Preparation of metallic single-wall carbon nanotubes

Metallic single-wall carbon nanotubes (m-SWCNTs) have a high electrical conductivity due to ballistic electron transport, and have a bright future for use in nanocircuitry, conductive fibers, and transparent conductive films. To realize these applications, it is essential to obtain pure, high-quality m-SWCNTs on a large scale. In recent years, many techniques such as density-gradient centrifugation, gel chromatography, selective etching, direct growth by catalyst design and external electric field assistance have been developed to prepare m-SWCNTs. Here we present a state-of-the-art overview of the preparation of m-SWCNTs focusing on the principles, methods, and their advantages and limitations. The key challenges remaining for obtaining high quality m-SWCNTs with a high yield are discussed, and the developing trend for the selective preparation of m-SWCNTs is examined. (c) 2019 Elsevier Ltd. All rights reserved.