Production of small binary carbon clusters by laser ablation of thin films of derivatised fullerenes

Abstract

The distribution of small carbon clusters derived by laser ablation (laser desorption/ionization) of thin films of derivatised fullerenes has been studied. The production of positive and negative ions has been monitored by time-of-flight (ToF) mass spectrometry. The materials under investigation included the [60]fullerene (C 60), hydrogenated and deuterated [60]fullerenes (C 60X 36 where X=H and D), fluorinated [60]fullerenes (C 60F x where x=46 and 48) and the aza[60]fullerene dimer ((C 59N) 2). Following laser ablation using a nitrogen laser, the efficient formation of small, negatively charged carbon clusters has been observed, while the corresponding positively charged clusters were not formed. Derivatised fullerenes display the co-formation of small binary carbon clusters of the type C n X −, where n shows odd/even alternation depending on X which represents the heteroatom initially linked to or networked with the fullerene cage. Although binary carbon clusters C n X − were formed where X=H, D and N, the ablation of fluorofullerene targets would not lead to the formation of C n F − clusters under the applied conditions, as confirmed by ablation experiments with chloro/fluoroalky-polymers. The formation of the binary carbon clusters has been also studied by laser fluence-dependent production of C n D − ions from C 60D 36, and by the production of C n P − ions using a composite C 60/P 4 target. Possible pathways leading to small binary carbon clusters are addressed.