Hierarchical lichee-like Fe₃O₄ assemblies and their high heating efficiency in magnetic hyperthermia

A nontoxic and biocompatible thermoseed is developed for the magnetic hyperthermia. Two kinds of thermoseed materials: hierarchical hollow and solid lichee-like Fe₃O₄ assemblies, are synthesized by a facile hydrothermal method. The crystal structure of Fe₃O₄ assemblies are characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Moreover, the prepared Fe₃O₄ assemblies are used as a magnetic heat treatment agent, and their heating efficiency is investigated. Compared to solid assembly, hollow lichee-like Fe₃O₄ assembly exhibits a higher specific absorption rate of 116.53 W/g and a shorter heating time, which is ascribed to its higher saturation magnetization, larger initial particle size, and the unique hierarchical hollow structure. Furthermore, the magnetothermal effect is primarily attributed to Néel relaxation. Overall, we propose a facile and convenient approach to enhance the heating efficiency of magnetic nanoparticles by forming hollow hierarchical assemblies.