Growth of highly single crystalline IrO 2 nanowires and their electrochemical applications

Abstract

We present the facile growth of highly single crystalline iridium dioxide (IrO2) nanowires on SiO2/Si and Au substrates via a simple vapor phase transport process under atmospheric pressure without any catalyst. Particularly, high-density needle-like IrO2 nanowires were readily obtained on a single Au microwire, suggesting that the melted surface layer of Au might effectively enhance the nucleation of gaseous IrO3 precursors at the growth temperature. In addition, all the electrochemical observations of the directly grown IrO2 nanowires on a single Au microwire support favorable electron-transfer kinetics of [Fe(CN6)](4-/3-) as well as Ru(NH3)(6)(3+/2+) at the highly oriented crystalline IrO2 nanowire surface. Furthermore, stable pH response is shown, revealing potential for use as a miniaturized pH sensor, confirmed by the calibration curve exhibiting super-Nernstian behavior with a slope of 71.6 mV pH(-1).