Electrochemistry of immobilised redox droplets: Concepts and applications

The use of microdroplet modified electrodes provides a simple methodology with which to study the biphasic electrochemistry of a plethora of species, encouraging the use of such techniques to mimic emulsion media. Furthermore, since the droplets may be miniaturised, this approach may assist in the field of biomimetic electrochemistry. For these reasons, this paper reviews the voltammetry of electrodes modified with electrochemically active droplets. The primary focus of the review is of unsupported droplets, where electron transfer processes occur at the three phase boundary, the base circumference of the individual droplets (of a volume range spanning nine orders of magnitude, going from microlitre to femtolitre volumes). The voltammetry of such systems is categorised via a semi-quantitative appreciation of the voltammetric characteristics. Finally, several topical examples illustrating the potential of application of this technology are described.