Magnetic Fe ₃ O ₄ @AuPd/PDA nanospheres exhibit enhanced catalytic effects and photothermal–magnetic coupling antibacterial properties

Pathogenic microorganisms and recalcitrant pollutants in water present a persistent and severe threat to human health. Consequently, there is an urgent need to develop an integrated solution that not only catalyzes the efficient degradation of pollutants but also exhibits potent antibacterial properties. In this study, Fe₃O₄@AuPd/PDA nanocomposites were synthesized <i>via in situ</i> redox polymerization. Owing to their active catalytic components and superior magnetic recyclability, the material can be used as an efficient and easily recycled catalyst. In the presence of NaBH₄, the material exhibited excellent catalytic activity for the reduction of 4-nitrophenol, with a reaction rate constant of 1.07 min^-1 mg^-1. Furthermore, the material demonstrated excellent cyclic stability. After 6 cycles, the catalytic conversion rate remained above 95%. Under near-infrared (NIR) light irradiation, the reaction rate can be increased to 3.47 min^-1 mg^-1. Similar NIR-enhanced catalytic effects were observed for 2-nitrophenol and 3-nitrophenol. In addition to its catalytic properties, the material also demonstrates excellent NIR photothermal response. This property makes it highly effective in eliminating both <i>Staphylococcus aureus</i> and <i>Escherichia coli</i>. Under the synergistic influence of NIR light and an external magnetic field, the antibacterial efficacy is markedly enhanced. This multimodal antimicrobial mechanism offers a promising approach for developing innovative antimicrobial strategies.