Chemistry

Home » Archives for Kayla Benson » Page 4
Author: Kayla Benson

Sokolov Group Published in Energy Storage Mater. and ACS Macro Lett.

by

The Sokolov Group recently published their work “Anomalously high elastic modulus of a poly(ethylene oxide)-based composite electrolyte” in Energy Storage Materials.

The practical use of lithium metal anodes in solid-state batteries requires a polymer membrane with high lithium-ion conductivity, thermal/electrochemical stability, and mechanical strength. The primary challenge is to effectively decouple the ionic conductivity and mechanical strength of the polymer electrolytes.

They report a remarkably facile single step synthetic strategy based on in-situ crosslinking of poly(ethylene oxide) (xPEO) in the presence of a woven glass fiber (GF). Such a simple method yields composite polymer electrolytes (CPE) of anomalously high elastic modulus up to 2.5 GPa over a broad temperature range (20 °C – 245 °C) that has never been previously documented.

An unsupervised machine learning algorithm, K-mean clustering analysis, was implemented on the hyperspectral Raman mapping at the xPEO/GF interface. Using such a unique means, we show for the first time that the promoted mechanical strength originates from xPEO and GF interactions through dynamic hydrogen and ionic bonding. High ionic conductivity is achieved by the addition plasticizer (e.g. tetraglyme), where trifluoromethanesulfonate anions are tethered to the xPEO matrix and Li+ cations are favorably transported through coordination with the plasticizer.

Further, stringent galvanostatic cycling tests indicates the CPE can be stably cycled for >3000 h in a Li-metal symmetric cell at a moderate temperature (nearly 1500 Coulombs/cm2 Li equivalents), outperforming most of the PEO-based electrolytes. The GF reinforced CPE reported here has multifunctional uses, such as solid electrolytes for all solid-state batteries and membranes for redox-flow batteries.

Although the focus of this study is on lithium-based batteries, the results are equally promising for other alkali metal based batteries such as sodium and potassium.

The Sokolov Group also had their work “Turning Rubber into a Glass: Mechanical Reinforcement by Microphase Separation” published in ACS Macro Letters.

Supramolecular associations provide a promising route to functional materials with properties such as self-healing, easy recyclability or extraordinary mechanical strength and toughness. The latter benefit especially from the transient character of the formed network, which enables dissipation of energy as well as regeneration of the internal structures. However, recent investigations revealed intrinsic limitations in the achievable mechanical enhancement.

This manuscript presents studies of a set of telechelic polymers with hydrogen-bonding chain ends exhibiting an extraordinarily high, almost glass-like, rubbery plateau. This is ascribed to the segregation of the associative ends into clusters and formation of an interfacial layer surrounding these clusters. An approach adopted from the field of polymer nanocomposites provides a quantitative description of the data and reveals the strongly altered mechanical properties of the polymer in the interfacial layer. These results demonstrate how employing phase separating dynamic bonds can lead to the creation of high-performance materials.

Vogiatzis Group’s Recent Publications

by

Research in the Vogiatzis Group centers on the development of computational methods based on electronic structure theory and machine learning algorithms for describing chemical systems relevant to clean, green technologies. They are particularly interested in new methods for non-covalent interactions and bond-breaking reactions of small molecules with transition metals. Their overall objectives are to elucidate the fundamental physical principles underlying the magnetic, catalytic, and sorption properties of polynuclear systems, as well as to assist in the interpretation of experimental data.

Recent work in Coordination Chemistry Reviews “Computational catalysis for metal-organic frameworks: An overview” explores Metal-organic frameworks (MOFs), a family of porous hybrid organic/inorganic materials, have shown great promise for many challenging chemical applications including gas separations, catalysis, and sensors.

“This review highlights recent work performed on catalytic reactions promoted by MOFs from a computational and theoretical standpoint. Computational modeling includes the elucidation of reaction mechanisms, the characterization of electronic structure effects of key intermediates and transition states, and the interpretation of experimental data.” said Gavin McCarver, graduate student.

