Preparation and Z-Scan nonlinear optical characterization of Au/SiO2- and Ag/SiO2-supported nanoparticles dispersed in silica sonogel films

Au/SiO 2 and Ag/SiO 2 supported metal-nanoparticles (MNPs) were implemented to fabricate SiO 2 -based inorganic–inorganic hybrid sonogel films. Prepared Au/SiO 2 - and Ag/SiO 2 -MNPs exhibited low 2D-HCP crystallinity with particle diameters below 10 nm and homogeneous size distribution. The catalyst-free (CF) sonogel route was successfully implemented to produce these optically active nanocomposite films by doping the liquid sol-phase with these MNP systems and its subsequent deposition onto glass substrates via standard spin-coating procedures. The easy MNP-loading within the mesoporous dielectric sonogel network evidenced a huge chemical affinity between the silica sonogel hosting system and the guest SiO 2 -supported MNPs. This fact allowed us to fabricate high quality hybrid films suitable for cubic nonlinear optical (NLO) characterizations via the Z-Scan technique. Indeed, the hosting sonogel network provided adequate thermal and mechanical stability protecting the active MNPs from environment conditions and diminished their tendency to aggregate; thus, preserving their pristine optical properties and morphology, giving rise to stable sol–gel hybrid films appropriate for photonic applications. Comprehensive morphological, structural, spectroscopic and nonlinear photophysical characterizations were optimally performed to the developed hybrid films. Our results have shown that the crystalline nature of the implemented MNPs, their small sizes and appropriate guest–host stabilizing interactions play a crucial role in the observation of improved cubic NLO-properties of these MNP structures embedded within the highly pure CF-sonogel confinement.