SWCNT Growth from Organic Precursors Without a Catalyst: Possibilities and Limitations Revealed by Theoretical Simulations

SWCNT Growth from Organic Precursors Without a Catalyst: Possibilities and Limitations Revealed by Theoretical Simulations
Hai-Bei Li, Alister J. Page, Stephan Irle, Keiji Morokuma
Department of applied chemistry, School of Ocean, Shandong University, Weihai, Shandong, China Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, Australia WPI-Institute of Transformative Bio-Molecules and Department of Chemistry, Nagoya University, Nagoya, Nagoya, Japan Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto, Kyoto, Japan
lihaibei@sdu.edu.cn
Our recent simulations of catalyst-free, chirality-controlled growth from cycloparaphenylene (CPP) precursors are presented. We will show that different chemical routes for chirality-controlled growth exist, and depend on the nature of the growth agent. We demonstrate this phenomenon using acetylene (C2H2) and the ethynyl radical (C2H) as growth agents, at temperatures ranging from 300 to 800 K. In the case of the ethynyl radical, we observe a strong dependence of the SWCNT growth rate on the chiral angle. This is consistent with a previously proposed screw-dislocation-like model of transition metal-catalyzed SWCNT growth. However, the absence of a catalyst in this case indicates that the SWCNT growth rate is an intrinsic property of the SWCNT edge itself. Additionally, the ability of a SWCNT to avoid defect formation during growth is also an intrinsic quality of the SWCNT edge, one that is maximized at lower temperatures. However, using the ethynyl radical as the growth agent, the SWCNT diameter does not influence the growth rate; acetylene-based growth is, on the other hand, strongly diameter-dependent. We therefore predict the existence of a maximum local growth rate for a particular (n,m) SWCNT at a given acetylene/ethynyl ratio.