Liu Dongxin, Lungerich Dominik, Nakamuro Takayuki, Harano Koji, Nakamura Eiichi
Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan.
Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan; Center for Nanomedicine, Institute for Basic Science, Seoul 03722, South Korea; Graduate Program of Nano Biomedical Engineering, Advanced Science Institute, Yonsei University, Seoul 03722, South Korea.
Micron. 2022 Sep;160:103316. doi: 10.1016/j.micron.2022.103316. Epub 2022 Jun 18.
Cinematographic recording of chemical reactions with transmission electron microscopy provides information unavailable by any other analytical methods. Studies have thus far remained mostly phenomenological, lacking information on the reactive species involved. To gain insight into the nature of the reactive species, we need to obtain kinetic information under various temperatures and variable acceleration voltages, i.e., electronic energy supply. We studied the mechanism of [2 + 2] dimerization of [70] fullerene in a carbon nanotube as an example. We describe herein a statistical analysis of individual reaction events of the dimerization that revealed dose-dependent first-order kinetics and voltage-dependent crossover from a singlet to a triplet mechanism, as highlighted by the pre-exponential factor (the frequency of excitation) that is a million times larger for the singlet reaction than for the triplet one. Comparison with the results of a recent study of [60] fullerene dimerization lets us propose that electron-impact excitation of the carbon nanotube is the first step, followed by energy transfer to fullerene molecules and their dimerization via an excited state. The results show that a variable-voltage kinetic study is indispensable for discussing the mechanism of chemical transformations under electron microscopic observation.
用透射电子显微镜对化学反应进行电影摄影记录可提供其他任何分析方法都无法获得的信息。到目前为止，相关研究大多仍停留在现象学层面，缺乏有关所涉及反应物种的信息。为深入了解反应物种的性质，我们需要在不同温度和可变加速电压（即电子能量供应）下获取动力学信息。我们以碳纳米管中[70]富勒烯的[2 + 2]二聚反应机制为例进行了研究。我们在此描述了对二聚反应单个反应事件的统计分析，该分析揭示了剂量依赖性一级动力学以及从单重态到三重态机制的电压依赖性转变，这一转变由预指数因子（激发频率）突出显示，单重态反应的预指数因子比三重态反应大一百万倍。与最近关于[60]富勒烯二聚反应的研究结果进行比较后，我们提出碳纳米管的电子碰撞激发是第一步，随后是能量转移到富勒烯分子并通过激发态使其二聚。结果表明，可变电压动力学研究对于在电子显微镜观察下讨论化学转化机制是必不可少的。
