Prairie - Past Meetings
Date: Wednesday, March 31, 2021 | 4 pm (Central), 5 pm (EDT)
Speaker: Julie G. Ezold, Oak Ridge National Laboratory
Title: Heavy Actinide Production Program at Oak Ridge National Laboratory
Virtual Student Chapter Meeting of the AVS Prairie Chapter
For more than 50 years, Oak Ridge National Laboratory’s (ORNL) unique research facilities and staff have provided the research community with heavy actinides through fermium (257Fm). ORNL’s facilities, the Radiochemical Engineering Development Center and the High Flux Isotope Reactor, are truly one-of-a-kind for the production of heavy actinides. All aspects of the reactor-produced heavy actinides will be addressed: fabrication of curium targets, irradiation, radiochemical separations and purification processing. Research activities for new production and separations techniques are being pursued at ORNL and will include novel irradiation schemes and shielding materials for berkelium and einsteinium production. To improve separations, replacement of the CLEANEX (HDEHP extraction) and the LiCl anion exchange processes are being investigated. Another focus area is the separation of americium from curium to enhance the quality of the current feedstocks for heavy actinide production.
Date: Wednesday, October 28, 2020 | 4 pm (Central), 5 pm (Eastern)
Speaker: Dr. Scott Chambers, Pacific Northwest National Laboratory
Title: X-ray photoelectron spectroscopy - a rich source of more than just chemical information
X-ray photoelectron spectroscopy (XPS) was first discovered in 1907 following Einstein’s explanation of the photoelectric effect. Over the years, XPS has became a tool of widespread utility in surface analysis, physical chemistry, materials science and condensed matter physics. The physics of XPS is rather complex.1 There are several physical drivers that determine what the spectra look like. However, as the popularity of XPS has expanded in the world of surface analysis, common understanding of the technique has been reduced to the point that most practitioners are only aware of XPS yielding information on elemental abundances and chemical states of atoms. As a result, the richness of physical insight into the electronic properties of materials has been largely lost and a multitude of misinterpretations of spectra have been reported in the literature. In this talk, I will first give an overview of the five primary physical effects that determine XPS binding energies and line shapes. I will then present a recent case study in which XPS provides an accurate, detailed explanation of a completely unexpected result in the world of oxide/semiconductor interface physics, namely the observation of a two-dimensional hole gas at the epitaxial interface of n-SrNbxTi1-xO3 and undoped Si(001) prepared by molecular beam epitaxy.2-4
Date: Monday, September 14, 2020 (online) | 1-5 pm (Central), 2-6 pm (Eastern)
AVS Prairie Chapter Annual Symposium 2020 (VIRTUAL/ONLINE)
The AVS Prairie Chapter Annual Symposium 2020 will be an online meeting featuring talks by our award winners, Nan Jiang and Luke Hanley, and an online poster session. We encourage broad participation in the poster session, especially from students and postdocs, to gain experience in communicating science and networking using online forms of communication. Undergraduate and graduate researchers are eligible for awards in the poster competition. Please indicate your willingness to enter your poster for judging.
Online session (times listed here are Central time)
1:00 pm Welcome
1:10 pm Prof. Nan Jian, Dept. of Chemistry, Univ. of Illinois at Chicago
AVS Prairie 2020 Early Career Award
1:40 pm Prof. Luke Hanley, Dept. of Chemistry, Univ. of Illinois at Chicago
AVS Prairie 2020 Research Award
2:10 pm Preview of posters (pre-recorded videos)
2:30 pm Online poster session on Twitter
5:00 pm Poster awards announcements
Date: August 26, 2020 (5 P.M. EDT)
Speaker: Prof. Ashleigh Baber (James Madison University)
Title: Controlling selectivity by modifying model catalyst surfaces
Through the use of temperature programmed desorption, we have studied how molecules influence surfaces, how molecules interact with each other on surfaces, and how surfaces influence molecules. The first part of the talk will highlight the low temperature exchange of hydrogen and deuterium through molecularly-adsorbed species on an inert gold substrate (Au(111)). Exchange beyond the acidic hydrogen in ethanol was not observed, and therefore is expected to occur via a Grotthuss-like mechanism, which relies on the presence of hydrogen-bonded molecular networks. This phenomenon was surprising to see on Au(111), which acts only as a support for the networks to form. In the second part of the talk, the role of modifications on Au(111) to enact chemical reactivity will be explored. Titania nanoparticles dispersed on Au(111) provide active sites for both the oxidation of ethanol to acetaldehyde and the elimination to form ethylene. Through careful control of the surface preparation procedures, the reaction can be driven towards the selective oxidation of ethanol to form acetaldehyde. In both projects discussed, we use surface science to gain insight into the fundamental interactions between molecules on surfaces and molecules with surfaces.
