Gold Nanoparticles on Mesoporous SiO₂-Coated Magnetic Fe₃O₄ Spheres: A Magnetically Separatable Catalyst with Good Thermal Stability

摘要

Fe₃O₄ spheres with an average size of 273 nm were prepared in the presence of CTAB by a solvothermal method. The spheres were modified by a thin layer of SiO₂, and then coated by mesoporous SiO₂ (m-SiO₂) films, by using TEOS as a precursor and CTAB as a soft template. The resulting m-SiO₂/Fe₃O₄ spheres, with an average particle size of 320 nm, a high surface area (656 m2/g), and ordered nanopores (average pore size 2.5 nm), were loaded with gold nanoparticles (average size 3.3 nm). The presence of m-SiO₂ coating could stabilize gold nanoparticles against sintering at 500 °C. The material showed better performance than a conventional Au/SiO₂ catalyst in catalytic reduction of p-nitrophenol with NaBH₄. It can be separated from the reaction mixture by a magnet and be recycled without obvious loss of catalytic activity. Relevant characterization by XRD, TEM, N₂ adsorption-desorption, and magnetic measurements were conducted.