Ultrasmall Fe₃O₄@Au Composite Nanoparticles With Different Sizes of Fe₃O₄ for Magnetic Hyperthermia

We present the synthesis and characterization of ultrasmall iron oxide/gold composite nanoparticles (Fe3O4@Au NPs) with different Fe3O4 sizes, along with an evaluation of their heating efficiency for potential use in magnetic hyperthermia (MH) applications. The Fe3O4 NPs of approximately 5, 10, and 13 nm were synthesized using the thermal decomposition method, followed by gold deposition via the reduction of gold acetate at 190 °C. The morphology, structure, and magnetic properties of as-prepared Fe3O4 and their Fe3O4@Au NPs were determined and characterized by transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM) analyses. The magnetization of Fe3O4 NPs increased with increasing their size, reaching 74.7 emu/g for ~13 nm NPs. The Fe3O4@Au NPs contained 94.3%, 96.3%, and 77.0% Au (wt%) for Fe3O4~5, Fe3O4~10, and Fe3O4~13 nm@Au, respectively, estimated from the magnetization values. The heating efficiency specific absorption rate (SAR) demonstrated an increasing trend with Fe3O4 size, reaching maximum values of 136.7 and 23.4 W/g under a magnetic field of 25.7 kA/m and 267 kHz for Fe3O4~13 nm and Fe3O4~13 nm@Au NPs, respectively. These results indicate high heating efficient capabilities and the potential use of NPs for MH applications.