NIR-induced improvement of catalytic activity and antibacterial performance over AuAg nanorods in Rambutan-like Fe3O4@AgAu@PDA magnetic nanospheres.

Pathogenic bacteria and difficult-to-degrade pollutants in water have been serious problems that always plague people. Therefore, finding a "one stone-two birds" method that can quickly catalyze the degradation of pollutants and show effective antibacterial behavior become an urgent requirement. This work reports a facile one-step strategy for fabricating a Rambutan-like Fe3O4@AgAu@PDA (Fe3O4@AgAu@Polydopamine) core/shell nanosphere with both catalytic and antibacterial activities which can be critically improved by externally applying an NIR laser irradiation (NIR, 808 nm) and a rotating magnetic field. Typically, the Rambutan-like Fe3O4@AgAu@PDA nanosphere have a rather rough surface due to the AuAg bimetallic nanorods sandwiched between the Fe3O4 core and the PDA shell. Owing to the penetrated PDA shell, AgAu nanorods show high and magnetically recyclable photothermal-enhanced catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol and they can also be applied to initiate TMB oxidation under the help of NIR heating condition. Moreover, Fe3O4@AgAu@PDA shows a moderate antibacterial activity due to the weak release of Ag+. Under applying a rotating external magnetic field, the rough-surface Fe3O4@AgAu@PDA nanospheres produce a controllable magnetolytic force on the bacterial due to their good affinity. As a result, the Fe3O4@AgAu@PDA nanospheres show a "magnetolytic-photothermal-Ag+" synergistic antibacterial behavior against E. coli and S. aureus.