Anomalous Pore Expansion of Highly Monodispersed Mesoporous Silica Spheres and Its Application to the Synthesis of Porous Ferromagnetic Composite

Abstract

In this paper, we report on the pore expansion of monodispersed mesoporous silica spheres (MMSS) by a swelling agent incorporation method, by which swelling agents such as various hydrocarbons were incorporated into mesopores. Mesopores were expanded to more than twice the size (5.5 nm) of the original one (2.5 nm). In this method, pore expansion of MMSS was achieved while radially ordered hexagonal mesopores with spherical morphology and high monodispersity were retained. In addition, we have successfully obtained highly monodispersed porous FePt—MMSS composites by incorporating FePt precursors into the pore-expanded MMSS. The composites had both ferromagnetic behavior with coercivity of 3.3 kOe at room temperature and mesoporosity with pore volume of 0.74 cm3g−1, which is enough to incorporate a variety of chemicals, nanoparticles, and proteins, such as drugs, quantum dots, enzymes, and DNA molecules. They have potential applications in drug delivery systems, gene delivery systems, magnetic hyperthermia treatments, and magnetic photonic crystals.