GRAPHENE Ribbons piece-by-piece

A team of researchers conducted a study to demonstrate assembly of atomically precise graphene nanoribbons (GNR) from molecular precursors on metallic substrates. The researchers devised an ingenious scheme that produced GNRs with atomic-scale precision. They synthesized specifically designed molecular precursors consisting of polycyclic aromatic hydrocarbons with two binding sites that were initially protected by halogens such as bromine. It was demonstrated that molecules easily lost their halogens when deposited on a metal surface, activating the binding sites. The surface was heated slightly, the molecules diffused until they located another precursor molecule, and linked up in a linear arrangement programmed by their active binding sites. The resulting polymer chains were heated again, causing the formation of more carbon-carbon bonds by cyclodehydrogenation. This process also resulted in producing a graphene nanoribbon with a predetermined structure that was well-defined.