A carbazole-benzothiazole-based fluorescent probe embedded in paper, cellulose, and chitosan sensors for visual and rapid detection of bisulfite in food samples.

Bisulfite (HSO3-) is widely used as a food additive, yet its excessive residue poses potential health risks. Herein, a novel fluorescent probe TC-FV-BT was developed for the detection of HSO3-. Upon addition of HSO3-, the nucleophilic addition disrupted the π-conjugation of the probe, giving rise to a distinct fluorescence enhancement with bright orange emission. TC-FV-BT exhibited a rapid response, a low detection limit of 0.077 μM, and excellent selectivity. The sensing mechanism was confirmed by 1H NMR titration, HRMS, and DFT calculations. Furthermore, TC-FV-BT was successfully immobilized onto paper, cellulose acetate (CA), and chitosan (CS) film substrates to construct a portable visual detection platform, which was applied to the analysis of HSO3- in ten complex food matrices. Notably, the CS film-based sensor displayed superior anti-interference performance in high-oil and high-pigment samples. This work provides a versatile and practical platform for on-site rapid monitoring of HSO3- in food safety applications.