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Sample records for porous silica supporter

  1. Porous Silica-Supported Solid Lipid Particles for Enhanced Solubilization of Poorly Soluble Drugs.

    PubMed

    Yasmin, Rokhsana; Rao, Shasha; Bremmell, Kristen E; Prestidge, Clive A

    2016-07-01

    Low dissolution of drugs in the intestinal fluid can limit their effectiveness in oral therapies. Here, a novel porous silica-supported solid lipid system was developed to optimize the oral delivery of drugs with limited aqueous solubility. Using lovastatin (LOV) as the model poorly water-soluble drug, two porous silica-supported solid lipid systems (SSL-A and SSL-S) were fabricated from solid lipid (glyceryl monostearate, GMS) and nanoporous silica particles Aerosil 380 (silica-A) and Syloid 244FP (silica-S) via immersion/solvent evaporation. SSL particles demonstrated significantly higher rate and extent of lipolysis in comparison with the pure solid lipid, depending on the lipid loading levels and the morphology. The highest lipid digestion was observed when silica-S was loaded with 34% (w/w) solid lipid, and differential scanning calorimeter (DSC) analysis confirmed the encapsulation of up to 2% (w/w) non-crystalline LOV in this optimal SSL-S formulation. Drug dissolution under non-digesting intestinal conditions revealed a three- to sixfold increase in dissolution efficiencies when compared to the unformulated drug and a LOV-lipid suspension. Furthermore, the SSL-S provided superior drug solubilization under simulated intestinal digesting condition in comparison with the drug-lipid suspension and drug-loaded silica. Therefore, solid lipid and nanoporous silica provides a synergistic effect on optimizing the solubilization of poorly water-soluble compound and the solid lipid-based porous carrier system provides a promising delivery approach to overcome the oral delivery challenges of poorly water-soluble drugs. PMID:27048207

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  3. Transport of nano zero-valent iron supported by mesoporous silica microspheres in porous media.

    PubMed

    Yang, Zhangmei; Qiu, Xinhong; Fang, Zhanqiang; Pokeung, Tsang

    2015-01-01

    Effective in situ remediation of groundwater requires the successful delivery of reactive iron particles through sand. However, the agglomeration of nano zero-valent iron (NZVI) particles limits the migration distance, which inhibits their usefulness. In the study described herein, NZVI supported by mesoporous silica microspheres covered with FeOOH (SiO2@FeOOH@Fe) was synthesized, and its mobility was demonstrated on the basis of transport in porous media. Degradation of decabromodiphenyl ether (BDE209) was more efficient by SiO2@FeOOH@Fe than by 'bare' NZVI. Breakthrough curves and mass recovery showed the mobility of SiO2@FeOOH@Fe in granular media was better than that of bare NZVI. It increased greatly in the presence of natural organic matter (NOM) and decreased when high Ca2+ and Mg2+ concentrations were encountered. Analysis of the transport data on the basis of filtration theory showed diffusion to be the main mechanism for particle removal in silicon sand. Increasing the NOM may decrease agglomeration of the grains of sand, which has a positive effect on the mobility of SiO2@FeOOH@Fe. Presumably, increasing the concentrations of Ca2+ and Mg2+ compresses the diffuse double layer of SiO2@FeOOH@Fe, resulting in a reduction of mobility. PMID:26067499

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

    PubMed

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

    2010-03-15

    An acrylic acid emulsion mixture is used for synthesis of novel porous silica (E-Si) material. The photocatalytic activity of TiO2 under solar light irradiation for isoproturon (herbicide) degradation is drastically increased when dispersed over E-Si support using solid state dispersion (SSD) technique. The composite material is characterized by XRD, nitrogen adsorption-desorption isotherms, UV-vis DRS, SEM and TEM measurements. The photocatalytic activities of the composite catalysts are evaluated for different parameters. The 5 wt% TiO2/E-Si is found to be highly active for isoproturon degradation. PMID:19962829

  5. Encapsulation of folic acid in different silica porous supports: A comparative study.

    PubMed

    Pérez-Esteve, Édgar; Ruiz-Rico, María; de la Torre, Cristina; Villaescusa, Luis A; Sancenón, Felix; Marcos, María D; Amorós, Pedro; Martínez-Máñez, Ramón; Barat, José Manuel

    2016-04-01

    Although folic acid is essential to numerous bodily functions, recent research indicates that a massive exposition to the vitamin could be a double-edged sword. In this study, the capacity of different caped mesoporous silica particles (i.e. Hollow Silica Shells, MCM-41, SBA-15 and UVM-7) to dose FA during its passage through the gastrointestinal tract has been evaluated. Results confirmed that the four capped materials were capable to hinder the delivery of FA at low pH (i.e. stomach) as well as able to deliver great amounts of the vitamin at neutral pH (i.e. intestine). Nevertheless, the encapsulation efficiency and the deliver kinetics differed among supports. While supports with large pore entrance exhibited an initial fast release, MCM-41, showed a sustained release along the time. This correlation between textural properties and release kinetics for each of the supports reveals the importance of a proper support selection as a strategy to control the delivery of active molecules. PMID:26593466

  6. Fluid diffusion in porous silica

    NASA Astrophysics Data System (ADS)

    McCann, Lowell I.

    Fluid motion in porous media has received a great deal of theoretical and experimental attention due to its importance in systems as diverse as ground water aquifers, catalytic processes, and size separation schemes. Often, the motion of interest is the random thermal motion of molecules in a fluid undergoing no net flow. This diffusive motion is particularly important when the size of the pores is nearly the same as the size of the molecules. In this study, fluid diffusion is measured in several varieties of porous silica whose pore structure is determined by the process by which it is made. The samples in this study have porosities (φ, the ratio of the pore volume to the total sample volume) that vary from 0.3 to 0.75 and average pore radii that range from approximately 15 to 120 A. Determining the effect of the pore structure on the diffusion of a liquid in a porous material is complicated by the chemical interactions between the diffusing molecules and the pore surface. In this study, ions in a hydrophilic fluid are used to block the adsorption of the diffusing dye molecules to the hydroxyl groups covering the silica surface. This technique is unlike typical surface treatments of silica in that it does not permanently alter the pore geometry. In this work, fluid diffusion is measured with a transient holographic grating technique where interfering laser beams create a periodic refractive index modulation in the fluid. The diffraction of a third laser off this grating is monitored to determine how quickly the grating relaxes, thereby determining the diffusion coefficient of the molecules in the fluid. Varying the grating periodicity controls the length scale of the diffusion measurement from 1.2 to 100 μm which is much larger than the average pore sizes of the samples. Therefore, over these large scales, we measure 'normal' diffusion, where the mean squared displacement of a diffusing particle varies linearly with time. In one particular type of porous silica

  7. Enhancing Nucleation rates using Porous Silica

    NASA Astrophysics Data System (ADS)

    Akella, Sathish; Fraden, Seth

    2013-03-01

    The role of nucleants in promoting protein crystal nucleation is an on-going field of research. Porous silica acts as heterogeneous nucleation centers and enhances nucleation rates. For the protein lysozyme there are multiple polymorphs and we demonstrate that porous silica preferentially increases one of the polymorphs. Preliminary studies are presented in which accurate nucleation rates for the different polymorphs as a function of nucleant concentration are obtained through optical microscopy studies of thousands of crystallization trials in identical water-in-oil emulsion drops produced using microfluidics. NSF-IDBR

  8. Dynamic Compaction Modeling of Porous Silica Powder

    NASA Astrophysics Data System (ADS)

    Borg, John P.; Schwalbe, Larry; Cogar, John; Chapman, D. J.; Tsembelis, K.; Ward, Aaron; Lloyd, Andrew

    2006-07-01

    A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized a linear Us-Up Hugoniot. The compaction events were modeled with CTH, a 3D Eulerian hydrocode developed at Sandia National Laboratory. Simulated pressures at two test locations are presented and compared with measurements.

  9. Chitosan-silica hybrid porous membranes.

    PubMed

    Pandis, Christos; Madeira, Sara; Matos, Joana; Kyritsis, Apostolos; Mano, João F; Ribelles, José Luis Gómez

    2014-09-01

    Chitosan-silica porous hybrids were prepared by a novel strategy in order to improve the mechanical properties of chitosan (CHT) in the hydrogel state. The inorganic silica phase was introduced by sol-gel reactions in acidic medium inside the pores of already prepared porous scaffolds. In order to make the scaffolds insoluble in acidic media chitosan was cross-linked by genipin (GEN) with an optimum GEN concentration of 3.2 wt.%. Sol-gel reactions took place with Tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) acting as silica precursors. GPTMS served also as a coupling agent between the free amino groups of chitosan and the silica network. The morphology study of the composite revealed that the silica phase appears as a layer covering the chitosan membrane pore walls. The mechanical properties of the hybrids were characterized by means of compressive stress-strain measurements. By immersion in water the hybrids exhibit an increase in elastic modulus up to two orders of magnitude. PMID:25063153

  10. Selective porous gates made from colloidal silica nanoparticles

    PubMed Central

    Avetta, Paola; Calza, Paola; Fabbri, Debora; Magnacca, Giuliana; Scalarone, Dominique

    2015-01-01

    Summary Highly selective porous films were prepared by spin-coating deposition of colloidal silica nanoparticles on an appropriate macroporous substrate. Silica nanoparticles very homogenous in size were obtained by sol–gel reaction of a metal oxide silica precursor, tetraethyl orthosilicate (TEOS), and using polystyrene-block-poly(ethylene oxide) (PS-b-PEO) copolymers as soft-templating agents. Nanoparticles synthesis was carried out in a mixed solvent system. After spin-coating onto a macroporous silicon nitride support, silica nanoparticles were calcined under controlled conditions. An organized nanoporous layer was obtained characterized by a depth filter-like structure with internal porosity due to interparticle voids. Permeability and size-selectivity were studied by monitoring the diffusion of probe molecules under standard conditions and under the application of an external stimulus (i.e., electric field). Promising results were obtained, suggesting possible applications of these nanoporous films as selective gates for controlled transport of chemical species in solution. PMID:26665082

  11. Preparation of silica-supported porous sorbent for heavy metal ions removal in wastewater treatment by organic-inorganic hybridization combined with sucrose and polyethylene glycol imprinting.

    PubMed

    Li, Feng; Du, Ping; Chen, Wei; Zhang, Shusheng

    2007-03-01

    A new porous sorbent for wastewater treatment of metal ions was synthesized by covalent grafting of molecularly imprinted organic-inorganic hybrid on silica gel. With sucrose and polyethylene glycol 4000 (PEG 4000) being synergic imprinting molecules, covalent surface coating on silica gel was achieved by using polysaccharide-incorporated sol-gel process starting from the functional biopolymer, chitosan and an inorganic epoxy-precursor, gamma-glycidoxypropyltrimethoxysiloxane (GPTMS) at room temperature. The prepared porous sorbent was characterized by using simultaneous thermogravimetry and differential scanning calorimeter (TG/DSC), scanning electron microscopy (SEM), nitrogen adsorption porosimetry measurement and X-ray diffraction (XRD). Copper ion, Cu(2+), was chosen as the model metal ion to evaluate the effectiveness of the new biosorbent in wastewater treatment. The influence of epoxy-siloxane dose, buffer pH and co-existed ions on Cu(2+) adsorption was assessed through batch experiments. The imprinted composite sorbent offered a fast kinetics for the adsorption of Cu(2+). The uptake capacity of the sorbent imprinted by two pore-building components was higher than those imprinted with only a single component. The dynamic adsorption in column underwent a good elimination of Cu(2+) in treating electric plating wastewater. The prepared composite sorbent exhibited high reusability. Easy preparation of the described porous composite sorbent, absence of organic solvents, cost-effectiveness and high stability make this approach attractive in biosorption. PMID:17386667

  12. Solid dispersions of carvedilol with porous silica.

    PubMed

    Kovačič, Borut; Vrečer, Franc; Planinšek, Odon

    2011-01-01

    Solid dispersion particles of carvedilol (CAR) were prepared with porous silica (Sylysia 350) by the solvent evaporation method in a vacuum evaporator to ensure an effective pore-filling procedure. Two sets were prepared, each with various amounts of CAR in solid dispersions, and with the pore-filling process differing each time. Set A was prepared by a one-step filling method and set B by a multiple-step pore-filling method of CAR into porous silica. The solid dispersions were then characterized using thermal analysis, X-ray diffraction, and nitrogen adsorption experiments. The results showed that the drug release can be significantly improved compared with the dissolution of the drug in its pure crystalline or amorphous state. Drug release from solid dispersion was faster when the drug content in the solid dispersion was low, which enabled the drug to be finely dispersed along the hydrophilic carrier's surface. The results also showed that a multiple-step pore-filling procedure is more effective for drug loading as indicated by the absence of a crystalline drug state, greatly reduced porosity, and improved wettability and physical stability of the amorphous CAR. PMID:21467668

  13. Skeletal silica characterization in porous-silica low-dielectric-constant films by infrared spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Takada, Syozo; Hata, Nobuhiro; Seino, Yutaka; Fujii, Nobutoshi; Kikkawa, Takamaro

    2005-06-01

    Porous-silica low-dielectric-constant (low-k) films were prepared using a sol-gel method based on the self-assembly of surfactant templates. No change in the refractive index at 633 nm nor in the infrared-absorption intensities of C-H and O-H stretching vibrations at around 2900 and 3400cm-1 of porous-silica low-k films were observed after annealing at each temperature from 523 to 723 K. On the other hand, the Young's elastic modulus and hardness increased with the increase of annealing temperature. The structure in the complex dielectric function of porous-silica low-k films observed in between 1000 and 1400cm-1 is assigned as the asymmetric stretching vibration mode of the Si-O-Si bond. By applying the effective-medium theory by Bruggeman to the experimental results from infrared spectroscopic ellipsometry, we analyzed the skeletal silica structures. The peak positions of transverse (ωTO) and longitudinal (ωLO) vibration modes for Si-O-Si network in the silica skeleton of porous-silica films changed from 1061 to 1068cm-1 and from 1219 to 1232cm-1, respectively, with the annealing temperature. It is shown that the ωLO2/ωTO2 of skeletal silica correlates with Young's elastic modulus of porous-silica low-k films.

  14. Porous thin films of functionalized mesoporous silica nanoparticles.

    PubMed

    Kobler, Johannes; Bein, Thomas

    2008-11-25

    The synthesis of extremely small mesoporous silica nanoparticles via a specific co-condensation process with phenyl groups is demonstrated. The suspensions are ideally suited for the production of nanoscale thin films by spin-coating. Thanks to the small particle size and the resulting low surface roughness, the films show excellent optical qualities and exhibit good diffusion properties and a highly accessible pore system. The availability of such homogeneous porous thin films made it possible to use ellipsometric porosimetry (EP) as a convenient method to determine the effective porosity of the films on their original support without destroying it. It was possible to record sorption isotherms of the thin films with ellipsometry and to correlate the data with nitrogen sorption data of dried powders of the same material. The thin films showed very low refractive indices of around 1.2. PMID:19206399

  15. A Sinter-Resistant Catalytic System Based on Platinum Nanoparticles Supported on TiO2 Nanofibers and Covered by Porous Silica

    SciTech Connect

    Dai, Yunqian; Lim, Byungkwon; Yang, Yong; Cobley, Claire M.; Li, Weiyang; Cho, Eun Chul; Grayson, Benjamin; Fanson, Paul T.; Campbell, Charles T.; Sun, Yueming; Xia, Younan

    2010-10-25

    Platinum is a key catalyst that is invaluable in many important industrial processes such as CO oxidation in catalytic converters, oxidation and reduction reactions in fuel cells, nitric acid production, and petroleum cracking.[1] Many of these applications utilize Pt nanoparticles supported on oxides or porous carbon.[2] However, in practical applications that involve high temperatures (typically higher than 3008C), the Pt nanoparticles tend to lose their specific surface area and thus catalytic activity during operation because of sintering. Recent studies have shown that a porous oxide shell can act as a physical barrier to prevent sintering of unsupported metal nanoparticles and, at the same time, provide channels for chemical species to reach the surface of the nanoparticles, thus allowing the catalytic reaction to occur. This concept has been demonstrated in several systems, including Pt@SiO2,[3] Pt@CoO,[4] Pt/CeO2@SiO2,[5] Pd@SiO2,[6] Au@SiO2,[7] Au@SnO2 [8] and Au@ZrO2 [9] core– shell nanostructures. Despite these results, a sinter-resistant system has not been realized in supported Pt nanoparticle catalysts.

  16. Synthesis design of polar polymers and nanostructured porous silica

    NASA Astrophysics Data System (ADS)

    Schmidt-Winkel, Patrick Niels

    Nanostructured and functional materials have attracted a great deal of attention because of their importance for scientific and technological progress in our society. We have proposed a novel concept for functional, polar organic polymers that is based on the ferrielectric ordering of electric dipoles along the polymer backbone. In this context, a polar odd-numbered aliphatic polysulfone and low-molecular weight model compounds possessing remarkable thermal stability, degrading at 100°C above previously prepared polysulfones, have been synthesized and characterized. Mesoporous molecular sieves with uniform pores ranging from 2--50 nm in size are promising materials for catalysis, host-guest chemistry, separation, immobilization, encapsulation, insulation, etc. We have described a novel synthesis method to produce hierarchically ordered mesoporous silica in which the ordering on meso- to macroscopic length scales is controlled and significantly improved in one step. In search of a simple, efficient procedure to synthesize porous materials with ultralarge mesopores (30--50 nm), we have discovered microemulsions as novel colloidal templates for mesostructured cellular foams (MCFs). MCFs represent a new class of materials with well-defined, adjustable, and continuous ultralarge mesopores (9--42 nm). The microemulsion templating route has opened up new possibilities to engineer mesoporous systems for applications such as catalyst supports where mass transport is often limited by narrow pore openings. The microemulsion templates used to prepare MCF materials have been characterized by small-angle neutron scattering (SANS) studies. The microemulsion droplet size increases linearly with the cube root of the oil concentration, ethanol is required as cosurfactant, and the temperature behavior of the microemulsions is similar to the pure surfactant solution. In situ SANS studies of acid-synthesized SBA-15- and MCF-type silica have shown that silica condensation is fast early

  17. Nucleic acid separations using superficially porous silica particles

    PubMed Central

    Close, Elizabeth D.; Nwokeoji, Alison O.; Milton, Dafydd; Cook, Ken; Hindocha, Darsha M.; Hook, Elliot C.; Wood, Helen; Dickman, Mark J.

    2016-01-01

    Ion pair reverse-phase liquid chromatography has been widely employed for nucleic acid separations. A wide range of alternative stationary phases have been utilised in conjunction with ion pair reverse-phase chromatography, including totally porous particles, non-porous particles, macroporous particles and monolithic stationary phases. In this study we have utilised superficially porous silica particles in conjunction with ion pair reverse-phase liquid chromatography for the analysis of nucleic acids. We have investigated a range of different pore-sizes and phases for the analysis of a diverse range of nucleic acids including oligonucleotides, oligoribonucleotides, phosphorothioate oligonucleotides and high molecular weight dsDNA and RNA. The pore size of the superficially porous silica particles was shown to significantly affect the resolution of the nucleic acids. Optimum separations of small oligonucleotides such as those generated in RNase mapping experiments were obtained with 80 Å pore sizes and can readily be interfaced with mass spectrometry analysis. Improved resolution of larger oligonucleotides (>19 mers) was observed with pore sizes of 150 Å. The optimum resolution for larger dsDNA/RNA molecules was achieved using superficially porous silica particles with pore sizes of 400 Å. Furthermore, we have utilised 150 Å pore size solid-core particles to separate typical impurities of a fully phosphorothioated oligonucleotide, which are often generated in the synthesis of this important class of therapeutic oligonucleotide. PMID:26948761

  18. Dynamic Compaction Modeling Comparison for Porous Silica Powder

    NASA Astrophysics Data System (ADS)

    Borg, John; Schwalbe, Larry; Chapman, D. J.; Lloyd, Andrew; Ward, Aaron

    2005-07-01

    A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized porous material models, P-lambda and P-alpha, in conjunction with a linear Us-up Hugoniot. Two hydrocodes were used to simulate the compaction event: CTH and KO. CTH is a three-dimensional Eulerian hydrocode developed at Sandia National Laboratory and KO is a one-dimensional Lagrangian hydrocode developed at Lawrence Livermore National Laboratory. A comparison of the advantages and disadvantages, along with a discussion of the salient features, of the two models are presented.

  19. Porous polylactic acid-silica hybrids: preparation, characterization, and study of mesenchymal stem cell osteogenic differentiation.

    PubMed

    Pandis, Christos; Trujillo, Sara; Matos, Joana; Madeira, Sara; Ródenas-Rochina, Joaquín; Kripotou, Sotiria; Kyritsis, Apostolos; Mano, João F; Gómez Ribelles, José Luis

    2015-02-01

    A novel approach to reinforce polymer porous membranes is presented. In the prepared hybrid materials, the inorganic phase of silica is synthesized in-situ and inside the pores of aminolyzed polylactic acid (PLA) membranes by sol-gel reactions using tetraethylorthosilicate (TEOS) and glycidoxypropyltrimethoxysilane (GPTMS) as precursors. The hybrid materials present a porous structure with a silica layer covering the walls of the pores while GPTMS serves also as coupling agent between the organic and inorganic phase. The adjustment of silica precursors ratio allows the modulation of the thermomechanical properties. Culture of mesenchymal stem cells on these supports in osteogenic medium shows the expression of characteristic osteoblastic markers and the mineralization of the extracellular matrix. PMID:25303745

  20. Positronium formation from porous silica in backscattering and transmission geometries

    NASA Astrophysics Data System (ADS)

    Andersen, Søren L.; Johansen, Rasmus R.; Overgaard, Jakob B.; Mortensen, Johan K.; Andersen, Kristoffer K.; Thomsen, Heine D.; Lund, Mikkel D.; Chevallier, Jacques; Knudsen, Helge; Uggerhøj, Ulrik I.

    2014-05-01

    The Aarhus positron beam line is utilised to measure the positronium formation fraction from porous silica thin films created by the Glancing Angle Deposition technique. The highest formation fraction found from these studies in a backscattering geometry is (57.7 ± 1.0)% in good agreement with other measurements. In transmission mode, the maximum positronium output is found to be (12.5 ± 0.5)%. These are the first measurements of positronium formation in transmission of a porous silica thin film, a starting point for future attempts to optimise the positronium formation in transmission. Contribution to the Topical Issue "Electron and Positron Induced Processes", edited by Michael Brunger, Radu Campeanu, Masamitsu Hoshino, Oddur Ingólfsson, Paulo Limão-Vieira, Nigel Mason, Yasuyuki Nagashima and Hajime Tanuma.

  1. Nanomachines on Porous Silica Nanoparticles for Cargo Delivery

    NASA Astrophysics Data System (ADS)

    Tarn, Derrick

    The field of nanomachines based on mesoporous and microporous silica nanoparticles is a relatively new one, but has quickly gained widespread popularity due to their large potential applications. These porous nanomaterials can both carry and release a therapeutic drug molecule at a targeted location. In order to regulate the movement of cargo, nanomachines are designed and assembled onto the silica nanoparticle, ultimately creating a delivery system on the nanoscale that is capable of a stimulus-responsive delivery of its cargo. This dissertation focuses on the design, synthesis and assembly of nanomachines on both meso- and microporous silica nanoparticles to achieve the goal of cargo delivery. The six chapters of this dissertation are presented as follows: 1) the design, synthesis and modification of silica nanoparticles for their use in biology, 2) a light activated, reversible nanovalve assembled on mesoporous silica nanoparticles to achieve a size-selective cargo delivery, 3) biological applications and the delivery of anti-cancer drugs using a pseudorotaxane-based light activated nanovalve, 4) a nanogate machine that is capable of the storage and delivery of both small metal ions and useful organic cargo molecules, 5) biological applications of the nanogate machine in order to deliver calcium ions to cancerous cells to induce cell apoptosis, and 6) thin wax coated microporous silica nanoparticles that are capable of delivering small ions including oxidizers.

  2. Liquid chromatography of dextrans on porous silica beds.

    PubMed

    Eltekov, A Yu

    2005-12-23

    Kinetics, equilibrium isotherms and chromatography retention times for sorption of dextrans T-10, T-20, T-40, T-70, T-110, T-161, T-250 and T-500 on porous silica were measured at 25 degrees C. The Henry constant and retention factors for the dextrans were obtained. The values of the partition coefficient for the distribution of the dextrans between the bulk solution and the pore space were calculated within the framework of a pore volume filling model with consideration given to the ratio between the sizes of the macromolecular coils and the pore inlet. The measurements showed that this parameter depends on the structure of the sorbent and the molecular mass distribution of the dextran. The interaction of aqueous dextran solution with porous silica is characterized by the sieve effect. Large macromolecular coils of dextran T-161 cannot penetrate into the pore space of the silica sorbent with pore diameter 14 nm. The difference in Henry law constants calculated from adsorption and chromatographic data for dextrans T-70 and T-110 can be explained by the slow diffusion of dextran macromolecules into silica pores under chromatographic conditions. PMID:16183069

  3. Preparation of silica nanospheres and porous polymer membranes with controlled morphologies via nanophase separation

    PubMed Central

    2012-01-01

    We successfully synthesized two different structures, silica nanospheres and porous polymer membranes, via nanophase separation, based on a sol–gel process. Silica sol, which was in situ polymerized from tetraorthosilicate, was used as a precursor. Subsequently, it was mixed with a polymer that was used as a matrix component. It was observed that nanophase separation occurred after the mixing of polymer with silica sol and subsequent evaporation of solvents, resulting in organizing various structures, from random network silica structures to silica spheres. In particular, silica nanospheres were produced by manipulating the mixing ratio of polymer to silica sol. The size of silica beads was gradually changed from micro- to nanoscale, depending on the polymer content. At the same time, porous polymer membranes were generated by removing the silica component with hydrofluoric acid. Furthermore, porous carbon membranes were produced using carbon source polymer through the carbonization process. PMID:22873570

  4. Temperature dependence of porous silica antireflective (AR) coating

    NASA Astrophysics Data System (ADS)

    Tang, Yongxing; Le, Yueqin; Zhang, Weiqing; Jiang, Minhua; Sun, Jinren; Liu, Xiaolin

    1998-02-01

    In this paper, the antireflective coatings consisting of porous silica particles from a silica sol are applied by dip method. The relationships among composition, viscosity and temperature have been studied. The coating homogeneity is opium for the laser wavelengths of 1064 nm, 532 nm and 355 nm. The peak transmission of coated BK-7 glass substrate is higher than 99.5%. The laser induced damage thresholds of the antireflective coatings were range of 7 - 10 J/cm2, for 1 ns pulse width and 1064 nm wavelength. These damage thresholds were suitable for our national ICF program. It is noted that the optical homogeneity of coating and the viscosity of coating sol were strongly influenced by the temperatures in the duration of sol ripening.

  5. A Compaction Model for Highly Porous Silica Powder.

    NASA Astrophysics Data System (ADS)

    Church, P. D.; Tsembelis, K.

    2005-07-01

    This paper describes research to develop an equation of state to describe the behaviour of a highly porous silica powder. It shows that whilst molecular modelling techniques can be readily applied to develop a description of a compact material the description of the compaction process is more problematic. An empirical model, based upon the Lennard-Jones potential, has been shown to be capable of describing the compaction process observed in simple experiments. This development and application of the model in the Eulerian hydrocode GRIM to reproduce experimental plate impact data over a wide range of impact velocities is described and the results compared with experimental data.

  6. Photothermally responsive gold nanoparticle conjugated polymer-grafted porous hollow silica nanocapsules.

    PubMed

    Paramelle, David; Gorelik, Sergey; Liu, Ye; Kumar, Jatin

    2016-08-01

    Polymer-grafted porous hollow silica nanoparticles prepared by reversible addition-fragmentation chain transfer polymerisation have an upper critical solution temperature of 45 °C. Conjugation of 5 nm gold nanoparticles onto polymer-grafted porous hollow silica nanoparticles enables remarkable specific photothermally-induced controlled release of encapsulated Rhodamine B by laser-stimulation at physiological temperature. PMID:27427407

  7. Porous silicon nanocrystals in a silica aerogel matrix.

    PubMed

    Amonkosolpan, Jamaree; Wolverson, Daniel; Goller, Bernhard; Polisski, Sergej; Kovalev, Dmitry; Rollings, Matthew; Grogan, Michael D W; Birks, Timothy A

    2012-01-01

    Silicon nanoparticles of three types (oxide-terminated silicon nanospheres, micron-sized hydrogen-terminated porous silicon grains and micron-size oxide-terminated porous silicon grains) were incorporated into silica aerogels at the gel preparation stage. Samples with a wide range of concentrations were prepared, resulting in aerogels that were translucent (but weakly coloured) through to completely opaque for visible light over sample thicknesses of several millimetres. The photoluminescence of these composite materials and of silica aerogel without silicon inclusions was studied in vacuum and in the presence of molecular oxygen in order to determine whether there is any evidence for non-radiative energy transfer from the silicon triplet exciton state to molecular oxygen adsorbed at the silicon surface. No sensitivity to oxygen was observed from the nanoparticles which had partially H-terminated surfaces before incorporation, and so we conclude that the silicon surface has become substantially oxidised. Finally, the FTIR and Raman scattering spectra of the composites were studied in order to establish the presence of crystalline silicon; by taking the ratio of intensities of the silicon and aerogel Raman bands, we were able to obtain a quantitative measure of the silicon nanoparticle concentration independent of the degree of optical attenuation. PMID:22805684

  8. Porous silicon nanocrystals in a silica aerogel matrix

    PubMed Central

    2012-01-01

    Silicon nanoparticles of three types (oxide-terminated silicon nanospheres, micron-sized hydrogen-terminated porous silicon grains and micron-size oxide-terminated porous silicon grains) were incorporated into silica aerogels at the gel preparation stage. Samples with a wide range of concentrations were prepared, resulting in aerogels that were translucent (but weakly coloured) through to completely opaque for visible light over sample thicknesses of several millimetres. The photoluminescence of these composite materials and of silica aerogel without silicon inclusions was studied in vacuum and in the presence of molecular oxygen in order to determine whether there is any evidence for non-radiative energy transfer from the silicon triplet exciton state to molecular oxygen adsorbed at the silicon surface. No sensitivity to oxygen was observed from the nanoparticles which had partially H-terminated surfaces before incorporation, and so we conclude that the silicon surface has become substantially oxidised. Finally, the FTIR and Raman scattering spectra of the composites were studied in order to establish the presence of crystalline silicon; by taking the ratio of intensities of the silicon and aerogel Raman bands, we were able to obtain a quantitative measure of the silicon nanoparticle concentration independent of the degree of optical attenuation. PMID:22805684

  9. Dependences of Young's modulus of porous silica low dielectric constant films on skeletal structure and porosity

    NASA Astrophysics Data System (ADS)

    Takada, Syozo; Hata, Nobuhiro; Seino, Yutaka; Fujii, Nobutoshi; Kikkawa, Takamaro

    2006-12-01

    Porous silica films were prepared by spin coating the mixtures of acidic silica sol and nonionic surfactant template. The (a) porosity and (b) skeletal structure of the films were varied by adjusting the (a) template concentration and the (b) annealing temperature, respectively. Fourier transform infrared spectroscopic ellipsometry was employed to evaluate the skeletal silica structure of the films. The analysis was focused on the midinfrared (1000-1300cm-1) spectral structure which is assigned as the asymmetric stretching vibration mode of Si-O-Si bonds [Kamitsos et al., Phys. Rev. B 48, 12499 (1993)]. The spectral structure depended on both porosity and chemical bonding structure. Bruggemann's effective medium theory was employed to obtain the spectrum of "skeletal" silica from that of "porous" silica. The skeletal silica structure was then discussed in terms of the peak positions of the transverse optical (ωTO) and longitudinal optical (ωLO) vibration modes of Si-O-Si network. It was shown that the Young's elastic modulus of skeletal silica correlates well with ωLO2/ωTO2. We have obtained good correlations between ωLO2/ωTO2 of skeletal silica and elastic modulus E for two series of porous silica films with around 55% and 40% porosity. The experimental results show that the structural change in silica skeleton strongly affects the mechanical properties of porous silica low-k films.

  10. Molecular engineering of porous silica using aryl templates

    DOEpatents

    Loy, Douglas A.; Shea, Kenneth J.

    1994-01-01

    A process for manipulating the porosity of silica using a series of organic template groups covalently incorporated into the silicate matrix. The templates in the bridged polysilsesquioxanes are selectively removed from the material by oxidation with oxygen plasma or other means, leaving engineered voids or pores. The size of these pores is dependent upon the length or size of the template or spacer. The size of the templates is measured in terms of Si-Si distances which range from about 0.67 nm to 1.08 nm. Changes introduced by the loss of the templates result in a narrow range of micropores (i.e. <2 nm). Both aryl and alkyl template groups are used as spacers. Novel microporous silica materials useful as molecular seives, dessicants, and catalyst supports are produced.

  11. Molecular engineering of porous silica using aryl templates

    DOEpatents

    Loy, D.A.; Shea, K.J.

    1994-06-14

    A process is described for manipulating the porosity of silica using a series of organic template groups covalently incorporated into the silicate matrix. The templates in the bridged polysilsesquioxanes are selectively removed from the material by oxidation with oxygen plasma or other means, leaving engineered voids or pores. The size of these pores is dependent upon the length or size of the template or spacer. The size of the templates is measured in terms of Si-Si distances which range from about 0.67 nm to 1.08 nm. Changes introduced by the loss of the templates result in a narrow range of micropores (i.e. <2 nm). Both aryl and alkyl template groups are used as spacers. Novel microporous silica materials useful as molecular sieves, desiccants, and catalyst supports are produced. 3 figs.

  12. Preparation and characterization of silica nanoparticulate polyacrylonitrile composite and porous nanofibers

    NASA Astrophysics Data System (ADS)

    Ji, Liwen; Saquing, Carl; Khan, Saad A.; Zhang, Xiangwu

    2008-02-01

    In this study, polyacrylonitrile (PAN) composite nanofibers containing different amounts of silica nanoparticulates have been obtained via electrospinning. The surface morphology, thermal properties and crystal structure of PAN/silica nanofibers are characterized using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, wide-angle x-ray diffraction (WAXD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The results indicate that the addition of silica nanoparticulates affects the structure and properties of the nanofibers. In addition to PAN/silica composite nanofibers, porous PAN nanofibers have been prepared by selective removal of the silica component from PAN/silica composite nanofibers using hydrofluoric (HF) acid. ATR-FTIR and thermal gravimetric analysis (TGA) experiments validate the removal of silica nanoparticulates by HF acid, whereas SEM and TEM results reveal that the porous nanofibers obtained from composite fibers with higher silica contents exhibited more nonuniform surface morphology. The Brunauer-Emmett-Teller (BET) surface area of porous PAN nanofibers made from PAN/silica (5 wt%) composite precursors is higher than that of pure nonporous PAN nanofibers.

  13. Nanocomposites obtained by embedding of conjugated polymers in porous silicon and silica

    NASA Astrophysics Data System (ADS)

    Errien, N.; Vellutini, L.; Froyer, G.; Louarn, G.; Simos, C.; Skarka, V.; Haesaert, S.; Joubert, P.

    2005-06-01

    Porous silicon and porous silica matrices are filled up by conjugated polymers in order to obtain nanocomposite with enhanced third order optical nonlinearity. The active component is either PDA-TS thermally polymerized in situ or PT12 electropolymerized in porous silicon. The first measurements of the nonlinear properties of these nanocomposites give evidence of a significant increase of the nonlinear refractive index with respect to the standard optical materials.

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

    SciTech Connect

    Xing, Jun-Ling; Jiang, Shu-Hua; Pang, Jun-Ling; Yuan, En-Hui; Ma, Xiao-Jing; Lam, Koon-Fung; Xue, Qing-Song; Zhang, Kun

    2015-09-15

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

  15. Formation of bimodal porous silica-titania monoliths by sol-gel route

    NASA Astrophysics Data System (ADS)

    Ruzimuradov, O. N.

    2011-10-01

    Silica-titania monoliths with micrometer-scale macroporous and nanometer-scale mesoporous structure and high titania contents are prepared by sol-gel process and phase separation. Titanium alkoxide precursor was not effective in the preparation of high titania content composites because of strong decrease in phase separation tendency. Bimodal porous gels with high titania content were obtained by using inorganic salt precursors such as titanium sulfate and titanium chloride. Various characterization techniques, including SEM, XRD, Hg porosimetry and N2 adsorption have been carried out to investigate the formation process and physical-chemical properties of silica-titania monoliths. The characterization results show that the silica-titania monoliths possess a bimodal porous structure with well-dispersed titania inside silica network. The addition of titania in silica improves the thermal stability of both macroporous and mesoporous structures.

