Air Force Research Laboratory, Materials and Manufacturing Directorate, RXBN, WPAFB, Ohio 45433, USA.
Nat Mater. 2012 Jan 29;11(3):213-6. doi: 10.1038/nmat3231.
Chiral-selective growth of single-walled carbon nanotubes (SWNTs) remains a great challenge that hinders their use in applications such as electronics and medicine. Recent experimental and theoretical reports have begun to address this problem by suggesting that selectivity may be achieved during nucleation by changing the catalyst composition or structure. Nevertheless, to establish a rational basis for chiral-selective synthesis, the underlying mechanisms governing nucleation, growth, and termination of SWNTs must be better understood. To this end, we report the first measurements of growth rates of individual SWNTs through in situ Raman spectroscopy and correlate them with their chiral angles. Our results show that the growth rates are directly proportional to the chiral angles, in agreement with recent theoretical predictions. Importantly, the evidence singles out the growth stage as responsible for the chiral distribution-distinct from nucleation and termination which might also affect the final product distribution. Our results suggest a route to chiral-selective synthesis of SWNTs through rational synthetic design strategies based on kinetic control.
手性选择生长的单壁碳纳米管（SWNTs）仍然是一个巨大的挑战，阻碍了它们在电子学和医学等应用中的使用。最近的实验和理论报告已经开始通过改变催化剂组成或结构来解决这个问题，提出选择性可能在成核过程中实现。然而，为了建立手性选择性合成的合理基础，必须更好地理解控制 SWNTs 成核、生长和终止的基本机制。为此，我们报告了通过原位拉曼光谱首次测量单个 SWNTs 的生长速率，并将其与手性角相关联。我们的结果表明，生长速率与手性角成正比，这与最近的理论预测一致。重要的是，这一证据将生长阶段确定为负责手性分布的因素，而与成核和终止不同，后者也可能影响最终产物分布。我们的结果表明，通过基于动力学控制的合理合成设计策略，有可能实现 SWNTs 的手性选择性合成。
