Electrode surface modified with heteropoly or isopoly anions: STM and AFM characterization

Abstract
It has been shown on two examples that STM and AFM techniques can be used to image oxometalates with molecular resolution. The shapes of these molecules are clearly distinguished and their dimensions have been determined. It has even been possible to correlate other results culled from the AFM image of the surface of a single crystal of an oxometalate with those of crystallography. These results served as reference images in the study of the basal plane of HOPG when it is used as a working electrode during the cyclic voltammetry of 10^-3 M H₂W₁₂O^6-₄₀, in a pH = 2 medium, with simultaneous STM monitoring of the surface morphology. A potential-dependent deposition of the oxometalate is superimposed on a strong alteration of the HOPG surface. When the potential domain is extended to include the third redox system of H₂W₁₂O^6-₄₀, a particularly well-ordered two-dimensional array is observed, the individual entities having the diameter of the oxometalate.