Purely Armchair or Partially Chiral: Noncontact Atomic Force Microscopy Characterization of Dibromo-Bianthryl-Based Graphene Nanoribbons Grown on Cu(111)

摘要

We report on the atomic structure of graphene nanoribbons (GNRs) formed via on-surface synthesis from 10,10′-dibromo-9,9′-bianthryl (DBBA) precursors on Cu(111). By means of ultrahigh vacuum noncontact atomic force microscopy with CO-functionalized tips we unveil the chiral nature of the so-formed GNRs, a structure that has been under considerable debate. Furthermore, we prove that—in this particular case—the coupling selectivity usually introduced by halogen substitution is overruled by the structural and catalytic properties of the substrate. Specifically, we show that identical chiral GNRs are obtained from 9,9′-bianthryl, the unsubstituted sister molecule of DBBA.