Tuneable nanocrystal gel offers applications in energy and defence

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A new type of tuneable nanocrystal gel has the potential to be used as thermal camouflage or as a temperature regulator for buildings.

nanocrystal gel
The material in its gelled state (left) and its non-gelled state (right). When the material is heated (right), the chemical bonds between the nanocrystals break and the gel breaks down. When the material is cooled (left), chemical bonds form between the nanocrystals and they organise themselves into a network (the gel). Molecular bonding (top) that controls gelation as a function of temperature is understood using supercomputer simulations (bottom). Credit: Kang, Valenzuela, et al./UT Austin

This the claim of a team from The University of Texas at Austin whose new material can be switched between two different states by changing the temperature. This allows it to work as an optical filter, absorbing different frequencies of light depending on whether it’s in a gelled state or not.

In one possible application, the team said the nanocrystal gel could be used on the outside of buildings to control heating or cooling dynamically. This type of optical filter also has applications for defence, particularly for thermal camouflage.

According to the team, the gels can be customised for applications because the nanocrystals and the molecular linkers that connect them into networks are designer components. Nanocrystals can be chemically tuned to be useful for routing communications through fibre optic networks or keep the temperature of space craft steady on remote planetary bodies. Linkers can be designed to cause gels to switch based on ambient temperature or detection of environmental toxins.

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

The new research is published in Science Advances.

The lab experiments allowed the team, led by graduate students Jiho Kang and Stephanie Valenzuela, to see the material change back and forth between its two states of gel and not-gel (free-floating nanocrystals suspended in liquid) that they triggered by specific temperature changes.

Supercomputer simulations done at UT’s Texas Advanced Computing Center helped them to understand what was happening in the gel at the microscopic level when heat was applied. The simulations revealed the types of chemical bonds that hold the nanocrystals together in a network, and how those bonds break when hit with heat, causing the gel to break down.

Kang is currently working to create a nanocrystal gel that can change between four states, making it even more versatile and useful. That gel would be a blend of two different types of nanocrystals, each able to switch between states in response to chemical signals or temperature changes.