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Mesoporous
Terms modified by Mesoporous Selected AbstractsElectroanalytical Applications of Microporous Zeolites and Mesoporous (Organo)Silicas: Recent TrendsELECTROANALYSIS, Issue 7 2008Alain WalcariusArticle first published online: 10 MAR 200 Abstract Microporous zeolites and ordered mesoporous (organo)silicas have been widely used as electrode modifiers because of their attractive properties (ion exchange and size selectivity of zeolites, well ordered nanoreactors containing a high number of widely accessible active centers in mesoporous (organo)silicas). These properties have been intelligently combined to selected redox processes to improve the response of the resulting modified electrodes or to design novel electrochemical detection schemes. This up-to-date review provides the recent advances made in the electroanalytical applications of zeolite modified electrodes and discusses the interest of ordered mesoporous (organo)silica materials in electroanalysis. [source] Copper impregnated mesoporous activated carbon as a high efficient catalyst for the complete destruction of pathogens in water,ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2008L. John Kennedy Abstract Copper impregnated mesoporous activated carbon catalyst was applied for the elimination of microorganisms in wastewater. The antibacterial activity of the catalyst was determined qualitatively by testing the removal of pathogens in water after contacting with the catalyst. Escherichia coli, Shigella flexneri, Shigella dysenteriae, Shigella sonnei, and Salmonella typhi were taken as the model pathogens in determining the antimicrobial activity of the catalyst. The catalyst developed for this purpose was thoroughly characterized using instrumental techniques such as BET analysis, X-ray diffraction, FTIR spectroscopy, and scanning electron microscope to determine the pore and surface area, structural phases, surface functional groups, and surface morphology respectively. The energy dispersive X-ray analysis carried out confirmed qualitatively the percentage of copper impregnated in the catalyst. The experimental studies revealed that the catalyst was highly efficient and advantageous to be employed for industrial applications because of the nonleacheablity of copper from the catalyst and nonreoccurrence of the pathogens in the treated water. The transmission electron microscopy evidenced the complete cell wall rupture of the microorganisms. All the experimental results revealed that the copper impregnated mesoporous activated carbon exhibited a strong and long term antibacterial activity throughout the studies for repeated cycles. © 2007 American Institute of Chemical Engineers Environ Prog, 2008 [source] Multilayer Amorphous-Si-B-C-N/,-Al2O3/,-Al2O3 Membranes for Hydrogen Purification,,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Ravi Mohan Prasad Abstract The hydrogen and carbon monoxide separation is an important step in the hydrogen production process. If H2 can be selectively removed from the product side during hydrogen production in membrane reactors, then it would be possible to achieve complete CO conversion in a single-step under high temperature conditions. In the present work, the multilayer amorphous-Si-B-C-N/,-Al2O3/,-Al2O3 membranes with gradient porosity have been realized and assessed with respect to the thermal stability, geometry of pore space and H2/CO permeance. The ,-Al2O3 support has a bimodal pore-size distribution of about 0.64 and 0.045 µm being macroporous and the intermediate ,-Al2O3 layer,deposited from boehmite colloidal dispersion,has an average pore-size of 8,nm being mesoporous. The results obtained by the N2 -adsorption method indicate a decrease in the volume of micropores,0.35 vs. 0.75,cm3,g,1,and a smaller pore size ,6.8 vs. 7.4 Å,in membranes with the intermediate mesoporous ,-Al2O3 layer if compared to those without. The three times Si-B-C-N coated multilayer membranes show higher H2/CO permselectivities of about 10.5 and the H2 permeance of about 1.05,×,10,8 mol m,2 s,1 Pa,1. If compared to the state of the art of microporous membranes, the multilayer Si-B-C-N/,-Al2O3/,-Al2O3 membranes are appeared to be interesting candidates for hydrogen separation because of their tunable nature and high-temperature and high-pressure stability. [source] Biomimetic Composites: Protein Localization in Silica Nanospheres Derived via Biomimetic Mineralization (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Mater. Abstract Lysozyme-templated precipitation of silica synthesized by sol-gel chemistry produces a composite material with antimicrobial properties. This study investigates the structural properties of the composite material that allow for retention of the antimicrobial