Spectroscopic Investigation of Structural Rearrangements in Silver Ion-Exchanged Silicate Glasses

The silver ion environment and the microstructural rearrangement of Ag+-Na+ ion-exchanged glasses were investigated by means of micro-Raman and photoluminescence spectroscopies. The samples were produced by immersing borosilicate glasses in NaNO3: AgNO3 molten salts baths with different molar ratios of silver nitrate. The modifications of the silica network microstructure were inspected by analysis of the Raman peak at about 1100 cm^1, and the evolution with the silver concentration at the glass surface of the spectral components related to the different silica tetrahedral groups was studied. The formation of silver metal nanoparticles was inferred from the occurrence of the low-frequency Raman peak due to confinement of acoustic vibrations in metal clusters, and their dimensions were evaluated from the position of its maximum. In the light of the structural analyses performed by means of Raman spectroscopy, a final assignment of the different luminescence bands of silver embedded in silicate glasses was attained.