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Long Research Group Publishes Study on Mechanochemical Synthesis of Mg/K Allyl Complex

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Members of the Long Research Group, a Department of Chemistry lab headed by Associate Professor Brian Long, published an article titled “An η3‐Bound Allyl Ligand on Magnesium in a Mechanochemically Generated Mg/K Allyl Complex” in the German Chemical Society’s journal Angewandte Chemie.

Members of the research group focus on the use of organic synthesis, polymer chemistry, organometallic design, and polymer science to design and create advanced polymeric materials and to develop and study next-generation polymerization catalysts.

The group’s article concentrates on the mechanochemical synthesis of a magnesium (Mg) and potassium (K) allyl complex.

“Mechanochemistry has emerged as an intriguing synthetic method that utilizes mechanical force or energy to drive reactions in a simplified and solvent free manner,” said Alicia Doerr, a graduate teaching assistant with the Long Research Group.

The study was done in conjunction with the Hanusa Research Group at Vanderbilt University.

“Through use of this synthetic technique, the Hanusa Research Group was able to access a unique Mg/K allyl complex that could not be accessed by conventional solution-based synthetic techniques,” Doerr said. “We evaluated the polymerization activity of these catalysts for a variety of monomers and found that they are particularly active for the polymerization of methyl acrylates. This collaboration combines the classic inorganic expertise of the Hanusa Research Group with the polymer chemistry expertise of the Long Research group to obtain and study this unique catalyst system.”

Written by Kelly Alley

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Dai Lab Publishes Study on High-Entropy Perovskite Fluorides

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Members of the Dai Lab, a Department of Chemistry lab headed by Professor Sheng Dai, recently published an article titled “High-Entropy Perovskite Fluorides: A New Platform for Oxygen Evolution Catalysis” in the Journal of The American Chemical Society.

Members of the Dai Lab focus their research projects on the synthesis and characterization of functional materials for energy-related applications, including electrical energy storage.

This study highlights oxygen evolution reactions (OERs) and the beneficial uses of high-entropy perovskite fluorides (HEPFs) in oxygen evolution catalysts.

“The oxygen evolution reaction is a critical process for many energy storage options, such as water splitting and metal-air batteries,” said Tao Wang, a post-doc working with the lab.

HEPFs consisting of cost-effective elements can act as excellent catalysts for OREs in an alkaline medium.

“HEPFs can provide a new platform for oxygen evolution catalysis,” Wang said. “Moreover, the flexible synthesis of HEPFs in a boiled solution combining the hydrothermal method with mechano-chemistry, provides a new concept for the low-temperature synthesis of high entropy materials.”

Written by Kelly Alley

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Dai Lab Publishes Study in Nature Communications

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Members of the Dai Lab, a Department of Chemistry lab headed by Professor Sheng Dai, recently published an article titled “Mechanochemical synthesis of pillar[5]quinone derived multi-microporous organic polymers for radioactive organic iodide capture and storage” in the Nature research journal Nature Communications.

Members of the Dai Lab studied porous organic polymers (POPs), high surface area materials with sponge-like qualities. These POPs can be easily designed and constructed at molecular levels.

The incorporation of supramolecular macrocycles with the reservation of their cavities into porous organic polymers may endow the material with enhanced uptake of specific guests through host−guest interactions,” said Kecheng Jie, a post-doctoral research associate working with the lab. “This work demonstrates not only a new synthetic pathway to porous polymers but also the superiority of the incorporation of a supramolecular host into porous polymers for guest uptake.”

Written by Kelly Alley

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Musfeldt Group Published in Inorganic Chemistry

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The Musfeldt Group recently published their work “Spin-Lattice Coupling Across the Magnetic Quantum-Phase Transition in Copper-Containing Coordination Polymers” in Inorganic Chemistry.

The group employs a series of copper-containing coordination polymers as a platform for exploring spin−lattice coupling across the magnetic quantum-phase transition. This interaction, which they quantify for the out-of-plane pyrazine bending mode as a function of the magnetic and structural dimensionality, reaches a maximum in ladderlike [Cu(pyz)1.5(4-HOpy)2](ClO4)2 because of the intermediate dimensionality.

