Reduced graphene oxide wrapped Fe3O4@TiO2 yolk–shell nanostructures as a magnetic recyclable photocatalytic antibacterial agent

Abstract

In this study, we report reduced graphene oxide wrapped Fe3O4@TiO2 yolk–shell nanostructures (G-Fe3O4@TiO2) as a magnetic recyclable photocatalytic antibacterial agent for medical wastewater treatment. The yolk–shell structure with a magnetic oxide core was synthesized using a template-assisted route and graphene wrapping was added using the one-step method. The obtained samples were characterized by TEM, XRD, XPS, FTIR, Raman and BET analysis. Owing to the photocatalysis property, TiO2 exhibits certain antibacterial effect by generating reactive oxygen species (ROS). As an excellent conductor, Fe3O4 improves the photocatalytic performance of TiO2 after forming a yolk–shell structure. Moreover, the synergistic effect of Fe3O4 magnetism and graphene adsorption ensure bacteria removal under external magnetic field. Graphene inhibits the recombination of photogenerated electron–hole pairs, maximizing the bactericidal activity of the material. With the dual functions of photocatalytic bactericidal and magnetic targeting to separate bacteria, the removal percentage of Staphylococcus aureus (S. aureus) cocultured with G-Fe3O4@TiO2 reached up to 99.9% in 4 h exposure to visible light and external magnetic field, higher than 61% in Escherichia coli (E. coli). Therefore, G-Fe3O4@TiO2 could effectively remove typical bacteria on the premise of biosafety, which provided an ideal recyclable material for medical wastewater treatment.