Environmentally benign magnetic chitosan/Fe3O4 composites as reductant and stabilizer for anchoring Au NPs and their catalytic reduction of 4-nitrophenol

We report the facile synthesis of environmentally benign Au NPs/chitosan composites and magnetic Au NPs/chitosan/Fe3O4 composites without employing any toxic reductants or capping agents. Renewable natural chitosan not only functioned as supporting matrix, but also served as a reductant and stabilizer for the formation and dispersions of Au NPs. Fe3O4 nanospheres were easily embedded into the chitosan matrix due to the strong complexation ability of chitosan with Fe3O4, which originated from the sharing of the lone electron pairs from the nitrogen atom in amine with Fe-II or Fe-III on the surface of Fe3O4. The as-prepared magnetic composites exhibited much higher activities, as well as more convenient magnetic recyclability than other supported Au NPs towards the reduction of 4-nitrophenol. From the practical point of view, apart from good performance of the reduction of nitro compounds, the biocompatibility and biodegradability of present Au NPs/chitosan/Fe3O4 composites promote the potential applications in the biochemical catalysis or therapy.