Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Polarized Particles Join Toolbox For Building Unique Structures

13.10.2006
Researchers at the University of Illinois at Urbana-Champaign have created polarized, spherical particles that spontaneously self-assemble into clusters with specific shapes and distributions of electric charge. The polarized particles can be used in the directional self-assembly of intricate shapes and unique structures.
"The world abounds with particles that have traditionally been treated as geometrically symmetric, chemically isotropic and electrically uniform," said Steve Granick, a professor of materials science and engineering, chemistry and physics. "We have muddied the waters a bit by asking: 'What happens when we build clusters from particles that have an uneven distribution of electric charge?' "

The polarized spheres are called Janus particles; Janus was the Roman god of change, often portrayed with two faces gazing in opposite directions. The spheres offer new opportunities in particle engineering for building particular structures. The clusters may also prove useful as simple systems in which to explore the role of charge interactions in determining how proteins aggregate. Granick and his collaborators describe their work in a paper accepted for publication in the journal Nano Letters, and posted on its Web site.

To make their Janus particles, the researchers begin with negatively charged beads one micron in diameter. Using electron beam deposition, they coat one hemisphere of the beads with a gold film, which is then made positively charged.

When placed in solution, the particles spontaneously self-assemble into specific geometrical shapes depending on the number of particles. For example, clusters of seven particles resemble a flywheel, which can revolve around a polar axle.

The compact shapes differ fundamentally from the strings and rings formed by magnetic particles, said Granick, who also is a researcher at the Frederick Seitz Materials Research Laboratory and at the Beckman Institute for Advanced Science and Technology.

"The observed shapes are in excellent agreement with computer simulations," said Erik Luijten, a professor of materials science and engineering, and a corresponding author of the paper. "The simulations not only show you the shapes, they also show you how the particles are oriented in the cluster."

Surprisingly, the charge distribution of the initial Janus particles is preserved in the clusters. One half of each cluster tends to be positively charged; the other half negatively charged. This uneven distribution of surface charge could be utilized, perhaps, in the directional self-assembly of particles into more elaborate and intricate shapes.

"Future work could consider particles whose shape is not just spherical, but also rod-like or oblate," Granick said. "This is just the beginning of something that will catch a lot of people's imaginations."

Lead authors of the paper were graduate student Liang Hong and postdoctoral research associate Angelo Cacciuto. The work was funded by the National Science Foundation and the Petroleum Research Fund.

Editor's note: To reach Steve Granick, call 217-333-5720; e-mail: sgranick@uiuc.edu.

To reach Erik Luijten, call 217-244-5622; e-mail: luijten@uiuc.edu.

James E. Kloeppel | University of Illinois
Further information:
http://www.uiuc.edu

More articles from Materials Sciences:

nachricht Mat4Rail: EU Research Project on the Railway of the Future
23.02.2018 | Universität Bremen

nachricht Atomic structure of ultrasound material not what anyone expected
21.02.2018 | North Carolina State University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>