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We report the results of measurements of thermal conductivity coefficient dependence on temperature of single crystals of SrIr4In2Ge4 and EuIr4In2Ge4. The measurements were carried out over the temperature range of ∼5–300 K. The EuIr4In2Ge4 crystal, unlike its strontium analog SrIr4In2Ge4, shows an amazing anisotropy: At low temperatures, it displays significantly smaller thermal conductivity in the ab plane than in the direction of c axis, while at the high ones the thermal conductivity in the direction perpendicular to the c axis increases well above that of in the c axis. The observed phenomena may be a result of the interaction of phonons with 1D chains of short-range ordered magnetic moment of europium atoms and the exchange energy between the chains in the paramagnetic phase of EuIr4In2Ge4. [ABSTRACT FROM AUTHOR]

Transition-metal and rare-earth borides are of considerable interest due to their electronic, mechanical, and magnetic properties as well as their structural stability under extreme conditions. Here, we report on a series of high-pressure Raman and x-ray diffraction experiments on the cubic rare-earth hexaboride EuB6 to an ultrahigh pressure of 187 GPa in a diamond anvil cell. In EuB6, divalent europium ions occupy the corners of the cubic structure, which encloses a rigid boron-bonded cage. So far, no structural phase transitions have been reported, while the nanoindentation studies indicate amorphization in nanoscale shear bands during plastic deformation. Our x-ray diffraction studies have revealed that the ambient cubic phase of EuB6 shows broadening and splitting of diffraction peaks starting at 72 GPa and the broadening continuing to 187 GPa. The high-pressure phase is recovered on decompression, and the Raman spectroscopy of the recovered sample from 187 GPa shows a downward frequency shift and broadening of T2g, Eg, and A1g modes of boron octahedron. The density functional theory simulations of EuB6 at 100 GPa have identified five possible lowest energy crystal structures. The experimental x-ray diffraction data at high pressures is compared with the theoretical predictions and the role of structural distortions induced by shear stresses is also discussed. [ABSTRACT FROM AUTHOR]

Polyvinylidene difluoride trifluoroethylene (PVDF-TrFE) has received widespread application in flexible electronics and biomedical devices but is limited in its sensing modalities to piezoelectricity and pyroelectricity. The addition of optically or magnetically active nanoparticles could provide additional sensing modalities in the same element, which could drive miniaturization of such sensors. Europium barium titanate (EBTO) is one such optically active nanoparticle that could add functionality to such a nanocomposite. In this work, multifunctional nanocomposites of PVDF-TrFE and EBTO are successfully synthesized and characterized for their material and electronic properties. The nanocomposite in this work is the first known multifunctional nanocomposite with PVDF-TrFE and a fluorescent nanoparticle. [ABSTRACT FROM AUTHOR]

Europium-hydroxyapatite (Eu-HA) nanocomposite was developed via continuous hydrothermal synthesis. Eu+3 ions partially replaced the Ca+2 ions within hydroxyapatite molecular structure. High quality Eu-HA nanorods of 20 nm width and 6 μm lengths were verified via TEM micrographs. Eu-HA maintained the crystalline structure of HA with minimum change; material studio software confirmed the partial replacement of Ca+2 by Eu+3. XPS analysis demonstrated Eu+3 content of 6.91 atom %. Ca/P ratio was found to be 1.405 and 0.118 for virgin HA and Eu-HA respectively; this was ascribed to the partial replacement of Ca+2 with Eu +3. The EDAX mapping verified the uniform dispersion of Eu ions within Eu-HA structure. Eu-HA nanocomposite was uniformly distributed in silica sol-gel matrix; subsequently it was applied on AZ31 magnesium alloy. The corrosion performance of Eu-HA sol-gel coating nanocomposite (Eu–S) was evaluated using different electrochemical techniques including Potentiodynamic Polarization (PDP), Electrochemical Impedance Spectroscope (EIS), and Electrochemical Noise (EN) in aerated 0.1 M NaCl solution. Corrosion protection was assessed to that of neat silica sol-gel coating (NSG). Pitting was detected over the whole NSG coated sample, after few hours of immersion in the corrosive solution. EuS coated AZ31 withstand up to 144 h without any sign of corrosion or delamination. EIS analysis with PDP parameters suggested the formation of protective layer; that is responsible for the corrosion resistance. Europium has unique ability to form a protective oxide layer acting as a barrier layer that could prevent the penetration of corrosive electrolyte to the underlying metal substrate. [ABSTRACT FROM AUTHOR]

The reaction of Re(CO)5Br with deprotonated 1H‐(5‐(2,2′:6′,2′′‐terpyridine)pyrid‐2‐yl)tetrazole yields a triangular assembly formed by tricarbonyl Re(I) vertices. Photophysical measurements reveal blue‐green emission with a maximum at 520 nm, 32 % quantum yield, and 2430 ns long‐lived excited state decay lifetime in deaerated dichloromethane solution. Coordination of lanthanoid ions to the terpyridine units red‐shifts the emission to 570 nm and also reveals efficient (90 %) and fast sensitisation of both Eu(III) and Yb(III) at room temperature, with a similar rate constant kET on the order of 107 s−1. Efficient sensitisation of Eu(III) from Re(I) is unprecedented, especially when considering the close proximity in energy between the donor and acceptor excited states. On the other hand, comparative measurements at 77 K reveal that energy transfer to Yb(III) is two orders of magnitude slower than that to Eu(III). A two‐step mechanism of sensitisation is therefore proposed, whereby the rate‐determining step is a thermally activated energy transfer step between the Re(I) centre and the terpyridine functionality, followed by rapid energy transfer to the respective Ln(III) excited states. At 77 K, the direct Re(I) to Eu(III) energy transfer seems to proceed via a ligand‐mediated superexchange Dexter‐type mechanism. [ABSTRACT FROM AUTHOR]

The temperature dependence of the heat capacity of Y2Ti2O7 and Eu2Ti2O7 with a pyrochlore structure in the temperature range of 7–1800 K has been studied. The existence of a small shallow anomaly of the heat capacity of europium titanate in the range of 10–60 K was confirmed. The thermodynamic properties (entropy, enthalpy change, and reduced Gibbs energy) were calculated. Based on the results of calculation of the Gibbs energy of formation of the titanates from oxides it was concluded that both titanates are thermodynamically stable in the high temperature region. [ABSTRACT FROM AUTHOR]

