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Hla team contributes to new nanotechnology research on supramolecule

Scanning tunneling microscopy image of the molecule (left) and its structural model (right). (Image credit: Yiming Li)
From Staff Reports
April 29, 2020

Ohio University physicist Saw Wai Hla examines how scientists can build and understand molecules and molecular machines at the nanoscale. Researchers believe that these nanotechnologies have great potential for use in the next generation of electronics—as they can store and analyze data and produce energy—as well as medical devices.

In the last several years, Hla has gained international attention in the scientific community for building molecular motors and a molecular propeller.

Earlier this month, Hla and colleagues at the University of South Florida published an article in the journal Nature Chemistry that announced another major development in their work—the synthesis of a 2D “supramolecule.”

“This achievement will enable advancing our understanding of the design principles governing the preparation of discrete 2D self-assembled molecular structures with desired functions for potential applications, including single molecule information storage devices and energy harvesting,” said Hla, a professor of physics and astronomy in the College of Arts and Sciences.

Why is this molecule so unique? The scientists were able to create it at a certain size—just over 20 nanometers in diameter—that had eluded them in previous experiments, Hla said. At this size range, these molecules can perform functions useful for electronic applications.

In principle, 2D symmetry already has quantum properties, but by reducing the lateral size, there may be more applications in data storage and quantum computation,” Hla explained.

Picture of Saw-Wai Hla
Saw-Wai Hla is a professor of physics and astronomy and member of the Nanoscale and Quantum Phenomena Institute. Credit: College of Arts and Sciences.

The supramolecule has a hexagonal structure, like a honeycomb, commonly found in nature, said Xiaopeng Li, an associate professor of chemistry at the University of South Florida who served as lead author on the Nature Chemistry paper.

“In the synthesis, we were inspired by the protein and DNA structures in nature to use sequence-specific building blocks to fold and assemble this giant supramolecule,” Li said. 

Unlike other shapes that have been hard to construct and study, the hexagon is a very stable structure. It is also similar to graphene, a material prized for its potential applications, the scientists noted.

In addition, researchers can use different types of metal atoms to construct the hexagonal structures in order to vary the levels of magnetism—a quality useful for energy harvesting, sensors, data storage and light emission applications, Hla explained.

Not only have scientists found it challenging to synthesize stable 2D nanostructures of certain sizes, but have faced difficulty studying them to understand their characteristics. In the new study, however, Hla’s team used state-of-the-art scanning tunneling microscopy techniques that gave the scientists a clear view of the supramolecule and its components, Li said.

Hla’s research team originally developed a process to allow scientists to capture images of molecules at the nanoscale using scanning tunneling microscopy in 2006. They now are performing this research at the Argonne National Laboratory’s Center for Nanoscale Materials, which is a U.S. Department of Energy facility near Chicago.

Two Ohio University students contributed to the Nature Chemistry study. Ryan Tumbleson, an Honors Tutorial College engineering physics student, received the prestigious Summer Undergraduate Laboratory Intern award from the U.S. Department of Energy to participate in the research, Hla said. Thomas Rojas, a graduate student in the Department of Physics and Astronomy, worked with Argonne scientist Anh Ngo—an Ohio University alumnus—to calculate the electronic structure of the molecule.

Hla confirmed that the methods and techniques used in the study could help scientists tackle additional nanotechnology questions.

“Both synthesis and atomic scale characterization demonstrated here are very powerful for designing novel metal-supramolecular complexes and solving nanoscale problems related to their structural and electronic properties,” he said.

Hla is a member of Ohio University’s Nanoscale and Quantum Phenomena Institute. His team’s use of the Center for Nanoscale Materials is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.