GB Tech, Inc. (Houston, TX) discloses in United States Patent 7,763,229 methods for isolating and purifying single wall carbon nanotubes from contaminant matrix material, methods for forming arrays of substantially aligned nanotubes, and products and apparatus comprising a plurality of nanotube structures.
According to inventors Pavel Nikolaev, Sivaram Arepalli, Mark S. F. Clarke and Daniel L. Feeback the three most common manufacturing methods developed for the production of SWCNT structures are high pressure carbon monoxide ("hipCO") processes, pulsed laser vaporization ("PLV") processes and arc discharge ("ARC") processes.
Each of these processes produce SWCNT structures by depositing free carbon atoms onto a surface at high temperature and/or pressure in the presence of metal catalyst particles. The raw material formed by these processes includes SWCNT structures formed as bundles of tubes embedded in a matrix of contamination material typically composed of amorphous carbon (i.e., graphene sheets of carbon atoms not forming SWCNT structures), metal catalyst particles, organic impurities and various fullerenes depending on the type of process utilized. The bundles of nanotubes that are formed by these manufacturing methods are extremely difficult to separate into individual nanotube filaments.
The invention provides a rapid and an effective method of isolating and purifying SWCNT structures disposed within a raw material containing contaminants to obtain a high product yield of quality SWCNT structures having appropriate lengths suitable for different applications.
Separation is achieved by by providing a method of dispersing a matrix of raw material including SWCNT structures and contaminants in an aqueous solution containing a suitable dispersal agent to separate the individual SWCNT structures from the matrix, thus purifying and dispersing the structures within the solution. In solution, the dispersal agent surrounds and coats the individual SWCNT structures, allowing the structures to maintain their separation rather than bundling together upon separation of the structures from the solution. Suitable dispersal agents useful in practicing the present invention are typically reagents exhibiting the ability to interact with hydrophobic compounds while conferring water solubility. Exemplary dispersal agents that can be used in the present invention include, but are not limited to, synthetic and natural detergents, deoxycholates, cyclodextrins, chaotropic salts and ion pairing agents