Double-wall carbon nanotubes

Abstract

Double-wall carbon nanotubes (DWNTs) are the simplest archetypical manifestation of MWNTs and as such combine the outstanding properties of SWNTs with the possibility to study concentric intertube interactions with high precision. Two complementary routes for the efficient growth of DWNTs are discussed. Firstly, SWNTs filled with various carbon sources, such as fullerenes or acenes can form inner-shell tubes by a high-temperature treatment under clean-room conditions. Inner-outer tube pairs can be identified with a well-defined mutual chirality. Isotope labeling and full isotope substitution is possible. Using different carbon sources, DWNTs with intrinsic functionality and special electronic and magnetic properties can be grown. Alternatively, a direct growth using chemical vapor deposition and subsequent purification is described. Large-scale growth of very long continuous DWNTs for application in composites and as advanced field emission sources are straightforward for this technique. The two techniques for growth of DWNTs are evaluated with respect to their scientific novelty and application potential. Stability, electronic structure, transport and mechanical properties are reviewed.