Facile synthesis and magnetic properties of monodisperse Fe_3O_4/silica nanocomposite microspheres with embedded structures via a direct solution-based route

摘要

A facile route for the production of high quality monodisperse Fe_3O_4/silica nanocomposite microspheres (NMs) with embedded structures has been successfully established by employing a solution-based route via direct decomposition of tetraethyl ortho-silicate (TEOS) in solution under, the presence of freshly synthesized Fe_3O_4 nanoparticles (NPs). This method is based on a two-step process, involving: (i) syn-thesis of Fe_3O_4 NPs by coprecipitaiton of Fe~(2+) and Fe~(3+) with NH_3H_2_O in solution at room temperature; (ii) formation of Fe304/silica NMs by direct decomposition of TEOS in the presence of dispersed Fe_3O_4 NPs of (i) under mechanical stirring at room temperature. The effects of the concentration of TEOS and pH value have been investigated in detail to optimize the synthetic conditions. XRD, XPS, FT1R, EDS, SEM, and TEM were used for the characterization of the synthesized products. It is found that the syn-thesized Fe_3O_4/silica NMs with as typical values average diameters of 025-4 um obtained under the optimized conditions were nearly monodisperse, superparamagnetic with a relatively high saturation magnetization value, which implies potentially promising applications in engineering and biomedicine areas. Moreover, a possible formation mechanism of NMs was also proposed. Meanwhile, this general approach could be extended to prepare other metal oxide/silica NMs.