Department of Physics, Friedrich-Alexander University Erlangen-Nürnberg, Erwin-Rommel-Strasse 1, 91058 Erlangen, Germany.
Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany.
Nat Commun. 2017 Mar 21;8:14765. doi: 10.1038/ncomms14765.
The fabrication of nanostructures in a bottom-up approach from specific molecular precursors offers the opportunity to create tailored materials for applications in nanoelectronics. However, the formation of defect-free two-dimensional (2D) covalent networks remains a challenge, which makes it difficult to unveil their electronic structure. Here we report on the hierarchical on-surface synthesis of nearly defect-free 2D covalent architectures with carbonyl-functionalized pores on Au(111), which is investigated by low-temperature scanning tunnelling microscopy in combination with density functional theory calculations. The carbonyl-bridged triphenylamine precursors form six-membered macrocycles and one-dimensional (1D) chains as intermediates in an Ullmann-type coupling reaction that are subsequently interlinked to 2D networks. The electronic band gap is narrowed when going from the monomer to 1D and 2D surface-confined π-conjugated organic polymers comprising the same building block. The significant drop of the electronic gap from the monomer to the polymer confirms an efficient conjugation along the triphenylamine units within the nanostructures.
从特定的分子前体进行自下而上的纳米结构制造为纳米电子学应用提供了创造定制材料的机会。然而，要形成无缺陷的二维（2D）共价网络仍然是一个挑战，这使得难以揭示它们的电子结构。在这里，我们报告了在 Au(111)上使用羰基功能化孔的近乎无缺陷的 2D 共价结构的分级表面合成，这是通过低温扫描隧道显微镜结合密度泛函理论计算进行研究的。羰基桥联的三苯胺前体在乌尔曼型偶联反应中形成六元大环和一维（1D）链作为中间体，随后交联成 2D 网络。当从单体到包含相同构建块的 1D 和 2D 表面限制的π共轭有机聚合物时，电子带隙变窄。从单体到聚合物的电子间隙的显著下降证实了在纳米结构中三苯胺单元的有效共轭。