While Eu2+ → Eu3+ energy transfer is well known, in this study the energy transfer from Eu3+ to Eu2+ is reported for the first time. The predominant condition for Eu3+ → Eu2+ energy transfer is a Eu2+ 4f55d band at lower energy than the position of the Eu3+ 4f6[5D0] level, which is fulfilled in Eu‐doped CaO. X‐ray powder diffraction, Eu Mössbauer spectroscopy and optical absorption measurements are employed to determine the Eu3+ and Eu2+ concentrations in the prepared CaO:1at.%Eu samples. Synthesis in an H2/N2 atmosphere and addition of graphite powder as a reducing agent to the starting mixture are found to result in respective Eu3+ and Eu2+ concentrations of 0.6–0.7% and 0.3–0.4%. For this sample, the Eu3+ → Eu2+ energy transfer efficiency is estimated to be high (> 90%). This is explained by the high oscillator strength of the 4f7 → 4f65d excitation transition of the Eu2+ ion to which energy is transferred. As the Eu2+ 4f55d band lies below the Eu3+ 4f6[5D0] level, Eu3+ does not act as a killer center for the near‐infrared (NIR) Eu2+ emission at about 720 nm. Therefore, a full reduction of Eu3+ is not required to attain a high quantum efficiency. Implications of the demonstrated Eu3+ → Eu2+ energy transfer for application of long wavelength Eu2+ phosphors are discussed. [ABSTRACT FROM AUTHOR]

Large dissymmetry factor of the circularly polarized luminescence (gCPL) was observed in ligand and coordination tuned chiral tetrakis europium (Eu(III)) complexes with ammonium cations. The gCPL value was estimated to be −1.54, which is the largest among chiral luminescent molecules. Through photophysical measurements, single crystal X‐ray structural analyses and quantum chemical calculations, changes in the geometric and electronic structures were observed for a series of chiral tetrakis Eu(III) complexes which enhanced the gCPL value. The emission quantum yield and photosensitized energy transfer efficiencies of chiral Eu(III) complexes with ammonium cations were also larger than those of chiral Eu(III) complex with Cs+. Based on the systematic modifications and analyses for chiral tetrakis Eu(III) complex, effect of the ammonium cation on enhanced CPL brightness is reported. [ABSTRACT FROM AUTHOR]

The successful adoption and widespread implementation of innovative acid mine drainage treatment and resource recovery methods hinge on their capacity to demonstrate enhanced performance, economic viability, and environmental sustainability compared to conventional approaches. Here, an evaluation of the efficacy of chromium-based metal–organic frameworks and amine-grafted SBA15 materials in adsorbing europium (Eu) from actual mining wastewater was conducted. The adsorbents underwent comprehensive characterization and examination for their affinity for Eu. Cr-MIL-PMIDA and SBA15-NH-PMIDA had a highest Langmuir adsorption capacity of 69 mg/g and 86 mg/g, respectively, for an optimum level of pH 4.8. Preferential adsorption tests followed using real AMD collected at a disused mine in the north of Norway. A comparative study utilizing pH-adjusted real AMD revealed that Cr-MIL-PMIDA (88%) exhibited slightly higher selectivity towards Eu compared to SBA15-NH-PMIDA (81%) in real mining wastewater. While Cr-MIL-PMIDA displays excellent properties for the selective recovery of REEs, practical challenges related to production costs and potential susceptibility to chromium leaching make it less appealing for widespread applications. A cost–benefit analysis was then undertaken to quantify the advantages of employing SBA15-NH-PMIDA material. The study disclosed that 193.2 g of EuCl3 with 99% purity can be recovered by treating 1000 m3 of AMD. [ABSTRACT FROM AUTHOR]

The solvothermal synthesis of LnCl3.nH2O with terephthalic acid (benzene-1,4-dicarboxylic acid, H2BDC) produced metal–organic frameworks (LnBDC), [Ln2(BDC)3(H2O)4]∞, where Ln = Sm, Eu, Tb, and Dy. The materials obtained were characterized by a number of physico-chemical techniques. The influence of the ionic radius of the lanthanides on the microstructural characteristics of the Ln-MOFs was evaluated by performing Rietveld refinement. The MOFs obtained were tested as fluorescent sensors for numerous cations and anions in water. The highly luminescent EuBDC and TbBDC demonstrated multi-responsive luminescence sensing functions to detect Ag(I), Fe(III), Cr(III), and Cr(VI), which are essential for their environmental applications. By applying the non-linear Stern–Volmer equation, the fluorescent quenching mechanism was determined. The stability of the obtained materials in water in a wide pH range (acidity pH = 4 and alkalinity pH = 9 solutions) was confirmed. [ABSTRACT FROM AUTHOR]

New heterometallic antenna terephthalate MOFs, namely, (EuxM1−x)2bdc3·4H2O (M = Y, La, Gd) (x = 0.001–1), were synthesized by a one-step method from aqueous solutions. The resulting compounds are isomorphic to each other; the crystalline phase corresponds to Ln2bdc3∙4H2O. Upon 300 nm excitation to the singlet excited state of terephthalate ions, all compounds exhibit a bright red emission corresponding to the of 5D0–7FJ (J = 0–4) f-f transitions of Eu3+ ions. The Eu(III) concentration dependence of the photophysical properties was carefully studied. We revealed that Gd-doping results in photoluminescence enhancement due to the heavy atom effect. To quantitatively compare the antenna effect among different compounds, we proposed the new approach, where the quantum yield of the 5D0 formation is used to characterize the efficiency of energy transfer from the ligand antenna to the Eu3+ emitter. [ABSTRACT FROM AUTHOR]

In this paper, the crystallization behavior of 50ZnO:47B2O3:3Nb2O3:0.5Eu2O3 (G-0 h) glass has been investigated in detail by DSC, XRD and TEM analysis. The luminescent properties of the resulting glass-ceramics were also investigated. By XRD and TEM analysis, crystallization of several crystalline phases has been proved (α-Zn3B2O6, β-Zn3B2O6 and ZnNb2O6). By calculating crystal parameters, it was found that europium ions are successfully incorporated in the β-Zn3B2O6. Photo-luminescent spectra showed increased emission in the resulting glass-ceramic samples compared to the parent glass sample due to higher asymmetry of Eu3+ ions in the obtained crystalline phases. It was established that the optimum emission intensity is registered for glass-ceramic samples obtained after 25 h heat treatment of the parent glass. [ABSTRACT FROM AUTHOR]

