Polymer films on electrodes. Part 23. Ellipsometric study of the electrochemical redox processes of a thionine film on a glassy carbon electrode

Ellipsometry was used to observe the in situ electrochemical redox processes of a thionine film that was electrochernically deposited (thickness > 70 nm) on a glassy carbon electrode at 1.2 V from a 0.05 M H₂SO₄ solution containing 50 μM thionine. To determine the spatial distribution of the oxidized and reduced states during the reduction and oxidation of the film, the conversion process was simulated by a multilayer film model, where 8 or 9 discrete film layers were considered. Such simulations of the ellipsometric results show that the redox conversion of a thionine film proceeds from the electrode/film interface towards the solution and is controlled by electron hopping.