Scientists Flip Molecular Switch
Source:
Discovery.com
November 1, 2000
Back in 1959, Richard P. Feynman - then a Caltech professor and
later a Nobel Laureate in physics - predicted the field of nanotechnology in a
lecture entitled "There's Plenty of Room at the Bottom." Decades later, we're
just beginning to realize the potential that nanotechnology offers. Although the
prospect of ultra-dense computer memories and cell-sized robots fires plenty of
imaginations, working on the scale of a billionth of a meter poses enormous
challenges.
Scientists have succeeded in creating molecules that function like
conventional electronic components, but integrating the molecules into nanoscale
devices requires control of electron flow across them. This week's issue of
Nature presents one solution: a reversible molecular switch developed by David
Schiffrin and colleagues in the Center for Nanoscale Science at the University
of Liverpool, U.K.
"If we're to have computers that run on molecularly sized objects,
we need to control the current," said Dan Feldheim of North Carolina State
University. "That's what the Schiffrin paper shows - that there's a way to
switch the current flowing through a molecule on or off."
Electronic switch design often limits the size of integrated
circuits, and electronic engineers strive continuously to make them smaller. But
to create their molecular switch, Schiffrin's team worked from the bottom up.
"Our approach was to develop a switch of very small dimensions by
chemically synthesizing components and then putting them together," said
Schiffrin.
The group linked a 6-nanometer-wide gold nanoparticle to a gold
electrode, using wires consisting of up to 60 individual organic molecules. The
molecules make up a "redox group" - a group into which the scientists can inject
electrons. Adding electrons lets current flow from the electrode and up the
molecular wire to the nanoparticle; removing electrons stops it. In other words,
the wires act just like a switch to turn the current on or off.
To solder the molecular wires between the gold electrode and
nanoparticle, the researchers attached "thiols" to both ends These sulfur atoms
stick to any nearby gold surface, making it possible for the switches to
assemble themselves. That capability will likely be crucial in nanoscale
manufacturing.
The work of Schiffrin and his team adds another piece to the
understanding of nanoscale electronic structures and their applications.
"We've demonstrated that you can control the flow of electrons
across these structures," said Schiffrin. "Now we're at the next stage -
figuring out how to transform them, to interconnect them, to produce functional
circuits."
by
Diane Kightlinger
http://www.discovery.com/news/briefs/20001101/te_nanotech.html