Y2BaZnO5:Er3+ microcapsules with enhanced upconversion by vanadium ion codoping

Abstract

Microcapsules of Y₂BaZnO₅:Er³⁺ nanocrystals were successfully prepared by a simple hydrothermal method using citric acid as chelating agent. The sizes of the spherical microcapsules varied between 1–5 μm with a wall thickness of about 50–100 nm. The underlying microcapsule formation mechanism was discussed using the gas-bubble-assisted Ostwald ripening process. The Y₂BaZnO₅:Er³⁺ microcapsules exhibited characteristic upconversion (UC) emissions of Er³⁺ with intense yellowish orange color under dual laser pumping at 808 nm as well as 980 nm. Concentration dependent studies revealed that the optimum Er³⁺ concentration for intense UC at 550 nm and 660 nm was 5 mol% and 7 mol%, respectively. In addition, the optimum Er concentration differed from the excitation wavelength indicating a different UC mechanism. Importantly, the optimum amount of the V⁵⁺ co-doping into the Y₂BaZnO₅:Er³⁺ phosphors intensified the UC intensity by more than 3 fold. The Y₂BaZnO₅:Er³⁺,V⁵⁺ phosphor exhibited intense yellowish UC pumped by an 808 nm laser and will have potential applications for in vivo biological labelling, and biomedical imaging and therapies.