Ultra-sonication 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 which 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 vapour pressure, viscosity, 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 ortho-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 vapour pressure and viscosity. It is demonstrated that the parameters associated with the sonication process rather than solvent solubility 2 parameters govern the dispersion process. It is further confirmed that significant degradation of the SWNTs is affected during the dispersion process.

Dispersions of as-produced HiPco single-walled carbon nanotubes (SWNTs) in a series of organic solvents were prepared by dilution with the aid of tip sonication. Mild centrifugation (~ 945 g) was carried out to remove large bundles. Atomic force microscopy (AFM) studies revealed that the bundle size decreased as the dispersion was diluted. By measuring the UV-vis-NIR absorption before and after centrifugation as a function of the concentration, the dispersion limit of SWNTs in each solvent can be determined. sonication times increase the amount of SWCNTs debundled and solubilised but do not appear to affect the dispersion limit. However, increased sonication also induces discernible changes to the SWNTs themselves and in itself influences their solubility, under which conditions no clear solubility parameters can be determined.

A systematic study of the effect of a series of organic solvents on the dispersion of as-produced HiPco single-walled carbon nanotubes (SWNTs) has been conducted. UV−vis−NIR absorption spectroscopy coupled with an integrating sphere was employed to differentiate absorbance and scattering. For each solvent, a concentration-dependent study of the absorbance in the normal chamber and in the integrating sphere enabled the calculation of the total extinction coefficient and absorption coefficient. A correlation between the extinction/absorption coefficient and the Hildebrand and Hansen solvent parameters was established, indicating that polar interactions and hydrogen bonding dominate.

The interaction between polycyclic aromatic hydrocarbons (PAHs) and single walled carbon nanotubes (SWNTs) has been studied by fluorescence spectroscopy. Fluorescence quenching as a function of concentration is modeled, revealing regions where the interaction causes a debundling of the carbon nanotubes. The binding energies between PAHs and SWNTs are obtained from the model. It is found that there is a linear correlation between the binding energy of PAHs with SWNTs and the molecular weight of the PAHs. By plotting these values of binding energy against the molecular weight of these PAHs, a good structure−property relationship governing the interaction has been demonstrated.

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