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A facile route has been established for the synthesis of PVP/CaF2: RE3+ and PVP/CaF2: Ce3+ nanoparticles (RE=Eu, Tb, Ce/Tb; PVP=Poly(N-vinyl-2-pyrrolidone)) heated at 70°C in ethanol at ambient pressure. The as-prepared nanoparticles were shown to be well dispersed in water. The nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The investigation of fluorescence properties showed that there exists energy transfer from the surface coating of PVP to Eu3+ and Tb3+ leading to the sensitized fluorescence emission of Eu3+ and Tb3+. Co-doping the PVP/CaF2: Tb3+ nanoparticles with Ce3+ results in significant increase in the emission intensity of Tb3+ and this has been attributed to the sensitization of Ce3+ and PVP on Tb3+. [ABSTRACT FROM AUTHOR]

Abstract: The two dinuclear rare earth complexes Eu2(PBa)6(Phen)2 and Tb2(PBa)6(Phen)2, (where PBa=4-pentylbenzoate group and Phen=1, 10-phenanthroline), were synthesized and characterized by elemental analysis, IR, and single crystal X-ray diffraction. Both of them crystallize in space group P-1 with similar cell parameters. Each Eu or Tb ion is nine-coordinated with one 1, 10-phenanthroline molecule, one bidentate chelating carboxylate group, two bidentate bridging carboxylate groups, and two tridentate bridging carboxylate groups. The fluorescent properties of the europium and terbium complexes were also investigated. Under the UV excitation, the two complexes exhibit extensive characteristic emissions of europium and terbium ions, respectively. [Copyright &y& Elsevier]

Abstract: The title compound was firstly synthesized by solid state reaction and its single crystals were successfully obtained using a selected flux. It is isotypic with the mineral buetschliite, K2Ca(CO3)2, and crystallizes in the trigonal space group R-3m with a = 5.4526(12) Å, c = 17.781(8) Å, Z = 3. In the structure, Ba and K atoms are disordered on a same site in the proportion of 0.492(4):0.508(4). The fundamental building units are YO6 octahedra and BO3 triangles. The structure consists of [YB2O6]∞ double layers constructed by corner-sharing YO6 and BO3 groups. Ba/K atoms occupy the spaces between these two layers and play the role of bridges. In addition, the luminescence properties of Eu3+ doped KBaY(BO3)2 were also studied. [Copyright &y& Elsevier]

Abstract: The OA-modified CaF2: Eu nanocrystals that can be well dispersed in chloroform to form a clear solution were synthesized and characterized. The nanocrystals have a roughly spherical shape with particle diameter of about 10nm. Possible mechanism was proposed to explain the growth process. Upon the excitation at 395nm, the room-temperature emission spectrum of the nanocrystals in chloroform presents the characteristic transitions 5D0→7F J of Eu3+ ions, with 5D0→7F2 (610nm) transition as the most prominent group. The luminescence decay of Eu3+ ions in CaF2 nanocrystals was also investigated and two luminescence lifetimes of 737μs (11.2%) and 2.08ms (88.8%) were obtained. [Copyright &y& Elsevier]

Terbium doped calcium fluoride (CaF 2 :Tb3+) and cerium co-doped CaF 2 :Tb3+ (CaF 2 :Ce3+, Tb3+) nanoparticles were synthesized by the hydrothermal method by using citric acid (Cit) as surfactant. The as-synthesized nanoparticles have good dispersibility in water to form an aqueous transparent dispersion at a concentration of 20 mg/mL. The nanoparticles have the CaF 2 -type cubic structures. Photoluminescence (PL) investigation showed that energy transfer can be occurred effectively from Ce3+ ions to Tb3+ ions in Cit/CaF 2 : Ce3+, Tb3+ nanoparticles. And the PL intensity of Cit/CaF 2 : Ce3+, Tb3+ nanoparticles is very strong at a low concentration of 1 mg/mL, which is 16-fold as high as that of Cit/CaF 2 : Tb3+ nanoparticles. The strong green emission from Cit/CaF 2 : Ce3+, Tb3+ nanoparticles can selectively be quenched by Cu2+ ions in comparison to other metal ions and its detection limit is 1.02 × 10−5 M in an aqueous solution. The PL quenching is reversible by the addition of ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) with the recovery of almost 80% of the original PL. The results revealed that Cit/CaF 2 : Ce3+, Tb3+ nanoparticles could find a promising application for the detection of Cu2+ ions in an aqueous solution. • CaF 2 :Tb3+ and CaF 2 :Ce3+, Tb3+ nanoparticles were synthesized by using Citrate as the surface modification. • The as-prepared nanoparticles formed a transparent aqueous dispersion with concentration up to 20 mg/mL. • Cit/CaF 2 : Ce3+, Tb3+ nanoparticles have strong green emission in an aqueous dispersion at a low concentration of 1 mg/mL. • Cit/CaF 2 : Ce3+, Tb3+ nanoparticles can selectively detect Cu2+ ions in water and detection limit is 1.02 × 10−5 M. [ABSTRACT FROM AUTHOR]

