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Alum Spotlight – Neal

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Sabine Neal, born and raised in western Montana, graduated with her PhD working with the Musfeldt Lab in May 2021.

“The Musfeldt lab provided me with a lot of opportunity. Musfeldt knew I was a single parent and looked past that, believing in me, and giving me so many invaluable experiences,” Neal said. “I had a chance to work at two national labs, collaborate with scientists all over the world, travel to conferences, and employ cutting edge technology to study two-dimensional systems.”

Neal began working at Brookhaven National Lab in January 2021 as a Research Associate in Materials Science as a part of the Interface Science and Catalysis group at the Center for Functional Nanomaterials.

Neal’s expertise primarily lies in infrared and Raman spectroscopy and currently works on a broad array of instrumentation including both NanoIR, Photothermal, and nanoprobe systems to study high energy materials. She also uses LEEM and LEED to grow and characterize thin films. 

“UT’s chemistry graduate program helped me prepare in several ways. First, the hands-on training in the lab was crucial. I know how to trouble shoot, maintain lab equipment, and work independently.  Second, the many conferences, visitor presentations, and group talks helped to cultivate my communication skills,” Neal said. “Being a TA also helped me learn how to communicate effectively to different groups/skill levels of people. I really enjoyed working with the students and general chemistry staff.  Finally, I had three stand-out professors that aided in my personal journey to obtain my degree: Musfeldt, Sharma, and Kilbey.”

“As a single parent, most people have told me what I couldn’t do. I couldn’t get a bachelor’s degree. I did. I couldn’t get a master’s. I did. And most wouldn’t have believed I could earn a PhD. But I did,” Neal said. “You can do anything that you want if you put your mind to it and work hard. Stand up for yourself. Do what makes you happy. There is no limit!”

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.”

Dai Group Published in Nature Communications

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The Dai Group published their collaborative research “Formation of three-dimensional bicontinuous structures via molten salt dealloying studied in real-time by in situ synchrotron X-ray nano-tomography” in Nature Communications.

Three-dimensional bicontinuous porous materials formed by dealloying contribute significantly to various applications including catalysis, sensor development and energy storage. This work studies a method of molten salt dealloying via real-time in situ synchrotron three-dimensional X-ray nano-tomography.

Quantification of morphological parameters determined that long-range diffusion is the rate-determining step for the dealloying process. The subsequent coarsening rate was primarily surface diffusion controlled, with Rayleigh instability leading to ligament pinch-off and creating isolated bubbles in ligaments, while bulk diffusion leads to a slight densification. Chemical environments characterized by X-ray absorption near edge structure spectroscopic imaging show that molten salt dealloying prevents surface oxidation of the metal.

“In this work, gaining a fundamental mechanistic understanding of the molten salt dealloying process in forming porous structures provides a nontoxic, tunable dealloying technique and has important implications for molten salt corrosion processes, which is one of the major challenges in molten salt reactors and concentrated solar power plants,” said Phillip Halstenberg, graduate student in the Dai Group.

Vogiatzis Group Published in J. Chem. Phys.

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Maria White, Graduate student in Vogiatzis GroupThe Vogiatzis Group published their research “Redox states of dinitrogen coordinated to a molybdenum atom” in The Journal of Chemical Physics. Virginia White, graduate student in the Vogiatzis Group, is the first author on this paper that explores the elucidation of ground and excited states of the MoN2 cluster.

Chemical structures bearing a molybdenum atom have been suggested for the catalytic reduction of N2 at ambient conditions. Previous computational studies on gas-phase MoN and MoN2 species have focused only on neutral structures. Here, an ab initio electronic structure study on the redox states of small clusters composed of nitrogen and molybdenum is presented. The complete-active space self-consistent field method and its extension via second-orderperturbative complement have been applied on [MoN]n and [MoN2]n[MoN2]n species (n = 0, 1±, 2±). Three different coordination modes (end-on, side-on, and linear NMoN) have been considered for the triatomic [MoN2]n[MoN2]n.

“Our results demonstrate that the reduced states of such systems lead to a greater degree of N2 activation, which can be the starting point of different reaction channels.” White said.

Xue Group Published in Chem. Eur. J.

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The Xue Group published their research “Applying Unconventional Spectroscopies to the Single-Molecule Magnets, Co(PPh3)2X2 (X=Cl, Br, I): Unveiling Magnetic Transitions and Spin-Phonon Coupling” in Chemistry—A European Journal. Alex Bone is a graduate student in the Xue and first author of this paper. 

