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

In this work, fluorescent beta- cyclodextrin (beta-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, CH---CCH2group was introduced into beta-CD by Williamson ether formation reaction. Finally, the target probes (beta-CD-PI, beta-CD-PY and beta-CD-TP) were obtained by Amino-Yne click reaction. These probes can efficiently recognize Hg2+/ Hg+. beta-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 mu M, 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.

Automated summary

Fluorescent beta-cyclodextrin (beta-CD) based probes containing naphthalimide group were synthesized to specifically recognize Hg2+/Hg+ in aqueous systems. The probes exhibit enhanced fluorescence intensity when binding with Hg2+/Hg+, and the hydrophobic parts of the probes form special micelle-like structures due to complexation with Hg2+/Hg+. The probes have the potential for detecting Hg2+/Hg+ in aqueous solutions without the use of organic solvents.