Perovskite compounds are always the focus in the material research field. Herein, the polycrystalline samples and single crystals of Na 2 ZrTeO 6 , a B-site ordered double-perovskite compound, were prepared successfully. Single crystal X-ray diffraction demonstrated that Na 2 ZrTeO 6 crystallizes in the cubic space group Fm-3m (No. 225) with unit parameters of a = b = c = 7.80360(10) Å. The crystal structure of Na 2 ZrTeO 6 , formed by ZrO 6 and TeO 6 octahedra through sharing the corner oxygen atoms, belongs to the typical rock-salt-type perovskite structure. The density functional theory calculations show that Na 2 ZrTeO 6 has a direct band gap with band gap of 3.21 eV, which is lower than the experimental value of 3.85 eV. Interestingly, the powder samples of Na 2 ZrTeO 6 exhibit a self-activated near-infrared emission centered at 780 nm under ultraviolet light excitation. And a strong luminescence thermal stability was also observed. Compared to room temperature, the luminescence intensity can maintain 64 % at 200 °C. [Display omitted] • The high-purity double-perovskite Na 2 ZrTeO 6 samples were synthesized by wet chemical method. • Structure analysis indicate that Na 2 ZrTeO 6 belongs to the typical rock-salt-type perovskite structure. • Na 2 ZrTeO 6 exhibits self-activated near-infrared emission centered at 780 nm excited by 308 nm. • The sample's emission intensity maintained 64 % of its room temperature peak intensity at 200 °C. [ABSTRACT FROM AUTHOR]

Abstract: Tb3+ single-doped SiO2 (SiO2:Tb3+) and Tb3+, Ag co-doped SiO2 (SiO2:Tb3+–Ag) nanostructured luminescent materials were prepared by a modified Stöber method. Their microstructure and optical property were investigated using scanning electron microscopy, ultraviolet visible absorption and photoluminescence spectrophotometry. Results show that the samples are composed of well-dispersed near-spherical particles with a diameter about 50nm, the highest fluorescence intensity is obtained when the doping concentration of Tb3+ is 4.86mol%, the corresponding internal quantum efficiency is 13.6% and the external quantum efficiency is 8.2%. The experimental results indicate that Ag nanoparticles can greatly enhance the light absorption at 226nm and the light emission at 543nm of SiO2:Tb3+–Ag, and the fluorescence lifetime reduces with increasing Ag concentration in SiO2:Tb3+–Ag. Additionally, the present results indicate that fluorescence enhancement is attributed to the local field enhancement and the increased radiative decay rates induced by Ag nanoparticles. [Copyright &y& Elsevier]

A new mixed-anion phosphate crystal Cs 2 Bi 2 Sr(P 2 O 7)(PO 4) 2 was obtained by molten salt method. Single-crystal X-ray diffraction data demonstrated that the compound crystallizes in monoclinic space group P 2 1 /c (No.14) with unit cell parameters a ​= ​17.708(10) Å, b ​= ​9.156(5) Å and c ​= ​9.221(5) Å, β ​= ​90.160(8) °. The structure exhibits a novel three-dimensional network, which is made up of BiO 6 , BiO 5 , SrO 6 and CsO 11 polyhedra sharing the corners with PO 4 tetrahedra and P 2 O 7 diphosphate groups. The band gap was estimated by the combined density functional theory and experimental study. Photoluminescence property of Cs 2 Bi 2- x Sr(P 2 O 7)(PO 4) 2 : x Eu3+ showed the excellent thermal stability and high quantum efficiency. The structure of a new mixed-anion phosphate Cs 2 Bi 2 Sr(P 2 O 7)(PO 4) 2 , belonging to a rare case with twinning structure, is herein reported. And the photoluminescence of Eu3+ doped Cs 2 Bi 2 Sr(P 2 O 7)(PO 4) 2 shows high quantum efficiency (92%). Image 1 • The structure of Cs 2 Bi 2 Sr(P 2 O 7)(PO 4) 2 (CBSP) exhibits rare twin structure. • The new CBSP crystals were firstly obtained using molten salt method. • The CBSP:0.25Eu3+ shows excellent thermal stability and high quantum efficiency. [ABSTRACT FROM AUTHOR]