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Nanoscale Science and Engineering - NSF
Silicon chips have made everything electronic smaller, faster, and cheaper.
As this ScienCentral News video reports, scientists are working hard to make
circuits so small, we won't see them at all.
A Nanotube Boutique
Carbon nanotubes, which consist of graphite sheets in extremely tiny tubular
shapes, now symbolize the huge potential of nanotechnology
to change materials, manufacturing, medicine, and electronics. But progress
in assembling them into anything useful has been slow. One nanotechnologist
decided to try building nanotubes from other molecules that are easier to
In 1991, Dr. Sumio Iijima, a physicist and materials scientist at NEC Corporation
in Japan, discovered carbon nanotubes, a miniscule new form of graphite, the
material in pencils. Researchers immediately plunged into looking for ways
to harness carbon nanotubesâ€™ impressive strength, flexibility, and potential
as electrical conductors. But the surfaces of carbon nanotubes proved to be
very slippery. Dr.
Pulickel Ajayan is a leading carbon nanotubes researcher at Rensselaer
Polytechnic Institute. He began his career working with Dr. Iijima. According
to Dr. Ajayan, “When things are small, things are different. A lot of
studies have been done, but we are certainly not at the end of the tunnel.
We have a long way to go before we can put
carbon nanotubes together in the way we want.”
Purdue University, Dr.
Hicham Fenniri, who trained as a biochemist and organic chemist, decided
to try making nanotubes out of something easier to control than the slippery
form of graphite in carbon nanotubes. In order to accomplish his goal in nanotechnology,
Fenniri, like many researchers, had to acquaint himself with another branch
of science. He looked for answers in synthetic
organic chemistry, which attempts to mimic the way living things build
useful structures. Subsequently, inspired by natureâ€™s approach to assembling
molecules and armed with the power of synthetic chemistry, he has been able
to design molecules which link together in groups of six to form ring-like
structures he calls rosettes.
The rosettes then form synthetic nanotubes.
On the outside of each synthetic nanotube, Fenniri can add electronic anchors
which serve as links for other molecules with the properties he wants each
tube to have: “The anchors can be used like a dock in a marina. You
can attach a boat, with whatever cargo you like.” Most recently, Fenniri
has been able to design nanotubes that can turn right or left. “Most
molecules in the natural world are organized in either a right-handed or left-handed
direction, and that determines their properties,” Fenniri explains.
“If you change the direction, you change the moleculesâ€™ properties.
For example, sugar loses its sweetness if its handedness is changed.”
Fenniriâ€™s “designer” nanotubes could be used to assemble
nano-circuits that could eventually be used in molecular electronics and photonics.
Next, he plans to experiment with two methods of using his synthetic nanotubes
to assemble circuitry on chips, where they could shuttle electrons through