title: Processing and properties of highly enriched double-wall carbon nanotubes.
abstract: Carbon nanotubes consist of one or more concentric graphene cylinders and are under investigation for a variety of applications that make use of their excellent thermal, mechanical, electronic and optical properties. Double-wall nanotubes are ideal systems for studying the interwall interactions influencing the properties of nanotubes with two or more walls. However, current techniques to synthesize double-wall nanotubes produce unwanted single- and multiwall nanotubes. Here, we show how density gradient ultracentrifugation can be used to separate double-wall nanotubes from mixtures of single- and multiwall nanotubes through differences in their buoyant density. This technique results in samples that are highly enriched in either single- or double-wall nanotubes of similar outer wall diameter, with the double-wall nanotubes being, on average, approximately 44% longer than the single-wall nanotubes. The longer average length of the double-wall nanotubes provides distinct advantages when they are used in transparent conductors.
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, USA.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Green
authors.forename: Mark C
authors.initials: MC
authors.lastname: Hersam