Synthesis and characterization of single-walled nanotubes produced with Ce/Ni as catalysts

SWNTs were synthesized in high yield in the presence of Ce/Ni as catalyst. Raman and SEM results show that a fraction of the tubes are chiral and have small diameters (the snallest one is 0.79 nm), indicating that Ce plays an important role in the formation. Acid treatment is effective in eliminatin g impurities but changes the morphology and the electric resistance of mats with increasing treatment time. The resistance of as-grown and shea time a cid-treated mats follow a 2D VRH behaviour while mats treated for a long ti me follow a 3D model. The results indicate that hopping conduction occurs o n bundles or on tubes and that there are intrinsic links between tubes in a s-grown mats. (C) 2000 Elsevier Science B.V. All rights reserved.