Diamond nanoelectrode arrays for the detection of surface sensitive adsorption

Nanocrystalline diamond nanoelectrode arrays (NEAs) have been applied to investigate surface-sensitive adsorption phenomena at the diamond-liquid interface. The adsorption of neutral methyl viologen (MV0) was used as a model system. The adsorption of MV0 was examined on hydrogen- and oxygen-terminated surfaces. On the hydrogenated nanoelectrode surface, a sharp anodic stripping peak was observed upon oxidation of MV0, revealing strong adsorption of MV0. In contrast, a sigmoidal voltammogram was recorded with an oxygenated electrode surface, indicating there was no MV0 adsorption. The changes in the shapes of these voltammograms are due to the drastic changes that occur in the diffusion profiles during the transition. The diffusion profile changes from hemispherical diffusion on oxygen-terminated surfaces to thin-layer electrochemistry upon adsorption on hydrogen-terminated surfaces. Different types and concentrations of buffer solutions were then used to vary the intera ction of MV0 with diamond NEAs. The results suggest that the adsorption of MV0 on hydrogen-terminated diamond NEAs is controlled by hydrophobic interactions. Therefore, diamond NEAs are ideal for the study of adsorption phenomena at the liquid-solid interface with voltammetry.