Lanthanides and actinides are emerging contaminants, but little is known about their uptake and distribution by plants and their interactions in the rhizosphere. To better understand the fate of these metals in plants, the bioassociation of 2, 20 and 200 µM Eu(III) by five hydroponically grown crops endemic to Europe was assessed. The metal's concentration and its speciation were monitored by inductively coupled plasma mass spectrometry and laser spectroscopy, whereas root exudation was investigated by chromatographic methods. It has been shown, that Eu(III) bioassociation is a two-stage process, involving rapid biosorption followed by accumulation in root tissue and distribution to the stem and leaves. Within 96 h of exposure time, the plant induces a change of Eu(III) speciation in the liquid medium, from a predominant Eu(III)aquo species, as calculated by thermodynamic modelling, to a species with longer luminescence lifetime. Root exudates such as citric, malic, and fumaric acid were identified in the cultivation medium and affect Eu(III) speciation in solution, as was shown by a change in the thermodynamic model. These results contribute to a comprehensive understanding of the fate of lanthanides in the biosphere and provide a basis for further investigations with the chemical analogues Cm(III) and Am(III). [ABSTRACT FROM AUTHOR]

The loss of soluble cationic species by adsorption to glass vial walls is problematic for experiments performed at tracer concentrations. Silanization increases glass hydrophobicity to reduce cation sorption to glass surfaces. This work examines the efficacy of silanization in decreasing europium and thorium loss through glass sorption in aqueous and mixed aqueous/organic phases. The influence of the solution pH, ionic strength, electrolyte, metal concentration, organic diluent's nature, and the addition of complexing extractants was investigated. Overall, results indicate that silanization effectively decreases cation loss to sorption to glass walls. [ABSTRACT FROM AUTHOR]

In recent decades, renewable and biodegradable polysaccharide-based hydrogels have enjoyed wide applicability among them also as adsorbents for heavy metal removal from wastewaters. Herein we prepared hydrogel beads from iota and kappa carrageenans using a variety of salts as crosslinkers, that were tested for the first time in europium ion (Eu3+) sorption from an aqueous solution as representative lanthanide. The type of the salt, and especially the valance and the hydrated radius of the cation, were found to dictate hydrogel bead formation and structure and, therefore, the Eu3+ sorption yield. The results of ATR-FTIR, SEM and TGA analyses to characterize the iota carrageenan hydrogel beads that were prepared with alkali cations, before and after interaction with Eu3+, indicate that the adsorbent prepared with LiCl was much stiffer and more stable than those prepared with NaCl or KCl. The iota carrageenan beads that were prepared with LiCl were also reused 5 times while exhibiting high adsorption capacities. [ABSTRACT FROM AUTHOR]

SrAl4O7 nano phosphors doped with different weight percentages of europium (1, 3, 5, and 12 wt%) were successfully synthesized using the sol-gel method. The phase purity of the synthesized samples was confirmed by powder X-ray diffraction and the average crystallite size increased with an increase in dopant concentration of europium. The band gap value increases with an increase in the dopant concentrations of europium in SrAl4O7. The decay kinetics and luminescence spectra of materials doped with Eu3+ were strongly concentration-dependent. TG curves show the decomposition of the organic compounds in the precursors together with the evaluation of great amounts of gases and crystallization of SrAl4O7. DSC curves show the breakdown of loosely bound organic molecules, the elimination of water molecules, and other surface dangling bonds responsible for the endothermic peaks. The dielectric constant decreases with an increase in frequency. The outcomes of these investigations made the focused materials worthy of applications in energy storage devices, solar cells, and lighting technology. Highlights: Eu doped SrAl4O7 nano phosphors were successfully synthesized by sol-gel method. Band gap energy increases with an increase in Eu dopant concentrations. 12 wt% of Eu-doped SrAl4O7 nano phosphor shows a decrease in phosphorescence emission intensity due to the quenching effect. Thermal effects on prepared nano phosphors revealed that these materials have high stability and homogeneity. These synthesized nano phosphors can be applied for high-frequency devices or power applications, solar cells, and other energy storage applications due to their low dielectric constants at higher frequencies which results in minimal electric power loss. [ABSTRACT FROM AUTHOR]

A two-dimensional zirconium-based metal–organic framework (2D Zr-MOF), ZrBTB (BTB = 1,3,5-tri(4-carboxyphenyl)benzene), is used as a platform to simultaneously immobilize terbium ions and europium ions with tunable ratios on its hexa-zirconium nodes by a post-synthetic modification. The crystallinity, morphology, porosity and photoluminescence (PL) properties of the obtained 2D Zr-MOFs with various europium-to-terbium ratios are investigated. With the energy transfer from the excited BTB linker to the installed terbium ions and the energy transfer from terbium ions to europium ions, a low loading of immobilized europium ions and a high loading of surrounding terbium ions in the 2D Zr-MOF result in the optimal PL emission intensities of europium; this phenomenon is not observable for the physical mixture of both terbium-installed ZrBTB and europium-installed ZrBTB. The role of installed terbium ions as efficient mediators for the energy transfer from the excited BTB linker to the installed europium ion is confirmed by quantifying PL quantum yields. As a demonstration, these materials with modulable PL characteristics are applied for the ratiometric detection of D2O in water, with the use of the stable emission from the BTB linker as the reference. With the strong emission of immobilized europium ions and the good dispersity in aqueous solutions, the optimal bimetal-installed ZrBTB, Eu-Tb-ZrBTB(1 : 10), can achieve the sensing performance outperforming those of the terbium-installed ZrBTB, europium-installed ZrBTB and the physical mixture of both. [ABSTRACT FROM AUTHOR]

The incorporation of luminescent lanthanide complexes in inorganic matrices opens appealing possibilities in the rational upstream conception of new luminescent materials with easier recyclability. In this regard, the influence of SBA‐15 mesoporous silica, as a host matrix, on the photophysical properties of europium‐trisdipicolinate cesium salt is investigated. The lanthanide complex can be completely and reversibly adsorbed on the silica, using incipient wetness impregnation (IWI) in WATER, without the need of anchoring groups or covalent bonding on the silica surface. This specific procedure allows the homogeneous dispersion of the lanthanide complex into the host silica matrix. Appropriately assessing the photophysical properties of the targeted luminescent material proved remarkably challenging, demanding utmost caution, particularly due to the strong scattering of the mesoporous matrices. Additionally, while the observations confirm an important increase of luminescence lifetimes of lanthanide complexes upon integration into these mediums, this variation is attributed to the differing refractive indexes and not to specific surface interactions or confinement effect. Indeed, it appeared that previous literature precedents depicted erroneous exhalations of the complexes intrinsic quantum yield due to the repeated use of erroneous refractive index values. In the meantime, the luminance of these materials under UV irradiation improves drastically in comparison to what is obtained with the physical dispersion of micro‐crystals of the lanthanide complex onto silica. It is demonstrated that this improvement is due to a reduced inner filter effect in the adsorbed samples. In this regard, IWI of lanthanide complexes in the mesoporous matrices method could be of interest in the development of recyclable emitting layers, less demanding in terms of emitter quantity. [ABSTRACT FROM AUTHOR]

