Controlled synthesis of single-chirality carbon nanotubes

摘要

单壁碳纳米管(SWCNTs)的电子性质对其精确结构特别敏感。为了充分发挥它们的技术潜力,需要只含一种SWCNT类型的样本。Juan Ramon Sanchez-Valencia等人将合成化学与材料工程相结合建立了一个方法,该方法经进一步优化有可能为基于纳米管的材料在光探测器、光伏电池、场效应晶体管和传感器方面的应用提供一条途径。他们采用一个"表面催化环化脱氢"反应来折叠沉积在一个Pt(111)表面上的合理设计的前体分子,以生成"端帽"(end caps),后者充当无缺陷的、结构纯粹的SWCNT的生长所需的"种子"。该方法只要求适度的温度,与今天的互补性金属氧化物半导体技术完全相匹配。封面：Konstantin Amsharovo.%Over the past two decades, single-walled carbon nanotubes (SWCNTs) have received much attention because their extraordinaiy properties are promising for numerous applications. 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 drcumferential vector in the hexagonal carbon lattice. Electronic properties are particularly strongly affected, with subtle structural changes switching tubes from metsdlic 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. Controlled synthesis through catalyst engineering, end-cap engineering or cloning strategies, and also tube sorting based on chromatography, density-gradient centrifugation, electrophoresis and other techniques, 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 holds great promise in this regard, but has hitherto had only limited practical success. 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.