Having fabricated the world’s smallest single-walled carbon nanotube, researchers at The Hong Kong University of Science and Technology are discovering some of its unique properties.
At 0.4 nanometres (1 million nanometres equal 1 mm), the tube is so small that it defies the normal behaviour of materials. One exciting discovery, said Prof Ping Sheng, director of HKUST’s Institute of Nano Science and Technology, is that the ultrathin nanontubes exhibit super conducting behaviour. “Here superconductivity refers to the phenomenon where a material loses all resistance to electricity. Pure carbon has never been known to possess this property so our discovery is significant,” said Prof Sheng.

Prof Sheng (right) and Prof Tang (left) using a scanning-tunnelling microscope (STM) which can magnify to atom level.

The carbon nanotubes could also one day be used in fuel cells. As a storage medium, they have twice the capacity of graphite used in everyday lithium batteries which power appliances including mobile phones and PDAs.
Whereas 1 gram of graphite can store enough lithium for a release of 374 milliamp hours, its carbon nanotube equivalent can help store more than 700 mA/hrs.
Researchers are also looking at the potential of carbon nanotubes for storing hydrogen for fuel cells. “The impact of hydrogen storage is great,” said Prof Shing “because hydrogen fuel causes zero pollution. Its by-product is pure water.”
The ultra-small nanotubes have optical properties too. As well as good polarizers of light, they can be photo luminescent with possible applications in optical communications such as light emitting diodes (LEDs) and lasers.
Said Prof Sheng: “If carbon, the element of life, can have light-emitting properties, the implications could be wide and very important.”
He added: “To me, nanoscience is the most exciting area of science today; it gives humans a handle on manipulating the basic properties of matter.”

Principal Investigator
Prof Zikang Tang : phzktang@ust.hk