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Order from a Mess: The Growth of 5-Armchair Graphene Nanoribbons
ACS Nano ( IF 15.8 ) Pub Date : 2021-10-11 , DOI: 10.1021/acsnano.1c06226
Alejandro Berdonces-Layunta 1, 2 , Fabian Schulz 3, 4 , Fernando Aguilar-Galindo 1 , James Lawrence 1, 2 , Mohammed S G Mohammed 1, 2 , Matthias Muntwiler 5 , Jorge Lobo-Checa 6, 7 , Peter Liljeroth 3 , Dimas G de Oteyza 1, 2, 8
Affiliation  

The 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.

中文翻译:

混乱中的秩序:5 扶手椅石墨烯纳米带的发展

真空下表面化学的出现极大地提高了我们以原子精度合成碳纳米材料的能力。在通过这些方法合成的目标结构类型中,石墨烯纳米带(GNRs)可能最受关注。在这种情况下,绝大多数 GNR 是由相同的化学反应合成的:乌尔曼偶联,然后是环化脱氢。在这里,我们详细研究了从二溴苝开始的五原子宽扶手椅 GNR 的生长过程。将扫描探针显微镜与温度相关的 XPS 测量和理论计算相结合,我们表明 GNR 的增长与传统的反应场景不同。反而,前体分子通过协同机制结合,从而同时形成两个共价键,同时伴随脱氢。事实上,尽管我们发现了反应物异构体与不规则金属有机中间体的初始混合物,但这种替代反应路径是导致 GNR 直线增长的原因。所提供的见解不仅有助于理解其他反应物的反应机制,而且还可以指导其他前体分子的设计。
更新日期:2021-10-26
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