Nanotubes in a New Light

From flat-panel television displays to fuel cells to building materials, extraordinarily strong nanotubes contain properties applicable to new technologies
--by Laura Mgrdichian

Nanotubes are tiny cylindrical molecules just a few nanometers (billionths of a meter) in diameter, but their potential for new technologies is vast. They are extraordinarily strong, conduct electricity well, and can even emit light. These properties are suitable for many applications, from flat-panel television displays to fuel cells to building materials. But nanotubes must be extensively studied before they can be used in industrial applications.

Above: Scanning electron microscope images of (a) MWNT powder, (b) SWNT powder, (c) SWNT buckypaper, and (d) aligned MWNTs.

At the National Synchrotron Light Source, a group of scientists has pioneered a way of using x-ray light to investigate the two main types of carbon nanotubes: multi-walled nanotubes (MWNTs), which resemble cylinders concentrically nested together like Russian dolls, and single-walled (“un-nested”) nanotubes (SWNTs).

The technique is known as “near-edge x-ray absorption fine structure,” or NEXAFS, and it has been used for years to study the properties of various materials – specifically, to investigate the materials’ surface chemistry (chemical phenomena occurring on a surface) and how their molecules are oriented. But for nanotubes, the application of NEXAFS is still quite new.

“The beauty of using NEXAFS to study nanotubes is that it gives us more detailed surface-chemistry information than other techniques are currently capable of. At the same time, it complements those techniques to give us a clearer picture of the sample’s behavior,” said scientist Daniel Fischer, who works for the National Institute of Standards and Technology, which owns and operates three research stations, called “beam lines” at the NSLS.