Chemical synthesis of monodisperse γ-Fe-Ni magnetic nanoparticles with tunable Curie temperatures for self-regulated hyperthermia

摘要

Magnetic nanoparticles (MNPs) possessing low Curie temperatures (T_C's) offer the possibility for self-regulated heating of cancer cells, where the T_C acts as an upper limit to heating to prevent damage to neighboring healthy tissue. We report the synthesis of monodisperse metastable fee γ-phase Fe-Ni MNPs possessing tunable T_C's, whose stoichiometries have been predicted from metastable extensions to an equilibrium Fe-Ni phase diagram. Metastable alloys have been predicted within the constructs of the T_0 construction in the Fe-Ni eutectoid phase diagram. Fe-Ni MNPs have been synthesized via chemical reduction in Fe- and Ni-precursors with stoichiometries ranging from Fe_(90)Ni_(10)to Fe_(70)Ni_(30). Mn-precursors have been added to further reduce the alloy's T_C. MNP morphology and structure have been confirmed by x-ray diffraction and transmission electron microscopy while magnetic properties were investigated using vibrating sample magnetometry. Fe_(70)Ni_(30) MNPs were found to have a T_C of 82℃ and specific magnetization of 66 emu/g. Addition of 1 wt % Mn to Fe_(75)Ni_(25) reduced the T_C to 78℃, which is the lowest reported for fee Fe-Ni alloys. We also report a model for radio frequency self-regulated heating, in which the maximum achievable temperature of water-MNP suspensions (T_C< 100℃) or octyl ether-MNP suspensions (T_C> 100℃) is approximately the T_C of the MNPs suspended in the solution.