Self-assembled three-dimensional NaY(WO4)2: Ln3+ architectures: Hydrothermal synthesis, growth mechanism and luminescence properties

Novel three-dimensional (3D) flower-like NaY(WO4)(2): Ln(3+) (Ln = Eu, Yb/Er, Yb/Tm and Yb/Ho) microstructures with uniform shape and dimension have been prepared using Y(OH)CO3 nanospheres as sacrificial template through a hydrothermal process and followed by a subsequent heat treatment process. The whole process was carried out in aqueous condition without using any organic solvents, surfactant, or catalyst. The phase, morphology, size, and photoluminescence (PL) properties were well characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) spectra, and kinetic decays, respectively. The results reveal that the as-prepared precursor of NaY(WO4)(2):Eu3+ exhibits interesting white light emission under UV excitation. After annealing, the as-obtained 3D flower-like NaY(WO4)(2):Eu3+ microstructures show exclusively red (Eu3+, D-5(0) -> F-7(2)) luminescence. Furthermore, the up-conversion (UC) luminescent properties and the emission mechanisms of NaY(WO4)(2):Yb3+/Ln(3+) (Ln = Er, Tm, Ho) microstructures have been systematically studied, which show respective green (Er3+, S-4(3/2), H-2(11/2) -> I-4(15/2)), blue (Tm3+, (1)G(4) -> H-3(6)) and yellow-green (Ho3+, S-5(2) -> I-5(8)) luminescence under 980 nm NIR excitation. (C) 2012 Elsevier B. V. All rights reserved.