2010 3rd International Nanoelectronics Conference (INEC), 2010
ABSTRACT Porous materials with hierarchical bimodal pore size distributions are a special type of... more ABSTRACT Porous materials with hierarchical bimodal pore size distributions are a special type of nanomaterials and have important applications in a wide variety of fields such as separation, catalysis, adsorption, and sensing. Here we present an exploratory study on the fabrication of hierarchically ordered porous silica membranes by a templating method. The obtained membranes have ordered hierarchical nanopore array structures with controlled pore size and large surface area.
Gas storage in a safe and economical way is an important aspect of modern life. This study report... more Gas storage in a safe and economical way is an important aspect of modern life. This study reports on the behavior of the zeolite potassium chabazite (Si/Al = 2.2) as a nanocontainer to store N 2 and CH 4 by a temperature controlled nanovalve. We reveal the effect of ...
Ordered mesostructured tungsten carbide and graphitic carbon composites (WC/C) with nanocrystalli... more Ordered mesostructured tungsten carbide and graphitic carbon composites (WC/C) with nanocrystalline walls are fabricated for the first time by a temperature‐programmed carburization approach with phosphotungstic acid (PTA) as a precursor and mesoporous silica materials as hard templates. The mesostructure, crystal phase, and amount of deposited graphitic carbon can be conveniently tuned by controlling the silica template (SBA‐15 or KIT‐6), carburizing temperature (700–1000 °C), the PTA‐loading amount, and the carburizing atmosphere (CH4 or a CH4/H2 mixture). A high level of deposited carbon is favorable for connecting and stabilizing the WC nanocrystallites to achieve high mesostructural regularity, as well as promoting the carburization reaction. Meanwhile, large pore sizes and high mesoporosity of the silica templates can promote WC‐phase formation. These novel, ordered, mesoporous WC/C nanocomposites with high surface areas (74–169 m2 g−1), large pore volumes (0.14–0.17 cm3 g−1),...
Lanthanum phosphate (LaPO 4) nanostructures with different morphologies were prepared by a facile... more Lanthanum phosphate (LaPO 4) nanostructures with different morphologies were prepared by a facile solution–precipitation process. The effect of different reaction conditions on the morphology of nanostructures was studied. When the molar ratio of La 3+: H 3 PO 4 was around 1: 2, 1: 20, 1: 100, and 1: 200, four different morphologies, such as near-spherical, snowflake-like, star-shaped, lens-like nanostructures and short nanorods, were obtained, respectively. Meanwhile, similar shapes developed when the molar ratio of H 3 PO 4 to ...
ABSTRACT Large-pore periodic mesoporous organosilica (PMO) hollow spheres with controllable pore ... more ABSTRACT Large-pore periodic mesoporous organosilica (PMO) hollow spheres with controllable pore size and high pore volume (2.5 cm3 g−1) were successfully synthesized at low-temperature (∼15 °C) by using the triblock copolymer Pluronic F127 as a template and 1,3,5-trimethylbenzene (TMB) as a swelling agent in the presence of inorganic salt (KCl). Transmission electron microscopy (TEM) measurements show that the PMO hollow spheres are uniform and well dispersed, and the composites have a large wall thickness. The influence of TMB, KCl, CTAB contents and media acidity on the mesostructure was systematically studied. The pore size (9.8–15.1 nm) of the hollow spheres can be gradually expanded by increasing TMB content together with a relatively high acidity. By controlling the content of CTAB, successive structural transformation from hollow sphere to wormlike mesostructure and eventually to ordered body-centered cubic (space group of Im-3m) mesostructure is observed. Our results reveal that the hydrophobicity of bis(triethoxysilyl)ethane (BTSE) and low-temperature approach contribute to the slow hydrolysis rate of silica precursors, which leads to weak interaction between individual TMB/F127 micelles and silicate oligomers. Furthermore, the salting-out effect of KCl may influence the swelling capacity of individual micelles as well as decrease the critical micelle concentration and critical micelle temperature, resulting in the formation of PMO hollow spheres from the assembly of individual TMB/F127 micelles with silicate oligomers. The composites exhibit efficient adsorption capacity (703 mg g−1) for toluene, suggesting they are a potentially useful adsorbent for removal of volatile organic compounds. The PMO hollow spheres allow biomolecules with large molecular weight to diffuse in, and show superior encapsulation capacity of bovine serum albumin (BSA) molecules (∼585 mg g−1) over other porous materials.
