We investigated the effect of the presence of an additive anion while forming a self-assembled monolayer of a thiol-functionalized redox active species upon the behavior in aqueous solutions. A bromide salt was added in an acetonitrile solution of a thiol-functionalized viologen (viologen-thiol: N-pentyl-N′-(11-mercapto)undecyl-4,4′-bipyridinium bishexafluorophosphate) in which the self-assembled monolayer was formed on a polycrystalline Au electrode. We examined the structure and electrochemical behavior of the resulting monolayer-modified electrode in three different aqueous electrolyte solutions. The viologen-thiol monolayer prepared in the presence of Br- exhibited obviously different behavior in both KBr and KF electrolyte solutions from that prepared in the absence of Br-. On the other hand, the difference was minor in KPF6 solution. The difference of the electrochemical behavior was represented by the coverage of the viologen-thiol and the formal potential of viologen dication/radical cation redox couple. The memory that the viologen-thiol monolayer was formed in the presence of Br- was retained in KF and KBr solutions, though it was erased in the electrolyte solution containing PF6-, which is a softer anion than Br-. However, no definitive difference of the film structure was deduced from the electroreflectance study in regard to the monomer content and the average orientation of the viologen moiety.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry
- Chemical Engineering(all)