A site-selective spectroscopy study of Ag nanoclusters dispersed in oxyfluoride glass hosts has been carried out. The nano- to millisecond, essentially non-exponential, luminescence kinetics of Ag nanoclusters has been detected in the spectral range from 450 to 1000 nm, when excited at discrete wavelengths in the range 250 to 450 nm. Based on these experimental observations, the energy level configuration coordinate diagram for the involved ground and excited singlet/triplet states of the Ag nanoclusters has been proposed and confirmed by the density functional theory (DFT). The sites for the Ag nanoclusters are argued to be multiple. The structure/geometry of the involved Ag nanoclusters has been suggested to involve spin-paired dimers Ag²⁺, or tetramers Ag₄²⁺, with a varying elongation/distortion along the tetramer diagonals.

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Transparent oxyfluoride nano-glass-ceramics have been prepared by melting-quenching and doped with five different Nd 3+ concentrations (0.1-2 mol%) to obtain the most efficient 4 F 3/2  4 I 11/2,13/2 emission. It was observed by differential thermal analysis (DTA) that the addition of Nd 3+ does not affect the crystallization mechanism which corresponds to a diffusioncontrolled volumetric process that starts from a constant number of nuclei. Nevertheless, the presence of the dopant affects the kinetics due to the progressive increase of T g on increasing the Nd 3+ content. LaF 3 crystals with a size between 9-12 nm are obtained after heat treatments at T g + 20-80 °C as confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM). Energy dispersive X-ray (EDX) analysis shows the incorporation of Nd 3+ ions into the LaF 3 nano-crystals. Judd-Ofelt analysis from the absorption spectra further demonstrate the incorporation of Nd 3+ ions into the fluoride phase and the most relevant parameters such as radiative lifetime and stimulated emission cross-section are calculated. A detailed optical characterisation clearly shows that Nd 3+ ions in the glass-ceramics are incorporated in both crystalline and amorphous phases. Low temperature site-selective emission and excitation spectra, together with the different lifetime values of the 4 F 3/2 state depending on the excitation and emission wavelengths, allow emission from Nd 3+ ions in the LaF 3 nanocrystals to be identified and correlated with the structural properties. As the Nd 3+ concentration is increased beyond 0.1 mol%, a stronger quenching of lifetime is observed for Nd 3+ ions residing in LaF 3 crystals than for those dispersed in the glass matrix. This strong concentration quenching is explained by the much higher concentration of Nd 3+ ions in the crystalline phase with respect to that in the glass matrix.

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