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

[Display omitted] •Polyethylenimine (PEI) was grafted onto carbon nitride (C3N4) nanosheets.•PEI/C3N4 composite shows remarkably enhanced photocatalytic bactericidal activity.•PEI promotes •O2− and H2O2 generation, and changes the disinfection pathway.•SEM and AFM force spectroscopy are used to study bacteria-photocatalyst interaction.•PEI on C3N4 promotes the bacteria-photocatalyst contact via electrostatic adhesion. 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.