Highly ordered TiO2 nanotube films photo-decorated with Ag nanoparticles as SERS platforms: Relationship between morphology and enhancement

Abstract

In this work, we synthesized TiO2 nanotube films (TiO2-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 TiO2-NTFs to UVC radiation following their pretreatment in an AgNO3 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 AgNO3 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 AgNO3 concentration inhibits the well-known water-assisted crystallization mechanism, typically promoted when TiO2-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.