Formation and aspect ratio control of rhabdophane-type yttrium orthophosphate hexagonal prism particles synthesized by a citrate-assisted hydrothermal process

The rhabdophane-type YPO4 particles have been synthesized in the presence of citrate ions under systematically varied reaction conditions.

Extensive tailoring of REPO4 and REVO4 crystallites via solution processing and luminescence

This article highlighted the recent achievements in crystal engineering of REPO4 and REVO4via solution processing, with an emphasis on solution chemistry, the role of chelate ion, crystallization mechanism and luminescence properties.

Malate-aided selective crystallization and luminescence comparison of tetragonal and monoclinic LaVO4:Eu nanocrystals

With malate (Mal2-) as a new type of chelate, tetragonal (t-) and monoclinic (m-) structured LaVO4:Eu crystals (∼10-60 nm) were selectively crystallized as nanosquares and nanorods via a hydrothermal reaction at 200 °C for 24 h. The effects of the Mal2-:(La,Eu)3+ molar ratio, solution pH and Eu3+ content on the phase structure and crystal morphology were systematically investigated and elucidated. The competition between OH- and Mal2- toward rare earth ions was discussed to play a critical role in phase selection, and the t-phase can only be fabricated at pH ∼ 6-8 with the assistance of Mal2-. The optimal Eu3+ content for luminescence was determined to be ∼5 at% under the VO43- → Eu3+ energy transfer mechanism. Experimental comparison showed that t-(La0.95Eu0.05)VO4 (λex = 275 nm, λem = 620 nm) emits ∼5.3 times as strong as m-(La0.95Eu0.05)VO4 does (λex = 313 nm, λem = 616 nm), while theoretical analysis revealed that the 5D0 level of Eu3+ has a quantum efficiency of ∼80% for the former and ∼70% for the latter. Besides, the t- and m-(La0.95Eu0.05)VO4 nanocrystal phosphors were analyzed to have fluorescence lifetimes of ∼1.53 ± 0.01 and 2.28 ± 0.01 ms for their 620 and 616 nm red emissions, respectively.

Yttrium(iii) coordination polymer micro/nanospheres with single ligand and dual ligands

In this work, yttrium(iii) coordination polymer (Y-CP) ball-flower-shaped microparticles with diameters ranging from 5 μm to 10 μm were synthesized using vanillin and asparagine as ligands under solvothermal conditions at 150 °C for 24 h. Then, we investigated the reaction influencing factors such as the concentration of reactants (involving vanillin, asparagine, and rare earth), reaction temperature, and reaction time. Both uniform and sphere-like nanoparticles with an average size of ∼50 nm were obtained using vanillin as a ligand at 120 °C for 12 h. Furthermore, the products were characterized and the results of cytotoxicity research demonstrated that the nanoparticles had low cytotoxicity and the coordination polymer nanospheres were perfectly biocompatible.

HDEHP assisted solvothermal synthesis of monodispersed REPO4 (RE = La–Lu, Y) nanocrystals and their photoluminescence properties

In this paper, a novel method is reported for the preparation of spherical REPO₄ particles.

Coordination polymer templated engineering of YVO4:Eu submicron crystals and photoluminescence

Cuboidal and octahedral (Y_0.95Eu_0.05)VO₄ crystals were selectively converted from a tartrate coordination polymer, and the mechanisms of phase/morphology evolution were revealed via a series of controlled experiments.

Crystal Structure of NaLuW2O8·2H2O and Down/Upconversion Luminescence of the Derived NaLu(WO4)2:Yb/Ln Phosphors (Ln = Ho, Er, Tm)

Hydrothermally reacting Lu(NO)₃ and Na₂WO₄·2H₂O at 200 °C and pH = 8 produced the new compound NaLuW₂O₈·2H₂O, which was analyzed via the Rietveld technique to crystallize in the orthorhombic system (space group: Cmmm) with cell parameters a = 21.655(1), b = 5.1352(3), and c = 3.6320(2) Å and cell volume V = 403.87(4) ų. The crystal structure presents -(NaO₆)-(NaO₆)- and -(LuO₄(H₂O)₂WO₅)-(LuO₄(H₂O)₂WO₅)- alternating layers linked together by the O^2- ion common to NaO₆ octahedron and WO₅ triangle bipyramid. Tetragonal structured and phase-pure Na(Lu_0.87Ln_0.03Yb_0.1)(WO₄)₂ phosphors (Ln = Ho, Er, and Tm) were directly produced by calcining their NaLuW₂O₈·2H₂O analogous precursors at 600 °C for 2 h, followed by a detailed study of their downconversion/upconversion (DC/UC) photoluminescence. It was shown that the UC luminescence is dominated by a red band at ∼650 nm for Ho³⁺ (⁵F₅ → ⁵I₈ transition), green bands at ∼500-575 nm for Er³⁺ (²H_11/2/⁴S_3/2 → ⁴I_15/2 transitions) and a blue band at ∼476 nm for Tm³⁺ (¹G₄ → ³H₆ transition), all via a three-photon process. DC luminescence of the phosphors is characterized by a ∼545 nm green emission for Ho³⁺ (⁵F₄/⁵S₂ → ⁵I₈ transition, λ_ex = 453 nm), ∼500-575 nm green emissions for Er³⁺ (²H_11/2/⁴S_3/2 → ⁴I_15/2 transitions, λ_ex = 380 nm), and a ∼455 nm blue emission for Tm³⁺ (¹D₂ → ³F₄ transition, λ_ex = 360 nm), with CIE chromaticity coordinates of around (0.27, 0.71), (0.26, 0.72), and (0.15, 0.04), respectively.

Enhanced hydrothermal crystallization and color tailorable photoluminescence of hexagonal structured YPO4:Sm/Tb nanorods

Mal²⁻ and superfluous PO₄³⁻ jointly ensured the hydrothermal crystallization of hexagonal structured YPO₄:Tb/Sm nanorods with color-tailorable photoluminescence and large aspect ratios of up to ∼32.

Combining complexing agent and solvothermal reaction for the morphology controlled synthesis of (Y,Eu)PO4crystals with size-dependent photoluminescence

An organic additive assisted solvothermal reaction has led to the phase/morphology controlled synthesis of YPO₄crystals, whose size-dependent luminescence was also investigated.