Self-assembled Alkanethiol Monolayer on Mercury

One important parameter of monolayers of alkanethiols, and more generally of thiols, is the amount of charge transferred from the sulfur atom of the sulphydryl group to the metal during their self-assembly. On the basis of the suggestion of Kolthoff82 mat thiols react very rapidly with mercury surfaces to form mercurous and mercuric adducts, it has often been taken for granted that the formation of thiol SAMs on mercury involves the total transfer of an electron from sulfur to 

The Integral Electrosorption Valency of Metal-Supported Thiol 

To better appreciate this point, let us express the potential difference - if across the interphase by taking into account 

as = -Vrs is the charge density on the -S groups of a hypothetical close-packed monolayer of thiolate anions, P is the distance of the center of charge of the sulfur atoms from the metal surface, d = p + y is the length of the thiol molecule, and p and y are the dielectric constants accounting for the distortional polarization in the (0 x P) and (p x d) portions of the monolayer. Moreover, %e is the surface dipole potential due to electron spillover and Xs is that due to any polar groups of the thiol molecule. For simplicity, the small potential difference (4/ across the diffuse layer is disregarded. 

The potential difference A across the interface of a thiol-free, bare electrode in the absence of ionic specific adsorption at the same applied potential, E = + constant, is likewise expressed by  

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