UC Berkeley

The functional integration of atomically defined graphene nanoribbons (GNRs) into single-ribbon electronic device architectures has been limited by access to nondestructive high-resolution imaging techniques that are both compatible with common supports such as Si or Si/SiO₂ wafers and capable of resolving individual ribbons in dilute samples. Conventional techniques such as scanning probe (AFM, STM) or electron microscopy (SEM, TEM) have been restricted by requisite sample preparation techniques that are incompatible with lithographic device fabrication. Here we report the design and synthesis of ultralong (∼10 μm) cove-type GNRs (cGNRs) featuring azide groups along the edges that can serve as a universal handle for late-stage functionalization with terminal alkynes. Copper-catalyzed click-chemistry with Cy5 fluorescent dyes gives rise to cGNRs decorated along the edges with fluorescent tags detectable by optical microscopy. The structures of individual dye-functionalized cGNRs spin-coated from a dilute solution onto transparent and opaque insulating substrates were resolved using diffraction-limited fluorescence microscopy and super-resolution microscopy (SRM) imaging techniques. Analysis of SRM images reveals an apparent width of cGNRs in the range 40-50 nm and lengths in excess of 10 μm, the longest GNRs imaged to date. Isolated cGNRs can even be distinguished from bundles and larger aggregates as long as the center-to-center distance is greater than the apparent width.