Self-assembled monolayer electron-transfer kinetics

Gray HB, Winkler JR (1996) Electron transfer in proteins. Annu Rev Biochem 65 537 Fedurco M (2000) Redox reactions of heme-containing metalloproteins dynamic effects of self-assembled monolayers on thermodynamics and kinetics of cytochrome c electron-transfer reactions. Coord Chem Rev 209 263... 

In the two-state approximation (TSA), ET kinetics for the DBA —> D" BA process may be modeled in terms of initial- ( ,) and final-state (T /) wave-functions, in which the transferring charge is localized primarily on the D and A sites, respectively. In the case of electrodes (e.g., metal or semiconductor), where multiple electronic states are involved, the D and A sites may still be taken to be localized and to involve atomic sites of the electrode near the site/or sites of attachment or contact with the bridge) SAM = self assembled monolayer STM = scanning tunneling microsccopy. 

M. T., Murray, R.W., RoweE, G.K., and Creager, S.E. (1995) Electron-transfer kinetics of self-assembled ferrocene octanethiol monolayers on gold and silver electrodes from 115K to 170K. Journal of Physical Chemistry, 99 (2), Jhh-Tn. 

El Kasmi, A., Wallace, J. M., Bowden, E. R, Binet, S. M., Linderman, R. J. (1998). Con-trolling interfacial electron-transfer kinetics of cytochrome c with mixed self-assembled monolayers, J. Am. Chem. Soc., 120 225. 

Electron Transfer Kinetics of Azurin at Methyl-terminated Alkanethiol Self-assembled Monolayers... 

Electrochemical techniques have been used extensively to investigate the kinetics of electron transfer (ET) through self-assembled monolayers (SAMs) of molecules connected to a gold smface, leading to information about the distance dependence and the influence of solvation. 

With regard to its electronic properties, no studies are available that clearly demonstrate that electron transfer through such a supramolecular assembly is possible. Solid-state electrochemical studies on the crystalline material are not available at the present time. The closest to supramolecular electrochemistry are studies of ordered two-dimensional peptide arrays on gold. For some Fc-peptide cystamines, self-assembled monolayers of Fc-peptide cystamines were prepared that allow the quantification of the electron transfer kinetics by electrochemical techniques. Similar to the supramolecular assemblies, H-bonding plays an important role. At the present time (2003), only a few systems were studied and offer a rather complex picture of the ET properties. Additional experimental work is required to obtain definite results on the influence of the peptide primary and secondary structure on ET kinetics. In addition, tile issue of lateral interactions needs to be addressed by detailed dilution studies with alkylthiols. 

In typical Au MFC ET experiments with SAMs, the clusters are linked to a metal electrode surface through a self-assembled alkyl chain monolayer with specific linking sites. The electron is presumed to be transferred to/from the tethered MFC through the chain linker to/from the electrode surface. Techniques used to measure ET rates in Au MFCs attached to SAMs are potential step voltammetry and electrochemical AC impedance. Rate constants determined through impedance measurements have the virtue of less distortion due to uncompensated resistance. Also, rate constants determined using cyclic voltammetry are explicitly based on the kinetic behavior of the subpopulation of MFCs that produces the most prominent current peaks. Fotential step voltammetry resolves more peaks and thus gives a better indication of the diversity of rate constants of the redox species in the monolayer. ... 

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