The properties of graphene nanoribbons (GNRs) make them good candidates for next-generation electronic materials. Whereas top-down methods, such as the lithographical patterning of graphene and the unzipping of carbon nanotubes, give mixtures of different GNRs, structurally well-defined GNRs can be made using a bottom-up organic synthesis approach through solution-mediated or surface-assisted cyclodehydrogenation reactions. Specifically, non-planar polyphenylene precursors were first built up from small molecules, and then graphitized and planarized to yield GNRs. However, fabrication of processable and longitudinally well-extended GNRs has remained a major challenge. Here we report a bottom-up solution synthesis of long (>200 nm) liquid-phase-processable GNRs with a well-defined structure and a large optical bandgap of 1.88 eV. Self-assembled monolayers of GNRs can be observed by scanning probe microscopy, and non-contact time-resolved terahertz conductivity measurements reveal excellent charge-carrier mobility within individual GNRs. Such structurally well-defined GNRs may prove useful for fundamental studies of graphene nanostructures, as well as the development of GNR-based nanoelectronics.

From: Akimitsu Narita, Xinliang Feng, Yenny Hernandez,
Søren A. Jensen,
Mischa Bonn, Huafeng Yang,Ivan A. Verzhbitskiy, Cinzia Casiraghi,
Michael Ryan Hansen, Amelie H. R. Koch, George Fytas, Oleksandr Ivasenko,
Bing Li, Kunal S. Mali, Tatyana Balandina, Sankarapillai Mahesh,
Steven De Feyter, Klaus Müllen
“Synthesis of structurally well-defined and liquid-phase-processable graphene nanoribbons“,
Nature Chemistry
6(2), 126-132 (2014).