Diamond-like Nanothreads Form Under Extreme Pressure

Using a high-pressure device at Oak Ridge National Laboratory, graduate student Thomas C. Fitzgibbons recently transformed a few cubic millimeters of liquid benzene into a white, crystalline powder. The solid was made of a substance never before observed: ultrathin threads of carbon atoms bound to one another in a pattern resembling diamond (Nat. Mater. 2014, DOI: 10.1038/nmat4088).

The threads, Fitzgibbons and colleagues hope, might one day be used to make strong, lightweight materials for vehicles and other objects.

Creating ordered nanomaterials from organic molecules such as benzene has been a longtime goal of the group, says John V. Badding, who is Fitzgibbons’s Ph.D. adviser at Pennsylvania State University. In the past, when Badding and his team put the squeeze on benzene, they produced only disordered substances, though. This time, crystalline order seems to have arisen because “the apparatus Tom used required us to compress and decompress slowly,” Badding explains.

Fitzgibbons ramped up to a pressure 200,000 times that of Earth’s atmosphere and back down over 20 hours. This glacial pace, the team proposes, allowed stacks of benzenes to poly­merize slowly enough to form the 6-Å-thick ordered threads (structure shown).

“This is pioneering work,” says Roald Hoffmann, a theoretical chemist at Cornell University. Hoffmann, who collaborates with Badding, predicted a structure related to that of the nanothreads while studying benzene polymerization a few years ago.