Past Seminars & Events
Professor Theodore Goodson III
Professor Theodore Goodson III
Department of Chemistry
University of Michigan
Host: Professor Aaron Massari
Optical Properties of Novel Functional Organic Materials
Organic conjugated molecules for optical and electronic applications have received great attention due to their versatility and relatively low manufacturing costs. While there has been great improvement of light conversion efficiency in certain photovoltaic materials, there still remain questions concerning the structural and inhomogeneity of the electron and energy transport processes. In this regard, understanding the fast processes (fs) at a local level (nm) in these systems is crucial in the design criteria for better performance in optical and electronic applications. In this presentation, the results of photo-physical dynamics of organic light harvesting materials will be described. These materials have been analyzed using time-resolved absorption and fluorescence spectroscopy and microscopy as well as a nonlinear and quantum optical spectroscopy. Ultra-fast interferometric microscopic measurements were carried out to investigate the role of coherent energy transport in these organic photovoltaic materials. The use of these methods provide insights in to the dynamics and degree of heterogeneity in novel organic materials for optical and electronic applications.
Research
Professor Goodson's research group utilizes a number of spectroscopic techniques towards investigating the optical properties and applications of novel organic macromolecular materials. A major emphasis is placed on the new properties observed in organic macromolecules with branching repeat structures as well as organic macromolecules encapsulated with small metal particles. These materials have been suggested to be candidates for variety of applications involving light emitting devices, artificial light harvesting, strong optical limiters, enhanced nonlinear optical effects, quantum optical effects and as sensors in certain organic and biological devices.
Professor Will Gutekunst
Department Seminar
Professor Will Gutekunst
Department of Chemistry & Biochemistry
Georgia Institute of Technology
Host: Professor Marc Hillmyer
Development of New Chemical Platforms for Polymer Synthesis
Synthetic polymers have permeated nearly every facet of modern life. From the ubiquity of polyolefins to recent advancements in 3-D printing, organic materials continue to shape the world around us. While tremendous accomplishments have been made with relatively few polymer families, the future requires the development of materials with increased control over structure to produce systems that can respond to programmed inputs, as well as the exploration of entirely new polymer compositions. Our group takes a chemistry-focused approach to address these challenges through the strategic application of organic methodologies to design new monomer families and reagents for precision polymer synthesis. This presentation will specifically highlight (1) the utility of enyne chemistry to impart degradability and expedite functionalization of metathesis-derived materials and (2) the development of a new class of living polymerization that is enabled by the unusual reactivity profiles of twisted amide molecules.
Professor Gutekunst's research
The Gutekunst Lab is interested in pushing the limits of complexity in macromolecular systems using innovative concepts from synthetic organic chemistry. Specific projects in the lab explore the design of novel monomers for the construction of functional polyamides, the development of small molecule reagents for the dynamic modulation of branched polymer architectures, and the investigation of new concepts for creating covalent bonds in challenging contexts. Each project enables the generation of new functional materials with structures or assemblies that were previously inaccessible for study.
Professor Jessica M. Anna
Department Seminar
Professor Jessica M. Anna
Department of Chemistry
University of Pennsylvania
Host: Professor Aaron Massari
Ultrafast Dynamics of Natural Light Harvesting Complexes and Model Systems
Photosynthetic organisms have developed the molecular level machinery to efficiently and effectively harvest solar energy. To accomplish this, they use natural multichromophoric assemblies called light harvesting complexes to absorb a photon and transfer the excitation energy to a reaction center where charge separation takes place with a high quantum efficiency. Elucidating the mechanism of energy transfer and electron transfer in these complexes is essential to (1) understanding their high quantum efficiencies and subsequently (2) incorporating this information into design principles for artificial photosynthetic systems, photocatalysts, and organic photovoltaic materials. However, despite much experimental and theoretical effort, there are still unanswered questions regarding energy and electron transfer in natural light harvesting complexes, and multichromophoric assemblies in general.
