Investigation on alcohol vapours/TiO2 nanocrystal thin film interaction by SPR technique for sensing application

Surface plasmon resonance (SPR) was explored as optical transduction technique for monitoring the response of TiO2 thin films as sensing layers for alcohol vapours. Organic solutions of surfactant-capped TiO2 nanocrystals were prepared by means of a colloidal chemistry route, and used as precursors for depositing the sensing layer onto Au/glass substrates. The sensing properties of the active material were examined in relation to the morphological features of both as-deposited and thermally annealed films and to the presence of the organic passivating shell on the TiO2 nanocrystals surface. Untreated titania thin films exhibited a high and reproducible SPR response to alcohol vapours than the corresponding organic-free material. A beneficial role in the sensing process may therefore be attributed to the organic passivating layer on the nanocrystals surface.