  16. Dopamine/Silica Nanoparticle Assembled, Microscale Porous Structure for Versatile Superamphiphobic Coating.

    PubMed

    Li, Fang; Du, Miao; Zheng, Qiang

    2016-02-23

    Artificial superamphiphobic surfaces, which could repel both water and low surface tension organic liquids, have been limited to particular kinds of materials or surfaces thus far. In this work, a kind of microscale porous coating was developed. Taking dopamine and hydrophilic fumed silica nanoparticles as initial building blocks, microscale porous coating was constructed via ice templation. Polydopamine bound silica nanoparticles together to form a porous structure network and rendered the coating to have potential for further postfunctionalization. After two-step CVD, the microscale porous coating changes from superhydrophilic to superamphiphobic, exhibiting super-repellency to droplets with surface tension of 73-23 mN/m. The influences of concentration of initial dopamine, hydrophilic fumed silica nanoparticles, and dry conditions on the formation of the porous structure have been studied to optimize the conditions. Coatings with different pore sizes and pore heights have been fabricated to discover the relationship between the structure parameters and the repellency of the porous coatings. Only with optimal pore size and pore height can the porous coating display superamphiphobicity. Compared with nanoscale, the microscale structure favors the achievement of superamphiphobicity. Given the outstanding adhesive ability of polydopamine, the superamphiphobic coatings have been successfully applied to various materials including artificial materials and natural materials. PMID:26828414

  17. Porous nanoparticle supported lipid bilayers (protocells) as delivery vehicles.

    PubMed

    Liu, Juewen; Stace-Naughton, Alison; Jiang, Xingmao; Brinker, C Jeffrey

    2009-02-01

    Mixing liposomes with hydrophilic particles induces fusion of the liposome onto the particle surface. Such supported bilayers have been studied extensively as models of the cell membrane, while their applications in drug delivery have not been pursued. In this communication, we report liposome fusion on mesoporous particles as a synergistic means to simultaneously load and seal cargo within the porous core. We find fusion of a cationic lipid (DOTAP) on an anionic silica particle loads an anionic fluorescent dye (calcein) into the particle to a concentration exceeding 100x that in the surrounding medium. The loaded "protocell" particles are taken up efficiently by Chinese hamster ovary cells, where, due to a reduced pH within endosomal compartments, calcein is effectively released. Compared to some other nanoparticle systems, protocells provide a simple construct for cargo loading, sealing, delivery, and release. They promise to serve as useful vectors in nanomedicine. PMID:19173660

  18. Characterization of stoichiometric nanocrystalline spinel ferrites dispersed on porous silica aerogel.

    PubMed

    Casula, M F; Concas, G; Congiu, F; Corrias, A; Loche, D; Marras, C; Spano, G

    2011-11-01

    Stoichiometric magnetic nanosized ferrites MFe2O4 (M = Mn, Co, Ni) were prepared in form of nearly spherical nanocrystals supported on a highly porous silica aerogel matrix, by a sol-gel procedure. X-ray diffraction and transmission electron microscopy indicate that these materials are made out of non-agglomerated ferrite nanocrystals having size in the 5-10 nm range. Investigation by Mössbauer Spectroscopy was used to gain insights on the superparamagnetic relaxation and on the inversion degree. Magnetic ordering at room temperature varies from superparamagnetic in the NiFe2O4 sample, highly blocked (approximately 70%) in the MnFe2O4 sample and nearly fully blocked in the CoFe2O4 sample. A fitting procedure of the Mössbauer data has been used in order to resolve the spectrum into the tetrahedral and octahedral components; in this way, an inversion degree of 0.68 (very close to bulk values) was obtained for 6 nm silica-supported CoFe2O4 nanocrystals. PMID:22413356

  19. Fabrication of autofluorescent porous silica nanoparticles for redox-responsive drug release.

    PubMed

    Cao, Na; Zhao, Yanbao; Sang, Bin; Wang, Zhihua; Cao, Liuqin; Sun, Lei; Zou, Xueyan

    2016-12-01

    Porous silica nanoparticles were prepared by emulsion-condensation route. The silica nanoparticles with diameter of 50nm have both accessible center-radial large pore channels (19.9nm) and small pore size of 3.5nm. The hierarchical porous structure endows them large pore volume for loading drugs and sustained release property. The silica nanoparticles were further modified with glucose-oxidized glutathione. The formulated Schiff base and disulfide bonds render the silica nanoparticles auto-fluorescent and redox-responsive properties. The cleavage of disulfide bonds caused by reactive thiols facilitates aminomethylbenzoic acid (AMA) release. The release of drug leads to the loss of fluorescence, which would be used to monitor the drug delivery and carrier distribution. PMID:27612720

  20. Enhancement of Li+ ion conductivity in solid polymer electrolytes using surface tailored porous silica nanofillers

    NASA Astrophysics Data System (ADS)

    Mohanta, Jagdeep; Singh, Udai P.; Panda, Subhendu K.; Si, Satyabrata

    2016-09-01

    The current study represents the design and synthesis of polyethylene oxide (PEO)-based solid polymer electrolytes by solvent casting approach using surface tailored porous silica as nanofillers. The surface tailoring of porous silica nanostructure is achieved through silanization chemistry using 3-glycidyloxypropyl trimethoxysilane in which silane part get anchored to the silica surface whereas epoxy group get stellated from the silica surface. Surface tailoring of silica with epoxy group increases the room temperature electrochemical performances of the resulting polymer electrolytes. Ammonical hydrolysis of organosilicate precursor is used for both silica preparation and their surface tailoring. The composite solid polymer electrolyte films are prepared by solution mixing of PEO with lithium salt in presence of silica nanofillers and cast into film by solvent drying, which are then characterized by impedance measurement for conductivity study and wide angle x-ray diffraction for change in polymer crystallinity. Room temperature impedance measurement reveals Li+ ion conductivity in the order of 10‑4 S cm‑1, which is correlated to the decrease in PEO crystallinity. The enhancement of conductivity is further observed to be dependent on the amount of silica as well as on their surface characteristics.

  1. Racetrack micro-resonators based on ridge waveguides made of porous silica

    NASA Astrophysics Data System (ADS)

    Girault, P.; Lorrain, N.; Lemaitre, J.; Poffo, L.; Guendouz, M.; Hardy, I.; Gadonna, M.; Gutierrez, A.; Bodiou, L.; Charrier, J.

    2015-12-01

    The fabrication of micro-resonators, made from porous silica ridge waveguides by using an electrochemical etching method of silicon substrate followed by thermal oxidation and then by a standard photolithography process, is reported. The design and fabrication process are described including a study of waveguide dimensions that provide single mode propagation and calculation of the coupling ratio between a straight access waveguide and the racetrack resonator. Scanning electronic microscopy observations and optical characterizations clearly show that the micro-resonator based on porous silica ridge waveguides has been well implemented. This porous micro-resonator is destined to be used as an optical sensor. The porous nature of the ridge waveguide constitutes the detection medium which will enhance the sensor sensitivity compared to usual micro-resonators based on the evanescent wave detection. A theoretical sensitivity of 1170 nm per refractive index unit has been calculated, taking into consideration experimental data obtained from the optical characterizations.

  2. Electrode With Porous Three-Dimensional Support

    DOEpatents

    Bernard, Patrick; Dauchier, Jean-Michel; Simonneau, Olivier

    1999-07-27

    Electrode including a paste containing particles of electrochemically active material and a conductive support consisting of a three-dimensional porous material comprising strands delimiting contiguous pores communicating via passages, characterized in that the average width L in .mu.m of said passages is related to the average diameter .O slashed. in .mu.m of said particles by the following equation, in which W and Y are dimensionless coefficients: wherein W=0.16 Y=1.69 X=202.4 .mu.m and Z=80 .mu.m

  3. Superwetting hierarchical porous silica nanofibrous membranes for oil/water microemulsion separation.

    PubMed

    Yang, Shan; Si, Yang; Fu, Qiuxia; Hong, Feifei; Yu, Jianyong; Al-Deyab, Salem S; El-Newehy, Mohamed; Ding, Bin

    2014-11-01

    Novel flexible, thermally stable and hierarchical porous silica nanofibrous membranes with superhydrophilicity and underwater superoleophobicity were prepared by a facile in situ synthesis method, which can effectively separate oil-in-water microemulsions solely driven by gravity, with an extremely high flux of 2237 L m(-2) h(-1). PMID:25260122

  4. Evaluation of the properties of a superficially porous silica stationary phase in hydrophilic interaction chromatography.

    PubMed

    McCalley, David V

    2008-06-01

    The sample capacity, column efficiency (and its variation with flow) of a superficially porous unbonded silica phase (Halo) was investigated using hydrophilic interaction chromatography (HILIC), particularly for separation of basic compounds. Sample capacity compared with totally porous silica phases was somewhat reduced, broadly in line with the decreased surface area, but still favourable compared with reversed-phase separations of these solutes. Efficiencies in excess of 100,000 plates were obtained at room temperature in reasonable analysis times by using a 45 cm coupled column, while generating back pressures compatible with conventional HPLC. Shorter columns offered the possibility of fast analysis of bases, and the unfavourable mass transfer properties reported by others at high flow rate for similar reversed-phase columns, were not apparent. While excellent peak shapes were obtained for many bases on silica HILIC phases, problems may still occur for some solutes. PMID:18440010

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

    DOEpatents

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

    2006-05-02

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

  6. Thermal-stable carbon nanotube-supported metal nanocatalysts by mesoporous silica coating.

    PubMed

    Sun, Zhenyu; Zhang, Hongye; Zhao, Yanfei; Huang, Changliang; Tao, Ranting; Liu, Zhimin; Wu, Zhenduo

    2011-05-17

    A universal strategy was developed for the preparation of high-temperature-stable carbon nanotube (CNT) -supported metal nanocatalysts by encapsulation with a mesoporous silica coating. Specifically, we first showed the design of one novel catalyst, Pt(@)CNT/SiO(2), with a controllable mesoporous silica coating in the range 11-39 nm containing pores ≈3 nm in diameter. The hollow porous silica shell offers a physical barrier to separate Pt nanoparticles from contact with each other, and at the same time the access of reactant species to Pt was not much affected. As a result, the catalyst showed high thermal stability against metal particle agglomeration or sintering even after being subjected to harsh treatments up to 500 °C. In addition, degradation in catalytic activity was minimized for the hydrogenation of nitrobenzene over the catalyst treated at 300 °C for 2 h. The scheme was also extended to coat porous silica onto the surfaces of CuRu(@)CNT and the resultant catalyst thereby can be reusable at least four times without loss of activity for the hydrogenolysis of glycerol. These results suggest that the as-prepared nanostructured CNT-supported catalysts may find promising applications, especially in those processes requiring rigorous conditions. PMID:21480615

  7. Combination of porous silica monolith and gold thin films for electrode material of supercapacitor

    NASA Astrophysics Data System (ADS)

    Pastre, A.; Cristini-Robbe, O.; Boé, A.; Raulin, K.; Branzea, D.; El Hamzaoui, H.; Kinowski, C.; Rolland, N.; Bernard, R.

    2015-12-01

    An all-solid electrical double layer supercapacitor was prepared, starting from a porous silica matrix coated with a gold thin-film. The metallization of the silica xerogel was performed by an original wet chemical process, based on the controlled growth of gold nanoparticles on two opposite faces of the silica monolith as a seed layer, followed by an electroless deposition of a continuous gold thin film. The thickness of the metallic thin film was assessed to be 700 nm. The silica plays two major roles: (1) it is used as a porous matrix for the gold electrode, creating a large specific surface area, and (2) it acts as a separator (non-metallized part of the silica). The silica monolith was soaked in a polyvinyl alcohol and phosphoric acid mixture which is used as polymer electrolyte. Capacitance effect was demonstrated by cyclic voltammetry experiments. The specific capacitance was found to be equal to 0.95 mF cm- 2 (9.5 F g-1). No major degradation occurs within more than 3000 cycles.

  8. Sol-gel synthesis of a multifunctional, hierarchically porous silica/apatite composite.

    PubMed

    Andersson, Jenny; Areva, Sami; Spliethoff, Bernd; Lindén, Mika

    2005-12-01

    In this study, a degradable, hierarchically porous silica/apatite composite material is developed from a simple low-temperature synthesis. Mesoporosity is induced in the silica portion by the use of supramolecular templating. The template is further removed by calcination. Firstly, hydroxyapatite is synthesized through a sol-gel method at near room temperature conditions. After the mineralization process, the crystal surface is coated with a mesoporous silica matrix using the templates already present in the bulk solution. The material is characterized by XRD, N(2)-sorption, FT-IR, SEM/EDS, and TEM. The coating layer is distributed fairly homogeneously over the apatite surface and the coating thickness is easily adjustable and dependent on the amount of added silica precursor. The hybrid material is shown to efficiently induce calcium phosphate formation under in vitro conditions and simultaneously work as a carrier system for drugs. PMID:15993485

  9. Porous Silica Sol-Gel Glasses Containing Reactive V2O5 Groups

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E.

    1995-01-01

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

  10. Anisotropic magnetic porous assemblies of oxide nanoparticles interconnected via silica bridges for catalytic application.

    PubMed

    Wacker, Josias B; Parashar, Virendra K; Gijs, Martin A M

    2011-04-19

    We report the microfluidic chip-based assembly of colloidal silanol-functionalized silica nanoparticles using monodisperse water-in-oil droplets as templates. The nanoparticles are linked via silica bridges, thereby forming superstructures that range from doublets to porous spherical or rod-like micro-objects. Adding magnetite nanoparticles to the colloid generates micro-objects that can be magnetically manipulated. We functionalized such magnetic porous assemblies with horseradish peroxidase and demonstrate the catalytic binding of fluorescent dye-labeled tyramide over the complete effective surface of the superstructure. Such nanoparticle assemblies permit easy manipulation and recovery after a heterogeneous catalytic process while providing a large surface similar to that of the individual nanoparticles. PMID:21417232

  11. Superwetting hierarchical porous silica nanofibrous membranes for oil/water microemulsion separation

    NASA Astrophysics Data System (ADS)

    Yang, Shan; Si, Yang; Fu, Qiuxia; Hong, Feifei; Yu, Jianyong; Al-Deyab, Salem S.; El-Newehy, Mohamed; Ding, Bin

    2014-10-01

    Novel flexible, thermally stable and hierarchical porous silica nanofibrous membranes with superhydrophilicity and underwater superoleophobicity were prepared by a facile in situ synthesis method, which can effectively separate oil-in-water microemulsions solely driven by gravity, with an extremely high flux of 2237 L m-2 h-1.Novel flexible, thermally stable and hierarchical porous silica nanofibrous membranes with superhydrophilicity and underwater superoleophobicity were prepared by a facile in situ synthesis method, which can effectively separate oil-in-water microemulsions solely driven by gravity, with an extremely high flux of 2237 L m-2 h-1. Electronic supplementary information (ESI) available: Detailed synthesis and structural confirmation of BA-CHO, FT-IR and EDX results, Movie S1-S3. See DOI: 10.1039/c4nr04668d

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    PubMed Central

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

    2015-01-01

    This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate. PMID:25644988

  14. Development of sensors for direct detection of organophosphates. Part I: Immobilization, characterization and stabilization of acetylcholinesterase and organophosphate hydrolase on silica supports.

    PubMed

    Singh, A K; Flounders, A W; Volponi, J V; Ashley, C S; Wally, K; Schoeniger, J S

    1999-12-01

    Biosensors for organophosphates in solution may be constructed by monitoring the activity of acetylcholinesterase (AChE) or organophosphate hydrolase (OPH) immobilized to a variety of microsensor platforms. The area available for enzyme immobilization is small (< 1 mm2) for microsensors. In order to construct microsensors with increased surface area for enzyme immobilization, we used a sol-gel process to create highly porous and stable silica matrices. Surface porosity of sol-gel coated surfaces was characterized using scanning electron microscopy; pore structure was found to be very similar to that of commercially available porous silica supports. Based upon this analysis, porous and non-porous silica beads were used as model substrates of sol-gel coated and uncoated sensor surfaces. Two different covalent chemistries were used to immobilize AChE and OPH to these porous and non-porous silica beads. The first chemistry used amine-silanization of silica followed by enzyme attachment using the homobifunctional linker glutaraldehyde. The second chemistry used sulfhydryl-silanization followed by enzyme attachment using the heterobifunctional linker N-gamma-maleimidobutyryloxy succinimide ester (GMBS). Surfaces were characterized in terms of total enzyme immobilized, total and specific enzyme activity, and long term stability of enzyme activity. Amine derivitization followed by glutaraldehyde linking yielded supports with greater amounts of immobilized enzyme and activity. Use of porous supports not only yielded greater amounts of immobilized enzyme and activity, but also significantly improved long term stability of enzyme activity. Enzyme was also immobilized to sol-gel coated glass slides. The mass of immobilized enzyme increased linearly with thickness of coating. However, immobilized enzyme activity saturated at a porous silica thickness of approximately 800 nm. PMID:10641290

  15. Modified porous silica antireflective coatings with laser damage resistance for Ti:sapphire

    NASA Astrophysics Data System (ADS)

    Jia, Qiaoying; Li, Haiyuan; Liu, Ruijun; Tang, Yongxing; Jiang, Zhonghong

    2005-04-01

    Porous SiO2 antireflective (AR) coatings are prepared from the colloidal silica solution modified with methyltriethoxysilane (MTES) based on the sol-gel route. The viscosity of modified silica suspensions changes but their stability keeps when MTES is introduced. The refractive indices of modified coatings vary little after bake treatment from 100 to 150 Celsius. The modified silica coatings on Ti:sapphire crystal, owning good homogeneity, display prominent antireflective effect within the laser output waveband (750-850 nm) of Ti:sapphire lasers, with average transmission above 98.6%, and own laser induced damage thresholds (LIDTs) of more than 2.2 J/cm2 at 800 nm with the pulse duration of 300 ps.

  16. The effect of elevated temperature on the strength parameters of silica acid ester consolidated porous limestones

    NASA Astrophysics Data System (ADS)

    Pápay, Zita; Török, Ákos

    2013-04-01

    The porous limestone is one of the most widespread construction materials of the monuments in Central Europe, with emblematic buildings in Vienna, Bratislava, Budapest and many other cities of Austria, Slovakia, Czech Republic and Hungary. The restoration of these monuments very often requires the consolidation of the porous limestone material, where various types of consolidants are used to strengthen the highly weathered stone. Our research focused on the understanding of the behaviour of consolidated porous limestone when the material is subjected to higher temperatures. Test procedure included the preparation of cylindrical test specimens from the Miocene porous limestone which was followed by consolidation by four various types of silica acid ester. The samples after consolidation were heated to 300 and 600 °C in electric oven. The material properties such as ultrasonic pulse velocity, density were tested before and after the treatment. Indirect tensile strength (Brazilian test) was used to compare the strength parameters of non treated and consolidated samples. Silica acid ester treated samples after heating were also measured in terms of strength, density and ultrasonic pulse velocity. The results show that there are significant changes in strength of various pre-treated samples after heating indicating the sensitivity of the materials to temperature changes and accidental fire.

  17. CO adsorption on a silica bilayer supported on Ru(0001)

    NASA Astrophysics Data System (ADS)

    Schlexer, Philomena; Pacchioni, Gianfranco; Włodarczyk, Radosław; Sauer, Joachim

    2016-06-01

    Silica bilayers are built up of two layers of corner sharing SiO4-tetrahedra and constitute an inert ultra-thin membrane supported on the Ru(0001) surface. We have investigated the adsorption of CO on that system using DFT with inclusion of dispersion corrections. The molecules adsorb at the interface between the SiO2 film and Ru(0001) surface. The estimated barrier for diffusion of CO through the silica bilayer is around 0.5 eV. The CO bond length, the C-O stretching frequency and the silica-ruthenium distance depend strongly on the CO coverage. The band observed at 2051 cm- 1 in previous experiments can be assigned to a CO coverage of around 0.5 ML on Ru(0001), with the silica bilayer floating above the CO molecules.

  18. Photocatalytic activity of erbium-doped TiO{sub 2} nanoparticles immobilized in macro-porous silica films

    SciTech Connect

    Castaneda-Contreras, J.; Maranon-Ruiz, V.F.; Chiu-Zarate, R.; Perez-Ladron de Guevara, H.; Rodriguez, R.; Michel-Uribe, C.

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Erbium-doped TiO{sub 2} nanoparticles were immobilized on macro-porous silica films. Black-Right-Pointing-Pointer The films were obtained by a phase separation process. Black-Right-Pointing-Pointer The samples exhibited photo-catalytic activity under visible light. Black-Right-Pointing-Pointer The sensitization of TiO{sub 2} was attributed to a red shift in the TiO{sub 2} band-gap. -- Abstract: A macro-porous silica film served as mechanical support to immobilize TiO{sub 2} nanoparticles, which were doped with erbium. The films and the nanoparticles were prepared by sol-gel route. The nanoparticles exhibited photocatalytic activity under visible light. We obtained a degradation rate of methylene blue that followed first order kinetics. The sensitization of the nanoparticles to visible light was attributed to a red shift in the band-gap of the TiO{sub 2} due to the addition of erbium ions.

  19. Porous silica coated spherical microresonator for vapor phase sensing of ammonia at a sub-ppm level

    NASA Astrophysics Data System (ADS)

    Mallik, Arun K.; Farrell, Gerald; Liu, Dejun; Kavungal, Vishnu; Wu, Qiang; Semenova, Yuliya

    2016-05-01

    A new type of fiber optic sensor for the detection and quantification of ammonia (NH3) vapor levels is proposed and experimentally demonstrated. This sensor is based on a spherical silica micro resonator coated with porous silica gel. Whispering gallery modes (WGMs) in the micro resonator are excited by evanescent coupling to a tapered fiber with a 3.3 μm waist diameter. The optical properties of the porous silica layer change when it is exposed to ammonia vapor, leading to a spectral shift of the WGM resonant wavelengths. The sensitivity of the proposed sensor has been tested by exposing it to different low level concentrations of ammonia: 4 ppm, 8 ppm, 12 ppm and 30 ppm at a constant relative humidity (50% RH) and constant temperature (23°C). The detection limit is calculated from experimental results as 57 ppb of ammonia for a 282 μm diameter porous silica coated microsphere.

  20. Evaluation of the acid properties of porous zirconium-doped and undoped silica materials

    SciTech Connect

    Fuentes-Perujo, D.; Santamaria-Gonzalez, J.; Merida-Robles, J.; Rodriguez-Castellon, E.; Jimenez-Lopez, A.; Maireles-Torres, P. . E-mail: maireles@uma.es; Moreno-Tost, R.

    2006-07-15

    A series of porous silica and Zr-doped silica molecular sieves, belonging to the MCM-41 and MSU families, were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N{sub 2} adsorption at 77 K. Their acid properties have been evaluated by NH{sub 3}-TPD, adsorption of pyridine and deuterated acetonitrile coupled to FT-IR spectroscopy and the catalytic tests of isopropanol decomposition and isomerization of 1-butene. The acidity of purely siliceous solids were, in all cases, very low, while the incorporation of Zr(IV) into the siliceous framework produced an enhancement of the acidity. The adsorption of basic probe molecules and the catalytic behaviour revealed that Zr-doped MSU-type silica was more acidic than the analogous Zr-MCM-41 solid, with a similar Zr content. This high acidity observed in the case of Zr-doped silica samples is due to the presence of surface zirconium atoms with a low coordination, mainly creating Lewis acid sites. - Graphical abstract: The adsorption of basic probe molecules and the catalytic behaviour have revealed that MSU-type materials are more acidic than the analogous MCM-41 solids, mainly after the incorporation of zirconium into the silica framework.

  1. Shape control of self-organized porous silica submicron particles and their strength evaluation

    NASA Astrophysics Data System (ADS)

    Kiyohara, Keita; Inoue, Keita; Inoue, Shozo; Namazu, Takahiro

    2016-06-01

    In this paper, precise control of the shape, size, and porosity of porous silica submicron particles and their strength evaluation are described. Self-organization phenomenon of silica nanopowders and submicron polystyrene latex (PSL) balls in an atomized mist is used for the fabrication of the particles. When temperatures of lower- and upper-zone heaters are 100 and 600 °C, and N2 gas flow rate is 0.4 l/min, spherical particles are produced. When PSL concentration increases, the number of pores increases. Particles with uniformly-arranged pores are produced at the PSL concentration of around 3 wt %. By using the PSL balls of different diameters, porous silica particles including different size pores are made. Also, compressive fracture test is conducted to check the effect of vacuum annealing on the strength of particles. The annealed particle shows higher fracture force than the unannealed particle, which indicates that the annealing would be effective for improving the mechanical reliability.

  2. Toward compositional design of reticular type porous films by mixing and coating titania-based frameworks with silica

    NASA Astrophysics Data System (ADS)

    Kimura, T.

    2015-12-01

    A recently developed reticular type porous structure, which can be fabricated as the film through the soft colloidal block copolymer (e.g., PS-b-PEO) templating, is very promising as the porous platform showing high-performance based on its high surface area as well as high diffusivity of targeted organic molecules and effective accommodation of bulky molecules, but the compositional design of oxide frameworks has not been developed so enough to date. Here, I report reliable synthetic methods of the reticular type porous structure toward simple compositional variations. Due to the reproducibility of reticular type porous titania films from titanium alkoxide (e.g., TTIP; titanium tetraisopropoxide), a titania-silica film having similar porous structure was obtained by mixing silicon alkoxide (e.g., tetraethoxysilane) and TTIP followed by their pre-hydrolysis, and the mixing ratio of Ti to Si composition was easily reached to 1.0. For further compositional design, a concept of surface coating was widely applicable; the reticular type porous titania surfaces can be coated with other oxides such as silica. Here, a silica coating was successfully achieved by the simple chemical vapor deposition of silicon alkoxide (e.g., tetramethoxysilane) without water (with water at the humidity level), which was also utilized for pore filling with silica by the similar process with water.

  3. Evaluation of the acid properties of porous zirconium-doped and undoped silica materials

    NASA Astrophysics Data System (ADS)

    Fuentes-Perujo, D.; Santamaría-González, J.; Mérida-Robles, J.; Rodríguez-Castellón, E.; Jiménez-López, A.; Maireles-Torres, P.; Moreno-Tost, R.; Mariscal, R.

    2006-07-01

    A series of porous silica and Zr-doped silica molecular sieves, belonging to the MCM-41 and MSU families, were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N 2 adsorption at 77 K. Their acid properties have been evaluated by NH 3-TPD, adsorption of pyridine and deuterated acetonitrile coupled to FT-IR spectroscopy and the catalytic tests of isopropanol decomposition and isomerization of 1-butene. The acidity of purely siliceous solids were, in all cases, very low, while the incorporation of Zr(IV) into the siliceous framework produced an enhancement of the acidity. The adsorption of basic probe molecules and the catalytic behaviour revealed that Zr-doped MSU-type silica was more acidic than the analogous Zr-MCM-41 solid, with a similar Zr content. This high acidity observed in the case of Zr-doped silica samples is due to the presence of surface zirconium atoms with a low coordination, mainly creating Lewis acid sites.

  4. YVO4:Eu3+ functionalized porous silica submicrospheres as delivery carriers of doxorubicin.

    PubMed

    Cheng, Ziyong; Ma, Pingan; Hou, Zhiyao; Wang, Wenxin; Dai, Yunlu; Zhai, Xuefeng; Lin, Jun

    2012-02-01

    Porous silica microspheres were fabricated by a facile surface-protected etching strategy. Polyvinylpyrrolidone (PVP) was used as a protecting polymer absorbed on the surface of silica microspheres and NaOH was employed as an etching agent. Owing to the protective action of PVP and inhomogeneous etching, mesopores were created in the silica microspheres. Then, based on the Pechini-type sol-gel and impregnating process, YVO(4):Eu(3+) nanocrystals were integrated into the channels to form highly luminescent YVO(4):Eu(3+)@SiO(2) composite microspheres. The biocompatibility tests on L929 fibroblast cells using MTT assay reveal low cytotoxicity of the system. Owing to the large interior space and electrostatic interaction, the porous microspheres show a relatively high loading capacity (438 mg DOX/YVO(4):Eu(3+)@SiO(2) g) and encapsulation efficiency (87.6%) for the anti-cancer drug doxorubicin hydrochloride (DOX). The drug release behavior and cytotoxic effect against human cervical carcinoma cells (HeLa cells) of the DOX-loaded YVO(4):Eu(3+)@SiO(2) carriers were investigated in vitro. It was found that the carriers present a highly pH-dependent drug release behavior due to electrostatic interaction between the silica surface and DOX molecules. The drug release rate became greater at low pH owing to the increased electrostatic repulsion. The DOX-loaded carriers demonstrate a similar or even greater anti-cancer activity with respect to the free DOX against HeLa cells. Furthermore, the PL intensity of the microspheres shows correlation with the cumulative release of DOX. These results suggest that the composite can potentially act as a multifunctional drug carrier system with luminescent tagging and pH-controlled release properties. PMID:22124278

  5. Thermal pretreatments of superficially porous silica particles for high-performance liquid chromatography: Surface control, structural characterization and chromatographic evaluation.

    PubMed

    Mignot, Mélanie; Sebban, Muriel; Tchapla, Alain; Mercier, Olivier; Cardinael, Pascal; Peulon-Agasse, Valérie

    2015-11-01

    This study reports the impact of thermal pretreatment between 400 and 1100°C on superficially porous silica particles (e.g. core-shell, fused-core; here abbreviated as SPP silica). The different thermally pretreated SPP silica (400°C, 900°C and 1100°C) were chemically bonded with an octadecyl chain under microwave irradiation. The bare SPP silica, thermally untreated and pretreated, as well as the chemically bonded phases (CBPs) were fully characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and solid state cross polarization magic angle spinning (CP-MAS) (29)Si NMR. The chromatographic properties of the overall set of C18-thermally pretreated SPP silica stationary phases were determined using the Tanaka test. Complementary, the simplified Veuthey test was used to deeply study the silanol activity, considering a set of 7 basic solutes with various physicochemical properties. Both tests were also performed on different commercial SPP silica columns and different types of bonding chemistry (C18, Phenyl-hexyl, RP-amide, C30, aQ). Multivariate data analyses (hierarchical cluster analysis and principal component analysis) were carried out to define groups of stationary phases with similar chromatographic properties and situate them in relation to those commercially available. These different C18-thermally pretreated SPP silicas represented a wide range of stationary phases as they were spread out along the score plot. Moreover, this study highlighted that the thermal pretreatment improved the chemical stability of the SPP silica compare to untreated SPP silica and untreated porous silica. Consequently, higher thermal pretreatment can be applied (up to 900°C) before functionalization without destruction of the silica matrix. Indeed, a significantly lower dissolution of the thermally pretreated SPP silica under aggressive conditions could allow the use of the corresponding functionalized stationary phases at high

  6. Biodiesel production from transesterification of palm oil with methanol over CaO supported on bimodal meso-macroporous silica catalyst.

    PubMed

    Witoon, Thongthai; Bumrungsalee, Sittisut; Vathavanichkul, Peerawut; Palitsakun, Supaphorn; Saisriyoot, Maythee; Faungnawakij, Kajornsak

    2014-03-01

    Calcium oxide-loaded porous materials have shown promise as catalysts in transesterification. However, the slow diffusion of bulky triglycerides through the pores limited the activity of calcium oxide (CaO). In this work, bimodal meso-macroporous silica was used as a support to enhance the accessibility of the CaO dispersed inside the pores. Unimodal porous silica having the identical mesopore diameter was employed for the purpose of comparison. Effects of CaO content and catalyst pellet size on the yield of fatty acid methyl esters (FAME) were investigated. The basic strength was found to increase with increasing the CaO content. The CaO-loaded bimodal porous silica catalyst with the pellet size of 325μm achieved a high %FAME of 94.15 in the first cycle, and retained an excellent %FAME of 88.87 after five consecutive cycles. PMID:24525218

  7. The role of porous nanostructure in controlling lipase-mediated digestion of lipid loaded into silica particles.

    PubMed

    Joyce, Paul; Tan, Angel; Whitby, Catherine P; Prestidge, Clive A

    2014-03-18

    The rate and extent of lipolysis, the breakdown of fat into molecules that can be absorbed into the bloodstream, depend on the interfacial composition and structure of lipid (fat) particles. A novel method for controlling the interfacial properties is to load the lipid into porous colloidal particles. We report on the role of pore nanostructure and surface coverage in controlling the digestion kinetics of medium-chain and long-chain triglycerides loaded into porous silica powders of different particle size, porosity, and hydrophobicity/hydrophilicity. An in vitro lipolysis model was used to measure digestion kinetics of lipid by pancreatic lipase, a digestive enzyme. The rate and extent of lipid digestion were significantly enhanced when a partial monolayer of lipid was loaded in porous hydrophilic silica particles compared to a submicrometer lipid-in-water emulsion or a coarse emulsion. The inhibitory effect of digestion products was clearly evident for digestion from a submicrometer emulsion and coarse emulsion. This effect was minimal, however, in the two silica-lipid systems. Lipase action was inhibited for lipid loaded in the hydrophobic silica and considered due to the orientation of lipase adsorption on the methylated silica surface. Thus, hydrophilic silica promotes enhanced digestion kinetics, whereas hydrophobic silica exerts an inhibitory effect on hydrolysis. Evaluation of digestion kinetics enabled the mechanism for enhanced rate of lipolysis in silica-lipid systems to be derived and detailed. These investigations provide valuable insights for the optimization of smart food microparticles and lipid-based drug delivery systems based on lipid excipients and porous nanoparticles. PMID:24552363

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

    PubMed

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

    2014-12-01

    Photolysis and poor solubility in water of Abamectin are key issues to be addressed, which causes low bioavailability and residual pollution. In this study, a novel hydrophilic delivery system through loading Abamectin with porous silica nanoparticles (Abam-PSNs) was developed in order to improve the chemical stability, dispersity, and the controlled release of Abamectin. These results suggest that Abam-PSNs can significantly improve the performance of controllable release, photostability, and water solubility of Abamectin by changing the porous structure of silica nanoparticles, which is favorable to improve the bioavailability and reduce the residues of pesticides. PMID:26088998

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  10. Characterization and structural investigation of fractal porous-silica over an extremely wide scale range of pore size.

    PubMed

    Ono, Yusuke; Mayama, Hiroyuki; Furó, István; Sagidullin, Alexander I; Matsushima, Keiichiro; Ura, Haruo; Uchiyama, Tomoyuki; Tsujii, Kaoru

    2009-08-01

    We have succeeded in creating Menger sponge-like fractal body, i.e., porous-silica samples with Menger sponge-like fractal geometries, by a novel template method utilizing template particles of alkylketene dimer (AKD) and a sol-gel synthesis of tetramethyl orthosilicate (TMOS). We report here the first experimental results on characterization and structural investigations of the fractal porous-silica samples prepared with various conditions such as calcination temperature and packing condition of the template particles. In order to characterize the fractal porous-silica samples, pore volume distribution, porosity and specific surface area were measured over an extremely wide scale from 1 nm to 100 microm by means of mercury porosimetry, (1)H NMR cryoporometry, nitrogen gas adsorption experiments together with direct evaluations of cross-sectional fractal dimension D(cs), and size limits of D(cs). We have found that the pore volume distribution and specific surface area of the fractal porous-silica samples can be discussed in terms of different fractal porous structures at different scale regions. PMID:19406424

  11. Guest–host interactions of a rigid organic molecule in porous silica frameworks

    PubMed Central

    Wu, Di; Hwang, Son-Jong; Zones, Stacey I.; Navrotsky, Alexandra

    2014-01-01

    Molecular-level interactions at organic–inorganic interfaces play crucial roles in many fields including catalysis, drug delivery, and geological mineral precipitation in the presence of organic matter. To seek insights into organic–inorganic interactions in porous framework materials, we investigated the phase evolution and energetics of confinement of a rigid organic guest, N,N,N-trimethyl-1-adamantammonium iodide (TMAAI), in inorganic porous silica frameworks (SSZ-24, MCM-41, and SBA-15) as a function of pore size (0.8 nm to 20.0 nm). We used hydrofluoric acid solution calorimetry to obtain the enthalpies of interaction between silica framework materials and TMAAI, and the values range from −56 to −177 kJ per mole of TMAAI. The phase evolution as a function of pore size was investigated by X-ray diffraction, IR, thermogravimetric differential scanning calorimetry, and solid-state NMR. The results suggest the existence of three types of inclusion depending on the pore size of the framework: single-molecule confinement in a small pore, multiple-molecule confinement/adsorption of an amorphous and possibly mobile assemblage of molecules near the pore walls, and nanocrystal confinement in the pore interior. These changes in structure probably represent equilibrium and minimize the free energy of the system for each pore size, as indicated by trends in the enthalpy of interaction and differential scanning calorimetry profiles, as well as the reversible changes in structure and mobility seen by variable temperature NMR. PMID:24449886

  12. Porous Silica-Coated Gold Nanorods: A Highly Active Catalyst for the Reduction of 4-Nitrophenol.

    PubMed

    Mohanta, Jagdeep; Satapathy, Smithsagar; Si, Satyabrata

    2016-02-01

    The successful coating of thin porous silica layers of various thicknesses [(10±1), (12±1), and (14±1) nm] on cetyl trimethylammonium bromide (CTAB) capped gold nanorods was achieved through a modified Stöber procedure. The resulting material was applied as a novel catalyst for the reduction of 4-nitrophenol. The catalytic activities of the gold nanorods increased up to eight times after coating with a layer of porous silica and the reaction followed a zero-order kinetics, having a rate constant as high as 2.92×10(-1) mol L(-1) min(-1). The spectral changes during the reduction reaction of 4-nitrophenol were observed within a very short span of time and a complete conversion to 4-aminophenol occured within 5-6 mins, including the induction period of ≈2 mins. The reusability of the catalyst was studied by running the catalytic reaction during five consecutive cycles with good efficiency without destroying the nanostructure. The methodology can be effectively applied to the development of composite catalysts with highly enhanced catalytic activity. PMID:26663755

  13. Incorporation, oxidation and pyrolysis of ferrocene into porous silica glass: a route to different silica/carbon and silica/iron oxide nanocomposites.

