Synthesis of Fe3O4@SiO2-Au/Cu magnetic nanoparticles and its efficient catalytic performance for the Ullmann coupling reaction of bromamine acid

Novel magnetic core/shell bimetallic Au/Cu nanoparticles (Fe₃O₄@SiO₂-Au/Cu NPs) were prepared using SiO₂-coated iron oxide (Fe₃O₄@SiO₂) as a supported material. The magnetic Fe₃O₄ colloidal nanocrystal clusters (CNCs) as nano-core were modified with a silica coating for improvement stability and superficial area of the Au-Cu particles. The morphological structure and chemical composition of the Fe₃O₄@SiO₂-Au/Cu NPs were characterized with high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analyses. The Au and Cu NPs were deposited on the SiO₂ surface in a highly dense and well dispersed manner with an average size of approximately 5 nm. The Fe₃O₄@SiO₂-Au/Cu NPs as magnetic nano-catalysts were applied to the Ullmann coupling reaction of bromamine acid to synthesize 4,4′-diamino-1,1′-dianthraquinonyl-3,3′-disulfonic acid (DAS). The prepared Fe₃O₄@SiO₂-Au/Cu NPs exhibited efficient catalytic activity with higher conversion and selectivity. A bromamine acid conversion of 97.35% and selectivity for DAS of 88.67% were obtained in aqueous medium. The magnetic nano-catalysts can be readily separated from the reaction system and reused. This new nano-catalytic reaction represents a useful and attractive cleaner production system. The new catalyst system has important and potential applications in dye and pigment industry.