High Surface Area (high + surface_area)

Distribution by Scientific Domains
Distribution within Chemistry

Selected Abstracts

Novel Method for Obtaining Corundum Layers of High Surface Area on Ceramic Supports for High-Temperature Catalysis

Alejandro Souto
The surface of an aluminosilicate ceramic was transformed to a corundum layer of high specific surface area by heating at 1300°,1450°C in a controlled reducing atmosphere. This procedure selectively reduced and volatilized the silica of the glass and mullite, and the alumina of the mullite formed a layer of corundum crystals with a thickness of ,20 ,m and a specific surface area of ,16 m2/g. Specific surface area remained stable at 10.5 m2/g after prolonged heating at 1300°C in air, and at 8.5 m2/g at 1450°C. These materials are well suited for use as catalyst supports in applications such as catalytic combustion at temperatures in this range. [source]

Targeted Synthesis of a Porous Aromatic Framework with High Stability and Exceptionally High Surface Area,

Teng Ben
Diamantenfieber: Ein Diamantgerüst, in dem C-C-Bindungen gegen Benzolringe ausgetauscht sind (siehe Bild), ist einerseits stabil und hat andererseits eine große innere Oberfläche. Das poröse aromatische Gerüst PAF-1 (Oberfläche 7100,m2,g,1) kann große Mengen an Wasserstoff und Kohlendioxid, Benzol- und Toluoldampf aufnehmen. [source]

High Surface Area, Mesoporous, Glassy Alumina with a Controllable Pore Size by Nanocasting from Carbon Aerogels

Wen-Cui Li Dr.
Abstract A strategy to synthesize amorphous, mesoporous alumina by nanocasting has been developed, involving carbon aerogel as a hard template and aluminum nitrate solution as an alumina precursor. The alumina generated exhibits small, transparent granules with a 3,6 mm diameter and has inherited the three-dimensional network structure of the carbon template. The mesopore surface area of the alumina can be as high as 365 m2,g,1, and the pore volume reaches 1.55 cm3,g,1 after calcination at 600,°C in air for 8 h. The pore parameters can be varied within a certain range by variation of the carbon aerogel template and the loading amount of the alumina precursor. At high loadings, the obtained glassy alumina clearly has a bimodal pore size distribution in the mesopore range. [source]

Mesoporous Anatase TiO2 Beads with High Surface Areas and Controllable Pore Sizes: A Superior Candidate for High-Performance Dye-Sensitized Solar Cells

Dehong Chen
Mesoporous anatase TiO2 beads with high surface areas and controllable pore sizes are prepared by using a combined sol,gel and solvothermal process. Dye-sensitized solar cells made from these mesoporous beads gave a total power conversion efficiency of 7.20% under AM 1.5 sunlight, higher than that obtained using Degussa P25 films of similar thickness (5.66%). [source]

Graphene Based Electrochemical Sensors and Biosensors: A Review

Yuyan Shao
Abstract Graphene, emerging as a true 2-dimensional material, has received increasing attention due to its unique physicochemical properties (high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and mass production). This article selectively reviews recent advances in graphene-based electrochemical sensors and biosensors. In particular, graphene for direct electrochemistry of enzyme, its electrocatalytic activity toward small biomolecules (hydrogen peroxide, NADH, dopamine, etc.), and graphene-based enzyme biosensors have been summarized in more detail; Graphene-based DNA sensing and environmental analysis have been discussed. Future perspectives in this rapidly developing field are also discussed. [source]

Novel negatively charged tentacle-type polymer coating for on-line preconcentration of proteins in CE

Liang Xu
Abstract A novel negatively charged tentacle-type polymer-coated capillary column was fabricated and applied for on-line extraction and preconcentration of proteins. The polymer coating was prepared by glycidyl-methacrylate graft polymerization in a silanized capillary column and the following sulfonic acid group functionalization. It had high surface area and offered high phase ratio for protein adsorption. In addition, the polymer-coated capillary column provided more stable EOF than a bare uncoated capillary. These features of the polymer coating facilitated the extraction of proteins through electrostatic interactions. This was used to extract proteins. The extracted analytes were then desorbed and focused by EOF in the direction opposite to the sample injection flow for subsequent CE. With this procedure, over 1500-fold sensitivity enhancement was realized for myoglobin (MB) as compared with a normal capillary zone electrophoresis. By comparison of the peak areas of the enriched protein, it was found that the polymer-coated column could capture proteins about 30 times more than the uncoated column. In addition, the separation of a protein mixture containing 0.4,,g/mL of MB and 0.4,,g/mL of insulin was demonstrated by the on-line preconcentration and electrophoretic separation with the polymer-coated column. [source]

