Development of paper-based chemosensor for the detection of mercury ions using mono- and tetra-sulfur bearing phenanthridines

Abstract

A new and simple fluorescent probe bearing mono-sulfur (1) and tetra-sulfur (2) tetrahydrodibenzo phenanthridine derivatives were synthesized and examined for their cation recognition abilities towards different cations in aqueous acetonitrile solution and paper strips. Both the probes showed high selectivity and sensitivity with strong affinity towards Hg²⁺ ions over other cations, such as Cu²⁺, Ca²⁺, Co²⁺, Cd²⁺, Pb²⁺, Zn²⁺, Ni²⁺, Mg²⁺, Mn²⁺, Al³⁺, Fe³⁺, La³⁺, Ag⁺, K⁺, Na⁺ and Li⁺. The binding stoichiometry ratios of 1–Hg²⁺ and 2–Hg²⁺ are recognized as 1 : 1 according to the UV-Vis absorption spectra, fluorescence measurements and computational (DFT) studies, and the possible binding mode of these receptors with Hg²⁺ is also proposed. The limit of detection with Hg²⁺ cation was found to be as low as 0.91 nM and 0.041 nM for probes 1 and 2, respectively. The results clearly indicate that the synthesised tetrahydrodibenzo phenanthridine derivatives 1 and 2 could be used as excellent chemosensors for Hg²⁺ detection in biological and environmental samples.