Rational synthesis of superparamagnetic core–shell structured mesoporous microspheres with large pore sizes

Abstract

Core–shell structured porous materials combining the functionalities of the core and shell have great application potential in various fields. Here, we report the synthesis of superparamagnetic core–shell structured microspheres which possess a core of nonporous silica-protected magnetite particle and an outer shell of ordered mesoporous silica with large pores. The synthesis adopts a co-surfactant templating approach under acidic conditions, with triblock-copolymer Pluronic P123 as a primary surfactant and a trace amount of cationic surfactant CTAB as an assistant template. The obtained magnetic mesoporous silica microspheres have uniform large pore size (4.5 nm), tuneable shell thickness (15–50 nm), high specific surface area (190–250 m² g⁻¹), large pore volume (0.17–0.38 cm³ g⁻¹) and high magnetization (29.3 emu g⁻¹). By using the obtained microspheres as an advanced magnetic absorbent, a fast, convenient, and efficient removal of large-size toxic microcystins in water solution was achieved in 60 seconds. The superparamagnetic properties and unique nanostructure enable the core–shell microspheres to be not only a novel absorbent for large size molecules, but also an ideal carrier for nanocatalysts like noble metallic nanoparticles and tools for peptide purification.