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The application of ultraviolet-C light in the field of surface treatment or photodynamic therapy is highly prospective. In this regard, the stable fluorescent silicate SrO-CaO-MgO-SiO2-Pr2O3 glasses able to effectively convert visible excitation on the ultraviolet praseodymium emission were fabricated and examined. An unusual wide-range visible-to-UVC up-conversion within 240–410 nm has been achieved in Pr3+-doped glasses, revealing their potential advantage in different sophisticated disinfection technologies. The integrated emission intensity was studied as a function of light excitation power to assess a mechanism attributed to UVC luminescence. Especially, it was revealed that the multicomponent silicate glass qualities and praseodymium 3PJ excited state peculiarities are favorable to obtaining useful broadband ultraviolet up-converted luminescence. The glass dispersion qualities were determined between 450–2300 nm. The impact of praseodymium concentration on Vis-NIR spectroscopic glass qualities was evaluated employing absorption spectra, emission spectra, and decay curves of luminescence associated with two involved praseodymium excited states. Especially, efficient interionic interactions can be inferred by investigating the decrease in 1D2 state experimental lifetime in the heavily doped samples. Examination of absorption spectra as a function of temperature implied that excitation at 445 nm should be quite effective up to T = 625 K. Contrary to this, temperature elevation gives rise to a moderate lowering of the visible praseodymium luminescence. [ABSTRACT FROM AUTHOR]

The co-existence of divalent tin activator and Nd3+/Yb3+ rare earths in the borate glasses were utilized and examined to achieve the effective enhancement of the useful near-infrared emission in the wide spectral region. The UV Sn2+ excitation is extremely relevant for the effectiveness of both (Nd,Yb) near-infrared emission, however, Sn-Nd energy transfer efficiency is particularly prominent. The different advantageous inter-ionic phenomena made it possible to explore the diverse energy transfer routes leading to the population of the relevant ytterbium and neodymium excited states. Consequently, adequate multi-model temperature sensing can be proposed and verified considering single-doped and co-doped borate glass systems. The dissimilar effect of temperature on the complementary Sn2+, Nd3+ and Yb3+ optical transitions was investigated in detail. Employing the temperature-dependent spectra of optically active ions, high values of temperature relative sensitivity (1.3 % K−1) were estimated especially in the physiological range (30 – 75 ⁰C). • Divalent tin activator enhances Near-Infrared Emission of Nd3+/Yb3+ rare earth ions in borate glass • Prominent Sn-Nd-Yb energy transfer routes significantly enhance Yb3+ emissions. • The temperature dependent and independent energy transfer allows for development of multi-model temperature sensing. • High values of temperature relative sensitivity (1.3 % K⁻¹) observed, especially in the physiological range (30–75 ⁰C). [ABSTRACT FROM AUTHOR]

The thermal stability of oxyfluorotellurite glass systems, (65-x)TeO2 -20ZnF2 -12PbO-3Nb2O5 - xPr2O3 , doped with praseodymium was examined. The different concentrations of praseodymium oxide (x = 0.5 and 2 mol%) were applied to verify the thermal, optical and luminescence properties of the materials under study. The relatively high values of the Dietzel (∆T) and Saad–Poulain (S or H′ ) thermal stability factors determined using a differential thermal analysis (DTA) indicate the good thermal stability of the glass matrix, which gradually improves with the content of the active dopant. The temperature dependence of optical spectra in the temperature range 300–675 K for the VIS–NIR region was investigated. The involved Pr3+ optical transition intensities and relaxation dynamic of the praseodymium luminescent level were determined. The ultrashort femtosecond pulses were utilized to examine a dynamic relaxation of the praseodymium luminescent levels. Although the measured emission of the Pr3+ active ions in the studied glass encompasses the quite broad spectral region, the observed luminescence may only be attributed to 3PJ excited states. As a result, the observed decrease in the experimental lifetime for the 3P0 level along with the increasing activator content was identified as an intensification of the Pr–Pr interplay and the associated self-quenching process. The maximum relative sensitivities (Sr) estimated over a relatively wide temperature range are ~0.46% K−1 (at 300 K) for FIR (I530/I497) and 0.20% K−1 (at 600 K) for FIR (I630/I497), which seems to confirm the possibility of using investigated glasses in optical temperature sensors. [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]

Abstract The thermal and optical properties of oxyfluorotellurite (65-x)TeO 2 -20ZnF 2 -12PbO-3Nb 2 O 5 -xSm 2 O 3 (x = 0.5, 2 and 5) glass systems were investigated. Glass thermal stability were monitored by differential thermal analysis (DTA) and adequate thermal stability criteria ΔT, H' and S were determined. It was shown that the thermal stability of the investigated materials increases with the increasing of samarium ions content. The absorption and emission spectra of Sm3+ ions in oxyfluorotellurite glass were recorded in the wide spectral range from UV to NIR. Based on the Judd-Ofelt (J–O) procedure oscillator strengths, phenomenological Judd-Ofelt intensity parameters Ω 2,4,6, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were determined. The luminescence decay curves of the 4G 5/2 (Sm3+) excited state were recorded for three different concentrations of Sm3+ and corresponding experimental lifetimes were determined. Photoluminescence emission spectra were measured in the temperature range from 300 K up to 725 K to evaluate the materials under study as luminescent temperature sensor. Highlights • (65-x)TeO2-20ZnF2-12PbO-3Nb2O5-xSm2O3 (x = 0.5, 2, 5 mol%) glasses were prepared. • Thermal properties of glasses were analyzed as a function the Sm3+ concentrations. • The optical properties of Sm3+ ions in oxyfluorotellurite glass were assessed. • The materials under study were evaluated as luminescent temperature sensors. [ABSTRACT FROM AUTHOR]

