Science.gov (United States)

    Glazer, Alexander N.; Benson, Scott C.

    1998-01-01

    Novel fluorescent heterodimeric DNA-staining energy transfer dyes are provided combining asymmetric cyanine azole-indolenine dyes, which provide for strong DNA affinity, large Stokes shifts and emission in the red region of the spectrum. The dyes find particular application in gel electrophoresis and for labels which may be bound to a variety of compositions in a variety of contexts. Kits and individual compounds are provided, where the kits find use for simultaneous detection of a variety of moieties, particularly using a single narrow wavelength irradiation source. The individual compounds are characterized by high donor quenching and high affinity to dsDNA as a result of optimizing the length of the linking group separating the two chromophores.

  8. Ratiometric Matryoshka biosensors from a nested cassette of green- and orange-emitting fluorescent proteins.

    Science.gov (United States)

    Ast, Cindy; Foret, Jessica; Oltrogge, Luke M; De Michele, Roberto; Kleist, Thomas J; Ho, Cheng-Hsun; Frommer, Wolf B

    2017-09-05

    Sensitivity, dynamic and detection range as well as exclusion of expression and instrumental artifacts are critical for the quantitation of data obtained with fluorescent protein (FP)-based biosensors in vivo. Current biosensors designs are, in general, unable to simultaneously meet all these criteria. Here, we describe a generalizable platform to create dual-FP biosensors with large dynamic ranges by employing a single FP-cassette, named GO-(Green-Orange) Matryoshka. The cassette nests a stable reference FP (large Stokes shift LSSmOrange) within a reporter FP (circularly permuted green FP). GO- Matryoshka yields green and orange fluorescence upon blue excitation. As proof of concept, we converted existing, single-emission biosensors into a series of ratiometric calcium sensors (MatryoshCaMP6s) and ammonium transport activity sensors (AmTryoshka1;3). We additionally identified the internal acid-base equilibrium as a key determinant of the GCaMP dynamic range. Matryoshka technology promises flexibility in the design of a wide spectrum of ratiometric biosensors and expanded in vivo applications.Single fluorescent protein biosensors are susceptible to expression and instrumental artifacts. Here Ast et al. describe a dual fluorescent protein design whereby a reference fluorescent protein is nested within a reporter fluorescent protein to control for such artifacts while preserving sensitivity and dynamic range.

  9. New insight into silica deposition in horsetail (Equisetum arvense

    Directory of Open Access Journals (Sweden)

    Exley Christopher

    2011-07-01

    Full Text Available Abstract Background The horsetails (Equisetum sp are known biosilicifiers though the mechanism underlying silica deposition in these plants remains largely unknown. Tissue extracts from horsetails grown hydroponically and also collected from the wild were acid-digested in a microwave oven and their silica 'skeletons' visualised using the fluor, PDMPO, and fluorescence microscopy. Results Silica deposits were observed in all plant regions from the rhizome through to the stem, leaf and spores. Numerous structures were silicified including cell walls, cell plates, plasmodesmata, and guard cells and stomata at varying stages of differentiation. All of the major sites of silica deposition in horsetail mimicked sites and structures where the hemicellulose, callose is known to be found and these serendipitous observations of the coincidence of silica and callose raised the possibility that callose might be templating silica deposition in horsetail. Hydroponic culture of horsetail in the absence of silicic acid resulted in normal healthy plants which, following acid digestion, showed no deposition of silica anywhere in their tissues. To test the hypothesis that callose might be templating silica deposition in horsetail commercially available callose was mixed with undersaturated and saturated solutions of silicic acid and the formation of silica was demonstrated by fluorimetry and fluorescence microscopy. Conclusions The initiation of silica formation by callose is the first example whereby any biomolecule has been shown to induce, as compared to catalyse, the formation of silica in an undersaturated solution of silicic acid. This novel discovery allowed us to speculate that callose and its associated biochemical machinery could be a missing link in our understanding of biosilicification.

  10. Plasmonic enhancement of ultraviolet fluorescence

    Science.gov (United States)

    Jiao, Xiaojin

    Plasmonics relates to the interaction between electromagnetic radiation and conduction electrons at metallic interfaces or in metallic nanostructures. Surface plasmons are collective electron oscillations at a metal surface, which can be manipulated by shape, texture and material composition. Plasmonic applications cover a broad spectrum from visible to near infrared, including biosensing, nanolithography, spectroscopy, optoelectronics, photovoltaics and so on. However, there remains a gap in this activity in the ultraviolet (UV, research. Motivating factors in the study of UV Plasmonics are the direct access to biomolecular resonances and native fluorescence, resonant Raman scattering interactions, and the potential for exerting control over photochemical reactions. This dissertation aims to fill in the gap of Plasmonics in the UV with efforts of design, fabrication and characterization of aluminium (Al) and magnesium (Mg) nanostructures for the application of label-free bimolecular detection via native UV fluorescence. The first contribution of this dissertation addresses the design of Al nanostructures in the context of UV fluorescence enhancement. A design method that combines analytical analysis with numerical simulation has been developed. Performance of three canonical plasmonic structures---the dipole antenna, bullseye nanoaperture and nanoaperture array---has been compared. The optimal geometrical parameters have been determined. A novel design of a compound bullseye structure has been proposed and numerically analyzed for the purpose of compensating for the large Stokes shift typical of UV fluorescence. Second, UV lifetime modification of diffusing molecules by Al nanoapertures has been experimentally demonstrated for the first time. Lifetime reductions of ~3.5x have been observed for the high quantum yield (QY) laser dye p-terphenyl in a 60 nm diameter aperture with 50 nm undercut. Furthermore, quantum-yield-dependence of lifetime reduction has been

  11. A fluorescent probe for ecstasy.

    Science.gov (United States)

    Masseroni, D; Biavardi, E; Genovese, D; Rampazzo, E; Prodi, L; Dalcanale, E

    2015-08-18

    A nanostructure formed by the insertion in silica nanoparticles of a pyrene-derivatized cavitand, which is able to specifically recognize ecstasy in water, is presented. The absence of effects from interferents and an efficient electron transfer process occurring after complexation of ecstasy, makes this system an efficient fluorescent probe for this popular drug.

  12. Particulate silica test agents for hepa filters

    International Nuclear Information System (INIS)

    Bauman, A.J.

    1987-01-01

    The authors developed a solid test aerosol (Dri-Test) and a versatile portable delivery system for it. The aerosol is based on thermal silica, modified chemically to make it surface-hydrophobic and fluorescent under UV illumination. The fluorescent tag enables one to identify tested filters. Primary particles are 7 nm in diameter, spherical, and of density 2.20 gm-cm/sup -3/ bulk aerosol powder has a density of 0.048 gm-cm/sup -3/. Tests by means of laser particle counters, TSI Nucleation counters and California Measurements Quartz Microbalance mass analyzer show that the delivered aerosol has a bimodal size distribution with peaks near 80 and 100 nm. An estimated 40-50% of the aerosol has a size below the limits of detectability by laser (Las-X) counters, i.e. 50 nm. The surfachydrophobic aerosol is unaffected by ambient humidity and unlike hydrophilic silicas is innocuous to health

  13. Preparation and Characterization of Highly Fluorescent, Glutathione-coated Near Infrared Quantum Dots for in Vivo Fluorescence Imaging

    Directory of Open Access Journals (Sweden)

    Yoshichika Yoshioka

    2008-10-01

    Full Text Available Fluorescent probes that emit in the near-infrared (NIR, 700-1,300 nm region are suitable as optical contrast agents for in vivo fluorescence imaging because of low scattering and absorption of the NIR light in tissues. Recently, NIR quantum dots (QDs have become a new class of fluorescent materials that can be used for in vivo imaging. Compared with traditional organic fluorescent dyes, QDs have several unique advantages such as size- and composition-tunable emission, high brightness, narrow emission bands, large Stokes shifts, and high resistance to photobleaching. In this paper, we report a facile method for the preparation of highly fluorescent, water-soluble glutathione (GSH-coated NIR QDs for in vivo imaging. GSH-coated NIR QDs (GSH-QDs were prepared by surface modification of hydrophobic CdSeTe/CdS (core/shell QDs. The hydrophobic surface of the CdSeTe/CdS QDs was exchanged with GSH in tetrahydrofuran-water. The resulting GSH-QDs were monodisperse particles and stable in PBS (phosphate buffered saline, pH = 7.4. The GSH-QDs (800 nm emission were highly fluorescent in aqueous solutions (quantum yield = 22% in PBS buffer, and their hydrodynamic diameter was less than 10 nm, which is comparable to the size of proteins. The cellular uptake and viability for the GSH-QDs were examined using HeLa and HEK 293 cells. When the cells were incubated with aqueous solutions of the GSH-QDs (10 nM, the QDs were taken into the cells and distributed in the perinuclear region of both cells. After 12 hrs incubation of 4 nM of GSH-QDs, the viabilities of HeLa and HEK 293 cells were ca. 80 and 50%, respectively. As a biomedical utility of the GSH-QDs, in vivo NIRfluorescence imaging of a lymph node in a mouse is presented.

  14. Highly Aminated Mesoporous Silica Nanoparticles with Cubic Pore Structure

    KAUST Repository

    Suteewong, Teeraporn

    2011-01-19

    Mesoporous silica with cubic symmetry has attracted interest from researchers for some time. Here, we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, for example, co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously taken up by cells as demonstrated by fluorescence microscopy.

  15. Highly Aminated Mesoporous Silica Nanoparticles with Cubic Pore Structure

    KAUST Repository

    Suteewong, Teeraporn; Sai, Hiroaki; Cohen, Roy; Wang, Suntao; Bradbury, Michelle; Baird, Barbara; Gruner, Sol M.; Wiesner, Ulrich

    2011-01-01

    Mesoporous silica with cubic symmetry has attracted interest from researchers for some time. Here, we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, for example, co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously taken up by cells as demonstrated by fluorescence microscopy.

  16. 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....

  17. Multifunctional Silica Nanoparticles Modified via Silylated-Decaborate Precursors

    Directory of Open Access Journals (Sweden)

    Fatima Abi-Ghaida

    2015-01-01

    Full Text Available A new class of multifunctional silica nanoparticles carrying boron clusters (10-vertex closo-decaborate and incorporating luminescent centers (fluorescein has been developed as potential probes/carriers for potential application in boron neutron capture therapy (BNCT. These silica nanoparticles were charged in situ with silylated-fluorescein fluorophores via the Stöber method and their surface was further functionalized with decaborate-triethoxysilane precursors. The resulting decaborate dye-doped silica nanoparticles were characterized by TEM, solid state NMR, DLS, nitrogen sorption, elemental analysis, and fluorescence spectroscopy.

  18. What Is Crystalline Silica?

    Science.gov (United States)

    ... and ceramic manufacturing and the tool and die, steel and foundry industries. Crystalline silica is used in manufacturing, household abrasives, adhesives, paints, soaps, and glass. Additionally, ...

  19. Preparation and spectroscopic properties of Yb-doped and Yb-Al-codoped high silica glasses

    International Nuclear Information System (INIS)

    Qiao Yanbo; Wen Lei; Wu Botao; Ren Jinjun; Chen Danping; Qiu Jianrong

    2008-01-01

    Yb-doped and Yb-Al-codoped high silica glasses have been prepared by sintering nanoporous glasses. The absorption, fluorescent spectra and fluorescent lifetimes have been measured and the emission cross-section and minimum pump intensities were calculated. Codoping aluminum ions enhanced the fluorescence intensity of Yb-doped high silica glass obviously. The emission cross-sections of Yb-doped and Yb-Al-codoped high silica glasses were 0.65 and 0.82 pm 2 , respectively. The results show that Yb-Al-codoped high silica glass has better spectroscopic properties for a laser material. The study of high silica glass doped with ytterbium is helpful for its application in Yb laser systems, especially for high-power and high-repetition lasers

  20. A low-cost method for visible fluorescence imaging.

    Science.gov (United States)

    Tarver, Crissy L; Pusey, Marc

    2017-12-01

    A wide variety of crystallization solutions are screened to establish conditions that promote the growth of a diffraction-quality crystal. Screening these conditions requires the assessment of many crystallization plates for the presence of crystals. Automated systems for screening and imaging are very expensive. A simple approach to imaging trace fluorescently labeled protein crystals in crystallization plates has been devised, and can be implemented at a cost as low as $50. The proteins β-lactoglobulin B, trypsin and purified concanavalin A (ConA) were trace fluorescently labeled using three different fluorescent probes: Cascade Yellow (CY), Carboxyrhodamine 6G (CR) and Pacific Blue (PB). A crystallization screening plate was set up using β-lactoglobulin B labeled with CR, trypsin labeled with CY, ConA labeled with each probe, and a mixture consisting of 50% PB-labeled ConA and 50% CR-labeled ConA. The wells of these plates were imaged using a commercially available macro-imaging lens attachment for smart devices that have a camera. Several types of macro lens attachments were tested with smartphones and tablets. Images with the highest quality were obtained with an iPhone 6S and an AUKEY Ora 10× macro lens. Depending upon the fluorescent probe employed and its Stokes shift, a light-emitting diode or a laser diode was used for excitation. An emission filter was used for the imaging of protein crystals labeled with CR and crystals with two-color fluorescence. This approach can also be used with microscopy systems commonly used to observe crystallization plates.

  1. 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

  2. Synthesis and fluorescence of new 3-biphenylpyrrolo[1,2-c]pyrimidines

    Directory of Open Access Journals (Sweden)

    Marian-Laurentiu Tatu

    2017-07-01

    Full Text Available New pyrrolo[1,2-c]pyrimidines derivates having a biphenyl moiety at position 3 have been synthesized by 1,3-dipolar cycloaddition of their corresponding N-ylides with activated alkynes. FTIR, 1H and 13C NMR spectroscopy and elemental analysis have been used to characterize the structures of the new nine pyrrolo[1,2-c]pyrimidine derivates. Absorption and fluorescence spectra have been recorded. The appropriate solvent for the photoluminescence properties of the studied compounds has been found to be chloroform:acetonitrile mixture (1:1. The main spectral features such as molar extinction coefficients (ε, Stokes shifts, quantum yields using quinine sulphate as standard, fluorescence quenching in the presence of benzoquinone and Stern-Volmer constants have been calculated. The substituent effects on intensity of absorption, maximum absorbance wavelengths and fluorescence parameters have been discussed. The highest quantum yield value was found for ethyl 3-(4-biphenylyl-7-(3,4-dimethoxybenzoylpyrrolo[1,2-c]pyrimidine-5-carboxylate (0.55. The obtained results suggest that the studied compounds are promising candidates for future study in order to evaluate their use in practical applications in fluorescent chemical sensors.

  3. Analogues of uracil nucleosides with intrinsic fluorescence (NIF-analogues): synthesis and photophysical properties.

    Science.gov (United States)

    Segal, Meirav; Fischer, Bilha

    2012-02-28

    Uridine cannot be utilized as fluorescent probe due to its extremely low quantum yield. For improving the uracil fluorescence characteristics we extended the natural chromophore at the C5 position by coupling substituted aromatic rings directly or via an alkenyl or alkynyl linker to create fluorophores. Extension of the uracil base was achieved by treating 5-I-uridine with the appropriate boronic acid under the Suzuki coupling conditions. Analogues containing an alkynyl linker were obtained from 5-I-uridine and the suitable boronic acid in a Sonogashira coupling reaction. The uracil fluorescent analogues proposed here were designed to satisfy the following requirements: a minimal chemical modification at a position not involved in base-pairing, resulting in relatively long absorption and emission wavelengths and high quantum yield. 5-((4-Methoxy-phenyl)-trans-vinyl)-2'-deoxy-uridine, 6b, was found to be a promising fluorescent probe. Probe 6b exhibits a quantum yield that is 3000-fold larger than that of the natural chromophore (Φ 0.12), maximum emission (478 nm) which is 170 nm red shifted as compared to uridine, and a Stokes shift of 143 nm. In addition, since probe 6b adopts the anti conformation and S sugar puckering favored by B-DNA, it makes a promising nucleoside analogue to be incorporated in an oligonucleotide probe for detection of genetic material.

  4. Improved Immunoassay Sensitivity in Serum as a Result of Polymer-Entrapped Quantum Dots: 'Papaya Particles'

    NARCIS (Netherlands)

    Ranzoni, A.; den Hamer, A.; Karoli, T.; Buechler, J.; Cooper, M.A.

    2015-01-01

    Fluorescent labels are widely employed in biomarker quantification and diagnostics, however they possess narrow Stokes shifts and can photobleach, limiting multiplexed detection applications and compromising sensitivity. In contrast, quantum dots do not photobleach and have much wider Stokes shifts,

  5. Oxygen configurations in silica

    International Nuclear Information System (INIS)

    Chelikowsky, James R.; Chadi, D. J.; Binggeli, N.

    2000-01-01

    We propose a transition state for oxygen in silica. This state is produced by the insertion of an oxygen molecule into the Si-O-Si bond, i.e., it consists of producing a Si-O-O-O-Si bond. This state allows molecular oxygen diffusion in silica without breaking the molecular O 2 bond and it is energetically more stable than a peroxy configuration. This configuration may allow for exchange of molecular oxygen with the oxygen in the silica framework. (c) 2000 The American Physical Society

  6. Silica coatings on clarithromycin.

    Science.gov (United States)

    Bele, Marjan; Dmitrasinovic, Dorde; Planinsek, Odon; Salobir, Mateja; Srcic, Stane; Gaberscek, Miran; Jamnik, Janko

    2005-03-03

    Pre-crystallized clarithromycin (6-O-methylerythromycin A) particles were coated with silica from the tetraethyl orthosilicate (TEOS)-ethanol-aqueous ammonia system. The coatings had a typical thickness of 100-150 nm and presented about 15 wt.% of the silica-drug composite material. The properties of the coatings depended on reactant concentration, temperature and mixing rate and, in particular, on the presence of a cationic surfactant (cetylpyridinium chloride). In the presence of cetylpyridinium chloride the silica coatings slightly decreased the rate of pure clarithromycin dissolution.

  7. Silica aerogel Cerenkov counter

    International Nuclear Information System (INIS)

    Yasumi, S.; Masaike, A.; Yamamoto, A.; Yoshimura, Y.; Kawai, H.

    1984-03-01

    In order to obtain silica aerogel radiators of good quality, the prescription used by Saclay group has been developed. We have done several experiments using beams from KEK.PS to test the performance of a Cerenkov counter with aerogel modules produced in KEK. It turned out that these modules had excellent quality. The production rate of silica aerogel in KEK is 15 -- 20 litres a week. Silica aerogel modules of 20 x 10 x 3 cm 3 having the refractive index of 1.058 are successfully being used by Kyoto University group in the KEK experiment E92 (Σ). Methodes to produce silica aerogel with higher refractive index than 1.06 has been investigated both by heating an module with the refractive index of 1.06 and by hydrolyzing tetraethyl silicate. (author)

  8. Fluorescence spectra of benign and malignant prostate tissues

    International Nuclear Information System (INIS)

    AlSalhi, M S; Masilamani, V; Atif, M; Farhat, K; Rabah, D; Al Turki, M R

    2012-01-01

    In this study, fluorescence emission spectrum (FES), Stokes' shift spectrum (SSS), and reflectance spectrum (RS) of benign (N = 12) and malignant prostate tissues (N = 8) were investigated to discriminate the two types of tissues. The FES was done with the excitation at 325 nm only; SSS with Δλ = 70 and Δλ = 0, the latter being equivalent to reflectance spectra. Of the three modes of spectra, SSS with Δλ = 70 nm showed the best discrimination. There were four important bands, one at 280 nm (due to tryptophan); 320 nm (due to elastin and tryptophan); 355 and 385 (due to NADH) and 440 nm (due to flavin). From the relative intensities of these bands, three ratios were evaluated. Similarly another two ratios were obtained from reflectance spectra and one more from FES. Thus, there are 6 ratio parameters which represent the relative concentration of tryptophan, elastin, nicotinamide adenine dinucleotide (NADH), and flavin. A statistical analysis showed that benign and malignant tissues could be classified with accuracy greater than 90%. This report is only for in vitro analysis; but employing optical fiber, this can be extended to in vivo analysis too, so that benign tumor could be distinguished without surgery

  9. 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.

  10. Fluorescent nanoparticles for intracellular sensing: A review

    International Nuclear Information System (INIS)

    Ruedas-Rama, Maria J.; Walters, Jamie D.; Orte, Angel; Hall, Elizabeth A.H.

    2012-01-01

    Highlights: ► Analytical applications of fluorescent nanoparticles (NPs) in intracellular sensing. ► Critical review on performance of QDots, metal NPs, silica NPs, and polymer NPs. ► Highlighted potential of fluorescence lifetime imaging microscopy (FLIM). - Abstract: Fluorescent nanoparticles (NPs), including semiconductor NPs (Quantum Dots), metal NPs, silica NPs, polymer NPs, etc., have been a major focus of research and development during the past decade. The fluorescent nanoparticles show unique chemical and optical properties, such as brighter fluorescence, higher photostability and higher biocompatibility, compared to classical fluorescent organic dyes. Moreover, the nanoparticles can also act as multivalent scaffolds for the realization of supramolecular assemblies, since their high surface to volume ratio allow distinct spatial domains to be functionalized, which can provide a versatile synthetic platform for the implementation of different sensing schemes. Their excellent properties make them one of the most useful tools that chemistry has supplied to biomedical research, enabling the intracellular monitoring of many different species for medical and biological purposes. In this review, we focus on the developments and analytical applications of fluorescent nanoparticles in chemical and biological sensing within the intracellular environment. The review also points out the great potential of fluorescent NPs for fluorescence lifetime imaging microscopy (FLIM). Finally, we also give an overview of the current methods for delivering of fluorescent NPs into cells, where critically examine the benefits and liabilities of each strategy.

  11. Fluorescent nanoparticles for intracellular sensing: A review

    Energy Technology Data Exchange (ETDEWEB)

    Ruedas-Rama, Maria J., E-mail: mjruedas@ugr.esmailto [Department of Physical Chemistry, Faculty of Pharmacy, University of Granada, Campus Cartuja, 18071, Granada (Spain); Walters, Jamie D. [Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge, UK CB2 1QT (United Kingdom); Orte, Angel [Department of Physical Chemistry, Faculty of Pharmacy, University of Granada, Campus Cartuja, 18071, Granada (Spain); Hall, Elizabeth A.H., E-mail: lisa.hall@biotech.cam.ac.uk [Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QT (United Kingdom)

    2012-11-02

    Highlights: Black-Right-Pointing-Pointer Analytical applications of fluorescent nanoparticles (NPs) in intracellular sensing. Black-Right-Pointing-Pointer Critical review on performance of QDots, metal NPs, silica NPs, and polymer NPs. Black-Right-Pointing-Pointer Highlighted potential of fluorescence lifetime imaging microscopy (FLIM). - Abstract: Fluorescent nanoparticles (NPs), including semiconductor NPs (Quantum Dots), metal NPs, silica NPs, polymer NPs, etc., have been a major focus of research and development during the past decade. The fluorescent nanoparticles show unique chemical and optical properties, such as brighter fluorescence, higher photostability and higher biocompatibility, compared to classical fluorescent organic dyes. Moreover, the nanoparticles can also act as multivalent scaffolds for the realization of supramolecular assemblies, since their high surface to volume ratio allow distinct spatial domains to be functionalized, which can provide a versatile synthetic platform for the implementation of different sensing schemes. Their excellent properties make them one of the most useful tools that chemistry has supplied to biomedical research, enabling the intracellular monitoring of many different species for medical and biological purposes. In this review, we focus on the developments and analytical applications of fluorescent nanoparticles in chemical and biological sensing within the intracellular environment. The review also points out the great potential of fluorescent NPs for fluorescence lifetime imaging microscopy (FLIM). Finally, we also give an overview of the current methods for delivering of fluorescent NPs into cells, where critically examine the benefits and liabilities of each strategy.

  12. Preparation and characterization of rice hull silica products

    International Nuclear Information System (INIS)

    Quirit, Leni L.; Llaguno, Elma C.; Pagdanganan, Fernando C.; Hernandez, Karen N.

    2008-01-01

    Rice hull is an abundant agricultural waste material which could be a renewable energy source when combusted. The combustion residue (called rice hull ash or RHA) contains a significant amount (20% of the hull) of potentially high grade silica. Silica gels prepared from rice hull were found to have properties comparable to two commercial desiccant silica gels (Blue Merck and FNG-A) in terms of chemical and amorphous structure, surface area, desiccant characteristics, microstructure and heats of adsorption. These properties were determined from water vapor adsorption measurements, electron microscopy, and from infrared and x-ray diffraction spectra. The acid treated rice hull gels were found to have fewer elemental impurities detected by qualitative x-ray fluorescence, compared to the commercial gels. Thermogravimetric analysis (TGA) data showed that this technique can also be used to indirectly compare impurity levels in the samples, in terms of the amorphous to crystalline phase transition. Using an improved acid treatment method, a silica gel sample was prepared from rice hull and compared to three commercial chromatographic silica gels using quantitative elemental x-ray fluorescence analysis. Elemental levels in the rice hull gel were within the range of levels or close to the detection limits of corresponding elements in the chromatographic gels. Water vapor adsorption, x-ray diffraction, infrared spectroscopy and scanning electron microscopy showed that the rice hull gel was similar to the commercial chromatographic silica gel Davison 12. Zeolites are crystalline aluminosilicates used as molecular sieves for purification and catalytic purposes. Zeolites X and Y were synthesized from rice hull silica gel and aluminum hydroxide. For comparison, controls were synthesized from commercial silica gel. The samples and controls exhibited characteristics infrared peaks corresponding to the vibrations of the TO 4 (T=Si, Al) of the zeolite framework. The x

  13. An excited-state intramolecular photon transfer fluorescence probe for localizable live cell imaging of cysteine

    Science.gov (United States)

    Liu, Wei; Chen, Wen; Liu, Si-Jia; Jiang, Jian-Hui

    2017-03-01

    Small molecule probes suitable for selective and specific fluorescence imaging of some important but low-concentration intracellular reactive sulfur species such as cysteine (Cys) pose a challenge in chemical biology. We present a readily available, fast-response fluorescence probe CHCQ-Ac, with 2-(5‧-chloro-2-hydroxyl-phenyl)-6-chloro-4(3 H)-quinazolinone (CHCQ) as the fluorophore and acrylate group as the functional moiety, that enables high-selectivity and high-sensitivity for detecting Cys in both solution and biological system. After specifically reacted with Cys, the probe undergoes a seven-membered intramolecular cyclization and released the fluorophore CHCQ with excited-state intramolecular photon transfer effect. A highly fluorescent, insoluble aggregate was then formed to facilitate high-sensitivity and high-resolution imaging. The results showed that probe CHCQ-Ac affords a remarkably large Stokes shift and can detect Cys under physiological pH condition with no interference from other analytes. Moreover, this probe was proved to have excellent chemical stability, low cytotoxicity and good cell permeability. Our design of this probe provides a novel potential tool to visualize and localize cysteine in bioimaging of live cells that would greatly help to explore various Cys-related physiological and pathological cellular processes in cell biology and diagnostics.

  14. Laser-induced fluorescence of se, as, and sb in an electrothermal atomizer.

    Science.gov (United States)

    Swart, D J; Ezer, M; Pacquette, H L; Simeonsson, J B

    1998-04-01

    Trace detection of Se, As, and Sb atoms has been performed by electrothermal atomization laser-induced fluorescence (ETA-LIF) approaches. Production of far-UV radiation necessary for excitation of As atoms at 193.696 nm and Se atoms at 196.026 nm was accomplished by stimulated Raman shifting (SRS) of the output of a frequency-doubled dye laser operating near 230 nm. Both wavelengths were obtained as second-order anti-Stokes shifts of the dye laser radiation and provided up to 10 μJ/pulse, which was shown through power dependence studies to be sufficient for saturation in the ETA. An excited-state direct line fluorescence approach using excitation at 206.279 nm was also investigated for the LIF detection of Se. High-sensitivity LIF of Sb atoms was accomplished using 206.833-nm excitation and detection at 259.805 nm. The accuracy of the ETA-LIF approaches was demonstrated by determining the As and Se content of aqueous reference samples. The limits of detection (absolute mass) were 200 fg by ground-state LIF and 150 fg by excited-state direct line fluorescence for Se, 200 fg for As, and 10 fg for Sb; these LODs compare favorably with results reported previously in the literature for ETA-LIF, GFAAS, and ICP-MS methods.

  15. The spectral properties of (--epigallocatechin 3-O-gallate (EGCG fluorescence in different solvents: dependence on solvent polarity.

    Directory of Open Access Journals (Sweden)

    Vladislav Snitsarev

    Full Text Available (--Epigallocatechin 3-O-gallate (EGCG a molecule found in green tea and known for a plethora of bioactive properties is an inhibitor of heat shock protein 90 (HSP90, a protein of interest as a target for cancer and neuroprotection. Determination of the spectral properties of EGCG fluorescence in environments similar to those of binding sites found in proteins provides an important tool to directly study protein-EGCG interactions. The goal of this study is to examine the spectral properties of EGCG fluorescence in an aqueous buffer (AB at pH=7.0, acetonitrile (AN (a polar aprotic solvent, dimethylsulfoxide (DMSO (a polar aprotic solvent, and ethanol (EtOH (a polar protic solvent. We demonstrate that EGCG is a highly fluorescent molecule when excited at approximately 275 nm with emission maxima between 350 and 400 nm depending on solvent. Another smaller excitation peak was found when EGCG is excited at approximately 235 nm with maximum emission between 340 and 400 nm. We found that the fluorescence intensity (FI of EGCG in AB at pH=7.0 is significantly quenched, and that it is about 85 times higher in an aprotic solvent DMSO. The Stokes shifts of EGCG fluorescence were determined by solvent polarity. In addition, while the emission maxima of EGCG fluorescence in AB, DMSO, and EtOH follow the Lippert-Mataga equation, its fluorescence in AN points to non-specific solvent effects on EGCG fluorescence. We conclude that significant solvent-dependent changes in both fluorescence intensity and fluorescence emission shifts can be effectively used to distinguish EGCG in aqueous solutions from EGCG in environments of different polarity, and, thus, can be used to study specific EGCG binding to protein binding sites where the environment is often different from aqueous in terms of polarity.

  16. 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.

  17. Acid-base equilibria inside amine-functionalized mesoporous silica.

    Science.gov (United States)

    Yamaguchi, Akira; Namekawa, Manato; Kamijo, Toshio; Itoh, Tetsuji; Teramae, Norio

    2011-04-15

    Acid-base equilibria and effective proton concentration inside a silica mesopore modified with a trimethyl ammonium (TMAP) layer were studied by steady-state fluorescence experiments. The mesoporous silica with a dense TMAP layer (1.4 molecules/nm(2)) was prepared by a post grafting of N-trimethoxysilylpropyl-N,N,N-trimethylammonium at surfactant-templated mesoporous silica (diameter of silica framework =3.1 nm). The resulting TMAP-modified mesoporous silica strongly adsorbed of anionic fluorescence indicator dyes (8-hydroxypyrene-1,3,6-trisulfonate (pyranine), 8-aminopyrene-1,3,6-trisulfonate (APTS), 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid disulfuric acid (TPPS), 2-naphthol-3,6-disulfonate (2NT)) and fluorescence excitation spectra of these dyes within TMAP-modified mesoporous silica were measured by varying the solution pH. The fluorescence experiments revealed that the acid-base equilibrium reactions of all pH indicator dyes within the TMAP-modified silica mesopore were quite different from those in bulk water. From the analysis of the acid-base equilibrium of pyranine, the following relationships between solution pH (pH(bulk)) and the effective proton concentration inside the pore (pH(pore)) were obtained: (1) shift of pH(pore) was 1.8 (ΔpH(pore)=1.8) for the pH(bulk) change from 2.1 to 9.1 (ΔpH(bulk)=7.0); (2) pH(pore) was not simply proportional to pH(bulk); (3) the inside of the TMAP-modified silica mesopore was suggested to be in a weak acidic or neutral condition when pH(bulk) was changed from 2.0 to 9.1. Since these relationships between pH(bulk) and pH(pore) could explain the acid-base equilibria of other pH indicator dyes (APTS, TPPS, 2NT), these relationships were inferred to describe the effective proton concentration inside the TMAP-modified silica mesopore. © 2011 American Chemical Society

  18. Development of UV-curable liquid for in-liquid fluorescence alignment in ultraviolet nanoimprint lithography

    Science.gov (United States)

    Ochiai, Kento; Kikuchi, Eri; Ishito, Yota; Kumagai, Mari; Nakamura, Takahiro; Nakagawa, Masaru

    2018-06-01

    We studied a fluorescent UV-curable resin suitable for fluorescence alignment in UV nanoimprinting. The addition of a cationic fluorescent dye caused radical photopolymerization of a UV-curable resin by exposure to visible excitation light for fluorescence microscope observation. The microscope observation of a resin film prepared by pressing resin droplets on a silica substrate with a fluorinated silica superstrate revealed that the cationic dye molecules were preferably adsorbed onto the silica surface. It was indicated that the dye molecules concentrated on the silica surface may cause the photocuring. A nonionic fluorescent dye was selected owing to its low polar symmetrical structure and its solubility parameter close to monomers. The fluorescent UV-curable resin with the nonionic dye showed uncured stability to exposure to visible excitation light for 30 min with a light intensity of 8.5 mW cm‑2 detected at 530 nm.

  19. Fluorescent sensors based on bacterial fusion proteins

    International Nuclear Information System (INIS)

    Mateu, Batirtze Prats; Pum, Dietmar; Sleytr, Uwe B; Toca-Herrera, José L; Kainz, Birgit

    2014-01-01

    Fluorescence proteins are widely used as markers for biomedical and technological purposes. Therefore, the aim of this project was to create a fluorescent sensor, based in the green and cyan fluorescent protein, using bacterial S-layers proteins as scaffold for the fluorescent tag. We report the cloning, expression and purification of three S-layer fluorescent proteins: SgsE-EGFP, SgsE-ECFP and SgsE-13aa-ECFP, this last containing a 13-amino acid rigid linker. The pH dependence of the fluorescence intensity of the S-layer fusion proteins, monitored by fluorescence spectroscopy, showed that the ECFP tag was more stable than EGFP. Furthermore, the fluorescent fusion proteins were reassembled on silica particles modified with cationic and anionic polyelectrolytes. Zeta potential measurements confirmed the particle coatings and indicated their colloidal stability. Flow cytometry and fluorescence microscopy showed that the fluorescence of the fusion proteins was pH dependent and sensitive to the underlying polyelectrolyte coating. This might suggest that the fluorescent tag is not completely exposed to the bulk media as an independent moiety. Finally, it was found out that viscosity enhanced the fluorescence intensity of the three fluorescent S-layer proteins. (paper)

  20. In vivo near-infrared fluorescence imaging of amyloid-β plaques with a dicyanoisophorone-based probe

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Jia-ying; Zhou, Lin-fu; Li, Yu-kun [School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, 510006 (China); Chen, Shuo-bin [School of Pharmaceutical Science, Sun Yat-sen University, Guangzhou, 510006 (China); Yan, Jin-wu, E-mail: yjw@scut.edu.cn [School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, 510006 (China); Zhang, Lei, E-mail: lzhangce@scut.edu.cn [School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, 510006 (China)

    2017-04-08

    A dicyanoisophorone-based probe with two-photon absorption and NIR emission was developed for the in vivo fluorescence imaging of amyloid-β plaques, which exhibited high selectivity toward Aβ aggregates over other intracellular proteins. The detection limit was calculated to be as low as 109 nM. In vivo imaging studies indicated that the probe could penetrate the blood–brain barrier and label Aβ plaques in the living transgenic mice, and its specific binding to cerebral Aβ plaques was further confirmed by one- and two-photon ex vivo fluorescence imaging. All these results featured its promising application prospects for amyloid-β sensing in basic research and biomedical research. - Highlights: • A two-photon probe (DCIP-1) with NIR emission based on dicyanoisophorone group, for the in vivo fluorescence imaging of amyloid-β plaques, was reported. • The probe showed turn-on fluorescence (13-fold) with a large Stokes shift upon inserting into the hydrophobic pockets of Aβ aggregates. • The in vivo imaging studies indicated that the probe can penetrate the blood–brain barrier efficiently and discriminate APP/PS1 transgenic mice from WT controls.

  1. In vivo near-infrared fluorescence imaging of amyloid-β plaques with a dicyanoisophorone-based probe

    International Nuclear Information System (INIS)

    Zhu, Jia-ying; Zhou, Lin-fu; Li, Yu-kun; Chen, Shuo-bin; Yan, Jin-wu; Zhang, Lei

    2017-01-01

    A dicyanoisophorone-based probe with two-photon absorption and NIR emission was developed for the in vivo fluorescence imaging of amyloid-β plaques, which exhibited high selectivity toward Aβ aggregates over other intracellular proteins. The detection limit was calculated to be as low as 109 nM. In vivo imaging studies indicated that the probe could penetrate the blood–brain barrier and label Aβ plaques in the living transgenic mice, and its specific binding to cerebral Aβ plaques was further confirmed by one- and two-photon ex vivo fluorescence imaging. All these results featured its promising application prospects for amyloid-β sensing in basic research and biomedical research. - Highlights: • A two-photon probe (DCIP-1) with NIR emission based on dicyanoisophorone group, for the in vivo fluorescence imaging of amyloid-β plaques, was reported. • The probe showed turn-on fluorescence (13-fold) with a large Stokes shift upon inserting into the hydrophobic pockets of Aβ aggregates. • The in vivo imaging studies indicated that the probe can penetrate the blood–brain barrier efficiently and discriminate APP/PS1 transgenic mice from WT controls.

  2. Benzothiadiazole Derivatives as Fluorescence Imaging Probes: Beyond Classical Scaffolds.

    Science.gov (United States)

    Neto, Brenno A D; Carvalho, Pedro H P R; Correa, Jose R

    2015-06-16

    This Account describes the origins, features, importance, and trends of the use of fluorescent small-molecule 2,1,3-benzothiadiazole (BTD) derivatives as a new class of bioprobes applied to bioimaging analyses of several (live and fixed) cell types. BTDs have been successfully used as probes for a plethora of biological analyses for only a few years, and the impressive responses obtained by using this important class of heterocycle are fostering the development of new fluorescent BTDs and expanding the biological applications of such derivatives. The first use of a fluorescent small-molecule BTD derivative as a selective cellular probe dates back to 2010, and since then impressive advances have been described by us and others. The well-known limitations of classical scaffolds urged the development of new classes of bioprobes. Although great developments have been achieved by using classical scaffolds such as coumarins, BODIPYs, fluoresceins, rhodamines, cyanines, and phenoxazines, there is still much to be done, and BTDs aim to succeed where these dyes have shown their limitations. Important organelles and cell components such as nuclear DNA, mitochondria, lipid droplets, and others have already been successfully labeled by fluorescent small-molecule BTD derivatives. New technological systems that use BTDs as the fluorophores for bioimaging experiments have been described in recent scientific literature. The successful application of BTDs as selective bioprobes has led some groups to explore their potential for use in studying membrane pores or tumor cells under hypoxic conditions. Finally, BTDs have also been used as fluorescent tags to investigate the action mechanism of some antitumor compounds. The attractive photophysical data typically observed for π-extended BTD derivatives is fostering interest in the use of this new class of bioprobes. Large Stokes shifts, large molar extinction coefficients, high quantum yields, high stability when stored in solution or

  3. 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

  4. Silica reinforced triblock copolymer gels

    DEFF Research Database (Denmark)

    Theunissen, E.; Overbergh, N.; Reynaers, H.

    2004-01-01

    The effect of silica and polymer coated silica particles as reinforcing agents on the structural and mechanical properties of polystyrene-poly(ethylene/butylene)-polystyrene (PS-PEB-PS) triblock gel has been investigated. Different types of chemically modified silica have been compared in order...

  5. Non-destructive evaluation of UV pulse laser-induced damage performance of fused silica optics.

    Science.gov (United States)

    Huang, Jin; Wang, Fengrui; Liu, Hongjie; Geng, Feng; Jiang, Xiaodong; Sun, Laixi; Ye, Xin; Li, Qingzhi; Wu, Weidong; Zheng, Wanguo; Sun, Dunlu

    2017-11-24

    The surface laser damage performance of fused silica optics is related to the distribution of surface defects. In this study, we used chemical etching assisted by ultrasound and magnetorheological finishing to modify defect distribution in a fused silica surface, resulting in fused silica samples with different laser damage performance. Non-destructive test methods such as UV laser-induced fluorescence imaging and photo-thermal deflection were used to characterize the surface defects that contribute to the absorption of UV laser radiation. Our results indicate that the two methods can quantitatively distinguish differences in the distribution of absorptive defects in fused silica samples subjected to different post-processing steps. The percentage of fluorescence defects and the weak absorption coefficient were strongly related to the damage threshold and damage density of fused silica optics, as confirmed by the correlation curves built from statistical analysis of experimental data. The results show that non-destructive evaluation methods such as laser-induced fluorescence and photo-thermal absorption can be effectively applied to estimate the damage performance of fused silica optics at 351 nm pulse laser radiation. This indirect evaluation method is effective for laser damage performance assessment of fused silica optics prior to utilization.

  6. Fluorescence spectroscopy

    DEFF Research Database (Denmark)

    Bagatolli, Luis

    2016-01-01

    Fluorescence spectroscopy is a powerful experimental tool used by scientists from many disciplines. During the last decades there have been important developments on distinct fluorescence methods, particularly those related to the study of biological phenomena. This chapter discusses the foundati......Fluorescence spectroscopy is a powerful experimental tool used by scientists from many disciplines. During the last decades there have been important developments on distinct fluorescence methods, particularly those related to the study of biological phenomena. This chapter discusses...

  7. Silica from Ash

    Indian Academy of Sciences (India)

    management, polymer composites and chemical process design. Figure 1 Difference in color of the ash ... The selection of ash is important as the quality of ash determines the total amount as well as quality of silica recoverable Ash which has undergone maximum extent of combustion is highly desirable as it contains ...

  8. 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

  9. Synthesis of a novel fluorescent Schiff base as a possible Cu(II) ion selective sensor.

    Science.gov (United States)

    Yildirim, Mehmet; Kaya, Ismet

    2010-05-01

    In this study a new fluorescent Schiff base; 1,1'-(4,4'-oxybis(4,1-phenylene)bis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol (2-HNA) was synthesized and characterized by FT-IR, UV-vis, and (1)H and (13)C-NMR techniques. Photoluminescent properties of 2-HNA were investigated in different solvents including methanol, THF, DMF, DMSO, acetone, acetonitrile, and dichloromethane. 2-HNA was found to have higher emission intensity and Stoke's shift value (lambda(ST)) in methanol solution. Relative emission intensity changes (I(0)-I/I(0)) of 2-HNA in methanol/water mixtures depending on different Cu(+2) ion concentrations were determined and a linearized plot was obtained. Possible interference of some other transition metal ions was also determined. Sensitivity limit of the new sensor was found to be higher than 5 x 10(-7) mol/L. 2-HNA has quite high selectivity against Cu(+2) ion and, thus, can be used as a new fluorescence Cu(+2) ion sensor in practice.

