Atomic-Scale Fabrication and Characterization of Carbon Nanomaterials

Scanning probe methods offer a versatile toolbox for the fabrication and atomic-scale characterization of carbon-based nanomaterials. By combining atomically precise single-molecule manipulation with on-surface synthesis, they enable synthesis of otherwise inaccessible carbon allotropes and their direct imaging and spectroscopic investigation. Using this approach, we established protocols for the atomically precise construction of nonbenzenoid sp2-carbon networks, whose properties deviate fundamentally from those of graphene. For example, the on-surface coupling of predesigned polymer chains led to the formation of the biphenylene network, a metallic carbon allotrope containing 4-, 6-, and 8-membered rings. SPM manipulation techniques further allow the stepwise construction and electronic structure investigation of ultralong acenes, which are key molecular models for one-dimensional carbon materials. We synthesized and characterized tridecacene and pentadecacene —the longest acenes known to date—revealing open-shell antiferromagnetic ground states and a singlet–triplet gap of about 124 meV for pentadecacene. Complexation with gold adatoms demonstrate the sensitivity of their multiradical electronic structure to local coordination. Finally, we extended these concepts to heteroatom-doped nanostructures, creating heteroatom-containing cycloarenes, curved carbon frameworks, and N-doped acenes and graphene nanoribbons. These examples highlight the capabilities of SPM-assisted on-surface synthesis to fabricate, visualize, and manipulate functional carbon nanomaterials with atomic precision.