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Germanate tellurite glasses doped with Eu3+ and Tb3+ were synthesized by the conventional melt-quenching method. There is no indication of the energy transfer between dopant ions in this host, but the co-dopants exhibit excellent color purity of 100% for Eu3+ and 80% for Tb3+. The co-doped glass exhibits yellow luminescence. The quantum yield of the Eu3+ emission is equal to 23% under 395 nm excitation. The thermal quenching of Eu3+ and Tb3+ luminescence occurs at different temperature ranges, which enables the thermal sensing properties of the material. The relative fluorescence intensity ratio (FIR) sensitivity of 0.16% K−1 was recorded in the wide range of temperatures spanning from −193 °C up to 0 °C. The temperature dependence of the decay times was also studied. The lifetime-based temperature sensitivity was determined to be 0.95% K−1 at 250 °C for Tb3+5D3 level emission and 0.3% K−1 at 225 °C for Eu3+5D1 level emission. [ABSTRACT FROM AUTHOR]

The shielding and spectroscopic properties of Pr + 3 and Pr3+/Ho3+-codoped tellurite glass were investigated. The intensity parameters (Ω2 = 3.24-, Ω4 = 1.64-, Ω6 = 1.10 × 10−20 cm2) as well as the radiative lifetimes of 3F4 + 5S2 and 5I6 excited states of Ho3+ ions were equal to 301 μs and 3.0 μs, respectively. The former value appears to be much higher than that obtained from the lifetime measurement, indicating the presence of various energy transfer processes. The NIR spectrum of Pr3+/Ho3+-co-doped tellurite glass is dominated by strong Ho3+: 5I6 emission at around 1200 nm, being the result of the energy transfer from Pr3+ to Ho3+ ions. The shielding effectiveness of the prepared glasses showed good performance against high-energy photons. These findings suggest that the prepared glasses could be used in laser technology such as photodynamic therapy (PDT) treatment procedures and as shielding for radiation protection. [ABSTRACT FROM AUTHOR]

Gd 3 (Al,Ga) 5 O 12 :RE3+, Yb3+ single crystals (RE3+ = Tm3+, Er3+, Ho3+, Pr3+) were fabricated by the Czochralski technique. Effect of Yb3+ concentration on spectral distribution of luminescence emitted by interacting RE3+-Yb3+ ion pairs and on the dynamics of excitation energy flow in systems under study was investigated and interpreted referring to previously reported spectroscopic features of Gd 3 (Al,Ga) 5 O 12 :RE3+ systems. It was concluded that observed quenching of the Yb3+ emission by co-doped rare earth ions results from an interplay between phenomena of quantum cutting, down shifting and energy dissipation by multiphonon emission. [ABSTRACT FROM AUTHOR]

Oxyfluorotellurite (65-x)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 –xLn 2 O 3 (Ln = Nd 3+ and Yb 3+ , x = 0.5, 2 and 5) and (65-x-y)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 –xNd 2 O 3 –yYb 2 O 3 (x = 0.5, y = 2 and x = 0.5, y = 5) glass systems were fabricated and their optical and thermal properties were investigated. Absorption and emission spectra of RE admixture ions in oxyfluorotellurite glasses were measured and examined at room temperature in the wide spectral region. Oscillator strengths, phenomenological Judd-Ofelt (J–O) intensity parameters, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were determined. Luminescence decay curves of the 4 F 3/2 (Nd 3+ ) and 2 F 5/2 (Yb 3+ ) excited states were recorded and comprehensively analyzed for the single-doped Nd 3+ and Nd 3+ –Yb 3+ co-doped samples. Relaxation dynamics of luminescent levels were studied as a function of the Nd 3+ and Yb 3+ concentrations. An effective non-resonant phonon assisted energy transfer from neodymium to ytterbium was observed and studied. It was found that good thermal stability combined with proper spectroscopic parameters of examined Nd, Yb-doped oxyfluorotellurite glasses imply the suitability of these materials for the design of NIR-emitting efficient optical devices. Furthermore, the ability of the Nd 3+ ions in oxyfluorotellurite glass host as luminescent temperature sensor was verified. Relative intensity ratios of neodymium transitions originated in 4 F 7/2 / 4 F 3/2 and 4 F 5/2 / 4 F 3/2 thermally coupled closely-located excited states have been adequately determined and studied. [ABSTRACT FROM AUTHOR]

Highlights: [•] Influence of temperature on optical properties of the Gd3Ga5O12:Sm single crystals. [•] Analysis of absorption and emission spectra as well as luminescence lifetimes. [•] Estimation of energies of crystal field components of Sm3+ in the Gd3Ga5O12 crystal. [•] Study on energy transfer phenomena using the classical Inokuti–Hirayama model. [ABSTRACT FROM AUTHOR]

