Carbon nanotube synthesis and organization

The synthesis, sorting and organization of carbon nanotubes are major challenges toward future applications. This chapter reviews recent advances in these topics, addressing both the bulk production and processing of carbon nanotubes, and their organization into ordered structures, such as fibers, and aligned arrays on surfaces. The bulk synthetic methods are reviewed with emphasis on the current advances toward mass production and selective synthesis. New approaches for the sorting of carbon nanotubes by structure and properties are described in the context of the specific physical or chemical interactions at play, and referring to the characterization methods described in the contribution by Jorio et al. Recent advances in the organization of carbon nanotubes into fibers are reviewed, including methods based on spinning from solution, from dry forests, and directly from the gas phase during growth. The organization of carbon nanotubes on surfaces, as a critical prerequisite toward future applications in nanoelectronics, is reviewed with particular emphasis given to the synthesis of both vertically and horizontally aligned arrays. Vertically aligned growth has been recently boosted by the development of highly efficient catalytic processes. Horizontally aligned growth on surfaces can yield a whole new array of carbon-nanotube patterns, with interesting physical properties and potential applications. Different mechanisms of horizontally aligned growth include field- and flow-directed growth, as well as recently developed methods of surface-directed growth on single-crystal substrates by epitaxial approaches. The proposed mechanisms pertinent to each technique are discussed throughout this review, as well as their potential applications and critical aspects toward future progress.