Multicolor fluorescent sensors based on a mixture of CdTe quantum dots and ionic liquid for the visual detection of sulfur dioxide residues in food

BACKGROUND Sulfur dioxide (SO 2 ) is commonly used as a preservative and antioxidant in food processing; however, its residues can pose significant health risks. The accurate and rapid detection of SO 2 residues in food is crucial for ensuring food safety and protecting consumer health. In this study, we have developed a novel multicolor fluorescent sensor system that combines N -acetyl- l -cysteine-modified CdTe quantum dots with a trihexyl(tetradecyl)phosphonium hydroxyphenylbenzoxazole ionic liquid. RESULTS The developed dual-response sensor exhibits a remarkable fluorescent color transition, shifting from blue to purple, pink and finally yellow, in response to SO 2 concentrations ranging from 10 to 800 mg kg −1 in acid-distilled samples. This color transition enables the semiquantitative visual detection of SO 2 residues, providing a rapid and intuitive assessment method. Furthermore, a smartphone application integrated with advanced machine learning algorithms has been developed to facilitate the precise quantification of SO 2 through the red–green–blue analysis of fluorescence images, achieving a limit of detection of 9.22 mg kg −1 . The sensor system exhibited high accuracy with recovery rates ranging from 94.86% to 109.28% for complex food matrices. CONCLUSION The proposed multicolor fluorescent sensor represents a significant advancement in the intelligence, simplicity and efficiency of SO 2 residue detection in food samples. This method also offers a valuable reference for improving food safety and quality assurance. © 2025 Society of Chemical Industry.