Highly sensitive and selective fluorescent monomer/polymer probes for Hg2+ and Ag+ recognition and imaging of Hg2+ in living cells.

The detection of heavy metals such as Hg2+ and Ag+ is important and urgent. In this work, - NO2/- NH2/C=S boron dipyrromethene small molecular derivatives were synthesized at first. Then they were incorporated into polymer chains. The macromolecular fluorescent probes were obtained via Sonogashira reaction using the small molecular probes as building blocks. The as-prepared small-molecule fluorescent probe BO3 exhibits high sensing performance for Hg2+. By introducing it into macromolecules, the sensing ability still remains, and even more, the recognition performance is improved. The macromolecular fluorescent probes P1, P2, and P3 also have high recognition ability for Ag+ with a binding ratio of 2:1 (metal ion to probe ratio). Through the study of the sensing mechanism and the recycling experiments, it is found that the probes responded by the photo-induced electron transfer mechanism and can be recycled and reused. At the same time, BO3, P2, and P3 show excellent recognition performance for Hg2+ in living cells and zebrafish. Living cell imaging experiments indicated that these fluorescent probes had good cell membrane permeability and low cytotoxicity, and could realize bioimaging of Hg2+. Therefore, the application value of these fluorescent probes could be enlarged. Graphical abstract.