Nanostructured silica based glass-ceramics samples of composition (100 – x)SiO2-xSnO2, with x from 1 to 10, have been synthesized by thermal treatment of precursor sol–gel glasses. The average size of the obtained SnO2
nanocrystals, calculated by using the X-ray diffraction, can be predetermined by using well-controlled concentration of tin precursor. The mean radius ranging from 1.6 to 5.5 nm, is comparable to the exciton Bohr radius, corresponding to wide band-gap semiconductor quantum-dots in an insulator
SiO2 glass. A spectroscopy study in terms of optical absorption and photoluminescence spectra has been carried out as a function of SnO2 concentration. Size-dependent red-shifts of excitation and emission bands, with increasing of tin precursor concentration, point to
the quantum confinement effect. The nanocrystal sizes have been obtained and compared by using the Brus and Scherrer equations. The band gap increase is in agreement with results, based on the effective mass model. The recombination of conduction band electron with oxygen vacancies is proposed
to explain the luminescence red-shift.
Fe-Doped Sol-Gel Glasses and Glass-Ceramics for Magnetic Hyperthermia