Chemistry Colloquium Program

 
Jason P. LeJeune, Ph.D.

Safety Seminar

Host: John A. Pojman

Matthew Chambers, Ph.D.

"Developing Molecular Catalysts for Sustainable and Energy-Efficient Petrochemical Processes"

The foundation of chemical industry continues to have an over-reliance on processes developed in the early 1900’s that leverage high temperatures and high pressures to drive a given reaction of need. Today, such strategies consume substantial energy while generating copious amounts of hazardous waste. While these industries produce critical commodities to support societies' survival and growth, there is a need for major scientific innovation to allow for chemical industry to continue to thrive in a more sustainable and energy-efficient manner. This presentation will describe two parallel approaches to modernizing catalysis to meet this challenge. The first approach will present a new class of carbonylation precatalysts based on mid-valent metal centers capable of supported catalysis at relatively mild temperatures and pressures. The characterization, activity, stability, and nature of the catalytic state will be discussed. The second approach will present the development of novel reaction pathways suitable for the direct formation of C–C bonds from unactivated hydrocarbon sources. The ability of metal oxo complexes to activate C–H bonds is combined with photochemical activation to generate a unique electronic configuration suitable to mediate the bond activation while allowing a diverse array of follow-up reactivity and product selectivity. Mechanistic insights, the nature of the excited state, the development of photocatalytic conditions, and strategies to control product selectivity will be presented.

Host: Justin Ragains

Manuel Hegelich, Ph.D. 

Joint Seminar: Chemistry with Physics & Astronomy
 

Host: Gerald J. Schneider

Revati Kumar, Ph.D. 

"Liquid electrolytes: From Aqueous Solid-Liquid Interfaces to Ion Solvation in Non-Aqueous Systems"

The research focus of my group is to investigate the effect of solvation environment on charge transport, structure and dynamics of both aqueous and non-aqueous electrolytes using molecular simulations.  An important aspect of our research is understanding the effect of secondary/non-covalent interactions on the properties of electrolytes both in the bulk and at the interface using molecular simulations. The interface is essentially a region wherein the symmetry of the bulk environment is broken and thus can include a wide range of systems from the surface of an electrode in contact with an electrolyte to an aggregate/micelle in contact with a solution. I will present two systems that my group is working on. The first part of my talk will focus on graphene oxide (GO)-aqueous solution interfaces. Graphene oxides (GOs) are nanoporous sheets of graphene with oxygen bearing defects. This interface is critical for many exciting GO-based separation technologies such as water purification and proton exchange membranes. Our group has used ab initio molecular dynamics simulations coupled with neural network force-field simulations to investigate the interfacial aqueous structure and the intrinsic reactivity of these aqueous interfaces.  Comparisons between conventional force-fields and first principles ab initio molecular simulations will be discussed and the results partially validated on recent vibrational sum frequency generation spectroscopy data. Furthermore, the effect of oxidation level of the sheet, from fully oxidized sheet to the unoxidized graphene-water interfaces,  on reactivity and interfacial ordering will be presented. The  effect of solvent polarity will be presented based on results obtained by changing the solvent to methanol. The classical force-fields that best reproduce the ab initio MD simulation interfacial solvent data was used to study the adsorption of organic aromatic molecules onto graphene oxide. The effect of the oxidation level of the graphene oxide sheet as well as the presence of two different halide salts, sodium chloride and sodium iodide, were examined and the  results will be presented. The second part of my talk will focus on glyme based electrolytes that unlike their aqueous analogues, have received comparatively little attention from a fundamental perspective. The structure of these linear chain ethers is reminiscent of crown ethers, hence they are excellent cation chelators. The efficient cation solvation of glymes in turn impacts counterion reactivity and transport. Solutions of metal salt in glymes have a wide range of applications, including but not limited to organic synthesis, biocatalysis, electrochemistry, and energy storage technologies. The focus of the Kumar group is to investigate the role of ion solvation on the chemical properties of glyme based sodium salt electrolytes that are relevant to energy storage applications. Given the inadequacies of "off the shelf" effective pair potential in describing these electrolytes, the development of inexpensive force-fields to study these systems is essential. The Kumar group uses data from ab initio quantum simulations in conjunction with experiments in the condensed phase to develop and test new empirical atomistic models of sodium triflate in diglyme. The details of the force-field development as well as the transferability of these models to glymes of different chain lengths as well as different anions with similar chemical motifs as triflate will be discussed. The results from the simulations on the solvation structure, charge transport and aggregation as a function of glyme chain length and anion identity as well as in the presence of electrode interfaces will be presented.

Host: Bin Chen

Patrick Mensah, Ph.D. 

"CREST Center for Next Generation Multifunctional Composites Research at Southern University"

Southern University and A&M College (SU) in Baton Rouge, LA, in collaboration with Louisiana State University (LSU), established Phase II  CREST Center for Next Generation Multifunctional Composites with NSF funding. CREST Center projects involves promoting advancements in multifunctional smart composites and related technology development, nanocomposites, novel microstructure design, and multiscale porous polymer composites, including materials synthesis and characterization, computational modeling and simulation, and additive manufacturing and applications.

Host: John A. Pojman

Haitao Liu, Ph.D.

"Intrinsic Surface Properties of Graphitic Carbon Materials"

Our research shows that the perceived hydrophobicity of graphitic carbons arises from the adsorption of airborne hydrocarbons on their surfaces. Additionally, this form of contamination significantly influences both the heterogeneous electron transfer rate constant and the double-layer capacitance of carbon electrodes. These findings underscore the critical role of surface cleanliness in characterizing and utilizing carbon materials in ambient conditions.

