BNL Home
January 2017
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  1. Center for Functional Nanomaterials Seminar

    10 am, CFN, Bldg. 735, First floor conference room - A

    Hosted by: 'Deyu Lu'

    Abstract: Near-edge x-ray spectroscopies such as x-ray absorption spectra (XAS) and resonant inelastic x-ray scattering (RIXS) are commonly used to elucidate the local electronic and atomic structure of materials. X-rays provide a bulk-sensitive, element-specific probe that is responsive to bonding, coordination, and charge states. The OCEAN code is a tool for calculating near-edge x-ray spectra (absorption, emission, RIXS, and NRIXS). Building upon a density functional theory foundation, OCEAN solves the Bethe-Salpeter equation to describe the electron-hole pair created by x-ray absorption or scattering. This allows us to predict spectra for a wide range of condensed matter systems wherein the molecular structure is the only free parameter. Today's talk will introduce some of the capabilities of the OCEAN code and walk through the steps necessary to create and run your own calculations. As an example we will look at some recent results of absorption and resonant emission at the nitrogen K edge in ammonium nitrate which highlight both vibrational disorder and many-body self-energy effects.

12

  1. Center for Functional Nanomaterials Colloquium

    4 pm, CFN, Bldg 735, 2nd Floor Seminar Room

    Hosted by: ''Matt Sfeir''

    The exceptional electronic properties of carbon nanotubes (CNTs) make them promising candidates for integration into a variety of future technologies. The key technical bottlenecks to progress on this front are mainly materials and chemistry related. How do we get the exact type of CNTs we want? How do we quantify the purity of these materials? How do we organize and place them on substrates? The solutions to these problems can enable a wide range of applications in the electronics industry. In this talk, I will present recent progress in trying to solve these problems. I will also discuss how these results have enabled the fabrication of transparent conducting electrodes (along with their integration in photovoltaic cells and OLEDs), high performance thin-film transistors on both rigid and flexible substrates and progress towards a CNT-based logic technology.

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  1. JAN

    19

    Thursday

    Center for Functional Nanomaterials Seminar

    10 am, CFN, Building 735, 1st floor conference room

    Thursday, January 19, 2017, 10:00 am

    Hosted by: 'Mark Hybertsen'

    First-principles quantum mechanical methods, e.g. density functional theory (DFT) and correlated wavefunction theories, have made possible accurate theoretical description of chemical processes such as chemical bond-breaking and forming, and charge transfer. To be able to describe surface processes on metal and metal oxides at the atomic level is of fundamental and practical interest because such processes give rise to or may affect macroscopic properties such as catalytic activity, chemical adsorption and absorption efficiency, and charge carrier conductivity, to name a few. The thermodynamics and kinetics of surface reconstruction in photocatalytic perovskite oxides, SrTiO3 and BaTiO3, are explored through DFT, and their implications for catalysis will be discussed. Secondly, the feasibility of light-driven catalysis on plasmonic metal nanoparticles (e.g., Au and Cu) will be presented. We studied the excited-state energetics of select heterogeneously catalyzed chemical reactions via the embedded correlated wavefunction method (e.g., multiconfigurational second order perturbation theory embedded in a density-functional-derived embedding potential). We evaluate if these excited-state reaction pathways are accessible via plasmon resonance and decay. N2 dissociation on Fe-doped Au(111) surface and CH4 activation on Ru-doped Cu(111) will be presented as examples.

  2. JAN

    19

    Thursday

    Center for Functional Nanomaterials Seminar

    2 pm, CFN, Bldg 735, Conference Room A, 1st Floor

    Thursday, January 19, 2017, 2:00 pm

    Hosted by: ''Oleg Gang''

    Nanoparticles (NPs) have been used to inhibit or modulate the peptide fibrillation as a potential therapeutic strategy and to understand the molecular mechanisms of amyloid diseases. Particularly, gold nanoparticles (AuNPs) have been widely used to study peptide/inorganic NP interactions due to the tunable size, surface and plamonic properties. In this talk, I will present the study of interaction of AuNPs with islet amyloid polypeptide (IAPP), which features in type 2 diabetes pathogenesis by self-assembly into fibrils and peptide-induced disruption of cell membranes. Amyloid fibrils share a distinct β-sheet structure, with the structural diversity controlled by the amino acid sequence. To elucidate the key mechanisms of amyloid self-assembly and provide unique viewpoints on the interactions with NPs, polymorphic fibril structures will firstly be discussed using amyloidogenic peptides that are designed based on the IAPP sequence. The observed amyloid fibrillation and hydrogelation controlled by the peptide structure also led to a proposed relationship between amyloid structure and self-assembly behaviour. Next, I will present the systematic study of IAPP/AuNP interactions, in which the strong binding is initiated by the metal-binding sequence in the hydrophilic peptide domain. Structural transition accelerated in a NP size-dependent manner also implies a facet-dependent IAPP/AuNP interaction. Based on these findings, liquid cell transmission electron microscopy was used for direct visualisation of the dynamic growth of AuNPs in presence of IAPP fibrils. The results show growth of branch(star)-shaped AuNPs in the presence of IAPP fibrils, suggesting a preferred nucleation site for Au binding and subsequent growth on the amyloid template.

