Scanning electrochemical microscopy (SECM) is a technique that is part of a broader range of techniques that are commonly referred to as scanning probe microscopy. It has a wide array of applications in chemistry, biology, and even the material sciences. SECM uses a ultramicroelectrode to measure the local electrochemical behavior of a substrate in a solution. When introduced, the ultramicroelectrode acts as the electron conductor in the substrate and the added electrolyte acts as the ionic conductor in the solution.
Scanning probe microscopy really started to take off in the early nineties with the invention of ultramicroelectrodes. Ultramicroelectrodes allowed scientists to gather high resolution topography data of various substrates and biological samples. Within a decade the field started to come into its own. By the late eighties various scanning probe microscopy techniques had gained attention from the scientific community. This included techniques such as scanning tunneling microscopy and electrochemical scanning tunneling microscopy. It was through thorough analysis of these early methods that scanning electrochemical microscopy was developed.
The first SECM experiments can be traced back to Royce C. Engstrom. Engstrom was able to observe reaction profiles, as well as short-lived intermediates using techniques similar to modern SECM.1 Though Engstrom was one of the first to run SECM experiments, it is Allen J. Bard who is credited with the development of the SECM technique. In the late eighties Bard began experimenting with the recently discovered electrochemical scanning tunneling microscopy (ESTM) technique. Through his experiments Bard found that that electrochemical scanning tunneling microscope was producing a current at much larger ultramicroelectrode tip to sample distances then was believed possible for the instrument. Bard believed that this phenomenon could be attributed to Faradic current, which is the current generated by the reduction or oxidation of some chemical substances at an electrode. This discovery compelled Bard to take a much more in depth look at electrochemical microscopy and a couple years after his initial discovery Bard published the paper that introduced the scientific community to SECM. It was in this paper that Bard coined the phrase scanning electrochemical microscopy and outlined the many different experimental modes that SECM can be performed in.
Today SECM has a wide array of uses. Much like cyclic voltammetry, SECM can be used to collect basic voltage vs. current voltammograms of a substrate. In the early SECM was used this way in order to gather quantitative data. As the method progressed scientists discovered that they were able to use not only gather quantitative data with the SECM, but they were also able to use the SECM for topographical mapping of a localized electrochemical reaction. Within just a few years of its discovery SECM was being used for both chemistry and biology related...