On-Surface Synthesis of Graphene Nanoribbons Catalyzed by Ni Atoms.

Nanometer-wide graphene nanoribbons can be synthesized from halogen aromatics through multistep on-surface reactions, but the catalytic role of extrinsic transition-metal atoms in these reactions are still to be explored. Here by low-temperature scanning tunneling microscopy, we investigated the on-surface synthesis of graphene nanoribbons from 10,10'-dibromo-9,9'-bianthryl precursors in the presence of Ni atoms. Ni atoms not only act as catalysts in debromination and lead to the formation of an organometallic intermediate at 300 K, but also prompt the fusion reaction between graphene nanoribbons at 673 K. Our work demonstrates a more efficient way to fabricate fused graphene nanoribbons.