Preparation and characterization of magnetic iron nanoparticles encapsulated in mesoporous silica: The effects of reduction procedure and pore size

摘要

Magnetite (Fe_3O_4) and metallic iron (Fe) nanoparticles (NPs) were encapsulated in mesoporous silica, SBA-15, with two pore diameters (6.4 and 15.8 nm) via vacuum-assisted impregnation and reduction in hydrogen gas. The formation of iron (Ⅱ) silicate (Fe_2SiO_4) was successfully avoided by using a relatively low reducing temperature (510℃) for the reduction of Fe_2O_3 to Fe NPs. When compared to SBA-15 with a typical pore diameter of approximately 6 nm, increases in the pore diameter led to increases in the saturation magnetization values of both the encapsulated NPs and the composite, while simultaneously leaving a larger pore volume in the composite. The as-prepared composites, with tunable magnetic properties and pore volumes, show attractive applications in various fields.