ATLANTA,
GA - Chemists and materials scientists often study “nanotubes” — capsule-shaped
molecules only a few billionths of a meter (nanometers) in width. In nanotube
form, many materials take on useful, unique properties, such as physical
strength and excellent conductivity. Carbon nanotubes are the most widely
investigated variety. Now, in pioneering research, scientists at the U.S.
Department of Energy’s Brookhaven National Laboratory have created and
investigated the properties of nanotubes made of a different, yet equally
interesting material: cerium oxide.
“Cerium oxide nanotubes have potential
applications as catalysts in vehicle emission-control systems and even
fuel cells,” says Brookhaven chemist Wei-Qiang Han, the lead scientist
involved in the work. “But until very recently, they haven’t been studied.”
Han and his colleagues are in the
midst of ongoing research into the structure and properties of cerium oxide
nanotubes. As part of this, they have devised a method to synthesize cerium
oxide nanotubes of high quality. First, they allow the compounds cerium
nitrate and ammonia hydroxide to chemically react. Initially, this reaction
forms “one-dimensional” nanostructures, such as rods and sheets, made of
the intermediate product cerium hydroxide. The intermediate product is
then quickly cooled to zero degrees Celsius, which freezes those structures
into place. By letting the chemical reaction proceed over a long period
of time, a process called “aging,” the hydrogen is eventually removed from
the intermediate product and a large quantity of the desired end product
— cerium oxide nanotubes — is formed.
Han will explain this synthesis method
at the American Chemical Society National Meeting in Atlanta, Georgia.
His talk will take place at 3:00 p.m. on Tuesday, March 28, 2006, in Room
B403 of the Georgia World Congress Center.
During his talk, Han will also discuss
his group’s recent study — how cerium oxide nanotubes release oxygen ions
when immersed in a low-oxygen environment, a process that is critical to
the nanotubes’ effectiveness as catalysts. To do this, the researchers
have used several techniques. These include “transmission electron microscopy,”
a very powerful imaging technique, and two x-ray techniques, which they
performed at Brookhaven’s National Synchrotron Light Source.
“We’re interested in studying oxygen-atom
vacancies in cerium oxide nanotubes because, when combined with their other
surface features, these vacancies may make them more functional and effective
in the applications mentioned,” Han said.
This work was funded by the Office
of Basic Energy Sciences within the U.S. Department of Energy’s Office
of Science.

|