Abstract: Li-free solid-state batteries, which contain no excess Li metal initially, are considered promising next-generation energy storage systems due to their high energy density and enhanced safety. However, heterogeneous Li plating onto the current collector leads to early failure and low energy efficiency. Porous interlayers positioned between the current collector and solid electrolyte have the potential to guide uniform Li plating and improve electrochemical performance. In this configuration, both the electrochemical reduction of Li ions and mechanical deformation, which allow Li metal to flow into the porous interlayer, occur simultaneously. These complexities make understanding Li plating kinetics challenging. Factors such as stack pressure, interlayer composition, current density, and the mechanical response of the interlayer can influence Li deposition kinetics. In this talk we discuss how heterogenous plating can cause fracture in the cathode and impacts the reversible operation of li-free solid state batters. We examine a model porous Ag-C interlayer with two different Ag particle sizes and observed Li plating behavior under various stack pressures and current densities. While Ag nanoparticles in the interlayer can facilitate Li movement, they can also induce internal stress, leading to void formation that impedes Li flow. Nanostructure analysis using cryo-FIB are combined with chemomechanical modeling to uncover the mechanical interaction of interlayer during the alloying reaction between Ag and Li. When comparing the morphology of Li electrodeposits at different conditions, morphological changes correlate with the creep strain rate over Li ion flux. The electrochemical performance is determined by the morphology of Li electrodeposits rather than the Li plating current density. 

Bio: Dr. Hatzell is an Associate Professor at Princeton University in the Andlinger Center for Energy and Environment and department of Mechanical and Aerospace Engineering. Dr. Hatzell earned her Ph.D. in Material Science and Engineering at Drexel University, her M.S. in Mechanical Engineering from Pennsylvania State University, and her B.S./B.A. in Engineering/Economics from Swarthmore College. Hatzell is the recipient of several awards including the ORAU Powe Junior Faculty Award (2017), NSF CAREER Award (2019), ECS Toyota Young Investigator Award (2019), finalist for the BASF/Volkswagen Science in Electrochemistry Award (2019), the Nelson “Buck” Robinson award from MRS (2019), Sloan Fellowship in Chemistry (2020), and POLiS Award of Excellence for Female Researchers (2021), NASA Early Career Award (2022), ONR Young investigator award (2023) and Camille-Dreyfus Teacher-Scholar Award (2024). 

The Hatzell Research Group works on understanding phenomena at solid|liquid, solid|gas, and solid|solid interfaces through non-equilibrium x-ray techniques, with particular interest in energy conversion and storage and separations applications. 

Abstract: After an introduction to organic light-emitting diodes, we will discuss our recent computational work dealing with three strategies to design efficient, purely organic emitters: 

The first strategy was introduced in 2012 by Chihaya Adachi and co-workers at Kyushu University, who proposed to harvest the triplet excitons in purely organic molecular materials via thermally activated delayed fluorescence (TADF). These materials now represent the third generation of OLED emitters. Impressive photo-physical properties and device performances have been reported, with internal quantum efficiencies reaching 100% (which means that, for each injected electron, one photon is emitted). In the most efficient materials, the TADF process has been shown to involve several singlet and triplet excited states. 

A second strategy, which has been applied more recently, was proposed by Feng Li and co-workers at Jilin University in 2015 and is based on the exploitation of stable organic radicals. In these materials, where the lowest excited state and the ground state usually belong both to the doublet manifold, we will describe how high efficiencies and photo-stability can be obtained. 

Finally, we will briefly discuss our very recent work on so-called multi-resonance (MR) TADF materials, initially developed by Takuji Hatakeyama and co-workers at Kwansei Gakuin University.

Bio: Jean-Luc Brédas received his B.Sc. (1976) and Ph.D. (1979) degrees from the University of Namur, Belgium. In 1988, he was appointed Professor at the University of Mons, Belgium, where he established the Laboratory for Chemistry of Novel Materials. While keeping an “Extraordinary Professorship” appointment in Mons, he joined the University of Arizona in 1999. In 2003, he moved to the Georgia Institute of Technology where he became Regents’ Professor of Chemistry and Biochemistry and held the Vasser-Woolley and Georgia Research Alliance Chair in Molecular Design. Between 2014 and 2016, he joined King Abdullah University of Science and Technology (KAUST) as a Distinguished Professor and served as Director of the KAUST Solar & Photovoltaics Engineering Research Center. He returned to Georgia Tech in 2017 before moving back to the University of Arizona in 2020. Prof. Brédas is an elected Member of the International Academy of Quantum Molecular Science, the Royal Academy of Belgium, and the European Academy of Sciences. He is the recipient of the 1997 Francqui Prize, the 2000 Quinquennial Prize of the Belgian National Science Foundation, the 2001 Italgas Prize, the 2003 Descartes Prize of the European Union, the 2010 ACS Charles Stone Award, the 2013 APS David Adler Award in Materials Physics, the 2016 ACS Award in the Chemistry of Materials, the 2019 Alexander von Humboldt Research Award, the 2020 MRS Materials Theory Award, and the 2021 RSC Centenary Prize. He has served as editor for Chemistry of Materials between 2008 and 2021 and scientific editor for Materials Horizons since 2022. His current Google Scholar h-index is 171.