Ordered micro-porous carbon molecular sieves containing highly dispersed platinum nanoparticles w... more Ordered micro-porous carbon molecular sieves containing highly dispersed platinum nanoparticles with tunable sizes from 1 to 6nm are synthesized in this work. The synthesis is simply realized by nanocasting of furfuryl alcohol precursor on Pt-impregnated NaY zeolite hard templates and complemented by chemical vapor deposition by propylene gas. During the carbonization, Pt ions can be reduced to form highly dispersed Pt nanoparticles on the carbon matrixes. This method allows a very high Pt-loading up to 40wt % while maintaining a high metal dispersion. X-ray diffraction and transmission electron microscopy measurements reveal the existence of uniformly dispersed Pt nanoparticles and microstructural regularity. Nitrogen adsorption isotherms show that the ordered micro-porous carbon molecular sieves possess a high surface area around 2750m2/g, large micro-pore volume 1.38cm3/g, and narrow pore size distribution (∼1nm) in the micropore-range. A high hydrogen uptake up to 2.8wt% at 77K and 1bar is observed. A high and relatively homogeneous value of hydrogen adsorption heat 11kJ/mol in 1% Pt contained carbon was obtained, which exceeds the literature reported values for other carbon based adsorbents or metal organic framework compounds and is very close to the optimal value, 15kJ/mol, recommended in the literature, suggesting a great potential for hydrogen storage or fuel cell applications.
Bulk synthesis of hollow carbon stacked-cone-helices of diameter from 10 nm to 0.5 μm is reported... more Bulk synthesis of hollow carbon stacked-cone-helices of diameter from 10 nm to 0.5 μm is reported. The fibres' walls are made up of parallel stacked-cone-like structures with an inter-cone distance from 3.38 to 3.5 Å. Apex angles observed are in the range from 30° to 110°, ...
Novel one dimensional (1D) nanostructured metallic electrodes have received much attention in the... more Novel one dimensional (1D) nanostructured metallic electrodes have received much attention in the area of the fuel cell because of their extremely high surface-to-volume ratios and excellent activities. Here, we report the one-step fabrication of Pt–Cu alloy nanotube ...
Accurate numerical solution of cyclic adsorption problems can be challenging and time consuming d... more Accurate numerical solution of cyclic adsorption problems can be challenging and time consuming due to the inherent non-linearity of the system conservation equations and the presence of strong temporal and spatial gradients. In addition, the wide variety of possible boundary conditions makes solution of a general cycle problematic. In this study we present a quadratic upwind finite volume technique that is at least second-order accurate in the spatial dimension and can easily handle any type of boundary condition (both one and two point) at either end of the adsorption column. The effect of bed pressure drop is readily accommodated. The oscillations at sharp gradients common in high-order upwind methods is significantly reduced by a solution-adaptive strategy which does not introduce significant diffusion unlike first order upwind methods. To ensure accurate simulation of sharp fronts, we find that the finite volume node width should be approximately one tenth of the width of the mass transfer zone. A comparison is made for linear isotherm systems with the analytic solution and excellent agreement is produced for very moderate grid sizing. The method is fast and robust and is ideally suited to cycle simulation.
Nanochannel alumina templates are used as templates for fabrication of porous gold nanowire array... more Nanochannel alumina templates are used as templates for fabrication of porous gold nanowire arrays by a direct electrodeposition method. After modification with glucose oxidase, a porous gold nanowire‐array electrode is shown to be an excellent electrochemical biosensor for the detection of glucose. The picture shows an SEM image of a nanowire array after removal of the alumina template by acid dissolution.magnified imageWe report the fabrication of porous gold nanowire arrays by means of a one‐step electrodeposition method utilizing nanochannel alumina templates. The microstructure of gold nanowires depends strongly on the current density. The formation of porous gold nanowires is attributed to disperse crystallization under conditions of low nucleation rate. Interfacial electron transport through the porous gold nanowires is studied by electrochemical impedance spectroscopy. Cyclic voltammetric studies on the porous gold nanowire arrays reveal a low‐potential electrocatalytic resp...
