Divalent Europium doped CaF₂ and BaF₂ nanocrystals from ionic liquids

A new, facile and quick synthesis method for Eu²⁺ doped the alkaline earth fluorides was developed using ionic liquids as solvent, precursor and capping agent. Reductive atmosphere and very high temperatures were avoided, while still attaining the desired structure, small particle sizes and divalent oxidation state of the lanthanide. This opens the door for the development of new Ln²⁺ doped nanomaterials. The successful Eu²⁺ incorporation was proven by optical spectroscopic measurements which showed the spin and parity allowed f-d transitions of Eu²⁺ in CaF₂:Eu²⁺/BaF₂:Eu²⁺. 4f⁷-4f⁷ transitions could be observed at low temperatures (7 K).