Superparamagnetic magnesium ferrite/silica core-shell nanospheres: A controllable SiO2 coating process for potential magnetic hyperthermia application

The control of coating shell becoming important to improve the applicability of magnetic nanoparticles. Herein, we present the scalable technique for preparing MgFe₂O₄/SiO₂ core-shell nanospheres with finely tuned shell thickness and their efficiency in magnetic hyperthermia heating agent. At first, MgFe₂O₄ dense nanosphere derived from one-step ultrasonic spray pyrolysis (USP) technique. Silica shells were then coated on the as prepared nanospheres with tunable thickness from 10 to 30 nm. We show that the thickness of this coating is finely controlled at allowing our proposed level by using the required amount of SiO₂ precursor (SiC₈H₂₀O₄)/acidic catalyst (HCl) ratio where the surface area of core nanospheres are significantly considered. X-ray diffraction reveals the cubic spinel ferrite structure of core particles with crystallite size 9.6 ± 1.8 nm and Fourier transform infrared spectrum analysis confirmed the formation of SiO₂. The morphological observation clarified the uniform and smooth SiO₂ shell where core-shell nanostructure is highly monodispersed in a liquid medium. M-H loops confirmed the superparamagnetic nature of all samples at room temperature. Significantly reduced ion release concentration in an aqueous solvent of the coated nanospheres compared with uncoated sample demonstrates the hermetically coating feature of dense SiO₂. This MgFe₂O₄/SiO₂ core-shell nanospheres with thine SiO₂ shell (10 nm) shows effective heating rate in the operative region (<46 °C) which makes them promising candidates for application as magnetic hyperthermia heating agent.