A ratiometric fluorescent sensor based on dual-emitting carbon dots for the rapid detection of sulfite

Sulfur dioxide (SO₂) derivatives are typically employed as antioxidants in food and pharmaceutical processing. However, excessive sulfite intake could trigger serious health problems. Hence, it is urgent to establish a rapid and effective system for monitoring SO₂. This study adopted a one-step hydrothermal method to synthesize dual-emitting nitrogen-doped carbon quantum dots (CECDs) and developed a ratiometric sensor for sulfite using CECDs-Cr (VI) composites. The emission intensity ratio (I₄₄₀/I₅₀₀) of the CECDs-Cr (VI) composites increased considerably with the addition of HSO₃^-. A method based on the ratiometric sensor was established for SO₂ derivatives with advanced efficiency and excellent linearity over a broad concentration range of 0-500 μM (R² = 0.9946). Four medicine-food homology materials (MFHMs) fumigated with sulfur have been accurately detected using this approach. Furthermore, a portable test tube was prepared to achieve rapid and semi-quantitative detection of SO₂ residues and applied to real samples. This work presents an effective approach to develop a rapid on-site detection platform for sulfite residues in food and pharmaceuticals.