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Nanophosphors are widely used, especially in biological applications in the first and second biological windows. Currently, nanophosphors doped with lanthanide ions (Ln3+) are attracting much attention. However, doping the matrix with lanthanide ions is associated with a narrow luminescence bandwidth. This paper describes the structural and luminescence properties of co-doped LaPO4 nanophosphors, fabricated by the co-precipitation method. X-ray structural analysis, scanning electron microscope measurements with EDS analysis, and luminescence measurements (excitation 395 nm) of LaPO4:Eu3+/Nd3+ and LaPO4:Eu3+/Nd3+/Yb3+ nanophosphors were made and energy transfer between rare-earth ions was investigated. Tests performed confirmed the crystal structure of the produced phosphors and deposition of rare-earth ions in the structure of LaPO4 nanocrystals. In the range of the first biological window (650–950 nm), strong luminescence bands at the wavelengths of 687 nm and 698 nm (5D0 → 7F4:Eu3+) and 867 nm, 873 nm, 889 nm, 896 nm, and 907 nm (4F3/2 → 4I9/2:Nd3+) were observed. At 980 nm, 991 nm, 1033 nm (2F5/2 → 2F7/2:Yb3+) and 1048 nm, 1060 nm, 1073 nm, and 1080 nm (4F3/2 → 4I9/2:Nd3+), strong bands of luminescence were visible in the 950 nm–1100 nm range, demonstrating that energy transfer took place. [ABSTRACT FROM AUTHOR]

Glass-ceramic is semi-novel material with many applications, but it is still problematic in obtaining fibers. This paper aims to develop a new glass-ceramic material that is a compromise between crystallization, thermal stability, and optical properties required for optical fiber technology. This compromise is made possible by an alternative method with a controlled crystallization process and a suitable choice of the chemical composition of the core material. In this way, the annealing process is eliminated, and the core material adopts a glass-ceramic character with high transparency directly in the drawing process. In the experiment, low phonon antimony-germanate-silicate glass (SGS) doped with Eu3+ ions and different concentrations of P2O5 were fabricated. The glass material crystallized during the cooling process under conditions similar to the drawing processes'. Thermal stability (DSC), X-ray photo analysis (XRD), and spectroscopic were measured. Eu3+ ions were used as spectral probes to determine the effect of P2O5 on the asymmetry ratio for the selected transitions (5D0 → 7F1 and 5D0 → 7F2). From the measurements, it was observed that the material produced exhibited amorphous or glass-ceramic properties, strongly dependent on the nucleator concentration. In addition, the conducted study confirmed that europium ions co-form the EuPO4 structure during the cooling process from 730 °C to room temperature. Moreover, the asymmetry ratio was changed from over 4 to under 1. The result obtained confirms that the developed material has properties typical of transparent glass-ceramic while maintaining high thermal stability, which will enable the fabrication of fibers with the glass-ceramic core. [ABSTRACT FROM AUTHOR]

• Optical properties of titanate-germanate glasses doped with Ho3+ ions were studied. • Near-IR emission spectra of Ho3+and their decays were examined with TiO 2 content. • Spectroscopic parameters for Ho3+ ions in titanate-germanate glass were determined. • Higher concentrations of TiO 2 are preferred for near-IR luminescence at 2 µm. Holmium-doped titanate-germanate glasses have been investigated for optical applications. Near-infrared luminescence at 2 μm due to 5I 7 → 5I 8 transition of holmium ions has been examined in function of TiO 2 concentration. Several spectroscopic parameters for holmium ions such as emission linewidth and lifetime, stimulated emission cross-section and quantum efficiency were determined based on absorption and luminescence experiments and calculated using the Judd-Ofelt theory. Systematic studies demonstrate that holmium-doped titanate-germanate glasses with higher TiO 2 concentration show excellent optical properties. Multicomponent glasses with molar ratios GeO 2 :TiO 2 = 1:2 and 1:3 are recommended for near-infrared luminescence at 2 μm. [Display omitted] [ABSTRACT FROM AUTHOR]

