Characterisation of Nanotubes


I hadn’t heard of it until recently, but a relatively new class of materials known as carbon nanotubes is proving to be very useful in a variety of applications and appears to offer scope for solutions in many branches of science and engineering. To make best use of that potential, these materials need to be characterised and assessed. In one of a range of application notes downloadable from the Beckman Coulter website, the use of DelsaMax PRO in such analysis is studied.

To date, carbon nanotubes have been used largely for reinforcement of materials. In the future, we are likely to see them increasingly applied in the medical field, in electronic systems and in energy storage and conversion devices.

In essence they are cylindrical, quasi-one-dimensional structures consisting of one or more rolled-up sheets grapheme. The single-sheeted structures are referred to as SWCNTs or single-walled carbon nanotubes, while the multi-sheeted are MWCNTs or multi-walled carbon nanotubes

Because they are made entirely from sp2 carbon (a form with one double and two single bonds), these structures are strongly hydrophobic – so dispersion of individual nanotubes in an aqueous solution is hard to achieve. Unless an amphiphilic surfactant is used to coat their surface fully, the nanotubes immediately aggregate.

SWCNTs and DWCNTs have a number of exceptional optical properties which make them ideal in, for example, biomedical imaging and biosensing, but it is not possible to take advantage of these except in solution. To gain an understanding of the stability and aggregation of the constructs, it is necessary to characterise both the carbon nanotubes and their surfactant coatings. Approaches available for determinations of this kind include dynamic light scattering and zeta potential, as well as analytical ultracentrifugation.

The Beckman Coulter application note highlights the suitability of DelsaMax PRO for measurement of carbon nanotube size and stability in aqueous solution, and shows how these factors vary with temperature.

Dispersing the samples in 2% sodium dodecyl sulphate or 2% sodium cholate, both of which are commonly employed to separate nanotubes, the material was analysed by DelsaMax PRO to measure zeta potential and hydrodynamic radius.

Reliable and repeatable results were delivered in less than a minute, using low volumes. Furthermore, thanks to the power of the DelsaMax analysis software, it was possible to display and analyse quickly – and in real time – the mobility, correlation and regularisation data. This allowed immediate assessment of measurement quality, so that determinations could be stopped and re-run at any time if necessary.

To see the full report, visit and click on the button which invites you to request application downloads. Then simply give your details and you will be given access to this and other documents.

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