Preparation, characterization and catalytic activity of core–satellite Au/Pdop/SiO2/Fe3O4 magnetic nanocomposites

Abstract

In this study, we report a facile method to synthesize core–satellite structured Au/Pdop/SiO2/Fe3O4 composite nanoparticles (NPs). Firstly, polydopamine-coated silica/magnetite nanoparticles (Pdop/SiO2/Fe3O4 composites) were synthesized by the combination of a sol–gel process and an in situ polymerization method, in which tetraethyl orthosilica (TEOS) as well as dopamine acted as the precursor for silica and polydopamine (Pdop), respectively. The Pdop/SiO2/Fe3O4 composites revealed a multilayer core–shell structure, where Pdop is the outer shell of the composite. Then, numerous ''satellites'' of gold nanoparticles were assembled on the surface of Pdop/SiO2/Fe3O4via the reduction of Au3+ by the Pdop/SiO2/Fe3O4 composite itself. In addition, the size and density of the gold nanoparticles can be easily adjusted by controlling the concentration of the HAuCl4 solution. The morphology, structure, and composition of the nanocomposites are characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectrometry (XPS), and vibrating sample magnetometry (VSM). The resulting Au/Pdop/SiO2/Fe3O4 composite NPs show not only a strong magnetic response to an externally applied magnetic field, but also a high catalytic performance on catalyzing the reduction of methylene blue (MB), at ambient temperature.