  Linear carbon chains (LCCs) have been shown to grow inside double-walled
carbon nanotubes (DWCNTs) but isolating them from this hosting material
represents one of the most challenging tasks towards applications. Herein we
report the extraction and separation of LCCs inside single-wall carbon
nanotubes (LCCs@SWCNTs) extracted from a double walled host LCCs@DWCNTs by
applying a combined tip-ultrasonic and density gradient ultracentrifugation
(DGU) process. High-resolution transmission electron microscopy (HRTEM),
optical absorption, and Raman spectroscopy show that not only short LCCs but
clearly long LCCs (LLCCs) can be extracted and separated from the host.
Moreover, the LLCCs can even be condensed by DGU. The Raman spectral frequency
of LCCs remains almost unchanged regardless of the presence of the outer tube
of the DWCNTs. This suggests that the major importance of the outer tubes is
making the whole synthesis viable. We have also been able to observe the
interaction between the LCCs and the inner tubes of DWCNTs, playing a major
role in modifying the optical properties of LCCs. Our extraction method
suggests the possibility towards the complete isolation of LCCs from CNTs.
