Conductive SnO2 electrodes modified with a 1–2 monolayer thick coating of a cationic silane bind Al13O4(OH)283+-pillared montmorillonite. The cationic polymer provides binding sites, which are electrochemically accessible to the SnO2 electrode, for iron(III) tetrakis(4-sulfonatophenyl)porphyrin (FeTPPS3−) anions. Electroactive cations such as Ru(NH3)63+ and Os(bpy)2pyCl+ adhere to the clay surface, at sites too remote for direct electron transfer with the electrode, and oxidation/reduction of these ions is mediated by FeTPPS3−. The axial ligation of the metalloporphyrin anions changes reversibly with solution pH, and in weakly basic solutions electron transfer between these anions and the electrode is very slow. Cyclic voltammetry and UV-visible spectroscopy show that the FeTPPS3− contained within the silane film behaves as a pH-sensitive gate for electron transfer to and from the cations bound to the clay surface. When the formal potential of the clay-bound cation is sufficiently different from that of FeTPPS3−, proton-gated current rectification can be observed electrochemically.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry