Synthesis of monodisperse Fe@SiO2 core-shell nanocapsules and investigation of their magnetic behavior

The monodisperse Fe@SiO2 core-shell nanocapsules were synthesised via hydrothermal reaction followed with heat treatment. Nanostructures were characterised by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The magnetic properties of Fe@SiO2 nanocapsules were evaluated with magnetic property measurement system. The results show that Fe@SiO2 core-shell nanocapsules are highly monodispersed. The silica thickness of Fe@SiO2 nanocapsules increased from 10–20 to 25–35 nm with increasing tetraethyl orthosilicate (TEOS) amount. In the Fe@SiO2 nanocapsules prepared with 900 μl TEOS, as the reaction temperature increases, the mean particle size of Fe@SiO2 nanocapsules increases from 328 to 546 nm. It is remarkable that the saturation magnetisation of Fe@SiO2 nanocapsules decreases with increasing silica thickness. However, the coercivity of nanocapsules has less influence with the variation of silica thickness and particles’ length.