A porphyrin-based near-infrared fluorescent sensor for sulfur ion detection and its application in living cells

Sulfide anion (S 2− ) has been known as toxic species for many years. Notably, hydrogen sulfide (H 2 S), as its protonated product, is recently recognized as the third endogenous gaseous transmitter and is related to many diseases. Thus, it is of vital importance to achieve rapid, sensitive and selective detection of S 2− in various conditions. Herein, we firstly report a novel porphyrin-based NIR turn-on fluorescent sensor for S 2− detection. The pristine sensor displays weak fluorescence due to the photo-induced electron transfer (PET) process which occurs from porphyrin fluorophore to the electron-withdrawing 2,4-dinitrobenzenesulfonyl group. Upon being with S 2− , the 2,4-dinitrobenzenesulfonyl group of the sensor is efficiently removed and the significant NIR fluorescence enhancement can be observed. Exhibiting a large NIR fluorescence turn-on signal, the sensor shows high sensitivity, high selectivity as well as quick response (∼60   s) when detecting S 2− . Moreover, it displays very low cytotoxicity and can be employed to monitor S 2− levels in tap water and living cells. Overall, this simple strategy may be used for development of NIR fluorescent sensors towards a wide variety of analytes.