Synthesis, Crystal Structure, and Luminescence Properties of a Novel Green-Yellow Emitting Phosphor LiZn_1−<i>x</i>PO₄:Mn_<i>x</i> for Light Emitting Diodes

Synthesis, Crystal Structure, and Luminescence Properties of a Novel Green-Yellow Emitting Phosphor LiZn1−xPO4:Mnx for Light Emitting Diode

Novel Reddish-Orange-Emitting BaLa₂Si₂S₈:Eu²⁺ Thiosilicate Phosphor for LED Lighting

A novel reddish-orange-emitting BaLa₂Si₂S₈:Eu²⁺ thiosilicate was prepared in a sealed fused silica ampule and its crystal structure was refined using Rietveld methods. The BaLa₂Si₂S₈:Eu²⁺ phosphor is excitable over a broad range from UV to blue (350–450 nm) and generated a reddish-orange broadband emission peaking at 645 nm with a quantum efficiency of ∼24%. The thermal luminescence quenching of BaLa₂Si₂S₈:Eu²⁺ was investigated over the range 25 to 150 °C. This phosphor was utilized to incorporate with two commercially available phosphors, blue BaMgAl₁₀O₁₇:Eu²⁺ and green (Ba,Sr)₂SiO₄:Eu²⁺, and a near-UV LED chip (405 nm), a white light with <i>Ra</i> of ∼94 was obtained

Synthesis and Characterization of Open-Framework Niobium Silicates: Rb₂(Nb₂O₄)(Si₂O₆)·H₂O and the Dehydrated Phase Rb₂(Nb₂O₄)(Si₂O₆)

A new niobium(V) silicate, Rb2(Nb2O4)(Si2O6)·H2O, has been synthesized by a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and solid-state NMR spectroscopy. It crystallizes in the tetragonal space group P4322 (No. 95) with a = 7.3431(2) Å, c = 38.911(3) Å, and Z = 8. Its structure contains tetrameric units of the composition Nb4O18, which share corners to form a layer of niobium oxide. The Nb−O layer is a slice of the pyrochlore structure. Neighboring Nb−O layers are linked by vierer single-ring silicates generating eight-ring and six-ring channels running parallel to directions, in which the Rb+ cations and water molecules reside. The tantalum analogue was prepared and characterized by powder X-ray diffraction. Upon heating to 500 °C, Rb2(Nb2O4)(Si2O6)·H2O loses lattice water molecules, while the framework structure is retained to give the anhydrous compound Rb2(Nb2O4)(Si2O6), whose structure was also characterized by single-crystal X-ray diffraction. The dehydrated sample absorbs water reversibly, as indicated by powder X-ray diffraction. Rb2(Nb2O4)(Si2O6) crystallizes in the tetragonal space group I41 (No. 80) with a = 10.2395(6) Å, c = 38.832(3) Å, and Z = 16

Synthesis and Luminescence Properties of Novel Ce³⁺- and Eu²⁺-Doped Lanthanum Bromothiosilicate La₃Br(SiS₄)₂ Phosphors for White LEDs

Novel Ce³⁺- and Eu²⁺-doped lanthanum bromothiosilicate La₃Br­(SiS₄)₂:Ce³⁺and La₃Br­(SiS₄)₂:Eu²⁺ phosphors were prepared by solid-state reaction in an evacuated and sealed quartz glass ampule. The La₃Br­(SiS₄)₂:Ce³⁺ phosphor generates a cyan emission upon excitation at 375 nm, whereas the La₃Br­(SiS₄)₂:Eu²⁺ phosphor could be excited with extremely broad range from UV to blue region (300 to 600 nm) and generates a reddish-orange broadband emission centered at 640 nm. In addition, thermal luminescence properties of La₃Br­(SiS₄)₂:Ce³⁺and La₃Br­(SiS₄)₂:Eu²⁺ phosphors from 20 to 200 °C were investigated. The combination of a 450 nm blue InGaN-based LED chip with the red-emitting La₃Br­(SiS₄)₂:Eu²⁺ phosphor, and green-emitting BOSE:Eu²⁺ commercial phosphor produced a warm-white light with the CRI value of ∼95 and the CCT of 5,120 K. Overall, these results show that the prepared phosphors may have potential applications in pc-WLED

