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Preparing semiconducting carbon nanotubes for nanotechnology applications

A method that eliminates metallic single walled carbon nanotubes from mixtures leaving fully functional semiconducting SWCNTs may open the way for various nanotech applications that require pure semiconducting SWCNTs. From the Cornell University Chronicle, written by Anne Ju “Carbon nanotube ‘ink’ may lead to thinner, lighter transistors and solar cells“:

Using a simple chemical process, scientists at Cornell and DuPont have invented a method of preparing carbon nanotubes for suspension in a semiconducting “ink,” which can then be printed into such thin, flexible electronics as transistors and photovoltaic materials.

The method, which involves treating carbon nanotubes with fluorine-based molecules, is reported in the Jan. 9 issue of the journal Science [abstract]. The research was jointly led by Graciela B. Blanchet [of] DuPont, and George Malliaras [of[ Cornell…

Carbon nanotubes are good candidates for transistors in low-cost, printable electronics, but only after large quantities of them have been converted into semiconductors. When carbon nanotubes are grown in the lab, some are semiconducting but others are metallic, and they are difficult to separate from each other.

This mix is a major drawback in creating transistors from nanotubes, Malliaras said. The Cornell/DuPont team concentrated on a new, inexpensive way to eliminate the metallic tubes, preparing them for such applications as suspension in semiconducting ink for printing.

To do so, the researchers brought fluorine-based molecules into contact with the nanotubes. Through a process called cycloaddition, the fluorine molecules efficiently attacked or converted the metallic nanotubes, leaving the semiconducting tubes alone, and creating a perfect 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,” Blanchet said.

Taken together with the recent report of a way to make pure armchair SWCNTs (which are metallic), it appears that it will soon be possible to prepare either metallic or semiconducting SWCNTs, as required by the application at hand. (Credit: PhysOrg.com for the link to the Cornell Chronicle story.)
—Jim

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