A Mechanistic Study of the Selective Retention of SDS-Suspended Single-Wall Carbon Nanotubes on Agarose Gels

The role of sodium dodecyl sulfate concentration in the separation of carbon nanotubes using gel chromatography

“…For the 2.25% SDS fraction the 1250 nm band experiences a large increase, while peaks at 912, 952, 1112 nm due to the (9, 1), (8,3) and (8,4) species respectively experience little to no change in intensity. The peaks at 975 and 1021 nm due to the (6, 5) and (7,5) nanotubes also exhibit no intensity change upon NaOH addition in the 3.5% SDS fraction. In summary, the addition of sodium hydroxide increases the absorbance intensity of most nanotubes species; however it has a much greater effect on semiconducting species with smaller band gaps.…”

“…In the 1.25% fraction sodium hydroxide reveals the presence of nanotube species with S 11 transitions in the 1100-1400 nm wavelength range that were not visible in the as-eluted spectrum. This is particularly noticeable for the species that contribute absorbance maxima at 1170, 1197, 1322 and 1372 nm, which are assigned to the (12, 1), (11,3), (9,7) and (11,4) nanotubes respectively. At 1.5% the intensity of the band associated with the (9, 5) and (11,1) species around 1250 nm is greatly increased by introduction of NaOH to the solution, while other species also experience increases but to a lesser extent, such as (10, 2) and (9, 4) at 1052 and 1100 nm, respectively.…”

“…In the ideal case, metallic species pass through the gel and are obtained in the initial eluate, while semiconducting species are adsorbed to the stationary phase and may be collected by changing the eluent [5,6]. The mechanism behind the separation is believed to be related to conformational differences between SDS adsorbed on metallic and semiconducting species [7], rather than any size exclusion effects due to selective aggregation or dispersion of either nanotube type [8]. A recent study has shown that for hydrogel media, metallic CNT species dispersed in 0008-6223/$ -see front matter Ó 2013 Elsevier Ltd. All rights reserved.…”

From metal/semiconductor separation to single‐chirality separation of single‐wall carbon nanotubes using gel

“…These results do not support the model of selective bundling and size separation. However, the selective adsorption mechanism has been supported by data from other research groups [31,32]. Initially, agarose gel was chosen for the electrophoresis medium because of its unique pore size; however, it became clear that the selective interaction between the S-SWCNTs and the gel due to the specific combination of surfactant and gel is very important.…”

Effects of purification on the diameter separation of metallic single‐walled carbon nanotubes by gel column chromatography

“…Tanaka et al have suggested that the appropriate dispersibility of SWCNTs coated by surfactants like SDS with a straight alkyl tail and a charged head group allows m‐ and s‐SWCNTs to be discriminated 15. Silvera‐Batista et al proposed that s‐SWCNTs in the initial suspension had a surfactant structure with SDS molecules lying flat on the sidewall of the SWCNTs while m‐SWCNTs had the surfactant oriented away from the nanotube surface 17. The s‐SWCNTs coated by less SDS molecules show stronger adsorption with gel than m‐SWCNTs.…”