Life on the Edge: Increasing the Diversity of Edge Structures in GNRs

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Life on the Edge: Increasing the Diversity of Edge Structures in GNRs

 

Amogh Kinikar
nanotech@surfaces Laboratory, Empa

 

Graphene nanoribbons (GNRs), which can be achieved with atomic precision via on-surface synthesis, have highly tunable properties that depend on their exact chemical structure. Tuning the properties of GNRs by controlling edge orientation and ribbon width or by heteroatom substitution is well established1. However, a third class of GNRs, with highly intriguing electronic properties, arises when the GNR edges cannot be simply described by crystallographic vectors of the graphene lattice. Edge-extended armchair GNRs, i.e. GNRs that extend along the armchair direction, but have periodic motifs embedded into their edges, have been made to host topological states2,3 and even encode spin-chains4. I will show our recent results in synthesizing edge-extended zigzag graphene nanoribbons (EE-ZGNR) and highlight the opportunities and pitfalls in their on-surface synthesis5,6.

The synthesis of such EE- ZGNR highlights a fundamental limitation in obtaining materials by on-surface synthesis: every new structure necessitates a new precursor, and this often entails extensive in-solution chemistry. This is because once synthesized, the GNRs usually have highly stable C-H bonds that passivate their edges. Edge-functionalization of graphene nanoribbons has the potential to greatly expand their applicability7. However, to covalently link functional groups to the edges would necessitate activating the edges chemically. In this talk, I will also present a synthetic pathway to eliminate all hydrogens from the GNR edges, leaving behind GNRs that are amenable to post-synthesis functionalization.