Solution-Based Synthesis of Atomically Precise Graphene Nanoribbons

Because of its extraordinary electronic, mechanical, thermal and optical properties, graphene is often considered as a complement to, and in some cases even a replacement for silicon in future electronics. However, the absence of an energy bandgap in graphene prevents its use in logic applications. Theoretical studies have shown that an energy gap can be induced in narrow strips of graphene with high aspect ratios, which are often referred to as graphene nanoribbons (GNRs). However, synthesis of high-quality narrow GNRs remains a great challenge. In this dissertation, we demonstrate that GNRs with different widths, geometries and edge structures can be synthesized by Yamamoto coupling of molecular precursors followed by Scholl oxidative cyclodehydrogenation. Electronic properties of GNRs could be further tuned via their doping with heteroatoms, such as boron or 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. We demonstrate that the same approach based on Yamamoto coupling of molecular precursors containing nitrogen atoms followed by cyclodehydrogenation via Scholl reaction can be used for the synthesis of high-quality N-GNRs as well. Several characterization techniques including solid-state NMR, X-ray photoelectron, UV-Vis-NIR, Raman spectroscopy, atomic force microscopy, scanning tunneling microscopy and scanning electron microscopy were employed to study GNRs. These studies confirmed the high structural quality of GNRs and N-GNRs, as well as their unusual aggregation behavior and intriguing electronic and optical properties. I will also discuss future challenges in the synthesis of GNRs with tunable properties, as well as progress in applications of GNRs in electronics, photovoltaics and composite materials