Pressure-tailored synthesis of confined linear carbon chains

Abstract

High-temperature annealing of carbon nanotubes in both vacuum and in inert gas has been approved to yield linear carbon chains (LCCs) inside the carbon nanotubes. How the environmental pressure utilized for the annealing affects the formation of the LCCs is not studied yet, although it is an important factor to be considered, since the gas molecules could move back and forth inside the carbon nanotubes to prevent the formation of the LCCs. In this paper, the LCCs were synthesized by controlling the pressure during the annealing, and we found that the yield of the LCCs can be indeed tuned by the pressure. Chemical reaction kinetic analysis reveals that the lower the pressure, the smaller the activation energy, which then explains that it is easier to enable the synthesis of the LCCs in better vacuum. In addition, we found that the applied pressures at 10${}^{-3}$ and 10${}^1$ Pa result in similar yields of the LCCs, suggesting that low vacuum is good enough for the synthesis, which would practically benefit the future large-scale synthesis and applications of the LCCs.