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Abstract:

Imparting supramolecular interactions on transition metal systems such as Iridium complexes (with various N^C ligands), can have a profound impact on their luminescence properties. These types of complexes are under intensive investigation due to their excellent performance when used as emitters in phosphorescent organic light emitting diodes (PhOLEDs).¹ The ideal interactions for holding supramolecular systems together are hydrogen bonds, as they combine relatively strong intermolecular attractions with excellent reversibility. In using DNA base-pair-like interactions in super strong hydrogen bonding arrays to drive assembly,² we can influence chromaticity efficiently.^3,4 Beyond molecular systems, we can also apply these principles in extended solid-state systems whose porosities are such that small molecule uptake can influence the inherent physical (and photophysical) properties of the host materials.⁵ In this lecture, a broad view of our research program will be presented, spanning molecular systems to solid-state materials, and how we can make use of inherent luminescence properties for chromaticity modulation, small molecule sensing, and diagnostics.^6,7

References:

1. A.F. Henwood, E. Zysman-Colman, Chem. Commun. 2017, 53, 807.
2. B.A. Blight, C.A. Hunter, D.A. Leigh, H. McNab, P.I.T. Thomson, Nature ����vlog�ٷ����, 2011, 3, 246.
3. B. Balónová, D.  Rota Martir, E.R. Clark, H.J. Shepherd, E. Zysman-Colman, B.A. Blight, Inorganic ����vlog�ٷ����, 2018, 57, 8581.
4. B. Balónová, H.J.  Shepherd, C.J. Serpell, B.A. Blight, Supramolecular ����vlog�ٷ����, 2019, DOI: 10.1080/10610278.2019.1649674
5. R.J. Marshall, Y. Kalinovskyy; S.L. Griffin, C. Wilson, B.A. Blight, R.S. Forgan, J. Am. Chem. Soc., 2017, 139, 6253.
6. S.J. Thomas, B. Balónová, J. Cinatl M.N. Wass, C.J. Serpell, B.A. Blight, M. Michaelis, ChemMedChem, 2020, 15(4), 349.
7. C.S. Jennings, J.S. Rossman, B.A. Hourihan, R.J. Marshall, R.S. Forgan, B.A. Blight, Soft Matter, 2021, In Press. DOI: 10.1039/D0SM02188A

Dr. Ampofo Darko

Assistant Professor

Department of ����vlog�ٷ����

University of Tennessee

Abstract: Dirhodium paddlewheel(Rh^II) complexes can mediate a number of transformations through the catalytic decomposition of diazo compounds. The reactivity and selectivity of these reactions are modulated partly by the modification bridging ligands surrounding the metal center. While general strategies for ligand design have largely involved modification of bridging ligands, additives in these reactions have also been observed to affect the reactivity and selectivity of the catalyst. It is speculated that coordination to the axial sites of the catalyst is responsible for the perturbations in catalyst performance. While there are current research efforts to probe the benefits of axial coordination, there is still need for robust methods to clarify their structural and electronic influence on catalyst reactivity and product selectivity. To adequately use axial coordination as a control element, we have designed paddlewheel complexes with tethered Lewis basic groups onto traditional bridging ligands.  In initial studies, thioether ligands proved to be the most robust Lewis base when tethered to oxazolindinate or carboxylate bridging ligands. The novel complexes were then used in diazo-mediated cyclopropanation reactions, Si-H reactions, and C-H insertion reactions. The results of the experiments, along with spectroscopic and computational analyses, provided insight into the role that tethered axial coordination plays in diazo-mediated reactions. This presentation will also discuss our efforts to develop a chromogenic detector based on Rh^II paddlewheel complexes. It is well studied that Rh^II complexes can bind a variety of neutral and anionic ligands at its electrophilic active site, which induces a chromogenic response depending of the identity of the incoming ligand. We aim to exploit this feature to detect organophosphate nerve agents based on the by-products of their degradation to enabling timely, selective, and naked-eye detection of all families of organophosphorus nerve agents.

