A high performance N-doped carbon quantum dots/5,5′-dithiobis-(2-nitrobenzoic acid) fluorescent sensor for biothiols detection

In this work, a simple, fast and sensitive fluorescent sensor based on N-doped carbon quantum dots (NCQDs) and 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) was fabricated for selective detection of biothiols. NCQDs were successfully prepared via hydrothermal method and characterized using TEM, XRD, Raman spectrometer, FT-IR and XPS. In the presence of biothiols in the mixture of NCQDs and DTNB, −SH of biothiols can interact with DTNB and subsequently affording yellow-colored 5-thio-2-nitrobenzoate (TNB), which can strongly absorb excitation light of NCQDs and lead to fluorescence quenching of NCQDs. As a consequence, quantitative screening of biothiols can be achieved. Under optimized conditions, good linear relationships in the range of 0.05-40 μM was obtained for L-cysteine (L-Cys), 0.01-40 μM for glutathione (GSH), and 0.05-40 μM for homocysteine (HCys). The detection limits of this assay for L-Cys, GSH and HCys were 1.01 nM, 3.23 nM, and 3.29 nM, respectively. And selectivity, reproducibility and stability of the sensor were also evaluated. These results demonstrated that the presented fluorescent sensor can be a promising sensing platform for biothiols analysis.