High-Zirconium-Content Nano-Sized Bimodal Mesoporous Silicas

David Ortiz de Zárate
Abstract Silica-based nanoparticulated bimodal mesoporous materials with high Zr content (43 , Si/Zr , 4) have been synthesized by a one-pot surfactant-assisted procedure from a hydroalcoholic medium using a cationic surfactant (CTMABr = cetyltrimethylammonium bromide) as structure-directing agent, and starting from molecular atrane complexes of Zr and Si as hydrolytic inorganic precursors. This preparative technique allows optimization of the dispersion of the Zr guest species in the silica walls. The bimodal mesoporous nature of the final high surface area nano-sized materials is confirmed by XRD, TEM, and N2 adsorption,desorption isotherms. The small intraparticle mesopore system (with pore sizes around 2,3 nm) is due to the supramolecular templating effect of the surfactant, while the large mesopores (around 12,24 nm) have their origin in the packing voids generated by aggregation of the primary nanometric mesoporous particles. The basicity of the reaction medium seems to be a key parameter in the definition of this last pore system. The effects induced by the progressive incorporation of Zr atoms on the mesostructure have been examined, and the local environment of the Zr sites in the framework has been investigated by UV/Vis spectroscopy. Observations based on the consequences of post-treatments of the as-synthesized materials with HCl/ethanol mixtures corroborate that the atrane method leads to Zr-rich materials showing enhanced site accessibility and high chemical homogeneity throughout the pore walls. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Enhanced Photocatalytic Activity using Layer-by-Layer Electrospun Constructs for Water Remediation

Jung Ah Lee
Abstract Endocrine disruptors such as bisphenol A (BPA) are environmental pollutants that interfere with the body's endocrine system because of their structural similarity to natural and synthetic hormones. Due to their strong oxidizing potential to decompose such organic pollutants, colloidal metal oxide photocatalysts have attracted increasing attention for water detoxification. However, achieving both long-term physical stability and high efficiency simultaneously with such photocatalytic systems poses many challenges. Here a layer-by-layer (LbL) deposition approach is reported for immobilizing TiO2 nanoparticles (NPs) on a porous support while maintaining a high catalytic efficiency for photochemical decomposition of BPA. Anatase TiO2 NPs ,7,nm in diameter self-assemble in consecutive layers with positively charged polyhedral oligomeric silsesquioxanes on a high surface area, porous electrospun polymer fiber mesh. The TiO2 LbL nanofibers decompose approximately 2.2,mg BPA per mg of TiO2 in 40,h of illumination (AM 1.5G illumination), maintaining first-order kinetics with a rate constant (k) of 0.15,h,1 for over 40,h. Although the colloidal TiO2 NPs initially show significantly higher photocatalytic activity (k,,,0.84,h,1), the rate constant drops to k,,,0.07,h,1 after 4,h of operation, seemingly due to particle agglomeration. In the BPA solution treated with the multilayered TiO2 nanofibers for 40,h, the estrogenic activity, based on human breast cancer cell proliferation, is significantly lower than that in the BPA solution treated with colloidal TiO2 NPs under the same conditions. This study demonstrates that water-based, electrostatic LbL deposition effectively immobilizes and stabilizes TiO2 NPs on electrospun polymer nanofibers for efficient extended photochemical water remediation. [source]

Dual-Function Scattering Layer of Submicrometer-Sized Mesoporous TiO2 Beads for High-Efficiency Dye-Sensitized Solar Cells

Fuzhi 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]

High Performance Carbon-Supported Core@Shell PdSn@Pt Electrocatalysts for Oxygen Reduction Reaction

FUEL CELLS, Issue 4 2010
W. Zhang
Abstract In this report, a low-cost and high performance PdSn@Pt/C catalyst with core,shell structure is prepared by two-stage route. X-ray diffraction (XRD) and transmission electron microscopy (TEM) examinations show that the composite catalyst particles distribution is quite homogeneous and has a high surface area and the PdSn@Pt/C catalyst has an average diameter of ca. 5.6,nm. The oxygen reduction reaction (ORR) activity of PdSn@Pt/C was higher than commercial Pt/C catalyst. Catalytic activity is studied by cyclic voltammetry. High electrocatalytic activities could be attributed to the synergistic effect between Pt and PdSn. [source]