  10. Calibrating the photo-thermal response of magneto-fluorescent gold nanoshells.

    Science.gov (United States)

    Biswal, Nrusingh C; Ayala-Orzoco, Ciceron; Halas, Naomi J; Joshi, Amit

    2011-01-01

    We report the photothermal response and Near Infrared (NIR) imaging sensitivities of magneto-fluorescent silica core gold nanocomplexes designed for molecular image guided thermal therapy of cancer. Approximately 160 nm Silica core gold nanoshells were designed to provide NIR fluorescent and Magnetic Resonance (MR) contrast by incorporating FDA approved dye indocyanine green (ICG) and iron-oxide within an outer silica epilayer. The imaging and therapeutic sensitivity, and the stability of fluorescence contrast for 12 microliters of suspension (containing approximately 7.9 × 10(8) or 1.3 femtoMole nanoshells) buried at depths of 2-8 mm in tissue mimicking scattering media is reported.

  11. Ratiometric fluorescent nanoparticles for sensing temperature

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Hong-Shang, E-mail: hillphs@yahoo.com.cn; Huang, Shi-Hua [Beijing Jiaotong University, Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology (China); Wolfbeis, Otto S. [University of Regensburg, Institute of Analytical Chemistry, Chemo- and Biosensors (Germany)

    2010-10-15

    A ratiometric type of fluorescent nanoparticle was prepared via an encapsulation-reprecipitation method. By introducing an alkoxysilanized dye as a reference, the nanoparticles (NPs) give both a green and a red fluorescence under one single-wavelength excitation. The resulted ratiometric fluorescence is found to be highly temperature-dependent in the physiological range (25-45 {sup o}C), with an intensity temperature sensitivity of -4.0%/{sup o}C. Given the small size (20-30 nm in diameter) and biocompatible nature (silica out layer), such kind of NPs were very promising as temperature nanosensors for cellular sensing and imaging.

  12. Uranyl adsorption kinetics within silica gel: dependence on flow velocity and concentration

    Science.gov (United States)

    Dodd, Brandon M.; Tepper, Gary

    2017-09-01

    Trace quantities of a uranyl dissolved in water were measured using a simple optical method. A dilute solution of uranium nitrate dissolved in water was forced through nanoporous silica gel at fixed and controlled water flow rates. The uranyl ions deposited and accumulated within the silica gel and the uranyl fluorescence within the silica gel was monitored as a function of time using a light emitting diode as the excitation source and a photomultiplier tube detector. It was shown that the response time of the fluorescence output signal at a particular volumetric flow rate or average liquid velocity through the silica gel can be used to quantify the concentration of uranium in water. The response time as a function of concentration decreased with increasing flow velocity.

  13. Controlling the synthesis conditions for silica nanosphere from semi-burned rice straw

    International Nuclear Information System (INIS)

    Hessien, M.M.; Rashad, M.M.; Zaky, R.R.; Abdel-Aal, E.A.; El-Barawy, K.A.

    2009-01-01

    Silica nanoparticles have been prepared through dissolution-precipitation process from rice straw ash (RSA) for different electronic applications. The dissolution of silica from RSA was carried out using alkali leaching process by sodium hydroxide. The precipitation of silica from the produced sodium silicate solution was carried out using sulphuric acid at pH 7. The factors affecting the precipitation process of the sodium silicate solution of dissociated RSA; such as; sodium silicate concentration, sulfuric acid concentration and addition of anionic surfactant (sodium dodecyl sulfate, SDS) on the particle size of the precipitated silica were studied. X-ray diffraction (XRD), X-ray fluorescence (XRF), specific surface area S BET and transmission electron microscope (TEM) have been used for the characterization of the produced nano-silica. The results showed that the optimum conditions of the dissolution efficiency of the silica of about 99% was achieved at 100 deg. C for 4 h, and NaOH/SiO 2 molar ratio three. The particle size of the precipitated silica gel was decreased with increasing Na 2 SiO 3 and SDS concentrations, while H 2 SO 4 concentration had insignificant effect. Particle size of about 16 nm can be achieved at 30% Na 2 SiO 3 , 4% H 2 SO 4 and 200 ppm SDS. The produced silica had 99.93% purity, amorphous and nanosphere particles with narrow size distribution. The produced silica can be used in many applications especially for chemical mechanical polishing (CMP) slurries for semiconductors industries.

  14. Dye-Doped Silica Nanoparticle Labels/Protein Microarray for Detection of Protein Biomarkers

    OpenAIRE

    Wu, Hong; Huo, Qisheng; Varnum, Susan; Wang, Jun; Liu, Guodong; Nie, Zimin; Liu, Jun; Lin, Yuehe

    2008-01-01

    We report a dye-encapsulated silica nanoparticle as a label, with the advantages of high fluorescence intensity, photostability, and biocompatibility, in conjunction with microarray technology for sensitive immunoassay of a biomarker, Interleukin-6 (IL-6), on a microarray format. The tris (2,2’-bipyridyl)ruthenium (II)chloride hexahydrate (Rubpy) dye was incorporated into silica nanoparticles using a simple one-step microemulsion synthesis. In this synthesis process, Igepal CA520 was used as ...

  15. Influence of Polyvinyl Alcohol (PVA) Addition on Silica Membrane Performance Prepared from Rice Straw

    Science.gov (United States)

    Wahyuningsih, S.; Ramelan, A. H.; Wardoyo, D. T.; Ichsan, S.; Kristiawan, Y. R.

    2018-03-01

    The utilization and modification of silica from rice straw as the main ingredient of adsorbent has been studied. The aim of this study was to determine the optimum composition of PVA (polyvinyl alcohol): silica to produce adsorbents with excellent pore characteristics, optimum adsorption efficiency and optimum pH for methyl yellow adsorptions. X-Ray Fluorescence (XRF) analysis results showed that straw ash contains 82.12 % of silica (SiO2). SAA (Surface Area Analyzer) analysis showed optimum composition ratio 5:5 of PVA: silica with surface area of 1.503 m2/g. Besides, based on the pore size distribution of PVA: silica (5:5) showed the narrow pore size distribution with the largest pore cumulative volume of 2.8 x 10-3 cc/g. The optimum pH for Methanyl Yellow adsorption is pH 2 with adsorption capacity = 72.1346%.

  16. 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.

  17. Silica particles and method of preparation thereof

    NARCIS (Netherlands)

    2015-01-01

    The invention is in the field of silica products. More in particular, the invention is in the field of amorphous silica particles. The invention is directed to amorphous silica particles and related products including clusters of said silica particles, a suspension of said silica particles, and an

  18. Optical properties of silica-coated Y2O3:Er,Yb nanoparticles in the presence of polyvinylpyrrolidone

    International Nuclear Information System (INIS)

    Fujii, Kunio; Kitamoto, Yoshitaka; Hara, Masahiko; Odawara, Osamu; Wada, Hiroyuki

    2014-01-01

    The optical properties of polyvinylpyrrolidone (PVP)-adsorbed and silica-coated Y 2 O 3 :Er,Yb nanoparticles produced by using PVP were studied for potential bio-applications of upconversion nanoparticles. We utilized PVP to better disperse Y 2 O 3 :Er,Yb nanoparticles in solution and to prepare silica-coated Y 2 O 3 :Er,Yb nanoparticles. The fluorescent intensity of PVP-adsorbed Y 2 O 3 :Er,Yb nanoparticles was 1.25 times higher than non-adsorbed Y 2 O 3 :Er,Yb nanoparticles, which was probably due to surface defects in Y 2 O 3 :Er,Yb nanoparticles being covered by the PVP. However, the fluorescent intensity of silica-coated Y 2 O 3 :Er,Yb nanoparticles decreased as silica layer thickness increased. This could be ascribed to the higher vibrational energy of PVP than that of the silica structure. Therefore, the optimum silica layer thickness is important in bio-applications to avoid deterioration of the optical properties of Y 2 O 3 :Er,Yb nanoparticles. - Highlights: • We prepared the silica-coated upconversion nanoparticles by using PVP. • We showed that PVP played an important role in coating nanoparticles. • PL intensity of silica-coated nanoparticles decreased as silica layer thickness increased

  19. Fiber optical assembly for fluorescence spectrometry

    Science.gov (United States)

    Carpenter, II, Robert W.; Rubenstein, Richard; Piltch, Martin; Gray, Perry

    2010-12-07

    A system for analyzing a sample for the presence of an analyte in a sample. The system includes a sample holder for containing the sample; an excitation source, such as a laser, and at least one linear array radially disposed about the sample holder. Radiation from the excitation source is directed to the sample, and the radiation induces fluorescent light in the sample. Each linear array includes a plurality of fused silica optical fibers that receive the fluorescent light and transmits a fluorescent light signal from the first end to an optical end port of the linear array. An end port assembly having a photo-detector is optically coupled to the optical end port. The photo-detector detects the fluorescent light signal and converts the fluorescent light signal into an electrical signal.

  20. Synthesis, characterisation and functionalisation of luminescent silica nanoparticles

    International Nuclear Information System (INIS)

    Labéguerie-Egéa, Jessica; McEvoy, Helen M.; McDonagh, Colette

    2011-01-01

    The synthesis of highly monodispersed, homogeneous and stable luminescent silica nanoparticles, synthesized using a process based on the Stöber method is reported here. These particles have been functionalised with the ruthenium and europium complexes: bis (2,2′-bipyridine)-(5-aminophenanthroline) Ru bis (hexafluorophosphate), abbreviated to (Ru(bpy) 2 (phen-5-NH 2 )(PF 6 )), and tris (dibenzoylmethane)-mono (5-aminophenanthroline) europium(III), abbreviated to (Eu:TDMAP). Both dyes have a free amino group available, facilitating the covalent conjugation of the dyes inside the silica matrix. Due to the covalent bond between the dyes and the silica, no dye leaching or nanoparticle diameter modification was observed. The generic and versatile nature of the synthesis process was demonstrated via the synthesis of both europium and ruthenium-functionalised nanoparticles. Following this, the main emphasis of the study was the characterisation of the luminescence of the ruthenium-functionalised silica nanoparticles, in particular, as a function of surface carboxyl or amino group functionalisation. It was demonstrated that the luminescence of the ruthenium dye is highly affected by the ionic environment at the surface of the nanoparticle, and that these effects can be counteracted by encapsulating the ruthenium-functionalised nanoparticles in a plain 15 nm silica layer. Moreover, the ruthenium-functionalised silica nanoparticles showed high relative brightness compared to the free dye in solution and efficient functionalisation with amino or carboxyl groups. Due to their ease of fabrication and attractive characteristics, the ruthenium-functionalised silica nanoparticles described here have the potential to be highly desirable fluorescent labels, particularly, for biological applications.

  1. Interactions between Food Additive Silica Nanoparticles and Food Matrices

    Directory of Open Access Journals (Sweden)

    Mi-Ran Go

    2017-06-01

    Full Text Available Nanoparticles (NPs have been widely utilized in the food industry as additives with their beneficial characteristics, such as improving sensory property and processing suitability, enhancing functional and nutritional values, and extending shelf-life of foods. Silica is used as an anti-caking agent to improve flow property of powered ingredients and as a carrier for flavors or active compounds in food. Along with the rapid development of nanotechnology, the sizes of silica fall into nanoscale, thereby raising concerns about the potential toxicity of nano-sized silica materials. There have been a number of studies carried out to investigate possible adverse effects of NPs on the gastrointestinal tract. The interactions between NPs and surrounding food matrices should be also taken into account since the interactions can affect their bioavailability, efficacy, and toxicity. In the present study, we investigated the interactions between food additive silica NPs and food matrices, such as saccharides, proteins, lipids, and minerals. Quantitative analysis was performed to determine food component-NP corona using HPLC, fluorescence quenching, GC-MS, and ICP-AES. The results demonstrate that zeta potential and hydrodynamic radius of silica NPs changed in the presence of all food matrices, but their solubility was not affected. However, quantitative analysis on the interactions revealed that a small portion of food matrices interacted with silica NPs and the interactions were highly dependent on the type of food component. Moreover, minor nutrients could also affect the interactions, as evidenced by higher NP interaction with honey rather than with a simple sugar mixture containing an equivalent amount of fructose, glucose, sucrose, and maltose. These findings provide fundamental information to extend our understanding about the interactions between silica NPs and food components and to predict the interaction effect on the safety aspects of food

  2. Serpentinization processes: Influence of silica

    Science.gov (United States)

    Huang, R.; Sun, W.; Ding, X.; Song, M.; Zhan, W.

    2016-12-01

    Serpentinization systems are highly enriched in molecular hydrogen (H2) and hydrocarbons (e.g. methane, ethane and propane). The production of hydrocarbons results from reactions between H2 and oxidized carbon (carbon dioxide and carbon monoxide), which possibly contribute to climate changes during early history of the Earth. However, the influence of silica on the production of H2 and hydrocarbons was poorly constrained. We performed experiments at 311-500 °C and 3.0 kbar using mechanical mixtures of silica and olivine in ratios ranging from 0 to 40%. Molecular hydrogen (H2), methane, ethane and propane were formed, which were analyzed by gas chromatography. It was found that silica largely decreased H2 production. Without any silica, olivine serpentinization produced 94.5 mmol/kg H2 after 20 days of reaction time. By contrast, with the presence of 20% silica, H2 concentrations decreased largely, 8.5 mmol/kg. However, the influence of silica on the production of hydrocarbons is negligible. Moreover, with the addition of 20%-40% silica, the major hydrous minerals are talc, which was quantified according to an established standard curve calibrated by infrared spectroscopy analyses. It shows that silica greatly enhances olivine hydration, especially at 500 °C. Without any addition of silica, reaction extents were serpentinization at 500 °C and 3.0 kbar. By contrast, with the presence of 50% silica, olivine was completely transformed to talc within 9 days. This study indicates that silica impedes the oxidation of ferrous iron into ferric iron, and that rates of olivine hydration in natural geological settings are much faster with silica supply.

  3. Fluorescent S-layer fusion proteins

    International Nuclear Information System (INIS)

    Kainz, B.

    2010-01-01

    This work describes the construction and characterisation of fluorescent S-layer fusion proteins used as building blocks for the fabrication of nanostructured monomolecular biocoatings on silica particles with defined fluorescence properties. The S-layer protein SgsE of Geobacillus stearothermophilus NRS 2004/3a was fused with the pH-dependant cyan, green and yellow variant of the green fluorescent protein (GFP) and the red fluorescent protein mRFP1. These fluorescent S-layer fusion proteins, acting as scaffold and optical sensing element simultaneously, were able to reassemble in solution and on silica particles forming 2D nanostructures with p2 lattice symmetry (a=11 ±0.5 nm, b=14 ±0.4 nm, g=80 ±1 o ). The pH-dependant fluorescence behaviour was studied with fluorimetry, confocal microscopy and flow cytometry. These fluorescent S-layer fusion proteins can be used as pH-sensor. 50% of the fluorescence intensity decreases at their calculated pKa values (pH6 - pH5). The fluorescence intensity of the GFP variants vanished completely between pH4 and pH3 whereas the chromophore of the red protein mRFP1 was only slightly affected in acidic conditions. At the isoelectric point of the S-layer coated silica particles (pH4.6 ±0.2) an increase in particle aggregation was detected by flow cytometry. The cyan and yellow fluorescent proteins were chosen to create a bi-fluorescent S-layer tandem fusion protein with the possibility for resonance energy transfer (FRET). A transfer efficiency of 20% and a molecular distance between the donor (ECFP) and acceptor (YFP) chromophores of around 6.2 nm could be shown. This bi-fluorescent ECFP-SgsE-YFP tandem fusion protein was able to reassemble on solid surfaces. The remarkable combination of fluorescence and self-assembly and the design of bi-functional S-layer tandem fusion protein matrices makes them to a promising tool in nanobiotechnology. (author) [de

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

    Science.gov (United States)

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

    2008-09-02

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

  5. Novel dansyl-appended calix[4]arene frameworks: fluorescence properties and mercury sensing.

    Science.gov (United States)

    Pandey, Shubha; Azam, Amir; Pandey, Siddharth; Chawla, H M

    2009-01-21

    Covalently-attached fluorophores may impart enhanced chemosensing capabilities to calixarene frameworks. Synthesis and characterization of six novel dansyl-appended calix[4]arenes, namely, H/Dan4, NO2/Dan4, H/(OH)2Dan2, H/(Ester)2(Dan)2, t-Bu/(OH)2Dan2, and t-Bu/(Ester)2Dan2, containing two or four dansyl moieties are reported. Among these, fluorescence intensity of NO2/Dan4 is observed to decrease significantly in the presence Hg2+ in the solution. Based on the decrease in fluorescence, a limit of detection for Hg2+ of 20 ppb is obtained. NO2/Dan4 as a chemosensing agent for Hg2+ shows excellent selectivity and adequate reversibility. Complexation of NO2/Dan4 with Hg2+ is investigated using fluorescence spectroscopy and is observed to be 2:1. The formation constant of (NO2/Dan4)2Hg2+ is estimated to be 5.2(+/- 0.8) x 10(10) M(-2) at ambient conditions. These observations are traced to the fact that while all other dansyl-appended calix[4]arenes show cone conformation in the solution, NO2/Dan4 is in the 1,3-alternate conformation. Stokes shift versus solvent orientational polarizability for NO2/Dan4 also indicates the difference in the ground- to excited-state dipole moment of this compound to be the maximum among all six, rendering it most sensitive to its environment. Fluorescence emission of NO2/Dan4 in nonpolar chloroform, polar-aprotic acetonitrile, and polar-protic ethanol is observed to be different than that of the rest of the dansyl-appended compounds as well.

  6. 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 ...

  7. Hydrothermal stability of microporous silica and niobia-silica membranes

    NARCIS (Netherlands)

    Boffa, V.; Blank, David H.A.; ten Elshof, Johan E.

    2008-01-01

    The hydrothermal stability of microporous niobia–silica membranes was investigated and compared with silica membranes. The membranes were exposed to hydrothermal conditions at 150 and 200 °C for 70 h. The change of pore structure before and after exposure to steam was probed by single-gas permeation

  8. Comparison between rice husk ash and commercial silica as filler in polymeric composites; Comparacao de cinza de casca de arroz e silica comercial como carga em compositos polimericos

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, I.J.; Calheiro, D.; Santos, E.C.A. dos; Oliveira, R.; Rocha, T.L.A.C.; Moraes, C.A.M., E-mail: ijk.fernandes@gmail.com [Universidade do Vale do Rio dos Sinos (UNISINOS), Sao Leopoldo, RS (Brazil). Pos-Graduacao em Engenharia Civil

    2014-07-01

    The use of rice husk ash (RHA) as filler in polymeric materials has been studied in different polymers. Research reported that RHA may successfully replace silica. The silica production process using ore demands high energy input and produces considerable amounts of waste. Therefore, the replacement of silica by RHA may be economically and environmentally advantageous, reducing environmental impact and adding value to a waste material. In this context, this study characterizes and compares RHA of different sources (travelling grate reactor and fluidized bed reactor) with commercially available silicas to assess performance as filler in polymeric materials. Samples were characterized by X-ray fluorescence, loss on ignition, X-ray diffraction, grain size, specific surface area and specific weight. The results show that RHA may be used as a filler in several polymeric materials.(author)

  9. Pecan drying with silica gel

    Energy Technology Data Exchange (ETDEWEB)

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

    1983-07-01

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

  10. A single pH fluorescent probe for biosensing and imaging of extreme acidity and extreme alkalinity.

    Science.gov (United States)

    Chao, Jian-Bin; Wang, Hui-Juan; Zhang, Yong-Bin; Li, Zhi-Qing; Liu, Yu-Hong; Huo, Fang-Jun; Yin, Cai-Xia; Shi, Ya-Wei; Wang, Juan-Juan

    2017-07-04

    A simple tailor-made pH fluorescent probe 2-benzothiazole (N-ethylcarbazole-3-yl) hydrazone (Probe) is facilely synthesized by the condensation reaction of 2-hydrazinobenzothiazole with N-ethylcarbazole-3-formaldehyde, which is a useful fluorescent probe for monitoring extremely acidic and alkaline pH, quantitatively. The pH titrations indicate that Probe displays a remarkable emission enhancement with a pK a of 2.73 and responds linearly to minor pH fluctuations within the extremely acidic range of 2.21-3.30. Interestingly, Probe also exhibits strong pH-dependent characteristics with pK a 11.28 and linear response to extreme-alkalinity range of 10.41-12.43. In addition, Probe shows a large Stokes shift of 84 nm under extremely acidic and alkaline conditions, high selectivity, excellent sensitivity, good water-solubility and fine stability, all of which are favorable for intracellular pH imaging. The probe is further successfully applied to image extremely acidic and alkaline pH values fluctuations in E. coli cells. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Synthesis and fluorescence study of sodium-2-(4'-dimethyl-aminocinnamicacyl)-3,3-(1',3'-alkylenedithio) acrylate

    International Nuclear Information System (INIS)

    Si Zhenjun; Shao Yun; Li Chunxia; Liu Qun

    2007-01-01

    We synthesized two new compounds: Sodium 2-(4'-dimethyl-aminocinnamicacyl)-3,3-(1',3'- ethyl- enedithio) acrylate (STAA-1) and Sodium 2-(4'-dimethyl-aminocinnamicacyl)-3, 3-(1',3'-propylenedithio) acrylate (STAA-2). The maximum absorption of these compounds ranges from 460 to 520 nm with different molecular structures in different solvents. Meanwhile, the emission peak of these compounds arranges from yellow (510 nm) to red (605 nm). The emission spectra show red shift according to the strength of the hydrogen bonding property of the solvent. But the absorption spectra do not show clearly relationship with the strength of the hydrogen bonding property of the solvent. The Stoke shift of the compounds ranges from 42 to 102 nm. It changes in the following order, EtOH>H 2 O>DMF, and STAA-1>STAA-2 in the same solvent. The fluorescent quantum yield of STAA-1 was measured to be 7.12% with quinine sulphate as the standard compound in ethanol. Furthermore, the relationship of the fluorescence of STAA-1 with pH (ranges form 4 to 14) in water (c=∼10 -4 ) was studied to make sure that these compounds could be used as proton sensors

  12. Using the fluorescence red edge effect to assess the long-term stability of lyophilized protein formulations.

    Science.gov (United States)

    Qian, Ken K; Grobelny, Pawel J; Tyagi, Madhusudan; Cicerone, Marcus T

    2015-04-06

    Nanosecond relaxation processes in sugar matrices are causally linked through diffusional processes to protein stability in lyophilized formulations. Long-term protein degradation rates track mean-squared displacement (⟨u(2)⟩) of hydrogen atoms in sugar glasses, a parameter describing dynamics on a time scale of picoseconds to nanoseconds. However, measurements of ⟨u(2)⟩ are usually performed by neutron scattering, which is not conducive to rapid formulation screening in early development. Here, we present a benchtop technique to derive a ⟨u(2)⟩ surrogate based on the fluorescence red edge effect. Glycerol, lyophilized trehalose, and lyophilized sucrose were used as model systems. Samples containing 10(-6) mole fraction of rhodamine 6G, a fluorophore, were excited at either 532 nm (main peak) or 566 nm (red edge), and the ⟨u(2)⟩ surrogate was determined based the corresponding Stokes shifts. Results showed reasonable agreement between ⟨u(2)⟩ from neutron scattering and the surrogate from fluorescence, although deviations were observed at very low temperatures. We discuss the sources of the deviations and suggest technique improvements to ameliorate these. We expect that this method will be a valuable tool to evaluate lyophilized sugar matrices with respect to their ability to protect proteins from diffusion-limited degradation processes during long-term storage. Additionally, the method may have broader applications in amorphous pharmaceutical solids.

  13. Retention of U(VI) onto silica in presence of model organic molecules

    International Nuclear Information System (INIS)

    Pham, T.T.H.; Mercier-Bion, F.; Drot, R.; Lagarde, G.; Simoni, E.; Lambert, J.

    2008-01-01

    It is well-known that the organic matter influences the retention of ions onto mineral surfaces. However, the major part of concerned studies implies humic substances and complex solids. Another approach for identifying the sorption mechanisms is possible by studying simpler solids than those present in natural medium. So, silica is chosen as mineral surface because of its abundance in soils and of the presence of Si-O groups in clayey minerals. Uranium (VI) is selected as cation. Simple organic molecules like acetic (one carboxylic group) and oxalic (two carboxylic functions) acids are considered as models of the natural organic matter for understanding their role in the retention of U(VI) onto powders and slides of silica. Binary (organics/silica, U(VI)/silica) and ternary systems (organics/silica/U(VI)) are studied by complementary approaches. Sorption edges as function of pH are obtained by liquid scintillation methods and capillary electrophoresis. Different spectroscopic techniques are used to deduce the interactions between the organic matter and U(VI) sorbed onto the silica whose: Time-Resolved Laser induced Fluorescence Spectroscopy (TRLFS), X-ray Photoelectron Spectroscopy (XPS), Nuclear Microprobe Analysis (NMA). The results of the effect of these model organic molecules onto the U(VI) retention showed a good agreement between the different techniques. Concerning the acetic acid, there are not differences in the sorption percentages of uranyl (see the figure). All these results indicate that the uranyl-acetate complexes stay in the aqueous solution rather than sorbing onto the silica. On the contrary, oxalic acid influences the sorption of U(VI) onto the silica surface. The sorption percentage of U(VI) in the ternary system (oxalic acid/silica/U(VI)) is lower than the binary system (U(VI)/silica) (see the figure). So, the presence of oxalic acid decreases the sorption of U(VI) onto the silica surface. (authors)

  14. Highly Fluorescent Group 13 Metal Complexes with Cyclic, Aromatic Hydroxamic Acid Ligands

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, Michael; Moore, Evan G.; Raymond, Kenneth N.

    2008-02-11

    The neutral complexes of two ligands based on the 1-oxo-2-hydroxy-isoquinoline (1,2-HOIQO) motif with group 13 metals (Al, Ga, In) show bright blue-violet luminescence in organic solvents. The corresponding transition can be attributed to ligand-centered singlet emission, characterized by a small Stokes shifts of only a few nm combined with lifetimes in the range between 1-3 ns. The fluorescence efficiency is high, with quantum yields of up to 37% in benzene solution. The crystal structure of one of the indium(III) complexes (trigonal space group R-3, a = b = 13.0384(15) {angstrom}, c = 32.870(8) {angstrom}, ? = {beta} = 90{sup o}, {gamma} = 120{sup o}, V = 4839.3(14) {angstrom}{sup 3}, Z = 6) shows a six-coordinate geometry around the indium center which is close to trigonal-prismatic, with a twist angle between the two trigonal faces of 20.7{sup o}. Time-dependent density functional theory (TD-DFT) calculations (Al and Ga: B3LYP/6-31G(d)); In: B3LYP/LANL2DZ of the fac and mer isomers with one of the two ligands indicate that there is no clear preference for either one of the isomeric forms of the metal complexes. In addition, the metal centers do not have a significant influence on the electronic structure, and as a consequence, on the predominant intraligand optical transitions.

  15. Uptake of silica covered Quantum Dots into living cells: Long term vitality and morphology study on hyaluronic acid biomaterials

    International Nuclear Information System (INIS)

    D'Amico, Michele; Fiorica, Calogero; Palumbo, Fabio Salvatore; Militello, Valeria; Leone, Maurizio; Dubertret, Benoit; Pitarresi, Giovanna; Giammona, Gaetano

    2016-01-01

    Quantum Dots (QDs) are promising very bright and stable fluorescent probes for optical studies in the biological field but water solubility and possible metal bio-contamination need to be addressed. In this work, a simple silica-QD hybrid system is prepared and the uptake in bovine chondrocytes living cells without any functionalization of the external protective silica shield is demonstrated. Moreover, long term treated cells vitality (up to 14 days) and the transfer of silica-QDs to the next cell generations are here reported. Confocal fluorescence microscopy was also used to determine the morphology of the so labelled cells and the relative silica-QDs distribution. Finally, we employ silica-QD stained chondrocytes to characterize, as proof of concept, hydrogels obtained from an amphiphilic derivative of hyaluronic acid (HA-EDA-C _1_8) functionalized with different amounts of the RGD peptide. - Highlights: • Non functionalized silica-quantum dots fluorescent nanoparticles uptake is observed. • Morphology studies of such cells could be done by confocal fluorescence microscopy. • Labelled chondrocytes are viable until at least 14 days. • RGD functionalized Hyaluronic Acid hydrogels are studied as cell scaffolds. • Chondrocyte are promptly attached on RGD-functionalized hydrogels.

  16. Uptake of silica covered Quantum Dots into living cells: Long term vitality and morphology study on hyaluronic acid biomaterials

    Energy Technology Data Exchange (ETDEWEB)

    D' Amico, Michele [Dip. Biomedico di Medicina Interna e Specialistica, Universitá degli Studi di Palermo, Piazza delle Cliniche, 2, 90127 Palermo (Italy); Dip. di Fisica e Chimica, Universitá degli Studi di Palermo, Viale delle Scienze, Ed. 18, 90128 Palermo (Italy); Fiorica, Calogero, E-mail: calogero.fiorica@unipa.it [Dip. di Scienze e Tecnologie Molecolari e Biomolecolari, Sezione di Chimica e Tecnologie Farmaceutiche, Universitá degli Studi di Palermo, Via Archirafi, 28, 90136 Palermo (Italy); Palumbo, Fabio Salvatore [Dip. di Scienze e Tecnologie Molecolari e Biomolecolari, Sezione di Chimica e Tecnologie Farmaceutiche, Universitá degli Studi di Palermo, Via Archirafi, 28, 90136 Palermo (Italy); Militello, Valeria; Leone, Maurizio [Dip. di Fisica e Chimica, Universitá degli Studi di Palermo, Viale delle Scienze, Ed. 18, 90128 Palermo (Italy); Dubertret, Benoit [Laboratoire de Physique et d’Etude des Matèriaux, ESPCI-ParisTech, PSL Research University, Sorbonne Universitè UPMC Univ. Paris 06, CNRS, 10 rue Vauquelin, 75005 Paris (France); Pitarresi, Giovanna; Giammona, Gaetano [Dip. di Scienze e Tecnologie Molecolari e Biomolecolari, Sezione di Chimica e Tecnologie Farmaceutiche, Universitá degli Studi di Palermo, Via Archirafi, 28, 90136 Palermo (Italy)

    2016-10-01

    Quantum Dots (QDs) are promising very bright and stable fluorescent probes for optical studies in the biological field but water solubility and possible metal bio-contamination need to be addressed. In this work, a simple silica-QD hybrid system is prepared and the uptake in bovine chondrocytes living cells without any functionalization of the external protective silica shield is demonstrated. Moreover, long term treated cells vitality (up to 14 days) and the transfer of silica-QDs to the next cell generations are here reported. Confocal fluorescence microscopy was also used to determine the morphology of the so labelled cells and the relative silica-QDs distribution. Finally, we employ silica-QD stained chondrocytes to characterize, as proof of concept, hydrogels obtained from an amphiphilic derivative of hyaluronic acid (HA-EDA-C {sub 18}) functionalized with different amounts of the RGD peptide. - Highlights: • Non functionalized silica-quantum dots fluorescent nanoparticles uptake is observed. • Morphology studies of such cells could be done by confocal fluorescence microscopy. • Labelled chondrocytes are viable until at least 14 days. • RGD functionalized Hyaluronic Acid hydrogels are studied as cell scaffolds. • Chondrocyte are promptly attached on RGD-functionalized hydrogels.

  17. Novel push-pull fluorescent dyes - 7-(diethylamino)furo- and thieno[3,2-c]coumarins derivatives: structure, electronic spectra and TD-DFT study

    Science.gov (United States)

    Akchurin, Igor O.; Yakhutina, Anna I.; Bochkov, Andrei Y.; Solovjova, Natalya P.; Medvedev, Michael G.; Traven, Valerii F.

    2018-05-01

    Novel push-pull fluorescent dyes - 7-(diethylamino)furo- and 7-(diethylamino)thieno[3,2-c]coumarins derivatives have been synthesized using formyl derivatives of furo- and thieno[3,2-c]coumarins as starting materials. Electron absorption and fluorescent spectra of the dyes have been recorded in different solvents. Structure and solvent effects on the dyes spectral characteristics were analyzed. The fusion of five-membered heterocycle to coumarin provides a definite increase of Stokes shifts in all solvents and results in higher quantum yields of fluorescence. The absorption and emission bands of thieno[3,2-c] coumarin derivatives are definitely shifted to the red region (3-30 nm) compared to similar derivatives of furo[3,2-c]coumarin. TD-DFT calculations of some of the studied compounds have shown that hybrid DFT functionals and adequate representation of molecular environment are essential for obtaining accurate UV-Vis absorption spectra for the dyes with extended π-system. The longest-wave electron transitions in the studied compounds were computationally shown to be of push-pull nature.

  18. Novel dual ligand co-functionalized fluorescent gold nanoclusters as a versatile probe for sensitive analysis of Hg(2+) and oxytetracycline.

    Science.gov (United States)

    Xu, Shenghao; Li, Xiaolin; Mao, Yaning; Gao, Teng; Feng, Xiuying; Luo, Xiliang

    2016-04-01

    In this work, we present a direct one-step strategy for rapidly preparing dual ligand co-functionalized fluorescent Au nanoclusters (NCs) by using threonine (Thr) and 11-mercaptoundecanoic acid (MUA) as assorted reductants and capping agents in aqueous solution at room temperature. Fluorescence spectra, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), and infrared (IR) spectroscopy were performed to demonstrate the optical properties and chemical composition of the as-prepared AuNCs. They possess many attractive features such as near-infrared emission (λem = 606 nm), a large Stoke's shift (>300 nm), high colloidal stability (pH, temperature, salt, and time stability), and water dispersibility. Subsequently, the as-prepared AuNCs were used as a versatile probe for "turn off" sensing of Hg(2+) based on aggregation-induced fluorescence quenching and for "turn-on" sensing of oxytetracycline (OTC). This assay provided good linearity ranging from 37.5 to 3750 nM for Hg(2+) and from 0.375 to 12.5 μM for OTC, with detection limits of 8.6 nM and 0.15 μM, respectively. Moreover, the practical application of this assay was further validated by detecting OTC in human serum samples.

  19. Angular shaping of fluorescence from synthetic opal-based photonic crystal.

    Science.gov (United States)

    Boiko, Vitalii; Dovbeshko, Galyna; Dolgov, Leonid; Kiisk, Valter; Sildos, Ilmo; Loot, Ardi; Gorelik, Vladimir

    2015-01-01

    Spectral, angular, and temporal distributions of fluorescence as well as specular reflection were investigated for silica-based artificial opals. Periodic arrangement of nanosized silica globules in the opal causes a specific dip in the defect-related fluorescence spectra and a peak in the reflectance spectrum. The spectral position of the dip coincides with the photonic stop band. The latter is dependent on the size of silica globules and the angle of observation. The spectral shape and intensity of defect-related fluorescence can be controlled by variation of detection angle. Fluorescence intensity increases up to two times at the edges of the spectral dip. Partial photobleaching of fluorescence was observed. Photonic origin of the observed effects is discussed.

  20. Mobile Phone Ratiometric Imaging Enables Highly Sensitive Fluorescence Lateral Flow Immunoassays without External Optical Filters.

    Science.gov (United States)

    Shah, Kamal G; Singh, Vidhi; Kauffman, Peter C; Abe, Koji; Yager, Paul

    2018-05-14

    Paper-based diagnostic tests based on the lateral flow immunoassay concept promise low-cost, point-of-care detection of infectious diseases, but such assays suffer from poor limits of detection. One factor that contributes to poor analytical performance is a reliance on low-contrast chromophoric optical labels such as gold nanoparticles. Previous attempts to improve the sensitivity of paper-based diagnostics include replacing chromophoric labels with enzymes, fluorophores, or phosphors at the expense of increased fluidic complexity or the need for device readers with costly optoelectronics. Several groups, including our own, have proposed mobile phones as suitable point-of-care readers due to their low cost, ease of use, and ubiquity. However, extant mobile phone fluorescence readers require costly optical filters and were typically validated with only one camera sensor module, which is inappropriate for potential point-of-care use. In response, we propose to couple low-cost ultraviolet light-emitting diodes with long Stokes-shift quantum dots to enable ratiometric mobile phone fluorescence measurements without optical filters. Ratiometric imaging with unmodified smartphone cameras improves the contrast and attenuates the impact of excitation intensity variability by 15×. Practical application was shown with a lateral flow immunoassay for influenza A with nucleoproteins spiked into simulated nasal matrix. Limits of detection of 1.5 and 2.6 fmol were attained on two mobile phones, which are comparable to a gel imager (1.9 fmol), 10× better than imaging gold nanoparticles on a scanner (18 fmol), and >2 orders of magnitude better than gold nanoparticle-labeled assays imaged with mobile phones. Use of the proposed filter-free mobile phone imaging scheme is a first step toward enabling a new generation of highly sensitive, point-of-care fluorescence assays.

  1. Fluorescence and physical properties of the organic salt 2-chloro-4-nitrobenzoate–3-ammonium-phenol

    Energy Technology Data Exchange (ETDEWEB)

    Mani, Rajaboopathi, E-mail: mrajaboopathi@gmail.com [Department of Physics, Periyar University, Salem 636 011, Tamilnadu (India); Rietveld, Ivo B.; Nicolaï, Béatrice [Laboratoire de Chimie Physique, Faculté de Pharmacie, Université Paris Descartes, 75006 Paris (France); Varadharajan, Krishnakumar, E-mail: vkrishna_kumar@yahoo.com [Department of Physics, Periyar University, Salem 636 011, Tamilnadu (India); Louhi-Kultanen, Marjatta [Department of Chemical Technology, Lappeenranta University of Technology, Lappeenranta 53851 (Finland); Narasimhan, Surumbarkuzhali [Department of Physics, Government Arts College (Autonomous), Salem 636 007, Tamilnadu (India)

    2015-09-08

    Highlights: • Organic salt of 2-chloro-4-nitrobenzoate–3-ammonium-phenol (CNBA{sup −} · AP{sup +}) was grown by solution growth technique. • Single crystal X-ray diffraction demonstrate that two molecules were linked via N{sup +}–H⋯O{sup −} interactions. • The narrow spatial overlap between HOMO and LUMO leads to low ΔE{sub ST} = 73 meV. • The fluorescence emission was observed at ≈338 nm with Stokes shift of 53 nm. • The melting point of CNBA{sup −} · AP{sup +} is 187 °C which is higher than the individual components. - Abstract: Organic salt 2-chloro-4-nitrobenzoate (CNBA{sup −}) 3-ammonium-phenol (AP{sup +}) exhibits fluorescence at 338 nm in solution and frontier molecular orbitals generated from TDDFT calculations indicate that the ground state and the excited state are physically separated on AP{sup +} and CNBA{sup −}. The crystal structure and physical–chemical properties of the CNBA{sup −} · AP{sup +} were investigated using X-ray single crystal and powder diffraction, SEM, FTIR, UV–Vis–NIR, and fluorescence spectrometry. X-ray diffraction demonstrates that the two molecules are linked via N{sup +}–H⋯O{sup −} ammonium–carboxylate interactions, as expected considering their interaction propensities. Proton transfer has been confirmed by FTIR analysis. The melting point of CNBA{sup −} · AP{sup +} was observed at 186 °C, which is higher than pure CNBA (140 °C) or AP (120 °C). The observation of a spatially separated HOMO and LUMO possessing a narrow ΔE{sub ST} = 73.3 meV and an emission in the blue region is promising as an alternative method for the production of OLED materials.

  2. Magnetic polymer-silica composites as bioluminescent sensors for bilirubin detection

    Energy Technology Data Exchange (ETDEWEB)

    Timin, Alexander S., E-mail: a_timin@mail.ru [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000, Ivanovo (Russian Federation); RASA Center in Tomsk, Tomsk Polytechnic University, pros. Lenina, 30, Tomsk (Russian Federation); Solomonov, Alexey V. [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000, Ivanovo (Russian Federation); Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, 7610001 (Israel); Kumagai, Akiko; Miyawaki, Atsushi [Cell Function Dynamics, Brain Science Institute RIKEN, 2-1 Hirosawa, Wako-city, Saitama, 351-0198 (Japan); Khashirova, Svetlana Yu; Zhansitov, Azamat [Kabardino-Balkar State University, 173 Chernyshevskogo St., Nal' chik, 360004, Kabardino-Balkaria (Russian Federation); Rumyantsev, Evgeniy V. [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000, Ivanovo (Russian Federation)

    2016-11-01

    The synthesis of multifunctional nano-sized materials is leading to the rapid development of key application, including improved drug delivery, bioimaging and protein separation. In this work, magnetic silica particles modified with novel guanidine containing co-polymers were manufactured via sol-gel method. To evaluate the chemical composition of our prepared samples, FT-IR spectroscopy and thermogravimetry were conducted. Scanning electron microscopy was used in order to investigate the morphology of final products after modification by guanidine containing co-polymers and iron nanoparticles. In addition, the surface of polymer-silica composites was functionalized by the novel bilirubin-inducible fluorescent protein UnaG. In an aqueous bilirubin solution, the silica particles decorated with the polymer-UnaG have showed bright fluorescence. Synthesis and characterization of these hybrid materials allow developing of new multifunctional nano-sized materials, which will be used for detection and separation of bilirubin, a lipophilic heme catabolite that is a clinical diagnostic for liver function. - Highlights: • Novel magnetic silicas grafted by guanidine containing co-polymers were prepared. • Unag protein was effectively loaded into polymer coated silicas. • The fluorescent properties depend on content of bilirubin.

  3. Magnetic polymer-silica composites as bioluminescent sensors for bilirubin detection

    International Nuclear Information System (INIS)

    Timin, Alexander S.; Solomonov, Alexey V.; Kumagai, Akiko; Miyawaki, Atsushi; Khashirova, Svetlana Yu; Zhansitov, Azamat; Rumyantsev, Evgeniy V.

    2016-01-01

    The synthesis of multifunctional nano-sized materials is leading to the rapid development of key application, including improved drug delivery, bioimaging and protein separation. In this work, magnetic silica particles modified with novel guanidine containing co-polymers were manufactured via sol-gel method. To evaluate the chemical composition of our prepared samples, FT-IR spectroscopy and thermogravimetry were conducted. Scanning electron microscopy was used in order to investigate the morphology of final products after modification by guanidine containing co-polymers and iron nanoparticles. In addition, the surface of polymer-silica composites was functionalized by the novel bilirubin-inducible fluorescent protein UnaG. In an aqueous bilirubin solution, the silica particles decorated with the polymer-UnaG have showed bright fluorescence. Synthesis and characterization of these hybrid materials allow developing of new multifunctional nano-sized materials, which will be used for detection and separation of bilirubin, a lipophilic heme catabolite that is a clinical diagnostic for liver function. - Highlights: • Novel magnetic silicas grafted by guanidine containing co-polymers were prepared. • Unag protein was effectively loaded into polymer coated silicas. • The fluorescent properties depend on content of bilirubin.

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

    International Nuclear Information System (INIS)

    Liao Yufeng; Li Wenjiang; He Sailing

    2007-01-01

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

  5. Silica research in Glasgow

    International Nuclear Information System (INIS)

    Barr, B W; Cagnoli, G; Casey, M M; Clubley, D; Crooks, D R M; Danzmann, K; Elliffe, E J; Gossler, S; Grant, A; Grote, H; Heptonstall, A; Hough, J; Jennrich, O; Lueck, H; McIntosh, S A; Newton, G P; Palmer, D A; Plissi, M V; Robertson, D I; Robertson, N A; Rowan, S; Skeldon, K D; Sneddon, P; Strain, K A; Torrie, C I; Ward, H; Willems, P A; Willke, B; Winkler, W

    2002-01-01

    The Glasgow group is involved in the construction of the GEO600 interferometer as well as in R and D activity on technology for advanced gravitational wave detectors. GEO600 will be the first GW detector using quasi-monolithic silica suspensions in order to decrease thermal noise significantly with respect to steel wire suspensions. The results concerning GEO600 suspension mounting and performance will be shown in the first section. Section 2 is devoted to the present results from the direct measurement of thermal noise in mirrors mounted in the 10 m interferometer in Glasgow which has a sensitivity limit of 4 x 10 -19 m Hz -1/2 above 1 kHz. Section 3 presents results on the measurements of coating losses. R and D activity has been carried out to understand better how thermal noise in the suspensions affects the detector sensitivity, and in section 4 a discussion on the non-linear thermoelastic effect is presented

  6. Silica nanodisks as platforms for fluorescence lifetime-based ...

    Indian Academy of Sciences (India)

    Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India ... The nanoconjugates are found to sense the pH of the medium, through systematic ..... form pH sensing with a good level of sensitivity, with.

