Single‐Step Synthesis of Sub‐10 nm Magnetic Nanoparticles with High Saturation Magnetization and Broad pH Stability

Abstract

Iron oxide nanoparticles hold great potential for future biomedical applications but, to date, usually suffer from reduced magnetic properties compared to their bulk counterparts. The replacement of Fe(III) ions with Zn(II) ions can enhance their magnetic properties while keeping their biocompatibility characteristics. Yet, common synthesis methods for these highly magnetic particles require using environmentally harmful solvents, multiple steps, and postfunctionalization, all while being affected by poor scalability and high polydispersity. To address these challenges, in this study, a single‐step coprecipitation‐based method is developed to fabricate gelatin‐coated, zinc‐substituted, sub‐10 nm‐sized iron oxide nanoparticles exhibiting high saturation magnetization. This single‐step synthesis benefits from simplicity and robustness, capable of yielding large amounts of highly magnetic nanoparticles without the utilization of environmentally harmful or highly toxic reagents. Furthermore, in situ gelatin coating during the synthesis ensures particle stability in aqueous solutions over a wide range of pH and enhances cell compatibility. Systematic investigations show a direct correlation between the particles’ magnetization and the concentrations of Zn(II) and NaOH, where particles with a zinc‐to‐iron ratio of Zn:Fe = 0.18:2.82 reach a maximum saturation magnetization of 91.2 emu g−1. Thus, these particles are promising candidates for biomedical applications.