Growth Processes of LuF₃ Upconversion Nanoflakes with the Assistance of Amorphous Nanoclusters

Improvement of the facile synthesis strategy is an effective way to tune the optical properties of lanthanide-doped upconversion nanoparticles. However, it is necessary to directly study the growth process to control the formation structure of the nanoparticles. Here, we propose to use the in situ TEM imaging technique to observe the growth kinetics of LuF₃ upconversion nanoflakes. It is discovered that the suppression of surface amorphous clusters, which act as the quenching centers, during the flake-to-flake growth process of nanoflakes can significantly improve the upconversion efficiency. Therefore, by controlling the concentration of amorphous nanoclusters in the precursor solution, we can manipulate the morphology and fabricate LuF₃ nanoflakes with maximized upconversion emission intensity.