Electrochemical and ellipsometric study of polypyrrol films in solutions containing ascorbic acid

The growth of polypyrrol layers on gold electrodes in phosphate solutions of pH = 6.7 was analyzed using “in situ” voltammetric and ellipsometric techniques. Significant variations in optical indices and thickness were detected as a function of the applied potential and the aging time of storage in phosphate solutions with or without ascorbic acid. More compact layers were grown at 1.4 V vs. RHE than by applying a lower potential. The more compact layers show a slow but progressive increase in thickness or swelling after several hours of storage in the electrolyte. This effect increases when the interface is cathodically polarized. Optical indices and thickness of the layers formed under the different applied potential/time programmes were estimated.