Scanning electrochemical microscopy charge-transfer processes

A few years ago Bard and his group developed the technique called scanning electrochemical microscopy (SECM) which makes possible a spatial analysi,s of charge transfer processes [9]. In this method an additional tip electrode of a diameter of about 2 pm is used as well as the three other electrodes (semiconductor, counter and reference electrode). Assuming that a redox system is reduced at the semiconductor, then the reduced species can be re-oxidized at the tip electrode, the latter being polarized positively with respect to the redox potential. The corresponding tip current / [ is proportional to the local concentration of the product formed at the semiconductor surface and therefore also to the corresponding local semiconductor current, provided... 

C Wei, AJ Bard, MV Mirkin. Scanning electrochemical microscopy. 31. Application of SECM to the study of charge-transfer processes at the liquid-liquid interface. J Phys Chem 99 16033-16042, 1995. 

Conventional approaches based on electrochemical techniques, surface tension, and extraction methods have allowed the estabhshment of thermodynamic and kinetic information concerning partition equilibrium, rate of charge transfer, and adsorption of surfactant and ionic species at the hquid/Uquid interface [4—6]. In particular, electrochemical methods are tremendously sensitive to charge transfer processes at this interface. For instance, conventional instm-mentation allowed the monitoring of ion transfer across a hquid/hquid interface supported on a single micron-sized hole [7, 8]. On the other hand, the concentration profile of species reacting at the interface can be accurately monitored by scanning electrochemical microscopy [9, 10]. However, a detailed picture of the chemical environment at the junction between the two immiscible liquids caimot be directly accessed by purely electrochemical means. The implementation of in-situ spectroscopic techniques has allowed access to key information such as ... 

Wei, C., Bard, A. J., Mirkin, M. V. Scanning electrochemical microscopy. 31. Application of SECM to the study of charge transfer processes at the liquid/liquid interface. J. Phys. Chem. 1995, 99, 16033. Tsionsky, M., Bard, A. J., Mirkin, M. V. Scanning electrochemical microscopy. 34. Potential dependence of the electron-transfer rate and film formation at the liquid/liquid interface. J. Phys. Chem. 1996, 100, 17881. 

C. Wei, A. J. Bard, and M. V. Mirkin,/. Phys. Chem., 99, 16033 (1995). Scanning Electrochemical Microscopy. 31. Application of SECM to the Study of Charge-Transfer Processes at the Liquid-Liquid Interface. 

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