Supercapacitor characteristics of manganese oxide/nickel ͑MnO x /Ni͒ and manganese oxide/carbon nanotubes/nickel ͑MnO x /CNTs/Ni͒ nanocomposite electrodes were investigated in this study. The CNTs were deposited on the Ni substrate by electrophoresis in a 0.5 mg CNT/1 mL dimethylformamide solution, whereas the MnO x were synthesized by anodic deposition in a 0.16 M manganese sulfate pentahydrate aqueous solution on substrates. The crystallinity and surface morphology of these electrodes were determined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The capacitive properties of these electrodes were demonstrated by cyclic voltammetry with scan rates ranging from 5 to 100 mV/s. The specific capacitances of the MnO x /CNT/Ni nanocomposite electrode were 415 and 388 F/g with scan rates of 5 and 100 mV/s, respectively. After 1000 cycles of operation, this electrode can maintain 79% of its original capacitance. These MnO x /CNT/Ni nanocomposite electrodes possessing good electrochemical reversibility and high capacitance may be appropriate for supercapacitor application in the future.

Articles you may be interested inOn the origin of enhanced photoconduction and photoluminescence from Au and Ti nanoparticles decorated aligned ZnO nanowire heterostructures The ZnO nanowires synthesized by vapor-liquid-solid growth mechanism with Cu and Au as the catalyst were investigated. The principal differences in morphology between Cu and Au catalyzed ZnO nanowires are observed and lead to significant differences in their field emission and photofluorescent characteristics. The Cu catalyzed ZnO nanowires with a high-quality wurtzite structure were grown vertically on p-type Si͑100͒ substrate along ͓0002͔ direction. A strong ultraviolet emission at 381 nm is observed. These ZnO nanowires show excellent field emission properties with turn-on field of 0.83 V/m and corresponding current density of 25 A/cm 2 . The emitted current density of the ZnO nanowires is 1.52 mA/cm 2 at a bias field of 8.5 V/m. The large field emission area factor, ␤ arising from the morphology of the nanowire field emitter, is partly responsible for the good emission characteristics. The ZnO nanowires with high emission current density and low turn-on field are expected to be used in field emission flat panel display.

Fabrication of multi-element nanoparticles on noncatalyzed gas diffusion electrodes (GDEs) by radio frequency sputter deposition was reported. X-ray diffraction analysis of the as-deposited films indicated crystalline fcc phases while energy dispersive X-ray spectroscope confirmed their composition as Pt 50 Fe 11 Co 10 Ni 11 Cu 10 Ag 8. Scanning electron microscopy images revealed nanoparticulate nodules growing on the carbon particles. Cyclic voltammetry (CV) was employed to analyze their methanol oxidation abilities for direct methanol fuel cells. The CV responses improved upon cycling and became stabilized after 70 cycles. The areas under the CV curves were proportional to the amount of nanoparticles deposited. In mass activities the GDE with 5 nm nanoparticles demonstrated the highest values of 400-600 mA/mg. In comparing with Pt and Pt 43 Ru 57 , the Pt 43 Ru 57 exhibited the lowest onset potential with the highest mass activities. Our work presents preliminary information on the catalytic behaviors of multi-element nanoparticles which is likely to bring new directions in catalyst design.

Sn doped ZnO (SZO) nanowires were fabricated by a vapour-liquid-solid growth process. The reaction temperature for the formation of the nanowires can be reduced to ∼100˚C due to Sn doping. The growth direction and morphology of SZO nanowires depend on the amount of Sn, which is attributed to the difference in sizes between Zn and Sn atoms. The ultraviolet emission of SZO nanowires varies from 380 to 396 nm since Sn acts as a doubly ionized donor and introduces deep states in the band gap. In addition, the SZO nanowires exhibit significantly improved field emission characteristics with a turn-on electric field of 0.05 V µm −1 under a current density of 0.5 mA cm −2 in comparison with undoped ZnO nanowires. The work function of the SZO nanowire decreases for higher carrier concentrations and the field enhancement factor increases for smaller diameters. Also, the resistance of the SZO nanowire is decreased for the higher Sn mole fraction. Therefore, it is expected that SZO nanowires can be applied in nano-lasers and flat panel displays in the future.

This study investigates the resistive switching behavior of Ga-doped ZnO (GZO) nanorod thin films with various Ga/Zn molar ratios. Vertically well-aligned and uniform GZO nanorod thin films were successfully grown on Au/Ti/SiO(2)/p-Si substrates using an aqueous solution method. X-ray diffraction (XRD) results indicate that GZO nanorods have [0001] highly preferred orientation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show the formation of highly ordered and dense nanorod thin films. These compact GZO nanorod thin films can be used to make resistive switching memory devices. Such memory devices can be reversibly switched between ON and OFF states, with a stable resistance ratio of ten times, narrow dispersion of ON and OFF voltages, and good endurance performance of over 100 cycles. The resistive switching mechanism in these devices is related to the formation and rupture of conducting filaments consisting of oxygen vacancies, occurring at interfaces between GZO nanorods (grain boundaries). Results show that the resulting compact GZO nanorod thin films have a high potential for resistive memory applications.