Light-sensitive particles change chemistry at the flick of a switch
A light-sensitive, self-assembled monolayer that provides unique control over particle interactions has been developed by scientists at the University of Illinois at Urbana-Champaign. Particles coated with the monolayer change their surface charge and chemistry upon exposure to ultraviolet light.
"Tailoring interactions between particles allows us to design colloidal fluids, gels and crystals for use as ceramic, photonic and pharmaceutical materials," said Jeffrey Moore, a William H. and Janet Lycan Professor of Chemistry and a researcher at the Frederick Seitz Materials Research Laboratory and at the Beckman Institute for Advanced Science and Technology. "We are assembling a toolkit of molecules that can be incorporated as monolayers on particles to achieve desired effects."
Light-induced modification of colloidal interactions provides an ’extra handle’ for tailoring system behavior, said Jennifer Lewis, the Thurnauer Professor of Materials Science and Engineering and interim director of the Frederick Seitz Materials Research Laboratory.
"The monolayer is designed so that light triggers the cleavage of a specific chemical bond, thereby exposing an underlying functional group of interest," said Lewis, who also is a professor of chemical and biomolecular engineering and a researcher at the Beckman Institute.
Moore and Lewis first demonstrated the technique in a paper published in the Sept. 30, 2005, issue of the Journal of the American Chemical Society. In that work, the surface charge and, thus, the electrostatic interactions between photosensitive silica microspheres, were modified by exposure to ultraviolet light.
In recent work, the researchers documented the gel-to-fluid transition in binary mixtures that initially were oppositely charged. "Exposure to ultraviolet light rendered all of the particles negative and converted the system into a colloidal fluid that settled to form a dense sediment," said Moore, who will present the team’s findings at the national meeting of the American Chemical Society, to be held in Atlanta, March 26-30.
"These light-responsive systems will enable novel assembly routes for creating colloidal structures in a variety of materials," Lewis said. "We are currently investigating the ability to locally photo-pattern such assemblies in three dimensions without requiring multiple processing steps."
Light-sensitive colloidal particles could also be used to "tune" the elastic properties, viscous response and microstructure of gel-based inks used in the direct-write assembly of complex, three-dimensional structures formed by robotic deposition.
The Moore group is developing multiple wavelength-specific triggers that would allow different wavelengths of light to induce changes sequentially.
James E. Kloeppel | EurekAlert!
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers
Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...
Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.
At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...
3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects
A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...