Highly fluorescent N, F co-doped carbon dots with tunable light emission for multicolor bio-labeling and antibacterial applications

Carbon dots (CDs) have emerged as potential biomaterials for bioimaging and antimicrobial applications. However, the lack of tunable long-wavelength emission performance and imprecise antibacterial mechanism limit their practical application. Thus, developing versatile CDs that combine outstanding optical performance and excellent antibacterial activity is of great practical significance. Herein, we prepared a novel nitrogen and fluorine co-doped CDs (N, F-CDs) from o-phenylenediamine and 2,3,5,6-tetrafluoroterephthalic acid, which exhibit high fluorescence quantum yield of 52.2%, large Stokes shift of 112 nm, as well tunable multicolor emission light from blue to red region. Thanks to the high biocompatibility and excellent photostability, the N, F-CDs were successfully implemented to multicolor biolabeling of mammalian cells, protozoan cells and plant cells. Moreover, the negatively charged N, F-CDs hold inherent efficient antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). By thoroughly studying the underlying antibacterial mechanisms at the molecular level through real-time quantitative PCR assay, we found the expression of related genes was notably down-regulated, further demonstrated that N, F-CDs against two bacterial strains had distinct target pathways. Our work provides a new reference for developing highly fluorescent multicolor CDs, and may facilitate the design and application of CDs-based nanomaterials in biological environment.