Size, phase-controlled synthesis, the nucleation and growth mechanisms of NaYF4:Yb/Er nanocrystals

Near-monodisperse NaYF4:Yb/Er nanoparticles (NPs) with controlled size, phases (alpha, beta) and shapes (sphere, and hexagonal plate) were synthesized by adjusting the NaF to RE (RE = Y, Yb, Er) ratios, the reaction temperature and time in the hot surfactant solutions (oleic acid, 1-octadecene) from the improved one-pot thermal decomposition metal trifluoroacetate, and the precursors were prepared via hydrothermal route. The growth kinetics of beta-NaYF4 NPs includes several stages: nucleation, growth of alpha-NaYF4, Ostwald ripening, size shrinkage and growth. The results prove that the temperatures are preferred to the phase transformation compared with the NaF content when other experimental conditions are unchanged. Our work will further facilitate the comprehension of the nucleation and growth mechanisms of the NPs, and provide guidance for their controlled synthesis. (C) 2018 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.