Band-gap engineering and structure evolution of confined long linear carbon chains@double-walled carbon nanotubes under pressure

Long linear carbon chains (LLCCs) with sp hybridization are emerging as a promising realization of carbyne, which has been predicted to be a semiconducting nanowire with tunable electronic properties by external stimuli. Here, the LLCCs confined in double-walled carbon nanotubes have been studied by resonant Raman spectroscopy and density functional theory under high pressure. Our results indicate that the band gap linearly decreases from 2.18 to 1.73 eV as pressure increases, which can be explained by the reduction of the bond length alternation of the chains due to the enhanced interaction between the inner tube and the carbon chain. Furthermore, both our experiment and theoretical calculations show that an irreversible pressure-induced interlinkage between inner tubes and carbon chains forms at the system collapse pressure. In our study this value is of 20 GPa, which is determined by the inner tube diameter. These findings provide important insights for tuning the structural and electronic properties of carbon chains, thus may open new perspectives for the realization of nanoscale cables and devices. (C) 2019 Elsevier Ltd. All rights reserved.