Growing carbon nanotubes from seed

Single-walled carbon nanotubes come in many types and sizes, with markedly different characteristics. For applications in electronics, purity and consistency are paramount, and this poses problems when it comes to sourcing suitable materials.

Existing production methods create multiple types of nanotube with a wide range of band gaps. Given that the semiconductor industry requires materials with well-defined electronic properties, a way of producing nanotubes of the required type and purity is much needed.

Researchers from Rice University in Texas have now found a way of doing exactly that. Their findings, available online and shortly to published in the Journal of the American Chemical Society, show how it is possible to cut long nanotubes of a particular type into short sections, or ‘seeds’, and use these to grow new nanotubes.

The study’s lead author, Richard Smalley, died last year, but his work has been continued under the guidance of James Tour, in collaboration with materials scientists working with IBM.

“Our proof of concept has shown us that we can take a long carbon nanotube and chop it up into small ones, put a catalyst particle on the end, dock it and grow just that type. The initial seed acts as a template, and once you’ve isolated the required type of nanotube, you duplicate it much like you do with cloning,” explains Tour, who likens the process to the polymerase chain reaction (PCR) technique used in genetics.

The challenge now is to scale the process beyond singular nanotubes, and prove that the grown tubes have the same chirality as the originals. Once this has been done, Tour envisages huge interest from industry.

Michael Dierks of Intel Capital, who has been closely following the work of Smalley and Tour, comments: “These materials should have an impact as they move out of the lab and into commercial applications, as they offer properties that can be engineered at the atomic and molecular level. This provides good flexibility to industries trying to develop materials with specialised properties.”

Article first published in Nanomaterials News. © 2006 Pira International – all rights reserved.