Santoshrupa Dumpala1, David Mudd2, Gamini U. Sumanasekera2, and Mahendra K. Sunkara3. (1) Chemical Engineering, University of Louisville, 106, Ernst hall, University of louisville,, Louisville, KY 40292, (2) Physics, University of louisville, 2210 south brook st, room 211, Louisville, KY 40208, (3) Department of Chemical Engineering, University of Louisville, 106 Ernst Hall, Department of Chemical Engineering,, University of Louisville, Louisville, KY 40292
Conical carbon nanotubes refer to structures that taper from micron-sized base to nanometer scale tips with central nanotube as hollow core1. The surfaces of these conical structures are composed of high density of graphene edge planes.2 Also, due to the conical geometry and high aspect ratio, the arrays of the conical carbon nanotubes contain their tips spaced from each other. So, these conical carbon tube arrays are expected to yield dramatically different behavior in terms of both electrochemical and field emission characteristics. However, for all the applications, large area (> 1 cm2 area) synthesis of these arrays on flat substrates has been challenging.
Here, we report our recent success with synthesizing these conical carbon tubular arrays over graphite and other metallic foils using a 3 kW microwave plasma enhanced chemical vapor deposition (MWCVD) reactor. Cylindrically rolled foils immersed vertically into the plasma, resulted in conical carbon tubes up to as long as 30 microns, at increased temperatures. The as-synthesized arrays show reversible behavior with electrochemical redox reactions involving neurotransmitters like Levodopa and Apomorphine. In addition, the field emission characteristics of conical carbon nanotubes show better field emission characteristics compared to multiwalled carbon nanotube arrays.
References:
1. R. C. Mani, X. Li, M. K. Sunkara, K. Rajan, Nano Lett. 2003, 3, 671
2. B. Chernomordik, S. Dumpala, Z. Chen and M.K. Sunkara, Chemical Vapor Deposition, Accepted for special issue on nanodiamond, (2008).