Controlled synthesis of single-chirality carbon nanotubes
Controlled synthesis of single-chirality carbon nanotubes
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DOI：
10.1038/nature13607
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发表时间：
2014-08-07
期刊：
影响因子：
64.8
通讯作者：
Fasel, Roman
中科院分区：
文献类型：
--
作者：
Sanchez-Valencia, Juan Ramon;Dienel, Thomas;Fasel, Roman
在过去的二十年里，单壁碳纳米管（SWCNT）受到了广泛的关注，因为它们的非凡性能在许多应用中很有希望（1，2）。这些性质中的许多敏感地取决于SWCNT结构，其特征在于手性指数（n，m），其表示六方碳晶格中的圆周矢量的长度和取向。电子特性受到特别强烈的影响，微妙的结构变化使电子管从金属转变为具有各种带隙的半导体。因此，需要单分散的“单手性”（即，具有单个（n，m）指数）SWCNT以充分利用其技术潜力（1，2）。通过催化剂工程（3-6）、封端工程（7）或克隆策略（8，9）的受控合成，以及基于色谱法（10，11）、密度梯度离心、电泳和其他技术（12）的管分选，已经提供了具有窄的管直径分布和大部分预定管类型的SWCNT样品。但是，真正单分散的单壁碳纳米管的有效途径仍然难以捉摸。使用模板分子来明确规定所得纳米管的直径和手性（8，13 -16）在这方面具有很大的希望，但迄今为止仅具有有限的实际成功（7，17，18）。在这里，我们表明，这种自下而上的策略可以产生有针对性的纳米管：我们使用铂（111）表面上的表面催化环化脱氢将分子前体转化为超短单封端（6，6）“扶手椅”纳米管种子，然后在随后的生长阶段将其拉长，以产生单手性和基本上无缺陷的SWCNT，长度可达几百纳米。我们希望我们的表面合成方法将为基于纳米管的材料提供一条路线，这些材料具有高度优化的特性，适用于光探测器，光电器件，场效应晶体管和传感器等应用（2）。
Over the past two decades, single-walled carbon nanotubes (SWCNTs) have received much attention because their extraordinary properties are promising for numerous applications(1,2). Many of these properties depend sensitively on SWCNT structure, which is characterized by the chiral index (n,m) that denotes the length and orientation of the circumferential vector in the hexagonal carbon lattice. Electronic properties are particularly strongly affected, with subtle structural changes switching tubes from metallic to semiconducting with various band-gaps. Monodisperse 'single-chirality' (that is, with a single (n, m) index) SWCNTs are thus needed to fully exploit their technological potential(1,2). Controlled synthesis through catalyst engineering(3-6), end-cap engineering(7) or cloning strategies(8,9), and also tube sorting based on chromatography(10,11), density-gradient centrifugation, electrophoresis and other techniques(12), have delivered SWCNT samples with narrow distributions of tube diameter and a large fraction of a predetermined tube type. But an effective pathway to truly monodisperse SWCNTs remains elusive. The use of template molecules to unambiguously dictate the diameter and chirality of the resulting nanotube(8,13-16) holds great promise in this regard, but has hitherto had only limited practical success(7,17,18). Here we show that this bottom-up strategy can produce targeted nanotubes: we convert molecular precursors into ultrashort singly capped (6,6) 'armchair' nanotube seeds using surface-catalysed cyclodehydrogenation on a platinum (111) surface, and then elongate these during a subsequent growth phase to produce single-chirality and essentially defect-free SWCNTs with lengths up to a few hundred nanometres. We expect that our on-surface synthesis approach will provide a route to nanotube-based materials with highly optimized properties for applications such as light detectors, photovoltaics, field-effect transistors and sensors(2).