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Controlled synthesis of single-chirality carbon nanotubes

2014; Nature Portfolio; Volume: 512; Issue: 7512 Linguagem: Inglês

10.1038/nature13607

1476-4687

Juan R. Sánchez‐Valencia, Thomas Dienel, Oliver Gröning, Ivan Shorubalko, Andreas Mueller, Martin Jansen, Konstantin Amsharov, Pascal Ruffieux, Román Fasel,

Fullerene Chemistry and Applications

Present preparation methods fail to meet fully the demand for structurally pure single-walled carbon nanotubes; surface-catalysed cyclodehydrogenation reactions are now shown to convert precursor molecules deposited on a platinum(111) surface into ultrashort nanotube seeds that can then be grown further into defect-free and structurally pure single-walled carbon nanotubes of single chirality. The electronic properties of single-walled carbon nanotubes (SWCNTs) are extraordinarily sensitive to their precise structure. To exploit their technological potential fully, samples containing only one SWCNT type are needed. Juan Ramon Sanchez-Valencia et al. have combined synthetic chemistry with materials engineering to develop a strategy that, with further optimization, could provide a route to nanotube-based materials for use in light detectors, photovoltaics, field-effect transistors and sensors. They use a surface-catalysed cyclodehydrogenation reaction to fold rationally designed precursor molecules deposited on a Pt(111) surface to produce 'end caps' that act as seeds for the growth of defect-free and structurally pure SWCNTs. The technique requires only modest temperatures and is fully compatible with today's complementary metal oxide semiconductor technologies. Cover: Konstantin Amsharov. Over the past two decades, single-walled carbon nanotubes (SWCNTs) have received much attention because their extraordinary properties are promising for numerous applications1,2. 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 bandgaps. Monodisperse ‘single-chirality’ (that is, with a single (n,m) index) SWCNTs are thus needed to fully exploit their technological potential1,2. Controlled synthesis through catalyst engineering3,4,5,6, end-cap engineering7 or cloning strategies8,9, and also tube sorting based on chromatography10,11, density-gradient centrifugation, electrophoresis and other techniques12, 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 nanotube8,13,14,15,16 holds great promise in this regard, but has hitherto had only limited practical success7,17,18. 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 sensors2.