Morphology and Melting Behavior of Ionic Liquids inside Single-Walled Carbon Nanotubes

Abstract

We report the synthesis and characterization of single-walled carbon nanotubes (SWNTs) filled with a zinc-containing quaternary ammonium based ionic liquid (ChZnCl(3)) inside. The threshold SWNT diameter for efficient encapsulation was determined to be ca. 0.97 nm. Different morphologies of the encapsulated ChZnCl(3) such as single-chain, double-helix, zigzag tubes, and random tubes were observed. The melting of ChZnCl(3) ionic liquid into "nanofluid" inside SWNTs was investigated by in situ TEM electron beam irradiation and compared with a high-temperature heat treatment. The thermal-decomposition temperature of the ChZnCl(3) ionic liquid confined in the SWNTs was much higher than in the bulk system. Furthermore, the doping effect of the encapsulated ChZnCl(3) on the host SWNTs can be varied (from p-type to n-type) by gradually reducing the filling ratio. The versatility of ionic liquids and the unique phase transition observed inside the SWNTs provide a new opportunity for modulating the electronic properties of carbon nanotubes.