Low dimensional self-organization of DNA-base molecules on Cu(111) surfaces

DNA base molecules form novel low dimensional superstructures on Cu(111) surfaces through hydrogen bonding among molecules and through their epitaxial nature on the surface. Scanning tunnelling microscope images have revealed that the chemical inertness of the Cu(111) substrate allows the molecules to diffuse over the surface to spontaneously self-assemble themselves into their own unique structure: adenine into one-dimensional molecular chains, thymine into two-dimensional islands, guanine into two-dimensional square lattices and cytosine into one-dimensional zigzag molecule-cluster networks. Molecular orbital calculations explain some of the observed self-assemblies induced by base-base hydrogen bonding. Novel superstructures of self-assembled uracil molecules have also been observed at 70 K, isolated uracil trimers are formed at low coverage, and two-dimensional islands with a hexagonal superstructure are built up at increased coverage. The dominant force responsible for the formation of the trimers and the islands is electrostatic interaction through anisotropic hydrogen bonds between uracil molecules. This paper also discusses the DNA base molecules surface interactions to form different adsorbed structures on various surfaces, such as SrTiO3(100), Pd(110) and Si(100)-(2 x 1), correlated with the chemical bonding and corrugation of the surface. (C) 1997 Elsevier Science B.V.