A new type of tunable nanocrystal gel synthesized at the University of Texas at Austin offers scope for use as thermal camouflage or as a temperature regulator for buildings.

The material can be switched between two different states by changing the temperature, enabling it to function as an optical filter, absorbing different frequencies of light depending on whether it is in a gelled state or not. Placed on the outside of buildings, the material could control heating or cooling dynamically. Such optical filter material also has applications for defense, particularly for thermal camouflage.

The research reported in Science Advances details how tin-doped indium oxide nanocrystals were functionalized with terpyridine-terminated ligands and dispersed in N,N-dimethylformamide with cobalt and excess chlorine, resulting in links between nanocrystals, gelation at room temperature and a red shift in the infrared localized face plasmon resonance absorption due to coupling. Higher temperatures break the bonds and cause the gel to break down.

The nanocrystals can be chemically tuned for use in routing communications through fiber 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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