Influence of oxygen and carbon dioxide on the electrochemical stability of poly(3,4-ethylenedioxythiophene) used as ion-to-electron transducer in all-solid-state ion-selective electrodes

The electrochemical stability of poly(3,4-ethylenedioxythiophene) (PEDOT) is studied in view of its use as ion-to-electron transducer (solid contact) in all-solid-state ion-selective electrodes (ISEs). PEDOT is electrochemically deposited on glassy carbon (GC) and the resulting GC/PEDOT electrodes are studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and potentiometry. Valinomycin-based all-solid-state K+-ISEs are constructed by placing a K+-selective poly(vinyl chloride) (PVC)-based membrane on the GC/PEDOT electrode (solid contact). The influence of dissolved O2 and CO2 on the potential of the GC/PEDOT electrodes and of all-solid-state K+-ISEs is studied. PEDOT is compared with polypyrrole (PPy) as the solid contact material. A significant difference between the two conducting polymers (CPs) is that PEDOT is less sensitive to O2 and CO2 (pH) than PPy. Therefore, PEDOT is a promising new candidate as ion-to-electron transducer (solid contact) in all-solid-state ISEs based on solvent polymeric membranes that are permeable to O2 and CO2.