    PubMed

    Schnitzler, Mariane C; Mangrich, Antônio S; Macedo, Waldemar A A; Ardisson, José D; Zarbin, Aldo J G

    2006-12-25

    This work reports the incorporation of ferrocene into a porous silica glass under ambient temperature and atmosphere. After or during the ferrocene incorporation, the spontaneous formation of ferricinium ions was observed by electron paramagnetic resonance (EPR), UV-visible, X-ray absorption near-edge structure (XANES), and 57Fe Mössbauer measurements. It was shown that the oxidation of ferrocene molecules to ferricinium ions was promoted by air and that the Si-O- groups on the surface of the pores act as counteranions. Pyrolysis of the porous glass/ferricinium material under argon atmosphere and variable temperature yields different glass/carbon nanocomposites, which were subsequently treated with an HF solution in order to remove the glassy fraction. The resulting insoluble carbon materials were characterized by transmission electron microscopy (TEM), Raman, and EPR spectroscopy and consisted of amorphous carbon when the pyrolysis was carried out at 900 or 1000 degrees C and of a mixture of carbon nanotubes and carbonaceous materials at a pyrolysis temperature of 1100 degrees C. When the pyrolysis was conducted under air, the incorporated ferricinium forms alpha-Fe2O3, and the resulting material is a transparent and highly homogeneous glass/iron oxide nanocomposite. PMID:17173419

  14. Kinetics of Oligonucleotide Hybridization to DNA Probe Arrays on High-Capacity Porous Silica Substrates

    PubMed Central

    Glazer, Marc I.; Fidanza, Jacqueline A.; McGall, Glenn H.; Trulson, Mark O.; Forman, Jonathan E.; Frank, Curtis W.

    2007-01-01

    We have investigated the kinetics of DNA hybridization to oligonucleotide arrays on high-capacity porous silica films that were deposited by two techniques. Films created by spin coating pure colloidal silica suspensions onto a substrate had pores of ∼23 nm, relatively low porosity (35%), and a surface area of 17 times flat glass (for a 0.3-μm film). In the second method, latex particles were codeposited with the silica by spin coating and then pyrolyzed, which resulted in larger pores (36 nm), higher porosity (65%), and higher surface area (26 times flat glass for a 0.3-μm film). As a result of these favorable properties, the templated silica hybridized more quickly and reached a higher adsorbed target density (11 vs. 8 times flat glass at 22°C) than the pure silica. Adsorption of DNA onto the high-capacity films is controlled by traditional adsorption and desorption coefficients, as well as by morphology factors and transient binding interactions between the target and the probes. To describe these effects, we have developed a model based on the analogy to diffusion of a reactant in a porous catalyst. Adsorption values (ka, kd, and K) measured on planar arrays for the same probe/target system provide the parameters for the model and also provide an internally consistent comparison for the stability of the transient complexes. The interpretation of the model takes into account factors not previously considered for hybridization in three-dimensional films, including the potential effects of heterogeneous probe populations, partial probe/target complexes during diffusion, and non-1:1 binding structures. The transient complexes are much less stable than full duplexes (binding constants for full duplexes higher by three orders of magnitude or more), which may be a result of the unique probe density and distribution that is characteristic of the photolithographically patterned arrays. The behavior at 22°C is described well by the predictive equations for

  15. Transport of Colloidal Silica in Fractured and Porous Media: Applications to Geothermal & Geological Carbon Sequestration

    NASA Astrophysics Data System (ADS)

    Roberts, S.; Ezzedine, S. M.; Bourcier, W. L.; Hunt, J. D.; Ryerson, F. J.

    2012-12-01

    Silica gels are abundant in various surface and subsurface applications, yet they have not been evaluated for geothermal and carbon sequestration reservoir management. For example, a) sustaining long term heat extraction from geothermal systems can be achieved by optimizing thermal sweeping of available conductive surface area; b) minimizing supercritical CO2 leaks through caprock can be insured by blocking any possible leakage pathways. Diverting and blocking agents have been effectively used in the petroleum industry to enhance recovery; however, these are often organic polymers that raise environmental concerns. Silicas are inorganic and environmentally friendly. In the current study we have developed a numerical model to simulate the flow mass and heat transport of silica gel in both geothermal and immiscible supercritical CO2 sequestration reservoirs. We illustrate the application of the model for a) maximizing thermal extraction and minimizing water loses for hydrothermal systems by using the gel as a diverter and blocking agent and b) minimizing CO2 leakages to the caprock by using the gel as blocking and coating agent. Several 2D and 3D examples in porous and fractured network will be presented and design criteria for both application will be discussed. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  16. Preparation of silica sphere with porous structure in supercritical carbon dioxide.

    PubMed

    Chatterjee, Maya; Chatterjee, Abhijit; Ikushima, Yutaka; Kawanami, Hajime; Ishizaka, Takayuki; Sato, Masahiro; Suzuki, Toshishige; Yokoyama, Toshirou

    2010-08-01

    Silica sphere with porous structure has been synthesized in supercritical carbon dioxide. The structure originates from a delicate CO(2) trapping phenomenon intended for void formation in the inorganic framework. Silicate polymerization and subsequent removal of CO(2) by depressurization leaves the porous architecture. The key factor to obtain stable porous spherical structure was CO(2) pressure. Different characterization techniques such as X-ray diffraction, scanning and transmission electron microscopy and N(2) adsorption-desorption isotherm were used to determine the framework structure, morphology and porosity of the material. Microscopic visualization of calcined material suggested that the spherical structure was consisted of macroporous windows of diameter approximately 100 nm and the space between macropores presents a wormhole like mesoporous/microporous structure. The pore diameter of the mesoporous structure has been calculated as approximately 3 nm. X-ray diffraction and N(2) adsorption isotherm analysis confirmed the presence of micropores and also the macropores. In addition, the resulting material possess high thermal and hydrothermal stability associated with fully SiO(4) cross-linking. The spherical structure with different types of porosity was successfully obtained without using any molding agent. PMID:20417524

  17. Thermally modulated porous silica multispectral filters and their application in remote imaging.

    PubMed

    Garcia Sega, Adrian; King, Brian H; Lee, Jessica Y; Sailor, Michael J; Miskelly, Gordon M

    2013-09-24

    We report a thermally tunable multispectral imaging filter based on reversible condensation of volatile organic fluids within a nanoporous one-dimensional photonic crystal. The photonic crystal (optical rugate filter) comprises oxidized porous silicon, prepared by electrochemical etch of silicon and subsequent air oxidation (porous silica rugate filter, pSiF). The reflectance spectrum of the pSiF is designed and constructed to match two of the red emission bands of the luminescent complex europium(III) tris-dipicolinate, [Eu(dpa)3](3-), which has been used as an indicator for anthrax spores. When the pSiF is fitted with a thermoelectric Peltier cooler/heater and sealed in a container with 2-propanol vapor, microcapillary effects drive the temperature-dependent condensation/evaporation of 2-propanol into/out of the porous nanostructure. Thermal cycling experiments show that the wavelengths of the spectral bands of the pSiF are reversibly tuned by ±35 nm for a temperature change of ±40 °C. Difference images of a UV-illuminated scene containing the [Eu(dpa)3](3-) target, obtained by reflection from pSiF that is continuously thermally cycled through the emission bands of the dye, show that the target can be discriminated from the background or from control targets with overlapping but dissimilar luminescence spectra. PMID:23968219

  18. Laser supported solid state absorption fronts in silica

    SciTech Connect

    Carr, C W; Bude, J D

    2010-02-09

    We develop a model based on simulation and experiment that explains the behavior of solid-state laser-supported absorption fronts generated in fused silica during high intensity (up to 5GW/cm{sup 2}) laser exposure. We find that the absorption front velocity is constant in time and is nearly linear in laser intensity. Further, this model can explain the dependence of laser damage site size on these parameters. This behavior is driven principally by the temperature-activated deep sub band-gap optical absorptivity, free electron transport and thermal diffusion in defect-free silica for temperatures up to 15,000K and pressures < 15GPa. The regime of parameter space critical to this problem spans and extends that measured by other means. It serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

  19. Impact of carbon on the surface and activity of silica-carbon supported copper catalysts for reduction of nitrogen oxides

    NASA Astrophysics Data System (ADS)

    Spassova, I.; Stoeva, N.; Nickolov, R.; Atanasova, G.; Khristova, M.

    2016-04-01

    Composite catalysts, prepared by one or more active components supported on a support are of interest because of the possible interaction between the catalytic components and the support materials. The supports of combined hydrophilic-hydrophobic type may influence how these materials maintain an active phase and as a result a possible cooperation between active components and the support material could occur and affects the catalytic behavior. Silica-carbon nanocomposites were prepared by sol-gel, using different in specific surface areas and porous texture carbon materials. Catalysts were obtained after copper deposition on these composites. The nanocomposites and the catalysts were characterized by nitrogen adsorption, TG, XRD, TEM- HRTEM, H2-TPR, and XPS. The nature of the carbon predetermines the composite's texture. The IEPs of carbon materials and silica is a force of composites formation and determines the respective distribution of the silica and carbon components on the surface of the composites. Copper deposition over the investigated silica-carbon composites leads to formation of active phases in which copper is in different oxidation states. The reduction of NO with CO proceeds by different paths on different catalysts due to the textural differences of the composites, maintaining different surface composition and oxidation states of copper.

  20. SEPARATION PROPERTIES OF SURFACE MODIFIED SILICA SUPPORTED LIQUID MEMBRANES FOR DIVALENT METAL REMOVAL/RECOVERY

    EPA Science Inventory

    The synthesis and separation properties of a mesoporous silica supported liquid membrane (SLM) were studied. The membranes consisted of a silica layer, from dip-coated colloidal silica, on a a-alumina support, modified with DCDMS (dichlorodimethyl silane) to add surface methyl g...

  1. PILOT-PLANT EVALUATION OF POROUS BIOMASS SUPPORTS (JOURNAL VERSION)

    EPA Science Inventory

    Several porous biomass-support systems are currently available for use in the activated-sludge process. One of these systems, Captor, utilizes polyurethane foam pads to provide biofilm growth sites that transform an aerobic suspended-growth reactor into a fixed-film reactor. In a...

  2. Montmorillonite-based porous clay heterostructures (PCHs) intercalated with silica-titania pillars-synthesis and characterization

    SciTech Connect

    Chmielarz, Lucjan; Gil, Barbara; Kustrowski, Piotr; Piwowarska, Zofia; Dudek, Barbara; Michalik, Marek

    2009-05-15

    Porous clay heterostructures (PCHs) were synthesized using natural montmorillonite as a raw material. Apart from pure silica pillars also silica-titania pillars were intercalated into the interlayer space of the parent clay. The detailed studies of the calcination process of the as-prepared PCH samples as well as thermal stability of the pillared structure of these materials were performed. The pillared structure of PCHs intercalated with both silica and silica-titania clusters was found to be thermally stable up to temperatures exceeding 600 deg. C. It was found that titanium incorporated into the silica pillars was present mainly in the form of separated tetracoordinated cations. For the samples with the higher Ti loading also small contribution of titanium in the form of the polymeric oxide species was detected. Titanium incorporated into the PCH materials significantly increased their surface acidity forming mainly Bronsted acid sites. - Graphical abstract: Synthesis of the montmorillonite based porous clay heterostructures (PCHs) intercalated with silica-titania pillars has been performed. The mechanism of the thermal degradation of organic templates in the pore system of PCHs was studied. PCHs were characterized with respect to structure, texture, composition, surface acidity, thermal stability and form of introduced titanium.

  3. Aging influence on sensing properties of porous silica films sensitized toward ammonia

    NASA Astrophysics Data System (ADS)

    Tyszkiewicz, Cuma; Rogoziński, Roman

    2015-12-01

    The sol-gel technology allows preparation of thin silica films ranging in porosity from dense to highly porous. These films can function as a matrix binding molecules of the pH-sensitive dyes and can be utilized as the sensitive films for intensity based planar evanescent wave chemical sensors. Sensitive properties of these dyes decreases in time due to aging processes. We report characterization of weakening of sensing properties of highly porous silica films doped with the bromocresole purple (BCP). In the presence of the gaseous ammonia, the absorption band (AB) of protonated BCP centered at λ=430 nm, is shifted toward λ=591 nm due to deprotonation, resulting in the increase of sensitive films absorption in the range of wavelengths of shifted AB. Two sets of films were investigated. Films from the first one were cyclically exposed to the ammonia and stored isolated from the daylight. Films from the second set weren't exposed to the ammonia and were stored in a staining jar exposed to the daylight. A depth of the AB at λ=430 nm was measured using a spectrophotometer. A sensitivity of the films toward ammonia was measured using LED emitting at center wavelength λ=610 nm. As was shown, the sensitivity of these films exposed to the ammonia diluted in dry air, and isolated from the daylight, decreases in time exponentially. The magnitude of that decrease monotonically depends on the ammonia concentration. It was also shown that the daylight causes quick aging of films not exposed to the ammonia. A depth of the AB centered at λ=430 nm relatively quickly decreased when compared with films isolated from the daylight and exposed to the ammonia.

  4. A silica-supported solid dispersion of bifendate using supercritical carbon dioxide method with enhanced dissolution rate and oral bioavailability.

    PubMed

    Cai, Cuifang; Liu, Muhua; Li, Yun; Guo, Bei; Chang, Hui; Zhang, Xiangrong; Yang, Xiaoxu; Zhang, Tianhong

    2016-01-01

    In this study, to enhance the dissolution rate and oral bioavailability of bifendate, a silica-supported solid dispersion (SD) of bifendate was prepared using supercritical carbon dioxide (ScCO2) technology. The properties of bifendate-silica SD were characterized by differential scanning calorimetry (DSC), X-ray diffraction (X-RD) and scanning electron microscopy. The pharmacokinetic study was carried out in beagle dogs using commercial bifendate dropping pills as a reference which is a conventional SD formulation of bifendate and PEG6000. A novel method of Ultra Performance Convergence Chromatography-tandem mass spectrometry (UPC(2)™-MS/MS) method was applied to determine bifendate concentration in plasma. The amorphous state of bifendate in bifendate-silica SD was revealed in X-RD and DSC when the ratios of bifendate and silica were 1:15 and 1:19, respectively. In vitro dissolution rate was significantly improved with cumulative release of 67% within 20 min relative to 8% for the physical mixture of bifendate and silica, and which was also higher than the commercial dropping pill of 52%. After storage at 75% relative humidity (RH) for 10 d, no recrystallization was found and reduced dissolution rate was obtained due to the absorption of moisture. In pharmacokinetic study, Cmax and AUC0-t for bifendate-silica SD were 153.1 ng/ml and 979.8 ng h/ml, respectively. AUC0-t of bifendate-silica SDs was ∼1.6-fold higher than that of the commercial dropping pills. These results suggest that adsorbing bifendate onto porous silica via ScCO2 technique could be a feasible method to enhance oral bioavailability together with a higher dissolution rate. PMID:26219343

  5. Ion-specific adsorption and electroosmosis in charged amorphous porous silica.

    PubMed

    Hartkamp, Remco; Siboulet, Bertrand; Dufrêche, Jean-François; Coasne, Benoit

    2015-10-14

    Monovalent and divalent aqueous electrolytes confined in negatively charged porous silica are studied by means of molecular simulations including free energy calculations. Owing to the strong cation adsorption at the surface, surface charge overcompensation (overscreening) occurs which leads to an effective positive surface next to the Stern layer, followed by a negatively charged diffuse layer. A simple Poisson-Boltzmann model in which the single-ion potential of mean force is introduced is shown to capture the most prominent features of ion density profiles near an amorphous silica surface. Nevertheless, due to its mean-field nature, which fails to account for correlations, this simple model does not predict overscreening corresponding to charge inversion at the surface. Such an overscreening drastically affects the transport of confined electrolytes as it leads to flow reversal when subjected to an electric field. A simple continuum theory is shown to capture how the electro-osmotic flow is affected by overscreening and by the apparent enhanced viscosity of the confined electrolytes. Comparison with available experimental data is discussed, as well as the implications of these phenomena for ζ-potential measurements. PMID:26343799

  6. Biodegradation of 2,4-dinitrophenol with laccase immobilized on nano-porous silica beads

    PubMed Central

    2013-01-01

    Many organic hazardous pollutants, including 2,4-dinitrophenol (2,4-DNP), which are water soluble, toxic, and not easily biodegradable make concerns for environmental pollution worldwide. In the present study, degradation of nitrophenols-contained effluents by using laccase immobilized on the nano-porous silica beads was evaluated. 2,4-DNP was selected as the main constituent of industrial effluents containing nitrophenols. The performance of the system was characterized as a function of pH, contact time, temperature, pollutant, and mediator concentrations. The laccase-silica beads were employed in a mixed-batch reactor to determine the degradation efficiency after 12 h of enzyme treatment. The obtained data showed that the immobilized laccase degraded more than 90% of 2,4-DNP within 12 h treatment. The immobilization process improved the activity and sustainability of laccase for degradation of the pollutant. Temperatures more than 50°C reduced the enzyme activity to about 60%. However, pH and the mediator concentration could not affect the enzyme activity. The degradation kinetic was in accordance with a Michaelis–Menten equation with Vmax and Km obtained as 0.25–0.38 μmoles/min and 0.13–0.017 mM, respectively. The stability of the immobilized enzyme was maintained for more than 85% of its initial activity after 30 days. Based on the results, it can be concluded that high resistibility and reusability of immobilized laccase on CPC-silica beads make it considerable choice for wastewater treatment. PMID:23547870

  7. ZnFe2O4 nanoparticles dispersed in a highly porous silica aerogel matrix: a magnetic study.

    PubMed

    Bullita, S; Casu, A; Casula, M F; Concas, G; Congiu, F; Corrias, A; Falqui, A; Loche, D; Marras, C

    2014-03-14

    We report the detailed structural characterization and magnetic investigation of nanocrystalline zinc ferrite nanoparticles supported on a silica aerogel porous matrix which differ in size (in the range 4-11 nm) and the inversion degree (from 0.4 to 0.2) as compared to bulk zinc ferrite which has a normal spinel structure. The samples were investigated by zero-field-cooling-field-cooling, thermo-remnant DC magnetization measurements, AC magnetization investigation and Mössbauer spectroscopy. The nanocomposites are superparamagnetic at room temperature; the temperature of the superparamagnetic transition in the samples decreases with the particle size and therefore it is mainly determined by the inversion degree rather than by the particle size, which would give an opposite effect on the blocking temperature. The contribution of particle interaction to the magnetic behavior of the nanocomposites decreases significantly in the sample with the largest particle size. The values of the anisotropy constant give evidence that the anisotropy constant decreases upon increasing the particle size of the samples. All these results clearly indicate that, even when dispersed with low concentration in a non-magnetic and highly porous and insulating matrix, the zinc ferrite nanoparticles show a magnetic behavior similar to that displayed when they are unsupported or dispersed in a similar but denser matrix, and with higher loading. The effective anisotropy measured for our samples appears to be systematically higher than that measured for supported zinc ferrite nanoparticles of similar size, indicating that this effect probably occurs as a consequence of the high inversion degree. PMID:24469688

  8. Understanding support mediated activity by investigating highly active, thermally stable, silica supported gold catalysts

    SciTech Connect

    Veith, Gabriel M; Lupini, Andrew R; Rashkeev, Sergey; Pennycook, Stephen J; Schwartz, Viviane; Mullins, David R; Dudney, Nancy J

    2009-01-01

    2.5 nm gold nanoparticles were grown on a fumed silica support using the physical vapor deposition technique magnetron sputtering. Combining electron microscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and catalytic studies revealed that the silica supported gold catalysts are thermally stable when annealed in an oxygen containing environment up to at least 500oC. This surprising stability is attributed to the absence of residual halide impurities and a strong bond between gold and defects at the silica surface (2.7 - 3.8 eV), as estimated from density functional theory (DFT) calculations. The Au/SiO2 catalysts are slightly less active for CO oxidation than the prototypical Au/TiO2 catalysts, however they can be regenerated far more easily, fully recovering the activity of a freshly prepared catalyst after deactivation.

  9. Electroassisted codeposition of sol-gel derived silica nanocomposite directs the fabrication of coral-like nanostructured porous gold.

    PubMed

    Farghaly, Ahmed A; Collinson, Maryanne M

    2014-05-13

    Herein, we report on a one-step coelectrodeposition method to form gold-silica nanocomposite materials from which high surface area nanostructured gold electrodes can be produced. The as-prepared Au-SiO2 films possess an interconnected three-dimensional porous framework with different silica-gold ratios depending on the deposition solutions and parameters. Chemical etching of the nanocomposite films using hydrofluoric acid resulted in the formation of nanostructured porous gold films with coral-like structures and pores in the nanometer range. The cross-linkage of the gold coral branches resulted in the generation of a porous framework. X-ray photoelectron spectroscopy confirms the complete removal of silica. Well-controlled surface area enhancement, film thickness, and morphology were achieved by manipulating the deposition parameters, such as potential, time, and gold ion and sol-gel monomer concentrations in the deposition solution. An enhancement in the surface area of the electrode up to 57 times relative to the geometric area has been achieved. The thickness of the as-prepared Au-SiO2 nanocomposite films is relatively high and varied from 8 to 15 μm by varying the applied deposition potential while the thickness of the coral-like nanostructured porous gold films ranged from 0.22 to 2.25 μm. A critical sol-gel monomer concentration (CSGC) was determined at which the deposited silica around the gold coral was able to stabilize the coral-like gold nanostructures, while below the CSGC, the coral-like gold nanostructures were unstable and the surface area of the nanostructured porous gold electrodes decreased. PMID:24766096

  10. Porous Carbon Supports: Recent Advances with Various Morphologies and Compositions

    DOE PAGESBeta

    Zhang, Pengfei; Zhu, Huiyuan; Dai, Sheng

    2015-08-31

    The importance of porous carbon as the support material is well recognized in the catalysis community, and it would be even more attractive if several characteristics are considered, such as the stability in acidic and basic media or the ease of noble metal recovery through complete burn off. Because it is still difficult to obtain constant properties even from batch to batch, activated carbons are not popular in industrial catalysis now.

  11. Mesoporous Silica-Supported Amidozirconium-Catalyzed Carbonyl Hydroboration

    DOE PAGESBeta

    Eedugurala, Naresh; Wang, Zhuoran; Chaudhary, Umesh; Nelson, Nicholas; Kandel, Kapil; Kobayashi, Takeshi; Slowing, Igor I.; Pruski, Marek; Sadow, Aaron D.

    2015-11-04

    The hydroboration of aldehydes and ketones using a silica-supported zirconium catalyst is reported. Reaction of Zr(NMe2)4 and mesoporous silica nanoparticles (MSN) provides the catalytic material Zr(NMe2)n@MSN. Exhaustive characterization of Zr(NMe2)n@MSN with solid-state (SS)NMR and infrared spectroscopy, as well as through reactivity studies, suggests its surface structure is primarily ≡SiOZr(NMe2)3. The presence of these nitrogen-containing zirconium sites is supported by 15N NMR spectroscopy, including natural abundance 15N NMR measurements using dynamic nuclear polarization (DNP) SSNMR. The Zr(NMe2)n@MSN material reacts with pinacolborane (HBpin) to provide Me2NBpin and the material ZrH/Bpin@MSN that is composed of interacting surface-bonded zirconium hydride and surface-bonded borane ≡SiOBpinmore » moieties in an approximately 1:1 ratio, as well as zirconium sites coordinated by dimethylamine. The ZrH/Bpin@MSN is characterized by 1H/2H and 11B SSNMR and infrared spectroscopy and through its reactivity with D2. The zirconium hydride material or the zirconium amide precursor Zr(NMe2)n@MSN catalyzes the selective hydroboration of aldehydes and ketones with HBpin in the presence of functional groups that are often reduced under hydroboration conditions or are sensitive to metal hydrides, including olefins, alkynes, nitro groups, halides, and ethers. Remarkably, this catalytic material may be recycled without loss of activity at least eight times, and air-exposed materials are catalytically active. These supported zirconium centers are robust catalytic sites for carbonyl reduction and that surface-supported, catalytically reactive zirconium hydride may be generated from zirconium-amide or zirconium alkoxide sites.« less

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

    SciTech Connect

    Bullita, S.; Casula, M. F.; Piludu, M.; Falqui, A.; Carta, D.; Corrias, A.

    2014-10-21

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

  13. Control of silica-zirconia nanoparticles for uniform porous SiO2-ZrO2 membranes.

    PubMed

    Ryeon Lee, Hye; Lee, Jinkyeong; Seo, Bongkuk

    2014-11-01

    Silica-zirconia composite sols were prepared by means of a sol-gel method, using tetraethylorthosilicate (TEOS) and zirconium tetra-n-butoxide (ZrTB) precursors. TEOS, ZrTB, HCl, H2O and EtOH were mixed at 70 degrees C for 24 hours to give molar ratios of 1:1:8-80:0.2-1.0:100-300. The mean particle size of the silica-zirconia sol was controlled by the concentration of the alkoxides and catalyst, as well as the water molar ratio in the starting solution. The particle size of the SiO2-ZrO2 sol, which was analyzed by dynamic light scattering (DLS) and field emission scanning electron microscopy (FE-SEM), was in the range of 20 to 350 nm. The SiO2-ZrO2 sol solutions of different sol sizes were coated onto porous stainless steel supports (O.D. 10 mm, length: 20 mm, 316L SUS, Mott corp. USA) by a dipping-rolling-freezing-fast drying (DRFF) and soaking-rolling-freezing-fast drying (SRFF) method. After coating with SiO2-ZrO2 sol, the single gas permeation characteristics (He, H2 and N2) of the resulting SiO2-ZrO2 membranes were evaluated at room temperature. This produced a decrease in the mean flow diameter and H2/N2 permselectivity in the range of 2.0-3.5. Finally, following the results of gas permeation testing, the pore size of the membranes was controlled by changing their particle size. PMID:25958574

  14. Porous Nanoparticle Supported Lipid Bilayers (Protocells) as Delivery Vehicles

    PubMed Central

    Liu, Juewen; Stace-Naughton, Alison; Jiang, Xingmao; Brinker, C. Jeffrey

    2009-01-01

    Mixing liposomes with hydrophilic particles will induce fusion of the liposome onto the particle surface. Such supported bilayers have been extensively studied as a model for the cell membrane, while its application in drug delivery has not been pursued. In this communication, we report the use of phospholipids to achieve synergistic loading and encapsulating of a fluorescent dye (calcein) in mesoporous silica nanoparticles, and its delivery into mammalian cells. We found that cationic lipid DOTAP provides the highest calcein loading with the concentration inside silica ∼110× higher than that in the solution under experimental conditions. Compared to some other nanoparticle systems, protocells provide a simple construct for loading, sealing, delivering and releasing, and should serve as a useful system in nanomedicine. PMID:19173660

  15. On the stabilization of gold nanoparticles over silica-based magnetic supports modified with organosilanes.

    PubMed

    Oliveira, Rafael L; Zanchet, Daniela; Kiyohara, Pedro K; Rossi, Liane M

    2011-04-11

    The immobilization of gold nanoparticles (Au NPs) on silica is made possible by the functionalization of the silica surfaces with organosilanes. Au NPs could only be stabilized and firmly attached to silica-support surfaces that were previously modified with amino groups. Au NPs could not be stabilized on bare silica surfaces and most of the NPs were then found in the solution. The metal-support interactions before and after the Au NP formation, observed by X-ray absorption fine structure spectroscopy (XAFS), indicate a stronger interaction of gold(III) ions with amino-modified silica surfaces than with the silanol groups in bare silica. An amino-modified, silica-based, magnetic support was used to prepare an active Au NP catalyst for the chemoselective oxidation of alcohols, a reaction of great interest for the fine chemical industry. PMID:21360597

  16. Synthesis and Characterisation of Porous Titania-Silica Composite Aerogel for NO(x) and Acetaldehyde Removal.

    PubMed

    Lee, Kwang Young; Park, Se Min; Kim, Jong Beom; El Saliby, Ibrahim; Shahid, Mohammad; Kim, Geon-Joong; Shon, Ho Kyong; Kim, Jong-Ho

    2016-05-01

    In this study, the synthesis of porous titania-silica (TiO2-SiO2) composite aerogel at ambient pressure by using non-hazardous chemicals as a source of silica was investigated. TiO2-SiO2 composite aerogels were characterised and their photocatalytic performances were investigated for the removal efficiency of acetaldehyde and NO(x) under UV light. Results showed that porous composite aerogel with aggregated morphology, high surface area and an increased mesoporosity were formed. TiO2-SiO2(1.8) composite, with high Ti/Si ratio, showed the best results in terms of photocatalytic removal of acetaldehyde and nitrogen oxide. PMID:27483782

  17. Fabrication of silica moth-eye structures by photo-nanoimprinting using ordered anodic porous alumina molds

    NASA Astrophysics Data System (ADS)

    Yanagishita, Takashi; Endo, Takahide; Nishio, Kazuyuki; Masuda, Hideki

    2014-01-01

    Moth-eye structures composed of an ordered array of tapered SiO2 pillars were fabricated by photo-nanoimprinting using anodic porous alumina as a mold. The formation of SiO2 moth-eye structures was carried out using a photosensitive polysilane solution as a precursor of silica. The SiO2 moth-eye structures formed on the surface of a glass plate effectively suppressed the reflection of incident light.

  18. In situ growth of hollow gold-silver nanoshells within porous silica offers tunable plasmonic extinctions and enhanced colloidal stability.

    PubMed

    Li, Chien-Hung; Jamison, Andrew C; Rittikulsittichai, Supparesk; Lee, Tai-Chou; Lee, T Randall

    2014-11-26

    Porous silica-coated hollow gold-silver nanoshells were successfully synthesized utilizing a procedure where the porous silica shell was produced prior to the transformation of the metallic core, providing enhanced control over the structure/composition of the bimetallic hollow core. By varying the reaction time and the precise amount of gold salt solution added to a porous silica-coated silver-core template solution, composite nanoparticles were tailored to reveal a readily tunable surface plasmon resonance that could be centered across the visible and near-IR spectral regions (∼445-800 nm). Characterization by X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed that the synthetic methodology afforded particles having uniform composition, size, and shape. The optical properties were evaluated by absorption/extinction spectroscopy. The stability of colloidal solutions of our composite nanoparticles as a function of pH was also investigated, revealing that the nanoshells remain intact over a wide range of conditions (i.e., pH 2-10). The facile tunability, enhanced stability, and relatively small diameter of these composite particles (∼110 nm) makes them promising candidates for use in tumor ablation or as photothermal drug-delivery agents. PMID:25321928

  19. Multifunctional nanocomposites constructed from Fe3O4-Au nanoparticle cores and a porous silica shell in the solution phase.

    PubMed

    Chen, Fenghua; Chen, Qingtao; Fang, Shaoming; Sun, Yu'an; Chen, Zhijun; Xie, Gang; Du, Yaping

    2011-11-01

    This work is directed towards the synthesis of multifunctional nanoparticles composed of Fe(3)O(4)-Au nanocomposite cores and a porous silica shell (Fe(3)O(4)-Au/pSiO(2)), aimed at ensuring the stability, magnetic, and optical properties of magnetic-gold nanocomposite simultaneously. The prepared Fe(3)O(4)-Au/pSiO(2) core/shell nanoparticles are characterized by means of TEM, N(2) adsorption-desorption isotherms, FTIR, XRD, UV-vis, and VSM. Meanwhile, as an example of the applications, catalytic activity of the porous silica shell-encapsulated Fe(3)O(4)-Au nanoparticles is investigated by choosing a model reaction, reduction of o-nitroaniline to benzenediamine by NaBH(4). Due to the existence of porous silica shells, the reaction with Fe(3)O(4)-Au/pSiO(2) core/shell nanoparticles as a catalyst follows second-order kinetics with the rate constant (k) of about 0.0165 l mol(-1) s(-1), remarkably different from the first-order kinetics with the k of about 0.002 s(-1) for the reduction reaction with the core Fe(3)O(4)-Au nanoparticles as a catalyst. PMID:21637876

  20. Bone Tissue Response to Porous and Functionalized Titanium and Silica Based Coatings

    PubMed Central

    Chaudhari, Amol; Braem, Annabel; Vleugels, Jozef; Martens, Johan A.; Naert, Ignace; Cardoso, Marcio Vivan; Duyck, Joke

    2011-01-01

    Background Topography and presence of bio-mimetic coatings are known to improve osseointegration. The objective of this study was to evaluate the bone regeneration potential of porous and osteogenic coatings. Methodology Six-implants [Control (CTR); porous titanium coatings (T1, T2); thickened titanium (Ti) dioxide layer (TiO2); Amorphous Microporous Silica (AMS) and Bio-active Glass (BAG)] were implanted randomly in tibiae of 20-New Zealand white rabbits. The animals were sacrificed after 2 or 4 weeks. The samples were analyzed histologically and histomorphometrically. In the initial bone-free areas (bone regeneration areas (BRAs)), the bone area fraction (BAF) was evaluated in the whole cavity (500 µm, BAF-500), in the implant vicinity (100 µm, BAF-100) and further away (100–500 µm, BAF-400) from the implant. Bone-to-implant contact (BIC-BAA) was measured in the areas where the implants were installed in contact to the host bone (bone adaptation areas (BAAs)) to understand and compare the bone adaptation. Mixed models were used for statistical analysis. Principal Findings After 2 weeks, the differences in BAF-500 for different surfaces were not significant (p>0.05). After 4 weeks, a higher BAF-500 was observed for BAG than CTR. BAF-100 for AMS was higher than BAG and BAF-400 for BAG was higher than CTR and AMS. For T1 and AMS, the bone regeneration was faster in the 100-µm compared to the 400-µm zone. BIC-BAA for AMS and BAG was lower after 4 than 2 weeks. After 4 weeks, BIC-BAA for BAG was lower than AMS and CTR. Conclusions BAG is highly osteogenic at a distance from the implant. The porous titanium coatings didn't stimulate bone regeneration but allowed bone growth into the pores. Although AMS didn't stimulate higher bone response, it has a potential of faster bone growth in the vicinity compared to further away from the surface. BIC-BAA data were inconclusive to understand the bone adaptation. PMID:21935382

  1. Adsorption characteristics of haloacetonitriles on functionalized silica-based porous materials in aqueous solution.

    PubMed

    Prarat, Panida; Ngamcharussrivichai, Chawalit; Khaodhiar, Sutha; Punyapalakul, Patiparn

    2011-09-15

    The effect of the surface functional group on the removal and mechanism of dichloroacetonitrile (DCAN) adsorption over silica-based porous materials was evaluated in comparison with powdered activated carbon (PAC). Hexagonal mesoporous silicate (HMS) was synthesized and functionalized by three different types of organosilanes (3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and n-octyldimethysilane). Adsorption kinetics and isotherm models were used to determine the adsorption mechanism. The selective adsorption of five haloacetonitriles (HANs) in the single and mixed solute systems was also studied. The experiments revealed that the surface functional groups of the adsorbents largely affected the DCAN adsorption capacities. 3-Mercaptopropyl-grafted HMS had a high DCAN adsorption capacity compared to PAC. The adsorption mechanism is believed to occur via an ion-dipole electrostatic interaction in which water interference is inevitable at low concentrations of DCAN. In addition, the adsorption of DCAN strongly depended on the pH of the solution as this related to the charge density of the adsorbents. The selective adsorption of the five HANs over PAC was not observed, while the molecular structure of different HANs obviously influenced the adsorption capacity and selectivity over 3-mercaptopropyl-grafted HMS. PMID:21752539

  2. A novel approach to a fine particle coating using porous spherical silica as core particles.

    PubMed

    Ishida, Makoto; Uchiyama, Jumpei; Isaji, Keiko; Suzuki, Yuta; Ikematsu, Yasuyuki; Aoki, Shigeru

    2014-08-01

    Abstract The applicability of porous spherical silica (PSS) was evaluated as core particles for pharmaceutical products by comparing it with commercial core particles such as mannitol (NP-108), sucrose and microcrystalline cellulose spheres. We investigated the physical properties of core particles, such as particle size distribution, flow properties, crushing strength, plastic limit, drying rate, hygroscopic property and aggregation degree. It was found that PSS was a core particle of small particle size, low friability, high water adsorption capacity, rapid drying rate and lower occurrence of particle aggregation, although wettability is a factor to be carefully considered. The aggregation and taste-masking ability using PSS and NP-108 as core particles were evaluated at a fluidized-bed coating process. The functional coating under the excess spray rate shows different aggregation trends and dissolution profiles between PSS and NP-108; thereby, exhibiting the formation of uniform coating under the excess spray rate in the case of PSS. This expands the range of the acceptable spray feed rates to coat fine particles, and indicates the possibility of decreasing the coating time. The results obtained in this study suggested that the core particle, which has a property like that of PSS, was useful in overcoming such disadvantages as large particle size, which feels gritty in oral cavity; particle aggregation; and the long coating time of the particle coating process. These results will enable the practical fine particle coating method by increasing the range of optimum coating conditions and decreasing the coating time in fluidized bed technology. PMID:23781858

  3. Interactions of Supercritical Carbon Dioxide with Porous Silica and Montmorillonite Clay

    NASA Astrophysics Data System (ADS)

    Rother, G.; Cole, D. R.; Ilton, E. S.; Anovitz, L.; Krukowski, E.

    2011-12-01

    The high and increasing level of carbon dioxide (CO2) in the atmosphere resulting from burning of fossil fuels is likely to cause global warming. Large-scale carbon capture and sequestration (CCS) of CO2 produced in power plants may play an important role in controlling the level of this greenhouse gas in the atmosphere. In this process, CO2 is stripped from the emissions, compressed, and stored in subsurface reservoirs in very large quantities. The specific CO2-rock interactions control the storage capacity of the reservoir and the fluid mobility. The dominant interactions of supercritical CO2 with reservoir rocks over the first couple of years after injection are sorption and capillary trapping. By combining sorption measurements and neutron scattering data in the Adsorbed Phase Model we obtain a full microstructural characterization of the pore fluid. We studied mesoporous CPG-10 silica materials with pore sizes of 75 Å and 350 Å at pressures from 0-200 bars and temperatures of 35°C and 50°C, covering a range typical for carbon storage sites. Porous silica glass serves as a proxy for quartz-rich rocks, including sandstones that may serve as reservoir rocks. The CO2 excess sorption isotherms were measured using a high-pressure sorption balance. Strong adsorption of CO2 to the silica was found at low fluid pressure and density, followed by formation of a maximum in the excess sorption isotherm. The excess sorption exhibited small or even negative values at high pressure. An inverse temperature dependence of the sorption strength was found in the adsorption region at low and intermediate pressure, while the excess sorption showed little temperature dependence at high pressure. A shift of the excess sorption maximum to higher fluid density was observed with increasing pore width. From small-angle neutron scattering data the density and volume of the sorption phase of CO2 is calculated. Caprocks overlying the porous reservoir rock serve to retain buoyant plumes

  4. Mesoporous Silica-Supported Amidozirconium-Catalyzed Carbonyl Hydroboration

    SciTech Connect

    Eedugurala, Naresh; Wang, Zhuoran; Chaudhary, Umesh; Nelson, Nicholas; Kandel, Kapil; Kobayashi, Takeshi; Slowing, Igor I.; Pruski, Marek; Sadow, Aaron D.