activity of lysozyme. Scanning (SEM) and transmission (TEM) electron microscopy reveal that the composite has a hierarchical structure composed of quasi-spherical structures (,450 nm diameter), which are in turn composed of closely packed spherical structures of ,8,10 nm in diameter. Using small-angle neutron scattering (SANS) with contrast variation, the scattering signatures of the lysozyme and silica within the composite were separated. It was determined that the lysozyme molecules are spatially correlated in the material and form clusters with colloidal silica particles. The size of the clusters determined by SANS agrees well with the structural architecture observed by TEM. BET analysis revealed that the surface area of the composite is relatively low (4.73 m2/g). However, after removal of the protein by heating to 200 °C, the surface area is increased by ,20%. In addition to demonstrating a well organized sol-gel synthesis which generates a functional material with antimicrobial applications, the analysis and modeling approaches described herein can be used for characterizing a wide range of mesoporous and ultrastructural materials. [source] Protein Localization in Silica Nanospheres Derived via Biomimetic MineralizationADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Mateus B. Cardoso Abstract Lysozyme-templated precipitation of silica synthesized by sol-gel chemistry produces a composite material with antimicrobial properties. This study investigates the structural properties of the composite material that allow for retention of the antimicrobial activity of lysozyme. Scanning (SEM) and transmission (TEM) electron microscopy reveal that the composite has a hierarchical structure composed of quasi-spherical structures (,450 nm diameter), which are in turn composed of closely packed spherical structures of ,8,10 nm in diameter. Using small-angle neutron scattering (SANS) with contrast variation, the scattering signatures of the lysozyme and silica within the composite were separated. It was determined that the lysozyme molecules are spatially correlated in the material and form clusters with colloidal silica particles. The size of the clusters determined by SANS agrees well with the structural architecture observed by TEM. BET analysis revealed that the surface area of the composite is relatively low (4.73 m2/g). However, after removal of the protein by heating to 200 °C, the surface area is increased by ,20%. In addition to demonstrating a well organized sol-gel synthesis which generates a functional material with antimicrobial applications, the analysis and modeling approaches described herein can be used for characterizing a wide range of mesoporous and ultrastructural materials. [source] Polysaccharide-Derived Carbons for Polar Analyte SeparationsADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Robin J. White Abstract Highly mesoporous (Brunauer,Emmett,Teller surface area, SBET,>,200,m2,g,1; mesopore volume,>,1,cm3,g,1) carbonaceous materials are prepared in a truly sustainable manner, from the naturally occurring polysaccharide alginic acid. This approach yields large mesoporous materials (pore diameter,>,14,nm) significantly without the use of a template or carbonization catalyst. The direct thermal decomposition of mesoporous forms of the acidic polysaccharide allows for an extremely flexible material preparation strategy. Materials can be prepared at any desired carbonization temperature (e.g., 200,1000,°C), possessing similar textural properties, but progressively presenting more uniform surface functionality through this temperature range, from more oxygenated surfaces at low temperatures to increasingly aromatic/graphitic-like surfaces. The high-temperature material (i.e., 1000,°C), while predominantly amorphous, presents some short range (turbostratic) ordering, providing sufficiently polarizable surfaces on which to perform challenging liquid phase separations of polar sugar analytes. [source] Dual-Function Scattering Layer of Submicrometer-Sized Mesoporous TiO2 Beads for High-Efficiency Dye-Sensitized Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Fuzhi Huang Abstract Submicrometer-sized (830,±,40,nm) mesoporous TiO2 beads are used to form a scattering layer on top of a transparent, 6-µm-thick, nanocrystalline TiO2 film. According to the Mie theory, the large beads scatter light in the region of 600,800,nm. In addition, the mesoporous structure offers a high surface area, 89.1,m2 g,1, which allows high dye loading. The dual functions of light scattering and electrode participation make the mesoporous TiO2 beads superior candidates for the scattering layer in dye-sensitized solar cells. A high efficiency of 8.84% was achieved with the mesoporous beads as a scattering layer, compared with an efficiency