Scientists at DuPont and Cornell University have used a simple chemical process to convert “as grown” mixtures of metallic and semiconducting carbon nanotubes into solely semiconducting carbon nanotubes with electrical characteristics well-suited for plastic electronics. This new finding, reported in the Jan. 9 issue (Vol. 323 No. 234) of the journal Science (http://www.sciencemag.org/), identifies a commercially viable path for the production of bulk quantities of organic semiconducting ink, which can be printed into thin, flexible electronics such as transistors and photovoltaic materials for solar cell technology.
The study, titled “Suppression of Metallic Conductivity of Single-Walled Carbon Nanotubes by Cycloaddition Reactions,” was authored by DuPont research fellow Graciela B. Blanchet; Cornell University associate professor of materials science and engineering George Malliaras; former Cornell post-doctoral fellow Mandakini Kanungo; and DuPont research chemist Helen Lu.The research was funded by a U.S. Air Force grant to Cornell University.
In an example that illustrates the effectiveness of industrial and academic collaborations, the group has developed a simple chemical process that 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. The resulting carbon nanotubes were dispersed into semiconducting ink and used in thin film transistors that are designed to be thinner, lighter and use less energy.
“It appears that cycloaddition, as opposed to the standard monovalent attachment of molecules, provides an effective method for suppressing the conductivity of the metallic nanotubes in a very controlled fashion,” Blanchet said. “Our work suggests that careful control of the chemical reaction enables the suppression of metallic tubes without degradation of semiconducting tubes.”
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