Lead phosphate based glasses doubly doped with Tb 3+ and Eu 3+ ions were prepared and next studied using different spectroscopic techniques. Structural and optical properties of Tb 3+ and Eu 3+ ions have been investigated in lead phosphate based systems, in which PbO:P 2 O 5 molar ratio were changed from 1:5 to 5:1 in glass composition. The fourier transform infrared (FT-IR) spectroscopy was used to verify local structure of glass-network. The FT-IR spectra clearly indicate that different structural phosphate groups are present in PbO-P 2 O 5 based glasses. Moreover, the areas of the FT-IR bands strongly depend on the relative ratio of PbO and P 2 O 5 components. The luminescence spectra for Eu 3+ and Tb 3+ ions in PbO-P 2 O 5 glasses were registered. Several emission bands associated to characteristic transitions of trivalent europium and terbium are observed under direct excitation of Tb 3+ ions. It indicates that the energy transfer process from Tb 3+ to Eu 3+ in lead phosphate glasses occurs. Spectroscopic parameters like 5 D 0 (Eu 3+ ) and 5 D 4 (Tb 3+ ) luminescence lifetimes were determined. Dependence of spectroscopic parameters on the increase of PbO:P 2 O 5 molar ratio from 1:5 to 5:1 in glass composition was established. [ABSTRACT FROM AUTHOR]

In present work, thermal, structural and optical properties of un-doped Li 2 MgGeO 4 and lanthanide - doped Li 2 MgGeO 4 :Ln3+ (Ln = Er, Ho) germanate ceramics have been studied. Based on DSC measurements, two reversible phase transitions were verified during heating and cooling process of germanate ceramics. The results obtained from the Rietveld refinement indicate that Li 2 MgGeO 4 ceramics crystallize in monoclinic crystal lattice. Structural aspects were also evidenced by Raman and infrared spectroscopy. Emission investigations indicate that the most intense green bands due to the 4S 3/2 → 4I 15/2 (Er3+) and 5F 4 ,5S 2 → 5I 8 (Ho3+) transitions are well overlapped with broad band located near 500 nm. Broad green emission is attributed with the presence of magnesium in ceramic matrix. Based on literature data it can be assigned to F-type centers. • un-doped and lanthanide doped germanate ceramics have been studied. • Li 2 ZnGeO 4 ceramics crystallize in a monoclinic crystal lattice. • Intensive emission is due to 4S 3/2 → 4I 15/2 (Er3+) and 5F 4 ,5S 2 → 5I 8 (Ho3+) transitions. • Emission bands of Ln3+ are overlapped with broad green band of ceramic matrix. • Broad green emission is due to presence of magnesium and assigned to F-type centers. [ABSTRACT FROM AUTHOR]

Spectroscopic properties of Er 3+ ions in lead-free oxyfluoride germanate glasses were studied. The absorption and luminescence spectra of Er 3+ ions were examined for glass samples with low and high BaF 2 content. From absorption spectra the bonding parameter was calculated and its value is reduced with increasing BaF 2 content. The maximum of absorption peak due to 4 I 15/2 − 2 H 11/2 hypersensitive transition is shifted to shorter wavelengths (blue shift) with increasing BaF 2 content. Luminescence spectra and their decays corresponding to main 4 I 13/2 − 4 I 15/2 laser transition of Er 3+ are also presented and discussed. Quite long-lived near-infrared luminescence of Er 3+ is observed for lead-free glass samples with low BaF 2 concentration. [ABSTRACT FROM AUTHOR]

Abstract: Structural and optical properties of Eu3+ and Dy3+ ions in PbO–Ga2O3–XO2 (X=Te, Ge, Si) glasses have been examined using X-ray diffraction, FT-IR and luminescence spectroscopy. Several crystalline phases such as TeO2, PbTe3O7, PbO and PbO2 were identified in lead tellurite system using X-ray diffraction analysis, in contrast to PbO–Ga2O3–XO2 (X=Ge, Si) glass samples. Characteristic emission bands due to the 5D0 → 7F J (J =0–4) transitions of Eu3+ and the 4F9/2 → 6H J /2 (J =15, 13, 11) transitions of Dy3+ were registered. Two spectroscopic parameters, such as luminescence intensity ratios associated to 5D0 → 7F2 and 5D0 → 7F1 transitions of Eu3+ as well as 4F9/2 → 6H13/2 and 4F9/2 → 6H15/2 transitions of Dy3+, and luminescence lifetimes for excited states of rare earth ions were determined. The luminescence intensity ratios for Eu3+ and Dy3+ ions decrease, whereas 5D0 (Eu3+) and 4F9/2 (Dy3+) luminescence lifetime increases, when covalence between Ln3+ and O2− ions is reduced and the phonon energy of the host glass is increased in PbO–TeO2 →PbO–GeO2 →PbO–SiO2 direction. It was confirmed by FT-IR measurements. [Copyright &y& Elsevier]

