Highly ordered TiO 2 nanotube films photo-decorated with Ag nanoparticles as SERS platforms: Relationship between morphology and enhancement

In this work, we synthesized TiO 2 nanotube films (TiO 2 -NTFs) photo-decorated with Ag nanoparticles for their application in Surface-Enhanced Raman Scattering. In situ growth of Ag nanoparticles was performed through the exposure of anodic TiO 2 -NTFs to UVC radiation following their pretreatment in an AgNO 3 aqueous solution. High nanoparticle surface densities, with uniform coverage on the film surface, and controllable size, were prepared by regulating the UVC exposure time and AgNO 3 concentration. Ag nanoparticles nucleation and growth also take place along the tubes, including at the bottoms. The evidence obtained also indicates that a high enough AgNO 3 concentration inhibits the well-known water-assisted crystallization mechanism, typically promoted when TiO 2 -NTFs are exposed for prolonged times in aqueous media. The performance of the photo-decorated films in Surface-Enhanced Raman Scattering shows that the presence of Ag nanoparticles plays a key role, and both the nanoparticle surface density and size must be regulated to promote a large number of hot-spots.