(706g) Amplification of SWNT Retaining n, m Distribution

Single-walled carbon nanotubes (SWNTs) have enormous potential for application in electronic applications such as field effect transistors, but the mixture of metallic and semiconducting nanotubes in bulk limits the reproducible production of these devices. Herein we present a method of amplifying a particular (n, m) SWNT sample in a manner scalable for industrial regrowth. The starting materials were two batches of SWNTs with different n, m distribution. The SWNTs were shortened using two different methods, liquid-phase oxidative/mechanical cutting and solid-state reaction cutting. The shortened SWNTs were then impregnated with cobalt catalysts and uniformly deposited onto fumed silica to form regrowth seeds. The regrowth seeds were pretreated by hydrogen followed by ethanol pyrolysis at different temperature initiating regrowth. After regrowth, the highest amplification factor achieved is 4X, as determined by thermogravimetric analysis. Photoluminescence excitation spectroscopy indicated that the SWNT-templated regrowth retained the (n, m) distribution from the original nanotube types. X-ray absorption spectroscopy was used to probe the state of the cobalt catalysts. This method requires little post-synthesis cleaning and produces high quality SWNTs.