Facile synthesis, structural and optical characterization of LnF3:Re nanocrystals by ionic liquid-based hydrothermal process

A novel and easy synthesis of highly luminescent rare-earth ion-doped LnF3 (LnF3:Re) nanocrystals by ionic liquid-based hydrothermal process was reported. Ionic liquids [bmim]BF4 (1-butyl, 2-methylimidazolium tetrafluoroborate) acts as co-solvent, template and reactant. X-ray diffraction and field emission scanning electron microscopy were used to characterize the structural properties of the products. The luminescent properties of LaF3:Re nanocrystals were evaluated under ultraviolet (397 nm for Eu3+, 254 nm for Ce3+, Tb3+) and (or) near-infrared (980 nm for Er3+) excitation. Under 980 nm laser excitation, intense green upconversion emissions were observed for LaF3:Er(1%) samples in the solid state and dispersion in water and ethanol. The quantum efficiency of LaF3:Ce(15%),Tb(5%) nanocrystals was about 34%. Our reports provide a facile method for the preparation of LnF3:Re nanocrystals with excellent photoluminescent properties.