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  1. CSI Q Seminar

    "Quantum Non-Demolition Measurement of a Transmon and Minimal Parameters in a VQE Ansatz"

    Presented by Bryan Gard, Virginia Tech

    Wednesday, May 13, 2020, 12:30 pm
    https: //bluejeans. com/15483 7752/4702?src=calend

    Hosted by: Adolfy Hoisie

    This talk will focus primarily on two areas of recent research. One area is the study of a circuit in which the qubit-cavity and the cavity-feedline coupling can be turned on and off, which helps to isolate the qubit. Too, by carefully choosing the detuning and interaction time, a recurrence in the qubit-cavity dynamics can be exploited in a way that makes it possible to perform very fast, high-fidelity, QND measurements. Here, the qubit measurement is performed in a step-by-step process, where the qubit and cavity interact in a time-dependent manner and the cavity state can be amplified, squeezed, and released for measurement. Second, one of the most promising applications of noisy intermediate-scale quantum computers involves simulating molecular Hamiltonians using the variational quantum eigensolver. Dr. Gard will discuss that encoding symmetries of the simulated Hamiltonian in the VQE ansatz reduces both classical and quantum resources compared to other widely available ansatze. Through simulations of a two hydrogen chain molecule, these improvements can be verified to persist in the presence of noise. This simulation is performed with IBM software using noise models from real devices and on public IBMQ hardware. Dr. Gard also will demonstrate how these techniques can be engaged to find molecular excited states of various symmetries using a noisy processor. BJ info: https: //bluejeans. com/15483 7752/4702?src=calendarLink Meeting ID: 154 837 752 Participant Passcode: 4702 Phone Dial-in +1.888.240.2560 (US Toll Free) +1.408.317.9253 (US Primary

  2. Chemistry Department Colloquium

    "Redox Hopping Water Oxidation Catalysis by Metal Organic Frameworks"

    Presented by Amanda Morris, Virginia Tech, Dept. of Chemistry

    Monday, March 9, 2020, 11 am
    Hamilton Seminar Room, Bldg. 555

    Hosted by: Gerald Manbeck

    Metal organic frameworks (MOFs) are supramolecular architectures comprised of metal nodes connected by multi-dentate organic/inorganic linkers. Incorporation of molecular chromophores into these solid-state structures has been exploited to develop luminescent sensors, light emitting diodes, photovoltaics, and photo/electro-catalysts. In terms of catalysis, the high surface area of MOFs can be exploited to produce a higher catalytic rate per geometric area than those realized by other approaches. The crux of catalysis, however, is diffusion. The Morris group has explored the diffusion of electrons and ions through MOFs as a function of applied electric field. The results indicate that under most cases, as expected, ion motion is restricted through the 3D MOF networks. The effect of ion size and electronic self-exchange rates will be presented. Additionally, the effect of 3D MOF structure and pore size will be discussed. We will conclude with a discussion of the implications for electrocatalytic water oxidation with respect to catalytic rate and turnovers.

  3. Environmental & Climate Sciences Department Seminar

    "Dilution impacts on smoke aerosol aging and photochemistry: Evidence in BBOP data"

    Presented by Jeffrey Pierce, Colorado State University

    Thursday, January 9, 2020, 11 am
    John Dunn Seminar Room, Bldg. 463

    Hosted by: Art Sedlacek

    Smoke aerosol properties and ozone evolve within plumes through physical and chemical processes, impacting smoke climate and health impacts. Many of these physical and chemical processes, in theory, depend strongly on smoke concentrations. Hence, the initial concentrations and dilution rates should affect smoke aging. In general, plumes from small fires should dilute more rapidly than those from large fires, all else equal; and in recent publications, we have used theory to demonstrate the smoke properties from small fires should evolve differently than those from large fires. However, until recently, we have been unable to test these findings with measurements due to a lack of Langrangian-style smoke aging field studies of small fires (due to the challenge of following small, fast-diluting plumes with time). In this talk, I will discuss how we have used observations of concentration gradients in large plumes from the Pacific Northwest portion of BBOP campaign to test these hypotheses. Using the high time resolution BBOP measurements, we have separated the dilute edges of the large plumes from the concentrated cores. We expect that the dilute edges of large plumes have similar chemical and physical process rates as small, fast-diluting plumes. The BBOP data show that the dilute portions of plumes (1) have faster number losses and diameter growth from coagulation, (2) transition more quickly POA-like to SOA-like aerosol composition potentially through faster OA evaporation and faster photochemistry, and (3) have higher enhancements of ozone. We recommend that future smoke studies compare concentrate plume cores to dilute edges to help elucidate physical/chemical processes and understand inter-plume differences.

