A novel ESIPT fluorescent probe based on 1,3,4-thiadiazole and coumarin for sequential detection of Cu2+ and H2S and its application in food samples

Here, 2-(2-hydroxy phenyl)-1,3,4-thiadiazole was used as fluorophore with ESIPT effect and a new fluorescent probe for sequential detection of Cu²⁺ and H₂S in food, environment and biological imaging was rationally designed and synthesized by the arrival of coumarin. The effects of molecular structure modification on ESIPT characteristic were investigated thoroughly. Identification mechanism, especially the recognition site was discussed in detail with the help of DFT calculations, ¹H NMR titration and HRMS analysis. Based on the settling effect of H₂S on Cu²⁺, significant “on-off-on” fluorescence change was obtained and sequential detection of Cu²⁺ and H₂S was achieved. The detection limits for sequential detection of Cu²⁺ and H₂S were as low as 78.0 nM and 52.2 nM. In view of the good performance, probe was successfully applied to precise quantitative detection of target substances in foodstuff such as actual water samples, traditional Chinese medicine, red wine and fruits.