They also sought to reveal spin−phonon coupling under compression but instead discovered a pressure-induced transition in the ladder to a state that is likely ferroelectric.

Dadmun Group Published in ACS Applied Nano Materials

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The research in Dadmun Group utilizes a variety of techniques to examine methods by which the properties of polymer mixtures can be optimized by control of dispersion size or by the selective migration of a polymeric additive to the surface.

The group was recently published in ACS Applied Nano Materials for their work “Impact of Substrate Rigidity on the Structure of Multilayer Nanoscale ITO Films: Implications for Flexible Electronic Devices.” 

This research looks into polymeric substrates, which have become increasingly important in the recent drive in technology to produce flexible displays and mechanically adaptable devices. Multi-nanoscale layer coatings are often necessary for specific device applications, and these complex coatings are often fabricated by sputtering onto the substrate.

The work presented here investigates the impact of depositing increasingly thick bilayer films of indium tin oxide (ITO) and tungsten (W) on flexible (poly(ethylene terephthalate) (PET)) and rigid (silicon) substrates by utilizing complementary characterization methods of X-ray and neutron reflectivity to study the nanoscale structures (depth profile and interfacial breadth) between layers. 

This fundamental study defines the influence of substrate properties on coating composition, density, and interfacial structure at the nanoscale—all of which play important roles in the application specific properties and function of the targeted bilayers. The findings from this study have implications on the nanoscale structure in flexible functional thin films used in a wide range of applications such as flexible television and smartphone displays.

Sharma Lab Published in Analytical Chemistry and Analyst

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The Sharma Raman Lab published their work “Direct Surface Enhanced Raman Spectroscopic Detection of Cortisol at Physiological Concentrations” in Analytical Chemistry.

Josh Moore is the first author on this piece and recently earned his PhD in the Chemistry program.

Cortisol is an important steroid hormone in vertebrate physiology and plays a role in acute and chronic stress response. Current methods for determination of cortisol concentrations in biofluids require extensive sample preparation and long run times. Raman spectroscopy is an attractive alternative because analysis is rapid and non-destructive to the sample.

The Sharma Lab has developed a surface-enhanced Raman spectroscopy (SERS)-based method for detection of cortisol in ethanol that shows a sigmoidal concentration response and a limit of detection of 177 nanomolar, which is in the physiologically relevant range. The method can be applied to more complex solvent environments through the use of multivariate analysis techniques, where principal components analysis (PCA) demonstrates a linear separation according to cortisol concentration in a serum mimic. “We are, to our knowledge, the first group to report on the detection of cortisol using label-free SERS, which does not require a Raman reporter molecule to obtain signal,” Moore said.

The Sharma Lab published their work “Surface-enhanced spatially-offset Raman spectroscopy (SESORS) for detection of neurochemicals through the skull at physiologically relevant concentrations” in Analyst. 

Detection techniques for neurotransmitters that are rapid, label-free, and non-invasive are needed to move towards earlier diagnosis of neurological disease. Surface-enhanced Raman spectroscopy (SERS) allows for sensitive and selective detection of target analytes. The combination of SERS with spatially offset Raman spectroscopy (SORS) in a technique termed surface enhanced spatially offset Raman spectroscopy (SESORS) permits a sensitive and selective detection of neurotransmitters through the skull.

In this piece, the group presents the SESORS detection of individual neurotransmitters and mixtures of neurotransmitters at physiologically relevant concentrations, while also establishing limits of detection.

Brantley Group Publishes in Polymer Chemistry

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The Brantley Group published their work “Ion Specific Fluorescence Modulation of Polyvinyl Alcohol-Boronate Matrices” in Polymer Chemistry. Brian Jacobs, graduate student in the Brantley Lab, is the primary author. 

Borylated polymers are emerging as valuable chemosensors that can report analyte binding through an array of responses. Fluorescent materials are particularly valuable in this regard, as modulation of their photophysical properties can facilitate rapid substrate detection and quantitation.

