From Trifluoroacetate Complex Precursors to Monodisperse Rare‐Earth Fluoride and Oxyfluoride Nanocrystals with Diverse Shapes through Controlled Fluorination in Solution Phase

Abstract

We report the first systematic synthesis of monodisperse rare‐earth (RE=La to Lu, Y) fluoride and oxyfluoride nanocrystals with diverse shapes (trigonal REF 3 triangular, truncated‐triangular, hexagonal, and polygonal nanoplates; orthorhombic REF 3 quadrilateral and zigzag‐shaped nanoplates; cubic REOF nanopolyhedra and nanorods) from single‐source precursors (SSP) of [RE(CF 3 COO)3] through controlled fluorination in oleic acid (OA)/oleylamine (OM)/1‐octadecene (ODE). To selectively obtain REF 3 or REOF nanocrystals, the fluorination of the REO bond to the REF bond at the nucleation stage was controlled by finely tuning the ratio of OA/ODE or OA/OM, and the reaction temperature. For phase‐pure REF 3 or REOF naocrystals, their shape‐selective syntheses could be realized by further modifying the reaction conditions. The two‐dimensional growth of the REF 3 nanoplates and the one‐dimensional growth of the REOF nanorods were likely due to the selective adsorption of the capping ligands on specific crystal planes of the nanocrystals. Those well‐shaped nanocrystals with diverse geometric symmetries (such as D3 h, D6 h, C2 h, O h, and D nh) displayed a remarkable capability to form self‐assembled superlattices. By manipulating the solvent–substrate combination, the plate‐shaped REF 3 nanocrystals could form highly ordered nanoarrays by means of either the face‐to‐face formation or the edge‐to‐edge formation. By using this SSP strategy, we also obtained high‐quality LaF 3:Eu and LaF 3:Eu/LaF 3 triangular nanoplates that showed photoluminescent red emissions of Eu 3+ ions sensitive to the surface effect.