A novel nanocomposite, [Eu(BTD)3(DPBT)]–BSA@MnO2, is reported to serve as an effective nanoprobe for bimodal time-gated luminescence (TGL) and magnetic resonance (MR) imaging of H2O2in vitro and in vivo. The nanoprobe was fabricated by immobilizing visible-light-excitable Eu3+ complexes in bovine serum albumin (BSA)-coated lamellar MnO2 nanosheets. The TGL of the Eu3+ complex was effectively quenched by the MnO2 nanosheets. Upon exposure to H2O2, the MnO2 nanosheets underwent reduction to Mn2+, which simultaneously triggered rapid, selective and sensitive "turn-on" responses toward H2O2 in both TGL and MR detection modes. The presence of a protective "corona" formed by BSA enables the nanoprobe to withstand high concentrations of glutathione (GSH), a strong reducing agent of MnO2 nanosheets. This capability allows the nanoprobe to be utilized for detecting H2O2 in living biosamples. The combined utilization of TGL and MR detection modes enables the nanoprobe to image H2O2 across a wide range of resolutions, from the subcellular level to the whole body, without any depth limitations. The results obtained from these modes can be cross-validated, enhancing the accuracy of the detection. The capability of the nanoprobe was validated by TGL imaging of endogenous and exogenous H2O2 in live HeLa cells, as well as bimodal TGL–MR imaging of H2O2 in tumor-bearing mice. The research achievements suggest that the integration of luminescent lanthanide complexes with protein-coated MnO2 nanosheets offers a promising bimodal TGL–MR sensing platform for H2O2in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Complex oxides Eu2MeO6 (Me–Mo, W), Eu2W2O9 were obtained by a solid‐phase reaction between binary oxides. The thermodynamic and kinetic mechanisms of the reaction processes were established using a variety of physical‐chemical methods. All compounds obtained in this work crystallize in the low‐symmetry monoclinic system, forming complex framework structures, which determine a set of very valuable physical‐chemical properties. Comparison of experimental Kubelka‐Munk functions and DFT‐ calculated absorption spectra shows adequate agreement and reveals the origin of the fundamental absorption. In addition, the deficiency in DFT calculations in the part of mutual contribution of CTBs of Mo−O and W−O, from one side, and Eu−O contributions, from the other side, is reported. Calculations of absorption spectra are shown to be superior to band structure analysis in the determination of optical band gaps. Additionally, luminescent properties of Eu2MeO6 and Eu2W2O9 compounds were investigated. These studies provide a better understanding of the electronic and optical properties of the compounds Eu2MeO6 and Eu2W2O9, along with their potential applications in various areas. [ABSTRACT FROM AUTHOR]

Crystals of the family of tetragonal, non‐centrosymmetric melilites have attracted interest as nonlinear optical, piezoelectric, and ferroelectric materials. This work presents an ab initio study of the optical properties of europium melilite, Eu2MgSi2O7. The study includes the calculation of refractive and absorption spectra, with respect to the density of states of the system. The obtained results demonstrate the correlation between the electronic structure of europium melilite and its optical characteristics. [ABSTRACT FROM AUTHOR]

A novel nanocomposite, [Eu(BTD)3(DPBT)]–BSA@MnO2, is reported to serve as an effective nanoprobe for bimodal time-gated luminescence (TGL) and magnetic resonance (MR) imaging of H2O2in vitro and in vivo. The nanoprobe was fabricated by immobilizing visible-light-excitable Eu3+ complexes in bovine serum albumin (BSA)-coated lamellar MnO2 nanosheets. The TGL of the Eu3+ complex was effectively quenched by the MnO2 nanosheets. Upon exposure to H2O2, the MnO2 nanosheets underwent reduction to Mn2+, which simultaneously triggered rapid, selective and sensitive "turn-on" responses toward H2O2 in both TGL and MR detection modes. The presence of a protective "corona" formed by BSA enables the nanoprobe to withstand high concentrations of glutathione (GSH), a strong reducing agent of MnO2 nanosheets. This capability allows the nanoprobe to be utilized for detecting H2O2 in living biosamples. The combined utilization of TGL and MR detection modes enables the nanoprobe to image H2O2 across a wide range of resolutions, from the subcellular level to the whole body, without any depth limitations. The results obtained from these modes can be cross-validated, enhancing the accuracy of the detection. The capability of the nanoprobe was validated by TGL imaging of endogenous and exogenous H2O2 in live HeLa cells, as well as bimodal TGL–MR imaging of H2O2 in tumor-bearing mice. The research achievements suggest that the integration of luminescent lanthanide complexes with protein-coated MnO2 nanosheets offers a promising bimodal TGL–MR sensing platform for H2O2in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Distally substituted bis-1,3-diketone derivatives of calix[4]arene were synthesized, in which chelate groups are attached via a carbonyl carbon atom to the p-positions of phenolic fragments of a macrocycle fixed in 1,3-alternate isomeric form. 1,3-Diketone derivatives were obtained by acylation of magnesium enolate of a calix[4]arene ketone with 1-benzoylbenzotriazoles. In the synthesized compounds, 1,3-diketone groups are conjugated with the π-aromatic system of calix[4]arene. It was found by means of UV spectroscopy and NMR diffusion methods in combination with quantum chemical (DFT) calculations that a mononuclear complex with bis-chelate coordination of the lanthanide ion is predominantly formed in the solution. The formation of the complex leads to a decrease in the conjugation degree in the ligand. The most effective sensitization of Eu3+ luminescence, compared to the p-F- or p-CF3-phenyl-substituted complexes is observed for calix[4]arene complexes with H-phenyl-substituted 1,3-diketone groups. [ABSTRACT FROM AUTHOR]

A study was carried out on the luminescence excitation spectra and photoluminescence (PL) spectra as well as the luminescence kinetics of low-density polyethylene composites with different contents of CaGa2S4:Eu2+ phosphor filler. The phospholuminescence was attributed to the 4f65d → 4f7 transition of the Eu3+ ion and was greatest when the filler concentration was 7 vol.%. The dependence of the PL intensity on the excitation power density up to 0.3 W/cm2 was found to be linear, indicating that these phosphors can be used as visible radiation sources in various lighting systems. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have witnessed a meteoric rise in device performance. However, maintaining photostability, particularly under thermal stress, remains a challenge due to defect formation in the perovskite layer. This study introduces europium (III) trifluoromethanesulfonate [Eu(OTF)3] as a multifunctional additive in two‐step processed perovskite films, significantly improving the performance and high‐temperature photostability of n‐i‐p PSCs. Density function theory (DFT) calculations reveal that the OTF− anion strongly coordinates with Pb2+, effectively inhibiting iodine vacancy defect formation. The addition of Eu(OTF)3 promotes perovskite grain growth to ≈2 µm and enhances film crystallinity. PSCs with a structure of ITO/SnO2/perovskite/PDCBT/NiOx/Au achieve a champion power conversion efficiency (PCE) of 23.8%. Under 85 ± 5 °C and 1 sun illumination at an open circuit in ambient air, the PSCs with Eu(OTF)3 retain 82% of their initial PCE after aging for 1500 h. [ABSTRACT FROM AUTHOR]