  7. Fluorescent nanoparticles for intracellular sensing: a review.

    Science.gov (United States)

    Ruedas-Rama, Maria J; Walters, Jamie D; Orte, Angel; Hall, Elizabeth A H

    2012-11-02

    Fluorescent nanoparticles (NPs), including semiconductor NPs (Quantum Dots), metal NPs, silica NPs, polymer NPs, etc., have been a major focus of research and development during the past decade. The fluorescent nanoparticles show unique chemical and optical properties, such as brighter fluorescence, higher photostability and higher biocompatibility, compared to classical fluorescent organic dyes. Moreover, the nanoparticles can also act as multivalent scaffolds for the realization of supramolecular assemblies, since their high surface to volume ratio allow distinct spatial domains to be functionalized, which can provide a versatile synthetic platform for the implementation of different sensing schemes. Their excellent properties make them one of the most useful tools that chemistry has supplied to biomedical research, enabling the intracellular monitoring of many different species for medical and biological purposes. In this review, we focus on the developments and analytical applications of fluorescent nanoparticles in chemical and biological sensing within the intracellular environment. The review also points out the great potential of fluorescent NPs for fluorescence lifetime imaging microscopy (FLIM). Finally, we also give an overview of the current methods for delivering of fluorescent NPs into cells, where critically examine the benefits and liabilities of each strategy. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Characterization of microenvironment polarity and solvent accessibility of polysilsesquioxane xerogels by the fluorescent probe technique

    Energy Technology Data Exchange (ETDEWEB)

    Shea, K.J.; Zhu, H.D. [Univ., of California, Irvine, CA (United States). Dept. of Chemistry; Loy, D.A. [Sandia National Labs., Albuquerque, NM (United States)

    1995-05-01

    Poly (1, 4 bis(triethoxysilyl)benzene) (PTESB), a representative of a new type of organic-inorganic hybrid polysilsesquioxane material, was characterized by fluorescence spectroscopy for both microenvironmental polarity and solvent accessibility. A dansyl fluorescent molecule was incorporated into the bulk as well as onto the surface of both PTESB and silica materials. Information about the microenvironment polarity and accessibility of PTESB to various organic solvents was determined and compared to that of silica gel. This study found that both the bulk and surface of PTESB are less polar than that of the silica material. The silica material is accessible to polar solvents and water, while YMB is accessible to polar solvents but not to water. The hydrophobicity of PTESB differentiates these new materials from silica gel.

  9. Cu(II) recognition materials: Fluorophores grafted on mesoporous silica supports

    International Nuclear Information System (INIS)

    Kledzik, Krzysztof; Orlowska, Maja; Patralska, Dorota; Gwiazda, Marcin; Jezierska, Julia; Pikus, Stanislaw; Ostaszewski, Ryszard; Klonkowski, Andrzej M.

    2007-01-01

    There were designed and synthesized naphthalene and pyrene derivatives consisting of fluorophore group and of receptor fragment with donor N and O atoms. These fluorosensors were covalently attached by grafting carboxyl group to surfaces of silica xerogel or mesoporous silicas (MCM-41 and MCM-48) functionalized either with 3-aminopropyl or 3-glycidoxypropyl groups. The pyrene derivatives 2 and 3 covalently grafted on MCM-48 silica functionalized with 3-aminopropyl groups are potential recognition elements of a fluorescence chemical sensor. Fluorescence emission of the prepared recognition materials is quenched specifically owing to photoinduced electron transfer (PET) effect after coordination reactions with Cu(II) ions. Moreover, both the materials exhibit selectivity for Cu(II) ions in aqueous solutions in presence of such metal ions as: alkali, alkaline earth and transition. During UV irradiation the studied recognition elements undergo slowly photochemical degradation

  10. Fluorescent strategy based on cationic conjugated polymer fluorescence resonance energy transfer for the quantification of 5-(hydroxymethyl)cytosine in genomic DNA.

    Science.gov (United States)

    Hong, Tingting; Wang, Tianlu; Guo, Pu; Xing, Xiwen; Ding, Fei; Chen, Yuqi; Wu, Jinjun; Ma, Jingwei; Wu, Fan; Zhou, Xiang

    2013-11-19

    DNA methylation is dynamically reprogrammed during early embryonic development in mammals. It can be explained partially by the discovery of 5-(hydroxymethyl)cytosine (5-hmC), 5-formylcytosine (5-fC), and 5-carboxylcytosine (5-caC), which are identified as key players involved in both active and passive demethylation pathways. As one of the ten-eleven translocation oxidation products, 5-hmC was found relatively abundant in neuron cells and embryonic stem cells. Herein we report a new method for 5-hmC quantification in genomic DNA based on CCP-FRET (cationic conjugated polymers act as the energy donor and induce fluorescence resonance energy transfer) assay combined with KRuO4 oxidation. 5-hmC in genomic DNA can be selectively transformed into 5-fC by the oxidation of KRuO4 and then labeled with hydroxylamine-BODIPY (BODIPY = 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) fluorophore through the reaction between 5-fC and hydroxylamine-BODIPY. After the fluorescently labeled DNA was captured by CCP through electrostatic interactions, a significant FRET between CCP and hydroxylamine-BODIPY fluorophore was observed. This CCP-FRET-based assay benefits from light-harvesting, large Stokes shift, and optical signal amplification properties of the CCP. Furthermore, this CCP-FRET-based assay was quite successfully demonstrated for the 5-hmC quantification in three types of cells (mESc, HeLa, HEK 293T), providing a much more convenient choice for 5-hmC quantification in genomic DNA.

  11. One Pot Synthesis, Photophysical and X-ray Studies of Novel Highly Fluorescent Isoquinoline Derivatives with Higher Antibacterial Efficacy Based on the In-vitro and Density Functional Theory.

    Science.gov (United States)

    Asiri, Abdullah M; Khan, Salman A; Al-Thaqafy, Saad H; Sharma, Kamlesh

    2015-05-01

    Series of cyano substituted isoquinoline dyes were synthesized by one-pot multicomponent reactions (MCRs) of aldehydes, malononitrile, 6-methoxy-1,2,3,4-tetrahydro-naphthalin-1-one and ammonium acetate. Results obtained from spectroscopic (FT-IR, (1)H-NMR, (13)C-NMR, EI-MS) and elemental analysis of synthesized compounds was in agreement with their chemical structures. Structure of the compound was further conformed by X-ray crystallographic. UV-vis and fluorescence spectroscopy measurements provided that all compounds are good absorbent and fluorescent. Fluorescence polarity study demonstrated that these compounds were sensitive to the polarity of the microenvironment provided by different solvents. In addition, spectroscopic and physicochemical parameters, including electronic absorption, extenction coefficient, Stokes shift, oscillator strength transition dipole moment and fluorescence quantum yield were investigated in order to explore the analytical potential of synthesized compounds. The anti-bacterial activity of these compounds were first studied in vitro by the disk diffusion assay against two Gram-positive and two Gram-negative bacteria. The minimum inhibitory concentration was then determined with the reference of standard drug chloramphenicol. The results displayed that compound 3 was better inhibitors of both types of the bacteria (Gram-positive and Gram-negative) than chloramphenicol. Furthermore, quantum chemistry calculations using DFT/6-31-G* level of theory confirm the results. Dipole moment and frontier molecular orbitals were also investigated.

  12. Spectroscopic studies of Cu ions in sol–gel derived silica matrix

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The Cu2+ ion doped silica gel matrices in monolithic shape were prepared by hydrolysis and condensation of tetraethyl orthosilicate (TEOS). The absorption, transmittance and fluorescence spectra of the gel matrices heat treated at different temperatures were monitored. The loss of water and hydroxyl group from.

  13. Fluorescence microscopy.

    Science.gov (United States)

    Sanderson, Michael J; Smith, Ian; Parker, Ian; Bootman, Martin D

    2014-10-01

    Fluorescence microscopy is a major tool with which to monitor cell physiology. Although the concepts of fluorescence and its optical separation using filters remain similar, microscope design varies with the aim of increasing image contrast and spatial resolution. The basics of wide-field microscopy are outlined to emphasize the selection, advantages, and correct use of laser scanning confocal microscopy, two-photon microscopy, scanning disk confocal microscopy, total internal reflection, and super-resolution microscopy. In addition, the principles of how these microscopes form images are reviewed to appreciate their capabilities, limitations, and constraints for operation. © 2014 Cold Spring Harbor Laboratory Press.

  14. Comparison between rice husk ash and commercial silica as filler in polymeric composites

    International Nuclear Information System (INIS)

    Fernandes, I.J.; Calheiro, D.; Santos, E.C.A. dos; Oliveira, R.; Rocha, T.L.A.C.; Moraes, C.A.M.

    2014-01-01

    The use of rice husk ash (RHA) as filler in polymeric materials has been studied in different polymers. Research reported that RHA may successfully replace silica. The silica production process using ore demands high energy input and produces considerable amounts of waste. Therefore, the replacement of silica by RHA may be economically and environmentally advantageous, reducing environmental impact and adding value to a waste material. In this context, this study characterizes and compares RHA of different sources (travelling grate reactor and fluidized bed reactor) with commercially available silicas to assess performance as filler in polymeric materials. Samples were characterized by X-ray fluorescence, loss on ignition, X-ray diffraction, grain size, specific surface area and specific weight. The results show that RHA may be used as a filler in several polymeric materials.(author)

  15. 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.

  16. Identification and Purification of Nyalo River Silica Sand as Raw Material for the Synthesis of Sodium Silicate

    Science.gov (United States)

    Aini, S.; Nizar, U. K.; NST, A. Amelia; Efendi, J.

    2018-04-01

    This research is on identification and purification of silica sand from Nyalo River. It will be used as a raw material for synthesis of sodium silicate. Silica sand was separated from clay by washing it with water, and then the existing alumina and iron oxide were removed by soaking the silica sand with 1 M HNO3 solution. Qualitative and quantitative analysis of the silica sand with X-ray diffraction and X-ray fluorescence revealed that, silica sand existed in quartz form and contained a small amount of impurity oxide such as Al2O3, K2O, MgO, CaO, Fe2O3 with percentage below the minimum threshold. The percentages of silica were 80.59% before purification. After three purificationsteps the silica percentage become 98.38%. It exceedsthe minimum threshold of silica percentage for industry.So, the silica sand from Nyalo River has high potency as a raw material for sodium silicate synthesizing.

  17. Synthesis and characterization of silica gel from siliceous sands of southern Tunisia

    Directory of Open Access Journals (Sweden)

    Ali Sdiri

    2014-09-01

    Full Text Available The present work aimed to achieve valorization of Albian sands for the preparation of sodium silicates that are commonly used as a precursor to prepare silica gel. A siliceous sand sample was mixed with sodium carbonate and heated at a high temperature (1060 °C to prepare sodium silicates. The sodium silicates were dissolved in distilled water to obtain high quality sodium silicate solution. Hydrochloric acid was then slowly added to the hydrated sodium silicates to obtain silica gel. The collected raw siliceous sands, as well as the prepared silica gels, were characterized by different techniques, such as X-ray fluorescence (XRF, X-ray diffraction (XRD, scanning electron microscopy (SEM and thermal analysis (DSC. XRF confirmed that the detrital sand deposits of southern Tunisia contain high amounts of silica, with content ranging from 88.8% to 97.5%. The internal porosity varied between 17% and 22%, and the specific surface area was less than 5 m2/g. After the treatment described above, it was observed that the porosity of the obtained silica gel reached 57% and the specific surface area exceeded 340 m2/g. Nitrogen adsorption isotherms showed that the prepared silica gels are microporous and mesoporous materials with high adsorption capacities. These results suggest that the obtained silica gels are promising materials for numerous environmental applications.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  19. Low cost and open source multi-fluorescence imaging system for teaching and research in biology and bioengineering.

    Directory of Open Access Journals (Sweden)

    Isaac Nuñez

    Full Text Available The advent of easy-to-use open source microcontrollers, off-the-shelf electronics and customizable manufacturing technologies has facilitated the development of inexpensive scientific devices and laboratory equipment. In this study, we describe an imaging system that integrates low-cost and open-source hardware, software and genetic resources. The multi-fluorescence imaging system consists of readily available 470 nm LEDs, a Raspberry Pi camera and a set of filters made with low cost acrylics. This device allows imaging in scales ranging from single colonies to entire plates. We developed a set of genetic components (e.g. promoters, coding sequences, terminators and vectors following the standard framework of Golden Gate, which allowed the fabrication of genetic constructs in a combinatorial, low cost and robust manner. In order to provide simultaneous imaging of multiple wavelength signals, we screened a series of long stokes shift fluorescent proteins that could be combined with cyan/green fluorescent proteins. We found CyOFP1, mBeRFP and sfGFP to be the most compatible set for 3-channel fluorescent imaging. We developed open source Python code to operate the hardware to run time-lapse experiments with automated control of illumination and camera and a Python module to analyze data and extract meaningful biological information. To demonstrate the potential application of this integral system, we tested its performance on a diverse range of imaging assays often used in disciplines such as microbial ecology, microbiology and synthetic biology. We also assessed its potential use in a high school environment to teach biology, hardware design, optics, and programming. Together, these results demonstrate the successful integration of open source hardware, software, genetic resources and customizable manufacturing to obtain a powerful, low cost and robust system for education, scientific research and bioengineering. All the resources developed here

  20. Low cost and open source multi-fluorescence imaging system for teaching and research in biology and bioengineering.

    Science.gov (United States)

    Nuñez, Isaac; Matute, Tamara; Herrera, Roberto; Keymer, Juan; Marzullo, Timothy; Rudge, Timothy; Federici, Fernán

    2017-01-01

    The advent of easy-to-use open source microcontrollers, off-the-shelf electronics and customizable manufacturing technologies has facilitated the development of inexpensive scientific devices and laboratory equipment. In this study, we describe an imaging system that integrates low-cost and open-source hardware, software and genetic resources. The multi-fluorescence imaging system consists of readily available 470 nm LEDs, a Raspberry Pi camera and a set of filters made with low cost acrylics. This device allows imaging in scales ranging from single colonies to entire plates. We developed a set of genetic components (e.g. promoters, coding sequences, terminators) and vectors following the standard framework of Golden Gate, which allowed the fabrication of genetic constructs in a combinatorial, low cost and robust manner. In order to provide simultaneous imaging of multiple wavelength signals, we screened a series of long stokes shift fluorescent proteins that could be combined with cyan/green fluorescent proteins. We found CyOFP1, mBeRFP and sfGFP to be the most compatible set for 3-channel fluorescent imaging. We developed open source Python code to operate the hardware to run time-lapse experiments with automated control of illumination and camera and a Python module to analyze data and extract meaningful biological information. To demonstrate the potential application of this integral system, we tested its performance on a diverse range of imaging assays often used in disciplines such as microbial ecology, microbiology and synthetic biology. We also assessed its potential use in a high school environment to teach biology, hardware design, optics, and programming. Together, these results demonstrate the successful integration of open source hardware, software, genetic resources and customizable manufacturing to obtain a powerful, low cost and robust system for education, scientific research and bioengineering. All the resources developed here are available under

  1. Silica research in Glasgow

    CERN Document Server

    Barr, B W; Casey, M M; Clubley, D; Crooks, D R M; Danzmann, K; Elliffe, E J; Gossler, S; Grant, A; Grote, H; Heptonstall, A; Hough, J; Jennrich, O; Lück, H B; McIntosh, S A; Newton, G P; Palmer, D A; Plissi, M V; Robertson, D I; Robertson, N A; Rowan, S; Skeldon, K D; Sneddon, P; Strain, K A; Torrie, C I; Ward, H; Willems, P A; Willke, B; Winkler, W

    2002-01-01

    The Glasgow group is involved in the construction of the GEO600 interferometer as well as in R and D activity on technology for advanced gravitational wave detectors. GEO600 will be the first GW detector using quasi-monolithic silica suspensions in order to decrease thermal noise significantly with respect to steel wire suspensions. The results concerning GEO600 suspension mounting and performance will be shown in the first section. Section 2 is devoted to the present results from the direct measurement of thermal noise in mirrors mounted in the 10 m interferometer in Glasgow which has a sensitivity limit of 4 x 10 sup - sup 1 sup 9 m Hz sup - sup 1 sup / sup 2 above 1 kHz. Section 3 presents results on the measurements of coating losses. R and D activity has been carried out to understand better how thermal noise in the suspensions affects the detector sensitivity, and in section 4 a discussion on the non-linear thermoelastic effect is presented.

  2. Nanosecond Time-Dependent Stokes Shift at the Tunnel Mouth of Haloalkane Dehalogenases

    Czech Academy of Sciences Publication Activity Database

    Jesenská, A.; Sýkora, Jan; Olžyńska, Agnieszka; Brezovský, J.; Zdráhal, Z.; Damborský, J.; Hof, Martin

    2009-01-01

    Roč. 131, č. 2 (2009), s. 494-501 ISSN 0002-7863 R&D Projects: GA ČR GA203/08/0114; GA MŠk(CZ) LC06063; GA MŠk(CZ) LC06010 Institutional research plan: CEZ:AV0Z40400503 Keywords : crystallographic analysis * active-site dynamics * solvent relaxation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 8.580, year: 2009

  3. 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

  4. Gas Separation through Bilayer Silica, the Thinnest Possible Silica Membrane.

    Science.gov (United States)

    Yao, Bowen; Mandrà, Salvatore; Curry, John O; Shaikhutdinov, Shamil; Freund, Hans-Joachim; Schrier, Joshua

    2017-12-13

    Membrane-based gas separation processes can address key challenges in energy and environment, but for many applications the permeance and selectivity of bulk membranes is insufficient for economical use. Theory and experiment indicate that permeance and selectivity can be increased by using two-dimensional materials with subnanometer pores as membranes. Motivated by experiments showing selective permeation of H 2 /CO mixtures through amorphous silica bilayers, here we perform a theoretical study of gas separation through silica bilayers. Using density functional theory calculations, we obtain geometries of crystalline free-standing silica bilayers (comprised of six-membered rings), as well as the seven-, eight-, and nine-membered rings that are observed in glassy silica bilayers, which arise due to Stone-Wales defects and vacancies. We then compute the potential energy barriers for gas passage through these various pore types for He, Ne, Ar, Kr, H 2 , N 2 , CO, and CO 2 gases, and use the data to assess their capability for selective gas separation. Our calculations indicate that crystalline bilayer silica, which is less than a nanometer thick, can be a high-selectivity and high-permeance membrane material for 3 He/ 4 He, He/natural gas, and H 2 /CO separations.

  5. Enhancing molecular logic through modulation of temporal and spatial constraints with quantum dot-based systems that use fluorescent (Förster) resonance energy transfer

    Science.gov (United States)

    Claussen, Jonathan C.; Algar, W. Russ; Hildebrandt, Niko; Susumu, Kimihiro; Ancona, Mario G.; Medintz, Igor L.

    2013-10-01

    Luminescent semiconductor nanocrystals or quantum dots (QDs) contain favorable photonic properties (e.g., resistance to photobleaching, size-tunable PL, and large effective Stokes shifts) that make them well-suited for fluorescence (Förster) resonance energy transfer (FRET) based applications including monitoring proteolytic activity, elucidating the effects of nanoparticles-mediated drug delivery, and analyzing the spatial and temporal dynamics of cellular biochemical processes. Herein, we demonstrate how unique considerations of temporal and spatial constraints can be used in conjunction with QD-FRET systems to open up new avenues of scientific discovery in information processing and molecular logic circuitry. For example, by conjugating both long lifetime luminescent terbium(III) complexes (Tb) and fluorescent dyes (A647) to a single QD, we can create multiple FRET lanes that change temporally as the QD acts as both an acceptor and donor at distinct time intervals. Such temporal FRET modulation creates multi-step FRET cascades that produce a wealth of unique photoluminescence (PL) spectra that are well-suited for the construction of a photonic alphabet and photonic logic circuits. These research advances in bio-based molecular logic open the door to future applications including multiplexed biosensing and drug delivery for disease diagnostics and treatment.

  6. A novel ''donor-π-acceptor'' type fluorescence probe for sensing pH: mechanism and application in vivo.

    Science.gov (United States)

    Chao, Jianbin; Wang, Huijuan; Zhang, Yongbin; Yin, Caixia; Huo, Fangjun; Song, Kailun; Li, Zhiqing; Zhang, Ting; Zhao, Yaqin

    2017-11-01

    A novel pH fluorescent probe 1-(pyren-1-yl)-3-(6-methoxypridin-3-yl)-acrylketone, (PMPA), which had a pyrene structure attached to methoxypyridine, was synthesized for monitoring extremely acidic and alkaline pH. The pH titrations indicated that PMPA displayed a remarkable emission enhancement with a pK a of 2.70 and responded linearly to minor pH fluctuations within the extremely acidic range of 1.26-3.97. Interestingly, PMPA also exhibited strong pH-dependent characteristics with pK a 9.32 and linear response to extreme-alkalinity range of 8.54-10.36. In addition, PMPA displayed a good selectivity, excellent photostability and large Stokes shift (167nm). Furthermore, the probe PMPA had excellent cell membrane permeability and was applied successfully to rapidly detect pH in living cells. pH value in these organs was closely related to many diseases, so these findings suggested that the probe had potential application in pH detecting for disease diagnosis. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Pumping Iron and Silica Bodybuilding

    Science.gov (United States)

    Mcnair, H.; Brzezinski, M. A.; Krause, J. W.; Parker, C.; Brown, M.; Coale, T.; Bruland, K. W.

    2016-02-01

    The availability of dissolved iron influences the stoichiometry of nutrient uptake by diatoms. Under nutrient replete conditions diatoms consume silicic acid and nitrate in a 1:1 ratio, this ratio increases under iron stress. Using the tracers 32Si and PDMPO, the total community and group-specific silica production rates were measured along a gradient of dissolved iron in an upwelling plume off the California coast. At each station, a control (ambient silicic acid) and +20 µM silicic acid treatment were conducted with each tracer to determine whether silicic acid limitation controlled the rate of silica production. Dissolved iron was 1.3 nmol kg-1 nearshore and decreased to 0.15 nmol kg-1 offshore. Silicic acid decreased more rapidly than nitrate, it was nearly 9 µM higher in the nearshore and 7 µM lower than nitrate in the middle of the transect where the iron concentration had decreased. The rate of diatom silica production decreased in tandem with silicic acid concentration, and silica production limitation by low silicic acid was most pronounced when iron concentrations were >0.4 nmol kg-1. The composition of the diatom assemblage shifted from Chaetoceros spp. dominated nearshore to a more sparse pennate-dominated assemblage offshore. Changes in taxa-specific silica production rates will be reported based on examination of PDMPO labeled cells using confocal microscopy.

  8. Chromo- and fluorophoric water-soluble polymers and silica particles by nucleophilic substitution reaction of poly(vinyl amine

    Directory of Open Access Journals (Sweden)

    Katja Hofmann

    2010-07-01

    Full Text Available Novel chromophoric and fluorescent carbonitrile-functionalized poly(vinyl amine (PVAm and PVAm/silica particles were synthesized by means of nucleophilic aromatic substitution of 8-oxo-8H-acenaphtho[1,2-b]pyrrol-9-carbonitrile (1 with PVAm in water. The water solubility of 1 has been mediated by 2,6-O-β-dimethylcyclodextrin or by pre-adsorption onto silica particles. Furthermore, 1 was converted with isopropylamine into the model compound 1-M. All new compounds were characterized by NMR, FTIR, UV–vis and fluorescence spectroscopy. The solvent-dependent UV–vis absorption and fluorescence emission band positions of the model compound and the carbonitrile-functionalized PVAm were studied and interpreted using the empirical Kamlet–Taft solvent parameters π* (dipolarity/polarizability, α (hydrogen-bond donating capacity and β (hydrogen-accepting ability in terms of the linear solvation energy relationship (LSER. The solvent-independent regression coefficients a, b and s were determined using multiple linear correlation analysis. It is shown, that the chains of the polymer have a significant influence on the solvatochromic behavior of 1-P. The structure of the carbonitrile 1-Si bound to polymer-modified silica particles was studied by means of X-ray photoelectron spectroscopy (XPS and Brunauer–Emmett–Teller (BET measurements. Fluorescent silica particles were obtained as shown by fluorescence spectroscopy with a diffuse reflectance technique.

  9. Silica nanoparticle stability in biological media revisited.

    Science.gov (United States)

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

    2018-01-09

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

  10. Development of silica RO membranes

    International Nuclear Information System (INIS)

    Ikeda, Ayumi; Kawamoto, Takashi; Matsuyama, Emi; Utsumi, Keisuke; Nomura, Mikihiro; Sugimoto, Masaki; Yoshikawa, Masato

    2012-01-01

    Silica based membranes have been developed by using a counter diffusion CVD method. Effects of alkyl groups in the silica precursors and deposition temperatures had investigated in order to control pore sizes of the silica membranes. In this study, this type of a silica membrane was applied for RO separation. Effects of silica sources, deposition temperatures and post treatments had been investigated. Tetramethoxysilane (TMOS), Ethyltrimethoxysilane (ETMOS) and Phenyltrimethoxysilane (PhTMOS) were used as silica precursors. A counter diffusion CVD method was carried out for 90 min at 270 - 600degC on γ-alumina capillary substrates (effective length: 50 mm, φ: 4 nm: NOK Co.). O 3 or O 2 was introduced into the inside of the substrate at the O 2 rate of 0.2 L min -1 . Ion beam irradiation was carried out for a post treatment using Os at 490 MeV for 1.0 x 10 10 ions cm -2 or 3.0 x 10 10 ions cm -2 . Single gas permeance was measured by using H 2 , N 2 and SF 6 . RO tests were employed at 3.0 or 5.4 MPa for 100 mg L -1 of feed NaCl solution. First, effects of the silica sources were investigated. The total fluxes increased by increasing N 2 permeance through the silica membrane deposited by ETMOS. The maximum NaCl rejection was 28.2% at 12.2 kg m -2 h -1 of the total flux through the membrane deposited at 270degC. N 2 permeance was 9.6 x 10 -9 mol m -2 s -1 Pa -1 . While, total fluxes through the membrane deposited by using PhTMOS were smaller than those through the ETMOS membranes. The phenyl groups for the PhTMOS membrane must be important for the hydrophobic properties through the membrane. Next, effects of ion beam irradiation were tested for the TMOS membranes. Water is difficult to permeate through the TMOS membranes due to the low N 2 permeance through the membrane (3.1 x 10 -11 mol m -2 s -1 Pa -1 ). N 2 permeance increased to 7.3 x 10 -9 mol m -2 s -1 Pa -1 by the irradiation. Irradiation amounts had little effects on N 2 permeance. However, NaCl rejections

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

    International Nuclear Information System (INIS)

    Ma Zhiya; Dosev, Dosi; Kennedy, Ian M

    2009-01-01

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

  12. Niobia-silica and silica membranes for gas separation

    NARCIS (Netherlands)

    Boffa, V.

    2008-01-01

    This thesis describes the development of ceramic membranes suitable for hydrogen separation and CO2 recovery from gaseous streams. The research work was focused on the three different parts of which gas selective ceramic membranes are composed, i.e., the microporous gas selective silica layer, the

  13. Effects of nano-silica on mechanical performance and microstructure of ultra-high performance concrete

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, T. M., E-mail: thiagomendes@utfpr.edu.br [Universidade Tecnologica Federal do Parana (UTFPR), Londrina, PR (Brazil). Departamento de Engenharia Ambiental; Repette, W.L., E-mail: wellington.repette@gmail.br [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Dept. de Engenharia Civil; Reis, P.J., E-mail: pjlondrina@yahoo.com.br [Univeridade Estadual de Londrina (UEL), PR (Brazil). Lab. de Fisica Nuclear Aplicada

    2017-07-15

    The use of nanoparticles in ultra-high strength concretes can result in a positive effect on mechanical performance of these cementitious materials. This study evaluated mixtures containing 10 and 20 wt% of silica fume, for which the optimum nano-silica content was determined, i.e. the quantity of nano-silica that resulted on the higher gain of strength. The physical characterization of raw materials was done in terms of particle size distribution, density and specific surface area. Chemical and mineralogical compositions of materials were obtained through fluorescence and X-ray diffraction. The mechanical performance was evaluated by compressive strength, flexural strength and dynamic elastic modulus measurements. The microstructural analysis of mixtures containing nano-silica was performed by X-ray diffraction, thermogravimetry, mercury intrusion porosimetry and scanning electron microscopy. Obtained results indicate an optimum content of nano-silica of 0.62 wt%, considering compressive and flexural strengths. This performance improvement was directly related to two important microstructural aspects: the packing effect and pozzolanic reaction of nano-silica. (author)

  14. 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.

  15. Effects of nano-silica on mechanical performance and microstructure of ultra-high performance concrete

    International Nuclear Information System (INIS)

    Mendes, T. M.; Repette, W.L.; Reis, P.J.

    2017-01-01

    The use of nanoparticles in ultra-high strength concretes can result in a positive effect on mechanical performance of these cementitious materials. This study evaluated mixtures containing 10 and 20 wt% of silica fume, for which the optimum nano-silica content was determined, i.e. the quantity of nano-silica that resulted on the higher gain of strength. The physical characterization of raw materials was done in terms of particle size distribution, density and specific surface area. Chemical and mineralogical compositions of materials were obtained through fluorescence and X-ray diffraction. The mechanical performance was evaluated by compressive strength, flexural strength and dynamic elastic modulus measurements. The microstructural analysis of mixtures containing nano-silica was performed by X-ray diffraction, thermogravimetry, mercury intrusion porosimetry and scanning electron microscopy. Obtained results indicate an optimum content of nano-silica of 0.62 wt%, considering compressive and flexural strengths. This performance improvement was directly related to two important microstructural aspects: the packing effect and pozzolanic reaction of nano-silica. (author)

  16. Sonochemical coating of magnetite nanoparticles with silica.

    Science.gov (United States)

    Dang, Feng; Enomoto, Naoya; Hojo, Junichi; Enpuku, Keiji

    2010-01-01

    Magnetite nanoparticles were coated with silica through the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under ultrasonic irradiation. The ultrasonic irradiation was used to prevent the agglomeration of the magnetite particles and accelerate the hydrolysis and condensation of TEOS. TEM, DLS, XRF, VSM, TG and sedimentation test were used to characterize the silica-coated magnetite particles. The dispersibility of silica-coated magnetite particles in aqueous solution was improved significantly and the agglomerate particle size was decreased to 110 nm. It was found that the agglomerate particle size of silica-coated magnetite particles was mainly decided by the coating temperature and the pH value in the silica-coating process. The weight ratio of silica in silica-coated magnetite particles was mainly decided by the pH value in the silica-coating process. The dispersibility of silica-coated magnetite particles was mainly decided by the agglomerate particle size of the suspension. The oxidation of magnetite particles in air was limited through the coated silica. The magnetism of silica-coated magnetite particles decreased slightly after silica-coating.

  17. 21 CFR 584.700 - Hydrophobic silicas.

    Science.gov (United States)

    2010-04-01

    ...) Product. Amorphous fumed hydrophobic silica or precipitated hydrophobic silica (CAS Reg. No. 68611-0944... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Hydrophobic silicas. 584.700 Section 584.700 Food... DRUGS, FEEDS, AND RELATED PRODUCTS FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE IN FEED AND...

  18. Defect-induced luminescence in sol-gel silica samples doped with Co(II) at different concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez-Sandoval, S. [Centro de Investigacion y Estudios Avanzados, Queretaro, Apdo. Postal 1-798, Queretaro, Qro. 76001 (Mexico); Estevez, M. [Fisica Aplicada y Tecnologia Avanzada, UNAM, Apdo. Postal 1-1010, Queretaro, Qro. 76000 (Mexico); Pacheco, S. [Instituto Mexicano del Petroleo, Av. 100 metros (Mexico); Vargas, S. [Fisica Aplicada y Tecnologia Avanzada, UNAM, Apdo. Postal 1-1010, Queretaro, Qro. 76000 (Mexico); Rodriguez, R. [Fisica Aplicada y Tecnologia Avanzada, UNAM, Apdo. Postal 1-1010, Queretaro, Qro. 76000 (Mexico)], E-mail: rogelior@servidor.unam.mx

    2007-12-20

    The defect-induced luminescence properties of silica samples prepared by the sol-gel method and doped with Co(II) are reported. Silica monoliths doped with different concentrations of Co(II) were laser irradiated (He-Ne 632.8 nm) producing fluorescence. However, this fluorescence is exponentially reduced with the irradiation time, to practically disappear. The rate the fluorescence decays can be well modeled with a double exponential function of the irradiation time, containing two different relaxation times; a baseline is also required to take into account some residual fluorescence. The characteristic times involved in this luminescence quenching process are in the range of seconds. This luminescence suppression can be associated to the local heating produced by the laser irradiation when focused in a small area (2 {mu}m in diameter) on the sample. This heating process reduces physical (grain boundaries, surface states) and chemical (oxygen vacancies produced by the dopant) defects in the sample.

  19. Multimodality Imaging with Silica-Based Targeted Nanoparticle Platforms

    International Nuclear Information System (INIS)

    Lewis, Jason S.

    2012-01-01

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

  20. Multimodality Imaging with Silica-Based Targeted Nanoparticle Platforms

    Energy Technology Data Exchange (ETDEWEB)

    Jason S. Lewis

    2012-04-09

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

  1. Poling of Planar Silica Waveguides

    DEFF Research Database (Denmark)

    Arentoft, Jesper; Kristensen, Martin; Jensen, Jesper Bo

    1999-01-01

    UV-written planar silica waveguides are poled using two different poling techniques, thermal poling and UV-poling. Thermal poling induces an electro-optic coefficient of 0.067 pm/V. We also demonstrate simultaneous UV-writing and UV-poling. The induced electro-optic effect shows a linear dependence...

  2. Functionalized silica materials for electrocatalysis

    Indian Academy of Sciences (India)

    To increase the efficiency of the electrocatalytic process and to increase the electrochemical accessibility of the immobilized electrocatalysts, functionalized and non-functionalized mesoporous organo-silica (MCM41-type-materials) are used in this study. These materials possess several suitable properties to be durable ...

  3. Silica-Coated Liposomes for Insulin Delivery

    Directory of Open Access Journals (Sweden)

    Neelam Dwivedi

    2010-01-01

    Full Text Available Liposomes coated with silica were explored as protein delivery vehicles for their enhanced stability and improved encapsulation efficiency. Insulin was encapsulated within the fluidic phosphatidylcholine lipid vesicles by thin film hydration at pH 2.5, and layer of silica was formed above lipid bilayer by acid catalysis. The presence of silica coating and encapsulated insulin was identified using confocal and electron microscopy. The native state of insulin present in the formulation was evident from Confocal Micro-Raman spectroscopy. Silica coat enhances the stability of insulin-loaded delivery vehicles. In vivo study shows that these silica coated formulations were biologically active in reducing glucose levels.

  4. Photoluminescence of carbon dots from mesoporous silica

    Science.gov (United States)

    Nelson, D. K.; Razbirin, B. S.; Starukhin, A. N.; Eurov, D. A.; Kurdyukov, D. A.; Stovpiaga, E. Yu; Golubev, V. G.

    2016-09-01

    Photophysical properties of carbon dots were investigated under various excitation conditions and over a wide temperature region - from room to liquid helium temperatures. The carbon dots (CDs) were synthesized using mesoporous silica particles as a reactor and (3-aminopropyl)triethoxysilane (APTES) as a precursor. The photoluminescence spectra of CDs exhibit a strong dependence on the excitation wavelength and demonstrate a significant inhomogeneous broadening. Lowering sample temperature reveals the doublet structure of the spectra, which is associated with the vibronic structure of radiative transitions. The vibration energy ∼1200 cm-1 is close to the energy of Csbnd O stretching vibration. Long-lived phosphorescence of carbon dots with its decay time ∼0.2 s at T = 80 K was observed. The fluorescence and phosphorescence spectra are shown to be spectrally separated. The long-lived component of the emission was ascribed to optically forbidden triplet-singlet transitions. The value of the singlet-triplet splitting was found to be about 0.3 eV. Photo-induced polarization of the luminescence of carbon dots was revealed. The degree of the linear polarization is dependent on the wavelengths of both excitation and emitted light. The effect indicates a hidden anisotropy of optical dipole transitions in the dots and demonstrates the loss of the dipole orientation during the electron energy relaxation.

  5. Improving colloidal properties of quantum dots with combined silica and polymer coatings for in vitro immuofluorenscence assay

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Bingbo [Tongji University, Institute for Advanced Materials and Nano Biomedicine (China); Xing Da [South China Normal University, MOE Key Laboratory of Laser Life Science (China); Lin Chao; Guo Fangfang; Zhao Peng [Tongji University, Institute for Advanced Materials and Nano Biomedicine (China); Wen Xuejun [Clemson University, Clemson-MUSC Bioengineering Program, Department of Bioengineering (United States); Bao Zhihao, E-mail: zbao@tongji.edu.cn; Shi Donglu [Tongji University, Institute for Advanced Materials and Nano Biomedicine (China)

    2011-06-15

    Semiconductor quantum dots (QDs) are promising fluorescence probes for immuofluorescence assay in the biological applications. However, water solubilization and non-specific binding are two critical issues to be addressed for the practical uses. Here, we reported a new type of QDs with combined silica and polymer coating. QDs with excellent colloidal properties were prepared via carboxylation of the amino groups on the surface of silica-coated QDs by reacting with multi-carboxyl poly (acrylic acid) (PAA). Hydrodynamic size of PAA-functionalized silica-coated QDs was around 40 nm. They were highly fluorescent (about 47.8% quantum yield). No precipitate of QDs was observed after 3 month storage at 4 Degree-Sign C. When cancer cells (HeLa) were used, the functionalized QDs exhibited little or no non-specific cellular binding. The results from in vitro experiments indicated that PAA-functionalized silica-coated QDs-antibody bioconjugates had excellent antigen-capture ability and exhibited little or no non-specific binding to polystyrene spheres which were used to immobilize the antigen for immuoflurescence assay. The PAA-functionalized silica-coated QDs with improved colloidal properties could serve as excellent alternative fluorescent probes for biodetection.

  6. Novel fluorescence adjustable photonic crystal materials

    Science.gov (United States)

    Zhu, Cheng; Liu, Xiaoxia; Ni, Yaru; Fang, Jiaojiao; Fang, Liang; Lu, Chunhua; Xu, Zhongzi

    2017-11-01

    Novel photonic crystal materials (PCMs) with adjustable fluorescence were fabricated by distributing organic fluorescent powders of Yb0.2Er0.4Tm0.4(TTA)3Phen into the opal structures of self-assembled silica photonic crystals (PCs). Via removing the silica solution in a constant speed, PCs with controllable thicknesses and different periodic sizes were obtained on glass slides. Yb0.2Er0.4Tm0.4(TTA)3Phen powders were subsequently distributed into the opal structures. The structures and optical properties of the prepared PCMs were investigated. Finite-difference-time-domain (FDTD) calculation was used to further analyze the electric field distributions in PCs with different periodic sizes while the relation between periodic sizes and fluorescent spectra of PCMs was discussed. The results showed that the emission color of the PCMs under irradiation of 980 nm laser can be easily adjusted from green to blue by increasing the periodic size from 250 to 450 nm.

  7. Testing Silica Fume-Based Concrete Composites under Chemical and Microbiological Sulfate Attacks

    Directory of Open Access Journals (Sweden)

    Adriana Estokova

    2016-04-01

    Full Text Available Current design practices based on descriptive approaches to concrete specification may not be appropriate for the management of aggressive environments. In this study, the durability of cement-based materials with and without the addition of silica fume, subjected to conditions that leach calcium and silicon, were investigated. Chemical corrosion was simulated by employing various H2SO4 and MgSO4 solutions, and biological corrosion was simulated using Acidithiobacillus sp. bacterial inoculation, leading to disrupted and damaged surfaces; the samples’ mass changes were studied following both chemical and biological attacks. Different leaching trends were observed via X-ray fluorescence when comparing chemical with biological leaching. Lower leaching rates were found for concrete samples fortified with silica fume than those without silica fume. X-ray diffraction and scanning electron microscopy confirmed a massive sulfate precipitate formation on the concrete surface due to bacterial exposure.

  8. Liquid Phase Deposition of Silica on the Hexagonally Close-Packed Monolayer of Silica Spheres

    Directory of Open Access Journals (Sweden)

    Seo Young Yoon

    2013-01-01

    Full Text Available Liquid phase deposition is a method used for the nonelectrochemical production of polycrystalline ceramic films at low temperatures, most commonly silicon dioxide films. Herein, we report that silica spheres are organized in a hexagonal close-packed array using a patterned substrate. On this monolayer of silica spheres, we could fabricate new nanostructures in which deposition and etching compete through a modified LPD reaction. In the early stage, silica spheres began to undergo etching, and then, silica bridges between the silica spheres appeared by the local deposition reaction. Finally, the silica spheres and bridges disappeared completely. We propose the mechanism for the formation of nanostructure.

  9. Silica aerogel and space astrophysics

    International Nuclear Information System (INIS)

    Koch-Miramond, L.

    1985-09-01

    Silica aerogels have been produced in large and transparent blocks for space astrophysics experiments since the beginning of the 1970's. They were used in cosmic ray experiments on board balloons by the Saclay group. A new space venture where aerogel Cerenkov radiators will play a decisive role is currently being prepared by a large collaboration of European and US Institutes. It will be part of the so-called International Solar Polar Mission (ISPM) which will explore the heliosphere over the full range of solar latitudes from the ecliptic (equatorial) plane to the magnetic poles of the sun. Comments on properties and long term behaviour of silica aerogel cerenkov radiators in space environment are given

  10. Comparison of Cherenkov excited fluorescence and phosphorescence molecular sensing from tissue with external beam irradiation.

