A kinetic model for the deterministic prediction of gel-based single-chirality single-walled carbon nanotube separation.

ABSTRACT

We propose a kinetic model that describes the separation of single-chirality semiconducting carbon nanotubes based on the chirality-selective adsorption to specific hydrogels. Experimental elution profiles of the (7,3), (6,4), (6,5), (8,3), (8,6), (7,5), and (7,6) species are well described by an irreversible, first-order site association kinetic model with a single rate constant describing the adsorption of each SWNT to the immobile gel phase. Specifically, we find first-order binding rate constants for seven experimentally separated nanotubes normalized by the binding site molarity (M(θ)) k7,3 = 3.5 × 10⁻5 M(θ)⁻¹ s⁻¹, k6,4 = 7.7 × 10⁻8 M(θ)⁻¹ s⁻¹, k8,3 = 2.3 × 10⁻9 M(θ)⁻¹ s⁻¹, k6,5 = 3.8 × 10⁻9 M(θ)⁻¹ s⁻¹, k7,5 = 1.9 × 10⁻¹¹ M(θ)⁻¹ s⁻¹, k8,6 = 7.7 × 10⁻¹² M(θ)⁻¹ s⁻¹, and k7,6 = 3.8 × 10⁻¹² M(θ)⁻¹ s⁻¹. These results, as well as additional control experiments, unambiguously identify the separation process as a selective adsorption. Unlike certain chromatographic processes with retention time dependence, this separation procedure can be scaled to arbitrarily large volumes, as we demonstrate. This study provides a foundation for both the mechanistic understanding of gel-based SWNT separation as well as the potential industrial-scale realization of single-chirality production of carbon nanotubes.