Chongmok Lee, Juhyoun Kwak, Larry J. Keply, and Allen J. Bard, "Polymer films on electrodes Part 23. Ellipsometric study of the electrochemical redox processes of a thionine film on a glassy carbon electrode," J. Electroanal. Chem., 289 (1), 239 - 252 (1990.04.10.)

Abstract
Ellipsometry was used to observe the in situ electrochemical redox process of a thionine film that was electrochemically deposited (thickness > 70 nm) on a glassy carbon electrode at 1.2 V from a 0.05 M H2SO4 solution containing 50 mM thionine. To determine the spatial distribution of the oxidized and reduced states during the reduction and oxidation of the film, the conversion process was stimulated 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.