World's First 4Å Single-walled Carbon Nanotubes

HKUST physicists--Assistant Professors Zikang Tang and Ning Wang, and team--have synthesized the world's narrowest single-walled carbon nanotubes.

75,000 times thinner than a human hair

The ultra small carbon cylinders they have fabricated are only 4Å (angstroms) or 0.4nm (nanometers) in diameter--that is, 75,000 times narrower than a single human hair.

  Schematic drawing of carbon nanotubes formed in zeolite channels

Nanotube theory holds these to be the narrowest stable single-walled carbon nanotubes possible.

Before Profs Tang and Wang's breakthrough, the narrowest single-walled nanotube fabricated measured 7Å in diameter.

Novel fabrication technique

On top of their "first past the post" satisfaction, the team are excited about the success of their innovative fabrication technique.

"Our 4Å single-walled carbon nanotubes are grown in the channels of zeolite crystals instead of by evaporating graphite in an arc-discharge," explains Prof Tang.

"We suspected we had succeeded in growing 4Å nanotubes in zeolite as long ago as 1998. However, our first proof was directly observing them by high-resolution transmission electron microscopy in March this year," adds Prof Wang.

Why these 4Å nanotubes are so exciting

The zeolite crystal method produces arrays of single-walled carbon nanotubes that are highly aligned and uniform in size. This will be a boon for experimental investigation of their electrical and mechanical properties.

"We are already observing new properties in the 4Å nanotubes not found in larger nanotubes. They are perfect one-dimensional quantum wires," reports Prof Wang.

"In the longer term, nanotubes this small could revolutionize microcomputers and other ultra-thin electronic devices. Another exciting avenue of research is their suitability as a storage medium for pollution-free hydrogen fuel."

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