Purity-enhanced bulk synthesis of thin single-wall carbon nanotubes using iron–coppercatalysts

Abstract

We report high purity and high yield synthesis of single-wall carbon nanotubes (SWCNTs)of narrow diameter from iron–copper bimetal catalysts. The SWCNTs with diameter of0.8–1.2 nm are synthesized using the zeolite-supported alcohol chemical vapour depositionmethod. Single metal and bimetal catalysts are systematically investigated to achieve boththe enhancement of SWCNT yield and the suppression of the undesired formation ofgraphitic impurities. The relative yield and purity of SWCNTs are quantified using opticalabsorption spectroscopy with an ultracentrifuge-based purification technique. For thesingle metal catalyst, iron shows the highest catalytic activity compared withthe other metals such as cobalt, nickel, molybdenum, copper, and platinum. Ithas been found that the addition of copper to iron results in the suppression ofcarbonaceous impurity formation without decreasing the SWCNT yield. Thepurity-enhanced SWCNT shows fairly low sheet resistance due to the improvement ofinter-nanotube contacts. This scalable design of SWCNT synthesis with enhancedpurity is therefore a promising tool for shaping future high performance devices.