An ESIPT-based fluorescent turn-on probe with isothiocyanate for detecting hydrogen sulfide in environmental and biological systems.

A probe with an isothiocyanate group was synthesized and evaluated for its H2S sensing ability. Upon addition of H2S, the probe exhibited ratiometric properties during absorption with a red-shift. The probe exhibited fluorescent off-on responses towards H2S via the ESIPT process, due to the conversion of isocyanate into amine. UV-vis, fluorescence, and 1H NMR spectroscopic analyses were performed to investigate the sensing mechanism. The probe has a large Stokes shift, short response time, and low detection limit. It can be used to estimate H2S levels within the range of 0-36 nM. The practical applicability of the probe was demonstrated using water samples and living cells.