SIMS characterization of surface-modified nanostructured titania electrodes for solar energy conversion devices

This paper deals with the investigation of a stepwise surface priming strategy based on zirconium phosphate-phosphonate chemistry (ZP priming), which was applied for the first time to nanostructured, micrometer-thick titanium dioxide electrodes. Through the extensive use of secondary ion mass spectrometry (SIMS) depth profiling technique, it was possible to monitor the composition of the titania samples after every single reaction step of the priming. In particular, the impregnation of the surface with zirconium was found to be the determining step of the whole treatment. SIMS data allowed for the identification of the diffusion mechanism that governs the uptake of zirconium from an aqueous Zr(IV)-containing solution. Furthermore, from the depth profiling results, it was possible to optimize the priming experimental conditions in order to achieve the desired uniform surface modification along the entire nanostructured TiO2 layer. ZP-priming of nanostructured titania electrodes could be exploited within the field of dye-sensitized devices for solar energy conversion, by providing an anchoring platform for stable binding, at the oxide surface, of photoactive molecular systems bearing phosphonic moieties.