| Abstract: | Bilayers composed of polypyrrole: doped by perchlorate ions (PPy(ClO4) – anion exchanging inner layer) and by dodecyl sulfate ions (PPy(DS) – cation exchanging outer layer) are very effective charge trapping systems that are usually not observed for other bilayers comprised of polypyrrole. Chronopotentiometric experiments carried out for oxidation and reduction showed that the trapping effect in the inner layer resulted from different ion exchange properties of the component polymers, leading to a low permeability of the reduced outer layer towards anions. Estimated diffusion coefficients of Cl? anions in the oxidized and reduced PPy(DS) are in the range of 10?9 and lower than 10?10 cm2 s?1, respectively. The presence of the outer layer limiting the ion transfer was found to be beneficial to improve the signal resolution in amperometric mode of ion sensing within wide KCl concentration range, from 10?5 M up to 3 M. The influence of experimental conditions (film thickness, response time) on optimization of this novel kind of polymeric bilayer ion sensors was studied. |
