Novel chitosan-naphthalimide-amino acid fluorescent powder for selective detection and removal of Hg2+/Hg+ and Fe2+ in aqueous solution

Heavy metal ions are harmful to the environment and the human beings and other creatures. Fluorescent agents play important roles in the detection of heavy metals. Chitosan-based fluorescent probes were synthesized and investigated in this work. Firstly, 4-bromo-1,8-naphthimide was introduced into chitosan through nucleophilic addition-elimination reaction, and then the Br was replaced by amino acid through substitution reaction. By this way, three chitosan-naphthalimide-amino acid fluorescent probes were obtained consequently. The structure and fluorescence properties of macromolecular probes were characterized and confirmed. These macromolecules have good selectivity and sensitivity to Hg2+/Hg+, and Fe2+ ions. When Hg+/Hg2+ ions are present, the probe P1 produces a significant increase in fluorescence intensity. The LOD of P1 to Hg+ and Hg2+ are 1.66 x 10(-6) M and 1.60 x 10(-6) M, respectively. When Fe2+ ions exist with the presence of P2 and P3 probes, P2 and P3 show significant fluorescence quenching, and their LODs are 1.09 x 10(-6) M and 6.65 x 10(-7) M, respectively. And these three chitosan derivatives also have good adsorption effect on ions, the maximum adsorption capacity of mercury can reach 108.7 mg/g, and the maximum adsorption capacity of ferrous iron can reach 52.0 mg/g. This mechanism of recognition and adsorption is formed as the complexation of N and ions on the probe. In this article, a material with good recognition, and removal of Hg+/Hg2+ and Fe2+ is developed, which also provides a way for the potential remediation of heavy metal polluted water.