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Progress Towards Single Crystals of Carbon Nanotubes

Kono, Junichiro (Rice University,USA)

Despite many years of worldwide efforts, there is presently no established method for producing large-area single-domain films of highly aligned, densely packed, and chirality-enriched single-wall carbon nanotubes (SWCNTs). If developed, such a method can eventually lead to the realization of a SWCNT crystal – i.e., a 3D object consising of a period array of SWCNTs that maintains the extraordinary properties of individual nanotubes. Here, we report a new, promising method for achieving this long-standing goal. Utilizing spontaneous alignment that occurs during vacuum filtration, we have produced a wafer-scale (i.e., inch-size) film of aligned SWCNTs [1]. This method is universal applicable to SWCNTs synthesized by different methods and can be scaled up in all three dimensions. We characterized the produced large-area films using a variety of microscopy, spectroscopy, and electronic transport techniques, demonstrating nearly perfect global alignment with a single domain. The strikingly high degree of alignment of our films with a nematic order parameter of ~ 1 and a thickness of ~100 nm distinguishes our method from previously reported 2D and 3D postgrowth assembly techniques. We investigated the mechanisms underlyng the observed global spntaneous alignment, based on a proposed model of 2D confinement induced phase transitions. We discuss how the degree of alignment depends on the filtration speed, the SWCNT concentration, the surfactant concentration, the hydrophilicity of the filter membrane surface, the SWCNT length, and the SWCNT diameter.

[1]. X. He, W. Gao, L. Xie, B. Li, Q. Zhang, S. Lei, J. M. Robinson, E. H. Hároz, S. K. Doorn, R. Vajtai, P. M. Ajayan, W. W. Adams, R. H. Hauge, and J. Kono

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