A dual chemosensor for Cu2+ and Hg2+ based on a rhodamine-terminated water-soluble polymer in 100% aqueous solution

Abstract

A novel water-soluble polymer bearing a rhodamine receptor (PEGSRh) was synthesized as a dual chemosensor for the recognition of Cu²⁺ and Hg²⁺ in 100% aqueous solution. PEGSRh not only exhibited a sensitive colorimetric response towards Cu²⁺ and Hg²⁺ but also showed a selective turn-on fluorescence response towards Hg²⁺ over other metal ions. The binding stoichiometry for the complexation of PEGSRh with Cu²⁺ and Hg²⁺ was confirmed to be 1 : 1 by Job plot analysis. The low detection limits were found to be 5.92 × 10⁻⁷ M for Cu²⁺ and 2.85 × 10⁻⁶ M for Hg²⁺. The responses of PEGSRh to Cu²⁺ and Hg²⁺ were both stable over wide pH ranges. In addition, the fluorescence intensity changes of PEGSRh solution by the inputs of Hg²⁺, Cu²⁺ and EDTA have been used to construct a combinational logic gate. Again, an INHIBIT logic gate was also obtained by employing Cu²⁺ and EDTA as the chemical inputs and the absorbance signal as the output. Moreover, test papers were prepared facilely using PEGSRh for practical on-site detection of Cu²⁺ and Hg²⁺.