of 7.87% for the electrode with the scattering layer of 400-nm TiO2 of similar thickness. [source] Synthesis of Magnetic, Up-Conversion Luminescent, and Mesoporous Core,Shell-Structured Nanocomposites as Drug CarriersADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Shili Gai Abstract The synthesis (by a facile two-step sol,gel process), characterization, and application in controlled drug release is reported for monodisperse core,shell-structured Fe3O4@nSiO2@mSiO2@NaYF4: Yb3+, Er3+/Tm3+ nanocomposites with mesoporous, up-conversion luminescent, and magnetic properties. The nanocomposites show typical ordered mesoporous characteristics and a monodisperse spherical morphology with narrow size distribution (around 80,nm). In addition, they exhibit high magnetization (38.0,emu g,1, thus it is possible for drug targeting under a foreign magnetic field) and unique up-conversion emission (green for Yb3+/Er3+ and blue for Yb3+/Tm3+) under 980,nm laser excitation even after loading with drug molecules. Drug release tests suggest that the multifunctional nanocomposites have a controlled drug release property. Interestingly, the up-conversion emission intensity of the multifunctional carrier increases with the released amount of model drug, thus allowing the release process to be monitored and tracked by the change of photoluminescence intensity. This composite can act as a multifunctional drug carrier system, which can realize the targeting and monitoring of drugs simultaneously. [source] Synthesis, Mechanism, and Gas-Sensing Application of Surfactant Tailored Tungsten Oxide NanostructuresADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Suman Pokhrel Abstract Widely applicable nonaqueous solution routes have been employed for the syntheses of crystalline nanostructured tungsten oxide particles from a tungsten hexachloride precursor. Here, a systematic study on the crystallization and assembly behavior of tungsten oxide products made by using the bioligand deferoxamine mesylate (DFOM) (product I), the two chelating ligands hexadecyltrimethylammoniumbromide (CTAB) (II) and poly(alkylene oxide) block copolymer (Pluronic P123) (III) is presented. The mechanistic pathways for the material synthesis are also discussed in detail. The tungsten oxide nanomaterials and reaction solutions are characterized by Fourier transform IR, 1H, and 13C NMR spectroscopies, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected-area electron diffraction. The indexing of the line pattern suggests WO3 is in its monoclinic structure with a,=,0.7297,nm, b,=,0.7539,nm, c,=,0.7688,nm, and ,-i;,=,90.91,°. The nanoparticles formed have various architectures, such as chromosomal shapes (product I) and slates (II), which are quite different from the mesoporous one (III) that has internal pores or mesopores ranging from 5 to 15,nm. The nanoparticles obtained from all the synthetic procedures are in the range of 40,60,nm. The investigation of the gas-sensing properties of these materials indicate that all the sensors have good baseline stability and the sensors fabricated from material III present very different response kinetics and different CO detection properties. The possibility of adjusting the morphology and by that tuning the gas-sensing properties makes the preparation strategies used interesting candidates for fabricating gas-sensing materials. [source] Hierarchic Nanostructure for Auto-Modulation of Material Release: Mesoporous Nanocompartment FilmsADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Qingmin Ji The preparation of mesoporous nanocompartment films composed of both hollow silica capsules and silica particles by using layer-by-layer (LbL) adsorption is described. The resultant nanocompartment films exhibit stepwise release of encapsulated water molecules without application of external stimuli. The hollow hierarchic pore structure of the silica capsules, including their internal void and mesoporous walls, is a key factor for the regulation and stepwise release of water, and is probably caused by the non-equilibrated concurrent evaporation of material from the mesopore and capillary penetration into the mesopores. The number of release steps and rate of release can be tuned by variation of several parameters including water content, ambient temperature, layer multiplicity, and co-adduct particle size. Application of the mesoporous nanocompartment films for the release of substances, including therapeutic agents and fragrances, indicates that the stepwise material release can be applied for a wide range of liquid substances. The films should lead to a novel material release system useful even for biomedical applications capable of controlled and sustained delivery of drug molecules. [source] In Situ Growth of Mesoporous SnO2 on Multiwalled