Chemistry Seminars


2017 - 2018 Seminars
  • Dr. Tendai Gadzikwa, Kansas State University, October 2017
  • Dr. Mark Fisher, University of Kansas Medical Center, December 2017

MULTIFUNCTIONAL METAL-ORGANIC FRAMEWORK MATERIALS FOR APPLICATION IN ASYMMETRIC CATALYSISTendai Gadzikwa

Metal-organic framework (MOF) materials are microporous, crystalline solids that have found application in the areas of separation, sequestration, detection, and catalysis, among many others.1 Possessing pores of small-molecule sized dimensions, and composed of organic ligands that are highly tailorable,2 MOF-based catalysts are particularly attractive targets for use in selective transformations.3 This presentation will detail recent progress in assembling multifunctionalizable MOF materials, with the eventual goal of constructing enzyme-inspired MOF catalysts. Catalytic centers isolated within confined spaces that are decorated with multiple organic functional groups call to mind the active-sites of enzymes, Nature's highly active and selective catalysts. The intention is to apply these materials to the asymmetric transformation of challenging substrates that cannot be converted selectively using traditional homogeneous catalysts.4

References
1. Zhou, H-. C.; Kitagawa, S. “Metal-Organic Frameworks (MOFs)” Chem. Soc. Rev. 2014, 43, 5415–5418 DOI: 10.1039/c4cs90059f
2. Cohen, S. M. “The Postsynthetic Renaissance in Porous Solids” J. Am. Chem. Soc. 2017, 139, 2855–2863 DOI: 10.1021/jacs.6b11259
3. Ma, L.; Abney, C.; Lin, W. “Enantioselective catalysis with homochiral metal–organic frameworks” Chem. Soc. Rev. 2009, 38, 1248–1256 DOI: 10.1039/B807083K
4. Y. Yang, Shi, S. - L.; Niu, D.; Liu, P.; Buchwald, S. L. “Catalytic Asymmetric Hydroamination of Unactivated Internal Olefins to Aliphatic Amines” Science, 2015, 349, 62–66 DOI: 10.1126/science.aab3753

Dr. Tendai Gadzikwa is at Kansas State University, she can be contacted at gadzikwa@ksu.edu or by phone at 785-532-6688.

BACTERIAL TOXIN ENTRY INTO CELLS: A Trojan Horse Story.Mark Fisher

This lecture will focus on the molecular mechanisms of anthrax toxin entry into cells. In order to understand this mechanism, the structure of the main transport system will be examined in light of data collected from our laboratory and our collaborators. The success of this transport system relies on acidification of the endosome which in turn results in a massive unfolding/refolding process enabling lethal toxin transport through and across membranes. This acidification process is exploited by anthrax as well as other numerous toxin and viral systems to gain entry into the cell. I will also present our strategy for developing novel anti-toxin small molecule prophylactic approaches based on blunting acid depend transitions.

Dr. Mark Fisher is at the University of Kansas Medical Center in the department of Biochemistry and Molecular Biology.

2016 - 2017 Seminars
  • Dr. Yolanda Vasquez, Oklahoma State University, September 2016
  • Dr. Manashi Nath, Missouri University of Science and Technology, February 2017
INTERFACING MATERIALS WITH CELLSYolanda Vasquez

The microenvironment on which mammalian cells are cultured can have a dramatic effect on their function. For example, the interplay between biochemical signals and mechanical cues at the cell-surface interface can result in morphological changes in the cell. Cues from the microenvironment can dictate whether the cell will migrate, grow, divide, or differentiate. The microenvironment or material can also affect adhesive cues, signaling, and proliferation. Our work uses nano and micropillar arrays with varying geometries as model surfaces to study how stem cells align and rearrange their actin cytoskeleton in response to the tension they experience from these model surfaces. The aim is to develop materials that will facilitate the differentiation of stem cells for use in tissue engineering.

Dr. Yolanda Vasquez is in the Department of Chemistry at Oklahoma State University in Stillwater, Oklahoma. She can be contacted at yolanda.vasquez@okstate.edu
DESIGNING SMART MATERIALS FOR EFFICIENT ENERGY CONVERSION: The Story of Transition Metal ChalcogenidesManashi Nath