    Science.gov (United States)

    Lin, Huiyun; Zhang, Rongxiao; Gunn, Jason R; Esipova, Tatiana V; Vinogradov, Sergei; Gladstone, David J; Jarvis, Lesley A; Pogue, Brian W

    2016-05-21

    Ionizing radiation delivered by a medical linear accelerator (LINAC) generates Cherenkov emission within the treated tissue. A fraction of this light, in the 600-900 nm wavelength region, propagates through centimeters of tissue and can be used to excite optical probes in vivo, enabling molecular sensing of tissue analytes. The success of isolating the emission signal from this Cherenkov excitation background is dependent on key factors such as: (i) the Stokes shift of the probe spectra; (ii) the excited state lifetime; (iii) the probe concentration; (iv) the depth below the tissue surface; and (v) the radiation dose used. Previous studies have exclusively focused on imaging phosphorescent dyes, rather than fluorescent dyes. However there are only a few biologically important phosphorescent dyes and yet in comparison there are thousands of biologically relevant fluorescent dyes. So in this study the focus was a study of efficacy of Cherenkov-excited luminescence using fluorescent commercial near-infrared probes, IRDye 680RD, IRDye 700DX, and IRDye 800CW, and comparing them to the well characterized phosphorescent probe Oxyphor PtG4, an oxygen sensitive dye. Each probe was excited by Cherenkov light from a 6 MV external radiation beam, and measured in continuous wave or time-gated modes. The detection was performed by spectrally resolving the luminescence signals, and measuring them with spectrometer-based separation on an ICCD detector. The results demonstrate that IRDye 700DX and PtG4 allowed for the maximal signal to noise ratio. In the case of the phosphorescent probe, PtG4, with emission decays on the microsecond (μs) time scale, time-gated acquisition was possible, and it allowed for higher efficacy in terms of the probe concentration and detection depth. Phantoms containing the probe at 5 mm depth could be detected at concentrations down to the nanoMolar range, and at depths into the tissue simulating phantom near 3 cm. In vivo studies showed that 5

  11. Silica Nanofiber Combat Hemostat (SINCH)

    Science.gov (United States)

    2008-10-13

    1.5mg 0.6 65 205 High aspect ratio silica fibers (30um x 60nm) 9mg 0.63 58.9 140 Kaolin (TEG control) 0.2mg n/a 59.8 155 TiO2 high aspect ratio...high surface area to volume ratio and thus the material is difficult to handle in an uncontrolled environment. It is easily dispersed and is not easy

  12. Incorporation of Znq2 complexes into mesoporous silica and their transparent polymer luminescent nanocomposites

    International Nuclear Information System (INIS)

    Du Yaying; Fu Yuqin; Shi Yongli; Lue Xiaodan; Lue Changli; Su Zhongmin

    2009-01-01

    Znq 2 -functionalized colloidal mesoporous silicas (Znq 2 -CMS)/polymer transparent nanocomposites were prepared by in situ bulk polymerization. CMS nanoparticles or nanorods with hydroxyl-, mercapto- and sulfonic-functionalized interiors were obtained by different synthetic routes in the nanosize dimensions between 50 and 500 nm. The luminescent Znq 2 complex was successfully introduced in the pores of different mesoporous silicas by chemical adsorption as the driving force. The different internal circumstances of mesoporous silicas had an obvious effect on the luminescence and lifetime of Znq 2 complex. The transparent fluorescent nanocomposites were fabricated from different Znq 2 -CMS and suitable monomers. The Znq 2 -CMS were uniformly dispersed in the polymer matrix without evident aggregation. The photoluminescence properties of Znq 2 -CMS in the transparent matrix exhibited a dependence on the inner surrounding of CMS due to the interaction between Znq 2 -CMS and polymers. The maximum emission peak of the nanocomposites had a red-shift of 28 nm as compared to pure Znq 2 -CMS. - Graphical abstract: Znq 2 -functionalized colloidal mesoporous silicas (Znq 2 -CMS)/polymer transparent fluorescent nanocomposites were prepared by in situ bulk polymerization. The figure shows the synthetic scheme for the Znq 2 -CMS and their transparent bulk nanocomposites.

  13. Quantum efficiency of silica-coated rare-earth doped yttrium silicate

    International Nuclear Information System (INIS)

    Cervantes-Vásquez, D.; Contreras, O.E.; Hirata, G.A.

    2013-01-01

    The photoluminescent properties of rare earth-activated white-emitting Y 2 SiO 5 :Ce,Tb nanocrystalline phosphor prepared by two different methods, pressure-assisted combustion synthesis and sol–gel, were studied. The synthesized phosphor samples were post-annealed at 1373 K and 1623 K in order to obtain the X1-Y 2 SiO 5 and X2-Y 2 SiO 5 phases, respectively, which were confirmed by X-ray diffraction measurements. Photoluminescence analysis showed the contribution of two blue-emission bands within the 380–450 nm region originating from 5d–4f transitions in Ce 3+ ions and a well-defined green emission of Tb 3+ ions located at 545 nm corresponding to 5 D 4 → 7 F 5 electronic transitions. Thereafter, Y 2 SiO 5 :Ce,Tb powders were coated with colloidal silica in order to investigate the effect of silica coatings on their luminescent properties. Absolute fluorescence quantum efficiency measurements were carefully performed, which revealed an increase of 12% of efficiency in coated compared with bare-Y 2 SiO 5 :Ce,Tb phosphor. -- Highlights: • Y 2 SiO 5 :Ce,Tb phosphor powders were successfully coated with colloidal silica. • Post-annealing treatments improved the quantum efficiency of silica-coated Y 2 SiO 5 :Ce,Tb phosphors. • Absolute fluorescence quantum efficiency measurements showed an increase of 12%

  14. Silica nanoparticle-based dual imaging colloidal hybrids: cancer cell imaging and biodistribution

    Directory of Open Access Journals (Sweden)

    Lee H

    2015-08-01

    Full Text Available Haisung Lee,1 Dongkyung Sung,2 Jinhoon Kim,3 Byung-Tae Kim,3 Tuntun Wang,4 Seong Soo A An,5 Soo-Won Seo,6 Dong Kee Yi4 1Molecular Diagnostics, In Vitro Diagnostics Unit, New Business Division, SK Telecom, 2Department of Life Sciences, Graduate School of Korea University, 3Interdisciplinary Graduate Program of Biomedical Engineering, School of Medicine, Sungkyunkwan University, Samsung Medical Center, 4Department of Chemistry, Myongji University, Seoul, 5Department of Bionanotechnology, Gachon Medical Research Institute, Gachon University, Seongnam, 6Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu, Republic of Korea Abstract: In this study, fluorescent dye-conjugated magnetic resonance (MR imaging agents were investigated in T mode. Gadolinium-conjugated silica nanoparticles were successfully synthesized for both MR imaging and fluorescence diagnostics. Polyamine and polycarboxyl functional groups were modified chemically on the surface of the silica nanoparticles for efficient conjugation of gadolinium ions. The derived gadolinium-conjugated silica nanoparticles were investigated by zeta potential analysis, transmission electron microscopy, inductively coupled plasma mass spectrometry, and energy dispersive x-ray spectroscopy. MR equipment was used to investigate their use as contrast-enhancing agents in T1 mode under a 9.4 T magnetic field. In addition, we tracked the distribution of the gadolinium-conjugated nanoparticles in both lung cancer cells and organs in mice. Keywords: dual bioimaging, MR imaging, silica colloid, T1 contrast imaging, nanohybrid

  15. Detection of norovirus virus-like particles using a surface plasmon resonance-assisted fluoroimmunosensor optimized for quantum dot fluorescent labels.

    Science.gov (United States)

    Ashiba, Hiroki; Sugiyama, Yuki; Wang, Xiaomin; Shirato, Haruko; Higo-Moriguchi, Kyoko; Taniguchi, Koki; Ohki, Yoshimichi; Fujimaki, Makoto

    2017-07-15

    A highly sensitive biosensor to detect norovirus in environment is desired to prevent the spread of infection. In this study, we investigated a design of surface plasmon resonance (SPR)-assisted fluoroimmunosensor to increase its sensitivity and performed detection of norovirus virus-like particles (VLPs). A quantum dot fluorescent dye was employed because of its large Stokes shift. The sensor design was optimized for the CdSe-ZnS-based quantum dots. The optimal design was applied to a simple SPR-assisted fluoroimmunosensor that uses a sensor chip equipped with a V-shaped trench. Excitation efficiency of the quantum dots, degree of electric field enhancement by SPR, and intensity of autofluorescence of a substrate of the sensor chip were theoretically and experimentally evaluated to maximize the signal-to-noise ratio. As the result, an excitation wavelength of 390nm was selected to excite SPR on an Al film of the sensor chip. The sandwich assay of norovirus VLPs was performed using the designed sensor. Minimum detectable concentration of 0.01ng/mL, which corresponds to 100 virus-like particles included in the detection region of the V-trench, was demonstrated. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  16. Preparation and fluorescent recognition properties for fluoride of a nanostructured covalently bonded europium hybrid material

    Institute of Scientific and Technical Information of China (English)

    余旭东; 李景印; 李亚娟; 耿丽君; 甄小丽; 于涛

    2015-01-01

    A novel covalently bonded Eu3+-based silica hybrid material was designed and its spectrophotometric anion sensing prop-erty was studied. The fluorescent receptor (europium complex) was covalently grafted to the silica matrix via a sol-gel approach. FTIR, UV-vis spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescent spectra were characterized, and the results revealed that the hybrid material with nanosphere structure displayed excellent photophysical property. In addition, the selective anion sensing property of the hybrid material was studied by UV-vis and fluorescence spectra. The results showed that the hybrid material exhibited a smart response with fluoride anions.

  17. Using STED and ELSM confocal microscopy for a better knowledge of fused silica polished glass interface

    International Nuclear Information System (INIS)

    Catrin, Rodolphe; Neauport, Jerome; Taroux, Daniel; Corbineau, Thomas; Cormont, Philippe; Maunier, Cedric; Legros, Philippe

    2013-01-01

    Characteristics and nature of close surface defects existing in fused silica polished optical surfaces were explored. Samples were deliberately scratched using a modified polishing process in presence of different fluorescent dyes. Various techniques including Epi-fluorescence Laser Scanning Mode (ELSM) or Stimulated Emission Depletion (STED) confocal microscopy were used to measure and quantify scratches that are sometimes embedded under the polished layer. We show using a nondestructive technique that depth of the modified region extends far below the surface. Moreover cracks of 120 nm width can be present ten micrometers below the surface. (authors)

  18. Functionalization of mesoporous silica membrane with a Schiff base fluorophore for Cu(II) ion sensing

    Energy Technology Data Exchange (ETDEWEB)

    Chen Xiaotong [Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku 980-8578, Sendai, Miyagi Prefecture (Japan); Department of Chemistry, Tsinghua University, Beijing 100084 (China); Yamaguchi, Akira [College of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512 (Japan); Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Tokai, Ibaraki 319-1106 (Japan); Namekawa, Manato [Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku 980-8578, Sendai, Miyagi Prefecture (Japan); Kamijo, Toshio [Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku 980-8578, Sendai, Miyagi Prefecture (Japan); Tsuruoka National College of Technology, Aza-Sawada, Tsuruoka 997-8511 (Japan); Teramae, Norio, E-mail: teramae@m.tohoku.ac.jp [Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku 980-8578, Sendai, Miyagi Prefecture (Japan); Tong, Aijun, E-mail: tongaj@mail.tsinghua.edu.cn [Department of Chemistry, Tsinghua University, Beijing 100084 (China)

    2011-06-24

    Graphical abstract: Highlights: > A hybrid mesoporous membrane (SB-HMM) functionalized by Schiff base fluorophores was fabricated. > SB-HMM showed strong fluorescence with aggregation-induced emission enhancement properties. > SB-HMM was applicable for the detection of Cu(II) in an aqueous solution with good reversibility and reproducibility. - Abstract: A Schiff base (SB) immobilized hybrid mesoporous silica membrane (SB-HMM) was prepared by immobilizing a Schiff base onto the pore surface of mesoporous silica (pore size = 3.1 nm) embedded in the pores of a porous anodic alumina membrane. In contrast to the non-fluorescent analogous SB molecule in homogeneous solutions, SB-HMM exhibited intense fluorescence due to emission enhancement caused by aggregation of SB groups on the pore surface. The high quantum efficiency of the surface SB groups allows SB-HMM to function as a fluorescent sensor for Cu(II) ions in an aqueous solution with good sensitivity, selectivity and reproducibility. Under the optimal conditions described, the linear ranges of fluorescence intensity for Cu(II) are 1.2-13.8 (M (R{sup 2} = 0.993) and 19.4-60 (R{sup 2} = 0.992) (M. The limit of detection for Cu(II) is 0.8 {mu}M on basis of the definition by IUPAC (C{sub LOD} = 3.3S{sub b}/m).

  19. Ultra-small dye-doped silica nanoparticles via modified sol-gel technique

    Science.gov (United States)

    Riccò, R.; Nizzero, S.; Penna, E.; Meneghello, A.; Cretaio, E.; Enrichi, F.

    2018-05-01

    In modern biosensing and imaging, fluorescence-based methods constitute the most diffused approach to achieve optimal detection of analytes, both in solution and on the single-particle level. Despite the huge progresses made in recent decades in the development of plasmonic biosensors and label-free sensing techniques, fluorescent molecules remain the most commonly used contrast agents to date for commercial imaging and detection methods. However, they exhibit low stability, can be difficult to functionalise, and often result in a low signal-to-noise ratio. Thus, embedding fluorescent probes into robust and bio-compatible materials, such as silica nanoparticles, can substantially enhance the detection limit and dramatically increase the sensitivity. In this work, ultra-small fluorescent silica nanoparticles (NPs) for optical biosensing applications were doped with a fluorescent dye, using simple water-based sol-gel approaches based on the classical Stöber procedure. By systematically modulating reaction parameters, controllable size tuning of particle diameters as low as 10 nm was achieved. Particles morphology and optical response were evaluated showing a possible single-molecule behaviour, without employing microemulsion methods to achieve similar results. [Figure not available: see fulltext.

  20. MASS BALANCE OF SILICA IN STRAW FROM THE PERSPECTIVE OF SILICA REDUCTION IN STRAW PULP

    Directory of Open Access Journals (Sweden)

    Celil Atik,

    2012-06-01

    Full Text Available The high silica content of wheat straw is an important limiting factor for straw pulping. High silica content complicates processing and black liquor recovery, wears out factory installations, and lowers paper quality. Each section of wheat straw has different cells and chemical compositions and thus different silica content. In this work, the silica content of balled straw samples were examined according to their physical components, including internodes, nodes, leaves (sheath and blade, rachis, grain, other plant bodies, and other plant spikes. Mass distribution of silica was determined by a dry ashing method. Half (50.90% of the silica comes from leaves, and its mechanical separation will reduce the silica content in wheat straw pulp significantly. Destroying silica bodies by sonication will increase the strength properties of straw pulp.

  1. Silica-Coated Liposomes for Insulin Delivery

    OpenAIRE

    Neelam Dwivedi; M. A. Arunagirinathan; Somesh Sharma; Jayesh Bellare

    2010-01-01

    Liposomes coated with silica were explored as protein delivery vehicles for their enhanced stability and improved encapsulation efficiency. Insulin was encapsulated within the fluidic phosphatidylcholine lipid vesicles by thin film hydration at pH 2.5, and layer of silica was formed above lipid bilayer by acid catalysis. The presence of silica coating and encapsulated insulin was identified using confocal and electron microscopy. The native state of insulin present in the formulation was evid...

  2. Mesoporous Silica: A Suitable Adsorbent for Amines

    Directory of Open Access Journals (Sweden)

    Abdollahzadeh-Ghom Sara

    2009-01-01

    Full Text Available Abstract Mesoporous silica with KIT-6 structure was investigated as a preconcentrating material in chromatographic systems for ammonia and trimethylamine. Its adsorption capacity was compared to that of existing commercial materials, showing its increased adsorption power. In addition, KIT-6 mesoporous silica efficiently adsorbs both gases, while none of the employed commercial adsorbents did. This means that KIT-6 Mesoporous silica may be a good choice for integrated chromatography/gas sensing micro-devices.

  3. Modification of mesoporous silica SBA-15 with different organic molecules to gain chemical sensors: a review

    Directory of Open Access Journals (Sweden)

    Negar Lashgari

    2016-01-01

    Full Text Available The recognition of the biologically and environmentally important ions is of great interest in the field of chemical sensors in recent years. The fluorescent sensors as a powerful optical analytical technique for the detection of low level of various analytes such as anions and metal cations have been progressively developed due to the simplicity, cost effective, and selectivity for monitoring specific analytes in various systems. Organic-inorganic hybrid nanomaterials have important advantages as solid chemosensors and various innovative hybrid materials modified by fluorescence molecules were recently prepared. On the other hand, the homogeneous porosity and large surface area of mesoporous silica make it a promising inorganic support. SBA-15 as a two-dimensional hexagonal mesoporous silica material with stable structure, thick walls, tunable pore size, and high specific surface area is a valuable substrate for modification with different organic chelating groups. This review highlights the fluorescent chemosensors for ionic species based on modification of the mesoporous silica SBA-15 with different organic molecules, which have been recently developed from our laboratory.

  4. COOH-functionalisation of silica particles

    Energy Technology Data Exchange (ETDEWEB)

    Majewski, Peter, E-mail: peter.majewski@unisa.edu.au [School of Advanced Manufacturing and Mechanical Engineering, Mawson Institute, University of South Australia, Adelaide (Australia); Albrecht, Trent [Ian Wark Research Institute, University of South Australia, Adelaide (Australia); Weber, Siegfried [Department of Biotechnology, University of Applied Sciences, Mannheim (Germany)

    2011-09-01

    In this study COOH-functionalised silica is synthesised using phosphonateN-(phosphonomethyl)iminodiacetic acid (PMIDA) in an aqueous solution. The presence of PMIDA on the silica particles was verified using Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy and titration. Experimentally, surface concentrations of COOH functional groups of up to about 3 mmol/g{sub silica} were achieved, whereas theoretical calculation of the maximum COOH functional group concentration gave about 1 mmol/g{sub silica}. The discrepancy may be caused by PMIDA multilayer formation on the particle.

  5. Cellular membrane trafficking of mesoporous silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Fang, I-Ju [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    This dissertation mainly focuses on the investigation of the cellular membrane trafficking of mesoporous silica nanoparticles. We are interested in the study of endocytosis and exocytosis behaviors of mesoporous silica nanoparticles with desired surface functionality. The relationship between mesoporous silica nanoparticles and membrane trafficking of cells, either cancerous cells or normal cells was examined. Since mesoporous silica nanoparticles were applied in many drug delivery cases, the endocytotic efficiency of mesoporous silica nanoparticles needs to be investigated in more details in order to design the cellular drug delivery system in the controlled way. It is well known that cells can engulf some molecules outside of the cells through a receptor-ligand associated endocytosis. We are interested to determine if those biomolecules binding to cell surface receptors can be utilized on mesoporous silica nanoparticle materials to improve the uptake efficiency or govern the mechanism of endocytosis of mesoporous silica nanoparticles. Arginine-glycine-aspartate (RGD) is a small peptide recognized by cell integrin receptors and it was reported that avidin internalization was highly promoted by tumor lectin. Both RGD and avidin were linked to the surface of mesoporous silica nanoparticle materials to investigate the effect of receptor-associated biomolecule on cellular endocytosis efficiency. The effect of ligand types, ligand conformation and ligand density were discussed in Chapter 2 and 3. Furthermore, the exocytosis of mesoporous silica nanoparticles is very attractive for biological applications. The cellular protein sequestration study of mesoporous silica nanoparticles was examined for further information of the intracellular pathway of endocytosed mesoporous silica nanoparticle materials. The surface functionality of mesoporous silica nanoparticle materials demonstrated selectivity among the materials and cancer and normal cell lines. We aimed to determine

  6. Practical Hydrogen Loading of Air Silica Fibres

    DEFF Research Database (Denmark)

    Sørensen, Henrik Rokkjær; Jensen, Jesper Bevensee; Jensen, Jesper Bo Damm

    2005-01-01

    A method for hydrogen-loading air-silica optical fibres has been developed allowing out-diffusion times comparable to standard step-index fibres. Examples of the first grating written in Ge-doped air-silica fibres using a 266nm UV-laser are shown.......A method for hydrogen-loading air-silica optical fibres has been developed allowing out-diffusion times comparable to standard step-index fibres. Examples of the first grating written in Ge-doped air-silica fibres using a 266nm UV-laser are shown....

  7. Using silicon-coated gold nanoparticles to enhance the fluorescence of CdTe quantum dot and improve the sensing ability of mercury (II)

    Science.gov (United States)

    Zhu, Jian; Chang, Hui; Li, Jian-Jun; Li, Xin; Zhao, Jun-Wu

    2018-01-01

    The effect of silicon-coated gold nanoparticles with different gold core diameter and silica shell thickness on the fluorescence emission of CdTe quantum dots (QDs) was investigated. For gold nanoparticles with a diameter of 15 nm, silica coating can only results in fluorescence recover of the bare gold nanoparticle-induced quenching of QDs. However, when the size of gold nanoparticle is increased to 60 nm, fluorescence enhancement of the QDs could be obtained by silica coating. Because of the isolation of the silica shell-reduced quenching effect and local electric field effect, the fluorescence of QDs gets intense firstly and then decreases. The maximum fluorescence enhancement takes place as the silica shell has a thickness of 30 nm. This enhanced fluorescence from silicon-coated gold nanoparticles is demonstrated for sensing of Hg2 +. Under optimal conditions, the enhanced fluorescence intensity decreases linearly with the concentration of Hg2 + ranging from 0 to 200 ng/mL. The limit of detection for Hg2 + is 1.25 ng/mL. Interference test and real samples detection indicate that the influence from other metal ions could be neglected, and the Hg2 + could be specifically detected.

  8. Integrated optical measurement system for fluorescence spectroscopy in microfluidic channels

    DEFF Research Database (Denmark)

    Hübner, Jörg; Mogensen, Klaus Bo; Jørgensen, Anders Michael

    2001-01-01

    A transportable miniaturized fiber-pigtailed measurement system is presented which allows quantitative fluorescence detection in microliquid handling systems. The microliquid handling chips are made in silica on silicon technology and the optical functionality is monolithically integrated with th...... with two dyes, fluorescein, and Bodipy 650/665 X, showed good linear behavior over a wide range of concentrations. Minimally detected concentrations were 250 pM for fluorescein and 100 nM for Bodipy....

  9. Multifunctional Magnetic-fluorescent Nanocomposites for Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Rakovich Yury

    2008-01-01

    Full Text Available AbstractNanotechnology is a fast-growing area, involving the fabrication and use of nano-sized materials and devices. Various nanocomposite materials play a number of important roles in modern science and technology. Magnetic and fluorescent inorganic nanoparticles are of particular importance due to their broad range of potential applications. It is expected that the combination of magnetic and fluorescent properties in one nanocomposite would enable the engineering of unique multifunctional nanoscale devices, which could be manipulated using external magnetic fields. The aim of this review is to present an overview of bimodal “two-in-one” magnetic-fluorescent nanocomposite materials which combine both magnetic and fluorescent properties in one entity, in particular those with potential applications in biotechnology and nanomedicine. There is a great necessity for the development of these multifunctional nanocomposites, but there are some difficulties and challenges to overcome in their fabrication such as quenching of the fluorescent entity by the magnetic core. Fluorescent-magnetic nanocomposites include a variety of materials including silica-based, dye-functionalised magnetic nanoparticles and quantum dots-magnetic nanoparticle composites. The classification and main synthesis strategies, along with approaches for the fabrication of fluorescent-magnetic nanocomposites, are considered. The current and potential biomedical uses, including biological imaging, cell tracking, magnetic bioseparation, nanomedicine and bio- and chemo-sensoring, of magnetic-fluorescent nanocomposites are also discussed.

  10. Fluorescent nanodiamonds embedded in biocompatible translucent shells.

    Science.gov (United States)

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

    2014-03-26

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

  11. Highly Sensitive Ratiometric Fluorescent Sensor for Trinitrotoluene Based on the Inner Filter Effect between Gold Nanoparticles and Fluorescent Nanoparticles.

    Science.gov (United States)

    Lu, Hongzhi; Quan, Shuai; Xu, Shoufang

    2017-11-08

    In this work, we developed a simple and sensitive ratiometric fluorescent assay for sensing trinitrotoluene (TNT) based on the inner filter effect (IFE) between gold nanoparticles (AuNPs) and ratiometric fluorescent nanoparticles (RFNs), which was designed by hybridizing green emissive carbon dots (CDs) and red emissive quantum dots (QDs) into a silica sphere as a fluorophore pair. AuNPs in their dispersion state can be a powerful absorber to quench CDs, while the aggregated AuNPs can quench QDs in the IFE-based fluorescent assays as a result of complementary overlap between the absorption spectrum of AuNPs and emission spectrum of RFNs. As a result of the fact that TNT can induce the aggregation of AuNPs, with the addition of TNT, the fluorescent of QDs can be quenched, while the fluorescent of CDs would be recovered. Then, ratiometric fluorescent detection of TNT is feasible. The present IFE-based ratiometric fluorescent sensor can detect TNT ranging from 0.1 to 270 nM, with a detection limit of 0.029 nM. In addition, the developed method was successfully applied to investigate TNT in water and soil samples with satisfactory recoveries ranging from 95 to 103%, with precision below 4.5%. The simple sensing approach proposed here could improve the sensitivity of colorimetric analysis by changing the ultraviolet analysis to ratiometric fluorescent analysis and promote the development of a dual-mode detection system.

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  13. Silica gel matrix immobilized Chlorophyta hydrodictyon africanum ...

    African Journals Online (AJOL)

    Chlorophyta hydrodictyon africanum was immobilized on a silica gel matrix to improve its mechanical properties. The algae-silica gel adsorbent was used for batch sorption studies of a cationic dye, methylene blue (MB). Optimum adsorption was obtained with a dosage of 0.8 g bio sorbent. Results from sorption studies ...

  14. Nanoporous silica membranes with high hydrothermal stability

    DEFF Research Database (Denmark)

    Boffa, Vittorio; Magnacca, Giualiana; Yue, Yuanzheng

    to improve the stability of nanoporous silica structure. This work is a quantitative study on the impact of type and concentration of transition metal ions on the microporous structure and stability of amorphous silica-based membranes, which provides information on how to design chemical compositions...

  15. Biomimetic silica encapsultation of living cells

    Science.gov (United States)

    Jaroch, David Benjamin

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

  16. Chemical immobilisation of humic acid on silica

    NARCIS (Netherlands)

    Koopal, L.K.; Yang, Y.; Minnaard, A.J.; Theunissen, P.L.M.; Riemsdijk, W.H. van

    1998-01-01

    Immobilisation of purified Aldrich humic acid (PAHA) on aminopropyl silica and glutaraldehyde-activated aminopropyl silica has been investigated. In general the humic acid is bound to the solid by both physical and chemical bonds. The physically adsorbed HA can be released to a large extent at high

  17. Silica artificial opal incorporated with silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Li Wenjiang, E-mail: wjli@zju.edu.cn [Center for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang University, Joint Research Center of Photonics of the Royal Institute of Technology and Zhejiang University, Zijingang Campus, Room 210, East Building 5, Hangzhou 310058 (China); Sun Tan [Center for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang University, Joint Research Center of Photonics of the Royal Institute of Technology and Zhejiang University, Zijingang Campus, Room 210, East Building 5, Hangzhou 310058 (China)

    2009-07-15

    The silica artificial opal with a three-dimensional (3D) periodic structure was prepared using highly monodispersed silica microspheres by a force packing method in ITO glass cell. The silica artificial opal incorporated with silver nanoparticles was fabricated by the electroplating technique. The optical microscope images of the synthetic sample and the corresponding optical properties were measured after each treatment of electroplating-washing-drying circle. The transmission and reflection spectra presented a red shift, showing that the effective refractive index of the complex silver/silica opal increased after each electroplating. Combining the SEM images, it was seen that the silver nanoparticles could be directly deposited on the surface of silica spheres in the opaline structure. The silver/silica complex opal film could provide a simple way to tune the opal properties by controlling silver nanoparticles in the silica opal. The silver/silica opal crystal structures could be used for nano-photonic circuits, white-light LEDs or as photocatalysts.

  18. Silica artificial opal incorporated with silver nanoparticles

    International Nuclear Information System (INIS)

    Li Wenjiang; Sun Tan

    2009-01-01

    The silica artificial opal with a three-dimensional (3D) periodic structure was prepared using highly monodispersed silica microspheres by a force packing method in ITO glass cell. The silica artificial opal incorporated with silver nanoparticles was fabricated by the electroplating technique. The optical microscope images of the synthetic sample and the corresponding optical properties were measured after each treatment of electroplating-washing-drying circle. The transmission and reflection spectra presented a red shift, showing that the effective refractive index of the complex silver/silica opal increased after each electroplating. Combining the SEM images, it was seen that the silver nanoparticles could be directly deposited on the surface of silica spheres in the opaline structure. The silver/silica complex opal film could provide a simple way to tune the opal properties by controlling silver nanoparticles in the silica opal. The silver/silica opal crystal structures could be used for nano-photonic circuits, white-light LEDs or as photocatalysts.

  19. Refractive index dispersion law of silica aerogel

    International Nuclear Information System (INIS)

    Bellunato, T.; Calvi, M.; Matteuzzi, C.; Musy, M.; Perego, D.L.; Storaci, B.

    2007-01-01

    This paper presents measurements of the refractive index of a hygroscopic silica aerogel block at several wavelengths. The measurements, performed with a monochromator, have been compared with different parameterisations for n(λ), in order to determine the best chromaticity law for the aerogel. This is an important input for design and operation of RICH detectors with silica aerogel radiator. (orig.)

  20. Magnetic core-shell silica particles

    NARCIS (Netherlands)

    Claesson, E.M.

    2007-01-01

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

  1. M2 polarization enhances silica nanoparticle uptake by macrophages

    Directory of Open Access Journals (Sweden)

    Jessica eHoppstädter

    2015-03-01

    Full Text Available While silica nanoparticles have enabled numerous industrial and medical applications, their toxicological safety requires further evaluation. Macrophages are the major cell population responsible for nanoparticle clearance in vivo. The prevailing macrophage phenotype largely depends on the local immune status of the host. Whereas M1-polarized macrophages are considered as pro-inflammatory macrophages involved in host defense, M2 macrophages exhibit anti-inflammatory and wound-healing properties, but also promote tumor growth.We employed different models of M1 and M2 polarization: GM-CSF/LPS/IFN-gamma was used to generate primary human M1 cells and M-CSF/IL-10 to differentiate M2 monocyte-derived macrophages. PMA-differentiated THP-1 cells were polarized towards an M1 type by LPS/IFN-gamma and towards M2 by IL-10. Uptake of fluorescent silica nanoparticles (Ø 26 and 41 nm and microparticles (Ø 1.75 µm was quantified. At the concentration used (50 µg/ml, silica nanoparticles did not influence cell viability as assessed by MTT assay. Nanoparticle uptake was enhanced in M2-polarized primary human monocyte-derived macrophages compared with M1 cells, as shown by flow cytometric and microscopic approaches. In contrast, the uptake of microparticles did not differ between M1 and M2 phenotypes. M2 polarization was also associated with increased nanoparticle uptake in the macrophage-like THP-1 cell line. In accordance, in vivo polarized M2-like primary human tumor-associated macrophages (TAM obtained from lung tumors took up more nanoparticles than M1-like alveolar macrophages isolated from the surrounding lung tissue.In summary, our data indicate that the M2 polarization of macrophages promotes nanoparticle internalization. Therefore, the phenotypical differences between macrophage subsets should be taken into consideration in future investigations on nanosafety, but might also open up therapeutic perspectives allowing to specifically target M2

  2. Fabrication, Light Emission, and Magnetism of Silica Nanoparticles Hybridized with AIE Luminogens and Inorganic Nanostructures

    Science.gov (United States)

    Faisal, Mahtab

    Much research efforts have been devoted in developing new synthetic approaches for fluorescent silica nanoparticles (FSNPs) due to their potential high-technological applications. However, light emissions from most of the FSNPs prepared so far have been rather weak. This is due to the emission quenching caused by the aggregation of fluorophores in the solid state. We have observed a novel phenomenon of aggregation-induced emission (AIE): a series of propeller-shaped molecules such as tetraphenylethene (TPE) and silole are induced to emit efficiently by aggregate formation. Thus, they are ideal fluorophors for the construction of FSNPs and my thesis work focuses on the synthesis of silica nanoparticles containing these luminogens and magnetic nanostructures. Highly emissive FSNPs with core-shell structures are fabricated by surfactant-free sol-gel reactions of tetraphenylethene- (TPE) and silole-functionalized siloxanes followed by the reactions with tetraethoxysilane. The FSNPs are uniformly sized, surface-charged and colloidally stable. The diameters of the FSNPs are tunable in the range of 45--295 nm by changing the reaction conditions. Whereas their TPE and silole precursors are non-emissive, the FSNPs emit strong visible lights, thanks to the novel aggregation-induced emission characteristics of the TPE and silole aggregates in the hybrid nanoparticles. The FSNPs pose no toxicity to living cells and can be utilized to selectively image cytoplasm of HeLa cells. Applying the same tool in the presence of citrate-coated magnetite nanoparticles, uniform magnetic fluorescent silica nanoparticles (MFSNPs) with smooth surfaces are fabricated. These particles exhibit appreciable surface charges and hence good colloidal stability. They are superparamagnetic, exhibiting no hysteresis at room temperature. UV irradiation of a suspension of MFSNPs in ethanol gives strong blue and green emissions. The MFSNPs can selectively stain the cytoplasmic regions of the living cells

  3. Reviews in fluorescence 2010

    CERN Document Server

    Geddes, Chris D

    2011-01-01

    ""Reviews in Fluorescence 2010"", the seventh volume of the book serial from Springer, serves as a comprehensive collection of current trends and emerging hot topics in the field of fluorescence and closely related disciplines. It summarizes the year's progress in fluorescence and its applications, with authoritative analytical reviews specialized enough to be attractive to professional researchers, yet also appealing to the wider audience of scientists in related disciplines of fluorescence. ""Reviews in Fluorescence"" offers an essential reference material for any lab working in the fluoresc

  4. Principles of fluorescence techniques

    CERN Document Server

    2016-01-01

    Fluorescence techniques are being used and applied increasingly in academics and industry. The Principles of Fluorescence Techniques course will outline the basic concepts of fluorescence techniques and the successful utilization of the currently available commercial instrumentation. The course is designed for students who utilize fluorescence techniques and instrumentation and for researchers and industrial scientists who wish to deepen their knowledge of fluorescence applications. Key scientists in the field will deliver theoretical lectures. The lectures will be complemented by the direct utilization of steady-state and lifetime fluorescence instrumentation and confocal microscopy for FLIM and FRET applications provided by leading companies.

  5. Preparation of mesoporous silica films SBA-15 over different substrates

    International Nuclear Information System (INIS)

    Campos, V.O.; Sousa, E.M.B. de; Macedo, W.A.A.

    2010-01-01

    Mesoporous materials have been target of frequent interest due to its wide application possibilities, for example development of gas sensors, catalysis, molecules transportation, pharmaceuticals release, synthesis of auto-organized nanostructures, among others. The possibilities of application are enhanced when such materials are disposed in the form of thin and ultrathin films. In this work the preparation of mesoporous SBA-15 silica films is explored by means of the dipcoating technique of a sol-gel on different substrates (glass slides, stainless steel, copper), using the surfactant poly(ethylene glycol)-block-poly(propylene glycol)- block-poly(ethylene glycol), known as P123, a block copolymer. Synthesis parameters surfactant concentration, aging time and temperature were investigated. In this work we present the morphological and structural characterization of the prepared films, which were obtained using atomic force microscopy and x-ray fluorescence and diffraction. (author)

  6. The Pozzolanic reaction of silica fume

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    2012-01-01

    Silica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone. In the ......Silica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone....... In the present paper different aspects of the pozzolanic reaction of silica fume are investigated. These include chemical shrinkage, isothermal heat development and strength development. Key data for these are given and compared with theoretical calculations, and based on presented measurements the energy...

  7. Quantitative Analysis and Efficient Surface Modification of Silica Nanoparticles

    Directory of Open Access Journals (Sweden)

    Hak-Sung Jung

    2012-01-01

    Full Text Available Aminofunctional trialkoxysilanes such as aminopropyltrimethoxysilane (APTMS and (3-trimethoxysilylpropyldiethylenetriamine (DETAS were employed as a surface modification molecule for generating monolayer modification on the surface of silica (SiO2 nanoparticles. We were able to quantitatively analyze the number of amine functional groups on the modified SiO2 nanoparticles by acid-base back titration method and determine the effective number of amine functional groups for the successive chemical reaction by absorption measurements after treating with fluorescent rhodamine B isothiocyanate (RITC molecules. The numbers of amine sites measured by back titration were 2.7 and 7.7 ea/nm2 for SiO2-APTMS and SiO2-DETAS, respectively, while the numbers of effective amine sites measured by absorption calibration were about one fifth of the total amine sites, namely, 0.44 and 1.3 ea/nm2 for SiO2-APTMS(RITC and SiO2-DETAS(RITC, respectively. Furthermore, it was confirmed that the reactivity of amino groups on the surface-modified silica nanoparticles could be maintained in ethanol for more than 1.5 months without showing any significant differences in the reactivity.

  8. Reviews in fluorescence 2008

    CERN Document Server

    Geddes, Chris D

    2010-01-01

    This volume serves as a comprehensive collection of current trends and emerging hot topics in the field of fluorescence spectroscopy. It summarizes the year's progress in fluorescence and its applications as well as includes authoritative analytical reviews.

  9. Fluorescent optical position sensor

    Science.gov (United States)

    Weiss, Jonathan D.

    2005-11-15

    A fluorescent optical position sensor and method of operation. A small excitation source side-pumps a localized region of fluorescence at an unknown position along a fluorescent waveguide. As the fluorescent light travels down the waveguide, the intensity of fluorescent light decreases due to absorption. By measuring with one (or two) photodetectors the attenuated intensity of fluorescent light emitted from one (or both) ends of the waveguide, the position of the excitation source relative to the waveguide can be determined by comparing the measured light intensity to a calibrated response curve or mathematical model. Alternatively, excitation light can be pumped into an end of the waveguide, which generates an exponentially-decaying continuous source of fluorescent light along the length of the waveguide. The position of a photodetector oriented to view the side of the waveguide can be uniquely determined by measuring the intensity of the fluorescent light emitted radially at that location.

  10. Safe biodegradable fluorescent particles

    Science.gov (United States)

    Martin, Sue I [Berkeley, CA; Fergenson, David P [Alamo, CA; Srivastava, Abneesh [Santa Clara, CA; Bogan, Michael J [Dublin, CA; Riot, Vincent J [Oakland, CA; Frank, Matthias [Oakland, CA

    2010-08-24

    A human-safe fluorescence particle that can be used for fluorescence detection instruments or act as a safe simulant for mimicking the fluorescence properties of microorganisms. The particle comprises a non-biological carrier and natural fluorophores encapsulated in the non-biological carrier. By doping biodegradable-polymer drug delivery microspheres with natural or synthetic fluorophores, the desired fluorescence can be attained or biological organisms can be simulated without the associated risks and logistical difficulties of live microorganisms.

  11. Photoluminescence properties of Bi/Al-codoped silica optical fiber based on atomic layer deposition method

    International Nuclear Information System (INIS)

    Wen, Jianxiang; Wang, Jie; Dong, Yanhua; Chen, Na; Luo, Yanhua; Peng, Gang-ding; Pang, Fufei; Chen, Zhenyi; Wang, Tingyun

    2015-01-01

    Highlights: • We report on a new fabrication method of producing Bi/Al-codoped silica optical fibers. • There are obvious Bi-type ions absorption peaks at 520, 700 and 800 nm. • The fluorescence peaks are 1130 and 1145 nm with 489 and 705 nm excitations, respectively. • Their fluorescence lifetimes are 701 and 721 μs, respectively. • And then there are obvious fluorescence bands in 600–850 and 900–1650 nm with 532 nm pump exciting. • There is a maximum fluorescence intensity peak at 1120 nm, and its full wave at half maximum (FWHM) is approximately 180 nm. • These may mainly result from the interaction between Bi and Al ions. • The Bi/Al-codoped silica optical fibers would be used in high power or broadly tunable laser sources, and optical fiber amplifier in the optical communication fields. - Abstract: The Bi/Al-codoped silica optical fibers are fabricated by atomic layer deposition (ALD) doping technique combing with conventional modified chemical vapor deposition (MCVD) process. Bi 2 O 3 and Al 2 O 3 are induced into silica optical fiber core layer by ALD technique, with Bis (2,2,6,6-tetra-methyl-3,5-heptanedionato) Bismuth(III) (Bi(thd) 3 ) and H 2 O as Bi and O precursors, and with Al(CH 3 ) 3 (TMA) as Al precursor, respectively. The structure features and optical properties of Bi/Al-codoped silica optical fibers are investigated. Bi 2 O 3 stoichiometry is confirmed by X-ray photoelectron spectroscopy (XPS). The valence state of Bi element is +3. Concentration distribution of Si, Ge and O elements is approximately 24–33, 9 and 66 mol%, respectively, in fiber preform core and cladding layer region. Bi and Al ions have been also slightly doped approximately 150–180 and 350–750 ppm in fiber preform core, respectively. Refractive index difference of the Bi/Al-codoped fiber is approximately 0.58% using optical fiber refractive index profiler analyzer. There are obvious Bi-type ions absorption peaks at 520, 700 and 800 nm. The fluorescence

  12. Photoluminescence properties of Bi/Al-codoped silica optical fiber based on atomic layer deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Jianxiang, E-mail: wenjx@shu.edu.cn [Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072 (China); Wang, Jie; Dong, Yanhua; Chen, Na [Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072 (China); Luo, Yanhua; Peng, Gang-ding [Photonics & Optical Communications, School of Electrical Engineering & Telecommunications, University of New South Wales, Sydney 2052, NSW (Australia); Pang, Fufei; Chen, Zhenyi [Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072 (China); Wang, Tingyun, E-mail: tywang@mail.shu.edu.cn [Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072 (China)

    2015-09-15

    Highlights: • We report on a new fabrication method of producing Bi/Al-codoped silica optical fibers. • There are obvious Bi-type ions absorption peaks at 520, 700 and 800 nm. • The fluorescence peaks are 1130 and 1145 nm with 489 and 705 nm excitations, respectively. • Their fluorescence lifetimes are 701 and 721 μs, respectively. • And then there are obvious fluorescence bands in 600–850 and 900–1650 nm with 532 nm pump exciting. • There is a maximum fluorescence intensity peak at 1120 nm, and its full wave at half maximum (FWHM) is approximately 180 nm. • These may mainly result from the interaction between Bi and Al ions. • The Bi/Al-codoped silica optical fibers would be used in high power or broadly tunable laser sources, and optical fiber amplifier in the optical communication fields. - Abstract: The Bi/Al-codoped silica optical fibers are fabricated by atomic layer deposition (ALD) doping technique combing with conventional modified chemical vapor deposition (MCVD) process. Bi{sub 2}O{sub 3} and Al{sub 2}O{sub 3} are induced into silica optical fiber core layer by ALD technique, with Bis (2,2,6,6-tetra-methyl-3,5-heptanedionato) Bismuth(III) (Bi(thd){sub 3}) and H{sub 2}O as Bi and O precursors, and with Al(CH{sub 3}){sub 3} (TMA) as Al precursor, respectively. The structure features and optical properties of Bi/Al-codoped silica optical fibers are investigated. Bi{sub 2}O{sub 3} stoichiometry is confirmed by X-ray photoelectron spectroscopy (XPS). The valence state of Bi element is +3. Concentration distribution of Si, Ge and O elements is approximately 24–33, 9 and 66 mol%, respectively, in fiber preform core and cladding layer region. Bi and Al ions have been also slightly doped approximately 150–180 and 350–750 ppm in fiber preform core, respectively. Refractive index difference of the Bi/Al-codoped fiber is approximately 0.58% using optical fiber refractive index profiler analyzer. There are obvious Bi-type ions absorption

  13. Optimization of fluorescent proteins

    NARCIS (Netherlands)

    Bindels, D.S.; Goedhart, J.; Hink, M.A.; van Weeren, L.; Joosen, L.; Gadella (jr.), T.W.J.; Engelborghs, Y.; Visser, A.J.W.G.

