A twisted intramolecular charge transfer probe for rapid and specific detection of trace biological SO2 derivatives and bio-imaging applications.

We reported a reactive probe for HSO3(-), which showed a colorimetric and ratiometric fluorescence response to HSO3(-) with fast response (t1/2 = 20 s), good specificity and low detection limit (3.0 nM). The probe was cell membrane permeable and successfully used for visualizing trace SO2 derivatives in living cells.