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 Fe3O4colloidal 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(HRTEM), energy-dispersive X-ray(EDX) and X-ray photoelectron spectroscopy(XPS) analyses. The Au and Cu NPs were deposited on the SiO2surface 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 4,40-diamino-1,10-dianthraquinonyl-3,30-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.