Temperature dependent separation of metallic and semiconducting carbon nanotubes using gel agarose chromatography

Abstract

Post-synthesis separation between metallic (m-SWNTs) and semiconducting (s-SWNTs) singlewall carbon nanotubes (SWNTs) is remaining a challenging process for the reliable fabrication of high performance electronic devices. Gel agarose chromatography is emerging as an efficient and large scale separation technique. However, the full (100%) separation of m-SWNTs and s-SWNTs has not been reached yet, mainly due to the lack of understanding of the separation mechanism. Here we study the temperature effect on the separation via gel agarose chromatography by varying the separation process temperatures between 6C and 50C, for four different SWNT sources. Exploiting the gel agarose micro-beads filtration technique we achieved up to 70% m-SWNTs and more than 90% s-SWNTs, independent of the source material. The process is temperature dependent, with improved yields up to 95% for s-SWNT (HiPco) at 6C. Temperature affects the sodium dodecyl sulfate SDS surfactant-micelle distribution along the SWNT sidewalls, thus helping to act as an aid in the sorting of SWNTs by electronic type. The sorted SWNTs are then used to fabricate transistors with very low OFF-currents (10^-13 A), high ON/OFF current ratio (>10^6) and improved charge carriers mobility.