Doping of Graphene Nanoribbons via Functional Group Edge Modification

TL;DR

This study demonstrates the successful incorporation of nitrile groups into graphene nanoribbons, revealing their role as effective n-dopants and providing insights into their chemical stability and electronic effects through experimental and theoretical analysis.

Contribution

It introduces a method for edge functionalization of graphene nanoribbons with nitrile groups and analyzes their impact on electronic properties using combined experimental and theoretical approaches.

Findings

Nitrile groups act as efficient n-dopants in GNRs.

Some nitrile groups survive the synthesis process.

Nitrile groups induce deep impurity levels in the electronic structure.

Abstract

We report on the on-surface synthesis of 7 armchair graphene nanoribbons (7-AGNRs) substituted with nitrile (CN) functional groups. The CN groups are attached to the GNR backbone by modifying the 7-AGNR precursor. While many of these groups survive the on-surface synthesis, the reaction process causes the cleavage of some CN from the ribbon backbone and the on-surface cycloisomerization of few nitriles onto pyridine rings. Scanning Tunneling Spectroscopy and Density Functional Theory reveal that CN groups behave as very efficient n-dopants, significantly downshifting the bands of the ribbon, and introducing deep impurity levels associated to the nitrogen electron lone pairs.