Room temperature crystallization of YVO4:Yb3+,Ho3+ nanoparticles using LYH and fabrication of transparent up-converter films

Layered yttrium hydroxide (LYH) was explored for the synthesis of a representative up-converting YVO4:20%Yb3+,0.4%Ho3+ particles in aqueous Na3VO4 solutions at room temperature. No formation of the VO43--intercalated LYH:Yb3+,Ho3+ phase during reaction suggested the sequential transformation from the outermost sheet of LYH:Yb3+,Ho3+ to YVO4:Yb3+,Ho3+ particles with regular shape and size without a general tendency to aggregate. Because of remnant hydroxyl groups in the particles transformed structurally from the hydroxide precursor, the up-conversion emission was too weak to be measured for the as-prepared YVO4:Yb3+,Ho3+ and after heating at lower than 200 degrees C. In contrast, the luminescence intensity of YVO4:Yb3+,Ho3+ was dramatically enhanced with increasing the annealing temperature up to 700 degrees C. The prepared elliptical shape particles maintained high dispersibility even after annealing at 700 degrees C so that they were exploited for the fabrication of transparent and flexible composite up-converter films with high efficiency via simple casting of PVA suspensions containing YVO4:Yb3+,Ho3+ particles. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

Layered yttrium hydroxide (LYH) was used to synthesize regular-shaped YVO4:Yb3+,Ho3+ particles in aqueous solution at room temperature. Annealing at higher temperatures dramatically enhanced the luminescence intensity of YVO4:Yb3+,Ho3+ particles. The prepared elliptical particles maintained high dispersibility and were utilized for the fabrication of transparent and flexible composite up-converter films.