Sensitive detection of Sudan dyes using tire-derived carbon dots as a fluorescent sensor

In this paper, we exploit an innovative strategy to reuse waste rubber tires as a low-cost source for the fabrication of a high-value material, fluorescent carbon dots (CDs). In the hydrothermal condition, ammonium persulphate is utilized to oxidize the tires and offer nitrogen atom for doping, to produce CDs with a high quantum yield (QY) of up to 23.8%. Such a QY is outstanding among the reported waste-derived CDs. It is found that the fluorescence of CDs can be remarkably quenched by Sudan I–IV with negligible interference from other substances. The corresponding linear ranges are 0.5–60, 0.5–60, 1–70, and 1–70 μM, and limits of detection are 0.17, 0.21, 0.53, and 0.62 μM for Sudan I, II, III, and IV, respectively. Systematic investigations reveal that the fluorescence quenching mainly stems from the inner filter effect. Moreover, the CD-based sensor shows an excellent applicability for the assay of Sudan dyes in chili powder sample.