Ferrocenes adsorption-diffusion

Schwenz and Moore introduced cyclic voltammetry as a modem approach to electrochemistry experiments. Three new experiments exploit this technique. One uses the technique as a probe or electrode surface area (82). A second uses the method to study adsorption of polyoxometalates on graphite electrodes (83). A third studies the effect of micelles on the diffusion and redox potentials of the well-studied ferrocene system (84). 

Alcohols are often used as cosurfactants in microemulsions, and insight has been obtained from the electrochemistry of ferrocene alcohols (4). Oxidations of FcOHCio, FcOHCu, and FcOHCig [34] were nearly reversible and controlled by diffusion in microemulsions of DDAB, CTAC, or SDS. In micellar solutions, electrode reactions were more complex and reflected strong adsorption of the ferrocene alcohols onto the electrode. 

However, there remains a possibility that the appearance of two pairs of voltammetric peaks may arise from particle adsorption onto the electrode surface. As in solid films, the ferrocene moieties might exhibit different energetic states and accessibility to counterions because of spatial effects. This hypothesis is discounted by results from two additional experiments. First, the cathodic and anodic current density of the redox peaks was found to be linearly proportional to the square root of potential scan rates, suggesting that the charge-transfer processes were under diffusion control. Second, after the electrochanical measurements in the Ru=CH-Fc particle solution, the Au electrode was taken out and rinsed with a copious amount of DMF and then immersed into a same electrolyte solution without the nanoparticles. Only featureless voltammetric responses were observed, as shown in Figure 3.13 (long dashed curve). In short, both measurements signify minimal surface adsorption of the particles. 

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