We successfully synthesized carbon nanotubes with very small diameters (5–10 nm) at room temperature by using high energy laser pulses (193 nm, 5 J/cm2 and 20 ns duration time) to re-excite the carbon species contained in the laser ejected plume. The carbon nanotubes, which presumably formed in gas phase, were preferentially collected by electro-statically biasing (∼ 5 kVDC) the substrates. High resolution transmission electron microscopic analysis reveals that thus obtained materials are multiwall carbon nanotubes.
The pure double-walled carbon nanotubes ͑DWNTs͒ and two endohedral DWNTs ͑DWNTs with materials filled inside͒ are produced. The filling materials are CoI 2 and KI, respectively. The ferromagnetism ͑FM͒ is observed in pure DWNTs. The content of residual catalyst Fe is too small to be responsible for the observed FM. On the other hand, after filling KI or CoI 2 into the tubes, over 87% of FM is suppressed. This suggests that the origin of FM in nanotubes is mainly from the hydrogen chemisorptions induced in the process of acid purification. With the knowledge of FM origin, it is then possible to enhance FM of carbon nanotubes or graphene for applications relying on magnetism.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.