Crystal Structure and Growth Mechanism of Unusually Long Fullerene (C60) Nanowires

Abstract

Exceptionally long C₆₀ nanowires, with a length to width aspect ratio as large as 3000, are grown from a 1,2,4-trimethylbenzene solution of C₆₀. They have been formed to possess a highly unusual morphology, with each nanowire being composed of two nanobelts joined along the growth direction to give a V-shaped cross section. The crystal structure of these nanowires is found to be orthorhombic, with the unit cell dimensions of a = 10.2 Å, b = 20.5 Å, and c = 25.6 Å. Structural and compositional analyses enable us to explain the observed geometry with an anisotropic molecular packing mechanism that has not been observed previously in C₆₀ crystal studies. The nanowires have been observed to be able to transform into carbon nanofibers following high-temperature treatment, but the original V-shaped morphology can be kept unchanged in the transition. A model for the nanowire morphology based upon the solvent−C₆₀ interactions and preferential growth directions is proposed, and potentially it could be extended for use to grow different types of fullerene nanowires.