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.