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Graduate Student Spotlight

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Graduate Student Earns Prestigious ACS Fellowship

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Miranda Limbach, graduate student in the Department of Chemistry, was chosen as one of four recipients of a 2024 American Chemical Society Analytical Graduate Research Fellowship.

A member of Assistant Professor Thanh Do’s research group, Limbach is currently finishing a summer internship with Merck. When she returns, Limbach will begin her fifth year of graduate studies at the university.

The goal of Limbach’s PhD research is to identify the underlying principles governing the membrane permeability of macrocyclic peptides. Macrocyclic peptides are being explored as a means of drug delivery that would target protein-protein interactions, potentially leading to new ways to treat a variety of diseases.

This prestigious fellowship awarded by the Analytical Division of the ACS is designed to support research, promote the growth of the discipline, and to recognize future leaders in analytical chemistry. The award will provide support to Limbach for 9 months, which will allow her to focus fully on her research without holding a GTA position.

Other winners of the nationally competitive award are from the University of Wisconsin-Madison, Florida State University, and the California Institute of Technology.

The American Chemical Society (ACS) was founded in 1876 and is one of the world’s largest scientific organizations. In addition to hosting regular conferences devoted to exploring new and continuing research across the discipline of chemistry, the ACS provides accreditation for undergraduate chemistry degrees, offers a variety of fellowships and awards for students and researchers, and publishes more than 80 peer-reviewed journals.

Smith diagram

Smith Breaks New Ground with Domain Wall Research

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Kevin Smith, recent Ph.D. graduate from the department of chemistry, and Professor of Chemistry Janice Musfeldt have published the results of a collaborative investigation into the properties of ferroelectric domain walls. This research has generated a greater understanding of both a specific material, and domain walls in general, expanding the foundational knowledge critical to effectively using domain walls in future technologies.

Smith joined the chemistry department as a graduate student in 2015 and very quickly began investigating domain walls. Domain walls act as the boundaries between regions, or domains, of materials and have the potential to impact the properties and uses of that material.

Smith’s work specifically investigates the domain walls of ferroelectric materials, which have been a source of interest in the development of electronics. Efforts have been made to use domain walls as functional parts of devices as they could offer high speed memory reading and writing while requiring less energy to function.

Before ferroelectric domain walls can be successfully leveraged, researchers must develop a fundamental understanding of them and how they behave. It has long been hypothesized that these domain walls are atomically thin and conductive, but this had never been confirmed with a direct measurement at the wall. Smith and Musfeldt began investigating ferroelectric domain walls not with the intention of addressing this long-held belief, but with the goal of uncovering foundational information that could contribute to a greater understanding of these materials.

A collaboration with a group of physicists at Rutgers university, led by Henry Rutgers Professor Sang-Wook Cheong, provided Smith the material with which to begin his exploration.

“Our synthetic collaborators at Rutgers grew the material for us and provided some basic mapping on where to look for the domain walls,” said Smith. “We performed a line scan of the material with the near-field infrared microscope at Beamline 2.4 of the Advanced Light Source, or ALS, at Lawrence Berkeley National Lab. That’s when we started seeing these differences that we weren’t expecting to see.”

When thinking of a solid object, the expectation is often that the object is fairly uniform and that the components creating it are evenly distributed throughout that object. However, with the material Smith was investigating, the scan’s results were pointing toward different organizations of the material’s component parts in different regions of the material.

Smith and Musfeldt knew if they were going to uncover the source of these differences, they were going to need to investigate the material further, using the high-resolution infrared technique at the ALS to scan the material more thoroughly.

Beamline 2.4 of the ALS couples an atomic force microscope with synchrotron-generated infrared light to perform nanospectroscopy to examine materials on a much smaller scale than traditional microscopes. The microscope uses extremely sharply focused light delivered to an object at a very close distance. The response of the light as it interacts with the object is then collected and used to determine what is happening in that object.

“Using the ALS allowed us to examine these differences we were seeing in much greater detail. The material that we were studying was grown in such a way that it had two different types of metals in its A-site, scandium and lutetium. The ALS let us tease out three compositional arrangements for these materials that explained the differences. We found regions that were fairly evenly distributed, as well as both scandium-rich and lutetium-rich regions,” said Smith.

