SURFACE ANISOTROPIC ELECTROREFLECTANCE RESPONSE AT AN EDGE-PLANE PYROLYTIC-GRAPHITE ELECTRODE

We found that the potential-modulated UV-vis reflectance (electrorefle ctance, ER) spectrum measured with linearly polarized incident light a t an edge-plane graphite (EPG) electrode with adsorbed redox species s hows surface anisotropy. At a hemin or methylene blue-adsorbed EPG ele ctrode, s-polarized incident light gave rise to greater ER response th an p-polarized when the c axis of the graphite electrode is parallel t o the plane of incidence, while when the c axis is perpendicular to th e plane of incidence p-polarized light gave rise to greater response. The anisotropy was also observed for an EPG electrode coated with a Na fion film in which adsorptive species was incorporated. In contrast, m ethylviologen-incorporated Nafion films did not produce the anisotropy . The possible origin of the anisotropy was discussed in light of the surface morphology of the EPG as observed by the SEM.