Graphene Nanoribbons via Crystal Engineering

Abstract

A new synthesis of graphene nanoribbons has been reported by Rubin and coworkers which combines the advantages of straightforward organic synthesis, intelligent crystal engineering, and high-yielding solid state transformations. 1 By carefully selecting simple aryl diyne monomer (6, Fig. 1), the authors report a crystal structure with very short intermolecular distances that favors topochemical polymerization in the crystalline state to long polydiacetylene (PDA, 7) chains. These rigid polymers can then be dispersed in an organic solvent, patterned onto a substrate and undergo full graphitization at moderate temperatures (300˚C, 8). This work represents a significant step forward as it proves that intelligent monomer design and crystal engineering can obviate the need for pyrolytic temperatures, tedious lithographic manipulation of graphene and the use of complex organic precursors and solution phase oxidative dehydrogenation.As progress accelerates to establish graphene as a post-silicon electronic material, interest has grown in the synthesis and applications of graphene nanoribbons (GNRs). 2 Two dimensional graphene sheets are ballistic conductors in all directions with a zero-energy Dirac point. For applications in transistors and related nanoelectronics, the development of a narrow but distinct bandgap in graphene is paramount. It has been established that confining the sheet in one direction to a narrow strip with a high aspect ratio offers the creation and control of a bandgap with energy inversely related to GNR width. GNRs have already shown good performance in OFET applications but the production of atomically precise ribbons on scale remains a significant barrier to the utility of nanoribbon transistors.GNRs exist in the often-explored frontier between small molecule and bulk material. From an electronics standpoint, this is where the action is. Where molecules like GNRs, Fullerenes, and monodisperse carbon nanotubes prove that confinement of materials dimensions and expansion beyond molecular architectures offers up