Sandwich-structured AgCl@Ag@TiO2 with excellent visible-light photocatalytic activity for organic pollutant degradation and E. coli K12 inactivation

• Sandwich-structured AgCl@Ag@TiO2 photocatalyst was synthesized by a facile multi-step route.
• AgCl@Ag@TiO2 showed excellent visible light activity for decomposing organics and bacteria.
• The interlayer Ag NPs, acting as a sensitizer, can absorb visible light by plasmon resonance.
• The sandwich-structure can effectively separate photo-generated electrons and holes.
• O2−, OH and Cl0 are the reactive species devoting to the decomposition of organics and bacteria.

Sandwich-structured AgCl@Ag@TiO2 plasmonic photocatalyst was synthesized by a facile multistep route, including a controllable double-jet precipitation technique to fabricate cubic AgCl core, a gradual temperature-rise process to coat TiO2 shell layer, and UV light reduction to generate Ag nanoparticles (NPs) between AgCl core and TiO2 shell. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectroscopy (DRS). Beneficial from the fact that Ag NPs can respond to visible light and sandwich-structure can effectively separate the photo-generated electrons and holes, AgCl@Ag@TiO2 exhibited excellent visible-light photocatalytic activity not only for the degradations of acid orange 7 and 2,4-dichlorophenol but also for the inactivation of Escherichia coli (E. coli) K12. The transient photocurrent tests proved that AgCl@Ag@TiO2 sandwich-structure has higher efficiency for the separation of photo-generated electrons and holes than AgCl@Ag core–shell structure. Electron spin resonance (ESR) tests with DMPO and the radical trapping experiments confirmed that O2−, OH and Cl0 are the reactive species responsible for the degradation of organic pollutants and bacteria.

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