Helically Coiled Graphene Nanoribbons.

Graphene is a zero-gap, semiconducting 2D material that exhibits outstanding charge-transport properties. One way to open a band gap and make graphene useful as a semiconducting material is to confine the electron delocalization in one dimension through the preparation of graphene nanoribbons (GNR). Although several methods have been reported so far, solution-phase, bottom-up synthesis is the most promising in terms of structural precision and large-scale production. Herein, we report the synthesis of a well-defined, helically coiled GNR from a polychlorinated poly(m-phenylene) through a regioselective photochemical cyclodehydrochlorination (CDHC) reaction. The structure of the helical GNR was confirmed by 1 H NMR, FT-IR, XPS, TEM, and Raman spectroscopy. This Riemann surface-like GNR has a band gap of 2.15 eV and is highly emissive in the visible region, both in solution and the solid state.