Growth of single wall carbon nanotubes from $^{13}$C isotope labelled   organic solvents inside single wall carbon nanotube hosts
  Exploring the synthesis of novel molecular nanostructures has been in the forefront of material research in the last decade. One of the most interesting nanostructures are single wall carbon nanotubes (SWCNTs). Their catalyst free growth, however, remains an elusive goal. Here, we present the growth of single wall carbon nanotubes from organic solvents such as benzene and toluene in a confined environment, inside a host SWCNT. The solvents encapsulated in SWCNTs are transformed to an inner tube when subject to a heat treatment under dynamic vacuum at 1270 $^{\circ}$C. We used isotope labeling of the different carbon sources to prove that the source of the inner tubes is indeed the solvent. Our results put constraints on the models explaining the inner tube growth and provides a simple alternative for the fullerene based inner tube growth. It also provides the possibility to study a completely new field of in-the-tube chemistry. 
Ferenc Simon and Hans Kuzmany