Effects of alkyl amide solvents on the dispersion of single-wall carbon nanotubes

Abstract

Stable dispersions of both as-produced (raw soot) and purified laser-generated single-wall carbon nanotubes (SWNTs) have been demonstrated with several alkyl amide solvents. Optical absorption analysis over a range of concentrations has been utilized to estimate the dispersion limits for as-produced SWNTs in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N,N-diethylacetamide (DEA), and N,N-dimethylpropanamide (DMP). In addition, extinction coefficients have been calculated using Beer's law for each solvent at energies of 1.27 and 1.77 eV, corresponding to the electronic transitions of semiconducting and metallic SWNTs, respectively. The results imply that high polarizability and optimal geometries (appropriate bond lengths and bond angles) may account for the favorable interaction between SWNTs and the alkyl amide solvents. The successful dispersion of purified SWNTs in DMA has enabled extinction coefficients of 43.4 and 39.0 mL·mg-1·cm-1 to be calculated at the selected energies, respectively. The magnitude of the dispersion limit and extinction coefficient values has been shown to be strongly dependent on the SWNT sample purity. These findings offer the potential for solution-phase analysis of SWNTs directed at purity assessment and electrophoretic separations in a simple organic solvent.