Fig. 1 - Zeolite single crystal containing SWNTs

Using microporous zeolite single crystals as hosts, Dr Zikang Tang and Dr Ning Wang from the Physics Department succeeded in fabricating the world's smallest single-walled carbon nanotubes (SWNTs) that are periodically aligned in the crystal channels. The diameter of the single-walled carbon nanotube is only 0.4nm (nanometer).

Carbon nanotubes are long, thin cylinders of carbon. Single-walled carbon nanotubes are formed by rolling single-atomic graphite layer into a cylinder. They are extremely small in size - a bundle of 1,000,000 carbon nanotubes equals the size of a hair. Their unique physical structures, electronic properties, and their intriguing potentials for wide applications have sparked an explosion of research into their understanding since they were discovered in 1991.

Fig. 2 - High-resolution electron microscopy image of SWNTs

Carbon nanotubes do not exist in nature. They can only be formed under special circumstances. The carbon nanotubes that are produced by traditional techniques are usually larger in size, and contain a mixture of various kinds of carbon specimens structured in a disorderly manner. The challenge for scientists is to produce smaller-sized, mono-dispersed and regularly arrayed carbon nanotubes.

The fabrication technology that was developed by Dr. Tang and Dr. Wang is unique, and the nanotubes produced are unprecedented. They have made an important step towards the research of carbon nanotubes by pushing its size to its theoretical limit. The carbon nanotube that they fabricated is an ideal one-dimensional conductor, and its novel properties are yet to be explored. This discovery will provide new samples for further research on nanotubes.

Key publications:
"Single-walled 4 Angstrom carbon nanotube arrays", N. Wang, Z. K. Tang, G. D. Li, J. S. Li, Nature 408(2000) 50-51.