DNA-Like Twisted Crystal Structure Created with Germanium Sulfide Nanowire

Crystals can be seen in many everyday objects: ice cubes, snowflakes, gemstones, table salt, are a few examples. Not visible to the naked eye, but of special significance to researchers, are crystalline “nanowires”—wires with a diameter of a just a few nanometers and a usual length of a micrometer.

Mostly in a rod-like shape, these wires are an appealing area of global research owing to their many prospective applications, such as semiconductors and miniaturized optoelectronic and optical devices.

As mentioned in a recent Nature paper, researchers at the Center for Nanoscale Materials (CNM), a U.S. Department of Energy (DOE) Office of Science User Facility situated at Argonne National Laboratory, played a crucial role in the discovery of a DNA-like twisted crystal structure developed with a germanium sulfide nanowire, also called a “van der Waals material.” The study was performed in partnership with the University of California at Berkeley and Lawrence Berkeley National Laboratory.

The helical DNA-like structure forms naturally by giving the nanowire an “Eshelby twist.” Co-first author Jie Wang, a former materials scientist in CNM (currently at Thorlabs, Inc.), explained that the word “Eshelby twist” is coined from the name of its discoverer, John Eshelby.

As a research associate working at the University of Illinois at Urbana-Champaign in the 1950s, Eshelby performed a crucial theoretical analysis of “screw dislocation” in a thin rod. Connecting the effect to crystals, Wang observed that the “screw dislocation occurs when stress is applied to a rod shape in which the atoms become rearranged in a helical pattern.”

When applied to a germanium sulfide nanowire, this twisting makes it elongate and broaden into a helical structure.

It is amazing that these inorganic germanium sulfide nanowires so closely resemble the organic DNA structure. Nature creates remarkable structures beyond our imagination.

Jianguo Wen, Study Co-Author and Materials Scientist, CNM

Similarly important, added CNM scientist and co-author Dafei Jin, was the finding that the nanostructure automatically splits into segments that look like helically stacked bricks. These brick-like segments arise from the discharge of energy as the wire diameter expands from tens of nanometers to micrometers.

“The discovered Eshelby twist here offers a new way to engineer nanomaterials,” said Wang. “We can tailor these nanowires in many different ways—twist periods from two to twenty micrometers, lengths up to hundreds of micrometers, and radial dimensions from several hundred nanometers to about ten micrometers.”

In that way, scientists can modify the optical and electrical properties of the nanowires to enhance performance for various applications.

This is an important materials discovery. We are excited to have figured out, using CNM’s high-resolution transmission electron microscope, the dislocation structures that drive the nanowires to have an Eshelby twist.

Jianguo Wen, Study Co-Author and Materials Scientist, CNM

The scientists’ research illustrated above has been published in the June 20^th issue of Nature and is titled “Helical van der Waals crystals with discretized Eshelby twist.” Authors are Yin Liu, Jie Wang, Su Jung Kim, Haoye Sun, Fuyi Yang, Zixuan Fang, Nobumichi Tamura, Ruopeng Zhang, Xiaohui Song, Jianguo Wen, Bo Z. Xu, Michael Wang, Shuren Lin, Qin Yu, Kyle B. Tom, Yang Deng, John Turner, Emory Chan, Dafei Jin, Robert O. Ritchie, Andrew M. Minor, Daryl C. Chrzan, Mary C. Scott, and Jie Yao.

This research was aided by the Office of Basic Energy Sciences, U.S. Department of Energy, and carried out, partially, at Argonne’s Center for Nanoscale Materials.