Potentiometric Ag+ sensors based on conducting polymers: A comparison between poly(3,4-ethylenedioxythiophene) and polypyrrole doped with sulfonated calixarenes

Potentiometric Ag+ sensors were prepared by galvanostatic electropolymerization of 3,4-ethylenedioxythiophene (EDOT) and pyrrole (Py) on glassy carbon electrodes by using sulfonated calixarenes as doping ions. Poly(3,4-ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy) doped with p-sulfonic calix[4]arene (C4S), p-sulfonic calix[6]arene (C6S) and p-sulfonic calix[8]arene (C8S) were compared. PEDOT and PPy doped with poly(styrene sulfonate) (PSS) were also included for comparison. The analytical performance of the conducting polymer-based Ag+ sensors was studied by potentiometric measurements. All conducting polymer and dopant combinations showed sensitivity and selectivity to Ag+ compared to several alkali, alkaline-earth, and transition-metal cations. The type of the conducting polymer used for the fabrication of the electrodes was found to have a more significant effect on the selectivity of the electrodes to Ag+ than the ring size of the sulfonated calixarenes used as dopants. Selected conducting polymer-based sensors were studied by cyclic voltammetry (CV) and energy dispersive analysis of X-rays (EDAX) measurements. Results from the EDAX measurements show that both PEDOT- and PPy-based membranes accumulate silver.