Efficient fluorescence of dissolved CaF2:Tb3+ and CaF2:Ce3+, Tb3+ nanoparticles through surface coating sensitization

► Dissolved oleic acid-modified CaF2:Tb3+ and CaF2:Ce3+, Tb3+ nanoparticles were synthesized. ► The oleic acid sensitized emission of Tb3+ was observed. ► CaF2:Tb3+ nanoparticles with 10 mol% Tb3+ concentrations possess the highest emission intensity. ► The emission intensity of CaF2:Ce3+, Tb3+ nanoparticles is about 4.5 times that of CaF2:Tb3+ (10 mol%) nanoparticles.