Cooperatively modulating reactive oxygen species generation and bacteria-photocatalyst contact over graphitic carbon nitride by polyethylenimine for rapid water disinfection

Graphitic carbon nitride (C₃N₄) has gained broad attention as a metal-free photocatalyst for water disinfection. However, the low photocatalytic bactericidal activity of pristine C₃N₄ limits its applications. Here, we report a facile method to boost the photocatalytic disinfection activity of C₃N₄ with polyethyleneimine (PEI). With PEI modification, the generation of long-lifespan reactive oxygen species (ROS,•O₂⁻ and H₂O₂) in photocatalysis is significantly improved. Additionally, scanning electron microscopy and the atomic force microscopy force spectroscopy characterization reveal that PEI promotes the bacteria-photocatalyst contact via electrostatic adhesion. Due to the synergistic modulation of ROS generation and bacteria-photocatalyst interaction, the photocatalytic bactericidal activity of C₃N₄ is dramatically enhanced after PEI modification. Notably PEI/C₃N₄ composite achieves 6.2 logs of inactivation efficiency for Escherichia coli within 45 min and 4.2 logs for Enterococcus faecalis within 60 min under simulated solar irradiation. Overall, this work provides insights on designing metal-free photocatalysts with judicious polymer for antibacterial applications.