Water soluble chitosan-amino acid-BODIPY fluorescent probes for selective and sensitive detection of Hg2+/Hg+ ions

Three chitosan-BODIPY probes were prepared in this work. The water solubility of original chitosan has been improved. Water soluble fluorescent probes were obtained. They also exhibited good sensing ability to Hg2+/Hg+ ions. Firstly, through the amidation reaction, arginine, cysteine, and tryptophan were grafted respectively onto chitosan chains. And then chitosan-BODIPY probes were produced by means of Schiff base formation reaction. By this way, the high structural regularity of chitosan polymer chains was changed with introducing amino acids and fluorescent groups. It also endowed fluorescence sensing ability. They could recognize Hg2+/Hg+ ions with the interaction of CN groups. It could selectively recognize Hg2+/Hg+ in aqueous solution, the detection limits reached 0.747μM/0.783 μM. Moreover, by the introduction of hydrophilic groups, the contact angle of modified chitosan film was improved as well. It realized performance transformation from the hydrophobic to hydrophilic. The viscoelasticity, thermal, rheological properties and fluorescence properties of the hydrogels were investigated. CN groups not only acted as a binding site to coordinate with heavy metals, but also could enhance the water solubility of the fluorescent chitosan.