Design and Synthesis of Hierarchical Nanowire Composites for Electrochemical Energy Storage

Zheng Chen
Abstract Nanocomposites of interpenetrating carbon nanotubes and vanadium pentoxide (V2O5) nanowires networks are synthesized via a simple in situ hydrothermal process. These fibrous nanocomposites are hierarchically porous with high surface area and good electric conductivity, which makes them excellent material candidates for supercapacitors with high energy density and power density. Nanocomposites with a capacitance up to 440 and 200,F g,1 are achieved at current densities of 0.25 and 10 A g,1, respectively. Asymmetric devices based on these nanocomposites and aqueous electrolyte exhibit an excellent charge/discharge capability, and high energy densities of 16,W h kg,1 at a power density of 75,W kg,1 and 5.5,W h kg,1 at a high power density of 3,750,W kg,1. This performance is a significant improvement over current electrochemical capacitors and is highly competetive with Ni,MH batteries. This work provides a new platform for high-density electrical-energy storage for electric vehicles and other applications. [source]

Catalyst-Free Efficient Growth, Orientation and Biosensing Properties of Multilayer Graphene Nanoflake Films with Sharp Edge Planes,

Nai Gui Shang
Abstract We report a novel microwave plasma enhanced chemical vapor deposition strategy for the efficient synthesis of multilayer graphene nanoflake films (MGNFs) on Si substrates. The constituent graphene nanoflakes have a highly graphitized knife-edge structure with a 2,3,nm thick sharp edge and show a preferred vertical orientation with respect to the Si substrate as established by near-edge X-ray absorption fine structure spectroscopy. The growth rate is approximately 1.6,µm min,1, which is 10 times faster than the previously reported best value. The MGNFs are shown to demonstrate fast electron-transfer (ET) kinetics for the Fe(CN)63,/4, redox system and excellent electrocatalytic activity for simultaneously determining dopamine (DA), ascorbic acid (AA) and uric acid (UA). Their biosensing DA performance in the presence of common interfering agents AA and UA is superior to other bare solid-state electrodes and is comparable only to that of edge plane pyrolytic graphite. Our work here, establishes that the abundance of graphitic edge planes/defects are essentially responsible for the fast ET kinetics, active electrocatalytic and biosensing properties. This novel edge-plane-based electrochemical platform with the high surface area and electrocatalytic activity offers great promise for creating a revolutionary new class of nanostructured electrodes for biosensing, biofuel cells and energy-conversion applications. [source]

Infiltration pattern in a regolith,fractured bedrock profile: field observation of a dye stain pattern

Jae Gon Kim
Abstract We examined the infiltration pattern of water in a regolith,bedrock profile consisting of two overburdens (OB1 and OB2), a buried rice paddy soil (PS), two texturally distinctive weathered materials (WM1 and WM2) and a fractured sedimentary rock (BR), using a Brilliant Blue FCF dye tracer. A black-coloured coating in conducting fractures in WM1, WM2 and BR was analysed by X-ray diffraction and scanning electron microscopy. The dye tracer penetrated to greater than 2 m depth in the profile. The macropore flow and saturated interflow were the major infiltration patterns in the profile. Macropore flow and saturated interflow were observed along fractures in WM1, WM2 and BR and at the dipping interfaces of PS,WM1, PS,WM2 and PS,BR respectively. Heterogeneous matrix flow occurred in upper overburden (OB1) and PS. Compared with OB1, the coarser textured OB2 acted as a physical barrier for vertical flow of water. The PS with low bulk density and many fine roots was another major conducting route of water in the profile. Manganese oxide and iron oxide were positively identified in the black coating material and had low crystallinity and high surface area, indicating their high reactivity with conducting contaminants. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Self-Assembly of Ordered Semiconductor Nanoholes by Ion Beam Sputtering

Qiangmin Wei
Periodic nanohole arrays are formed on a Ge substrate by self-assembly using focused ion beam sputtering at normal incidence with an energy of 5,keV. The figure shows an SEM image of a hexagonally ordered hole domain that has hexagonally ordered quantum dots,20,nm diameter and 3,nm height,around each hole The structured Ge has high surface area and a considerably blue-shifted energy gap. [source]