Large separation of magnetic levels and slow relaxation in metal complexes are desirable properties of single-molecule magnets (SMMs). Spin-phonon coupling (interactions of magnetic levels with phonons) is ubiquitous, leading to magnetic relaxation and loss of memory in SMMs and quantum coherence in qubits.

“Direct observation of magnetic transitions and spin-phonon coupling in molecules is challenging,” Bone said. “We have found that far-IR magnetic spectra (FIRMS) of Co(PPh3)2X2 (Co-X; X=Cl, Br, I) reveal rarely observed spin-phonon coupling as avoided crossings between magnetic and u-symmetry phonon transitions.”

Inelastic neutron scattering (INS) gives phonon spectra. Calculations using VASP and phonopy programs gave phonon symmetries and movies. Magnetic transitions among zero-field split (ZFS) levels of the S=3/2 electronic ground state were probed by INS, high-frequency and -field EPR (HFEPR), FIRMS, and frequency-domain FT terahertz EPR (FD-FT THz-EPR), giving magnetic excitation spectra and determining ZFS parameters (D, E) and g values. Ligand-field theory (LFT) was used to analyze earlier electronic absorption spectra and give calculated ZFS parameters matching those from the experiments. DFT calculations also gave spin densities in Co-X, showing that the larger Co(II) spin density in a molecule, the larger its ZFS magnitude.

The current work reveals dynamics of magnetic and phonon excitations in SMMs. Studies of such couplings in the future would help to understand how spin-phonon coupling may lead to magnetic relaxation and develop guidance to control such coupling.

Honors Day 2021

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Department of Chemistry recognized the achievements among students, faculty and staff members of the department. Below, you will find a complete list of recipients for the Honors Day 2021.

UNDERGRADUATE AWARDS

ACS-Hach Land Grant Scholarship Allyssa C. Evans, Natalie J. Parsons
CRC Press General Chemistry Award Amy N. Okafor
C.W. Keenan Outstanding General Chemistry Student Award Matthew P. McCoig
Department of Chemistry Scholarships Rowan K. Borsari, Macy M. Hudson
Dr. Lucy E. Scroggie Scholarship Rachel L. Sparks
Halbert and Anne Carmichael Scholarship Isabelle M. Dancer, Ghaeath S. Abbas
C.A. Buehler Chemistry Scholarship Nicholas M. Legaux
Melaven-Rhenium Scholarships Rowan K. Borsari, Macy M. Hudson, Clayton T. West

GRADUATE AWARDS

Keenan Teaching Award Aleksandra Antevska
Outstanding Teaching Award Kevin M. Blatchford, Avery L. Wood
Gleb Mamantov Graduate Chemistry Scholar Jinchao Lou
Jerome Eastham Fellowship in Organic Chemistry Shelby L. Strausser
Eugene John Barber Fellowship in Physical Chemistry Gavin A. McCarver
Judson Hall Robertson Fellowship in Analytical Chemistry Amber L. H. Gray

STUDENT RECOGNITIONS

Goldwater Scholarship Elijah G. Hix
Winners of the Board of Visitor’s Poster Competition Alan D. Fried, Luther J. Langston II
Shull Wollan Center Graduate Research Fellowship Pagnareach Tin
Selected to Attend NX School Alexandria N.  Bone

FACULTY AWARDS

Ziegler Professorship S. Michael Kilbey
2021 Emerging Leader in Molecular Spectroscopy Bhavya Sharma
OpenEye Outstanding Junior Faculty Award Kostas Vogiatzis
Excellence in Research Award Bin Zhao

FACULTY RECOGNITION

New Faculty Viktor Nemykin, Joshua A. Baccile
In Memoriam Fred M. Schell, Albert A. Tuinman

Jenkins Group Published in Langmuir and Chemical Science

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The Jenkins Group published their work “Imidazolinium N-Heterocyclic Carbene Ligands for Enhanced Stability on Gold Surfaces” in Langmuir. This work explores the preparation and stability of NHC-coated gold surfaces using imidazolium and imidazolinium NHC ligands. X-ray photoelectron spectroscopy and surface-enhanced Raman spectroscopy demonstrate the attachment of NHC ligands to the gold surface and show enhanced stability of imidazolinium compared to the traditional imidazolium under harsh acidic conditions.

The Jenkins Group also published their work “Actinide tetra-N-heterocyclic carbene ‘sandwiches’” in Chemical Science. “We synthesized new “sandwich” complexes by placing two NHC macrocycles around a single actinide ion,” Jenkins said. “I am particularly excited about this paper since it is work that I began on my sabbatical at the University of Edinburgh almost four years ago.  It is the beginning of a new research area in my group, which is f-block NHC chemistry.” 