Abstract: The KGd2F7:Tb and KGd2F7:Tb,Eu samples were obtained using a solid state reaction. Excitation spectra and emission spectra are reported and analyzed within the VUV–UV–vis spectral range. The intense green luminescence is observed in the KGd2F7:Tb while the combined emission of terbium and europium in the KGd2F7:Tb,Eu covers substantially the region of white light. The materials under study can be effectively excited making use of intense f–d transitions of Tb3+ in the VUV–UV region. Experimental lifetimes of luminescent levels have been measured and discussed. It was found that the considerable energy transfer from Tb3+ to Eu3+ occurs. [Copyright &y& Elsevier]

Using steady-state luminescence measurements, the luminescence spectra of Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Dy3+, Er3+ and Yb3+ for the agrellite sample from the Kipawa River region have been measured. The emission spectra of Eu3+ and Dy3+ next to those of Sm3+ and Pr3+ have been measured for characteristic excitation conditions. The most efficient luminescence activator in the studied sample was Ce3+. This ion was also a sensitizer of Pr3+, Sm3+, Eu3+, and Dy3+ luminescence. [ABSTRACT FROM AUTHOR]

For studied LiAlSi 2 O 6 spodumene crystals, afterglow effect was observed and explained. The luminescence spectra under femtosecond excitation have been presented for this crystal for the first time. The emission bands of point defects in blue, besides those of Mn2+ in orange, have been measured. We demonstrate that emission from defects causes sustaining of emission of Mn2+, and thus, the afterglow phenomenon occurs. The various quantitative ratio of Mn2+ to defects causes the changes in afterglow phenomenon. Image 1 • Lattice defects change color and luminescence intensity of Mn-bearing silicate. • Energy transfer from lattice defects to Mn2+ enhance afterglow effect. • Irradiation changes the mutual contribution of emission from defects and Mn2+. [ABSTRACT FROM AUTHOR]

The Y 2-x Te 4 O 11 (x = 0.1, 0.5, 1.0, 2.0 and 5.0 at%) microcrystalline powders were successfully synthesized by a conventional solid state reaction method. Optical absorption (300 K) and fluorescence spectra (300 K) as well as fluorescence decay curves (300 K) of the emitting levels of Tm 3+ ion in Y 2 Te 4 O 11 powders are presented and analyzed in details. The Judd-Ofelt theory was applied to analyze experimental data for the quantitative determination of phenomenological Ω λ ( λ  = 2, 4, 6) parameters, radiative transition probabilities ( A ), branching ratios ( β ) of luminescence and radiative lifetimes ( τ rad ) of the 1 D 2 , 1 G 4 , 3 H 4 and 3 F 4 levels. The observed non-exponential decays nature and concentration quenching of the 1 G 4 and 3 H 4 states have been attributed to cross-relaxation processes and this phenomena has been analyzed by Inokuti-Hirayama model. The stimulated emission cross-section for the 3 F 4 → 3 H 6 transition equals to 1.12 × 10 −20 cm 2 at 1809 nm was calculated using the Füchtbauer-Ladenburg method and compared with the corresponding values of other Tm 3+ -doped laser hosts. From obtained results, follow that the Tm 3+ :Y 2 Te 4 O 11 is a potential candidate for a solid-state laser host operating at 1.8 µm. [ABSTRACT FROM AUTHOR]

Spectroscopic and luminescent properties of the Pr-doped and Pr–Ag co-doped borate glasses with Li 2 B 4 O 7 (Li 2 O–2B 2 O 3) composition are studied and discussed. Experimental and theoretical oscillator strengths (f exp and f theor), phenomenological parameters (Ω 2 , Ω 4 , Ω 6), radiative properties (A rad , β , τ rad), and quantum efficiencies (η) of the Pr3+ luminescence were calculated basing on the obtained experimental results and Judd–Ofelt theory. Most intense band of the Pr3+ luminescence is peaked at 601 nm (1D 2 → 3H 4 transition). Presence of the isolated Ag+ (4 d 10, 1S 0) ions, small non-plasmonic Ag aggregates (Ag m n + nanoclusters), and plasmonic Ag metallic nanoparticles in the Li 2 B 4 O 7 :Pr,Ag glass was proposed basing on analysis of the photoluminescence and optical absorption spectra. Observed enhancement of luminescence intensity and increasing of stimulated emission cross-section and quantum efficiency of luminescence in the Li 2 B 4 O 7 :Pr,Ag glass is explained by energy transfer from Ag species to the Pr3+ ions as wells local-field effect induced by Ag nanoparticles. • The Pr-doped and Pr–Ag co-doped Li 2 B 4 O 7 glasses of high optical quality were obtained. • Optical absorption, EPR, photoluminescence spectra and decay kinetics were studied. • Judd-Ofelt parameters (Ω 2 , Ω 4 , Ω 6) and radiative properties (A rad , β , τ rad , σ em , η) were calculated. • Enhancement of the Pr3+ emission intensity in the Li 2 B 4 O 7 :Pr,Ag glass was observed. • Mechanisms of the Pr3+ luminescence improvement in the Li 2 B 4 O 7 :Pr,Ag glass is proposed. [ABSTRACT FROM AUTHOR]

