Raman Investigations of Adsorbate-Substrate Interactions on Composite Ag (or Cu)/TiO2 Nanotubes/Ti Substrates

A tubular array of TiO2 nanotubes on Ti matrix was used as a support for Ag or Cu sputter-deposited layers intended for surface-enhanced Raman scattering (SERS) investigations. Composite samples of Ag/TiO2-nanotube/Ti and Cu/TiO2nanotube/Ti were studied with the aid of scanning electron microscopy (SEM) and Auger electron spectroscopy (AES and SAM) to reveal their characteristic morphological and chemical features. Raman spectra of pyridine (as a probe molecule) were measured after it had been adsorbed on the TiO2-nanotube/Ti substrates covered with thin Ag or Cu deposit as well as on the bulk electrochemically roughened Ag or Cu reference substrates. The Ag/TiO2−nanotubes/Ti samples appeared very Raman active, whereas these with a Cu deposit, were less active, resulting in weaker Raman signals. The SERS activity of the Ag/TiO2−nanotubes/Ti composite samples was strongly dependent on the amount of the Ag deposit. The SERS intensity vs. electrode potential dependences measured for the these samples were interpreted in terms of the modified electronic structure of the Ag deposits due to the interaction of the Ag clusters with the TiO2 nanotube/Ti substrate.