    2015-11-04

    The hydroboration of aldehydes and ketones using a silica-supported zirconium catalyst is reported. Reaction of Zr(NMe2)4 and mesoporous silica nanoparticles (MSN) provides the catalytic material Zr(NMe2)n@MSN. Exhaustive characterization of Zr(NMe2)n@MSN with solid-state (SS)NMR and infrared spectroscopy, as well as through reactivity studies, suggests its surface structure is primarily ≡SiOZr(NMe2)3. The presence of these nitrogen-containing zirconium sites is supported by 15N NMR spectroscopy, including natural abundance 15N NMR measurements using dynamic nuclear polarization (DNP) SSNMR. The Zr(NMe2)n@MSN material reacts with pinacolborane (HBpin) to provide Me2NBpin and the material ZrH/Bpin@MSN that is composed of interacting surface-bonded zirconium hydride and surface-bonded borane ≡SiOBpin moieties in an approximately 1:1 ratio, as well as zirconium sites coordinated by dimethylamine. The ZrH/Bpin@MSN is characterized by 1H/2H and 11B SSNMR and infrared spectroscopy and through its reactivity with D2. The zirconium hydride material or the zirconium amide precursor Zr(NMe2)n@MSN catalyzes the selective hydroboration of aldehydes and ketones with HBpin in the presence of functional groups that are often reduced under hydroboration conditions or are sensitive to metal hydrides, including olefins, alkynes, nitro groups, halides, and ethers. Remarkably, this catalytic material may be recycled without loss of activity at least eight times, and air-exposed materials are catalytically active. These supported zirconium centers are robust catalytic sites for carbonyl reduction and that surface-supported, catalytically reactive zirconium hydride may be generated from zirconium-amide or zirconium alkoxide sites.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  6. Studies of Immobilized Homogeneous Metal Catalysts on Silica Supports

    SciTech Connect

    Keith James Stanger

    2003-05-31

    The tethered, chiral, chelating diphosphine rhodium complex, which catalyzes the enantioselective hydrogenation of methyl-{alpha}-acetamidocinnamate (MAC), has the illustrated structure as established by {sup 31}P NMR and IR studies. Spectral and catalytic investigations also suggest that the mechanism of action of the tethered complex is the same as that of the untethered complex in solution. The rhodium complexes, [Rh(COD)H]{sub 4}, [Rh(COD){sub 2}]{sup +}BF{sub 4}{sup -}, [Rh(COD)Cl]{sub 2}, and RhCl{sub 3} {center_dot} 3H{sub 2}O, adsorbed on SiO{sub 2} are optimally activated for toluene hydrogenation by pretreatment with H{sub 2} at 200 C. The same complexes on Pd-SiO{sub 2} are equally active without pretreatments. The active species in all cases is rhodium metal. The catalysts were characterized by XPS, TEM, DRIFTS, and mercury poisoning experiments. Rhodium on silica catalyzes the hydrogenation of fluorobenzene to produce predominantly fluorocyclohexane in heptane and 1,2-dichloroethane solvents. In heptane/methanol and heptane/water solvents, hydrodefluorination to benzene and subsequent hydrogenation to cyclohexane occurs exclusively. Benzene inhibits the hydrodefluorination of fluorobenzene. In DCE or heptane solvents, fluorocyclohexane reacts with hydrogen fluoride to form cyclohexene. Reaction conditions can be chosen to selectively yield fluorocyclohexane, cyclohexene, benzene, or cyclohexane. The oxorhenium(V) dithiolate catalyst [-S(CH{sub 2}){sub 3}s-]Re(O)(Me)(PPh{sub 3}) was modified by linking it to a tether that could be attached to a silica support. Spectroscopic investigation and catalytic oxidation reactivity showed the heterogenized catalyst's structure and reactivity to be similar to its homogeneous analog. However, the immobilized catalyst offered additional advantages of recyclability, extended stability, and increased resistance to deactivation.

  7. XPS studies of Pt catalysts supported on porous carbon

    NASA Astrophysics Data System (ADS)

    Tyagi, Deepak; Varma, Salil; Bharadwaj, S. R.

    2016-05-01

    Pt catalysts supported on porous carbon were prepared by hard templating route and used for HI decomposition reaction of Sulfur Iodine thermochemical cycle. These catalysts were characterized by X-ray photoelectron spectroscopy for oxidation state of platinum as well as nature of carbon present in the catalysts. It was found that platinum is present in metallic state and carbon is present in both sp2 and sp3 hybridization states. The catalysts were evaluated for their activity and stability for liquid phase HI decomposition reaction and it was observed that mesoporous carbon based catalysts were more active and stable under the reaction conditions.

  8. Experimental study on heat transfer of supercritical carbon dioxide in a long silica-based porous-media tube

    NASA Astrophysics Data System (ADS)

    Hsieh, Jui-Ching; Lin, David T. W.; Lee, Bo-Heng; Chung, Ming-Che

    2016-07-01

    The heat transfer phenomena of supercritical carbon dioxide were experimentally investigated in a vertical tube containing silica-based porous media. The experiment was conducted at various levels of static pressure, flow rates, and initial wall temperatures as well as with silica sand of porous media in a long test section to study the heat transfer characteristics of supercritical carbon dioxide (CO2). The results indicated that the average heat transfer coefficient and outlet temperature at an initial wall temperature of 150 °C were higher and lower than that of 200 °C. The heat transfer performance was significantly influenced by flow rate of supercritical CO2. The porous media was provided large heat exchange surface between particles and CO2 to increase the heat transfer coefficient, especially when small diameter of particles. When the inlet temperature was higher than the pseudocritical temperature, the heat transfer coefficient sharply dropped when x/L ≥ 0.5, because of the development of a thermal boundary and the decrease of CO2 thermophysical properties of CO2 in a far pseudocritical temperature. When the pseudocritical temperature was higher than the inlet temperature of the fluid, the local heat transfer coefficient was affected by a thermal boundary and thermophysical properties of CO2 in pseudocritical point at a higher initial wall temperature or lower supercritical pressure when x/L ≤ 0.75; only the thermophysical properties of supercritical CO2 in pseudocritical point played a pivotal role when x/L > 0.75 at a lower initial wall temperature or higher supercritical pressure. In the present study, the supercritical pressure of 10.5 MPa constituted an optimal operating condition for supercritical CO2 a long silica-based porous-media tube because of the high heat transfer performance at 150 and 200 °C.

  9. N-doped mesoporous carbons supported palladium catalysts prepared from chitosan/silica/palladium gel beads.

    PubMed

    Zeng, Minfeng; Wang, Yudong; Liu, Qi; Yuan, Xia; Feng, Ruokun; Yang, Zhen; Qi, Chenze

    2016-08-01

    In this study, a heterogeneous catalyst including palladium nanoparticles supported on nitrogen-doped mesoporous carbon (Pd@N-C) is synthesized from palladium salts as palladium precursor, colloidal silica as template, and chitosan as carbon source. N2 sorption isotherm results show that the prepared Pd@N-C had a high BET surface area (640m(2)g(-1)) with large porosity. The prepared Pd@N-C is high nitrogen-rich as characterized with element analysis. X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), and Raman spectroscopy characterization of the catalyst shows that the palladium species with different chemical states are well dispersed on the nitrogen-containing mesoporous carbon. The Pd@N-C is high active and shows excellent stability as applied in Heck coupling reactions. This work supplies a successful method to prepare Pd heterogeneous catalysts with high performance from bulk biopolymer/Pd to high porous nitrogen-doped carbon supported palladium catalytic materials. PMID:27155234

  10. Direct-writing of PbS nanoparticles inside transparent porous silica monoliths using pulsed femtosecond laser irradiation

    PubMed Central

    2011-01-01

    Pulsed femtosecond laser irradiation at low repetition rate, without any annealing, has been used to localize the growth of PbS nanoparticles, for the first time, inside a transparent porous silica matrix prepared by a sol-gel route. Before the irradiation, the porous silica host has been soaked within a solution containing PbS precursors. The effect of the incident laser power on the particle size was studied. X-ray diffraction was used to identify the PbS crystallites inside the irradiated areas and to estimate the average particle size. The localized laser irradiation led to PbS crystallite size ranging between 4 and 8 nm, depending on the incident femtosecond laser power. The optical properties of the obtained PbS-silica nanocomposites have been investigated using absorption and photoluminescence spectroscopies. Finally, the stability of PbS nanoparticles embedded inside the host matrices has been followed as a function of time, and it has been shown that this stability depends on the nanoparticle mean size. PMID:21970510

  11. Magnetic Silica Supported Copper: A Modular Approach to Aqueous Ullmann-type Amination of Aryl Halides

    EPA Science Inventory

    One-pot synthesis of magnetic silica supported copper catalyst has been described via in situ generated magnetic silica (Fe3O4@SiO2); the catalyst can be used for the efficacious amination of aryl halides in aqueous medium under microwave irradiation.

  12. Magnetic isotope effects in the photolysis of dibenzyl ketone on porous silica. /sup 13/C and /sup 17/O enrichments

    SciTech Connect

    Turro, N.J.; Cheng, C.C.; Wan, P.; Chung, C.; Mahler, W.

    1985-04-25

    The photolysis of dibenzyl ketone (DBK) on porous silica has been investigated. Both /sup 13/C and /sup 17/O isotopic enrichment in the ketone remaining after partial photolysis is demonstrated. The efficiency of /sup 13/C enrichment was found to be relatively insensitive to the average pore diameter of the silica host, to the percent coverage by DBK, and to the application of an external magnetic field. A significant dependence of /sup 13/C enrichment with temperature, with a maximum in the enrichment-temperature profile, was observed. The results are interpreted in terms of the competition between pathways available to the triplet C/sub 6/H/sub 5/CH/sub 2/COCH/sub 2/C/sub 6/H/sub 5/ radical pair produced by photolysis of DBK.

  13. Supported metal nanoparticles on porous materials. Methods and applications.

    PubMed

    White, Robin J; Luque, Rafael; Budarin, Vitaliy L; Clark, James H; Macquarrie, Duncan J

    2009-02-01

    Nanoparticles are regarded as a major step forward to achieving the miniaturisation and nanoscaling effects and properties that have been utilised by nature for millions of years. The chemist is no longer observing and describing the behaviour of matter but is now able to manipulate and produce new types of materials with specific desired physicochemical characteristics. Such materials are receiving extensive attention across a broad range of research disciplines. The fusion between nanoparticle and nanoporous materials technology represents one of the most interesting of these rapidly expanding areas. The harnessing of nanoscale activity and selectivity, potentially provides extremely efficient catalytic materials for the production of commodity chemicals, and energy needed for a future sustainable society. In this tutorial review, we present an introduction to the field of supported metal nanoparticles (SMNPs) on porous materials, focusing on their preparation and applications in different areas. PMID:19169462

  14. Effect of content of chiral selector and pore size of core-shell type silica support on the performance of amylose tris(3,5-dimethylphenylcarbamate)-based chiral stationary phases in nano-liquid chromatography and capillary electrochromatography.

    PubMed

    Rocchi, Silvia; Fanali, Salvatore; Farkas, Tivadar; Chankvetadze, Bezhan

    2014-10-10

    In this study the separation performance of various chiral stationary phases (CSPs) made of polysaccharide-based chiral selectors coated onto superficially porous (core-shell or fused-core) silica supports were evaluated. The CSPs obtained by coating of various amounts of chiral selector (1-5%) onto supports of various pore size (100 and 300 Å) were studied. Their evaluation was pursued in both chiral nano-liquid chromatography (nano-LC) and chiral capillary electrochromatography (CEC). Among the goals of this study was to re-examine our previous unexpected finding of better performance of superficially porous CSP under CEC conditions compared to nano-LC conditions for a new set of chiral compounds, as well as to study the effect of varying the chiral selector content and nominal pore size of supporting silica on the performance of core-shell silica-based polysaccharide-type CSPs. Based on the results of this study it can be seen that CSPs based on superficially porous silica can successfully be used for the separation of enantiomers in both nano-LC and CEC mode. Only a slight advantage of CEC over nano-LC mode was observed in this study from the viewpoint of plate numbers, especially at higher mobile phase flow rates. It must also be noted that the optimal theoretical plate height is still too high and further optimization of superficially porous CSPs is necessary for both nano-LC and CEC applications. PMID:24908153

  15. Physical and chemical immobilization of choline oxidase onto different porous solid supports: Adsorption studies.

    PubMed

    Passos, Marieta L C; Ribeiro, David S M; Santos, João L M; Saraiva, M Lúcia M F S

    2016-08-01

    This work carries out for the first time the comparison between the physical and chemical immobilization of choline oxidase onto aminated silica-based porous supports. The influence on the immobilization efficiency of concentration, pH, temperature and contact time between the support and choline oxidase, was evaluated. The immobilization efficiency was estimated taking into consideration the choline oxidase activity, which was assessed by using cadmium telluride (CdTe) quantum dots (QDs), obtained by hydrothermal synthesis, as photoluminescent probes. Hydrogen peroxide produced by enzyme activity was capable of quenching CdTe QDs photoluminescence. The magnitude of the PL quenching process was directly related with the enzyme activity. By comparing the chemical process with the physical adsorption, it was observed that the latter provided the highest choline oxidase immobilization. The equilibrium data were analyzed using Langmuir and Freundlich isotherms and kinetic data were fitted to the pseudo-first-order and pseudo-second-order models. Thermodynamic parameters, such as Gibbs free energy and entropy were also calculated. These results will certainly contribute to the development of new sensing schemes for choline, taking into account the growing demand for its quantification in biological samples. PMID:27241295

  16. New support for high-performance liquid chromatography based on silica coated with alumina particles.

    PubMed

    Silveira, José Leandro R; Dib, Samia R; Faria, Anizio M

    2014-01-01

    A new material based on silica coated with alumina nanoparticles was proposed for use as a chromatographic support for reversed-phase high-performance liquid chromatography. Alumina nanoparticles were synthesized by a sol-gel process in reversed micelles composed of sodium bis(2-ethylhexyl)sulfosuccinate, and the support material was formed by the self-assembly of alumina layers on silica spheres. Spectroscopic and (29)Si nuclear magnetic resonance results showed evidence of chemical bonds between the alumina nanoparticles and the silica spheres, while morphological characterizations showed that the aluminized silica maintained the morphological properties of silica desired for chromatographic purposes after alumina incorporation. Stability studies indicated that bare silica showed high dissolution (~83%), while the aluminized silica remained practically unchanged (99%) after passing one liter of the alkaline mobile phase, indicating high stability under alkaline conditions. The C18 bonded aluminized silica phase showed great potential for use in high-performance liquid chromatography to separate basic molecules in the reversed-phase mode. PMID:24521917

  17. Preparing mesoporous carbon and silica with rosin-silica composite gel.

    PubMed

    Liu, Haidi; Du, Shangfeng; Chen, Yunfa

    2009-02-01

    Mesoporous carbon and mesoporous silica were prepared respectively with a same rosin-silica nanocomposite gel which was synthesized by cogelating tetra-ethyl-oxy-silane (silica source) and rosin (carbon source). Carbonizing the gel in nitrogen and then etching away silica with alkaline solution, mesoporous carbon with specific surface area larger than 800 m2/g was obtained. If calcining the gel at high temperature in air for given time, porous silica with surface area higher than 700 m2/g was done. BET measurement was employed to investigate the pore distribution and surface area of the samples. Most of the pores in both the porous carbon and porous silica were mesoscale, which makes the materials potential in enzyme supports for bio-catalyzed reaction or adsorbents for contaminants with large molecular size. PMID:19441395

  18. Interplay of carbon-silica sources on the formation of hierarchical porous composite materials for biological applications such as lipase immobilization.

    PubMed

    Higuita, Mario; Bernal, Claudia; Mesa, Monica

    2014-10-01

    The porous inorganic materials, with hierarchical structures, find application in many processes where the chemical stability and pore connectivity are key points, such as separation, adsorption and catalysis. Here, we synthesized carbon-silica composite materials, which combine hydrolytic stability of the carbon with the surface chemical reactivity of silica in aqueous media. The polycondensation of carbonaceous and siliceous species from sucrose, Triton X-100 surfactant and tetraethylortosilicate during the hydrothermal synthesis led to the formation of hydrochar composite materials. The subsequent carbonization process of these composite hydrochars gave carbon-silica hierarchical porous materials. The study of the micellar reaction system and the characterization of the derivate materials (carbon-silica composite, carbon and silica) were carried out. The results indicate that synthesis conditions allowed the formation of a silica network interpenetrated with a carbon one, which is produced from the incorporated organic matter. The control of the acidity of the reaction medium and hydrothermal conditions modulated the reaction yield and porous characteristics of the materials. The composite nature in conjunction with the hierarchical porosity increases the interest of these materials for future biological applications, such as lipase immobilization. PMID:25175205

  19. Thin porous alumina sheets as supports for stabilizing gold nanoparticles.

    PubMed

    Wang, Jie; Lu, An-Hui; Li, Mingrun; Zhang, Weiping; Chen, Yong-Sheng; Tian, Dong-Xu; Li, Wen-Cui

    2013-06-25

    Thin porous alumina sheets have been synthesized using a lysine-assisted hydrothermal approach resulting in an extraordinary catalyst support that can stabilize Au nanoparticles at annealing temperatures up to 900 °C. Remarkably, the unique architecture of such an alumina with thin sheets (average thickness ~15 nm and length 680 nm) and rough surface is beneficial to prevent gold nanoparticles from sintering. HRTEM observations clearly showed that the epitaxial growth between Au nanoparticles and alumina support was due to strong interfacial interactions, further explaining the high sinter-stability of the obtained Au/Al2O3 catalyst. Consequently, despite calcination at 700 °C, the catalyst maintains its gold nanoparticles of size predominantly 2 ± 0.8 nm. Surprisingly, catalyst annealed at 900 °C retained the highly dispersed small gold nanoparticles. It was also observed that a few gold particles (6-25 nm) were encapsulated by an alumina layer (thickness less than 1 nm) to minimize the surface energy, revealing a surface restructuring of the gold/support interface. As a typical and size-dependent reaction, CO oxidation is used to evaluate the performance of Au/Al2O3 catalysts. The results obtained demonstrated Au/Al2O3 catalyst calcined at 700 °C exhibited excellent activity with a complete CO conversion at ∼30 °C (T100% = 30 °C), and even after calcination at 900 °C, the catalyst still achieved its T50% at 158 °C. In sharp contrast, Au catalyst prepared using conventional alumina support shows almost no activity under the same preparation and catalytic test conditions. PMID:23682983

  20. Study of the dispersion of molybdenum(VI) supported on silica and. gamma. -alumina

    SciTech Connect

    Rodrigo, L.; Marcinkowska, K.; Adnot, A.; Roberge, P.C.; Kaliaguine, S.; Stencel, J.M.; Makovsky, L.E.; Diehl, J.R.

    1986-06-05

    A comparative study of O/sub 2/ chemisorption on molybdenum supported on silica and ..gamma..-alumina is reported. The catalysts had been prepared either by pore-filling impregnation or by reaction of the surface OH groups with the eta-allyl complex of Mo. The same catalysts have been the object of a systematic study of ESCA intensity ratio showing that this last method yields information concerning Mo dispersion and surface segregation. The two series of silica-supported catalysts were also analyzed by laser Raman spectroscopy and ion-scattering spectroscopy. In particular, the LRS study shows the presence of MoO/sub 3/ microcrystals at Mo loadings as low as 2% on impregnated silica catalysts and of silicomolybdic anions down to 1 wt % Mo on both series of silica-supported catalysts.

  1. Gated silica mesoporous supports for controlled release and signaling applications.

    PubMed

    Coll, Carmen; Bernardos, Andrea; Martínez-Máñez, Ramón; Sancenón, Félix

    2013-02-19

    Blending molecular and supramolecular advances with materials science has resulted in recent years in the development of new organic-inorganic hybrid materials displaying innovative functionalities. One appealing concept in this field is the development of gated nanodevices. These materials are prepared by grafting molecular or supramolecular caps onto the external surface of mesoporous inorganic scaffolds loaded with a particular cargo. The caps or "gates" can then be opened and the cargo delivered at will upon the application of a given stimulus. In this Account, we report some of the recent advances we have made in designing such materials for drug delivery and as new chromo-fluorogenic probes. For controlled release applications, we have prepared capped hybrid mesoporous supports capable of being selectively opened by applying certain physical and chemical stimuli. We report examples of gated materials opened by changes in pH (using polyamines as caps), light (employing spiropyran derivatives or gold nanoparticles), and temperature (using selected paraffins). We also report gated materials opened by enzymes that cleave capping molecules based on lactose, hydrolyzed starch, and peptides. The use of enzymes is especially appealing because molecular caps built of enzyme-specific sequences made of peptides or other cleavable molecules could allow on-command delivery of drugs and biomolecules in specialized contexts. In the second part of the manuscript, we revisit the possibility of using hybrid gated nanomaterials as sensory systems. In such systems, when target analytes interact with the cap, their presence triggers the transport of a dye from pores to the solution, resulting in a chromo-fluorogenic signal that allows their detection. Two approaches are possible. In the first one, pores remain open and the dye can diffuse into the solution, until the presence of a target analyte binds to receptors in the caps and closes the gate. In the second approach, the caps

  2. [Preparation of 1 µm non-porous C18 silica gel stationary phase for chiral-pressurized capillary electrochromatography].

    PubMed

    Lu, Yangfang; Wang, Hui; Wang, Guiming; Wang, Yan; Gu, Xue; Yan, Chao

    2015-03-01

    Non-porous C18 silica gel stationary phase (1 µm) was prepared and applied to chiral separation in pressurized capillary electrochromatography (pCEC) for the enantioseparation of various basic compounds. The non-porous silica particles (1 µm) were synthesized using modified St6ber method. C18 stationary phase (1 µm) was prepared by immobilization of chloro-dimethyl-octadecylsilane. Using carboxymethyl-β-cyclodextrin (CM-β-CD) as the chiral additive, the pCEC conditions including the content of acetonitrile (ACN), concentration of buffer, pH, the concentration of chiral additive and flow rate as well as applied voltage were investigated to obtain the optimal pCEC conditions for the separation of four basic chiral compounds. The column provided an efficiency of up to 190,000 plates/m. Bupropion hydrochloride, clenbuterol hydrochloride, metoprolol tartrate, and esmolol hydrochloride were baseline separated under the conditions of 5 mmol/L ammonium acetate buffer at pH 4. 0 with 20% (v/ v) acetonitrile, and 15 mmol/L CM-β-CD as the chiral additive. The applied voltage was 2 kV and flow rate was 0.03 mL/min with splitting ratio of 300:1. The resolution were 1.55, 2.82, 1. 69, 1. 70 for bupropion hydrochloride, clenbuterol hydrochloride, metoprolol tartrate, esmolol hydrochloride, respectively. The C18 coverage was improved by repeating silylation method. The synthesized 1 µm C18 packings have better mechanical strength and longer service life because of the special, non-porous structure. The column used in pCEC mode showed better separation of the racemates and a higher rate compared with those used in the capillary liquid chromatography (cLC) mode. This study provided an alternative way for the method of pCEC enantioseparation with chiral additives in the mobile phase and demonstrated the feasibility of micron particle stationary phase in chiral separation. PMID:26182460

  3. Porous silica particles grafted with an amphiphilic side-chain polymer as a stationary phase in reversed-phase high-performance liquid chromatography.

    PubMed

    Shahruzzaman, Md; Takafuji, Makoto; Ihara, Hirotaka

    2015-07-01

    The amphiphilic polymer-grafted silica was newly prepared as a stationary phase in high-performance liquid chromatography. Poly(4-vinylpyridine) with a trimethoxysilyl group at one end was grafted onto porous silica particles and the pyridyl side chains were quaternized with 1-bromooctadecane. The obtained poly(octadecylpyridinium)-grafted silica was characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy and Brunauer-Emmett-Teller analysis. The degree of quaternization of the pyridyl groups on the obtained stationary phase was estimated to be 70%. The selective retention behaviors of polycyclic aromatic hydrocarbons including some positional isomers were investigated using poly(octadecylpyridinium)-grafted silica as an amphiphilic polymer stationary phase in high-performance liquid chromatography and results were compared with commercially available polymeric octadecylated silica and phenyl-bonded silica columns. The results indicate that the selectivity toward polycyclic aromatic hydrocarbons exhibited by the amphiphilic polymer stationary phase is higher than the corresponding selectivity exhibited by a conventional phenyl-bonded silica column. However, compared with the polymeric octadecylated silica phase, the new stationary phase presents similar retention behavior for polycyclic aromatic hydrocarbons but different retention behavior particularly for positional isomers of disubstituted benzenes as the aggregation structure of amphiphilic polymers on the surface of silica substrate has been altered during mobile phase variation. PMID:25944152

  4. Removal of formaldehyde from air using functionalized silica supports.

    PubMed

    Ewlad-Ahmed, Abdunaser M; Morris, Michael A; Patwardhan, Siddharth V; Gibson, Lorraine T

    2012-12-18

    This paper demonstrates the use of functionalized meso-silica materials (MCM-41 or SBA-15) as adsorbents for formaldehyde (H₂CO) vapor from contaminated air. Additionally new green nanosilica (GNs) materials were prepared via a bioinspired synthesis route and were assessed for removal of H₂CO from contaminated indoor air. These exciting new materials were prepared via rapid, 15 min, environmentally friendly synthesis routes avoiding any secondary pollution. They provided an excellent platform for functionalization and extraction of H₂CO demonstrating similar performance to the conventional meso-silica materials. To the authors' knowledge this is the first reported practical application of this material type. Prior to trapping, all materials were functionalized with amino-propyl groups which led to chemisorption of H₂CO; removing it permanently from air. No retention of H₂CO was achieved with nonfunctionalized material and it was observed that best extraction performance required a dynamic adsorption setup when compared to passive application. These results demonstrate the first application of GNs as potential adsorbents and functionalized meso-silica for use in remediation of air pollution in indoor air. PMID:23181357

  5. Efficient Immobilization of Ammonium Tungstophosphate at the Mesoporous Silica Support for the Removal of Cs Ion.

    PubMed

    Park, Younjin; Shin, Won Sik; Choi, Sang-June

    2015-09-01

    The ammonium salt of phosphotugstic acid (NH4PTA) deposited on the surface of mesoporous silica (SBA-15) support was prepared and characterized using several analytical techniques. The spectroscopic results showed that the NH4PTA was evenly dispersed on the internal and external silica surfaces. The ion exchange capacity tests demonstrated that the specific activity for Cs removal increased with insertion of the NH4PTA phase on the silica surface. The results showed that the ion exchange capacity of Cs increased with increasing the PTA loading. The NH4PTA at a loading of 50 wt% supported on silica showed the highest ion exchange capacity for Cs ion among the loading range of 20-50 wt%. The effects of co-existing cations and nitric acid on the Cs sorption efficiency onto the composites were also studied. PMID:26716312

  6. The effect of porous support composition and operating parameters on the performance of supported liquid membranes

    SciTech Connect

    Takigawa, D.Y.

    1991-02-01

    Factors, such as porous support composition and operating parameters, that influence the performance of supported liquid membranes (SLMs) were investigated. SLMs of varying porous support compositions and structures were studied for the transport of metal ions. A microporous polybenzimidazole support was synthesized and prepared in the form of an SLM. This SLM containing the selective extractant di-(2-ethylhexyl)phosphoric acid was evaluated for the transport of copper and neodymium. Dramatically improved performance over that of commercially available membranes was found in tests for removing the metal ions from solution. Metal ion transport reaches near completion in less than 3 hours, whereas Celgard-polypropylene and Nuclepore-polycarbonate reaches only 50% completion even after 15 hours. The transport driving force for acidic extractants is a pH gradient between the feed and strip solutions. Polybenzimidazole, an acid- and radiation-resistant polymer, has two protonatable tertiary nitrogens per repeat unit that may help sustain the pH driving force. Another factor may be the ability of the polybenzimidazole to hydrogen bond with the extractant. Transport through the flat-sheet SLMs were tested using a unique cell design. Countercurrent flow of the feed and strip solutions was established through machined channels in half-cell faceplates that are in a spiral, mirror-image pattern with respect to each other, with the flat-sheet SLM interposed between the two channeled solutions. 7 refs., 14 figs.

  7. Refractive index detection range adjustable liquid-core fiber optic sensor based on surface plasmon resonance and a nano-porous silica coating

    NASA Astrophysics Data System (ADS)

    Chen, Yuzhi; Li, Xuejin; Zhou, Huasheng; Hong, Xueming; Geng, Youfu

    2016-09-01

    A liquid-core fiber optic surface plasmon resonance sensor with an adjustable nano-porous silica coating is first presented in this paper. By adjusting the refractive index of the nano-porous silica coating, the sensor can be used in different refractive index detection ranges. A low refractive index interval of 1.33–1.34 and a high refractive index interval of 1.42–1.44 are taken as examples to be investigated. Results show that our sensor works well in these two intervals by using appropriate nano-porous silica coatings. The highest sensitivities of the low and high refractive index intervals are obtained to be 5840 nm/RIU and 5120 nm/RIU, respectively. In addition, the sensing performances and the working wavelengths can be adjusted to meet different working requirements by changing the refractive index of the nano-porous silica coating. We also take the single mode incidence cases to explain the effects of different single incident light modes on the sensing performances.

  8. Fabrication of Hollow Porous Silica Using a Combined Emulsion Sol-Gel Process and Amphiphilic Triblock Copolymer for Loading of Quercetin.

    PubMed

    Lee, Sang Gil; Kim, Young Ho; Bae, Jun Tae; Lee, Chung Hee; Pyo, Hyeong Bae; Kang, Kuk Hyoun; Lee, Dong Kyu

    2015-10-01

    Flavonoids have recently attracted significant interest as potential reducing agents, hydrogen-donating antioxidants, and singlet oxygen-quenchers. Quercetin, in particular, induces the expression of a gene, known to be associated with cell protection, in dose- and time-dependent manners. Therefore, quercetin may be used as an effective cosmeceutical material useful in the protection of dermal skin. In this study, hollow porous silica spheres used to load quercetin were prepared by using a combined emulsion sol-gel process and triblock copolymer as a template. Fabrication of hollow porous silica spheres was performed under various conditions such as the molar ratios of H2O/TEOS (Rw) and weight ratios of poloxamer 184/poloxamer 407. Loading of quercetin in hollow porous silica spheres was devised to improve the stability of quercetin and to consider the possibility as a raw cosmetic material. The surface of inclusion complexes of quercetin in hollow porous silicas was modified to enhance the stability of quercetin. The physicochemical properties of the samples were investigated using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA)-differential thermal analysis (DTA) and Brunauer-Emmett-Teller (BET) surface area and porosity analysis. Determination of quercetin concentration was carried out by high-performance liquid chromatography (HPLC) analysis. PMID:26726443

  9. Covalent immobilization of glucose oxidase onto new modified acrylonitrile copolymer/silica gel hybrid supports.

    PubMed

    Godjevargova, Tzonka; Nenkova, Ruska; Dimova, Nedyalka

    2005-08-12

    New polymer/silica gel hybrid supports were prepared by coating high surface area of silica gel with modified acrylonitrile copolymer. The concentrations of the modifying agent (NaOH) and the modified polymer were varied. GOD was covalently immobilized on these hybrid supports and the relative activity and the amount of bound protein were determined. The highest relative activity and sufficient amount of bound protein of the immobilized GOD were achieved in 10% NaOH and 2% solution of modified acrylonitrile copolymer. The influence of glutaraldehyde concentration and the storage time on enzyme efficiency were examined. Glutaraldehyde concentration of 0.5% is optimal for the immobilized GOD. It was shown that the covalently bound enzyme (using 0.5% glutaraldehyde) had higher relative activity than the activity of the adsorbed enzyme. Covalently immobilized GOD with 0.5% glutaraldehyde was more stable for four months in comparison with the one immobilized on pure silica gel, hybrid support with 10% glutaraldehyde and the free enzyme. The effect of the pore size on the enzyme efficiency was studied on four types of silica gel with different pore size. Silica with large pores (CPC-Silica carrier, 375 A) presented higher relative activity than those with smaller pore size (Silica gel with 4, 40 and 100 A). The amount of bound protein was also reduced with decreasing the pore size. The effect of particle size was studied and it was found out that the smaller the particle size was, the greater the activity and the amount of immobilized enzyme were. The obtained results proved that these new polymer/silica gel hybrid supports were suitable for GOD immobilization. PMID:16080168

  10. Reactions of methyl radicals with silica supported silver nanoparticles in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Zidki, Tomer; Hänel, Andreas; Bar-Ziv, Ronen

    2016-07-01

    Silica supported silver nanoparticles (Ag°-SiO2-NCs, NCs=nanocomposites) suspended in aqueous solutions are efficient catalysts for the dimerization of methyl radicals to produce ethane, while bare silica is quite inert towards the interaction with methyl radicals. In the presence of small amounts of ethanol adsorbed on the SiO2 surface, the reaction path with methyl radicals is changed and methane is formed as the major product.

  11. Synthesis and properties of porous silica obtained by the template method

    NASA Astrophysics Data System (ADS)

    Kuznetsova, T. F.; Rat'ko, A. I.; Eremenko, S. I.

    2012-10-01

    Micromesoporous samples of SiO2 were synthesized by the sol-gel method using tetraethoxysilane as a starting reagent and 1-5 wt % cetylpyridinium chloride as a template under the conditions of preadsorption of colloid silica by polyethyleneglycol macromolecules. The adsorption and texture of the samples were studied by the low-temperature nitrogen adsorption-desorption technique. Preadsorption of silica sol was shown to affect the adsorption and capillary-condensation properties of silica. The surface area and the volume of mesopores increased at cetylpyridinium concentrations higher than 1 wt %. The micropore volume increased to a maximum. The capillary-condensation hysteresis loop of H4 type transformed into an H3 loop according to the IUPAC classification.

  12. Nanoscale zero-valent iron supported on mesoporous silica: characterization and reactivity for Cr(VI) removal from aqueous solution.

    PubMed

    Petala, Eleni; Dimos, Konstantinos; Douvalis, Alexios; Bakas, Thomas; Tucek, Jiri; Zbořil, Radek; Karakassides, Michael A

    2013-10-15

    MCM-41-supported nanoscale zero-valent iron (nZVI) was sytnhesized by impregnating the mesoporous silica martix with ferric chloride, followed by chemical reduction with NaHB4. The samples were studied with a combination of characterization techniques such as powder X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Mössbauer spectroscopy, N2 adsorption measurements, transmission electron microscopy (TEM), magnetization measurements, and thermal analysis methods. The experimental data revealed development of nanoscale zero-valent iron particles with an elliptical shape and a maximum size of ∼80 nm, which were randomly distributed and immobilized on the mesoporous silica surface. Surface area measurements showed that the porous MCM-41 host matrix maintains its hexagonal mesoporous order structure and exhibits a considerable high surface area (609 m(2)/g). Mössbauer and magnetization measurements confirmed the presence of core-shell iron nanoparticles composed of a ferromagnetic metallic core and an oxide/hydroxide shell. The kinetic studies demonstrated a rapid removal of Cr(VI) ions from the aqueous solutions in the presence of these stabilized nZVI particles on MCM-41, and a considerably increased reduction capacity per unit mass of material in comparison to that of unsupported nZVI. The results also indicate a highly pH-dependent reduction efficiency of the material, whereas their kinetics was described by a pseudo-first order kinetic model. PMID:23959249

  13. Quantitative investigation of a hybrid Ziegler-Natta catalyst support prepared by grafting di(n-butyl)magnesium onto partially dehydroxylated silica.

