The mechanism underlying the chemical charge release is not trivial: where does the electron transfer take place? Two scenarios are plausible: (i) the reduction agent diffuses into the film structure, followed by electron transfer, and (ii) the electron transfer takes places at the thin film-water interface (Fig- ). The latter process includes a cascade of electron transfer processes between the iron complexes of the MAs. To distinguish between these two possibilities, we carried out the following experiments: The CV of bare ITO/PET in an aqueous solution of ferrocyanide (5.0 mM) showed the oxidation and reduction of the reducing agent (range: -1.0 V to 1.1 V) (Figure , black). However, no electrochemical signal was observed at the expected voltage (E 0 = 0.2 V) when the working electrode was modified with six layers of the iron complex (3) (Figure , purple). This observation indicates that the modified electrode prohibits the ferrocyanide from interacting directly with the metal-oxide surface of the working electrode. In addition, by scanning to higher potentials, we observed a catalytic peak starting at the onset potential (Vox= 0.7 V) of complex 3 (Figure , red). This observation suggests a continuous regeneration of the film by ferrocyanide; the absence of an electrochemical reduction peak proves the chemical reduction pathway of [Fe] 3+ . Although other pathways cannot be rigorously excluded, these results and the fast kinetics of the chemical reduction make an electron transfer process at the thin film-water interface likely.