In order to be able to characterize biomolecular processes, new analytical methods need to be developed. In the Micro- and Nanosenors research department at the Frauenhofer Institute of Applied Solid-Sate Physics in Freiburg, Germany, Jakob Hees, Nianjun Yang, and co-workers are particularly interested in the use of diamond in the preparation of electro- and biochemical sensors. They have prepared ultramicroelectrode arrays (UMEAs) and nanoelectrode arrays (NEAs) that contain boron-doped nanocrystalline diamond. The team have demonstrated the potential of NEAs to discriminate diffusion-controlled from adsorption-controlled processes.

Using neutral methyl viologen (MV⁰) as a model system, they investigated its absorption on hydrogen- and oxygen-terminated diamond surfaces. They found that MV⁰ absorbs preferentially on a hydrogen-terminated surface, resulting in a sharp anodic peak stripping peak in the voltammogram (pictured, below), and depends very much on the type and the concentration of the electrolyte. In contrast, a sigmoidal voltammogram was recorded with an oxygenated electrode surface, indicating there was no MV⁰ adsorption (pictured, above).

The differences in the shapes of these voltammograms are attributed to differences in the diffusion profiles of the two systems, which changes from hemispherical diffusion on oxygen-terminated surfaces to thin-layer electrochemistry upon adsorption on hydrogen-terminated surfaces. Hence, diamond NEAs are ideal for the study of adsorption phenomena at the liquid–solid interfaces with voltammetry that would not necessarily be accessible using conventional macroscopic electrodes.

• Diamond Nanoelectrode Arrays for the Detection of Surface Sensitive Adsorption,
  J. Hees, R. Hoffmann, N. Yang, C. E. Nebel,
  Chem. Eur. J. 2013.
  DOI: 10.1002/chem.201301763