Paper SS2-MoA2
Molecular Self-assembly of Terephthalic Acid and Sodium Chloride on the Cu(100) Surface

Monday, October 31, 2011, 2:20 pm, Room 110

To expand the catalogue of available interactions for the efficient self-assembly of highly-ordered nanoscale structures, we have investigated the formation of new supramolecular networks of terephthalic acid (TPA) and sodium chloride (NaCl) on the copper (100) surface. The mixture of this organic species with salt is prepared by vapor deposition in an ultra-high vacuum system and represents a model system for ionic self-assembly in two-dimensions. Several structures have been observed by means of scanning tunneling microscopy molecular resolution imaging. Chemical shifts in the sodium 1s photoelectron peak have been observed by X-ray photoelectron spectroscopy upon addition of TPA to the surface, confirming a direct interaction. Our research indicates that TPA and sodium produce new structures due to favorable ionic interactions between sodium cations and the negatively charged carboxylate groups in TPA’s deprotonated form. Interactions with the metal surface and organic molecules appear to be sufficient to break the ionic bonds of the NaCl lattice. The formation of new TPA-Na structures illustrates the interplay between adsorbate-substrate and ionic interactions and opens new possibilities for ionic self-assemblies at surfaces with highly ordered structure and specific chemical function.