Response mechanism of potentiometric Ag+ sensor based on poly(3,4-ethylenedioxythiophene) doped with silver hexabromocarborane

Potentiometric Ag+ sensors were prepared by galvanostatic electropolymerization of 3,4-ethylenedioxythiophene (EDOT) on glassy carbon electrodes by using silver 7,8,9,10,11,12-hexabromocarborane (Ag+CB11H6Br6-) as supporting electrolyte. The analytical performance of the resulting GC/PEDOT(CB11H6Br6-) sensors was studied by potentiometric measurements. The electrodes showed a selective response to Ag+ compared to several alkali, alkaline-earth, and transition-metal cations. Pretreatment of the electrodes by cyclic voltammetry was found to enhance their analytical performance. In order to elucidate the response mechanism, PEDOT(CB11H6Br6-) films were studied using scanning electron microscopy (SEM)/energy dispersive analysis of X-rays (EDAX), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Results from SEM/EDAX and AFM measurements showed that PEDOT(CB11H6Br6-) films accumulate silver after being conditioned in silver solution. XPS measurements show that the accumulated silver is mainly in the elemental form, in the outermost surface of the conducting polymer. CV shows two redox peaks from Ag+, which can be attributed to the presence of Ag+ complexes in the polymer film.