Graphical abstract: Actinide tetra-N-heterocyclic carbene ‘sandwiches’The complexes were characterized by a range of experimental methods and DFT calculations. X-ray crystallography confirms the geometry at the metal centre can be set by the size of the macrocyclic ring, leading to either square prismatic or square anti-prismatic shapes; the geometry of the latter is retained in solution, which also undergoes reversible, electrochemical one-electron oxidation or reduction for the uranium variant. DFT calculations reveal a frontier orbital picture that is similar to thorocene and uranocene, in which the NHC ligands show almost exclusively σ-donation to the metal without π-backbonding.

Musfeldt Group Published in 2D Materials

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The Musfeldt group published their work “Exploring few and single layer CrPS4 with near-field infrared spectroscopy” in 2D Materials. First author is Sabine Neal, UT chemistry alum.

“We combine synchrotron-based near-field infrared spectroscopy and first principles lattice dynamics calculations to explore the vibrational response of CrPS4 in bulk, few-, and single-layer form,” Neal said. “Analysis of the mode pattern reveals a C2 polar + chiral space group, no symmetry crossover as a function of layer number, and a series of non-monotonic frequency shifts in which modes with significant intralayer character harden on approach to the ultra-thin limit whereas those containing interlayer motion or more complicated displacement patterns soften and show inflection points or steps.”

This is different from MnPS3 where phonons shift as 1/size2 and are sensitive to the three-fold rotation about the metal center that drives the symmetry crossover. “We discuss these differences as well as implications for properties such as electric polarization in terms of presence or absence of the P–P dimer and other aspects of local structure, sheet density, and size of the van der Waals gap,” Neal said.

Figure 1. (a) Crystal structure of CrPS4 at 300 K [23]. The sheet thickness and size of the van der Waals gap are indicated. (b) Schematic of the near-field infrared technique in which an atomic force microscope (AFM) cantilever tip directs light to the sample surface. (c) High resolution AFM image of exfoliated CrPS4. (d) Schematic diagram of the symmetry subgroup relationships as they pertain to the presence or absence of a phosphorus dimer.

Chemistry of Learning: Machines and Humans

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New courses the Department of Chemistry is offering:

Artificial intelligence (AI) rapidly changes many aspects of chemical sciences, from drug discovery, material design, and the discovery of new reactions and molecules till the acceleration of computer sciences and robotics for chemical applications. In Fall 2021, Dr. Vogiatzis will be teaching Machine Learning for Chemical Applications (CHEM420). This course will cover the key aspects of AI and modern chemoinformatics and how they are applied on chemical sciences.
For more information on this course please email kvogiatz@utk.edu.

In the Spring 2022, students may register for Chemistry of the Brain (CHEM340) with Dr. Sharma. This course will be an overview of basic principles of neuroscience with a focus on the function of key neurochemicals and their receptors. Topics include the chemical bases for neuronal membrane transport, electrical excitability, and ion channels; axonal transport; energy metabolism; synaptic transmission; cellular signaling; Ca2+ homeostasis; neurotransmitters; oxidative stress; apoptosis and necrosis; application of neurochemical principles to the molecular bases of neurodegenerative disorders. Co-Requisite: Organic Chemistry. For more information on this course please email bhavya.sharma@utk.edu.

Long Group Published in Chem. Eur. J.

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The Long Group published their research “Mechanochemical Formation, Solution Rearrangements, and Catalytic Behavior of a Polymorphic Ca/K Allyl Complex” in Chemistry—A European Journal. Authors Brian Long and Alicia Doerr, graduate student, collaborated with Vanderbilt University and the University of Rochester. 

Without solvents present, the often far‐from‐equilibrium environment in a mechanochemically driven synthesis can generate high‐energy, non‐stoichiometric products not observed from the same ratio of reagents used in solution. Ball milling 2 equiv. K[A´] (A´ = [1,3‐(SiMe3)2C3 H3]– ) with CaI2  yields a non‐stoichiometric calciate, K[CaA´3], which initially forms a structure (1) likely containing a mixture of pi‐ and sigma‐bound allyl ligands. Dissolved in arenes, the compound rearranges over the course of several days to a structure (2) with only  η3‐bound allyl ligands, and that can be crystallized as a coordination polymer. If dissolved in alkanes, however, the rearrangement of 1 to 2 occurs within minutes. The structures of 1 and 2 have been modeled with DFT calculations, and 2 initiates the anionic polymerization of methyl methacrylate and isoprene; for the latter, under the mildest conditions yet reported for a heavy Group 2 species (one‐atm pressure and room temperature).

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