Chapter 4: Electrochemistry within nanogaps

Electrochemical processes in micro-gap and nano-gap electrochemical systems are of increasing interest and may be regarded as the “missing link” between tunnel processes (< 1–2nm) and micro-gap processes (>1μm gap). This is the length scale of charge hopping processes (with typically D_app=10⁻¹⁵ m²s⁻¹) and therefore for processes related to charge storage, photoelectrochemistry, bioelectrochemistry, and sensing. A range of important electrochemical phenomena and processes are encountered in nano-gap electrode systems including the direct observation of slow charge hopping at surfaces, coupled surface-chemical processes in mesoporous oxides, fast feedback current measurements for low concentration analysis down to single molecules, chemical signal filtering for sensor, and stochastic effects due to single molecule/low concentration fluctuations. There are interesting future applications in particular in progressing fundamental science and in enabling new types of micro-fabricated electroanalytical sensing devices.