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Abstract: The current atmospheric CO₂ level reaches 426 ppm according to the latest measurement by NASA in July 2024; therefore, the development of carbon capture, utilization, and storage technologies (CCUS) has become urgent to cut CO₂ emissions to avoid the most severe consequences of climate change. CO₂ conversion to commodity chemicals, materials, feedstocks, and fuels driven by renewable electricity offers one of the most effective pathways to mitigate the greenhouse effect and reduce global demand for traditional fossil fuels, while simultaneously achieving sustainable energy and carbon neutrality. 

This seminar will briefly overview diverse research areas of National Energy Technology Laboratory (NETL) to advance energy and environmental sustainability along with carbon management. Our electrochemistry efforts on carbon conversion directly support the US goal of achieving carbon-free power sector by 2035 and net zero emissions by 2050. Since CO₂ electroreduction is highly structure sensitive, NETL ongoing research has been focused on the rational design and engineering of electrocatalysts, i.e. tuning the particle size, shape, dimension, or manipulating chemical composition, surface structure, defects, etc., to facilitate the CO₂ conversion to desirable products with good selectivity, activity, and durability. Different classes and types of electrocatalytic materials will be covered in this talk, from well-defined atomic-scale model catalysts to heterogenous, scalable powder systems at nano- and micro-scale for “real world” performance evaluation. Several ex situ and in situ spectroscopic, microscopic, and electrochemical characterization techniques along with computational findings will be additionally discussed to gain more insights into the structure-activity relation. 

Besides catalyst development, the intensive efforts have been devoted to optimizing the device architecture and membrane electrode assembly components of CO₂ electrolysis cell to better respond to practical industrial applications (current density higher than 200 mA/cm² and lifetime beyond 1,000 hours). The last part of this seminar will provide more detail on how NETL has transitioned from the most common aqueous H-type reactor for lab-scale validation to more realistic full electrolyzer cell in bench-scale prototype. The knowledge, electrocatalytic materials, and device validation achieved from NETL in-house research will be translated to industrial sector for large scale deployment and the anticipated outcome will help advance the development of low temperature CO₂ electrolysis technologies.

Bio: Dr. Thuy Duong Nguyen Phan is currently a Research Scientist at the U.S Department of Energy’s National Energy Technology Laboratory (NETL). Her research interests focus on functional materials for energy conversion (carbon capture and conversion, renewable chemicals/fuel production, hydrogen production/utilization), energy storage (battery, supercapacitor, oxygen storage), and environmental sustainability (wastewater/air/metal purification, indoor odor removal, self-cleaning window). She earned her Ph.D. in Chemical Engineering from University of Ulsan (South Korea) in 2010 and then worked there as Postdoctoral Research Fellow and Research Professor. Prior to working at NETL in 2017, she worked as Research Associate at Brookhaven National Laboratory. She has strong track record of 50+ high impact journal publications and 7 patent awards/pending applications (Google scholar).

Abstract: Stable isotope ratios can act as tracers in environmental systems. Nitrate isotope ratios can differentiate the system's dominant sources, particularly synthetic fertilizer, manure, and atmospheric nitrate via precipitation. In this study, we utilize the stable isotope ratios of nitrate (δ¹⁵N_NO3- and δ¹⁸O _NO3-) in a local karst-influenced watershed to constrain the sources and flow paths of nutrients during a range of precipitation events.  

Preliminary results of storm event nitrate isotope ratios show the significant influence of precipitation on nitrate isotopic compositions. We observe more positive δ¹⁵N and δ¹⁸O values during a storm event compared to baseline conditions. Storm δ¹⁵N values suggest a predominant contribution from agricultural runoff, likely mobilized by increased surface flow and infiltration. Concurrently, δ¹⁸O values indicated an influx of atmospheric nitrate from direct precipitation and rapid surface runoff. These shifts in isotope signatures during storm events support a blending of sources via dynamic mixing. 