Distally substituted bis-1,3-diketone derivatives of calix[4]arene were synthesized, in which chelate groups are attached via a carbonyl carbon atom to the p-positions of phenolic fragments of a macrocycle fixed in 1,3-alternate isomeric form. 1,3-Diketone derivatives were obtained by acylation of magnesium enolate of a calix[4]arene ketone with 1-benzoylbenzotriazoles. In the synthesized compounds, 1,3-diketone groups are conjugated with the π-aromatic system of calix[4]arene. It was found by means of UV spectroscopy and NMR diffusion methods in combination with quantum chemical (DFT) calculations that a mononuclear complex with bis-chelate coordination of the lanthanide ion is predominantly formed in the solution. The formation of the complex leads to a decrease in the conjugation degree in the ligand. The most effective sensitization of Eu3+ luminescence, compared to the p-F- or p-CF3-phenyl-substituted complexes is observed for calix[4]arene complexes with H-phenyl-substituted 1,3-diketone groups. [ABSTRACT FROM AUTHOR]

Rare earth elements (REE) of the host rocks (Fe-siliceous rocks) and manganese ores of the Nchwaning Mine (Hotazel Formation, Kalahari manganese field) were studied. An important feature of manganese ores and host rocks (Fe-silicites) is the presence of negative and positive cerium (Ce/Ce*) and europium (Eu/Eu*) anomalies. This testifies to the complex and long history of the formation of manganese ores. Initial metal-bearing (Mn, Fe) sediments of a shallow-water basin with a negative cerium anomaly (Ce/Ce*) were enriched in europium (positive Eu/Eu*) at different stages of lithogenesis both during sedimentation (underwater discharge of hydrothermal fluids), and subsequent processes of hydrothermal transformation of the ore-bearing strata. The source of manganese could be basaltic andesites of the underlying Ongeluk Formation. [ABSTRACT FROM AUTHOR]

Fluorescent hydrogel as an advanced material has been used for anti‐counterfeiting, probe detection, and optical devices. A facile strategy to prepare fluorescent hydrogel is developed by carboxymethyl cellulose (CMC) with Europium(III) and polyvinyl alcohol (PVA). The hydrogel forms a physical cross‐linking network under mild reaction conditions without using volatile organic chemicals. The addition of CMC‐Eu(III) improves the mechanical properties of the hydrogel. At 15% CMC‐Eu(III), the hydrogel reaches its maximum tensile and compressive stress, which are 47.25 ± 10.35 and 10.14 ± 1.90 kPa, respectively. Meanwhile, the hydrogels exhibit a 5D0→7F2 characteristic emission peak assigned to Eu3+, which emits stable red fluorescence under 254 nm ultraviolet (UV) light. When this hydrogel is applied to paper, the paper showed hidden fluorescent dots under UV light. This additive also enhances the mechanical properties of the paper, which reveals the multifunctionality of this fluorescent hydrogel for anti‐counterfeiting and reinforcement. [ABSTRACT FROM AUTHOR]

In this work, bisarsine oxides were evaluated as novel bridging ligands, aiming to develop practical and efficient luminescent lanthanide coordination polymers. We have synthesized one‐dimensional (1D) Eu3+ coordination polymers that incorporate bisarsine oxide bridging ligands and hexafluoroacetylacetonate anions. These polymers exhibited a denser packing of chains compared to analogous polymers bridged with bisphosphine oxides. The coordination polymers demonstrated exceptional thermal stability and substantial emission quantum yields. Additionally, the bisarsine oxides induced a pronounced polarization effect, facilitating a sensitive electric dipole transition that yields considerably narrow band red emission. Remarkably, the Eu3+ coordination polymers with bisarsine oxides maintained intense emission even at 550 K. A distinctive feature of these polymers is their heating‐induced emission enhancement observed when the temperature was increased from 300 K to 400 K. [ABSTRACT FROM AUTHOR]

Graphene‐like materials were prepared by thermal copolymerization using melamine as a precursor, and chemical methods successfully synthesized Eu/g‐C3N4 composites containing different europium elements. Degradation rates of 64.3 %, 91.9 %, and 72.8 % were observed in the photocatalytic degradation of Pefloxacin, Enrofloxacin, and Ciprofloxacin under visible light (λ>550 nm). Determine the photocatalytic activity of the composite. When the doping amount was Eu/g‐C3N4‐2 with k=0.0135 min−1, four times greater than that of g‐C3N4, the best photocatalytic effect was obtained. Repeated studies revealed that the Eu/g‐C3N4 composite samples had good cycle stability, and a potential degradation process was postulated. [ABSTRACT FROM AUTHOR]

Glasses with the compositions in mol % of 50ZnO:(50 − x)B2O3:0.5Eu2O3:xWO3, x = 0, 1, 3, 5 and 10 were obtained by applying the melt-quenching method and investigated by Raman spectroscopy, DSC analysis and photoluminescence (PL) spectroscopy. Raman spectra revealed that tungstate ions incorporate into the base zinc borate glass as tetrahedral [WO4]2− groups, and octahedral [WØ4O2]2− species with four bridging and two non-bridging oxygen atoms. There are also metaborate, [BØ2O]− and pyroborate units, [B2O5]4−, in the glass networks. The glasses are characterized by good transmission in the visible region, at about 80%. Photoluminescence (PL) spectra evidenced that WO3 is an appropriate constituent for the modification of zinc borate glass structure and for enhancing the Eu3+ luminescent intensity. The most intense luminescence peak observed, at 612 nm, suggests that the glasses are potential materials for red emission. [ABSTRACT FROM AUTHOR]

Efficient separation of europium (Eu) from aqueous solution is pivotal for the sustainable development of nuclear industry and rare earth industry. In this work, bis(2-ethylhexyl) phosphate (P204) was employed to separate Eu(III) by solvent extraction method using kerosene as diluent. The extraction equilibrium could reach within 30-min contact time. The extraction ratio enhanced as the increased O:A phase ratio, extractant concentration, and temperature. However, the HCl introduction caused its clear descent. Combined with the slope method and FT-IR analysis, extraction mechanism could be unveiled, which is the coordination between P=O double bond and Eu(III) ions in a proportion of 3:1. [ABSTRACT FROM AUTHOR]

