Electrochemical microscopy

By its very nature, electrochemistry makes a contribution of the utmost importance to the development of nanoscience. One need only consider, for example, that basic processes such as corrosion or electrocrystallization alter the appearance and composition of metal/solution interfaces at the atomic scale, with obvious implications at the nanoscale. Furthermore, electrochemistry enables, primarily through a bottom-up approach, the formation of diverse and varied structures—crystalline or amorphous, organic, inorganic, or metallic—on conductive surfaces, starting from solutions containing dissolved species that are ionic or neutral, monoatomic or molecular. These structures can take the form of localized deposits that are more or less sparse, or even uniform thin films. Through rigorous control of the deposition conditions (electrochemical parameters, composition of the electrolyte solution used, etc.), electrochemistry thus enables the creation, at the electronic conductor/solution interface, of a wide variety of nano-objects (nanopins, nanowires, nanotubes, nanocrystals, nanoparticles, nanopatterns, submicrometer-thick films, etc.) at least one dimension of which is limited to a few nanometers.

Furthermore, conventional electrochemical techniques allow for the direct, global, or local characterization of the electrochemical reactivity or chemical composition of electrochemical interfaces. They also allow for the study—sometimes indirect—of a number of properties, such as the metabolism of biological systems (e.g., cells) via the electrochemical detection of their metabolites (especially when these are electroactive, of course).

At the local scale, the (electro)chemical and topographical properties of a sample can be characterized using scanning electrochemical microscopy (SECM), through the use of a miniaturized electrode acting as a probe. SECM is a local probe microscopy technique that enables the imaging of the electrochemical reactivity of various types of samples or the local modification of their properties. It allows the surface of samples to be examined by scanning them with miniaturized electrodes, which collect a signal indicative of their local redox reactivity, thereby providing a micrometer-scale image of the surface. The use of SECM represents a major advance in electrochemistry, made possible by the miniaturization of electrodes and the ability to measure very small currents. It offers a wide range of applications, from in situ electrochemical imaging to local microscopic surface structuring.

Development of SECM began in the late 1980s simultaneously in two electrochemistry laboratories