Construction of g-C3N4/TiO2/Ag composites with enhanced visible-light photocatalytic activity and antibacterial properties

In this study, the multifunctional carbon nitride based composite graphitic-C3N4 (g-C3N4)/TiO2/Ag was prepared through a simple and efficient vacuum freeze-drying route. TiO2 and Ag nanoparticles were demonstrated to decorate onto the surface of g-C3N4 sheet. In the ultraviolet–visible absorption test, a narrower band gap and red-shift of light absorption edge were observed for g-C3N4/TiO2/Ag compared to pristine g-C3N4 and single-component modified g-C3N4/TiO2. The photodegradation property of g-C3N4/TiO2/Ag was investigated toward the degradation of methylene blue (abbreviated as MB) under the irradiation of visible light. These results indicated that the degradation performance of organic dyes for g-C3N4/TiO2/Ag was obviously improved compared with g-C3N4/TiO2 and g-C3N4. The reaction rate constant of MB degradation for g-C3N4/TiO2/Ag was 4.24 times higher than that of pristine g-C3N4. In addition, such rationally constructed nanocomposite presented evidently enhanced antibacterial performance against the Gram-negative Escherichia coli. Concentration dependent antibacterial performance was systematically investigated. And 84% bacterial cell viability loss had been observed at 500 μg/mL g-C3N4/TiO2/Ag within 2 h visible light irradiation.