Energy harvesting from solar and water has created ripples in materials energy research for the last several decade. Among these, water electrolysis leading to generation of oxygen and hydrogen, has been one of the most promising routes towards sustainable alternative energy generation and storage, with applications ranging from metal-air batteries, fuel cells, to solar-to-fuel energy conversion systems. Oxygen and Hydrogen evolution reaction (OER and HER respectively) are the two half reactions for water electrolysis, amongst which OER is the most challenging uphill process with a high electron count. Hence, designing efficient catalysts for OER process from earth-abundant resources has been one of the primary concerns for advancing this field. In the Nath group we have focused on transition metal chalcogenides as efficient OER electrocatalysts. We have proposed the idea that these chalcogenides, specifically, selenides and tellurides will show much better OER catalytic activity due to increasing covalency in the metal-selenium bond compared to the oxides caused by decreasing electronegativity of the anion, which in turn leads to variation of chemical potential around the transition metal center, [e.g. lowering the Ni2+ --> Ni3+ oxidation potential in Ni-based catalysts where Ni3+ is the actually catalytically active species]. Based on such hypothesis, we have synthesized a plethora of transition metal selenides including those based on Ni, Ni-Fe, Co, and Ni-Co, which show high catalytic efficiency characterized by low onset potential and overpotential at 10 mA/cm2 [Ni3Se2 - 200 - 290 mV; Co7Se8 - 260 mV; FeNi2Se4-NrGO - 170 mV (NrGO - N-doped reduced graphene oxide); NiFe2Se4 - 210 mV; NiCo2Se4 - 190 mV]. In this presentation we will highlight the importance of this increasing covalency in enhancing the catalytic activity with the help of experimental evidence in selenide compositions ranging from binary Ni-selenides (Ni3Se2, NiSe2, NiSe), ternary mixed metal selenides (Ni-Co-Se, Ni-Fe-Se) as well as seleno-based molecular complex containing NiSe4 tetrahedral core. We will illustrate how the Ni(II) --> Ni(III) oxidation potential is indeed lowered within the selenide coordination compared to the oxide, in pure single crystals of the seleno-based coordination complex which is devoid of any surface impurities and adsorbates. The later part of the talk will be focused on designing nanostructured arrays for these catalysts and integrating them with nanostructured photoanodes to create an efficient solar-to-fuel energy conversion device. We will illustrate the technology, confined electrodeposition on lithographically patterned nanoelectrodes, to grow arrays of photovoltaic nanorods and nanotubes for high efficiency solar energy conversion, and how this technique can be utilized for a hybrid energy conversion device.

Dr. Manashi Nath is in the Department of Chemistry at the Missouri University of Science and Technology in Rolla, Missouri.
2015 - 2016 Seminars
  • Dr. John Simpson, University of Tennessee, August 2015
  • Dr. Daniel Graiver, Michigan State Univ. February 2016
  • Dr. Karthik Ramasamy, Los Alamos National Laboratory, February 2016
THE WORLDS MOST WATER REPELLENT MATERIAL AND BEYONDJohn Simpson

Retired Oak Ridge National Laboratory researcher and current University of Tennessee Research Professor Dr. John Simpson lead an Oak Ridge National Laboratory research team that developed a series of superhydrophobic (extremely water repellant) materials.
This specific research began over nine years ago with the initial goal of making a nano-structured material that would be the most water-repellant material theoretically possible. This talk will describe the essence of this research and discuss its possible commercial and scientific uses. In addition, there will be a demonstration of the water repellency of these materials.
A superhydrophobic surface is a hydrophobic surface enhanced by micro and nanostructured features. With the correct surface features and chemistry, such a surface can tremendously amplify the effects of the water’s surface tension. These surfaces are so water repellant that surface water gets replaced with a thin layer of air on the material’s surface. Dr. Simpson will demonstrate and discuss several spectacular effects which result from the interaction of water and the pinned layer of air on superhydrophobic surfaces. Superhydrophobic materials have many potential applications including watercraft drag reduction, water-repellent coatings, self-cleaning surfaces, anti-corrosion, anti-biofouling, and anti-icing properties.

Dr Simpson is at the University of Tennessee, Knoxville, Tennessee.
SELECTED CONTEMPORARY TOPICS IN ORGANOSILICONSDaniel Graiver

Silanes and polysiloxanes are well known and have been used for many years to provide some unique properties to a wide range of useful products. Some new aspects in silicone chemistry and technology will be described related to grafting of common silanes onto organic molecules and the preparation of hydrophilic polysiloxanes.

Typical grafting of silanes onto organic compounds is accomplished by hydrosilylation whereby a silane (Si-H) is reacted with a vinyl (C=C) group. However, this reaction is very ineffective if the vinyl group in a non-terminal position. We have grafted silanes onto non-terminal double bonds of unsaturated fatty acids in high yields using the ‘Ene’ reaction route. This reaction, which is a subset of the famous Diels Alder reaction, enables grafting of vinyl silanes onto unsaturated organic molecules irrespective of the position of the double bonds. Thus, grafting vinyltrimethoxysilane onto natural oils such as Soybean, Canola and Abyssinian oils led to a convenient one-component, moisture activated cure system of these natural oils that provided cost effective, excellent moisture barrier coating of paper.

Polysiloxanes are noted for their high energy siloxane bonds and flexible polymer chains resulting in polymers that are liquid even at high molecular weights, stable over a wide temperature range with outstanding weather resistance properties. However, these polymers are hydrophobic with weak intermolecular interactions. We prepared hydrophilic polysiloxanes having short side chains containing terminal hydroxyl groups attached to each silicon atom in the polymer chain that in many respects resemble polyvinyl alcohol (PVOH). These polysiloxanes are water soluble and their solubility is independent of the water pH or the molecular weight of the polymers. Films cast from aqueous solutions are elastomeric due to the presence of strong intermolecular hydrogen bonds. Coatings of these polymers were shown to act as protective coating and anti-graffiti paints. They were used in various interpenetrating polymer networks (IPNs) as convenient environmentally degradable control release systems or simply as polyols in the preparation of polyurethane, polyesters, polyacetals and phenolics. Alternatively, they can be crosslinked to yield hydrogels for a variety of applications in pharmaceutics and agriculture or act as high performance electrolytes in Lithium ion batteries.

