Physical Oral Presentations

Ultrahigh Field NMR: A New Frontier for 73Ge NMR Spectroscopy

Greer, Brandon

  • Brandon J. Greer, Vladimir K Michaelis, Scott Kroeker*
  • Organization: University of Manitoba
  • Funding: UofM, NSERC, CFI

Abstract: Germanium is a key component in semiconductors, mesoporous materials, and optical glasses. Nuclear magnetic resonance (NMR) spectroscopy appears to be an attractive technique for characterising these materials, but experiments are difficult in practice. Germanium-73 is a spin-9/2 nucleus with a low magnetogyric ratio and low resonance frequency. Consequently, only a handful of publications employing solid-state 73Ge NMR exist. We have probed the NMR behaviour of germanium halides to explore applications for solids with Ge in high and low symmetry environments. Two series of germanium halides (GeX2 and GeX4, where X = Cl, Br, I) were studied at applied magnetic fields of 11.7 T and 21.1 T, providing comparisons between the NMR parameters for different coordination environments and oxidation states, as well as trends arising from the halide substituents. These experiments have defined a large range of chemical shifts and quadrupole coupling constants, and permitted estimates of Ge-X J-coupling for the first time. Experimental studies are complemented by DFT calculations to probe the capabilities of computer software in predicting NMR parameters. We find that while the magnitudes of the quadrupole couplings are generally accurately predicted, chemical shielding parameters are less reliable. These studies provide a foundation for future solid-state 73Ge NMR spectroscopy of advanced materials.

Phase Transitions of Mixed 1,2,6-Trihydroxyhaxane and Ammonium Sulfate and 4-Hydroxy-3-Methoxymandelic Acid and Ammonium Sulfate Particles

Liu, Chen Cen

  • Chen Cen (Aileen) Liu, Aidan Bodsworth, Allan Bertram*
  • Organization: University of British Columbia
  • Funding: NSERC

Abstract: The studies on aerosol particles indicate that they cool the Earth's atmosphere by reflecting radiation. This is known as global dimming and has the opposite effect of global warming. The phase in which an aerosol particle is in determines its global dimming effects. Mixed organic-inorganic particles are abundant in the atmosphere. However, only a limited variety of particles have been studied. My project will investigate the phase transitions of these mixed aerosol particles, in particular, ammonium sulfate mixed with 1,2,6-trihyroxyhexane (AS-Triol) and ammonium sulfate mixed with 4-hydroxy-3-methoxymandelic acid (AS-HMMA). All the particles undergo three distinctly different phase transitions. When decreasing the RH from 90% to 25% two phase transitions are observed. The first is a liquid-liquid phase separation, for AS-Triol the separation RH is about 66% and for AS-HMMA it is about 77%. The second phase transition is the efflorescence of the inner AS inclusions, for AS-Triol this occurs around 33% and for AS-HMMA around 36%. When increasing the RH from 25% to 90% only one phase transition, deliquescence, is observed. The deliquescence RH for AS-Triol is about 77% and for AS-HMMA is 80%. The results of my work will shed light on the understanding of phase transitions of AS-Triol and AS-HMMA particles. The phase transitions that these particles undergo tell researchers the kinetics and thermodynamics involved in the process. This knowledge combined with reaction studies of the particle will result in more accurate atmospheric models. Hence, more accurate predictions regarding the effects of global dimming.

A Solid-State NMR Study of Compounds Exhibiting Anomalous Thermal Expansion

Palech, Alexandra

  • Alexandra Palech, Rod Wasylishen*
  • Organization: University of Alberta
  • Funding: NSERC, UofA

Abstract: Compounds exhibiting negative thermal expansion, or contraction upon heating, are both interesting and useful. The compound In[Au(CN)2]3, shown by x-ray powder diffraction to undergo anomalously large relative positive and negative thermal expansion, was studied via solid-state NMR spectroscopy. The compound was studied at different field strengths and at variable temperatures at the field strength of B0 = 11.75 T. The results of these studies are examined to determine the electric field gradient at the nucleus 115In, the z component of which lies along the crystal axis undergoing negative thermal expansion.

A Solid-State NMR Study of Compounds Exhibiting Anomalous Thermal Expansion

Palech, Alexandra

  • Alexandra Palech, Rod Wasylishen*
  • Organization: University of Alberta
  • Funding: NSERC, UofA

Abstract: Compounds exhibiting negative thermal expansion, or contraction upon heating, are both interesting and useful. The compound In[Au(CN)2]3, shown by x-ray powder diffraction to undergo anomalously large relative positive and negative thermal expansion, was studied via solid-state NMR spectroscopy. The compound was studied at different field strengths and at variable temperatures at the field strength of B0 = 11.75 T. The results of these studies are examined to determine the electric field gradient at the nucleus 115In, the z component of which lies along the crystal axis undergoing negative thermal expansion.

A Tale of Two Toxins: An NMR Study of the Trichothecenes T-2 and Deoxynivalenol

Shank, Roxanne

  • Roxanne Shank, Nora Foroud, Praveen Chaudhary, Paul Hazendonk*, Francois Eudes*
  • UofL, Agriculture and Agri-Food Canada
  • UofL, CFI, NSERC, ANPI, AAFC

Abstract: Fungal toxins, such as those produced by the Fusareum genus, are secondary metabolites which can infect and destroy wheat and cereal crops in the field. These toxins have been shown to stall protein synthesis through their interaction with the Peptidyl Transferase Center (PTC) of the Ribosome. Among the most toxic are the members of the trichothecene family, T-2 toxin and deoxynivalenol (DON) toxin. Previous investigations have determined that the epoxide ring is crucial for toxicity; however, little investigation was done into the internal dynamics of these molecules. Solution and Solid State NMR studies were able to determine the rigidity of the structure and the hydrogen bonding interactions present in these toxins, not only internally, but to bound water molecules. We demonstrate differences in the interaction to water when in the solid state as compared to when the molecule is in solution, which is highly suggestive that the configurations are slightly different. This may provide some insight into the reasons why these molecules are not toxic when in solution, but are extremely dangerous when in the solid form. Furthermore, this may provide insight into the mechanism for toxicity within plant cells, and the interaction of these toxins with the ribosome.