Photoinduced transformations at semiconductor/metal interfaces: X-ray absorption studies of titania/gold films

Abstract

We have measured x-ray absorption fine structure of pre- and post-ultraviolet(UV)-irradiated gold (Au) deposited- titania $({\mathrm{TiO}}_2)$ nanocomposites in order to study the effect of UV irradiation on the charge state and local structures around Au in ${\mathrm{TiO}}_2.$ Our results indicate a positive oxidation state of Au in ${\mathrm{TiO}}_2$ following UV irradiation and, in addition, a remarkable change is observed in the local environment between these samples as an effect of UV irradiation. The environment around Au, which is comprised mostly of Ti and O atoms prior to UV illumination, is seen to form Au clusters following UV illumination. The photoinduced chemical transformation established in this study demonstrates the nature of semiconductor/metal interface under UV irradiation, and its role in dictating long-term photoelectrochemical performance of nanocomposite photocatalysts.