Sulfur-rich carbon quantum dots based on Alternanthera philoxeroides and thiourea for the detection of tartrazine

Tartrazine is used as a synthetic colorant to improve the color of food. Excessive intake of tartrazine will seriously harm human health. In this paper, a green and facile one-pot hydrothermal approach is proposed for the preparation of sulfur-doped carbon quantum dots ( S- CQDs) with Alternanthera philoxeroides (AP) powder and thiourea. The S- CQDs were developed as a highly sensitive “turn-off” fluorescent sensor for the detection of tartrazine. The S- CQDs displayed superior fluorescence characteristics of CQDs with a quantum yield (QY) up to 20.19%. S- CQDs exhibited the maximum fluorescence emission intensity at λ em  = 462 nm under excitation at λ ex  = 390 nm. The standard curve of S- CQDs had good linearity in the range of 7.8 ~ 125 μmol/L tartrazine, and the linear correlation coefficient ( R 2 ) was 0.9983. The S- CQDs were demonstrated to selectively react with tartrazine, leading to fluorescence quenching effect, which was successfully used for the detection of tartrazine with a limit of detection at 0.45 μmol/L, which was lower than the national standard detection limit of 187.14 μmol/L. The feasibility of practical application was assessed by the detection of tartrazine in real samples.