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.