Antibacterial PEI-CDs as versatile fluorescent sensors for monitoring clarithromycin in serum and aluminum ions.

In this study, a novel polyethyleneimine‑carbon dots (PEI-CDs) was developed with dual functions of antibacterial activity and fluorescence sensing. PEI-CDs were synthesized via a one-step hydrothermal method, exhibiting uniform morphology, strong blue fluorescence (λex/λem = 355/418 nm), and a high quantum yield of 59.6%. In addition, PEI-CDs demonstrated potent antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) (MIC = 1.25 mg/mL) while maintaining low cytotoxicity, with 84.25% of cell viability at 1400 μg/mL, highlighting their outstanding biocompatibility. PEI-CDs also showed remarkable optical stability, salt tolerance, and pH resistance. The fluorescence of PEI-CDs was dynamically quenched by CLA, enabling sensitive detection of CLA with a broad linear range of 0.8-110 μmol/L and a low detection limit of 0.24 μmol/L. Subsequent addition of Al3+ restored the quenched fluorescence through competitive binding, allowing selective detection of Al3+ across a wide linear range of 0.7-150 μmol/L with a detection limit (LOD) of 0.21 μmol/L. Furthermore, PEI-CDs exhibited excellent selectivity, strong anti-interference capability, and high accuracy in real samples, achieving recovery rates of 98.47-102.90% for CLA in fetal bovine serum (FBS) and 99.60-112.68% for Al3+ in tap water. Overall, this work demonstrates the dual functionality of PEI-CDs as both an efficient antibacterial agent and a robust fluorescent nanomaterial for environmental and biological monitoring.