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Reports: ND1051719-ND10: New Strategies for the Preparation of Graphene Nanoribbons

Jean-Francois Morin, Universite Laval

The goal of our research with this project funded by the PRF was to develop new strategies for the preparation of graphene nanoribbons using the tools of organic chemistry. The idea of using solution chemistry rather than well-known physical methods for the preparation of such materials was to have better control over the size, the shape and chemical nature of the resulting graphene nanoribbons to meet the requirement of the electronics industry in terms of materials purity, uniformity and properties. The methodology used to prepare graphene nanoribbons was not exactly the same we described in the proposal. However, we can say for sure that our methodology is by far superior in terms of synthetic feasibility and rapidity. Previous to this grant, we have developed a method to efficiently prepare aryl-appended polydiacetylenes (PDAs) for optical sensors applications. With the ACS-PRF grant money, we decided to investigate these PDAs as starting materials for the preparation of graphene nanoribbons. The initial hypothesis is that the arylenyne moieties within the PDA scaffold could be cycloaromatized to form fused aromatic systems (graphene nanoribbons) upon irradiation with UV light or gentle heating (Figure 1).

Figure 1. Synthesis of graphene-type materials from aryl-appended PDA

After one year and a half, we are now at determining the exact chemical nature of the materials we obtained. Although not perfect, the chemical structure of the graphene nanoribbons we obtained present unique electronic and optical properties that could be exploited in many applications. Moreover, we have undertaken the modification of the chemical functions present on the nanoribbons in order to obtain new electronic and optical properties.       

In the first year of the grant, we reported the synthesis of two-dimensional graphene-like materials from long butadiyne-containing, reactive organic precursors (Figure 2).

Figure 2. Synthesis of graphene-like materials from reactive precursors

In the second year of the grant, we applied what we learned in the first year to different architectures. We prepare one-dimension (nanotubes and wires) structures on which we made different chemical modifications to change their properties. Among others, we used thermal treatment on one- and two-dimensional materials to completely graphitize their structure (Figure 3). Although we have not obtained the expect results, the experiments allowed us to understand a great a deal about chemical reactivity of PDA.

Figure 3. TEM imaging of pyrolyzed cobalt-containing PDA-walled nanorods. The scales are: (a) 100 nm and (b) 20 nm.

The ACS-PRF New Direction grant has had a great impact in my early career. The money I got accounted for a significant part of all the grants I had from different sources in the past two years. Only in the past year, it allows me to hire 3 graduate students to work on the development of new methodologies for the preparation of graphene nanoribbons and two-dimensional graphene-like materials. In only two years, this project has become the main focus of my research group with 4 graduate students now working on it full time. Without this money, I would not have started this successful project. The students I have been able to hire with this money got training in a highly hot topic and one of them is now a postdoc fellow at Stanford University. Because this project is multidisciplinary, it allows the student to learn different techniques, going from chemical synthesis to materials characterization. With several papers published on graphene-related materials, this project is undoubtedly a real success in term of scientific production and advancement of scientific knowledge.