The Potentiostatic Electrodeposition of Gold Nanowire/Nanotube in HAuCl4 Solutions Based on the Model of Recessed Cylindrical Ultramicroelectrode Array

Abstract

The mechanism of gold nanowire (AuNW) and nanotube (AuNT) electrodeposition in a cyanide–free solution is investigated for the first time based on the analytical model of Szabo et al. (A. Szabo et al., J. Electroanal. Chem. 217 (1987) 417) for recessed cylindrical ultramicroelectrode (UME). Track–etched Polycarbonate Template (PCT) is served as cylindrical UME ensemble/arrays. Firstly, Au is nucleated through a charge transfer step and when the Nernst thickness exceeds the pore length, the radial diffusion is established around pore mouths. By overlapping of these domains, the planar diffusion toward the whole PCT surface is obtained. An analytic expression for global diffusion coefficient (D) is derived as a function of the electroactive concentration (Cb), reduction overpotential (η) and pore size (r0 = 100 nm). The radial diffusion coefficient of AuCl4− is found 1.40 × 10−5 cm2/s which is about 7.7 times greater than the electrostatic component of diffusion coefficient. In diluted electrolytes (up to 10 mM), the electrostatic and longitudinal linear components of diffusion predominantly determine the rate of mass transport. At higher electrolyte concentrations (about 50mM), the linear component of diffusion coefficient increases to 4.8 × 10−5 cm2/s and the rate controlling phenomenon is mainly the electrostatic diffusion.