chemistry seminar

Exit Seminar - Plasmon Mediated Single Molecule Fluorescence Enhancement in "Zero Mode Waveguides" (ZMWs)

Date: 
Thursday, June 24, 2021 - 1:00pm to 2:00pm
Location: 
Zoom

Abstract:: Plasmonic nanostructures have been extensively studied for their potential application in numerous fields such as nanophotonics, biosensors, and bioimaging. One of the key properties of nanostructures that can be manipulated for practical applications is their capabilities to modulate the optical and photophysical properties of fluorophores residing nearby. Surface plasmons (SP), which can be defined as the collective oscillation of the delocalized electrons, are the fundamental characteristic of nanostructures that are primarily responsible for altering those properties. Elucidating fluorophores at the single-molecule level has received significant attention since more specific information can be extracted from single molecule-based studies, which otherwise, could be obscured in ensemble studies. However, single-molecule studies are inherently challenging because the signal from a single molecule is usually deem, which makes it difficult to detect. The situation is even worse in the case of a crowded environment due to higher background noise, such as cellular autofluorescences in the case of cell-based studies. Thus, one of the possible ways out of this single-molecule detection problem is to couple the fluorophore with a plasmonic nanostructure which can potentially enhance the fluorescence intensity of the single fluorophore leading to the improvement in signal to noise ratio. Throughout the projects presented here, I studied the fluorescence characteristics of single fluorophore molecules coupled in a plasmonic nano-aperture which is termed as Zero Mode Waveguides (ZMWs). I utilized single fluorophores of different origins, such as organic dyes and quantum dots (QDs), in ZMWs of different metallic compositions. By probing ZMWs made from the mixture of Aluminum and gold, with a range of ATTO dyes emitting across the visible wavelength, we found that the surface plasmon resonance of ZMWs is tunable by optimizing the metal ratio. Apart from the ATTO dyes, I investigated the photoluminescence (PL) behavior of single QDs in ZMWs and observed a significant enhancement in PL intensity and a substantial improvement in the blinking characteristics of the QDs, which are beneficial for the utility of QDs as a bio-imaging agent or a single-photon source. Single QDs in ZMWs exhibited a significant enhancement in biexciton quantum yield, which is crucial for their potential application in lasing where materials with a high optical gain are desired. I also examined the fluorescence properties of the single fluorophores in gold ZMWs in the presence of a gold nanoparticle (AuNP) and observed a more significant enhancement in fluorescence intensity in the gap between AuZMW and AuNP compared to the case of only AuZMW or only AuNP. The experimental design and the resulting findings throughout the three projects presented here should be a valuable resource for the future development of plasmon-mediated single-molecule studies.

Join the seminar at

https://uky.zoom.us/j/88903093777

Plastic Electronics: Simple solutions to their complex problems

Date: 
Friday, April 30, 2021 - 4:00pm to 5:00pm
Location: 
Zoom
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Abstract: Plastic semiconductors incorporated into transistors have shown enormous potential for flexible, printable electronics as well as bioelectronics that communicate with the body. In my talk I will discuss the background and potential applications of these exotic transistors, as well as novel, state-of-the-art materials systems I have developed to overcome their intrinsic bottlenecks. I will show how these simple, low-cost solutions to organic transistor problems work towards the realization of a broad suite of organic electronic technologies.

Converting Captured CO2 Directly into Fuels

Date: 
Wednesday, April 28, 2021 - 4:00pm to 5:00pm
Location: 
Zoom
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Bio: Curtis P. Berlinguette is a Professor of Chemistry and Chemical & Biological Engineering at the University of British Columbia. He is also a CIFAR Program Co-Director and a Principal Investigator at the Stewart Blusson Quantum Matter Institute (SBQMI), and the CEO of Miru Smart Technologies.

Prof. Berlinguette leads a large, interdisciplinary team seeking ways to discover and scale disruptive clean energy materials. His academic group has advanced a range of clean energy applications including CO2 utilization, next-generation solar cells, and self-driving labs. Prof. Berlinguette also likes to work on high-risk, high-impact clean energy projects like cold fusion. He has authored more than 100 scientific articles and 20 patent applications, and has participated in over 190 invited lectures at leading universities and international conferences. Prof. Berlinguette has been recognized with several awards, including an Alfred P. Sloan Research Fellowship and an NSERC E.W.R. Steacie Memorial Fellowship.