Rare-earth elements (REEs) are critical to our modern economy, yet their mining from natural ores bears a profound environmental impact. Traditional separation techniques are chemical and energy-intensive because their chemical similarities make REEs very challenging to purify, requiring multiple extraction steps to achieve high purity products. This emphasizes the need for sustainable and straightforward separation methods. Here we introduce a strategy for the direct separation of europium (Eu) from complex mixtures under ambient conditions, leveraging on the redox non innocence of purely inorganic tungsten tetrathiolate (WS42−) ligands. The recovery of Eu is achieved upon reduction of Eu(III) to a Eu(II) coordination polymer, driven by an induced internal electron transfer from the tetrathiotungstate ligand. Applying this strategy to unconventional feedstock such as spent energy-saving lamps allows selective europium recovery with separation factors over 1000 and recovery efficiency as high as 99% without pre-treatment of the waste. Rare-earth elements (REEs) are vital to the modern economy, yet their mining poses both geopolitical and environmental challenges. Here, authors present a highly selective method for the recovery of europium from spent fluorescent lamps using redox active tetrathiotungstate ligands. [ABSTRACT FROM AUTHOR]

Two new lanthanide complexes with the general formula [Ln(hqtsc)2Cl], where Ln = Eu3+/Tb3+ and hqtsc is (E)-2-((8-hydroxyquinolin-2-yl)methylene)hydrazine-1-carbothioamide have been synthesized. The structures of the complexes have been elucidated through IR, 1H NMR, 13C NMR and HR-mass spectroscopy. The coordination behavior of the ligand was investigated with proton and two trivalent lanthanides, Eu(III) and Tb(III), by potentiometric and spectrophotometric methods in a highly aqueous medium. The studies reveal that the two lanthanides form complexes of the type ML2H2, ML2H1, ML2, ML2H−1, and ML2H−2. The high formation constants of ML with log β = 26.55 and 27.13 indicate that these complexes will become promising candidates for chelation therapy, radioimmunotherapy, and other biomedical applications. Further, the change in colour and electronic spectra of the complexes in the presence of anions showed the selective colorimetric sensing ability towards H2PO4− (orange/yellow→, colorless) and CN− (orange/yellow → red). The DFT studies were also carried out to establish the structure, bonding, and sensing mechanism of the complexes. [ABSTRACT FROM AUTHOR]

Efficient and stable blue is the holy grail of OLED. beeOLED pioneers intra‐metallic Europium emitter that offer a unique combination of deep blue single peak emission spectrum, open shell electronic configuration for 100% efficiency, and potential of high operational stability as no organic bonds are weakened during light generation. [ABSTRACT FROM AUTHOR]

Olaquindox (OLA) and quinocetone (QCT) have been prohibited in aquatic products due to their significant toxicity and side effects. In this study, rapid and visual europium nanoparticle (EuNP)-based lateral flow strip biosensors (LFSBs) were developed for the simultaneous quantitative detection of OLA, QCT, and 3-methyl-quinoxaline-2-carboxylic acid (MQCA) in fish feed and tissue. The EuNP-LFSBs enabled sensitive detection for OLA, QCT, and MQCA with a limit of detection of 0.067, 0.017, and 0.099 ng/mL (R2 ≥ 0.9776) within 10 min. The average recovery of the EuNP-LFSBs was 95.13%, and relative standard deviations were below 9.38%. The method was verified by high-performance liquid chromatography (HPLC), and the test results were consistent. Therefore, the proposed LFSBs serve as a powerful tool to monitor quinoxalines in fish feeds and their residues in fish tissues. [ABSTRACT FROM AUTHOR]

In this paper, we present the characteristics of photoluminescent YBO3 successfully synthesized through a solid-state reaction and a microwave-assisted method. We used yttrium oxide and boric acid in excess as the starting reagents. The synthesis conditions were reflected in the fluorescent characteristics and the structure. Excess boric acid caused structural changes, as observed by the FTIR spectroscopy analysis. Powder X-ray diffraction (XRD) analysis confirmed the crystalline phases and purity of the samples. We observed improved photoluminescence properties in the samples synthesized by the microwave-assisted method. These findings enhance the understanding of the material's properties and indicate potential applications in illumination, displays, and narrow-band fluorescent smartphone-readable markers. [ABSTRACT FROM AUTHOR]

Europium ion doped silicate glasses are prepared by melt quench method with a novel composition for white Light Emitting Diode (LED). The investigating sample is having high density and refractive index which is useful for optical applications. The Hruby criteria value of these glass material is high and having high thermal stability. These glasses are assigned to Si–O- Eu and Si–O-Si stretch and bending bonds are forms with respect to their frequencies. High intensity absorption peaks are observed at 377 and 609 nm, the direct and indirect energy band gap values are decreasing as the europium ion concentration increases. The Judd – Ofelt parameters are calculated by using emission spectra of prepared glass sample. Ω2, Ω4 and Ω6 are the intensity parameters of Europium ion-doped Silicate glasses. Since the parameter Ω2 directly relates to the asymmetry of the local environment around the trivalent rare earth ions (Eu3+), it indicates the covalent nature between Europium ions and ligand anions. The CIE plot shows that the prepared 5 glass sample SiEu 1 to SiEu 5 emits white light at an excitation wavelength of 377 nm; these glare are utilized for white LEDs. europium-doped silicate glasses play a crucial role in LED technology by enhancing the color quality, efficiency, and versatility of LED lighting for a wide range of applications, from general lighting to displays and more. Their ability to convert high-energy light into visible light with specific colors makes them valuable components in the world of LED technology. [ABSTRACT FROM AUTHOR]

This study explores the utilization of metal–organic frameworks (MOFs), particularly those incorporating lanthanide-based elements for their fluorescence capabilities, to create an advanced barcode system. By exploiting the modular nature of MOFs, we have developed a material capable of dynamic information encoding and robust against counterfeiting efforts. We introduce a novel barcode prototype that exhibits visible color shifts and fluorescence modulation when exposed to a specific sequence of chemical and thermal stimuli. The barcode is composed of MOF-808, which is modified with transition metals like iron or cobalt, and europium cations. These components are embedded within polyvinylidene fluoride (PVDF) to form a composite. This embedding process ensures that the MOF particles remain reactive to specific trigger molecules, enabling a distinct read-out sequence. The decoding process, involving exposure to ammonia, heating at 120 °C, and treatment with HCl, triggers observable changes in fluorescence and color, depending on the transition metal used. Our investigations with Eu,Co-MOF-808, and Eu,Fe-MOF-808 composites have resulted in the creation of a barcode prototype that demonstrates the feasibility of using europium-modified and unmodified transition metal modified MOF-808@PVDF composites for enhanced security applications. [ABSTRACT FROM AUTHOR]

