  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.
