Polyethyleneimine induced highly dispersed Ag nanoparticles over g-C3N4 nanosheets for efficient photocatalytic and antibacterial performance

Improving the efficiency of Ag nanoparticles (NPs) in an antibacterial system remains a problem to be solved. Herein, a simple polyethyleneimine (PEI) modification strategy has been developed for realizing the high dispersion of Ag NPs with average size of 10 nm over two dimensional nanosheets of g-C3N4 photocatalyst, and the as-prepared ternary Ag/PEI/CN hybrid demonstrates enhanced bifunctional performance of antibiotics (e.g., tetracycline, TC) degradation and antibacterial activity. The enhanced mechanism is investigated and proposed to be a synergy effect between reactive oxygen-containing species (ROS, e.g., center dot OH and O-2(center dot)) derived from PEI modified g-C3N4 photocatalyst and slow released Ag+ ions generated by the highly dispersed Ag NPs as antimicrobial agent. Furthermore, the surface plasmonic effect of Ag NPs and coupling of PEI can increase light absorption and accelerate the electron-hole separation and mobility. Consequently, more availability of ROS along with holes and Ag+ ions can accelerate the death of bacteria via destructing biomolecules. As a result, under visible-light irradiation, Ag/PEI/CN hybrid presents greatly improved antibacterial activity against E. coli, including a low MIC100% of 30 ppm and MBC97% of 10 ppm and enhanced photocatalytic performance towards TC degradation (similar to 80% TC can be degraded within 60 min).