Heavy metal oxide and oxyfluoride lead silicate glasses doped with rare-earth ions were prepared. Next, they were heat treated in order to obtain transparent glass-ceramics. The rare-earths as optically active ions were limited to trivalent Eu3+ and Dy3+. Correlation between the local structure and the luminescence properties of Eu3+ and Dy3+ ions in the studied glass and glass-ceramic systems was examined using X-ray diffraction, FT-IR and optical measurements. Especially, the ratio of integrated emission intensity of the 5D0--7F2 transition to that of the 5D0--7F1 transition of Eu3+, defined as the luminescence intensity ratio R (Eu3+) as well as the ratio of integrated emission intensity of the 4F9/2--6H13/2 transition to that of the 4F9/2--6H15/2 transition of Dy3+, defined as the luminescence intensity ratio Y/B (Dy3+), have been analyzed in details. Their values are reduced due to part incorporation of rare-earth ions into cubic β-PbF2 crystalline phase. The excitation and luminescence spectra of rare-earth ions in glass samples before and after heat treatment are presented and discussed in relation to potential application in optoelectronics. [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]

Oxychloroborate glasses containing Dy3+ ions in the B2O3-PbCl2-PbO-Al2O3-WO3 system were studied using X-ray diffraction, Raman, FT-IR, absorption, excitation and luminescence spectroscopy. The results concerning glass preparation, short-range order structure and optical properties are reported. X-ray diffraction analysis evidently indicates that the fully amorphous system was prepared. Coexistence of trigonal BO3 and tetrahedral BO4 units was evidenced by Raman and FT-IR spectroscopy. The electronic states belonging to the 4f 9 configuration of trivalent Dy3+ were determined from the absorption and excitation spectra. The luminescence bands at 480, 573 and 662 nm were registered in oxychloride glasses, which correspond to transitions originating from the 4F9/2 state to the 6HJ/2 (J = 11, 13, 15) states of Dy3+. [ABSTRACT FROM AUTHOR]

Energy transfer processes from Cr3+ to Nd3+ and NIR luminescence of Nd3+ ions at 1.06 µm in Cr-Nd co-doped lead borate glasses have been investigated. The spectroscopic investigation indicates that Cr3+ ions are located at strong-field and weak-field sites. Replacing PbO by PbF2 in lead borate glasses slightly influences the energy transfer processes between Cr3+ and Nd3+ and NIR luminescence of Nd3+ ions. The energy transfer process occurs in both oxide and oxyfluoride glass systems, which may be due to the thermally induced population of the 4T2 excited state of Cr3+ ions and the participation of lattice phonons. [ABSTRACT FROM AUTHOR]

Abstract: Results of X-ray diffraction, infrared spectroscopy, differential scanning calorimetry and optical emission together with lifetime measurements of phosphate fluoroindate glasses activated by Pr3+ ions are reported. Structural, thermal and optical behavior of multicomponent oxyfluoride glasses has been analyzed as a function of P2O5 concentration. Short glass-forming region exists for InF3-based system with P2O5 additives. For low (4–12%) P2O5 concentration, thermally stable and transparent non-crystalline oxyfluoride samples based on InF3 with relatively high ΔT factors were prepared, which can be promising for fiber drawing. For higher (16%) P2O5 concentrations, several diffraction lines due to the InOF polycrystalline phase were identified. Absorption edge and luminescence bands for Pr3+ ions in fluoroindate glasses are shifted in the direction of the lower frequency region with increasing of P2O5 content. Luminescence from both 3P0 and 1D2 excited states of Pr3+ ions was registered. The 1D2 luminescence lifetime close to about 35μs is independent on P2O5 concentration. [Copyright &y& Elsevier]

