Laboratory study on the fullerene–PAH-derived cluster cations in the gas phase

Abstract

ABSTRACT It is possible that fullerene–polycyclic aromatic hydrocarbon (PAH) clusters or associations of fullerenes with PAHs contain a large fraction of interstellar fullerenes in the interstellar medium. Herein, we report the formation and photofragmentation behaviour of fullerene–PAH derivatives, fullerene/9-vinylanthracene (C16H12) and fullerene/9-methylanthracene (C15H12) cluster cations. Experiments are carried out using a quadrupole ion trap in combination with time-of-flight mass spectrometry in the gas phase. The results show that fullerene (C60)/9-vinylanthracene (e.g. [(C16H12)3C60]+), fullerene (C56 and C58)/9-vinylanthracene (e.g. [(C16H12)4C56]+ and [(C16H12)4C58]+), fullerene (C60)/9-methylanthracene (e.g. [(C15H12)3C60]+), and fullerene (C56 and C58)/9-methylanthracene (e.g. [(C15H12)4C56]+ and [(C15H12)4C58]+) cluster cations, i.e. large fullerene-derived molecules, are formed in the gas phase through the ion–molecule reaction pathway. With irradiation, all fullerene–PAH-derived cluster cations lose their monomolecular groups without other fragmentation channels (e.g. dehydrogenation). The structure of newly formed fullerene–PAH-derived cluster cations and the bond energy for these adduction formation pathways are investigated with theoretical calculations. The obtained results provide a general molecular growth route towards large fullerene–PAH derivatives (e.g. large fullerene-derived molecules) with functional PAHs in a bottom-up formation process and insights into the effect of functional groups (e.g. vinyl, –C2H3, and methyl, –CH3) on their formation and photoevolution behaviours. In addition, the fullerene–PAH-derived clusters (from 83 to 170 atoms in total, or ∼2 nm in size) offer a good model of carbon dust grains, and the relevance to the nanometre-sized carbon dust grain in space is briefly discussed.