HOUSTON,
Oct. 20, 2005 Rice University scientists have
constructed the world¹s smallest car ‹ a
single molecule ³nanocar² that contains
a chassis, axles and four buckyball wheels.
The ³nanocar² is described in a research
paper that is available online and due to appear
in an upcoming issue of the journal Nano Letters.
³The synthesis and testing of nanocars and other
molecular machines is providing critical insight
in our investigations of bottom-up molecular manufacturing,² said
one of the two lead researchers, James M. Tour, the
Chao Professor of Chemistry, professor of mechanical
engineering and materials science and professor of
computer science. ³We¹d eventually like
to move objects and do work in a controlled fashion
on the molecular scale, and these vehicles are great
test beds for that. They¹re helping us learn
the ground rules.²
The nanocar consists of a chassis and axles made
of well-defined organic groups with pivoting suspension
and freely rotating axles. The wheels are buckyballs,
spheres of pure carbon containing 60 atoms apiece.
The entire car measures just 3-4 nanometers across,
making it slightly wider than a strand of DNA. A
human hair, by comparison, is about 80,000 nanometers
in diameter.
Other research groups have created nanoscale objects
that are shaped like automobiles, but study co-author
Kevin F. Kelly, assistant professor of electrical
and computer engineering, said Rice¹s vehicle
is the first that actually functions like a car,
rolling on four wheels in a direction perpendicular
to its axles.
Kelly and his group, experts in scanning tunneling
microscopy (STM), provided the measurements and experimental
evidence that verified the rolling movement.
³It¹s fairly easy to build nanoscale objects
that slide around on a surface,² Kelly said. ³Proving
that we were rolling not slipping and sliding was
one of the most difficult parts of this project.²
To do that, Kelly and graduate student Andrew Osgood
measured the movement of the nanocars across a gold
surface. At room temperature, strong electrical bonds
hold the buckyball wheels tightly against the gold,
but heating to about 200 degrees Celsius frees them
to roll. To prove that the cars were rolling rather
than sliding, Kelly and Osgood took STM images every
minute and watched the cars progress. Because nanocars¹ axles
are slightly longer than the wheelbase the
distance between axles they could determine
the way the cars were oriented and whether they moved
perpendicular to the axles.
In addition, Kelly¹s team found a way to grab
the cars with an STM probe tip and pull them. Tests
showed it was easier to drag the cars in the direction
of wheel rotation than it was to pull them sideways.
Synthesis of the nanocars also produced major challenges.
Tour¹s research group spent almost eight years
perfecting the techniques used to make them.
Much of the delay involved finding a way to attach
the buckyball wheels without destroying the rest
of the car. Palladium was used as a catalyst in the
formation of the axle and chassis, and buckyballs
had a tendency to shut down the palladium reactions,
so finding the right method to attach the wheels
involved a good bit of trial and error.
The Rice team has already followed up the nanocar
work by designing a light-driven nanocar and a nanotruck
that¹s capable of carrying a payload.
Other members of the research team include chemistry
graduate student Yasuhiro Shirai and post doctoral
associate Yuming Zhao.
The research was funded by the Welch Foundation,
Zyvex Corporation and the National Science Foundation.
Rice University is consistently ranked one of America¹s
best teaching and research universities. It is distinguished
by its: size‹2,850 undergraduates and 1,950
graduate students; selectivity‹10 applicants
for each place in the freshman class; resources‹an
undergraduate student-to-faculty ratio of 6-to-1,
and the fifth largest endowment per student among
American universities; residential college system,
which builds communities that are both close-knit
and diverse; and collaborative culture, which crosses
disciplines, integrates teaching and research, and
intermingles undergraduate and graduate work. Rice¹s
wooded campus is located in the nation¹s fourth
largest city and on America¹s South Coast.
DOWNLOADABLE HIGH-REZ ART:
http://www.rice.edu/media/nanocar.html
Rice University Office of News & Media Relations
News Release
CONTACT: Jade Boyd
PHONE: (713) 348-6778
E-MAIL: jadeboyd@rice.edu
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