1 The Electrochemistry of Sodiumdodecylsulfonate on Au(111) in sulfuric acid – Voltammetry, Adsorbate structure and Friction

This study deals with the adsorption of sodiumdodecylsulfonate (SDS*) on the single crystalline Au(111) surface in 0.1 M sulfuric acid. As demonstrated by cyclic voltammetry and atomic force microscopy (AFM), the SDS* adsorbate shows a transition from a flat adsorbed phase to a condensed phase with increasing electrode potential. These observations are similar to those on sodiumdodecylsulfate (SDS) 1-3, where a condensed, disordered bilayer was found 4. For the SDS* we found a well-ordered structure of the condensed layer and thus were able to suggest a structure for the condensed layer. Comparing the condensed and the flat phase, the condensed phase shows lower friction at low normal loads (tip follows corrugation) and higher friction at high normal loads (tip compresses/penetrates the layer).