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Archives for 2019

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.        

BOV 2019

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The Department of Chemistry’s Board of Visitors (BOV) is a volunteer advisory body dedicated to helping the Department successfully fulfill its teaching, research and service missions and become one of the preeminent chemistry departments in the nation. The BOV has a vision of enriching the research and teaching endeavors and the intellectual capital of the Department.

This year’s annual meeting was held November 1-2, 2019. Activities included dinner downtown, faculty presentations, 10 year academic program review discussion, student poster session, invited speaker, Shea Kidd Houze, Homecoming Parade, banquet dinner at the Foundry, alumni tailgate, and attending the UAB football game.

Two graduate students were awarded for their posters presentations:

  • Jinchao Lou from the Best group titled”Calcium-triggered release of contents from liposomes for drug delivery applications”
  • Brandon Colon from the Calhoun group titled “Imaging excited-state dynamics of IR-144 with total internal reflection transient absorption microscopy (TIRTAM)”

View Poster Session Program 

The department recognizes and appreciates all of the support and interaction it receives from its engaged board.

Pictures from event

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.

2019 National Chemistry Week

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Last Thursday, October 17, about 60 people of all ages were in 555 Buehler Hall at the University of Tennessee, Knoxville Department of Chemistry for Al Hazari’s 29th Annual “Magic of Chemistry Show.” This year’s theme was “Marvelous Metals!”

The audience came from all over the East Tennessee area. In attendance were local American Chemical Society members, faculty and staff members, area K-16 students and teachers. Emeritus Professor Bob Compton and his family attended the show.

Hazari had help from Avery Blockmon, third year grad student, and John Hymel, senior undergraduate student. The department’s professor Ben Xue was a “guest star” lit up the evening with a fiery natural gas – soap bubble demonstration.   

On Tuesday, October 17, a preview of the show was presented on Knoxville’s WBIR TV-10 “Live @5 @ 4” program.

Vogiatzis’s Hot Paper

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Metal-organic frameworks (MOFs) are a class of hybrid inorganic/organic materials with exceptional properties that have been used in many chemical applications such as catalysis, gas separations, and sensors.

For the first time, gas‐phase catalytic activity occurring at the metal nodes of a crystalline MOF was reported in a recent collaborative work among the groups of Professor Kostas Vogiatzis (theory), and Professors Donna Chen (catalysis, characterization) and Natalia Shustova (synthesis) from the University of South Carolina. 

Vogiatzis said, “Also, this study shows for the first time a rhodium at oxidation state II can be introduced in a MOF. “

The electronic structure of the heterobimetallic Cu-Rh node and the reaction mechanism of the hydrogenation of propylene was elucidated by post-doctoral associate Rajesh Thayalan in Professor Vogiatzis research group.

The conclusions of this collaborative work were published in Angewandte Chemie International Edition in an article that was selected as “hot paper” by the editor.

 

Kilbey Group Alumni Recognized at ACS

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Dayton Street

 

 

Dayton Street earned his PhD in the University of Tennessee’s Department of Chemistry during the spring and was one of six selected as a finalist for the Eastman Chemical Student Award in Applied Polymer Science, and as part of this, he presented aspects of his dissertation research at the Fall ACS meeting. Dayton is a National Research Council (NRC) postdoctoral fellow at the Air Force Research Laboratory.

Graham Collier

 

 

Graham Collier earned his PhD in 2017 and was selected for inclusion in the PMSE Future Faculty symposium at the Fall ACS meeting. Graham is currently a postdoctoral research scientist at Georgia Tech.

Department Welcomes New Faculty Member

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Fred Heberle Aug. 2019
Photo by Steven Bridges

Fred Heberle joined the Department of Chemistry as an assistant professor. Heberle comes from a small town in eastern Montana, and earned his PhD at Cornell University in the lab of Gerald Feigenson. Heberle spent five years in the Neutron Sciences Division at Oak Ridge National Laboratory for his postdoctoral research and is a PI on an NSF grant for the study of asymmetric membranes. 

“Our lab uses biophysical, biochemical, and computational methods to answer fundamental questions about biomembrane structure and organization,” Heberle said. “We use model systems spanning a vast range of complexity, from simple liposomes made from a single type of lipid, to multicomponent vesicles with engineered lipid asymmetry, to the plasma membrane of a living cell itself. We use techniques ranging from calorimetry, to fluorescence, to neutron and X-ray scattering.”