Abstract Spectroscopic properties of Gd 3 Ga 3 Al 2 O 12 (GGAG) single crystals co-doped with various configurations of (Eu + Tb); (Eu + Ce); (Tb + Ce) and (Eu+ Tb + Ce) ions have been investigated. The effect of distinct Ln3+ co-doping variations on luminescence of garnet crystals was studied using the different excitation wavelengths. The Ln3+-Ln3+ and host-Ln3+ interplays have been considered in doubly and triply doped GGAG:Ln3+. The crystals containing cerium ions are characterized by mainly broadband emission in the 450–750 nm spectral region that is adequately modified in green and red spectral range in the samples co-doped with terbium and europium, respectively. The Eu3+ luminescence in materials under study is selectively excited employing solely f-f europium transitions. Contrary to that, emission of terbium and cerium occur as result of interaction with Gd3+ and adjacent co-dopants. Graphical abstract Image 1 Highlights • Novel doubly and triply - doped GGAG garnet crystals for lighting system applications. • Luminescent and excitation properties of GGAG:Ce,Tb,Eu crystals. • Optimization of phosphor color by various combination of Ce, Tb, Eu dopants. • Evaluation of Ln3+-Ln3+ and host-ion interactions. [ABSTRACT FROM AUTHOR]

The optical temperature sensing properties of a low-phonon fluoroindate glass co-doped with different trivalent lanthanide ions (IFG:Ln3+/Yb3+, Ln = Er, Tm, and Tm-Ho) were assessed using the fluorescence intensity ratio (FIR) technique. The temperature-dependent upconverted luminescence was carried out in the temperature range between 300 and 583 K using the thermally-coupled energy levels, non-thermally coupled levels, and their additional combinations. The highest relative sensitivity was obtained in the IFG:Tm3+/Yb3+ sample at 355 K (1.4% K−1), from 3F 2 , 3H 4 → 3H 6 FIR evaluation, while the maximum absolute sensitivity was found in the IFG:Ho3+/Yb3+ system at 583 K (0.020 K−1), from Tm(1G 4 →3H 6 +3H 4 →3H 6)-Ho(3F 4 →5I 7) FIR assessment. Furthermore, the chromaticity diagram (CIE) evidenced an important change of color when the temperature increased in IFG:Er3+/Yb3+ sample, because this showed an evident transition from green to yellowish. Also, the heating effect caused by 980 nm excitation is negligible in most of the samples. Additionally, their amorphous nature was confirmed by X-ray diffraction and their thermal stability was evaluated using differential thermal analysis resulting in a great glass thermal stability up to 583 ± 2 K. Therefore, IFG:RE3+/Yb3+ glass systems are considered as excellent candidate for temperature sensing. [Display omitted] • The temperature induces changes in the emission color of Er3+, Tm3+, and Ho3+ ions. • The fluoroindate glass matrix promoted thermal excitation between energy levels. • Thermal excitation favors some negligible radiative transitions. • The assessment of non-TCLs overcomes energy gap limitations and enhances sensitivity. • The FIR repeatability indicates good viability in optical temperature applications. [ABSTRACT FROM AUTHOR]

Fluorides have a wide bandgap and therefore, when doped with the appropriate ions, exhibit emissions in the ultraviolet C (UVC) region. Some of them can emit two photons in the visible region for one excitation photon, having a quantum efficiency greater than 100%. In a novel exploration, praseodymium (Pr3+) ions were introduced into KLaF4 crystals for the first time. The samples were obtained according to a high-temperature solid-state reaction. They exhibited an orthorhombic crystal structure, which has not been observed for this lattice yet. The optical properties of the material were investigated in the ultraviolet (UV) and visible ranges. The spectroscopic results were used to analyze the Pr3+ electronic-level structure, including the 4f5d configuration. It has been found that KLaF4:Pr3+ crystals exhibit intense luminescence in the UVC range, corresponding to multiple 4f → 4f transitions. Additionally, under vacuum ultraviolet (VUV) excitation, distinct transitions, specifically 1S0 → 1I6 and 3P0 → 3H4, were observed, which signifies the occurrence of photon cascade emission (PCE). The thermal behavior of the luminescence and the thermometric performance of the material were also analyzed. This study not only sheds light on the optical behavior of Pr3+ ions within a KLaF4 lattice but also highlights its potential for efficient photon management and quantum-based technologies. [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]

The electron absorption-, photoluminescence- and electron paramagnetic-resonance spectra of Mn3+ in red beryl from Wah Wah Mountains (Utah USA) and of pink- and purple vesuvianite from Jeffrey Mine (Asbestos, Canada) were measured at room- and low temperatures. The crystal field stabilization energies are equal to 130.9 kJ/mol for the red beryl, and 151.5-158.0 and 168.0 kJ/mol for for the pink- and the purple vesuvianite, respectively. The red photoluminescence of Mn3+ was not intensive either at room- or at low temperatures. The high Mn content in the crystals caused the emergence of an additional emission band and short photoluminescence-decay lifetimes. The latter are only 183 μs for beryl and 17 μs for vesuvianite. [ABSTRACT FROM AUTHOR]

The CsCaI 3 single crystals doped with Tm 2+ were grown by Bridgman technique. Divalent thulium luminescence related to the 4f 13 -4f 13 intra-configurational and 4f 12 5d 1 -4f 13 inter-configurational transitions were analyzed as a function of temperature. Excited state excitation spectroscopy has been applied within a wide spectral range to examine peculiarities of transitions between different 4f 12 5d 1 excited states of Tm 2+ . This two-color excitation experiment was useful to assess d-d photon-absorption processes that are relevant to observed up-conversion phenomena attributed to effective anti-Stokes green luminescence around 550 nm. Furthermore, activation energy of 4f 12 5d 1 → 4f 13 luminescence quenching was estimated and high value of 2 F 5/2 → 2 F 7/2 emission cross-section was determined in CsCaI 3 :Tm 2+ . Our spectroscopic study was performed to complement and verify the previous investigation in this field. [ABSTRACT FROM AUTHOR]

Oxyfluoride glasses doped with erbium and ytterbium have been fabricated at T = 1460 °C. To prepare glass-ceramic systems, the precursor glasses were annealed at temperature 750 °C for 2 h. The ordered fluoride-like crystalline phases were recognized applying XRD, SAED and EDS methods. The spectroscopic properties of the glass-ceramic samples were significantly different as compared to those observed in the precursor glass. Particularly, the emission spectra of glass-ceramics are evidence that some of Er 3 + and Yb 3 + ions reside into the ordered environment. Up-conversion phenomena attributed to visible anti-stokes emission of Er 3 + has been observed under excitation of Yb 3 + ions by a 980 nm diode laser. Especially, the substantial enhancement of red up-converted luminescence was observed in the glass-ceramic system. Dissimilar spectral characteristic and relation of both aforementioned emissions examined in glass and glass-ceramic samples point at different contributions of processes relevant to up-conversion phenomena. The detailed analysis of the crucial Er 3 + and Yb 3 + excited states relaxation dynamics and their spectroscopic qualities has been performed to determine the mechanisms which lead to conversion of the infrared excitation into visible emission. [ABSTRACT FROM AUTHOR]

