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