Recyclable Au-TiO2 nanocomposite SERS-active substrates contributed by synergistic charge-transfer effect.

In this study, Au deposited TiO2 (Au-TiO2) nanocomposites were prepared by photocatalytic reduction of Au species (HAuCl4) on TiO2 nanoparticles (NPs) and served as efficient SERS-active substrates. The observed considerable SERS enhancement of 4-MBA molecules on Au-TiO2 NPs compared with that on pure TiO2 NPs can be attributed to the synergistic contribution of semiconductors and metals by the charge-transfer mechanism from the substrate to the molecule. In the preparation of Au-TiO2 nanocomposites, the photo-reduction time and concentration of HAuCl4 have an important influence on the SERS enhancement effect of the composite substrate. Moreover, for the recycle of substrates, the photocatalytic experiment of Au-TiO2 nanocomposites was carried out. The results show that these nanocomposite substrates are characterized by a self-cleaning property and can be repeatedly used in SERS experiments without losing their activity and with high stability.