Calendar

Feb
3
Wed
Spring 2021 Seminar Series: Daniel Grave @ Online
Feb 3 @ 2:30 pm – 3:30 pm

Daniel Grave

Ben University of the Negev

Host:  Patty McGuiggan

Photoelectrochemical solar fuel production is a promising route for converting solar energy into clean, renewable fuel such as hydrogen. The greatest challenge towards efficient solar fuel production is in the design of photoelectrode materials that harvest light and drive electrochemical processes. Metal-oxides are particularly suitable as photoelectrode materials due to their abundance, low cost, and stability in aqueous solution – requirements that traditional semiconductors do not meet. Despite much progress, a path forward towards designing devices with high efficiency has remained elusive, partly due to electron-electron and electron-lattice interactions in these materials, which introduce deviation from conventional semiconductor behavior.
In this talk, I will demonstrate how we use epitaxial thin films as model systems to study the effect of light-matter interaction on photoelectrochemical behavior in complex metal-oxides. We combine these observations with time-resolved spectroscopy to show that excitation-wavelength-dependent charge carrier localization is an overlooked, yet fundamental limitation for achieving high efficiencies in several metal-oxide materials. We then develop a new method to quantify the spectral profile of the mobile charge carrier photogeneration yield in any thin film photoelectrode material and provide a path forward towards improved devices for solar energy conversion and storage.

 

Zoom Seminar Info:

Meeting ID: 982 0915 3548

Passcode:  621450

Feb
10
Wed
Spring 2021 Seminar Series: Ana-Nicoleta Bondar @ Online
Feb 10 @ 2:30 pm – 3:30 pm

Ana-Nicoleta Bondar

Freie Universität Berlin

Host:  Kalina Hristova

 

Structural plasticity required for protein function is largely governed by dynamic hydrogen(H)-bonds and H-bond networks, and H-bond interactions are often central to formulating hypotheses about the reaction mechanism of the protein. G Protein Coupled Receptors (GPCRs) and the spike protein S of SARS-CoV-2 are prominent examples of proteins for which H-bonding plays a major role for the structural dynamics along the reaction path, including for interactions with other proteins.

To characterize the role of H-bonds and H-bond networks in GPCRs and spike protein, and in other large bio-systems, we have developed graph-based algorithms that allow us to derive two-dimensional representations of H-bond networks of the protein. Once computed, the two-dimensional H-bond graph can be queried to characterize the dynamics of the protein and protein-water H-bonding, and centrality measures enable groups of the protein to be ranked according to their relative importance for connectivity within the graph. From computations of conserved H-bond graphs we catalogue internal H-bond networks of sets of protein structures.

During my talk I will present the graph-based algorithms we developed, and applications from recent work on the conformational dynamics of GPCRs and of the SARS-CoV-2 protein S.

Research was supported in part by funding from the Excellence Initiative via the Freie Universität Berlin, the German Research Foundation (DFG) Collaborative Research Center SFB 1078 Project C4, and computing resources from the North German Supercomputing Center, HLRN.

 

Zoom Seminar Info:

Meeting ID: 982 0915 3548

Passcode:  621450

 

Feb
17
Wed
Spring 2021 Seminar Series: Amy Clarke @ Online
Feb 17 @ 2:30 pm – 3:30 pm

Amy Clarke

Colorado School of Mines

Host:  Tim Weihs

Structure, processing, property, and performance relationships are the cornerstone of materials science and engineering. Yet, we are often left to infer what critical microstructural characteristic(s) and/or defect(s) in metallic alloys result in performance degradation and the failure of parts. Today, state-of-the-art characterization techniques available in the laboratory and at national user facilities are enabling unprecedented, real-time studies of metallic alloys during processing, deformation, and simulated service and manufacturing. The use of x-rays, protons, and electrons to study multiscale solidification dynamics in metallic alloys relevant to processes like casting and additive manufacturing are highlighted. Experimental results such as these, along with complementary ex-situ characterization, are used to inform, develop, and validate computational models. The new knowledge gained by in-situ/ex-situ characterization will aid in the prediction and control of metallic alloy microstructures and properties by design with advanced manufacturing.

