(201d) Automated and High Precision Measurement of Carbon Nanotube (n,m) Dependent Extraction Conditions in Aqueous Two Phase Extraction

Aqueous two-polymer phase extraction is a sensitive method for separating specific (n,m) structures of single-walled carbon nanotubes (SWCNTs). For surfactant-dispersed SWCNTs, the selecting mechanism for top versus bottom phase extraction in a given separation depends sensitively on the type and chemistry of the adsorbed surfactant layer on each (n,m) species. In practice, two surfactants, sodium dodecyl sulfate (SDS) and sodium deoxycholate (DOC), are generally competed for adsorption on the SWCNT-solution interface, with SDS-coated and DOC-coated (n,m)s partitioning to opposite polymer phases. Recently we demonstrated that the nature of the adsorbed interfacial surfactant layer on each (n,m) species could be determined using near-infrared fluorescence spectroscopy as a function of the solution concentrations of both surfactants. This allows determination of the critical surfactant concentration necessary to change the phase of extraction without actually conducting a separation, and enabled initial determination of such values (PCCC values) for several (n,m) species and determination of surfactant type, surfactant structure, and solution condition effects on the ATPE separation. In this presentation I will describe the extension of the PCCC measurement to greater precision and scope through the automated measurement of gradients in surfactant compositions, including measurements on separability of enantiomers for a greater range of (n,m) SWCNT species and overall impacts to control of (n,m) selection through separation design.