    PubMed

    Lee, Ming-Yung; Scott, Susannah L

    2011-04-11

    MgCl(2)-modified silica is an important component of some Ziegler-Natta catalysts used in the manufacture of polyethylene. Information about the structure of the dispersed magnesium sites formed by the reaction of di-n-butylmagnesium (nBu(2)Mg) with silica was sought to provide a basis for understanding their subsequent interactions with transition-metal or co-catalyst components. From infrared spectra and elemental analysis, we deduced that nBu(2)Mg reacts with porous silica in two ways: about half (47%, 0.99 mmol g(-1)) is grafted through protonolysis by surface hydroxyl groups (≡SiOH), whereas the other half (53%, 1.11 mmol g(-1)) reacts directly with siloxane bonds (≡SiOSi≡). In the (29)Si and (13)C CP/MAS NMR spectra of Sylopol-2100 silica pretreated at 500 °C then modified with nBu(2)Mg at room temperature, both alkylsilicon and alkylmagnesium sites are evident. The alkylmagnesium-modified silica surface is proposed to contain dimers and/or tetramers with the empirical formula [≡SiOMg(nBu)](n). Upon exposure of nBu(2)Mg-modified silica to anhydrous HCl, alkanes are liberated, hydroxyl groups are regenerated, and water is formed. The appearance of water suggests condensation of hydroxyl group pairs, induced by the coordinatively unsaturated nanoclusters (MgCl(2))(n) that arise by ligand exchange on the silica-supported n-butylmagnesium oligomers. PMID:21433118

  14. The effect of porous support composition and operating parameters on the performance of supported liquid membranes

    SciTech Connect

    Takigawa, D.Y. )

    1992-03-01

    Supported liquid membranes (SLMs) of varying porous support compositions and structures were studied for the transport of metal ions. A microporous polybenzimidazole support was synthesized and prepared in the form of an SLM. This SLM, containing the selective extractant di-(2-ethylhexyl) phosphoric acid, was evaluated for the transport of copper and neodymium. Metal ion transport reaches near completion in less than 3 h, whereas Celgard-polypropylene and Nucleopore-polycarbonate reaches only 50% completion even after 15 h. The transport driving force for acidic extractants is a pH gradient between the feed and strip solutions. Polybenzimidazole, an acid-and radiation-resistant polymer, has two protonatable tertiary nitrogens per repeat unit that may help sustain the pH driving force. Another factor may be the ability of the polybenzimidazole to hydrogen bond with the extractant. Transport through the flat-sheet SLMs was tested by using a unique cell design. Countercurrent flow of the feed and strip solutions was established through machined channels in half-cell face plates that are in a spiral, mirror-image pattern with respect to each other, with the flat-sheet SLM interposed between the two channeled solutions. Advantages comprised in the design of the two clamped half-cells (tangential entry, zero primary pressure, zero pressure differential, controlled flow regimes, no sharp turns, and channeled flow) give operating parameters that will not physically dislodge the liquid membrane from the porous support; consequently, the lifetime of the support is increased. Permeability coefficients remained unchanged after a month of daily use versus 20 to 100% declines for membranes in other cell configurations.

  15. Ligand-tailored single-site silica supported titanium catalysts: Synthesis, characterization and towards cyanosilylation reaction

    SciTech Connect

    Xu, Wei; Li, Yani; Yu, Bo; Yang, Jindou; Zhang, Ying; Chen, Xi; Zhang, Guofang Gao, Ziwei

    2015-01-15

    A successive anchoring of Ti(NMe{sub 2}){sub 4}, cyclopentadiene and a O-donor ligand, 1-hydroxyethylbenzene (PEA), 1,1′-bi-2-naphthol (Binol) or 2,3-dihydroxybutanedioic acid diethyl ester (Tartrate), on silica was conducted by SOMC strategy in moderate conditions. The silica, monitored by in-situ Fourier transform infrared spectroscopy (in-situ FT-IR), was pretreated at different temperatures (200, 500 and 800 °C). The ligand tailored silica-supported titanium complexes were characterized by in-situ FT-IR, {sup 13}C CP MAS-NMR, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) and elemental analysis in detail, verifying that the surface titanium species are single sited. The catalytic activity of the ligand tailored single-site silica supported titanium complexes was evaluated by a cyanosilylation of benzaldehyde. The results showed that the catalytic activity is dependent strongly on the dehydroxylation temperatures of silica and the configuration of the ligands. - Graphical abstract: The ligand-tailored silica supported “single site” titanium complexes were synthesized by SOMC strategy and fully characterized. Their catalytic activity were evaluated by benzaldehyde silylcyanation. - Highlights: • Single-site silica supported Ti active species was prepared by SOMC technique. • O-donor ligand tailored Ti surface species was synthesized. • The surface species was characterized by XPS, {sup 13}C CP-MAS NMR, XANES etc. • Catalytic activity of the Ti active species in silylcyanation reaction was evaluated.

  16. Synthesis of poly(N-[tris(hydroxymethyl)methyl]acrylamide) functionalized porous silica for application in hydrophilic interaction chromatography.

    PubMed

    Bui, Nhat Thi Hong; Jiang, Wen; Sparrman, Tobias; Irgum, Knut

    2012-12-01

    Porous silica coated by a highly hydrophilic and nonionic tentacle-type polymeric layer was synthesized by free radical "grafting from" polymerization of N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]-2-propenamide (TRIS-acrylamide) in partly aqueous solutions. The radical initiator sites were incorporated on the silica surfaces via a two-step reaction comprising thionyl chloride activation and subsequent reaction with tert-butyl hydroperoxide. The surface-bound tert-butylperoxy groups were then used as thermally triggered initiators for graft polymerization of TRIS-acrylamide. The synthesized materials were characterized by diffusive reflectance Fourier transform infrared specotroscopy, X-ray photoelectron spectroscopy, and CHN elemental analysis. Photon correlation spectroscopy was used to determine changes in ζ-potentials resulting from grafting, (29)Si magic angle spinning nuclear magnetic resonance spectroscopy (MAS-NMR) spectroscopy was used to assess the ratio of silanol to siloxane groups in the substrate and the grafted material, and the changes in surface area and mesopore distribution were determined by nitrogen cryosorption. Chromatographic evaluation in hydrophilic interaction chromatography (HILIC) mode showed that the materials were suitable for use as stationary phases, featuring good separation efficiency, a comparatively high retention, and a selectivity that differed from most commercially available HILIC phases. A comparison of this neutral phase with a previously reported N-(2-hydroxypropyl)-linked TRIS-type hydrophilic tentacle phase with weak anion exchange functionality revealed substantial differences in retention patterns. PMID:23184369

  17. Embedding of individual ferritin molecules in large, self-supporting silica nanofilms.

    PubMed

    Fujikawa, Shigenori; Muto, Emi; Kunitake, Toyoki

    2007-04-10

    We report herein the fabrication of ferritin-embedded self-supporting silica nanofilms via a simple spin-coating process. Ferritin was employed as a template molecule, and solutions of ferritin and silica were spread on a polymer-coated silicon substrate, in this order. After dissolving the polymer underlayer by simply immersing ethanol, a centimeter-sized self-supporting nanofilm of ferritin/silica composite with a thickness of 15 nm was successfully transferred onto an alumina membrane without the film breaking. Ozone and hydrochloric acid solution treatment removed the template ferritin molecules from the composite film to produce corresponding transmembrane nanoholes. The reported method is very simple, and the fabrication of a protein-embedded self-supporting nanofilm enables the design of biomembrane-mimetic devices. PMID:17328567

  18. Hydrogen and oxygen adsorption stoichiometries on silica supported ruthenium nanoparticles

    SciTech Connect

    Berthoud, Romain; Delichere, Pierre; Gajan, David; Lukens, Wayne; Pelzer, Katrin; Basset, Jean-Marie; Candy, Jean-Pierre; Coperet, Christophe

    2008-12-01

    Treatment under H{sub 2} at 300 C of Ru(COD)(COT) dispersed on silica yields 2 nm ruthenium nanoparticles, [Ru{sub p}/SiO{sub 2}], according to EXAFS, HRTEM and XPS. H{sub 2} adsorption measurements on [Ru{sub p}/SiO{sub 2}] in the absence of O{sub 2} show that Ru particles adsorb up to ca. 2 H per surface ruthenium atoms (2H/Ru{sub s}) on various samples; this technique can therefore be used to measure the dispersion of Ru particles. In contrast, O{sub 2} adsorption on [Ru{sub p}/SiO{sub 2}] leads to a partial oxidation of the bulk at 25 C, to RuO{sub 2} at 200 C and to sintering upon further reduction under H{sub 2}, showing that O{sub 2} adsorption cannot be used to measure the dispersion of Ru particles.

  19. Porous carbon-coated silica macroparticles as anode materials for lithium ion batteries: Effect of boric acid

    NASA Astrophysics Data System (ADS)

    Kim, Young-Kuk; Moon, Jong-Woo; Lee, Jung-Goo; Baek, Youn-Kyung; Hong, Seong-Hyun

    2014-12-01

    We report carbon-coated porous silica macroparticles (SiO2@C) prepared using polymeric templates and subsequent carbonization with sucrose for improved electrochemical energy storage in lithium-ion batteries (LIBs). In addition, boron is introduced to improve the stability of electrochemical cells by pyrolyzing mixtures of sucrose and boric acid (SiO2@C + B) under inert atmosphere. The initially large surface area of porous SiO2 (SBET ˜ 658 m2 g-1) is reduced to 102 m2 g-1 after carbonization and introduction of boric acid. Surface of both SiO2@C and SiO2@C + B are covered with amorphous carbon. In particular, SiO2@C + B particles containing borosilicate (Si-O-B) phase and B-O bondings and Si-C-O bondings are also detected from the X-ray photoelectron spectra. The SiO2@C + B macroparticles shows high reversible charge capacity up to 503 mAh g-1 after 103 cycles of Li intercalation/de-intercalation although initial capacity was 200 mAh g-1. The improved charge capacity of SiO2@C + B is attributed to formation of advantageous microstructures induced from boric acid.

  20. Porous carbon-coated silica macroparticles as anode materials for lithium ion batteries: Effect of boric acid

    NASA Astrophysics Data System (ADS)

    Kim, Young-Kuk; Moon, Jong-Woo; Lee, Jung-Goo; Baek, Youn-Kyung; Hong, Seong-Hyun

    2014-12-01

    We report carbon-coated porous silica macroparticles (SiO2@C) prepared using polymeric templates and subsequent carbonization with sucrose for improved electrochemical energy storage in lithium-ion batteries (LIBs). In addition, boron is introduced to improve the stability of electrochemical cells by pyrolyzing mixtures of sucrose and boric acid (SiO2@C + B) under inert atmosphere. The initially large surface area of porous SiO2 (SBET ∼ 658 m2 g-1) is reduced to 102 m2 g-1 after carbonization and introduction of boric acid. Surface of both SiO2@C and SiO2@C + B are covered with amorphous carbon. In particular, SiO2@C + B particles containing borosilicate (Si-O-B) phase and B-O bondings and Si-C-O bondings are also detected from the X-ray photoelectron spectra. The SiO2@C + B macroparticles shows high reversible charge capacity up to 503 mAh g-1 after 103 cycles of Li intercalation/de-intercalation although initial capacity was 200 mAh g-1. The improved charge capacity of SiO2@C + B is attributed to formation of advantageous microstructures induced from boric acid.

  1. Encapsulation of protein molecules in transparent porous silica matrices via an aqueous colloidal sol-gel process

    SciTech Connect

    Liu, D.M.; Chen, I.W.

    1999-12-10

    Encapsulation of several biologically important proteins, cytochrome c, catalase, myoglobin, and hemoglobin, into transparent porous silica matrices by an aqueous colloidal sol-gel process that requires no alcohol is reported. Optical characterization indicates a successful retention of protein conformation after encapsulation. The conformation retention is strongly correlated to both the rate of gelation and the subsequent drying speed. Using hemoglobin as a model protein, a higher colloidal solid concentration and a lower synthesis pH were found, both causing faster gelation, resulting in a better retention of conformation. Hemoglobin encapsulated in a thin film, which dries faster, also showed a better retention than in the bulk. This is attributed to the fact that when a protein is isolated, and especially when it is confined to a space close to its own dimensions, conformational changes are sterically hindered, hence the structural stability. Enzymatic activity of bovine liver catalase was also monitored and showed a remarkable improvement when encapsulated using the aqueous colloidal process, compared to using the conventional alkoxide-based process. Thus, the aqueous colloidal sol-gel process offers a promising alternative to the conventional sol-gel process for encapsulating biomolecules into transparent, porous matrices.

  2. Controllable synthesis of hollow mesoporous silica spheres and application as support of nano-gold

    SciTech Connect

    Wang, Tao; Ma, Weihua Shangguan, Junnan; Jiang, Wei; Zhong, Qin

    2014-07-01

    Hollow silica spheres with mesoporous structure were synthesized by sol–gel/emulsion method. In the process, the surfactant, cetyltrimethylammonium bromide (CTAB) was used to stabilize the oil droplet and also used as structure direct agent. The diameter of the hollow silica spheres, ranging from 895 nm to 157 nm, can be controlled by changing the ratio of ethanol to water and the concentration of the surfactant as well. The shell thickness of the spheres decreased when the ratio of ethanol to water decreased. The proposed mechanism of the formation of silica spheres could elucidate the experimental results well. Furthermore, the resultant hollow mesoporous silica spheres were then employed as support of nano-gold which was used to catalyze the isomerization reaction of propylene oxide to produce allyl alcohol. - Graphical abstract: It is the schematic mechanism for the formation of hollow mesoporous silica spheres. - Highlights: • The formation mechanism of the hollow spheres is proposed. • The isomerization of propylene oxide can be catalyzed by the nano-gold/SiO{sub 2}. • The hollow silica spheres can be prepared controllably.

  3. A new high-throughput method utilizing porous silica-based nano-composites for the determination of partition coefficients of drug candidates.

    PubMed

    Yu, Chih H; Tam, Kin; Tsang, Shik C

    2011-09-01

    We show that highly porous silica-based nanoparticles prepared via micro-emulsion and sol-gel techniques are stable colloids in aqueous solution. By incorporating a magnetic core into the porous silica nano-composite, it is found that the material can be rapidly separated (precipitated) upon exposure to an external magnetic field. Alternatively, the porous silica nanoparticles without magnetic cores can be equally separated from solution by applying a high-speed centrifugation. Using these silica-based nanostructures a new high-throughput method for the determination of partition coefficient for water/n-octanol is hereby described. First, a tiny quantity of n-octanol phase is pre-absorbed in the porous silica nano-composite colloids, which allows an establishment of interface at nano-scale between the adsorbed n-octanol with the bulk aqueous phase. Organic compounds added to the mixture can therefore undergo a rapid partition between the two phases. The concentration of drug compound in the supernatant in a small vial can be determined by UV-visible absorption spectroscopy. With the adaptation of a robotic liquid handler, a high-throughput technology for the determination of partition coefficients of drug candidates can be employed for drug screening in the industry based on these nano-separation skills. The experimental results clearly suggest that this new method can provide partition coefficient values of potential drug candidates comparable to the conventional shake-flask method but requires much shorter analytical time and lesser quantity of chemicals. PMID:21780284

  4. EPR in functional structures based on doped (nano, meso)-porous silica and titanium dioxide

    NASA Astrophysics Data System (ADS)

    Kassiba, A.; Makowska-Janusik, M.; Mehdi, A.

    2011-04-01

    EPR investigations are performed on mesoporous silica (SBA15) functionalized by Nickel-cyclam complexes (1,4,8,11-tetraazacyclotetradecane groups chelating nickel ions) and on mesoporous titanium dioxide with nitrogen doping. For functionalized silica, the magnetic behaviour of organometallic groups, their mutual interactions and dispersion in the host matrices are compared with respect to the doping rates and the synthesis procedures. The relaxation processes were analyzed from the thermal evolution of the paramagnetic spin susceptibilities and EPR line-widths. Particularly, some samples show the formation of clusters where phonon assisted one dimensional (1D) ferromagnetic ordering occurs below 45 K. For the mesoporous TiO2, systematic EPR investigations were performed on two main classes of materials with regard to the porosity degrees. The EPR experiments point out the efficiency of EPR method to probe the degree of functionalization of mesoporous silica or the nitrogen doping achievement in TiO2, and in general to give a valuable feedback to improve the synthesis routes of smart materials.

  5. Supported porous carbon and carbon-CNT nanocomposites for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Schopf, Dimitri; Es-Souni, Mohammed

    2016-03-01

    Supported porous carbon and porous carbon-MWCNT-nanocomposite films are produced by pyrolysis of porous polyvinylidene fluoride (PVDF) or porous PVDF-MWCNT-nanocomposite films on thermally resistant substrates. All films are characterized by SEM, RAMAN and XRD. The application of these films as supercapacitors is explored with outstanding supercapacitance values ranging from 80 to 120 F g-1 (up to 70 mF cm-2) in a three-electrode set-up in 1 M KOH, depending on microstructure. Additionally, the implementation of porous nanocarbon-MWCNT-nanocomposite films as electrodes in a symmetrical supercapacitor device is investigated. In all cases, long-term charge-discharge stability is demonstrated.

  6. Preparation and characterization of titania-deposited silica composite hollow fiber membranes with high hydrothermal stability.

    PubMed

    Kwon, Young-Nam; Kim, In-Chul

    2013-11-01

    Hydrothermal stability of a porous nickel-supported silica membrane was successfully improved by deposition of titania multilayers on colloidal silica particles embedded in the porous nickel fiber support. Porous nickel-supported silica membranes were prepared by means of a dipping-freezing-fast drying (DFF) method. The titania layers were deposited on colloidal silica particles by repeating hydrolysis and condensation reactions of titanium isopropoxide on the silica particle surfaces. The deposition of thin titania layers on the nickel-supported silica membrane was verified by various analytical tools. The water flux and the solute rejection of the porous Ni fiber-supported silica membranes did not change after titania layer deposition, indicating that thickness of titania layers deposited on silica surface is enough thin not to affect the membrane performance. Moreover, improvement of the hydrothermal stability in the titania-deposited silica membranes was confirmed by stability tests, indicating that thin titania layers deposited on silica surface played an important role as a diffusion barrier against 90 degrees C water into silica particles. PMID:24245310

  7. Switching on the Metathesis Activity of Re Oxo Alkylidene Surface Sites through a Tailor-Made Silica-Alumina Support.

    PubMed

    Valla, Maxence; Stadler, David; Mougel, Victor; Copéret, Christophe

    2016-01-18

    Re oxo alkylidene surface species are putative active sites in classical heterogeneous Re-based alkene-metathesis catalysts. However, the lack of evidence for such species questions their existence and/or relevance as reaction intermediates. Using Re(O)(=CH-CH=CPh2)(OtBuF6)3(THF), the corresponding well-defined Re oxo alkylidene surface species can be generated on both silica and silica-alumina supports. While inactive on the silica support, it displays very good activity, even for functionalized olefins, on the silica-alumina support. PMID:26756446

  8. Ligand-tailored single-site silica supported titanium catalysts: Synthesis, characterization and towards cyanosilylation reaction

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Li, Yani; Yu, Bo; Yang, Jindou; Zhang, Ying; Chen, Xi; Zhang, Guofang; Gao, Ziwei

    2015-01-01

    A successive anchoring of Ti(NMe2)4, cyclopentadiene and a O-donor ligand, 1-hydroxyethylbenzene (PEA), 1,1‧-bi-2-naphthol (Binol) or 2,3-dihydroxybutanedioic acid diethyl ester (Tartrate), on silica was conducted by SOMC strategy in moderate conditions. The silica, monitored by in-situ Fourier transform infrared spectroscopy (in-situ FT-IR), was pretreated at different temperatures (200, 500 and 800 °C). The ligand tailored silica-supported titanium complexes were characterized by in-situ FT-IR, 13C CP MAS-NMR, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) and elemental analysis in detail, verifying that the surface titanium species are single sited. The catalytic activity of the ligand tailored single-site silica supported titanium complexes was evaluated by a cyanosilylation of benzaldehyde. The results showed that the catalytic activity is dependent strongly on the dehydroxylation temperatures of silica and the configuration of the ligands.

  9. Magnetic silica supported palladium catalyst: synthesis of allyl aryl ethers in water

    EPA Science Inventory

    A simple and benign procedure for the synthesis of aryl allyl ethers has been developed using phenols, allyl acetates and magnetically recyclable silica supported palladium catalyst in water; performance of reaction in air and easy separation of the catalyst using an external mag...

  10. Investigation of porous silica nanostructures in diatoms isolated from Kurichi and Sulur lakes of Coimbatore, India using field emission scanning electron microscopy.

    PubMed

    N, Seethalakshmi; R, Selvakumar

    2015-12-01

    Diatoms are unicellular algae that possess cell wall made of silica. These diatoms play a pivotal role in synthesis of variety of silica nanostructures and have adorning morphology in nature. In the present study, we have used field emission scanning electron microscopy (FE-SEM) to investigate their morphological features like pore size, shape, and porous pattern in various diatoms isolated from Kurichi and Sulur fresh water lakes, Coimbatore, Tamil Nadu, India. Diatoms were identified as Nitzschia sp., Cyclotella meneghiniana, Coscinodiscus sp. and Cyclotella atomus based on their morphological features. The arrangement of porous nanostructures in these diatoms have been characterized. The change in the nanostructures present in the diatoms have been correlated to the contamination of water bodies. PMID:26296232

  11. Accessibility control on copper(II) complexes in mesostructured porous silica obtained by direct synthesis using bidentate organosilane ligands.

    PubMed

    Zhou, Wen-Juan; Albela, Belén; Perriat, Pascal; He, Ming-Yuan; Bonneviot, Laurent

    2010-08-17

    The accessibility of metal(II) complexes in 2D hexagonal mesostructured porous silicas obtained by direct synthesis is controlled using an appropriate organosilane ligand. This is exemplified here using copper(II) as a transition metal probe and a neutral or negatively charged ligand: N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, L(A), and, N-salicylaldimine-propylamine-trimethoxysilane, L(B)(-), respectively. L(A) leads to inaccessible complexes located into the pore wall and called "embedded" sites here where silanolate groups from the siliceous network block the access to Cu(II) ions. By contrast, L(B)(-) generates accessible complexes, named "showing-on" sites here. The copper-containing silicas were synthesized with various metal molar ratios (M/SiO(2) = 0.5-3%) in basic media, with cetyltrimethylammonium p-toluenesulfonate (CTATos) as template and with sodium silicate solution as silicon source. A soft template extraction procedure has been developed to preserve the complex integrity of the showing-on copper sites during the treatment. The embedded copper(II) and nickel(II) sites were compared. Materials containing embedded, showing-on, and grafted sites were also compared with regard to pore size, surface polarity, and metal leaching. The material containing showing-on sites was found to be catalytically active for the hydroxylation of phenol into catechol and hydroquinone. Both textural and structural properties of the material and the copper sites were investigated using XRD, TEM, N(2) sorption isotherms, TGA, FT-IR, UV-visible, and EPR spectroscopies. PMID:20695596

  12. Preparation of alumina nanoshell coated porous silica spheres for inorganic anions separation.

    PubMed

    Song, Zhihua; Wu, Dapeng; Ding, Kun; Guan, Yafeng

    2016-02-12

    It had been reported that alumina nanoshell coating could be obtained on the external surface of various substrates in one-nanometer precision in aqueous solution. In this work, alumina nanoshell coated mesoporous silica microbeads (nanoAl2O3/mesoSiO2) were prepared with the similar method, and were successfully applied to inorganic anions separation. As the mass transfer speed is largely constrained in the mesopore compared with that on the open surface, it was found that a complete alumina nanoshell coating could be obtained within the mesopore until the five-time coating was carried out. After characterization by BET, SEM and FTIR, it was found that the obtained nanoAl2O3/mesoSiO2 particles are smooth and well dispersed, and the mesopores are well reserved. In addition, the full coverage of nanoAl2O3 shell in mesopores was also confirmed by the binding capacity experiments with berberine. Finally, the nanoAl2O3/mesoSiO2 particles were packed in silica capillary for the separation of inorganic anions I(-), SCN(-), Br(-), NO2(-) and NO3(-) with ion chromatography (IC), and a column efficiency of 3.8 × 10(4) plates per meter was obtained for I(-). PMID:26803440

  13. Decolorization of two synthetic dyes using the purified laccase of Paraconiothyrium variabile immobilized on porous silica beads

    PubMed Central

    2014-01-01

    Background Decolorization of hazardous synthetic dyes using laccases in both free and immobilized form has gained attention during the last decades. The present study was designed to prepare immobilized laccase (purified from Paraconiothyrium variabile) on porous silica beads followed by evaluation of both free and immobilized laccases for decolorization of two synthetic dyes of Acid Blue 25 and Acid Orange 7. Effects of laccase concentration, pH and temperature alteration, and presence of 1-hydroxybenzotriazole (HBT) as laccase mediator on decolorization pattern were also studied. In addition, the kinetic parameters (K m and V max ) of the free and immobilized laccases for each synthetic dye were calculated. Results Immobilized laccase represented higher temperature and pH stability compare to free one. 39% and 35% of Acid Blue 25 and Acid Orange 7 was decolorized, respectively after 65 min incubation in presence of the free laccase. In the case of immobilized laccase decolorization percent was found to be 76% and 64% for Acid Blue 25 and Acid Orange 7, respectively at the same time. Increasing of laccase activity enhanced decolorization percent using free and immobilized laccases. Relative decolorization of both applied dyes was increased after treatment by laccase-HBT system. After nine cycles of decolorization by immobilized laccase, 26% and 31% of relative activity were lost in the case of Acid Blue 25 and Acid Orange 7, respectively. Conclusions To sum up, the present investigation introduced the immobilized laccase of P. variabile on porous beads as an efficient biocatalyst for decolorization of synthetic dyes. PMID:24393474

  14. Adsorption dynamics of CO on copper and gold clusters supported on silica - How special is nanogold?

    NASA Astrophysics Data System (ADS)

    Shan, J.; Komarneni, M.; Burghaus, U.

    2011-11-01

    A twist about an atomistic explanation for the unusual particle size-dependent reactivity enhancement of supported gold clusters still exists in the surface science and catalysis communities. A molecular beam scattering technique allowed the active sites of a catalyst to be mapped. In doing so, copper and gold clusters, both supported on silica, were studied. Indeed, Au clusters showed quite unusual behavior, however, that would be consistent with the influence of defects rather than quantum size effects.

  15. Monodisperse metal nanoparticle catalysts on silica mesoporous supports: synthesis, characterizations, and catalytic reactions

    SciTech Connect

    Somorjai, G.A.

    2009-09-14

    The design of high performance catalyst achieving near 100% product selectivity at maximum activity is one of the most important goals in the modern catalytic science research. To this end, the preparation of model catalysts whose catalytic performances can be predicted in a systematic and rational manner is of significant importance, which thereby allows understanding of the molecular ingredients affecting the catalytic performances. We have designed novel 3-dimensional (3D) high surface area model catalysts by the integration of colloidal metal nanoparticles and mesoporous silica supports. Monodisperse colloidal metal NPs with controllable size and shape were synthesized using dendrimers, polymers, or surfactants as the surface stabilizers. The size of Pt, and Rh nanoparticles can be varied from sub 1 nm to 15 nm, while the shape of Pt can be controlled to cube, cuboctahedron, and octahedron. The 3D model catalysts were generated by the incorporation of metal nanoparticles into the pores of mesoporous silica supports via two methods: capillary inclusion (CI) and nanoparticle encapsulation (NE). The former method relies on the sonication-induced inclusion of metal nanoparticles into the pores of mesoporous silica, whereas the latter is performed by the encapsulation of metal nanoparticles during the hydrothermal synthesis of mesoporous silica. The 3D model catalysts were comprehensively characterized by a variety of physical and chemical methods. These catalysts were found to show structure sensitivity in hydrocarbon conversion reactions. The Pt NPs supported on mesoporous SBA-15 silica (Pt/SBA-15) displayed significant particle size sensitivity in ethane hydrogenolysis over the size range of 1-7 nm. The Pt/SBA-15 catalysts also exhibited particle size dependent product selectivity in cyclohexene hydrogenation, crotonaldehyde hydrogenation, and pyrrole hydrogenation. The Rh loaded SBA-15 silica catalyst showed structure sensitivity in CO oxidation reaction. In

  16. Ion channel mimetic membranes and silica nanotubes prepared from porous aluminum oxide templates

    NASA Astrophysics Data System (ADS)

    Mitchell, David Tanner

    Chapter 1 provides background information on the template synthesis of nanomaterials. The template synthesis method is examined with special attention to the use of membranes containing monodisperse cylindrical pores as templates. Several examples of the utility of template-synthesized nanomaterials are given. The production of one type of template membrane, nanopore alumina, is reviewed. Reviews of sol-gel and silane chemistry are also provided. In Chapter 2, a sol-gel template synthesis process is used to produce silica nanotubes within the pores of alumina templates. The nanotubes can be modified using a variety of chemistries, typically via a silanization process. Because the nanotubes are formed in a template, the interior and exterior surface can be modified independently. Modified nanotubes can be used for drug detoxification or as extractants for the removal of metal ions. The nanotube surface can also be biotinylated, which causes binding to avidinated surfaces. Composite microtubes of silica and various polymers are also prepared. Additionally, Au nanowires are shown to assemble with colloidal Au particles using dithiols as linkers. Chapter 3 describes the attachment of proteins onto template-synthesized silica nanotubes. The proteins are covalently linked via an aldehyde silane bridge that binds to pendant primary amino moieties on the protein. Protein-modified nanotubes function as highly specific extractants. Avidin-modified nanotubes extract biotin-coated Au nanoparticles from solution with high extraction efficiency. Immunoprotein-modified nanotubes extract the corresponding antibody from solution with high specificity. Antibody-modified nanotubes extract one enantiomer from a racemic mix. Enzymes, including drug detoxification enzymes, were also attached to the nanotubes and were shown to retain their catalytic activity. Immunoproteins on the outside of nanotubes can be used to direct nanotube binding, creating specific labeling agents. Chapter 4

  17. Competitive sorption of cis-DCE and TCE in silica gel as a model porous mineral solid.

    PubMed

    Avila, Manuel Alejandro Salaices; Breiter, Roman

    2008-08-01

    The competitive sorption of 1,2-cis-dichloroethene (cis-DCE) and trichloroethene (TCE) was investigated by means of column experiments using a model porous mineral solid represented by silica gel. The experimental isotherms were obtained by employing a chromatographic method. The competitive sorption isotherms were modelled with the extended Freundlich and extended Langmuir isotherms, using the parameters from single-solute experiments. The breakthrough curves were modelled with the advection-dispersion transport equation coupled with the lumped pore diffusion model. The best results were obtained when the extended Freundlich isotherm was employed. The competitive sorption was revealed with the presence of an overshoot in the breakthrough curve of cis-DCE and a decrease in the degree of sorption of cis-DCE (20%) and TCE (12%). A linear dependency of the overshoot with an increase in the concentration of cis-DCE at a fixed concentration of TCE was observed, between 16% and 20%, and at least at concentrations <6 mg L(-1) in the liquid phase. The displaced molecules of cis-DCE by TCE were accumulated through the column causing its overshoot; thus short columns may hinder its observation. Thermodynamic analysis shows an exothermic adsorption process of -34 to -41 kJ mol(-1), which is enhanced by sorption in micropores. The Gibbs free energy is positive for cis-DCE in the multi-component case, due to its displacement by TCE. PMID:18541287

  18. Silica-particle-supported zwitterionic polymer monolith for microcolumn liquid chromatography.

    PubMed

    An, Ran; Weng, Qianfeng; Li, Jinxiang

    2014-10-01

    A silica-particle-supported zwitterionic polymeric monolithic column, shortened as supported column (S-column), was prepared by the in situ polymerization of methacrylic acid, ethylene dimethacrylate, and 2-(dimethylamino)ethyl methacrylate in the presence of a ternary porogenic solvent containing water, methanol, and cyclohexanol in a 250 μm id fused-silica capillary prepacked with 5 μm bare silica particles. In the S-column, a thin layer of the polymers was formed around the silica particles in the form of nanoglobules, leaving the interstitial spaces between the particles free for liquid flow. The effects of the preparation conditions on the morphology of the monolith were investigated by scanning electron microscopy and backpressure measurements. The selected volumetric ratio of porogens, monomer concentration, polymerization time, and temperature are 1:1:8 (water/methanol/cyclohexanol), 25% v/v, 5 h, and 60°C, respectively. The S-column was evaluated by comparison with its conventional organic counterpart in terms of morphology, mechanical stability, permeability, swelling-shrinking behavior, capacity, and efficiency. The results demonstrate that the S-column is superior to its counterpart in all the terms with the exception of permeability. The above merits and zwitterionic property of the S-column were further confirmed by separate separations of four inorganic anions and three organic cations. PMID:25044794

  19. Crosslinking Amine-Modified Silica Aerogels with Epoxies: Mechanically Strong Lightweight Porous Materials

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Fabrizio, Eve F.; Ilhan, Faysal; Dass, Amala; Zhang, Guo-Hui; Vassilaras, Plousia; Johnston, J. Chris; Leventis, Nicholas

    2005-01-01

    The mesoporous surfaces of TMOS-derived silica aerogels have been modified with amines by co-polymerization of TMOS with APTES. The amine sites have become anchors for crosslinking the nanoparticles of the skeletal backbone of the aerogel by attachment of di-, tri and tetra-functional epoxies. The resulting conformal coatings increase the density of the native aerogels by a factor of 2-3 but the strength of the resulting materials may increase by more than two orders of magnitude. Processing variables such as amount of APTES used to make the gels, the epoxy type and concentration used for crosslinking, as well as the crosslinking temperature and time were varied according to a multivariable design-of-experiments (DOE) model. It was found that while elastic modulus follows a similar trend with density, maximum strength is attained neither at the maximum density nor at the highest concentration of -NH2 groups, suggesting surface saturation effects. Aerogels crosslinked with the tri-functional epoxide always show improved strength compared with aerogels crosslinked with the other two epoxides under identical conditions. Solid C-13 NMR studies show residual unreacted epoxides, which condense with ne another by heating crosslinked aerogels at 150 C.

  20. The AMWCNTs supported porous nanocarbon composites for high-performance supercapacitor

    SciTech Connect

    Fu, Yu; Sun, Li; Tian, Chungui; Lin, Haibo

    2013-11-15

    Graphical abstract: The AMWCNTs supported porous nanocarbon composites were prepared by a easy method. The composites had shown good performances for electrochemical energy storage with high specific capacitance and good stability. - Highlights: • The AMWCNTs supported porous nanocarbon composites were prepared. • The composites have good conductivity and large BET specific surface areas. • The composites had shown high specific capacitance, and good stability. - Abstract: The porous nanocarbons supported by acid-treated multiwall carbon nanotubes (PC@ACNTs) were prepared by the combination of the hydrothermal polymerization of glucose on ACNTs, carbonization under N{sub 2} protection and final activation with ZnCl{sub 2}. The materials were characterized by transmission electron microscopy, X-ray powder diffraction and Raman spectra. The results indicated that the ACNTs distributed uniformly into the framework of the porous carbon. The composites showed the high BET specific surface area up to 1712 m{sup 2} g{sup −1} and good conductivity. The electrochemical measurements indicated that the composites processed good performances for electrochemical energy storage (210 F g{sup −1} at 0.5 A g{sup −1}), and high stability (>99.9%), much higher than the corresponding ACNTs, porous carbons and the samples prepared by using raw MWCNTs as source. The good performance of PC@ACNTs composites was relative with the synergy of good conductivity of ACNTs and large specific surface areas of PC.

  1. Sintering of highly porous silica-particle samples: analogues of early Solar-System aggregates

    NASA Astrophysics Data System (ADS)

    Poppe, T.

    2003-07-01

    I describe a new method to make particle layers which consist of SiO 2 spheres with 0.78 μm radius. The layers were produced by sedimentation of aggregates which had grown in ballistic particle collisions, and the layers had a porosity of 0.95. They were used for experiments on sintering, i.e., the samples were heated in an oven at varying temperatures and heating durations, and the samples were analyzed by scanning electron microscopy. Based on the change of particle diameter, surface diffusion sintering and viscous flow are identified as important transformation mechanisms. The first effect dominated at the start of restructuring and the latter at higher temperatures. The neck growth of adjacent particles was fitted to a surface diffusion sintering model and predicts neck radii as a heating temperature and duration function. Between the temperature range of neck formation and of melting, further restructuring occurred which lead to dissolution of particulate structure and to densification and which resulted in a porous object consisting of straight elongated substructures which connected kinks of higher material density. The thermal transformation is important for the change of strength, collisional behavior, light-scattering properties, and thermal conductivity with relevance to dust aggregates, planetesimals, comets, interplanetary dust particles, and regolith-covered celestial bodies.