 

Zoom Seminar Info:

Meeting ID: 982 0915 3548

Passcode:  621450

Feb
24
Wed
Spring 2021 Seminar Series: Christopher Murray @ Online
Feb 24 @ 2:30 pm – 3:30 pm

Christopher Murray

University of Pennsylvania

Host:  Shoji Hall

 

The synthesis of monodisperse colloidal nanocrystals (NCs) with controlled composition, size, and shape provides ideal building blocks for the assembly of new thin films and devices. These monodisperse colloidal NCs act as “artificial atoms” with tunable electronic, optical, magnetic properties that are allowing the development of a new periodic table for design at the Mesoscale.  In this talk, I will briefly outline the current state of the art in synthesis, purification, and integration of single-phase NCs and core-shell (heterostructures) NCs emphasizing the design of semiconductor building blocks with tunable shapes (spheres, roads, cubes, discs, octahedra, etc. I will then share how these tailored NCs can be directed to assemble into single-component, binary, ternary NC superlattices providing a scalable route to the production of multifunctional thin films. The modular assembly of these NCs allows the desirable features of the underlying quantum phenomena to be enhanced even as the interactions between the NCs allow new delocalized properties to emerge.   Synergies in the electronic and optical coupling between NCs will be emphasized as we pushing toward the realization of artificial solids with a new 3D and structure and high mobilities (>30 cm2V-1S-1) device integration. I will share specific case studies in thin-film transistors, thermoelectric materials, and solution-processable photovoltaic devices build with these strongly coupled nanocrystal solids highlighting the recent developments in wafer-scale NC superlattice deposition and patterning may provide a path to scalable fabrication.   I will also share progress in microfluidic superparticle assembly approaches.  Creating mesoscale structures that span 100s of nanometer to 10s of microns as the next scale of building units.

 

Zoom Seminar Info:

Meeting ID: 982 0915 3548

Passcode:  621450

Mar
3
Wed
Spring 2021 Seminar Series: Valentino Cooper @ Online
Mar 3 @ 2:30 pm – 3:30 pm

Valentino Cooper

Oak Ridge National Laboratory

Host:  Michael Falk

 

High entropy, multi-component metal alloys (HEA), have superior mechanical properties and high radiation tolerances; which are, in part, driven by configurational entropy. Recently, an oxide analogue comprised of MgO, CoO, NiO, CuO and ZnO was synthesized; exhibiting a truly entropy-stabilized, reversible phase transition from a multiphase material to a single rock salt-ordered phase above 850-900°C. This entropy-driven stabilization may engender many unique properties, such as high melting temperatures, radiation resistance and other anomalous responses. Here, we discuss a design strategy for the prediction of synthesizable disordered oxides. Our effort employs first principles studies of 2-component oxides to develop design rules based on the relationship between pairwise enthalpies of formation, DH, and configurational entropy of the disordered material. A similar chemical identity-to-DH map was previously explored using the class of high entropy alloys, where the stability of multicomponent metal alloys was correlated to the enthalpy of mixing of binary and ternary compounds.

In this presentation, I will focus on our recent efforts to employ this local enthalpy map as an effective strategy for the discovery of new classes of entropy stabilized oxides. In particular, we are able to use our first principles calculations with Monte Carlo simulations in order to build chemical bonding maps to study the local environment preferences that determine whether a material will phase segregate, to form a single phase with clustered regions, or form a disordered solid solution. This enables us to identify compounds that may be synthesizable or could be stabilized by entropy – thus allowing for more reliable materials discovery and design.

 

Zoom Seminar Info:

Meeting ID: 982 0915 3548

Passcode:  621450

Mar
10
Wed
Spring 2021 Seminar Series: Jonthan Rivnay @ Online
Mar 10 @ 2:30 pm – 3:30 pm

Jonthan Rivnay

Northwewestern University

Host: Howard Katz

 

Direct measurement and stimulation of ionic, biomolecular, cellular, and tissue-scale activity is a staple of bioelectronic diagnosis and/or therapy. Bi-directional interfacing can be enhanced by a unique set of properties imparted by organic electronic materials. These materials, based on conjugated polymers, can be adapted for use in biological settings and show significant molecular-level interaction with their local environment, readily swell, and provide soft, seamless mechanical matching with tissue. At the same time, their swelling and mixed conduction allows for enhanced ionic-electronic coupling for transduction of biosignals. These properties serve to enable new capabilities in bioelectronics. In the first part of my talk I will focus on the design of polymer bioelectronic materials for enhanced electrophysiological sensors based on electrochemical transistors. Synthetic design and processing can yield high performance mixed conductors with large volumetric capacitance, high transconductance, and steep subthreshold switching characteristics for low power sensing. Rising areas in stability and circuit integration are highlighted. I will then discuss the unique form factors enabled by polymer electronics, and their applications in regenerative engineering, including the development of biohybrid composites based on water soluble conducting polymers. The developments highlight the role of materials design for addressing critical needs in bio-electronic interfacing.

