Synthesis of P-Doped Carbon Quantum Dots from Keratin and Their Antibacterial Activity

The misuse of antibiotics drives clinical antimicrobial resistance, with detrimental impacts for human health. Therefore, some new antibacterial materials should be developed to address the overuse of clinical antimicrobials. As a new nanomaterial with good biocompatibility and low toxicity, carbon quantum dots (CQDs) are excellent candidates as novel antimicrobial agents. In this study, we prepared blue-emitting phosphorus-doped carbon quantum dots (P-CQDs) with an optimal excitation wavelength of 370 nm and an optimal emission wavelength of 445 nm by a simple and environmentally-friendly one-step hydrothermal method using keratin as the carbon source. We found that P-CQDs exhibited inhibitory effects on microorganisms, with the minimal inhibitory concentration (MIC) values of 0.19 mg/mL against Gram-positive bacteria (S. aureus) and 0.31 mg/mL against Gram-negative bacteria (E. coli). The experimental results implied these stable fluorescence properties of P-CQDs possess good antibacterial activity. Thus, these findings indicate the P-CQDs based on biosynthesized keratin could potentially be used as an excellent antibacterial agent.