Carbon Nanotubes: A Novel Composite with Porous-Tube Structure as Anode for Lithium Batteries,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007Z. Wen Abstract A novel mesoporous-nanotube hybrid composite, namely mesoporous tin dioxide (SnO2) overlaying on the surface of multiwalled carbon nanotubes (MWCNTs), was prepared by a simple method that included in situ growth of mesoporous SnO2 on the surface of MWCNTs through hydrothermal method utilizing Cetyltrimethylammonium bromide (CTAB) as structure-directing agents. Nitrogen adsorption,desorption, X-ray diffraction and transmission electron microscopy analysis techniques were used to characterize the samples. It was observed that a thin layer tetragonal SnO2 with a disordered porous was embedded on the surface of MWCNTs, which resulted in the formation of a novel mesoporous-nanotube hybrid composite. On the base of TEM analysis of products from controlled experiment, a possible mechanism was proposed to explain the formation of the mesoporous-nanotube structure. The electrochemical properties of the samples as anode materials for lithium batteries were studied by cyclic voltammograms and Galvanostatic method. Results showed that the mesoporous-tube hybrid composites displayed higher capacity and better cycle performance in comparison with the mesoporous tin dioxide. It was concluded that such a large improvement of electrochemical performance within the hybrid composites may in general be related to mesoporous-tube structure that possess properties such as one-dimensional hollow structure, high-strength with flexibility, excellent electric conductivity and large surface area. [source] Low-Temperature Ionic-Liquid-Based Synthesis of Nanostructured Iron-Based Fluoride Cathodes for Lithium BatteriesADVANCED MATERIALS, Issue 33 2010Chilin Li A mesoporous iron-based fluoride cathode for lithium batteries is fabricated by a novel low-temperature non-aqueous synthesis based on ionic liquid medium. The hydration-water-induced microstructural optimization and morphological decoration are expected to contribute positively to both the large reversible Li-storage capacity and the high reactive voltage of carbon-free FeF3 · 0.33H2O at room temperature. [source] Porous One-Dimensional Photonic Crystals Improve the Power-Conversion Efficiency of Dye-Sensitized Solar CellsADVANCED MATERIALS, Issue 7 2009Silvia Colodrero The solar-to-electric power-conversion efficiency (,) of dye-sensitized solar cells can be greatly enhanced by integrating a mesoporous, nanoparticle-based, 1D photonic crystal as a coherent scattering layer in the device. The photogenerated current is greatly improved without altering the open-circuit voltage of the cell, while keeping the transparency of the cell intact. Improved average , values between 15% and 30% are attained. [source] Exploration of a Standing Mesochannel System with Antimatter/Matter Atomic Probes,ADVANCED MATERIALS, Issue 24 2008Hiroyuki K. M. Tanaka Positronium, a system consisting of an electron and its antimatter, a positron, offers a new technique to explore vertical accessibility and connectivity. Here, we show how this technique can be used to map out the vertical profile of mesoporous silica channel systems by comparing a standing (perpendicular to the substrate) 2D hexagonal with a lying (parallel to the substrate) 2D hexagonal mesoporous film. [source] SiOC Ceramic Monoliths with Hierarchical PorosityINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2010Cekdar Vakifahmetoglu SiOC glass monoliths possessing hierarchical porosity were produced by a one-pot processing method. Periodic mesoporous organosilica (PMO) particles were embedded into a foamed siloxane preceramic polymer. After pyrolysis at 1000°C in inert atmosphere, open celled, permeable SiOC ceramic monoliths with a high amount of pores, ranging in size from hundred of micrometers to a few nanometers, were obtained. The components possessed a specific surface area of 137 m2/g, indicating the retention of most of the mesopores after the pyrolytic conversion of the PMO precursor particles. These fillers converted to truncated rhombic dodecahedral SiOC mesoporous micron-sized grains, homogeneously distributed throughout the SiOC cellular matrix. The produced porous ceramics possessed compression strength of about 1.7 MPa, which is adequate for their use in several engineering applications. [source] Carbon Nanofibers Uniformly Grown on ,-Alumina Washcoated Cordierite Monoliths,ADVANCED MATERIALS, Issue 12 2006E. García-Bordejé A uniform layer of carbon nanofibers is grown on a cordierite monolith by first coating the monolith with a thin layer of ,-alumina. The nanofibers form a thick, uniform layer on the monolith walls as shown in the figure, leading to the formation of a mesoporous