Nanocrystalline TiO2/Au films: Photocatalytic deposition of gold nanocrystals and plasmonic enhancement of Raman scattering from titania

Photocatalytic reduction of NaAuCl 4 by ethanol on the surface of mesoporous TiO 2 films illuminated by UV light results in the formation of nanocrystalline TiO 2 /Au heterostructures with an average size of gold nanoparticles varying in a range of 20−60 nm depending on the photoprocess conditions. Raman spectra of the TiO 2 /Au heterostructures excited in the surface plasmon resonance bands of the Au nanoparticles were obtained. The TiO 2 /Au films pre-illuminated with relatively high power density of the laser beam used in Raman experiment (100 W/cm 2 ) exhibit plasmonic enhancement of Raman scattering by titania excited subsequently with relatively low-intensity (10 W/cm 2 ) laser light. This effect sheds some light on the mechanistic aspects of plasmonic photocatalysis observed for many gold-based metal-semiconductor heterostructures.