Voltammetric,chronoamperometric and chronoabsorptometric studies of the nucleation of n-heptyl viologen films on SnO2, silane-modified SnO2 and ion-beam-treated ito-metallized polymer films

Nucleation of the first monolayers of the n-heptyl viologen-bromide or-biphthalate films on SnO₂ electrodes was found to be accelerated by the addition of one molecular layer of dimethyldiethoxy (dmde)-silane to the SnO₂ surface. Partitioning of the reactant viologen into the non-polar surface layer and lowering of the surface tension against nucleation site growth in the silane layer may both be responsible for the enhanced nucleation rates. Similar acceleration of the nucleation of n-HV⁺ was found on ion-beam-etched indium-tin oxide-metallized polymer electrodes (MPOTE). A second nucleation site with a much lower, and distinguishable rate of nucleation, was produced on this type of electrode surface. Chronoamperometry and chronoabsorptometry were used to confirm that the nucleation of n-heptyl viologen cation-radical salts follows an instantaneous rather than progressive nucleation mechanism, on any of the surfaces studied.