Luminescence of LaF3:Ln3+ Nanocrystal Dispersions in Ionic Liquids

Ionic liquids were used as solvents for dispersing luminescent lanthanide-doped LaF3:Ln3+ nanocrystals (Ln3+ = Eu3+ and Nd3+). To increase the solubility of the inorganic nanoparticles in the ionic liquids, the nanocrystals were prepared with different stabilizing ligands, i.e., citrate, N,N,N-trimethylglycine (betaine), and lauryldimethylglycine (lauryl betaine). LaF3:5%Ln3+:betaine could successfully be dispersed in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [C4mpyr][Tf2N], 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate [C4mpyr][TfO], and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C4mim][Tf2N] but only in limited amounts. Red photoluminescence was observed for the europium(III)-containing nanoparticles and near-infrared luminescence for the neodymium(III)-containing systems.