Controlled synthesis and morphology dependent upconversion luminescence of NaYF₄:Yb, Er nanocrystals

Abstract

Size and morphology controlled NaYF 4 :Yb, Er nanocrystals were synthesized via the hydrothermal method. Polydentate ligands, such as EDTA and citrate, were used in the synthesis of cubic and hexagonal Yb 3+ , Er 3+ codoped NaYF 4 nanocrystals as a means of controlling the size and morphology of the nanocrystals. Subsequently, the particle size was found to be dependent on the nucleation rate, which, in turn, was governed by the reactant concentration, molar ratio and choice of ligand. The phase transformation from cubic to hexagonal was found to be sensitive to reaction time and reactant concentration. The upconversion photoluminescence of the nanocrystals demonstrated morphology dependence, which provides a means to characterize their crystalline quality and structure.