On-site fluorescent sensing of saccharin using a novel AIE Cd-MOF based on the competitive coordination reaction

This study introduces an on-site ratiometric fluorescence method for saccharin detection based on a novel AIE fluorescent Cd-MOF (MOF-1/Rh6G). The sulfur atom in saccharin competitively coordinates with the Cd(II) centers in MOF-1, disrupting the framework and releasing the AIE ligands into the solvent. This collapse triggers fluorescence quenching at 438 nm and furnishes the responsive signal, while the fluorescence of Rh6G at 551 nm remains stable and serves as an internal reference. Upon saccharin addition, the F₅₅₁/F₄₃₈ ratio increases linearly, accompanied by a visible color change from light blue to yellow-green. The fluorescent intensity ratio F₅₅₁/F₄₃₈ shows a good linear relationship with saccharin concentration and achieves a LOD of 0.884 μM. A point-of-care testing method integrating smartphone color hue recognition for saccharin sensing was developed. Furthermore, this proposed method has been successfully applied to monitor saccharin in food samples, and its accuracy has been verified using high-performance liquid chromatography method.