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Nanoparticles 'tailor' complex fluids for photonics, ceramics applications
Source : University of Illinois
August 1, 2001
CHAMPAIGN, Ill. — Researchers at the
University of Illinois have discovered a fundamentally new approach for tailoring the
stability of colloidal suspensions.
 |
Photo by Bill
Wiegand |
Jennifer Lewis and her colleagues
have devised a process that they call nanoparticle haloing. This
self-organizing process imparts stability to otherwise attractive colloidal microspheres
by decorating regions near their surface with highly charged nanoparticles. |
|
Colloidal suspensions are complex fluids utilized in numerous applications
ranging from advanced materials to drug delivery. Controlling the stability
of these fluids can influence such characteristics as flow behavior,
structure and mechanical response, and may result in materials with improved
optical and electrical properties.
As reported in the July 31 issue of the Proceedings of the National Academy of Sciences,
Jennifer Lewis and her colleagues have devised a process that they call nanoparticle
haloing. This
self-organizing process imparts stability to otherwise attractive colloidal microspheres
by decorating regions near their surface with highly charged nanoparticles.
 |
| Negligibly charged colloidal
microspheres (blue) aggregate in aqueous solution but undergo a stabilizing transition
upon addital of highly charged nanoparticles (red). |
|
"Using this nanoparticle haloing
approach, we can control the phase behavior and structure of materials assembled from
colloidal systems," said Lewis, a UI professor of materials science and engineering
and of chemical engineering. "Our approach complements traditional stabilization
techniques, such as electrostatic stabilization, by allowing systems of negligible charge
or high ionic strength to be stabilized."
Tailoring the interactions between particles allows the researchers to engineer the
desired degree of colloidal stability into the mixture.
"That means we can create designer colloidal fluids, gels and even crystals,"
Lewis said. "Our ability to control colloidal forces and phase behavior depends not
only on the charge of the nanoparticles, but also on their size. Through nanoparticle
engineering, we can assemble structures with properties that would not be possible through
traditional stabilization routes."
For example, Lewis has teamed up with co-author Paul Braun, a UI professor of materials
science and engineering, to explore the use of these nanoparticle-stabilized colloidal
microsphere mixtures in assembling robust periodic templates for photonic band gap
materials. The researchers recently were awarded funding by the National Science
Foundation to pursue such efforts.
Lewis and her students are also studying the structure and flow behavior of colloidal
fluids and gels assembled from these microsphere-nanoparticle mixtures. By compositionally
modulating interparticle forces, the researchers can produce systems whose properties vary
dramatically. Such studies provide the foundation of ongoing efforts in the area of
colloidal processing of electrical ceramics.
In addition to Lewis and Braun, the research
team included UI doctoral students Valeria Tohver and James Smay, and Carnegie Mellon
University graduate student Alan Braem. The National Aeronautics and Space Administration
Microgravity Research Program funded the work.
By James E. Kloeppel, Physical Sciences Editor
(217) 244-1073; kloeppel@uiuc.edu
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