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Abstract: Hybrid borate glasses containing different concentrations (0.5–2.0mg in 12g of boric acid) of Mesoporphyrin(IX)dimethylester, Protoporphyrin(IX)dimethylester and Hematoporphyrin(IX)dimethylester were prepared by rapid melt quench technique at 230°C. The hybrid glass samples were characterized by X-ray diffraction, optical absorption, steady state and time-resolved fluorescence emission. The optical absorption spectrum shows red-shift in Soret band along with change in Q-band pattern. The intensity of Q-band was found to increase with increase in the concentration of porphyrin in the glass. Steady state emission spectrum shows strong S2→S0 emission in the range 462–495nm and blue shift in S1→S0 emission. Time-resolved fluorescence emission and fluorescence excitation spectra showed that different structures of porphyrins were exist in the glass samples. The variation in the spectral behaviour in the glass was correlated with those in solution medium and possible structures of porphyrin in borate glass were explored. [ABSTRACT FROM AUTHOR]

Abstract: ZnF2–As2O3–TeO2 glasses mixed with different concentrations of V2O5 (ranging from 0 to 0.6mol%) were synthesized. The amorphous nature of these glasses was checked by X-ray diffraction and scanning electron microscopy techniques. A variety of properties, i.e. optical absorption, photoluminescence, infrared, ESR spectra and dielectric properties (constant ε′, loss tan δ, ac conductivity σ ac over a wide range of frequency and temperature) of these glasses have been explored. The optical absorption, electron spin resonance studies together indicated vanadium ions coexist in V4+ with V5+state in these samples. The IR spectra of these samples have exhibited bands due to ν s-TeO2ax and AsO3 structural groups; these results indicated the most structural disorder in the network as the concentration of V2O5 is increased. Luminescent emission spectra recorded at room temperature of these glasses excited at 640nm have exhibited a broad emission band in the spectral wavelength range of 750–850nm. The luminescence efficiency is found to be the highest for the sample doped with 0.6mol%. The dielectric parameters viz., ε′, tan δ and σ a.c are found to increase and the activation energy for ac conduction is found to decrease with the increase in the concentration of V2O5 up to 0.6mol%, reflecting an increase in the concentration of V4+ ions that take part modifying positions in the glass network. The ac conduction in these glasses could satisfactorily be explained by both classical activation energy and the tunneling phenomena. [Copyright &y& Elsevier]

Abstract: Li2O–CaF2–P2O5 glasses mixed with different concentrations of Cr2O3 (ranging from 0 to 1.0mol%) were crystallized. The samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy (EDS), differential thermal analysis and conventional spectroscopic techniques. The X-ray diffraction and scanning electron microscopic studies reveal the presence of lithium phosphate, calcium phosphate and chromium phosphate (complexes of Cr3+, Cr5+ and Cr6+ ions) crystal phases. The study on DTA suggests that the crystallization is predominantly due to the surface crystallization when the concentration of nucleating agent Cr2O3 is around 0.8mol%. The IR and Raman spectral studies of these samples indicate that the sample crystallized with 0.8mol% Cr2O3 is more compact and possesses high rigidity due to the presence of chromium ions largely in tetrahedral positions. [Copyright &y& Elsevier]

Abstract: Li2O–ZrO2–SiO2: Ho3+ glasses mixed with three interesting d-block elemental oxides, viz., Nb2O5, Ta2O5 and La2O3, were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature. The luminescence spectra of Nb2O5 and Ta2O5 mixed Li2O–ZrO2–SiO2 glasses (free of Ho3+ ions) have also exhibited broad emission band in the blue region. This band is attributed to radiative recombination of self-trapped excitons (STEs) localized on substitutionally positioned octahedral Ta5+ and Nb5+ ions in the glass network. The Judd–Ofelt theory was successfully applied to characterize Ho3+ spectra of all the three glasses. From this theory various radiative properties, like transition probability A, branching ratio β r and the radiative lifetime τ r, for 5S2 emission levels in the spectra of these glasses have been evaluated. The radiative lifetime for 5S2 level of Ho3+ ions has also been measured and quantum efficiencies were estimated. Among the three glasses studied the La2O3 mixed glass exhibited the highest quantum efficiency. The reasons for such higher value have been discussed based on the relationship between the structural modifications taking place around the Ho3+ ions. [Copyright &y& Elsevier]

SeO 2 based glasses of the composition 39 PbO–(60- x) B 2 O 3 – x SeO 2 :1.0 Yb 2 O 3 (with 10 ≤ x ≤ 50) was synthesized. Analysis of the results of structural studies of the samples revealed that the glass network consists of [SeO 4 ]2− and [SeO 3 ]2− units; the studies further indicated an increasing fraction of [SeO 3 ]2− units and decreasing concentration of [SeO 4 ]2− groups with increase of SeO 2 content. Optical Absorption (OA) and photoluminescence (PL) spectra have exhibited bands due to 2F 7/2 → 2F 5/2 and 2F 5/2 → 2F 7/2 transitions, respectively. Evaluated absorption and emission cross-sections and lifetime of the excited state of Yb3+ ions exhibited an increase with increase of SeO 2 content. Results of PL studies indicated nearly fourfold increase of PL output with increase of SeO 2 content up to 50%. Such increase is attributed to the increased concentration of isolated [SeO 3 ]2- pyramidal groups. Overall, the rise of SeO 2 content in Yb3+ doped PbO–B 2 O 3 –SeO 2 glass system facilitated the increase of PL emission of Yb3+ ions largely. [ABSTRACT FROM AUTHOR]