Date: June 24, 2020 (5 P.M. EDT)
Speaker: Prof. Sally McArthur from Swinburne University of Technology
Title: Four ToF-SSIMS Instruments and a QCM-D – Adventures in Biointerface Engineering from Down Under
Control and the ability to elicit specific responses from a biological system lies at the heart of most bioengineering. We want to immobilize proteins on biosensors but ask them to as sensitive as they are in solution or in the body, stimulate cells to assemble into tissues, reconstructing our bodily functions. We want methods that prevent bacteria forming biofilms and better still we would like them to stop bacteria attaching to surfaces full stop.
But biology is soft and normally has lots of water associated with it, so how and why would you want to use vacuum based techniques to create coatings or characterise these systems? This talk will explore how in my group and our collaborators, have tackled the challenges associated with interfacing vacuum deposited plasma polymers with water, proteins, lipids and cells to create a wide number of model systems and devices. At the same time, we have developed methods for chemically characterising these systems in vacuum, integrating XPS and ToF-SIMS with a range of other surface analytical and biological tools to gain insight into the materials we create and their interactions with biological systems.
Date: May 27, 2020 (5 P.M. EDT)
Speaker: Prof. James Whitten (UMass Lowell)
Title: Surface Chemistry of Zinc Oxide Nanoparticles: Optochemical Sensing and Photocatalysis
Zinc oxide nanoparticles have a wide range of applications that include catalysis and optoelectronics. ZnO is unique in that its surface is fairly reactive with respect to gas adsorption, and it has a bimodal room temperature photoluminescence (PL) spectrum consisting of UV excitonic and surface defect-related visible emission peaks. The surface chemistry of a variety of adsorbates on ZnO nanoparticles and single crystal surfaces will be discussed. Adsorbates studied include water, sulfur dioxide, nitrogen dioxide, methanol and methanethiol. It is found that chemisorption has a dramatic effect on the PL spectrum of ZnO, and this may be used to accomplish so-called “optochemical sensing”. Experimental surface science studies, including X-ray photoelectron spectroscopy measurements, have been accompanied by density functional theory (DFT) calculations to understand the surface chemistry that occurs and to correlate it with observed PL changes. Adsorbed hydroxyl groups, which act as charge traps and may be replaced by chemisorption of molecules such as sulfur dioxide and methanethiol, are found to play a key role in the PL changes. A portable UV LED, two wavelength flurometer optimized for monitoring PL changes of metal oxide nanoparticles has also been constructed, and its applications have been demonstrated. The surface chemistry of zinc oxide and its affinity for chemisorption of thiols has also been exploited to attach gold nanoparticles (AuNPs) to ZnO nanorods using dithiol linkers. The AuNPs enhance the photocatalytic activity of ZnO nanorods by reducing the recombination rate of electron-hole pairs. The photocatalytic properties of these composite materials are discussed.
April 29, 2020 - Virtual Student Chapter Meeting
Speaker: Prof. Gerald Seidler
Title: Core Level Spectroscopy
Core-shell spectroscopies such as x-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), x-ray absorption fine structure (XAFS) and x-ray emission spectroscopy (XES) play a major role in vacuum and nonvacuum characterization of materials spanning contemporary research and industrial product development while also having some footprint in environmental safety and regulatory compliance. XPS and EELS have long been available in the lab for routine application, but the same is not true of XAFS and XES which have instead been almost exclusively been available at synchrotron x-ray facilities. In this talk, I will describe my group’s work that has helped lead to the ongoing renaissance of lab-based XAFS and XES using only conventional x-ray tubes. After giving an overview of the fundamentals of core-shell spectroscopies and summarizing the technology that we have developed at the University of Washington, I will present many applications that share a common characteristic: progress requires iterated rapid feedback in exactly the common meaning of the term “routine analytical chemistry”. To be specific, the term "routine' requires first that the technique would have very high availability and second that interpretations should be accessible to, for example, chemists,chemical engineers, and materials scientists who have had usual undergraduate coursework and training. While such measurements are obviously technically feasible at synchrotron light sources, they are a poor fit with both the facility mission and its access model. Examples will include in situ XANES studies of pouch cell batteries under fast charging conditions, nanophase identification, comparison of XPS and XANES to determine differences in surface and bulk oxidation states in metal-oxide supercapacitor electrodes, phosphorus XES of quantum dots for next-generation QD-LEDs, and the analysis of hexavalent Cr faction in plastics to address regulatory safety.