Optically modulated charge transfer in TiO sub(2)-Au nanocomplexes

Highly ordered TiO sub(2) nanotube array (TNA) films were fabricated by anodic oxidation of Ti foil. Au nanoparticles (NPs) are decorated onto the top of TNA films with the aid of ion-sputtering and thermal annealing. The steady-state photoluminescence (PL) spectra, as well as x-ray photoelectron spectroscopy (XPS) and Raman analysis, confirm the presence of Ti super(3+) valence states in the prepared TNA films. The UV-vis absorption spectra show that the photo-response of as-prepared samples is extended from UV to the visible light region. From the nanosecond time-resolved transient photoluminescence (NTRT-PL) spectra, Ti super(3+)-related PL intensity is observed to vary distinctly with the deposition time of Au NPs. Such a phenomenon could be explained by considering the modulation of oxygen vacancy densities and charge states in TNA films by surface loading Au NPs. The enhanced visible-light photocatalytic activities of the Au-TNA composite were evaluated through the photodegradation of methyl orange (MO) in aqueous solution by UV-vis absorption spectrometry. The decoration of Au NPs plays an essential role in enhancing visible-light photocatalytic activity, because energetic photoelectrons are able to inject to the conduction band of TiO sub(2) owing to the surface plasmon resonance (SPR) effect. It is hoped that our current work will provide a simple strategy to synthesize defect-related composite for photocatalytic applications.