Originally Published EMDM
March/April 2004
Technology News
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| A group of DuPont-led scientists has discovered a way to sort carbon nanotubes by using DNA. Unsorted nanotubes in solution appear in black (far left), while conductive nanotubes are pinkish in colour and those that are semiconducting have a greenish cast. |
Carbon nanotubes are believed to be stronger and to have the ability to conduct electricity and heat better than any known material. They offer potential applications in many nanoscale structures, including diagnostic devices. The material’s electrical properties, however, are compromised because carbon nanotubes of different electronic types form random clumps after fabrication.
A research team led by scientists from DuPont (Wilmington, DE, USA) has discovered a way to use DNA to sort carbon nanotubes and thus achieve uniform conductivity. The discovery is expected to have a substantial impact on polymer chemistry as well as on electronics. In particular, it could lead to the fabrication of electronics that are 100 times smaller than those currently available. Highly sensitive diagnostic devices could also achieve dramatic size reductions.
Initially, researchers at DuPont found that single-stranded DNA interacts with carbon nanotubes to form a stable hybrid that effectively disperses carbon nanotubes in an aqueous solution. In a follow-up project, the DuPont researchers teamed with peers from the Massachusetts Institute for Technology and the University of Illinois to discover a method for separating and sorting the carbon nanotubes.
They found that a particular sequence of single-stranded DNA self-assembles into a helical structure around individual carbon nanotubes. The resulting hybrid materials’ electrostatic properties allow them to be separated and sorted by means of anion-exchange chromatography.
The technique can be used to segregate metallic from semiconducting carbon nanotubes. It can also sort semiconducting nanotubes by diameter.
The researchers have published an article titled “Structure-Based Carbon Nanotube Sorting by Sequence-Dependent DNA Assembly” that offers an in-depth summary of their work. It can be accessed for a fee at
www.sciencemag.org [6].
Norbert
Sparrow [7]
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