In this talk, I will discuss our recent studies in this area where we apply ultrafast pump-probe and multidimensional spectroscopies in the visible and mid-IR spectral regions to the natural light harvesting complex, photosystem I (PSI), and structurally simpler model systems that mimic specific properties of light harvesting complexes, including artificial light harvesting chromophores, isolated cofactors, and host-guest complexes. From our studies, we gain insight into pathways of energy equilibration among different electronic states, information on solvation dynamics, and insight into how non-covalent interactions act to alter the properties and dynamics of cofactors.
Research
Professor Anna's group uses ultrafast nonlinear spectroscopy to understand photoinitiated processes and dynamics. In order to explore these processes we employ multidimensional spectroscopic methods in both the visible and infrared spectral regions. The major benefit of employing multidimensional spectroscopic techniques is that the resulting spectrum is a frequency-frequency correlation map where each excitation frequency is correlated to each detection frequency. This enables for direct information on couplings, mechanistic pathways and system-bath interactions to be obtained.
4th-Year Graduate Research Seminar Series: Session 15
Bach T. Nguyen at 9:30 a.m.
Adviser: Professor Jiali Gao
In silico investigation of solution phase decarboxylation mechanism for 5-carboxyluracil
Yangzesheng Sun at 10 a.m.
Advisers: Professor J. Ilja Siepmann
Machine Learning and Neural Networks for Modeling the Adsorption Equilibria in Nanoporous Materials
4th-Year Graduate Research Seminar Series: Session 14
Christopher L. Warkentin at 9:30 a.m.
Adviser: Professor Renee R. Frontiera
Surface-Enhanced Raman Spectroscopy for Characterization of Plasmon-Mediated Reactions
Brianna A. Collins at 10 a.m.
Adviser: Professor Jason Goodpaster
Organometallic Reactivity of Nickel Complexes Bearing PAlP Pincer-Type Ligands
Siriluk Kanchanakungwankul at 10:30 a.m.
Adviser Professor Donald Truhlar
Reduction of Cu(II) to Cu(0) Supported on Metal-Organic Framework NU-1000
Professor Mark Pederson
Chemical Theory Center Seminar
Professor Mark Pederson
Professor and Dr. C. Sharp Cook Chair in Physics
University of Texas at El Paso
Host: Professor Ilja Siepmann
Triangular Molecular Magnets: Chemical Models for Protons, Qubits, or Quantum Sensors?
The size range and deceptive complexity albeit behavioral simplicity of molecular magnets attracts physical scientists from many disciplines and challenges them to understand how 50-100 nuclei and 200-1000 electrons can exhibit such simple collective behavior. For example, quantum tunneling of magnetization, which occurs in broken-spin-symmetry magnetic molecules illustrates the power of density-functional-based pictures for predicting both the magnetic strength of molecules and the magnetic fields at which quantum tunneling occurs. Alternatively, the spin-electric effect[1-4] explicitly challenges the notion that single-determinantal theories can describe the physics leading this phenomenon. However, the large molecular size resists quantitative quantum chemical explanations and a combination of model Hamiltonians with density-functional treatments are the optimal means for exploring these intrinsically multi-configurational problems. I will review previous work on the Cu3 molecular magnet and show how the combination of broken symmetry density-functional theory, with simple self-interaction corrections and spin-orbit inclusion, can be used to derive three-spin Heisenberg Hamiltonians that describe the Dzyaloshinskii-Moriya induced splitting of degenerate low-energy Kramer doublets into S=1/2 chiral and anti-chiral pairs. The resulting energy level diagrams will be compared to that of a three-quark system.
