Carbon Nanowire Made of a Long Linear Carbon Chain Inserted Inside a Multiwalled Carbon Nanotube

A new type of one-dimensional (1D) carbon structure, carbon nanowires (CNWs), was discovered in the cathode deposits prepared by hydrogen arc discharge evaporation of carbon rods. Observation of high-resolution transmission electron microscopy (HRTEM) indicates that a CNW consists of a multiwalled carbon nanotube (MWNT) with a long 1D linear carbon chain (C chain) inserted into its innermost tube of 0.7 nm in diameter. The characteristic Raman peaks of CNWs appeared at around $1850{\mathrm{c}\mathrm{m}}^{-1}$. Raman scattering and HRTEM studies show the formation of a long linear C chain involving more than 100 carbon atoms inside a MWNT. This novel 1D carbon allotrope has potential applications in nanoelectronics, nanomechanics, and nanomaterials.

Figure 1

Proposed atomic model of carbon nanowire (a linear carbon chain inserted inside the innermost tube of a MWNT). The innermost tube is the armchair (5,5) with a diameter of $\sim 0.7\mathrm{n}\mathrm{m}$.

Figure 2

(a) HRTEM micrograph showing both MWNT (left-hand part) and CNW (right-hand part). The carbon chain of CNW and the innermost tube of MWNT are indicated by the arrow and double lines, respectively. (b) HRTEM micrograph of two horizontally aligned CNWs, including the C chains with the length of 20 nm. The left ends of each CNW are capped with hemispheres, especially each of the innermost tubes are capped with a hemisphere of ${\mathrm{C}}_{60}$.

Figure 3

(a) Polarized Raman spectra taken from a straight bundle consisting of MWNTs and CNWs. The bundle oriented along the $Z$ direction and the light propagated along the $Y$ direction. The region of C chain Raman peaks is marked by a dotted rectangle. (b) Result of Lorentzian line shape analysis of the C chain peaks in the ($ZZ$) polarization geometry in (a). (c) Result of Lorentzian line shape analysis of the C chain peaks in the ($ZX$) polarization geometry in (a).