Subject：Potential means of controlling single-walled carbon nanotube’s chirality during nucleation and growth —theoretical prediction and experimental evidences

Speaker：Prof. Feng Ding

Emcee：Prof. Qinghong Yuan

Time：2:00pm, 27^th Dec, 2018

Place：Science Building A814

Abstract：

With more than 10 years’ efforts, the mechanisms of single-walled carbon nanotubes (SWNTs) growth at atomic level and potential routes towards the chirality growth becomes more and more clear. In this talk, I will present four aspects regarding the mechanism of SWNTs growth and the chirality-selection during growth:

1. The insertion of carbon atoms at the SWNT-catalyst interface determines the growth rate of SWNTs and the potential formation of topological defects determines frequency of chirality changes during growth. It was found that the atomic details of carbon atom insertion are growth mode dependent and the favor of armchair SWNTs and chiral (2n, n) SWNTs for tangent and perpendicular modes of growth, respectively.

2. The formation of the cap structure determines the chirality of the consequent SWNT and the addition of the last pentagon can turn the SWCNT into any possible chiral angles and is a kinetic process. Therefore, the random formation of the last pentagon will lead to the formation of all types of SWNTs, which explains the even distribution of chiral angles in most SWNT samples.

3. During the cap formation, an external bias that affects the addition of the last pentagon may lead to the chirality-selected SWCNT growth and, therefore, as suggested by many previous studies, the solid catalyst might be able to lead to the growth of specific type of SWNTs. Detailed theoretical and experimental study suggests that the growth of (12,6)- and (8, 4)-rich SWNT samples are possible if catalyst surface has near-six or near four-fold symmetries, respectively.

4. Besides the nucleation stage, varying the chirality during SWNT growth is predicted to be another route towards the chirality-specific SWNTs synthesis because of the biased SWNT-catalyst interfacial energy. Such a predication has been successfully realized by experimental studies and the synthesized SWNTs show exact chirality distribution as predicated theoretically.

About the Speaker:

Prof. Feng Ding obtained his Bs, Ms and PhD degrees from Huazhong University of Science and Technology, Fudan University and Nanjing University in 1993, 1996 and 2002, respectively. Then he was a Postdoctoral Research Fellow in Gothenburg University and Chalmers University in Sweden from 2003 to 2005. From 2005, he joined Rice University as a Research Scientist until the end of 2008. From 2009-2016, he worked in the Institute of Textile and Clothing of Hong Kong Polytechnic University as an Assistant Professor and Associate Professor (from 2013). From the beginning of 2017, he joined UNIST as a Distinguished Professor and the IBS-CMCM as a group leader.

Prof. Ding’s research group’s research interests mainly focus on the computational method development, theoretical exploration of various carbon materials and 2D materials, especially on their formation mechanism, the kinetics of their nucleation, growth and etching. Prof. Ding has published more than 200 SCI papers in leading journals of natural science, with ~ 30 in Science, Nature serious journals, PNAS, Sci Adv., PRL, JACS, ACIE. These publications were cited by > 7200 times (SCI) and his personal h-index is 49.