ACS Nano 6, 8424–8431 (2012)

Growth conditions and processing can affect the lengths of single-walled carbon nanotubes, which can, in turn, impact cellular uptake and the performance of nanotube-based devices. Atomic force microscopy and dynamic light scattering are widely used to characterize the lengths of nanotubes, but these methods are either tedious, sensitive to artefacts from aggregates and impurities, or offer only average lengths rather than full length distributions. Bruce Weisman and colleagues have now shown that length distributions can be obtained by analysing the diffusional motions of individual nanotubes.

The researchers — who are based at Rice University, Ensysce Biosciences and the National Institute of Standards and Technology — placed a drop of a suspension enriched with the (6,5) species of single-walled carbon nanotubes in a microwell and imaged the individually diffusing tubes using a near-infrared video microscope. Using customized image analysis software, the trajectories and diffusion coefficients of the nanotubes were analysed. From this the length distributions could be calculated and were found to be in good agreement with results obtained from the conventional atomic force microscopy method. Furthermore, the technique was able to characterize approximately 800 nanotubes in about 2 h and is less susceptible to artefacts.