College of Engineering and Department of Physics and Astronomy, University of Georgia, Athens, GA 30602, USA.
Sci Rep. 2013;3:2353. doi: 10.1038/srep02353.
The rolling up of a graphene sheet into a tube is a standard visualization tool for illustrating carbon nanotube (CNT) formation. However, the actual processes of rolling up graphene sheets into CNTs in laboratory syntheses have never been demonstrated. Here we report conformal growth of graphene by carbon self-assembly on single-wall and multi-wall CNTs using chemical vapor deposition (CVD) of methane without the presence of metal catalysts. The new graphene layers roll up into seamless coaxial cylinders encapsulating the existing CNTs, but their adhesion to the primary CNTs is weak due to the existence of lattice misorientation. Our study shows that graphene nucleation and growth by self-assembly of carbon on the inactive carbon basal plane of CNTs occurs by a new mechanism that is markedly different from epitaxial growth on metal surfaces, opening up the possibility of graphene growth on many other non-metal substrates by simple methane CVD.
将石墨烯片卷起成管是说明碳纳米管（CNT）形成的标准可视化工具。然而，实验室合成中将石墨烯片卷起成 CNT 的实际过程从未得到证明。在这里，我们使用甲烷的化学气相沉积（CVD）在没有金属催化剂存在的情况下，报告了单壁和多壁 CNT 上通过碳自组装进行的石墨烯的共形生长。新的石墨烯层卷起形成无缝同轴圆柱，包裹现有 CNT，但由于晶格取向失配的存在，它们与原始 CNT 的附着力很弱。我们的研究表明，通过 CNT 碳基面上的碳自组装进行的石墨烯成核和生长发生在一种与金属表面上的外延生长明显不同的新机制下，为通过简单的甲烷 CVD 在许多其他非金属衬底上生长石墨烯开辟了可能性。
