A novel flavone-based ESIPT ratiometric fluorescent probe for selective sensing and imaging of hydrogen polysulfides.

Hydrogen polysulfides (HS) as an important member of reactive sulfur species is closely relevant to many physiological functions in redox homeostasis and metabolism. Dual-channel monitor the changes of HS level in vivo is highly desired. Herein we design a simple ratiometric fluorescent probe based on flavone skeleton for highly selective detection of HS. The probe HF-NA-MC bearing 2-fluoro-5-nitrobenzoic acid group inhibited the intramolecular ESIPT process, which show the blue fluorescence of adjacent naphthalene unit. In the presence of HS, the enol form of probe is converted to conjugated keto form, resulted in a 90 nm red-shift of fluorescence emission from 450 nm to 540 nm. The ratiometric intensity (I/I) of the probe exhibits a good linear relationship toward HS in the range of 0-120 μM, and the detection limit is estimated to be 0.63 μM. The ratiometric fluorescent probe shows high specificity and anti-interference ability for HS over other related reactive sulfur species. The probe HF-NA-MC shows promising outlook and could be applied to the confocal imaging of HS by dual emission channels in Hela cells.