Improved photocatalytic activity of shell-isolated plasmonic photocatalyst Au@SiO₂/TiO₂ by promoted LSPR

The effect localized surface plasmon resonance (LSPR) of Au nanoparticles was studied on the photocatalytic activity of TiO₂ film. We used the thermal hydrolysis method to prepare 300 nm TiO₂ film and the sodium citrate reduced method to synthesize gold nanoparticles. The photocatalytic activities of Au/TiO₂, Au@SiO₂/TiO₂, and TiO₂ films were evaluated by the degree of MB photodegradation under similar conditions with simultaneous UV (365 nm) and visible-light (400 nm < λ < 700 nm) irradiation for 5 h. The degree of MB photodegradation was in the following order: Au@SiO₂/TiO₂ > Au/TiO ₂ > TiO₂. Although the SiO₂ shell prevented the electron trap effect, the MB photodegradation efficiency of Au@SiO ₂/TiO₂ was superior to that of Au/TiO₂ because its LSPR was much higher. To validate the experimental results, the electric field intensity around the gold nanoparticles was simulated by the finite element method (FEM). In the presence of gold nanoparticles, the LSPR effect increased the surrounding intensity of electric field that enhanced the photocatalytic activities. Furthermore, from the simulation results, Au@SiO ₂/TiO₂ showed EM field improvement of nearly 9 times compared with Au/TiO₂. The SiO₂ coating significantly increased the LSPR effect of gold nanoparticles. We named this new core-shell structure "shell-isolated plasmonic photocatalyst". © 2012 American Chemical Society.