TiO2 sol-gel thin films containing Au and Pt nanoparticles with controlled morphology: optical study and gas sensing properties

Au and Pt nanoparticles are prepared with colloidal techniques in order to achieve high morphological quality, capped with a polymer and then embedded inside a TiO2 sol-gel matrix, resulting in a homogeneous dispersion of both metal colloids, confirmed by TEM analyses. Refractive index values measured with ellipsometry increase with the annealing temperature, with quite a linear trend, and at the same time the Au surface plasmon resonance peak undergoes a red shift: the refractive index evaluated from the Au plasmon band is slightly lower than the measured value, indicating that the refractive index just around metal particles is different from the average of the matrix, likely because of the polymeric capping agent. Optical gas sensing tests towards CO and H-2 are presented as one of the possible applications of these nanocomposites.