Optimization of synthesis conditions to prepare desired shell thickness of superparamagnetic MgFe2O4@SiO2 core-shell nanosphere for biomedical applications

H. Das, N. Debnath, T. Arai, N. Sakamoto, K. Shinozaki, H. Suzuki, N. Wakiya
Shizuoka University,

Keywords: nanosphere, core-shell, superparamagnetic, hyperthermia


We have described here a simple way for the fabrication of superparamagnetic MgFe2O4@SiO2 core-shell spherical nanoparticles with controlled shell thickness. First, core MgFe2O4 dense nano-spheres were directly synthesized by ultrasonic spray pyrolysis (USP) technique from the aqueous metal nitrate precursor solution. Afterward, silica was coated on the obtained nanosphere for various desired shell thickness (10, 20 and 30 nm) by using theoretically calculated amount of tetraethyl orthosilicate (TEOS, as SiO2 precursor) and appropriate ratio of HCl (as acidic catalyst) via modified sol-gel approach. Acidic catalyst plays an important role to form dense amorphous silica mono layer which improve biocompatibility. The effect of different shell thickness on the structural, morphological and magnetic properties of core-shell nanospheres were detail studied by using XRD, FTIR, FESEM, TEM, EDS, DLS and VSM etc. These results demonstrate that core-shell structure have only a single core MgFe2O4 which is homogeneously covered by dense amorphous silica layer with appropriate thickness. The measured shell thickness (~ 10, 20 and 30 nm) by TEM image is almost same as our proposed shell thickness. All core-shell nanospheres have excellent superparamagnetic properties where magnetization decrease with increase nonmagnetic silica shell thickness which have good correlation with theoretical value. From our investigation, it can be proposed that the silica shell thickness can be conveniently controlled and predetermined by using the calculated volume of TEOS. These superparamagnetic core/shell nanospheres can be used for several biomedical applications especially magnetically induced hyperthermia due to having higher heating ability of core MgFe2O4 and better biocompatibility of silica shell.