Graphene Nanoribbons Through Directed Self-Assembly

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Professor Yves F. Rubin of the Department of Chemistry and Biochemistry at the University of California-Los Angeles is supported by the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program of the Division of Chemistry to develop a novel synthetic approach for the preparation of graphene nanoribbons from small organic molecule starting materials using only light and heat. The project addresses a unique synthesis method which promises to expand the toolbox for polymeric and two-dimensional materials while creating a variety of graphene nanoribbons of controlled compositions and widths. Graphene is one of the thinnest and strongest materials known. It exhibits excellent electricity and heat conduction and light absorption properties. This project addresses the challenges and limitations of preparing graphene nanoribbons with various chemical groups incorporated during the fabrication of the next generation of nanoelectronic devices and technologically important applications. The students involved in the project are trained in organic synthesis, material characterization and device fabrication. A student exchange program with the Department of Materials Science and Engineering at UC Merced (an Hispanic serving institution) promotes research collaborations that are beneficial to a diverse group of graduate and undergraduate students from both institutions. The project offers a new approach to making graphene nanoribbons with structures that would otherwise be difficult to access using currently-available, bottom-up synthesis methodologies. The approach utilizes the topochemical polymerization of 1,4-diarylbutadiyne monomers to build the corresponding polydiacetylenes, which are then converted thermally to graphene nanoribbons in a separate, quantitative step via a series of cyclizations and dehydrogenations. This approach has a strong advantage in that the graphene nanoribbon synthesis can be carried out without the use of any reagent other than light and heat. The availability of a number of self-associating 1,4-diarylbutadiynes, including heterocyclics, assures the creation of a variety of graphene nanoribbons of controlled compositions and widths varying between 0.5 - 2.0 nm, depending on the alkyne precursor used. The project resolves one of the synthetic challenges for preparing graphene nanoribbons by completely removing external chemicals during the two main chemical transformations involved in the synthesis, thus allowing for the preparation of graphene nanoribbons in situ in electronic devices. The sought-after graphene nanoribbon products are expected to have properties similar to silicon with bandgaps varying between 0.5 and 2.5 eV, depending on nanoribbon composition, structure and width.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.