An approach to self-cleaning SERS sensors by arraying Au nanorods on TiO 2 layer

We have demonstrated stable surface-enhanced Raman spectroscopy (SERS) on arrays of Au nanorods aligned on a photocatalytic TiO₂ layer. We used dynamic oblique deposition (DOD) in order to control the morphology of both the Au nanorods and the TiO₂ layer so that both Au and TiO₂ appear on the surface and play the roles of Raman enhancer and self-cleaner, respectively. TiO₂ template layer was formed by depositing Ti₂O₃ onto heated glass substrate in an oxygen atmosphere so that it was ready as photocatalyst when the deposition was over, without post annealing in the air. A serial bideposition technique (SBD) at a deposition angle of 85° was used to control the morphology of TiO₂ layer suitable for the growth of Au nanorods. Then, Au nanorods were arrayed by depositing Au with different deposition angles and thicknesses on the TiO₂ layer. We investigated the photocatalysis and SERS properties of the samples and found that they show both good photocatalysis and strong signals of SERS although these properties varies depend on the deposition angle and thickness of Au layer. Most importantly, we found that the SERS signals measured on our samples have shown spatially-, temporally-stable characters which have not been observed before on the Ag or Au nanorods deposited on a SiO₂ layer. This stability is interpreted in terms of the self-cleaning character due to the photocatalytic TiO2 template layer.