2010 3rd International Nanoelectronics Conference (INEC), 2010
ABSTRACT Porous materials with hierarchical bimodal pore size distributions are a special type of... more ABSTRACT Porous materials with hierarchical bimodal pore size distributions are a special type of nanomaterials and have important applications in a wide variety of fields such as separation, catalysis, adsorption, and sensing. Here we present an exploratory study on the fabrication of hierarchically ordered porous silica membranes by a templating method. The obtained membranes have ordered hierarchical nanopore array structures with controlled pore size and large surface area.
Gas storage in a safe and economical way is an important aspect of modern life. This study report... more Gas storage in a safe and economical way is an important aspect of modern life. This study reports on the behavior of the zeolite potassium chabazite (Si/Al = 2.2) as a nanocontainer to store N 2 and CH 4 by a temperature controlled nanovalve. We reveal the effect of ...
Ordered mesostructured tungsten carbide and graphitic carbon composites (WC/C) with nanocrystalli... more Ordered mesostructured tungsten carbide and graphitic carbon composites (WC/C) with nanocrystalline walls are fabricated for the first time by a temperature‐programmed carburization approach with phosphotungstic acid (PTA) as a precursor and mesoporous silica materials as hard templates. The mesostructure, crystal phase, and amount of deposited graphitic carbon can be conveniently tuned by controlling the silica template (SBA‐15 or KIT‐6), carburizing temperature (700–1000 °C), the PTA‐loading amount, and the carburizing atmosphere (CH4 or a CH4/H2 mixture). A high level of deposited carbon is favorable for connecting and stabilizing the WC nanocrystallites to achieve high mesostructural regularity, as well as promoting the carburization reaction. Meanwhile, large pore sizes and high mesoporosity of the silica templates can promote WC‐phase formation. These novel, ordered, mesoporous WC/C nanocomposites with high surface areas (74–169 m2 g−1), large pore volumes (0.14–0.17 cm3 g−1),...
Lanthanum phosphate (LaPO 4) nanostructures with different morphologies were prepared by a facile... more Lanthanum phosphate (LaPO 4) nanostructures with different morphologies were prepared by a facile solution–precipitation process. The effect of different reaction conditions on the morphology of nanostructures was studied. When the molar ratio of La 3+: H 3 PO 4 was around 1: 2, 1: 20, 1: 100, and 1: 200, four different morphologies, such as near-spherical, snowflake-like, star-shaped, lens-like nanostructures and short nanorods, were obtained, respectively. Meanwhile, similar shapes developed when the molar ratio of H 3 PO 4 to ...
ABSTRACT Large-pore periodic mesoporous organosilica (PMO) hollow spheres with controllable pore ... more ABSTRACT Large-pore periodic mesoporous organosilica (PMO) hollow spheres with controllable pore size and high pore volume (2.5 cm3 g−1) were successfully synthesized at low-temperature (∼15 °C) by using the triblock copolymer Pluronic F127 as a template and 1,3,5-trimethylbenzene (TMB) as a swelling agent in the presence of inorganic salt (KCl). Transmission electron microscopy (TEM) measurements show that the PMO hollow spheres are uniform and well dispersed, and the composites have a large wall thickness. The influence of TMB, KCl, CTAB contents and media acidity on the mesostructure was systematically studied. The pore size (9.8–15.1 nm) of the hollow spheres can be gradually expanded by increasing TMB content together with a relatively high acidity. By controlling the content of CTAB, successive structural transformation from hollow sphere to wormlike mesostructure and eventually to ordered body-centered cubic (space group of Im-3m) mesostructure is observed. Our results reveal that the hydrophobicity of bis(triethoxysilyl)ethane (BTSE) and low-temperature approach contribute to the slow hydrolysis rate of silica precursors, which leads to weak interaction between individual TMB/F127 micelles and silicate oligomers. Furthermore, the salting-out effect of KCl may influence the swelling capacity of individual micelles as well as decrease the critical micelle concentration and critical micelle temperature, resulting in the formation of PMO hollow spheres from the assembly of individual TMB/F127 micelles with silicate oligomers. The composites exhibit efficient adsorption capacity (703 mg g−1) for toluene, suggesting they are a potentially useful adsorbent for removal of volatile organic compounds. The PMO hollow spheres allow biomolecules with large molecular weight to diffuse in, and show superior encapsulation capacity of bovine serum albumin (BSA) molecules (∼585 mg g−1) over other porous materials.
