SiO 2 @AuAg/PDA hybrid nanospheres with photo-thermally enhanced synergistic antibacterial and catalytic activity.

Wastewater discharged from industrial, agricultural and livestock production contains a large number of harmful bacteria and organic pollutants, which usually cause serious harm to human health. Therefore, it is urgent to find a "one-stone-two-birds" strategy with good antimicrobial and pollutant degradation activity for treating waste water. In this paper, SiO2 @AuAg/Polydopamine (SiO2 @AuAg/PDA) core/shell nanospheres, which possessed synergistic "Ag+ -release-photothermal" antibacterial and catalytic behaviors, have been successfully prepared via a simple in situ redox polymerization method. The SiO2 @AuAg/PDA nanospheres showed good catalytic activity in reducing 4-nitrophenol to 4-aminophenol (0.576 min-1 mg-1 ). Since the AuAg nanoclusters contain both gold and silver elements, they provided a high photothermal conversion efficiency (48.1%). Under NIR irradiation (808 nm, 2.5 W-2 ), the catalytic kinetics were improved by 2.2 times. Besides the intrinsic Ag+ -release, the photothermal behavior originating from the AuAg bimetallic nanoclusters and the PDA component of SiO2 @AuAg/PDA also critically improved the antibacterial performance. Both E. coli and S. aureus could be basically killed by SiO2 @AuAg/PDA nanospheres at a concentration of 90 μg mL-1 under NIR irradiation. This "Ag+ -release-photothermal" coupled sterilization offers a straightforward and effective approach to antimicrobial therapy, and further exhibits high potential in nanomedicine for combating bacterial contamination in environmental treatment and biological fields.