Synthesis of monodisperse magnetic sandwiched gold nanoparticle as an easily recyclable catalyst with a protective polymer shell

Monodisperse magnetic sandwiched magnetite@gold/poly(ethyleneglycol methacrylate) (Fe3O4@Au/PEGDMA) core–shell microspheres were designed and prepared. The whole synthetic procedure mainly involved hydrothermal method for preparation of magnetite core with subsequent modification of (3-aminopropyl)trimethoxysilane (APS) for introduction of the surface amino groups, distillation precipitation polymerization for preparation of the P(EGDMA) shell and in situ reduction of gold precursor HAuCl4 for formation of the sandwiched Au nanoparticles. The thicknesses of the outer polymeric shells were well-controlled via altering the weight ratios of EGDMA monomers to magnetite core during polymerization. The catalytic activity of the sandwiched Fe3O4-Au@P(EGDMA) magnetic microsphere was studied by the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AnP) as a model reaction. These magnetic microspheres were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared spectra (FT-IR), thermogravimetric analysis (TGA) and vibrating sample magnetometry (VSM).