Vogiatzis also published a paper with his undergraduate advisor, Dimitris Georgiadis. “Professor Georgiadis is the person who taught me first how to do research and follow my scientific goals” said Vogiatzis. Their work  “A Carbodiimide-Mediated P-C Bond-Forming Reaction: Mild Amidoalkylation of P-Nucleophiles by Boc-Aminals” in Organic Letters shares the first example of a carbodiimide-mediated P–C bond-forming reaction. 

The reaction involves activation of β-carboxyethylphosphinic acids and subsequent reaction with Boc-aminals using acid-catalysis. Mechanistic experiments using 31P NMR spectroscopy and DFT calculations support the contribution of unusually reactive cyclic phosphinic/carboxylic mixed anhydrides in a reaction pathway involving ion-pair “swapping”. The utility of this protocol is highlighted by the direct synthesis of Boc-protected phosphinic dipeptides, as precursors to potent Zn-aminopeptidase inhibitors.

Inorganic Chemistry published their work “Electrocatalytic Dechlorination of Dichloromethane in Water Using a Heterogenized Molecular Copper Complex.” 

The remediation of organohalides from water is a challenging process in environment protection and water treatment. They report a molecular copper(I) complex with two triazole units, CuT2, in a heterogeneous aqueous system that is capable of dechlorinating dichloromethane (CH2Cl2) to afford hydrocarbons (methane, ethane, and ethylene). Computational studies provided additional insight into the reaction mechanism and the selectivity toward the CH4 formation. The findings in this study demonstrate that complex CuT2 is an efficient and stable catalyst for the dehalogenation of CH2Cl2 and could potentially be used for the exploration of the removal of halogenated species from aqueous systems.

Dai Group Published in Nano Energy and Chem. Commun.

by

The Dai Group published their work “Room temperature synthesis of high-entropy Prussian blue analogues” in Nano Energy.

High-entropy Prussian blue analogues (HEPBAs) integrating the highly dispersed active sites of high-entropy materials with intrinsic 3D diffusion channels and the redox-active sites of Prussian blue analogues have great potential in electrochemical applications but have not been realized. In this work, a series of HEPBAs were successfully synthesized under room temperature combining mechanochemistry with wet chemistry for the first time.

High-entropy Prussian blue analogues (HEPBAs) were fabricated by combining mechanochemistry with wet chemistry. As an optimal element combination, high-entropy K(MgMnFeNiCu)Fe(CN)6 exhibited enhanced higher capacitances than all the single-component PBAs.

The group also published their work “Overcoming the phase separation within high-entropy metal carbide by poly(ionic liquid)s†” in Chemical Communications. 

High-entropy crystalline materials are attracting more attention. In principle, high-entropy metal carbides (HMCs) that contain five or more metal ions, possess more negative free energy value during catalysis. But its preparation is challenging because of the immiscibility of multi metal cations in a single carbide solid solution.

Here, a rational strategy for preparing HMC is proposed via a coordination-assisted crystallization process in the presence of Br-based poly(ionic liquids). Through this method, Mo0.2W0.2V0.2Cr0.2Nb0.2C nanoparticles, with a single cubic phase structure, incorporated on porous carbon, are obtained (HMC@NC). By combination of well dispersed small particle size (∼4 nm), high surface area (∼270 m2 g−1), and high-entropy phase, HMC@NC can function as a promising catalyst for the dehydrogenation of ethylbenzene. Unexpected activity (EB conv.: 73%) and thermal stability (>100 h on steam) at 450 °C are observed. Such a facile synthetic strategy may inspire the fabrication of other types of HMCs for more specific tasks.

Dadmun Published in Chemical Reviews

by

Deep eutectic solvents (DESs) are an emerging class of mixtures characterized by significant depressions in melting points compared to those of the neat constituent components. These materials are promising for applications as inexpensive “designer” solvents exhibiting a host of tunable physicochemical properties.