    2014-01-01

    Nowadays, fluorescent protein (FP) variants have been engineered to fluoresce in all different colors; to display photoswitchable, or photochromic, behavior; or to show yet other beneficial properties that enable or enhance a still growing set of new fluorescence spectroscopy and microcopy

  14. Silica and lung cancer: a controversial issue.

    Science.gov (United States)

    Pairon, J C; Brochard, P; Jaurand, M C; Bignon, J

    1991-06-01

    The role of crystalline silica in lung cancer has long been the subject of controversy. In this article, we review the main experimental and epidemiological studies dealing with this problem. Some evidence for a genotoxic potential of crystalline silica has been obtained in the rare in vitro studies published to date. In vivo studies have shown that crystalline silica is carcinogenic in the rat; the tumour types appear to vary according to the route of administration. In addition, an association between carcinogenic and fibrogenic potency has been observed in various animal species exposed to crystalline silica. An excess of lung cancer related to occupational exposure to crystalline silica is reported in many epidemiological studies, regardless of the presence of silicosis. However, most of these studies are difficult to interpret because they do not correctly take into account associated carcinogens such as tobacco smoke and other occupational carcinogens. An excess of lung cancer is generally reported in studies based on silicosis registers. Overall, experimental and human studies suggest an association between exposure to crystalline silica and an excess of pulmonary malignancies. Although the data available are not sufficient to establish a clear-cut causal relationship in humans, an association between the onset of pneumoconiosis and pulmonary malignancies is probable. In contrast, experimental observations have given rise to a pathophysiological mechanism that might account for a putative carcinogenic potency of crystalline silica.

  15. Agmatine attenuates silica-induced pulmonary fibrosis.

    Science.gov (United States)

    El-Agamy, D S; Sharawy, M H; Ammar, E M

    2014-06-01

    There is a large body of evidence that nitric oxide (NO) formation is implicated in mediating silica-induced pulmonary fibrosis. As a reactive free radical, NO may not only contribute to lung parenchymal tissue injury but also has the ability to combine with superoxide and form a highly reactive toxic species peroxynitrite that can induce extensive cellular toxicity in the lung tissues. This study aimed to explore the effect of agmatine, a known NO synthase inhibitor, on silica-induced pulmonary fibrosis in rats. Male Sprague Dawley rats were treated with agmatine for 60 days following a single intranasal instillation of silica suspension (50 mg in 0.1 ml saline/rat). The results revealed that agmatine attenuated silica-induced lung inflammation as it decreased the lung wet/dry weight ratio, protein concentration, and the accumulation of the inflammatory cells in the bronchoalveolar lavage fluid. Agmatine showed antifibrotic activity as it decreased total hydroxyproline content of the lung and reduced silica-mediated lung inflammation and fibrosis in lung histopathological specimen. In addition, agmatine significantly increased superoxide dismutase (p Agmatine also reduced silica-induced overproduction of pulmonary nitrite/nitrate as well as tumor necrosis factor α. Collectively, these results demonstrate the protective effects of agmatine against the silica-induced lung fibrosis that may be attributed to its ability to counteract the NO production, lipid peroxidation, and regulate cytokine effects. © The Author(s) 2014.

  16. Metal-silica sol-gel materials

    Science.gov (United States)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  17. SCC modification by use of amorphous nano-silica

    NARCIS (Netherlands)

    Quercia Bianchi, G.; Spiesz, P.R.; Hüsken, G.; Brouwers, H.J.H.

    2014-01-01

    In this study two different types of nano-silica (nS) were applied in self-compacting concrete (SCC), both having similar particle size distributions (PSD), but produced through two different processes: fumed powder silica and precipitated silica in colloidal suspension. The influence of nano-silica

  18. Synthesis of cristobalite from silica sands of Tuban and Tanah Laut

    Science.gov (United States)

    Nurbaiti, U.; Pratapa, S.

    2018-03-01

    Synthesis of SiO2 cristobalite powders has been successfully carried out by a coprecipitation method by making use of local silica sands from districts of Tuban and Tanah Laut, Indonesia. Cristobalite is a phase of SiO2 polymorphs which can be used as a composite filler, a coating material, a surface finishing media, and structural ceramics. In the first stage of the synthesis, the as-received sands were processed by a magnetic separation, grinding, and soaking with HCl to increase the purity of silica content. X-ray fluorescence (XRF) spectroscopy showed that the atomic content of Si (excluding oxygen) in both powders reached 95.3 and 97.4%. A coprecipitation process was then performed by dissolving the silica powders in a 7M NaOH solution followed by a titration with 2M HCl to achieve a normal pH and to form a gel. Furthermore, the silica gel is washed, dried and then calcined at a temperature of between 950-1200 °C with a variation of holding time for 1, 4 dan 10 hrs to produce white powders. X-ray diffraction (XRD) data analyses showed that the powder with calcination temperature of 1150 °C for 4 hrs exhibited the highest cristobalite content of up to 95wt%. Its scanning electron microscopy (SEM) image showed that its grain morphology was relatively homogeneous.

  19. Amorphous silica from rice husk at various temperatures

    International Nuclear Information System (INIS)

    Javed, S.J.; Feroze, N.; Tajwar, S.

    2008-01-01

    Rice husk is being used as a source of energy in many heat generating system because of its high calorific value and its availability in many rice producing areas. Rice husk contains approximately 20% silica which is presented in hydrated form. This hydrated silica can be retrieved as amorphous silica under controlled thermal conditions. Uncontrolled burning of rice husk produces crystalline silica which is not reactive silica but can be used as filler in many applications. Amorphous silica is reactive silica which has better market value due to its reactive nature in process industry. The present study deals with the production of amorphous silica at various temperatures from rice husk. Various ashes were prepared in tube furnace by changing the burning temperatures for fixed time intervals and analyzed by XRD. It has been observed that for two hours calculation's of rice husk renders mostly amorphous silica at 650 degree C where as at higher temperatures crystalline silica was obtained. (author)

  20. Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tiwen [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Jia, Zhixin, E-mail: zxjia@scut.edu.cn [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Luo, Yuanfang; Jia, Demin [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Peng, Zheng [Agricultural Product Processing Research Institute, Chinese Academy of Tropical Agriculture Sciences, Zhanjiang 524001 (China)

    2015-02-15

    Highlights: • Substantiate the ring open reaction between Si-OH of silica and epoxy groups of ENR. • ENR can act as a bridge between NR and silica to enhance the interfacial interaction. • As a modifier, ENR gets the potential to be used in the tread of green tire for improving the wet skid resistance apparently. - Abstract: The epoxidized natural rubber (ENR) as an interfacial modifier was used to improve the mechanical and dynamical mechanical properties of NR/silica composites. In order to reveal the interaction mechanism between ENR and silica, the ENR/Silica model compound was prepared by using an open mill and the interfacial interaction of ENR with silica was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and stress–strain testing. The results indicated that the ring-opening reaction occurs between the epoxy groups of ENR chains and Si-OH groups on the silica surfaces and the covalent bonds are formed between two phases, which can improve the dispersion of silica in the rubber matrix and enhance the interfacial combination between rubber and silica. The ring-opening reaction occurs not only in vulcanization process but also in mixing process, meanwhile, the latter seems to be more important due to the simultaneous effects of mechanical force and temperature.

  1. Effect of silica concentration on electrical conductivity of epoxy resin-carbon black-silica nanocomposites

    International Nuclear Information System (INIS)

    Zhang Wei; Blackburn, Richard S.; Dehghani-Sanij, Abbas A.

    2007-01-01

    Electrical properties of nanocomposites are determined by the conductive paths of carbon black and influenced by a 'network' of silica. With increasing content of silica, carbon black (CB) particles are optimally dispersed, contributing to the generation of a conductive network between CB particles via direct particle contact and a tunneling effect; maximum conductivity for the epoxy resin-CB-silica nanocomposite described herein occurs at a ratio of 0.6:1.0 (SiO 2 :CB). As a non-conductive component, excessive silica will prevent electron flow, giving rise to low conductivity

  2. Cathodoluminescence microcharacterization of ballen silica in impactites

    International Nuclear Information System (INIS)

    Okumura, T.; Ninagawa, K.; Toyoda, S.; Gucsik, A.; Nishido, H.

    2009-01-01

    The ballen silica shows fairly weak (faint) CL with homogeneous feature in its grain exhibiting almost same spectral pattern with two broad band peaks at around 390 and 650 nm, which might be assigned to self-trapped excitons (STE) or an intrinsic and nonbridging oxygen hole centers (NBOHC), respectively, recognized in amorphous and crystalline silica. In addition, ballen silica from Lappajaervi crater shows bright and heterogeneous CL with a broad band centered at around 410 nm, presumably attributed to [AlO 4 /M + ] 0 centers or self-trapped excitons (STE). Micro-Raman and micro-XRD analyses show that fairly homogeneous CL part is α-quartz and heterogeneous CL part is composed of α-cristobalite and α-quartz. These indicate that ballen silica could be formed in the quenching process from relatively high temperature.

  3. Anomalous enthalpy relaxation in vitreous silica

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    2015-01-01

    scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here, we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy...... relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hyperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas...... the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica....

  4. 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

  5. Fluorescence spectra of Rhodamine 6G for high fluence excitation laser radiation

    CERN Document Server

    Hung, J; Olaizola, A M

    2003-01-01

    Fluorescence spectral changes of Rhodamine 6G in ethanol and glycerol solutions and deposited as a film on a silica surface have been studied using a wide range of pumping field fluence at 532 nm at room temperature. Blue shift of the fluorescence spectra and fluorescence quenching of the dye molecule in solution are observed at high excitation fluence values. Such effects are not reported for the film sample. The effects are interpreted as the result of population redistribution in the solute-solvent molecular system induced by the high fluence field and the fluence dependence of the radiationless decay mechanism.

  6. Microporous Silica Based Membranes for Desalination

    Directory of Open Access Journals (Sweden)

    João C. Diniz da Costa

    2012-09-01

    Full Text Available This review provides a global overview of microporous silica based membranes for desalination via pervaporation with a focus on membrane synthesis and processing, transport mechanisms and current state of the art membrane performance. Most importantly, the recent development and novel concepts for improving the hydro-stability and separating performance of silica membranes for desalination are critically examined. Research into silica based membranes for desalination has focussed on three primary methods for improving the hydro-stability. These include incorporating carbon templates into the microporous silica both as surfactants and hybrid organic-inorganic structures and incorporation of metal oxide nanoparticles into the silica matrix. The literature examined identified that only metal oxide silica membranes have demonstrated high salt rejections under a variety of feed concentrations, reasonable fluxes and unaltered performance over long-term operation. As this is an embryonic field of research several target areas for researchers were discussed including further improvement of the membrane materials, but also regarding the necessity of integrating waste or solar heat sources into the final process design to ensure cost competitiveness with conventional reverse osmosis processes.

  7. Grassy Silica Nanoribbons and Strong Blue Luminescence

    Science.gov (United States)

    Wang, Shengping; Xie, Shuang; Huang, Guowei; Guo, Hongxuan; Cho, Yujin; Chen, Jun; Fujita, Daisuke; Xu, Mingsheng

    2016-09-01

    Silicon dioxide (SiO2) is one of the key materials in many modern technological applications such as in metal oxide semiconductor transistors, photovoltaic solar cells, pollution removal, and biomedicine. We report the accidental discovery of free-standing grassy silica nanoribbons directly grown on SiO2/Si platform which is commonly used for field-effect transistors fabrication without other precursor. We investigate the formation mechanism of this novel silica nanostructure that has not been previously documented. The silica nanoribbons are flexible and can be manipulated by electron-beam. The silica nanoribbons exhibit strong blue emission at about 467 nm, together with UV and red emissions as investigated by cathodoluminescence technique. The origins of the luminescence are attributed to various defects in the silica nanoribbons; and the intensity change of the blue emission and green emission at about 550 nm is discussed in the frame of the defect density. Our study may lead to rational design of the new silica-based materials for a wide range of applications.

  8. Mesoporous Silica from Rice Husk Ash

    Directory of Open Access Journals (Sweden)

    S.A. Mandavgane

    2010-12-01

    Full Text Available Mesoporous silica is used as a raw material in several areas: in preparation of catalysts, in inks, as aconcrete hardening accelerator, as a component of detergents and soaps, as a refractory constituent etc.Sodium silicate is produced by reacting rice hull ash (RHA with aqueous NaOH and silica is precipitatedfrom the sodium silicate by acidification. In the present work, conversion of about 90% of silica containedin RHA into sodium silicate was achieved in an open system at temperatures of about 100 °C. The resultsshowed that silica obtained from RHA is mesoporous, has a large surface area and small particle size.Rice Husk is usually mixed with coal and this mixture is used for firing boilers. The RHA therefore, usuallycontains carbon particles. Activated carbon embedded on silica has been prepared using the carbon alreadypresent in RHA. This carbon shows good adsorption capacity. ©2010 BCREC UNDIP. All rights reserved(Received: 25th April 2010, Revised: 17th June 2010, Accepted: 24th June 2010[How to Cite: V.R. Shelke, S.S. Bhagade, S.A. Mandavgane. (2010. Mesoporous Silica from Rice Husk Ash. Bulletin of Chemical Reaction Engineering and Catalysis, 5 (2: 63-67. doi:10.9767/bcrec.5.2.793.63-67

  9. Mesoporous Silica from Rice Husk Ash

    Directory of Open Access Journals (Sweden)

    V.R. Shelke

    2011-01-01

    Full Text Available Mesoporous silica is used as a raw material in several areas: in preparation of catalysts, in inks, as a concrete hardening accelerator, as a component of detergents and soaps, as a refractory constituent etc. Sodium silicate is produced by reacting rice hull ash (RHA with aqueous NaOH and silica is precipitated from the sodium silicate by acidification. In the present work, conversion of about 90% of silica contained in RHA into sodium silicate was achieved in an open system at temperatures of about 100 °C. The results showed that silica obtained from RHA is mesoporous, has a large surface area and small particle size. Rice Husk is usually mixed with coal and this mixture is used for firing boilers. The RHA therefore, usually contains carbon particles. Activated carbon embedded on silica has been prepared using the carbon already present in RHA. This carbon shows good adsorption capacity. ©2010 BCREC UNDIP. All rights reserved(Received: 25th April 2010, Revised: 17th June 2010, Accepted: 24th June 2010[How to Cite: V.R. Shelke, S.S. Bhagade, S.A. Mandavgane. (2010. Mesoporous Silica from Rice Husk Ash. Bulletin of Chemical Reaction Engineering and Catalysis, 5 (2: 63-67. doi:10.9767/bcrec.5.2.793.63-67][DOI: http://dx.doi.org/10.9767/bcrec.5.2.793.63-67

  10. Capped Mesoporous Silica Nanoparticles for the Selective and Sensitive Detection of Cyanide.

    Science.gov (United States)

    Sayed, Sameh El; Licchelli, Maurizio; Martínez-Máñez, Ramón; Sancenón, Félix

    2017-10-18

    The development of easy and affordable methods for the detection of cyanide is of great significance due to the high toxicity of this anion and the potential risks associated with its pollution. Herein, optical detection of cyanide in water has been achieved by using a hybrid organic-inorganic nanomaterial. Mesoporous silica nanoparticles were loaded with [Ru(bipy) 3 ] 2+ , functionalized with macrocyclic nickel(II) complex subunits, and capped with a sterically hindering anion (hexametaphosphate). Cyanide selectively induces demetallation of nickel(II) complexes and the removal of capping anions from the silica surface, allowing the release of the dye and the consequent increase in fluorescence intensity. The response of the capped nanoparticles in aqueous solution is highly selective and sensitive towards cyanide with a limit of detection of 2 μm. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Staphylococcus aureus detection in blood samples by silica nanoparticle-oligonucleotides conjugates.

    Science.gov (United States)

    Borsa, Baris A; Tuna, Bilge G; Hernandez, Frank J; Hernandez, Luiza I; Bayramoglu, Gulay; Arica, M Yakup; Ozalp, V Cengiz

    2016-12-15

    A fast, specific and sensitive homogeneous assay for Staphylococcus aureus detection was developed by measuring the activity of secreted nuclease from the bacteria via a modified DNA oligonucleotide. As biosensor format, an effective system, Nanokeepers as previously reported, were used for triggered release of confined fluorophores, and hence specific detection of S. aureus on nuclease activity was obtained. The interference from blood components for fluorescent quantification was eliminated by a pre-purification by aptamer-functionalized silica magnetic nanoparticles. The reported assay system was exclusively formed by nucleic acid oligos and magnetic or mesoporous silica nanoparticles, that can be used on blood samples in a stepwise manner. The assay was successfully used as a sensing platform for the specific detection of S. aureus cells as low as 682 CFU in whole blood. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Grafting of polymer onto silica surface in the presence of γ-ray irradiated silica

    International Nuclear Information System (INIS)

    Tsuchida, A.; Yokoyama, R.; Takami, M.; Chen, J.; Ohta, M.; Tsubokawa, N.

    2002-01-01

    Complete text of publication follows. We have reported the graft polymerization of vinyl monomers initiated by surface radicals formed by the decomposition of azo and peroxide groups previously introduced onto the surface. In addition, the grafting of polymers onto carbon black has been reported by the reaction of polymer radicals with the surface. On the other hand, it is well known that the relatively stable radicals are generated on the surface by the γ-ray irradiation. In this paper, the grafting of polystyrene onto silica surface during the thermal polymerization of styrene in the presence of γ-ray irradiated silica, grafting mechanism and thermal stability of grafted polymer will be discussed. The grafting of polymers onto silica surface by irradiation of polymer-adsorbed silica was also investigated. Silica obtained from Mitsubishi Chemical Co., Japan was used after pulverization: the particle size was 0.037-0.088 mm. Irradiation was performed in Cs-137 source at room temperature. The silica was irradiated at 50 Gy with dose rate of 3.463 Gy/min. Into a polymerization tube, styrene and irradiated silica was charged and the polymerization was carried out under argon under stirring. The percentage of polystyrene grafting was determined from weight loss when polystyrene-grafted silica was heated at 600 deg C by a thermal analyzer. Untreated silica did not affect the thermal polymerization of styrene. On the contrary, the thermal polymerization of styrene was remarkably retarded in the presence of the irradiated silica at 60 deg C. Similar tendency was reported during the polymerization of vinyl monomers in the presence of carbon black. In the initial stage of the polymerization in the presence of the irradiated silica below 50 deg C, the polymerization was accelerated. During the polymerization in the presence of irradiated silica, polystyrene was grafted onto the surface: the percentage of grafting was 5-11%. The amount of polystyrene grafted onto silica

  13. Quantum efficiency of silica-coated rare-earth doped yttrium silicate

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes-Vásquez, D., E-mail: dcervant@cnyn.unam.mx [Centro de Investigación Científica y de Educación Superior de Ensenada, Carretera Ensenada-Tijuana No. 3918, Zona Playitas, C.P. 22860 Ensenada, B.C., México (Mexico); Contreras, O.E.; Hirata, G.A. [Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Km. 107 Carretera Tijuana-Ensenada, C.P. 22800 Ensenada, B.C., México (Mexico)

    2013-11-15

    The photoluminescent properties of rare earth-activated white-emitting Y{sub 2}SiO{sub 5}:Ce,Tb nanocrystalline phosphor prepared by two different methods, pressure-assisted combustion synthesis and sol–gel, were studied. The synthesized phosphor samples were post-annealed at 1373 K and 1623 K in order to obtain the X1-Y{sub 2}SiO{sub 5} and X2-Y{sub 2}SiO{sub 5} phases, respectively, which were confirmed by X-ray diffraction measurements. Photoluminescence analysis showed the contribution of two blue-emission bands within the 380–450 nm region originating from 5d–4f transitions in Ce{sup 3+} ions and a well-defined green emission of Tb{sup 3+} ions located at 545 nm corresponding to {sup 5}D{sub 4}→{sup 7}F{sub 5} electronic transitions. Thereafter, Y{sub 2}SiO{sub 5}:Ce,Tb powders were coated with colloidal silica in order to investigate the effect of silica coatings on their luminescent properties. Absolute fluorescence quantum efficiency measurements were carefully performed, which revealed an increase of 12% of efficiency in coated compared with bare-Y{sub 2}SiO{sub 5}:Ce,Tb phosphor. -- Highlights: • Y{sub 2}SiO{sub 5}:Ce,Tb phosphor powders were successfully coated with colloidal silica. • Post-annealing treatments improved the quantum efficiency of silica-coated Y{sub 2}SiO{sub 5}:Ce,Tb phosphors. • Absolute fluorescence quantum efficiency measurements showed an increase of 12%.

  14. Silica ecosystem for synergistic biotransformation

    Science.gov (United States)

    Mutlu, Baris R.; Sakkos, Jonathan K.; Yeom, Sujin; Wackett, Lawrence P.; Aksan, Alptekin

    2016-06-01

    Synergistical bacterial species can perform more varied and complex transformations of chemical substances than either species alone, but this is rarely used commercially because of technical difficulties in maintaining mixed cultures. Typical problems with mixed cultures on scale are unrestrained growth of one bacterium, which leads to suboptimal population ratios, and lack of control over bacterial spatial distribution, which leads to inefficient substrate transport. To address these issues, we designed and produced a synthetic ecosystem by co-encapsulation in a silica gel matrix, which enabled precise control of the microbial populations and their microenvironment. As a case study, two greatly different microorganisms: Pseudomonas sp. NCIB 9816 and Synechococcus elongatus PCC 7942 were encapsulated. NCIB 9816 can aerobically biotransform over 100 aromatic hydrocarbons, a feat useful for synthesis of higher value commodity chemicals or environmental remediation. In our system, NCIB 9816 was used for biotransformation of naphthalene (a model substrate) into CO2 and the cyanobacterium PCC 7942 was used to provide the necessary oxygen for the biotransformation reactions via photosynthesis. A mathematical model was constructed to determine the critical cell density parameter to maximize oxygen production, and was then used to maximize the biotransformation rate of the system.

  15. 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.

  16. 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.

  17. Atomic-fluorescence spectrophotometry

    International Nuclear Information System (INIS)

    Bakhturova, N.F.; Yudelevich, I.G.

    1975-01-01

    Atomic-fluorescence spectrophotometry, a comparatively new method for the analysis of trace quantities, has developed rapidly in the past ten years. Theoretical and experimental studies by many workers have shown that atomic-fluorescence spectrophotometry (AFS) is capable of achieving a better limit than atomic absorption for a large number of elements. The present review examines briefly the principles of atomic-fluorescence spectrophotometry and the types of fluorescent transition. The excitation sources, flame and nonflame atomizers, used in AFS are described. The limits of detection achieved up to the present, using flame and nonflame methods of atomization are given

  18. Fluorescence of irradiated hydrocarbons

    International Nuclear Information System (INIS)

    Gulis, I.G.; Evdokimenko, V.M.; Lapkovskij, M.P.; Petrov, P.T.; Gulis, I.M.; Markevich, S.V.

    1977-01-01

    A visible fluorescence has been found out in γ-irradiated aqueous of carbohydrates. Two bands have been distinguished in fluorescence spectra of the irradiated solution of dextran: a short-wave band lambdasub(max)=140 nm (where lambda is a wave length) at lambdasub(β)=380 nm and a long-wave band with lambdasub(max)=540 nm at lambdasub(β)=430 nm. A similar form of the spectrum has been obtained for irradiated solutions of starch, amylopectin, lowmolecular glucose. It has been concluded that a macromolecule of polysaccharides includes fluorescent centres. A relation between fluorescence and α-oxiketon groups formed under irradiation has been pointed out

  19. Synthesis and characterization of monodisperse, mesoporous, and magnetic sub-micron particles doped with a near-infrared fluorescent dye

    International Nuclear Information System (INIS)

    Le Guevel, Xavier; Nooney, Robert; McDonagh, Colette; MacCraith, Brian D.

    2011-01-01

    Recently, multifunctional silica nanoparticles have been investigated extensively for their potential use in biomedical applications. We have prepared sub-micron monodisperse and stable multifunctional mesoporous silica particles with a high level of magnetization and fluorescence in the near infrared region using an one-pot synthesis technique. Commercial magnetite nanocrystals and a conjugated-NIR-dye were incorporated inside the particles during the silica condensation reaction. The particles were then coated with polyethyleneglycol to stop aggregation. X-ray diffraction, N 2 adsorption analysis, TEM, fluorescence and absorbance measurements were used to structurally characterize the particles. These mesoporous silica spheres have a large surface area (1978 m 2 /g) with 3.40 nm pore diameter and a high fluorescence in the near infrared region at λ=700 nm. To explore the potential of these particles for drug delivery applications, the pore accessibility to hydrophobic drugs was simulated by successfully trapping a hydrophobic ruthenium dye complex inside the particle with an estimated concentration of 3 wt%. Fluorescence imaging confirmed the presence of both NIR dye and the post-grafted ruthenium dye complex inside the particles. These particles moved at approximately 150 μm/s under the influence of a magnetic field, hence demonstrating the multifunctionality and potential for biomedical applications in targeting and imaging. - Graphical Abstract: Hydrophobic fluorescent Ruthenium complex has been loaded into the mesopores as a surrogate drug to simulate drug delivery and to enhance the multifunctionality of the magnetic NIR emitting particles. Highlights: → Monodisperse magnetic mesoporous silica particles emitting in the near infrared region are obtained in one-pot synthesis. → We prove the capacity of such particles to uptake hydrophobic dye to mimic drug loading. → Loaded fluorescent particles can be moved under a magnetic field in a microfluidic

  20. Structure and Properties of LENRA/ Silica Composite

    International Nuclear Information System (INIS)

    Mahathir Mohamed; Dahlan Mohd

    2010-01-01

    The sol-gel reaction using tetra ethoxysilane (TEOS) was conducted for modified natural rubber (NR) matrix to obtain in situ generated NR/ silica composite. The present of acrylate group in the modified NR chain turns the composite into radiation-curable. The maximum amount of silica generated in the matrix was 50 p hr by weight. During the sol-gel process the inorganic mineral was deposited in the rubber matrix forming hydrogen bonding between organic and inorganic phases. The composites obtained were characterized by various techniques including thermogravimetric analysis and infrared spectrometry to study their molecular structure. The increase in mechanical properties was observed for low silica contents ( 30 p hr) where more silica were generated, agglomerations were observed at the expense of the mechanical properties. From the DMTA data, it shows an increase of the interaction between the rubber and silica phases up to 30 p hr TEOS. Structure and morphology of the heterogeneous system were analyzed by transmission electron microscopy. The average particle sizes of between 150 nm to 300 nm were achieved for the composites that contain less than 20 p hr of TEOS. (author)

  1. Membranes and Fluorescence microscopy

    DEFF Research Database (Denmark)

    Bagatolli, Luis

    2009-01-01

    Fluorescence spectroscopy-based techniques using conventional fluorimeters have been extensively applied since the late 1960s to study different aspects of membrane-related phenomena, i.e., mainly relating to lipid-lipid and lipid-protein (peptide) interactions. Even though fluorescence...

  2. Multimodal fluorescence imaging spectroscopy

    NARCIS (Netherlands)

    Stopel, Martijn H W; Blum, Christian; Subramaniam, Vinod; Engelborghs, Yves; Visser, Anthonie J.W.G.

    2014-01-01

    Multimodal fluorescence imaging is a versatile method that has a wide application range from biological studies to materials science. Typical observables in multimodal fluorescence imaging are intensity, lifetime, excitation, and emission spectra which are recorded at chosen locations at the sample.

  3. Simultaneous determination of Hg, Pb, As, Cu, Zn and Ni in natural waters (with humic material) by energy dispersive X-ray fluorescence

    International Nuclear Information System (INIS)

    Morales S, E.A.; Zepeda L, E.

    1988-05-01

    Standardization of a method for simultaneous quantification of Hg, Pb, As, Cu, Zn and Ni in natural waters with humic acid contents was carried out. APDC for complexing free ions and silica gel as adsorber of metallic humates and further filtration were employed. X-ray fluorescence analysis was performed on filters. Good results were found for silica-gel as adsorber. Detection limits of 4 nanograms/milliliter were determined. (author)

  4. Multifunctional nanomedicine with silica: Role of silica in nanoparticles for theranostic, imaging, and drug monitoring.

    Science.gov (United States)

    Chen, Fang; Hableel, Ghanim; Zhao, Eric Ruike; Jokerst, Jesse V

    2018-07-01

    The idea of multifunctional nanomedicine that enters the human body to diagnose and treat disease without major surgery is a long-standing dream of nanomaterials scientists. Nanomaterials show incredible properties that are not found in bulk materials, but achieving multi-functionality on a single material remains challenging. Integrating several types of materials at the nano-scale is critical to the success of multifunctional nanomedicine device. Here, we describe the advantages of silica nanoparticles as a tool for multifunctional nano-devices. Silica nanoparticles have been intensively studied in drug delivery due to their biocompatibility, degradability, tunable morphology, and ease of modification. Moreover, silica nanoparticles can be integrated with other materials to obtain more features and achieve theranostic capabilities and multimodality for imaging applications. In this review, we will first compare the properties of silica nanoparticles with other well-known nanomaterials for bio-applications and describe typical routes to synthesize and integrate silica nanoparticles. We will then highlight theranostic and multimodal imaging application that use silica-based nanoparticles with a particular interest in real-time monitoring of therapeutic molecules. Finally, we will present the challenges and perspective on future work with silica-based nanoparticles in medicine. Copyright © 2018 Elsevier Inc. All rights reserved.

  5. Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

    Science.gov (United States)

    Xu, Tiwen; Jia, Zhixin; Luo, Yuanfang; Jia, Demin; Peng, Zheng

    2015-02-01

    The epoxidized natural rubber (ENR) as an interfacial modifier was used to improve the mechanical and dynamical mechanical properties of NR/silica composites. In order to reveal the interaction mechanism between ENR and silica, the ENR/Silica model compound was prepared by using an open mill and the interfacial interaction of ENR with silica was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and stress-strain testing. The results indicated that the ring-opening reaction occurs between the epoxy groups of ENR chains and Si-OH groups on the silica surfaces and the covalent bonds are formed between two phases, which can improve the dispersion of silica in the rubber matrix and enhance the interfacial combination between rubber and silica. The ring-opening reaction occurs not only in vulcanization process but also in mixing process, meanwhile, the latter seems to be more important due to the simultaneous effects of mechanical force and temperature.

  6. 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

  7. Influence of Nano Silica on Alkyd Films

    DEFF Research Database (Denmark)

    Nikolic, Miroslav

    . The present work centers on the reinforcement of alkyd binders emulsified in water and used in exterior wood coatings with nano silica. Raman spectroscopy was used throughout the study to maintain the reproducibility of results as it was found that colloidal nano silica can increase or decrease the speed...... of alkyd curing affecting the tested mechanical properties. Hydrophilic, colloidal nano silica was seen to have limited effect in improving the mechanical properties due to problems in properly dispersing and attaining good surface interactions with the hydrophobic alkyd polymer. Efforts in increasing...... the interactions with the alkyd polymer while keeping the nano filler stable in the water phase did not show further improvements of mechanical properties. The best results in respect to mechanical properties, as measured under static and dynamic loading, were obtained with the use of hexamethyldisilazane treated...

  8. Study of the pluronic-silica interaction in synthesis of mesoporous silica under mild acidic conditions.

    Science.gov (United States)

    Sundblom, Andreas; Palmqvist, Anders E C; Holmberg, Krister

    2010-02-02

    The interaction between silica and poly(ethylene oxide) (PEO) in water may appear trivial and it is generally stated that hydrogen bonding is responsible for the attraction. However, a literature search shows that there is not a consensus with respect to the mechanism behind the attractive interaction. Several papers claim that only hydrogen bonding is not sufficient to explain the binding. The silica-PEO interaction is interesting from an academic perspective and it is also exploited in the preparation of mesoporous silica, a material of considerable current interest. This study concerns the very early stage of synthesis of mesoporous silica under mild acidic conditions, pH 2-5, and the aim is to shed light on the interaction between silica and the PEO-containing structure directing agent. The synthesis comprises two steps. An organic silica source, tetraethylorthosilicate (TEOS), is first hydrolyzed and Pluronic P123, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymer, is subsequently added at different time periods following the hydrolysis of TEOS. It is shown that the interaction between the silica and the Pluronic is dependent both on the temperature and on the time between onset of TEOS hydrolysis and addition of the copolymer. The results show that the interaction is mainly driven by entropy. The effect of the synthesis temperature and of the time between hydrolysis and addition of the copolymer on the final material is also studied. The material with the highest degree of mesoorder was obtained when the reaction was performed at 20 degrees C and the copolymer was added 40 h after the start of TEOS hydrolysis. It is claimed that the reason for the good ordering of the silica is that whereas particle formation under these conditions is fast, the rate of silica condensation is relatively low.

  9. Molecular Dynamics Simulations of Water Droplets On Hydrophilic Silica Surfaces

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

    2009-01-01

    and DNA microarrays technologies.Although extensive experimental, theoretical and computational work has been devoted to study the nature of the interaction between silica and water, at the molecular level a complete understanding of silica-water systems has not been reached. Contact angle computations...... dynamics (MD) simulations of a hydrophilic air-water-silica system using the MD package FASTTUBE. We employ quantum chemistry calculation to obtain air-silica interaction parameters for the simulations. Our simulations are based in the following force fields: i) The silica-silica interaction is based...... of water droplets on silica surfaces offers a useful fundamental and quantitative measurement in order to study chemical and physical properties of water-silica systems. For hydrophobic systems the static and dynamic properties of the fluid-solid interface are influenced by the presence of air. Hence...

  10. Respiratory health effects of exposure to crystalline silica epidemiology.

    CSIR Research Space (South Africa)

    Hnzido, E

    1999-01-01

    Full Text Available The present report describes two additional studies of exposure-response relationship between respiratory disease and silica dust in gold mines. Section 3 describes a study of pulmonary tuberculosis in relation to silica dust, and section 4...

  11. Thermodynamics of the silica-steam system

    Energy Technology Data Exchange (ETDEWEB)

    Krikorian, Oscar H [Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)

    1970-05-01

    In most nuclear cratering and cavity formation applications, the working fluid in the expanding cavity consists primarily of vaporized silica and steam. The chemical reaction products of silica and steam under these conditions are not known, although it is known that silica is very volatile in the presence of high-pressure steam under certain geologic conditions and in steam turbines. A review is made of work on the silica-steam system in an attempt to determine the vapor species that exist, and to establish the associated thermo-dynamic data. The review indicates that at 600-900 deg K and 1-100 atm steam pressure, Si(OH){sub 4} is the most likely silicon-containing gaseous species. At 600-900 deg. K and 100-1000 atm steam, Si{sub 2}O(OH){sub 6} is believed to predominate, whereas at 1350 deg K and 2000-9000 atm, a mixture of Si(OH){sub 4} and Si{sub 2}O(OH){sub 6} is consistent with the observed volatilities. In work at 1760 deg. K in which silica was reacted either with steam at 0.5 and 1 atm, or with gaseous mixtures of H{sub 2}/H{sub 2}O and O{sub 2}/H{sub 2}O at 1 atm total pressure, only part of the volatility could be accounted for by Si(OH){sub 4}. Hydrogen was found to greatly enhance the volatility of silica, and oxygen to suppress it. The species most likely to explain this behavior is believed to be SiO(OH). A number of other species may also be significant under these conditions. Thermodynamic data have been estimated for all species considered. The Si-OH bond dissociation energy is found to be {approx}117 kcal/mole in both Si(OH){sub 4} and Si{sub 2}O(OH){sub 6}. (author)

  12. A ratiometric fluorescent quantum dots based biosensor for organophosphorus pesticides detection by inner-filter effect.

    Science.gov (United States)

    Yan, Xu; Li, Hongxia; Han, Xiaosong; Su, Xingguang

    2015-12-15

    In this work, we develop a novel and sensitive sensor for the detection of organophosphorus pesticides based on the inner-filter effect (IFE) between gold nanoparticles (AuNPs) and ratiometric fluorescent quantum dots (RF-QDs). The RF-QDs has been designed by hybridizing two differently colored CdTe QDs, in which the red emissive QDs entrapped in the silica sphere acting as the reference signal, and the green emissive QDs covalently attached on the silica surface serving as the response signal.The fluorescence of RF-QDs could be quenched by AuNPs based on IFE. Protamine could effectively turn on the fluorescence due to the electrostatic attraction between protamine and AuNPs. Trypsin can easily hydrolyze protamine, leading to the quench of the fluorescence. Then, the fluorescence could be recovered again by the addition of parathion-methyl (PM) which could inhibit the activity of trypsin. By measuring the fluorescence of RF-QDs, the inhibition efficiency of PM to trypsin activity was evaluated. Under the optimized conditions, the inhibition efficiency was proportional to the logarithm of PM concentration in the range of 0.04-400 ng mL(-1), with a detection limit of 0.018 ng mL(-1). Furthermore, the simple and convenient method had been used for PM detection in environmental and agricultural samples with satisfactory results. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Fluorescence-enhanced gadolinium-doped zinc oxide quantum dots for magnetic resonance and fluorescence imaging.

    Science.gov (United States)

    Liu, Yanlan; Ai, Kelong; Yuan, Qinghai; Lu, Lehui

    2011-02-01

    We report here the development of Gd-doped ZnO quantum dots (QDs) as dual modal fluorescence and magnetic resonance imaging nanoprobes. They are fabricated in a simple, versatile and environmentally friendly method, not only decreasing the difficulty and complexity, but also avoiding the increase of particle's size brought about by silica coating procedure in the synthesis of nanoprobes reported previously. These nanoprobes, with exceptionally small size and enhanced fluorescence resulting from the Gd doping, can label successfully the HeLa cells in short time and present no evidence of toxicity or adverse affect on cell growth even at the concentration up to 1 mm. These results show that such nanoprobes have low toxicity, especially in comparison with the traditional PEGylated CdSe/ZnS or CdSe/CdS QDs. In MRI studies, they exert strong positive contrast effect with a large longitudinal relaxivity (r(1)) of water proton of 16 mm(-1) s(-1). Their capability of imaging HeLa cells with MRI implies that they have great potential as MRI contrast agents. Combining the high sensitivity of fluorescence imaging with high spatial resolution of MRI, We expect that the as-prepared Gd-doped Zno QDs can provide a better reliability of the collected data and find promising applications in biological, medical and other fields. Copyright © 2010 Elsevier Ltd. All rights reserved.

  14. 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.

  15. Silica-scaled chrysophytes of Lake Baikal

    Directory of Open Access Journals (Sweden)

    A. Yu. Bessudova

    2017-12-01

    Full Text Available The list of silica-scaled chrysophytes of Lake Baikal has been enlarged using electron microscopy. It has been supplemented with 12 species and 2 forms. Spiniferomonas takahashii has been observed for the first time in the water bodies of Russia. According to our data, the list of silica-scaled chrysophytes of Lake Baikal includes 25 species and intra-species taxa: Chrysosphaerella – 3, Paraphysomonas – 2, Clathromonas – 1, Spiniferomonas – 7, Mallomonas – 8 and Synura – 4. We have also analyzed their seasonal dynamics and observed algal species that are dominant in spring, summer and autumn.

  16. Formation of Uniform Hollow Silica microcapsules

    Science.gov (United States)

    Yan, Huan; Kim, Chanjoong

    2013-03-01

    Microcapsules are small containers with diameters in the range of 0.1 - 100 μm. Mesoporous microcapsules with hollow morphologies possess unique properties such as low-density and high encapsulation capacity, while allowing controlled release by permeating substances with a specific size and chemistry. Our process is a one-step fabrication of monodisperse hollow silica capsules with a hierarchical pore structure and high size uniformity using double emulsion templates obtained by the glass-capillary microfluidic technique to encapsulate various active ingredients. These hollow silica microcapsules can be used as biomedical applications such as drug delivery and controlled release.

  17. Measurement and modelization of silica opal optical properties

    OpenAIRE

    Avoine , Amaury; Ngoc Hong , Phan; Frederich , Hugo; Aregahegn , Kifle; Bénalloul , Paul; Coolen , Laurent; Schwob , Catherine; Thu Nga , Pham; Gallas , Bruno; Maître , Agnès

    2014-01-01

    International audience; We present the synthesis process and optical characterization of artificial silica opals. The specular reflection spectra are analyzed and compared to band structure calculations and finite difference time domain (FDTD) simulations. The silica optical index is a key parameter to correctly describe an opal and is usually not known and treated as a free parameter. Here we propose a method to infer the silica index, as well as the silica spheres diameter, from the reflect...

  18. Synthesis of Various Silica Nanoparticles for Foam Stability

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  19. Fluorescence and Spectral Imaging

    Directory of Open Access Journals (Sweden)

    Ralph S. DaCosta

    2007-01-01

    Full Text Available Early identification of dysplasia remains a critical goal for diagnostic endoscopy since early discovery directly improves patient survival because it allows endoscopic or surgical intervention with disease localized without lymph node involvement. Clinical studies have successfully used tissue autofluorescence with conventional white light endoscopy and biopsy for detecting adenomatous colonic polyps, differentiating benign hyperplastic from adenomas with acceptable sensitivity and specificity. In Barrett's esophagus, the detection of dysplasia remains problematic because of background inflammation, whereas in the squamous esophagus, autofluorescence imaging appears to be more dependable. Point fluorescence spectroscopy, although playing a crucial role in the pioneering mechanistic development of fluorescence endoscopic imaging, does not seem to have a current function in endoscopy because of its nontargeted sampling and suboptimal sensitivity and specificity. Other point spectroscopic modalities, such as Raman spectroscopy and elastic light scattering, continue to be evaluated in clinical studies, but still suffer the significant disadvantages of being random and nonimaging. A recent addition to the fluorescence endoscopic imaging arsenal is the use of confocal fluorescence endomicroscopy, which provides real-time optical biopsy for the first time. To improve detection of dysplasia in the gastrointestinal tract, a new and exciting development has been the use of exogenous fluorescence contrast probes that specifically target a variety of disease-related cellular biomarkers using conventional fluorescent dyes and novel potent fluorescent nanocrystals (i.e., quantum dots. This is an area of great promise, but still in its infancy, and preclinical studies are currently under way.

  20. Development of a Biosensor for Environmental Monitoring Based on Microalgae Immobilized in Silica Hydrogels

    Directory of Open Access Journals (Sweden)

    Claude Durrieu

    2012-12-01

    Full Text Available A new biosensor was designed for the assessment of aquatic environment quality. Three microalgae were used as toxicity bioindicators: Chlorella vulgaris, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii. These microalgae were immobilized in alginate and silica hydrogels in a two step procedure. After studying the growth rate of entrapped cells, chlorophyll fluorescence was measured after exposure to (3-(3,4-dichlorophenyl-1,1-dimethylurea (DCMU and various concentrations of the common herbicide atrazine. Microalgae are very sensitive to herbicides and detection of fluorescence enhancement with very good efficiency was realized. The best detection limit was 0.1 µM, obtained with the strain C. reinhardtii after 40 minutes of exposure.

