A universal green approach for the synthesis of NPS-codoped carbon quantum dots with enhanced broad-spectrum antibacterial and antioxidant activities

Abstract

Bio-inspired quantum dots have received widespread attention in recent years due to their great potential for biological applications. Herein, we report a one pot hydrothermal synthesis of nitrogen–phosphorus–sulphur (NPS)-codoped carbon quantum dots from endophytic bacteria without using any additional doping precursor. The synthesized CQDs were thoroughly characterized and interestingly found to have a graphene like structure. The synthesized CQDs were then utilized in bactericidal activities against Gram-negative bacteria like Salmonella typhi, Pseudomonas aeruginosa and Gram-positive bacteria like the Bacillus subtilis strain. The strains were treated with different concentrations ranging from 5–100 µg ml⁻¹. The 5 µg ml⁻¹ concentration appeared to be the MIC (minimum inhibitory concentration) and 100 µg ml⁻¹ is the MBC (minimum bactericidal concentration) maintaining a short incubation period of one hour. A simple, cost-effective and eco-friendly approach to synthesize multi-elemental doped CQDs would certainly cause the method to be used in future for diverse biological applications. As compared to the broadly used antibiotics, the developed CQDs have some added advantages including lower cytotoxicity, excellent photo-stability and high selectivity.