Designing of a high-performance fluorescent small molecule enables dual-mode and ultra-sensitive fluorescence visualizing of HSO3− and HClO in dried fruit, beverage, and water samples

Herein, a novel hemicyanine derivative (E)-3-(1,1-dimethyl-2-(4-(methylthio)styryl)-1H-benzo[e]indol-3-ium-3-yl)propane-1-sulfonate (BIS) has been reasonably designed. Compound BIS is long-wavelength emissive and water-soluble with a large Stokes shift. Intriguingly, probe BIS provides a dual-mode fluorescence response pattern for the sensing of bisulfite (HSO3-) and hypochlorous acid (HClO) with great limit of detections (3.6 and 57.4 nM). First, the 1,4-Michael addition of HSO3- on the conjugated double bond triggers a ratiometric response (I465/I575). Second, the rapid oxidation of HClO on the thioether moiety provides a turn-on response (I575). Evaluation of HSO3- and HClO levels in dried fruit, beverage, and water samples has been carried out with satisfactory results. Moreover, motivated by an impressive chromatic variation (red to blue), smartphone-assisted signal readout system and thin-film sensing platform are facilely constructed for real-time and on-site measurement of HSO3- levels. Furthermore, probe BIS is used for the in vivo imaging of HSO3- in edible fish models.