Influence of temperature on spectroscopic and thermal properties of Tm 3+ and Er 3+ -doped GdVO 4 and LuVO 4 crystals was examined. Polarized absorption and emission spectra as well as excited state luminescence lifetimes have been measured and analyzed especially at cryogenic temperatures in the 1.5–1.6 μm and 1.8–1.9 μm spectral ranges to assess laser qualities of these materials. The emission cross sections for 4 I 132 → 4 I 15/2 (Er) and 3 F 4 → 3 H 6 (Tm) transitions at T = 77 K were determined and confronted to the results obtained at room temperature. Effective emission cross sections estimated for aforementioned erbium and thulium transitions indicate that effective laser operation at cryogenic temperatures can be achieved in the gadolinium and lutetium vanadate crystals. Efficiency of laser material depends on its ability to heat distribution upon high-power energy pumping process. Accordingly, it has been found that the anisotropy of thermal conductivity for the undoped crystals is weakly influenced by the temperature albeit conductivity values for the GdVO 4 are higher than those for LuVO 4 at all temperatures. Incorporation of erbium or thulium ions results in a decrease of thermal conductivity in the two vanadate crystals and an anomalous temperature dependence of thermal conductivity in the LuVO 4 was observed. Anisotropy of temperature dependence of thermal conductivity was found for the LuVO 4 :3.2 at%Tm 3+ crystal. In this case the thermal conductivity along c-axis is inferior to that along a-axis of the crystal. [ABSTRACT FROM AUTHOR]

The paper shows some results related to thermal and optical properties of Eu 3+ -doped (65-x)TeO 2 -20ZnF 2 -12PbO-3Nb 2 O 5 -xEu 2 O 3 glass systems. Concentration of the Eu 2 O 3 was different (x = 0.5, 2 and 5 mol%) so it could determine the influence of active admixture on relevant properties of oxyfluorotellurite glass. Thermal stability and crystalline phases formed by the glass matrix were examined by differential thermal analysis (DTA). The characteristic temperatures (glass transition temperature and oxide glass crystallization temperature) have been determined. Optical absorption and emission spectra of Eu 3+ ions in oxyfluorotellurite glasses have been investigated at room temperature in the ultraviolet (UV), visible (VIS) and near-infrared (NIR) region. Oscillator strengths, phenomenological Judd-Ofelt intensity parameters Ω 2,4,6 , radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels have been also estimated. Lifetimes and the luminescence dynamics were studied as a function of the Eu 2 O 3 concentration. [ABSTRACT FROM AUTHOR]

Optical absorption and emission spectra of Dy 3+ ions in Gd 3 Ga 3 Al 2 O 12 single crystal were investigated at room temperature and T = 5 K in the visible (VIS) and near-infrared (NIR) region. Low-temperature spectra were utilized to determine the energy level structure of Dy 3+ in the GGAG host. The detailed analysis implied that optically active ions reside mainly into well-defined sites in the crystal studied. Judd–Ofelt (JO) theory was used to calculate oscillator strengths, transitions intensity parameters Ω 2,4,6 , radiative transition probabilities, luminescence branching ratios and radiative lifetime of dysprosium luminescent level. Relaxation dynamic of 4 F 9/2 excited state was examined as a function of temperature. High quantum efficiency of dysprosium luminescence level, value of the 4 F 9/2 → 6 H 13/2 yellow emission cross-section and the quality of remaining spectroscopic parameters indicate that the Gd 3 Ga 3 Al 2 O 12 :Dy 3+ optical system can be considered as promising phosphor and visible laser material. [ABSTRACT FROM AUTHOR]

Single crystals of YAl 3 (BO 3 ) 4 doped with trivalent samarium were grown by the top-seeded high temperature solution method and their absorption and emission spectra were investigated. Optical pumping into prominent absorption band around 405 nm feeds the 4 G 5/2 metastable level giving rise to intense visible luminescence distributed in several spectral lines with the most intense line around 600 nm characterized by a branching ratio of 0.42 and peak emission cross section of 0.25×10 −20 cm 2 . Optical amplification at 600 nm with a gain coefficient of 2.9 cm −1 was achieved during a pump-and-probe experiment. [ABSTRACT FROM AUTHOR]

• Oxyfluorotellurite glasses singly-doped and co-doped Ho3+ and Yb3+ were prepared. • Influence of dopant concentration on thermal and spectroscopic properties. • The materials under study were evaluated as luminescent temperature sensors. The paper presents a thermal and spectroscopic properties of oxyfluorotellurite glasses (65- x)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 – x Ho 2 O 3 (x = 0.5, 2 and 5) and (65- x - y)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 – x Ho 2 O 3 – y Yb 2 O 3 (x = 0.5, y = 2 and x = 0.5, y = 5). The obtained data show that the thermal stability of TZPN glass samples depends on the content of rare earth elements (holmium (Ho3+) and/or ytterbium (Yb3+) ions) in the glassy matrix. It was also found that the spectroscopic characteristics of TZPN:Ho and TZPN:Ho,Yb glasses are found to be suitable as optical medium for mid infrared emission at ∼2.0 μm. The effective emission cross section was determined to be around 0.89 × 10−20 cm2 for transition 5I 7 → 5I 8 in TZPN:Ho glasses. However, the maximum absolute and relative sensitivities S A = 4.53 × 10−3 K−1 and S R = 0.53% K−1 at T = 675 K were established for TZPN:0.5%Ho,2%Yb. [Display omitted] [ABSTRACT FROM AUTHOR]

