Dr. Liane Moreau, Washington State University
Host: Dr. Vela
Abstract: Nanostructures (particularly with sizes below 10 nm) are inherently challenging to characterize on the atomic scale, due to broadening which occurs in diffraction-based characterization methods, and the high concentration of surface defects and energy-minimization effects. Characterization challenges compound when investigating nanoscale actinide oxides, such as uranium oxide, due to radioactive sample constraints and rich electronic structure which can potentially stabilize a wide range of crystallographic arrangements. To address these challenges, x-ray spectroscopic and scattering based methods are used to probe challenging nanoscale systems in detail over multiple length scales. In particular, synthetic developments are paired with robust characterization, in order to improve knowledge of heavy element nanoparticle growth and transformation, as well as develop ways to make advanced x-ray characterization analysis more informed and accessible, in tandem.
Two key synthetic systems and associated x-ray characterization approaches will be presented. The first involves the use of kinetics to control the atomic scale alloy distributions within bimetallic noble metal nanoparticles. Through x-ray absorption spectroscopy, atomic scale coordination environments reveal that changing kinetic parameters within nanoparticle synthesis reactions can indeed affect the nature and homogeneity of alloys that result. This finding has important implications for the use of such particles in heterogeneous catalysis. The second system involves the synthesis of nanoscale uranium oxides, which are of interest towards the development of accident-tolerant nuclear fuels and are also relevant to the migration of actinides in environmental systems. Synthetic methods will be presented, including colloidal and hard-template based reactions, which have enabled preliminary investigation into the size dependent properties of actinide oxides. These synthetic pursuits have been paired with x-ray spectroscopy (XAFS and HERFD-XAS) and x-ray scattering to determine a detection limit for mixed phases within actinide oxides, and to create new analysis strategies for decoupling surface vs. interior chemistry of nanoparticles.
Bio: Dr. Moreau joined the Chemistry faculty at Washington State University in July 2020 after completing postdoctoral research at Lawrence Berkeley National Laboratory under the direction of Dr. Corwin Booth in the heavy element chemistry group. Prior to that, she completed her PhD at Northwestern University as an NDSEG fellow, researching under Drs. Chad Mirkin and Michael Bedzyk, and BS degree at Cornell University researching under Dr. Richard Robinson. In all cases, Dr. Moreau’s research has been dedicated to using advanced X-ray characterization methods paired with synthetic developments in nanochemistry to explore structural transformations in nanomaterials. Dr. Moreau is very happy to be at WSU, where she is joining ongoing efforts towards understanding the properties of radioactive materials.
Dr. Moreau leads a research group dedicated to exploring what happens when we make actinide materials like uranium and plutonium down to the nanometer length scale, and how they interface with other proximal materials, both structurally and electronically. Her research group aims to apply what they learn about these size-dependent properties to make advances in the areas of nuclear energy, nuclear medicine and consider new possibilities for environmental remediation. It is also Dr. Moreau's goal to make X-ray characterization methods more accessible to those working with radioactive materials and to study complex problems that occur at surface-solution interfaces.