Heating Efficiency of Iron Oxide Nanoparticles in Hyperthermia: Effect of Preparation Conditions

The correlation between magneto-structural properties of iron oxide nanoparticles and their heating efficiency in ac magnetic fields is investigated. Nanoparticles with an average size of 13 nm and narrow size distribution are synthesized by coprecipitation of ferrous and ferric salts in an alkaline medium in which the salts ratio is systematically varied. To obtain nanoparticles with single-phase composition, the prepared samples are annealed at 200 °C. The lattice parameters of all nanoparticles deduced from X-ray diffraction analysis correspond to multiphase composition, i.e., to a mixture of magnetite and maghemite phases. However, low-temperature Mossbauer spectroscopy revealed complete transformation of magnetite to maghemite in annealed samples. The annealed samples show slightly higher value of specific loss power at a certain frequency and amplitude of ac magnetic field compared with other samples.