and mechanically robust composite. The absence of microporosity in the composite and the ability to tune the thickness of the nanofiber layer suggests that these nanofibers/monolith composites may be useful as catalyst supports for liquid-phase catalytic reactions. [source] Platinum Surface Modification of SBA-15 by ,-Radiation Treatment,ADVANCED MATERIALS, Issue 6 2003T. Yamada Modification of the mesoporous surface of SBA-15 with platinum has been successfully carried out by means of ,-radiation treatment. This novel treatment allows the selective growth of platinum in the SBA-15 micropores (see Figure). This is in contrast to traditional temperature treatment, in which platinum particles or rods also grow in the mesopores. [source] Evaluation of trimedlure dispensers by a method based on thermal desorption coupled with gas chromatography,mass spectrometryJOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2008C. Alfaro Abstract Knowledge about the behaviour of trimedlure (TML) dispensers is essential to ensure the efficacy of monitoring and control methods based on TML as attractant. There are several commercially available TML dispensers, and each of them has a different useful life and TML release profile. Their emission is also affected differently by environmental factors. Even the same type of dispenser sometimes shows an important variability in the TML release rate. Because of the importance of methods based on TML lures in the control of the Mediterranean fruit fly and the influence of the TML dispenser on the efficacy of these control methods, we developed a non-destructive flow-through system to measure the TML release rate. This volatile collection method (VCM) adsorbs TML vapour on a Tenax TA desorption tube, and TML is quantified by Thermal desorption coupled with gas chromatography/mass spectrometry. Two types of TML dispensers, a polymeric (Aralure) and a mesoporous (Epalure), were field aged during 3 months. The TML release rates of these dispensers were determined by both, VCM and solvent extraction method. In this study, the correlation between both measurement methods is shown. A field trial has also been carried out to correlate trap catches and TML emission of each type of tested dispenser. The VCM allows a quick and accurate evaluation of the current behaviour of commercial dispensers along their useful life. It also allows comparing the TML release rate between different dispensers. We believe that the VCM can be useful for dispenser manufacturers to determine seasonal dispenser performance before a new product is introduced in the market, and to rapidly verify TML dispenser release when field-aged dispenser efficacy is in question. Thus, it can be employed as a quality control of commercial dispensers. [source] Towards waste minimisation in WWTP: activated carbon from biological sludge and its application in liquid phase adsorptionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2002Maria J Martin Abstract Surplus sludge produced during the biological treatment of wastewater requires costly disposal procedures. With increasing environmental and legislative constraints, increasing sludge production and more limited disposal options, new recycling alternatives have to be found. The possibility of obtaining activated carbons from surplus biological sludge by chemical activation with H2SO4 has been investigated. Operational parameters such as the amount of H2SO4 added, the temperature, and activation time were modified to ascertain their influence on the quality of the activated carbon obtained. The quality of the sludge-based activated carbons was evaluated by established characterisation parameters for adsorption from solution such as phenol value, iodine number, methylene blue number and tannin value and compared with commercial activated carbons. Activation at 700,°C for 30,min in the presence of 0.5,cm3 H2SO4,g,1 dry solids in the sludge led to an activated carbon with a good capacity for iodine and tannic acid. The sludge-derived activated carbon obtained is mesoporous in nature with a high presence of large macropores. Weak and moderate acidic surface functional groups were detected on the surface, which impart a hydrophilic nature to the solid. When compared with a commercial activated carbon, the sludge-derived activated carbon performed better when removing dyes with a high presence of anionic solubilising groups and heavy metals. The results indicate that COD adsorption from a biologically-treated effluent may also be an area for application. © 2002 Society of Chemical Industry [source] Porosity and surface characteristics of activated carbons produced from waste tyre rubberJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2002Guillermo San Miguel Abstract Waste tyre rubber has proven to