Synthesis and Characterization of Open-Framework Niobium Silicates: Rb₂(Nb₂O₄)(Si₂O₆)·H₂O and the Dehydrated Phase Rb₂(Nb₂O₄)(Si₂O₆)

A new niobium(V) silicate, Rb2(Nb2O4)(Si2O6)·H2O, has been synthesized by a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and solid-state NMR spectroscopy. It crystallizes in the tetragonal space group P4322 (No. 95) with a = 7.3431(2) Å, c = 38.911(3) Å, and Z = 8. Its structure contains tetrameric units of the composition Nb4O18, which share corners to form a layer of niobium oxide. The Nb−O layer is a slice of the pyrochlore structure. Neighboring Nb−O layers are linked by vierer single-ring silicates generating eight-ring and six-ring channels running parallel to directions, in which the Rb+ cations and water molecules reside. The tantalum analogue was prepared and characterized by powder X-ray diffraction. Upon heating to 500 °C, Rb2(Nb2O4)(Si2O6)·H2O loses lattice water molecules, while the framework structure is retained to give the anhydrous compound Rb2(Nb2O4)(Si2O6), whose structure was also characterized by single-crystal X-ray diffraction. The dehydrated sample absorbs water reversibly, as indicated by powder X-ray diffraction. Rb2(Nb2O4)(Si2O6) crystallizes in the tetragonal space group I41 (No. 80) with a = 10.2395(6) Å, c = 38.832(3) Å, and Z = 16

Ni@NiO Core–Shell Structure-Modified Nitrogen-Doped InTaO₄ for Solar-Driven Highly Efficient CO₂ Reduction to Methanol

This investigation demonstrates the photocatalytic properties and activities of N-doped InTaO4 photocatalysts, which were prepared by impregnating Ni and the use of a modified Ni@NiO core–shell nanostructure-cocatalytic method for the reduction of CO2 to methanol. X-ray absorption spectroscopy (XAS) clearly indicates the oxygen vacancies and mechanism of a series of InTaO4-based photocatalysts. Nitrogen doping produces visible-light-responsive photocatalytic activity and further enhances absorbance. The cocatalytic method not only dramatically enhances absorbance, but also efficiently avoids electron–hole recombination that would otherwise be caused by electrons and holes separated from the crystal. The photocatalytic activity that was determined by the methanol yield demonstrates that N-doped samples give approximately twice the yield of undoped ones, whereas the cocatalytic method gives about triple the yield. A mechanism is aided in attempts to elucidate the correlation between structures and activities

New Ce³⁺-Activated Thiosilicate Phosphor for LED LightingSynthesis, Luminescence Studies, and Applications

A new Ce³⁺-activated thiosilicate phosphor, BaLa₂Si₂S₈:Ce³⁺, was synthesized by using solid-state methods in a fused silica ampule and found to crystallize in the structure type of La₂PbSi₂S₈. The crystal structure has been characterized by synchrotron X-ray diffraction and refined with Rietveld methods. This novel cyan-emitting phosphor can be excited over a broad range from UV to blue light (380–450 nm) and generates a broadband emission peaking at 471 nm with a quantum efficiency of 36%. Nonradiative transitions between Ce³⁺ ions in BaLa₂Si₂S₈:Ce³⁺ have also been demonstrated to be attributable to dipole–dipole interactions, and the critical distance was calculated to be 17.41 Å. When BaLa₂Si₂S₈:Ce³⁺ phosphor was utilized to incorporate with yellow-emitting (Sr,Ca)₂SiO₄:Eu²⁺ phosphor and red-emitting CaAlSiN₃:Eu²⁺ phosphor on a 430 nm blue LED chip, a warm white light LED device with color rendering index of ∼96 was obtained. The results indicate that cyan-emitting BaLa₂Si₂S₈:Ce³⁺ can serve as a potential phosphor for incorporation in fabrication of solid-state lighting. The preparation, spectroscopic characterization, quantum efficiency, decay lifetime, thermal-quenching behavior, and related LED device data are also presented

