Design of a novel naked-eye and turn-on fluorescence sensor based on the 5,10,15,20-(4-sulphonatophenyl) porphyrin (TPPS4)-Hg2+ system: Monitoring of glutathione (GSH) in real samples and DFT calculation

In the present work, we proposed a novel naked-eye and turn-on fluorescence sensor based on the 5,10,15,20-(4-sulphonatophenyl) porphyrin (TPPS 4 )-Hg 2+ system with short assay time and high sensitivity to detect glutathione (GSH) in real samples. The TPPS 4 was the first time to detect GSH because of its high fluorescence quantum yield. The initial fluorescence from TPPS 4 was quenched by Hg 2+ with an electron transfer process. However, when put a certain concentration of GSH into this system, the fluorescence sensor was turned to the “on” state, which was related to a competitive affinity of Hg 2+ to GSH and the N atoms of porphyrin ring. Under the optimal conditions, the naked-eye detection limit was 0.43   nM and the limit of detection (LOD) was arrived to 16 fM (S/N   =   3) for GSH. The linear regions are obtained by two ranges varying from 0 to 28.5   μM and from 38.15 to 61.87   μM. Furthermore, it was confirmed that the TPPS 4 -Hg 2+ fluorescence probe has excellent selectivity, high sensitivity and quick fluorescence response for GSH.