Polyvinyl alcohol/chitosan nanofiber membranes loaded with oxygenated graphitic carbon nitride nanosheets for enhanced photocatalytic bacteriostasis

The visible light catalytic antibacterial nanofiber membranes as a novel functional material were designed to solve the problem of bacterial infection and water pollution. In this work, oxygenated graphite carbon nitride nanosheets (O-g-C3N4) with 12% oxygen content were synthesized through thermal polycondensation followed by chemical oxidation. Exfoliation and dispersion of O-g-C3N4 were strongly enhanced compared to pristine g-C3N4 due to rich hydrophilic carboxyl and hydroxyl groups. The amount of ROS generated by O-g-C3N4 was about 13.8% more than that of g-C3N4. Then, the polyvinyl alcohol (PVA)/chitosan (CS)/O-g-C3N4 (PCO) composite nanofiber membranes were prepared by electrospinning. The contact angle of the PCO nanofiber membranes decreased from 55.0 degrees +/- 0.5 to 45.9 degrees +/- 0.2 along with the increased amount of O-g-C3N4, indicating the improvement of hydrophilicity. Meanwhile, the diameter of nanofibers increased from 148.0 +/- 22.9 nm to 244.0 +/- 52.3 nm with the loading ratio from 0% to 17%. The PCO nanofiber membranes exhibited significantly higher antibacterial activity compared to the blank nanofiber membranes and bare O-g-C3N4. The maximum diameter of the inhibition zone against Escherichia coli and Staphylococcus aureus could reach 26 +/- 0.1 mm and 16 +/- 0.2 mm, respectively. The inhibition rate against E. coli could reach 97% in 24 h under the irradiation of simulated sunlight. Based on reactive oxygen species (ROS) testing, zeta potential, and bacterial inhibition experiments, a possible synergistic mechanism was proposed. The electrostatic adsorption effect of PCO nanofiber membranes and ROS could effectively decompose the organic components of bacteria and destroy their structural integrity. The results indicated that the antibacterial PCO composite nanofiber membranes have wide application prospects in biomedical-related fields.