A FRET-based NCA fluorescent probe for highly sensitive and selective detection of hydrogen sulfide

A Förster resonance energy transfer (FRET)-based fluorescent probe (NCA) was developed for highly sensitive and selective detection of hydrogen sulfide (H₂S). In this design, coumarin (CA) serves as the fluorescent donor and nitrobenzoxadiazole (NB) acts as an energy acceptor and reactive site. Upon exposure to H₂S, cleavage of the NB unit interrupts the FRET process and restores CA fluorescence, producing a 16-fold signal enhancement at 463 nm with a detection limit of 0.11 µM. Under optimized conditions (Britton–Robinson (BR) buffer, pH 8, 15 min), NCA enables rapid and selective detection of H₂S over competing biological species. Practical applications were demonstrated by integrating NCA into a smartphone-assisted test strip platform, which achieved recoveries of 98.7–109.9% in tap and lake water. Furthermore, NCA successfully imaged both endogenous and exogenous H₂S in human lung carcinoma (A549) cells with low cytotoxicity. These results highlight the potential of NCA as a versatile tool for environmental monitoring and biological studies of H₂S.