Rational Design of A NIR Ratiometric Fluorescent Probe with Large Stokes Shift for Sulfite Detection

Sulfite (SO3 (2-)), as an SO2 derivative and important reactive sulfur, plays a vital role in the food industry and various physiological processes. So, it is urgent to seek out an effective method for SO3 (2-) detection. This work, inspired by the increase of electron-donating groups or electron-withdrawing groups in the molecular structure has a significant effect on the shift of fluorescence emission spectrum, and the nucleophilic addition reaction of SO3 (2-) to C=C double bond can make a noticeable change in fluorescence spectra. Two cyanine-based fluorescent probes BBHy and NBHy were reasonably designed and synthesized. Among them, near-infrared emitting NBHy with large Stokes shift (277 nm) and fluorescence intensity change in the presence of SO3 (2-) was selected, and then NBHy displayed superior recoveries for SO3 (2-) detection in food samples. Besides, NBHy was also successfully applied for SO3 (2-) sensing in living cells through dual-channel fluorescence imaging, which confidently confirmed the feasibility of our probe design.