Synthesizing carbon nanotubes in space
Synthesizing carbon nanotubes in space
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DOI：
10.1051/0004-6361/201935789
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发表时间：
2019-09
影响因子：
6.5
通讯作者：
T. Chen;Aigen Li
中科院分区：
文献类型：
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作者：
T. Chen;Aigen Li
上下文作为宇宙中第四丰富的元素，碳（C）以各种同素异形体的形式广泛存在于星际介质（ISM）中（例如，富勒烯已在许多天文环境中被明确识别，多环芳烃分子在太空中的存在已被普遍承认，以及太阳前石墨和纳米金刚石已在陨石中被识别）。作为这些物种的稳定同素异形体，碳纳米管（CNT）及其氢化对应物是否也存在于ISM中还是未知的。目标。本工作的目的是探索在ISM中形成碳纳米管的可能途径，并计算其在红外（IR）中的指纹振动光谱特征。方法.我们研究了抽氢乙炔加成反应机理，并利用密度泛函理论（DFT）研究了纳米管的合成。用密度泛函理论计算了碳纳米管和氢化碳纳米管及其阳离子的红外振动光谱。结果我们发现碳纳米管可以通过一个可行的形成途径在太空中合成。碳纳米管和阳离子碳纳米管，以及它们的氢化对应物，表现出强烈的振动跃迁的IR。他们可能存在的ISM可以通过比较计算的振动光谱与天文观测的红外空间天文台，斯皮策太空望远镜，特别是即将到来的詹姆斯韦伯太空望远镜。
Context. As the fourth most abundant element in the universe, carbon (C) is widespread in the interstellar medium (ISM) in various allotropic forms (e.g. fullerenes have been identified unambiguously in many astronomical environments, the presence of polycyclic aromatic hydrocarbon molecules in space has been commonly acknowledged, and presolar graphite, as well as nanodiamonds, have been identified in meteorites). As stable allotropes of these species, whether carbon nanotubes (CNTs) and their hydrogenated counterparts are also present in the ISM or not is unknown. Aims. The aim of the present works is to explore the possible routes for the formation of CNTs in the ISM and calculate their fingerprint vibrational spectral features in the infrared (IR). Methods. We studied the hydrogen-abstraction and acetylene-addition (HACA) mechanism and investigated the synthesis of nanotubes using density functional theory (DFT). The IR vibrational spectra of CNTs and hydrogenated nanotubes (HNTs), as well as their cations, were obtained with DFT. Results. We find that CNTs could be synthesized in space through a feasible formation pathway. CNTs and cationic CNTs, as well as their hydrogenated counterparts, exhibit intense vibrational transitions in the IR. Their possible presence in the ISM could be investigated by comparing the calculated vibrational spectra with astronomical observations made by the Infrared Space Observatory, Spitzer Space Telescope, and particularly the upcoming James Webb Space Telescope.