Feigerle Gives Talk About Diamond Foils for ORNL’s SNS

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Chuck Feigerle, head of the Department of Chemistry at the University of Tennessee, Knoxville, spent a summer learning how to make diamond films with Jim Butler from the Naval Research Laboratory in Washington, D.C. Feigerle and his associates grew the first diamond films for Buehler Hall’s Spallation Neutron Source (SNS). Then, with Department of Energy funds, a microwave plasma reactor was purchased for Bob Shaw’s lab at ORNL, where diamond foils were grown and tested for the SNS over the next few years. Shaw and Feigerle led the research group. He credits Leslie Wilson with carrying out much of the research.

 Each foil is grown by chemical vapor deposition on a silicon wafer formed to have a desired corrugated surface pattern that makes the film rigid. The silicon substrate is dissolved away using acid, leaving just enough to serve as a handle for mounting the foil.

diamond foils

Feigerle spoke about ORNL and UT research in developing and testing this key component of the SNS in a recent talk.

The SNS employs nanocrystalline diamond foils made at ORNL to strip the electrons from negatively charged hydrogen atoms in a beam accelerated to almost 90 percent the speed of light.

Feigerle presented results on the development and use of nanocrystalline diamond stripper foils at the SNS. He described studies at ORNL of the transformations that occur in crystalline structure, emissivity and the carbon state of the foils from deposition of beam energy into the foil.

One finding is that after long exposure to high beam currents that increase the temperature to above 1,500 degrees Celsius, the diamond foils become more like a graphite, gray, crystalline, form of carbon used as a solid lubricant, in pencils and as a moderator in nuclear reactors (e.g., the Graphite Reactor, the world’s first continuously operated reactor that originally made ORNL famous).

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Calhoun Lab Illuminates ‘Dark’ States in Nano Letters Paper

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Researchers in the Department of Chemistry at the University of Tennessee, Knoxville, are shooting lasers at quantum dots to illuminate ‘dark’ states and provide new insights that can steer the design of future materials.

Tiny crystals known as quantum dots have become so ubiquitous that you can find them in modern commercial televisions. Yet there are still key questions that have remained unanswered despite decades of research about how these crystals work. In particular, it is not clear exactly how the surfaces of quantum dots affect how they interact with light.

When light hits a quantum dot, the energy is stored in energy levels or states. When this energy moves to states on the surface of the quantum dot, it becomes “trapped” and lost for potential use. These surface states, however, are invisible to basic optical experiments because they cannot directly absorb the light, and this leaves the energies of these surface states unknown.

That was until a collaborative UT/Oak Ridge National Laboratory research team, led by Tessa Calhoun in the University of Tennessee’s Department of Chemistry, developed a new way to shed light on them. Their electronic sum frequency generation microspectroscopy technique simultaneously mixes different colors of ultrashort laser pulses to generate new colors of light that describe these elusive ‘dark stats’ on the quantum dots and is detailed in their recent paper published in Nano Letters.

“I was excited by just how many energy levels we could detect with a single measurement at ambient conditions,” Calhoun said.

In addition to being able to match dozens of known energy levels from literature, their studies were able to detect multiple elusive surface states.

“While many other experiments had suggested the presence of one or more of these states, we are the first to be able to directly show that there is more than one surface state in these quantum dots.” Calhoun said.

In addition to Calhoun, other team members were Brianna Watson, the lead author, and Benjamin Doughty, a staff scientist in the Chemical Sciences Division at ORNL. Brianna was a graduate student in the UT Department of Chemistry and is now conducting postdoctoral research using microscopy at Boston Children’s Hospital.

This new information about the energies of dark states promises to provide an avenue to control these generally undesirable defects to improve performance in devices.

Knowing more about these surface states will allow scientists to design better nanoparticles and Calhoun’s group is excited for the future systems they can explore with their new microspectroscopy.

Read more about this research in the paper titled “Energetics at the Surface: Direct Optical Mapping of Core and Surface Electronic Structure in CdSe Quantum Dots using Broadband Electronic Sum Frequency Generation Microspectroscopy.”