Oligomerization of Dehydrogenated Polycyclic Aromatic Hydrocarbons on Highly Oriented Pyrolytic Graphite

Electron impact ionization was used to generate dehydrogenated monocationic fragments of polycyclic aromatic hydrocarbons (PAHs) coronene, pentacene, hexabenzocoronene, dicoronylene, and rubrene. Upon mass-selective soft-landing deposition onto highly oriented pyrolytic graphite (HOPG) surfaces, these dehydrogenated monomeric species can form strongly bound dimers and oligomers interlinked via newly formed annulated benzene rings as detected by subsequent desorption experiments. The oligomerization degree can be influenced by varying the cation beam composition. The largest desorbable oligomers ranged up to pentamers for both coronene and pentacene fragments. PAH oligomers formed in this way can be considered as short sublimable graphene nanoribbons (GNRs).