On-Off-On fluorescent sensing platform based on nitrogen-doped carbon dots for biothiols detection

Abnormal levels of biothiols in the human body are closely related to a variety of diseases, thus it is crucial for the selective detection of biothiols in the biological system. In this work, a Fe3+-triggered multifunctional nitrogen-doped carbon quantum dots (N-CQDs) on-off-on fluorescent sensing platform for the ultrasensitive detection of biothiols (GSH, Cys and Hcy) was successfully established. In detail, Fe3+ could adsorb on the surface of N-CQDs through coordination with the phenolic hydroxyl group of N-CQDs, resulting in the quenching of the fluorescence of N-CQDsdue to the photoinduced electron transfer (PET) effect from N-CQDs to Fe3+. After the addition of biothiols, there was stronger coordination between Fe3+ and biothiols than N-CQDs-Fe3+, resulting in fluorescence recovery of N-CQDs. On basis of the on-off-on principle, the N-CQDs-Fe3+ fluorescent probe was applied to determine biothiols. Under optimal parameters, the N-CQDs-Fe3+ fluorescent probe exhibited a relatively lower limit of detection (LOD) of 20.39 nM (GSH), 9.31 nM (Hcy) and 1.93 nM (Cys), respectively, which was better or comparable compared with previous reports. Further, the constructed N-CQDs-Fe3+ fluorescent sensing platform was validated with strong anti-interference ability, good reproducibility and repeatability, and also performed well in serum samples, demonstrating a promising potential in clinical diag-nosis for biothiols analysis.