Surfactant free fractions of metallic and semiconducting single-walled carbon nanotubes via optimised gel chromatography

Removal of sodium dodecyl sulfate surfactant from aqueous dispersions of single-wall carbon nanotubes

“…Although concentrated HCl (37%) was excluded during the initial qualitative screening, the HCl-SWCNT control sample was fabricated using dilute acid (6 M) based on a previously established literature protocol. [20] A reduction in processing time was observed for the HCl-SWCNT samples (~34%); however, the improvement is not as significant compared to the reagent treatments due to the increased number of processing steps. The EtOH-, DMA-, and CHP-treatments yielded total processing times between 0.5 -1 h, which is ≥82% improvement compared to the SDS-SWCNT control sample.…”

“…A third control sample (referred to as HCl-SWCNT) was prepared using a previously reported procedure for removing sodium deoxycholate from SWCNTs [20]. In short, a 120 mL aliquot of SWCNTs in 2.0 wt% SDS was removed from the stock and mixed with an equal volume of 6 M HCl.…”

“…Alternate approaches have examined the removal of residual SDS and other common surfactants by soaking SWCNT samples in concentrated nitric acid, which is proposed to remove the residual SDS, as well as defective SWCNTs from the sample [9][10][11][12]19]. Furthermore, acidification of the surfactant salt with HCl creates a byproduct that can be solubilized and washed away with ethanol [20]. More sophisticated techniques have focused on the decomposition of organic compounds, such as surfactants, through the use of the Fenton reaction [21]; however, as with the acid treatments this is a time consuming process that has not been shown to fully remove the residual SDS from the SWCNTs.…”

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

“…Carbon nanotubes (CNTs) are carbon-carbon extended polymers in 2 dimensions with fused sp2 orbitals having aromaticity [4][5]. The sheets form long tubes, the nanotubes; when they remain sheet-like they The semi-conducting species of carbon nanotubes have been separated by density gradient ultracentrifugation [5,11] ion exchange, gel chromatography and electrophoresis [12][13][14][15]. Separation methods also include chiral nano-tweezers [16].…”

“…The nanotubes are solubilized in water by binding with anionic surfactants such as sodium dodecyl sulfate SDS [12] and DNA [13], and processes separate on the basis of surface charge which varies with the sizes of the particles. Since CNTs can bind with dextran [15], column and ATPE (aq. phase extraction) methods using dextran [17] or related materials are used.…”