  1. Smart phone based bacterial detection using bio functionalized fluorescent nanoparticles

    International Nuclear Information System (INIS)

    Rajendran, Vinoth Kumar; Bakthavathsalam, Padmavathy; Ali, Baquir Mohammed Jaffar

    2014-01-01

    We are describing immunochromatographic test strips with smart phone-based fluorescence readout. They are intended for use in the detection of the foodborne bacterial pathogens Salmonella spp. and Escherichia coli O157. Silica nanoparticles (SiNPs) were doped with FITC and Ru(bpy), conjugated to the respective antibodies, and then used in a conventional lateral flow immunoassay (LFIA). Fluorescence was recorded by inserting the nitrocellulose strip into a smart phone-based fluorimeter consisting of a light weight (40 g) optical module containing an LED light source, a fluorescence filter set and a lens attached to the integrated camera of the cell phone in order to acquire high-resolution fluorescence images. The images were analysed by exploiting the quick image processing application of the cell phone and enable the detection of pathogens within few minutes. This LFIA is capable of detecting pathogens in concentrations as low as 10 5 cfu mL −1 directly from test samples without pre-enrichment. The detection is one order of magnitude better compared to gold nanoparticle-based LFIAs under similar condition. The successful combination of fluorescent nanoparticle-based pathogen detection by LFIAs with a smart phone-based detection platform has resulted in a portable device with improved diagnosis features and having potential application in diagnostics and environmental monitoring. (author)

  2. Concentration Dependence of Gold Nanoparticles for Fluorescence Enhancement

    Science.gov (United States)

    Solomon, Joel; Wittmershaus, Bruce

    Noble metal nanoparticles possess a unique property known as surface plasmon resonance in which the conduction electrons oscillate due to incoming light, dramatically increasing their absorption and scattering of light. The oscillating electrons create a varying electric field that can affect nearby molecules. The fluorescence and photostability of fluorophores can be enhanced significantly when they are near plasmonic nanoparticles. This effect is called metal enhanced fluorescence (MEF). MEF from two fluorescence organic dyes, Lucifer Yellow CH and Riboflavin, was measured with different concentrations of 50-nm colloidal gold nanoparticles (Au-NP). The concentration range of Au-NP was varied from 2.5 to 250 pM. To maximize the interaction, the dyes were chosen so their emission spectra had considerable overlap with the absorption spectra of the Au-NP, which is common in MEF studies. If the dye molecules are too close to the surface of Au-NP, fluorescence quenching can occur instead of MEF. To try to observe this difference, silica-coated Au-NP were compared to citrate-based Au-NP; however, fluorescence quenching was observed with both Au-NP. This material is based upon work supported by the National Science Foundation under Grant Number NSF-ECCS-1306157.

  3. Fluorescent discharge lamp

    Science.gov (United States)

    Mukai, E.; Otsuka, H.; Nomi, K.; Honmo, I.

    1982-01-01

    A rapidly illuminating fluorescent lamp 1,200 mm long and 32.5 mm in diameter with an interior conducting strip which is compatible with conventional fixtures and ballasts is described. The fluorescent lamp is composed of a linear glass tube, electrodes sealed at both ends, mercury and raregas sealed in the glass tube, a fluorescent substance clad on the inner walls of the glass tube, and a clad conducting strip extending the entire length of the glass tube in the axial direction on the inner surface of the tube.

  4. Highly thermostable fluorescent proteins

    Science.gov (United States)

    Bradbury, Andrew M [Santa Fe, NM; Waldo, Geoffrey S [Santa Fe, NM; Kiss, Csaba [Los Alamos, NM

    2011-03-22

    Thermostable fluorescent proteins (TSFPs), methods for generating these and other stability-enhanced proteins, polynucleotides encoding such proteins, and assays and method for using the TSFPs and TSFP-encoding nucleic acid molecules are provided. The TSFPs of the invention show extremely enhanced levels of stability and thermotolerance. In one case, for example, a TSFP of the invention is so stable it can be heated to 99.degree. C. for short periods of time without denaturing, and retains 85% of its fluorescence when heated to 80.degree. C. for several minutes. The invention also provides a method for generating stability-enhanced variants of a protein, including but not limited to fluorescent proteins.

  5. Structure of the red fluorescent protein from a lancelet (Branchiostoma lanceolatum): a novel GYG chromophore covalently bound to a nearby tyrosine

    Energy Technology Data Exchange (ETDEWEB)

    Pletnev, Vladimir Z., E-mail: vzpletnev@gmail.com; Pletneva, Nadya V.; Lukyanov, Konstantin A.; Souslova, Ekaterina A.; Fradkov, Arkady F.; Chudakov, Dmitry M.; Chepurnykh, Tatyana; Yampolsky, Ilia V. [Russian Academy of Sciences, Moscow (Russian Federation); Wlodawer, Alexander [National Cancer Institute, Frederick, MD 21702 (United States); Dauter, Zbigniew [National Cancer Institute, Argonne, IL 60439 (United States); Pletnev, Sergei, E-mail: vzpletnev@gmail.com [National Cancer Institute, Argonne, IL 60439 (United States); SAIC-Frederick, Argonne, IL 60439 (United States); Russian Academy of Sciences, Moscow (Russian Federation)

    2013-09-01

    The crystal structure of the novel red emitting fluorescent protein from lancelet Branchiostoma lanceolatum (Chordata) revealed an unusual five residues cyclic unit comprising Gly58-Tyr59-Gly60 chromophore, the following Phe61 and Tyr62 covalently bound to chromophore Tyr59. A key property of proteins of the green fluorescent protein (GFP) family is their ability to form a chromophore group by post-translational modifications of internal amino acids, e.g. Ser65-Tyr66-Gly67 in GFP from the jellyfish Aequorea victoria (Cnidaria). Numerous structural studies have demonstrated that the green GFP-like chromophore represents the ‘core’ structure, which can be extended in red-shifted proteins owing to modifications of the protein backbone at the first chromophore-forming position. Here, the three-dimensional structures of green laGFP (λ{sub ex}/λ{sub em} = 502/511 nm) and red laRFP (λ{sub ex}/λ{sub em} ≃ 521/592 nm), which are fluorescent proteins (FPs) from the lancelet Branchiostoma lanceolatum (Chordata), were determined together with the structure of a red variant laRFP-ΔS83 (deletion of Ser83) with improved folding. Lancelet FPs are evolutionarily distant and share only ∼20% sequence identity with cnidarian FPs, which have been extensively characterized and widely used as genetically encoded probes. The structure of red-emitting laRFP revealed three exceptional features that have not been observed in wild-type fluorescent proteins from Cnidaria reported to date: (i) an unusual chromophore-forming sequence Gly58-Tyr59-Gly60, (ii) the presence of Gln211 at the position of the conserved catalytic Glu (Glu222 in Aequorea GFP), which proved to be crucial for chromophore formation, and (iii) the absence of modifications typical of known red chromophores and the presence of an extremely unusual covalent bond between the Tyr59 C{sup β} atom and the hydroxyl of the proximal Tyr62. The impact of this covalent bond on the red emission and the large Stokes shift (

  6. Synthesis and application of luminescent single CdS quantum dot encapsulated silica nanoparticles directed for precision optical bioimaging

    Directory of Open Access Journals (Sweden)

    Veeranarayanan S

    2012-07-01

    Full Text Available Srivani Veeranarayanan, Aby Cheruvathoor Poulose, M Sheikh Mohamed, Yutaka Nagaoka, Seiki Iwai, Yuya Nakagame, Shosaku Kashiwada, Yasuhiko Yoshida, Toru Maekawa, D Sakthi KumarBio Nano Electronics Research Centre, Graduate School of Interdisciplinary New Science, Toyo University, Kawagoe, JapanAbstract: This paper presents the synthesis of aqueous cadmium sulfide (CdS quantum dots (QDs and silica-encapsulated CdS QDs by reverse microemulsion method and utilized as targeted bio-optical probes. We report the role of CdS as an efficient cell tag with fluorescence on par with previously documented cadmium telluride and cadmium selenide QDs, which have been considered to impart high levels of toxicity. In this study, the toxicity of bare QDs was efficiently quenched by encapsulating them in a biocompatible coat of silica. The toxicity profile and uptake of bare CdS QDs and silica-coated QDs, along with the CD31-labeled, silica-coated CdS QDs on human umbilical vein endothelial cells and glioma cells, were investigated. The effect of size, along with the time-dependent cellular uptake of the nanomaterials, has also been emphasized. Enhanced, high-specificity imaging toward endothelial cell lines in comparison with glioma cells was achieved with CD31 antibody-conjugated nanoparticles. The silica-coated nanomaterials exhibited excellent biocompatibility and greater photostability inside live cells, in addition to possessing an extended shelf life. In vivo biocompatibility and localization study of silica-coated CdS QDs in medaka fish embryos, following direct nanoparticle exposure for 24 hours, authenticated the nanomaterials' high potential for in vivo imaging, augmented with superior biocompatibility. As expected, CdS QD-treated embryos showed 100% mortality, whereas the silica-coated QD-treated embryos stayed viable and healthy throughout and after the experiments, devoid of any deformities. We provide highly cogent and convincing evidence for such

  7. Single-Molecule Imaging of DNAs with Sticky Ends at Water/Fused Silica Interface

    Energy Technology Data Exchange (ETDEWEB)

    Isailovic, Slavica [Iowa State Univ., Ames, IA (United States)

    2005-01-01

    Total internal reflection fluorescence microscopy (TIRFM) was used to study intermolecular interactions of DNAs with unpaired (sticky) ends of different lengths at water/fused silica interface at the single-molecule level. Evanescent field residence time, linear velocity and adsorption/desorption frequency were measured in a microchannel for individual DNA molecules from T7, Lambda, and PSP3 phages at various pH values. The longest residence times and the highest adsorption/desorption frequencies at the constant flow at pH 5.5 were found for PSP3 DNA, followed by lower values for Lambda DNA, and the lowest values for T7 DNA. Since T7, Lambda, and PSP3 DNA molecules contain none, twelve and nineteen unpaired bases, respectively, it was concluded that the affinity of DNAs for the surface increases with the length of the sticky ends. This confirms that hydrophobic and hydrogen-bonding interactions between sticky ends and fused-silica surface are driving forces for DNA adsorption at the fused-silica surface. Described single-molecule methodology and results therein can be valuable for investigation of interactions in liquid chromatography, as well as for design of DNA hybridization sensors and drug delivery systems.

  8. New Silica Magnetite Sorbent: The Influence of Variations of Sodium Silicate Concentrations on Silica Magnetite Character

    Science.gov (United States)

    Azmiyawati, C.; Pratiwi, P. I.; Darmawan, A.

    2018-04-01

    The adsorption capacity of an adsorbent is determined by the adsorbent and the adsorbate properties. The character of the adsorbent will play a major role in its ability to adsorb the corresponding adsorbate. Therefore, in this study we looked at the effects of variations of sodium silicate concentrations on the resulting magnetite silica adsorbent properties. The application of silica coating on the magnetite was carried out through a sol-gel process with sodium silicate and HCl precursors. Based on the characterization data obtained, it was found that the silica coating on magnetite can increase the resistance to acid leaching, increase the particle size, but decrease the magnetic properties of the magnetite. Based on Gas Sorption Analyzer (GSA) and X-ray Difraction (XRD) data it can successively be determined that increase in concentration of sodium silicate will increase the surface area and amorphous structure of the Silica Magnetie.

  9. Reviews in fluorescence 2007

    CERN Document Server

    Lakowicz, Joseph R; Geddes, Chris D

    2009-01-01

    This fourth volume in the Springer series summarizes the year's progress in fluorescence, with authoritative analytical reviews specialized enough for professional researchers, yet also appealing to a wider audience of scientists in related fields.

  10. Introduction to fluorescence

    CERN Document Server

    Jameson, David M

    2014-01-01

    "An essential contribution to educating scientists in the principles of fluorescence. It will also be an important addition to the libraries of practitioners applying the principles of molecular fluorescence."-Ken Jacobson, Kenan Distinguished Professor of Cell Biology and Physiology, University of North Carolina at Chapel Hill"An exquisite compendium of fluorescence and its applications in biochemistry enriched by a very exciting historical perspective. This book will become a standard text for graduate students and other scientists."-Drs. Zygmunt (Karol) Gryczynski and Ignacy Gryczynski, University of North Texas Health Science Center"… truly a masterwork, combining clarity, precision, and good humor. The reader, novice or expert, will be pleased with the text and will not stop reading. It is a formidable account of the fluorescence field, which has impacted the life sciences so considerably in the last 60 years."-Jerson L. Silva, M.D., Ph.D., Professor and Director, National Institute of Science and Tech...

  11. Health hazards due to the inhalation of amorphous silica

    International Nuclear Information System (INIS)

    Merget, R.; Bruening, T.; Bauer, T.; Kuepper, H.U.; Breitstadt, R.; Philippou, S.; Bauer, H.D.

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic (''thermal'' or ''fumed'') silica, and (3) chemically or physically modified silica. According to the different physico-chemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or emphysema cannot be excluded. There is no

  12. Synthesis of silica nanosphere from homogeneous and ...

    Indian Academy of Sciences (India)

    WINTEC

    avoid it, reaction in heterogeneous system using CTABr was carried out. Nanosized silica sphere with ... Homogeneous system contains a mixture of ethanol, water, aqueous ammonia and ... heated to 823 K (rate, 1 K/min) in air and kept at this.

  13. Nanostructured Mesoporous Silicas for Bone Tissue Regeneration

    Directory of Open Access Journals (Sweden)

    Isabel Izquierdo-Barba

    2008-01-01

    Full Text Available The research on the development of new biomaterials that promote bone tissue regeneration is receiving great interest by the biomedical scientific community. Recent advances in nanotechnology have allowed the design of materials with nanostructure similar to that of natural bone. These materials can promote new bone formation by inducing the formation of nanocrystalline apatites analogous to the mineral phase of natural bone onto their surfaces, i.e. they are bioactive. They also stimulate osteoblast proliferation and differentiation and, therefore, accelerate the healing processes. Silica-based ordered mesoporous materials are excellent candidates to be used as third generation bioceramics that enable the adsorption and local control release of biological active agents that promote bone regeneration. This local delivery capability together with the bioactive behavior of mesoporous silicas opens up promising expectations in the bioclinical field. In this review, the last advances in nanochemistry aimed at designing and tailoring the chemical and textural properties of mesoporous silicas for biomedical applications are described. The recent developed strategies to synthesize bioactive glasses with ordered mesopore arrangements are also summarized. Finally, a deep discussion about the influence of the textural parameters and organic modification of mesoporous silicas on molecules adsorption and controlled release is performed.

  14. 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

  15. 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 ...

  16. Kinetics of silica-phase transitions

    International Nuclear Information System (INIS)

    Duffy, C.J.

    1993-07-01

    In addition to the stable silica polymorph quartz, several metastable silica phases are present in Yucca Mountain. The conversion of these phases to quartz is accompanied by volume reduction and a decrease in the aqueous silica activity, which may destabilize clinoptilolite and mordenite. The primary reaction sequence for the silica phases is from opal or glass to disordered opal-CT, followed by ordering of the opal-CT and finally by the crystallization of quartz. The ordering of opal-CT takes place in the solid state, whereas the conversion of opal-CT takes place through dissolution-reprecipitation involving the aqueous phase. It is proposed that the rate of conversion of opal-CT to quartz is controlled by diffusion of defects out of a disordered surface layer formed on the crystallizing quartz. The reaction rates are observed to be dependent on temperature, pressure, degree of supersaturation, and pH. Rate equations selected from the literature appear to be consistent with observations at Yucca Mountain

  17. Silica nanoparticles with a substrate switchable luminescence

    International Nuclear Information System (INIS)

    Bochkova, O D; Mustafina, A R; Fedorenko, S V; Konovalov, A I

    2011-01-01

    Silica nanoparticles with visible (Tb and Ru doped), near IR (Yb doped) and dual visible-near IR luminescence (Ru-Yb doped) were obtained by reverse w/o microemulsion procedure. Plenty of luminescent complexes (from 4900 to 10000) encapsulated into each nanoparticle ensures the intensive luminescence of nanoparticles and their applicability as biomarkers. The silica surface decoration by definite anchor groups is the required step for the gaining to these nanoparticles marking and sensing functions. Thus covalent and non-covalent surface modification of these nanoparticles was developed to provide the binding with biotargets and sensing of anions. The dicationic surfactant coating of negatively charged Tb(III)-TCAS doped silica nanoparticles was chosen as the basis for the anion responsible system. The reversible insertion of the quenching anions (namely phenol red) into the surfactant based layer at the surface of luminescent nanoparticles switches off the Tb-centered luminescence. In turn the reversible reestablishment of the luminescence results from the competitive insertion of the non-quenching anions into the surfactant layer at the silica/water interface. The hydrophobic anions exemplified by dodecylsulfates versus hydrophilic ones (hydrophosphates) are preferable in the competition with phenol red anions.

  18. Photo darkening of rare earth doped silica

    DEFF Research Database (Denmark)

    Mattsson, Kent Erik

    2011-01-01

    /2/11/2 chemical bond is formed on dioxasilirane which comprises the PD color center for the visible and near-infrared. Difference in solid acidity of the silica material co-doped with Yb/Al and Yb/P may explain the observed difference in spectral shapes by change of bond order to the formed chemical bond. © 2011...

  19. Silica gel matrix immobilized Chlorophyta hydrodictyon africanum ...

    African Journals Online (AJOL)

    Aghomotsegin

    2015-08-05

    Aug 5, 2015 ... The algae-silica gel adsorbent was used for batch sorption studies of a cationic dye, ... traditional methods of treating industrial effluent, these ... Author(s) agree that this article remains permanently open access under the terms of the Creative ... sodium silicate solution (v/v) and 25 mL of distilled water. With.

  20. Silica incorporated membrane for wastewater based filtration

    Science.gov (United States)

    Fernandes, C. S.; Bilad, M. R.; Nordin, N. A. H. M.

    2017-10-01

    Membrane technology has long been applied for waste water treatment industries due to its numerous advantages compared to other conventional processes. However, the biggest challenge in pressure driven membrane process is membrane fouling. Fouling decreases the productivity and efficiency of the filtration, reduces the lifespan of the membrane and reduces the overall efficiency of water treatment processes. In this study, a novel membrane material is developed for water filtration. The developed membrane incorporates silica nanoparticles mainly to improve its structural properties. Membranes with different loadings of silica nanoparticles were applied in this study. The result shows an increase in clean water permeability and filterability of the membrane for treating activated sludge, microalgae solution, secondary effluent and raw sewage as feed. Adding silica into the membrane matrix does not significantly alter contact angle and membrane pore size. We believe that silica acts as an effective pore forming agent that increases the number of pores without significantly altering the pore sizes. A higher number of small pores on the surface of the membrane could reduce membrane fouling because of a low specific loading imposed to individual pores.

  1. Investigation of fused silica dynamic behaviour

    International Nuclear Information System (INIS)

    Malaise, F.; Chevalier, J.M.; Bertron, I.; Malka, F.

    2006-01-01

    The survivability of the fused silica shields to shrapnel impacts is a key factor for the affordable operation of the intense laser irradiation future facility Laser Mega Joule (LMJ). This paper presents experimental data and computational modelling for LMJ fused silica upon shock wave loading and unloading. Gas-gun flyer plate impact and explosively driven tests have been conducted to investigate the dynamic behaviour of this material. Hugoniot states and the Hugoniot Elastic Limit of LMJ fused silica have been obtained. These experimental data are useful for determining some constitutive model constants of the 'Crack-Model', a continuum tensile and compressive failure model with friction based. This model has been improved by taking into account nonlinear elasticity. The numerical results obtained by performing computations of the previous tests and some ballistic impact tests are discussed. The numerical comparisons with the experimental data show good agreement. Further developments to simulate the permanent densification and the solid-to-solid phase transformation of fused silica are required. (authors)

  2. Cyclic olefin copolymer-silica nanocomposites foams

    Czech Academy of Sciences Publication Activity Database

    Pegoretti, A.; Dorigato, A.; Biani, A.; Šlouf, Miroslav

    2016-01-01

    Roč. 51, č. 8 (2016), s. 3907-3916 ISSN 0022-2461 R&D Projects: GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 Keywords : cyclic olefin copolymer * nanocomposites * silica Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.599, year: 2016

  3. Hydrothermal Diamond Anvil Cell Investigations Into the Alumina-Silica-Water System up to 1073 K and 4 GPa

    Science.gov (United States)

    Davis, M. K.; Stixrude, L. P.

    2004-12-01

    Understanding fluid chemistry in the subduction zone environment is key to unraveling the details of element transport from the slab to the surface. Solubility of different mineral assemblages in predominantly water-rich fluid along with pressure and temperature conditions control the chemical structure of the aqueous fluid and govern the transport opportunities for various chemical components away from the subducting slab. In-situ Raman experiments were performed in the alumina-silica-water system in an externally heated Bassett-type hydrothermal diamond anvil cell in the Department of Geological Sciences at the University of Michigan. Natural quartz samples (from the Owl Creek Mountains, Wyoming) were used as the silica source and synthetic ruby was used for the alumina source. Temperatures inside the diamond cell were monitored using type-K thermocouples wrapped around the diamonds and the pressure calibrated by the Raman shift of diamond or quartz or the fluorescence of ruby depending on conditions. Raman measurements of the aluminosilicate fluid show the presence of multiple alumina, silica, and mixed species. As predicted by calculations an aluminosilicate specie possibly of the form (HO)3SiOAl(OH)32- as well as the silica monomer and dimer specie were observed in the aluminosilicate fluid. There also appeared to be at least one hydrous alumina specie based on the presence of a Raman peaks at 228 cm-1, 339 cm-1 and 970 cm-1 in the fluid and a comparative analysis between Raman peaks in aqueous fluid in the silica-water, alumina-water, and alumina-silica-water systems. Solid phases formed during experiments (diaspore, kyanite) were confirmed with Raman spectroscopy.

  4. Effect of silver ions on the energy transfer from host defects to Tb ions in sol–gel silica glass

    Energy Technology Data Exchange (ETDEWEB)

    Abbass, Abd Ellateef [Department of Physics, University of the Free State, Bloemfontein (South Africa); Department of Physics, Sudan University of Science and Technology (Sudan); Swart, H.C. [Department of Physics, University of the Free State, Bloemfontein (South Africa); Kroon, R.E., E-mail: KroonRE@ufs.ac.za [Department of Physics, University of the Free State, Bloemfontein (South Africa)

    2015-04-15

    Plasmonic metal structures have been suggested to enhance the luminescence from rare-earth (RE) ions, but this enhancement is not yet well understood or applied to phosphor materials. Although some reports using Ag nanoparticles (NPs) in glass have attributed enhancement of RE emission to the strong electric fields associated with Ag NPs, it has also been proposed that the enhancement is instead due to energy transfer from Ag ions to RE ions. Our work using sol–gel silica shows a third possibility, namely that enhancement of the RE (e.g. Tb) emission is due to energy transfer from defects of the host material to the Tb ions, where the addition of Ag influences the silica host defects. The oxidation state of Ag as a function of annealing temperature was investigated by x-ray diffraction, transmission electron microscopy, UV–vis measurements and x-ray photoelectron spectroscopy, while optical properties were investigated using a Cary Eclipse fluorescence spectrophotometer or by exciting samples with a 325 nm He–Cd laser. The results showed that Ag ions have a significant effect on the silica host defects, which resulted in enhancement of the green Tb emission at 544 nm for non-resonant excitation using a wavelength of 325 nm. - Highlights: • Conversion of Ag ions to metallic nanoparticles after annealing of sol–gel silica. • Addition of Ag resulted in enhanced green luminescence from Tb ions in silica. • Enhancement is attributed to the effect of added Ag on the host defects of silica.

  5. Fluorescence (Multiwave) Confocal Microscopy.

    Science.gov (United States)

    Welzel, J; Kästle, Raphaela; Sattler, Elke C

    2016-10-01

    In addition to reflectance confocal microscopy, multiwave confocal microscopes with different laser wavelengths in combination with exogenous fluorophores allow fluorescence mode confocal microscopy in vivo and ex vivo. Fluorescence mode confocal microscopy improves the contrast between the epithelium and the surrounding soft tissue and allows the depiction of certain structures, like epithelial tumors, nerves, and glands. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Targeting pancreatic cancer with magneto-fluorescent theranostic gold nanoshells.

    Science.gov (United States)

    Chen, Wenxue; Ayala-Orozco, Ciceron; Biswal, Nrusingh C; Perez-Torres, Carlos; Bartels, Marc; Bardhan, Rizia; Stinnet, Gary; Liu, Xian-De; Ji, Baoan; Deorukhkar, Amit; Brown, Lisa V; Guha, Sushovan; Pautler, Robia G; Krishnan, Sunil; Halas, Naomi J; Joshi, Amit

    2014-01-01

    We report a magneto-fluorescent theranostic nanocomplex targeted to neutrophil gelatinase-associated lipocalin (NGAL) for imaging and therapy of pancreatic cancer. Gold nanoshells resonant at 810 nm were encapsulated in silica epilayers doped with iron oxide and the near-infrared (NIR) dye indocyanine green, resulting in theranostic gold nanoshells (TGNS), which were subsequently conjugated with antibodies targeting NGAL in AsPC-1-derived xenografts in nude mice. Anti-NGAL-conjugated TGNS specifically targeted pancreatic cancer cells in vitro and in vivo providing contrast for both NIR fluorescence and T2-weighted MRI with higher tumor contrast than can be obtained using long-circulating, but nontargeted, PEGylated nanoparticles. The nanocomplexes also enabled highly specific cancer cell death via NIR photothermal therapy in vitro. TGNS with embedded NIR and magnetic resonance contrasts can be specifically targeted to pancreatic cancer cells with expression of early disease marker NGAL, and enable molecularly targeted imaging and photothermal therapy.

  7. Picosecond laser damage of fused silica at 355 nm

    International Nuclear Information System (INIS)

    Meng Xiangjie; Liu Hongjie; Wang Fang; Zhang Zhen; An Xinyou; Huang Jin; Jiang Xiaodong; Wu Weidong; Ren Weiyi

    2013-01-01

    This paper studies the initiated damage threshold, the damage morphology and the subsequent damage growth on fused silica's input-surface and exit-surface under picosecond laser irradiation at 355 nm. Defects induced fluorescence on surface of the optical component is observed. The results demonstrate a significant dependence of the initiated damage on pulse duration and surface defects, and that of the damage growth on self-focusing, sub-surface defects. The damage-threshold is 3.98 J/cm 2 of input surface and 2.91 J/cm 2 of exit surface. The damage morphologies are quite different between input surface and exit surface. Slow growth behavior appears for the diameter of exit-surface and linear growth one for the depth of exit-surface in the lateral side of damage site with the increase of shot number. Defects have changed obviously compared with nanosecond laser damage in the damage area. Several main reasons such as electric intensification and self-focusing for the observed initiated damage and damage growth behavior are discussed. (authors)

  8. Characterization of silica quartz as raw material in photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Boussaa, S. Anas, E-mail: sabiha.anas@gmail.com; Kheloufi, A.; Kefaifi, A.; Kerkar, F. [Division croissance cristalline et procédés métallurgiques CCPM Centre de recherche en technologie des semi-conducteurs pour l’énergétique (C.R.T.S.E) 02 Bd Frantz Fanon BP. 140 Alger 7 merveilles, Alger 16200 (Algeria); Zaourar, N. Boutarek [Laboratoire des technologies des matériaux, USTHB, B.P. 32 El Alia, Bab Ezzouar, Alger, Algérie 16111 (Algeria)

    2016-07-25

    Raw materials are essential for the functioning of modern societies, and access to these raw materials is vital to the world economy. Sustainable development, both globally level, raises important new challenges associated with access and efficient use of raw materials. High purity quartz, is consider as a critical raw material and it is a rare commodity that only forms under geological conditions where a narrow set of chemical and physical parameters is fulfilled. When identified and following special beneficiation techniques, high purity quartz obtains very attractive prices and is applied in high technology sectors that currently are under rapid expansion such as photovoltaic solar cells, silicon metal - oxide wafers in the semiconductor industry and long distance optical fibers that are used in communication networks. Crystalline silicon remains the principal material for photovoltaic technology. Metallurgical silicon is produced industrially by the reduction of silica with carbon in an electric arc furnace at temperatures higher than 2000 °C in the hottest parts, by a reaction that can be written ideally as: SiO{sub 2} + 2C = Si + 2CO. The aim of this study has been to test experimental methods for investigating the various physical and chemical proprieties of Hoggar quartz with different techniques: X Ray Fluorescence, infra-red spectroscopy, Scanning Electron Microscopy, Optic Microscopy, Carbon Analyzer and Vickers Hardness. The results show finally that the quartz has got good result in purity but need enrichment for the photovoltaic application.

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

    Science.gov (United States)

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

    2014-07-01

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

  10. Crystallization of biogenic hydrous amorphous silica

    Science.gov (United States)

    Kyono, A.; Yokooji, M.; Chiba, T.; Tamura, T.; Tuji, A.

    2017-12-01

    Diatom, Nitzschia cf. frustulum, collected from Lake Yogo, Siga prefecture, Japan was cultured in laboratory. Organic components of the diatom cell were removed by washing with acetone and sodium hypochlorite. The remaining frustules were studied by SEM-EDX, FTIR spectroscopy, and synchrotron X-ray diffraction. The results showed that the spindle-shaped morphology of diatom frustule was composed of hydrous amorphous silica. Pressure induced phase transformation of the diatom frustule was investigated by in situ Raman spectroscopic analysis. With exposure to 0.3 GPa at 100 oC, Raman band corresponding to quartz occurred at ν = 465 cm-1. In addition, Raman bands known as a characteristic Raman pattern of moganite was also observed at 501 cm-1. From the integral ratio of Raman bands, the moganite content in the probed area was estimated to be approximately 50 wt%. With the pressure and temperature effect, the initial morphology of diatom frustule was completely lost and totally changed to a characteristic spherical particle with a diameter of about 2 mm. With keeping the compression of 5.7 GPa at 100 oC, a Raman band assignable to coesite appeared at 538 cm-1. That is, with the compression and heating, the hydrous amorphous silica can be readily crystallized into quartz, moganite, and coesite. The first-principles calculations revealed that a disiloxane molecule stabilized in a trans configuration is twisted 60o and changed into the cis configuration with a close approach of water molecule. It is therefore a reasonable assumption that during crystallization of hydrous amorphous silica, the Si-O-Si bridging unit with the cis configuration would survive as a structural defect and then crystallized into moganite by keeping the geometry. This hypothesis is adaptable to the phase transformation from hydrous amorphous silica to coesite as well, because coesite has the four-membered rings and easily formed from the hydrous amorphous silica under high pressure and high

  11. Fluorescence detection of single molecules using pulsed near-field optical excitation and time correlated photon counting

    International Nuclear Information System (INIS)

    Ambrose, W.P.; Goodwin, P.M.; Martin, J.C.; Keller, R.A.

    1994-01-01

    Pulsed excitation, time correlated single photon counting and time gated detection are used in near-field optical microscopy to enhance fluorescence images and measure the fluorescence lifetimes of single molecules of Rhodamine 6G on silica surfaces. Time gated detection is used to reject prompt scattered background and to improve the image signal to noise ratio. The excited state lifetime of a single Rhodamine 6G molecule is found to depend on the position of the near-field probe. We attribute the lifetime variations to spontaneous emission rate alterations by the fluorescence reflected from and quenching by the aluminum coated probe

  12. Fluorescence Image Segmentation by using Digitally Reconstructed Fluorescence Images

    OpenAIRE

    Blumer, Clemens; Vivien, Cyprien; Oertner, Thomas G; Vetter, Thomas

    2011-01-01

    In biological experiments fluorescence imaging is used to image living and stimulated neurons. But the analysis of fluorescence images is a difficult task. It is not possible to conclude the shape of an object from fluorescence images alone. Therefore, it is not feasible to get good manual segmented nor ground truth data from fluorescence images. Supervised learning approaches are not possible without training data. To overcome this issues we propose to synthesize fluorescence images and call...

  13. Effect of the Silica Content of Diatoms on Protozoan Grazing

    Directory of Open Access Journals (Sweden)

    Shuwen Zhang

    2017-06-01

    Full Text Available This study examined the effect that silica content in diatom cells has on the behavior of protists. The diatoms Thalassiosira weissflogii and T. pseudonana were cultured in high or low light conditions to achieve low and high silica contents, respectively. These cells were then fed to a heterotrophic dinoflagellate Noctiluca scintillans and a ciliate Euplotes sp. in single and mixed diet experiments. Our results showed that in general, N. scintillans and Euplotes sp. both preferentially ingested the diatoms with a low silica content rather than those with a high silica content. However, Euplotes sp. seemed to be less influenced by the silica content than was N. scintillans. In the latter case, the clearance and ingestion rate of the low silica diatoms were significantly higher, both in the short (6-h and long (1-d duration grazing experiments. Our results also showed that N. scintillans required more time to digest the high silica-containing cells. As the high silica diatoms are harder to digest, this might explain why N. scintillans exhibits a strong preference for the low silica prey. Thus, the presence of high silica diatoms might limit the ability of the dinoflagellate to feed. Our findings suggest that the silica content of diatoms affects their palatability and digestibility and, consequently, the grazing activity and selectivity of protozoan grazers.

  14. Effect of silica particle size on macrophage inflammatory responses.

    Directory of Open Access Journals (Sweden)

    Toshimasa Kusaka

    Full Text Available Amorphous silica particles, such as nanoparticles (<100 nm diameter particles, are used in a wide variety of products, including pharmaceuticals, paints, cosmetics, and food. Nevertheless, the immunotoxicity of these particles and the relationship between silica particle size and pro-inflammatory activity are not fully understood. In this study, we addressed the relationship between the size of amorphous silica (particle dose, diameter, number, and surface area and the inflammatory activity (macrophage phagocytosis, inflammasome activation, IL-1β secretion, cell death and lung inflammation. Irrespective of diameter size, silica particles were efficiently internalized by mouse bone marrow-derived macrophages via an actin cytoskeleton-dependent pathway, and induced caspase-1, but not caspase-11, activation. Of note, 30 nm-1000 nm diameter silica particles induced lysosomal destabilization, cell death, and IL-1β secretion at markedly higher levels than did 3000 nm-10000 nm silica particles. Consistent with in vitro results, intra-tracheal administration of 30 nm silica particles into mice caused more severe lung inflammation than that of 3000 nm silica particles, as assessed by measurement of pro-inflammatory cytokines and neutrophil infiltration in bronchoalveolar lavage fluid of mice, and by the micro-computed tomography analysis. Taken together, these results suggest that silica particle size impacts immune responses, with submicron amorphous silica particles inducing higher inflammatory responses than silica particles over 1000 nm in size, which is ascribed not only to their ability to induce caspase-1 activation but also to their cytotoxicity.

  15. Mesoporous silica nanoparticles functionalized with folic acid/methionine for active targeted delivery of docetaxel

    Directory of Open Access Journals (Sweden)

    Khosravian P

    2016-12-01

    Full Text Available Pegah Khosravian,1 Mehdi Shafiee Ardestani,2 Mehdi Khoobi,3 Seyed Naser Ostad,4 Farid Abedin Dorkoosh,1 Hamid Akbari Javar,1,* Massoud Amanlou5,6,* 1Department of Pharmaceutics, 2Department of Radiopharmacy, 3Department of Pharmaceutical Biomaterials, 4Department of Pharmacology and Toxicology, 5Department of Medicinal Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences Research Center, 6Drug Design and Development Research Center, Tehran University of Medical Sciences, Tehran, Iran *These authors contributed equally to this work Abstract: Mesoporous silica nanoparticles (MSNs are known as carriers with high loading capacity and large functionalizable surface area for target-directed delivery. In this study, a series of docetaxel-loaded folic acid- or methionine-functionalized mesoporous silica nanoparticles (DTX/MSN-FA or DTX/MSN-Met with large pores and amine groups at inner pore surface properties were prepared. The results showed that the MSNs were successfully synthesized, having good pay load and pH-sensitive drug release kinetics. The cellular investigation on MCF-7 cells showed better performance of cytotoxicity and cell apoptosis and an increase in cellular uptake of targeted nanoparticles. In vivo fluorescent imaging on healthy BALB/c mice proved that bare MSN-NH2 are mostly accumulated in the liver but MSN-FA or MSN-Met are more concentrated in the kidney. Importantly, ex vivo fluorescent images of tumor-induced BALB/c mice organs revealed the ability of MSN-FA to reach the tumor tissues. In conclusion, DTX/MSNs exhibited a good anticancer activity and enhanced the possibility of targeted drug delivery for breast cancer. Keywords: targeted delivery, mesoporous silica nanoparticle, folic acid, methionine, docetaxel

  16. Functionalization of silica nanoparticles for polypropylene nanocomposites applications

    International Nuclear Information System (INIS)

    Bracho, Diego; Palza, Humberto; Quijada, Raul; Dougnac, Vivianne

    2011-01-01

    Synthetic silica nanospheres of different diameters produced via the sol-gel method were used in order to enhance the barrier properties of the polypropylene-silica nanocomposites. Modification of the silica surface by reaction with organic chlorosilanes was performed in order to improve the particles interaction with the polypropylene matrix and its dispersion. Unmodified and modified silica nanoparticles were characterized using electronic microscopy (TEM), elemental analysis, thermo gravimetric analysis (TGA), and solid state nuclear magnetic resonance (NMR) spectroscopy. Preliminary permeability tests of the polymer-silica nanocomposite films showed no significant change at low particles load (3 wt%) regardless its size or surface functionality, mainly because of the low aspect ratio of the silica nanospheres. However, it is expected that at a higher concentration of silica particles differences will be observed. (author)

  17. Biological Applications and Transmission Electron Microscopy Investigations of Mesoporous Silica Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Trewyn, Brian G. [Iowa State Univ., Ames, IA (United States)

    2006-01-01

    The research presented and discussed within involves the development of novel biological applications of mesoporous silica nanoparticles (MSN) and an investigation of mesoporous material by transmission electron microscopy (TEM). Mesoporous silica nanoparticles organically functionalized shown to undergo endocytosis in cancer cells and drug release from the pores was controlled intracellularly and intercellularly. Transmission electron microscopy investigations demonstrated the variety of morphologies produced in this field of mesoporous silica nanomaterial synthesis. A series of room-temperature ionic liquid (RTIL) containing mesoporous silica nanoparticle (MSN) materials with various particle morphologies, including spheres, ellipsoids, rods, and tubes, were synthesized. By changing the RTIL template, the pore morphology was tuned from the MCM-41 type of hexagonal mesopores to rotational moire type of helical channels, and to wormhole-like porous structures. These materials were used as controlled release delivery nanodevices to deliver antibacterial ionic liquids against Escherichia coli K12. The involvement of a specific organosiloxane function group, covalently attached to the exterior of fluorescein doped mesoporous silica nanoparticles (FITC-MSN), on the degree and kinetics of endocytosis in cancer and plant cells was investigated. The kinetics of endocystosis of TEG coated FITC-MSN is significantly quicker than FITC-MSN as determined by flow cytometry experiments. The fluorescence confocal microscopy investigation showed the endocytosis of TEG coated-FITC MSN triethylene glycol grafted fluorescein doped MSN (TEG coated-FITC MSN) into both KeLa cells and Tobacco root protoplasts. Once the synthesis of a controlled-release delivery system based on MCM-41-type mesoporous silica nanorods capped by disulfide bonds with superparamagnetic iron oxide nanoparticles was completed. The material was characterized by general methods and the dosage and kinetics of the

  18. Permeability Characteristics of Compacted and Stabilized Clay with Cement, Peat Ash and Silica Sand

    Directory of Open Access Journals (Sweden)

    Seyed Esmaeil Mousavi

    2016-06-01

    Full Text Available The present paper investigates the influence of stabilization with cement, peat ash, and silica sand on permeability coefficient (kv of compacted clay, using a novel approach to stabilize the clay with peat ash as a supplementary material of cement in the compacted and stabilized soil. In order to assess the mentioned influence, test specimens of both untreated and stabilized soil have been tested in the laboratory so that their permeability could be evaluated. Falling head and one dimensional consolidation tests of laboratory permeability were performed on the clay specimens and the chemical compositions of the materials as well as microstructure of the stabilized soil with 18% cement, 2% peat ash, and 5% silica sand were investigated, using X-ray fluorescence and scanning electron microscopy respectively. Results show that for soil stabilization with up to 8% cement content (of the dry weight of the soil, the average value of coefficient of permeability (kv is very close to that of untreated soil, whereas the kv value decreases drastically for 18% cement under identical void ratio conditions. It is further revealed that addition of 18% cement, 2% peat ash, and 5% silica sand had decreased the coefficient of permeability by almost 2.2 folds after 24 h, while about 1.7 folds increase was observed in coefficient of permeability once 13.5% of cement, 1.5% of peat ash, and 20% of silica sand were added. The partial replacement of cement with the 2% peat ash can reduce the consumption of cement for soil stabilization.

  19. Silica fractionation and reactivity in soils

    Science.gov (United States)

    Unzué Belmonte, Dácil; Barão, Lúcia; Vandevenne, Floor; Schoelynck, Jonas; Struyf, Eric; Meire, Patrick

    2014-05-01

    The Si cycle is a globally important biogeochemical cycle, with strong connections to other biogeochemical cycles, including C. Silica is taken up by plants to form protective structures called phytoliths, which become a part of the soil and contribute strongly to soil Si cycling upon litter burial. Different silica fractions are found in soils, with phytoliths among the most easily soluble, especially compared to silicate minerals. A whole set of secondary non-biogenic fractions exist, that also have a high reactivity (adsorbed Si, reactive secondary minerals…). A good characterization of the different fractions of reactive silica is crucial to move forward knowledge on ecosystem Si cycling, which has been recognized in the last decade as crucial for terrestrial Si fluxes. A new method to analyze the different fractions of silica in soils has been described by Koning et al. (2002) and adapted by our research team (Barão et al. 2013). Using a continuous extraction of Si and aluminum in 0.5M NaOH, biogenic and non-biogenic reactive fractions are separated based on their Si/Al ratios and their reactivity in NaOH. Applying this new method I will investigate three emerging ideas on how humans can affect directly terrestrial Si fluxes. -Land use. I expect strong silica fractionation and reactivity differences in different land uses. These effects due to agricultural and forestry management have already been shown earlier in temperate soils (Vandevenne et al. 2012). Now we will test this hypothesis in recently deforested soils, in the south of Brazil. 'Pristine' forest, managed forest and tobacco field soils (with and without rotation crops) will be studied. This research belongs to an interdisciplinary project on soils and global change. -Fire. According to the IPCC report, extreme events such as fires (number and intensity) would increase due to climate change. We analyzed litter from spruce forest, beech forest and peat soils at two burning levels, after 350°C and

  20. Fluorescent pH sensor based on Ag@SiO2 core-shell nanoparticle.

    Science.gov (United States)

    Bai, Zhenhua; Chen, Rui; Si, Peng; Huang, Youju; Sun, Handong; Kim, Dong-Hwan

    2013-06-26

    We have demonstrated a novel method for the preparation of a fluorescence-based pH sensor by combining the plasmon resonance band of Ag core and pH sensitive dye (HPTS). A thickness-variable silica shell is placed between Ag core and HPTS dye to achieve the maximum fluorescence enhancement. At the shell thickness of 8 nm, the fluorescence intensity increases 4 and 9 times when the sensor is excited at 405 and 455 nm, respectively. At the same time, the fluorescence intensity shows a good sensitivity toward pH value in the range of 5-9, and the ratio of emission intensity at 513 nm excited at 455 nm to that excited at 405 nm versus the pH value in the range of 5-9 is determined. It is believed that the present pH sensor has the potential for determining pH real time in the biological sample.

  1. Highly Sensitive Fluorescence Probe Based on Functional SBA-15 for Selective Detection of Hg2+

    Directory of Open Access Journals (Sweden)

    Wang Xiaoyu

    2010-01-01

    Full Text Available Abstract An inorganic–organic hybrid fluorescence chemosensor (DA/SBA-15 was prepared by covalent immobilization of a dansylamide derivative into the channels of mesoporous silica material SBA-15 via (3-aminopropyltriethoxysilane (APTES groups. The primary hexagonally ordered mesoporous structure of SBA-15 was preserved after the grafting procedure. Fluorescence characterization shows that the obtained inorganic–organic hybrid composite is highly selective and sensitive to Hg2+ detection, suggesting the possibility for real-time qualitative or quantitative detection of Hg2+ and the convenience for potential application in toxicology and environmental science.

