Invited Paper NS+NC-FrM1
Synthesis of Controlled (/n,m/) Identity Single-Walled Carbon Nanotubes

Friday, October 24, 2008, 8:20 am, Room 311

Advanced electronic applications using single-walled carbon nanotubes (SWNT) require uniform property SWNT that are not degraded by compositional variation (/n,m/ plurality) or side wall damage induced by cleaning or separation processes. The lack of uniform (/n,m/) identity SWNT with a low level of side-wall defects presents a major hurdle to device development. Thus, the ultimate goal of nanotube synthesis is to produce specific (/n,m/) nanotubes at high selectivity. In this talk we will discuss methods for controlling the diameter and /n,m/ identity of a nanotubes produced in synthesis. Many investigators have shown that the use of a second metal or transition metal oxide in the catalyst can anchor small domains of the active phase or alter their morphology to narrow the distribution of nanotubes identities produced. In addition such methods can produce highly enriched semiconducting or metallic samples. In some of these catalyst systems using CO disproportionation as the growth reaction, changing reaction temperature can dramatically vary the diameter of the nanotubes produced. We will show our recent work and that of others using X-ray absorption spectroscopy to explore the interaction between the catalyst components and how the size of the active phase varies and is related to the nanotubes diameters observed. Longer term, in order to gain almost pure n,m identity nanotubes in an economically viable manner, regrowth of specific (/n,m/) nanotube would be the most effective technique. We have recently demonstrated regrowth of SWNT chopped into short “seeds”, filled with iron or nickel functionalities and activated in a simple reaction step prior to the regrowth. Our exploratory results from the regrowth processes to be described in this talk resulted in a significant increase in SWNT weight, while at the same time showing a clear potential for retaining the (/n,m/)-distribution of the seed. This methodology offers advantages (e.g. scalability, fidelity, and does not require specialized seed cutting or functionalization) compared to other recent pioneering demonstration of SWNT regrowth by the Smalley research group.^1,2

¹ Smalley, R. E.; Li, Y.; Moore, V. C.; Price, B. K.; Colorado, R., Jr.; Schmidt, H. K.; Hauge, R. H.; Barron, A. R.; Tour, J. M., Single Wall Carbon Nanotube Amplification: En Route to a Type-Specific Growth Mechanism. /Journal of the American Chemical Society /*2006,* 128, (49), 15824-15829.
² Wang, Y.; Kim, M. J.; Shan, H.; Kittrell, C.; Fan, H.; Ericson, L. M.; Hwang, W.-F.; Arepalli, S.; Hauge, R. H.; Smalley, R. E., Continued growth of single-walled carbon nanotubes. /Nano Letters /*2005,* 5, (6), 997-1002.