A novel carbazole-based highly sensitive and selective turn-on fluorescent probe for mercury (II) ions in aqueous THF

Based on the known deprotection reaction of thioacetal initiated by Hg 2+ , a new type of fluorescent probe 3-(4-(1,3-dithiolan-2-yl) phenyl)-9H-carbazole (DTCB) is designed and synthesized successfully. The probe shows a good fluorescence response to Hg 2+ in THF-H 2 O ( f w  = 5%) mixed system. The addition of Hg 2+ greatly enhances the fluorescence intensity of the probe and changed from dark blue to green fluorescence. Within a large Hg 2+ concentration range (0–6×10 −5 mol·L −1 ), the fluorescence intensity at 480nm presents good linear with the Hg 2+ concentration (R 2  = 0.993), and the detection limit of the probe to Hg 2+ is below 2.05×10 −7 mol·L −1 . The DTCB probe shows good selectivity and anti-interference performance, and many metal ions and anions hardly effect on its detection performance. The sensing mechanism is confirmed by theory calculation based on DFT and TD-DFT theories, and the intramolecular charge transfer (ICT) is responsible for the significant fluorescence change of probe DTCB. Meanwhile, the probe is applied to the detection of Hg 2+ in real water samples; and it is interesting that the DTCB-based test strip firstly reveals the strong fluorescence from solid-state 3-(4-formylphenyl)-9H-carbazole (FCB) with Hg 2+ adding. The results show that the probe based on DTCB has potential application prospect in actual sample analysis.