Raman spectroscopy and transmission electron microscopy of long linear atomic carbon chains generated by field electron emission accompanied with electrical discharge of carbon nanotube films

Carbyne is a carbon allotrope whose structure is a one-dimensional chain of sp-hybridized carbon atoms. Carbyne's mechanical and electrical properties, as predicted by theoretical studies, have attracted great interest because they would lead to many promising applications. Thus, much effort has been devoted to the synthesis of carbyne. Long linear atomic carbon chains encapsulated in carbon nanotubes have recently been produced by high-temperature heat treatment of double-wall carbon nanotubes (DWCNTs). Here, we present an alternative approach to produce long linear carbon chains: field electron emission accompanied by electrical discharge from single-wall carbon nanotube (SWCNT) films. Raman spectroscopy and transmission electron microscopy were performed on SWCNT films after the electrical discharge during field electron emission. The results showed that a large number of long linear carbon chains were formed within the SWCNTs and DWCNTs. For DWCNTs with an inner diameter of 0.7 nm, the atomic carbon chains lay directly along the central tube axis. However, for SWCNTs with an inner diameter of 1.0 nm, the encapsulated carbon chains were bent in some places and positioned close to the nanotube wall, away from the central tube axis.