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

Iron oxide nanoparticles hold great potential for future biomedical applicationsbut, to date, usually suffer from reduced magnetic properties compared to theirbulk counterparts. The replacement of Fe(III) ions with Zn(II) ions can enhancetheir magnetic properties while keeping their biocompatibility characteristics.Yet, common synthesis methods for these highly magnetic particles require usingenvironmentally harmful solvents, multiple steps, and postfunctionalization, allwhile being affected by poor scalability and high polydispersity. To address thesechallenges, in this study, a single-step coprecipitation-based method is developedto fabricate gelatin-coated, zinc-substituted, sub-10 nm-sized iron oxide nano-particles exhibiting high saturation magnetization. This single-step synthesisbenefits from simplicity and robustness, capable of yielding large amounts ofhighly magnetic nanoparticles without the utilization of environmentally harmfulor highly toxic reagents. Furthermore, in situ gelatin coating during the synthesisensures particle stability in aqueous solutions over a wide range of pH andenhances cell compatibility. Systematic investigations show a direct correlationbetween the particles’ magnetization and the concentrations of Zn(II) andNaOH, where particles with a zinc-to-iron ratio of Zn:Fe = 0.18:2.82 reach amaximum saturation magnetization of 91.2 emu g1 . Thus, these particles arepromising candidates for biomedical applications.RESEARCH ARTICLEwww.aem-journal.comAdv. Eng. Mater. 2024, 26, 2400307 2400307 (1 of 7) © 2024 The Author(s). Advanced Engineering Materials published by Wiley-VCH GmbH