Viscosities and densities at several temperatures from 293.15 K to 313.15K are reported for L-ascorbic acid in aqueous glucose and sucrose solutions at different concentrations. The parameters of density, viscosity co...Viscosities and densities at several temperatures from 293.15 K to 313.15K are reported for L-ascorbic acid in aqueous glucose and sucrose solutions at different concentrations. The parameters of density, viscosity coefficient B and partial molar volume are calculated by regression. The experimental results show that densities and viscosities decrease as temperature increases at the same solute and solvent (glucose and sucrose aqueous solution) concentrations, and increase with concentration of glucose and sucrose at the same solute concentration and temperature. B increases with concentration of glucose and sucrose and temperature. L-ascorbic acid is structure-breaker or structure-making for the glucose and sucrose aqueous solutions. Furthermore, the solute-solvent interactions in ternary systems of water-glucose-electrolyte and water-sucrose-electrolyte are discussed.展开更多
In the current studies a miniature silicon wafer fuel cell(FC) using L-ascorbic acid as fuel was developed. The cell employs L-ascorbic acid and air as reactants and a thin polymer electrolyte as a separator. Inductiv...In the current studies a miniature silicon wafer fuel cell(FC) using L-ascorbic acid as fuel was developed. The cell employs L-ascorbic acid and air as reactants and a thin polymer electrolyte as a separator. Inductively coupled plasma(ICP) silicon etching was employed to fabricate high aspect-ratio columns on the silicon substrate to increase the surface area. A thin platinum layer deposited directly on the silicon surface by the sputtering was used as the catalyst layer for L-ascorbic acid electro-oxidation. Cyclic voltammetry shows that the oxidation of L-ascorbic acid on the sputtered platinum layer is irreversible and that the onset potentials for the oxidation of L-ascorbic acid are from 0.27 V to 0.35 V versus an Ag/AgCl reference electrode. It is found that at the room temperature,with 1 mol/L L-ascorbic acid/PBS(phosphate buffered solution) solution pumped to the anode at 1 ml/min flow rate and air spontaneously diffusing to the cathode as the oxidant,the maximum output power density of the cell was 1.95 mW/cm2 at a current density of 10 mA/cm2.展开更多
Highly stable dispersions of nanosized copper （Cu） particles with an average size of （2.6 ± 0.5） nm were synthesized by in situ reduction of Cu（II） to immobilize Cu nanoparticles on the amino-enriched surfa...Highly stable dispersions of nanosized copper （Cu） particles with an average size of （2.6 ± 0.5） nm were synthesized by in situ reduction of Cu（II） to immobilize Cu nanoparticles on the amino-enriched surface of chitosan （CTS）. The synthetic process and stability of the L-ascorbic acid-stabilized Cu-CTS nanocomposites were investigated by X-ray photoelectron spectroscopy and Fourier transform Infrared spectroscopy. The antimicrobial efficiency and potency of the Cu-CTS nanocomposites were studied. The Cu-CTS nanocomposites were found to exhibit a broad antimicrobial spectrum and high antimicrobial activity against Gram-positive bacterial pathogen Staphylococcus aureus and fungal pathogen Monilia albican. The minimum inhibitory concentration of the Cu-CTS nanocomposites toward S. aureus was found to be 6.4 μg mL^-1, much lower than those reported in the literature. Furthermore, the Cu-CTS nanocomposites were stable and main- tained good disinfection potential even after 90-day shelf-time under ambient conditions.展开更多
基金Supported by the Educational Department Doctor Foundation of China(No.2000005608).
文摘Viscosities and densities at several temperatures from 293.15 K to 313.15K are reported for L-ascorbic acid in aqueous glucose and sucrose solutions at different concentrations. The parameters of density, viscosity coefficient B and partial molar volume are calculated by regression. The experimental results show that densities and viscosities decrease as temperature increases at the same solute and solvent (glucose and sucrose aqueous solution) concentrations, and increase with concentration of glucose and sucrose at the same solute concentration and temperature. B increases with concentration of glucose and sucrose and temperature. L-ascorbic acid is structure-breaker or structure-making for the glucose and sucrose aqueous solutions. Furthermore, the solute-solvent interactions in ternary systems of water-glucose-electrolyte and water-sucrose-electrolyte are discussed.
基金the National Natural Science Foundation of China (No. 30670535)the Program for New Century Excellent Talents in University (No. NCET-07-0752), China
文摘In the current studies a miniature silicon wafer fuel cell(FC) using L-ascorbic acid as fuel was developed. The cell employs L-ascorbic acid and air as reactants and a thin polymer electrolyte as a separator. Inductively coupled plasma(ICP) silicon etching was employed to fabricate high aspect-ratio columns on the silicon substrate to increase the surface area. A thin platinum layer deposited directly on the silicon surface by the sputtering was used as the catalyst layer for L-ascorbic acid electro-oxidation. Cyclic voltammetry shows that the oxidation of L-ascorbic acid on the sputtered platinum layer is irreversible and that the onset potentials for the oxidation of L-ascorbic acid are from 0.27 V to 0.35 V versus an Ag/AgCl reference electrode. It is found that at the room temperature,with 1 mol/L L-ascorbic acid/PBS(phosphate buffered solution) solution pumped to the anode at 1 ml/min flow rate and air spontaneously diffusing to the cathode as the oxidant,the maximum output power density of the cell was 1.95 mW/cm2 at a current density of 10 mA/cm2.
基金partially supported by theNational Natural Science Foundation of China(21173047 and21073036)
文摘Highly stable dispersions of nanosized copper （Cu） particles with an average size of （2.6 ± 0.5） nm were synthesized by in situ reduction of Cu（II） to immobilize Cu nanoparticles on the amino-enriched surface of chitosan （CTS）. The synthetic process and stability of the L-ascorbic acid-stabilized Cu-CTS nanocomposites were investigated by X-ray photoelectron spectroscopy and Fourier transform Infrared spectroscopy. The antimicrobial efficiency and potency of the Cu-CTS nanocomposites were studied. The Cu-CTS nanocomposites were found to exhibit a broad antimicrobial spectrum and high antimicrobial activity against Gram-positive bacterial pathogen Staphylococcus aureus and fungal pathogen Monilia albican. The minimum inhibitory concentration of the Cu-CTS nanocomposites toward S. aureus was found to be 6.4 μg mL^-1, much lower than those reported in the literature. Furthermore, the Cu-CTS nanocomposites were stable and main- tained good disinfection potential even after 90-day shelf-time under ambient conditions.
