Hit Multiple Targets with One Arrow: Pb and ClO Detection by Edge Functionalized Graphene Quantum Dots and Their Applications in Living Cells.

Recently, multimodal detection of analytes through a single nanoprobe has become an eminent approach for researchers. Herein a fluorescent nanoprobe, functionalized-GQD (F-GQD), has been designed through edge functionalization of graphene quantum dots (GQDs) by 2,6-diaminopyridine molecules. The fluorescence of F-GQD is quite sensitive to medium pH, making it a suitable pH sensor within the pH range 2-6. Interestingly, F-GQD shows dual sensing of Pb and ClO by entirely different pathways; Pb exhibits fluorescence turn-on performance while ClO triggers turn-off fluorescence quenching. The fluorescence enhancement may originate from the Pb-induced aggregation of the nanodots. The limit of detection (LOD) was also impressive, 1.2 μM and 12.6 nM for Pb and ClO, respectively. The detailed mechanistic investigations reveal that both dynamic and static quenching effects operate together in the F-GQD-ClO system. The dynamic quenching was attributed to the energy migration from F-GQD to ClO through hydrogen bonding interaction (static quenching) between the amine group at the F-GQD surface and ClO. The F-GQD nanodot reveals excellent sensitivity toward the detection of ClO in real samples. Moreover, the F-GQDs also serve as multicolor fluorescent probes for cell imaging; the probe can easily penetrate the cell membrane and successfully detect intracellular ClO.