Tailorable Curie Temperature in Zinc Ferrite Nanoparticles With Finely Tunable Induction Heating Profiles Between...

Magnetic nanoparticles (NPs) are widely studied as heat mediators in induction heating in fields like hyperthermia, drug delivery, debonding-on-demand, and industrial processing, where precise thermal control is essential. By adjusting NP size, morphology, and composition, magnetic characteristics including the Curie temperature are engineered to define heating thresholds and prevent overheating. However, achieving customizable induction heating behavior, particularly below 100°C, remains challenging. Herein, a scalable synthesis of nontoxic zinc (Zn) ferrite NPs (Zn_xFe_{3- x}O₄) with freely tailorable induction heating temperatures between room temperature and 250°C is presented. The heating performance is governed by two key parameters: Zn doping level and postsynthesis annealing temperature, with remarkably high Zn contents up to X = 0.75. Higher annealing temperatures and lower Zn contents yield higher maximum heating temperatures. These trends are observed both in dried NPs and dispersions, with the latter combining exceptional colloidal stability and effective heating performance. Furthermore, the heating temperature can be adjusted externally by varying the amplitude of the applied alternating magnetic field, providing further thermal control. This study establishes a versatile strategy for designing zinc ferrite NPs with precisely adjustable induction heating across a broad temperature range, enabling applications from high-temperature industrial processes to low-temperature biomedical use.