Dr. Graiver is in BioPlastic Polymers and Composites, and Department of Chemical engineering and Materials Science, Michigan State University, East Lansing, Michigan. He can be contacted at graiverd@erg.msu.edu.
DEVELOPMENT OF NANOSTRUCTURED INORGANIC MATERIALS FOR ENERGY APPLICATIONSKarthik Ramasamy

Energy generation from non-fossil fuels has been accelerating over the past decade to meet the persistent global needs. Solar-based technologies are one of the major contributors towards meeting these energy requirements. The solar cells based on Si, CdTe and CIGS have attained considerable energy conversion efficiencies. However, the cost of energy production from solar cells is yet to meet the grid parity. The major issues associated with these technologies that hinder their wide-spread applicability are high material and manufacturing cost, use of less abundant and toxic elements. For instance, the active absorbing layer of Si photovoltaic (PV) cells must be 100s of µm thick due to the inefficient light collection of indirect band gap Si and this account for the majority of the high manufacturing cost of the entire device. CdTe and CIGS based devices are composed of toxic and less abundant elements of Cd, Te and In. The presentation will describe our efforts in addressing these issues by enhancing the light collection property of Group IV (Si & Ge) elements by alloying with tin in its nanocrystalline form1,2 and developing alternate solar energy materials consisting of less-toxic and earth abundant elements such as copper-antimony-sulfur together with their electronic structure calculations to evaluate their optical properties.3-5 In addition, I will also talk about the success we have achieved in development of single molecular precursor approach for the phase controlled growth of various metal sulfide nanostructures and thin films and its extension for the growth of pin-hole and crack-free films of Cu2ZnSnS4.6

Dr. Ramasamy is in the Los Alamos National Laboratory, New Mexico. He can be contacted at kramasamy@lanl.gov.
2014 - 2015 Seminars
  • Dr. Claire Hartmann-Thompson, Solvay Specialty Polymers, January 2015
  • Dr. Fan Zhang, Nat. Institute of Standards and Technology, April 2015
HYPERBRANCHED SILICON-CONTAINING POLYMERS AND THEIR APPLICATIONS IN SPACE SOLAR CELLSClaire Hartmann-Thompson

The synthesis and structure-property relationships of two series of hyperbranched silicon-containing polymers prepared via bi-molecular non-linear polymerization are described.
Polycarbosiloxanes and polycarbosilanes were prepared in hydrosilylation reactions between A2 and B3 (or B4) monomers, in conditions specially designed to avoid gelation.
This chemistry was then applied to systems with an A2 monomer and a B8 monomer, where the B8 moiety was an octafunctional polyhedral oligomeric silsesquioxane (POSS). High performance hyperbranched adhesives and coatings for space solar cells were developed, exploiting the high transmission and radiation resistance of POSS materials, and combining two intriguing nanobuilding blocks (hyperbranched polymers and POSS) in one hybrid platform.

Dr Hartmann-Thompson is in the Solvay Specialty Polymers, Alpharetta, Georgia. She can be contacted at hartmannthompson@gmail.com.
A SYNCHROTRON GLIMPSE INTO MESOSCOPIC STRUCTURE AND DYNAMICSFan Zhang

Mesoscopic length scales, residing between atomic and microscopic scales, are often associated with structural complexity due to the forms of energy that affects the static or dynamic spatial arrangement of mesoscopic elements. Despite the challenge, a detailed understanding of mesoscopic structure and dynamics is far-reaching and has a profound impact on not only fundamental physics but also material science and engineering.
To meet these measurement needs, through a collaboration between the National Institute of Standards and Technology and Argonne National Laboratory, we has developed characterization capabilities based on high-brilliance synchrotron X-rays, which allow determination of mesoscopic structures and dynamics for large classes of materials of major technological importance, including polymers, colloids, ceramics, and advanced alloys.
In this seminar, we will present two scientific explorations into the mesoscopic length scales using these measurement capabilities. The first addresses the statistically-significant static structures and dynamics of various colloid-based complex fluids, and carries fundamental significance in our comprehension of the basic forces that determine colloidal interaction and stability. The second is linked to the detailed formation kinetics of precipitates in aluminum alloy that make aluminum alloy suitable as lightweight materials applicable for components used in vehicles to increase fuel efficiency and reduce emissions. Finally, we will provide a brief outlook of the future promised by diffraction-limited storage rings, which potentially could lead to a revolution in terms of our understanding of mesoscopic structures and dynamics.

Dr Zhang is in the Materials Measurement Science Division, Material Measurement Laboratory, National Institute of Standards and technology, Gaithersburg, Maryland. He can be contacted at fan.zhang@nist.gov.