Photoluminescence of silver in glassy matrices

This work studies the behavior of Ag+ ions incorporated in different silica-based glassy matrices. To this end, Ag-doped silica coatings, prepared via sol-gel and deposited on pure silica and soda-lime glasses, are investigated by means of structural and optical spectroscopy techniques. Silver tends to segregate towards the interface during the annealing process, but in the case of soda-lime glassy substrates the exchange process favors its diffusion into the substrate. The environment of Ag+ ions during the annealing process determines their final oxidation state. In the pure silica matrix, Ag+ ions are found to be unstable and tend to reduce to Ag-0, with the subsequent formation of metallic nanoparticles. However, the presence of network formers and modifiers gives rise to the appearance of nonbridging oxygen, which allows the stabilization of Ag+ ions in the matrix.