  The extreme instability and strong chemical activity of carbyne, the infinite
sp1 hybridized carbon chain, are responsible for its low possibility to survive
in ambient conditions. Therefore, much less has been possible to explore about
carbyne as compared to other novel carbon allotropes such as fullerenes,
nanotubes and graphene. Although end-capping groups can be used to stabilize
carbon chains, length limitation is still a barrier for its actual production,
and even more for applications. Here, we report a novel route for bulk
production of record long acetylenic linear carbon chains protected by thin
double-walled carbon nanotubes. A corresponding extremely high Raman band is
the first proof of a truly bulk yield formation of very long arrangements,
which is unambiguously confirmed by transmission electron microscopy and
near-field Raman spectroscopy. Our production establishes a way to
exceptionally long stable carbon chains including more than 2300 carbon atoms,
and an elegant forerunner towards the final goal of a bulk production of
essentially infinite carbyne.