Synthesis and Catalytic Applications of Self-Assembled Carbon Nanofoams,

J. García-Martínez
A new surfactant-templated carbon material, carbon nanofoam (CNF), has been synthesized with a semicrystalline and conductive framework, high surface area and interconnected porous structure, and prepared in a wide variety of bulk shapes and forms. CNF was also successfully applied as a support for palladium in the Heck coupling reaction. Pd/CNF catalyst exhibited negligible Pd cluster growth and agglomeration, and retained high activity even after multiple runs. [source]

Comparison of performance of heat regenerators: Relation between heat transfer efficiency and pressure drop

Françoise Duprat
Abstract Heat regenerators transfer heat from one gas to another, with an intermediate storage in solids. The heat transfer surface for gas flow application should provide at the same time high surface area and low friction factor. Three geometries of heat transfer surface, monolith, stack of woven screens and bed of spheres, have been compared. Their performance was evaluated from the pressure drop of the heat regenerator working at a given heat transfer efficiency. The comparison was performed using numerical simulation and published measurements of heat transfer and flow friction characteristics. By adjusting the length and the period of the exchanger, it is possible to obtain the same heat transfer efficiency with the three geometries. Beds of spheres give very short and compact heat regenerators, working at high pressure drop. At the opposite, monoliths form long regenerators working at low pressure drop. Stacks of woven screens cover a wide range of performance: low porosity woven screens give high heat transfer efficiency and high pressure drop, while high porosity woven screens offer performance similar to that of the monoliths. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Silica-Templated Continuous Mesoporous Carbon Films by a Spin-Coating Technique ,

J. Pang
Continuous mesoporous carbon thin films (see Figure) have been synthesized through direct carbonization of sucrose/silica nanocomposite films and subsequent removal of the silica to create a mesoporous carbon network. This method provides a simple and efficient method to synthesize continuous, high surface area and pore volume mesoporous carbon thin films with uniform-sized and interconnected pore channels. [source]

Kinetics of adsorption of 2-CEES and HD on impregnated silica nanoparticles under static conditions

AICHE JOURNAL, Issue 5 2009
Amit Saxena
Abstract Silica nanoparticles of high surface area (887.3 m2/g) were synthesized using aerogel route and, thereafter, impregnated with those reactive chemicals, which have already been proven to be effective against sulfur mustard (HD). Thus, developed adsorbents were tested for their potential by conducting studies on kinetics of adsorption of 2-chloroethylethyl sulfide (2-CEES) and HD under static conditions. Kinetics of adsorption was studied using linear driving force model and Fickian diffusion model. The kinetic parameters such as equilibration constant, equilibration capacity, diffusional exponent, and adsorbate-adsorbent interaction constant were also determined. Trichloroisocyanuric acid impregnated silica nanoparticles (10% w/w) showed the maximum uptake of 2-CEES (1824 mg/g) and HD (1208 mg/g). Values of diffusional exponent indicated the mechanisms to be Fickian and anomalous. Chemical interaction seemed to be another mechanism involved in the toxicant uptake rate. Hydrolysis, dehydrochlorination, and oxidation reactions were found to be the route of degradation of toxicants. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Modeling of air separation in a LSCF hollow-fiber membrane module

AICHE JOURNAL, Issue 7 2002
Xiaoyao Tan
Mixed ion-conducting ceramic membranes are promising in oxygen separation from air due to their infinite permselectivity. Hollow-fiber-shaped membranes can provide a high surface area for such an application. A mathematical model for a hollow-fiber La0.6Sr0.4Co0.2F0.8O3,,(LSCF) membrane module for air separation was developed and a performance of the module at various operating conditions was studied theoretically. The simulation results reveal that the cocurrent is a better operating flow pattern than the countercurrent flow pattern. The vacuum operation on the lumen side of the membrane module is preferable to the elevated pressure operation on the shell side for achieving high oxygen productivity. A high vacuum level and a desired membrane area are essential to produce the pure oxygen and nitrogen simultaneously. Experimental results and kinetic parameters in the literature obtained from the LSCF membrane for air separation agreed satisfactorily with the theoretical solutions. [source]

An investigation into the mechanism of dissolution rate enhancement of poorly water-soluble drugs from spray chilled gelucire 50/13 microspheres