The second half of this talk features the Fe3O(NC5H5)3(O2CC6H5)6 molecule[4] that is the first possible spin-electric system based upon spin 5/2.centers. As a curiosity, I discuss the rather unusual point-group symmetry, which includes a set of rotation matrices that are hauntingly similar to those that appear in elementary particle wavefunctions. We call the generator of these rotations matrices (above) RQ[2]. Using standard density-functional methods we show that the spin-electric behavior of this molecule could be more interesting due to energetically competitive reference states with high and low local spins (S=5/2 vs. S=1/2) on the Fe3+ ions. We provide spectroscopies to deduce the presence of both states and note that similar multiferroic behavior exists in the Mn3 molecular magnet[3]. Rationale for use of a new version to self-interaction corrections, FLOSIC, to improve quantitative predictions, especially in lanthanide systems and periodic systems will be included.[5]
- M.F. Islam, J.F. Nossa, C.M. Canali & MRP, First-principles study of spin-electric coupling in a Cu3 single molecular magnet, PRB 82 155446 (2010).
- A.I. Johnson, M.F. Islam, C.M. Canali & MRP, A Multiferroic molecular magnetic qubit, JCP. 151, 174105 (2019).
- Z. Hooshmand & MRP, Control of spin-ordered Mn3 Qubits: A density-functional study, Physical Chemistry and Chemical Physics (2020) DOI: 10.1039/D0CP04455E
- A.K. Boudalis, J. Robert & P. Turek, 1st demonstration of magnetoelectric coupling in a polynuclear molecular nanomagnet via EPR studies Fe3O(O2CPh)6(Py)3ClO4, Chem. Eur. J 24 14896-14900 (2018).
- MRP, A. Ruzsinszky and J.P. Perdew, Communication: Self-Interaction correction with unitary invariance in density functional theory, J.Chem. Phys. 140 121105 (2014)
Research
Professor Pederson's research is in chemical physics, condensed-matter physics, and computational physics. He has continuously concentrated on next-generation computing paradigms for quantum mechanics. His pioneering work demonstrated the quantitative computational prediction of quantum tunneling of magnetization (QTM) and spin-electric effects in molecular magnets. Both of these different collective phenomena arise from the spin of the electron. Quantitatively understanding conditions that allows for such coherent phenomena, is necessary from the standpoint of spin-Qubit design in quantum information science and may also unlock the mysteries of bio-navigation. He is currently attempting to link the fields of molecular magnetism and photocatalytic water splitting by demonstrating that variations in QTM, in reacting systems, can be used to spectroscopically sense conversion of water into oxygen and hydrogen without pumping energy into the system. Professor Pederson is the primary author of a computer code, the Naval Research Laboratory Molecular Orbital Library (NRLMOL), that describes how nanoscale systems interact with electromagnetic radiation. The opportunity to concentrate on developing this code over a long period has enabled these unique computational investigations and predictions.
Professor Tianquan "Tim" Lian
Professor Tianquan "Tim" Lian
Department of Chemistry
Emory University
Host: Professor & Department Head David Blank
Exciton Dynamics and Solar H2 Generation in Quantum Confined Nanoheterostructures
Quantum confined semiconductor nanocrystals (0D quantum dots, 1D quantum rods and 2D quantum wells) have been intensively investigated as light harvesting and charge separation materials for photovoltaic and photocatalytic applications. The efficiency of these semiconductor nanocrystal-based devices depends on many fundamental processes, including light harvesting, carrier relaxation, exciton localization and transport, charge separation and charge recombination. The competition between these processes determines the overall solar energy conversion (solar to electricity or fuel) efficiency. Quantum confined semiconductor nano-heterostructures, combining two or more material components (such as CdSe/CdS dot-in-rod nanorods or core/crown nanosheets), offer unique opportunities to control their charge separation properties by tailoring their compositions, dimensions and spatial arrangement. Further integration of catalysts (heterogeneous or homogeneous) to these materials form multifunctional nano-heterostructures, such as CdSe/CdS/Pt, that are shown to be efficient photocatalysts for light driven H2 generation. Using 0D, 1D and 2D nano- heterostructures as model systems, we directly probe the above-mentioned fundamental exciton and carrier processes by transient absorption and time-resolved fluorescence spectroscopy. We are examining how to control these fundamental processes through the design of heterostructures to achieve long-lived charge separation and efficient H2 generation. In this talk, we will discuss the mechanism of exciton transport, dissociation, and key factors limiting H2 generation efficiency in 1D and 2D nanoheterostructures.
