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Phthalocyanines (Pc) based compounds having central metallic atoms of Ni were successfully embedded in
mesoporous silica gels via a catalyst-free sol-gel (sonogel) process in order to fabricate optically active solid-state
hybrid glasses in both bulk and thin film formats at different dopant concentrations. The organic-inorganic
hybrid composites obtained at room temperature processing showed stable mechanical
performance, controllable geometrical shapes, good transparency and homogeneity suitable for linear and
nonlinear optical (NLO) characterizations. Hybrid samples were studied via the NLO third-harmonic
generation (THG) technique. AFM studies, epi-microscopy surface evaluation, refractive-index measurements
and UV-Vis spectroscopy studies were also performed in selected bulk and film samples. The morphological
and spectroscopic results showed a homogeneous dispersion of the organometallic compounds within the
highly pure SiO2-sonogel network. Moreover, Brewster's angle measurements have demonstrated the
feasibility of tuning the refractive index of the samples by varying the chromophore dopant concentration.
Additionally, the electronic absorption spectra showed band shifts in the two characteristic bands of the
organometallic compound within sonogel environment, which evidence the formation of molecular H-aggregates
for the developed hybrids and the consequent modifications of their optical properties. Finally,
THG measurements in hybrid film samples exhibited an important NLO activity. We conclude that the optical
effects of these composites can be tuned as function of the nickel-Pc concentration and that the sonogel matrix
mainly acts as an inert protective shell, giving stable mechanical and thermal properties to the guest dopant
compounds.
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