In addition to explaining the differences in domains with slightly different local composition, Smith and Musfeldt were able to determine the domain walls themselves were, in fact, much wider than traditionally believed. They also concluded that while they may have different conductivity than the surrounding regions, the domain walls were not metallic.

By successfully imaging ferroelectric domain walls, Smith and Musfeldt have accomplished something that has never been done before. As a result, they not only created a deeper understanding of these domain walls in a specific material, but also upended long-held beliefs about domain walls in general, paving the way for future innovation. Their work further highlights the importance of foundational and exploratory research in the development of future breakthroughs.

“This project really highlights the importance of curiosity in research,” said Musfeldt. “Kevin took an exploratory project and turned it into the most exciting thing in our lab with far-reaching implications.”

New materials are one potential path to improving existing technologies and generating new means of meeting the modern needs of people and society. Materials, however, are only useful insofar as they can be understood. Smith and Musfeldt’s work digs into the fundamental science behind a material’s properties, simultaneously creating a better understanding of that material and creating a roadmap for more effective uses for it in the future.

The full publication describing this research can be read here.

Jones Wins NVIDIA GPU Poster Award

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Grier Jones, fifth year chemistry PhD student, recently won a poster competition at the spring meeting of the American Chemical Society (ACS). His poster, entitled “Exploring the topology of electronic correlation with graph neural networks” earned the NVIDIA GPU Award for Best GPU Poster. The award targets excellent computational chemistry research using a graphical processing unit (GPU).

GPUs are most often associated with the high-quality images seen on gaming computers. However, the highly parallelized architecture of GPUs offers an acceleration platform that can outperform central processing units (CPUs) when processing large amounts of data in parallel. This has implications for scientific computing and machine learning applications, which have traditionally used CPUs.

Jones has developed a novel computational model that incorporates GPUs with graph neural networks (GNNs) and topological data analysis (TDA) to explore the topology of electron correlation. By incorporating two central motifs of the machine learning projects in the Vogiatzis lab, Data-Driven Quantum Chemistry (DDQC) and the application of persistent homology this study provides new perspectives on both the topological nature of electron correlation and the data-driven algorithms used to capture electron correlation.

For the purposes of this study, GPUs provided by the Infrastructure for Scientific Applications and Advanced Computing (ISAAC) cluster at the University of Tennessee were used. Training machine learning models on GPUs allows for the exploration of large datasets by reducing the computational time required to train the models. As a second step, persistent homology was used to characterize the transferability in the machine learning models between system size.

Jones expressed his gratitude to the Graduate Student Senate Travel Award and the Vogiatzis’ NSF-CAREER award for providing financial support for his participation in the ACS Spring 2023 National Meeting in Indianapolis. The award provides a professional workstation-level NVIDIA GPU, which Grier is excited to incorporate into his current and future projects.

The NVIDIA GPU Award for Best GPU Poster is a competitive biannual award sponsored by NVIDIA and the American Chemical Society’s Division of Computers in Chemistry.

Limbach Wins Student Poster Award

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Miranda Limbach, third year PhD student, recently earned an Outstanding Student Poster award at the fall meeting of the American Chemical Society (ACS). Limbach’s poster, entitled “Atomic View of Aqueous Cyclosporine A: Unpacking a Decades-Old Mystery,” was one of eight student posters in the division of physical chemistry to be honored at the meeting. 

“This was my first time at the ACS Conference,” said Limbach. “Presenting the poster was lots of fun. Everyone who stopped seemed really interested and the judges were anonymous so you didn’t know who was or wasn’t a judge.”

Limbach’s presentation and poster were based on a collaborative effort between the department, the neutron scattering division at Oak Ridge National Laboratory (ORNL), and the University of Vanderbilt. 

Limbach’s work investigates cyclosporine A, a macrocyclic immunosuppressant. Macrocycles are a class of molecules with the ability to permeate the cell membrane and bind to a number of target proteins. Macrocycles have important applications in the pharmaceutical industry and can contribute to both the development of new drugs, including antibiotics, and the successful delivery of those drugs in the human body.

Earlier in 2022, this work was published in the Journal of the American Chemical Society, with a number of UT Chemistry co-authors, including graduate students Aleksandra Antevska, Damilola Oluwatob, and Amber Gray, Assistant Professor Thanh Do, and Director of Nuclear Magnetic Resonance (NMR) Core Facilities Carlos Steren.

