Preparation and photocatalytic properties of quartz/gold nanostructures/TiO2 lamellar structures

A novel class of visible light activated titanium oxide (TiO2) photocatalytic surfaces were prepared by depositing gold nanostructures (Au NSs) onto quartz substrates and subsequent coating with 20–200 nm thick TiO2 thin films. The Au NSs were obtained by thermal evaporation and post-annealing of 4 nm thick gold films, while the TiO2 thin layers were deposited using reactive magnetron sputtering. The resulting interfaces were characterized using scanning electron microscopy (SEM) and UV-vis absorption spectroscopy. UV-vis spectra showed strong absorption peaks between 570 and 680 nm due to the plasmonic response of the lamellar structure. The photocatalytic activity of the interfaces for the oxidative degradation of rhodamine B was evaluated under ultraviolet and visible light illumination. The interface coated with 100 nm TiO2 exhibited pronounced photocatalytic activity under UV light irradiation compared to substrates with thinner or thicker TiO2 films or without TiO2 coating. A quartz/Au NSs/100 nm TiO2 interface showed higher photocatalytic activity compared to quartz/100 nm TiO2, while retarded photodegradation of rhodamine B is observed with quartz/Au NSs coated with thinner or thicker TiO2 films. The results clearly highlight the positive effect of the Au NSs on the performance of thin TiO2 photocatalysts. Furthermore, the deposition of TiO2 on top of Au NSs improves the poor stability encountered in TiO2/Au NSs photocatalytic systems.