APPLICATION OF SQUARE-WAVE VOLTAMMETRY TO STRONGLY ADSORBED QUASI-REVERSIBLE REDOX MOLECULES

The theory and application of square wave voltammetry to surface-confined quasi-reversible redox molecules (Ox + ne-= Red) is described. Theoretical voltammograms were calculated based on the following assumptions: (1) stable redox states; (2) monolayer or less surface coverage; (3) equivalent surface sites and adsorbates; (4) no adsorbate-adsorbate interactions; (5) no diffusional contributions to the current; and (6) Butler-Volmer electrode kinetics. A working curve strategy based on peak separation between positive-scan and negative-scan net current voltammograms was developed to facilitate the semiquantitative determination of electron-transfer rate constants. Major theoretical predictions were experimentally confirmed through characterization of strongly adsorbed cytochrome con carboxylic acid-terminated self-assembled monolayer electrodes of the alkanethiol/gold type.