[en] Nanostructured plasmonic sensors are fabricated as sinusoidal surface plasmon metallic gratings (SPGs) embedded in a functional and porous hybrid sol–gel material, phenyl-bridged polysilsesquioxane (ph-PSQ). The metal layer is in contact with the environment through the sol–gel film, which works as sensitive element, changing its dielectric properties upon interaction with aromatic hydrocarbons. The combination of sensitivity, transparency and patternability offered by ph-PSQs gives the exceptional possibility to fabricate innovative optical sensors with straightforward processes. An embedded SPG is a thin metal slab waveguide, in which the surface plasmon polaritons (SPPs) at the two metal–dielectric interfaces superpose, resulting in two physical coupled modes: the long range SPPs (LRSPPs) and the short range SPPs (SRSPPs). An extended experimental and theoretical characterization of the optical properties of the plasmonic device was performed. The sensor performance was tested against the detection of 30 ppm xylene, monitoring the influence of the target gas on the SPPs modes. A reversible red-shift of the reflectance dips of both LRSPP and SRSPP resonances in the 1.9–2.9 nm range was observed and correlated to the interaction with the analyte. An enhancement in sensitivity associated with the rotation of the grating grooves with respect to the scattering plane (azimuthal rotation) was verified within the experimental errors. Collected data are compatible with theoretical predictions assuming a variation of the film refractive index of 0.011 ± 0.005. (paper)

[en] A sol–gel route for TiO₂ nanocrystals (NCs) synthesis has been developed at low temperature without surfactants. Synthetic and processing parameters have been optimized to maximize particles’ colloidal stability and crystallinity. The obtained TiO₂ NCs can be homogeneously dispersed in a sol–gel derived organic–inorganic hybrid material, resulting in homogeneous composite films when prepared by spin coating. High refractive index films were obtained with high TiO₂ NCs loading and good transparency. Furthermore, TiO₂ colloidal solutions can be used for depositing porous crystalline films, whose structural evolution has been followed under different annealing treatments. Nanocrystals were characterized by UV–Vis absorption, TEM, FT-Raman, and XRD techniques, while nanocomposite and TiO₂ films were analyzed by SEM, TEM, and spectroscopic ellipsometry.