A new fluorescent turn-on probe for highly sensitive and selective detection of sulfite and bisulfite

Sulfur dioxide is a common air pollutant and extremely harmful to human health. After inhalation, SO2 is easily hydrated to two derivatives, sulfite and bisulfite. So it is valuable to develop an effective probe for these anions. In this work, a green-emissive fluorescent probe 1 is designed and synthesized, which employ 4-hydrazinyl-1, 8-naphthalimide as intramolecular charge transfer (ICT) fluorophore. Probe 1 is able to sense sulfite and bisulfite through fluorescence “turn-on” manner, and the detection limit for sufite is 0.56 μM. The green emission induced by sulfite and bisulfate can be observed by naked eyes under UV irradiation. Compared with other anions used, probe 1 shows great selectivity toward sulfite or bisulfite. We illustrate the possible recognition mechanism of probe 1 and sulfite by NMR analysis and molecular modeling experiments. The real-time monitoring of SO2 release and cell imaging of sulfite is also investigated.