Zinc doped carbon dots (Zn-CDs) as a dual functional platform for antibacterial applications and metronidazole detection

The new Zn-CDs were synthesized with a fluorescence quantum yield of 31.72%. • Zn-CDs exhibited strong antibacterial activity against both E. coli and S. aureus. • Zn-CDs were successfully utilized for MTZ detection by IFE and static quenching. Bacterial infections pose a major global health threat, highlighting the need for the development of effective antibacterial materials. Metronidazole (MTZ), a widely used antimicrobial agent, has raised concerns due to its misuse, emphasizing reliable detection methods. In this study, we synthesized zinc-doped carbon dots (Zn-CDs) via a hydrothermal method using hexahydrate zinc nitrate and histidine as precursors. Zn-CDs were thoroughly characterized for their optical properties, antibacterial activity, cytotoxicity, and potential for MTZ detection. Zn-CDs displayed a uniform spherical morphology with an average particle size of 4.65 nm and excitation-dependent fluorescence. Antibacterial assays revealed their effectiveness against Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ), with a minimum inhibitory concentration (MIC) of 313 μg/mL for both bacterial strains. Its antibacterial mechanism relied on the damage of bacterial cell membranes. Furthermore, Zn-CDs exhibited low cytotoxicity and hemolytic activity showing their excellent biocompatibility. Zn-CDs also displayed remarkable photostability, salt tolerance, and pH adaptability, making them suitable for diverse environments. For MTZ detection, Zn-CDs exhibited high specificity and anti-interference properties, with the fluorescence quenching mechanism attributed to the static quenching and internal filter effect (IFE). Furthermore, Zn-CDs were successfully applied to detect MTZ residues in honey, with recovery rates ranging from 92.3% to 101.7%. Overall, this study highlights the dual functionality of Zn-CDs as antibacterial agents and fluorescence-based sensors, offering promising applications in environmental monitoring and food safety analysis. Download: Download high-res image (109KB) Download: Download full-size image