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

Abstract Based on the known deprotection reaction of thioacetal initiated by Hg2+, 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 Hg2+ in THF-H2O (fw = 5%) mixed system. The addition of Hg2+ greatly enhances the fluorescence intensity of the probe and changed from dark blue to green fluorescence. Within a large Hg2+ concentration range (0–6×10−5 mol·L−1), the fluorescence intensity at 480nm presents good linear with the Hg2+ concentration (R2 = 0.993), and the detection limit of the probe to Hg2+ 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 Hg2+ 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 Hg2+ adding. The results show that the probe based on DTCB has potential application prospect in actual sample analysis.