article · Science Advances
On-surface synthesis offers notable potential for fabricating atomically precise nanographenes, yet complex cascade reactions often trigger competing pathways that restrict product yields. A new approach achieves ultrahigh-yield synthesis of circumcoronene molecules on a copper Cu(111) substrate. The process proceeds through surface-assisted intramolecular dehydrogenation of a tailored precursor, followed by methyl radical-radical coupling and aromatisation. Electrostatic interactions between the circumcoronene molecules and the metallic surface direct the molecules to self-organise into an extended superlattice. Bond-resolved scanning probe microscopy along with density functional theory and tight-binding calculations demonstrate that the hexagonal zigzag topology and periodic electrostatic landscape confine the two-dimensional electron gas of the copper surface. This confinement produces a chiral electronic Kagome-honeycomb lattice with two emergent flat bands, providing an effective method to generate nanographenes with zigzag topologies.
Synthesising carbon nanomaterials with exact atomic configurations is often hindered by low yields from side reactions. By establishing an efficient, high-yield route to assemble nanographenes on metal surfaces, this research demonstrates how to create structured superlattices that alter electronic behaviour. Such systems host distinct electronic flat bands, providing a foundation for studying exotic electronic states and developing advanced quantum materials.
This work represents early-stage fundamental research in surface chemistry and physics. Potential future applications could include specialised electronic or quantum devices that rely on nanographene superlattices with distinct topological properties. Likely users at this stage are academic and industrial materials research laboratories. The findings are based on laboratory synthesis and microscopic characterisation on single-crystal surfaces, meaning practical commercial deployment remains distant.
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On-surface synthesis has revealed remarkable potential in the fabrication of atomically precise nanographenes. However, surface-assisted synthesis often involves multiple-step cascade reactions with competing pathways, leading to a limited yield of target nanographene products. Here, we devise a strategy for the ultrahigh-yield synthesis of circumcoronene molecules on Cu(111) via surface-assisted intramolecular dehydrogenation of the rationally designed precursor, followed by methyl radical-radical coupling and aromatization. An elegant electrostatic interaction between circumcoronenes and metallic surface drives their self-organization into an extended superlattice, as revealed by bond-resolved scanning probe microscopy measurements. Density functional theory and tight-binding calculations reveal that unique hexagonal zigzag topology of circumcoronenes, along with their periodic electrostatic landscape, confines two-dimensional electron gas in Cu(111) into a chiral electronic Kagome-honeycomb lattice with two emergent electronic flat bands. Our findings open up a new route for the high-yield fabrication of elusive nanographenes with zigzag topologies and their superlattices with possible nontrivial electronic properties.
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DOI: 10.1126/sciadv.abf0269
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