Abstract: Organic metal halide perovskites are promising materials for various optoelectronic device applications such as light emitting diodes (LED) and photovoltaic (PV) cells. Perovskite solar cells (PSCs) have shown dramatic increases in power conversion efficiency over the previous ten years, far exceeding the rate of improvement of all other PV technologies. PSCs have attracted significant attention due to their strong absorbance throughout the visible region, high charge carrier mobilities, color tunability, and ability to make ultralight weight devices. However, organic metal halide perovskites still face several challenges. For example, their environmental stability issue must be overcome to enable widespread commercialization. Meeting this challenge involves material and interface development and optimization throughout the whole PV device stack. Fundamental understanding of the optical properties, electrical properties, interfacial energetics, and device physics is key to overcome current challenges with PSCs. In this dissertation, we report a new family of triarylaminoethynyl silane molecules as hole transport layers (HTLs), which are in part used to investigate how the PV performance depends on the ionization energy (IE) of the HTL and provide a new and versatile HTL material platform. We found that triarylamoniethynyl silane HTLs show comparable PV performance to the state-of-the art HTLs and demonstrated that different processing conditions can influence IE of methylammonium lead iodide (MAPbI3).

Surface ligand treatment provides a promising approach to passivate defect states and improve the photoluminescence quantum yield (PLQY), charge-carrier mobilities, material and device stability, and photovoltaic (PV) device performance of PSCs. Numerous surface treatments have been applied to PSC thin films and shown to passivate defect states and improve the PLQY and PV performance of PSCs, but it is not clear which surface ligands bind to the surface and to what extent. As surface ligands have the potential to passivate defect states, alter interface energetics, and manipulate material and device stability, it is important to understand how different functional groups interact with the surfaces of PSC thin films. We investigate a series of ligand binding groups and systematically probe the stability of the bound surface ligands, how they influence energetics, PLQYs, film stability, and PV device performance. We further explore ligand penetration and whether surface ligands prefer to remain on the surface or penetrate into the perovskite. Three variations of tail groups including aryl groups with varying extents of fluorination, bulky groups of varying size, and linear alkyl groups of varying length are examined to probe ligand penetration and the impact on material stability.

Abstract: Organic metal halide perovskites are promising materials for various optoelectronic device applications such as light emitting diodes (LED) and photovoltaic (PV) cells. Perovskite solar cells (PSCs) have shown dramatic increases in power conversion efficiency over the previous ten years, far exceeding the rate of improvement of all other PV technologies. PSCs have attracted significant attention due to their strong absorbance throughout the visible region, high charge carrier mobilities, color tunability, and ability to make ultralight weight devices. However, organic metal halide perovskites still face several challenges. For example, their environmental stability issue must be overcome to enable widespread commercialization. Meeting this challenge involves material and interface development and optimization throughout the whole PV device stack. Fundamental understanding of the optical properties, electrical properties, interfacial energetics, and device physics is key to overcome current challenges with PSCs. In this dissertation, we report a new family of triarylaminoethynyl silane molecules as hole transport layers (HTLs), which are in part used to investigate how the PV performance depends on the ionization energy (IE) of the HTL and provide a new and versatile HTL material platform. We found that triarylamoniethynyl silane HTLs show comparable PV performance to the state-of-the art HTLs and demonstrated that different processing conditions can influence IE of methylammonium lead iodide (MAPbI3).

Surface ligand treatment provides a promising approach to passivate defect states and improve the photoluminescence quantum yield (PLQY), charge-carrier mobilities, material and device stability, and photovoltaic (PV) device performance of PSCs. Numerous surface treatments have been applied to PSC thin films and shown to passivate defect states and improve the PLQY and PV performance of PSCs, but it is not clear which surface ligands bind to the surface and to what extent. As surface ligands have the potential to passivate defect states, alter interface energetics, and manipulate material and device stability, it is important to understand how different functional groups interact with the surfaces of PSC thin films. We investigate a series of ligand binding groups and systematically probe the stability of the bound surface ligands, how they influence energetics, PLQYs, film stability, and PV device performance. We further explore ligand penetration and whether surface ligands prefer to remain on the surface or penetrate into the perovskite. Three variations of tail groups including aryl groups with varying extents of fluorination, bulky groups of varying size, and linear alkyl groups of varying length are examined to probe ligand penetration and the impact on material stability.

Yu Seung Kim (yskim@lanl.gov)

Los Alamos National Laboratory

Abstract: A proper design of polymer electrolytes may result in significant performance and durability improvement in electrochemical devices. In this talk, I show some examples of how polymer electrolytes can bring remarkable performance improvement in low-temperature fuel cells, high-temperature fuel cells, alkaline anion-exchange membrane fuel cells, and alkaline water electrolyzers. Critical factors such as ionomer adsorption on the catalyst surface, the concentration of ionic functional groups, and polymer relaxation will be discussed to give insights to design high-performing electrochemical devices. 

