Exploring synthetic approaches to non-alternant ring topologies in graphene nanostructures

自2004年Geim和Novoselov的开创性报告以来，石墨烯吸引了广泛的研究兴趣。在接下来的几年里，人们发现石墨烯具有许多特殊的性质。特别是，其优异的电荷载流子迁移率使石墨烯成为未来用于纳米电子学的最有前途的材料之一。然而，石墨烯是没有带隙的半金属，这排除了其在数字晶体管中的应用。这使得在开发石墨烯电子器件之前找到一种打开带隙的方法变得至关重要。最突出的方法是在具有纳米级宽度的石墨烯的一维半导体条带中实现电荷载流子的量子限制-即石墨烯纳米带（GNRs）。最近确定了两种主要方法来编制GNR，即“自上而下”和“自下而上”方法。“自下而上”的方法，一种受有机化学启发的收敛的全合成方法，为GNR提供了原子精确的边缘结构和明确定义的宽度。这种自下而上的方法可以经典地在溶液介导的环境中或在贵金属基底如金、银或铜上进行。影响石墨烯的电子结构的另一途径是在石墨烯的基面中引入缺陷/缺陷。理论计算已经描述了石墨烯中的拓扑缺陷强烈地影响其电子、光学、化学、热和机械性质。从能量稳定性的观点来看，五边形-七边形对是合理的缺陷模型之一，并且可以由原子位错引起。拓扑缺陷的存在已被实验证实，使用透射电子显微镜（TEM）和扫描隧道显微镜（STM）的研究，为此，大多数这样的研究迄今只集中在其结构表征。因此，石墨烯中拓扑缺陷的物理化学方面仍然知之甚少，这激发了从基础和应用角度的透彻理解。在这项瑞士-德国联合提案中，我们将TUD和EMPA结合在一起，建立了一条新的研究路线，在溶液和表面上以原子精确的方式合成纳米石墨烯和GNR中的非六方环，作为赋予新特性的途径，例如大开壳双自由基特性，增加化学活性和新的电子功能。这项建议旨在促进两国研究人员在这一具有潜在经济重要性的关键和战略研究领域的流动。

Graphene has attracted extensive research interests since the ground breaking report by Geim and Novoselov in 2004. In the years to follow, graphene has been found to possess a number of exceptional properties. In particular, its excellent charge carrier mobility has rendered graphene one of the most promising materials for future use in nanoelectronics. However, graphene is a semimetal without a bandgap which precludes its application in digital transistors. This makes it crucial to find a way of opening a bandgap before graphene-based electronic devices can be developed. The most prominent way is to realize quantum confinement of charge carriers in one-dimensional semiconducting stripes of graphene with nanometer-scale width – namely, graphene nanoribbons (GNRs). Two main methods have been recently established to prepare GNRs, namely “top-down” and “bottom-up” approaches. The “bottom-up” approach, a convergent, total-synthetic approach inspired by organic chemistry, provides GNRs with atomically precise edge structures and well-defined width. This bottom-up approach can be conducted classically in a solution-mediated environment or on noble metal substrates such as gold, silver or copper. Another pathway to influence the electronic structure of graphene is to introduce the imperfections/defects in the basal plane of graphene. Theoretical calculations have described that topological defects in graphene strongly affect its electronic, optical, chemical, thermal and mechanical properties. The pentagon-heptagon pair is one of the reasonable defect models from the view point of energetic stability and can be induced by atom dislocation. Existence of topological defects have been experimentally confirmed using transmission electron microscopy (TEM) and scanning tunneling microscopy (STM) studies, and to this end, most such studies have hitherto focused only on their structural characterization. Consequently, physico-chemical aspects of topological defects in graphene remain poorly understood, which motivates a thorough understanding both from a fundamental and applied perspective. In this joint Swiss-German proposal, we bring together the TUD and EMPA, to establish a new line of research in atomically-precise synthesis of non-hexagonal rings in nanographenes and GNRs, both in the solution and on the surface, as a route to impart novel properties such as large open-shell biradical character, increased chemical activities and new electronic functionalities. This proposal aims at stimulating mobility of researchers between both countries within this key and strategic field of research with potential economic importance.