Presence of free gastric cancer cells in the peritoneal cavity of patients who underwent surgical treatment for gastric cancer is a negative prognostic factor and caused rapid disease recurrence, manifested as peritoneal metastases. Positive peritoneal cytology despite lack of visible peritoneal metastases was regarded as M1 class in the TNM classification (7th edition) in 2010. The aim of the study was to analyze factors associated with positive peritoneal cytology and identify groups of patients in whom diagnostic laparoscopy plus peritoneal lavage in the diagnostic process could affect therapeutic decisions. Material and methods. The study enrolled patients with gastric cancer who underwent surgical treatment at the Department of Surgery, Wielkopolskie Oncology Center in Poznań. During the laparotomy, after opening of the peritoneal cavity, 200 ml of physiological saline at 37°C was administered in the tumor region. After this fluid was mixed, 100 ml of lavage fluid was collected. This fluid was subsequently spun many times to obtain sediment for cytology and immunohistochemistry investigation using anti-BerEp-4, CK 7/20, and B72.3. Results of peritoneal cytology were analyzed jointly with clinical factors - patient's age, sex and pathology factors - tumor invasion, involvement of lymph nodes, histological grade, histological type according to Lauren and localization of the cancer in the stomach. Results. Analysis of the peritoneal fluid for presence of free cancer cells was done in 51 patients. Positive peritoneal cytology was found in 12 (23.5%) patients. In the group of patients with positive cytology, all patients had T3/T4 tumors and all were found to have lymph node metastases, while G3 cancer was found in 83.3% of patients. In patients with positive cytology, diffuse gastric cancer according to Lauren predominated (9 of 12 patients, 75%), while in patients with negative cytology - intestinal type (20 of 39 patients, 51.2%). In the group of patients with positive histology, the whole stomach was involved by the cancer process in 7 of 12 patients (58.3%), while in the group with negative histology, in 29 of 39 patients the tumor was located in the gastric body and prepyloric part (74.4%). Conclusions. Based on this study we can conclude that determinants of positive peritoneal cytology include: tumor stage T3/T4, N+, G3, cancer located in the whole stomach, diffuse histological type according to Lauren. [ABSTRACT FROM AUTHOR]

Highlights: [•] LGT:Er single crystals obtained by Czochralski method. [•] Analysis of absorption and emission spectra as well as decay curves of luminescence. [•] Influence of the temperature on the LGT:Er spectroscopic properties. [•] Spectroscopic evaluation of the LGT:Er potential laser qualities. [ABSTRACT FROM AUTHOR]

Highlights: [•] Samarium doped langatate crystal was grown by Czochralski method. [•] Thermal dependences of Sm3+ emission and absorption have been measured. [•] Judd–Ofelt analysis was carried out and radiative transition rates were calculated. [•] Inhomogeneous broadening of spectral lines has been observed. [ABSTRACT FROM AUTHOR]

Single crystal of LaGaTaO (LGT) containing intentionally 0.5 % of Ho and 1 % of Yb was grown by the Czochralski method. Examination of chemical composition of the grown crystal revealed that luminescent holmium and ytterbium ions are preferably retained in the melt and their actual concentrations are 0.12 and 0.24 %, respectively. Spectroscopic investigation performed encompassed IR host absorption spectra and Raman spectra at room temperature, optical absorption and luminescence spectra of Ho and Yb at room temperature and at 5 K, and luminescence decay curves at room temperature. It was found that all spectral bands recorded show important inhomogeneous line broadening. This feature was attributed to structural disorder inherent to the crystal lattice in which pentavalent Ta ions occupy octahedral Ga(1) sites together with trivalent Ga ions. Despite small concentrations of luminescent ions, the occurrence of nonradiative interaction that feeds the I and I levels of Ho ions by transfer of an excitation from the F level of Yb ions was evidenced. Based on examination of spectroscopic parameters evaluated, it was concluded that LGT:Ho, Yb may be considered as a potential intermediate-gain laser active material able to emit infrared radiation from the I → I transition of Ho around 2 micrometres upon laser-diode pumping into Yb absorption band. [ABSTRACT FROM AUTHOR]

Highlights: [•] Optical and structural investigation of (Lu0.4Gd0.55Sm0.05)2SiO5 single crystal. [•] Absorption and emission spectra highly influenced by optical anisotropy of material. [•] Cross-relaxation between samarium ions. [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: Praseodymium and cerium co-doped yttrium silicate (Pr,Ce:YSO) crystal with high optical quality was grown by the Czochralski method. The segregation coefficient of Pr3+ and Ce3+ is measured to be 0.547 and 0.136, respectively. The polarized absorption bands centered at 268nm, 299nm and 356nm were assigned to 4f (2F5/2)→5d inter-configuration transitions of Ce3+, while bands centered at 220nm and 250nm were assigned to 4fn–4fn−15d transitions of Pr3+. The VUV–UV excitation spectra for monitoring Pr3+ emissions centered at 610nm (1D2→3H4) and 489nm (3P0→3H4), as well as Ce3+ emission centered at 450nm were recorded at T=8K in the range of 100nm–320nm. Polarized excitation spectra for Ce3+ emission centered at 424nm and Pr3+ emission centered at 611nm were recorded at T=300K. Polarized emission spectra were obtained upon excitation at 365nm and 456nm at T=300K. Lifetimes were estimated to be 170μs for Pr3+ (1D2), 3μs for Pr3+ (3P0) and 39ns for Ce3+ (5d1). [Copyright &y& Elsevier]

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]

