Adsorption controls positive absorption control

To study FT responses of Fc Au MFCs on more explicitly controlled electrode surfaces, Murray et al. performed voltammetry on Au225(SCgFc)43 adsorbed onto anionic SAMs (Figure 3.27). From this study, it was concluded that there are three different interactions that can contribute to MFC adsorption (1) interaction between MFCs and SAM surface (if present), (2) lateral interactions between MFCs due to bridging electrolyte ions, and (3) specific adsorption between electrolyte ions and the bare electrode surface. The use of SAMs for Fc MFC attachment yields the strongest absorption, which is important for stable Fc voltammetry. In another study, some positively charged tetraethyl ammonium-thiolate ligands were incorporated into the shell of the Fc MFC to yield a similarly robust adsorption onto the electrode surface, without the use of SAMs. This supports the hypothesis that multiple ion-pair interactions are central in the irreversibility of adsorption. 

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