Electrode modified by sulfonated calixarenes immobilized into a polypyrrole film: A step towards new ion-sensitive layers

Sulfonated calixarenes, calix[4]-p-tetrasulfonate and calix[6]-p-hexasulfonate have been included as dopants into polypyrrole films during their electrodeposition at the surface of a glassy carbon electrode. Taking into account the bulkiness of these cage molecules, they are irreversibly immobilized into the polypyrrole matrix. The complexation of the guest trimethyl(ferrocenylmethyl) ammonium cation, FcTMA(+), by these sulfonated calixarenes in solution has been used as a model host/guest reaction to detect the specific entrapment of the FcTMA(+) cation into the functionalized polypyrrole coating. The shift of the redox potential of the FcTMA(+) after complexing in solution or entrapping into the film are very closed. This confirms that the polypyrrole affinity for the FcTMA(+) cation is due to the specific recognition by the free cavity of the included sulfonated calixarenes.