Fluorescent dialdehyde-BODIPY chitosan hydrogel and its highly sensing ability to Cu²⁺ ion

Fluorescent hydrogel with proper hydrophilicity and thermal stability, excellent sensitivity and high selectivity has important practical and scientific significance, especially in heavy metal ion detection. In this work, by adjusting the content of [2, 6-Bis-[4-formylthiophene]]-1,3,5,7-tetramethyl-8-phenyl-4, 4-difluoroborazaindoloene (B3), as a cross-linking agent, a series of chitosan- fluoroboron dipyrrole-chitosan-based fluorescent hydrogels (CBC) with large stokes shift were designed and prepared. The hydrogels can be used as fluorescent probes for identifying Cu²⁺ in aqueous solution. The linear quenching range of Cu²⁺ is 0-50 μM, and the detection limit and quenching constant are 4.75 μM and 3.52 × 10⁴ M^-1, respectively. Under the interaction of Cu²⁺, the imine bond CN was converted to C- N bond, which causes the phenomenon of fluorescence quenching. In addition, relatively high crosslink density improves hydrophilicity and thermal stability of initial chitosan, and made the swelling ability better.