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

• Applicant: Professor Dr. Xinliang Feng
• Subject Area: Polymer Materials
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 429265950

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.

• DFG Programme: Research Grants
• International Connection: Switzerland
• Partner Organisation: Schweizerischer Nationalfonds (SNF)
• Cooperation Partner: Dr. Pascal Ruffieux