be a suitable precursor for the production of high quality activated carbons. The performance of these carbons in commercial applications such as water treatment or gas purification is highly dependent on their surface characteristics. This paper presents an in-depth investigation on how production conditions may affect the yield and characteristics of activated carbons produced from tyre rubber. For this purpose, three tyre rubbers of different particle sizes were consecutively pyrolysed and then activated in a steam atmosphere at 925,°C using a laboratory-scale rotary furnace. Activation was conducted at different intervals over 80,640,min to achieve different degrees of carbon burn-off. The resulting carbons were analysed for their elemental composition, ash content and nitrogen gas adsorption characteristics. The BET and t -plot models were used to investigate various aspects of their porosity and surface area characteristics. SEM analyses were also conducted for visual examination of the carbon surface. Results show that pyrolytic chars, essentially mesoporous materials, developed a very narrow microporosity during the initial stages of the activation process (up to 15,25,wt% burn-off). Further activation resulted in the progressive enlargement of the average micropore width and a gradual development of the mesoporous structure. Total micropore volumes and BET surface areas increased continuously with the degree of activation to reach values up to 0.498,cm3g,1 and 1070,m2g,1 respectively, while external surface areas developed more rapidly at degrees of activation above 45,wt% burn-off. Results presented in this work also illustrate that carbons produced from powdered rubber developed a narrower and more extensive porosity, both in the micropore and mesopore range, than those produced from rubber of a larger particle size. © 2001 Society of Chemical Industry [source] Structure, texture and surface acidity studies of a series of mixed zinc,aluminum (60,90 molar % Al) phosphate catalystsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2001Karim Mtalsi Abstract A series of mixed zinc,aluminum phosphate (ZnAlP) catalysts containing 40,90 aluminum molar % were synthesized by a coprecipitation method and characterized by nitrogen adsorption,desorption, X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature programmed desorption (TPD) of ammonia. The presence of aluminum greatly affected the surface properties of Zn3(PO4)2 by delaying the crystallization process of Zn3(PO4)2. All amorphous samples were shown to be mesoporous and they contained two types of aluminum surface hydroxyl groups and one type of phosphorus hydroxyl group, as shown by DRIFT spectra. The specific surface area and the acidity of ZnAlP increased on increasing the aluminum content. On the other hand, a great difference in the texture and the concentration of surface acid sites was found by changing the precipitating agent and calcination temperature. Thus these factors also play an important role in the final properties of these catalysts. © 2001 Society of Chemical Industry [source] Effect of metal-support interface on hydrogen permeation through palladium membranesAICHE JOURNAL, Issue 3 2009Ke Zhang Abstract Thin palladium membranes of different thicknesses were prepared on sol-gel derived mesoporous ,-alumina/,-alumina and yttria-stabilized zirconia/,-alumina supports by a method combining sputter deposition and electroless plating. The effect of metal-support interface on hydrogen transport permeation properties was investigated by comparing hydrogen permeation data for these membranes measured under different conditions. Hydrogen permeation fluxes for the Pd/,-Al2O3/,-Al2O3 membranes are significantly smaller than those for the Pd/YSZ/,-Al2O3 membranes under similar conditions. As the palladium membrane thickness increases, the difference in permeation fluxes between these two groups of membranes decreases and the pressure exponent for permeation flux approaches 0.5 from 1. Analysis of the permeation data with a permeation model shows that both groups of membranes have similar hydrogen permeability for bulk diffusion, but the Pd/,-Al2O3/,-Al2O3 membranes exhibit a much lower surface reaction rate constant with higher activation energy, due possibly to the formation of Pd-Al alloy, than the Pd/YSZ/,-Al2O3 membranes. