Modification of Anodic TiO2 Nanotubes with Au

Abstract

For many years gold has been considered as catalytically inactive until Haruta and Hutchings demonstrated its catalytic behaviour in low-temperature CO oxidation.1 The bulk gold is generally considered as a poor catalyst and becomes surprisingly active when its size is reduced to nanoscale dimension. The recently emerging field of plasmonics require precise control of gold structure at the nanometer and subnanometer scales particularly if combined with secondary materials such as titania. Herein, we aim to control the structure of Au on TiO2 nanotubes by means of anodizing of TiAu alloys and two step process of anodizing of titanium and subsequent electrodeposition of gold in nanotubes.2,3 Figure 1a shows comparison of Ti and TiAu alloy anodized in mono-ethylene-glycol electrolyte containing 0.1 mol.dm-3 ammonium fluoride and 1 mol.dm-3 of water.2 The accumulation of gold at cell boundaries and resulting modification of TiO2 nanotube outer-shell can be clearly recognized from backscattered SEM images. Figure 1b shows the nanostructure formed by gold electrodeposition in between TiO2 nanotubes synthesised in di-ethylene-glycol electrolyte containing 2 wt.% HF and 2 wt.% of H2O.3 The details of nanostructures growth and possible applications will be discussed.