Versatile “nanocrystal gel” could enable adva

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video: This video shows the tunability of the material with temperature change. The sample starts in its ungelled state (called “dispersion”). As the material is cooled, the material begins to transform into a nanocrystalline gel (called the “sol-gel transition”), until the entire sample is in gel form. Then heat is applied and the nanocrystal gel decomposes again.
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Credit: Cockrell School of Engineering, University of Texas at Austin

New applications in energy, defense and telecommunications could get a boost after a team from the University of Texas at Austin created a new type of “nanocrystal gel” – a gel composed of tiny nanocrystals each 10,000 times smaller than the width of a human hair that are linked together in an organized network.

The gist of the team’s discovery is that this new material is easily adjustable. That is, it can be switched between two different states by changing the temperature. This means that the material can function as an optical filter, absorbing different frequencies of light depending on whether it is in a gel state or not. So it could be used, for example, outside buildings to dynamically control heating or cooling. This type of optical filter also finds applications for defence, in particular for thermal camouflage.

Gels can be customized for these large-scale applications because the nanocrystals and the molecular linkers that link them into networks are design components. Nanocrystals can be chemically tuned to be useful for routing communications through fiber optic networks or for keeping spacecraft temperatures stable on distant planetary bodies. Linkers can be designed to tilt gels based on ambient temperature or detection of environmental toxins.

“You can change an object’s apparent heat signature by changing the infrared properties of its skin,” said Delia Milliron, professor and chair of the McKetta Department of Chemical Engineering at the Cockrell School of Engineering. “It could also be useful for telecommunications which all use infrared wavelengths.”

The new research is published in the recent issue of the journal Scientists progress.

The team, led by graduate students Jiho Kang and Stephanie Valenzuela, carried out this work through the university’s Center for Materials Dynamics and Control, a materials research and engineering center in the National Science Foundation which brings together engineers and scientists from across campus to collaborate on materials. Scientific Research.

The lab experiments allowed the team to see the material change back and forth between its two states of gel and non-gel (i.e. floating nanocrystals suspended in liquid) that they triggered by specific temperature changes.

Supercomputer simulations performed at UT’s Texas Advanced Computing Center helped them understand what was happening in the gel at the microscopic level when heat was applied. Based on theories of chemistry and physics, the simulations revealed the types of chemical bonds that hold the nanocrystals together in a lattice, and how these bonds break when touched by heat, causing the decomposition of the gel.

This is the second unique nanocrystalline gel created by this team, and they continue to pursue advances in this area. Kang is currently working on creating a nanocrystalline gel that can change between four states, making it even more versatile and useful. This gel would be a mixture of two different types of nanocrystals, each capable of switching between states in response to chemical signals or temperature changes. Such tunable nanocrystal gels are called “programmable” materials.

Images and captions available for use: https://utexas.box.com/s/wy5nek41th883vrh35s6oah23v0h74ok


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