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

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+.