Architecting ultra-thin SiO2 shell for high magnetic performance of Fe3O4 nanoparticles for biomedical applications

This research focuses on the architectural design of the silica shell on Fe3O4 nanoparticle to precisely control and minimize its thickness, with the aim of achieving a final product with optimal saturation magnetization (Ms) for biomedical applications. A rapid and facile microwave-assisted synthesis method was developed for the synthesis of Fe3O4@SiO2 and Fe3O4@SiO2@NH2 core–shell nanoparticles with ultra-thin SiO2 shell and excellent magnetic performance. The distribution of particle size of the Fe3O4@SiO2 nanoparticles was found to be in the range of 15–35 nm, with a mean particle size of ∼ 21 nm. FTIR analysis also confirmed the successful silica coating on Fe3O4 nanoparticles and the successful amino-functionalization of silica-coated Fe3O4 nanoparticles. The Ms of Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@NH2 nanoparticles was found to be 64.4, 59.8, and 52.4 emu/g, respectively. It has been confirmed that that the ultra-thin SiO2 coating has a negligible effect on the magnetic characteristics of the nanoparticles. The developed microwave-assisted synthesis method in this study not only provides an interesting, rapid, and facile synthesis route but also results in a product with a narrow particle size distribution, an ultra-thin SiO2 shell, favorable magnetic properties, and improved cell compatibility which may be used in several different applications, particularly biomedical applications.