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Thin films of silicon nanoparticles
roll into flexible nanotubes
Kloeppel, Physical Sciences Editor
photo to enlarge
by Kwame Ross
Chaieb, a professor of mechanical and industrial engineering
at Illinois and a researcher at the Beckman Institute
for Advanced Science and Technology, has created flexible
silicon nanotubes that could prove useful as catalysts,
guided laser cavities and nanorobots.
CHAMPAIGN, Ill. —
By depositing nanoparticles onto a charged surface, researchers at the
University of Illinois at Urbana-Champaign have crafted nanotubes from
silicon that are flexible and nearly as soft as rubber.
“Resembling miniature scrolls, the nanotubes could prove useful
as catalysts, guided laser cavities and nanorobots,” said Sahraoui
Chaieb, a professor of mechanical
and industrial engineering at Illinois and a researcher at the Beckman
Institute for Advanced Science and Technology.
To create their flexible nanotubes, Chaieb and his colleagues –
physics professor Munir Nayfeh and graduate research assistant Adam
Smith – start with a colloidal suspension of silicon nanoparticles
(each particle is about 1 nanometer in diameter) in alcohol. By applying
an electric field, the researchers drive the nanoparticles to the surface
of a positively charged substrate, where they form a thin film.
Upon drying, the film spontaneously detaches from the substrate and
rolls into a nanotube. Nanotubes with diameters ranging from 0.2 to
5 microns and up to 100 microns long have been achieved.
Using an atomic force microscope, the researchers found that the Young’s
modulus (a measure of a material’s elasticity) of the film was
about 5,000 times smaller than that of bulk silicon, but just 30 times
larger than that of rubber.
“We suspect that the nanotubes consist of silicon nanoparticles
held together by oxygen atoms to form a three-dimensional network,”
Chaieb said. “The nanotubes are soft and flexible because of the
presence of the oxygen atoms. This simple bottom-up approach will give
other researchers ideas how to build inexpensive active structures for
“Because the silicon nanoparticles – which are made using
a basic electrochemical procedure – have properties such as photoluminescence,
photostability and stimulated emission, the resulting nanotubes might
serve as nanodiodes and flexible lasers that could be controlled with
an electric field,” Nayfeh said.
The results will be reported in an upcoming issue of the journal Applied
Physics Letters. The work was funded by the National Science Foundation
and the state of Illinois.
Editor’s note: To reach Sahraoui Chaieb, call 217-333-4130; e-mail: email@example.com