Fabrication and application of magnetic nanoreactor with multiple ultrasmall cores and mesoporous shell in Fenton-like oxidation

Abstract

A new and facile method has been developed in this study for the fabrication of multicore–shell type nanoreactor. On the basis of the characterization results from X-ray diffraction, scanning and transmission electron microscopy, Raman and X-ray photoelectron spectroscopy, and N2 adsorption/desorption analysis, it has been proved that ultrasmall iron oxide particles (∼10 nm) were firstly encapsulated in the matrix of polystyrene spheres via a microemulsion-polymerization-assisted approach, and then were introduced as movable cores inside mesoporous SiO2 shell. The size of iron oxide particles retained almost unchanged even during the calcination procedure in air, indicating high thermal stability, due to the protection of polystyrene matrix. The obtained nanoreactor was applied as an effective heterogeneous catalyst for total oxidation of methylene blue with aqueous hydrogen peroxide and the ultrasmall iron oxide particles within the hollow interior proved to be active sites for such reaction. Mesoporous SiO2 shell not only protects the nanometer-sized iron oxide particles against leaching from the nanoreactor into reaction solution, but also enriches the reactant molecules around multiple ultrasmall iron oxide cores and thus enhances the catalytic activity and reaction rate. Importantly, the nanoreactor can be easily recovered by external magnetic field and reused in successive catalytic cycles without significant loss of activity.