The bulky β‐diketiminate ligand frameworks [BDIDCHP]− and [BDIDipp/Ar]− (BDI=[HC{C(Me)2N‐Dipp/Ar}2]− (Dipp=2,6‐diisopropylphenyl (Dipp); Ar=2,6‐dicyclohexylphyenyl (DCHP) or 2,4,6‐tricyclohexylphyenyl (TCHP)) have been developed for the kinetic stabilisation of the first europium (II) hydride complexes, [(BDIDCHP)Eu(μ‐H)]2, [(BDIDipp/DCHP)Eu(μ‐H)]2 and [(BDIDipp/TCHP)Eu(μ‐H)]2, respectively. These complexes represent the first step beyond the current lanthanide(II) hydrides that are all based on ytterbium. Tuning the steric profile of β‐diketiminate ligands from a symmetrical to unsymmetrical disposition, enhanced solubility and stability in the solution–state. This provides the first opportunity to study the structure and bonding of these novel Eu(II) hydride complexes crystallographically, spectroscopically and computationally, with their preliminary reactivity investigated. [ABSTRACT FROM AUTHOR]

The capacity to discern the highest temperature that an object is subjected to is a crucial diagnostic tool. Consequently, the pursuit of materials that enable the luminescence‐based investigation of the thermal history of an object with high sensitivity is of great importance from the functional applications standpoint. This study aims to present a multiparametric thermal history phosphor based on the luminescent coordination polymer [Eu(BTC)(H2O)6] [Eu(BTC)‐1, where H3BTC = 1,3,5‐benzenetricarboxylic acid]. The progressive dehydration that Eu(BTC)‐1 undergoes as a function of temperature increase in the 343–425 K range results in significant alterations in both the shape of the Eu3+ ions emission spectrum and the depopulation kinetics of their 5D0 level. Based on this occurrence, a thermal history phosphor with an unprecedentedly high relative sensitivity of 11.3% K−1 in ratiometric mode, and 1.8% K−1 in lifetime‐based mode, is developed. The outcomes of this research are expected to stimulate a wide interest in the exploitation of (porous) coordination polymer‐type materials for the development of thermal history phosphors. [ABSTRACT FROM AUTHOR]

Simple Summary: The analysis of the toxicity of lanthanides, and among them europium, has grown in recent years due to its multiple applications in different human technologies. In the present research work, we analyze its toxicity in the eukaryotic microorganism model Tetrahymena thermophila, comparing strains adapted to high concentrations of two europium compounds (chloride and oxide forms) with the wild-type strain. The oxidative stress caused by europium oxide is reduced by overexpression of genes encoding various antioxidant enzymes. Similarly, metallothionein genes of this microorganism are overexpressed, which could indicate the possible chelation of this lanthanide by these proteins. Lipid metabolism and autophagy are involved in the cellular stress response to europium. Both bioaccumulation in vacuoles, and their subsequent release, as well as a possible biotransformation to europium phosphate are involved in the europium detoxification process in these cells. A better understanding of the cellular mechanisms of lanthanide detoxification is very useful information for solving bioremediation problems and possible intoxications in animals and humans. Europium is one of the most reactive lanthanides and humans use it in many different applications, but we still know little about its potential toxicity and cellular response to its exposure. Two strains of the eukaryotic microorganism model Tetrahymena thermophila were adapted to high concentrations of two Eu(III) compounds (EuCl3 or Eu2O3) and compared to a control strain and cultures treated with both compounds. In this ciliate, EuCl3 is more toxic than Eu2O3. LC50 values show that this microorganism is more resistant to these Eu(III) compounds than other microorganisms. Oxidative stress originated mainly by Eu2O3 is minimized by overexpression of genes encoding important antioxidant enzymes. The overexpression of metallothionein genes under treatment with Eu(III) compounds supports the possibility that this lanthanide may interact with the -SH groups of the cysteine residues from metallothioneins and/or displace essential cations of these proteins during their homeostatic function. Both lipid metabolism (lipid droplets fusing with europium-containing vacuoles) and autophagy are involved in the cellular response to europium stress. Bioaccumulation, together with a possible biomineralization to europium phosphate, seems to be the main mechanism of Eu(III) detoxification in these cells. [ABSTRACT FROM AUTHOR]

Defects in phosphors affect not only luminescence intensity but also emission peak width, decay time, and afterglow. The green phosphor β -SiAlON:Eu2+ exhibits the green emission of Eu2+ at 520 nm and the blue emission of nitrogen vacancies at 460 nm in time-resolved fluorescence measurements. The decay time of the intrinsic Eu2+ transition is 0.7 μ s, but afterglow is detected from 50 μ s to 0.01 s. This afterglow decay curve is the same for the green emission of Eu2+ and the blue emission of nitrogen vacancies, suggesting that the defect levels of the nitrogen vacancies affect the Eu2+ transition. The afterglow decay curves were analyzed using the formula of the general-order kinetics, 1 + t / τ B − n , where n is the decay power and τ B is the decay time. This equation is generally used when analyzing afterglow on the order of seconds to hours but has not been examined systematically applied in samples with different concentrations of Eu2+ and temperatures on the order of nanoseconds to milliseconds. The decay power n is approximately 1 for all Eu2+ concentrations (x = 0.001–0.3) and undoped β -SiAlON. The decay time τ B is correlated with the density of the nitrogen vacancies determined by electron spin resonance. Furthermore, the value of n is approximately 1 for 50 μ s to 0.01 s and 0.3 for 1–1000 s. Thus, the luminescence mechanism of Eu2+ can be discussed by comparing n and τ B obtained from the decay curves. In addition, several different Eu2+-doped phosphors, namely SrAl2O4:Eu2+, Dy3+, CaAlSiN3:Eu2+, and CaS:Eu2+, Tm3+, are studied. [ABSTRACT FROM AUTHOR]

