Carbon electrodes, SECM studies

An SECM feedback response to an electroactive polymer film can be controlled either by ET kinetics at the film-solution interface or by film conductivity. The contribution of lateral film conductivity to the effective ET rate measured by SECM was addressed in the recent study of polyaryl multilayers attached with ferrocenes [65] or ferrocene-terminated dendrimers [69] on unbiased carbon electrodes. In the latter study, the dependence of apparent ET rate constant, feei. on the generation of dendrimers (Table 6.2) was ascribed to the different efficiencies of electron transport inside and between dendrimers (Figure 6.22). Interestingly, the theory of the aforementioned triple potential step method predicts its potential to separately determine heterogeneous ET rate and lateral conductivity for a thin polymer film coated on an insulating surface [70]. 

Similarly, a commercial Ca + ionophore-based micropipette electrode was used by Etienne et al. to investigate the applicability of the potentiometric mode of SECM to the study of dissolution kinetics at solid-liquid interfaces. Using the shear force technique, they were able to precisely control the tip-substrate distance and perform imaging of the ion activity at constant distance over the substrate. The local dissolution of crystal plates of different orientations, as well as that of different parts of calcium carbonate shells of Mya arenaria, was obtained. 

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