Atomic cable with protective cover

Stable chains of single atoms generated inside carbon nanotubes

Production of nanowires in nanotubes © Gesellschaft Deutscher Chemiker
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Nanowires are considered as a component of the future, but are not very easy to manufacture. Now Japanese researchers have developed a new, amazingly simple method: They simply store metal atoms in nanocarbon beads and use them as a template, but also as a protective cover. The researchers now present their procedure in the journal Angewandte Chemie.

The trend towards miniaturization in electronics seems to be continuing. The research on new components on the nanometer scale is correspondingly intensive. Wires in atomic dimensions are considered to be particularly interesting components for future nanoscopic applications. Such fine wires also show completely new electronic properties. In addition to the not very easy production of metallic nanowires their major chemical reactivity is the main problem: they oxidize easily in air and are not stable.

Carbon tubes as a template

Japanese researchers led by R. Kitaura and H. Shinohara have now developed a new method that is simple yet provides stable nanowires: they trap the metal atoms inside carbon nanotubes. As the scientists report, metal wires are created from individual atoms arranged next to each other, which are protected so well by their shell that they remain stable over the long term.

The manufacturing method is to heat carbon nanotubes and a metal powder under vacuum. It works for all metals that pass into the gaseous state at relatively low temperatures, such as europium, samarium, ytterbium and strontium. The metal atoms almost completely fill the cavity within the carbon nanotubes. With europium and carbon nanotubes with an inner diameter of about 0.76 nanometers, the researchers were able to obtain wires that consist of only a single chain of juxtaposed atoms. This first truly one-dimensional nanowire was still stable after a month in the air.

... and as a protective cover

By using carbon nanotubes of different internal diameters, ultrathin wires of various diameters could be made, for example, two or four atomic chains. Compared to the macroscopic europium crystal, the atomic wires showed distinctly different electronic and magnetic properties. The nanowires are also an ideal model for studying one-dimensional phenomena. The researchers now want to test the properties of the wires with regard to their suitability as "cabling" for nanoelectronic components. display

(Society of German Chemists, 08.10.2009 - NPO)