Quantitative Evaluation of Surfactant-stabilized Single-walled Carbon Nanotubes: Dispersion Quality and Its Correlation with Zeta Potential

Abstract

Stable dispersions of single-walled carbon nanotubes in deionized water were prepared using six common surfactants: sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), lithium dodecyl sulfate (LDS), tetradecyl trimethyl ammonium bromide (TTAB), sodium cholate (SC), and Fairy liquid (FL). For all nanotube dispersions (CNT = 1 mg/mL), the optimum concentration of surfactant was found to be close to CSurf = 10 mg/mL by measuring the fraction of nanotubes remaining after centrifugation for a range of surfactant concentrations. The aggregation state of each nanotube−surfactant dispersion was characterized as a function of nanotube concentration by AFM analysis of large numbers of nanotubes/bundles deposited onto substrates. The dispersion quality could then be quantified by four parameters: the saturation value (at low concentration) of the root-mean-square bundle diameter, the maximum value of the total number of dispersed objects (individuals and bundles) per unit volume of dispersion, the ...