Abstract: The electrochemical conversion of CO2 by the CO2 reduction reaction (CO2RR) is a promising strategy that enables renewable energy to be stored in carbon chemicals and fuels using atmospheric or emitted CO2. Pilot-scale electrolyzers utilizing gaseous CO2 feedstocks can mediate high rates of CO2RR, however, this approach relies on several complex and energy-intensive steps required to produce purified, high-pressure CO2 from carbon capture. This presentation will focus on the direct conversion of aqueous carbon capture solutions (i.e., those rich in bicarbonate anions) into useful chemicals (i.e., CO) over extended periods of time. I will show how to design an electrolyzer that converts liquid bicarbonate feedstocks into carbon products at comparable rates and greater efficiencies than reactors relying on pressurized CO2. Our work demonstrates bicarbonate electrolysis as a practical strategy for storing renewable energy in carbon chemicals while bypassing CO2 separation and pressurization processes in upstream CO2 capture.

Development of Genetic Algorithms to Predict Material Structures

Date: 
Friday, April 9, 2021 - 1:00pm to 2:00pm
Location: 
Zoom
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Abstract:

Materials are chemicals that we use every day for tools, tasks, and technology. For most of history, making a material required trial-and-error, synthesizing and testing, a costly endeavor in time and money. With modern computing, not only can the trial-and-error be hastened, but sometimes avoided altogether. The application of a material depends on its properties, which arise from its structure, thus by exploring chemical structure we can predict properties and design materials to suit. One tool to accomplish this is the genetic algorithm (GA), which can build and test chemical structures for a desired property, and then produce new chemical structures through reproduction. Genetic algorithms have been applied to chemistry for 30 years in solving X-ray diffraction patterns, protein folding, and predicting surface structures. Here a GA is applied to solve the structure of Li-Al layered double hydroxide (LDH), given an experimental X-ray diffraction pattern and debate in the literature. The resulting GA can build a wide variety of LDH structures by stacking layers of crystal and molecule together, eventually providing a set of structures that can be used for further quantum mechanical calculations. The GA was then generalized to a wider variety of layered structures, resulting in the development of the Genetic Algorithm for Layered Structures (GALS). GALS is able to generate LDH structures with multiple elements and molecules, structures with different coordinating groups, molecular crystals, and perovskites. Initial results are promising, with testing under a small number of generations showing significant improvements in fitness, and room for generalization down the road.

Reaction Profiling in Unlimited Detail: Applications of Online HPLC

Date: 
Friday, April 16, 2021 - 4:00pm to 5:00pm
Location: 
Zoom
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Abstract: Process analytical technology (PAT) plays an essential role in understanding and optimization chemical manufacturing routes by furnishing data-dense reaction profiles. However, each PAT tool presents certain limitations with respect to chemical component resolution, reaction compatibility or useful operational domain. High-pressure liquid chromatography (HPLC) represents one of the most versatile analytical tools available for providing detailed reaction progress analysis. Yet this technology introduces a new set of challenges relating to sample acquisition and preparation, especially when trying to utilize HPLC as a real time analytical technology.

Our lab has developed a comprehensive set of automated tools, which allow nearly any chemical process to be visualized in real time by HPLC. This includes reactions performed under inert atmosphere, systems with heterogenous reagents, and complex competition reactions with many components. The combination of excellent resolving power of UHPLC, coupled to the high dynamic range of standard UV/Vis and MSD detectors has allowed this tool to be broadly deployed. This has allowed complex reactions to be visualized in exceptional details with unprecedented ease. This presentation will discuss several case studies to demonstrate the flexibility and fidelity of this new online HPLC technology. Examples will include studying reaction mechanisms, measuring crystallization processes and deployment as an in-process control for reaction automation.

Machine learning properties of solid-state materials: Considerations for interpretability, reliability, and data-efficiency.

Date: 
Friday, April 9, 2021 - 4:00pm to 5:00pm
Location: 
Zoom
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Abstract: Advances in machine learning (ML) are making a large impact in many disciplines, including materials and computational chemistry. A particularly exciting application of ML is the prediction of quantum mechanical (QM) properties (e.g., formation energy, bandgap, etc.) using only the structure as input. Assuming sufficient accuracies in the ML models, these methods enable screening of a considerably large chemical space at orders of magnitude lower computational cost than available QM methods. Despite the promise of ML in chemistry, several key challenges remain in both applying and interpreting the results of ML algorithms. Here, we will discuss our efforts in addressing these issues, including our recent work on opening the black box of ML methods by identifying the domain of applicability, i.e., where a given model is reliable.

Bio: Chris Sutton is an Assistant Professor in the Department of Chemistry & Biochemistry at the University of South Carolina. Chris received his PhD at the Georgia Institute of Technology under the direction of Professor Jean-Luc Bredas, and then moved to Duke University for postdoctoral research with Professor Weitao Yang. Chris received the Alexander von Humboldt postdoctoral fellowship to work in the Theory Department at the Fritz Haber Institute in Berlin, Germany where Matthias Scheffler was the Director. Chris’ current research is focused on computational materials discovery through a combination of   electronic structure calculations, machine learning, and stochastic sampling techniques to speed up the traditional computational design of materials.