Mark Dadmun, professor and ORNL-UT joint faculty member, contributed to this collaborative piece “Deep Eutectic Solvents: A Review of Fundamentals and Applications” in Chemical Reviews.

A detailed review of the current literature reveals the lack of predictive understanding of the microscopic mechanisms that govern the structure–property relationships in this class of solvents. Complex hydrogen bonding is postulated as the root cause of their melting point depressions and physicochemical properties; to understand these hydrogen bonded networks, it is imperative to study these systems as dynamic entities using both simulations and experiments.

This review emphasizes recent research efforts in order to elucidate the next steps needed to develop a fundamental framework needed for a deeper understanding of DESs. It covers recent developments in DES research, frames outstanding scientific questions, and identifies promising research thrusts aligned with the advancement of the field toward predictive models and fundamental understanding of these solvents.

Nemykin Published in Angewandte Chemie-International Edition

by

Viktor Nemykin was published in a collaborative piece “β-Isoindigo-azaDIPYs: Fully Conjugated Hybrid Systems with Broad Absorption in the Visible Region” in Angewandte Chemie-International Edition.

A one-step synthetic pathway for the preparation of fully conjugated β-isoindigo-azaDIPY hybrid chromophores comprised of β-isoindigo and azadipyrromethene moieties is reported. The target compounds were characterized by spectroscopic, crystallographic, and theoretical methods and show unprecedented broad absorption across the visible region of the electromagnetic spectrum. The X-ray crystal structure of the octa(n-butyl)-β-isoindigo-azaDIPY derivative revealed that a trans-configuration of the β-isoindigo fragment accompanies a planar conjugated core.

Vogiatzis Wins OpenEye Outstanding Junior Faculty Award

by

Kostas Vogiatzis, assistant professor with the Department of Chemistry, is one of the recipients of the American Chemical Society, Computers in Chemistry Division (ACS COMP) OpenEye Outstanding Junior Faculty Award for Spring 2021.

This competitive and prestigious award identifies junior faculty of promise in the area of computational chemistry and modeling. Vogiatzis will present his research in the upcoming (online) National Meeting of the American Chemical Society. The title of his talk is “Data-driven Computational Chemistry for Noncovalent Interactions of CO2”.

For more information about the award visit https://www.acscomp.org/awards/the-comp-acs-outstanding-junior-faculty-award.

For more information about Dr. Vogiatzis’ research visit https://vogiatzis.utk.edu.

Graduate Student Research Aids in Search for Extraterrestrial Life

by

In 1996, NASA administrators made a historic announcement: proof that life had existed on Mars at some point in its history. Their proof was a Martian rock that they claimed contained the same combination of minerals and carbon compounds as those created by microbes on Earth. Searching for chemicals that indicate the presence of life is at the heart of the research being done by Grace Sarabia, a doctoral candidate in the Department of Chemistry.

Although most scientists now agree that the Martian rock presented in 1996 does not prove the existence of life on Mars, it could possibly point in that direction. Scientists have continued the search for extraterrestrial life through the Mars Rover program.

The Mars 2020 Perseverance Rover is scheduled to land this month, continuing the search for signs of ancient life. Perseverance will collect rock and soil samples that will help advance the understanding of Martian geologic history by identifying organic compounds and minerals that are indicative of past life on Mars.

In addition to geologic surveys, Perseverance is also testing technologies that could be used to identify potentially habitable extraterrestrial environments. Sarabia’s research centers on one such technology, called Raman spectroscopy, which provides a structural fingerprint to identify molecules. This non-destructive process examines how light is scattered from a sample when illuminated by a laser. Because the scatter is the result of chemical bonding and structure, it is unique to each compound—like a fingerprint is unique to each person.

