Single wall carbon nanotubes (SWCNT) have been heralded to be transformative for electronic devices; however, to date very few transformative commercial products have been launched. A key barrier that has hindered wide-scale adoption of SWCNTs is that single chirality forms are needed and current separation techniques are still far from providing an economical large scale chiral separation with reasonable purity, especially for large diameter SWCNTs. This is due to a variety of reasons, the most important of which is that these methods tend to lack sufficient “tuning” parameters which permit the facile sorting of large numbers of SWNT chiral forms with minimal cross contamination between the sorted fractions. To address this challenge, we employed differential surface properties of various chiral forms as a driving force in order to achieve chiral separation. Zeta potential measurements were used to demonstrate that a wide variation in SWCNT surface charge exist at a fixed pH. We furthermore demonstrated that this change is chiral dependent and due to the existence of functional groups that are introduced inadvertently during SWCNT synthesis. These groups give the SWCNT surface some degree of ionic and hydrophilic character, in addition to its main hydrophobic nature. In our work we not only recognized the existence of these groups, but we exploit their presence for chiral separations and even enhance their existence to develop new and more effective methods for separating SWCNTs. Using this approach, various chromatography methods have been developed, and the results obtained from these methods indicate that the surface charges on large diameter SWCNTs are chiral dependent and a strong function of pH, that pH and salt concentration (as well as the selection of the adsorbent base material) can be used to control the chiral-based SWCNT adsorption to, and the desorption from, cation exchangers, anion exchangers and multimodal adsorbents in a rational manner. By exploiting these effects, new and highly effective methods can be developed for fractionating SWCNT into individual chiral forms.<br/>

Investigation of charge-based chromatographic methods for sorting carbon nanotube chiral forms

255th National Meeting (2018)

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