Synthesis and growth mechanism of differently shaped C-60 nano/microcrystals produced by evaporation of various aromatic C-60 solutions

We present a detailed study of the synthesis of C-60 nano- and microrods as well as crystals with normal shapes by the evaporation of C-60 solutions based on different aromatic solvents. C-60 nano- and microrods are grown with high yield by vaporizing C-60 solutions in meta-isomers of aromatic solvents on different substrates while para-isomers give a different type of growth leading to highly crystalline two- and three-dimensional nano- and microcrystals with fcc structure. The role of solvent properties was investigated by using positional isomers containing different halogen radicals. The as-grown crystal rods form hexagonal structures but transform into fcc structure on annealing in vacuum. IR and EDX analysis indicate that solvents remain in the hexagonal nano- and microrods, while it is hard to detect any trace of solvents in the two- or three-dimensional nano- and microcrystals. Furthermore, we present direct proof of the nucleation-growth mechanism for C-60 rods. By the vaporization method, the solubility of C-60 in the studied halogen aromatic solvents is found to correlate with the diameter distribution of the C-60 rods and we suggest that the chemical affinity of the aromatic solvent molecules to C-60 may determine its ability to force C-60 to form rod-shaped crystals. (C) 2009 Elsevier Ltd. All rights reserved.