US Patent 7662298 - Density gradient separation of CNTs

http://www.freepatentsonline.com/7662298.html

This patent is from Northwestern University and teaches a technique called density gradient ultracentrifugation allowing for segregation of single walled carbon nanotubes based on their bandgap. An article on the process is available here. Claim 1 reads:

1. A method of using a density gradient to separate single-walled carbon nanotubes, said method comprising:

centrifuging a nanotube composition in contact with a fluid medium comprising a density gradient; and

separating the nanotube composition into two or more separation fractions,

wherein said nanotube composition comprises single-walled carbon nanotubes of mixed nanotube diameters, chiralities, electronic types, or combinations thereof and at least one surface active component; and

at least one of said two or more separation fractions is enriched with single-walled carbon nanotubes of a selected nanotube diameter, chirality, electronic type, or combinations thereof relative to the nanotube composition.