Abstract: The selected glasses and glass–ceramics pertinent to following chemical composition in mol%:48%SiO2–11%Al2O3–7%Na2O–10%CaO–10%PbO–11%PbF2–3%ErF3 and 48%SiO2–11%Al2O3–7%Na2O–10%CaO–10%PbO–10%PbF2–1%ErF3–3%YbF3 have been manufactured from high purity components (Aldrich) at 1450°C in normal atmosphere. Glass optical fibers were successfully drawn. Subsequently they were subject to the heat-treatment at 700°C in various time periods. The preceding differential thermal analysis (DTA) studies allowed estimating both the fiber drawing temperature and the controlled crystallization temperature of glass fibers. It has been observed that the controlled heat-treatment of oxyfluoride glass fibers results in the creation of Pb5Al3F19, Er4F2O11Si3 and Er3FO10Si3 crystalline phases. The identified phases were characterized by X-ray powder diffraction (XRD) and confirmed by selected area electron diffraction (SAED). The fibers consist of mixed amorphous–crystalline microstructure with nano-crystals of size even below 10nm distributed in the glassy host. Their morphology was investigated applying high-resolution transmission electron microscopy. Optical properties and excited state relaxation dynamics of optically active ions (Er3+, Yb3+) in glass and glass–ceramics have been studied. Based on absorption spectra the Judd–Ofelt analysis was carried out. The main attention was directed to NIR luminescence at. 1.6μm related to 4I13/2 → 4I15/2 Er3+ and less effective emission associated with 4I11/2 → 4I15/2 Er3+ and 2F5/2 → 2F7/2 Yb3+ transitions. The dissimilar spectroscopic properties have been revealed for glasses and glass–ceramic samples, respectively. The reduction of emission linewidth at 1.6 and 1.0μm combined with substantial increase of 4I13/2 lifetimes of erbium in glass–ceramics appear to be evidences that Er3+ ions are accommodated in crystalline phases. The structural and optical characteristics of oxyfluoride glass–ceramic fibers indicate that these optical systems may be considered as promising materials for Er-doped optical amplifiers operating within third telecommunication window. [Copyright &y& Elsevier]

Abstract: This work is concentrated on growth, spectroscopy and laser performance of thulium-doped vanadate crystals. At the beginning the growth techniques are analyzed and then the matrix of vanadates crystal, its structure and physicochemical properties are explained together with the rare earth activators influence. Detailed spectroscopy of the thulium-doped vanadate crystals then follows. On the background of this theoretical analysis and state of the art of the subject the description of thulium vanadate lasers (especially Tm:YVO4, Tm:GdVO4, and Tm:LuVO4) together with their generated output radiation characteristics are presented. [Copyright &y& Elsevier]

Oxyhalide lead borate glasses doped with rare earth ions have been studied before and after thermal treatment. The rare earths as optically active ions were limited to the Er3+ ions. Near-infrared luminescence due to the main 4I13/2-4I15/2 laser transition of Er3+ was registered. The introduction of PbX2 to the borate glass results in a reduction of spectral linewidth and an increase of luminescence lifetime of 4I13/2 state of Er3+ ions. The unusual large spectral linewidth for 4I13/2-4I15/2 transition of Er3+ in the oxide glass host was obtained, whereas the luminescence decay from 4I13/2 state is longer for a sample with PbF2 than PbCl2 and PbBr2. Heat treatment introduces transformation from a glass to transparent glass-ceramic (TGC). The coordination sphere around Er3+ ions is changed, giving important contribution to the luminescence characteristics. The spectroscopic consequence of this transformation is the increase of luminescence lifetime and the narrowing of spectral lines of Er3+. [ABSTRACT FROM AUTHOR]

Abstract: Er3+-doped KCaY(VO4)2 microcrystalline samples were synthesized using a high temperature solid-state reaction technique. Spectroscopic properties of Er3+: KCaY(VO4)2 are studied and the nature of emissions is discussed. A strong green and infrared luminescence were observed under excitation at 314nm in the O2−→V5+ charge-transfer transitions and direct excitation of Er3+ ions at 435nm. A strong emission lines in the blue region are due to the transitions of VO4 3− ions have been observed at 77K. The Judd–Ofelt parametrization scheme has been applied to the analysis of the room temperature absorption spectra in order to evaluate the intensity parameters, the branching ratios and the radiative lifetimes of the 4I13/2, 4I11/2, 4F9/2 and 4S3/2 emitting levels. The effective cross-section has been calculated for the 4I13/2→4I15/2 transition, indicating that the title compounds is a promising active medium for application in the three-level laser system. The up-conversion emission in Er3+: KCaY(VO4)2 was investigated at 300K. The decay profiles of the Stokes and anti-Stokes emissions were measured and the mechanism of up-conversion luminescence is discussed. [Copyright &y& Elsevier]

Abstract: Transparent single crystals of erbium-doped LaVO4 in form of platelets having an average size 0.5×2×2mm3 were obtained by the flux method using Pb2V2O7 as the solvent. Inductively coupled plasma (ICP) measurement revealed that the actual Er/La=0.3% molar ratio in the crystals is lower than Er/La=1% nominal molar ratio due to significant difference of ionic radii of La and Er. Luminescence spectra and luminescence decay curves for Er3+ transitions in the visible and near infrared region were recorded. Unpolarized Raman spectrum of undoped LaVO4 crystal was acquired, too. Up-converted green emission following excitation at 808 and 970nm was observed and dependence of its intensity on incident excitation power was determined. Based on experimental data gathered the relaxation dynamics of excited states of Er3+ was analyzed and mechanisms involved in the up-conversion phenomena were discussed. [Copyright &y& Elsevier]

Abstract: LaPO4 single crystals lightly doped with Er3+, and codoped with Er3+ and Yb3+ have been grown by spontaneous nucleation in a lead phosphate flux. Absorption and luminescence spectra have been measured in the visible and near-IR regions and the excited state dynamics has been studied upon pulsed laser excitation. The obtained results have allowed the evaluation of the effective emission cross-sections around 1.5μm, that have been found to be similar to important oxide laser crystals doped with Er3+. Efficient visible upconversion has been observed upon excitation at 980nm in the codoped crystals. This behaviour is attributed to Yb3+–Er3+ energy transfer processes. [Copyright &y& Elsevier]

The cause of the split of 4A4E(4G) Mn2+ excited level measured on minerals spectra is discussed. It is our view that ∆E = |4E(4G) − 4A(4G)| should be considered an important spectroscopic parameter. Among the possible reasons for the energy levels splitting taken under consideration, such as the covalent bond theory, the geometric deformation of the coordination polyhedron and the lattice site's symmetry, the first one was found to be inappropriate. Two studied willemite samples showed that the impurities occur in one of the two available lattice sites differently in both crystals. Moreover, it was revealed that the calculated crystal field Dq parameter can indicate which of the two non-equivalent lattice sites positions in the willemite crystal structure was occupied by Mn2+. The above conclusions were confirmed by X-ray structure measurements. Significant differences were also noted in the Raman spectra of these willemites. [ABSTRACT FROM AUTHOR]