Abstract: Luminescence of lead bismuthate glasses PbO-Bi2O3-Ga2O3 containing Dy3+ ions has been studied. Two overlapping luminescence bands corresponding to 3P1–1S0 transition of Bi3+ and 4F9/2 –6H13/2 transition of Dy3+ were detected under 480nm excitation. Comparison of luminescence features for the system under study to those reported for dysprosium-doped lead borate glass PbO-B2O3-Ga2O3 indicates that the luminescence of Dy3+ is efficiently quenched by Bi3+ ions. Analysis of luminescence dynamics implies that the excitation energy transfer from Dy3+ to Bi3+ is nonradiative. The theoretical calculations using Inokuti–Hirayama model confirm strong luminescence of Dy3+ ions in lead bismuthate glasses. [Copyright &y& Elsevier]

GdAl 3 (BO 3) 4 (GAB) compound doped with Tb3+ and Eu3+ was synthetized. The excited states of these lanthanide ions were analyzed up to VUV range 125 000 cm-1 (80 nm). VUV multiplets of Tb3+ and Eu3+ has been determined. The Eg has been estimated to be 7.15 eV and it was assigned to the O 2p → B 2p, 2s transitions within the isolated BO3− groups. The strong and effective coupling between terbium and europium was observed and examined. The efficient impact of temperature on inter-ionic energy transfer was found and examined. The yields of energy transfer (η) at room temperature were determined to be: ca. 20% and 60% for GAB: 20 at.%Tb, 3 at.%Eu and GAB: 20 at.%Tb, 20 at.%Eu, respectively. When the europium 5D 0 multiplet is excited via terbium multiplets, the decay curve becomes non-exponential with build-up part maximum situated at ca. 0.7 ms after initial pulses. Based on the low- and room temperature excitation and luminescence spectra, experimental free-ion levels, located between 0 and 35 000 cm-1, were determined and used for the free-ion analysis. [Display omitted] • Novel terbium-europium crystal has been synthesized. • Addition of Eu changes the symmetry. • The positions of 4f and 5d states have been determined. • Energy transfer processes and quenching mechanism have been appointed. • The influence of temperature on the energy transfer has been given. [ABSTRACT FROM AUTHOR]

Detailed spectroscopic investigation of YVO 4 :5 at% Eu 3+ , 1 at % Tm 3+ single crystal encompassing analysis of absorption, excitation and time resolved emission spectra recorded at 5 K and 300 K made it possible to determine energies, intensities and bandwidths of transitions within 4f n configurations of trivalent thulium and europium. Transients recorded upon femtosecond pulse excitation made it possible to determine dynamics of population build-up and relaxation of excited states involved in luminescence phenomena. It was found that in YVO 4 :Eu, Tm system the metastable 5 D 0 level of Eu 3+ and 1 G 4 level of Tm 3+ can be populated by energy transfer from excited VO 4 3− group and respective intra-ion relaxation processes from higher energy levels. Recorded excitation spectra of the 5 D 0 luminescence of Eu 3+ and of the 1 G 4 luminescence of Tm 3+ do not evidence the Eu 3+ ↔Tm 3+ energy transfer. Nevertheless, an examination of acquired luminescence decay curves, performed with reference to available information on relaxation dynamics of YVO 4 :Tm 3+ system, reveals that the incorporation of Eu 3+ accelerates decays of the 1 G 4 and 3 H 4 levels of Tm 3+ . Spectroscopic parameters characterising the donor–acceptor interaction involved in the 3 H 4 decay were evaluated applying the Inokuti–Hirayama model. Relevance of donor and acceptor transition peculiarities for energy transfer processes contributing to the 1 G 4 and 3 H 4 decays was assessed in the framework of phenomenological model proposed by Kushida and discussed. It was concluded that the intensity ratio of the blue 1 G 4 luminescence to orange–red 5 D 0 luminescence; hence the colour of visible emission in UV-excited YVO 4 :Eu 3+ , Tm 3+ phosphor, may be adjusted by appropriate choice of Eu 3+ and Tm 3+ concentrations. [ABSTRACT FROM AUTHOR]

A new neodymium [Nd(BCPN) 3 (NO 3) 3 (H 2 O) 2 complex with 3-bromo-2-chloro-6-picolinic N-oxide was synthesized and characterized by means of spectroscopic studies and DFT quantum chemical calculations. The IR, Raman, electron UV-VIS and emission spectra measurements were performed. The femtosecond excitation was used to establish an excited energy level depopulation mechanism. The influence of the halo-groups position on the structural and optical properties of the studied compound was discussed. Ligand-to-metal energy transfer in the studied neodymium complex was analysed. Image, graphical abstract [ABSTRACT FROM AUTHOR]