A facile green and one-pot synthesis of grape seed-derived carbon quantum dots as a fluorescence probe for Cu(II) and ascorbic acid

In this study, an on–off–on fluorescence probe for the detection of trace Cu(II) and ascorbic acid (AA) based on biomass-derived sulfur and nitrogen double heteroatom-doped carbon dots (N,S-CDs) was designed. For the first time, the probe (N,S-CDs) was prepared from grape seeds and thiourea as the precursor. Cu(II) was added to the carbon point solution, the fluorescence intensity (FL) of N,S-CDs was strongly quenched (switch OFF) and the fluorescence probe turned to “ON” (switch ON) with the addition of AA. Under the optimal conditions, the as-synthesized N,S-CDs had a good detection performance for Cu(II) and AA assay with the linearity ranges from 150–500 μg mL−1 and 0.1–400 μg mL−1, and the LODs were 0.048 mg L−1 and 0.036 mg L−1, respectively. The as-prepared N,S-CDs exhibited a low cytotoxicity and a good biocompatibility, which show their potential for application in the biological imaging of living cells.