Sulfur dioxide (SO₂) maintains a certain steady state balance in the body, high concentration SO₂ will be harmful to human health. Seeking a suitable detection method to monitor sulfur dioxide in real time becomes an urgent requirement owing to the transient nature of sulfur dioxide in organisms. Here, a novel NIR ratiometric fluorescent probe for detection of SO₂ was developed based on a conjugation of coumarin and indol salt with excellent water solubility. The probe Mito-CI displayed highly sensitive (69 nM), fast response time (30 s), large Stokes shift (174 nm) and the NIR fluorescence emission wavelength (655 nm). In the reversibility process of the SO₃⁻-probe Mito-CI system induced by HCHO in vitro was also detected. Besides, cell imaging showed that Mito-CI possesses mitochondria-targeted ability. Particularly, Mito-CI was proved to reversibly detect SO₂/HCHO in living cells.

二氧化硫（SO ₂）在体内保持一定的稳态平衡，高浓度的SO ₂对人体健康有害。由于生物体内二氧化硫的瞬态性质，寻求一种实时监测二氧化硫的合适检测方法已成为当务之急。在此，基于香豆素和吲哚盐的共轭物，具有优异的水溶性，开发了一种新型的用于检测SO _2的近红外比率荧光探针。Mito-CI探针显示高灵敏度（69 nM），快速响应时间（30 s），大斯托克斯频移（174 nm）和近红外荧光发射波长（655 nm）。在SO的可逆性过程₃ ^- -probe三刀-CI还检测到了HCHO体外诱导的系统。此外，细胞成像表明，Mito-CI具有线粒体靶向能力。特别是，证明了Mito-CI可逆地检测活细胞中的SO ₂ / HCHO。