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  1. JAN

    19

    Thursday

    Center for Functional Nanomaterials Seminar

    "Modeling Surface Phenomena via First-Principles Quantum Mechanics"

    Presented by John Mark P. Martirez, Princeton University

    10 am, CFN, Building 735, 1st floor conference room

    Thursday, January 19, 2017, 10:00 am

    Hosted by: 'Mark Hybertsen'

    First-principles quantum mechanical methods, e.g. density functional theory (DFT) and correlated wavefunction theories, have made possible accurate theoretical description of chemical processes such as chemical bond-breaking and forming, and charge transfer. To be able to describe surface processes on metal and metal oxides at the atomic level is of fundamental and practical interest because such processes give rise to or may affect macroscopic properties such as catalytic activity, chemical adsorption and absorption efficiency, and charge carrier conductivity, to name a few. The thermodynamics and kinetics of surface reconstruction in photocatalytic perovskite oxides, SrTiO3 and BaTiO3, are explored through DFT, and their implications for catalysis will be discussed. Secondly, the feasibility of light-driven catalysis on plasmonic metal nanoparticles (e.g., Au and Cu) will be presented. We studied the excited-state energetics of select heterogeneously catalyzed chemical reactions via the embedded correlated wavefunction method (e.g., multiconfigurational second order perturbation theory embedded in a density-functional-derived embedding potential). We evaluate if these excited-state reaction pathways are accessible via plasmon resonance and decay. N2 dissociation on Fe-doped Au(111) surface and CH4 activation on Ru-doped Cu(111) will be presented as examples.

  2. JAN

    19

    Thursday

    Center for Functional Nanomaterials Seminar

    "Amyloid Self-Assembly and Sequence-Dependent Interactions with Plasmonic Nanoparticles"

    Presented by Shih-Ting (Christine) Wang, Imperial College London, United Kingdom

    2 pm, CFN, Bldg 735, Conference Room A, 1st Floor

    Thursday, January 19, 2017, 2:00 pm

    Hosted by: ''Oleg Gang''

    Nanoparticles (NPs) have been used to inhibit or modulate the peptide fibrillation as a potential therapeutic strategy and to understand the molecular mechanisms of amyloid diseases. Particularly, gold nanoparticles (AuNPs) have been widely used to study peptide/inorganic NP interactions due to the tunable size, surface and plamonic properties. In this talk, I will present the study of interaction of AuNPs with islet amyloid polypeptide (IAPP), which features in type 2 diabetes pathogenesis by self-assembly into fibrils and peptide-induced disruption of cell membranes. Amyloid fibrils share a distinct β-sheet structure, with the structural diversity controlled by the amino acid sequence. To elucidate the key mechanisms of amyloid self-assembly and provide unique viewpoints on the interactions with NPs, polymorphic fibril structures will firstly be discussed using amyloidogenic peptides that are designed based on the IAPP sequence. The observed amyloid fibrillation and hydrogelation controlled by the peptide structure also led to a proposed relationship between amyloid structure and self-assembly behaviour. Next, I will present the systematic study of IAPP/AuNP interactions, in which the strong binding is initiated by the metal-binding sequence in the hydrophilic peptide domain. Structural transition accelerated in a NP size-dependent manner also implies a facet-dependent IAPP/AuNP interaction. Based on these findings, liquid cell transmission electron microscopy was used for direct visualisation of the dynamic growth of AuNPs in presence of IAPP fibrils. The results show growth of branch(star)-shaped AuNPs in the presence of IAPP fibrils, suggesting a preferred nucleation site for Au binding and subsequent growth on the amyloid template.

  3. FEB

    2

    Thursday

    Center for Functional Nanomaterials Colloquium

    "Structure and reactivity of anatase TiO2 surfaces and interfaces from first principles simulations"

    Presented by Annabella Selloni, Princeton University

    4 pm, CFN, Bldg 735, 2nd Floor Seminar Room

    Thursday, February 2, 2017, 4:00 pm

    Hosted by: 'Deyu Lu'

    Anatase is the form of TiO2 that is most widely used in photocatalysis and solar energy conversion. Anatase is also more active than rutile for most photocatalytic reactions, which has been attributed to various reasons such as the longer charge-carrier lifetime, the higher charge-carrier mobility, and the higher production of reactive OH radicals. In this talk I shall present recent applications of first principles electronic structure calculations and molecular dynamics simulations to study the structure and chemistry of anatase surfaces, with focus on their interactions with water and molecular oxygen, the influence of charge carriers on the reactivity, and the different behaviors of anatase and rutile.