Determination of carbon nanotube density by gradient sedimentation.
Density gradient centrifugation is a high-resolution technique for the separation and characterization of large molecules and stable complexes. We have analyzed various nanotube structures by preparative centrifugation in sodium metatungstate-water solutions. Bundled, isolated and acid-treated single-walled nanotubes (SWNTs) and multiwall nanotubes (MWNTs) formed sharp bands at well-defined densities. The structure of the material in each band was confirmed by transmission electron microscopy and Raman spectroscopy. Our data suggest respective densities of 1.87, 2.13, 1.74, and 2.1 g/cm(3) for bundled, isolated, and acid-treated SWNTs and MWNTs. These measured results compare well with their calculated densities.
Lu
Qi
Q
Department of Physics and Astronomy, Department of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634, USA.
Keskar
Gayatri
G
Ciocan
Razvan
R
Rao
Rahul
R
Mathur
Rakesh B
RB
Rao
Apparao M
AM
Larcom
Lyndon L
LL