Facile method to synthesize fluorescent chitosan hydrogels for selective detection and adsorption of Hg2+/Hg+

Fluorescent chitosan-based hydrogel for the selective detection and adsorption of Hg 2+ /Hg + in aqueous environment was prepared through three-step synthesis strategy. NO 2 -Boron-dipyrrolemethene (BODIPY) was prepared firstly, and then the -NO 2 group was reduced to -NH 2 group. Finally, the NH 2 -BODIPY was introduced to chitosan by Schiff base formation reaction through bi-aldehyde. Eventually, fluorescent chitosan hydrogel was obtained. The as-prepared fluorescent hydrogel probe could detect Hg 2+ /Hg + through PET mechanism with the detection limit of 0.3 μM. The recognition site which combines Hg 2+ /Hg + is C N, it is just formed in the reaction with chitosan and the amino group on BODIPY. Adsorption capacity of the fluorescent hydrogel is 121 mg·g −1 , which is almost seven times of the original chitosan. The isotherm and kinetics of Hg 2+ /Hg + removal follows Langmuir isotherm and pseudo-second order kinetics , respectively. Besides, a series of fluorescent hydrogels were prepared to compare the elasticity, hydropHilicity , fluorescence intensity and adsorption capacity.