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Significant changes in the optical properties of nanometer-size Ag clusters embedded in high-purity silica were obtained. Samples were prepared by 2 MeV Ag-ion implantation with fluences in the 2.8–3.8×1016 ions/cm2 range and subsequent annealing at various temperatures in air (oxidizing atmosphere) or in a hydrogen-rich atmosphere (reducing atmosphere). Changes consisted of large and small blueshifts of the resonance surface plasmon peak position, light absorption modification in the ultraviolet (UV) region, increased optical extinction in all the spectrum wavelength range, and different resonance peak height depending on annealing atmosphere. Optical property changes were analyzed in terms of Ag cluster size, interaction at cluster–matrix interface, cluster hydrogen content, diffusivity and conductivity. Bands in the UV region are reported.

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Samples in the MgO-TiO 2 system were prepared via the sol-gel technique with titanium and magnesium ethoxides as precursors and HNO 3 as hydrolysis catalyst. The analyzed magnesia to titania weight ratios were 0.1:0.9, 0.5:0.5, and 0.9:0.1 (0.05, 0.5, and 4.0 MgO: TiO 2 molar ratios). Samples were characterized with X-ray powder diffraction, differential thermal analysis, and thermogravimetry. To quantify the concentration and the crystallography of the phases in the samples, their crystalline structures were refined by using the Rietveld method. In addition to periclase, anatase, and rutile, three intermediate compounds were observed: karooite (MgTi 2 O 5 ), geikielite (MgTiO 3 ), and qandilite (Mg 2 TiO 4 ). The formation of the above crystalline phases in the samples occurred after an exothermic reaction at 200°C, and their dehydroxylation above 300°C. Karooite was abundant only in titania-rich samples, while geikielite and qandilite concentrations were high in the samples with equal magnesia to titania weight percent. Phase concentrations depended on the annealing temperature of the sample and its MgO content. Magnesium was soluble in anatase, but not in rutile; the solubility, however, was low.

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