Graphene nanoribbons—narrow and straight-edged stripes of graphene, or single-layer graphite—are predicted to exhibit electronic properties that make them attractive for the fabrication of nanoscale electronic devices1, 2, 3. In particular, although the two-dimensional parent material graphene4, 5 exhibits semimetallic behaviour, quantum confinement and edge effects2, 6 should render all graphene nanoribbons with widths smaller than 10 nm semiconducting. But exploring the potential of graphene nanoribbons is hampered by their limited availability: although they have been made using chemical7, 8, 9, sonochemical10 and lithographic11, 12 methods as well as through the unzipping of carbon nanotubes13, 14, 15, 16, the reliable production of graphene nanoribbons smaller than 10 nm with chemical precision remains a significant challenge. Here we report a simple method for the production of atomically precise graphene nanoribbons of different topologies and widths, which uses surface-assisted coupling17, 18 of molecular precursors into linear polyphenylenes and their subsequent cyclodehydrogenation19, 20. The topology, width and edge periphery of the graphene nanoribbon products are defined by the structure of the precursor monomers, which can be designed to give access to a wide range of different graphene nanoribbons. We expect that our bottom-up approach to the atomically precise fabrication of graphene nanoribbons will finally enable detailed experimental investigations of the properties of this exciting class of materials. It should even provide a route to graphene nanoribbon structures with engineered chemical and electronic properties, including the theoretically predicted intraribbon quantum dots21, superlattice structures22 and magnetic devices based on specific graphene nanoribbon edge states3.
Figures at a glance
Figure 1: Bottom-up fabrication of atomically precise GNRs. 
Basic steps for surface-supported GNR synthesis, illustrated with a ball-and-stick model of the example of 10,10′-dibromo-9,9′-bianthryl monomers (1). Grey, carbon; white, hydrogen; red, halogens; underlying surface atoms shown by large spheres. Top, dehalogenation during adsorption of the di-halogen functionalized precursor monomers. Middle, formation of linear polymers by covalent interlinking of the dehalogenated intermediates. Bottom, formation of fully aromatic GNRs by cyclodehydrogenation.
Figure 2: Straight GNRs from bianthryl monomers. 
a, Reaction scheme from precursor 1 to straight N = 7 GNRs. b, STM image taken after surface-assisted C–C coupling at 200 °C but before the final cyclodehydrogenation step, showing a polyanthrylene chain (left, temperature T = 5 K, voltage U = 1.9 V, current I = 0.08 nA), and DFT-based simulation of the STM image (right) with partially overlaid model of the polymer (blue, carbon; white, hydrogen). c, Overview STM image after cyclodehydrogenation at 400 °C, showing straight N = 7 GNRs (T = 300 K, U = −3 V, I = 0.03 nA). The inset shows a higher-resolution STM image taken at 35 K (U = −1.5 V, I = 0.5 nA). d, Raman spectrum (532 nm) of straight N = 7 GNRs. The peak at 396 cm−1 is characteristic for the 0.74 nm width of the N = 7 ribbons. The inset shows the atomic displacements characteristic for the radial-breathing-like mode at 396 cm−1. e, High-resolution STM image with partly overlaid molecular model (blue) of the ribbon (T = 5 K, U = −0.1 V, I = 0.2 nA). At the bottom left is a DFT-based STM simulation of the N = 7 ribbon shown as a greyscale image.
Figure 3: Chevron-type GNRs from tetraphenyl-triphenylene monomers. 
a, Reaction scheme from 6,11-dibromo-1,2,3,4-tetraphenyltriphenylene monomer 2 to chevron-type GNRs. b, Overview STM image of chevron-type GNRs fabricated on a Au(111) surface (T = 35 K, U = −2 V, I = 0.02 nA). The inset shows a high-resolution STM image (T = 77 K, U = −2 V, I = 0.5 nA) and a DFT-based simulation of the STM image (greyscale) with partly overlaid molecular model of the ribbon (blue, carbon; white, hydrogen). c, Monolayer sample of chevron GNRs on Au(111): STM image and corresponding ribbon length distribution. d, XPS survey of a monolayer sample of chevron-type GNRs with core levels and valence band (VB) labelled. The C1s core level spectrum (inset) consists of a single component located at 284.5 eV binding energy (full-width at half-maximum, FWHM 0.87 eV). The absence of oxygen-related spectral features proves the chemical inertness of the GNRs with respect to ambient conditions: blue bars indicate the energy position for C–O, C = O and COOH (with increasing chemical shift); see text.
Figure 4: Versatility of bottom-up GNR synthesis. 
