Preparation and characterization of magnetic nanocomposite catalysts with double Au nanoparticle layers

Abstract

In this paper magnetic nanocomposite catalysts, with a single gold catalytic layer (Fe₃O₄@SiO₂-Au and Fe₃O₄@SiO₂-Au@mSiO₂), double gold catalytic layers (Fe₃O₄@SiO₂-Au@mSiO₂-Au), and with one gold layer and one silver layer (Fe₃O₄@SiO₂-Au@mSiO₂-Ag), were prepared through simple steps. Different techniques were used for characterization of the as prepared nanocomposite catalysts, such as transmission electron microscopy (TEM), X-ray diffraction (XRD), a vibrating sample magnetometer (VSM), energy-dispersive X-ray spectroscopy (EDX) etc. The catalysts were used for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaHB₄. All the nanocomposite catalysts showed very good catalytic activity; however the nanocomposites with double catalytic layers (Fe₃O₄@SiO₂-Au@mSiO₂-Au and Fe₃O₄@SiO₂-Au@mSiO₂-Ag) showed excellent catalytic activity for the reduction reaction of 4-nitrophenol. Due to the magnetic core, the nanocomposite catalysts showed magnetic properties and can be easily separated and recycled many times without any loss in activity. In the case of nanocomposite catalysts with Au nanoparticles protected by silica (Fe₃O₄@SiO₂-Au@mSiO₂) indicated better recyclability compared to other nanocomposites.