Multifunctional Hybrid Nanomaterials from Water Dispersible CaF2:Eu3+, Mn2+ and Fe3O4 for Luminescence and Hyperthermia Application

CaF2 nanoparticles doped with 1 at. % Eu3+and codoped with Mn2+ ions (1, 2, and 3 at. %) were synthesized at 180 °C by using ethylene glycol as a capping agent and solvent medium. The emission spectra of these nanomaterials show two main peaks at 590 and 612 nm after excitation at 240 or 394 nm. Enhancement in luminescence is found upon codoping of Mn2+. Parts of Eu3+ ions are substituted into Ca2+ sites (having a symmetry environment), which is reflected in the higher probability of magnetic dipole transition over that of electric dipole transition. The polymer film of polyvinyl alcohol incorporated with CaF2:1Eu shows the red emission. The prepared nanomaterials are highly water dispersible. The hybrid of CaF2:1Eu and Fe3O4 shows the heating ability up to 42 °C under an AC magnetic field. This is suitable for cancer therapy through hyperthermia. A very high specific absorption rate (SAR) of 283 W/g is observed. This can be ascribed to the increased magnetocrystalline anisotropy and Brownian relaxation. ...