Functional Polymers for Electronics

Date: 
Friday, April 2, 2021 - 4:00pm to 5:00pm
Location: 
Zoom
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Michael Chabinyc

Materials Department

University of California Santa Barbara

 

Abstract: Polymers are essential for wearable electronic systems as active and passive materials.  We will discuss the role of molecular structure on the behavior of semiconducting polymers and dielectric elastomers. In both cases, the molecular architecture of polymers controls their ultimate functional behavior. First, we will discuss how relatively small changes in the design of the sidechains of semiconducting polymers can be used to modify donor-acceptor interactions with molecular dopants. These subtle changes control whether charge transfer is complete leading to an electrically conductive state, or partial leading to a poorly conducting charge-transfer state.  Second, we will discuss how polymers with a bottlebrush architecture can be used to form super-soft elastomers useful for pressure sensors. The low mechanical modulus of bottlebrush elastomers, which is comparable to that of hydrogels, allows for the simple formation of capacitive pressure sensors with sensitivity comparable to human touch. Recent results on 3D printing of super-soft materials will also be described.

 

 

Biography: Professor Michael Chabinyc is Chair of the Materials Department at the University of California Santa Barbara. He received his Ph.D. in chemistry from Stanford University and was an NIH postdoctoral fellow at Harvard University. He was a Member of Research Staff at (Xerox) PARC prior to joining UCSB in 2008. His research group studies fundamental properties of organic semiconducting materials and thin film inorganic semiconductors with a focus on materials useful for energy conversion. He has authored more than 200 papers across a range of topics and is inventor on more than 40 patents in the area of thin film electronics.  He is a fellow of the Materials Research Society (MRS), the American Physical Society (APS), the National Academy of Inventors (NAI), and the American Association for the Advancement of Science (AAAS).

Supramolecular Influences on Luminescence: From Coordination Complexes to Porous Solids

Date: 
Friday, February 26, 2021 - 3:00pm to 4:00pm
Location: 
Zoom
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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 Chemistry, 2011, 3, 246.
  3. B. Balónová, D.  Rota Martir, E.R. Clark, H.J. Shepherd, E. Zysman-Colman, B.A. Blight, Inorganic Chemistry, 2018, 57, 8581.
  4. B. Balónová, H.J.  Shepherd, C.J. Serpell, B.A. Blight, Supramolecular Chemistry, 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.2017139, 6253.
  6. S.J. Thomas, B. Balónová, J. Cinatl M.N. Wass, C.J. Serpell, B.A. Blight, M. Michaelis, ChemMedChem202015(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


 

Using Electricity to Efficiently Drive the Synthesis of Chemicals and Materials

Date: 
Friday, March 26, 2021 - 4:00pm to 5:00pm
Location: 
Zoom

Joel Rosenthal


Department of Chemistry and Biochemistry,

University of Delaware, Newark, DE, 19716

 

Abstract: Development of new electrosynthetic tools and methods has attracted much interest
in recent years as a means to prepare chemicals and materials that are either
inaccessible or whose preparation is inefficient using traditional thermal chemistries. In
addition to opening up routes to new compounds and materials, implementation of
electrosynthetic strategies can enable reduced waste streams and more streamlined
synthetic routes, while circumventing the use of expensive, acutely toxic, and highly
reactive reagents. Driving synthetic chemistry with electric current as opposed to heat
also represents a direct way to power chemical processes using renewable energy (such
as electricity from wind or sunlight), and therefore provides an opportunity for more
sustainable chemical syntheses and renewable energy storage.
Our lab has developed efficient electrosynthetic routes to prepare commodity
chemicals and fuels, fine chemicals, and new inorganic materials. In this presentation, we
will provide an overview of our efforts in each of these areas, which include 1) controlling
the electrochemical reduction of carbon dioxide to switch between the formation of either
formic acid or carbon monoxide depending on the electrolysis conditions; 2) the
electrosynthesis of α,β-ynones en route to polyphenols that show anti-cancer and anti-
HIV activity; and 3) the electrochemical synthesis of new classes of metal-organic
frameworks and other porous materials that are based upon non-traditional metal ions
and organic linkers. Throughout the presentation, we will show how the ability to drive
challenging transformations that require the activation of strong bonds or access to highly
reactive chemical intermediates is greatly facilitated through an electrochemical
approach. We will also demonstrate how controlling the chemical dynamics and
environments at working electrode interfaces can be leveraged to promote interesting
energy conversion processes, solar fuel generation, and porous material construction.
Implications for the future development of efficient electrosynthetic strategies and
platforms will also be discussed.

Polymer Electrolytes for Advanced Electrochemical Devices

Date: 
Friday, November 6, 2020 - 4:00pm to 5:00pm
Location: 
Zoom
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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 Chemistry 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. 

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