  2. Highly porous silica-polyaniline nanocomposite as a novel solid-phase microextraction fiber coating.

    PubMed

    Gholivand, Mohammad B; Abolghasemi, Mir M; Fattahpour, Peyman

    2012-01-01

    A highly porous fiber-coated SBA-15/polyaniline material was prepared for solid-phase microextraction (SPME). The SBA-15/polyaniline nanocomposite was synthesized via chemical polymerization. The prepared SBA-15/polyaniline particles were analyzed by scanning electron microscopy analysis. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. The fiber was evaluated for the extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample solutions in combination with gas chromatography-mass spectrometry (GC-MS). In optimum conditions (extraction temperature 60°C, extraction time 40 min, ionic strength 20%, stirring rate: 500 rpm, desorption temperature 260°C, desorption time 2 min), the repeatability for one fiber (n=3), expressed as relative standard deviation (RSD%), was between 5.3 and 8.6% for the test compounds. For deionized water, spiked with selected PAHs, the detection limits for the studied compounds were between 2 and 20 pg/mL. PMID:22144100

  3. Carvedilol dissolution improvement by preparation of solid dispersions with porous silica.

    PubMed

    Planinšek, Odon; Kovačič, Borut; Vrečer, Franc

    2011-03-15

    Impregnation of porous SiO(2) (Sylysia) with carvedilol from acetone solution was used to improve dissolution of this poorly water-soluble drug. Solvent evaporation in a vacuum evaporator and adsorption from acetone solution were the methods used to load various amounts of carvedilol into the Sylysia pores. The impregnated carriers were characterized using nitrogen-adsorption experiments, X-ray diffraction, wettability measurements, attenuated total reflectance FTIR spectroscopy and thermal analysis. The impregnation procedures resulted in a significant improvement of drug release compared to dissolution of pure carvedilol or its physical mixtures with Sylysia. The results showed that when the drug precipitated in a thin layer within the carrier the dispersion retained a high specific surface area, micropore volume, and drug-release rate from the solid dispersion. Increasing the amount of drug in the solid dispersion caused particle precipitation within the pores that decreased the carrier's specific surface area and pore volume and decreased the release rate of the drug. The results also suggest that the amorphous form of carvedilol, the improved wettability and weak interactions between the drug and carrier in the solid dispersion also contribute to improved dissolution of the drug from the dispersion. PMID:21219991

  4. Protocells: Modular Mesoporous Silica Nanoparticle-Supported Lipid Bilayers for Drug Delivery.

    PubMed

    Butler, Kimberly S; Durfee, Paul N; Theron, Christophe; Ashley, Carlee E; Carnes, Eric C; Brinker, C Jeffrey

    2016-04-27

    Mesoporous silica nanoparticle-supported lipid bilayers, termed 'protocells,' represent a potentially transformative class of therapeutic and theranostic delivery vehicle. The field of targeted drug delivery poses considerable challenges that cannot be addressed with a single 'magic bullet'. Consequently, the protocell has been designed as a modular platform composed of interchangeable biocompatible components. The mesoporous silica core has variable size and shape to direct biodistribution and a controlled pore size and surface chemistry to accommodate diverse cargo. The encapsulating supported lipid bilayer can be modified with targeting and trafficking ligands as well as polyethylene glycol (PEG) to effect selective binding, endosomal escape of cargo, drug efflux prevention, and potent therapeutic delivery, while maintaining in vivo colloidal stability. This review describes the individual components of the platform, including the mesoporous silica nanoparticle core and supported lipid bilayer, their assembly (by multiple techniques) into a protocell, and the combined, often synergistic, performance of the protocell based on in vitro and in vivo studies, including the assessment of biocompatibility and toxicity. In closing, the many emerging variations of the protocell theme and the future directions for protocell research are commented on. PMID:26780591

  5. Particle size effect of redox reactions for Co species supported on silica

    NASA Astrophysics Data System (ADS)

    Chotiwan, Siwaruk; Tomiga, Hiroki; Katagiri, Masaki; Yamamoto, Yusaku; Yamashita, Shohei; Katayama, Misaki; Inada, Yasuhiro

    2016-09-01

    Conversions of chemical states during redox reactions of two silica-supported Co catalysts, which were prepared by the impregnation method, were evaluated by using an in situ XAFS technique. The addition of citric acid into the precursor solution led to the formation on silica of more homogeneous and smaller Co particles, with an average diameter of 4 nm. The supported Co3O4 species were reduced to metallic Co via the divalent CoO species during a temperature-programmed reduction process. The reduced Co species were quantitatively oxidized with a temperature-programmed oxidation process. The higher observed reduction temperature of the smaller CoO particles and the lower observed oxidation temperature of the smaller metallic Co particles were induced by the higher dispersion of the Co oxide species, which apparently led to a stronger interaction with supporting silica. The redox temperature between CoO and Co3O4 was found to be independent of the particle size.

  6. POPC Bilayers Supported on Nanoporous Substrates: Specific Effects of Silica-Type Surface Hydroxylation and Charge Density.

    PubMed

    Duro, Nalvi; Gjika, Marion; Siddiqui, Ahnaf; Scott, H Larry; Varma, Sameer

    2016-07-01

    Recent advances in nanotechnology bring to the forefront a new class of extrinsic constraints for remodeling lipid bilayers. In this next-generation technology, membranes are supported over nanoporous substrates. The nanometer-sized pores in the substrate are too small for bilayers to follow the substrate topology; consequently, the bilayers hang over the pores. Experiments demonstrate that nanoporous substrates remodel lipid bilayers differently from continuous substrates. The underlying molecular mechanisms, however, remain largely undetermined. Here we use molecular dynamics (MD) simulations to probe the effects of silica-type hydroxylation and charge densities on adsorbed palmitoyl-oleoylphosphatidylcholine (POPC) bilayers. We find that a 50% porous substrate decorated with a surface density of 4.6 hydroxyls/nm(2) adsorbs a POPC bilayer at a distance of 4.5 Å, a result consistent with neutron reflectivity experiments conducted on topologically similar silica constructs under highly acidic conditions. Although such an adsorption distance suggests that the interaction between the bilayer and the substrate will be buffered by water molecules, we find that the substrate does interact directly with the bilayer. The substrate modifies several properties of the bilayer-it dampens transverse lipid fluctuations, reduces lipid diffusion rates, and modifies transverse charge densities significantly. Additionally, it affects lipid properties differently in the two leaflets. Compared to substrates functionalized with sparser surface hydroxylation densities, this substrate adheres to bilayers at smaller distances and also remodels POPC more extensively, suggesting a direct correspondence between substrate hydrophilicity and membrane properties. A partial deprotonation of surface hydroxyls, as expected of a silica substrate under mildly acidic conditions, however, produces an inverse effect: it increases the substrate-bilayer distance, which we attribute to the formation of

  7. Solid polymer electrolyte composite membrane comprising laser micromachined porous support

    DOEpatents

    Liu, Han; LaConti, Anthony B.; Mittelsteadt, Cortney K.; McCallum, Thomas J.

    2011-01-11

    A solid polymer electrolyte composite membrane and method of manufacturing the same. According to one embodiment, the composite membrane comprises a rigid, non-electrically-conducting support, the support preferably being a sheet of polyimide having a thickness of about 7.5 to 15 microns. The support has a plurality of cylindrical pores extending perpendicularly between opposing top and bottom surfaces of the support. The pores, which preferably have a diameter of about 5 microns, are made by laser micromachining and preferably are arranged in a defined pattern, for example, with fewer pores located in areas of high membrane stress and more pores located in areas of low membrane stress. The pores are filled with a first solid polymer electrolyte, such as a perfluorosulfonic acid (PFSA) polymer. A second solid polymer electrolyte, which may be the same as or different than the first solid polymer electrolyte, may be deposited over the top and/or bottom of the first solid polymer electrolyte.

  8. Method of making porous conductive supports for electrodes. [by electroforming and stacking nickel foils

    NASA Technical Reports Server (NTRS)

    Schaer, G. R. (Inventor)

    1973-01-01

    Porous conductive supports for electrochemical cell electrodes are made by electroforming thin corrugated nickel foil, and by stacking pieces of the corrugated foil alternatively with pieces of thin flat nickel foil. Corrugations in successive corrugated pieces are oriented at different angles. Adjacent pieces of foil are bonded by heating in a hydrogen atmosphere and then cutting the stack in planes perpendicular to the foils.

  9. High strength porous support tubes for high temperature solid electrolyte electrochemical cells

    DOEpatents

    Rossing, Barry R.; Zymboly, Gregory E.

    1986-01-01

    A high temperature, solid electrolyte electrochemical cell is made, having an electrode and a solid electrolyte disposed on a porous, sintered support material containing thermally stabilized zirconia powder particles and from about 3 wt. % to about 45 wt. % of thermally stable oxide fibers.

  10. Preparation and evaluation of monodispersed, submicron, non-porous silica particles functionalized with β-CD derivatives for chiral-pressurized capillary electrochromatography.

    PubMed

    Yangfang, Lu; Hui, Wang; Yun, Xue; Xue, Gu; Yan, Wang; Chao, Yan

    2015-09-01

    Submicron, non-porous, chiral silica stationary phase has been prepared by the immobilization of functionalized β-CD derivatives to isocyanate-modified silica via chemical reaction and applied to the pressurized capillary electrochromatography (pCEC) enantio-separation of various chiral compounds. The submicron, non-porous, cyclodextrin-based chiral stationary phases (sub_μm-CSP2) exhibited excellent chiral recognition of a wide range of analytes including clenbuterol hydrochloride, mexiletine hydrochloride, chlorpheniramine maleate, esmolol hydrochloride, and metoprolol tartrate. The synthesized submicron particles were regularly spherical and uniformly non-porous with an average diameter of around 800 nm and a mean pore size of less than 2 nm. The synthesized chiral stationary phase was packed into 10 cm × 100 μm id capillary columns. The sub_μm-CSP2 column used in the pCEC system showed better separation of the racemates and at a higher rate compared to those used in the capillary liquid chromatography mode (cLC) system. The sub_μm-CSP2 possessed high mechanical strength, high stereoselectivity, and long lifespan, demonstrating rapid enantio-separation and good resolution of samples. The column provided an efficiency of up to 170,000 plates/m for n-propylbenzene. PMID:25990895

  11. Supported and inserted monomeric niobium oxide species on/in silica: a molecular picture.

    PubMed

    Tranca, Diana C; Wojtaszek-Gurdak, Anna; Ziolek, Maria; Tielens, Frederik

    2015-09-14

    The geometry, energetic, and spectroscopic properties of molecular structures of silica-supported niobium oxide catalysts are studied using periodic density functional calculations (DFT) and compared with experimental data. The calculations are done for Nb oxide species inserted or grafted in/on an amorphous hydroxylated silica surface. Different positions of the Nb atom/atoms in the silica structure have been investigated. By means of DFT calculations the geometry and the degree of hydration of Nb oxide species with oxidation state +5 have been studied. The local Nb geometry depends on different parameters such as the number of Nb-O-Si groups vs. Nb-O-H groups, the formation of H bonds and the distance between Nb atoms. The interaction between the oxide and silanol groups occurs by formation of Si-O-Nb bonds with chemically and thermally stable Brønsted and Lewis acid sites. UV-Vis, reflection absorption infrared vibrational spectra (RAIRS) as well as various thermodynamic properties have also been investigated in order to get a better insight into the system studied and to provide support to possible experimental studies. PMID:26250394

  12. Synthesis and Nanofiltration Membrane Performance of Oriented Mesoporous Silica Thin Films on Macroporous Supports.

    PubMed

    Clark Wooten, M Kaitlyn; Koganti, Venkat R; Zhou, Shanshan; Rankin, Stephen E; Knutson, Barbara L

    2016-08-24

    Silica thin films with accessible hexagonal close-packed (HCP) pores have been deposited on macroporous supports to achieve composite nanofiltration membranes. The properties of these pore channels have been characterized through solvent flux and solute diffusion experiments. A chemically neutral surface (provided by a cross-linked layer of P123 copolymer) for silica thin film synthesis on the alumina macroporous support promotes the alignment of HCP channels vertical to the substrate, where the mesopore templating agent is block copolymer P123 (poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)). Vertical pore alignment is achieved for thin films (less than ∼100 nm) on a neutral surface and by sandwiching thicker films (∼240 nm) between two chemically neutral surfaces. Solvent flux through the composite membranes is consistent with accessible 10 nm diameter pores. Size selectivity of the membranes is characterized from the permeability of fluorescently tagged solutes (ranging from 4000 to 70 000 Da), where a size cut off occurs at 69 000 Da for the model protein bovine serum albumin. These permeability studies of the nanofiltration membranes serve to demonstrate solute transport in oriented silica thin film membranes and also highlight their versatility for membrane-based separations. PMID:27479791

  13. Thermal Stability and Catalytic Activity of Gold Nanoparticles Supported on Silica

    SciTech Connect

    Veith, G.; Lupini, A; Rashkeev, S; Pennycook, S; Mullins, D; Schwartz, V; Bridges, C; Dudney, N

    2009-01-01

    2.5 nm gold nanoparticles were grown on a fumed silica support, using the physical vapor deposition technique of magnetron sputtering, that are thermally stable when annealed in an oxygen containing environment up to at least 500 C. Traditional Au/TiO{sub 2} catalysts rapidly sinter to form large 13.9 nm gold clusters under these annealing conditions. This surprising stability of Au/SiO{sub 2} is attributed to the absence of residual impurities (ensured by the halide-free production method) and a strong bond between gold and defects at the silica surface (about 3 eV per bond) estimated from density functional theory (DFT) calculations. The Au/SiO{sub 2} catalysts are less active for CO oxidation than the prototypical Au/TiO2 catalysts, however they can be regenerated far more easily, allowing the activity of a catalyst to be fully recovered after deactivation.

  14. Solid polymer electrolyte composite membrane comprising plasma etched porous support

    DOEpatents

    Liu, Han; LaConti, Anthony B.

    2010-10-05

    A solid polymer electrolyte composite membrane and method of manufacturing the same. According to one embodiment, the composite membrane comprises a rigid, non-electrically-conducting support, the support preferably being a sheet of polyimide having a thickness of about 7.5 to 15 microns. The support has a plurality of cylindrical pores extending perpendicularly between opposing top and bottom surfaces of the support. The pores, which preferably have a diameter of about 0.1 to 5 microns, are made by plasma etching and preferably are arranged in a defined pattern, for example, with fewer pores located in areas of high membrane stress and more pores located in areas of low membrane stress. The pores are filled with a first solid polymer electrolyte, such as a perfluorosulfonic acid (PFSA) polymer. A second solid polymer electrolyte, which may be the same as or different than the first solid polymer electrolyte, may be deposited over the top and/or bottom of the first solid polymer electrolyte.

  15. Resolving Interparticle Heterogeneities in Composition and Hydrogenation Performance between Individual Supported Silver on Silica Catalysts

    PubMed Central

    2015-01-01

    Supported metal nanoparticle catalysts are commonly obtained through deposition of metal precursors onto the support using incipient wetness impregnation. Typically, empirical relations between metal nanoparticle structure and catalytic performance are inferred from ensemble averaged data in combination with high-resolution electron microscopy. This approach clearly underestimates the importance of heterogeneities present in a supported metal catalyst batch. Here we show for the first time how incipient wetness impregnation leads to 10-fold variations in silver loading between individual submillimeter-sized silica support granules. This heterogeneity has a profound impact on the catalytic performance, with 100-fold variations in hydrogenation performance at the same level. In a straightforward fashion, optical microscopy interlinks single support particle level catalytic measurements to structural and compositional information. These detailed correlations reveal the optimal silver loading. A thorough consideration of catalyst heterogeneity and the impact thereof on the catalytic performance is indispensable in the development of catalysts. PMID:26618052

  16. Selective adsorption mechanisms of antilipidemic and non-steroidal anti-inflammatory drug residues on functionalized silica-based porous materials in a mixed solute.

    PubMed

    Suriyanon, Nakorn; Permrungruang, Jutima; Kaosaiphun, Jidanan; Wongrueng, Aunnop; Ngamcharussrivichai, Chawalit; Punyapalakul, Patiparn

    2015-10-01

    The selective adsorption mechanisms of naproxen (NAP), acetaminophen (ACT), and clofibric acid (CFA) on silica-based porous materials were examined by single and mixed-batch adsorption. Effects of the types and densities of surface functional groups on adsorption capacities were determined, including the role of hydrophobic and hydrophilic dissolved organic matters (DOMs). Hexagonal mesoporous silica (HMS), superparamagnetic HMS (HMS-SP) and SBA-15 were functionalized and applied as adsorbents. Compared with powdered activated carbon (PAC), amine-functionalized HMS had a better adsorption capacity for CFA, but PAC possessed a higher adsorption capacity for the other pharmaceuticals than HMS and its two derivatives. In contrast to PAC, the adsorption capacity of the mesoporous silicas varied with the solution pH, being highest at pH 5. Electrostatic interactions and hydrogen bonding were found to be the main mechanisms. Increase in grafted amine group density on silica surfaces can enhance the CFA adsorption capacity. Further, hydrophilic DOM can decrease CFA adsorption capacities on amino-grafted adsorbents by adsorption site competition, while hydrophobic DOM can interfere with CFA adsorption by the interaction between hydrophobic DOM and CFA. Finally, in a competitive adsorption study, the adsorption capacity of hydrophilic adsorbents for acidic pharmaceuticals varied with their pKa values. PMID:26025186

  17. Mixtures of Supported and Hybrid Lipid Membranes on Heterogeneously Modified Silica Nanoparticles

    PubMed Central

    Piper-Feldkamp, Aundrea R.; Wegner, Maria; Brzezinski, Peter; Reed, Scott M.

    2013-01-01

    Simple supported lipid bilayers do not accurately reflect the complex heterogeneity of cellular membranes; however, surface modification makes it possible to tune membrane properties to better mimic biological systems. Here, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (DETAS), a silica modifier, facilitated formation of supported lipid bilayers on silica nanoparticles. Evidence for a stable supported bilayer came from the successful entrapment of a soluble fluorophore within an interstitial water layer. A fluorescence-quenching assay that utilized a pore-forming peptide was used to demonstrate the existence of two separate lipid leaflets. In this assay, fluorescence was quenched by dithionite in roughly equal proportions prior to and after addition of melittin. When a hydrophobic modifier, octadecyltriethoxysilane, was co-deposited on the nanoparticles with DETAS, there was a decrease in the amount of supported bilayer on the nanoparticles and an increase in the quantity of hybrid membrane. This allowed for a controlled mixture of two distinct types of membranes on a single substrate, one separated by a water cushion and the other anchored directly on the surface, thereby providing a new mimic of cellular membranes. PMID:23387352

  18. Rhizopus oryzae lipase immobilized on hierarchical mesoporous silica supports for transesterification of rice bran oil.

    PubMed

    Ramachandran, Prashanth; Narayanan, Guru Krupa; Gandhi, Sakthivel; Sethuraman, Swaminathan; Krishnan, Uma Maheswari

    2015-03-01

    The tunable textural properties of self-oriented mesoporous silica were investigated for their suitability as enzyme immobilization matrices to support transesterification of rice bran oil. Different morphologies of mesoporous silica (rod-like, rice-like, and spherical) were synthesized and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption-desorption isotherms. The surface area, pore size, and ordered arrangement of the pores were found to influence the immobilization and activity of the enzyme in the mesopores. The immobilization in rod-like silica was highest with an immobilization efficiency of 63 % and exhibited minimal activity loss after immobilization. Functionalization of the mesoporous surface with ethyl groups further enhanced the enzyme immobilization. The free enzyme lost most of its activity at 50 °C while the immobilized enzyme showed activity even up to 60 °C. Transesterified product yield of nearly 82 % was obtained for 24 h of reaction with enzyme immobilized on ethyl-functionalized SBA-15 at an oil:methanol ratio of 1:3. Fourier transform infrared spectroscopy (FT-IR) and Gas chromatography-mass spectrometry (GC-MS) were used to characterize the transesterified product obtained. The reusability of the immobilized enzyme was studied for 3 cycles. PMID:25488500

  19. Wettability of modified silica layers deposited on glass support activated by plasma

    NASA Astrophysics Data System (ADS)

    Terpiłowski, Konrad; Rymuszka, Diana; Goncharuk, Olena V.; Sulym, Iryna Ya.; Gun'ko, Vladimir M.

    2015-10-01

    Fumed silica modified by hexamethyldisilazane [HDMS] and polydimethylsiloxane [PDMS] was dispersed in a polystyrene/chloroform solution. To increase adhesion between deposited silica layers and a glass surface, the latter was pretreated with air plasma for 30 s. The silica/polystyrene dispersion was deposited on the glass support using a spin coater. After deposition, the plates were dried in a desiccator for 24 h. Water advancing and receding contact angles were measured using the tilted plate method. The apparent surface free energy (γS) was evaluated using the contact angle hysteresis approach. The surface topography was determined using the optical profilometry method. Contact angles changed from 59.7° ± 4.4 (at surface coverage with trimethylsilyl groups Θ = 0.14) to 155° ± 3.1 at Θ = 1. The value of γS decreased from 51.3 ± 2.8 mJ/m2 (for the sample at the lowest value of Θ) to 1.0 ± 0.4 mJ/m2 for the most hydrophobic sample. Thus, some systems with a high degree of modification by HDMS showed superhydrophobicity, and the sliding angle amounted to about 16° ± 2.1.

  20. Cooperative Effect of Monopodal Silica-Supported Niobium Complex Pairs Enhancing Catalytic Cyclic Carbonate Production.

    PubMed

    D'Elia, Valerio; Dong, Hailin; Rossini, Aaron J; Widdifield, Cory M; Vummaleti, Sai V C; Minenkov, Yury; Poater, Albert; Abou-Hamad, Edy; Pelletier, Jérémie D A; Cavallo, Luigi; Emsley, Lyndon; Basset, Jean-Marie

    2015-06-24

    Recent discoveries highlighted the activity and the intriguing mechanistic features of NbCl5 as a molecular catalyst for the cycloaddition of CO2 and epoxides under ambient conditions. This has inspired the preparation of novel silica-supported Nb species by reacting a molecular niobium precursor, [NbCl5·OEt2], with silica dehydroxylated at 700 °C (SiO(2-700)) or at 200 °C (SiO(2-200)) to generate diverse surface complexes. The product of the reaction between SiO(2-700) and [NbCl5·OEt2] was identified as a monopodal supported surface species, [≡SiONbCl4·OEt2] (1a). The reactions of SiO(2-200) with the niobium precursor, according to two different protocols, generated surface complexes 2a and 3a, presenting significant, but different, populations of the monopodal surface complex along with bipodal [(≡SiO)2NbCl3·OEt2]. (93)Nb solid-state NMR spectra of 1a-3a and (31)P solid-state NMR on their PMe3 derivatives 1b-3b led to the unambiguous assignment of 1a as a single-site monopodal Nb species, while 2a and 3a were found to present two distinct surface-supported components, with 2a being mostly monopodal [≡SiONbCl4·OEt2] and 3a being mostly bipodal [(≡SiO)2NbCl3·OEt2]. A double-quantum/single-quantum (31)P NMR correlation experiment carried out on 2b supported the existence of vicinal Nb centers on the silica surface for this species. 1a-3a were active heterogeneous catalysts for the synthesis of propylene carbonate from CO2 and propylene oxide under mild catalytic conditions; the performance of 2a was found to significantly surpass that of 1a and 3a. With the support of a systematic DFT study carried out on model silica surfaces, the observed differences in catalytic efficiency were correlated with an unprecedented cooperative effect between two neighboring Nb centers on the surface of 2a. This is in an excellent agreement with our previous discoveries regarding the mechanism of NbCl5-catalyzed cycloaddition in the homogeneous phase. PMID:25950495

  1. Stopping the growth of particles to silica-supported mono-nuclear Ru hydride surface species by tuning silica with surface silanes

    SciTech Connect

    Berthoud, Romain; Fenet, Bernard; Lukens, Wayne; Pelzer, Katrin; Basset, Jean-Marie; Candy, Jean-Pierre; Coperet, Christophe

    2007-07-11

    Tuning silica by replacing surface silanols with silanes allows chemical grafting of Ru(COD)(COT) through a covalent Ru-Si bond, as evidenced by elemental analysis, IR spectroscopy and EXAFS. Treatment of these surface species under H2 at 300 oC yields a mononuclear Ru hydride species, without any sintering of the metal according to TEM and EXAFS analyses. This supported system displays catalytic properties different from those of supported Ru particles (2 nm), selectively hydrogenating olefins over aromatics.

  2. Iniferter-mediated grafting of molecularly imprinted polymers on porous silica beads for the enantiomeric resolution of drugs.

    PubMed

    Gutiérrez-Climente, Raquel; Gómez-Caballero, Alberto; Halhalli, Mahadeo; Sellergren, Börje; Goicolea, M Aránzazu; Barrio, Ramón J

    2016-03-01

    A surface-imprinted chiral stationary phase for the enantiomeric resolution of the antidepressant drug, citalopram, is presented in this work. N, N'-diethylaminodithiocarbamoylpropyl(trimethoxy)silane has been used as silane iniferter for the surface functionalization of the solid silica support. A molecularly imprinted polymer thin film, in the nm scale, was then grafted on the silanized silica using itaconic acid as the functional monomer and ethylene glycol dimethacrylate as the cross-linker in the presence of the template S-citalopram. The total monomer amount was calculated to obtain the desired thickness. Non-imprinted stationary phases were prepared similarly in the absence of S-citalopram. Characterization of the materials was carried out by scanning electron microscopy, thermogravimetric analysis, elemental analysis and Fourier transform infrared spectroscopy. Stationary phases have been applied to the chromatographic separation of the target. Conditions for best chromatographic resolution of the enantiomers were optimized, and it was found that a mobile phase consisting of a mixture of formate buffer (40 mM, pH 3) and acetonitrile (30:70 v/v) at 40 °C provided best results. Binding behaviour of the developed material was finally assessed by batch rebinding experiments. The obtained binding isotherm was fitted to different binding models being the Freundlich-Langmuir model, the one that best fitted the experimental data. The developed material has shown high selectivity for the target enantiomer, and the stationary phase could be undoubtedly exploited for chiral separation of the drug. PMID:25683741

  3. Silica Supported Ceria Nanoparticles: A Hybrid Nanostructure To Increase Stability And Surface Reactivity Of Nano-crystalline Ceria

    SciTech Connect

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Varga, Tamas; Thevuthasan, Suntharampillai

    2014-01-21

    The mixed oxidation state (3+/4+) of ceria nanoparticles of smaller sizes make them attractive materials for their catalytic antioxidant biological properties. However the unmodified smaller ceria nanoparticles are limited in their use due to particles agglomeration and reduced surface chemical reactivity in the solutions used to disperse the nanoparticles. This work describes an effort to stabilize small ceria nanoparticles, retaining their desired activity, on a larger stable silica support. The ceria nanoparticles attached to silica was synthesized by a solution synthesis technique in which the surface functional groups of silica nanoparticles were found to be essential for the formation of smaller ceria nanoparticles. The surface chemical and vibrational spectroscopy analysis revealed cerium–silicate (Ce-O-Si) covalent bond linkage between silica and cerium oxide nanoparticles. The colloidal properties (agglomerate particle size and suspension stability) of ceria attached to silica was significantly improved due to inherent physico-chemical characteristics of silica against random collision and gravitation settling as opposed to unmodified ceria nanoparticles in solution. The bio-catalytic activity of ceria nanoparticles in the 3+ oxidation state was not found to be limited by attachment to the silica support as measured by free radical scavenging activity in different biological media conditions.

  4. Synthesis of silica supported titania nanocomposite in controllable phase content and morphology

    NASA Astrophysics Data System (ADS)

    Lim, Yew Von; Fan, Haiming; Shen, Zexiang; Kang, Chiang Huen; Feng, Yuanping; Wang, Shijie

    2009-05-01

    The silica supported titania nanocomposite thin films with controllable particle size and phase content were successfully prepared by a convenient post annealing approach involving in solid-solid interfacial reaction. The effects of growth conditions, such as the annealing temperature and silicon concentration on the particle size and phase content, were systematically studied by using Atomic force microscopy (AFM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray spectroscopy (XPS). The results indicate that the silicon concentration is a dominant factor in the morphology, crystallization and phase transformation of these nanocomposites. A mechanism for the high temperature phase transformation is also proposed based on the migration of the oxygen vacancies.

  5. Functionalized porous silica&maghemite core-shell nanoparticles for applications in medicine: design, synthesis, and immunotoxicity

    PubMed Central

    Zasońska, Beata A.; Líšková, Aurélia; Kuricová, Miroslava; Tulinská, Jana; Pop-Georgievski, Ognen; Čiampor, Fedor; Vávra, Ivo; Dušinská, Mária; Ilavská, Silvia; Horváthová, Mira; Horák, Daniel

    2016-01-01

    Aim To determine cytotoxicity and effect of silica-coated magnetic nanoparticles (MNPs) on immune response, in particular lymphocyte proliferative activity, phagocytic activity, and leukocyte respiratory burst and in vitro production of interleukin-6 (IL-6) and 8 (IL-8), interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and granulocyte macrophage colony stimulating factor (GM-CSF). Methods Maghemite was prepared by coprecipitation of iron salts with ammonia, oxidation with NaOCl and modified by tetramethyl orthosilicate and aminosilanes. Particles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier-transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). Cytotoxicity and lymphocyte proliferative activity were assessed using [3H]-thymidine incorporation into DNA of proliferating human peripheral blood cells. Phagocytic activity and leukocyte respiratory burst were measured by flow cytometry; cytokine levels in cell supernatants were determined by ELISA. Results γ-Fe2O3&SiO2-NH2 MNPs were 13 nm in size. According to TEM, they were localized in the cell cytoplasm and extracellular space. Neither cytotoxic effect nor significant differences in T-lymphocyte and T-dependent B-cell proliferative response were found at particle concentrations 0.12-75 μg/cm2 after 24, 48, and 72 h incubation. Significantly increased production of IL-6 and 8, and GM-CSF cytokines was observed in the cells treated with 3, 15, and 75 µg of particles/cm2 for 48 h and stimulated with pokeweed mitogen (PHA). No significant changes in TNF-α and IFN-γ production were observed. MNPs did not affect phagocytic activity of monocytes and granulocytes when added to cells for 24 and 48 h. Phagocytic respiratory burst was significantly enhanced in the cultures exposed to 75 µg MNPs/cm2 for 48 h. Conclusions The cytotoxicity and in vitro immunotoxicity were found to be minimal in the newly developed porous core-shell γ-Fe2

  6. Silica-Supported Oligomeric Benzyl Phosphate (Si-OBP) and Triazole Phosphate (Si-OTP) Alkylating Reagents.

    PubMed

    Maity, Pradip K; Faisal, Saqib; Rolfe, Alan; Stoianova, Diana; Hanson, Paul R

    2015-10-16

    The syntheses of silica-supported oligomeric benzyl phosphates (Si-OBP(n)) and triazole phosphates (Si-OTP(n)) using ring-opening metathesis polymerization (ROMP) for use as efficient alkylating reagents is reported. Ease of synthesis and grafting onto the surface of norbornenyl-tagged (Nb-tagged) silica particles has been demonstrated for benzyl phosphate and triazole phosphate monomers. It is shown that these silica polymer hybrid reagents, Si-OBP(n) and Si-OTP(n), can be used to carry out alkylation reactions with an array of different nucleophiles to afford the corresponding benzylated and (triazolyl)methylated products in good yield and high purity. PMID:26430955

  7. Silica xerogel/aerogel-supported lipid bilayers: consequences of surface corrugation.

    PubMed

    Goksu, Emel I; Hoopes, Matthew I; Nellis, Barbara A; Xing, Chenyue; Faller, Roland; Frank, Curtis W; Risbud, Subhash H; Satcher, Joe H; Longo, Marjorie L

    2010-04-01

    The objective of this paper was to review our recent investigations of silica xerogel and aerogel-supported lipid bilayers. These systems provide a format to observe relationships between substrate curvature and supported lipid bilayer formation, lipid dynamics, and lipid mixtures phase behavior and partitioning. Sensitive surface techniques such as quartz crystal microbalance and atomic force microscopy are readily applied to these systems. To inform current and future investigations, we review the experimental literature involving the impact of curvature on lipid dynamics, lipid and phase-separated lipid domain localization, and membrane-substrate conformations and we review our molecular dynamics simulations of supported lipid bilayers with the atomistic and molecular information they provide. PMID:19766590

  8. Investigation of Hexagonal Mesoporous Silica-Supported Composites for Trace Moisture Adsorption

    NASA Astrophysics Data System (ADS)

    Li, Li; Tang, Nian; Wang, Yaxue; Cen, Wanglai; Liu, Jie; Zhou, Yongyan

    2015-11-01

    Moisture control is an important part of effective maintenance program for gas-insulated switchgear (GIS). Herein, hexagonal mesoporous silica (HMS) materials were synthesized by adopting dodecylamine as a structure directing agent, which was then employed as a host for supporting polyethylenimine (PEI) without further calcinations or extraction treatment. The physicochemical properties of the silica support and composites were characterized, and the moisture adsorption capacity of these composites was determined. The reserved template agents resulted in a dramatic improvement in moisture adsorption amount. Among them, 50PEI/DHMS showed the highest adsorption value. The enhanced adsorption could be attributed to the generated hydrogen bonding between amino groups and H2O molecules and the improved diffusion of moisture into the bulk networks of PEI polymers due to its better spatial dispersion imposed by the long alkyl chains of template agents, which was confirmed by thermogravimetry results and hydrogen efficiency analysis. Moreover, the maintained terminal amino groups of templates could also function as active sites for moisture adsorption. The results herein imply that the PEI/DHMS composites could be appealing materials for capturing moisture in GIS.

  9. Investigation of Hexagonal Mesoporous Silica-Supported Composites for Trace Moisture Adsorption.

    PubMed

    Li, Li; Tang, Nian; Wang, Yaxue; Cen, Wanglai; Liu, Jie; Zhou, Yongyan

    2015-12-01

    Moisture control is an important part of effective maintenance program for gas-insulated switchgear (GIS). Herein, hexagonal mesoporous silica (HMS) materials were synthesized by adopting dodecylamine as a structure directing agent, which was then employed as a host for supporting polyethylenimine (PEI) without further calcinations or extraction treatment. The physicochemical properties of the silica support and composites were characterized, and the moisture adsorption capacity of these composites was determined. The reserved template agents resulted in a dramatic improvement in moisture adsorption amount. Among them, 50PEI/DHMS showed the highest adsorption value. The enhanced adsorption could be attributed to the generated hydrogen bonding between amino groups and H2O molecules and the improved diffusion of moisture into the bulk networks of PEI polymers due to its better spatial dispersion imposed by the long alkyl chains of template agents, which was confirmed by thermogravimetry results and hydrogen efficiency analysis. Moreover, the maintained terminal amino groups of templates could also function as active sites for moisture adsorption. The results herein imply that the PEI/DHMS composites could be appealing materials for capturing moisture in GIS. PMID:26577389

  10. Hydrodynamic and dispersion behavior in a non-porous silica monolith through fluid dynamic study of a computational mimic reconstructed from sub-micro-tomographic scans.

    PubMed

    Loh, Kai-Chee; Vasudevan, Vivek

    2013-01-25

    An analysis of the transport properties of the bulk homogeneous core of a commercially available silica monolith (Chromolith(®)) is presented via direct numerical simulations in a topological model reconstructed from 3D nanotomographic scans at isotropic resolutions of 390 nm, 290 nm and 190 nm. The pore and skeleton size distributions were calculated from image analysis and a representative unit cell from each resolution was reconstructed to simulate the hydrodynamic transport properties using Computational Fluid Dynamics (CFD). A 30 μm × 30 μm × 30 μm unit cell extracted at 190 nm resolution was found to be representative of hydrodynamic permeability. Numerical peak parking simulations yielded an axial external obstruction factor (γ(e)) of 0.8. Mass transfer characteristics of a large non-penetrating molecule (BSA) were evaluated under non-retained conditions so as to elucidate the eddy dispersion contribution to total HETP. Transverse and axial dispersion length scales in the reconstructed model were resolved and related to the structural heterogeneities in the silica monolith. Deviations of simulated HETP from experimental measurements were attributed to a transcolumn dispersion contribution, which amounted to about 90% of the total HETP. The presented approach provides great scope to analyze the contributions of pore network topology to separation performance of silica monoliths (and other porous media) in HPLC applications. A significant reduction in simulation time and memory resources has been observed due to the lower scanning resolution, without significant loss in prediction accuracy. PMID:23290336

  11. Porous metallic MoO2-supported MoS2 nanosheets for enhanced electrocatalytic activity in the hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Yang, Linjing; Zhou, Weijia; Hou, Dongman; Zhou, Kai; Li, Guoqiang; Tang, Zhenghua; Li, Ligui; Chen, Shaowei

    2015-03-01

    Advanced materials for electrocatalytic water splitting are central to renewable energy research. In this work, MoS2 nanosheets supported on porous metallic MoO2 (MoS2/MoO2) were produced by sulfuration treatments of porous and highly conductive MoO2 for the hydrogen evolution reaction. Porous MoO2 with one-dimensional channel-like structures was prepared by calcination at elevated temperatures using phosphomolybdic acid as the precursor and mesoporous silica (SBA-15) as the template, and the subsequent hydrothermal treatment in the presence of thioacetamide led to the transformation of the top layers to MoS2 forming MoS2/MoO2 composites. Electrochemical studies showed that the obtained composites exhibited excellent electrocatalytic activity for HER with an onset potential of -104 mV (vs. RHE), a large current density (10 mA cm-2 at -0.24 V), a small Tafel slope of 76.1 mV dec-1 and robust electrochemical durability. The performance might be ascribed to the high electrical conductivity and porous structures of MoO2 with one-dimensional channels of 3 to 4 nm in diameter that allowed for fast charge transport and collection.Advanced materials for electrocatalytic water splitting are central to renewable energy research. In this work, MoS2 nanosheets supported on porous metallic MoO2 (MoS2/MoO2) were produced by sulfuration treatments of porous and highly conductive MoO2 for the hydrogen evolution reaction. Porous MoO2 with one-dimensional channel-like structures was prepared by calcination at elevated temperatures using phosphomolybdic acid as the precursor and mesoporous silica (SBA-15) as the template, and the subsequent hydrothermal treatment in the presence of thioacetamide led to the transformation of the top layers to MoS2 forming MoS2/MoO2 composites. Electrochemical studies showed that the obtained composites exhibited excellent electrocatalytic activity for HER with an onset potential of -104 mV (vs. RHE), a large current density (10 mA cm-2 at -0.24 V), a

  12. Recycling of fly ash for preparing porous mullite membrane supports with titania addition.

    PubMed

    Dong, Yingchao; Hampshire, Stuart; Zhou, Jian-er; Lin, Bin; Ji, Zhanlin; Zhang, Xiaozhen; Meng, Guangyao

    2010-08-15

    In order to effectively utilize industrial waste fly ash, porous mullite ceramic membrane supports were prepared from fly ash and calcined bauxite with chemically pure titania as sintering additive. The effects of TiO(2) on the sintering behaviors and main properties of porous mullite were studied in detail. Due to the addition of titania, the sintering of the flyash-based mullite was inhibited at low temperatures, but effectively improved at high temperatures, the latter is suitable for preparing porous mullite membrane supports by incomplete sintering. Titania entered into liquid glassy phase with low high-temperature viscosity during sintering, resulting in the improvement of sintering activity, as well as the lowering of secondary mullitization temperature (where 2.0% titania). Between 1300 and 1500 degrees C, with increasing titania content, the samples exhibit increased trends in both linear shrinkage percent and bulk density, but a slightly decreased trend in open porosity, at all sintering temperatures. At 1300-1500 degrees C, the samples sintered at 1450 degrees C for 2h exhibit the lowest shrinkage and bulk density, as well as the highest open porosities in the investigated titania content range of 0-6.0 wt.%. Also, with increasing titania content, the pore size decreases slightly but the three-point flexural strength increases gradually at 1450 degrees C. PMID:20452727

  13. Porous Carbon-Supported Gold Nanoparticles for Oxygen Reduction Reaction: Effects of Nanoparticle Size.

    PubMed

    Wang, Likai; Tang, Zhenghua; Yan, Wei; Yang, Hongyu; Wang, Qiannan; Chen, Shaowei

    2016-08-17

    Porous carbon-supported gold nanoparticles of varied sizes were prepared using thiolate-capped molecular Au25, Au38, and Au144 nanoclusters as precursors. The organic capping ligands were removed by pyrolysis at controlled temperatures, resulting in good dispersion of gold nanoparticles within the porous carbons, although the nanoparticle sizes were somewhat larger than those of the respective nanocluster precursors. The resulting nanocomposites displayed apparent activity in the electroreduction of oxygen in alkaline solutions, which increased with decreasing nanoparticle dimensions. Among the series of samples tested, the nanocomposite prepared with Au25 nanoclusters displayed the best activity, as manifested by the positive onset potential at +0.95 V vs RHE, remarkable sustainable stability, and high numbers of electron transfer at (3.60-3.92) at potentials from +0.50 to +0.80 V. The performance is comparable to that of commercial 20 wt % Pt/C. The results demonstrated the unique feasibility of porous carbon-supported gold nanoparticles as high-efficiency ORR catalysts. PMID:27454707

  14. Capping-agent-free synthesis of substrate-supported porous icosahedral gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Wu, Ji Hong; Guan, Zhenping; Yang, Su Ke; Yuan, Peiyan; Xu, Qing-Hua; Xu, Guo Qin

    2013-03-01

    We report a new capping-agent-free strategy for the synthesis of substrate-supported porous icosahedral Au nanoparticles (NPs) with rough naked surfaces, based on the crystallization from substrate-supported thin solution layers followed by solid-phase thermolysis. The plasmonic properties of icosahedral Au NPs have been studied using single particle dark-field scattering microscopy and spectroscopy. The two distinct localized surface plasmon resonance (LSPR) bands observed in the single particle dark-field spectra can be ascribed to the quadrupole resonance at ca. 425 nm and the size-dependent dipole resonance in the red region (645-708 nm). The unique rough naked surface, the facile synthesis, together with the ability to control the nanoparticle size and to vary the LSPR frequency in the red region, would make the substrate-supported porous icosahedral Au NPs promising on multiple levels in the applications of catalysis, ultrasensitive biosensors, and in surface-enhanced Raman scattering (SERS).We report a new capping-agent-free strategy for the synthesis of substrate-supported porous icosahedral Au nanoparticles (NPs) with rough naked surfaces, based on the crystallization from substrate-supported thin solution layers followed by solid-phase thermolysis. The plasmonic properties of icosahedral Au NPs have been studied using single particle dark-field scattering microscopy and spectroscopy. The two distinct localized surface plasmon resonance (LSPR) bands observed in the single particle dark-field spectra can be ascribed to the quadrupole resonance at ca. 425 nm and the size-dependent dipole resonance in the red region (645-708 nm). The unique rough naked surface, the facile synthesis, together with the ability to control the nanoparticle size and to vary the LSPR frequency in the red region, would make the substrate-supported porous icosahedral Au NPs promising on multiple levels in the applications of catalysis, ultrasensitive biosensors, and in surface

  15. Effect of particle size on CO hydrogenation activity of silica supported cobalt catalysts

    SciTech Connect

    Ho, Suiwen; Houalla, M.; Hercules, D.M. )

    1990-08-09

    Two series of silica supported cobalt catalysts were prepared by incipient wetness impregnation, one by varying the calcination temperature (200-400{degree}C, 3 wt % Co) and the other by changing the cobalt loading (1-10 wt % Co). Examination by ESCA, XRD, and H{sub 2} chemisorption showed that Co{sub 3}O{sub 4} is the dominant phase. The cobalt phase is reduced to cobalt metal at 400{degree}C. The cobalt particle sizes obtained from ESCA correlated well with those derived from H{sub 2} chemisorption and XRD line broadening. The turnover frequency of Co/SiO{sub 2} for CO hydrogenation was invariant with cobalt dispersion in the range of 6-20% dispersion.

