Search

Lead tungstate PbWO4 nanocrystals in transparent lead borate glass-ceramics containing Er3+ ions were fabricated. Luminescence spectra at about 1530 nm due to main 4 I13/2-4 I15/2 laser transition of Er3+ ions were examined for glass samples before and after heat treatment. Near-infrared luminescence of Er3+ ions in glass-ceramics is enhanced and long-lived in comparison to precursor glasses. It suggests that the Er3+ ions are partially incorporated into PbWO4 crystalline phase. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) luminescence of Pr3+ and Tm3+ ions in titanate‐germanate glasses has been studied for laser and fiber amplifier applications. The effect of the molar ratio GeO2:TiO2 (from 5:1 to 1:5) on spectroscopic properties of glass systems was studied by absorption, luminescence measurements, and theoretical calculations using the Judd–Ofelt theory. It was found that independent of the TiO2 concentration, intense NIR emissions at 1.5 and 1.8 μm were observed for glasses doped with Pr3+ and Tm3+ ions, respectively. Moreover, several spectroscopic and NIR laser parameters for Pr3+ and Tm3+ ions, such as emission bandwidth, stimulated emission cross‐section, quantum efficiency, gain bandwidth, and figure of merit, were determined. The results were discussed in detail and compared to the different laser glasses. Systematic investigations indicate that Pr3+‐doped system with GeO2:TiO2 = 2:1 and Tm3+‐doped glass with GeO2:TiO2 = 1:2 present profit laser parameters and could be successfully applied to NIR lasers and broadband optical amplifiers. [ABSTRACT FROM AUTHOR]

The near-infrared luminescence properties of Pr3+/Yb3+: PLZT ferroelectric ceramics have been examined for the first time. Independently, upon either 450 nm (Pr3+) or 980 nm (Yb3+) excitation, luminescence centered at 1340 nm was observed, which corresponds to the 1G4→3H5 transition of Pr3+. Several spectroscopic parameters for the 1G4→3H5 transition of Pr3+ ions were determined. The average product of emission cross section and radiative lifetime were relatively large for all x/65/35 PLZT samples ( x=6-10) studied, with values close to 105±2 (×10−26 cm2·s). These spectroscopic investigations indicate that Pr3+/Yb3+: PLZT ferroelectric ceramics are promising candidate for efficient sources emitting near-infrared radiation at 1340 nm. [ABSTRACT FROM AUTHOR]

Dy-doped borate glasses with PbO and PbX2 (X = F, Cl) were examined using Raman and luminescence spectroscopy. The Raman spectra show the structural changes of a glass network with B2O3/PbO ratios and presence of PbX2 (X = F or Cl). The photoluminescence spectra measured in the visible range present two bands located at 480 and 573 nm, which correspond to 4F9/2-6H15/2 (blue) and 4F9/2-6H13/2 (yellow) transitions of Dy3+. Luminescence decays from the 4F9/2 state and yellow/blue luminescence intensity ratios (Y/B) were analyzed as a function of glass composition (B2O3/PbO) and PbX2 (X = F, Cl) content. The branching ratios of yellow/blue luminescence increase, whereas the 4F9/2 lifetime of Dy3+ ions decreases with increasing PbO concentration. An introduction of PbX2 to the borate glass results in the increasing of 4F9/2 lifetime and decreasing of the yellow-to-blue luminescence intensity ratio. These phenomena are related to reduction of covalency between Dy3+ and O2−/X− ions. [ABSTRACT FROM AUTHOR]

In this study, a series of Eu3+‐doped silicate xerogels with modified initial compositions is prepared and heat treated at 350 °C to fabricate glass‐ceramic materials containing CaF2 nanocrystals. The impact of an N,N‐dimethylformamide (DMF) additive and a catalyst agent (CH3COOH, HNO3) on the sol–gel transformation from liquid sols through silicate gels and xerogels into glass‐ceramics is investigated using infrared spectroscopy. To verify the formation of CaF2 nanocrystals, X‐ray diffraction (XRD) measurements are performed. The optical behavior of Eu3+ ions in the prepared sol–gel materials is evaluated based on photoluminescence excitation (PLE) and photoluminescence emission (PL) spectra as well as luminescence decay analysis. The distribution of Eu3+ ions between the amorphous silicate hosts and CaF2 nanocrystals in the prepared glass‐ceramic samples is found due to the biexponential character of registered decay curves. In addition, R/O‐ratio (R/O is defined as ratio I(D50‐F72)/I(D50‐F71) analysis is conducted to characterize the efficiency of Eu3+ ion migration into precipitated CaF2 nanocrystals. The lack of DMF as well as HNO3 as a catalyst in the initial composition significantly promotes the incorporation of Eu3+ ions into CaF2 nanocrystals, resulting in long‐lived luminescence with an estimated lifetime τ(D50) = 12.84 ms. [ABSTRACT FROM AUTHOR]