“In this manuscript, we report the condensation of aryl boronic acids onto polyvinyl alcohol (PVA) to afford fluorescent polymers, a phenomenon that has been widely overlooked,” Jacobs said. “ Importantly, selective modulation of the photophysical properties was observed in the presence of borophilic anions (e.g. fluoride, hydroxide, and cyanide).”

Density functional theory (DFT) calculations, performed by collaborator Jacob Townsend in the Vogiatzis Research Group, suggested that a combination of covalent and non-covalent interactions were crucial for anion binding. Time-dependent DFT computations were also performed to explain the appearance of a distinct peak in the polymer’s absorbace profile.

“Lastly, films of these PVA-aryl boronates were employed in ion extraction studies, highlighting a useful secondary function these materials possess,” Jacobs said. “Given the ease with which these polymers can be accessed, they could serve as general platforms for developing ion selective membranes or detectors.”

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Awards Within the Vogiatzis Group

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The Vogiatzis Group’s research 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. We are particularly interested in new methods for non-covalent interactions and bond-breaking reactions of small molecules with transition metals. Our 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 group awards:

    1. Mrs. Alexa Griffith, an undergraduate student pursuing research in my group, was awarded a DAAD exchange fellowship for pursuing research for three months at the Technical University of Kaiserslautern, Germany (2018).
    2. Mr. John Hymel, an undergraduate student pursuing research in the Vogiatzis Group, won the Award of Excellence in Natural Sciences and Office of Research and Engagement Bronze Award at the Exhibition of Undergraduate Research and Creative Achievement (EUReCA) (2018).
    3. Mr. Jacob Townsend, graduate student in the Vogiatzis Group, won the best Lightning Talk Award at PsiCon, the annual Psi4 software developers meeting (2018).
    4. Mr. Grier Jones, graduate student the Vogiatzis Group, received a travel grant from the Molecular Science Software Institute (MolSSI) to attend the MolSSI Workshop: The Open Molecular Science Cloud in Perugia and Rome, Italy (2019).
    5. Ms. Rebekah Duke, REU student who worked in the Vogiatzis Group during Summer 2019, was accepted to present her results that obtained at the University of Tennessee at the Posters on the Hill, an annual undergraduate poster session on Capitol Hill, Washington, DC (2020).

Kent & Zhao’s Most Read Article

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Shape Changing Brush Polymers Are Receiving Attention. 

Molecular bottlebrushes are complex polymers composed of polymeric side chains densely grafted on a relatively long backbone polymer. These types of polymers are found in our body and show important biological functions, e.g., joint lubrication by lubricin.

In an effort to develop smart polymers mimicking the function of the von Willebrand Factor, a protein important in the blood clotting cascade, Ethan W. Kent, a doctoral graduate student in Bin Zhao’s research laboratory, recently designed and synthesized dually responsive shape-changing star molecular bottlebrushes.

At acidic pH values and lower temperatures, the molecules take on a three-arm star shape with a span size of ~ 180 nm. When the pH is increased to basic or temperature is raised, the molecules undergo dramatic shape changes from stars to spheres with an average dimension of ~ 80 nm. 

“It is really cool to see these molecules change their shapes spontaneously,” Kent said. These brush polymers have potential in drug delivery, molecular actuators, and sensors. Ethan is currently applying his responsive brush polymers in sensors.

This work has been published in Macromolecules, an ACS journal in polymer science. The paper has been on the list of Most Read Articles in Macromolecules for nearly two months. “It is really exciting to see our paper garner a lot of attention” Kent said.        

New Instrument in the PCL

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Small Angle X-Ray Scattering

The Xenocs Xeuss 3.0 SAXS instrument is a powerful technique that allows for the determination of size, distribution, shape, and order of nanoparticles and macromolecules. This instrument has 2 radiation sources, Cu and Mo, that can be switched and aligned automatically. It can operate over different configurations that spans a variety of q-ranges; WAXS, SAXS, MSAXS, and USAXS. Accessories include a low-noise flow cell for dilute or low scattering samples, BioCube for low volume samples, capillary holder for liquid samples, gel and powder sample holder, GISAXS sample holder for thin film and surface analysis, heating stage, and humidity stage.