Difluorinated H2S probe 1 is a fluorescent probe for hydrogen sulfide (H2S).1It selectively fluoresces in the presence of H2S over Zn2+, Fe3+, S2O32-, ClO-, SO32-, H2O2, NO2-, cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) when used at a concentration of 1 μM. Difluorinated H2S probe 1 displays excitation/emission maxima of 365/450 nm, respectively.