Phase Behavior of DNA-Based Dispersions containing Carbon Nanotubes: Effects of Added Polymers and Ionic Strength on Excluded Volume

Abstract

Ordered phases containing single-walled carbon nanotubes (SWNTs) are essential to exploit the highly anisotropic properties of such nanoparticles. Knowledge of the phase behavior for the above dispersions is therefore needed. Unfortunately, the processing of nanotubes at high concentration remains experimentally challenging. To date, solvent evaporation and ultracentrifugation procedures have been used to increase the volume fraction of carbon nanotubes and obtain (pseudo)-binary phase diagrams. We present here a novel phase separation strategy, allowing investigations of the phase behavior of concentrated dispersions of DNA-stabilized carbon nanotubes. This strategy is based on the osmotic compression due to added polymers such as sodium dextransulfate (SDxS) or polyethylene glycol (PEG) and on the control of the ionic strength. The phase behavior of the compressed DNA/SWNTs complexes is analyzed and discussed. It is observed that added polymers induce the separation of a SWNT-rich anisotropic phase in equilibrium with an isotropic polymer-rich one. The volume fraction of the ordered phase can be controlled by the concentration of added polymer, making this strategy efficient for investigations of concentrated nanotube dispersions and developments of novel materials based on the anisotropic phases containing such nanoparticles

Anisotropic micro-cloths fabricated from DNA-stabilized carbon nanotubes: one-stop manufacturing with electrode needles

“…Accordingly, we investigated the effect of density ratio, α = C CNT /C DNA , in the range of 0.6 ≤ α ≤ 2 while maintaining the CNT density at C CNT = 0.1 wt.%. It is to be noted that the formation of a nematic phase has been reported at α = 1 in more concentrated suspensions (C CNT > 1 wt.%) [11,[33][34][35][36].…”

“…To this end, we used the dielectrophoretic assembly method [12][13][14][15][16][17][18][19] using AC electric fields in DNA-stabilized CNT suspensions [11,23,[25][26][27][33][34][35][36] to produce aligned * frusawa.hiroshi@kochi-tech.ac.jp arrays of CNTs. The dielectrophoretic method provides a notable advantage over other techniques because this electronic method is able to selectively collect metallic CNTs and separate them from semiconducting CNTs [15,16].…”

Dispersability of Carbon Nanotubes in Biopolymer-Based Fluids

“…It is orders of magnitude higher than that pertinent to bare nanotubes and can be as high as 6.0 wt% [58]. The resulting ss-DNA/CNT complexes are extremely stable, and it is inconceivable to get back the components by dilution.…”

“…The two-phase area between the dispersion and the liquid crystalline region is usually wide. Definition of the phase boundaries is hardly attained, unless a solid polyelectrolyte bearing a negative charge is added to ss-DNA/CNT dispersions [58]. Addition results in the onset of a "segregative" phase separation mechanism [62].…”

“…More detailed information is given in the original papers, to which the reader is referred. See, in particular [13,31,47,56,58,59,65,66].…”