Chemistry Researchers Bend Nanowires

A group of researchers in the lab of chemistry professor Charles M. Lieber have found a way to synthesize two- and three-dimensional versions of the microscopic strands known as nanowires—a breakthrough that researchers say may greatly increase the reach and applicability of the field by allowing scientists to design vastly more complex structures.

The discovery may prove useful in areas ranging from photovoltaics to recording voltages inside and outside cells, according to the study’s lead author Bozhi Tian, a graduate student in the Department of Chemistry and Chemical Biology. Colleagues in the department yesterday acknowledged the significance of the research.

“One of the big problems in the nanotube community is how you take all these different Lego building blocks of nanoscience and put them together into more complex sort of structures,” said Thomas J. Kempa, a chemistry graduate student and author. “Any segment or element which allows you to break free from the one-dimensional space and move in another direction is key.”

Tian’s method hinges on the introduction of bends known as “kinks” into the previously linear structure of the nanowire. He told The Crimson this week that his discovery was inspired by what he saw in nature—both the “kinks” in organic molecules that give them specific geometries and the crystalline structure of many minerals.

“In my work, I designed this kinked nanowire molecule by inserting joints into a straight backbone,” Tian said. “The segments and joints are quite similar to the chemical bonds and atoms in an organic molecule, although our material is almost four orders of magnitude larger in size.”

Tian added that he has been able to introduce kinks at angles of 120 degrees and 109.5 degrees, which correspond to the bond angles in two common molecular geometries.

“The amazing thing about the bent nanowires is the ability to control the direction that the nanowire is going at any particular time,” said David C. Bell, one of the authors and the manager of the imaging and analysis facility at the Center for Nanoscale Systems, referencing the discovery’s electrical application. “If you can control the direction of the nanowires, in theory you can build any sort of circuit you want.”

Aside from their potential use as a means of conducting electricity, the nanowires may serve to localize functionality at a particular point within the nanostructure, said Ping Xie, a postdoctoral fellow and author. With one-dimensional nanowires, it is currently difficult to determine where activity is concentrated within the linear wire.

According to Kempa, the researchers noticed while performing previous experiments that under some conditions their one-dimensional nanowires would kink.

“We said, ‘Hmm, that’s kind of interesting,’” said Kempa. “Bozhi took it a step further and found a way to controllably induce these kinks exactly where we want them during the nanowire synthesis.”

—Staff writer Alissa M. D’Gama can be reached at adgama@fas.harvard.edu.

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