Optimization of synthesis conditions to prepare desired shell thickness of superparamagnetic MgFe_2O_4@SiO_2 core-shell nanosphere for biomedical applications

摘要

We have described here a simple way for the fabrication of superparamagnetic MgFe_2O_4@SiO_2 core-shell spherical nanoparticles with controlled shell thickness. First, core MgFe_2O_4 dense nanospheres 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 SiO_2 precursor) and appropriate ratio of HC1 (as acidic catalyst) via modified sol-gel approach. The effect of different shell thickness on the structural and morphological properties of core-shell nanospheres were detail studied by variuos characterization techniques. These results demonstrate that core-shell structure have only a single core MgFe_2O_4 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. TGA curves shows the better thermal stability of coated nanosphere and have shows higher monodispersibity for thin shell (～ 10 nm) due to less agglomeration.