In this paper, we performed a comparative spectroscopic analysis of Tm3+-doped glasses based on GeO 2 -BaO-Ga 2 O 3 (GBG) and TiO 2 -GeO 2 -BaO-Ga 2 O 3 (TGBG) to achieve broadband luminescence at 1.8 μm. Glasses were prepared at different doping concentrations (0.05 mol% and 1mol%) in order to investigate the effect of Tm3+ ions as well as host composition (GeO 2 :TiO 2 molar ratios) on near-IR luminescence properties. We report on the hypersensitivity of the transition 3H 6 → 3F 4 of Tm3+ in a series of titanate-germanate glasses, which was shifted to longer wavelengths with increasing TiO 2 concentration. The relative intensity of the main near-IR emission band corresponding to the 3F 4 → 3H 6 (1.8 μm) transition of Tm3+ was 4.8-fold enhanced for glass with molar ratio GeO 2 :TiO 2 = 1:5 compared to GBG glass system. We observed the luminescence quenching phenomena for samples containing more than 0.5 mol% of Tm3+ ions. The calculated spectroscopic parameters, such as measured luminescence lifetime (τ m) and the quantum efficiency (η), were discussed and compared to the different laser glasses. Importantly, luminescence decay curves have been examined using the Inokuti-Hirayama model. Additionally, the correlation between optical properties and local structure in glasses was well evidenced by Raman spectroscopy. The proposed strategy, in combination with various chemical composition of glass host activated by various Tm 2 O 3 concentration, might be beneficial for modern near-infrared photonics. • NIR emission of Tm3+ in BGG glass was examined with TiO 2 and activator content. • The main band due to 3F 4.→ 3H 6 transition of Tm3+ was 4.8-fold enhanced. • The hypersensitive 3H 6.→ 3F 4 transition of Tm3+ was shifted to longer wavelengths. • The luminescence decay curves were examined by the Inokuti-Hirayama model. • Tm3+-doped glasses with GeO 2 :TiO 2 = 1:1, 1:2, 1:3 can be attractive for photonics. [ABSTRACT FROM AUTHOR]

In this paper, we report on fabricating optical fibers with a controlled process of crystallization core during the drawing process. The research and synthesis of the core material of silica-germanium-antimony oxide glass were discussed. We also investigated the optical and luminescence properties were in relation to concentrating Eu 2 O 3 and P 2 O 5. Based on this investigation, we selected the most promising material for optical fiber core. In the next step, we drew optical fibers using a well-known rod-in-tube method. After drawing, we examine the optical fibers for luminescence shape changes. We observed a promising similarity between optical fibers and heat-treated samples with confirmed nanocrystals. Finally, XRD and TEM measurements confirm EuPO 4 nanocrystals at the core of the optical fiber. Highlighting the successful control of crystallization in the one-step method used to draw optical fibers. [ABSTRACT FROM AUTHOR]

In this work, the electrical and optical properties of glasses and glass-ceramics are presented and discussed in details. Several electrical and optical parameters for glasses and glass-ceramics were determined. The conduction activation energy and DC conductivity depend on temperature, glass composition and concentration of glass modifiers. The optical properties of glasses and glass-ceramics containing Er 3+ (or Er 3+ /Yb 3+ ) ions have been analyzed for near-infrared luminescence centered at about 1.5 μm and up-conversion applications. In particular, luminescence bandwidths and lifetimes for the 4 I 13/2  →  4 I 15/2 transition of Er 3+ were determined as a function of host-matrices and then examined for near-infrared solid-state lasers and broadband optical amplifiers. The green up-conversion luminescence spectra for Er 3+ and Er 3+ /Yb 3+ doped systems are temperature-dependent and can be used to optical sensors. [ABSTRACT FROM AUTHOR]

In the paper analysis of structural and luminescent properties of antimony-germanate-borate glasses and glass fiber co-doped with 0.6AgNO 3 /0.2Eu 2 O 3 are presented. Heat treatment of the fabricated glass and optical fiber (400 °C, 12 h) enabled to obtain Ag nanoparticles (NPs) with average size 30–50 nm on their surface. It has been proofed that silver ions migrate to the glass surface, where they are reduced to Ag 0 nanoparticles. Simultaneously, FTIR analysis showed that heat treatment of the glass and optical fiber increases the local symmetry of the Eu 3+ site. [ABSTRACT FROM AUTHOR]

Lead borate glasses doubly doped with Dy 3+ –Tb 3+ were investigated using optical spectroscopy: photoluminescence and decay time measurements. The main green emission band due to the 5 D 4 → 7 F 5 transition of Tb 3+ was observed under excitation of Dy 3+ . The energy transfer process from Dy 3+ to Tb 3+ occurs through nonradiative processes. The energy transfer efficiencies and transfer probabilities as a function of a square of the total rare earth ions concentration using Förster method were calculated. The nonlinear behavior of the energy transfer probability and the luminescence intensity ratio for a higher concentration of acceptor was studied taking into account the possible processes: concentration quenching and partial crystallization of the lead borate glasses. [ABSTRACT FROM AUTHOR]

