Luminescence properties of LaF3:Ce nanoparticles encapsulated by oleic acid

Cerium ions doped lanthanum fluoride (LaF3:Ce) nanopowder as well as LaF3:Ce nanopowder whose surfaces was modified by oleic acid (OA) were synthesized by using an in-situ hydrothermal process under the various doping concentrations. Based on the XRD spectra and TEM images, it was confirmed that the crystalline structured hexagonal LaF3:Ce nanopowder was synthesized. Oleic acid was efficient for conversion of the water dispersible LaF3:Ce nanoparticles to hydrophobic ones. Surface modification was verified by FTIR absorption spectrum as well as TEM images, showing no agglomeration between 5 and 10 nm scaled particles. Photoluminescence based on 5d ⟶ 4f electronic transition of cerium ions excited at λex ∼256 nm for both neat and OA encapsulated LaF3:Ce nanoparticles decreases as the cerium concentration increases, while the quantum yields of OA encapsulated nanoparticles were much lower than the neat particles due to low photon transmittance of OA at the range longer than ∼350 nm.