Abstract: In this work, silica powders and transparent glass‐ceramic materials containing LaF3:Eu3+ nanocrystals were synthesized using the low‐temperature sol‐gel technique. Prepared samples were characterized by TG/DSC analysis as well as X‐ray diffraction and IR spectroscopy. The transformation from liquid sols toward bulk powders and xerogels was also examined and analyzed. The optical behavior of prepared Eu3+‐doped sol‐gel samples were evaluated based on photoluminescence excitation (PLE: λem = 611 nm) and emission (PL: λexc = 393 nm, λexc = 397 nm) spectra as well as luminescence decay analysis. The series of luminescence lines located within reddish‐orange spectral scope were registered and identified as the intra‐configurational 4f6‐4f6 transitions originated from Eu3+ optically active ions (5D0 → 7FJ, J = 0‐4). Moreover, the R/O‐ratio was also calculated to estimate the symmetry in local framework around Eu3+ ions. The luminescence spectra and double‐exponential character of decay curves recorded for fabricated nanocrystalline sol‐gel samples (τ1(5D0) = 2.07 ms, τ2(5D0) = 8.07 ms and τ1(5D0) = 0.79 ms, τ2(5D0) = 9.76 ms for powders and glass‐ceramics, respectively) indicated the successful migration of optically active Eu3+ ions from amorphous silica framework to low phonon energy LaF3 nanocrystal phase. [ABSTRACT FROM AUTHOR]

Rare-earth-doped oxyfluoride germanate and borate glasses were synthesized and next studied using spectroscopic methods. Influence of fluoride modifier on luminescence properties of rare earths in different glass hosts was examined. The excitation and emission spectra of Pr3+ and Er3+ ions in the studied glasses were registered. The emission spectra of Pr3+ ions in germanate and borate glasses are quite different and depend strongly on the glass host. In samples doped with Er3+ ions emission bands located around 1530 nm corresponding to the main 4I13/2→4I15/2 laser transition were registered, independently of the glass host. Quite long-lived near-infrared luminescence of Er3+ ions was observed for germanate glasses with low BaF2 content, while in borate glass systems influence of barium fluoride on luminescence lifetimes is not so evident. The Judd-Ofelt calculations were used in order to determine quantum efficiencies of excited states of rare-earth ions in germanate and borate glasses. [ABSTRACT FROM AUTHOR]

New quinolines bearing a 2,2′-bithiophene motif have been prepared through Ru- and In-catalyzed reactions as well as by Suzuki cross-coupling reactions. The novel quinolines have been characterized by using EI-HRMS and NMR spectroscopy. Additionally, the molecular structures of the novel quinolines were confirmed by X-ray crystallography. The photophysical and electrochemical properties of all quinoline derivatives were investigated by using absorption and luminescence spectroscopy and cyclic voltammetry. The main intense absorption bands associated with the quinoline derivatives were located between 350 and 450 nm. Intense blue-green and orange-red fluorescence, moderate Stokes shifts, and microsecond lifetimes were observed. Quinolines containing one bithiophene moiety underwent oxidation leading to dimerization, whereas bis(bithiophenyl)-substituted quinoline underwent polymerization. All the studied quinolines showed multistep reversible reduction, with 6-nitro-4-phenylquinoline being the easiest to reduce. The study of novel quinoline derivatives indicates a strong correlation between their electrochemical and spectroscopic properties and the character of the substituent (electron-donating or electron-withdrawing) in the quinoline ring. [ABSTRACT FROM AUTHOR]