Sheng Qi
Abstract The production and physicochemical characterisation of spray chilled Gelucire 50/13 microspheres is described with a view to improving the dissolution of a poorly water-soluble drug, piroxicam, and understanding the fundamental mechanisms associated with the improved drug release. Thermorheological testing was developed as a fast screening method for predicting the processability of dispersions for spray chilling preparation. Spray chilled piroxicam loaded microspheres were spherical in shape with a median diameter of circa 150,µm. DSC indicated no interaction between piroxicam and lipid matrix, while HSM studies performed in polarized light mode indicated that the spheres contained distinct drug crystals. Polarising light microscopy and small-angle XRD investigations on the hydration behaviour of the lipid and the spray chilled microspheres revealed the formation of liquid crystalline phases depending on the degree of hydration. The dissolution behaviour of the piroxicam loaded microspheres showed significant improvements compared to drug alone. The particle size, drug loading and aging of the microspheres were all found to have an influence on the release behaviour. It was proposed that Gelucire 50/13 microspheres release the entrapped piroxicam via formation of a lyotropic liquid crystalline phase, which allows dissolution of the drug particles in a finely divided, high surface area and well-wetted state. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:262,274, 2010 [source]

Spherical ordered mesoporous silicas and silica monoliths as stationary phases for liquid chromatography

Anne Galarneau
Abstract Ordered mesoporous silicas such as micelle-templated silicas (MTS) feature unique textural properties in addition to their high surface area (,1000 m2/g): narrow mesopore size distributions and controlled pore connectivity. These characteristics are highly relevant to chromatographic applications for resistance to mass transfer, which has never been studied in chromatography because of the absence of model materials such as MTS. Their synthesis is based on unique self-assembly processes between surfactants and silica. In order to take advantage of the perfectly adjustable texture of MTS in chromatographic applications, their particle morphology has to be tailored at the micrometer scale. We developed a synthesis strategy to control the particle morphology of MTS using the concept of pseudomorphic transformation. Pseudomorphism was recognized in the mineral world to gain a mineral that presents a morphology not related to its crystallographic symmetry group. Pseudomorphic transformations have been applied to amorphous spherical silica particles usually used in chromatography as stationary phases to produce MTS with the same morphology, using alkaline solution to dissolve progressively and locally silica and reprecipitate it around surfactant micelles into ordered MTS structures. Spherical beads of MTS with hexagonal and cubic symmetries have been synthesized and successfully used in HPLC in fast separation processes. MTS with a highly connected structure (cubic symmetry), uniform pores with a diameter larger than 6 nm in the form of particles of 5 ,m could compete with monolithic silica columns. Monolithic columns are receiving strong interest and represent a milestone in the area of fast separation. Their synthesis is a sol-gel process based on phase separation between silica and water, which is assisted by the presence of polymers. The control of the synthesis of monolithic silica has been systematically explored. Because of unresolved yet cladding problems to evaluate the resulting macromonoliths in HPLC, micromonoliths were synthesized into fused-silica capillaries and evaluated by nano-LC and CEC. Only CEC allows to gain high column efficiencies in fast separation processes. Capillary silica monolithic columns represent attractive alternatives for miniaturization processes (lab-on-a chip) using CEC. [source]

Preparation of Porous Tin Oxide Nanobelts Using the Electrospinning Technique

An Yang
The electrospinning method is adopted to prepare utralong PEO/stannic hydroxide composite nanofibers. Tin-oxide nanobelts can be obtained by calcination of the composite nanofibers in an open atmosphere. The nanobelts were characterized by a field emission scanning electron microscope, X-ray diffraction, a transmission electron microscope, a Raman spectromicroscope, and Fourier transform infrared spectroscopy. Microstructural analysis has shown that the nanobelts prepared consist of a continuous network of interconnected SnO2 grains. As a result, the SnO2 nanobelts possess a high surface area and continuous porosity, which may be applied for the fabrication of sensitive gas sensors. [source]

Effect of Nano-Aluminum and Fumed Silica Particles on Deflagration and Detonation of Nitromethane