In the laboratory, Sarabia attempts to mimic extraterrestrial environments, such as Martian soil or icy worlds like Europa, one of Jupiter’s 79 moons. Then, with the use of Raman spectroscopy, Sarabia is able to analyze these artificial environments to detect biosignatures—clues that indicate a planet’s atmosphere has been influenced by life. This research could not only provide insight into whether life has existed in the past, but also the potential for supporting life in the future.

Currently, her research provides her the opportunity to combine a lifelong curiosity about space with an inherited interest in chemistry. “My grandfather was a chemist, so he used to talk to me about different chemistry concepts when I was small,” Sarabia explains. “My mom used to tell him I didn’t understand him, so he should cut it out. It must have made an impact on me, however, because I did end up pursuing chemistry in college.”

Before coming to the University of Tennessee, Sarabia graduated from Berry College in Georgia, where she majored in Chemistry. Sarabia credits her career path to the terrific chemistry teachers she had there. “I attribute my interest in chemistry not only to my grandfather,” Sarabia said, “but also my terrific chemistry teachers, especially during my freshman year of college.”

Sarabia hopes that her research will assist the scientific community with analysis and, building upon the findings made during the Perseverance mission, possibly pave the way for future human expeditions to the red planet. Raman spectroscopy is just one of the technologies that Perseverance will test to determine the possibility of supporting human presence on Mars. Discoveries made on Mars could be applied to other planets and moons throughout the solar system.

Sarabia plans to continue her work in Raman spectroscopy, while also keeping her eyes on the stars. “Ideally, I would like to continue working with space-based research using Raman spectroscopy,” Sarabia explained. “It would be amazing to find life or signs of life beyond Earth. The implications for something like that would be major for everyone!”

Zhao Receives Excellence in Research Award

by

Each year, Dean Theresa Lee and members of her cabinet, with help from department heads, recognize faculty in the College of Arts and Sciences for their excellence in teaching, research and creative activity, and lifetime achievements.

Due to the ongoing pandemic, however, we were unable to host the annual awards banquet in-person. Each faculty member received a plaque and congratulations from the dean. We posted a video to the college YouTube channel here, which features each faculty award winner.

We seek to recognize faculty members who excel in scholarship and creative activity while also being fully engaged in the other responsibilities of faculty jobs, primarily teaching and service. To this end, the college honors faculty in three stages of their research careers – early, mid, and senior – with awards for excellence in research or creative achievement, as well as honoring a faculty with an award for Distinguished Research Career at UT.

Bin ZhaoBin Zhao is the Paul and Wilma Ziegler Professor in the Department of Chemistry, received a senior career excellence in research award. He has made significant contributions to the field of macromolecular brush materials, from precise synthesis to fundamental understanding and potential applications of surface brushes, polymer brush-grafted particles (hairy particles), and brush polymers. He is widely recognized, nationally and internationally, as one of the leading figures in this field. His work on stimuli-responsive polymers has also received wide attention. Zhao is a dedicated research mentor who seeks to use research opportunities to cultivate scientific reasoning and spirit in his graduate and undergraduate students.

“I am very excited to receive this great honor and recognition from our college” Zhao said. “I look forward to continuing contributing to the research mission of our university in the years ahead.”

Musfeldt Group Published in Nano Letters

by

The Musfeldt Group published their work “Excitations of Intercalated Metal Monolayers in Transition Metal Dichalcogenides” in Nano Letters.

They combine Raman scattering spectroscopy and lattice dynamics calculations to reveal the fundamental excitations of the intercalated metal monolayers in the FexTaS2 (x = 1/4, 1/3) family of materials. Both in- and out-of-plane modes are identified, each of which has trends that depend upon the metal–metal distance, the size of the van der Waals gap, and the metal-to-chalcogenide slab mass ratio.

They test these trends against the response of similar systems, including Cr-intercalated NbS2 and RbFe(SO4)2, and demonstrate that the metal monolayer excitations are both coherent and tunable.

They discuss the consequences of intercalated metal monolayer excitations for material properties and developing applications.