K W Hipps - Temperature Stability of Three Commensurate Surface Structures of Coronene Adsorbed on Au(111) from Heptanoic Acid in the 0 to 60 °C Range

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      Publication Details (including relevant citation   information):

      Jahanbekam, Abdolreza, Vorpahl, Sarah, Mazur, Ursula, Hipps, K.   W. The Journal of Physical Chemistry C  2013 117 (6) 2914-2919

      Abstract: For the first time, accurate   quantitative data on the temperature evolution of a surface   monolayer formed at the solution solid interface are reported. In   addition, a detailed analysis is provided of the structures of   three different monolayers formed when coronene in heptanoic acid   is in contact with Au(111). All three monolayer structures are   well-defined epitaxial structures that are extremely stable for   temperature variations between 0 and 60 °C. At high   concentrations, a dense hexagonal structure with molecular   separation of 1.19 ± 0.04 nm is observed. At reduced   concentration, the most often observed structure is an open   hexagonal epitaxial structure with one molecule per unit cell and   a molecular separation of 1.45 ± 0.04 nm. This structure is   stabilized by solvent molecule adsorption. If the dense phase is   exposed to pure solvent, or occasionally with low concentration   direct adsorption, then a different hexagonal phase is formed   with three molecules per unit cell but exactly the same density   (lattice length of 2.46 ± 0.04 nm). Under some conditions, all   three phases can be simultaneously present. It is notable that   even when the least stable triangular phase is present on a large   fraction of the surface, the low-density hexagonal phase is often   observed decorating the reconstruction lines. The energy   difference between the two low density phases is due to   surface–solvent and coronene-adsorbed solvent interactions as the   coronene–gold interactions in the two phases are essentially the   same. The barrier to thermal conversion between the two low   density phases must be several kT or greater than 2 kcal/mol.

      Address (URL): http://dx.doi.org/10.1021/jp3115435