Abstract The heterogeneous interaction between nitromethane (NM), particles of nanoscale aluminum (38 and 80,nm diameter), and fumed silica is examined in terms of the deflagration and detonation characteristics. Burning rates are quantified as functions of pressure using an optical pressure vessel up to 14.2,MPa, while detonation structure is characterized in terms of failure diameter. Nitromethane is gelled using fumed silica (CAB-O-SIL®), as well as by the nanoaluminum particles themselves. Use of nanoaluminum particles with fumed silica slightly increases burning rates compared to the use of larger diameter Al particles; however distinct increases in burning rates are found when CAB-O-SIL is removed and replaced with more energetic aluminum nanoparticles, whose high surface area allows them to also act as the gellant. Mixtures including fumed silica yield a reduced burning rate pressure exponent compared to neat NM, while mixtures of aluminum particles alone show a significant increase. Failure diameters of mixture detonations are found to vary significantly as a function of 38,nm aluminum particle loading, reducing more than 50% from that of neat nitromethane with 12.5% (by mass) aluminum loading. Failure diameter results indicate a relative minimum with respect to particle separation (% loading) which is not observed in other heterogeneous mixtures. [source]

Real-time measurement of protein leaching from micro-particulate larval fish feeds

Peter M Nicklason
Abstract The small size and high surface area to volume ratio of larval fish feed presents challenges for nutrient retention in micro-particulate diets. A method for the accurate and rapid measurement of nutrient retention or loss from micro-particulate feed in water is needed to help develop micro-particulate feeds with good nutrient retention characteristics. The present study developed and validated an instrument method using fibre optic technology that measures protein leaching in real time. Larval fish feed particles of different sizes (100,500 ,m) and formulations were measured. Under consistent experimental conditions, a feed could be assayed for the rate of mass loss and the half-life or time of 50% total soluble mass loss. The results closely approximated natural decay models with coefficients of determination (r2) >0.95. The end result is a fast and accurate method to quantify and provide solid reference data for a feed formulation or particle size. Using this method allows different feeds to be compared and conclusions drawn for relative performance. [source]

Progress toward a biomimetic leaf: 4,000 h of hydrogen production by coating-stabilized nongrowing photosynthetic Rhodopseudomonas palustris

Jimmy L. Gosse
Abstract Intact cells are the most stable form of nature's photosynthetic machinery. Coating-immobilized microbes have the potential to revolutionize the design of photoabsorbers for conversion of sunlight into fuels. Multi-layer adhesive polymer coatings could spatially combine photoreactive bacteria and algae (complementary biological irradiance spectra) creating high surface area, thin, flexible structures optimized for light trapping, and production of hydrogen (H2) from water, lignin, pollutants, or waste organics. We report a model coating system which produced 2.08 ± 0.01 mmol H2 m,2 h,1 for 4,000 h with nongrowing Rhodopseudomonas palustris, a purple nonsulfur photosynthetic bacterium. This adhesive, flexible, nanoporous Rps. palustris latex coating produced 8.24 ± 0.03 mol H2 m,2 in an argon atmosphere when supplied with acetate and light. A simple low-pressure hydrogen production and trapping system was tested using a 100 cm2 coating. Rps. palustris CGA009 was combined in a bilayer coating with a carotenoid-less mutant of Rps. palustris (CrtI,) deficient in peripheral light harvesting (LH2) function. Cryogenic field emission gun scanning electron microscopy (cryo-FEG-SEM) and high-pressure freezing were used to visualize the microstructure of hydrated coatings. A light interaction and reactivity model was evaluated to predict optimal coating thickness for light absorption using the Kubelka-Munk theory (KMT) of reflectance and absorptance. A two-flux model predicted light saturation thickness with good agreement to observed H2 evolution rate. A combined materials and modeling approach could be used for guiding cellular engineering of light trapping and reactivity to enhance overall photosynthetic efficiency per meter square of sunlight incident on photocatalysts. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source]

Structural Evolvement of Heating Treatment of Mg/Al-LDH and Preparation of Mineral Mesoporous Materials

CHEN Tianhu
Abstract, Although hydrotalcite, or layered double hydroxides (LDHs), is not a common mineral, it is an important material that can be easily synthesized in laboratory. In this study, structural evolvement and BET surface area changes of heat treated Mg/Al-LDH is evaluated by XRD, TEM and N2 -BET analyses. The results indicate that the magnesium-aluminum LDH with carbonate as interlayer anion, periclase-like oxides was formed at temperatures of 400,800°C. Meanwhile, 2,3 nanometer mesoporous were formed during decomposition of LDH. However, the heat treated samples still preserve the morphology of the original LDH plates. Periclase-like formed from LDH heat treatment may re-hydrolyze and recover the structure of LDH. However, crystallinity of the recovered LDH is lower than that of the original LDH. This heat treatment will result in formation of (Mg, Al)-oxide nano-crystals and nanopores among the nano-crystals. When heating temperature exceeds 1000, the periclase-like (Mg, Al)-oxide is transformed into a composite with periclase (MgO) and spinel phases. The periclase can be re-hydrolyzed and dissolved in HCI solution. After acid treatment, the sample with a high surface area is composed of spinel nano-crystals and nanopores among them. Our results will provide a new and economic way to synthesize mesoporous materials through pathways of phase transformation of precursor materials with different composition. [source]

