Fluorescent chitosan-BODIPY macromolecular chemosensors for detection and removal of Hg2+ and Fe3+ ions.

The detection of heavy metals, such as Hg2+ and Fe3+, is of great significance. In this work, fluorescent small-molecule BODIPY (BY-3) bearing CC group was synthesized firstly. And then, the chitosan-based polymer sensor CY-1 was synthesized through the spontaneous NH2/C≡C click reaction. The synthesized CY-1 can effectively bind and recognize Hg2+/Hg+ by the -C=N groups formed in the click reaction. Moreover, the macromolecular sensors CS-1 and CS-2 were synthesized by incorporating another recognition sites to CY-1. These synthesized macromolecular sensors can not only recognize Hg2+/Hg+, but also effectively recognize Fe3+/Fe2+. All of them exhibited significant quenching effect, visible to the naked eye under UV irradiation. The detection limit of CY-1 for Hg2+ was 1.51 × 10-6 mol/L, and the detection limit of CS-2 for Fe3+ was 2.30 × 10-6 mol/L. The BODIPY-chitosan sensors synthesized in this work have the functions of removing heavy metal ions besides the identifying ability. The maximum adsorption capacity of 1 g chitosan to Hg2+ was 108 mg as the best one. This article provides a new method to prepare macromolecular sensors for the detection and removal of heavy metal ions. As a useful natural polymer, chitosan's application scope was enlarged.