Confined Synthesis of Subnanometer-Wide Nitrogen-Doped Graphene Nanoribbons

Graphene nanoribbons (GNRs) with well-defined structures have been prepared via on-surface synthesis through polymerization and dehydrocyclization of on-purpose designed precursor molecules. Although nitrogen-doped (N-doped) GNRs have been achieved using nitrogen-containing precursors, the synthesis of N-doped armchair GNRs with subnanometer width remains challenging due to the difficulties associated with designing appropriately small nitrogen-containing precursor molecules. Here, a confined synthesis approach is employed to synthesize N-doped GNRs with subnanometer width using nitrogen-containing molecules through a decomposition-recombination mechanism. Raman spectroscopy and X-ray photoelectron spectroscopy analyses confirmed the effectiveness of aminoferrocene and cyanoferrocene as precursor molecules for synthesizing N-doped GNRs, achieving nitrogen-to-carbon ratios of ≈9.20 and 5.96 at.%, respectively. Additionally, using a dual precursor mixture of ferrocene and cyanoferrocene allows for the synthesis of N-doped GNRs with tunable doping levels by adjusting the precursor ratio. The thermal conductivity of N-doped GNRs is increased by a factor of 1.4 compared to its undoped counterpart. These findings contribute to the precision synthesis of GNRs with controlled edge structures, widths, and doping levels, paving the way for expanded applications of N-doped GNRs.