Monodispersing Eu^sup 3+^ and Li^sup +^ codoped CaF^sub 2^ nanoparticles for efficient luminescence

Monodisperse oleic acid (OA) modified Eu3+ and Li+ codoped CaF2 nanoparticles are presented in this work. The as-obtained nanoparticles, with a hexagonal shape, can be well-dispersed in organic apolar solvents. The incorporation of Li+ ions in CaF2:Eu3+ does not lead to new crystalline phases. The main diffraction peaks are found to shift to small angles when codoped with 7 mol% Li+, while a reverse shift can be noted with the codoping amount increasing to 9 mol% Li+, indicating that the codoped Li+ enables the crystal field environment of Eu3+ to be changed. The excitation and luminescence intensities of all peaks indexed to Eu3+ have enhanced apparently when codoped with 7 mol% Li+ ions. The lifetime of the 5D0 state of Eu3+ ions is also increased by introducing 7 mol% of Li+ ions.