Size-controlled synthesis of Fe3O4 and Fe3O4@SiO2 nanoparticles and their superparamagnetic properties tailoring

Superparamagnetic properties and fine-tuning of colloidal Fe3O4 nanoparticles are important for their widespread biomedical applications. Herein, colloidal Fe3O4 nanoparticles (NPs) of different sizes (8–20 ​nm) were prepared, and their hydrophilization with SiO2 shell coating to be Fe3O4@SiO2 core-shell had been realized successively. The size of Fe3O4 NPs was controlled by different heating rates. Transmission electron microscope (TEM), powder X-ray diffractometry (XRD), and vibrating sample magnetometer (VSM) were performed to examine the morphology, crystallinity, and magnetic properties of the prepared Fe3O4 and Fe3O4@SiO2 core-shell NPs, respectively. In addition, high resolution transmission electron microscope (HRTEM) results suggested that Fe3O4 NPs had well crystallization. Enabled by such, their superparamagnetic properties can be fine-tuned accordingly and cater to their potential applications.