Series of lead-free borate glasses with different oxide modifiers and lanthanide ions were prepared. The effect of oxide modifiers MO (M = Ca, Sr, Ba) on spectroscopic properties of trivalent Ln 3+ (Ln = Eu, Er, Pr) were systematically investigated. Especially, the luminescence spectra of Ln 3+ -doped lead-free borate glasses are presented and discussed in relation to the impact of selective components (CaO, SrO and BaO). Several spectroscopic parameters, such as the fluorescence intensity ratio R/O (Eu 3+ ) and measured luminescence lifetimes for the 5 D 0 (Eu 3+ ), 4 I 13/2 (Er 3+ ) and 1 D 2 (Pr 3+ ) excited states of lanthanide ions were analyzed in details. The research proved that spectroscopic properties of trivalent Ln 3+ depend significantly on kind of presence oxide modifiers MO (M = Ca, Sr, Ba) in glass host matrices. [ABSTRACT FROM AUTHOR]

Rare earth doped lead-free oxide and oxyfluoride germanate glasses were synthesized. The rare earths as an optically active ions were limited to trivalent Eu 3 + . One of the glass modifier components is MO (M = Ca, Sr or Ba), which was partially or totally substituted by MF 2 in chemical composition. The influence of glass modifiers on structure of lead-free-germanate glasses was examined using X-ray diffraction analysis. In contrast to samples containing modifier MO (M = Ca or Sr), samples with BaO and/or BaF 2 are fully amorphous. For the amorphous samples, the emission properties of Eu 3 + ions were studied. The emission spectra of Eu 3 + ions and their decays in glass samples with different BaF 2 contents were analyzed. Several spectroscopic parameters, such as fluorescence intensity ratio R/O (Eu 3 + ) and measured luminescence lifetime for 5 D 0 state of Eu 3 + are presented and discussed in details. [ABSTRACT FROM AUTHOR]

Four novel cyclometalated iridium(III) complexes: [Ir(q-bt-Ph) 2 (phen)]PF 6 , [Ir(q-bt-Ph) 2 (acac)], [Ir(q-bt-Me) 2 (bpy)]PF 6 and [Ir(q-bt-Me) 2 (acac)] (where q-bt-Ph, q-bt-Me correspond to 2-(2,2’-bithien-5-yl)-4-phenylquinoline and 2-(2,2’-bithien-5-yl)-4-methylquinoline), are reported. The complexes were characterized by NMR, FTIR and HRMS. The optical, electrochemical properties and thermal stability of novel iridium(III) complexes were thoroughly investigated. The complexes emit a light in the narrow range of 693–707 nm. The optical study showed that replacement of fragment in the main quinoline ligand did not affect wavelength of the emitted light. On the other hand, the modification of the ancillary ligand and substituent in the quinoline ring caused the increase of the photoluminescence quantum yields. Electrochemical experiments demonstrate that the oxidation process for complexes [Ir(q-bt-Ph) 2 (phen)]PF 6 and [Ir(q-bt-Ph) 2 (acac)] was reversible (or quasi-reversible) and well detectable whereas for complexes with quinoline substituted by methyl group was irreversible, even at low temperature (−70 °C). The electrochemical and photophysical studies have been well confirmed by density functional theory (DFT) calculations. In addition, bulk heterojunction polymer solar cells based on complexes [Ir(q-bt-Ph) 2 (phen)]PF 6 and [Ir(q-bt-Ph) 2 (acac)] were fabricated. Only the solar cell incorporating [Ir(q-bt-Ph) 2 (acac)] exhibited a photovoltaic effect. The architecture of the cell was ITO/PEDOT:PSS/P3HT:PCBM:[Ir(q-bt-Ph) 2 (acac)]/Al. A power conversion efficiency of 0.25% was measured under 1 sun illumination using an AM 1.5G filter to simulate the solar spectrum. [ABSTRACT FROM AUTHOR]

New multicomponent europium-doped lead phosphate based glasses with various PbO:P 2 O 5 molar ratios were prepared and next studied using optical spectroscopy. Based on excitation and luminescence spectra measurements, some spectroscopic parameters like the phonon energy of the glass host and the fluorescence intensity ratio R of the 5 D 0 → 7 F 2 to 5 D 0 → 7 F 1 transition of Eu 3+ ions were determined. Luminescence lifetimes ( τ m ) for the 5 D 0 state of Eu 3+ ions were also evaluated. Optical properties of Eu 3+ ions have been investigated in lead phosphate based systems, in which PbO:P 2 O 5 molar ratio were changed from 1:5 to 5:1 in glass composition. The value of the phonon energy of the host decreases with increasing PbO concentration. In addition, the spectral lines are shifted toward higher wavelengths. Non-monotonic dependence of fluorescence intensity ratio R (Eu 3+ ) upon PbO:P 2 O 5 content has been observed. Influence of PbO:P 2 O 5 molar ratio on spectroscopic parameters for Eu 3+ are presented and discussed. [ABSTRACT FROM AUTHOR]