Nonionic Electrophoretic Sorting of SWCNTs into Metallic and Semiconducting Tubes
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Nonionic Electrophoretic Sorting of SWCNTs into Metallic and Semiconducting Tubes Kiley A. Johns1, Katie J. Koontz2, Danhao Ma3, Kathryn J. Carruba5 and Kofi W. Adu4,5 1
Department of Architectural Engineering, The Pennsylvania State University, University Park, PA 16802, U.S.A. 2 Department of Civil Engineering, The Pennsylvania State University, University Park, PA 16802, U.S.A. 3 Department of Energy Engineering, The Pennsylvania State University, University Park, PA 16802, U.S.A. 4 Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, U.S.A. 5 Department of Physics, The Pennsylvania State University, Altoona College, Altoona, PA 16601, U.S.A.
ABSTRACT We present our preliminary results on a novel technique to electrophoretically sort singlewall carbon nanotubes into metallic and semiconducting tubes using a free-solution nonionic surfactant in a homemade electrophoretic vertical cell. The technique is used to sort purified commercial product SWCNTs, (Thomas Swan Elicarb) into metallic and semiconducting tubes. In contrast to conventional electrophoresis techniques, which takes more than 24 hours to obtain efficient separation, our approach takes ~ 6 hours to achieve efficient separation, which reduces the separation time by four fold. Characterization of the sorted tubes with micro-Raman spectroscopy analysis shows very strong enrichment of both metallic and semiconducting tubes.
INTRODUCTION Carbon nanotube (CNT), a one dimensional filamentous structure formed by seamless rolling of 2-dimensional graphene into a tube, has been a significant focus of the scientific research community since its discovery by Ijima in 1991[1]. The broad interest stems from its unique physicochemical properties, the diverse potential applications it offers, and the fact that CNTs are an ideal prototype to investigate quantum phenomena in one-dimensional systems. The properties of carbon nanotubes depend strongly on the geometrical structure represented by the chiral index (n, m). In general, when n-m = 3p, where p is an integer, the carbon nanotube is metallic, and semiconducting when n-m≠3p. Thus, CNTs exist as either metallic (armchair CNT with n = m) or semiconducting (zigzag with m=0 or chiral with n≠m) depending on the chirality of the carbon framework; i.e., the orientation of the tube axis with respect to the carbon atoms network of the skeletal structure[2]. Different variations of CNTs (single-wall, double-wall and multiwall) based on the number of cylindrical layer(s) contained in the CNT skeletal structure
have been synthesized and are commercially available[3-9]. Up to date, the available synthesis methods generally produce a mixture of metallic and semiconducting SWCNTs. However, for special niche applications in areas such as electronics and optoelectronics that require either metallic or semiconducting CNTs, post-synthesis sorting of the SWCNTs is critical. Thus, several separation techniques have been pursued and are intensively being explored to separate SWCNTs. Different t
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