Electron-transfer studies in a lyotropic columnar hexagonal liquid crystalline medium

Abstract

We have studied the electron-transfer properties of some redox systems on a gold electrode in a lyotropic hexagonal columnar liquid crystalline phase (H1 phase) using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The liquid crystalline medium consists of the nonionic surfactant Triton X-100 and water. The redox reactions that have been studied are ferrocene/ferricenium, [Fe(CN)6]3-/4-, and [Ru(NH3)6]3+/2+. We have confirmed by polarizing optical microscopy that the liquid crystalline nature of the medium is maintained even after the addition of the redox species and the supporting electrolyte. The CV studies show a significant shift in the half-peak potentials of these redox reactions in the liquid crystalline medium. From the EIS studies, we have measured the diffusion coefficients and the kinetic parameters for the redox species. These results are discussed and compared with the values obtained in the conventional solvent medium. The CV and impedance studies demonstrate that the hexagonal columnar phase provides a novel controlled environment for the study of electron-transfer reactions in biological and physiological media.