Rhodamine-based conjugated polymers: potentiometric, colorimetric and voltammetric sensing of mercury ions in aqueous medium.

Herein, we report the synthesis and characterization of a new rhodamine-based monomer (RD-CZ), and an investigation of the optical and electrochemical properties of the corresponding polymer (P(RD-CZ)), which was electropolymerized on an ITO electrode. The resulting P(RD-CZ) polymer film was used as a simple and novel multi-signal sensor platform, which demonstrates ion-selective potentiometric, colorimetric and voltammetric responses in aqueous media for the first time. P(RD-CZ) exhibits excellent selectivity for Hg ions compared with Cd, Cu Zn, and Fe using the potentiometric technique, which depends on the increasing charge carrier transport through rhodamine-bound Hg with a limit of detection (LOD) of 9.77 × 10 M. The P(RD-CZ) polymer film also exhibits a distinct color change from orange to purple, which is detectable even by the naked eye, in the presence of Hg ions. The LOD for Hg ions obtained using the colorimetric method is 3.16 × 10 M. The same material has also been used for the voltammetric sensing of Hg in aqueous media with a detection limit of 1 × 10 M. In this study, a conductive polymer-based sensor platform for detecting mercury ions via three different methods has been designed for the first time. By doing so, a disposable planar paper-based ion-sensing platform, which is suitable for low-cost point-of-care and in-field testing applications, could be fabricated with a highly reproducible and linear response towards different concentrations of analyte ions in aqueous and biological samples.