The electrochemistry of peptide self-assembled monolayers

Abstract

The self-assembly ability of molecules is of fundamental importance in modern science and technology, making possible to produce nanostructures with a precision that is not achievable with classical lithographic miniaturization techniques. In particular, self-assembled monolayers (SAMs) formed by helical oligopeptides are very promising materials, used as archetypal systems in various fields of current nanoscience research, materials science, molecular biology, and surface science, and with potential application as molecular sensors and optoelectronic devices. The motivation for fabricating polypeptide SAMs is to exploit the unique features of polypeptide primary and secondary structures: it is possible to create a designed peptide sequence (a sequence of side chains with specified functionality) that in turn would be manifested in the corresponding SAM as spatially resolved, chemically distinct functionalities localized in a series of strata coplanar with the substrate. Moreover, the macrodipole moment associated with the vector sum of the individual peptide dipoles in an α-helical secondary structure gives rise to an intrinsically polar SAM, which favors electron-transfer in one precise direction and facilitates light-induced electron-hole separation, for appropriately placed chromophores. In this chapter we review the electrochemical properties of peptide SAMs, both in their fundamental and excited electronic states, focusing on their characterization and on their chargetransport properties.