(566d) Synthesis and Applications of Magnetic Au-Ag-?-Fe2O3 Nanocomposites on Reduced Graphene Oxide

Over the years, nanoparticles have been utilized widely in the fields of energy, biomedicine and environmental pollution prevention. Compared with bulk materials, noble metal nanoparticles are applied more broadly to heterogeneous catalytic processes because of their distinctive physicochemical properties, such as large specific surface area and high Fermi potential. Especially, polymetallic nanoparticles show enhanced catalytic properties caused by synergistic effect. However, the aggregation of nanoparticles may result in the decrease of catalytic activity. To maximizing the activity of noble metal nanoparticles, a suitable support is necessary for their dispersion. Graphene is a promising candidate which has attracted great attention due to its excellent chemical and physical properties, such as large specific surface area, outstanding mechanical strength, and unique thermal and electronic properties. As a derivative of graphene, graphene oxide becomes a common choice for support. It has unique properties just as graphene and is convenient to prepare. It should be noted that the nanocatalysts are difficult to use in continuous flow systems due to their tiny size and high stability in reaction systems. To solve this problem, nanocatalysts are combined with magnetic nanoparticles such as Fe₃O₄ and γ-Fe₂O₃. These hybrids are easy to retrieve from the reaction system under a magnetic field due to their magnetic properties. Magnetic separate technology has been widely used in separate fields and is quite desirable in industries because it can overcome the disadvantages of batch operation and other issues in filtration or centrifugation. In this paper, a facile route has been developed to prepare magnetic trimetallic Au-Ag-γ-Fe₂O₃/rGO nanocomposites. The nanocomposites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The prepared nanocomposites show fine catalytic activity towards the reduction reaction of 4-nitrophenol. The nanocomposites also have superparamagnetism at room temperature, which can be easily separated from the reaction systems by applying an external magnetic field. The multiplexing experiments were also preformed giving remarkable reusability and stability.