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Order from a Mess: The Growth of 5‑Armchair Graphene Nanoribbons
journal contribution
posted on 2021-10-11, 12:41 authored by Alejandro Berdonces-Layunta, Fabian Schulz, Fernando Aguilar-Galindo, James Lawrence, Mohammed S. G. Mohammed, Matthias Muntwiler, Jorge Lobo-Checa, Peter Liljeroth, Dimas G. de OteyzaThe
advent of on-surface chemistry under vacuum has vastly increased
our capabilities to synthesize carbon nanomaterials with atomic precision.
Among the types of target structures that have been synthesized by
these means, graphene nanoribbons (GNRs) have probably attracted the
most attention. In this context, the vast majority of GNRs have been
synthesized from the same chemical reaction: Ullmann coupling followed
by cyclodehydrogenation. Here, we provide a detailed study of the
growth process of five-atom-wide armchair GNRs starting from dibromoperylene.
Combining scanning probe microscopy with temperature-dependent XPS
measurements and theoretical calculations, we show that the GNR growth
departs from the conventional reaction scenario. Instead, precursor
molecules couple by means of a concerted mechanism whereby two covalent
bonds are formed simultaneously, along with a concomitant dehydrogenation.
Indeed, this alternative reaction path is responsible for the straight
GNR growth in spite of the initial mixture of reactant isomers with
irregular metal–organic intermediates that we find. The provided
insight will not only help understanding the reaction mechanisms of
other reactants but also serve as a guide for the design of other
precursor molecules.
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ullmann coupling followedsynthesize carbon nanomaterialsdependent xps measurementsconventional reaction scenarioalternative reaction pathstraight gnr growthgnr growth departsprecursor molecules coupleprecursor moleculesreaction mechanismschemical reactiongrowth processvastly increasedvast majoritytheoretical calculationstarget structuressurface chemistryreactant isomersprovided insightprobably attractedinitial mixturehelp understandinggraphene nanoribbonsformed simultaneouslydetailed studyconcomitant dehydrogenationatomic precisionalso serve