When single wall carbon nanotubes are produced, they are always formed as a mixture of metallic-conducting and semiconducting types. Generally, the metallic ones spoil the operation of any active electronic device made with the mixture.
Passing a current through the nanotubes is an uncontrolled way to improve the metallic/semiconducting ratio, but now chemists at Cornell University in New York and DuPont claim to be able to remove all of the metallic tubes.
Through a process called cycloaddition, fluorine-based molecules attack the metallic nanotubes, leaving the semiconducting tubes alone, and creating a batch of solely semiconducting nanotubes.
"Our work suggests that careful control of the chemical reaction enables the complete conversion of metallic tubes without the degradation of semiconducting tubes," said DuPont research fellow Graciela Blanchet.
This research is part of a research programme to produce semiconducting inks for flexible electronics - a field in which Cornell and DuPont have collaborated for several years.
It was supported by a grant from the US Air Force for developing transistors from carbon nanotubes.
An atomic force microscope image of both metallic and semiconducting carbon nanotubes.
After the cycloaddition process, the metallic tubes are gone.