Length distribution of single walled carbon nanotubes determined by ac   atomic force microscopy
  A simple method to disperse individual single walled carbon nanotubes (SWCNT ) on an atomically flat substrate is presented. Proper tuning of ac modes of atomic force microscopes(AFM) is discussed. This is needed to discriminate between individual nanotubes and very small bundles. The distribution of lengths of the nanotubes measured by these methods is reported. 
Richard Piner and Rodney S. Ruoff