Solvent extraction of Zr(IV) in an undiluted phosphonium based ionic liquid (IL) and its selective separation from Ln(III) and An(III) has been investigated in the present study. Eu(III)/Am(III) were chosen as the representative Ln(III)/An(III). Tri(hexyl)tetradecylphosphonium nitrate ([P66614][NO3]) was chosen as IL phase and the feed phase was nitric acid containing the target metal ions. The extraction process was accomplished at different experimental parameters such as the concentration of initial nitric acid, initial feed metal concentration and equilibration time to explore the extractability of the proposed IL towards Zr(IV). The efficient extraction of Zr(IV) without any external ligand in IL phase and negligible extraction of Eu(III)/Am(III) were distinctly discerned leading to noteworthy separation factors for Zr(IV). The loading experiment revealed a noticeable growth of equilibrium concentrations of Zr(IV) in IL phase while that of Eu(III) was very less irrespective of the initial feed concentration. The association of two IL moieties in the complex formation process has been inferred. Nitrate ion was found to be superior as IL anion in terms of metal loading in comparison to other anions. Thermodynamics of extraction and the stripping of the loaded Zr(IV) from IL phase using a suitable stripping solution have also been investigated. [ABSTRACT FROM AUTHOR]

Lanthanides (Ln2O3) and elements like Zr and Y find application in the highest temperature‐resistant thermal and/or environmental barrier coatings. Such coatings are routinely exposed to silicate particles (e.g., sand, dust, volcanic ash), leading to chemical reactions that degrade the coating. The dissolution of 13.5 wt.% Ln2O3 into a calcium–magnesium–aluminum‐silicate (CMAS) melt leads to a viscosity reduction for the light lanthanides, while viscosity increases toward heavier lanthanides. For Gd, Y, and Zr, various amounts up to 13.5 wt.% (Gd2O3, Y2O3, ZrO2) were added to the CMAS melt, showing a tendency of increased viscosity for low concentrations (2.5‐3 wt.%) and a decreasing viscosity for higher values of the added component. [ABSTRACT FROM AUTHOR]

Europium (Eu) ion–doped luminescent materials have attracted considerable attention for their numerous optical applications. Eu‐doped Ca–Al–Si–O(–N) glasses were synthesized from a mixture of oxynitride glasses and Eu2O3 powder using a standard melt‐quenching technique in a radiofrequency furnace. The source Eu trivalent ions primarily changed to Eu2+ during melting, and the ratio of Eu2+ ions increased with an increase in Eu content in the starting mixture. All the prepared glasses exhibited photoluminescence (PL) owing to the 5d–4f transition of Eu2+ ions. The absorption edge and PL wavelength shifted to longer wavelength with an increase in Eu content. Moreover, oxynitride glasses exhibited a longer wavelength than those of oxide glasses. The internal quantum efficiency (IQE) increased with the increase in Eu content until it reached a maximum. X‐ray absorption structure and electron spin resonance spectroscopies were used to determine the local structure of Eu ions, which confirmed that changes in the local structure of Eu ions were responsible for the shift in PL peak and the change in IQE. The development of the Eu‐doped Ca–Al–Si–O–N glasses is highly inspiring for transparent phosphors. [ABSTRACT FROM AUTHOR]

In this work, five phenanthroline derivatives substituted with different methyl groups have been selected to synthesize β‐diketonate‐based europium complexes to check the influence of the substitutions on the degradation effect of those complexes in poly(methyl methacrylate) (PMMA) films. The photophysical properties of Eu(III) complexes, including absorbance, excitation, and emission have been carefully investigated in solution, solid‐state, and doped in PMMA film. In all these states, the complexes exhibit an impressive red emission at 614 nm with a high photoluminescence quantum yield of up to 85 %. The films have been exposed under outdoor, indoor, and dark storage stability lifetime conditions for 1200 hours. The photoluminescence measurements recorded every 400, 800, and 1200 hours demonstrated that the film containing europium complex with phenanthroline ligand substituted by a high number of methyl groups (Eu(TTA)3L5) showed good photoluminescent stability in indoor and dark conditions, and exhibited better resistance to degradation in outdoor conditions compared to other complexes. This study has proved that phenanthroline ligands could be tuned chemically leading to better stability of those types of complexes in films which can be end‐used for future stable optoelectronic devices such as luminescent solar concentrators. [ABSTRACT FROM AUTHOR]

Thermometry of thermal barrier coatings (TBCs) is essential for designing effective thermal management systems and prolonging the service life of components in aeroengines and gas turbines. However, conducting on-line thermometry in these systems is challenging because it requires physical or optical access to components during operation. A promising alternative is off-line thermometry, in which phosphorescent thermal-history sensors are used to record exposure temperatures after operation. In this study, we synthesized europium (III)-ion-doped barium aluminate (BaAl 2 O 4 :Eu3+) via a solid-state reaction and confirmed its ability to function as a thermal history sensor. Subsequently, we developed a new thermal-sensing strategy based on the self-reduction of Eu3+ to Eu2+ in a BaAl 2 O 4 :Eu3+ phosphor exposed to high temperatures (900–1300 °C) in ambient air. The Eu3+ concentration decreased as the heat exposure temperature increased due to self-reduction of Eu3+ to Eu2+, which irreversibly changed the phosphorescence of BaAl 2 O 4 :Eu3+, i.e., its spectra, the ratio of the phosphorescence intensities of Eu3+ and Eu2+, and the lifetime of Eu3+. As the heat exposure temperature increased, the ratio of the phosphorescence intensities of Eu3+ and Eu2+ monotonically decreased due to self-reduction, whereas the phosphorescence lifetime of Eu3+ initially gradually increased until the heat exposure temperature reached 1000 °C because of the degeneration of concentration quenching, and then decreased as the temperature exceeded 1000 °C because of the degeneration of lattice distortions. This demonstrates that heat exposure temperatures exceeding 1000 °C can be quantitatively evaluated through off-line analysis of Eu3+ and Eu2+ phosphorescence intensity ratios and Eu3+ lifetime at room temperature. Thus, BaAl 2 O 4 :Eu3+, a self-reducing phosphor, is a potential sensor for off-line thermometry of TBCs. [ABSTRACT FROM AUTHOR]

The advancement of bioimaging and theranostics necessitates the development of highly biocompatible multifunctional agents. Here, we introduce a potential multimodal agent based on nanosized hydroxyapatite (HAp) co-doped with europium(III) and gadolinium(III) (Eu3+ and Gd3+) ions. The study presents a detailed characterization of the HAp:Eu3+/Gd3+ nanoparticles synthesized via the co-precipitation method. The structure and morphology were analyzed using X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The study of spectroscopic properties (emission, excitation, emission kinetics) as a function of optically active ions was carried out. Moreover, various dopant ratio combinations were studied to optimize the optical and magnetic properties. HAp:Eu3+/Gd3+ demonstrates tunable PL intensity with different concentrations of Eu3+ and Gd3+ ions and increased magnetization with higher doping with Gd3+ ions. Furthermore, co-doping with Gd3+ ions results in an enhancement of Eu3+ emission intensity, rendering HAp:Eu3+/Gd3+ a potentially promising candidate for bioimaging applications. [ABSTRACT FROM AUTHOR]