Formation of 2-D Crystalline Intermixed Domains at the Molecular Level in Binary Self-Assembled Monolayers from a Lyotropic Mixture

Abstract

The organization and intermolecular interactions of mixed self-assembled monolayers (SAMs) of 1-decanethiol (DT) and 11-mercaptoundecanoic acid (MUA) formed on Au(111) from a lyotropic medium have been studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and infrared reflection–absorption spectroscopy (IRRAS) as a function of their surface composition. The presence of a single reductive desorption peak in the voltammograms and thiol surface coverages close to 7.6 × 10–10 mol/cm2 reveal the formation of homogeneous mixtures of both molecules in an upright configuration in the mixed SAMs. Despite this fact, two different distributions of the individual components have been found in these MUA-enriched SAMs according to their different electron transfer blocking behavior and conformational order shown by EIS and IRRAS results. At short modification times, MUA–MUA and DT–DT homomolecular interactions prevail during the assembly process, and nanodomains of like molecules are probabl...