Carbon nanotube mixture characterisation

Single-walled carbon nanotubes have been detected and measured in mixtures with multiwalled carbon nanotubes using a portable Raman spectrometer. Miguel Valcárcel and co-researchers from the University of Cordoba in Spain used the relative intensities of the D band (the disorder peak) and the G band (corresponding to the tangential mode) to characterise the mixtures and determine the relative amounts of SWNTs and MWNTs, as they explain in Analyst.

The mixtures cannot be analysed in solid form because they are damaged by poor heat dissipation under laser irradiation. This problem is overcome by working with dispersions of the nanotubes in surfactant to break up any unwanted aggregates of the material. In this way, neither the laser power nor the solution acidity affected the intensity ratio of the D and G peaks and measurements were completed within 50 seconds.

The D/G intensity ratios varied in a linear fashion with the percentage of SWNTs, providing a rapid and inexpensive way to characterise industrial samples and check batch-to-batch reproducibility using an inexpensive portable Raman spectrometer.

Image: Glenn Research Center / NASA