Water-soluble β-cyclodextrin based turn-on amplifying fluorescent probes for sensitive and selective detection of Hg2+/Hg+ ions

Abstract

In this work, fluorescent β- cyclodextrin (β-CD) based probes containing naphthalimide group were synthesized to realize the specific recognition of Hg2+/Hg+ in aqueous system. Firstly, three small fluorescent molecules (N1, N2 and N3) with -NH2 groups were synthesized from 4-bromo-1, 8-naphthalene anhydride. Secondly, CHCCH2- group was introduced into β-CD by Williamson ether formation reaction. Finally, the target probes (β-CD-PI, β-CD-PY and β-CD-TP) were obtained by Amino-Yne click reaction. These probes can efficiently recognize Hg2+/Hg+. β-CD-PI emits bright yellow fluorescence after binding with Hg2+/Hg+, which is a turn-on fluorescent probe. When the Hg2+/Hg+ concentration exceeds 26 μM, the fluorescence intensity amplifies sharply (20 folds). The hydrophobic parts of the probes aggregated together to form a micelle-like structure due to complexation with Hg2+/Hg+, resulting in special micelle-sensitizing properties. Meanwhile, the HOMO-LUMO energy levels of the probes were calculated by cyclic voltammetry (CV). The probe is expected to be used for the detection of Hg2+/Hg+ in aqueous solutions without any organic solvents.