Smallest carbon nanowires made easy: Long linear carbon chains confined inside single-walled carbon nanotubes

Abstract The carbon nanowires are defined as long linear carbon chains (LLCCs) or carbynes confined inside carbon nanotubes (CNTs). LLCCs were synthesized previously inside multi-walled CNTs (LLCCs@MWCNTs) and double-walled CNTs (LLCCs@DWCNTs). In this work, a feasible, efficient, controllable and scalable method was developed to mass-produce the smallest carbon nanowires (LLCCs@SWCNTs) consisting of LLCCs encapsulated inside single-walled CNTs (SWCNTs) with diameters of 0.70–0.95 nm. The polyynes were inserted into the open-ended SWCNTs, and then polyynes@SWCNTs were heated at 700 °C in argon gas. A combination of Raman spectra studies and high-resolution transmission electron microscopy observations demonstrated the formation of LLCCs@SWCNTs nanostructure. Density functional theory calculations and reactive molecular dynamics simulations indicated that the polyynes could fuse and grow to LLCCs inside the hollow space of SWCNTs. This work opened new avenues for exploring various physical properties of both LLCCs (carbyne) and LLCCs@SWCNTs, as well as their potential applications in nanoelectronics, nanomechanics and composite nanomaterials.