In contrast to the zero-bandgap graphene, laterally confined graphene nanoribbons (GNRs) possess open bandgaps while preserving the high charge-carrier mobilities, making them promising materials for the nanoelectronic and opto-electronic applications. The properties of the GNRs critically depend on their chemical structures such as the width and the edge configuration. Therefore, precise structural control is essential to reproducibly obtain GNRs with desired (opto-)electronic properties. However, the required precision cannot be achieved by the predominant “top-down” fabrication methods, including lithographic “cutting” of graphene sheets and “unzipping” of carbon nanotubes. In this talk, I will present our “bottom-up” approach for the synthesis of atomically precise GNRs, which can be performed “in solution” by the conventional synthetic chemistry1–3 as well as “on surface” using the modern techniques in physics.4,5 By changing the monomer design, a great variety of GNRs can be obtained with different widths, lengths, and edge structures, allowing for the tuning of their bandgaps.6 Time-resolved ultrafast terahertz spectroscopy analysis revealed their excellent photoconductivities, suggesting their potential for transistor applications.1,7 GNRs extending over 600 nm have been achieved by the solution synthesis,1 which enabled fabrication of working transistor devices on isolated GNR strands.8 Moreover, nitrogen (N)-doped GNRs could be synthesized by the surface synthesis, which could be further connected with non-doped GNRs to form molecular heterojunctions.5
1. A. Narita, X. Feng, Y. Hernandez, S. A. Jensen et al., Nature Chem. 2014, 6, 126.
2. A. Narita, I. A. Verzhbitskiy, W. Frederickx, K. S. Mali et al., ACS Nano 2014, 8, 11622.
3. M. G. Schwab, A. Narita, Y. Hernandez et al., J. Am. Chem. Soc. 2012, 134, 18169.
4. J. Cai, P. Ruffieux, R. Jaafar, M. Bieri et al., Nature 2010, 466, 470.
5. J. Cai, C. A. Pignedoli, L. Talirz, P. Ruffieux et al., Nature Nanotech. 2014, 9, 896.
6. A. Narita, X. Feng, K. Müllen, Chem. Rec. 2015, 15, 295.
7. S. A. Jensen, R. Ulbricht, A. Narita, X. Feng et al., Nano Lett. 2013, 13, 5925.
8. A. N. Abbas, G. Liu, A. Narita, M. Orosco et al., J. Am. Chem. Soc. 2014, 136, 7555.