Magnetic core/shell nanocomposites MgFe$_{2}$O$_{4}$/SiO$_{2}$ for biomedical application: synthesis and properties

Magnetic core/shell (CS) nanocomposites (MNCs) are synthesized using a simple method, in which a magnesium ferrite nanoparticle (MgFe$_{2}$O$_{4}$) is a core, and an amorphous silicon dioxide (silica SiO$_2$) layer is a shell. The composition, morphology, and structure of synthesized particles are studied using X-ray diffraction, field emission electron microscopy, transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), scattering electrophoretic photometer, thermogravimetric analysis (TGA), and Mössbauer spectroscopy. It is found that the MgFe$_{2}$O$_{4}$/SiO$_2$ MNC has the core/shell structure formed by the Fe–O–Si chemical bond. After coating with silica, the MgFe$_{2}$O$_{4}$/SiO$_2$ MNC saturation magnetization significantly decreases in comparison with MgFe$_{2}$O$_{4}$ particles without a SiO$_2$ shell. Spherical particles agglomerated from MgFe$_2$O$_4$ nanocrystallites $\sim$9.6 and $\sim$11.5 nm in size function as cores coated with SiO$_2$ shells $\sim$30 and $\sim$50 nm thick, respectively. The total size of obtained CS MNCs is $\sim$200 and 300 nm, respectively. Synthesized CS MgFe$_2$O$_4$/SiO$_2$ MNCs are very promising for biomedical applications, due to the biological compatibility of silicon dioxide, its sizes, and the fact that the Curie temperature is in the region required for hyperthermal therapy, 320 K.