Hosts: Graça Vicente, Slava Baranets

Ognjen Miljanic, Ph.D.

Host: Victor Garcia-Lopez

 

Fereshteh Emami, Ph.D. 

"Assessment of Chemical Contaminants in Lake Maurepas"

Lake Maurepas in southeastern Louisiana (USA) is a vital aquatic ecosystem with significant ecological, recreational, and economic value. Recently, concerns have arisen regarding the deterioration of aquatic and water quality within the lake, largely attributed to the industrial activities. Our study aims to investigate the chemical contaminants and the quality of water, sediment, and aquatic samples collected from various locations and depths of the lake. The primary objectives of this study are to assess the current state of organic pollutants, nutrients and heavy metal concentrations, and to identify the monthly concentration trends and spatial contaminants distribution patterns throughout the lake. The behavior of these chemicals was analyzed and forecasted using parametric and non-parametric statistical analyses, as well as machine learning-based modeling. The findings of this study contribute to the understanding of aquatic ecosystems and provide insights into the effects of pollution on the ecosystem.

Host: John A. Pojman

Elisabeth Fatila, Ph.D.

 

"Mechanochemical synthesis for coordination chemistry: a solution to synthetic issues with the larger lanthanides?"  

The importance of lanthanides to new and emerging technologies cannot be overstated. Coordination chemistry is key to developing compounds that harness the magnetic and optical properties of the lanthanides. While lanthanides are often treated interchangeably because of their similar chemical properties, the decrease in ionic radius across the series can have substantial consequences to their coordination chemistry. The larger, more charge diffuse early lanthanides tend to have higher coordination numbers for the same ligand set with reduced stability constants. With the greater synthetic flexibility of the larger lanthanides, there can be challenges with obtaining targeted products reproducibly. In addition, the dynamic and labile nature of Ln3+ cations means that solvents can have a detrimental impact on yield and purity. 

We look critically at the role mechanochemistry plays in optimizing yields and reducing side products. Both manual grinding and automated ball milling were used for mechanochemical reactions. While mechanochemistry can remove the impact of solvent, other strategies were used alongside mechanochemical synthesis. Additional synthetic strategies including tuning the steric features of ligands were found to play a role in stabilizing complexes of the early lanthanides and affording greater reaction reproducibility.

Future work includes using mechanochemistry and our ligand strategy for the coordination chemistry of larger and more charge diffuse cations. 

Hosts: Natalie Stewart, Noémie Elgrishi, Matthew Chambers

Vicky Colvin, Ph.D. 

"Nanoscale Iron Oxide Surfaces: From Low Temperature Graphene to Supersensitive Magnets"

Nanoparticles present an enormous amount of surface to the world: a small speck of nanoparticulate rust, for example, can possess the surface area of a basketball court. We are now able to design this interface with a great deal of molecular precision opening the door for new applications. This talk will illustrate this in three case studies. In the first, nanoparticle-polymer interfaces are used as a template for biomolecular association leading to soft assembly driven by biomolecular crystallization. When the nanoparticle-polymer interface is less densely packed, these complexes rapidly nucleate crystallization of Albumin and Lysozyme. The resulting single crystals are examples of novel biomolecule-nanoparticle composites with unique properties and applications. The second case study illustrates how the hard interface between adjacent magnetic nanoparticles in supercrystals can lead to collective magnetic properties distinct from isolated particles or bulk materials. When iron oxide nanoparticles share crystalline interfaces, as they do in these porous and aligned assemblies, then their collective properties are defined both by dipolar interactions as well as exchange interactions. The latter feature is particularly powerful as it results in highly sensitive soft magnets that can be fully magnetized at extremely low external magnetic fields. The last case study illustrates how it is possible to leverage the reactive surfaces of iron oxide at low temperatures in a liquid phase to generate graphitic carbons through thermal decomposition of fatty acid feedstocks. Normally such conversions require elevated temperatures and solid-state processing. This chemical approach opens up a new avenue for exploring more sustainable methods for generating conductive carbon materials.

Host: John A. Pojman

Jason P. LeJeune, Ph.D.

Safety Seminar

Host: John A. Pojman

Vicente A. Talanquer, Ph.D. 

Host: Zakiya S Wilson-Kennedy

Martin Head-Gordon, Ph.D.

Host: Kenneth Lopata

P. Shiv Halasyamani, Ph.D. 

Host: Slava Baranets

Gina Frey, Ph.D. 

Host: Zakiya S Wilson-Kennedy

Sidney Creutz, Ph.D. 

Host: Clifton Wagner

Joseph Schlenoff, Ph.D. 

Host: Amy Xu

Erin McCauley, Ph.D. 

Hosts: Jose M. Garfias, Fatima Rivas

Scott Snyder, Ph.D. 

Host: Fatima Rivas

Mihaela C. Stefan, Ph.D. 

Host: David Spivak

Chris Mundy, Ph.D. 

Host: Revati Kumar

 

Kelly Ayers

"Introduction to Topics in Crime Scene Investigation"

Hosts: Gerald Schneider, Julia Carroll representing the Student Affiliates of the American Chemical Society (SAACS)

Yan Xia, Ph.D. 

Joint Seminar: Chemistry and Chemical Engineering

Hosts: Anthony Engler, Donghui Zhang