A non-precious metal catalyst MnHMTA/C to oxygen reduction reaction was prepared by py- rolyzing a precursor from manganese chloride, hexamethylenetetramine and acetylene black in nitrogen gas atmosphere. The effect o...A non-precious metal catalyst MnHMTA/C to oxygen reduction reaction was prepared by py- rolyzing a precursor from manganese chloride, hexamethylenetetramine and acetylene black in nitrogen gas atmosphere. The effect of heat treatment temperature and flowing of nitrogen gas were investigated. A catalyst with the highest activity can be obtained at 700 ℃. Mn（Ⅱ） ion was changed to MnO in heat treatment, which improved the catalytic activity of the catalyst. Hexamethylenetetramine takes part in the formation of active site of the catalyst as its decomposed gases. The flowing of protective gas takes the decomposed gases out of the tube furnace and brings negative effect on the catalytic activity of the MnHMTA/C catalyst.展开更多
The computer molecular simulation technique was applied to study the chemisorption of thiophene and tetramethylthiophene as the model sulfides on the simple oxides and complex oxides of some transition metals as the c...The computer molecular simulation technique was applied to study the chemisorption of thiophene and tetramethylthiophene as the model sulfides on the simple oxides and complex oxides of some transition metals as the catalytic materials. The study disclosed that the thiophene sulfides could enter into chemisorption with metal oxides such as VO, ZnO, NiO and Zn-Al-spinel. This interaction could lead to thiophene molecular structure deformation to be in an activated adsorption state, which could help to promote the conversion of thiophene sulfides in the course of catalytic cracking. The VO with a valence of 2 could provide relatively strong selective adsorption sites for the conversion of thiophene sulfides to apparently transform the molecular structures and electron cloud states of such heterocyclic sulfur compounds such as thiophene and tetramethylthiophene into an activated adsorption state. The effect of this interaction was more pronounced with respect to tetramethylthiophene.展开更多
Bell-metal, mainly an alloy of copper and tin has been in different uses since many years in the history of human civilization. This work provides an efficient and eco-friendly method to protect bell-metal from oxidat...Bell-metal, mainly an alloy of copper and tin has been in different uses since many years in the history of human civilization. This work provides an efficient and eco-friendly method to protect bell-metal from oxidation when left in the atmosphere for a long duration which enables the bell-metal to retain its bright golden yellow colour. Titanium nitride thin film deposition by reactive cylindrical magnetron sputtering method is done for this purpose. Besides retaining the bright golden colour of the bell-metal, the deposited titanium nitride film also provides hardness and corrosion resistance to the bell-metal surface thereby providing durability to the material.展开更多
Arrays of chemical vapor sensors based on graphene field effect transistors functionalized with single-stranded DNA have been demonstrated. Standard photolithographic processing was adapted for use on large-area graph...Arrays of chemical vapor sensors based on graphene field effect transistors functionalized with single-stranded DNA have been demonstrated. Standard photolithographic processing was adapted for use on large-area graphene by including a metal protection layer, which protected the graphene from contamination and enabled fabrication of high quality field-effect transistors （GFETs）. Processed graphene devices had hole mobilities of 1,640 ± 250 cm2.V-1.s-1 and Dirac voltages of 15 ± 10 V under ambient conditions. Atomic force microscopy was used to verify that the graphene surface remained uncontaminated and therefore suitable for controlled chemical functionalization. Single-stranded DNA was chosen as the functionalization layer due to its affinity to a wide range of target molecules and π-π stacking interaction with graphene, which led to minimal degradation of device characteristics. The resulting sensor arrays showed analyte- and DNA sequence-dependent responses down to parts-per-billion concentrations. DNA/GFET sensors were able to differentiate among chemically similar analytes, including a series of carboxylic acids, and structural isomers of carboxylic acids and pinene. Evidence for the important role of electrostatic chemical gating was provided by the observation of understandable differences in the sensor response to two compounds that differed only by the replacement of a （deprotonating） hydroxyl group by a neutral methyl group. Finally, target analytes were detected without loss of sensitivity in a large background of a chemically similar, volatile compound. These results motivate further development of the DNA/graphene sensor family for use in an electronic olfaction system.展开更多
文摘A non-precious metal catalyst MnHMTA/C to oxygen reduction reaction was prepared by py- rolyzing a precursor from manganese chloride, hexamethylenetetramine and acetylene black in nitrogen gas atmosphere. The effect of heat treatment temperature and flowing of nitrogen gas were investigated. A catalyst with the highest activity can be obtained at 700 ℃. Mn（Ⅱ） ion was changed to MnO in heat treatment, which improved the catalytic activity of the catalyst. Hexamethylenetetramine takes part in the formation of active site of the catalyst as its decomposed gases. The flowing of protective gas takes the decomposed gases out of the tube furnace and brings negative effect on the catalytic activity of the MnHMTA/C catalyst.
