New optical materials based on natural extracts immobilized in different silica polymeric matrices

This study aims at investigating the effect of grape seed extract (GSE) immobilization into individual pores and cages of silica/silsesquioxane networks. It might be considered that, since chemically stable guest molecules are already present in the precursor solution for the synthesis, the entrapping of vegetable extract proceeds without significant modification or other adverse changes during the synthesis. As a consequence, some organic chromophore contained in grape seed extract with enhanced optical functions such as fluorescence and nonlinear optical properties can be perfectly incorporated and preserved into the silica based materials. The grape seed extract was immobilized into inorganic and hybrid silica-silsesquioxane matrices by the sol-gel method and it has been proved to be present as an integral part within the matrices pores and with a uniform size distribution. The fluorescence spectrum was discussed in terms of the effect of the host-guest interaction on these properties, and as a function of template type (glucidic and nonionic template). The formation of GSE doped glassy silica materials was investigated and demonstrated by extensive characterization through UV-VIS and FT-IR spectroscopy, estimation method of polymeric aggregates size (DLS), atomic force microscopy (AFM), and optical properties (by fluorescence and non-linear optical measurements). The results of this study demonstrate that GSE entrapped in inorganic and hybrid polymer networks have promising potential as optical systems, due to the extensive conjugation of polyphenolic mixture from the extract and the protective and optical properties of silica polymers.