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

    Science.gov (United States)

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

    2016-03-23

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

  3. Nine New Fluorescent Probes

    Science.gov (United States)

    Lin, Tsung-I.; Jovanovic, Misa V.; Dowben, Robert M.

    1989-06-01

    Absorption and fluorescence spectroscopic studies are reported here for nine new fluorescent probes recently synthesized in our laboratories: four pyrene derivatives with substituents of (i) 1,3-diacetoxy-6,8-dichlorosulfonyl, (ii) 1,3-dihydroxy-6,8-disodiumsulfonate, (iii) 1,3-disodiumsulfonate, and (iv) l-ethoxy-3,6,8-trisodiumsulfonate groups, and five [7-julolidino] coumarin derivatives with substituents of (v) 3-carboxylate-4-methyl, (vi) 3- methylcarboxylate, (vii) 3-acetate-4-methyl, (viii) 3-propionate-4-methyl, and (ix) 3-sulfonate-4-methyl groups. Pyrene compounds i and ii and coumarin compounds v and vi exhibit interesting absorbance and fluorescence properties: their absorption maxima are red shifted compared to the parent compound to the blue-green region, and the band width broadens considerably. All four blue-absorbing dyes fluoresce intensely in the green region, and the two pyrene compounds emit at such long wavelengths without formation of excimers. The fluorescence properties of these compounds are quite environment-sensitive: considerable spectral shifts and fluorescence intensity changes have been observed in the pH range from 3 to 10 and in a wide variety of polar and hydrophobic solvents with vastly different dielectric constants. The high extinction and fluorescence quantum yield of these probes make them ideal fluorescent labeling reagents for proteins, antibodies, nucleic acids, and cellular organelles. The pH and hydrophobicity-dependent fluorescence changes can be utilized as optical pH and/or hydrophobicity indicators for mapping environmental difference in various cellular components in a single cell. Since all nine probes absorb in the UV, but emit at different wavelengths in the visible, these two groups of compounds offer an advantage of utilizing a single monochromatic light source (e.g., a nitrogen laser) to achieve multi-wavelength detection for flow cytometry application. As a first step to explore potential application in

  4. Two-dimensional silica opens new perspectives

    Science.gov (United States)

    Büchner, Christin; Heyde, Markus

    2017-12-01

    In recent years, silica films have emerged as a novel class of two-dimensional (2D) materials. Several groups succeeded in epitaxial growth of ultrathin SiO2 layers using different growth methods and various substrates. The structures consist of tetrahedral [SiO4] building blocks in two mirror symmetrical planes, connected via oxygen bridges. This arrangement is called a silica bilayer as it is the thinnest 2D arrangement with the stoichiometry SiO2 known today. With all bonds saturated within the nano-sheet, the interaction with the substrate is based on van der Waals forces. Complex ring networks are observed, including hexagonal honeycomb lattices, point defects and domain boundaries, as well as amorphous domains. The network structures are highly tuneable through variation of the substrate, deposition parameters, cooling procedure, introducing dopants or intercalating small species. The amorphous networks and structural defects were resolved with atomic resolution microscopy and modeled with density functional theory and molecular dynamics. Such data contribute to our understanding of the formation and characteristic motifs of glassy systems. Growth studies and doping with other chemical elements reveal ways to tune ring sizes and defects as well as chemical reactivities. The pristine films have been utilized as molecular sieves and for confining molecules in nanocatalysis. Post growth hydroxylation can be used to tweak the reactivity as well. The electronic properties of silica bilayers are favourable for using silica as insulators in 2D material stacks. Due to the fully saturated atomic structure, the bilayer interacts weakly with the substrate and can be described as quasi-freestanding. Recently, a mm-scale film transfer under structure retention has been demonstrated. The chemical and mechanical stability of silica bilayers is very promising for technological applications in 2D heterostacks. Due to the impact of this bilayer system for glass science

  5. Integrated Micro-Optical Fluorescence Detection System for Microfluidic Electrochromatography

    International Nuclear Information System (INIS)

    ALLERMAN, ANDREW A.; ARNOLD, DON W.; ASBILL, RANDOLPH E.; BAILEY, CHRISTOPHER G.; CARTER, TONY RAY; KEMME, SHANALYN A.; MATZKE, CAROLYN M.; SAMORA, SALLY; SWEATT, WILLIAM C.; WARREN, MIAL E.; WENDT, JOEL R.

    1999-01-01

    The authors describe the design and microfabrication of an extremely compact optical system as a key element in an integrated capillary-channel electrochromatograph with laser induced fluorescence detection. The optical design uses substrate-mode propagation within the fused silica substrate. The optical system includes a vertical cavity surface-emitting laser (VCSEL) array, two high performance microlenses and a commercial photodetector. The microlenses are multilevel diffractive optics patterned by electron beam lithography and etched by reactive ion etching in fused silica. Two generations of optical subsystems are described. The first generation design is integrated directly onto the capillary channel-containing substrate with a 6 mm separation between the VCSEL and photodetector. The second generation design separates the optical system onto its own module and the source to detector length is further compressed to 3.5 mm. The systems are designed for indirect fluorescence detection using infrared dyes. The first generation design has been tested with a 750 nm VCSEL exciting a 10(sup -4) M solution of CY-7 dye. The observed signal-to-noise ratio of better than 100:1 demonstrates that the background signal from scattered pump light is low despite the compact size of the optical system and meets the system sensitivity requirements

  6. Self-organized fluorescent nanosensors for ratiometric Pb2+ detection.

    Science.gov (United States)

    Arduini, Maria; Mancin, Fabrizio; Tecilla, Paolo; Tonellato, Umberto

    2007-07-31

    Silica nanoparticles (60 nm diameter) doped with fluorescent dyes and functionalized on the surface with thiol groups have been proved to be efficient fluorescent chemosensors for Pb2+ ions. The particles can detect a 1 microM metal ion concentration with a good selectivity, suffering only interference from Cu2+ ions. Analyte binding sites are provided by the simple grafting of the thiol groups on the nanoparticles. Once bound to the particles surface, the Pb2+ ions quench the emission of the reporting dyes embedded. Sensor performances can be improved by taking advantage of the ease of production of multishell silica particles. On one hand, signaling units can be concentrated in the external shells, allowing a closer interaction with the surface-bound analyte. On the other, a second dye can be buried in the particle core, far enough from the surface to be unaffected by the Pb2+ ions, thus producing a reference signal. In this way, a ratiometric system is easily prepared by simple self-organization of the particle components.

  7. Production and Application of Olivine Nano-Silica in Concrete

    Science.gov (United States)

    Mardiana, Oesman; Haryadi

    2017-05-01

    The aim of this research was to produce nano silica by synthesis of nano silica through extraction and dissolution of ground olivine rock, and applied the nano silica in the design concrete mix. The producing process of amorphous silica used sulfuric acid as the dissolution reagent. The separation of ground olivine rock occurred when the rock was heated in a batch reactor containing sulfuric acid. The results showed that the optimum mole ratio of olivine- acid was 1: 8 wherein the weight ratio of the highest nano silica generated. The heating temperature and acid concentration influenced the mass of silica produced, that was at temperature of 90 °C and 3 M acid giving the highest yield of 44.90%. Characterization using Fourier Transform Infrared (FTIR ) concluded that amorphous silica at a wavenumber of 1089 cm-1 indicated the presence of siloxane, Si-O-Si, stretching bond. Characterization using Scanning Electron Microscope - Energy Dispersive Spectroscopy (SEM-EDS) showed the surface and the size of the silica particles. The average size of silica particles was between 1-10 μm due to the rapid aggregation of the growing particles of nano silica into microparticles, caused of the pH control was not fully achieved.

  8. Mesoporous silica formulation strategies for drug dissolution enhancement: a review.

    Science.gov (United States)

    McCarthy, Carol A; Ahern, Robert J; Dontireddy, Rakesh; Ryan, Katie B; Crean, Abina M

    2016-01-01

    Silica materials, in particular mesoporous silicas, have demonstrated excellent properties to enhance the oral bioavailability of poorly water-soluble drugs. Current research in this area is focused on investigating the kinetic profile of drug release from these carriers and manufacturing approaches to scale-up production for commercial manufacture. This review provides an overview of different methods utilized to load drugs onto mesoporous silica carriers. The influence of silica properties and silica pore architecture on drug loading and release are discussed. The kinetics of drug release from mesoporous silica systems is examined and the manufacturability and stability of these formulations are reviewed. Finally, the future prospects of mesoporous silica drug delivery systems are considered. Substantial progress has been made in the characterization and development of mesoporous drug delivery systems for drug dissolution enhancement. However, more research is required to fully understand the drug release kinetic profile from mesoporous silica materials. Incomplete drug release from the carrier and the possibility of drug re-adsorption onto the silica surface need to be investigated. Issues to be addressed include the manufacturability and regulation status of formulation approaches employing mesoporous silica to enhance drug dissolution. While more research is needed to support the move of this technology from the bench to a commercial medicinal product, it is a realistic prospect for the near future.

  9. Arachidonic acid metabolism in silica-stimulated bovine alveolar macrophages

    International Nuclear Information System (INIS)

    Englen, M.D.

    1989-01-01

    The in vitro production of arachidonic acid (AA) metabolites in adherent bovine alveolar macrophages (BAM) incubated with silica was investigated. BAM were pre-labelled with 3 H-AA, and lipid metabolites released into the culture medium were analyzed by high performance liquid chromatography (HPLC). Lactate dehydrogenase (LDH) release was simultaneously assayed to provide an indication of cell injury. Increasing doses of silica selectively stimulated the 5-lipoxygenase pathway of AA metabolism, while cyclooxygenase metabolite output was suppressed. LDH release increased in a linear, dose-dependent fashion over the range of silica doses used. Moreover, within 15 min following addition of a high silica dose, a shift to the production of 5-lipoxygenase metabolites occurred, accompanied by a reduction in cyclooxygenase products. This rapid alteration in AA metabolism preceded cell injury. To examine the relationship between cytotoxicity and AA metabolite release by BAM exposed to silicas with different cytotoxic and fibrogenic activities, BAM were exposed to different doses of DQ-12, Minusil-5, and Sigma silicas, and carbonyl iron beads. The median effective dose (ED 50 ) of each particulate to stimulate the release of AA metabolites and LDH was calculated. The ED 50 values for DQ-12, Minusil-5, and Sigma silica showed that the relative cytotoxicities of the different silicas for BAM corresponded to the relative potencies of the silicas to elicit 5-lipoxygenase metabolites from BAM. These results indicate that the cytotoxic, and presumed fibrogenic potential, of a silica is correlated with the potency to stimulate the release of leukotrienes from AM

  10. Silica sol as grouting material: a physio-chemical analysis.

    Science.gov (United States)

    Sögaard, Christian; Funehag, Johan; Abbas, Zareen

    2018-01-01

    At present there is a pressing need to find an environmentally friendly grouting material for the construction of tunnels. Silica nanoparticles hold great potential of replacing the organic molecule based grouting materials currently used for this purpose. Chemically, silica nanoparticles are similar to natural silicates which are essential components of rocks and soil. Moreover, suspensions of silica nanoparticles of different sizes and desired reactivity are commercially available. However, the use of silica nanoparticles as grouting material is at an early stage of its technological development. There are some critical parameters such as long term stability and functionality of grouted silica that need to be investigated in detail before silica nanoparticles can be considered as a reliable grouting material. In this review article we present the state of the art regarding the chemical properties of silica nanoparticles commercially available, as well as experience gained from the use of silica as grouting material. We give a detailed description of the mechanisms underlying the gelling of silica by different salt solutions such as NaCl and KCl and how factors such as particle size, pH, and temperature affect the gelling and gel strength development. Our focus in this review is on linking the chemical properties of silica nanoparticles to the mechanical properties to better understand their functionality and stability as grouting material. Along the way we point out areas which need further research.

  11. Mechanical losses in thin fused silica fibres

    International Nuclear Information System (INIS)

    Bilenko, I A; Braginsky, V B; Lourie, S L

    2004-01-01

    Intracavity topology of the readout system for LIGO III project and table-top QND mechanical measurements under development require the use of small probe masses and suspensions with a very low level of internal losses. A good choice is to use thin fused silica fibres similar to LIGO II mirrors suspensions. Mechanical losses of silica fibres are investigated in this work through the study of quality factor dependence on diameter for pendulum and violin modes of oscillations with diameters ranging from 1.5 to 40 μm. The estimated values of effective mechanical loss angle show noticeably greater growth with lower diameters than might be expected while extrapolating known results of research done for thicker fibres

  12. Mechanical losses in thin fused silica fibres

    Energy Technology Data Exchange (ETDEWEB)

    Bilenko, I A; Braginsky, V B; Lourie, S L [Department of Oscillatory Physics, Physics Faculty, Moscow State University (Russian Federation)

    2004-03-07

    Intracavity topology of the readout system for LIGO III project and table-top QND mechanical measurements under development require the use of small probe masses and suspensions with a very low level of internal losses. A good choice is to use thin fused silica fibres similar to LIGO II mirrors suspensions. Mechanical losses of silica fibres are investigated in this work through the study of quality factor dependence on diameter for pendulum and violin modes of oscillations with diameters ranging from 1.5 to 40 {mu}m. The estimated values of effective mechanical loss angle show noticeably greater growth with lower diameters than might be expected while extrapolating known results of research done for thicker fibres.

  13. Densification of silica glass at ambient pressure

    International Nuclear Information System (INIS)

    Zheng Lianqing; An Qi; Fu Rongshan; Ni Sidao; Luo, S.-N.

    2006-01-01

    We show that densification of silica glass at ambient pressure as observed in irradiation experiments can be attributed to defect generation and subsequent structure relaxation. In our molecular dynamics simulations, defects are created by randomly removing atoms, by displacing atoms from their nominal positions in an otherwise intact glass, and by assigning certain atom excess kinetic energy (simulated ion implantation). The former forms vacancies; displacing atoms and ion implantation produce both vacancies and 'interstitials'. Appreciable densification is induced by these defects after equilibration of the defective glasses. The structural and vibrational properties of the densified glasses are characterized, displaying resembling features regardless of the means of densification. These results indicate that relaxation of high free-energy defects into metastable amorphous structures enriched in atomic coordination serves as a common mechanism for densification of silica glass at ambient pressure

  14. Active and passive silica waveguide integration

    DEFF Research Database (Denmark)

    Hübner, Jörg; Guldberg-Kjær, Søren Andreas

    2001-01-01

    . The increasing complexity and functionality of optical networks prompts a demand for highly integrated optical circuits. On-board optical amplifiers, monolithically integrated with functionalities like switching or multiplexing/demultiplexing will allow flexible incorporation of optical integrated circuits...... in existing and future networks without affecting the power budget of the system. Silica on silicon technology offers a unique possibility to selectively dope sections of the integrated circuit with erbium where amplification is desired. Some techniques for active/passive integration are reviewed and a silica......Integrated optical amplifiers are currently regaining interest. Stand-alone single integrated amplifiers offer only limited advantage over current erbium doped fiber amplifiers, whereas arrays of integrated amplifiers are very attractive due to miniaturization and the possibility of mass production...

  15. Are Time-Dependent Fluorescence Shifts at the Tunnel Mouth of Haloalkane Dehalogenase Enzymes Dependent on the Choice of the Chromophore?

    Czech Academy of Sciences Publication Activity Database

    Amaro, Mariana; Brezovský, J.; Kováčová, S.; Maier, L.; Chaloupková, R.; Sýkora, Jan; Paruch, K.; Damborský, J.; Hof, Martin

    2013-01-01

    Roč. 117, č. 26 (2013), s. 7898-7906 ISSN 1520-6106 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388955 Keywords : DYNAMIC STOKES SHIFT * WATER-PROTEIN FLUCTUATIONS * POLAR SOLVATION DYNAMICS Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.377, year: 2013

  16. Silica removal in industrial effluents with high silica content and low hardness.

    Science.gov (United States)

    Latour, Isabel; Miranda, Ruben; Blanco, Angeles

    2014-01-01

    High silica content of de-inked paper mill effluents is limiting their regeneration and reuse after membrane treatments such as reverse osmosis (RO). Silica removal during softening processes is a common treatment; however, the effluent from the paper mill studied has a low hardness content, which makes the addition of magnesium compounds necessary to increase silica removal. Two soluble magnesium compounds (MgCl₂∙6H₂O and MgSO₄∙7H₂O) were tested at five dosages (250-1,500 mg/L) and different initial pH values. High removal rates (80-90%) were obtained with both products at the highest pH tested (11.5). With these removal efficiencies, it is possible to work at high RO recoveries (75-85%) without silica scaling. Although pH regulation significantly increased the conductivity of the waters (at pH 11.5 from 2.1 to 3.7-4.0 mS/cm), this could be partially solved by using Ca(OH)₂ instead of NaOH as pH regulator (final conductivity around 3.0 mS/cm). Maximum chemical oxygen demand (COD) removal obtained with caustic soda was lower than with lime (15 vs. 30%). Additionally, the combined use of a polyaluminum coagulant during the softening process was studied; the coagulant, however, did not significantly improve silica removal, obtaining a maximum increase of only 10%.

  17. Degradability and Clearance of Silicon, Organosilica, Silsesquioxane, Silica Mixed Oxide, and Mesoporous Silica Nanoparticles

    KAUST Repository

    Croissant, Jonas G.

    2017-01-13

    The biorelated degradability and clearance of siliceous nanomaterials have been questioned worldwide, since they are crucial prerequisites for the successful translation in clinics. Typically, the degradability and biocompatibility of mesoporous silica nanoparticles (MSNs) have been an ongoing discussion in research circles. The reason for such a concern is that approved pharmaceutical products must not accumulate in the human body, to prevent severe and unpredictable side-effects. Here, the biorelated degradability and clearance of silicon and silica nanoparticles (NPs) are comprehensively summarized. The influence of the size, morphology, surface area, pore size, and surface functional groups, to name a few, on the degradability of silicon and silica NPs is described. The noncovalent organic doping of silica and the covalent incorporation of either hydrolytically stable or redox- and enzymatically cleavable silsesquioxanes is then described for organosilica, bridged silsesquioxane (BS), and periodic mesoporous organosilica (PMO) NPs. Inorganically doped silica particles such as calcium-, iron-, manganese-, and zirconium-doped NPs, also have radically different hydrolytic stabilities. To conclude, the degradability and clearance timelines of various siliceous nanomaterials are compared and it is highlighted that researchers can select a specific nanomaterial in this large family according to the targeted applications and the required clearance kinetics.

  18. Monodisperse Magneto-Fluorescent Bifunctional Nanoprobes for Bioapplications

    Science.gov (United States)

    Zhang, Hongwang; Huang, Heng; Pralle, Arnd; Zeng, Hao

    2013-03-01

    We present the work on the synthesis of dye-doped monodisperse Fe/SiO2 core/shell nanoparticles as bifunctional probes for bioapplications. Magnetic nanoparticles (NP) have been widely studied as nano-probes for bio-imaging, sensing as well as for cancer therapy. Among all the NPs, Fe NPs have been the focus because they have very high magnetization. However, Fe NPs are usually not stable in ambient due to the fast surface oxidation of the NPs. On the other hand, dye molecules have long been used as probes for bio-imaging. But they are sensitive to environmental conditions. It requires passivation for both so that they can be stable for applications. In this work, monodisperse Fe NPs with sizes ranging from 13-20 nm have been synthesized through the chemical thermal-decomposition in a solution. Silica shells were then coated on the Fe NPs by a two-phase oil-in-water method. Dye molecules were first bonded to a silica precursor and then encapsulated into the silica shell during the coating process. The silica shells protect both the Fe NPs and dye molecules, which makes them as robust probes. The dye doped Fe/SiO2 core/shell NPs remain both highly magnetic and highly fluorescent. The stable dye doped Fe/SiO2NPs have been used as a dual functional probe for both magnetic heating and local nanoscale temperature sending, and their performance will be reported. Research supported by NSF DMR 0547036, DMR1104994.

  19. Nanosecond fluorescence spectroscopy

    International Nuclear Information System (INIS)

    Leskovar, B.

    1985-03-01

    This article is a summary of a short course lecture given in conjunction with the 1984 Nuclear Science Symposium. Measuring systems for nanosecond fluorescence spectroscopy using single-photon counting techniques are presented. These involve systems based on relaxation-type spark gap light pulser and synchronously pumped mode-locked dye lasers. Furthermore, typical characteristics and optimization of operating conditions of the critical components responsible for the system time resolution are discussed. A short comparison of the most important deconvolution methods for numerical analysis of experimental data is given particularly with respect to the signal-to-noise ratio of the fluorescence signal. 22 refs., 8 figs

  20. Fluorescence uranium determination

    International Nuclear Information System (INIS)

    Fernandez Cellini, R.; Crus Castillo, F. de la; Barrera Pinero, R.

    1960-01-01

    An equipment for analysis of uranium by fluorescence was developed in order to determine it at such a low concentration that it can not be determined by the most sensible analytical methods. this new fluorimeter was adapted to measure the fluorescence emitted by the phosphorus sodium fluoride-sodium carbonate-potasium carbonate-uranyl, being excited by ultraviolet light of 3,650 A the intensity of the light emitted was measure with a photomultiplicator RCA 5819 and the adequate electronic equipment. (Author) 19 refs

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

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  2. A flexible, bolaamphiphilic template for mesoporous silicas.

    Science.gov (United States)

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

    2013-08-28

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

  3. Novel silica-based ion exchange resin

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-11-01

    Eichrom`s highly successful Diphonixo resin resembles a conventional ion exchange resin in its use of sulfonic acid ligands on a styrene- divinylbenzene matrix. Diphonix resin exhibits rapid exchange kinetics that allow economical operation of ion exchange systems. Unlike conventional resins, Diphonix resin contains chelating ligands that are diphosphonic acid groups that recognize and remove the targeted metals and reject the more common elements such as sodium, calcium and magnesium. This latter property makes Diphonix ideal for many industrial scale applications, including those involving waste treatment. For treatment of low-level, transuranic (TRU) and high- level radioactive wastes, Diphonix`s polystyrene backbone hinders its application due to radiolytic stability of the carbon-hydrogen bonds and lack of compatibility with expected vitrification schemes. Polystyrene-based Diphonix is approximately 60% carbon- hydrogen. In response to an identified need within the Department of Energy for a resin with the positive attributes of Diphonix that also exhibits greater radiolytic stability and final waste form compatibility, Eichrom has successfully developed a new, silica-based resin version of Diphonix. Target application for this new resin is for use in environmental restoration and waste management situations involving the processing of low-level, transuranic and high-level radioactive wastes. The resin can also be used for processing liquid mixed waste (waste that contains low level radioactivity and hazardous constituents) including mixed wastes contaminated with organic compounds. Silica-based Diphonix is only 10% carbon-hydrogen, with the bulk of the matrix silica.

  4. Elastic Moduli of Permanently Densified Silica Glasses

    Science.gov (United States)

    Deschamps, T.; Margueritat, J.; Martinet, C.; Mermet, A.; Champagnon, B.

    2014-01-01

    Modelling the mechanical response of silica glass is still challenging, due to the lack of knowledge concerning the elastic properties of intermediate states of densification. An extensive Brillouin Light Scattering study on permanently densified silica glasses after cold compression in diamond anvil cell has been carried out, in order to deduce the elastic properties of such glasses and to provide new insights concerning the densification process. From sound velocity measurements, we derive phenomenological laws linking the elastic moduli of silica glass as a function of its densification ratio. The found elastic moduli are in excellent agreement with the sparse data extracted from literature, and we show that they do not depend on the thermodynamic path taken during densification (room temperature or heating). We also demonstrate that the longitudinal sound velocity exhibits an anomalous behavior, displaying a minimum for a densification ratio of 5%, and highlight the fact that this anomaly has to be distinguished from the compressibility anomaly of a-SiO2 in the elastic domain. PMID:25431218

  5. A Series of Fluorescent and Colorimetric Chemodosimeters for Selective Recognition of Cyanide Based on the FRET Mechanism.

    Science.gov (United States)

    Hua, Ying-Xi; Shao, Yongliang; Wang, Ya-Wen; Peng, Yu

    2017-06-16

    A series of fluorescence "turn-on" probes (PY, AN, NA, B1, and B2) have been developed and successfully applied to detect cyanide anions based on the Michael addition reaction and FRET mechanism. These probes demonstrated good selectivity, high sensitivity, and very fast recognition for CN - . In particular, the fluorescence response of probe NA finished within 3 s. Low limits of detection (down to 63 nM) are also obtained in these probes with remarkable fluorescence enhancement factors. In addition, fluorescence colors of these probes turned to blue, yellow, or orange upon sensing CN - . In UV-vis mode, all of them showed ratiometric response for CN - . 1 H NMR titration experiments and TDDFT calculations were taken to verify the mechanism of the specific reaction and fluorescence properties of the corresponding compounds. Moreover, silica gel plates with these probes were also fabricated and utilized to detect cyanide.

  6. 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.

  7. 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

  8. Measurement and modelization of silica opal reflection properties: Optical determination of the silica index

    Science.gov (United States)

    Avoine, Amaury; Hong, Phan Ngoc; Frederich, Hugo; Frigerio, Jean-Marc; Coolen, Laurent; Schwob, Catherine; Nga, Pham Thu; Gallas, Bruno; Maître, Agnès

    2012-10-01

    Self-assembled artificial opals (in particular silica opals) constitute a model system to study the optical properties of three-dimensional photonic crystals. The silica optical index is a key parameter to correctly describe an opal but is difficult to measure at the submicrometer scale and usually treated as a free parameter. Here, we propose a method to extract the silica index from the opal reflection spectra and we validate it by comparison with two independent methods based on infrared measurements. We show that this index gives a correct description of the opal reflection spectra, either by a band structure or by a Bragg approximation. In particular, we are able to provide explanations in quantitative agreement with the measurements for two features : the observation of a second reflection peak in specular direction, and the quasicollapse of the p-polarized main reflection peak at a typical angle of 54∘.

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

    Science.gov (United States)

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

    2016-12-01

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

  10. Monitoring by fluorescence measurements

    International Nuclear Information System (INIS)

    Malcolme-Lawes, D.J.; Gifford, L.A.

    1981-01-01

    A fluorimetric detector is described in which the fluorescence excitation source may be 3 H, 14 C, 35 S, 147 Pm or 63 Ni. Such a detector can be adapted for use with flowing liquid systems especially liquid chromatography systems. (U.K.)

  11. Fluorescence lifetime based bioassays

    Science.gov (United States)

    Meyer-Almes, Franz-Josef

    2017-12-01

    Fluorescence lifetime (FLT) is a robust intrinsic property and material constant of fluorescent matter. Measuring this important physical indicator has evolved from a laboratory curiosity to a powerful and established technique for a variety of applications in drug discovery, medical diagnostics and basic biological research. This distinct trend was mainly driven by improved and meanwhile affordable laser and detection instrumentation on the one hand, and the development of suitable FLT probes and biological assays on the other. In this process two essential working approaches emerged. The first one is primarily focused on high throughput applications employing biochemical in vitro assays with no requirement for high spatial resolution. The second even more dynamic trend is the significant expansion of assay methods combining highly time and spatially resolved fluorescence data by fluorescence lifetime imaging. The latter approach is currently pursued to enable not only the investigation of immortal tumor cell lines, but also specific tissues or even organs in living animals. This review tries to give an actual overview about the current status of FLT based bioassays and the wide range of application opportunities in biomedical and life science areas. In addition, future trends of FLT technologies will be discussed.

  12. Fluorescent Lamp Replacement Study

    Science.gov (United States)

    2017-07-01

    not be cited for purposes of advertisement. DISPOSITION INSTRUCTIONS: Destroy this document when no longer needed. Do not return to the... recycling , and can be disposed safely in a landfill. (2) LEDs offer reduced maintenance costs and fewer bulb replacements, significantly reducing... recycling . Several fixtures, ballasts and energy efficient fluorescent bulbs that were determined to be in pristine condition were returned to ATC

  13. Statistical filtering in fluorescence microscopy and fluorescence correlation spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Macháň, Radek; Kapusta, Peter; Hof, Martin

    Roč. 406 , č. 20 (2014), s. 4797-4813 ISSN 1618-2642 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388955 Keywords : Filtered fluorescence correlation spectroscopy * Fluorescence lifetime correlation spectroscopy * Fluorescence spectral correlation spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.436, year: 2014

  14. Spectrophotometric determination of silica in water. Low range

    International Nuclear Information System (INIS)

    Acosta L, E.

    1992-07-01

    The spectrophotometric method for the determination of the silica element in water, demineralized water, raw waters, laundry waters, waters treated with ion exchange resins and sea waters is described. This method covers the determination of the silica element in the interval from 20 to 1000 μg/l on 50 ml. of base sample. These limits its can be variable if the size of the used aliquot one is changed for the final determination of the silica element. (Author)

  15. Who's who in fluorescence 2008

    CERN Document Server

    Geddes, Chris D

    2008-01-01

    The Journal of Fluorescence's sixth Who's Who directory publishes the names, contact details, specialty keywords, and a brief description of scientists employing fluorescence methodology and instrumentation in their working lives. This is a unique reference.

  16. Silica scale prevention technology using organic additive, Geogard SX

    Energy Technology Data Exchange (ETDEWEB)

    Baltazar, Almario; Garcia, Serafin; Solis, Ramonito; Fragata, Jimmy; Ellseworth, Lucero; Llenarizas, Leonardo; Tabuena, Joseph Erwin (PNOC Energy Development Corporation, Makati City (Philippines))

    1998-09-15

    A field trial on the application of an organic additive, phosphino carboxylic acid copolymer, was conducted in a geothermal system to evaluate its effectiveness in preventing silica deposition from brine containing ultra high silica concentration (1000-1300 ppm). Low polymer concentration was applied for about five months, and treatment efficiency based on silica concentrations in various sampling points ranged from 64 to 98%. Treatment efficiency improved as a function of time. Massive silica scaling in the fluid collection and disposal system was minimized.

  17. Molecular Dynamics Simulations of Water Nanodroplets on Silica Surfaces

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

    2009-01-01

    and DNA microarrays technologies.4,5,6,7,8 Although extensive experimental, theoretical and computational work has been devoted to study the nature of the interaction between silica and water,2,9-16 at the molecular level a complete understanding of silica-water systems has not been reached. Contact angle...... computations of water droplets on silica surfaces offers a useful fundamental and quantitative measurement in order to study chemical and physical properties of water-silica systems.3,16,17,18 For hydrophobic systems the static and dynamic properties of the fluid-solid interface are influenced by the presence...

  18. Measurement and modelization of silica opal optical properties

    Science.gov (United States)

    Avoine, Amaury; Hong, Phan Ngoc; Frederich, Hugo; Aregahegn, Kifle; Bénalloul, Paul; Coolen, Laurent; Schwob, Catherine; Thu Nga, Pham; Gallas, Bruno; Maître, Agnès

    2014-03-01

    We present the synthesis process and optical characterization of artificial silica opals. The specular reflection spectra are analyzed and compared to band structure calculations and finite difference time domain (FDTD) simulations. The silica optical index is a key parameter to correctly describe an opal and is usually not known and treated as a free parameter. Here we propose a method to infer the silica index, as well as the silica spheres diameter, from the reflection spectra and we validate it by comparison with two independent infrared methods for the index and, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements for the spheres diameter.

  19. Measurement and modelization of silica opal optical properties

    International Nuclear Information System (INIS)

    Avoine, Amaury; Ngoc Hong, Phan; Frederich, Hugo; Aregahegn, Kifle; Bénalloul, Paul; Coolen, Laurent; Schwob, Catherine; Gallas, Bruno; Maître, Agnès; Thu Nga, Pham

    2014-01-01

    We present the synthesis process and optical characterization of artificial silica opals. The specular reflection spectra are analyzed and compared to band structure calculations and finite difference time domain (FDTD) simulations. The silica optical index is a key parameter to correctly describe an opal and is usually not known and treated as a free parameter. Here we propose a method to infer the silica index, as well as the silica spheres diameter, from the reflection spectra and we validate it by comparison with two independent infrared methods for the index and, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements for the spheres diameter. (paper)

  20. Photooxidation of ethylene over Cu-modified and unmodified silica

    OpenAIRE

    Ichihashi, Yuichi; Matsumura, Yasuyuki

    2003-01-01

    Silica catalyzes photooxidation of ethylene to carbon dioxide and modification of copper on silica results in the lower reaction rate and partial production of ethylene oxide. The reaction does not proceed by the light irradiation through a color filter (λ>280 nm). ESR measurement indicates that radical oxygen species assignable T-shape Si − O3− can be produced on silica by UV irradiation at 77 K. The same species are also found on silica modified with copper by UV irradiation whi...

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

    Directory of Open Access Journals (Sweden)

    Milan Nikolić

    2010-06-01

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

  2. Stimulated resonant scattering at stressed fused silica surface

    International Nuclear Information System (INIS)

    Bouchut, Philippe; Reymermier, Maryse

    2015-01-01

    The radiative emission in CO 2 laser heated stressed fused silica is radically modified when gold microspheres are on the surface. At high heating rates, the emission dynamics changes from thermoluminescence to stimulated resonant scattering with an emission rate that is increased tenfold and the near infrared (NIR) spectrum is red-shifted. We show that the dynamic tensile stress that rises in heated silica is coupled with a fluctuating electromagnetic field that enables electromagnetic friction between moving OH emitters from silica bulk and NIR resonant scatterers at the silica surface. (paper)

  3. Silica scintillating materials prepared by sol-gel methods

    International Nuclear Information System (INIS)

    Werst, D.W.; Sauer, M.C. Jr.; Cromack, K.R.; Lin, Y.; Tartakovsky, E.A.; Trifunac, A.D.

    1993-01-01

    Silica was investigated as a rad-hard alternative to organic polymer hosts for organic scintillators. Silica sol-gels were prepared by hydrolysis of tetramethoxysilane in alcohol solutions. organic dyes were incorporated into the gels by dissolving in methanol at the sol stage of gel formation. The silica sol-gel matrix is very rad-hard. The radiation stability of silica scintillators prepared by this method is dye-limited. Transient radioluminescence was measured following excitation with 30 ps pulses of 20 MeV electrons

  4. Tailoring silver nanoparticle construction using dendrimer templated silica networks

    International Nuclear Information System (INIS)

    Liu Xiaojun; Kakkar, Ashok

    2008-01-01

    We have examined the role of the internal environment of dendrimer templated silica networks in tailoring the construction of silver nanoparticle assemblies. Silica networks from which 3,5-dihydroxybenzyl alcohol based dendrimer templates have been completely removed, slowly wet with an aqueous solution of silver acetate. The latter then reacts with internal silica silanol groups, leading to chemisorption of silver ions, followed by the growth of silver oxide nanoparticles. Silica network constructed using generation 4 dendrimer contains residual dendrimer template, and mixes with aqueous silver acetate solution easily. Upon chemisorption, silver ions get photolytically reduced to silver metal under a stabilizing dendrimer environment, leading to the formation of silver metal nanoparticles

  5. Winter climate change and fine root biogenic silica in sugar maple trees (Acer saccharum): Implications for silica in the Anthropocene

    Science.gov (United States)

    Maguire, Timothy J.; Templer, Pamela H.; Battles, John J.; Fulweiler, Robinson W.

    2017-03-01

    Winter temperatures are projected to increase over the next century, leading to reductions in winter snowpack and increased frequency of soil freezing in many northern forest ecosystems. Here we examine biogenic silica (BSi) concentrations in sugar maple (Acer saccharum) fine roots collected from a snow manipulation experiment at Hubbard Brook Experimental Forest (New Hampshire, USA). Increased soil freezing significantly lowered the BSi content of sugar maple fine roots potentially decreasing their capacity to take up water and dissolved nutrients. The reduced silica uptake (8 ± 1 kmol silica km-2) by sugar maple fine roots is comparable to silica export from temperate forest watersheds. We estimate that fine roots account for 29% of sugar maple BSi, despite accounting for only 4% of their biomass. These results suggest that increased frequency of soil freezing will reduce silica uptake by temperate tree roots, thereby changing silica availability in downstream receiving waters.

  6. Synthesis and Fluorescence Spectra of Triazolylcoumarin Fluorescent Dyes

    Institute of Scientific and Technical Information of China (English)

    PENG Xian-fu; LI Hong-qi

    2009-01-01

    Much attention is devoted to fluorescent dyes especially those with potential in versatile applications. Reactions under "click" conditions between nonfluorescent 3 - azidocoumarins and terminal alkynes produced 3 -(1, 2, 3- triazol- 1 - yl)cournarins, a novel type of fluorescent dyes with intense fluorescence. The structures of the new coumarins were characterized by 1H NMR, MS, and IR spectra. Fluorescence spectra measurement demonstrated excellent fluorescence performance of the triazolylcoumarins and this click reaction is a promising candidate for bioconjugation and bioimaging applications since both azide and alkynes are quite inert to biological systems.

  7. Fluorescence spectroscopy of dental calculus

    International Nuclear Information System (INIS)

    Bakhmutov, D; Gonchukov, S; Sukhinina, A

    2010-01-01

    The aim of the present study was to investigate the fluorescence properties of dental calculus in comparison with the properties of adjacent unaffected tooth structure using both lasers and LEDs in the UV-visible range for fluorescence excitation. The influence of calculus color on the informative signal is demonstrated. The optimal spectral bands of excitation and registration of the fluorescence are determined

  8. Fluorescence spectroscopy of dental calculus

    Science.gov (United States)

    Bakhmutov, D.; Gonchukov, S.; Sukhinina, A.

    2010-05-01

    The aim of the present study was to investigate the fluorescence properties of dental calculus in comparison with the properties of adjacent unaffected tooth structure using both lasers and LEDs in the UV-visible range for fluorescence excitation. The influence of calculus color on the informative signal is demonstrated. The optimal spectral bands of excitation and registration of the fluorescence are determined.

  9. Fluorescence Imaging Reveals Surface Contamination

    Science.gov (United States)

    Schirato, Richard; Polichar, Raulf

    1992-01-01

    In technique to detect surface contamination, object inspected illuminated by ultraviolet light to make contaminants fluoresce; low-light-level video camera views fluorescence. Image-processing techniques quantify distribution of contaminants. If fluorescence of material expected to contaminate surface is not intense, tagged with low concentration of dye.

  10. Who's who in fluorescence 2005

    CERN Document Server

    Geddes, Chris D

    2006-01-01

    The Journal of Fluorescence's third Who's Who directory publishes the names, contact details, specialty keywords, photographs, and a brief description of scientists employing fluorescence methodology and instrumentation in their working livesThe directory provides company contact details with a brief list of fluorescence-related products.

  11. Effect of support on hydro-metathesis of propene: A comparative study of W(CH 3 ) 6 anchored to silica vs. silica-alumina

    KAUST Repository

    Tretiakov, Mykyta; Samantaray, Manoja; Saidi, Aya; Basset, Jean-Marie

    2018-01-01

    Hydro-metathesis of propene was carried out by using well-defined W(CH3)6 supported on silica and silica-alumina. It was observed that W(CH3)6 supported silica-alumina catalyst is much better (TON 4577) than the silica supported catalyst (TON 2104

  12. Coupling gold nanoparticles to silica nanoparticles through disulfide bonds for glutathione detection

    International Nuclear Information System (INIS)

    Shi Yupeng; Zhang Heng; Zhang Zhaomin; Yi Changqing; Yue Zhenfeng; Teng, Kar-Seng; Li Meijin; Yang Mengsu

    2013-01-01

    Advances in the controlled assembly of nanoscale building blocks have resulted in functional devices which can find applications in electronics, biomedical imaging, drug delivery etc. In this study, novel covalent nanohybrid materials based upon [Ru(bpy) 3 ] 2+ -doped silica nanoparticles (SiNPs) and gold nanoparticles (AuNPs), which could be conditioned as OFF–ON probes for glutathione (GSH) detection, were designed and assembled in sequence, with the disulfide bonds as the bridging elements. The structural and optical properties of the nanohybrid architectures were characterized using transmission electron microscopy, UV–vis spectroscopy and fluorescence spectroscopy, respectively. Zeta potential measurements, x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were employed to monitor the reaction processes of the SiNPs–S–S–COOH and SiNPs–S–S–AuNPs synthesis. It was found that the covalent nanohybrid architectures were fluorescently dark (OFF state), indicating that SiNPs were effectively quenched by AuNPs. The fluorescence of the OFF–ON probe was resumed (ON state) when the bridge of the disulfide bond was cleaved by reducing reagents such as GSH. This work provides a new platform and strategy for GSH detection using covalent nanohybrid materials. (paper)

  13. Silica/Perfluoropolymer nanocomposites fabricated by direct melt-compounding: a novel method without surface modification on nano-silica.

    Science.gov (United States)

    Tanahashi, Mitsuru; Hirose, Masaki; Watanabe, Yusuke; Lee, Jeong-Chang; Takeda, Kunihiko

    2007-07-01

    A novel method for the fabrication of silica/perfluoropolymer nanocomposites was investigated, whereby nano-sized silica particles without surface modification were dispersed uniformly through mechanical breakdown of loosely packed agglomerates of silica nanoparticles with low fracture strength in a polymer melt during direct melt-compounding. The method consists of two stages. The first stage involves preparation of the loose silica agglomerate, and the second stage involves melt-compounding of a completely hydrophobic perfluoropolymer, poly(tetrafluoroethyleneco-perfluoropropylvinylether), with the loose silica agglomerates prepared in the first stage. In the first stage, the packing structure and the fracture strength of the silica agglomerate were controlled by destabilizing an aqueous colloidal silica solution with a mean primary diameter of 190 nm via pH control and salt addition. In the next stage, the silica/perfluoropolymer nanocomposite was fabricated by breaking down the prepared loose silica agglomerates with low fracture strength by means of a shear force inside the polymer melt during melt-compounding.

  14. One-step synthesis of solid state luminescent carbon-based silica nanohybrids for imaging of latent fingerprints

    Science.gov (United States)

    Li, Feng; Li, Hongren; Cui, Tianfang

    2017-11-01

    Fluorescent carbon-based nanomaterials(CNs) with tunable visible emission are biocompatible, environment friendly and most suitable for various biomedical applications. Despite the successes in preparing strongly fluorescent CNs, preserving the luminescence in solid materials is still challenging because of the serious emission quenching of CNs in solid state materials. In this work, fluorescent carbon and silica nanohybrids (SiCNHs) were synthesized via a simple one-step hydrothermal approach by carbonizing sodium citrate and (3-aminopropyl)triethoxysilane(APTES), and hydrolysis of tetraethyl orthosilicate(TEOS). The resultant SiCNs were characterized through X-ray diffraction (XRD), transmission electron microscopy (TEM), FT-IR, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The SiCNs exhibited strong fluorescence in both aqueous and solid states. The luminescent solid state SiCNs power were successfully used as a fluorescent labeling material for enhanced imaging of latent fingerprints(LFPs) on single background colour and multi-coloured surfaces substrates in forensic science for individual identification.

  15. Development of empirical potentials for amorphous silica

    Energy Technology Data Exchange (ETDEWEB)

    Carre, A.

