Abstract
Aqueous dispersions of single-walled carbon nanotubes are often made using sodium dodecylsulfate (SDS), which adsorbs to the nanotube surface to stabilise them. Despite SDS being commonly used with single-walled carbon nanotubes, there is no consensus on the structure of the adsorbed layer. Small-angle neutron and X-ray scattering results reported here show that the data can be fitted to a relatively simple core-shell cylinder model, consistent with a polydisperse nanotube core of radius 10Å, surrounded by an adsorbed surfactant layer of thickness 18Å and volume fraction of 0.5. This is consistent with small nanotube bundles surrounded by an adsorbed layer of extended SDS molecules.
Highlights
Aqueous dispersions of single-walled carbon nanotubes are often made using sodium dodecylsulfate (SDS), which adsorbs to the nanotube surface to stabilise them
Molecular dynamics simulations on SDS and sodium cholate (SC) interacting with Single-walled carbon nanotubes (SWCNTs) suggest that SDS and SC have similar binding energies when adsorbed to SWCNTs, suggesting that the binding energy cannot be the sole reason for their difference in buoyancy and subsequent separation when dispersed with SDS and SC [4]
The relative concentrations of SWCNT in each sample was evaluated by comparing the UV–vis absorption in each case, which were compared to a reference SC/SWCNT dispersion, whose concentration was determined as follows
Summary
Aqueous dispersions of single-walled carbon nanotubes are often made using sodium dodecylsulfate (SDS), which adsorbs to the nanotube surface to stabilise them. Small-angle neutron and X-ray scattering results reported here show that the data can be fitted to a relatively simple core-shell cylinder model, consistent with a polydisperse nanotube core of radius 10 Å, surrounded by an adsorbed surfactant layer of thickness 18 Å and volume fraction of 0.5. This is consistent with small nanotube bundles surrounded by an adsorbed layer of extended SDS molecules. The authors proposed a model whereby the adsorbed layer of SDS on s-SWCNTs consisted of SDS molecules lying flat on the SWCNT surface, whereas SDS adsorbed on m-SWCNTs formed a cylindrical micelle-like structure [7]
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