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 (Fe 3 O 4 @Au NPs) with different Fe 3 O 4 sizes, along with an evaluation of their heating efficiency for potential use in magnetic hyperthermia applications. The Fe 3 O 4 NPs of approximately 5 nm, 10 nm, 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 Fe 3 O 4 and their Fe 3 O 4 @Au NPs were determined and characterized by TEM, EDX, XRD, and VSM analyses. The magnetization of Fe 3 O 4 NPs increased with increasing their size, reaching 74.7 emu/g for ~13 nm NPs. The Fe 3 O 4 @Au NPs contained 94.3%, 96.3%, 77.0% Au (wt%) for Fe 3 O 4 ~5 nm@Au, Fe 3 O 4 ~10 nm@Au, Fe 3 O 4 ~13 nm@Au, respectively, estimated from the magnetization values. The heating efficiency (specific absorption rate, SAR) demonstrated an increasing trend with Fe 3 O 4 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 Fe 3 O 4 ~13 nm, Fe 3 O 4 ~13 nm@Au NPs, respectively. These results indicate high heating efficient capabilities and the potential use of NPs for magnetic hyperthermia applications.