科研之友
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摘要
The power of binary mixtures of dodecyl trimethyl ammonium bromide and sodium dodecyl sulfate for dispersion of multi-wall carbon nanotubes (MWCNTs) in aqueous media was investigated. Stable dispersions were obtained at lower total surfactant concentration as compared to their concentration when used alone, indicative a synergistic effect in these catanionic mixtures. The dispersion of carbon nanotubes was characterized using UV-vis spectroscopy and zeta potential measurement. Optimal surfactant concentrations for dispersions of MWCNTs were determined by UV-vis spectroscopy. Surface tension observations demonstrated that the surfactant molecules have more tendency to the surface of CNTs than air/solution interface. This tendency is more in binary suspensions in comparison with individual surfactant suspensions. Based on the concerns of the cost and environmental effect, the use of mixed surfactants should be more encouraging for the stable dispersion of MWCNTs. Raman analysis shows that the non-covalent functionalization used in this study does not disturb sp(2) structure of the CNTs significantly. Also, for the first time, we have introduced a new simple approach to estimate surface charge of surfactant-covered CNTs. To do this, we have utilized the well-known Poisson-Boltzmann equation and thermo gravimetric analysis (TGA) results. According to the Poisson equation, calculation of electric potential needs charge density, a parameter which we have estimated using thermo gravimetric results in this new approach. The TGA-based estimated potentials are in good agreement with experimental results. Ultimately, using the surface charge results, we have calculated interaction energy between two parallel tubes. Calculated results clearly show that the dispersions could be stable, which has been observed experimentally too.
- 出版日期2017-10-20
