Optical Absorption of Ag Particles Dispersed in a SiO2 Amorphous Matrix

Composite materials of Ag species embedded in SiO₂ matrix were prepared by the sol-gel method. Two kinds of sample preparation were used. In the first one, the Ag aggregates were synthesized using two different reduction solutions, obtaining fine particles with a quasi-spherical shape and particles with a dendrite-like form, that were later added to the SiO₂ matrix. In the second one, the Ag aggregates were formed in the SiO₂ matrix from silver nitrate solutions. The prepared samples were annealed in air at different temperatures. By using uv-visible spectroscopy, X-ray diffraction, EDS, DTA, TGA and SEM, the structures of all the samples were studied. It was found that the embedded species and the heat treatments modify strongly the optical properties of the samples.