Excited state modulation of C70 dimerization in a carbon nanotube under a variable electron acceleration voltage
Excited state modulation of C70 dimerization in a carbon nanotube under a variable electron acceleration voltage
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DOI：
10.1016/j.micron.2022.103316
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发表时间：
2022-06-29
期刊：
影响因子：
2.4
通讯作者：
Nakamura, Eiichi
中科院分区：
文献类型：
--
作者：
Liu, Dongxin;Lungerich, Dominik;Nakamura, Eiichi
使用透射电子显微镜对化学反应进行电影记录可提供任何其他分析方法无法获得的信息。迄今为止的研究大多仍然是现象学的，缺乏有关所涉及的活性物质的信息。为了深入了解活性物质的性质，我们需要获得不同温度和可变加速电压下的动力学信息，即电子能量供应。我们以碳纳米管为例，研究了[70]富勒烯的[2+2]二聚机理。我们在此描述了对二聚化的各个反应事件的统计分析，揭示了从单线态到三线态机制的剂量依赖性一级动力学和电压依赖性交叉，正如单线态反应比三线态反应大一百万倍的指前因子（激发频率）所强调的那样。与最近对富勒烯二聚化的研究结果进行比较[60]，我们提出碳纳米管的电子碰撞激发是第一步，然后能量转移到富勒烯分子并通过激发态进行二聚化。结果表明，变电压动力学研究对于讨论电子显微镜观察下的化学转变机制是必不可少的。
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 dosedependent 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.