Bismuth-doped carbon quantum dots as an effective fluorescent probe for metronidazole detection through inner filter effect, cytotoxicity studies, and bioimaging in Zebrafish

Herein we report that Walnut Shell-derived bismuth-doped Carbon Quantum Dots (Bi-CQDs) in rice morphology with an average size of 3-4 nm were used for the highly selective nanomolar (nM) detection of metronidazole (MNZ) through the inner filter effect (IFE). The excitation-dependent Bi-CQDs show high selectivity, sensitivity, and fluorescence detection on different pH (1 -> 13) with a limit of detection (LoD) of 15.72 nM (R2 = 0.99092). The fluorescence quenching mechanism was evaluated by the interaction of Bi-CQSs with various MNZ concentrations (200 nM-2 mu M), with binding constant as Ka = 1.081 x 10-3 M-1, increase in fluorescence lifetime values (5.60 -> 5.88 ns). The interference studies, the effect of pH, the effect of time on MNZ detection, and the stability of the Bi-CQD center dot MNZ complex were also investigated. Further, in vitro bioimaging of Zebra fish and cytotoxicity studies were also conducted. Fluorescence imaging of Bi-CWDS in Zebra fishes distinguishes the morphology changes and embryogenesis. These results suggest that the developed sensor is highly biocompatible for fluorescence sensing and biological applications.