Eu²⁺-Activated Sr₈ZnSc(PO₄)₇: A Novel Near-Ultraviolet Converting Yellow-Emitting Phosphor for White Light-Emitting Diodes

The crystal structure of Eu2+-activated Sr8ZnSc­(PO4)7:Eu2+ phosphor was refined and determined from XRD profiles by the Rietveld refinement method using a synchrotron light source. This phosphor crystallizes in the monoclinic structure with the I2/a space group. The SZSP:xEu2+ phosphors showed a broad yellow emission band centered at 511 and 571 nm depending on the concentration of Eu2+, and the composition-optimized concentration of Eu2+ in the Sr8ZnSc­(PO4)7:Eu2+ phosphor was determined to be 2 mol %. The estimated crystal-field splitting and CIE chromaticity coordinates of Sr8ZnSc­(PO4)7:xEu2+ (x = 0.001–0.05 mol) were 20181–20983 cm–1 and (0.3835, 0.5074) to (0.4221, 0.5012), respectively, and the emission band showed a redshift from 547 to 571 nm with increasing Eu2+ concentration. The nonradiative transitions between the Eu2+ ions in the Sr8ZnSc­(PO4)7 host were attributable to dipole–dipole interactions, and the critical distance was approximately 19.8 Å. The combination of a 400 nm NUV chip with a blend of Sr8ZnSc­(PO4)7:0.02Eu2+ and BAM:Eu2+ phosphors (light converters) gave high color rendering indices between 79.38 and 92.88, correlated color temperatures between 4325 and 7937 K, and tuned CIE chromaticity coordinates in the range (0.381, 0.435) to (0.294, 0.310), respectively, depending on the SZSP:0.02Eu2+/BAM:Eu2+ weight ratio. These results suggest that the Sr8ZnSc­(PO4)7:0.02Eu2+/BAM:Eu2+ phosphor blend has potential applications in white NUV LEDs

Turn the Trash into Treasure: Egg-White-Derived Single-Atom Electrocatalysts Boost Oxygen Reduction Reaction

Egg provides human beings the nutrition and economical products, such as antimicrobial and cosmetics. However, we mainly employ egg yolk, causing tons of egg white as the industrial waste to be further reprocessed. On account of the sustainable issue, we adopt the egg white to prepare single-atom electrocatalysts, achieving a half-wave potential (E1/2) of 0.927 V vs reversible hydrogen electrode (RHE) for oxygen reduction reaction, overperforming the commercial Pt/C (0.857 V) and the conventional iron single-atom electrocatalyst (0.835 V). Using in situ X-ray absorption spectroscopy (XAS) studies and density functional theory (DFT) calculations, we decrypt that electrons transfer through the dyz­(dxz) orbitals in egg-white-derived single-atom electrocatalysts, facilitating their hybridization with the p orbital in oxygen, reducing the energy barrier in the rate-determining step, and boosting the overall catalytic activity. Our discovery provides an alternative perception to turn trash into treasure and promote sustainability

Versatile Phosphate Phosphors ABPO₄ in White Light-Emitting Diodes: Collocated Characteristic Analysis and Theoretical Calculations

The orthophosphate host family, AIBIIPO4 (AI = monovalent cation, BII = divalent cation), has recently been made available as phosphors that combine with near-UV lighting chips for use in solid-state white light-emitting diodes (LEDs). This study elucidates the crystalline structure and lattice parameters of the products via a solid-state reaction, using powder X-ray diffraction (XRD) and GSAS refinement. The versatility of the phosphor host AIBIIPO4 is established by examining isovalent substitutions of four cations in the structureLi or K for AI, Sr or Ba for BIIand three doped activators, RE = Eu2+, Tb3+, and Sm3+. The luminescence properties, decay time, and Commission Internationale de l’Éclairage (CIE) chromaticity index are determined for various concentrations of these activators and metal constituents of the host. The thermal stabilities of all of these compounds are determined for the first time from the crystal structure and the coordination environment of the rare-earth metal. The morphology, composition, and particle size were measured in detail. Finally, density functional calculations were performed using the generalized gradient approximation plus an on-site Coulombic interaction correction (GGA+U) scheme to investigate the electronic structures of the KSrPO4 system. A concise model was proposed to explain the luminescence mechanism