Multi-Angle Depolarized Dynamic Light Scattering of Short Functionalized Single Walled Carbon Nanotubes

Precise characterization of single-walled carbon nanotube (SWCNT) length and diameter is essential in a number of areas, particularly for optimizing and predicting their electrical, optical and rheological properties. Current characterization methods, such as AFM and TEM, are time intensive, and potentially suffer from serious systematic errors due to the effects of drying and surface deposition. We introduce the method of multi-angle depolarized dynamic light scattering (MA-DDLS), which is a solution-based technique to characterize the length and diameter of single-walled carbon nanotubes (SWCNTs). We have used covalently functionalized SWCNT with poly(amino benzene sulfonic acid) (PABS) and poly(ethylene glycol) (PEG) for this study. MA-DDLS yields simultaneous characterization of the mean translational and rotational diffusivities of dilute solutions of SWCNTs. Using an anisotropic rigid rod model, we uniquely determine the length and diameter of the SWCNTs from the independent measurements of rotational and translational diffusion. The multi-angle depolarized light scattering technique is found to be a fast, non-invasive and reproducible method for identifying the average length and diameter of SWCNTs in solution. Furthermore this method can be performed in situ and is compatible with continuous separation methods such as size-exclusion chromatography.