Near-infrared photo-responsive Er3+-K+ co-doped Y2O3 phosphors with enhanced UC luminescence

Y₂O₃: x% Er³⁺ (x=5, 7, 10, 12, 15) and Y₂O₃: 10% Er³⁺，x% K⁺ (x=0, 1, 3, 5, 7, 10, 15) phosphors were successfully prepared by a low-temperature combustion method. The structure as well as the absorption/emission spectra of phosphors were investigated. The effect of doping concentration of K⁺ ions on the upconversion (UC) luminescence of Y₂O₃: 10% Er³⁺ phosphor was examined and the possible optical transitions were discussed. The results showed that K⁺ ion doping not only changed the microstructure and crystallinity of the phosphors, but also enhanced its UC luminescence intensity. The Y₂O₃: 10% Er³⁺, 7% K⁺ phosphor exhibit the strongest UC emission intensity. Compared with the Y₂O₃: 10% Er³⁺ phosphor, the UC luminescence intensity at 563 nm and 661 nm was enhanced by 67.8 and 27.3 times for the K-codoped samples, respectively. The phosphor with the optimal doping concentration was mixed with a polymer to form a composite film, which was employed for the fabrication of near-infrared (NIR) photo-responsive detection devices. The device exhibited strong photo-current response to NIR light at 980 nm, implying that our work could inspire new design strategy for the development of NIR photo-detection devices.     

Coordination chemistry of surface-associated ligands for solid-liquid adsorption of rare-earth elements

General guidelines for the design of ligands for the enrichment of rare-earth elements by solid-liquid adsorption are described using coordination chemistry.Relevant properties of ligands include selectivity of metal ions based on adjustment of donor atom polarizability,denticity,and the pK_a range of the binding sites.The selectivity of solid-phase materials for the enrichment of rare-earth ions by the ligand design guidelines is outlined,with special consideration of additional varia...     

Insights into structure,local site symmetry,and energy transfer for regulating luminescent properties of SrLaLiTeO6: Dy/Eu and its application in wLEDs

A series of spectrally tunable Dy³⁺/Eu³⁺-coactivated double perovskites SrLaLiTeO₆ (SLLT) were synthesized via solid-state ceramic route under air condition. Considering differences of ionic radius and valences among the dopants and host cations, Dy³⁺/Eu³⁺ are all inclined to enter La site, though slight occupations in Sr site cannot be completely ruled out. Dy shows narrow band emissions in blue (B) to yellow (Y) region, which is stemmed from magnetic (⁴F_9/2 → ⁶H_15/2) and electric (⁴F_9/2 → ⁶H_13/2) dipole transitions, respectively. Eu³⁺ exhibits orange-red (O–R) emissions, with two dominant peaks located at ∼ 593 and 617 nm from magnetic (⁵D₀ → ⁷F₁) and electric (⁵D₀ → ⁷F₂) dipole transitions, which could be used as compensation for the red-emitting portion in pc-wLEDs via energy transfer (ET) from Dy to Eu to overcome the disadvantage of low excitation efficiency. The substitutional local site symmetry could be regularly modified along with severely impacting on Y/B and R/O ratios for Dy and Eu emission colors via simply modifying the doping contents, due to changes in bond lengths and Coulomb potentials from interconnected octahedrons [LiO₆] and [TeO₆] around the dopants. The fabricated pc-wLED via combining a commercial n-UV LED chip with the SLLT: Dy/Eu, exhibited splendid EL performance, with the CIE coordinate is calculated to be (0.3690, 0.3539), CCT of 3232 K, and CRI (R_a) of 86.5. Altogether, it manifests that the stable SLLT: Eu and SLLT: Dy/Eu are potentially good candidates for applications as red and white phosphors, respectively in indoor plant growth LED and pc-wLEDs.     

Relationship among morphology,photoluminescence emission,and photocatalytic activity of Eu-doped ceria nanostructures: A surface-type effect

Herein, we discuss the synthesis of Eu-doped ceria nanostructures via the microwave-assisted hydrothermal method. The morphological analysis showed that Eu-doped ceria nanoparticles, nanorods, nanocubes, and nanopolyhedrons with different sets of exposed facets were obtained. The structural characterization revealed that the samples were crystalline and without secondary phases. The optical analysis showed a decrease in the bandgap energies of the Eu-doped nanostructures compared with pure ceria nanoparticles, and different photoluminescence emissions were found depending on the morphology. The photocatalytic activity of each nanostructure was evaluated, and Eu-doped nanopolyhedrons were the most promising photocatalyst, exhibiting a 60% and 80% increase in RhB discoloration compared to the Eu-doped and pure ceria nanoparticles, respectively. The better performance of the nanopolyhedrons is probably associated with the presence of different exposed facets, such as (111), (200), (220), and (311). The main species involved in the photocatalytic process were holes. The performances of each nanostructure were associated with their different exposed facets, the concentration of oxygen vacancies, and surface defects.     

Effect of the Rare Earth Metals (Tb,Nd, Dy) addition for the modification of nickel catalysts supported on alumina in CO2 Methanation

In the current research, a group of rare-earth metals functionalized mesoporous Ni-M/Al₂O₃ (M = Tb, Dy, Nd) composite oxides were prepared by the one-pot sonochemical pathway and applied in the CO₂ methanation procedure. Promoters can partially influence the textural and catalytic characteristics of Ni–Al₂O₃ catalysts. Physicochemical characteristics of the as-fabricated catalysts were identified utilizing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Energy-dispersive X-ray spectroscopy (EDS), Temperature Programmed Reduction (H₂-TPR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analyses. Among the specimens, the catalyst modified by Terbium (Tb) manifested better catalytic performance and CH₄ selectivity, particularly at low temperatures (350–400 °C). The influence of reaction temperature (200–500 °C) was scrutinized below space velocity (GHSV) of 25,000 ml/g_cath, atmospheric pressure, and stoichiometric ratio of CO₂ to H₂ (1: 4). The impact of the desired content of nickel and terbium was examined. The 25Ni–5Tb–Al₂O₃ operates the best function for CO₂ methanation, which can attain the highest CO₂ conversion of 66.93% at 400 °C at atmospheric pressure. The superior catalytic performance of 25Ni–5Tb–Al₂O₃ could be assigned to the appropriate fabrication method and the promotion effect of Terbium. The synthesis effect could be assigned to its large surface area, obtaining by the hot spot mechanism. The addition of Terbium promotes the Ni distribution on the supports as well as accelerates the positive reaction due to the oxygen vacancies of Terbium. Besides, these outcomes could be defined with the maximum distribution of active nickel sites on the catalyst and improvement in the catalyst reduction ability at low temperatures.