  16. High-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles for phenol hydrogenation

    NASA Astrophysics Data System (ADS)

    Huang, Chao; Yang, Xu; Yang, Hui; Huang, Peiyan; Song, Huiyu; Liao, Shijun

    2014-10-01

    A high-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles (MSN), PdRu/MSN, was prepared by a facile impregnation-hydrogen reduction method. It was found that PdRu/MSN showed 5 times higher activity than that of Pd/MSN towards the liquid-phase hydrogenation of phenol. The catalysts were characterized comprehensively by multiple techniques, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and hydrogen temperature program reduction (TPR). It was revealed that adding Ru could effectively improve the Pd dispersion and promote the electronic interaction between the Pd and Ru, both of which contribute to enhancing the catalytic activity.

  17. Size control of rhodium particles of silica-supported catalysts using water-in-oil microemulsion

    NASA Astrophysics Data System (ADS)

    Kishida, Masahiro; Hanaoka, Toshiaki; Kim, Won Young; Nagata, Hideo; Wakabayashi, Katsuhiko

    1997-11-01

    Effects of components of water-in-oil microemulsions on rhodium particle sizes of silica-supported rhodium catalysts were investigated in the catalyst preparation method using microemulsion. In the case of the microemulsion of polyoxyethylene(23)dodecyl ether/ n-alcohols/RhCl 3 aq., the rhodium particle size increased from 3.4 to 5.0 nm as the specific permittivity of the organic solvent increased. The chain length of hydrophilic group of polyoxyethylene- p-nonylphenyl ether ( n = 5 to 15) employed as surfactants had an effect on the rhodium particle size where the rhodium size ranged between 2.0 and 3.6 nm. The rhodium particle size was 1.5 nm in the case of sodium bis(2-ethylhexyl) sulfocuccinate and this value was found to be the smallest. These results could be interpreted in terms of the adsorption of the surfactant on rhodium-hydrazine particle surface.

  18. Organically functionalized mesoporous silica as a support for synthesis and catalysis

    NASA Astrophysics Data System (ADS)

    McEleney, Kevin Andrew

    Mesoporous silicates are excellent materials for supported catalysis due to their ease of functionalization, tunable pore size and high surface areas. Mesoporous silicates have been utilized in a variety of applications such as drug delivery scaffolds and catalyst supports. Functionalization of the surface can be achieved by either grafting of alkoxy silanes or co-condensation of the organosilane with the inorganic silica source. My research in this area can be divided into two components. In the first, we address the significant issue of metal contamination after reactions that are catalyzed by transition metals. In the second, we examine the design of new catalysts based on organic/inorganic composites. Ruthenium catalyzed processes such as olefin metathesis or asymmetric hydrogenation, are often underutilized due to the difficulty of removing the ruthenium by-products. Attempts to remove ruthenium involve treating the solution with a scavenging reagent followed by silica chromatography. Often these scavenging agents are expensive phosphines or toxic agents like lead tetra-acetate. SBA-15 functionalized with aminopropyl triethoxysilane displays a high affinity for ruthenium. Furthermore, it can be utilized to remove ruthenium by-products from olefin metathesis or hydrogenation reactions without the need for silica chromatography. We have also prepared sulfur-functionalized mesoporous silicates that have a high affinity for palladium. The materials after loading prove to be active catalysts for a variety of palladium catalyzed processes such as Suzuki-Miyaura and Sonogashira couplings. The catalysts are recyclable with moderate loss of activity and structure, depending on the method of incorporation of the thiol. We have characterized the as-synthesized and used catalysts by nitrogen sorption, TEM, X-ray photoelectron spectroscopy (XPS) and a variety of homogeneity tests were performed on the catalysts. Periodic mesoporous organosilicates (PMOs) are a well known

  19. Formation of supported lipid bilayers on silica: relation to lipid phase transition temperature and liposome size.

    PubMed

    Jing, Yujia; Trefna, Hana; Persson, Mikael; Kasemo, Bengt; Svedhem, Sofia

    2014-01-01

    DPPC liposomes ranging from 90 nm to 160 nm in diameter were prepared and used for studies of the formation of supported lipid membranes on silica (SiO2) at temperatures below and above the gel to liquid-crystalline phase transition temperature (Tm = 41 °C), and by applying temperature gradients through Tm. The main method was the quartz crystal microbalance with dissipation (QCM-D) technique. It was found that liposomes smaller than 100 nm spontaneously rupture on the silica surface when deposited at a temperature above Tm and at a critical surface coverage, following a well-established pathway. In contrast, DPPC liposomes larger than 160 nm do not rupture on the surface when adsorbed at 22 °C or at 50 °C. However, when liposomes of this size are first adsorbed at 22 °C and at a high enough surface coverage, after which they are subject to a constant temperature gradient up to 50 °C, they rupture and fuse to a bilayer, a process that is initiated around Tm. The results are discussed and interpreted considering a combination of effects derived from liposome-surface and liposome-liposome interactions, different softness/stiffness and shape of liposomes below and above Tm, the dynamics and thermal activation of the bilayers occurring around Tm and (for liposomes containing 33% of NaCl) osmotic pressure. These findings are valuable both for preparation of supported lipid bilayer cell membrane mimics and for designing temperature-responsive material coatings. PMID:24651504

  20. Multi-wavelength Raman Spectroscopic Study of Silica-supported Vanadium Oxide Catalysts

    SciTech Connect

    Wu, Zili; Dai, Sheng; Overbury, Steven {Steve} H

    2010-01-01

    The molecular structure of silica-supported vanadium oxide (VOx) catalysts over wide range of surface VOx density (0.0002 8 V/nm2) has been investigated in detail under dehydrated condition by in situ multi-wavelength Raman spectroscopy (laser excitations at 244, 325, 442, 532, and 633 nm) and in situ UV-Vis diffuse reflectance spectroscopy. Resonance Raman scattering is clearly observed using 244 and 325-nm excitations while normal Raman scattering occurs using excitation at the three visible wavelengths. The observation of strong fundamentals, overtones and combinational bands due to selective resonance enhancement effect helps clarify assignments of some of the VOx Raman bands (920, 1032, and 1060 cm-1) whose assignments have been controversial. The resonance Raman spectra of dehydrated VOx/SiO2 show V=O band at smaller Raman shift than that in visible Raman spectra, an indication of the presence of two different surface VOx species on dehydrated SiO2 even at sub-monolayer VOx loading. Quantitative estimation shows that the two different monomeric VOx species coexist on silica surface from very low VOx loadings and transform to crystalline V2O5 at VOx loadings above monolayer. It is postulated that one of the two monomeric VOx species has pyramidal structure and the other is in partially hydroxylated pyramidal mode. The two VOx species show similar reduction-oxidation behavior and may both participate in redox reactions catalyzed by VOx/SiO2 catalysts. This study demonstrates the advantages of multi-wavelength Raman spectroscopy over conventional single-wavelength Raman spectroscopy in structural characterization of supported metal oxide catalysts.

  1. Electron beam-induced immobilization of laccase on porous supports for waste water treatment applications.

    PubMed

    Jahangiri, Elham; Reichelt, Senta; Thomas, Isabell; Hausmann, Kristin; Schlosser, Dietmar; Schulze, Agnes

    2014-01-01

    The versatile oxidase enzyme laccase was immobilized on porous supports such as polymer membranes and cryogels with a view of using such biocatalysts in bioreactors aiming at the degradation of environmental pollutants in wastewater. Besides a large surface area for supporting the biocatalyst, the aforementioned porous systems also offer the possibility for simultaneous filtration applications in wastewater treatment. Herein a "green" water-based, initiator-free, and straightforward route to highly reactive membrane and cryogel-based bioreactors is presented, where laccase was immobilized onto the porous polymer supports using a water-based electron beam-initiated grafting reaction. In a second approach, the laccase redox mediators 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and syringaldehyde were cross-linked instead of the enzyme via electron irradiation in a frozen aqueous poly(acrylate) mixture in a one pot set-up, yielding a mechanical stable macroporous cryogel with interconnected pores ranging from 10 to 50 µm in size. The membranes as well as the cryogels were characterized regarding their morphology, chemical composition, and catalytic activity. The reactivity towards waste- water pollutants was demonstrated by the degradation of the model compound bisphenol A (BPA). Both membrane- and cryogel-immobilized laccase remained highly active after electron beam irradiation. Apparent specific BPA removal rates were higher for cryogel- than for membrane-immobilized and free laccase, whereas membrane-immobilized laccase was more stable with respect to maintenance of enzymatic activity and prevention of enzyme leakage from the carrier than cryogel-immobilized laccase. Cryogel-immobilized redox mediators remained functional in accelerating the laccase-catalyzed BPA degradation, and especially ABTS was found to act more efficiently in immobilized than in freely dissolved state. PMID:25111026

  2. Adsorption of simazine on zeolite H-Y and sol-gel technique manufactured porous silica: A comparative study in model and natural waters.

    PubMed

    Sannino, Filomena; Marocco, Antonello; Garrone, Edoardo; Esposito, Serena; Pansini, Michele

    2015-01-01

    In this work, we studied the removal of simazine from both a model and well water by adsorption on two different adsorbents: zeolite H-Y and a porous silica made in the laboratory by using the sol-gel technique. The pH dependence of the adsorption process and the isotherms and pseudo-isotherms of adsorption were studied. Moreover, an iterative process of simazine removal from both the model and well water, which allowed us to bring the residual simazine concentration below the maximum concentration (0.05 mg L(-1)) of agrochemicals in wastewater to be released in surface waters or in sink allowed by Italian laws, was proposed. The results obtained were very interesting and the conclusions drawn from them partly differed from what could reasonably be expected. PMID:26357888

  3. Immobilization of pectinase on silica-based supports: Impacts of particle size and spacer arm on the activity.

    PubMed

    Alagöz, Dilek; Tükel, S Seyhan; Yildirim, Deniz

    2016-06-01

    The pectinase was separately immobilized onto Florisil and nano silica supports through both glutaraldehyde and 3-glyoxypropyltrietoxysilane spacer arms. The effects of spacer arm, particle size of support and ionic liquids on the activities of pectinase preparations were investigated. The immobilization of pectinase onto Florisil and nano silica through 3-glyoxypropyltrietoxysilane spacer arm completely led to inactivation of enzyme; however, 10 and 75% pectinase activity were retained when it was immobilized through glutaraldehyde spacer arm onto Florisil and nano silica, respectively. The pectinase immobilized onto nano silica through glutaraldehyde spacer arm showed 6.3-fold higher catalytic efficiency than that of the pectinase immobilized onto Florisil through same spacer arm. A 2.3-fold increase in thermal stability of pectinase was provided upon immobilization onto nano silica at 35°C. The effects of IL/buffer mixture and volume ratio of IL/buffer mixture on the catalytic activities of free and immobilized pectinase preparations were also tested. All the pectinase preparations showed highest activity in 10% (v/v) 1-butyl-3-methylimidazolium hexafluorophosphate containing medium and their activities significantly affected from the concentration of 1-butyl-3-methylimidazolium hexafluorophosphate. PMID:26964525

  4. Corrugation of Phase-Separated Lipid Bilayers Supported by Nanoporous Silica Xerogel Surfaces

    SciTech Connect

    Goksu, E I; Nellis, B A; Lin, W; Satcher Jr., J H; Groves, J T; Risbud, S H; Longo, M L

    2008-10-30

    Lipid bilayers supported by substrates with nanometer-scale surface corrugations holds interest in understanding both nanoparticle-membrane interactions and the challenges of constructing models of cell membranes on surfaces with desirable properties, e.g. porosity. Here, we successfully form a two-phase (gel-fluid) lipid bilayer supported by nanoporous silica xerogel. Surface topology, diffusion, and lipid density in comparison to mica-supported lipid bilayers were characterized by AFM, FRAP, FCS, and quantitative fluorescence microscopy, respectively. We found that the two-phase lipid bilayer follows the xerogel surface contours. The corrugation imparted on the lipid bilayer results in a lipid density that is twice that on a flat mica surface. In direct agreement with the doubling of actual bilayer area in a projected area, we find that the lateral diffusion coefficient (D) of lipids on xerogel ({approx}1.7 {micro}m{sup 2}/s) is predictably lower than on mica ({approx}4.1 {micro}m{sup 2}/s) by both FRAP and FCS techniques. Furthermore, the gel-phase domains on xerogel compared to mica were larger and less numerous. Overall, our results suggest the presence of a relatively defect-free continuous two-phase bilayer that penetrates approximately midway into the first layer of {approx}50 nm xerogel beads.

  5. Comparison of stress, strain, and elastic properties for porous silicon layers supported by substrate and corresponding membranes

    NASA Astrophysics Data System (ADS)

    Dariani, R. S.; Nazari, M.

    2016-09-01

    This paper describes characterization of mechanical properties of porous silicon (PS) layers with different porosities using high resolution XRD. The XRD measurement determined various mechanical properties of PS such as; Young modulus, Poisson's ratio, and lattice parameter expansion. Our results indicated that mechanical properties reduce with increasing porosity. Also, the mechanical properties of two different porous layers, either supported by or detached from the substrate were examined. Comparison of the two porous layers showed that the constraint in the interatomic spacing is the origin of the lattice constant expansion in the planes perpendicular to the surface. This phenomenon can be useful for gas sensor applications.

  6. Rapid and efficient synthesis of 4(3H)-quinazolinones under ultrasonic irradiation using silica-supported Preyssler nanoparticles.

    PubMed

    Heravi, Majid M; Sadjadi, Samaheh; Sadjadi, Sodeh; Oskooie, Hossein A; Bamoharram, Fatemeh F

    2009-08-01

    A new synthesis of 4(3H)-quinazolinone from the reaction of 2-amino-benzamide, and acylchlorides in the presence of catalytic amounts of silica-supported Preyssler nano particles as green, reusable and efficient catalyst under ultra sonic irradiation is reported. PMID:19362508

  7. A convenient sol-gel approach to the preparation of nano-porous silica coatings with very low refractive indices.

    PubMed

    Zhang, Yulu; Zhao, Chaoxia; Wang, Pingmei; Ye, Longqiang; Luo, Jianhui; Jiang, Bo

    2014-11-18

    Silica coatings with refractive indices as low as 1.10 were prepared via a one-step base-catalysed sol-gel process using methyltriethoxysilane and tetraethoxysilane as co-precursors. No expensive equipment was required and the method did not require etching or high-temperature calcination. PMID:25253239

  8. Thin Porous Metal Sheet-Supported NaA Zeolite Membrane for Water/Ethanol Separation

    SciTech Connect

    Zhang, Jian; Liu, Wei

    2011-04-01

    This paper reports preparation and separation testing results of water-selective zeolite membrane, such as NaA (or 4A-type), supported on a robust, porous metal sheet of 50um thickness. The thin sheet support is of large potential for development of a low-cost, inorganic membrane module of high surface area packing density. The porous Ni alloy sheet of micrometer or sub-micrometer mean pore size, which was prepared by a proprietary process, is used to evaluate different zeolite membrane deposition methods and conditions. The membranes are characterized by SEM, XRD and water/ethanol separation tests. Quality NaA zeolite membrane at thickness <2um is obtained with the secondary hydrothermal growth method. This membrane shows water/ethanol separation factor of >10,000 and water permeation flux of about 4 kg/(m2•h) at 75ºC with a feed of 10wt% water in ethanol. The membrane is also demonstrated with good stability in 66-hour continuous testing at 75ºC and 90ºC.

  9. Planar, Polysilazane-Derived Porous Ceramic Supports for Membrane and Catalysis Applications

    PubMed Central

    Konegger, Thomas; Williams, Lee F.; Bordia, Rajendra K.

    2015-01-01

    Porous, silicon carbonitride-based ceramic support structures for potential membrane and catalysis applications were generated from a preceramic polysilazane precursor in combination with spherical, ultrahigh-molecular weight polyethylene microparticles through a sacrificial filler approach. A screening evaluation was used for the determination of the impact of both porogen content and porogen size on pore structure, strength, and permeability characteristics of planar specimens. By optimizing both the composition as well as cross-linking parameters, maximum characteristic biaxial flexural strengths of 65 MPa and porosities of 42% were achieved. The evolution of an interconnected, open-pore network during thermal porogen removal and conversion of the preceramic polymer led to air permeabilities in the order of 10−14 m2. The materials were further exposed to long-term heat treatments to demonstrate the stability of properties after 100 h at 800°C in oxidizing, inert, and reducing environments. The determined performance, in combination with the versatile preparation method, illustrates the feasibility of this processing approach for the generation of porous ceramic support structures for applications at elevated temperatures in a variety of fields, including membrane and catalysis science. PMID:26681809

  10. The thermal stability of porous alumina/stainless steel catalyst support obtained by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Novaković, Tatjana; Radić, Nenad; Grbić, Boško; Dondur, Vera; Mitrić, Miodrag; Randjelović, Danijela; Stoychev, Dimitar; Stefanov, Plamen

    2008-12-01

    Active porous alumina coatings were obtained by deposition of boehmite sol on stainless steel (SS) substrate by spray pyrolysis method. The temperature and the doping of polyethylene glycol (PEG) and La 3+ in the boehmite sol effects on the textural and structural properties and surface morphology of alumina coatings on stainless steel samples are presented. It was found that the addition of polyethylene glycol combined with La 3+ to the boehmite sol before spraying improves the thermal stability of porous alumina coatings. X-ray diffraction patterns of a doped sample, even after 5 h at 1000 °C, point out to the presence only of δ-Al 2O 3, with a SBET of 74 m 2/g. XPS data and SEM photographs of coated samples show that alumina were well deposited on the metallic supports. The absence of any lanthanum compounds indicates very well homogeneous dispersion of La 3+-ions on the surface of alumina crystallites. AFM images show sphere like alumina grains and agglomerates with surface roughness from 60 to 180 nm, depending on temperature and doping. Surface roughness of doped alumina samples was higher than that of non-doped. It was pointed out that spray pyrolysis method enables preparation of alumina layers with relatively high specific surface area, suitable for applications as catalysts supports.

  11. Carbon molecular sieve membranes on porous composite tubular supports for high performance gas separations

    DOE PAGESBeta

    Lee, Pyung -Soo; Bhave, Ramesh R.; Nam, Seung -Eun; Kim, Daejin

    2016-01-11

    Thin carbon molecular sieve membranes (<500 nm) were fabricated inside of long geometry (9 inch) of stainless steel tubes with all welded construction. Alumina intermediate layer on porous stainless steel tube support was used to reduce effective support pore size and to provide a more uniform surface roughness. Novolac phenolic resin solution was then coated on the inside of porous stainless steel tube by slip casting while their viscosities were controlled from 5 centipoises to 30 centipoises. Carbonization was carried out at 700 °C in which thermal stress was minimized and high quality carbon films were prepared. The highest separationmore » performance characteristics were obtained using 20 cP phenolic resin solutions. The fabricated CMSM showed good separation factor for He/N2 462, CO2/N2 97, and O2/N2 15.4. As the viscosity of polymer precursor solution was reduced from 20 cP to 15 cP, gas permeance values almost doubled with somewhat lower separation factor He/N2 156, CO2/N2 88, and O2/N2 7.7.« less

  12. Mesoporous silica-supported lipid bilayers (protocells) for DNA cargo delivery to the spinal cord

    PubMed Central

    Dengler, Ellen C.; Liu, Juewen; Kerwin, Audra; Torres, Sergio; Olcott, Clara M.; Bowman, Brandi N.; Armijo, Leisha; Gentry, Katherine; Wilkerson, Jenny; Wallace, James; Jiang, Xingmao; Carnes, Eric C.; Brinker, C. Jeffrey; Milligan, Erin D.

    2013-01-01

    Amorphous mesoporous silica nanoparticles (‘protocells’) that support surface lipid bilayers recently characterized in vitro as carrier constructs for small drug and DNA delivery are reported here as highly biocompatible both in vitro and in vivo, involving the brain and spinal cord following spinal delivery into the lumbosacral subarachnoid space (intrathecal; i.t.). Specifically, positively charged, 1, 2-Dioleoyl-3-Trimethylammonium-Propane (DOTAP) -cholesterol (DOTAP:Chol) liposome-formulated protocells revealed stable in vitro cargo release kinetics and cellular interleukin-10 (IL-10) transgene transfection. Recent approaches using synthetic non-viral vector platforms to deliver the pain-suppressive therapeutic transgene, IL-10, to the spinal subarachnoid space has yielded promising results in animal models of peripheral neuropathy, a condition involving aberrant neuronal communication within sensory pathways in the nervous system. Non-viral drug and gene delivery protocell platforms offer potential flexibility because cargo release-rates can be pH-dependent. We report here that i.t. delivery of protocells, with modified chemistry supporting a surface coating of DOTAP:Chol liposomes and containing the IL-10 transgene, results in functional suppression of pain-related behavior in rats for extended periods. This study is the first demonstration that protocell vectors offer amenable and enduring in vivo biological characteristics that can be applied to spinal gene delivery. PMID:23517784

  13. Mesoporous silica-supported lipid bilayers (protocells) for DNA cargo delivery to the spinal cord.

    PubMed

    Dengler, Ellen C; Liu, Juewen; Kerwin, Audra; Torres, Sergio; Olcott, Clara M; Bowman, Brandi N; Armijo, Leisha; Gentry, Katherine; Wilkerson, Jenny; Wallace, James; Jiang, Xingmao; Carnes, Eric C; Brinker, C Jeffrey; Milligan, Erin D

    2013-06-10

    Amorphous mesoporous silica nanoparticles ('protocells') that support surface lipid bilayers recently characterized in vitro as carrier constructs for small drug and DNA delivery are reported here as highly biocompatible both in vitro and in vivo, involving the brain and spinal cord following spinal delivery into the lumbosacral subarachnoid space (intrathecal; i.t.). Specifically, positively charged, 1, 2-Dioleoyl-3-Trimethylammonium-Propane (DOTAP)-cholesterol (DOTAP:Chol) liposome-formulated protocells revealed stable in vitro cargo release kinetics and cellular interleukin-10 (IL-10) transgene transfection. Recent approaches using synthetic non-viral vector platforms to deliver the pain-suppressive therapeutic transgene, IL-10, to the spinal subarachnoid space have yielded promising results in animal models of peripheral neuropathy, a condition involving aberrant neuronal communication within sensory pathways in the nervous system. Non-viral drug and gene delivery protocell platforms offer potential flexibility because cargo release-rates can be pH-dependent. We report here that i.t. delivery of protocells, with modified chemistry supporting a surface coating of DOTAP:Chol liposomes and containing the IL-10 transgene, results in functional suppression of pain-related behavior in rats for extended periods. This study is the first demonstration that protocell vectors offer amenable and enduring in vivo biological characteristics that can be applied to spinal gene delivery. PMID:23517784

  14. Anchoring and promotion effects of metal oxides on silica supported catalytic gold nanoparticles.

    PubMed

    Luo, Jingjie; Ersen, Ovidiu; Chu, Wei; Dintzer, Thierry; Petit, Pierre; Petit, Corinne

    2016-11-15

    The understanding of the interactions between the different components of supported metal doped gold catalysts is of crucial importance for selecting and designing efficient gold catalysts for reactions such as CO oxidation. To progress in this direction, a unique supported nano gold catalyst Au/SS was prepared, and three doped samples (Au/SS@M) were elaborated. The samples before and after test were characterized by Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). It is found that the doping metal species prefer to be located on the surface of gold nanoparticles and that a small amount of additional reductive metal leads to more efficient reaction. During the catalytic test, the nano-structure of the metal species transforms depending on its chemical nature. This study allows one to identify and address the contribution of each metal on the CO reaction in regard to oxidative species of gold, silica and dopants. Metal doping leads to different exposure of interface sites between Au and metal oxide, which is one of the key factors for the change of the catalytic activity. The metal oxides help the activation of oxygen by two actions: mobility inside the metal bulk and transfer of water species onto of gold nanoparticles. PMID:27501036

  15. Spectroscopic Investigation into Oxidative Degradation of Silica-Supported Amine Sorbents for CO2 Capture

    PubMed Central

    Srikanth, Chakravartula S; Chuang, Steven S C

    2012-01-01

    Oxidative degradation characteristics of silica-supported amine sorbents with varying amounts of tetraethylenepentamine (TEPA) and polyethylene glycol (PEG; P200 or P600 represents PEG with molecular weights of 200 or 600) have been studied by IR and NMR spectroscopy. Thermal treatment of the sorbents and liquid TEPA at 100 °C for 12 h changed their color from white to yellow. The CO2 capture capacity of the TEPA/SiO2 sorbents (i.e., SiO2-supported TEPA with a TEPA/SiO2 ratio of 25:75) decreased by more than 60 %. IR and NMR spectroscopy studies showed that the yellow color of the degraded sorbents resulted from the formation of imide species. The imide species, consisting of NH associated with two C—O functional groups, were produced from the oxidation of methylene groups in TEPA. Imide species on the degraded sorbent are not capable of binding CO2 due to its weak basicity. The addition of P200 and P600 to the supported amine sorbents improved both their CO2 capture capacities and oxidative degradation resistance. IR spectroscopy results also showed that TEPA was immobilized on the SiO2 surface through hydrogen bonding between amine groups and the silanol groups of SiO2. The OH groups of PEG interact with NH2/NH of TEPA through hydrogen bonding. Hydrogen bonds disperse TEPA on SiO2 and block O2 from accessing TEPA for oxidation. Oxidative degradation resistance and CO2 capture capacity of the supported amine sorbents can be optimized through adjusting the ratio of hydroxyl to amine groups in the TEPA/PEG mixture. PMID:22744858

  16. Porous hollow carbon spheres for electrode material of supercapacitors and support material of dendritic Pt electrocatalyst

    NASA Astrophysics Data System (ADS)

    Fan, Yang; Liu, Pei-Fang; Huang, Zhong-Yuan; Jiang, Tong-Wu; Yao, Kai-Li; Han, Ran

    2015-04-01

    Porous hollow carbon spheres (PHCSs) are prepared through hydrothermal carbonization of alginic acid and subsequent chemical activation by KOH. The porosity of the alginic acid derived PHCSs can be finely modulated by varying activation temperature in the range of 600-900 °C. The PHCSs activated at 900 °C possess the largest specific surface area (2421 m2 g-1), well-balanced micro- and mesoporosity, as well as high content of oxygen-containing functional groups. As the electrode material for supercapacitors, the PHCSs exhibit superior capacitive performance with specific capacitance of 314 F g-1 at current density of 1 A g-1. Pt nanodendrites supported on the PHCSs are synthesized by polyol reduction method which exhibit high electrocatalytic activity towards methanol oxidation reaction (MOR). Moreover, CO-poisoning tolerance of the Pt nanodendrites is greatly enhanced owing to the surface chemical property of the PHCSs support.

  17. Tubular solid oxide fuel cells with porous metal supports and ceramic interconnections

    DOEpatents

    Huang, Kevin; Ruka, Roswell J.

    2012-05-08

    An intermediate temperature solid oxide fuel cell structure capable of operating at from 600.degree. C. to 800.degree. C. having a very thin porous hollow elongated metallic support tube having a thickness from 0.10 mm to 1.0 mm, preferably 0.10 mm to 0.35 mm, a porosity of from 25 vol. % to 50 vol. % and a tensile strength from 700 GPa to 900 GPa, which metallic tube supports a reduced thickness air electrode having a thickness from 0.010 mm to 0.2 mm, a solid oxide electrolyte, a cermet fuel electrode, a ceramic interconnection and an electrically conductive cell to cell contact layer.

  18. A study on the preparation and gas permeation of porous alumina supports

    SciTech Connect

    Ting-Chia Huang; Huey-Ing Chen

    1995-06-01

    The preparation and gas permeation of porous alumina supports were studied. The influence of the amount of PVA on the properties of the alumina slips, microstructure of the supports, and gas permeation were investigated. The experimental results show that the addition of PVA in the preparation process is useful for controlling the porosity of the supports without significantly changing other microstructural properties. Permeation measurements of H{sub 2}, He, Ch{sub 4}, N{sub 2}, O{sub 2}, and CO{sub 2} showed that gas transport through various supports under low transmembrane pressures (100-220 kPa) at room temperature (26.5{degrees}C) was in the transition region, which combined the Knudsen diffusion and Poiseuille flow. The average radii of active pores for the supports, calculated from the gas permeability method, were compared with those measured by mercury porosimetry. The porosity-tortuosity factors and the tortuosity factors of the supports were also estimated and are discussed.

  19. Magnetic Silica-Supported Ruthenium Nanoparticles: An Efficient Catalyst for Transfer Hydrogenation of Carbonyl Compounds

    EPA Science Inventory

    One-pot synthesis of ruthenium nanoparticles on magnetic silica is described which involve the in situ generation of magnetic silica (Fe3O4@ SiO2) and ruthenium nano particles immobilization; the hydration of nitriles and transfer hydrogenation of carbonyl compounds occurs in hi...

  20. Hydrazine N-N Bond Cleavage over Silica-Supported Tantalum-Hydrides.

    PubMed

    Jia, Hong-Peng; Gouré, Eric; Solans-Monfort, Xavier; Llop Castelbou, Jessica; Chow, Catherine; Taoufik, Mostafa; Eisenstein, Odile; Quadrelli, Elsje Alessandra

    2015-12-21

    Hydrazine reacts with silica-supported tantalum-hydrides [(≡SiO)2TaHx] (x = 1, 3), 1, under mild conditions (100 °C). The IR in situ monitoring of the reaction with N2H4 or (15)N2H4, and the solid-state MAS NMR spectra of the fully (15)N labeled compounds (CP (15)N, (1)H-(15)N HETCOR, (1)H-(1)H double-quantum, and (1)H-(1)H triple-quantum spectra) were used to identify stable intermediates and products. DFT calculations were used for determining the reaction pathway and calculating the (15)N and (1)H NMR chemical shifts. Combining the experimental and computational studies led to the following results. At room temperature, only hydrazine adducts, 1-N2H4, are formed. Upon heating at 100 °C, the hydrazine adducts are converted to several species among which [(≡SiO)2Ta(═NH)(NH2)], 2, [(≡SiO)2TaH(NH2)2], 3, and [(≡SiO)2TaH2(NH-NH2)], 4, were identified. The final product 2 is also formed in the reaction of N2 with the same silica-supported tantalum-hydride complexes, and the species identified as 3 and 4 had been previously suggested by DFT studies as intermediates on the reaction pathway for N-N cleavage in N2. The present computational studies (cluster models with M06 functional complemented by selected calculations with periodic calculations) show that 2 is formed via 3 and 4, with either N2 or N2H4. This strengthens the previous proposal of the existence of 3 and 4 as intermediates in the reaction of N2 with the tantalum-hydrides. However, the reaction of N2 does not imply the formation of N2H4 or its hydrazido monoanionic or dianionic ligand as an intermediate. For this reason, this study informs both on the similarities and differences of the reaction pathways involving N2 and N2H4 with tantalum-hydrides. PMID:26650850

  1. Silylated mesoporous silica membranes on polymeric hollow fiber supports: synthesis and permeation properties.

    PubMed

    Kim, Hyung-Ju; Brunelli, Nicholas A; Brown, Andrew J; Jang, Kwang-Suk; Kim, Wun-gwi; Rashidi, Fereshteh; Johnson, Justin R; Koros, William J; Jones, Christopher W; Nair, Sankar

    2014-10-22

    We report the synthesis and organic/water separation properties of mesoporous silica membranes, supported on low-cost and scalable polymeric (polyamide-imide) hollow fibers, and modified by trimethylsilylation with hexamethyldisilazane. Thin (∼1 μm) defect-free membranes are prepared, with high room-temperature gas permeances (e.g., 20,000 GPU for N2). The membrane morphology is characterized by multiple techniques, including SEM, TEM, XRD, and FT-ATR spectroscopy. Silylation leads to capping of the surface silanol groups in the mesopores with trimethylsilyl groups, and does not affect the integrity of the mesoporous silica structure and the underlying hollow fiber. The silylated membranes are evaluated for pervaporative separation of ethanol (EtOH), methylethyl ketone (MEK), ethyl acetate (EA), iso-butanol (i-BuOH), and n-butanol (n-BuOH) from their dilute (5 wt %) aqueous solutions. The membranes show separation factors in the range of 4-90 and high organic fluxes in the range of 0.18-2.15 kg m(-2) h(-1) at 303 K. The intrinsic selectivities (organic/water permeability ratios) of the silylated membranes at 303 K are 0.33 (EtOH/water), 0.5 (MEK/water), 0.25 (EA/water), 1.25 (i-BuOH/water), and 1.67 (n-BuOH/water) respectively, in comparison to 0.05, 0.015, 0.005, 0.08, and 0.14 for the unmodified membranes. The silylated membranes allow upgradation of water/organics feeds to permeate streams with considerably higher organics content. The selective and high-flux separation is attributed to both the organophilic nature of the modified mesopores and the large effective pore size. Comparison with other organics/water separation membranes reveals that the present membranes show promise due to high flux, use of scalable and low-cost supports, and good separation factors that can be further enhanced by tailoring the mesopore silylation chemistry. PMID:25255051

  2. An Efficient, Versatile, and Safe Access to Supported Metallic Nanoparticles on Porous Silicon with Ionic Liquids

    PubMed Central

    Darwich, Walid; Haumesser, Paul-Henri; Santini, Catherine C.; Gaillard, Frédéric

    2016-01-01

    The metallization of porous silicon (PSi) is generally realized through physical vapor deposition (PVD) or electrochemical processes using aqueous solutions. The former uses a strong vacuum and does not allow for a conformal deposition into the pores. In the latter, the water used as solvent causes oxidation of the silicon during the reduction of the salt precursors. Moreover, as PSi is hydrophobic, the metal penetration into the pores is restricted to the near-surface region. Using a solution of organometallic (OM) precursors in ionic liquid (IL), we have developed an easy and efficient way to fully metallize the pores throughout the several-µm-thick porous Si. This process affords supported metallic nanoparticles characterized by a narrow size distribution. This process is demonstrated for different metals (Pt, Pd, Cu, and Ru) and can probably be extended to other metals. Moreover, as no reducing agent is necessary (the decomposition in an argon atmosphere at 50 °C is fostered by surface silicon hydride groups borne by PSi), the safety and the cost of the process are improved. PMID:27271608

  3. An Efficient, Versatile, and Safe Access to Supported Metallic Nanoparticles on Porous Silicon with Ionic Liquids.

    PubMed

    Darwich, Walid; Haumesser, Paul-Henri; Santini, Catherine C; Gaillard, Frédéric

    2016-01-01

    The metallization of porous silicon (PSi) is generally realized through physical vapor deposition (PVD) or electrochemical processes using aqueous solutions. The former uses a strong vacuum and does not allow for a conformal deposition into the pores. In the latter, the water used as solvent causes oxidation of the silicon during the reduction of the salt precursors. Moreover, as PSi is hydrophobic, the metal penetration into the pores is restricted to the near-surface region. Using a solution of organometallic (OM) precursors in ionic liquid (IL), we have developed an easy and efficient way to fully metallize the pores throughout the several-µm-thick porous Si. This process affords supported metallic nanoparticles characterized by a narrow size distribution. This process is demonstrated for different metals (Pt, Pd, Cu, and Ru) and can probably be extended to other metals. Moreover, as no reducing agent is necessary (the decomposition in an argon atmosphere at 50 °C is fostered by surface silicon hydride groups borne by PSi), the safety and the cost of the process are improved. PMID:27271608

  4. In Situ Reductive Synthesis of Structural Supported Gold Nanorods in Porous Silicon Particles for Multifunctional Nanovectors.

