Effect of the Al2O3 addition on the formation of silver nanoparticles in heat treated soda-lime silicate glasses

We investigate the formation and evolution of silver nanoparticles in the non-irradiated thermally treated glass system Ag:(37-x)Na2O-10CaO-xAl2O3-53SiO2 mol%, where x = 0.0, 0.5, 1, 2 and 5, doped with 0.2 mol% AgNO3. Using optical absorption and transmission electron microscopy we studied the effect of the gradual addition of Al2O3 to the chemical composition of the soda aluminosilicate glasses. A quantitative method for the evaluation of the relative nanoparticles concentration, proportional to the optical absorption intensity of the silver Surface Plasmon Resonance band, was developed and applied to the study of the behavior of the number of particles precipitated in samples thermally treated at temperatures of 400, 500, and 600 °C. Three mechanisms were found, as consequence of the substitution of SiO4 by AlO4 glass forming local tetrahedral structural units, resulting in the gradual suppression of the negatively charged NBOs−, which are the only reducing sources available in the present non-irradiated glass system. The effects produced by the glass chemical and structural changes on the Ag nanoparticles production are discussed.