文摘The computer molecular simulation technique was applied to study the chemisorption of thiophene and tetramethylthiophene as the model sulfides on the simple oxides and complex oxides of some transition metals as the catalytic materials. The study disclosed that the thiophene sulfides could enter into chemisorption with metal oxides such as VO, ZnO, NiO and Zn-Al-spinel. This interaction could lead to thiophene molecular structure deformation to be in an activated adsorption state, which could help to promote the conversion of thiophene sulfides in the course of catalytic cracking. The VO with a valence of 2 could provide relatively strong selective adsorption sites for the conversion of thiophene sulfides to apparently transform the molecular structures and electron cloud states of such heterocyclic sulfur compounds such as thiophene and tetramethylthiophene into an activated adsorption state. The effect of this interaction was more pronounced with respect to tetramethylthiophene.
文摘Bell-metal, mainly an alloy of copper and tin has been in different uses since many years in the history of human civilization. This work provides an efficient and eco-friendly method to protect bell-metal from oxidation when left in the atmosphere for a long duration which enables the bell-metal to retain its bright golden yellow colour. Titanium nitride thin film deposition by reactive cylindrical magnetron sputtering method is done for this purpose. Besides retaining the bright golden colour of the bell-metal, the deposited titanium nitride film also provides hardness and corrosion resistance to the bell-metal surface thereby providing durability to the material.
基金This research was supported by the Nano/Bio Interface Center through the National Science Foundation Nanoscale Science and Engineering Center （NSEC） DMR08-32802, and the work involved use of its facilities. Support from Lockheed Martin is also gratefully acknowledged. M.L. acknowledges the support of the Science, Mathematics, And Research for Transformation （SMART） Fellowship.
文摘Arrays of chemical vapor sensors based on graphene field effect transistors functionalized with single-stranded DNA have been demonstrated. Standard photolithographic processing was adapted for use on large-area graphene by including a metal protection layer, which protected the graphene from contamination and enabled fabrication of high quality field-effect transistors （GFETs）. Processed graphene devices had hole mobilities of 1,640 ± 250 cm2.V-1.s-1 and Dirac voltages of 15 ± 10 V under ambient conditions. Atomic force microscopy was used to verify that the graphene surface remained uncontaminated and therefore suitable for controlled chemical functionalization. Single-stranded DNA was chosen as the functionalization layer due to its affinity to a wide range of target molecules and π-π stacking interaction with graphene, which led to minimal degradation of device characteristics. The resulting sensor arrays showed analyte- and DNA sequence-dependent responses down to parts-per-billion concentrations. DNA/GFET sensors were able to differentiate among chemically similar analytes, including a series of carboxylic acids, and structural isomers of carboxylic acids and pinene. Evidence for the important role of electrostatic chemical gating was provided by the observation of understandable differences in the sensor response to two compounds that differed only by the replacement of a （deprotonating） hydroxyl group by a neutral methyl group. Finally, target analytes were detected without loss of sensitivity in a large background of a chemically similar, volatile compound. These results motivate further development of the DNA/graphene sensor family for use in an electronic olfaction system.
