A comparative study on antibacterial activity of sulfur- and phosphorus- doped carbon quantum dots

Effectively killing microbial pathogens without inducing resistance is a challenge, especially in the treatment of infectious diseases. In this study, sulfur (S)- and phosphorus (P)-doped carbon quantum dots (CQDs) were synthesized by one-step hydrothermal method using m-aminophenol as carbon source, thiourea and phosphoric acid as S and P dopants, respectively. Compared with S-CQDs, P doping could lead to a red-shift of the maximum emission wavelength. In addition, the as-prepared S-CQDs and S, P-CQDs exhibited unique antibacterial efficacy against both E. coli and S. aureus without developing drug resistance. In contrast, the S, P-CQDs had no preference for Gram-positive and Gram-negative bacteria, and they had a somewhat reduced bactericidal efficacy than that of S-CQDs, but S, P-CQDs had better bacteriostatic stability than S-CQDs. Such an excellent antibacterial effect might be attributed to the generation of a large number of intracellular reactive oxygen species (ROS), which disrupted the structure and the regular surface of bacterial cell. Consequently, the prepared S-CQDs and S, P-CQDs could be applied as antibacterial drugs with broad-spectrum antibacterial activity and without drug resistance.