Novel ternary fluoro-germano-tellurite (GTS) glasses doped with Er3+ ions with 0.5 mol% and 1.0 mol% were fabricated by a conventional melt and quenching method and investigated using methods of optical spectroscopy. The room-temperature absorption spectrum was recorded and analyzed to determine radiative transition rates, radiative lifetimes, and branching ratios of Er3+ luminescence. Decay curves of Er3+ luminesccence were recorded and analyzed. Temperature dependences of emission spectra and absorption spectra in the region from RT (room-temperature) up to 675 K were studied in detail. The contribution of competing radiative and nonradiative processes to the relaxation of luminescent levels of Er3+ was assessed. Absolute and relative sensitivity were established utilizing the comprehensive model based on thermally coupled 2H11/2/4S3/2 excited states of erbium. The high quantum efficiency of the first erbium-excited state and value of gain coefficient indicate that GTS:Er glass system can be considered as conceivable NIR (near infrared) laser material as well. [ABSTRACT FROM AUTHOR]

Optical absorption spectra and luminescence spectra were recorded as a function of temperature between 295 K and 800 K for single crystal samples of Gd2SiO5:Dy3+, Lu2SiO5:Dy3+, LiNbO3:Dy3+, and Gd3Ga3Al2O12:Dy3+ fabricated by the Czochralski method and of YAl3(BO3)4:Dy3+ fabricated by the top-seeded high temperature solution method. A thermally induced change of fluorescence intensity ratio (FIR) between the 4I15/2→ 6H15/2 and 4F9/2 → 6H15/2 emission bands of Dy3+ was inferred from experimental data. It was found that relative thermal sensitivities SR at 350 K are higher for YAl3(BO3)4:Dy3+ and Lu2SiO5:Dy3+than those for the remaining systems studied. Based on detailed examination of the structural peculiarities of the crystals it was ascertained that the observed difference between thermosensitive features cannot be attributed directly to the dissimilarity of structural factors consisting of the geometry and symmetry of Dy3+ sites, the number of non-equivalent Dy3+ sites, and the host anisotropy. Instead, it was found that a meaningful correlation between relative thermal sensitivity SR and rates of radiative transitions of Dy3+ inferred from the Judd–Ofelt treatment exists. It was concluded that generalization based on the Judd–Ofelt parameters and luminescence branching ratio analysis may be useful during a preliminary assessment of thermosensitive properties of new phosphor materials. [ABSTRACT FROM AUTHOR]

Responding to the latest trends in luminescence thermometry, a new material of TZPN glass doped with Tb3+ ions was investigated for its use in the single band ratiometric approach. In contrast to the most of the Tb3+ doped phosphors emission intensity of Tb3+ ions in TZPN glass upon excitation matched to transitions from the ground 7F 6 level show strong thermal quenching of luminescence intensity. On the other hand for an excitation line matched to the absorption from the thermally coupled excited 7F 5 level, the emission intensity increases for temperature elevation. The ratio of these two signals is known to be an excellent temperature dependent parameter enabling a highly sensitive temperature readout. Strong thermal quenching of Tb3+ emission was discussed in terms of the thermally induced electron transfer from f state to the conduction band of the glass. In this work, it has been shown that optimization of the thermal quenching process is as important as the previously proposed optimizations of the intensity variability upon stimulation matched to excited state absorption. High relative sensitivities reaching 1–2%/°C were achieved, mainly because of the strong thermal quenching of the luminescence exhibited by the TZPN: Tb3+ glasses with different concentrations of dopant ions. • TZPN glasses doped with Tb3+ ions were applied to luminescence thermometry. • Excitation lines matching GSA and ESA allowed for SBR approach to be applied. • The observed rapid thermal quenching of GSA-excited luminescence was discussed. • Optimizing the GSA-excited emission allowed to achieve high sensitivities. [ABSTRACT FROM AUTHOR]

• Five different temperature sensing models were established for TZPN: Er glass system. • Glass material for optical systems operating in elevated temperature regimes. • Optical gain medium in the C- and L- telecom wavelength bands. • Stable intensity of laser emission in NIR region up to 525 K. In a comprehensive and novel approach, a diverse set of five functional models of temperature sensing were established for erbium-doped oxyfluorotellurite glass systems using temperature dependences of emission spectra and luminescence dynamics in the range from RT to up to 675 K. Maximum relative sensitivity at 300 K was established at 1.52%K−1 for the model based on thermally coupled levels and at 1.92%K−1 at 675 K utilizing the green-to-red ratio. To confirm usefulness of the models established for the considered glasses, material and spectroscopic analyses were performed. Differential thermal analysis yielded favorable results in terms of glass thermal stability, further improving with increase of dopant concentration. Radiative transition analysis was performed, along with calculation of absorption, emission and effective emission cross sections, yielding information on the lasing performance of the material. It was found that TZPN:Er is a promising material for temperature sensing and optical amplification in the C and L telecom bands. [ABSTRACT FROM AUTHOR]

Abstract: Upon UV–VUV excitation terbium doped K5Li2LaF10 emits white light coming from the 5D3 and 5D4 multiplets for content of Tb3+ up to 10at%. For higher concentrations (80 and 100at%) the emission becomes green. In excitation spectrum, recorded at 12K, the positions of the zero-phonon lines are not well determined. The spin allowed f–d transitions in this spectrum are similar to the cerium one in K5Li2LaF10: Ce3+, as van Pieterson proposed in the frames of Dorenbos’ model. The maxima of these terbium f–d transitions are found at: 46,976, 57,124, 59,404, 60,629 and 67,110cm−1. The lowest forbidden, high-spin d band is situated at 39,193cm−1. The lifetime of the 5D4 multiplet is 7.5ms and does not depend on the terbium concentration, but the 5D3 lifetimes are strongly influenced and amount to: 2710, 2130, 14.1, 9.5μs for 2, 10, 80, 100at% of terbium, respectively. This is in agreement with the colour rendering of these samples. [Copyright &y& Elsevier]