Additionally, new methods for isotope ratio measurement will be presented.  The Orbitrap high resolution mass spectrometer has been recently reconfigured with a focus on isotope ratio measurements. This technology opens up the possibility of “easy” measurement of rare and clumped isotope species, tracking bacterial processes, temperature relationships, and tracing the fate of degradation products.  A brief introduction and possible avenues for future collaborations will be explored. 

Bio: Dr. Erhardt started as an Environmental Engineer at Northwestern University, discovering geology her senior year.  After working as an engineer on acid mine drainage remediation, she returned to graduate school for an M.S. from the Colorado School of Mines and a PhD from Stanford University focused on isotope geochemistry.  After three years at the University of Cambridge as a CIFAR postdoctoral fellow, she has been at the University of Kentucky since 2016.  Additionally, she is an Anna Boysken Fellow for the Institute for Advanced Study and was a Global Visiting Professor with the Institute of Analytical and Water Chemistry at the Technical University of Munich. She is the director of the Kentucky Stable Isotope Geochemistry Laboratory, focused on isotope analysis of carbon, nitrogen, hydrogen, oxygen, and sulfur isotopes in a wide range of geologic and environmental samples. 

Abstract: Within a bottom/up approach of molecular complexity, the study of substrate- and solvent-free isolated species is crucial, as they can be considered as unperturbed elementary bricks of matter for which the interplay with state-of-the-art calculations can be pushed as far as possible. 

In this context, probing isolated gas phase matter with VUV (5-40 eV, ie 250-30 nm) allows by photoionization to probe electronic and molecular structures via Photoelectron Spectroscopy (PES), a universal highly sensitive technique. The additional coupling of ion detection in coincidence with the departing photoelectrons (PEPICO) opens large alleys of research in physical chemistry especially when one deals with complex media (molecular beams, chemical/combustion reactors) for which mass-selection of a given species is mandatory. Reciprocally, pure mass-spectrometric analysis capabilities of chemical reactions can be greatly enhanced by the addition of the electronic fingerprint (via PES) allowing the identification of isomers and sometimes conformers of cations with a given m/z.

After a broad introduction to the VUV Beamline DESIRS @ Synchrotron SOLEIL (see https://www.synchrotron-soleil.fr/en/beamlines/desirs) and its scientific case, the capabilities of our double imaging PEPICO spectrometer coupled to a versatile molecular beam chamber will be illustrated by several examples, relevant to basic physical chemistry as well to interfaces with biology, planetary science and astrochemistry, and dealing with cold molecules, radicals and reaction intermediates, weakly bonded-clusters up to aerosols. Some emphasis will be also given to chiral species probed by a specific chiroptical process based upon photoionization. 

Bio: After a PhD in molecular physics obtained at Université Paris-Saclay (1991) and a post-doctoral stay at the Department Chemistry of UC Berkeley (1992-1993), I joined the French synchrotron centers LURE and now SOLEIL. At the head of two VUV beamlines (especially DESIRS @ Synchrotron SOLEIL), for more than 25 years, I have been working on VUV photodynamics (absorption, photoionization, fragmentation) on a wide range of samples, mainly isolated species such as cold molecules, radicals, clusters, trapped ionic biopolymers and nanoparticles. My work is centered on fundamental molecular physics and gas phase physical chemistry, with strong interfaces with chemistry, life sciences, planetary sciences and astrophysics. 

Among this large field, part of my activity is focused onto the interaction of Circularly Polarized Light and chiral species and in particular onto Photoelectron Circular Dichroism (PECD) at the field crossing between molecular photoionization and chirality.

Abstract: State-of-the-art infrared (IR) photon detection is accomplished using III-V or II-VI compound semiconductors such as HgCdTe, InGaAs, and InSb, among others. These materials feature low dark current densities and high external quantum efficiencies but must be cryogenically cooled, crystalline, and require flip-chip hybridization to readout integrated circuits (ROIC). These requirements add cost and complexity to IR detection systems. Newer technologies such as strained layer superlattices and other high operating temperature IR sensors can use thermoelectric cooling but still require epitaxial growth and hybridization. We have recently began developing IR sensors using classical doped, conjugated polymers as well as newer materials such as open shell, triplet diradical conjugated polymers which have intrinsic electrical conductivity. Our polymer-based IR sensors are principally active in the shortwave infrared (λ = 1-3 μm), with response extending well into the midwave infrared (λ = 3-5 μm) and longwave infrared (λ = 8-14 μm). This new generation of very low cost IR sensors will enable hybrid-free detectors where the materials are disordered semiconductors; they can be deposited using spin-coating, drop-casting or oxidative chemical vapor deposition directly onto a ROIC. This eliminates the need for hybridization and epitaxial quality materials. The detectors operate at room temperature, also eliminating the need for cooling. Current device challenges principally involve fabricating vertical (parallel) detector geometries and dark noise reduction.

