Preparation of gold/silver/titania trilayered nanorods and their photocatalytic activities.

Gold/silver/titania trilayered nanorods have been prepared by the successive deposition of silver and titania layers on gold nanorod cores, and their photocatalytic activities were investigated under visible-light illumination (λ > 420 nm). The photocatalytic activity of the trilayered nanorods in the oxidation of 2-propanol depends on both the Au/Ag composition and the thickness of the TiO2 shell. It increases with increasing Ag content up to [Au]/[Ag] = 1:5 (molar ratio) and then decreases with further increasing Ag content. The photocatalytic activity also increases with increasing TiO2 shell thickness up to 10 nm and then decreases with further increases in the shell thickness. These effects were explained by electron-transfer and energy-transfer mechanisms.