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

Photocatalytic reduction of NaAuCl4 by ethanol on the surface of mesoporous TiO2 films illuminated by UV light results in the formation of nanocrystalline TiO2/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 TiO2/Au heterostructures excited in the surface plasmon resonance bands of the Au nanoparticles were obtained. The TiO2/Au films pre-illuminated with relatively high power density of the laser beam used in Raman experiment (100 W/cm2) exhibit plasmonic enhancement of Raman scattering by titania excited subsequently with relatively low-intensity (10 W/cm2) laser light. This effect sheds some light on the mechanistic aspects of plasmonic photocatalysis observed for many gold-based metal-semiconductor heterostructures.