Synthesis of Ultrathin Nitrogen-Doped Graphitic Carbon Nanocages as Advanced Electrode Materials for Supercapacitor

E-mail Addresses: [email protected]; [email protected] of nitrogen-doped carbons with large surface area, high conductivity, and suitable pore size distribution is highly desirable for high-performance supercapacitor applications. Here, we report a novel protocol for template synthesis of ultrathin nitrogen-doped graphitic carbon nanocages (CNCs) derived from polyaniline (PAN!) and their excellent capacitive properties. The synthesis of CNCs involves one-pot hydrothermal synthesis of Mn3O4@PANI core-shell nanoparticles, carbonization to produce carbon coated MnO nanoparticles, and then removal of the MnO cores by acidic treatment. The CNCs prepared at an optimum carbonization temperature of 800 degrees C (CNCs-800) have regular frameworks, moderate graphitization, high specific surface area, good mesoporosity, and appropriate N doping. The CNCs-800 show high specific capacitance (248 F g(-1) at 1.0 A g(-1)), excellent rate capability (88% and 76% capacitance retention at 10 and 100 A g(-1), respectively), and outstanding cycling stability (similar to 95% capacitance retention after 5000 cycles) in 6 M KOH aqueous solution. The CNCs-800 can also exhibit great pseudocapacitance in 0.5 M H2SO4 aqueous solution besides the large electrochemical double-layer capacitance. The excellent capacitance performance coupled with the facile synthesis of ultrathin nitrogen-doped graphitic CNCs indicates their great application potential in supercapacitors.MOST of China 2011CB932403 National Natural Science Foundation of China 21075036 21175042 21131005 20925103 Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province Start-Up Fund for Young Teachers in Hunan Normal Universit

A response model for surface acoustic wave enzyme sensor applied to the kinetic study of urease-catalytic reaction and urea determination

288-294A binary substrate-enzyme complex response model based on a surface acoustic wave (SAW) enzyme sensor has been derived to study enzymatic-catalytic reactions. It is applied to a non-linear least squares metho based on Marquardt algorithm by fitting urease-catalytic reaction data. The effect of initial values of rate constants on the programme convergence of the proposed method is discussed. The kinetic parameters have been estimated and these are of the same order of magnitude as those reported in the literature. As a comparison, the substrate (urea) concentration has been analyzed by the proposed method, the calibration method and the iterative Kalman filter method .The recovery in the case of the proposed method ranges from 98.0% to 103.2% while that for other two methods is in the range of 96.0- 104.4% and 97.2-103.8% respectively. These methods are also used to determine the urea content in human blood. The proposed method compares favourably with other methods and gives more precise results

A series piezoelectric quartz crystal response model for ferrous ion oxidation in the presence of <i>T. ferrooxdians</i>

939-942A novel and simple method, series piezoelectric quartz crystal (SPQC) has been used to monitor ferrous ion oxidation in the presence of T. ferrooxidans. By combination of a general SPQC response model with the kinetics of the bacterial growth, a SPQC response model for ferrous ion oxidation in the presence of T.ferrooxidans has been built. The response model can describe the bacterial growth process well. Some important kinetic parameters, such as μm (the maximum specific growth rate of bacterium), K (saturation constant, i.e., the ferrous iron concentration at which the half-maximal growth rate occurs), X0 / Y (ratio of initial bacterial concentration to cell yield coefficient), have been obtained by fitting the model to the experimental curves

Synergistic extraction of copper(II) and zinc(II) with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and tri-<i>n</i>-butyl phosphate by two-phase <i>p</i>H titration

108-110The extraction of Cu(II) and Zn(II) with 1-phenyl-3- methyl-4-benzoyl-5-pyrazolone (PMBP) and tri-n-butyl phosphate(TPB) in benzene has been studied by two-phase pH titration. The formation constants of the extracted complexes have been computed with computer program SCTPT. The effects of pH and nature of extractants on the extraction have been investigated

A Study on Tannic Acid-doped Polypyrrole Films on Gold Electrodes for Selective Electrochemical Detection of Dopamine

Tannic acid-doped polypyrrole (PPY/TA) films have been grown on goldelectrodes for selective electrochemical detection of dopamine (DA). Electrochemicalquartz crystal microbalance (EQCM) studies revealed that, in vivid contrast toperchlorate-doped polypyrrole films (PPY/ClO4-), the redox switching of PPY/TA filmsin aqueous solutions involved only cation transport if the solution pH was greater than3~4. The PPY/TA Au electrodes also exhibited attractive permselectivity forelectroactive cations, namely, effectively blocking the electrochemical reactions ofanionic ferricyanide and ascorbic acid (AA) while well retaining the electrochemicalactivities of hexaammineruthenium (III) and dopamine as cationic species. A 500 HzPPY/TA film could effectively block the redox current of up to 5.0 mM AA. Thecoexistence of ascorbic acid in the measurement solution notably enhanced the currentsignal for dopamine oxidation, due probably to the chemical regeneration of dopaminethrough an ascorbic acid-catalyzed reduction of the electro-oxidation product ofdopamine (EC’ mechanism), and the greatest amplification was found at an ascorbic acidconcentration of 1.0 mM. The differential pulse voltammetry peak current for DAoxidation was linear with DA concentration in the range of 0 to 10 μM, with sensitivityof 0.125 and 0.268 μA/μM, as well as lower detection limit of 2.0 and 0.3 μM in a PBSsolution without AA and with 1.0 mM coexisting AA, respectively