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Copper–alkali ion exchange is used for doping superficial layers of different silicate glasses (commercial soda-lime and BK7) with copper ions. Spectroscopic and time-resolved photoluminescence properties of the obtained systems are studied in the range of 80–294 K. Analysis indicates the presence of Cu+ ions located in distorted octahedral sites, and a different position of the triplet electronic levels for the two glass matrices. The luminescence decay-time signal is simulated by a biexponential behavior, interpreted on the basis of a four-level scheme

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In this paper, we report on the preparation and magnetic properties of small Pt nanoparticles (2-5 nm size). The control of the preparation conditions allow the physical properties of the nanoparticles to be tuned, giving rise to properties different from those of bulk Pt. We show here the first experimental observation of ferromagnetic behavior for carbon-coated platinum nanoparticles with coercivity up to room temperature (i.e., surprisingly there are no superparamagnetic effects despite the small size of the nanoparticles). Measurements of the surface plasmon resonance showed the presence of itinerant electrons. TEM studies confirmed that the nanoparticles exhibit a large concentration of twin boundaries which reduce the surface energy. The lack of cubic symmetry at the twin boundaries could give rise to permanent magnetic moments. The large spin-orbit coupling of platinum accounts for a huge magnetic anisotropy and therefore for the surprisingly high blocking temperature, above 300 K. The relationship of the magnetic properties with the particle structure is also discussed.

This work studies the behavior of Ag + ions incorporated in different silica-based glassy matrices. To this end, Ag-doped silica coatings, prepared via sol-gel and deposited on pure silica and soda-lime glasses, are investigated by means of structural and optical spectroscopy techniques. Silver tends to segregate towards the interface during the annealing process, but in the case of soda-lime glassy substrates the exchange process favors its diffusion into the substrate. The environment of Ag + ions during the annealing process determines their final oxidation state. In the pure silica matrix, Ag + ions are found to be unstable and tend to reduce to Ag 0 , with the subsequent formation of metallic nanoparticles. However, the presence of network formers and modifiers gives rise to the appearance of nonbridging oxygen, which allows the stabilization of Ag + ions in the matrix.

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