  4. Chemistry Department Colloquium

    "Design of high voltage all-solid-state batteries based on sulfide electrolytes"

    Presented by Xin Li, John A. Paulson School of Engineering and Applied Sciences, Harvard University

    Tuesday, January 7, 2020, 2 pm
    Hamilton Seminar Room, Bldg. 555

    Hosted by: Enyuan Hu

    Ceramic sulfide solid-electrolytes are amongst the most promising materials for enabling solid-state lithium ion batteries. The ionic conductivities can meet or exceed liquid-electrolytes for such ceramic sulfides, however, there is a theoretical concern about the narrow electrochemical stability window of approximately 1.7-2.1 V vs lithium metal. In addition, ceramic sulfides are frequently plagued by interfacial reactions when combined with common electrode active materials. In this talk, methods for the stabilization of both the bulk electrochemical decompositions and the interfacial reactions will be discussed. Ceramic sulfides are known to substantially swell during electrochemical decay. Such swelling has been shown to provide viable means by which to stabilize electrochemical decomposition in lithium ion batteries. Experimental evidence and theoretical understanding of stability window expansion as the result of mechanical constriction will be discussed. An advanced mechanical constriction technique is applied on all-solid-state batteries constructed with Li10GeP2S12 (LGPS) as the electrolyte and lithium metal as the anode. The decomposition pathway of LGPS at the anode interface is modified by this mechanical constriction and the growth of lithium dendrite is inhibited, leading to excellent rate and cycling performances. On the cathode side, 5V all-solid-state batteries using layered LiCoO2 and spinel as cathodes will be presented and the stabilization mechanisms will be discussed. A combination of electrochemical battery tests, SEM, XAS, XPS and XRD characterizations, and DFT simulations was used. Biosketch Xin Li is an associate professor of materials science at School of Engineering and Applied Sciences (SEAS) at Harvard University, who was an assistant professor at SEAS from 2015 to 2019. Xin Li's research group designs new energy storage materials through advanced characterizations and simulations, with the current focus on solid s

  5. Chemistry Department Colloquium

    "Electronic Cooperativity in Supported Single and Multinuclear-Sites for Catalytic C-C and C-H Bond Functionalization"

    Presented by Dr. Massimiliano Delferro, Argonne National Laboratory

    Monday, October 28, 2019, 11 am
    Hamilton Seminar Room, Bldg. 555

    Hosted by: Sanjaya Senanayake

    Systematic study of the interactions between organometallic catalysts and metal oxide support materials is essential for the realization of rational design in heterogeneous catalysis. In this talk, I will describe the stoichiometric and catalytic chemistry of a series of organometallic complex chemisorbed on a variety of metal oxides as a multifaceted probe for stereoelectronic communication between the support and organometallic center. Electrophilic bond activation was explored in the context of stoichiometric hydrogenolysis as well as catalytic hydrogenation, dehydrogenation, and H/D exchange. Strongly acidic modified metal oxides such as sulfated zirconia engender high levels of activity toward electrophilic bond activation of both sp2 and sp3 C–H bonds, including the rapid activation of methane at room temperature; however, the global trend for the supports studied here does not suggest a direct correlation between activity and surface Brønsted acidity, and more complex metal surface interactions are at play.

  6. NSLS-II Friday Lunchtime Seminar

    "Plant-fungal symbiosis and their potential impacts on terrestrial biogeochemistry"

    Presented by Ko-Hsuan (Koko) Chen, University of Florida

    Friday, October 25, 2019, 12 pm
    NSLS-II Bldg. 743 Room 156

    Hosted by: Ignace Jarrige

    Fungi are associated with all lineages of land plants. While plant-fungal symbiosis is common, many of their interactions, ranging from mutualism, commensalism, to parasitism are yet to be determined. As plant-fungal symbiosis are tightly linked to nutrient cycling, different interaction types have substantial impacts on biogeochemistry. Here, we will use two plant-fungal symbiosis examples: 1) Pine and their ectomycorrhizal fungi, and 2) mosses and their associated fungi, to illustrate how considering plant-fungal interaction and biogeochemistry together can further our understanding toward a better understanding of plant-fungal biology.

