Design and Synthesis of two novel carbazole-based fluorescent probes and their application in detecting Hg²

Mercury is a highly toxic and non-degradable heavy metal pollutant that poses great harm to human health and the ecological environment. Two novel carbazole based thioacetal fluorescent probes 4a and 4b for highly sensitive and selective detection of Hg²⁺ have been designed and synthesized. Though both probes 4a and 4b can detect Hg²⁺ through thioacetal deprotection reaction, due to the difference in structural stability and the AIE effect of probe 4a, probe 4a has higher selectivity and sensitivity, with a detection limit as low as 5.1 × 10^-8 M and a response time of approximately 25 s. In addition, probe 4a can detect Hg²⁺ under the solvent systems with high water content, thus we have successfully applied probe 4a to the detection of Hg²⁺ in actual water and soil samples, and used it as test strips.