C.M. Sims, T. Hicks, J.A. Fagan
National Institute of Standards and Technology (NIST),
United States
Keywords: carbon nanotube, CNT, fluorescence, automation, separation, metrology
Summary:
The exceptional optical, thermal, and electronic properties of single-wall carbon nanotubes (SWCNTs) have enabled their use across a broad range of applications, including sensing, photonics, and digital logic. However, the full realization of these properties, and thus, SWCNT technology development, requires the separation of each (n,m) species from commercially synthesized SWCNT mixtures. One effective and scalable approach to isolating these individual (n,m) species, and their handed enantiomers, is surfactant-controlled aqueous two-phase extraction (ATPE), which operates by manipulating differences in solvation energies to isolate target SWCNT species. Despite the utility of the ATPE method for these SWCNT isolations, its vast parameter space complicates its development and optimization. Towards this, we recently developed an automated fluorescence-based spectroscopy titration method that offers significant advances in the throughput and resolution in determining extraction conditions for SWCNTs. Using this method, we have quantified the effects of several ATPE solution parameters on SWCNT extraction conditions, such as temperature, surfactant concentration, or surfactant identity. Here, we use the automated titration method to quantify the effects of additional additives on typical ATPE systems as well as select combinations of these additives. Specifically, the effects of electrolyte additions to the ATPE system as well as the introduction of additional bile salt surfactants were quantified, culminating in the exploration of combinations of the two parameters and their impact on the resultant ATPE separations. Initial results illustrate the potential of these combinations to be used in new and unique ATPE mixtures that could better isolate difficult to separate (n,m) species and their handed enantiomers.