    PubMed

    Zhu, Guixian; Liu, Jen-Tsai; Wang, Yuzhen; Zhang, Dechen; Guo, Yi; Tasciotti, Ennio; Hu, Zhongbo; Liu, Xuewu

    2016-05-11

    Porous silicon nanodisks (PSD) were fabricated by the combination of photolithography and electrochemical etching of silicon. By using PSD as a reducing agent, gold nanorods (AuNR) were in situ synthesized in the nanopores of PSD, forming PSD-supported-AuNR (PSD/AuNR) hybrid particles. The formation mechanism of AuNR in porous silicon (pSi) was revealed by exploring the role of pSi reducibility and each chemical in the reaction. With the PSD support, AuNR exhibited a stable morphology without toxic surface ligands (CTAB). The PSD/AuNR hybrid particles showed enhanced plasmonic property compared to free AuNR. Because high-density "hot spots" can be generated by controlling the distribution of AuNR supported in PSD, surface-enhanced raman scattering (SERS) using PSD/AuNR as particle substrates was demonstrated. A multifunctional vector, PSD/AuNR/DOX, composed of doxorubicin (DOX)-loaded PSD/AuNR capped with agarose (agar), was developed for highly efficient, combinatorial cancer treatment. Their therapeutic efficacy was examined using two pancreatic cancer cell lines, PANC-1 and MIA PaCa-2. PSD/AuNR/DOX (20 μg Au and 1.25 μg DOX/mL) effectively destroyed these cells under near-IR laser irradiation (810 nm, 15 J·cm(-2) power, 90 s). Overall, we envision that PSD/AuNR may be a promising injectable, multifunctional nanovector for biomedical application. PMID:27123698

  5. Silica supported palladium nanoparticles for the decarboxylation of high-acid feedstocks: Design, deactivation and regeneration

    NASA Astrophysics Data System (ADS)

    Ping, Eric Wayne

    2011-12-01

    The major goals of this thesis were to (1) design and synthesize a supported catalyst with well-defined monodisperse palladium nanoparticles evenly distributed throughout an inorganic oxide substrate with tunable porosity characteristics, (2) demonstrate the catalytic activity of this material in the decarboxylation of long chain fatty acids and their derivatives to make diesel-length hydrocarbons, (3) elucidate the deactivation mechanism of supported palladium catalysts under decarboxylation conditions via post mortem catalyst characterization and develop a regeneration methodology thereupon, and (4) apply this catalytic system to a real low-value biofeedstock. Initial catalyst designs were based on the SBA-15 silica support, but in an effort to maximize loading and minimize mass transfer limitations, silica MCF was synthesized as catalyst support. Functionalization with various silane ligands yielded a surface that facilitated even distribution of palladium precursor salts throughout the catalyst particle, and, after reduction, monodisperse palladium nanoparticles approximately 2 nm in diameter. Complete characterization was performed on this Pd-MCF catalyst. The Pd-MCF catalyst showed high one-time activity in the decarboxylation of fatty acids to hydrocarbons in dodecane at 300°C. Hydrogen was found to be an unnecessary reactant in the absence of unsaturations, but was required in their presence---full hydrogenation of the double bonds occurs before any decarboxylation can take place. The Pd-MCF also exhibited good activity for alkyl esters and glycerol, providing a nice hypothetical description of a stepwise reaction pathway for catalytic decarboxylation of acids and their derivatives. As expected, the Pd-MCF catalyst experienced severe deactivation after only one use. Substantial effort was put into elucidating the nature of this deactivation via post mortem catalyst characterization. H2 chemisorption confirmed a loss of active surface area, but TEM and

  6. Transformations of cyclohexene over silica-supported copper in the presence of deuterium

    SciTech Connect

    Fasi, A.; Palinko, I.; Katona, T.

    1997-04-01

    The transformations of cyclohexene were investigated over a silica-supported copper catalyst in a static circulation reactor in the presence of varying amount of D{sub 2} at 443 K and in a flow system in the 323-573 K temperature range under D{sub 2} flow. In the static system D{sub 2} pressure significantly influenced the types of reactions taking place (distinct regions for dehydrogenation, dehydrogenation plus hydrogenation, and hydrogenation were observed). In the flow reactor benzene and cyclohexane were always formed together, due to the partial reactivation of the catalytic surface. The temperature of the reaction significantly influenced product distribution. During transformations, the deuterium content and the deuterium distribution were also monitored in both reactor types. The half-hydrogenated state, i.e., the adsorbed d{sub 1}-cyclohexyl species, was found to be the key intermediate; nevertheless, {pi}-allyl adsorption was also significant at higher D{sub 2} pressure and in the flow system. 35 refs., 3 figs., 6 tabs.

  7. Catalytic etherification of glycerol to produce biofuels over novel spherical silica supported Hyflon® catalysts.

    PubMed

    Frusteri, Francesco; Frusteri, Leone; Cannilla, Catia; Bonura, Giuseppe

    2012-08-01

    Etherification of glycerol (GLY) with isobutylene (IB) to produce biofuels was investigated in liquid phase using spherical silica supported Hyflon® catalysts (SSHC). As reference catalyst, Amberlyst® 15 (A-15) acid ion-exchange resin was used. Experiments were carried out in batch mode at a reaction temperature ranging from 323 to 343 K. SSHC were found to be very effective systems in etherification of glycerol with IB, providing cumulative di- and tri-ethers yields higher than that obtained by using A-15 catalyst. Furthermore, such catalysts were stable and easily reusable; no leaching of active phase was observed. The formation of poly-substituted ethers, suitable additives for conventional fuels, was favored by operating at an isobutylene/glycerol molar ratio >3 and low reaction time (<6 h); however, the concentration of mono-ether reached values lower than 3 wt.% only when SSHC catalyst was used. Turnover frequency of glycerol (TOF(GLY)) highlighted that SSHC systems were much more active than A-15 catalyst: the accessibility and nature of active sites and the surface properties of catalysts were indicated as the main factors affecting the catalytic behavior. A lower acid site density of SSHC than that of A-15 catalyst was decisive in preventing the occurrence of oligomerization reaction which leads to the formation of di-isobutylene (DIB), precursors of gummy products. PMID:22705542

  8. Mechanistic investigation of ultrasonic enhancement of glycerol bioconversion by immobilized Clostridium pasteurianum on silica support.

    PubMed

    Khanna, Swati; Goyal, Arun; Moholkar, Vijayanand S

    2013-06-01

    Glycerol, the principal byproduct of biodiesel production, can be a valuable carbon source for bioconversion into diverse class of compounds. This article attempts to investigate the mechanistic aspects of ultrasound mediated bioconversion of glycerol to ethanol and 1,3-propanediol (1,3-PDO) by immobilized Clostridium pasteurianum cells on silica support. Our approach is of coupling experimental results with simulations of cavitation bubble dynamics and enzyme kinetics. In addition, the statistical analysis (ANOVA) of experimental results was also done. The glycerol uptake by cells was not affected by either immobilization or with ultrasonication. Nonetheless, both immobilization and ultrasonication were found to enhance glycerol consumption. The enhancement effect of ultrasound on glycerol consumption was most marked (175%) at the highest glycerol concentration of 25 g/L (271.7 mM). The highest glycerol consumption (32.4 mM) was seen for 10 g/L (108.7 mM) initial glycerol concentration. The immobilization of cells shifted the metabolic pathway almost completely towards 1,3-PDO. No formation of ethanol was seen with mechanical shaking, while traces of ethanol were detected with ultrasonication. On the basis of analysis of enzyme kinetics parameters, we attribute these results to increased substrate-enzyme affinity and decreased substrate inhibition for 1,3-PDO dehydrogenase in presence of ultrasound that resulted in preferential conversion of glycerol into 1,3-PDO. PMID:23322632

  9. Dehydration of Glycerin to Acrolein Over Heteropolyacid Nano-Catalysts Supported on Silica-Alumina.

    PubMed

    Kang, Tae Hun; Choi, Jung Ho; Choi, Jun Seon; Song, In Kyu

    2015-10-01

    A series of H3PW12O40 nano-catalysts supported on silica-alumina (XH3PW12O40/SA (X = 10, 15, 20, 25, and 30)) with different H3PW12O40 content (X, wt%) were prepared, and they were applied to the dehydration of glycerin to acrolein. The effect of H3PW12O40 content on the physicochemical properties and catalytic activities of XH3PW12O40/SA nano-catalysts was investigated. Surface area and pore volume of XH3PW12O40/SA catalysts decreased with increasing H3PW12O40 content. Formation of H3PW12O40 aggregates was observed in the catalysts with high H3PW12O40 loading. Brønsted acidity of the catalysts showed a volcano-shaped trend with respect to H3PW12O40 content. It was revealed that yield for acrolein increased with increasing Brønsted acidity of XH3PW12O40/SA catalysts. Brønsted acidity of XH3PW12O40/SA catalysts served as a crucial factor determining the catalytic performance in the dehydration of glycerin. Among the catalysts tested, 25H3PW12O40/SA catalyst with the largest Brønsted acidity showed the best catalytic performance. PMID:26726511

  10. Effect of the reduction treatment on the structure and reactivity of silica-supported copper particles

    SciTech Connect

    Van Der Grift, C.J.G.; Wielers, A.F.H.; Joghi, B.P.J.; Van Beijnum, J.; De Boer, M.; Versluijs-Helder, M.; Geus, J.W. )

    1991-09-01

    Silica-supported copper particles of high thermostability have been subjected to oxidation-reduction treatments after which the metal particle size, the surface structure, and the catalytic hydrogenolysis of methyl acetate were investigated. The metal particle size was assessed from the dissociative adsorption of nitrous oxide, x-ray line broadening, and transmission electron microscopy. The surface structure of the copper particles was derived from infrared spectra of adsorbed carbon monoxide. The hydrogenolysis of methyl acetate was used as a structure-sensitive test reaction to illustrate the effect of the surface structure on the activity of the catalyst. The copper particle size is not affected by reduction treatments up to 873 K, whereas the surface structure of the copper particles and thereby the oxygen uptake during dissociative adsorption of nitrous oxide and the activity of the catalyst in the hydrogenolysis of methyl acetate strongly depend upon the temperature and duration of the reduction treatment. Without a change of the copper particle size, prolonged reduction of the catalyst results in more densely packed copper surfaces that are more susceptible to penetration of oxygen during passivation with nitrous oxide and less active in the hydrogenolysis of methyl acetate. The rearrangement of the surface structure of the copper particles is reversible upon repeated oxidation-reduction cycles.

  11. Strong, Lightweight, Porous Materials

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas; Meador, Mary Ann B.; Johnston, James C.; Fabrizio, Eve F.; Ilhan, Ulvi

    2007-01-01

    A new class of strong, lightweight, porous materials has been invented as an outgrowth of an effort to develop reinforced silica aerogels. The new material, called X-Aerogel is less hygroscopic, but no less porous and of similar density to the corresponding unmodified aerogels. However, the property that sets X-Aerogels apart is their mechanical strength, which can be as much as two and a half orders of magnitude stronger that the unmodified aerogels. X-Aerogels are envisioned to be useful for making extremely lightweight, thermally insulating, structural components, but they may also have applications as electrical insulators, components of laminates, catalyst supports, templates for electrode materials, fuel-cell components, and filter membranes.

  12. Fabrication of silica nanotubes with an anisotropic functionality as a smart catalyst supporter.

    PubMed

    Seo, Young Deok; Lee, Choonghyeon; Lee, Kyung Jin; Jang, Jyongsik

    2016-08-14

    An anisotropic nanomaterial with different internal and external functionalities can serve as a versatile nanocarrier for smart nanocatalysts. Anisotropically functionalized silica nanotubes were prepared using a vapor phase synthesis (VPS) method with anodic aluminum oxide (AAO) as the hard template. The anisotropically functionalized silica nanotubes were used for the olefination of aryl iodide by embedded palladium nanoparticles and the highest olefination efficiency was 99%. PMID:27426837

  13. In situ assembly of porous Au-paper electrode and functionalization of magnetic silica nanoparticles with HRP via click chemistry for Microcystin-LR immunoassay.

    PubMed

    Ge, Shenguang; Liu, Weiyan; Ge, Lei; Yan, Mei; Yan, Jixian; Huang, Jiadong; Yu, Jinghua

    2013-11-15

    A simple, low-cost and sensitive origami electrochemical immunoassay-device was developed based on a novel gold nanoparticle modified porous paper working electrode (Au-PWE) for point-of-care testing. Azide-functionalized Au-PWE was prepared by the functionalization of Au-PWE with 1-azidoundecan-11-thiol. Alkyne end-terminated antibody was prepared with 4-pentynoic acid and antibody by the 1-ethyl-3-(3-(dimethylamino) propyl) carbodiimide hydrochloride and N-hydroxysuccinimide activation reaction. Alkyne-antibody was coupled to azido-Au-PWE by click reaction as a recognition element. Nearly monodispersed sphere-like silica-coated ferroferric oxide (Fe3O4@SiO2) nanoparticles were prepared via the reverse microemulsion method. Azide-functionalized Fe3O4@SiO2 was prepared by the functionalization of silica shell with 3-bromopropyltrichlorosilane followed by substitution with sodium azide. Alkyne-functionalized antibody and horse radish peroxidase were coupled to azide-functionalized Fe3O4@SiO2 by click reaction as signal label. Horse radish peroxidase and ferroferric oxide could catalyze the oxidation of thionine in the presence of hydrogen peroxide. After the sandwich immunoreaction, the current was proportional to the logarithm of the Microcystin-LR. The linear regression equation was i(μA)=119.89+46.27 log cMC-LR (μg/mL) in the range from 0.01 to 200 μg/mL. The limit of detection was 0.004 μg/mL. This immunoassay would provide a universal immunoassay method in environmental monitoring and public health. PMID:23728196

  14. C,N-bipyrazole receptor grafted onto a porous silica surface as a novel adsorbent based polymer hybrid.

    PubMed

    Radi, Smaail; Attayibat, Ahmed; El-Massaoudi, Mohamed; Bacquet, Maryse; Jodeh, Shehdeh; Warad, Ismail; Al-Showiman, Salim S; Mabkhot, Yahia N

    2015-10-01

    A simple heterogeneous synthesis of pure adsorbent based polymer hybrid made by condensing a functionalized C,N-bipyrazole with a 3-glycidoxypropyl-trimethoxysilane silylant agent, previously anchored on a silica surface was developed. The formed material (SG2P) was characterized through elemental analysis, FT-IR spectroscopy, (13)C NMR of solid state, scanning electron microscope (SEM), and was studied and evaluated by determination of the surface area using the BET equation, the adsorption and desorption capability using the isotherm of nitrogen and B.J.H. pore sizes. The new material exhibits good thermal stability determined by thermogravimetry curves and good chemical stability was examined in various acidic and buffer solutions (pH 1-7). The binding and adsorption abilities of SG2P were investigated for Hg(2+), Cd(2+), Pb(2+), Zn(2+), K(+), Na(+) and Li(+) cations and compared to the results of classical liquid-liquid extraction with the unbound C,N-bipyrazole compound. The grafting at the surface of silica does not affect complexing properties of the ligand and the SG2P exhibits a high selectivity toward Hg(2+) ion with no complexation being observed towards zinc and alkali metals. The extracted and the complexing cation percentages were determined by atomic absorption measurements. PMID:26078121

  15. Osseointegration properties of titanium dental implants modified with a nanostructured coating based on ordered porous silica and bioactive glass nanoparticles

    NASA Astrophysics Data System (ADS)

    Covarrubias, Cristian; Mattmann, Matías; Von Marttens, Alfredo; Caviedes, Pablo; Arriagada, Cristián; Valenzuela, Francisco; Rodríguez, Juan Pablo; Corral, Camila

    2016-02-01

    The fabrication of a nanoporous silica coating loaded with bioactive glass nanoparticles (nBG/NSC) on titanium dental implant surface and its in vitro and in vivo evaluation is presented. The coating was produced by a combined sol-gel and evaporation induced self-assembly process. In vitro bioactivity was assessed in simulated body fluid (SBF) and investigating the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). A rat tibial model was employed to analyze the bone response to nBG/NSC-modified titanium implant surface in vivo. The nBG/NSC coating was confirmed at nano level to be constituted by a highly ordered nanoporous silica structure. The coating nanotopography in conjunction with the bioactivity of the BG particles accelerate the in vitro apatite formation and promote the osteogenic differentiation of hBMSCs in absence of osteogenic supplements. These properties accelerate the formation of bone tissue in the periphery of the implant after 3 weeks of implantation. Backscattered scanning electron microscopy images revealed the presence of gaps and soft tissue in the unmodified implant after 6 weeks, whereas the nBG/NSC-modified implant showed mature bone in intimate contact with the implant surface. The nBG/NSC coating appears promising for accelerating the osseointegration of dental implants.

  16. Silica Embedded Metal Hydrides

    SciTech Connect

    Heung, L.K.; Wicks, G.G.

    1998-08-01

    A method to produce silica embedded metal hydride was developed. The product is a composite in which metal hydride particles are embedded in a matrix of silica. The silica matrix is highly porous. Hydrogen gas can easily reach the embedded metal hydride particles. The pores are small so that the metal hydride particles cannot leave the matrix. The porous matrix also protects the metal hydride particles from larger and reactive molecules such as oxygen, since the larger gas molecules cannot pass through the small pores easily. Tests show that granules of this composite can absorb hydrogen readily and withstand many cycles without making fines.

  17. A Simple, Efficient Synthesis of 2-Aryl Benzimidazoles Using Silica Supported Periodic Acid Catalyst and Evaluation of Anticancer Activity

    PubMed Central

    Sontakke, Vyankat A.; Ghosh, Sougata; Lawande, Pravin P.; Chopade, Balu A.; Shinde, Vaishali S.

    2013-01-01

    A new, efficient method for the synthesis of 2-aryl substituted benzimidazole by using silica supported periodic acid (H5IO6-SiO2) as a catalyst has been developed. The salient feature of the present method includes mild reaction condition, short reaction time, high yield and easy workup procedure. The synthesized benzimidazoles exhibited potent anticancer activity against MCF7 and HL60 cell lines. PMID:24052861

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

    PubMed

    Numpilai, Thanapha; Muenmee, Suthaporn; Witoon, Thongthai

    2016-02-01

    Impact of pore characteristics of porous silica supports on loading capacity and release behavior of ibuprofen was investigated. The porous silica materials and ibuprofen-loaded porous silica materials were thoroughly characterized by N2-sorption, thermal gravimetric and derivative weight analyses (TG-DTW), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) to determine the physical properties of materials, amount of ibuprofen adsorbed and position of ibuprofen. The detailed characterization reveals that the ibuprofen molecules adsorbed inside the mesopores. Increasing the mesopore size from 5nm to 10nm increased the ibuprofen loading from 0.74 to 0.85mmol/g, respectively. Incorporation of macropore into the structure of porous silica materials enhanced the ibuprofen loading capacity of 11.8-20.3%. The ibuprofen-loaded bimodal meso-macroporous silica materials exhibited the highest dissolution of 92wt.% within an hour. The ibuprofen particles deposited on the external surface of the porous silica materials showed a lower dissolution rate than the ibuprofen adsorbed inside the mesopores due to the formation of ibuprofen crystalline. PMID:26652347

  19. Tailoring Silica-alumina Supported Pt-Pd As Poison Tolerant Catalyst For Aromatics Hydrogenation

    SciTech Connect

    Yu, Yanzhe; Gutierrez, Oliver Y.; Haller, Gary L.; Colby, Robert J.; Kabius, Bernd C.; Rob van Veen, J. A.; Jentys, Andreas; Lercher, Johannes A.

    2013-08-01

    The tailoring of the physicochemical and catalytic properties of mono- and bimetallic Pt-Pd catalysts supported on amorphous silica-alumina is studied. Electron energy loss spectroscopy and extended X-ray absorption fine structure analyses indicated that bimetallic Pt-Pd and relatively large monometallic Pd particles were formed, whereas the X-ray absorption near edge structure provided direct evidence for the electronic deficiency of the Pt atoms. The heterogeneous distribution of metal particles was also shown by high resolution transmission electron microscopy. The average structure of the bimetallic particles (Pt-rich core and Pd-rich shell) and the presence of Pd particles led to surface Pd enrichment, which was independently shown by IR spectra of adsorbed CO. The specific metal distribution, average size, and surface composition of the Pt-Pd particles depend to a large extent on the metal precursors. In the presence of NH3 ligands, Pt-Pd particles with a fairly homogeneous bulk and surface metal distribution were formed. Also high Lewis acid site concentration of the carrier leads to more homogeneous bimetallic particles. All catalysts were active for the hydrogenation of tetralin in the absence and presence of quinoline and dibenzothiophene (DBT). Monometallic Pt catalysts had the highest hydrogenation activity in poison-free and quinoline-containing feed. When DBT was present, bimetallic Pt-Pd catalysts with the most homogenous metal distribution showed the highest activity. The higher resistance of bimetallic catalysts towards sulfur poisoning compared to their monometallic Pt counterparts results from the weakened metal-sulfur bond on the electron deficient Pt atoms. Thus, increasing the fraction of electron deficient Pt on the surface of the bimetallic particles increases the efficiency of the catalyst in the presence of sulfur.

  20. Selective, ultrathin membrane skins prepared by deposition of novel polymer films on porous alumina supports

    NASA Astrophysics Data System (ADS)

    Balachandra, Anagi Manjula

    Membrane-based separations are attractive in industrial processes because of their low energy costs and simple operation. However, low permeabilities often make membrane processes uneconomical. Since flux is inversely proportional to membrane thickness, composite membranes consisting of ultrathin, selective skins on highly permeable supports are required to simultaneously achieve high throughput and high selectivity. However, the synthesis of defect-free skins with thicknesses less than 50 nm is difficult, and thus flux is often limited. Layer-by-layer deposition of oppositely charged polyelectrolytes on porous supports is an attractive method to synthesize ultrathin ion-separation membranes with high flux and high selectivity. The ion-transport selectivity of multilayer polyelectrolyte membranes (MPMs) is primarily due to Donnan exclusion; therefore increase in fixed charge density should yield high selectivity. However, control over charge density in MPMs is difficult because charges on polycations are electrostatically compensated by charges on polyanions, and the net charge in the bulk of these films is small. To overcome this problem, we introduced a templating method to create ion-exchange sites in the bulk of the membrane. This strategy involves alternating deposition of a Cu2+-poly(acrylic acid) complex and poly(allylamine hydrochloride) on a porous alumina support followed by removal of Cu2+ and deprotonation to yield free -COO- ion-exchange sites. Diffusion dialysis studies showed that the Cl-/SO42-. Selectivity of Cu2+-templated membranes is 4-fold higher than that of membranes prepared in the absence of Cu2+. Post-deposition cross-linking of these membranes by heat-induced amide bond formation further increased Cl-/SO42- selectivity to values as high as 600. Room-temperature, surface-initiated atom transfer radical polymerization (ATRP) provides another convenient method for formation of ultrathin polymer skins. This process involves attachment of

  1. A simple and rapid determination of valproic acid in human plasma using a non-porous silica column and liquid chromatography with tandem mass spectrometric detection.

    PubMed

    Matsuura, Katsuhiko; Ohmori, Tomofumi; Nakamura, Mitsuhiro; Itoh, Yoshinori; Hirano, Kazuyuki

    2008-04-01

    A liquid chromatographic tandem mass spectrometric (LC-MS/MS) assay was developed and validated to determine valproic acid in human plasma. The method involved a solid-phase extraction of valproic acid and betamethasone valerate, an internal standard, from plasma and detection using an LC-MS/MS system with electrospray ionization source in negative ion mode. Separation was achieved within 3 min on a non-porous silica column with mobile phase containing ammonium acetate and methanol. Multiple reaction monitoring was utilized for detection monitoring at 142.89-142.89 for valproic acid and 457.21-457.21 for the internal standard. The calibration curve for valproic acid was linear over the range of 0.5-150 microg/mL. The limit of detection was 0.17 microg/mL and the lower limit of quantification was 0.5 microg/mL, when 0.2 mL plasma was used for extraction. The percentage coefficient of validation for accuracy and precision (inter- and intra-day) for this method was less than 9.5% with recovery ranging from 82.3 to 86.9% for valproic acid. PMID:18004739

  2. Bimodal porous silica microspheres decorated with polydopamine nano-particles for the adsorption of methylene blue in fixed-bed columns.

    PubMed

    Ataei-Germi, Taher; Nematollahzadeh, Ali

    2016-05-15

    Bimodal meso/macro-porous silica microspheres (MSM) were synthesized by a modified sol-emulsion-gel method and then the surface was coated with polydopamine (PDA) nano-particles of 39nm in size. Focusing on the encouraging properties of the synthesized adsorbent, such as high specific surface area (612.3m(2)g(-1), because of mesopores), fast mass transfer (0.9-2.67×10(-3)mLmin(-1)mg, because of macropores), and abundant "adhesive" functional groups of PDA, it was used for the removal of methylene blue (MB) from aqueous solution in a fixed-bed column. The effect of different parameters such as pH, initial concentration, and flow rate was studied. The results revealed that an appropriate sorption condition is an alkaline solution of MB (e.g., pH 10) at low flow rate (less than 5mLmin(-1)). Furthermore, the compatibility of the experimental data with mathematical models such as Thomas and Adams-Bohart was investigated. Both of the models showed a good agreement with the experimental data (R(2)=0.9954-0.9994), and could be applied for the prediction of the column properties and breakthrough curves. Regeneration of the column was performed by using HCl solution with a concentration of 0.1M as an eluent. PMID:26943002

  3. Development and characterization of ultra-porous silica films made by the sol-gel method. Application to biosensing

    NASA Astrophysics Data System (ADS)

    Desfours, Caroline; Calas-Etienne, Sylvie; Horvath, Robert; Martin, Marta; Gergely, Csilla; Cuisinier, Frédéric; Etienne, Pascal

    2014-02-01

    The aim of this work is to demonstrate the sensing ability of reverse-symmetry waveguides to investigate adsorption of casein and build-up of poly-L-lysine mediated casein multilayers. A first part of this study is dedicated to the elaboration and characterization of ultra-porous thin films with very low refractive indices by an appropriate sol-gel method. This will form the basis of our planar optical sensors. Optical waveguide light mode spectroscopy is a real-time and sensitive method to study protein adsorption kinetics and lipid bilayers. We used it to test the obtained waveguides for in-situ monitoring of biomolecule adsorption. As a result, significant changes in the incoupling peak position were observed during the layer-by-layer adsorption. Finally, refractive index and thickness of the adsorbed layers were established.

  4. Micro-tubular solid oxide fuel cell based on a porous yttria-stabilized zirconia support

    PubMed Central

    Panthi, Dhruba; Tsutsumi, Atsushi

    2014-01-01

    Solid oxide fuel cells (SOFCs) are promising electrochemical energy conversion devices owing to their high power generation efficiency and environmentally benign operation. Micro-tubular SOFCs, which have diameters ranging from a few millimeters to the sub-millimeter scale, offer several advantages over competing SOFCs such as high volumetric power density, good endurance against thermal cycling, and flexible sealing between fuel and oxidant streams. Herein, we successfully realized a novel micro-tubular SOFC design based on a porous yttria-stabilized zirconia (YSZ) support using multi-step dip coating and co-sintering methods. The micro-tubular SOFC consisted of Ni-YSZ, YSZ, and strontium-doped lanthanum manganite (LSM)–YSZ as the anode, electrolyte, and cathode, respectively. In addition, to facilitate current collection from the anode and cathode, Ni and LSM were applied as an anode current collector and cathode current collector, respectively. Micro-crystalline cellulose was selected as a pore former to achieve better shrinkage behavior of the YSZ support so that the electrolyte layer could be densified at a co-sintering temperature of 1300°C. The developed micro-tubular design showed a promising electrochemical performance with maximum power densities of 525, 442, and 354 mW cm−2 at 850, 800, and 750°C, respectively. PMID:25169166

  5. Micro-tubular solid oxide fuel cell based on a porous yttria-stabilized zirconia support

    NASA Astrophysics Data System (ADS)

    Panthi, Dhruba; Tsutsumi, Atsushi

    2014-08-01

    Solid oxide fuel cells (SOFCs) are promising electrochemical energy conversion devices owing to their high power generation efficiency and environmentally benign operation. Micro-tubular SOFCs, which have diameters ranging from a few millimeters to the sub-millimeter scale, offer several advantages over competing SOFCs such as high volumetric power density, good endurance against thermal cycling, and flexible sealing between fuel and oxidant streams. Herein, we successfully realized a novel micro-tubular SOFC design based on a porous yttria-stabilized zirconia (YSZ) support using multi-step dip coating and co-sintering methods. The micro-tubular SOFC consisted of Ni-YSZ, YSZ, and strontium-doped lanthanum manganite (LSM)-YSZ as the anode, electrolyte, and cathode, respectively. In addition, to facilitate current collection from the anode and cathode, Ni and LSM were applied as an anode current collector and cathode current collector, respectively. Micro-crystalline cellulose was selected as a pore former to achieve better shrinkage behavior of the YSZ support so that the electrolyte layer could be densified at a co-sintering temperature of 1300°C. The developed micro-tubular design showed a promising electrochemical performance with maximum power densities of 525, 442, and 354 mW cm-2 at 850, 800, and 750°C, respectively.

  6. Surface spectroscopic studies of a model silica-supported copper catalyst: Adsorption and reactions of CO, H[sub 2]O, and NO

    SciTech Connect

    Xu, X.; Vesecky, S.M.; He, J.; Goodman, D.W. )

    1993-07-01

    A model silica-supported copper catalyst has been studied with temperature programmed desorption, x-ray photoelectron spectroscopy, infrared reflection--absorption spectroscopy, and scanning tunneling microscopy. The reactions of water and nitric oxide on the Cu/SiO[sub 2] catalyst were also investigated. The model catalyst was prepared by evaporating copper onto a silica thin film ([similar to]100 A) which was, in turn, supported on a Mo(110) surface. Copper forms small metallic clusters on the silica surface with a small fraction being partially oxidized. Water dissociates on the Cu/SiO[sub 2] catalyst to yield dihydrogen at 400 K and surface oxygen during temperature programmed reaction. Nitric oxide reacts with the model silica-supported copper catalyst to produce nitrous oxide and surface oxygen, which does not desorb until copper evaporates at high temperatures.

  7. Highly Porous Carbon Derived from MOF-5 as a Support of ORR Electrocatalysts for Fuel Cells.

    PubMed

    Khan, Inayat Ali; Qian, Yuhong; Badshah, Amin; Nadeem, Muhammad Arif; Zhao, Dan

    2016-07-13

    The development of highly competent electrocatalysts for the sluggish oxygen reduction reaction (ORR) at cathodes of proton-exchange membrane fuel cells (PEMFCs) is extremely important for their long-term operation and wide applications. Herein, we present highly efficient ORR electrocatalysts based on Pt/Ni bimetallic nanoparticles dispersed on highly porous carbon obtained via pyrolysis of a metal-organic framework MOF-5. In comparison to the commercial Pt/C (20%), the electrocatalyst Pt-Ni/PC 950 (15:15%) in this study exhibits a pronounced positive shift of 90 mV in Eonset. In addition, it also demonstrates excellent long-term stability and durability during the 500-cycle continue-oxygen-supply (COS) accelerating durability tests (ADTs). The significantly improved activity and stability of Pt-Ni/PC 950 (15:15%) can be attributed to the Pt electron interaction with Ni and carbon support as has been proved in X-ray and microscopic analysis. PMID:27327655

  8. Tubular ceramic-supported sol-gel silica-based membranes for flue gas carbon dioxide capture and sequestration.

    SciTech Connect

    Tsai, C. Y.; Xomeritakis, George K.; Brinker, C. Jeffrey; Jiang, Ying-Bing

    2009-03-01

    Pure, amine-derivatized and nickel-doped sol-gel silica membranes have been developed on tubular Membralox-type commercial ceramic supports for the purpose of carbon dioxide separation from nitrogen under coal-fired power plant flue gas conditions. An extensive synthetic and permeation test study was carried out in order to optimize membrane CO{sub 2} permeance, CO{sub 2}:N{sub 2} separation factor and resistance against densification. Pure silica membranes prepared under optimized conditions exhibited an attractive combination of CO{sub 2} permeance of 2.0 MPU (1 MPU = 1 cm{sup 3}(STP) {center_dot} cm{sup -2} min{sup -1} atm{sup -1}) and CO{sub 2}:N{sub 2} separation factor of 80 with a dry 10:90 (v/v) CO{sub 2}:N{sub 2} feed at 25 C. However, these membranes exhibited flux decline phenomena under prolonged exposure to humidified feeds, especially in the presence of trace SO{sub 2} gas in the feed. Doping the membranes with nickel (II) nitrate salt was effective in retarding densification, as manifested by combined higher permeance and higher separation factor of the doped membrane compared to the pure (undoped) silica membrane after 168 hours exposure to simulated flue gas conditions.

  9. Temperature-programmed desorption study of the selective oxidation of alcohols on silica-supported vanadium oxide.

    PubMed

    Feng, T; Vohs, J M

    2005-02-17

    The partial oxidation of methanol and ethanol on silica-supported vanadium oxide catalysts was studied using temperature-programmed desorption (TPD), Raman spectroscopy, and diffuse reflectance infrared spectroscopy (DRIFTS). Methanol TPD results for V2O5/SiO2 samples as a function of vanadia loading in conjunction with X-ray diffraction data and Raman spectra indicated that dispersed vanadia on silica agglomerates into vanadia crystallites during a CH3OH TPD experiment. For ethanol-dosed samples, agglomeration of the dispersed vanadia was less severe, and it was possible to measure the activation energy for the dehydrogenation of adsorbed ethoxides to produce CH3CHO. Assuming a preexponential factor of 10(13) s(-1), the activation energy for this reaction was estimated to be 132 kJ/mol. The results of this study further demonstrate that there is a relatively weak interaction between vanadia and silica and suggest that adsorbed methoxide species help facilitate agglomeration of dispersed vanadia. PMID:16851203

  10. Preparation and characterization of micro-cell membrane chromatographic column with silica-based porous layer open tubular capillary as cellular membrane carrier.

    PubMed

    Zhang, Fugeng; Zhao, Xinchao; Xu, Bei; Cheng, Shuai; Tang, Cheng; Duan, Hongquan; Xiao, Xuefeng; Du, Wuxun; Xu, Liang

    2016-04-01

    Cell membrane chromatography (CMC) is a powerful tool to study membrane protein interactions and to screen active compounds extracted from natural products. Unfortunately, a large amount of cells are typically required for column preparation in order to carry out analyses in an efficient manner. Micro-CMC (mCMC) has recently been developed by using a silica capillary as a membrane carrier. However, a reduced retention of analytes is generally associated with mCMC mostly due to a low ligand (cellular membrane) capacity. To solve this common problem, in this work a silica-based porous layer open tubular (PLOT) capillary was fabricated and, to the best of our knowledge, for the first time applied to mCMC. The mCMC column was prepared by physical adsorption of rabbit red blood cell (rRBC) membranes onto the inner surface of the PLOT capillary. The effects of the PLOT capillaries fabricated by different feed compositions, on the immobilization amount of cellular membranes (represented by the fluorescence intensity of the capillary immobilized with fluorescein isothiocyanate isomer-labeled cellular membranes) and on the dynamic binding capacity (DBC) of verapamil (VP, a widely used calcium antagonist which specific interacts with L-type calcium channel proteins located on cellular membrane of rRBC) have been systematically investigated. The fluorescence intensity of the mCMC column when combined with the PLOT capillary was found to be more than five times higher than the intensity using a bare capillary. This intriguing result indicates that the PLOT capillary exhibits a higher cellular membrane capacity. The DBC of VP in the PLOT column was found to be more than nine times higher than that in the bare capillary. An rRBC/CMC column was also prepared for comparative studies. As a result, mCMC provides similar chromatographic retention factors and stability with common CMC; however, the cellular membrane consumption for mCMC was found to be more than 460 times lower than