Pre-Polarized Hydrophobic Conducting Polymer Solid-Contact Ion-Selective Electrodes with Improved Potential Reproducibility

Electrically conducting polymers (ECPs) are one of the most popular types of materials to interface ion-selective membranes (ISMs) with electron-conducting substrates to construct solid-contact ion-selective electrodes (SCISEs). For optimal ion-to-electron transduction and potential stability, the p-doped ECPs with low oxidation potentials such as PPy need to be generally in their conducting form along with providing a sufficiently hydrophobic interface to counteract the aqueous layer formation. The first criterion requires that the ECPs are in their oxidized state, but the high charge density of this state is detrimental for the prevention of the aqueous layer formation. We offer here a solution to this paradox by implementing a highly hydrophobic perfluorinated anion (perfluorooctanesulfonate, PFOS–) as doping ion by which the oxidized form of the ECP becomes hydrophobic. The proof of concept is shown by using polypyrrole (PPy) films doped with PFOS– (PPy-PFOS) as the solid contact in K+-selective SCISE...