title: Self-assembly of thiophene derivatives on highly oriented pyrolytic graphite: hydrogen bond effect.
abstract: In this paper, to elucidate the hydrogen bond effect on the assembly behavior, we studied the assembly structures of two carboxylic substituted thiophene derivatives on highly oriented pyrolytic graphite (HOPG) by scanning tunneling microscopy. Here thiophene-2-carboxylic acid (TCA) and thiophene-2,5-dicarboxylic acid (TDA) were employed. TDA molecules spontaneously adsorb on the HOPG surface and self-organize into a two-dimensional (2D) assembly with well-defined structure. Two types of domain could be observed. Each TDA molecule appears as a round circle with two small faint dots and forms hydrogen bonds with neighbours. Besides monolayer structure, a bilayer structure of TDA adlayer on HOPG was also observed in this research. Remnant TDA molecules adsorb on the monolayer of TDA and bilayer structure is formed. In contrast to TDA, no ordered structure of TCA on HOPG can be observed. TCA molecules have high propensity to form dimers through H-bond between carboxylic groups. But TCA dimer is not stable enough for either adsorption or imaging. Our result provides a new example for understanding hydrogen effect on stabilizing and controlling two-dimensional assembly structure and is helpful for surface nanofabrication and development of electric nanodevices.
authors: Research Center for Bioengineering and Sensing Technology, University of Science and Technology Beijing, Beijing 100083, PR China.
authors: Li-Ping
authors: LP
authors: Xu
authors: Yibiao
authors: Y
authors: Liu
authors: Jing
authors: J
authors: Zhao
authors: Shuqi
authors: S
authors: Wang
authors: Chen-Sheng
authors: CS
authors: Lin
authors: Rui-Qin
authors: RQ
authors: Zhang
authors: Yongqiang
authors: Y
authors: Wen
authors: Hongwu
authors: H
authors: Du
authors: Xueji
authors: X
authors: Zhang
mesh_terms: D006108:Graphite / Q000737:chemistry*; D006860:Hydrogen Bonding; D017348:Microscopy, Electron, Scanning Transmission; D008958:Models, Molecular; D013876:Thiophenes / Q000737:chemistry*
chemical_list: D013876:Thiophenes; D006108:Graphite