Homochiral polymerization-driven selective growth of graphene nanoribbons

Abstract

The surface-assisted bottom-up fabrication of graphene nanoribbons (GNRs), which consists of the radical polymerization of precursors followed by dehydrogenation, has attracted attention because of the method's ability to control the edges and widths of the resulting ribbon. Although these reactions on a metal surface are believed to be catalytic, the mechanism has remained unknown. Here, we demonstrate 'conformation-controlled surface catalysis': the two-zone chemical vapour deposition of a 'Z-bar-linkage' precursor, which represents two terphenyl units linked in a 'Z' shape, results in the efficient formation of acene-type GNRs with a width of 1.45 nm through optimized cascade reactions. These precursors exhibit flexibility that allows them to adopt chiral conformations with height asymmetry on a Au(111) surface, which enables the production of self-assembled homochiral polymers in a chain with a planar conformation, followed by dehydrogenation via a conformation-controlled mechanism. This is conceptually analogous to enzymatic catalysis and will be useful for the fabrication of new nanocarbon materials.

Controllable conversion of quasi-freestanding polymer chains to graphene nanoribbons

“…13) and Cu (refs 14, 15). Surface-assisted cyclodehydrogenations161718, a key step in GNR formation, appear to take place only on the catalytic metal substrates1920. Efforts of growing GNRs from molecular precursors directly on an insulating TiO 2 substrate only succeeded in deriving polymerization but not the cyclodehydrogenation20.…”

Fluorescence from graphene nanoribbons of well-defined structure

“…For instance, armchair edge GNRs with various widths, "cove"-type edge GNRs, and even zigzag edge GNRs showing the theoretically predicted localized states have been achieved [13,15]. The electronic properties of the GNRs have been intensively studied e.g., by scanning tunneling spectroscopy, angleresolved photoelectron spectroscopy, high-resolution electron energy loss spectroscopy, and fabrication of field-effect transistor devices [17][18][19]. In contrast, there is an obvious lack of knowledge about their optical properties.…”

Recent Progress in the Fabrication of Low Dimensional Nanostructures via Surface-Assisted Transforming and Coupling

“…Hence this type of sequential activation selectively couples adjacent C with H 2 molecules separated due to Ullmann coupling creating a dynamite position of C atoms. A set of GNR with the diversity of topological edge [74,[86][87][88] or different sized porous nanosheets have been fabricated leading to the opening of substantial electronic band gaps that are directly linked to their structural boundary conditions [89]. Another novel hierarchical polymerization is the lithography followed by Ullmann coupling in mechanism 2 to realize high degree of structural controlled synthesis of organometallic chains and macrocycles by employing a Cu(110)-(2 × 1) nanotemplate [16].…”