Figure 4. Photodynamic antimicrobial activity of the CDs. (a) Schematic illustration of the antibacterial effect of the CDs onE. coli and S. aureus under different conditions. (b-c) Comparison of bacterial survival rate of E. coli upon treatment with different concentrations of the CD for different times in the dark (b) and under light irradiation (c). (d-e) Comparison of bacterial survival rate of S. aureus upon treatment with different concentrations of the CD at different times in the dark (d) and in the light irradiation (e). (f-g) ROS levels of E. coli (f) and S. aureus (g) upon treatment with different concentrations of the CD at 30 min under light irradiation and in the dark. The groups treated with H2O2 were used as the positive control. (h) Time courses of the normalized absorbance at 410 nm of the CDs, DPBF, and the mixture of the CDs and DPBF under light irradiation and in the dark. Note that the CD and DPBF used in the corresponding samples were of 100 μg/mL and 100 μM in final concentration, respectively.