School of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634, United States.
Langmuir. 2011 Nov 15;27(22):13451-60. doi: 10.1021/la2028466. Epub 2011 Oct 19.
In this paper, we present the analyses of surface tension of surfactant-stabilized dispersions of carbon nanotubes. This method allows one to study interactions of carbon nanotubes with surfactants at different levels of nanotube loading when optical methods fall short in quantifying the level of nanotube separation. Sodium dodecyl sulfate was used as a stabilizing agent to uniformly disperse single-walled carbon nanotubes in an aqueous media. We show that surface tension is very sensitive to small changes of nanotube and surfactant concentrations. The experimental data suggest that, at moderate concentrations, surfactant displaces carbon nanotubes from the air-water interface and the nanotubes are mostly moved into the bulk of the liquid. By analyzing the surface tension as a function of surfactant concentration, we obtained the dependence of critical micelle concentration on nanotube loading. We then constructed the adsorption isotherm for dodecyl sulfate on carbon nanotubes and bundles of carbon nanotubes. The results of these experiments enabled us to extend the phase diagram of the produced dispersions to a broader range of surfactant and nanotube concentrations.
在本文中，我们对表面活性剂稳定的碳纳米管分散体的表面张力进行了分析。当光学方法无法量化碳纳米管的分离程度时，这种方法可以在不同的碳纳米管负载水平下研究碳纳米管与表面活性剂的相互作用。我们使用十二烷基硫酸钠作为稳定剂，将单壁碳纳米管均匀分散在水介质中。结果表明，表面张力对碳纳米管和表面活性剂浓度的微小变化非常敏感。实验数据表明，在中等浓度下，表面活性剂将碳纳米管从气-液界面置换出来，纳米管主要被转移到液体主体中。通过分析表面张力随表面活性剂浓度的变化，我们得到了临界胶束浓度随碳纳米管负载的依赖关系。然后，我们构建了十二烷基硫酸钠在碳纳米管和碳纳米管束上的吸附等温线。这些实验的结果使我们能够将所制备的分散体的相图扩展到更宽的表面活性剂和碳纳米管浓度范围。