Self-Assembling of Er2O3,TiO2 Mixed Oxide Nanoplatelets by a Template-Free Solvothermal Route

Beatriz Julián-López Dr.
Abstract An easy solvothermal route has been developed to synthesize the first mesoporous Er2O3,TiO2 mixed oxide spherical particles composed of crystalline nanoplatelets, with high surface area and narrow pore size distribution. This synthetic strategy allows the preparation of materials at low temperature with interesting textural properties without the use of surfactants, as well as the control of particle size and shape. TEM and Raman analysis confirm the formation of nanocrystalline Er2O3,TiO2 mixed oxide. Mesoscopic ordered porosity is reached through the thermal decomposition of organic moieties during the synthetic process, thus leading to a template-free methodology that can be extended to other nanostructured materials. High specific surface areas (up to 313,m2,g,1) and narrow pore size distributions are achieved in comparison to the micrometric material synthesized by the traditional sol,gel route. This study opens new perspectives in the development, by solvothermal methodologies, of multifunctional materials for advanced applications by improving the classical pyrochlore properties (magnetization, heat capacity, catalysis, conductivity, etc.). In particular, since catalytic reactions take place on the surface of catalysts, the high surface area of these materials makes them promising candidates for catalysts. Furthermore, their spherical morphology makes them appropriate for advanced technologies in, for instance, ceramic inkjet printers. [source]

TiO2 -Modified Macroporous Silica Foams for Advanced Enrichment of Multi-Phosphorylated Peptides

Jingjing Wan
Abstract Enriching peptides: Novel TiO2 -modified macroporous materials (Ti-MOSF, see figure) have been synthesized with high surface area, large pore volume, and functional surfaces that are rich in coordinatively unsaturated TiIV species, which can be applied in the specific extraction of phosphopeptides and which show a preferential capture of multi-phosphorylated peptides with low detection limits and high selectivity. [source]

Oriented Nanostructures for Energy Conversion and Storage

Jun Liu Dr.
Abstract Recently, the role of nanostructured materials in addressing the challenges in energy and natural resources has attracted wide attention. In particular, oriented nanostructures demonstrate promising properties for energy harvesting, conversion, and storage. In this Review, we highlight the synthesis and application of oriented nanostructures in a few key areas of energy technologies, namely photovoltaics, batteries, supercapacitors, and thermoelectrics. Although the applications differ from field to field, a common fundamental challenge is to improve the generation and transport of electrons and ions. We highlight the role of high surface area to maximize the surface activity and discuss the importance of optimum dimension and architecture, controlled pore channels, and alignment of the nanocrystalline phase to optimize the transport of electrons and ions. Finally, we discuss the challenges in attaining integrated architectures to achieve the desired performance. Brief background information is provided for the relevant technologies, but the emphasis is focused mainly on the nanoscale effects of mostly inorganic-based materials and devices. [source]

Thermally Stable Nanocrystalline Mesoporous Gallium Oxide Phases

Chinmay A. Deshmane
Abstract Semicrystalline and fully crystalline mesoporous galliumoxide phases were synthesized in the presence of ionic and non-ionic structure directing agents via Evaporation-Induced Self-Assembly (EISA) and Self-Assembly Hydrothermal-Assisted (SAHA) methods respectively. EISA led to partially crystalline mesoporous gallium oxide phases displaying unimodal pore size distribution in the range of ca. 2,5 nm and surface areas as high as 300 m2/g. SAHA led to nanocrystalline mesoporous uniform micron-sized gallium oxide spheres (ca. 0.3,6.5 ,m) with narrow size distribution displaying cubic spinel type structure. These mesophases displayed surface areas as high as ca. 221 m2/g and unimodal pore size distribution in the 5,15 nm range. Textural properties such as surface areas and pore sizes were effectively fine-tuned by the nature and relative concentration of the structure directing agents. Due to their high surface areas, tunability of pore sizes and the nature of the wall structure, these gallium oxide mesophases could find potential applications as heterogeneous catalysts.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]