Spectra and decay curves of luminescence induced in a single crystal of LiTaO 3 :Pr3+ by femtosecond light pulses at different wavelengths from the UV-Blue and NIR regions were recorded and analyzed. It was found that excited levels involved in the broad UV absorption band of LiTaO 3 : Pr3+ are not able to relax via radiative transitions but they feed nonradiatively excited states of the ground Pr3+ configuration. Femtosecond pulse excitation in the NIR region results in an up-converted visible luminescence weakly affected by the pulse wavelength within the 1200 nm–1800 nm region. Spectra acquired imply that the supercontinuum (SC) generated does not promote single - or double-photon processes that may feed the 3P 0 or 1D 2 levels via transitions within the ground 4f2 configuration. It was concluded that the excitation mechanism is consistent with the multiphoton excitation (MPE) that feeds the 5d levels of Pr3+. • Conversion of femtosecond pulses into optically uniaxial system. • Down and up-conversion phenomena in LiTaO 3 :Pr3+ crystal. • Effect of supercontinuum generation on Pr3+ excited states excitation. • Ultrashort pulses induced change of electrical conductivity. [ABSTRACT FROM AUTHOR]

The color change of the pink and colorless LiAlSi2O6 spodumene crystal due to irradiation and heating is explained. The hypothesis about the change of Mn3+ to Mn4+ after irradiation was rejected. For the studied crystals, it was shown that both Mn2+ and Mn3+ occupy the M2 (not the M1) crystal site. Spodumene crystals which are primary pink (kunzite) contain Mn3+ (and Mn2+) at the M1 site. By contrast, those that become pink due to irradiation and heating contain Mn3+ and Mn2+ at the M2 site. The emission band of the former is 625 nm, and for the latter, it is 591 nm. [ABSTRACT FROM AUTHOR]

Oxyfluorotellurite (65- x)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 – x Tm 2 O 3 (x = 0.5, 2 and 5) and (65- x - y)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 – x Tm 2 O 3 – y Yb 2 O 3 (x = 0.5, y = 2 and x = 0.5, y = 5) glass systems were manufactured. Glass thermal stability was examined by means of differential thermal analysis (DTA) and some thermal stability criteria ΔT , H ' and S were determined. Absorption spectrum was utilized to prepare Judd-Ofelt (J-O) calculations and consequently oscillator strengths, intensity parameters Ω 2,4,6 , radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were estimated. Emission spectra and luminescence decay curves were measured as a function of temperature in the 300–625 K range. Based on the upconversion luminescence of Tm3+ the optical temperature sensor qualities have been evaluated for Tm3+/Yb3+ co-doped sample. The fluorescence intensity ratio (FIR) between transitions 700 nm (Tm3+:3F 2,3 → 3H 6)/800 nm (Tm3+:3H 4 → 3H 6) for 975 nm excitation and 700 nm (Tm3+:3F 2,3 → 3H 6)/470 nm (Tm3+:1G 4 → 3H 6) for 803 nm excitation were determined and an adequate relative thermal sensitivity S was estimated. The significant value of relative thermal sensitivity 1.12 %K−1 was determined when NIR Yb3+ and Tm3+ emission bands were analyzed, however. Effective emission cross section was calculated for 3F 4 → 3H 6 potential laser transition of thulium around 1.9 μm in single-doped Tm3+ glass. Furthermore, effect of temperature on down-converted and up-converted thulium and ytterbium emission and on relaxation dynamic of involved excited states was studied in details. • Oyfluorotellurite glasses singly-doped and co-doped Tm3+ and Yb3+ were prepared. • Thermal and optical properties of tested materials were determined. • Thermal properties of glasses depend on the Tm3+/Yb3+ ions concentrations. • Investigated materials have advantageous properties for NIR optical gain. • TZPN glasses activated with RE3+ ions can be used in luminescence thermometry. [ABSTRACT FROM AUTHOR]

• Er,Yb co-doped oxyfluorotellurite glasses for optical applications. • Down and up-conversion phenomena in TZPN:Er,Yb glasses. • Fluorescence Intensity Ratio for erbium thermally coupled excited states. • Influence of temperature-activated excitation energy flow on optical thermometry sensitivity. Oxyfluorotellurite glasses co-doped with erbium (0.5%) and ytterbium (2%, 5%) were manufactured from high purity reagents at 840 °C in air. Differential thermal analysis was used to estimate the temperatures of glass transition and glass crystallization of 2% and 5%Yb co-doped glasses. The effect of Yb3+ co-doping on relaxation dynamics of erbium excited states was demonstrated by the means of excitation, emission and fluorescence lifetime spectroscopy. Up-conversion luminescence spectra were studied in a function of temperature in the 295–675 K range, yielding information on thermal quenching of the emission and a temperature sensing model based on 2H 11/2 –4I 15/2 to 4S 3/2 –4I 15/2 erbium fluorescence intensity ratio. Application potential of the investigated material in optical sensor thermometry was evaluated. Maximum absolute and relative sensitivities were established at 6.45 × 10−3 K−1 at T = 675 K and 0.46 %K−1 at T = 400 K, respectively. [ABSTRACT FROM AUTHOR]

Single crystal of La 3 Ga 5.5 Ta 0.5 O 14 (LGT) doped with Dy3+ was fabricated by the Czochralski technique and investigated employing methods of optical spectroscopy. Polarized optical absorption spectra and luminescence spectra were recorded at room temperature. Unpolarized absorption and luminescence spectra were recorded at 10 K. Spectra of blue luminescence related to transitions 4I 15/2 , 4F 9/2 → 6H 15/2 were recorded at several temperatures in the 300–773 K region. Dy3+ ions have the same symmetry sites in LGT but their spectra show inhomogeneous broadening due to structural disorder of the host and are markedly anisotropic. Results of the Judd-Ofelt treatment made it possible to assess emission cross sections for the 4F 9/2 → 6H 15/2 blue luminescence and for the 4F 9/2 → 6H 13/2 yellow luminescence employing Fuchtbauer-Ladenburg formula and reciprocity method. In particular, a spectral distribution of La 3 Ga 5.5 Ta 0.5 O 14 : Dy3+ σ-polarized luminescence band with an emission cross section σ em = 0.51 × 10−20 cm2 at 573.5 nm is favorable for a laser operation in the visible. Interpretation of the effect of temperature on the blue emission spectra leads to the conclusion that La 3 Ga 5.5 Ta 0.5 O 14 : Dy3+ is promising for application as luminescent thermometer. • Novel single crystal La 3 Ga 5.5 Ta 0.5 O 14 :Dy (LGT:Dy). • Detailed analysis of optical spectra and luminescence decay curves. • Potential visible laser operation at 573.5 nm. • Temperature sensitivity of LGT:Dy luminescence. [ABSTRACT FROM AUTHOR]

