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Scientists weave together nanomaterials for the first time

"We have taken the art of weaving into the atomic and molecular level," researcher Omar Yaghi said.
By Brooks Hays   |   Jan. 22, 2016 at 1:28 PM

BERKELEY, Calif., Jan. 22 (UPI) -- The art of weaving is one of the oldest methods of fabric-making, but until now, it hasn't been used at the nanoscale.

For the first time, scientists have created 3D covalent organic frameworks by weaving helical organic threads. Covalent organic frameworks, or COFs, are porous and crystalline materials made of common elements and commonly used for gas storage, as well as photonic and catalytic applications.

Early tests suggest woven COFs boast improved structural flexibility, resiliency and reversibility.

"We have taken the art of weaving into the atomic and molecular level, giving us a powerful new way of manipulating matter with incredible precision in order to achieve unique and valuable mechanical properties," researcher Omar Yaghi, a chemist with Lawrence Berkeley National Laboratory and the University of California Berkeley, said in a press release.

"Weaving in chemistry has been long sought after and is unknown in biology," Yaghi added. "However, we have found a way of weaving organic threads that enables us to design and make complex two- and three-dimensional organic extended structures."

Because of their strong molecular bonds, large internal surface areas and sponge-like qualities, COFs and metal organic frameworks, or MOFs, have been increasingly employed in carbon sequestration technologies. Researchers are also experimenting with these materials with the hopes of building better gas storage devices for hydrogen-powered vehicles.

Yahgi and his colleagues at Berkeley Labs were able to create a new type of organic framework by weaving together threads of an organic compound called "phenanthroline" using a copper complex. They call the new nanomaterial COF-505.

Using X-ray and electron diffraction, scientists can remove and restore the copper complex from the framework.

"That our system can switch between two states of elasticity reversibly by a simple operation, the first such demonstration in an extended chemical structure, means that cycling between these states can be done repeatedly without degrading or altering the structure," Yaghi explained. "Based on these results, it is easy to imagine the creation of molecular cloths that combine unusual resiliency, strength, flexibility and chemical variability in one material."

Researchers say the new technology could allow scientists to weave nanothreads into thin films or polymers to be used in electronic devices.

"Our weaving technique allows long threads of covalently linked molecules to cross at regular intervals," Yaghi said. "These crossings serve as points of registry, so that the threads have many degrees of freedom to move away from and back to such points without collapsing the overall structure, a boon to making materials with exceptional mechanical properties and dynamics."

The creation of COF-505 is described in a new paper published in the journal Science.

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