Time and Spatial Dependence of the Concentration of Less Than 105 Microelectrode-Generated Molecules

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Science  03 Mar 1989:
Vol. 243, Issue 4895, pp. 1176-1178
DOI: 10.1126/science.243.4895.1176


The time and spatial dependence of the concentration of as few as 40,000 electrogenerated, redox-active molecules has been determined. The distance between generator and detector microelectrodes in an array used in the study could be varied from 0.8 to 28 micrometers. Measurements of a sufficiently small ensemble of molecules allowed the experimental results to be compared with a quantitative simulation of the random movement of each member of the ensemble. The transit time of an electrogenerated species from the generator to a collector microelectrode was measured as a function of viscosity, diffusivity, and distance.

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