A simple assay platform for sensitive detection of Sudan I-IV in chilli powder based on CsPbBr₃ quantum dots

Sudan dyes are phenyl-azoic derivatives widely used in industry. Classified as carcinogenic and are strictly forbidden in foodstuffs; however, some unscrupulous businessmen adopted it for coloring foodstuffs. Here, a simple and effective fluorescence (FL) assay platform has been developed for the detection of Sudan I-IV based on CsPbBr₃ perovskite quantum dots (QDs). It was found that the fluorescent emission of CsPbBr₃ QDs can be effectively quenched by Sudan I-IV. Under the optimized conditions, the FL quenching efficiency of CsPbBr₃ QDs was quantitatively correlated to the logarithmic concentrations of Sudan I-IV over the ranges of 100-10,000, 0.1-1000, 0.1-2000 and 0.4-1000 ng mL^-1 for Sudan I-IV, and the corresponding limits of detection were 3.33, 0.03, 0.03 and 0.04 ng mL^-1 (at 3σ/slope), respectively. CsPbX₃ QDs (X = Cl, Br, and I or mixed halide systems Cl/Br and Br/I) was utilized as sensor in FL assay, which have unique optical properties of high FL quantum yields (up to 90%), narrow half peak width (26 nm) and tunable FL emissions spectra (410-700 nm). Meanwhile, the practical use of this assay platform for Sudan I-IV detection in chilli powder samples was also demonstrated, which indicated the potential in practical applications.