Synthesis and Application of Triazolothiadiazole-Coumarin Based Ratiometric Fluorescent Probes for Highly Selective Detection of H2S

Three triazolothiadiazole-coumarin based ratiometric fluorescent probes (4a similar to 4c) for detection of H2S were designed and synthesized. Their structures were confirmed by IR, NMR and HRMS. Through fluorescence spectra, the probes expressed excellent fluorescent properties, which indicates that the design of the molecular structure was rational. The three probes all displayed highly quantum yields ( 0.6752, 0.6639, 0.6128), large Stokes shift (138, 131, 128 nm).They all exhibited high selectivity and sensitivity against H2S. The limit of detection were 0.19, 0.21 and 0.25 mu mol.L-1 respectively. Especially, probe 4a has the optimum efficiency,this result shows that the electron-donating group at 4-position of benzene is in favor of the optimization of fluorescent properties, owing to the accretion of electron density of the conjugated system. Besides, the three probes were all able to sense H2S by "naked-eye" according to the change in color from colorless to deep yellow. The probes can be applied to recognize H2S in actual water samples qualitatively and quantitatively.