Synthesis and growth mechanism of differently shaped C_(60) nano/microcrystals produced by evaporation of various aromatic C_(60) solutions

摘要

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 micro-crystals. 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.