Size and shape evolution of upconverting nanoparticles using microwave assisted synthesis

Abstract

This article presents the results of a systematic study to control the size and shape of upconverting AYF₄:Yb, Er (with A = Na, Li) nanocrystals using microwave assisted synthesis. It has been found that the size of the nanoparticles can be controlled by changing the time of nanocrystal growth. The morphology of the resulting nanocrystals can be controlled by reactant concentration and composition. Low reactant concentrations result always in monodisperse, spherical nanocrystals. At higher concentrations, nanocrystals grow into ‘flowers’ when the crystallographic lattice is cubic, into wires at a sodium : lithium ratio of 1 : 4 and into rhombic shape for pure LiYF₄:Yb, Er nanocrystals.