TiO₂ Nanofoam-Nanotube Array for Surface-Enhanced Raman Scattering

By tuning the anodic voltage and electrochemical reaction time, we have synthesized a series of TiO₂ nanofoam-nanotube array structures via a two-step anodic oxidation process. The produced nanofoam-nanotube array demonstrated a remarkable Raman scattering enhancement. The maximum enhancement factors are 2.3 × 10⁵ for methylene blue. Factors such as the nanotube pore size, nanofoam, and solute concentration have been investigated. The Raman scattering enhancement is attributed to the existence of the nanofoam structure, which enables multiple laser scatterings among the periodic voids and allows for the occurrence of Raman scattering. The proposed simple and inexpensive approach can promote the use of TiO₂ materials for surface-enhanced Raman scattering applications in chemistry, biology, and nanoscience.