Preparation and characterization of poly(5-aminoindole) by using electrochemical quartz crystal nanobalance technique

The electrochemical quartz crystal nanobalance (EQCN) was employed to study the electropolymerization of 5-aminoindole on platinum electrodes in acidic media. Potentiostatic or potential cycling electrooxidation of 5-aminoindole below 0.62 V vs. SCE leads to the formation of uniform, yellow, electrochemically active polymeric films. A scheme of the redox transformations of poly(5-aminoindole) which involves protonation-deprotonation steps accompanying the electron transfer is suggested. At higher positive potentials, further oxidation takes place resulting in different blue-purple, indigo-type materials which remain attached to the metal surface but show decreased or no redox activity.