Luminescent enhancement study of 3Tb,5Ce,5Li:CaF2: effect of Li+ ion concentration and hyperthermia applications of 3Tb:CaF2/Fe3O4 nanocomposite

CaF2 nanomaterials doped with Tb3+ ions (3Tb:CaF2) were synthesized using ethylene glycol as a capping agent. Further, a requisite amount of Ce3+ ions and Li+ ions were codoped into 3Tb:CaF2 to produce 3Tb,5Ce,5Li:CaF2 with the optimal concentrations of 5 at% each for the Ce3+ and Li+ ions. Lanthanide and alkaline ions were successfully incorporated into the host lattice, and the tensile strain produced during their incorporation into the host CaF2 nanoparticles was also calculated. A good luminescence improvement was observed in the nanoparticles containing the Ce3+ and Tb3+ ion-codoped CaF2 due to the strong energy transfer from the Ce3+ ions to Tb3+ ions. The luminescence intensity of these green light-emitting nanomaterials was further intensified 2.2 fold after the addition of Li+ ions as a codopant. The enhancement in luminescence intensity with Li+ ion codoping is related to the decrease in both non-radiative rate and tensile strain. The 3Tb:CaF2/Fe3O4 nanocomposite showed heating ability up to 42 °C (hyperthermia temperature) under an AC magnetic field within a short time. Furthermore, this nanocomposite showed high biocompatibility with HeLa cancer cells.