Anisotropic Shaped Fe3O4 Nanoparticles: Microwave-assisted Thermal Decomposition Synthesis and Their Electromagnetic Properties

Investigating the electromagnetic properties of magnetite nanoparticles (Fe3O4 NPs) is beneficial for expanding their biomedical applications, especially in tumor hyperthermia. In this study, monodisperse Fe3O4 NPs of various shapes (i.e., quadrilateral-like, hexagon-like, rod-like, and triangle-like) were successfully prepared by a microwave-assisted thermal decomposition approach. The magnetic properties and inductive heating performance, as well as electromagnetic properties were analyzed systematically. The results showed that quadrilateral-like Fe3O4 NPs possessed excellent magneto-thermal effects and maximum specific absorption rate values of 226.4 W/g and 1409.6 W/g (390 kHz and 780 kHz, 12 A). Moreover, a sample filled with 70 wt. % quadrilateral-like NPs in paraffin showed a minimum reflection loss (RL) value of −33.4 dB, along with a broad absorption bandwidth of RL < −10 dB covering 2 GHz–18 GHz. The high magnetic loss may be derived from the eddy current loss and natural resonance. This study would deepen the understanding of microwave absorption properties of Fe3O4 NPs and enrich their microwave applications based on shape anisotropy.