Bulk oxyfluoride glasses doped with Ag nanoclusters have been prepared using the melt quenching technique. When pumped in the absorption band of Ag nanoclusters between 300 to 500 nm, these glasses emit a very broad luminescence band covering all the visible range with a weak tail extending into the near infrared. The maximum of the luminescence band and its color shifts to the blue with a shortening of the excitation wavelength and an increasing ratio of oxide to fluoride components, resulting in white color luminescence at a particular ratio of oxide to fluoride; with a quantum yield above 20%.

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.

Glass ceramics of composition 95SiO2-5SnO2 doped with 0.4mol% Eu3+ have been prepared by thermal treatment of sol-gel glasses. The segregated SnO2 nanocrystals present a mean size comparable to the bulk exciton Bohr radius (about 2.4nm), corresponding to a wide band-gap quantum-dot system in an insulator SiO2 glass. A fraction of the Eu3+ ions is incorporated to the SnO2 nanocrystals in the process. In these strong confinement conditions, the energy gap presents a high dependence on the nanocrystal size. Taking advantage of this effect, it has been possible to excite selectively the Eu3+ ions located in the SnO2 nanocrystals, by energy transfer from the host, obtaining emission spectra that depend on the nanocrystal size. The Eu3+ ions environment in small nanocrystals (radius under 2nm) are very distorted, meanwhile they are like crystalline for nanocrystals with a radius of some nanometers.

Broadband and fluorescence line narrowing optical spectroscopic studies have been used to investigate the local environments of Eu 3ϩ ions in lithium fluoroborate glasses. From the vibronic spectra, different borate groups coupled with the Eu 3ϩ ions have been identified. A pulsed tunable dye laser has been used to selectively excite the 5 D 0 level of the Eu 3ϩ ion and the subsequent 5 D 0 → 7 F 1 fluorescence spectra have been monitored as a function of the exciting wavelength. From these FLN studies, three 7 F 1 Stark levels have been identified and a C 2v orthorhombic symmetry has been assumed in the subsequent calculation of the crystal-field parameters for the different environments occupied by the Eu 3ϩ ions in the glass. The second rank crystal-field parameters have been systematically analyzed for the Eu 3ϩ :lithium fluoroborate glass from the site dependent behavior of the 7 F 1 level splitting. The importance of the J-mixing in the crystal-field analysis has been emphasized. An appropriate method for comparing the crystal-field interactions in different glasses has been proposed by analyzing the 7 F 1 level. Thus, results obtained for the Eu 3ϩ :fluoroborate have been compared with recalculated results in other Eu 3ϩ doped fluoride, borate, silicate, and borosilicate glasses. An intermediate behavior between Eu 3ϩ :oxide and Eu 3ϩ :fluoride glasses is observed for the local structure of the Eu 3ϩ ions in the fluoroborate glass, indicating the active participation of fluorine ions in the immediate environments of the lanthanide ion in this glass.

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