An ESIPT characteristic "turn-on" fluorescence sensor for Hg2+ with large Stokes shift and sequential "turn-off" detection of S2- as well as the application in living cells

An excited state intramolecular proton transfer (ESIPT) characteristic "turn-on" fluorescence sensor for Hg2+ with large Stokes shift was fabricated and then it had ability to sequentially detect S2- by the "turn-off" fluorescent signal in aqueous media. On account of it, a simple fluorescence probe ol-PIP based on the phenanthro [9,10-d]imidazole moiety bearing two phenol fragments was synthesized, Probe ol-PIP showed gradually the fluorescence enhancement with the increasing of water fraction due to the aggregation affect. Sequentially, the moderate fluorescence emission of ol-PIP in aqueous media was continuously and selectively illumined by the successive addition of Hg2+ with about 180 nm Stokes shift. Furthermore, the persistent "turn-on" fluorescence intensity could be quenched to the original state of ol-PIP in presence of S-2(-). This on-off sensing process was sustained for five times with the alternative addition of Hg2+ and S2-. The limits of detection for Hg2+ and S2- were 6.45 x 10(-7) and 3.46 x 10(-7) M, respectively. In addition, ol-PIP was successfully applied in Hg2+ detection in real water samples; simultaneously, ol-PIP with low cytotoxicity was also successfully used as a bioimaging reagent to detect Hg2+ and S2- in living cells.