DNA-assisted dispersion and separation of carbon nanotubes


Carbon nanotubes are man-made one-dimensional carbon crystals with different diameters and chiralities. Owing to their superb mechanical and electrical properties, many potential applications have been proposed for them. However, polydispersity and poor solubility in both aqueous and non-aqueous solution impose a considerable challenge for their separation and assembly, which is required for many applications. Here we report our finding of DNA-assisted dispersion and separation of carbon nanotubes. Bundled single-walled carbon nanotubes are effectively dispersed in water by their sonication in the presence of single-stranded DNA (ssDNA). Optical absorption and fluorescence spectroscopy and atomic force microscopy measurements provide evidence for individually dispersed carbon nanotubes. Molecular modelling suggests that ssDNA can bind to carbon nanotubes through π-stacking, resulting in helical wrapping to the surface. The binding free energy of ssDNA to carbon nanotubes rivals that of two nanotubes for each other. We also demonstrate that DNA-coated carbon nanotubes can be separated into fractions with different electronic structures by ion-exchange chromatography. This finding links one of the central molecules in biology to a technologically very important nanomaterial, and opens the door to carbon-nanotube-based applications in biotechnology.

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Figure 1: Electronic absorption spectra of DNA-CNT: in 0.05 M sodium acetate/0.1 M sodium chloride (pH 4.8), 0.05 M sodium phosphate/0.1 M sodium chloride (pH 7), and 0.05 M sodium bicarbonate/0.1 M sodium chloride (pH 10.3), respectively.
Figure 2: Binding model of a (10,0) carbon nanotube wrapped by a poly(T) sequence.
Figure 3: Separation of DNA-CNT by anion exchange chromatography.
Figure 4: Analysis of DNA-CNT fractions by atomic force microscopy (AFM).


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We would like to thank Nancy Rizzo, Debby Preston, Bruce Chase and Dennis Walls for microscopy and spectroscopy measurements, Xueying Huang, Bibiana Onoa and Hong Wang for technical support and helpful discussions.

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Correspondence to Ming Zheng.

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Zheng, M., Jagota, A., Semke, E. et al. DNA-assisted dispersion and separation of carbon nanotubes. Nature Mater 2, 338–342 (2003). https://doi.org/10.1038/nmat877

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