Anisotropic Magnetite Nanorods for Enhanced Magnetic Hyperthermia

There is an increasing need for new strategies to improve the heating efficiency or the specific absorption rate (SAR) of magnetite (Fe₃ O₄ ), which is the only FDA approved magnetic material. We propose a facile approach to obtain well-dispersed highly crystalline Fe₃ O₄ nanorods (NRs) by the reduction of β-FeOOH in an organic solvent and demonstrate that the SAR of Fe₃ O₄ NRs can be enhanced by tuning their aspect ratios. Fe₃ O₄ NRs with an aspect ratio of 4.5 have a much higher SAR as compared with 15 nm Fe₃ O₄ nanoparticles and Fe₃ O₄ NRs counterparts with an aspect ratio of 10. The highest SAR is greatly increased up to 1072 W g^-1 for an ac field of 33 kA m^-1 and a concentration of 5 mg mL^-1 , which is mostly attributed to hysteresis losses. These findings pave a new pathway for the design and synthesis of novel anisotropic iron oxide nanostructures with an optimal heating efficiency for advanced hyperthermia.