Biography: Jarrett Vella is a Senior Research Chemist in the Electro-Optical and Infrared Components Branch of the Sensors Directorate, Air Force Research Laboratory. He obtained his Ph.D. from the University of Florida and received postdoctoral training at the Materials and Manufacturing Directorate, Air Force Research Laboratory. His research seeks to identify ultralow cost infrared sensors with minimal size and weight requirements for use in terrestrial and space applications.

DNA is a programmable building block for sequence-encoded materials that are governed by Nature’s base pairing rules. The design space of such materials could be significantly expanded by harnessing metal-nucleic acid chemistry, but the “sequence-structure-property” relationships of these hybrid materials remain poorly understood. This talk presents a data-driven approach to overcome this challenge, centered on a new class of DNA-based materials with promise in biophotonics: atomically precise DNA-templated silver nanoclusters (Ag_N-DNAs). We harnessed high-throughput synthesis and fluorimetry together with machine learning to discern how DNA sequence dictates the photoluminescence properties of Ag_N-DNAs. This approach enables the design of new Ag_N-DNAs that fluoresce in the near-infrared tissue transparency window, a key area of need for biomedical imaging. We also combined preparation of atomically precise Ag_N-DNAs together with native mass spectrometry and circular dichroism to advance understanding of Ag_N-DNA ligand chemistry. Our discovery of a new class of Ag_N-DNAs with additional halido ligands recently enabled the first electronic structure calculations for Ag_N-DNAs and significantly enhances Ag_N-DNA stability. Together, these advances present new opportunities to expand the science and applications of DNA-based nanoclusters.

The mortality rate of cancer establishes it as a leading global health concern, prompting significant investment into cancer research. While the effects of cancer are well known, the understanding of specific sources of cancer therapy resistance are not. In this study, our goal was to develop innovative methods to address current shortcomings in cancer treatment and understanding. To do this, we studied exosome-mimetic nanovesicles as an immunotherapeutic platform and fluorescence lifetime imaging as a means to measure cancer-associated enzyme activity at a single cell level.

Through the use of a novel method of production, we generated nanovesicles from dendritic cells in high yields and leveraged the antigen-presenting and costimulatory properties of dendritic cells for induction of a T cell immune response. We demonstrate that these nanovesicles are able to present antigens in functional immune stimulatory complexes and retain parental ability to activate CD8+ T cells. Additionally, these nanovesicles were shown to mediate activation of T cells through indirect means. Here, nanovesicles are taken up by bystander dendritic cells, thereby delivering antigen to the dendritic cell and conferring T cell stimulatory capability. Next, we investigated the application of fluorescence lifetime imaging to measure cancer-associated cytochrome P450 enzyme activity at the single-cell level. We demonstrated this approach provides detailed insights into cellular heterogeneity and localized enzyme activity. Additionally, we showed that sensitivity and dynamic range can be tuned to enzyme activity and levels by altering excitation and emission wavelengths.

These advancements offer new and promising avenues to enhance nanoparticle-based immunotherapy and understanding of the role of enzyme activity and cellular heterogeneity in cancer progression. Ultimately, the methods developed contribute to improving therapeutic strategies and personalized medicine.

Abstract: The energy band structure (dispersion relation between energy and wavenumber) is fundamental information essential for elucidating the charge transport properties of semiconductors. For organic semiconductors, the valence band structure, which is responsible for
hole transport, has been measured by energy-dependent and angle-resolved photoelectron spectroscopy since the 1990s. However, the conduction band structure, which is responsible for electron transport, has not yet been reported.
 

We have developed a new technique, angle-resolved low-energy inverse photoelectron spectroscopy [1], and succeeded in measuring the conduction band structure of organic semiconductors for the first time [2]. Based on the experimental results, we propose a new polaron model, "partially-dressed polaron" model. This study evidences the polaron formation in high-mobility organic semiconductors has a significant impact on electronic conduction.

[1] Y. Kashimoto, S. Ideta, H. Sato, H. Orio, K. Kawamura, H. Yoshida,
Rev. Sci. Instrum., 94, 063903 (2023). Selected as Editor’s Pick
[2] H. Sato, S. A. Abd. Rahman, Y. Yamada, H. Ishii, H. Yoshida, Nature
Mat. 21, 910 (2022).