  7. Center for Functional Nanomaterials Seminar

    "Heterogeneous Chemistry at Liquid/Vapor Interfaces Investigated with Photoelectron Spectroscopy"

    Presented by Hendrik Bluhm, Fritz Haber Institute of the Max Planck Society, Department of Inorganic Chemistry, Faradayweg, Berlin, Germany

    Monday, October 21, 2019, 11 am
    Bldg.735 (CFN) 1st floor conference room

    Hosted by: Ashley Head

    Aqueous solution/vapor interfaces govern important phenomena in the environment and atmosphere, including the uptake and release of trace gases by aerosols and CO2 sequestration by the oceans.[1] A detailed understanding of these processes requires the investigation of liquid/vapor interfaces with chemical sensitivity and interface specificity under ambient conditions, i.e., temperatures above 200 K and water vapour pressures in the millibar to tens of millibar pressure range. This talk will discuss opportunities and challenges for investigations of liquid/vapor interfaces using X-ray photoelectron spectroscopy and describe some recent experiments that have focused on the propensity of certain ions and the role of surfactants at the liquid/vapor interface. [1] O. Björneholm et al., Chem. Rev. 116, 7698 (2016).

  8. Chemistry Department Seminar

    "Advancing Nanomaterials Research with In Situ TEM"

    Presented by Jordan Moering, Protochips, Inc. 3800 Gateway Centre Blvd, Morrisville NC, 27560

    Wednesday, October 9, 2019, 2 pm
    CFN, Bldg 735, Conference Room A

    Hosted by: Fernando Camino

    The advent of in situ thermal and electrical sample control within realistic environments has transformed the Transmission Electron Microscope (TEM) from a simple high-resolution image acquisition tool into a nanoscale materials research and development laboratory. For example, to support the growing need of photovoltaic and quantum materials researchers, the Fusion Select system couples precise pA-level electrical control with a friction-free tilting stage, allowing users to simultaneously characterize samples at high tilt and high temperature. Featuring a user-friendly software interface, a series of FIB-optimized sample supports, and extensive training material, the Fusion Select system is optimized for new users attempting their first in situ electrical or thermal TEM studies For environmental TEM analysis, the Catalysis Package for the Atmosphere System is the first commercial closed-cell system with an integrated mass spectrometer and flexible gas handling system specifically designed for catalyst materials research. Recognized as one of the top ten microscopy innovations of 2019, the Atmosphere system has been designed specifically for electron microscopy by maximizing gas mixing and pressure control while minimizing mechanical vibrations and new user learning curve. This talk will review these and other capabilities as they relate to the aims of the CFN – enabling external users to carry out high-impact nanoscience projects, while enhancing the in-house functional nanomaterial research conducted by staff scientists.

  9. Chemistry Department Colloquium

    "Coupling Molecular Catalysts with Light-Harvesting Surfaces for Solar CO2 Reduction"

    Presented by Gonghu Li, Dept. of Chemistry, University of New Hampshire

    Monday, October 7, 2019, 11 am
    Hamilton Seminar Room, Bldg. 555

    Hosted by: David Grills and Anatoly Frenkel

    There is a critical need for robust photosynthetic systems that can achieve efficient solar fuel production by CO2 reduction or water splitting. We combine highly efficient molecular catalysts with light-harvesting solid surfaces for use in solar CO2 reduction. In particular, coordination complexes of rhenium and cobalt have been coupled with mesoporous SiO2, TiO2, C3N4, and Si nanostructures. A variety of techniques, including infrared and X-ray absorption spectroscopies, were utilized to investigate CO2-reduction catalysis in these hybrid systems. Appropriate covalent linkages and catalyst/surface interactions were found to be important in promoting selective CO2 reduction.

  10. Chemistry Department Seminar

    ""Probing the Excited-State Reactivity of Transition-Metal Compounds Using Photophysics""

    Presented by Dr. Daniela M. Arias-Rotondo, Department of Chemistry

    Monday, September 23, 2019, 10 am
    Hamilton Seminar Room, Bldg. 555

    Hosted by: Matt Bird

    Transition metal compounds are ubiquitous throughout the chemical sciences, their presence broadly impacting fields such as organic synthesis and solar energy conversion. This talk illustrates how spectroscopic techniques can be used to understand the intricacies of reactions involving transition metal compounds towards two different applications. The first part of this presentation will focus on the conservation of spin in chemical reactions. Our group has previously shown that spin must be conserved for energy transfer to occur.1 To further our understanding of the effect of spin on other types of reactions, we have combined Ru(II) polypyridyls and Fe(III) oxo/hydroxo-bridged dimers to study how the spin state of the acceptor affects the rate of electron transfer. Through a combination of time-resolved spectroscopy and electrochemical techniques we have shown that excited spin states may be involved in electron transfer, as was predicted by Bominaar and coworkers in their studies involving metalloproteins.2 The second half of this seminar describes the use of energy transfer to activate traditional organometallic catalysts to unlock novel reactivity patterns. In particular, we studied the use of an Ir(III) photosensitizer in combination with a Ni(II) catalyst in the coupling of aryl halides and carboxylic acids.3 Mechanistic studies showed that energy transfer from the photocatalyst to the nickel species promotes the latter to an excited state that can promote a novel C-O bond formation.

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