Gold-capped TiO2 nanocomposite particles have been synthesized by reducing [AuCl4](-) on the surface of preformed TiO2 colloids in acetonitrile. Such semiconductor-metal nanocomposites are considered to be beneficial toward improving the efficiency of the photocatalytic oxidation process. Whereas photogenerated electrons of TiO2 colloids readily reduce Au(III) ions in deaerated solution, the photogenerated holes are capable of oxidizing the preexisting gold layer on TiO2 particles in aerated solutions. The experimental conditions under which photocatalysis experiments are carried out dictate the net concentration of metal and metal ion species at the semiconductor/metal interface and hence the overall catalytic activity. Using photocatalytic oxidation of SCN- as a probe, we have investigated the influence of Au-0 and Au(III) on interfacial hole transfer. The ratio of metal/metal ion concentration (viz., [Au-0]/[Au(III)]) at the TiO2 interface was found to dictate the overall photocatalytic process in the semiconductor/metal nanocomposite.