A Molecular Simulation Probing of Structure and Interaction for Supramolecular Sodium Dodecyl Sulfate/Single-Wall Carbon Nanotube Assemblies

Abstract

Here we report a larger-scale atomic-level molecular dynamics (MD) simulation for the self-assembly of sodium dodecyl sulfate (SDS) surfactant on single-walled carbon nanotube (SWNT) surfaces and the interaction between supramolecular SDS/SWNT aggregates. We make an effort to address several important problems in regard to carbon nanotube dispersion/separation. At first, the simulation provides comprehensive direct evidence for SDS self-assembly structures on carbon nanotube surfaces, which can help to clarify the relevant debate over the exact adsorption structure. We also, for the first time, simulated the potential of mean force (PMF) between two SWNTs embedded in SDS surfactant micelles. A novel unified PMF approach has been applied to reveal various cooperative interactions between the SDS/SWNT aggregates, which is different from the previous electrostatic repulsion explanation. The unique role of sodium ions revealed here provides a new microscopic understanding of the recent experiments in the electrolyte tuning of the interfacial forces on the selective fractionation of SDS surrounding SWNTs.

Molecular recognition using corona phase complexes made of synthetic polymers adsorbed on carbon nanotubes

“…Meanwhile, sodium dodecyl sulphate (SDS, Fig. 4d) adsorbed SWNT shows a non-selective wavelength-shift response, presumably from a more loosely packed adsorbed layer 36,37 , allowing greater molecular access to the SWNT surface. Comparison of the radii of various polymer-SWNT complexes using multiple characterization methods is available in Supplementary Table 3 (Supplementary section 'Materials and Methods').…”

Assessment of the Performance of B2PLYP-D for Describing Intramolecular π-π and σ-π Interactions

“…Figure 1 shows the chemical structures of both molecules and indicates three (ϕ, θ, and τ) and two (β and π) flexible coordinates in the HNBPA and TRA structures, respectively. These intramolecular π-π and σ-π interactions closely related to the prediction of the molecular shapes and separations of the macromolecules [30][31][32][33][34][35][36][37] such as base stacking of DNA, 30,31 the stability of proteins, 32,33 and the dispersion separation of the single wall carbon nanotube (SWNT). [34][35][36] The authors applied the B2PLYP and B2PLYP-D methods to the conformers of HNBPA and TRA and compared them to the most popular B3LYP and second order Møller-Plesset (MP2) levels of theory 19 as well as the coupled cluster singles doubles with the perturbative triples (CCSD(T)) method, 38,39 which is used as reference data in the present work.…”

In-Situ Structural Characterization of Single-Walled Carbon Nanotubes in Dispersion

“…In such a case, the double sum in Eq. (5a) equals to n. With these results and bear in mind that, for a finite-sized scattering system with uniformly distributed scatterers, the non-zero scattering contribution at a scattering angle other than zero is due to the scatterer density fluctuation on the surface, one can derive a power-law relationship for the scattering intensity of a fractal aggregate with respect to the inherent length scale of 1/q (Xu et al, 2010). It is stated as:…”

“…One recent molecular dynamic simulation study on the SDS aggregation on SWCNTs (Tummala & Striolo, 2009) supports such a viewpoint. However, another MD simulation study (Xu et al, 2010) reveals a much delicate situation for the SDS structure formation on SWCNTs. Depending upon the diameter of SWCNT as well as the coverage density, the SDS molecules can organize into cylinder-like monolayer structure, hemicylindrical aggregates, and randomly organized structures on the surface of a SWCNT.…”