Facile synthesis and magnetic properties of monodisperse Fe 3O 4/silica nanocomposite microspheres with embedded structures via a direct solution-based route

Abstract

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) synthesis of Fe 3O 4 NPs by coprecipitaiton of Fe 2+ and Fe 3+ with NH 3·H 2O in solution at room temperature; (ii) formation of Fe 3O 4/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, FTIR, EDS, SEM, and TEM were used for the characterization of the synthesized products. It is found that the synthesized Fe 3O 4/silica NMs with as typical values average diameters of 0.25–4 μm 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.