Limbach credits her experience in the Department of Chemistry and time in Thanh Do’s research group with preparing her for a successful presentation.

“The nice thing about Dr. Do’s lab is we use a lot of techniques so we get to learn a little bit of everything,” said Limbach. “I’ve been learning a little bit of mass spectrometry and x-ray diffraction and I learned a lot about 2D NMR. The department has been great. Everyone’s really open to making sure you learn everything you need.”

Limbach plans to continue exploring the significance of cyclosporine analogues during her academic career and, after graduation, is considering a future working with NMR facilities or industry.

Graduate Student Spotlight – Halstenberg

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Phillip Halstenberg is a chemistry graduate student currently conducting research in the Dai Group.

Halstenberg is originally from Kannapolis, North Carolina and attended the University of North Carolina at Wilmington for his BS in chemistry where he began working in the chemistry laboratories under the guidance of Dr. S. Bart Jones and Dr. Robert Hancock.

Sheng Dai, Professor and ORNL-UT Joint Faculty was invited to give a presentation during the UNCW’s guests lecture series. Dai visited the labs and met Halstenberg as their lab was collaborating with Dai on complexometric titrations related to the Uranium from Seawater Project. “We spoke about my efforts toward the research objectives and my plans for medical school and my intention to work for a year or so prior to applying,” Halstenberg said. “He told me that if I was interested, I could continue my work toward the Uranium from Seawater Project at Oak Ridge National Laboratory during my gap year. I quickly expressed interest in the opportunity and subsequently began work as an intern via the Higher Education Research Experience program offered by Oak Ridge Associated Universities.”

“A few years later I was still working at ORNL now a Post Bachelor Research Associate long since deciding my calling was not toward medical, but chemical sciences,” Halstenberg said. “I soon realized that in competitive research environments, such as a national laboratory, a PhD can be a requirement for certain advancement opportunities.

Halstenberg had been working on projects related to the most recently developed, generation IV, nuclear reactors for about a year when he decided to apply to chemistry PhD programs. “I feel strongly that technology related to the latest molten salt reactors will have a substantial societal impact if developed and implemented correctly,” Halstenberg said “My goal was to enter a graduate program where I could work toward furthering our understanding of these systems from a fundamental chemistry perspective.”

Sheng Dai had joined the efforts of recently established Energy Frontier Research Center: Molten Salts in Extreme Environments and the Nuclear Energy University Program. “We spoke about my efforts toward molten salt, and I decided to attend UTK and complete my PhD working for these programs,” Halstenberg said. “It helped my decision when I realized that UTK was home to Gleb Mamantov, who made many of the first breakthroughs in molten salt research ~60 years ago. ORNL has also always been on the cutting edge of these molten salt reactors.”

Halstenberg’s research focus is molten chloride salts. Over the last three years, he has built a world class experimental salt chemistry facility in Buehler Hall on UTK’s main campus. These labs support research efforts related to molten chloride salts  worldwide. All the experiments are related to understanding the fundamental chemical interaction in molten chloride systems. The facility provides the salt matrices required across all of the collaborating institutions and assist in the development of their experimental methodology.

“In addition to providing the salt mixtures, the focus of my molten salt work in the UTK laboratory is the quantifying impurities, spectroscopic speciation studies, characterization of thermophysical properties, characterization of colloidal mixture properties, development of ultra-high temperature magnets, bulk metallic glass formation and analysis, containment corrosion studies, and novel synthetic pathways,” Halstenberg said.

“I enjoy the diversity of research being conducted within the Dai group,” Halstenberg said.  “This coupled with the encouragement of a collaborative group effort results in an environment that is very conducive to research progress.”

“Much of my work prior to graduate school was covered under various confidentiality agreements that prohibited its open publishing,” Halstenberg said. “Although, I have coauthored 16 peer reviewed journal articles since entering graduate school in 2018.”

“Upon graduation, I will continue working with national laboratories on research toward advancing the fundamental chemical understanding of these molten chloride systems. After proper technological maturation, I intend to move from research to development,” Halstenberg said. “I will take the knowledge I have gained synthesizing and purifying these materials on a laboratory scale and use it to build the supply chains needed to provide materials for industrial scale production of molten salt reactors.”