Centrifugal Length Separation of Carbon Nanotubes

Abstract

Separation of single-wall carbon nanotubes (SWCNTs) by length via centrifugation in a high density medium, and the characterization of both the separated fractions and the centrifugation process are presented. Significant quantities of the separated SWCNTs ranging in average length from <50 nm to approximately 2 microm were produced, with the distribution width being coupled to the rate of the separation. Less rapid separation is shown to produce narrower distributions; these length fractions, produced using sodium deoxycholate dispersed SWCNTs, were characterized by UV-visible-near-infrared absorption and fluorescence spectroscopy, dynamic light scattering, Raman scattering, and atomic force microscopy. Several parameters of the separation were additionally explored: SWCNT concentration, added salt concentration, liquid density, rotor speed, surfactant concentration, and the processing temperature. The centrifugation technique is shown to support 10 mg per day scale processing and is applicable to all of the major SWCNT production methods. The cost per unit of the centrifugation-based separation is also demonstrated to be significantly less than size exclusion chromatography-based separations.

Edge and confinement effects allow in situ measurement of size and thickness of liquid-exfoliated nanosheets

“…Fractionation then allows the collection of size-selected samples. Similar techniques have previously been described in literature to sort carbon nanotubes 40,41 , graphene oxide nanosheets 42 and nanoparticles 43 by their lateral dimensions. While the higher density of the race layer is normally achieved using a density gradient medium, we use a combination of water and deuterated water to minimize the additive content and avoid potential interactions between gradient medium and MoS 2 .…”

Optimizing sonication parameters for dispersion of single-walled carbon nanotubes

“…4, A and B show the three-dimensional (3-D) mappings of the A R and the A R /A NR ratio as a function of the sonication power and the time duration, respectively. The resonant optical absorption depends on the concentration and the average length of isolated SWCNTs, and thus can be used to characterize the degree of debundling of the SWCNTs in the solution [25,29,33]. The initial concentration of SWCNTs was the same, therefore the changes are due to the various sonication parameters.…”

“…In contrast, the resonant absorption shows a strong dependence on the length of the SWCNTs. The long individual SWCNTs can contribute to the high optical absorption intensity [33]. The relative effects of the length, degree of debundling and the concentration of SWCNTs on the resonant absorption and the nonresonant backgroundis shown in Table 1.…”

Empirical evaluation of attractive van der Waals potentials for type-purified single-walled carbon nanotubes

“…Recent advances in the separation of SWCNTs by length and electronic type, however, have ushered in a new era of research focused on the physical attributes and potential applications of highly monodisperse nanotube materials. [17][18][19][20][21][22] In particular, such purified SWCNTs show tremendous promise for flexible electronics applications, 23 where the mechanics of vdW contact forces will play a potentially profound role in dictating device durability and performance. 24,25 One recent study, for example, offered compelling evidence that electronic type can have a significant influence on the durability of flexible transparent SWCNT films, with metallic nanotubes offering improved performance over semiconducting nanotubes.…”