A phase transfer assisted solvo-thermal strategy for the synthesis of REF₃ and Ln³⁺-doped REF₃ nano-/microcrystals

Monodisperse orthorhombic-phase rare earth fluorides nano-/microcrystals with a special shape of disk-stacked cylinder have been synthesized via a facile phase transfer assisted solvo-thermal route, where an acid-base-coupled extractant has been employed to transfer hydrofluoric acid into an oil phase as a fluoride source. The synthetic parameters have been optimized and a possible formation mechanism has also been proposed. More importantly, the adopted acid-base-coupled extractant in this route can be recycled. Surveying all of the lanthanides from La to Lu, most of the heavy rare earths, such as Tb, Dy, Ho, Er, Tm and Yb, can form LnF₃ nanocrystals with the similar morphologies. Furthermore, Ln³⁺-doped YF₃ (Ln=Tb, Yb/Er) nanocrystals have also been synthesized, and their down-conversion and up-conversion (980nm) luminescent properties were examined. The current approach could be extended to synthesize other metal fluorides nanoparticles.