 

Zoom Seminar Info:

Meeting ID: 982 0915 3548

Passcode:  621450

Mar
17
Wed
Spring 2021 Seminar Series: Xiaoming He @ Online
Mar 17 @ 2:30 pm – 3:30 pm

Xiaoming He

University of Maryland

Host:  Hai-Quan Mao

 

Over the past decades, tremendous advances have been made in discovering new therapeutic agents for medicine, from the traditional small molecules to peptides/proteins, genetic materials, and more recently cells and tissues. However, the challenge to safely and effectively deliver these agents from their procurement to the clinical use in human body is still enormous. The issues range from poor bioavailability, systemic toxicity, and low specificity for the acellular agents, to poor survival after long-term storage, non-physiological cultivation in vitro, and immune rejection in vivo for cell-based medicine. We have been working on addressing these issues facing today’s medicine using a bioinspired multiscale biomaterials engineering approach. In this talk, I will show our recent data on developing novel bioinspired multiscale biomaterials systems to engineer acellular therapeutics, normal and cancer stem cells, and immune cells for treating ischemic diseases, modulating immune reactions, and combating cancer.

 

Zoom Seminar Info:

Meeting ID: 982 0915 3548

Passcode:  621450

Mar
31
Wed
Spring 2021 Seminar Series: Myriam Cotten @ Online
Mar 31 @ 2:30 pm – 3:30 pm

Myriam Cotten

College of William & Mary

Host: Kalina Hristova

 

Host-defense peptides play a crucial role in preventing and fighting infections and inflammation. Beyond their ability to directly eradicate pathogens by permeabilizing their membranes or targeting intracellular processes, they can also perform immunomodulatory functions that include immune cell chemotaxis and trained innate immunity. Piscidins, which were the first host defense peptides discovered in the mast cells of animals, exhibit antibacterial, antiviral, antifungal, anticancer, anti-inflammatory, anti-endotoxin, and anesthetic properties. Our research investigates piscidins in terms of their molecular targets and mechanisms of action. Employing biochemical and biophysical tools, such as high-resolution solid-state NMR, neutron diffraction, oriented circular dichroism, permeabilization assays, biological-activity testing, and confocal microscopy, we map at the molecular level the landscape of intrinsic structural features and environmental conditions that confer to a single peptide family a multiplicity of functions in support of host defense. Our most recent work explores the triangle of interactions that exist between piscidins, redox ions, and bioactive lipids. Principles learned from these studies could help design novel therapeutics to treat drug-resistant infections and immune-related diseases.

 

Zoom Seminar Info:

Meeting ID: 982 0915 3548

Passcode:  621450

Apr
28
Wed
Spring 2021 Seminar Series: Jeff Klauda @ Online
Apr 28 @ 2:30 pm – 3:30 pm

Jeff Klauda

University of Maryland

Host:  Kalina Hristova

 

The interaction profile within and between molecules determines the physical properties observed in experimental bulk measurements. The interaction surface leading to attraction and repulsion forces is the cause for instantaneous motion of molecules. One focus of research in my lab is improving and parameterizing the mathematical description of molecular interaction, known as the force field (FF). I will present our work in improving the lipid FF and new algorithms to systematically develop accurate parameters. Accurate lipid FFs allow for accurate modeling of cellular membranes. This talk will give an example of applying simulations to probe the complex structure and dynamics of the outer layer of the skin (stratum corneum). Although lipids in a lipid bilayer serve as a barrier for cells and their organelles, proteins that reside in the membrane are key to various diseases and virial infection. For the last year, my lab has been involved in studies of SARS-CoV-2 and its spike protein and two accessory proteins (ORF7a and ORF7b). I will briefly discuss our work on the spike protein and its ability to evade antibodies but focus on ORF7a and ORF7b. Prior studies have demonstrated that these proteins localize to the endoplasmic reticulum-Golgi intermediate compartment (ERGIC). Furthermore, expression of both proteins is correlated with virulence in vivo; for ORF7a, a direct association with host bone marrow stromal antigen 2 (BST-2) suppresses its anti-viral activity, whereas for ORF7b, the ability to form homooligomers is suggested to be a key mechanism by which it can remain ERGIC associated. However, specific, structural models of these homo- and heterooligomeric interfaces are not known, nor are the key protein-protein interfaces for each. We are using multi-scale modeling and collaborating with Dr. Bryan Berger’s lab at the University of Virginia to probe ORF7a/BST-2 dimeriztaion and the ORF7b homodimerization. Our goal is to better understand the dimerization of these proteins and their function, but ultimately develop a SARS-CoV-2 therapeutic that inhibits protein dimerization and function.

 

Zoom Seminar Info:

Meeting ID: 982 0915 3548

Passcode:  621450

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