A vacuum nano-casting route to magnetite cores/ mesoporous silica shell composites

Hollow mesoporous silica spheres with magnetite cores (HMSMC) have been fabricated by Vacuum Nano-casting Route. The amount of magnetite cores and saturation magnetization value can be easily adjusted by changing the concentration of iron nitrate solution used in the synthesis procedure. Furthermore, the as-prepared HMSMCs still maintain narrow mesopore distribution, high surface area and large pore volume after the hollow cores of hollow mesoporous silica spheres were filled with magnetite particles. Specially, when the saturation magnetization value of as-prepared HMSMCs reaches 22.0 emu/g, the surface area and pore volume of corresponding HMSMCs are 149 m²/g and 0.19 cm³/g, respectively, and the pore size is 2.30 nm. The corresponding samples are characterized by X-ray diffraction, N₂ sorption isotherms, transmission electron microscopy and vibrating-sample magnetometer.