Influence of Au particles on the photocurrent of TiO2 films

Au/TiO₂ composite films were employed in an attempt to improve the photon-electron conversion efficiency of TiO₂ film in the visible region, using the surface plasma resonance (SPR) of Au nanoparticles. For investigating the relationship between SPR of Au particle and photocurrent of TiO₂ film, a series of Au/TiO₂ films with different Au concentrations were synthesized by sol-gel method. Results of studies on the influence of Au particle size on crystallization of TiO₂ film, UV-vis absorption and photocurrents generated are discussed. It was shown that SPR performance of the Au nanoparticles was not only related to their size, but also to their distribution in the TiO₂ matrix. Even in TiO₂ films with large Au particle sizes (100 nm), SPR in visible region was still observed. However, this SPR performance did not contribute to the photon-electron conversion of TiO₂ film in the visible region. Contrarily, embedded Au nanoparticles depressed the photocurrent generated by the TiO₂ film in UV region. The reason for this decrease is thought to be partly due to the Au simply blocking some of the light and partly because the extent of crystallization of TiO₂ decreased with high Au levels.