Unsymmetrical graphene nanoribbons: tuning the edges through regioselective photochemical cyclodehydrochlorination

Novel graphene nanoribbons (GNRs) were prepared from polychlorinated polyphenylene precursors by the photochemical cyclodehydrochlorination (CDHC) reaction. The successful preparation of both laterally symmetrical and unsymmetrical GNRs demonstrates the regioselectivity, edge configuration control, and efficiency of the CDHC reaction. 1 H NMR, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy confirmed the structures of the GNRs. The optical and electronic properties of the GNRs were studied by UV–vis and photoluminescence analysis. The laterally symmetrical and unsymmetrical GNRs have a bandgap of 3.10 and 2.70 eV, respectively, and both are emissive in the visible region.