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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 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]

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]

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]

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]