Assembly of electroactive ordered multilayer films of cobalt phthalocyanine tetrasulfonate and polycations

Films with alternating layers of the anion cobalt phthalocyanine tetrasulfo nate ((CoPcTS4-)-Pc-II) and cationic polydimethyldiallylammonium chloride ( PDDA) were prepared by electrostatic layer-by-layer adsorption. Quartz crys tal microbalance and optical studies demonstrated formation of smooth ultra thin films with a linear increase in thickness with the number of depositio n steps. Films containing 1, 2, 3, 4, and 5 bilayers of (CoPcTS4-)-Pc-II/PD DA on a gold electrode gave reversible, reproducible steady state cyclic vo ltammetry for the Co-II/Co-I redox couple with midpoint potential at -0.28 V vs a saturated calomel reference electrode. Voltammetry was controlled pr edominantly by charge transport processes in the film, even for films conta ining only a bilayer of PDDA/(CoPcTS4-)-Pc-II. The peak reduction current i ncreased with the number of layers and showed a tendency to saturation afte r a deposition of 4-5 bilayers, (C) 1999 Academic Press.