Self-Limited Embedding Alternating 585-Ringed Divacancies and Metal Atoms into Graphene Nanoribbons

Because of their theoretically predicted intriguing properties, it is interesting to embed periodic 585-ringed divacancies into graphene nanoribbons (GNRs), but it remains a great challenge. Here, we develop an on-surface cascade reaction from periodic hydrogenated divacancies to alternating 585-ringed divacancies and Ag atoms via intramolecular cyclodehydrogenation in a seven carbon-wide armchair GNR on the Ag(111) surface. Combining scanning tunneling microscopy/spectroscopy and noncontact atomic force microscopy combined with first-principles calculations, we in-situ-monitor the evolution of the distinct structural and electronic properties in the reaction intermediates. The observation of embedded Ag atoms and further nudged elastic band calculations provide unambiguous evidence for Ag adatom-mediated C-H activation in the intramolecular cyclodehydrogenation pathway, where the strain-induced selflimiting effect contributes to the formation of the GNR superlattice with alternating 585-ringed divacancies and Ag atoms, which shows a band gap of about 1.4 eV. Our findings open an avenue to introducing periodic impurities of single metal atoms and nonhexagonal rings in on-surface synthesis, which may provide a novel route for multifunctional graphene nanostructures.

Automated summary

In this study, a cascade reaction from periodic hydrogenated divacancies to alternating 585-ringed divacancies and Ag atoms on the Ag(111) surface was successfully developed. The evolution of the structural and electronic properties in the reaction intermediates was in situ monitored using various characterization techniques combined with theoretical calculations. The observation of embedded Ag atoms and the analysis of the reaction pathway provided evidence for Ag adatom-mediated C-H activation. This research opens up a new avenue for introducing periodic impurities in on-surface synthesis and has potential implications in the fabrication of multifunctional graphene nanostructures.