Ordered micro-porous carbon molecular sieves containing highly dispersed platinum nanoparticles w... more Ordered micro-porous carbon molecular sieves containing highly dispersed platinum nanoparticles with tunable sizes from 1 to 6nm are synthesized in this work. The synthesis is simply realized by nanocasting of furfuryl alcohol precursor on Pt-impregnated NaY zeolite hard templates and complemented by chemical vapor deposition by propylene gas. During the carbonization, Pt ions can be reduced to form highly dispersed Pt nanoparticles on the carbon matrixes. This method allows a very high Pt-loading up to 40wt % while maintaining a high metal dispersion. X-ray diffraction and transmission electron microscopy measurements reveal the existence of uniformly dispersed Pt nanoparticles and microstructural regularity. Nitrogen adsorption isotherms show that the ordered micro-porous carbon molecular sieves possess a high surface area around 2750m2/g, large micro-pore volume 1.38cm3/g, and narrow pore size distribution (∼1nm) in the micropore-range. A high hydrogen uptake up to 2.8wt% at 77K and 1bar is observed. A high and relatively homogeneous value of hydrogen adsorption heat 11kJ/mol in 1% Pt contained carbon was obtained, which exceeds the literature reported values for other carbon based adsorbents or metal organic framework compounds and is very close to the optimal value, 15kJ/mol, recommended in the literature, suggesting a great potential for hydrogen storage or fuel cell applications.
Bulk synthesis of hollow carbon stacked-cone-helices of diameter from 10 nm to 0.5 μm is reported... more Bulk synthesis of hollow carbon stacked-cone-helices of diameter from 10 nm to 0.5 μm is reported. The fibres' walls are made up of parallel stacked-cone-like structures with an inter-cone distance from 3.38 to 3.5 Å. Apex angles observed are in the range from 30° to 110°, ...
Novel one dimensional (1D) nanostructured metallic electrodes have received much attention in the... more Novel one dimensional (1D) nanostructured metallic electrodes have received much attention in the area of the fuel cell because of their extremely high surface-to-volume ratios and excellent activities. Here, we report the one-step fabrication of Pt–Cu alloy nanotube ...
Accurate numerical solution of cyclic adsorption problems can be challenging and time consuming d... more Accurate numerical solution of cyclic adsorption problems can be challenging and time consuming due to the inherent non-linearity of the system conservation equations and the presence of strong temporal and spatial gradients. In addition, the wide variety of possible boundary conditions makes solution of a general cycle problematic. In this study we present a quadratic upwind finite volume technique that is at least second-order accurate in the spatial dimension and can easily handle any type of boundary condition (both one and two point) at either end of the adsorption column. The effect of bed pressure drop is readily accommodated. The oscillations at sharp gradients common in high-order upwind methods is significantly reduced by a solution-adaptive strategy which does not introduce significant diffusion unlike first order upwind methods. To ensure accurate simulation of sharp fronts, we find that the finite volume node width should be approximately one tenth of the width of the mass transfer zone. A comparison is made for linear isotherm systems with the analytic solution and excellent agreement is produced for very moderate grid sizing. The method is fast and robust and is ideally suited to cycle simulation.
Nanochannel alumina templates are used as templates for fabrication of porous gold nanowire array... more Nanochannel alumina templates are used as templates for fabrication of porous gold nanowire arrays by a direct electrodeposition method. After modification with glucose oxidase, a porous gold nanowire‐array electrode is shown to be an excellent electrochemical biosensor for the detection of glucose. The picture shows an SEM image of a nanowire array after removal of the alumina template by acid dissolution.magnified imageWe report the fabrication of porous gold nanowire arrays by means of a one‐step electrodeposition method utilizing nanochannel alumina templates. The microstructure of gold nanowires depends strongly on the current density. The formation of porous gold nanowires is attributed to disperse crystallization under conditions of low nucleation rate. Interfacial electron transport through the porous gold nanowires is studied by electrochemical impedance spectroscopy. Cyclic voltammetric studies on the porous gold nanowire arrays reveal a low‐potential electrocatalytic resp...
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