Bio: Yu Seung Kim is a technical staff scientist at Los Alamos National Laboratory, USA. He received his B.S. degree from Korea University (1994) and his Ph.D. degree from Korea Advanced Institute of Science and Technology (1999) in the field of Chemical Engineering. He spent three years as a post-doctoral fellow at the ����vlog�ٷ���� Department of Virginia Tech before joining the fuel cell group at Los Alamos (2003). He received the Outstanding Technical Contribution and Achievements Award from US DOE Hydrogen and Fuel Cell Program (2016). His current research interest is materials for fuel cells and electrolyzers. 

Contact Dr. Susan Odom for Zoom link.

Reporting on flow battery environment using the intrinsic fluorescence of an organic redoxmer

Lily A. Robertson

Chemical Sciences & Engineering Division, Argonne National Laboratory

Abstract: To meet increasing discrepancies between the supply and demand of the electric grid, large-scale energy storage devices are needed. Redox flow batteries are frequently proposed to fill this gap as their liquid-filled tanks of redox-active material are highly scalable. Liquid electrolytes using nonaqueous solvents are of particular interest due to their wide electrochemical stability windows with inexpensive organic compounds acting as the redox-active species. In general, methods to track the state of health of the batteries lag far behind the development and study of new materials. The questions of how and why materials fail and whether batteries may be cured like a patient are pertinent. Most monitoring techniques examine state of charge changes and/or require aliquots of the flow battery solution. Not as many focus on in situ methods or other health issues such as species crossover. Therefore, we pursued a detailed study of new organic redox-active species (“redoxmers”) that are both strong flow battery performers and have an orthogonal “self-reporting” property that does not interfere with battery operation.[i] Here, we show that an organic anolyte redoxmer, 2,1,3-benzothiadiazole, can be synthetically modified using π-extending acetamide groups to have strong emissive properties useful for self-reporting. The redoxmer design had substantial impact on electrochemical performance with simple N-alkylation of the acetamide group giving optimal performance. Strong ion-molecule interactions were observed depending on supporting electrolyte choice in both states of charge. Finally, we used the strong emission of the redoxmer to track crossover of several practical flow solution conditions in real time. To our knowledge, our study is the first time fluorescence has been used to monitor a state of health property in a flow cell design.

Seth C. Rasmussen, Department of ����vlog�ٷ���� and Biochemistry, North Dakota State University

Abstract: Ethyl alcohol, or ethanol, is one of the most ubiquitous chemical compounds in the history of the chemical sciences. The generation of alcohol via fermentation is also one of the oldest forms of chemical technology, with the production of fermented beverages such as mead, beer, and wine predating the smelting of metals. By the 12th century, the ability to isolate alcohol from wine had moved this chemical species from a simple component of alcoholic beverages to both a new medicine and a powerful new solvent. Of course, this also began the long tradition of production of liqueurs and strong spirits for consumption. A general overview of the early history and chemistry of alcohol production and isolation will be presented, as well as some discussion of its early uses in both the chemical arts and medicine.

Contact Dr. Susan Odom for Zoom link.

Affiliation:

Research:

Abstract: Few aspects are as prevalent and important to energy conversion and storage as the dimension control of porous nanomaterial architectures. The study of nanostructure-dependent electrochemical behavior, however, has been broadly limited by access to well-defined nanomaterials with independent control over the pore and wall dimensions. This historic limitation is partially due to reliance upon dynamic self-assembly processes that progress towards equilibrium. We have developed a kinetically controlled micelle approach as a new nanofabrication tool kit.^1-5 Kinetic control is historically difficult to reproduce, a challenge that we have resolved, in part with switchable micelle entrapment^6-7 to yield reproducible and homogeneous nanomaterial series that follow model predictions. This approach enables seamless access from meso-to-macroporous materials with unprecedented ~2 Å precision of tuning, commensurate with the underlying atomic dimensions. This precision and independent control of architectures also opens new opportunities for nano-optimized devices.

Bio: Morgan Stefik obtained a B.E. in Materials Engineering from Cal Poly SLO in 2005 and a Ph.D. in Materials Science from Cornell University in 2010. After postdoctoral research at École Polytechnique Fédérale de Lausanne, he joined the University of South Carolina in 2013 in the Department of ����vlog�ٷ���� and Biochemistry. He was awarded an NSF-CAREER in 2018 and is the founding director of the South Carolina SAXS Collaborative. He was highlighted as a “rising star of materials chemistry” by RSC in 2017, was recognized as a Breakthrough Star by USC in 2018, and was elected to the council of the International Mesostructured Materials Association in 2018. Most recently, he was promoted to Associate Professor with tenure in 2019.