Comparison of the Quality of Aqueous Dispersions of Single Wall Carbon Nanotubes Using Surfactants and Biomolecules

Abstract

The use of single wall carbon nanotubes (SWCNTs) in current and future applications depends on the ability to process SWCNTs in a solvent to yield high-quality dispersions characterized by individual SWCNTs and possessing a minimum of SWCNT bundles. Many approaches for the dispersion of SWCNTs have been reported. However, there is no general assessment which compares the relative quality and dispersion efficiency of the respective methods. Herein we report a quantitative comparison of the relative ability of "wrapping polymers" including oligonucleotides, peptides, lignin, chitosan, and cellulose and surfactants such as cholates, ionic liquids, and organosulfates to disperse SWCNTs in water. Optical absorption and fluorescence spectroscopy provide quantitative characterization (amount of SWCNTs that can be suspended by a given surfactant and its ability to debundle SWCNTs) of these suspensions. Sodium deoxy cholate (SDOCO), oligonucleotides (GT)(15), (GT)(10), (AC)(15), (AC)(10), C(10-30), and carboxymethylcellulose (CBMC-250K) exhibited the highest quality suspensions of the various systems studied in this work. The information presented here provides a good framework for further study of SWCNT purification and applications.

Photophysics of Individual Single-Walled Carbon Nanotubes

“…160 In particular, the large variation in Stokes shifts highlights the importance of the local environment surrounding the SWNT. 149 For most surfactants, the relatively small Stokes shift was well within the range of accepted literature values (~45 cm -1 ); 87 the Stokes shift observed for CAS was larger than expected (125.1 cm -1 ). In all spectra, corresponding peaks in the absorption and fluorescence spectra (i.e., that arose from the same SWNT structures) exhibited only small Stokes shifts, indicating a set of chromophores with minimal differences in the amount of electron-phonon coupling occurring in the ground and excited states.…”

“…For example, complete luminescence quenching has been observed when SWNTs directly contact metallic nanotubes in bundles 71 and when they touch some substrates such as silicon; however, it is important to note that these substrates were also coated with catalyst particles and residual carbon deposits from SWNT CVD syntheses. 154,189 Attenuation of nanotube fluorescence also accompanies dispersal in polar solvents, 218 encapsulation in certain surfactant systems, 149 protonation at low pH, 167 and shortening of the nanotube length. 212 In addition, the presence of defect sites, impurities, and oxygen is expected to decrease the QY via hole doping, which effectively removes an electron from the valence band and provides a trap for the excited state.…”

Optimizing sonication parameters for dispersion of single-walled carbon nanotubes

“…Thus it is possible to sort these SWCNTs using density gradient ultracentrifugation (DGU) [18][19][20]. The dispersion mechanism has been explored and results indicate that the adsorption of surfactants on the surface of SWCNTs forms stronger p-p stacking interactions than those between the SWCNTs [21]. For the non-covalent functionalization of SWCNTs, the useful agents include surfactants, polymers, as well as biomolecules such as DNA [5,[22][23][24][25].…”

Congo Red Interactions with Single-Walled Carbon Nanotubes

“…Other compounds used for the noncovalent functionalization and dispersing of CNT include: ionic liquids (ILs) -which form bucky gels, polymers -especially those with aromatic rings in their structure [24], other compounds with an aromatic ring [25] (for example ammonium salts containing pyrene rings [26]) and or deoxycholic acid sodium salts [27].…”