Synthesis of structurally pure carbon nanotubes using molecular seeds

For 20 years, carbon nanotubes (CNTs) have been the subject of intensive fundamental as well as applied research. With their extraordinary mechanical, thermal and electronic properties, these tiny tubes with their graphitic honeycomb lattice have become the paragon of nanomaterials. They could help to create next-generation electronic and electro-optical components that are smaller than ever before, and thus to achieve even faster switching times.

With a diameter of roughly one nanometre, single-wall CNTs (or SWCNTs) need to be considered as quantum structures; the slightest structural changes, such as differences in diameter or in the alignment of the atomic lattice, may result in dramatic changes to the electronic properties: one SWCNT may be metallic, whilst another one with a slightly different structure is a semiconductor. Hence, there is a great deal of interest in reliable methods of making SWCNTs as structurally uniform as possible. In fact, corresponding synthesis concepts were formulated about 15 years ago. However, it is only now that surface physicists at Empa and chemists at the Max Planck Institute have successfully implemented one of these ideas in the laboratory. In the latest issue of "Nature," they describe how, for the first time, it has been possible to "grow" structurally homogenous SWCNTs and, hence, managed to clearly define their electronic properties.