Professor Lian
Tianquan “Tim” Lian is the William Henry Emerson Professor of Chemistry at Emory University, and editor-in-chief of the Journal of Chemical Physics. He earned a bachelor’s degree from Xiamen University, a master’s degree in chemical physics from the Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences, and a doctorate in physics from the University of Pennsylvania. He was a post-doctoral fellow at the University of California, Berkeley. He has been a professor at Emory University since 1996. A few notable recognitions include Kavli Frontier of Science fellow, American Physical Society fellow, National Science Foundation CAREER award, and Alfred P. Sloan fellowship.
Research interests
Professor Lian’s research is focused on ultrafast energy and charge transfer dynamics in photovoltaic and photocatalytic nanomaterials and at their interfaces. The long term goal of Professor Lian's research program is to contribute to the advancement of solar energy conversion science and technology through basic research. Currently, his research efforts are focused on the preparation, characterization and fundamental understanding of photovoltaic and photocatalytic nanomaterials. Of particular interest are fundamental dynamical processes in the materials and their interfaces (such as charge transfer, solvation, energy transfer and relaxation) which are not only essential to their functions, but also relevant to many other materials and applications. Researchers in Lian's lab utilize state-of-the-art laser spectroscopic and imaging techniques (femtosecond transient absorption in the visible and IR, nonlinear second harmonic and sum frequency generation, and single molecule/particle fluorescence) to investigate these processes. They aim at achieving fundamental understanding of these processes by designing experiments that can be used to test modern theory and computational modeling.
Bryce L. Crawford Memorial Lectureship
Bryce L. Crawford Jr. was a renowned Department of Chemistry professor and scientist. He died in September 2011, at the age of 96. He joined the department in 1940, and became a full professor of physical chemistry in 1946. He was chair of the department from 1955 to 1960, and was dean of the graduate school from 1960 to 1972. He retired in 1985. He loved studying molecular vibrations and force constants, and the experimental side of molecular spectroscopy and molecular structure. During World War II, Crawford worked in research on rocket propellants, making significant contributions to rocketry, and the development of solid propellants for the much larger rockets that evolved after the war. Crawford received many honors during his career, including the prestigious American Chemical Society Priestley Medal; and being named a Fellow of the Society for Applied Spectroscopy, a Guggenheim Fellow at the California Institute of Technology, and a Fulbright Fellow at Oxford University. He held the distinction of membership in three honorary science academies, and was actively involved in many professional associations.
DEI Rant & Rave
With current overwhelming situations and obligations that we deal with, need time to destress? If you are the type of person who loves to rant about their day or the type of person who loves to completely unplug, luckily we have an event for you! Rants & Raves will allow you to converse with your fellow chemistry peers, speak your mind about diversity, inclusion, and equity and everything else while also playing some fun games!
4th-Year Graduate Research Seminar Series: Session 13
Christian P. Hettich at 9:30 a.m.
Adviser: Professor Jiali Gao
A Multi-state Density Functional Theory (MSDFT) Calculation on the Photodissociation of CH3
Adel Soroush at 10 a.m.
Advisers: Professor R. Lee Penn and Professor William Arnold
Assessing the reactivity of mineral nanoparticles to remediate groundwater under realistic chemical and flow conditions
4th-Year Graduate Research Seminar Series: Session 12
Rebecca L. Combs at 9:30 a.m.
Adviser: Professor Lee Penn
Controlling Size and Aspect Ratio of MOF NU-1000 Using Solvent Identity
Nathan Love at 10 a.m.
Adviser: Professor Kenneth Leopold
A Microwave Study of a Superacid Ion Pair and Applications of an Intelligent Fitting Algorithm
Minog Kim at 10:30 a.m.
Adviser: Professor Andreas Stein
Three-Dimensionally Ordered Macroporous Mixed Metal Oxide as an Indicator for Monitoring the Stability of ZIF-8