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Increased gas solubility in nanoliquids: Improved performance in interfacial catalytic membrane contactorsAICHE JOURNAL, Issue 2 2009Marc Pera-Titus Abstract The kinetics of gas-liquid catalytic reactions can be strongly promoted when these are performed in interfacial catalytic membrane reactors instead of other three-phase reactors such as slurry stirrers or trickle beds. The well-defined gas-liquid-catalyst contact in this system avoiding diffusional limitations is usually argued as the main reason for such enhancement. In this work, using nitrobenzene hydrogenation as a model reaction, we propose that this increased catalytic performance might also be attributed, at least partially, to increased gas solubilities in mesoconfined solvents (or simply "nanoliquids") in interfacial contactors overcoming the values predicted by Henry's Law. To support this hypothesis, we provide experimental evidence of a dramatic increase of H2 solubility in confined ethanol using mesoporous ,-Al2O3 as confining solid. Gas-liquid solubilities can be enhanced up to five times over the corresponding bulk values for nanoliquid sizes lower than 15 nm as long as the gas-liquid interface is confined in a mesoporous array. In such a situation, the volume of the gas-liquid interface is no longer negligible compared to the total volume of the confined liquid, and the high surface excess concentrations of the gas adsorbed on the liquid surface make solubility grow up dramatically. According to these measurements, we discuss how nanoliquids might form in catalytic membrane contactors, which gas-liquid configuration in the reactor appears to be more appropriate, and how the structure of the mesoporous catalytic layer contributes to their increased gas solubilization performance. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Fast and Almost Complete Nitridation of Mesoporous Silica MCM-41 with Ammonia in a Plug-Flow ReactorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010Fumitaka Hayashi The title reaction proceeded well to yield silicon (oxy)nitride at 973,1323 K using a plug-flow reactor. The degree of nitridation was studied as a function of temperature and time of nitridation, the sample weight, and the flow rate of ammonia. It was dependent on the reaction temperature and the amount of ammonia supplied per sample weight. The nitridation at 1273 K for 10,25 h yielded the oxynitride with 36,39 wt% nitrogen, which was very close to 40 wt% of Si3N4. Characterization with X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy measurements, and nitrogen adsorption revealed the conversion of MCM-41 to the corresponding oxynitride without essential loss of the mesoporous structure, the decrements of the lattice constant and the pore diameter by 20,35%, and the increments of the wall thickness by ca. 45%. Solid-state 29Si nuclear magnetic resonance spectra during the nitridation clearly showed fast decrease in SiO4 species and slow in SiO3(OH). Various intermediate species, SiOxNy(NH2 or NH)z, were observed to be formed and finally, ca. 70% SiN4 species, ca. 20% SiN3(NH2 or NH), and ca. 10% SiON2(NH2 or NH) were produced, being consistent with the results of the above mentioned elemental analysis. [source] Chemical Synthesis of Nanocrystalline Strontium Bismuth Tantalate Powders Using Tantalum,Tartarate ComplexJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2006Asit Baran Panda Nanocrystalline strontium bismuth tantalate (SrBi2Ta2O9; SBT) powders have been synthesized through complete dehydration of an aqueous solution mixture of tantalum tartarate, strontium salt of ethylenediaminetetraacetic acid, and bismuth,triethanolamine complex. Single-step calcination of the fluffy, mesoporous, carbonaceous dehydrated precursor mass at 700°C/2 h results in nanosized SBT powders, with average particle size ,15 nm. When palletized and sintered at 950°C/4 h these powders show a relative density of 97.6% of theoretical value, and a maximum dielectric constant value of 1387 at Tc (Curie temperature)=279°C, when measured at 100 kHz. [source] Location-dependent controlled release kinetics of model hydrophobic compounds from mesoporous silicon/biopolymer composite fibersPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2009Dongmei Fan Abstract In this study, biodegradable mesoporous Si (BioSiliconTM) was loaded with cis-(2,2,-bipyridine) dichlororuthenium (II) (Ru complex) as a model hydrophobic compound. This ruthenium complex-loaded BioSiliconTM was either partially embedded on the surface of electrospun polycaprolactone (PCL) fibers or fully encapsulated within the fibers. To study release profiles in the above model delivery systems, porous Si/PCL constructs were soaked in DI water at 37 °C and the UV,Vis absorption spectrum of the supernatant was measured as a function of time. These results show that the Ru complex was released in a sustained manner over 7-day period. In addition, it is shown that the controlled-release of this complex depends on both the spatial location of the complex in the PCL fibrous scaffolds as well as the amount of Ru compound loaded in the mesoporous Si. