Ionophore-based ion-selective electrodes: signal transduction and amplification from potentiometry

Ionophore-based ion-selective electrodes (ISEs) are traditionally used in potentiometry to measure the open circuit potential against a reference electrode. However, the sensitivity of ISEs is limited by the well-
known Nernstian slope, which is not satisfactory for application in a narrow sample concentration range.Recently, several innovative methods have been proposed to develop chemical ion sensors by transducing the electrode potential into other electrochemical and optical signals including charge, current,electrochemiluminescence, fluorescence, and color change. These approaches result in signal
amplification and increased sensitivity. Moreover, they enable user-friendly colorimetric and self-powered sensing concepts that are very attractive to point-of-care testing and environmental monitoring. The
sensing concepts are highlighted in this perspective along with a discussion on the outstanding issues and challenges for the future.