Gold Nanoparticles on Mesoporous SiO(2)-Coated Magnetic Fe(3)O(4) Spheres: A Magnetically Separatable Catalyst with Good Thermal Stability

Fe(3)O(4) 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 SiO(2), and then coated by mesoporous SiO(2) (m-SiO(2)) films, by using TEOS as a precursor and CTAB as a soft template. The resulting m-SiO(2)/Fe(3)O(4) spheres, with an average particle size of 320 nm, a high surface area (656 m(2)/g), and ordered nanopores (average pore size 2.5 nm), were loaded with gold nanoparticles (average size 3.3 nm). The presence of m-SiO(2) coating could stabilize gold nanoparticles against sintering at 500 °C. The material showed better performance than a conventional Au/SiO(2) catalyst in catalytic reduction of p-nitrophenol with NaBH(4). 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, N(2) adsorption-desorption, and magnetic measurements were conducted.