(588a) Selective Colloidal Self-Assembly As a Means of Single-Walled Carbon Nanotube Purification

Colloidal dispersion of single-walled carbon nanotubes (SWCNTs) with DNA, forming the DNA-SWCNT hybrid colloid, has opened up many possibilities in the field of SWCNT purification. DNA-SWCNT can be chromatographically fractionated both by length and chirality, achieving samples of un-paralleled homogeneity.  However, available methods require a high level of equipment and expertise. Here, we report a series of simple methods based on the selective self-assembly of colloidal DNA-SWCNT. Under molecular crowding conditions, DNA-SWCNT self-assemble into nematic rod-like clusters. When the crowding polymer is non-interacting, e. g. polyethylene glycol (PEG), self-assembly is length dependent. We use this effect to fractionate DNA-SWCNT by length. When the polymer is interacting, e. g. polyvinyl pyrrolidone (PVP), self-assembly becomes SWCNT chirality dependent. This selectivity varies with the identity of the salt ions present, as per the Hofmeister effect, and with the sequence of the DNA dispersant. We identify two sequences, (GT)₂₀ and (AC)₂₀, able to produce useful samples with low SWCNT chirality variability. Finally, we report that DNA-SWCNT self-assembly can be induced simply by a high concentration of salt. This effect is length dependent, and can also be used for length fractionation. The solubility behavior suggests a high degree of cooperatively in self-assembly, especially for long SWCNTs. Furthermore, solubility shows the Hofmeister effect with a partial inversion of the series, reportedly associated with comparatively hydrophobic colloids. The many colloidal self-assembly phenomena observed in DNA-SWCNT suggest this versatile particle may be useful for the testing of theoretical formulations on self-assembly.