Preparation and thermogenic performance of monodisperse ferromagnetic Fe/SiO₂ nanoparticles for magnetic hyperthermia and thermal ablation*

Ferromagnetic nanoparticles have great potential to be used in the field of magnetic hyperthermia and thermal ablation due to its high saturation magnetization (M_s) and high heating efficiency. In this paper, monodisperse spherical α-Fe₂O₃ nanoparticles were prepared by hydrothermal method using FeCl₃, NaHCO₃ and Na₂SO₄ as reactants. Then monodisperse Fe/SiO₂ nanoparticles with core/shell structure were obtained by coating SiO₂ on the surface of α-Fe₂O₃ nanoparticles and reducing at 500℃ in hydrogen atmosphere. The diameter of Fe core is about 230 nm and the thickness of SiO₂ coating is about 75 nm. Magnetic measurements show that Fe/SiO₂ nanoparticles exhibit typical ferromagnetic properties with M_s about 132.5 emu/g at 25 ℃. As-obtained Fe/SiO₂ nanoparticles have higher heating efficiency than superparamagnetic ferrite nanoparticles. The high heating ability of the Fe/SiO₂ nanoparticles is estimated to be related to the hysteresis loss and Brownian relaxation mechanism during alternating magnetization. The results show that Fe/SiO₂ nanoparticles are promising for the applications of magnetic hyperthermia and thermal ablation.