Extracting subnanometer single shells from ultralong multiwalled carbon nanotubes

doi:10.1073/pnas.0505219102

Extracting subnanometer single shells from ultralong multiwalled carbon nanotubes

^*Nanoscale Science and Engineering Center, Columbia University, New York, NY 10027; and ^†National Creative Research Initiative Center for Superfunctional Materials, Department of Chemistry, Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea

Edited by Charles M. Lieber, Harvard University, Cambridge, MA (received for review June 22, 2005)

Abstract

We report a simple but powerful method for engineering multi-walled carbon nanotubes (MWNTs) by using manipulation by an atomic-force microscope. The successive shell-by-shell extraction process of ultralong MWNTs allows the exposure of the innermost single-walled carbon nanotubes (SWNTs), which have diameters as small as ≈0.4 nm. The inner-shell extraction process changes the electrical characteristics of the MWNTs. Whereas the outer hollowed-out nanotubes show either metallic or semiconducting character, the innermost SWNTs of small diameter exhibit predominantly metallic transport properties.

Footnotes

↵ ‡ To whom correspondence may be addressed. E-mail: pkim{at}phys.columbia.edu or kim{at}postech.ac.kr.
Author contributions: B.H.H., P.K., and K.S.K. designed research; B.H.H., J.P.S., M.S.P., A.M., M.Y.S., F.W., and J.Y.L. performed research; B.H.H. contributed new reagents/analytic tools; B.H.H., T.F.H., L.E.B., P.K., and K.S.K. analyzed data; and B.H.H., T.F.H., L.E.B., P.K., and K.S.K. wrote the paper.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: MWNT, multi-walled carbon nanotube; AFM, atomic-force microscope; SWNT, single-walled carbon nanotube; SEM, scanning electron microscope.