By Kim Tae-gyu
Staff Reporter


A team of scientists developed the thinnest carbon nanotube ever, as slim as 0.4 nanometers in diameter. A nanometer is equal to one billionth of a meter.

The team, headed by Prof. Kim Kwang-soo at Pohang University of Science and Technology in Korea, Thursday said they extracted the world’s first sub-nanometer carbon tube.

``Thus far, the thickness of the slimmest carbon nanotube was just over 1 nanometer. We broke through the barrier using a new idea,’’ Kim said.

Carbon nanotubes are cylindrical carbon molecules found in the early 1990s.

They are called dream materials because of their unique physical and chemical properties, which make them useful in extremely small-scale electron and mechanical applications.

Included in its potential usages are next-generation field emitters, precision machines, optical elements, molecular filters and artificial muscles.

The would-be star substances are categorized into two main types of single-walled nanotubes and multi-walled ones, which are composed of many single-walled shells.

The 0.4-milimeter nanotubes are single-walled. Kim’s team obtained the ultra-thin nanotubes simply by pulling them apart from the multi-walled ones.

``It is like peeling onions. We used a needle tip of an atomic force microscope to get rid of many outer layers of a multi-walled nanotube to gain the innermost one, a super-slim single-walled nanotube,’’ Kim said.

Scientists cannot create single-walled sub-nanometer-sized nanotubes due to their instability. So Kim’s team searched for an alternative way of making them through peeling away outer layers of stable multi-walled nanotubes.

``Technologically, it is not difficult at all. But scientists failed to come up with the idea. It required a conceptual shift,’’ Kim beamed.

In addition, Kim’s team reeled out the thin nanotubes to very long distances, 1 millimeter. It is about 1,000 times longer than the previous length of 1 micrometer.

``We also confirmed the hypothesis that sub-nanometer nanotubes will be metallic rather than being semi-conductive. With our findings, we will be able to open up a new era in the study of nanotubes in full swing,’’ Kim said.

Kim plans to apply for international patents on the process. The Proceedings of the National Academy of Sciences and the Journal of American Chemical Society, two U.S.-based peer-reviewed scientific journals, recently featured the findings on their Web sites.

voc200@koreatimes.co.kr