Optical, structural and morphological properties of Tm3+/Yb3+ co-doped NaYF 4 -based nano-glass-ceramic and a precursor glass have been investigated. The controlled heat-treatment of multicomponent oxyfluoride glass at 640 °C for 2 h was used to obtain crystalline precipitations. The differences in optical characteristics have been discussed analysing spectra recorded within wide VUV–VIS–NIR spectral range and considering relaxation dynamic of involved excited states. Optical spectra and luminescence decay curves were measured as a function of temperature in the range of 295–725 K. Based on up-converted emission spectra excited at 975 nm, temperature sensing properties of glass-ceramic were verified. The fluorescence intensity ratio between the up-converted emission bands located at around 795 nm (Tm3+:3H 4 –3H 6) and 695 nm (Tm3+:3F 3,2 –3H 6) was studied. The maximum relative temperature sensitivity was determined to be 0.35% K−1 at 445 K. • Tm3+,Yb3+ co-doped NaYF 4 -based oxufluoride nano-glass-ceramic. • Conversion of VUV excitation into thulium visible emission. • Impact of 295–725 K temperature on emission efficiency of Tm3+ and Yb3+. • Verification of Tm,Yb –co-doped glass-ceramic temperature sensor quality. [ABSTRACT FROM AUTHOR]

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]

Single crystals of Gd 3 (Al,Ga) 5 O 12 with intentional stoichiometry Gd 3 Ga 2.5 Al 2.5 O 12 doped with 1%Tm3++x%Yb3+; (x = 1, 3, 5); were grown by the Czochralski method. Spectra and intensities of up-converted luminescence excited at 975 nm or 803 nm were measured as a function of temperature within 295 K–775 K region. It was found that for the two excitation wavelengths the growth of temperature brings about a decrease of an up-converted blue luminescence intensity. Thermally enhanced growth of nonradiative relaxation rates for excited states involved in the up-conversion process was determined based on an analysis of respective luminescence decay curves. Temperature-dependent change of fluorescence intensity ratio (FIR) for the 3F 3,2 – 3H 6 /3H 4 – 3H 6 up-converted bands was observed and resulting absolute temperature sensitivity of 0.058 K-1 was found for GAGG:1%Tm,3%Yb at 725 K. • Single crystals for high temperature applications. • Thulium thermally coupled excited states in novel co-doped GAGG:Tm, Yb garnet crystals. • Impact of temperature-activated excitation energy flow on optical thermometry sensitivity. • Effect of optically active ions interplays and energy transfer phenomena on temperature sensitivity. [ABSTRACT FROM AUTHOR]

The recent COVID-19 pandemic has made everyone aware of the threat of viruses and the growing number of antibiotic-resistant bacteria. It has become necessary to find new methods to combat these hazards. One tool that could be used is UVC radiation, i.e., 100–280 nm. Currently, the available sources of this light are mercury vapor lamps. However, the modern world requires more compact, mercury-free, and less energy-consuming light sources. This work presents the results of our research on a new material in which efficient UVC radiation was obtained. Here, we present the results of research on Ca9Y(PO4)7 polycrystals doped with Pr3+ ions prepared using the solid-state method. The absorption, excitation, emission, and emission decay profiles of praseodymium(III) ions were measured and analyzed. The upconversion emission in the UVC region excited by blue light was observed. Parameters such as energy bandgap, refractive index, and thermal stability of luminescence were determined. The studied phosphate-based phosphor possesses promising characteristics that show its potential in luminescent applications in future use in medicine or for surface disinfection. [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]

Terbium ions in Gd 3 Ga 3 Al 2 O 12 (GGAG) single crystal exhibit strong luminescence originated in the 5D 3 and 5D 4 multiplets. The decay time of the 5D 3 state is 1072 μs and 724 μs at 5 K and 300 K, respectively. The time dependence of luminescence originated from the 5D 4 multiplet is consistent with single exponential decay, with lifetime values 3579 μs at low temperature and 2902 μs at 300 K. The non-exponential decay curves have been fitted in the frame of Inokuti-Hirayama model, indicating that the dipole-dipole interaction plays an important role in the fluorescence quenching of the 5D 3 level. The calculated R 0 parameter values are equal to 11.56 Å and 12.86 Å for 5 and K 300 K, respectively. The positions of multiplets up to 40000 cm−1 are determined employing the f-shell empirical programs. CIE 1931 coordinates are x = 0.298 , y = 0.664 (green) at 5 K and x = 0.360, y = 0.538 (yellowish green) at 300 K. • A new material has been obtained in the form of single crystal. • A starting stoichiometry is given to minimize segregation process. • Low temperature positions of 4f and 5d states have been determined. • Energy transfer processes have been examined. • Influence of temperature on the Tb transition ratio has been investigated. [ABSTRACT FROM AUTHOR]

Membranes produced by crosslinking chitosan with magnesium phytate were prepared using highly deacetylated chitosan and its N-carboxymethyl, O-carboxymethyl and N,O-carboxymethyl derivatives. The conditions of the membrane production were described. IR, Raman, electron absorption and emission spectra were measured and analyzed for all the substrates. It was found that O-carboxymethyl chitosan derivative is the most effectively crosslinked by magnesium phytate, and the films formed on this substrate exhibit good mechanical parameters of strength, resistance and stability. Strong O–H···O hydrogen bonds proved to be responsible for an effective crosslinking process. Newly discovered membrane types produced from chitosan and magnesium phytate were characterized as morphologically homogenous and uniform by scanning electron microscopy (SEM) and IR measurements. Due to their good covering properties, they do not have pores or channels and are proposed as packaging materials. [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]