Structural evolution of self-assembled monolayer of 1-mercapto-2-propanol on Au(1 1 1) in a N2 flow: an electrochemical and STM study

The structural evolution of 1-mercapto-2-propanol layer on Au(1 1 1) during a treatment in a N2 flow was investigated using STM and cyclic voltammetry. The pristine layer showed a striped structure of (2p3 p3) with coverage of 0.33. As the SAM was treated in the N2 flow, the superlattice evolved sequentially and irreversibly to the structures of (p21 p3) and (p3 p3)R308 without any coverage change and ultimately to amorphous domains with coverage less than 0.33. In cyclic voltammetric studies, it was found that the coverage of 1-mercapto-2-propanol was 0.33 and that the N2 treatment induced a partial desorption of the adsorbed thiol molecules. In addition to this, the reductive stripping potential shifted to the anodic direction, signaling that the SAM of 1-mercapto-2-propanol became unstable. The structural evolution and destabilization of the 1-mercapto-2-propanol layer on Au(1 1 1) was discussed in terms of the attractive force between the OH groups via hydrogen bonding and the repulsive force between the methyl groups. # 2004 Elsevier B.V. All rights reserved