    2007-09-15

    Amorphous silica (SiO{sub 2}) is of great importance in geoscience and mineralogy as well as a raw material in glass industry. Its structure is characterized as a disordered continuous network of SiO{sub 4} tetrahedra. Many efforts have been undertaken to understand the microscopic properties of silica by classical molecular dynamics (MD) simulations. In this method the interatomic interactions are modeled by an effective potential that does not take explicitely into account the electronic degrees of freedom. In this work, we propose a new methodology to parameterize such a potential for silica using ab initio simulations, namely Car-Parrinello (CP) method [Phys. Rev. Lett. 55, 2471 (1985)]. The new potential proposed is compared to the BKS potential [Phys. Rev. Lett. 64, 1955 (1990)] that is considered as the benchmark potential for silica. First, CP simulations have been performed on a liquid silica sample at 3600 K. The structural features so obtained have been compared to the ones predicted by the classical BKS potential. Regarding the bond lengths the BKS tends to underestimate the Si-O bond whereas the Si-Si bond is overestimated. The inter-tetrahedral angular distribution functions are also not well described by the BKS potential. The corresponding mean value of the SiOSi angle is found to be {approx_equal} 147 , while the CP yields to a SiOSi angle centered around 135 . Our aim is to fit a classical Born-Mayer/Coulomb pair potential using ab initio calculations. To this end, we use the force-matching method proposed by Ercolessi and Adams [Europhys. Lett. 26, 583 (1994)]. The CP configurations and their corresponding interatomic forces have been considered for a least square fitting procedure. The classical MD simulations with the resulting potential have lead to a structure that is very different from the CP one. Therefore, a different fitting criterion based on the CP partial pair correlation functions was applied. Using this approach the resulting

  16. Silica uptake in aquatic and wetland macrophytes: a strategic choice between silica, lignin and cellulose?

    Science.gov (United States)

    Schoelynck, Jonas; Bal, Kris; Backx, Hans; Okruszko, Tomasz; Meire, Patrick; Struyf, Eric

    2010-04-01

    *Although silica (Si) is not an essential element for plant growth in the classical sense, evidence points towards its functionality for a better resistance against (a)biotic stress. Recently, it was shown that wetland vegetation has a considerable impact on silica biogeochemistry. However, detailed information on Si uptake in aquatic macrophytes is lacking. *We investigated the biogenic silica (BSi), cellulose and lignin content of 16 aquatic/wetland species along the Biebrza river (Poland) in June 2006 and 2007. The BSi data were correlated with cellulose and lignin concentrations. *Our results show that macrophytes contain significant amounts of BSi: between 2 and 28 mg BSi g(-1). This is in the same order of magnitude as wetland species (especially grasses). Significant antagonistic correlations were found between lignin, cellulose and BSi content. Interestingly, observed patterns were opposite for wetland macrophytes and true aquatic macrophytes. *We conclude that macrophytes have an overlooked but potentially vast storage capacity for Si. Study of their role as temporal silica sinks along the land-ocean continuum is needed. This will further understanding of the role of ecosystems on land ocean transport of this essential nutrient.

  17. Health hazards due to the inhalation of amorphous silica

    Energy Technology Data Exchange (ETDEWEB)

    Merget, R.; Bruening, T. [Research Institute for Occupational Medicine (BGFA), Bochum (Germany); Bauer, T. [Bergmannsheil, University Hospital, Department of Internal Medicine, Division of Pneumonology, Allergology and Sleep Medicine, Bochum (Germany); Kuepper, H.U.; Breitstadt, R. [Degussa-Huels Corp., Wesseling (Germany); Philippou, S. [Department of Pathology, Augusta Krankenanstalten, Bochum (Germany); Bauer, H.D. [Research Institute for Hazardous Substances (IGF), Bochum (Germany)

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic (''thermal'' or ''fumed'') silica, and (3) chemically or physically modified silica. According to the different physico-chemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or

  18. Phosphoryl functionalized mesoporous silica for uranium adsorption

    International Nuclear Information System (INIS)

    Xue, Guo; Yurun, Feng; Li, Ma; Dezhi, Gao; Jie, Jing; Jincheng, Yu; Haibin, Sun; Hongyu, Gong; Yujun, Zhang

    2017-01-01

    Highlights: • Phosphoryl functionalized mesoporous silica (TBP-SBA-15) is synthesized. • The amino and phosphoryl groups are successfully grafted on SBA-15. • TBP-SBA-15 has high and rapid uranium adsorption capacity in broad pH range. • The U(VI) adsorption of TBP-SBA-15 is spontaneous and belongs to chemical adsorption. - Abstract: Phosphoryl functionalized mesoporous silica (TBP-SBA-15) was synthesized by modified mesoporous silica with γ-amino propyl triethoxy silane and tributyl phosphate. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), small angle X-ray diffraction (SAXRD), thermo-gravimetric/differential thermalanalyzer (TG/DTA), N_2 adsorption–desorption (BET) and Fourier transform infrared spectroscopy (FT-IR) techniques. Results showed that TBP-SBA-15 had large surface areas with ordered channel structure. Moreover, the effects of adsorption time, sorbent dose, solution pH, initial uranium concentration and temperature on the uranium adsorption behaviors were investigated. TBP-SBA-15 showed a high uranium adsorption capacity in a broad range of pH values. The U(VI) adsorption rate of TBP-SBA-15 was fast and nearly achieved completion in 10 min with the sorbent dose of 1 g/L. The U(VI) adsorption of TBP-SBA-15 followed the pseudo-second-order kinetic model and Freundlich isotherm model, indicating that the process was belonged to chemical adsorption. Furthermore, the thermodynamic parameters (ΔG"0, ΔH"0 and ΔS"0) confirmed that the adsorption process was endothermic and spontaneous.

  19. Phosphoryl functionalized mesoporous silica for uranium adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Guo; Yurun, Feng; Li, Ma; Dezhi, Gao; Jie, Jing; Jincheng, Yu; Haibin, Sun [Key Laboratory for Liquid-Solid Structural Evolution & Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Hongyu, Gong, E-mail: gong_hongyu@163.com [Key Laboratory for Liquid-Solid Structural Evolution & Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Yujun, Zhang, E-mail: yujunzhangcn@163.com [Key Laboratory for Liquid-Solid Structural Evolution & Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, Shandong University, Jinan 250061 (China)

    2017-04-30

    Highlights: • Phosphoryl functionalized mesoporous silica (TBP-SBA-15) is synthesized. • The amino and phosphoryl groups are successfully grafted on SBA-15. • TBP-SBA-15 has high and rapid uranium adsorption capacity in broad pH range. • The U(VI) adsorption of TBP-SBA-15 is spontaneous and belongs to chemical adsorption. - Abstract: Phosphoryl functionalized mesoporous silica (TBP-SBA-15) was synthesized by modified mesoporous silica with γ-amino propyl triethoxy silane and tributyl phosphate. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), small angle X-ray diffraction (SAXRD), thermo-gravimetric/differential thermalanalyzer (TG/DTA), N{sub 2} adsorption–desorption (BET) and Fourier transform infrared spectroscopy (FT-IR) techniques. Results showed that TBP-SBA-15 had large surface areas with ordered channel structure. Moreover, the effects of adsorption time, sorbent dose, solution pH, initial uranium concentration and temperature on the uranium adsorption behaviors were investigated. TBP-SBA-15 showed a high uranium adsorption capacity in a broad range of pH values. The U(VI) adsorption rate of TBP-SBA-15 was fast and nearly achieved completion in 10 min with the sorbent dose of 1 g/L. The U(VI) adsorption of TBP-SBA-15 followed the pseudo-second-order kinetic model and Freundlich isotherm model, indicating that the process was belonged to chemical adsorption. Furthermore, the thermodynamic parameters (ΔG{sup 0}, ΔH{sup 0} and ΔS{sup 0}) confirmed that the adsorption process was endothermic and spontaneous.

  20. Fluorescence fluctuation spectroscopy (FFS)

    CERN Document Server

    Tetin, Sergey

    2012-01-01

    This new volume of Methods in Enzymology continues the legacy of this premier serial with quality chapters authored by leaders in the field. This volume covers fluorescence fluctuation spectroscopy and includes chapters on such topics as Förster resonance energy transfer (fret) with fluctuation algorithms, protein corona on nanoparticles by FCS, and FFS approaches to the study of receptors in live cells. Continues the legacy of this premier serial with quality chapters authored by leaders in the field Covers fluorescence fluctuation spectroscopy Contains chapters on such topics as Förster resonance energy transfer (fret) with fluctuation algorithms, protein corona on nanoparticles by FCS, and FFS approaches to the study of receptors in live cells.

  1. Fluorescent quantification of melanin.

    Science.gov (United States)

    Fernandes, Bruno; Matamá, Teresa; Guimarães, Diana; Gomes, Andreia; Cavaco-Paulo, Artur

    2016-11-01

    Melanin quantification is reportedly performed by absorption spectroscopy, commonly at 405 nm. Here, we propose the implementation of fluorescence spectroscopy for melanin assessment. In a typical in vitro assay to assess melanin production in response to an external stimulus, absorption spectroscopy clearly overvalues melanin content. This method is also incapable of distinguishing non-melanotic/amelanotic control cells from those that are actually capable of performing melanogenesis. Therefore, fluorescence spectroscopy is the best method for melanin quantification as it proved to be highly specific and accurate, detecting even small variations in the synthesis of melanin. This method can also be applied to the quantification of melanin in more complex biological matrices like zebrafish embryos and human hair. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  2. Functionalized mesoporous silica materials for molsidomine adsorption: Thermodynamic study

    Energy Technology Data Exchange (ETDEWEB)

    Alyoshina, Nonna A.; Parfenyuk, Elena V., E-mail: evp@iscras.ru

    2013-09-15

    A series of unmodified and organically modified mesoporous silica materials was prepared. The unmodified mesoporous silica was synthesized via sol–gel synthesis in the presence of D-glucose as pore-forming agent. The functionalized by phenyl, aminopropyl and mercaptopropyl groups silica materials were prepared via grafting. The fabricated adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, N{sub 2} adsorption/desorption and elemental analysis methods. Then their adsorption properties for mesoionic dug molsidomine were investigated at 290–313 K and physiological pH value. Thermodynamic parameters of molsidomine adsorption on the synthesized materials have been calculated. The obtained results showed that the adsorption process of molsidomine on the phenyl modified silica is the most quantitatively and energetically favorable. The unmodified and mercaptopropyl modified silica materials exhibit significantly higher adsorption capacities and energies for molsidomine than the aminopropyl modified sample. The effects are discussed from the viewpoint of nature of specific interactions responsible for the adsorption. - Graphical abstract: Comparative analysis of the thermodynamic characteristics of molsidomine adsorption showed that the adsorption process on mesoporous silica materials is controlled by chemical nature of surface functional groups. Molsidomine adsorption on the phenyl modified silica is the most quantitatively and energetically favorable. Taking into account ambiguous nature of mesoionic compounds, it was found that molsidomine is rather aromatic than dipolar. Display Omitted - Highlights: • Unmodified and organically modified mesoporous silica materials were prepared. • Molsidomine adsorption on the silica materials was studied. • Phenyl modified silica shows the highest adsorption capacity and favorable energy. • Molsidomine exhibits the lowest affinity to aminopropyl modified silica.

  3. Functionalized mesoporous silica materials for molsidomine adsorption: Thermodynamic study

    International Nuclear Information System (INIS)

    Alyoshina, Nonna A.; Parfenyuk, Elena V.

    2013-01-01

    A series of unmodified and organically modified mesoporous silica materials was prepared. The unmodified mesoporous silica was synthesized via sol–gel synthesis in the presence of D-glucose as pore-forming agent. The functionalized by phenyl, aminopropyl and mercaptopropyl groups silica materials were prepared via grafting. The fabricated adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, N 2 adsorption/desorption and elemental analysis methods. Then their adsorption properties for mesoionic dug molsidomine were investigated at 290–313 K and physiological pH value. Thermodynamic parameters of molsidomine adsorption on the synthesized materials have been calculated. The obtained results showed that the adsorption process of molsidomine on the phenyl modified silica is the most quantitatively and energetically favorable. The unmodified and mercaptopropyl modified silica materials exhibit significantly higher adsorption capacities and energies for molsidomine than the aminopropyl modified sample. The effects are discussed from the viewpoint of nature of specific interactions responsible for the adsorption. - Graphical abstract: Comparative analysis of the thermodynamic characteristics of molsidomine adsorption showed that the adsorption process on mesoporous silica materials is controlled by chemical nature of surface functional groups. Molsidomine adsorption on the phenyl modified silica is the most quantitatively and energetically favorable. Taking into account ambiguous nature of mesoionic compounds, it was found that molsidomine is rather aromatic than dipolar. Display Omitted - Highlights: • Unmodified and organically modified mesoporous silica materials were prepared. • Molsidomine adsorption on the silica materials was studied. • Phenyl modified silica shows the highest adsorption capacity and favorable energy. • Molsidomine exhibits the lowest affinity to aminopropyl modified silica

  4. Fibrous composites comprising carbon nanotubes and silica

    Science.gov (United States)

    Peng, Huisheng [Shanghai, CN; Zhu, Yuntian Theodore [Cary, NC; Peterson, Dean E [Los Alamos, NM; Jia, Quanxi [Los Alamos, NM

    2011-10-11

    Fibrous composite comprising a plurality of carbon nanotubes; and a silica-containing moiety having one of the structures: (SiO).sub.3Si--(CH.sub.2).sub.n--NR.sub.1R.sub.2) or (SiO).sub.3Si--(CH.sub.2).sub.n--NCO; where n is from 1 to 6, and R.sub.1 and R.sub.2 are each independently H, CH.sub.3, or C.sub.2H.sub.5.

  5. Ordered mesoporous silica-based inorganic nanocomposites

    International Nuclear Information System (INIS)

    Wang Qingqing; Shantz, Daniel F.

    2008-01-01

    This article reviews the synthesis and characterization of nanoparticles and nanowires grown in ordered mesoporous silicas (OMS). Summarizing work performed over the last 4 years, this article highlights the material properties of the final nanocomposite in the context of the synthesis methodology employed. While certain metal-OMS systems (e.g. gold in MCM-41) have been extensively studied this article highlights that there is a rich set of chemistries that have yet to be explored. The article concludes with some thoughts on future developments and challenges in this area. - Graphical abstract: HAADF TEM image of gold nanoparticles in amine-functionalized MCM-41 (from Ref. [22])

  6. Fluorescent nanodiamond for biomedicine

    International Nuclear Information System (INIS)

    Milos Nesladek

    2014-01-01

    NV centers in diamond have gained strong interest as a novel tool for quantum information processing, quantum computing and quantum photonics. These applications are based on fluorescent and spin properties of NV-centres. However, in some conditions NV- can lose an electron and turn to NV0. The occupation of NV0 and NV- charge states depend on the position of their ground states with respect to the Fermi level and the mechanism of the charge transfer. Interestingly, that the charge switch has important implications on applications of fluorescent nanodiamond (fND) to nano-biology and nano-medicine. fND can be used for bio-marking and bio-tracking but also for the monitoring of targeted delivery to the cells. In this presentation we review the current state-of-the art for using fND particles for fluorescent bio imaging in cells and discuss the charge transfer and its luminescence stability by using ultra high sensitive spectroscopy methods to study the NV0 and NV- state occupation. (author)

  7. The Effect of Hydrothermal Treatment on Olivine Nano-Silica

    NARCIS (Netherlands)

    Griend, van de M.C; Lazaro, A.; Brouwers, H.J.H.

    2012-01-01

    This paper provides an overview of the effects of ripening the olivine nano-silica to form particles with a lower specific surface area for optimal use in high performance concrete. The nano-silica was ripened using a hydrothermal treatment in a mixed batch reactor at 90 C, pH ranging from 8 to 10

  8. Study of radon transport through concrete modified with silica fume

    International Nuclear Information System (INIS)

    Chauhan, R.P.; Kumar, Amit

    2013-01-01

    The concentration of radon in soil usually varies between a few kBq/m 3 and tens or hundreds of kBq/m 3 depending upon the geographical region. This causes the transport of radon from the soil to indoor environments by diffusion and advection through the pore space of concrete. To reduce indoor radon levels, the use of concrete with low porosity and a low radon diffusion coefficient is recommended. A method of reducing the radon diffusion coefficient through concrete and hence the indoor radon concentration by using silica fume to replace an optimum level of cement was studied. The diffusion coefficient of the concrete was reduced from (1.63 ± 0.3) × 10 −7 to (0.65 ± 0.01) × 10 −8 m 2 /s using 30% substitution of cement with silica fume. The compressive strength of the concrete increased as the silica-fume content increased, while radon exhalation rate and porosity of the concrete decreased. This study suggests a cost-effective method of reducing indoor radon levels. -- Highlights: • Radon diffusion study through silica fume modified concrete was carried out. • Radon diffusion coefficient of concrete decreased with increase of silica fume contents. • Compressive strength increased with increase of silica fume. • Radon exhalation rates and porosity of samples decreased with addition of silica fume. • Radon diffusion coefficient decreased to 2.6% by 30% silica fume substitution

  9. Fused silica thermal conductivity dispersion at high temperature

    International Nuclear Information System (INIS)

    Bouchut, P.; Decruppe, D.; Delrive, L.

    2004-01-01

    A continuous CO 2 laser is focused to locally anneal small fused silica spots. A noncontact radiometry diagnostic enables us to follow surface temperature variation that occurs from site to site. A 'steady state' dispersion of surface temperature is observed across our sample. We show that nonhomogeneous silica thermal conductivity, above 1000 K is responsible for this temperature dispersion

  10. Functionalized Mesoporous Silica Membranes for CO2 Separation Applications

    Directory of Open Access Journals (Sweden)

    Hyung-Ju Kim

    2015-01-01

    Full Text Available Mesoporous silica molecular sieves are emerging candidates for a number of potential applications involving adsorption and molecular transport due to their large surface areas, high pore volumes, and tunable pore sizes. Recently, several research groups have investigated the potential of functionalized mesoporous silica molecular sieves as advanced materials in separation devices, such as membranes. In particular, mesoporous silica with a two- or three-dimensional pore structure is one of the most promising types of molecular sieve materials for gas separation membranes. However, several important challenges must first be addressed regarding the successful fabrication of mesoporous silica membranes. First, a novel, high throughput process for the fabrication of continuous and defect-free mesoporous silica membranes is required. Second, functionalization of mesopores on membranes is desirable in order to impart selective properties. Finally, the separation characteristics and performance of functionalized mesoporous silica membranes must be further investigated. Herein, the synthesis, characterization, and applications of mesoporous silica membranes and functionalized mesoporous silica membranes are reviewed with a focus on CO2 separation.

  11. Community Geothermal Technology Program: Silica bronze project. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Bianchini, H.

    1989-10-01

    Objective was to incorporate waste silica from the HGP-A geothermal well in Pohoiki with other refractory materials for investment casting of bronze sculpture. The best composition for casting is about 50% silica, 25% red cinders, and 25% brick dust; remaining ingredient is a binder, such as plaster and water.

  12. Sonochemical synthesis of silica particles and their size control

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hwa-Min [Advanced Materials and Chemical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of); Lee, Chang-Hyun [Electronic and Electrical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of); Kim, Bonghwan, E-mail: bhkim@cu.ac.kr [Electronic and Electrical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of)

    2016-09-01

    Graphical abstract: - Highlights: • Silica particles were easily prepared by an ultrasound-assisted sol–gel method. • The particle size was controlled by the ammonium hydroxide/water molar ratio. • The size-controlled diameter of silica particles ranged from 40 to 400 nm. • The particles were formed in a relatively short reaction time. - Abstract: Using an ultrasound-assisted sol–gel method, we successfully synthesized very uniformly shaped, monodisperse, and size-controlled spherical silica particles from a mixture of ethanol, water, and tetraethyl orthosilicate in the presence of ammonia as catalyst, at room temperature. The diameters of the silica particles were distributed in the range from 40 to 400 nm; their morphology was well characterized by scanning electron microscopy. The silica particle size could be adjusted by choosing suitable concentrations of ammonium hydroxide and water, which in turn determined the nucleation and growth rates of the particles during the reaction. This sonochemical-based silica synthesis offers an alternative way to produce spherical silica particles in a relatively short reaction time. Thus, we suggest that this simple, low-cost, and efficient method of preparing uniform silica particles of various sizes will have practical and wide-ranging industrial applicability.

  13. Enhancement of nonlinear optical properties of compounds of silica

    Indian Academy of Sciences (India)

    The aim of this paper is to introduce a method for enhancing the nonlinear optical properties in silica glass by using metallic nanoparticles. First, the T-matrix method is developed to calculate the effective dielectric constant for the compound of silica glass and metallic nanoparticles, both of which possess nonlinear dielectric ...

  14. Bragg gratings in air-silica structured fibers

    NARCIS (Netherlands)

    Groothoff, N.; Canning, J.; Buckley, E.; Lyttikainen, K.; Zagari, J.

    2003-01-01

    We report on grating writing in air-silica structured optical fibers with pure silica cores by use of two-photon absorption at 193 nm. A decrease in propagation loss with irradiation was observed. The characteristic growth curves were obtained. © 2003 Optical Society of America.

  15. Precipitate coarsening and self organization in erbium-doped silica

    DEFF Research Database (Denmark)

    Sckerl, Mads W.; Guldberg-Kjær, Søren Andreas; Poulsen, Mogens Rysholt

    1999-01-01

    The influence of heat treatment at and above 1100 degrees C on thin erbium-rich silica layers embedded in silica has been studied experimentally by secondary ion-mass spectrometry and cross-sectional transmission electron microscopy. Redistribution of erbium atoms is observed at these temperature...

  16. Bioinspired silica as drug delivery systems and their biocompatibility

    DEFF Research Database (Denmark)

    Steven, Christopher R.; Busby, Grahame A.; Mather, Craig

    2014-01-01

    Silica nanoparticles have been shown to have great potential as drug delivery systems (DDS), however, their fabrication often involves harsh chemicals and energy intensive laborious methods. This work details the employment of a bioinspired "green" method for the controlled synthesis of silica, use...

  17. Dependence of thermal conductivity in micro to nano silica

    Indian Academy of Sciences (India)

    This work presents the measurement of thermal conductivity of nano-silica particles using needle probe method. The validation test of thermal probe was conducted on ice and THF hydrates using our experimental set up and the results are satisfactory when compared with the literature data. The nano silica used in this ...

  18. Drag reduction in silica nanochannels induced by graphitic wall coatings

    DEFF Research Database (Denmark)

    Wagemann, Enrique; Walther, Jens Honore; Zambrano, Harvey

    . In this work, we propose the use of graphitic materials as wall coatings in hydrophilic silica nanopores. Specifically, by conducting atomistic simulations, we investigate the flow inside slit and cylindrical silica channels with walls coated with graphene (GE) layers and carbonnanotubes (CNTs), respectively...

  19. Thermally stable silica-coated hydrophobic gold nanoparticles.

    Science.gov (United States)

    Kanehara, Masayuki; Watanabe, Yuka; Teranishi, Toshiharu

    2009-01-01

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

  20. Water evaporation in silica colloidal deposits.

    Science.gov (United States)

    Peixinho, Jorge; Lefèvre, Grégory; Coudert, François-Xavier; Hurisse, Olivier

    2013-10-15

    The results of an experimental study on the evaporation and boiling of water confined in the pores of deposits made of mono-dispersed silica colloidal micro-spheres are reported. The deposits are studied using scanning electron microscopy, adsorption of nitrogen, and adsorption of water through attenuated total reflection-infrared spectroscopy. The evaporation is characterized using differential scanning calorimetry and thermal gravimetric analysis. Optical microscopy is used to observe the patterns on the deposits after evaporation. When heating at a constant rate and above boiling temperature, the release of water out of the deposits is a two step process. The first step is due to the evaporation and boiling of the surrounding and bulk water and the second is due to the desorption of water from the pores. Additional experiments on the evaporation of water from membranes having cylindrical pores and of heptane from silica deposits suggest that the second step is due to the morphology of the deposits. Copyright © 2013 Elsevier Inc. All rights reserved.

  1. 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.

  2. Accelerated hydration of high silica cements

    International Nuclear Information System (INIS)

    Walker, Colin; Yui, Mikazu

    2012-01-01

    Current Japanese designs for high level radioactive waste (HLW) repositories anticipate the use of both bentonite (buffer and backfill material) and cement based materials. Using hydrated Ordinary Portland Cement (OPC) as a grouting material is undesirable because the associated high pH buffer will have an undisputed detrimental effect on the performance of the bentonite buffer and backfill and of the host rock by changing its porosity. Instead, hydrated low pH cement (LopHC) grouting materials are being developed to provide a pH inferior or equal to 11 to reduce these detrimental effects. LopHC grouting materials use mixtures of superfine OPC (SOPC) clinker and silica fume (SF), and are referred as high silica cements (HSC). The focus of the present study was to identify the development of the unhydrated and hydrated mineral assemblage and the solution chemistry during the hydration of HSC. Since hydration experiments of cementitious materials are notably slow, a ball mill was used to accelerate hydration. This was done for two reasons. Firstly, to develop a method to rapidly hydrate cement based materials without the need for higher temperatures (which can alter the mineral assemblage), and secondly, to ensure that the end point of hydration was reached in a reasonable time frame and so to realize the final mineralogy and solution chemistry of hydrated HSC

  3. Refractive index engineering in silica glass

    DEFF Research Database (Denmark)

    Kristensen, Martin

    2003-01-01

    . This way the glass undergoes significant physical and chemical changes and in some cases very large non-linear effects have been demonstrated. This includes a non-linear coefficient around 22 pm/V in a wavelength range near 800 nm. The author believes this is due to the combined action of silver nano......The thesis covers research performed durint the last eight years by the author in collaboration with members of his group within the field of UV-written gratings and poling of silica-based materials. The subjects cover several steps on the value chain from basic physics and chemistry via component...... in detail in chapters 4,5 and 6. Chapter 4 describes the semi-classsical model developed by the author to describe the basic UV-induced processes in germanium-doped silica. The idea behind the model is that oxygen-deficient germanium centres in the glass work as gates for the UV-photon energy, which...

  4. Structural refinement of vitreous silica bilayers

    Science.gov (United States)

    Sadjadi, Mahdi; Wilson, Mark; Thorpe, M. F.

    The importance of glasses resides not only in their applications but in fundamental questions that they put forth. The continuous random network model can successfully describe the glass structure, but determining details, like ring statistics, has always been difficult using only diffraction data. But recent atomic images of 2D vitreous silica bilayers can offer valuable new insights which are hard to be observed directly in 3D silica models/experiments (for references see). However, the experimental results are prone to uncertainty in atomic positions, systematic errors, and being finite. We employ special boundary conditions developed for such networks to refine the experimental structures. We show the best structure can be found by using various potentials to maximize information gained from the experimental samples. We find a range of densities, the so-called flexibility window, in which tetrahedra are perfect. We compare results from simulations using harmonic potentials, MD with atomic polarizabilities included and DFT. We should thank David Drabold and Bishal Bhattarai for useful discussions. Support through NSF Grant # DMS 1564468 is gratefully acknowledged.

  5. Mechanisms of anomalous compressibility of vitreous silica

    Science.gov (United States)

    Clark, Alisha N.; Lesher, Charles E.; Jacobsen, Steven D.; Sen, Sabyasachi

    2014-11-01

    The anomalous compressibility of vitreous silica has been known for nearly a century, but the mechanisms responsible for it remain poorly understood. Using GHz-ultrasonic interferometry, we measured longitudinal and transverse acoustic wave travel times at pressures up to 5 GPa in vitreous silica with fictive temperatures (Tf) ranging between 985 °C and 1500 °C. The maximum in ultrasonic wave travel times-corresponding to a minimum in acoustic velocities-shifts to higher pressure with increasing Tf for both acoustic waves, with complete reversibility below 5 GPa. These relationships reflect polyamorphism in the supercooled liquid, which results in a glassy state possessing different proportions of domains of high- and low-density amorphous phases (HDA and LDA, respectively). The relative proportion of HDA and LDA is set at Tf and remains fixed on compression below the permanent densification pressure. The bulk material exhibits compression behavior systematically dependent on synthesis conditions that arise from the presence of floppy modes in a mixture of HDA and LDA domains.

  6. Mechanical and Thermal Characterization of Silica Nanocomposites

    Science.gov (United States)

    Cunningham, Anthony Lamar

    Polymer nanocomposites are a class of materials containing nanoparticles with a large interfacial surface area. Only a small quantity of nanoparticles are needed to provide superior multifunctional properties; such as mechanical, thermal, electrical, and moisture absorption properties in polymers. Nanoparticles tend to agglomerate, so special techniques are required for homogeneous distribution. Nanosilica is now readily available as colloidal sols, for example; Nanopox RTM F400 (supplied by Evonik Nanoresins AG, Germany). The nanoparticles are first synthesized from aqueous sodium silicate solution, and then undergo a surface modification process with organosilane and matrix exchange. F400 contains 40%wt silica nanoparticles colloidally dispersed in a DGEBA epoxy resin. The mean particle diameter is about 20 nm with a narrow distribution range of about 5 to 35 nm. The objectives of this study are to develop a reproducible processing method for nanosilica enhanced resin systems used in the manufacturing of fiber reinforced composites that will be characterized for mechanical and thermal properties. Research has concluded that shows improvements in the properties of the matrix material when processed in loading variations of 0 to 25%wt silica nanoparticles. The loadings were also used to manufacture fiberglass reinforced nanocomposite laminates and also tested for mechanical and thermal properties.

  7. Pegylated silica nanoparticles: cytotoxicity and macrophage uptake

    Science.gov (United States)

    Glorani, Giulia; Marin, Riccardo; Canton, Patrizia; Pinto, Marcella; Conti, Giamaica; Fracasso, Giulio; Riello, Pietro

    2017-08-01

    Here, we present a thorough study of pegylated silica nanoparticle (SNP) interaction with different biological environments. The SNPs have a mean diameter of about 40 nm and are coated with polyethylene glycol (PEG) of different molecular weights. The physicochemical characterization of SNPs allowed the confirmation of the binding of PEG chains to the silica surface, the reproducibility of the synthesis and the narrow size-dispersion. In view of clarifying the SNP interaction with biological environments, we first assessed the SNP reactivity after the incubation with two cell lines (macrophages RAW 264.7 and primary human fibroblasts), observing a reduced toxicity of pegylated SNPs compared to the bare ones. Then, we investigated the effect of the protein adsorption on the SNP surface using the model serum protein, bovine serum albumin (BSA). We found that the protein adsorption takes place more heavily on poorly pegylated SNPs, promoting the uptake of the latter by macrophages and leading to an increased mortality of these cells. To better understand this mechanism by means of flow cytometry, the dye Ru(bpy)3Cl2 was incorporated in the SNPs. The overall results highlight the SNP potentialities as a drug delivery system, thanks to the low interactions with the macrophages.

  8. Enhanced emission of nile red fluorescent nanoparticles embedded in hybrid sol-gel glasses.

    Science.gov (United States)

    Ferrer, Maria L; del Monte, Francisco

    2005-01-13

    Highly fluorescent Nile Red (NR) nanoparticles embedded in a hybrid sol-gel glass are reported. The crystallite growth within the confined system created by the porous hybrid matrix results in NR nanoparticles of averaged dimensions below 36 nm. The preparation process allows for the control of both the conformation adopted by single NR molecules prior to aggregation (e.g., near planar) and the configuration of the aggregates (e.g., oblique with phi architecture which ultimately forms the nanoparticles. The full preservation of the fluorescent configuration of the aggregates in the nanoparticles is confirmed through the application of the exciton theory, and it is responsible for the significant increase of the fluorescence emission intensity (e.g., up to 525- and 70-fold as compared to that obtained for single NR molecules embedded in pure and hybrid silica glasses, respectively).

  9. Fluorescent nanosensors for intracellular measurements: synthesis, characterisation, calibration and measurement

    Directory of Open Access Journals (Sweden)

    Arpan Shailesh Desai

    2014-01-01

    Full Text Available Measurement of intracellular acidification is important for understanding fundamental biological pathways as well as developing effective therapeutic strategies. Fluorescent pH nanosensors are an enabling technology for real-time monitoring of intracellular acidification. The physicochemical characteristics of nanosensors can be engineered to target specific cellular compartments and respond to external stimuli. Therefore nanosensors represent a versatile approach for probing biological pathways inside cells. The fundamental components of nanosensors comprise a pH-sensitive fluorophore (signal transducer and a pH-insensitive reference fluorophore (internal standard immobilised in an inert non-toxic matrix. The inert matrix prevents interference of cellular components with the sensing elements as well as minimizing potentially harmful effects of some fluorophores on cell function. Fluorescent nanosensors are synthesised using standard laboratory equipment and are detectable by non-invasive widely accessibly imaging techniques. The outcomes of studies employing this technology are dependent on reliable methodology for performing measurements. In particular special consideration must be given to conditions for sensor calibration, uptake conditions and parameters for image analysis. We describe procedures for: 1 synthesis and characterisation of polyacrylamide and silica based nanosensors 2 nanosensor calibration and 3 performing measurements using fluorescence microscopy.

  10. A novel method for preparation of 8-hydroxyquinoline functionalized mesoporous silica: Aluminum complexes and photoluminescence studies

    Energy Technology Data Exchange (ETDEWEB)

    Badiei, Alireza, E-mail: abadiei@khayam.ut.ac.ir [School of Chemistry, College of Science, University of Tehran, P.O. Box 14155-6455, Tehran (Iran, Islamic Republic of); Goldooz, Hassan [Department of Chemistry, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Ziarani, Ghodsi Mohammadi [Department of Chemistry, Faculty of Science, Alzahra University, Tehran (Iran, Islamic Republic of)

    2011-03-15

    8-Hydroxyquinoline (8-HQ) was attached to mesoporous silica by sulfonamide bond formation between 8-hydroxyquinoline-5-sulfonyl chloride (8-HQ-SO{sub 2}Cl) and aminopropyl functionalized SBA-15 (designated as SBA-SPS-Q) and then aluminum complexes of 8-HQ was covalently bonded to SBA-SPS-Q using coordinating ability of grafted 8-HQ.The prepared materials were characterized by powder X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier transform infrared (FT-IR), thermal analysis (TGA-DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis and fluorescence spectra. The environmental effects on the emission spectra of grafted 8-HQ and its complexes were studied and discussed in details.

  11. Luminescent hybrid films obtained by covalent grafting of terbium complex to silica network

    International Nuclear Information System (INIS)

    Liu Fengyi; Fu Lianshe; Wang Jun; Liu Ze; Li Huanrong; Zhang Hongjie

    2002-01-01

    Luminescent hybrid thin films consisting of terbium complex covalently bonded to a silica-based network have been obtained in situ via a sol-gel approach. A new monomer, N-(4-benzoic acid-yl), N'-(propyltriethoxysilyl)urea (PABI), has been synthesized by grafting isocyanatopropyltriethoxysilane (ICPTES) to p-aminobenzoic acid and characterized by 1 H NMR, IR and MS. The monomer acts as a ligand for Tb 3+ ion and as a sol-gel precursor. Band emission from Tb 3+ ion due to an efficient ligand-to-metal energy transfer was observed by UV excitation. The decay curves of Tb 3+ in the hybrid films were measured. The energy difference between the triplet state energy of PABI and the 5 D 4 level of Tb 3+ ion falls in the exciting range to sensitize Tb 3+ ion fluorescence

  12. 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

  13. Inorganic Nanocrystals Functionalized Mesoporous Silica Nanoparticles: Fabrication and Enhanced Bio-applications

    Directory of Open Access Journals (Sweden)

    Tiancong Zhao

    2017-12-01

    Full Text Available Mesoporous SiO2 nanoparticles (MSNs are one of the most promising materials for bio-related applications due to advantages such as good biocompatibility, tunable mesopores, and large pore volume. However, unlike the inorganic nanocrystals with abundant physical properties, MSNs alone lack functional features. Thus, they are not sufficiently suitable for bio-applications that require special functions. Consequently, MSNs are often functionalized by incorporating inorganic nanocrystals, which provide a wide range of intriguing properties. This review focuses on inorganic nanocrystals functionalized MSNs, both their fabrication and bio-applications. Some of the most utilized methods for coating mesoporous silica (mSiO2 on nanoparticles were summarized. Magnetic, fluorescence and photothermal inorganic nanocrystals functionalized MSNs were taken as examples to demonstrate the bio-applications. Furthermore, asymmetry of MSNs and their effects on functions were also highlighted.

  14. On the role of the colloidal stability of mesoporous silica nanoparticles as gene delivery vectors

    International Nuclear Information System (INIS)

    Cebrián, Virginia; Yagüe, Clara; Arruebo, Manuel; Martín-Saavedra, Francisco M.; Santamaría, Jesus; Vilaboa, Nuria

    2011-01-01

    Mesoporous silica nanoparticles have been synthesized and functionalized with four different types of molecules containing amino groups, i.e., with primary amines only, with quaternary amines, with quaternized cyclic amines, or with polyethylenimine (PEI), which is formed by primary, secondary, and tertiary amines. These nanoparticles were then incubated with reporter plasmids and the ability of the resulting complexes to transfect human cells was studied. Only nanoparticles functionalized with PEI were efficient for transfection. The agglomeration behavior and the electrokinetic potential of the nanoparticle–plasmid complexes have been studied, as well as their cell internalization behavior using a fluorescent-labeled plasmid that allows its monitorization by confocal microscopy. The results indicate that the efficiency of PEI-functionalized nanoparticles for transfection resides to some extent in the different characteristics imparted to the nanoparticles regarding agglomeration and surface charge behavior.

  15. On the role of the colloidal stability of mesoporous silica nanoparticles as gene delivery vectors

    Energy Technology Data Exchange (ETDEWEB)

    Cebrian, Virginia [Hospital Universitario La Paz-IdiPAZ (Spain); Yaguee, Clara; Arruebo, Manuel, E-mail: arruebom@unizar.es [University of Zaragoza, Aragon Nanoscience Institute (INA), C/Mariano Esquillor, Edif. I-D (Spain); Martin-Saavedra, Francisco M. [Hospital Universitario La Paz-IdiPAZ (Spain); Santamaria, Jesus [CIBER de Bioingenieria, Biomateriales y Nanomedicina, CIBER-BBN (Spain); Vilaboa, Nuria [Hospital Universitario La Paz-IdiPAZ (Spain)

    2011-09-15

    Mesoporous silica nanoparticles have been synthesized and functionalized with four different types of molecules containing amino groups, i.e., with primary amines only, with quaternary amines, with quaternized cyclic amines, or with polyethylenimine (PEI), which is formed by primary, secondary, and tertiary amines. These nanoparticles were then incubated with reporter plasmids and the ability of the resulting complexes to transfect human cells was studied. Only nanoparticles functionalized with PEI were efficient for transfection. The agglomeration behavior and the electrokinetic potential of the nanoparticle-plasmid complexes have been studied, as well as their cell internalization behavior using a fluorescent-labeled plasmid that allows its monitorization by confocal microscopy. The results indicate that the efficiency of PEI-functionalized nanoparticles for transfection resides to some extent in the different characteristics imparted to the nanoparticles regarding agglomeration and surface charge behavior.

  16. 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.

  17. Surface characterization of polyethylene terephthalate/silica nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Parvinzadeh, Mazeyar, E-mail: mparvinzadeh@gmail.com [Department of Textile, Islamic Azad University, Science and Research Branch, Tehran (Iran, Islamic Republic of); Moradian, Siamak [Department of Polymer and Color Engineering, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Rashidi, Abosaeed [Department of Textile, Islamic Azad University, Science and Research Branch, Tehran (Iran, Islamic Republic of); Yazdanshenas, Mohamad-Esmail [Department of Textile, Islamic Azad University, Yazd Branch, Yazd (Iran, Islamic Republic of)

    2010-02-15

    Poly(ethylene terephthalate) (PET) based nanocomposites containing hydrophilic (i.e. Aerosil 200 or Aerosil TT 600) or hydrophobic (i.e. Aerosil R 972) nano-silica were prepared by melt compounding. Influence of nano-silica type on surface properties of the resultant nanocomposites was investigated by the use of Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), contact angle measurement (CAM), scanning electron microscopy (SEM) and reflectance spectroscopy (RS). The possible interaction between nano-silica particles and PET functional groups at bulk and surface were elucidated by transmission FTIR and FTIR-ATR spectroscopy, respectively. AFM studies of the resultant nanocomposites showed increased surface roughness compared to pure PET. Contact angle measurements of the resultant PET composites demonstrated that the wettability of such composites depends on surface treatment of the particular nano-silica particles used. SEM images illustrated that hydrophilic nano-silica particles tended to migrate to the surface of the PET matrix.

  18. High-average-power laser medium based on silica glass

    Science.gov (United States)

    Fujimoto, Yasushi; Nakatsuka, Masahiro

    2000-01-01

    Silica glass is one of the most attractive materials for a high-average-power laser. We have developed a new laser material base don silica glass with zeolite method which is effective for uniform dispersion of rare earth ions in silica glass. High quality medium, which is bubbleless and quite low refractive index distortion, must be required for realization of laser action. As the main reason of bubbling is due to hydroxy species remained in the gelation same, we carefully choose colloidal silica particles, pH value of hydrochloric acid for hydrolysis of tetraethylorthosilicate on sol-gel process, and temperature and atmosphere control during sintering process, and then we get a bubble less transparent rare earth doped silica glass. The refractive index distortion of the sample also discussed.

  19. Toxicity of silica nanoparticles and the effect of protein corona

    DEFF Research Database (Denmark)

    Foldbjerg, Rasmus; Jespersen, Lars Vesterby; Wang, Jing

    2010-01-01

      The cytotoxicity of silica nanoparticles (NPs) was investigated in the human lung cell line, A549. Silica NPs of different sizes (DLS size; 16-42 nm) were used to determine appropriate dose metrics whereas the effect of the NP corona was tested by coating the NPs with bovine serum albumin (BSA......). The NPs were characterized by TEM and DLS as monodisperse and non-aggregated in solution and the NP suspensions were free of metal and endotoxin impurities as tested by ICP-MS and the LAL test. Cellular uptake and binding of the silica NPs was indirectly assessed by flow cytometry side scatter and SEM...... upon silica NP exposure. The silica NP surface area was found to be the best dose metric for predicting cytotoxicity and IL-8 release. Generally, the NPs were only cytotoxic at high concentrations and BSA-coating of the NPs significantly decreased the cytotoxicity and cellular IL-8 secretion. All...

  20. Genotyping of single nucleotide polymorphism by probe-gated silica nanoparticles.

    Science.gov (United States)

    Ercan, Meltem; Ozalp, Veli C; Tuna, Bilge G

    2017-11-15

    The development of simple, reliable, and rapid approaches for molecular detection of common mutations is important for prevention and early diagnosis of genetic diseases, including Thalessemia. Oligonucleotide-gated mesoporous nanoparticles-based analysis is a new platform for mutation detection that has the advantages of sensitivity, rapidity, accuracy, and convenience. A specific mutation in β-thalassemia, one of the most prevalent inherited diseases in several countries, was used as model disease in this study. An assay for detection of IVS110 point mutation (A > G reversion) was developed by designing probe-gated mesoporous silica nanoparticles (MCM-41) loaded with reporter fluorescein molecules. The silica nanoparticles were characterized by AFM, TEM and BET analysis for having 180 nm diameter and 2.83 nm pore size regular hexagonal shape. Amine group functionalized nanoparticles were analysed with FTIR technique. Mutated and normal sequence probe oligonucleotides)about 12.7 nmol per mg nanoparticles) were used to entrap reporter fluorescein molecules inside the pores and hybridization with single stranded DNA targets amplified by PCR gave different fluorescent signals for mutated targets. Samples from IVS110 mutated and normal patients resulted in statistically significant differences when the assay procedure were applied. Copyright © 2017 Elsevier Inc. All rights reserved.