Creation and Characterization of Aligned Single-Wall Carbon Nanotube Films

The one-dimensional nature of individualized single-wall carbon nanotubes (SWCNTs) enables highly anisotropic thermal, optical, and electronic behavior. Commercial applications, like optical polarizers and electrical current delivery, are thus possible from ensembles of aligned SWCNTs. However, the relative absence of easy-to-perform SWCNT alignment techniques, and thus the lack of polarized nanotube films, has hindered scientific and technical investigations of anisotropic phenomena in SWCNT ensembles. Here, we demonstrate macroscopic SWCNT alignment of both semiconductor and metallic nanotubes using slow vacuum filtration, which builds on a recently discovered method for nanotube alignment. Utilizing polyvinylpyrrolidone-coated filter membranes and surfactant-separated SWCNTs, we are able to produce highly polarized nanotube thin films. We measure the degree of the nanotube polarization using both optical microscopy and polarized optical absorption. From the latter, we find that a nematic ordering parameter of over 0.2 can be achieved, which is close to the theoretical maximum of 0.6; polarized Raman spectroscopy confirms these results. Future measurements using temperature-dependent electrical transport will investigate the feasibility of using these aligned nanotubes for very large electrical current-delivery applications.