Surface enhanced Raman spectroscopy for adsorption studies on semiconductor nanostructured films

A way of extending Raman Spectroscopy to the study of adsorbates on nanostructured thin films (electrodes) is presented. A thin layer of anatase particles is deposited on a gold substrate previously roughened through electrochemical oxidation and reduction cycles in order to induce surface enhanced Raman scattering. The electromagnetic contribution to the enhancement extends spatially toward the first layer(s) of TiO2 nanoparticles, allowing an intensification not only of the bands corresponding to bulk anatase, but also of those corresponding to vibrations of molecules adsorbed on the semiconductor nanoparticles. In our case the adsorption of phthalic acid from aqueous HClO4 solutions on TiO2 has been demonstrated. Interference from the gold substrate is avoided by applying a potential triggering the oxidation of its surface. As the enhancement of the Raman scattering is provided by the gold substrate of the nanoparticulate film, this procedure may, in principle, be applied to different semiconductor nanoporous film/adsorbate couples.