Aspect-Ratio Controlled Synthesis and Tunable Luminescence of YF3:Yb-3/Er3+ Upconversion Nanocrystals

Abstract

We report a facile synthetic method for high-aspect-ratio YF3:Yb3+/Er3+ nanocrystals by controlling-the composition of the precursor and" saltsto manipulate the structures-of YF3:Yb3+/Er3+ nanocrystals. A controlled aspect ratio is attained by tufting the-molar:ratio of NH4+/RE3+ (NH4+ is the counterion- released from the fluoride precursor (NH4F) and RE3 indicates the total amount of Y, Yb, and Er)-and the presence of specific inorganic salts. A low molar ratio of NH4+/RE3+ induced the production of high-aspect-ratio YF3:Yb3+/Er3+ nanocrystals, while a high molar ratio of NH4+/RE3+ induced the formation of irregular=nanoplates. The selection of the inorganic salt as an additive is critical in controlling the aspect ratio and crystallinity-of YF3:Yb3+/Er3+ nanocrystals. The cation showed limited control over the aspect "ratio, but the anions, Cl- and Br-, induced the production of the highest aspect ratio for YF3:Yb3+/Er3+ nanocrystals. We round that the aspect ratio affected the luminescence properties of YF3:Yb3+/Er3+ nanocrystals. The green emission from nanorod structures changed to orange when the morphology is transformed to nanoplates.