A method for treating carbon nanotubes with microwave energy to selective
remove metallic-type carbon nanotubes is provided. A sample containing
carbon nanotubes is positioned in a microwave cavity at a location
corresponding to a maximum in the electric field component of a
stationary wave having a microwave frequency. The sample is exposed to
the microwave energy for a sufficient period of time to increase the
proportion of semiconducting-type carbon nanotubes within the sample.
Alternatively, a sample consisting essentially of metallic-type and
semiconducting-type carbon nanotubes is exposed to microwave energy for a
sufficient period of time to increase the proportion of
semiconducting-type carbon nanotubes within the sample.