Electronic properties of graphene nanoribbons (GNRs) can be tuned by their doping with heteroatoms, such as nitrogen. This possibility has been extensively studied theoretically, but only a few experimental attempts to synthesize nitrogen-doped GNRs (N-GNRs) by bottom-up approaches have been reported. This talk will be focused on the recently developed bottom-up solution method for gram quantities of narrow GNRs and N-GNRs that are less than 2 nm wide and have atomically precise armchair edges. The method is based on Yamamoto coupling of presynthesized molecular precursors followed by cyclodehydrogenation using Scholl reaction. GNRs and NGNRs were characterized by a number of microscopic (STM, AFM, SEM, TEM) and spectroscopic (XPS, UPS/IPES, UV-vis-NIR, IR and Raman spectroscopy) techniques. GNRs and N-GNRs have large electronic bandgaps, which makes them promising for applications in field-effect transistors with high on-off ratios and photovoltaic devices.<br/><br/>Also discussed in this talk will be self-assembly of GNRs and N-GNRs. We demonstrate that the substitutional doping with nitrogen atoms can trigger the hierarchical self-assembly of nanoribbons into highly ordered structures. This phenomenon is observed both on metal surfaces and in an unrestricted three-dimensional (3D) solution environment. On a surface, N-doping mediates the formation of hydrogen-bonded GNR sheets. In solution, sheets of side-by-side coordinated N-GNRs can in turn assemble via van der Waals and π-stacking interactions into 3D stacks, a process that ultimately produces macroscopic crystalline structures. The optoelectronic properties of these semiconducting NGNR crystals are determined entirely by those of the individual nanoscale constituents, which are tunable by varying their width, edge orientation, termination, and so forth. The atomically precise bottom-up synthesis of bulk quantities of basic N-GNR units and their subsequent self-assembly into crystalline structures suggests that the rapidly developing toolset of organic and polymer chemistry can be harnessed to realize families of novel carbon-based materials with<br/>engineered properties.

Bottom-up synthesis and self-assembly of atomically precise pristine and nitrogen-doped graphene nanoribbons

253rd National Meeting (2017)

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