Morphology controllable synthesis of NaLa(WO4)2: the morphology dependent photoluminescent properties and single-phased white light emission of NaLa(WO4)2: Eu3+/Tb3+/Tm3+

Abstract

Uniform single-crystalline NaLa(WO₄)₂ microspindles were successfully prepared via a hydrothermal method in combination with a post annealing process by adding an extremely small amount of EDTA-2Na into the reaction system. Meanwhile, the product morphology could also be tuned into microplates, nanocrystals, submicrodumbbells and connected twin-microspheres by simply altering the amount of additive used and the ratio of the mixed solvents. The prepared NaLa(WO₄)₂ nanocrystals could be homogeneously dispersed in the distilled water for a very long time, and thus might find potential application in the field of biological labeling. The photoluminescent (PL) performance of the NaLa(WO₄)₂: Eu³⁺ microspindles and microplates was investigated and it was found that the NaLa(WO₄)₂: Eu³⁺ microspindles had a much more intensive emission, and furthermore, the possible reasons responsible for the improved photoluminescent performance of the microspindles were discussed. More importantly, due to the efficient energy transfer from Tm³⁺, Tb³⁺ to Eu³⁺, a novel single-phased and near-UV-pumped white-light-emitting phosphor NaLa(WO₄)₂: Eu³⁺/Tb³⁺/Tm³⁺ was also successfully fabricated through optimizing the molar ratio among Eu³⁺, Tb³⁺ and Tm³⁺ in the NaLa(WO₄)₂ microspindle host. This NaLa(WO₄)₂: Eu³⁺/Tb³⁺/Tm³⁺ microspindle phosphor might be promising in the field of near-UV-pumped white LEDs.