Ultrasound-Assisted SWNTs Dispersion: Effects of Sonication Parameters and Solvent Properties

Ultrasonication is widely used for preparing Single-Walled Carbon Nanotube (SWNT) dispersions in different solvent media and it has been shown to play a critical role in dispersing and debundling SWNTs. The strong shear force that can exfoliate the SWNT bundles during sonication comes from cavitation, which entails a process of bubble formation, growth, and collapse. The efficiency of the cavitation process is closely correlated to many solvent parameters, including vapor pressure, viscosity, and surface tension, as well as the sonication frequency, intensity, and time. In this study, SWNTs were dispersed in a range of organic solvents assisted by tip sonication. The effects of sonication intensity and time were investigated in o-dichlorobenzene (o-DCB) and dimethylformamide (DMF). The aggregation fraction below the dispersion limit of SWNTs in the range of organic solvents was found to be influenced by the solvent parameters, particularly solvent vapor pressure and viscosity. It is demonstrated that the parameters associated with the sonication process rather than solvent solubility parameters govern the dispersion process. It is further confirmed that significant degradation of the SWNTs is affected during the dispersion process.