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Porous silicon-based potentiometric biosensor for triglyceridesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2007S. Setzu Abstract In this paper we report on the fabrication and characterization of a potentiometric biosensor for the detection of triglycerides. This is constituted by a lipase immobilized on a mesoporous Si matrix. Prototypes, realized on 1 × 1 cm n+ -type silicon wafers, show a very high enzymatic activity. Moreover the properties of these biosensors have been shown to be stable in a several months time interval, clearly showing their advantages with respect to traditional triglycerides detection systems. The Michaelis Menten curve is obtained to demonstrate the absence of diffusion problems. Potentiometric measurements are also shown. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Si/SiO2 nanocomposite by CVD infiltration of porous SiO2PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005G. Amato Abstract The aim of the present paper is to report first results on an innovative method for producing Si/SiO2 nanocomposites. Starting from a porous oxide structure, we infiltrated Si by Chemical Vapour Deposition of SiH4, under controlled conditions. In this way, we succeeded in infiltrating Si into the SiO2 template. Porous oxide is obtained by dry oxidation of mesoporous Si. By means of the electrochemical process used for producing porous Si, an interconnected pore structure is obtained. This allows for Si infiltration, giving rise, in principle, to an interconnected network of Si crystallites, in which electrical carriers are easily driven. Efficient charge injection in Si nanocrystals is of crucial importance for several applications, from electroluminescence to memory devices. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of the OMCs pore structures on the capacitive performances of supercapacitorASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Gu-Zhen Nong Abstract In the present study, two mesoporous carbons OMC-KIT-6 and OMC-SBA-16 were nanocasted using mesoporous silica of KIT-6 and SBA-16 as templates and furfuryl alcohol as carbon precursor. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) characterizations confirmed that the resultant samples are mesoporous carbons, and the as-prepared OMC-KIT-6 has an Ia3d ordered structure, whereas OMC-SBA-16 belongs to Im3m space group. The surface area and the average pore size are (1658 m2 g,1 and 3.4 nm) for OMC-KIT-6 and (1638 m2 g,1 and 2.9 nm) for OMC-SBA-16, respectively. The results of cyclic voltammograms and galvanostatic charge-discharge tests show that these two mesoporous carbons have excellent capacitive performances. But the difference of capacitive behavior between OMC-KIT-6 and OMC-SBA-16 may be a result of the difference of pore geometries of these two carbons. In order to find out the function of mesopore in a supercapacitor, we compared the capacitive properties of mesoporous and microporous carbons; the experiment results indicated that these two kinds of carbon exhibit nearly ideal capacitive behavior at low scan rate. When the scan rate is enhanced up to 50 mV s,1 the performance of mesoporous carbon is more stable than microporous carbon. This outcome demonstrated that mesopore plays an important role in forming double layers in the electrode materials. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Selective extraction of polyunsaturated triacylglycerols using a novel ionic liquid precursor immobilized on a mesoporous complexing adsorbentBIOTECHNOLOGY PROGRESS, Issue 5 2009Patrisha J. Pham Abstract Mesoporous silica (SBA-15) synthesized by using Pluronic123 as the structure-directing template was functionalized by imidazolium-based ionic liquid precursors. Silver salts were then immobilized onto the supported ionic liquids using the incipient wetness impregnation technique. The separation of unsaturated species was achieved through the reversible and specific interaction between silver ions and carbon,carbon double bonds. This adsorbent was examined for the selective separation of polyunsaturated triacylglycerols (PUTAG) using High Pressure Liquid Chromatography (HPLC) with Evaporative Light Scattering Detection (ELSD) as the quantification methodology. AgBF4/SBA15·HPSiOEtIM·PF6 showed an adsorption capacity for linolenin of about 217 mg adsorbed/gram of sorbent. This adsorbent had good selectivity and a high capacity for the most highly unsaturated triacylglycerol when applied to a mixture of triacylglycerols with varying degrees of unsaturation. Consequently, a stepwise methodology was also developed to increase the recovery of the adsorbed components. This adsorbent retained its selectivity and capacity when recycled up to five times. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] | |||||||||||||||||||||||||||||||