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

自从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，石墨烯被发现具有许多特殊的性质。特别是，其优异的载流子迁移率使石墨烯成为未来最有希望用于纳米电子的材料之一。然而，石墨烯是一种没有带隙的半金属，这阻碍了它在数字晶体管中的应用。因此，在开发基于石墨烯的电子器件之前，找到一种打开禁带的方法至关重要。最突出的方法是在一维纳米宽度的半导体石墨烯条纹中实现载流子的量子限制--即石墨烯纳米带(GNRs)。最近确定了两种编制国民总收入的主要方法，即“自上而下”和“自下而上”方法。“自下而上”方法是一种受有机化学启发的会聚的、全合成的方法，为GNR提供了原子上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在溶液中介的环境中经典地进行，也可以在金、银或铜等贵金属衬底上进行。影响石墨烯电子结构的另一种途径是在石墨烯的基面引入缺陷。理论计算表明，石墨烯中的拓扑缺陷对其电子、光学、化学、热和机械性能有很大影响。从能量稳定性的观点来看，五边形-七角体对是一种合理的缺陷模型，可以由原子位错诱导。利用透射电子显微镜和扫描隧道显微镜的研究已经在实验上证实了拓扑缺陷的存在，为此，到目前为止，大多数这类研究只集中在它们的结构表征上。因此，石墨烯中拓扑缺陷的物理化学方面仍然知之甚少，这促使人们从基础和应用的角度进行彻底的理解。在这项瑞士和德国的联合提案中，我们将TUD和EMPA结合在一起，建立了一条新的研究路线，在溶液和表面上原子精确合成纳米级和GNR中的非六角环，作为一条途径来赋予新的性质，如大的开壳双自由基特性，增加的化学活性和新的电子功能。这项提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内的流动。

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.