Purification of semiconducting single-walled carbon nanotubes by spiral counter-current chromatography

Abstract

Over the last decade man-made carbon nanostructures have shown great promise in electronic applications, but they are produced as very heterogeneous mixtures with different properties so the achievement of a significant commercial application has been elusive. The dimensions of single-wall carbon nanotubes are generally a nanometer wide, up to hundreds of microns long and the carbon nanotubes have anisotropic structures. They are processed to have shorter lengths but they need to be sorted by diameter and chirality. Thus counter-current chromatography methods developed for large molecules are applied to separate these compounds. A modified mixer-settler spiral CCC rotor made with 3 D printed disks was used with a polyethylene glycol-dextran 2-phase solvent system and a surfactant gradient to purify the major species in a commercial preparation. We isolated the semi-conducting single walled carbon nanotube chiral species identified by UV spectral analysis. The further development of spiral counter-current chromatography instrumentation and methods will enable the scalable purification of carbon nanotubes useful for the next generation electronics.

Carbon Nanotubes for Photovoltaics: From Lab to Industry

“…These techniques are based on continuous liquid-liquid phase partitioning and are capable of performing all steps including mixing, centrifugation and extraction of the two phases in an automated flow through manner. For this reason they are already being used in the separation of natural products, [51] biological products, [13a,52] and enantiomers [53] by the chemical and pharmaceutical industries and recently, Zhang et al [54] and Knight et al [55] performed preliminary experiments on SWCNTs. Although there are still many issues with the use of these techniques, including the high viscosity of the two-phase components and low stationary phase retention which leads to low separation purity, [54] this single-step process looks promising to provide industrial-scale single chirality (n,m) species in the future.…”

Production of multi-wall carbon nanotubes starting from a commercial graphite pencil using an electric arc discharge in aqueous medium

“…The lower the ratio, the higher the graphitization degree and the higher the quality and quantity of CNTs present in the sample [32]. The MWCNTs we synthesized had a ratio of 0.243 I D /I G , indicating an elevated graphitization degree and, consequently, the formation of high-quality CNTs [24].…”

“…Over the years, several theoretical and experimental studies of CNT synthesis and purification have been conducted. Most of these synthesis techniques do not achieve the minimum standards, especially concerning nanostructure purity [22][23][24][25]. Most of these methods (CVD, Combustion, HiPco, and others) use metal catalysts, leading to post-synthesis purification processes [26,27].…”

Analytical, Preparative, and Industrial-Scale Separation of Substances by Methods of Countercurrent Liquid-Liquid Chromatography

“…X jn (t) = X j1n (t) + X j2n (t) (33) where a j and N efj are the parameters defined by Equations (28) and (32), respectively; n is the number of cycles (the number of passages of the component j through the column) required to achieve the desired separation. Thus, the continuous SS CLR CCC separation is carried out in three repetitive operating steps: (1)-sample solution loading; (2)-separation of compounds in recycling closed-loop; (3)-elution of the separated compounds with the mobile phase.…”

“…In CCC separations, to hold the stationary phase in a column, centrifugal chromatographs of various designs have been developed and tested [9][10][11][12][13][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. Two types of chromatographs have found practical application: (1) hydrostatic devices, commonly known as centrifugal partition chromatography (CPC), using a constant-gravity field and two rotary-seal joints for inlet and outlet of the mobile phase-a cascade of chambers connected in series by ducts, is placed in a conventional centrifuge [26][27][28][29][30][31][32]40,41]; (2) hydrodynamic devices using a variable-gravity field-a coil column is wound in one or several layers onto the drum of a planetary centrifuge [9][10][11][12][13][32][33][34][35][36]…”