Preparation and characterization of magnetic mesoporous silica nanoparticles with a core-shell structure

Magnetic mesoporous silica nanoparticles with small and uniform pore size have been extensively researched owning to its biological functionalization and unique magnetic properties. In the paper, core-shell structural Fe₃O₄@SiO₂ magnetic mesoporous nanoparticles were successfully prepared by a sol-gel homogeneous coprecipitation process, using Fe₃O₄ as core, cetyltrimethylammonium bromide as surfactant, tetraethyl orthosilicate (TEOS) as silica source, and diethanolamine as homogeneous precipitating agent (instead of traditional inorganic alkaline or ammonia). The prepared Fe₃O₄@SiO₂ magnetic mesoporous nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscope (TEM) and nitrogen adsorption-desorption isotherm. The results indicated that the surface of Fe₃O₄ nanoparticles was successfully coated by the silica. The size of the prepared Fe₃O₄@SiO₂ magnetic mesoporous nanoparticles was uniform with an average diameter of 120 nm, surface area of 768.5 m²·g^-1, average pore size of 2.32 nm and pore volume of 0.23 cm³·g ^-1. Fe₃O₄ and SiO₂ components existed in division phase in the spherical nanoparticles. In addition, it was proved in the paper that the particle size of the prepared Fe₃O₄@SiO₂ magnetic mesoporous nanoparticles and its dispersion state in solution were affected by the pH value in reaction system.