Maghemite (γ-FeO) and γ-FeO-TiO Nanoparticles for Magnetic Hyperthermia Applications: Synthesis, Characterization and Heating Efficiency.

In this report, the heating efficiencies of γ-FeO and hybrid γ-FeO-TiO nanoparticles NPs under an alternating magnetic field (AMF) have been investigated to evaluate their feasible use in magnetic hyperthermia. The NPs were synthesized by a modified sol-gel method and characterized by different techniques. X-ray diffraction (XRD), Mössbauer spectroscopy and electron microscopy analyses confirmed the maghemite (γ-FeO) phase, crystallinity, good uniformity and 10 nm core sizes of the as-synthesized composites. SQUID hysteresis loops showed a non-negligible coercive field and remanence suggesting the ferromagnetic behavior of the particles. Heating efficiency measurements showed that both samples display high heating potentials and reached magnetic hyperthermia (42 °C) in relatively short times with shorter time (~3 min) observed for γ-FeO compared to γ-FeO-TiO. The specific absorption rate (SAR) values calculated for γ-FeO (up to 90 W/g) are higher than that for γ-FeO-TiO (~40 W/g) confirming better heating efficiency for γ-FeO NPs. The intrinsic loss power (ILP) values of 1.57 nHm/kg and 0.64 nHm/kg obtained for both nanocomposites are in the range reported for commercial ferrofluids (0.2-3.1 nHm/kg). Finally, the heating mechanism responsible for NP heat dissipation is explained concluding that both Neel and Brownian relaxations are contributing to heat production. Overall, the obtained high heating efficiencies suggest that the fabricated nanocomposites hold a great potential to be utilized in a wide spectrum of applications, particularly in magnetic photothermal hyperthermia treatments.