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  1. CFN Colloquium

    "Atomic layer level tunneling experiments on the pairing symmetry of cuprates and Fe-based superconductors"

    Presented by Qi-Kun XUE, Tsinghua University

    Thursday, August 6, 2020, 9 am

    Hosted by: Jurek Sadowski

    We investigate the pairing mechanism of high Tc superconductivity with atomic-layer resolution in cuprates and iron-pnictides by using state-of-the-art molecular beam epitaxy (MBE)-scanning tunneling microscopy (STM) and exfoliation technique. With these techniques, we are able to investigate the gap structure and pairing symmetry of superconducting copper oxides and FeSe planes directly by STM, as well as Josephson tunneling down to few layers in junction structures. We show that the pairing symmetry in both systems is isotropic or contains significant isotropic component. Bio: Qi-Kun Xue received his BSc in Shandong University in 1984, and PhD degree in condensed matter physics from Institute of Physics, the Chinese Academy of Sciences (CAS) in 1994. From 1994 to 1999, he worked as a Research Associate at IMR, Tohoku University, Japan and a visiting Assistant Professor at Department of Physics, North Carolina State University, USA. He became a professor at Institute of Physics, CAS in 1999. He was elected into The Chinese Academy of Sciences in 2005. Since 2005, he has been a distinguished professor at Department of Physics, Tsinghua University. From 2010 to 2013, he was the Chair of Department of Physics and the Dean of School of Sciences. He has been the Vice President for Research of Tsinghua University since 2013 and the Director of Beijing Academy of Quantum Information Sciences since 2017. He was elected as a Fellow of American Physical Society in 2016. He won the TWAS Prize in Physics in 2010, the Future Science Prize for Physical Sciences in 2016, State Natural Science Award (the First Prize) in 2018 and The Fritz London Memorial Prize in 2020. His research interests include scanning tunneling microcopy/spectroscopy, molecular beam epitaxy, low-dimensional and interface-related superconductivity, topological insulators, and quantum size effects in various low-dimensional structures. He has authored/coauthored ~500 papers and presented 180 invited/keynote/plenary talks at international meetings/conferences. Currently, he is the Associate Editors-in-Chief of National Science Review, the Editors-in-Chief of Surface Review & Letters, and on the Editorial Board of Applied Physics Letters, Journal of Applied Physics, AIP Advances, Surface Science Reports and Nano Letters.

  2. CFN Colloquium (Virtual)

    "Using Machine-Learning to Enable Autonomous X-ray Scattering"

    Presented by Dr. Kevin Yager, Brookhaven National Lab, Center for Functional Nanomaterials

    Thursday, July 2, 2020, 4 pm
    BlueJeans Event - see "more information"

    Hosted by: Deyu Lu

    Autonomous experimentation holds the promise of revolutionizing scientific studies and accelerating materials discovery, through instruments that can explore scientific problems without human intervention. This talk will introduce basic machine-learning concepts, and describe our ongoing development of autonomous experimentation at synchrotron x-ray scattering beamlines. Deep learning (convolutional neural networks) are used to classify x-ray detector images, with performance improving when "physics awareness" is included. To close the autonomous loop, we deploy a general-purpose algorithm that selects high-value experiments to conduct, attempting to minimize both uncertainty and experimental cost. Examples from recent autonomous experiments will be presented, including measuring nanoparticle ordering, combinatorial libraries of block copolymer materials, and realtime photo-thermal processing. *** 1) Web Browser a) *** 2) Laptop paired with room system (Best Experience) a) Dial: or in the room system. b) Go to c) Enter the pairing code displayed on your room system screen into your browser. *** 3) Room System a) Dial: or in the room system. b) Enter Meeting ID: 712959100 and Passcode: 5736 *** 4)Joining via a mobile device? a) Open this link: b) Download the app if you don't have it already. c) Enter event ID : hxuzwcjf *** 5) Phone a) Dial one of the following numbers: +1 (415) 466-7000 (US) b) Enter the participant PIN: 4639035 followed by # to confirm. Joining from outside the US?

  3. CFN Colloquium

    "CANCELED - Using Machine-Learning to Enable Autonomous X-ray Scattering"

    Presented by Kevin Yager, Brookhaven National Laboratory, Center for Functional Nanomaterials

    Thursday, April 23, 2020, 4 pm
    CFN, Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Deyu Lu

    Autonomous experimentation holds the promise of revolutionizing scientific studies and accelerating materials discovery, through instruments that can explore scientific problems without human intervention. This talk will introduce basic machine-learning concepts, and describe our ongoing development of autonomous experimentation at a synchrotron x-ray scattering beamline. Deep learning (convolutional neural networks) are used to classify x-ray detector images, with performance improving when "physics awareness" is included. To close the autonomous loop, we deploy a general-purpose algorithm that selects high-value experiments to conduct, attempting to minimize both uncertainty and experimental cost. Examples from recent autonomous experiments will be presented, including measuring nanoparticle ordering, combinatorial libraries of block copolymer materials, and real-time photo-thermal processing.

  4. CFN Colloquium

    "Tackling CO2 Issues by Chemical Conversion and by Reducing CO2 Emission"

    Presented by Jingguang Chen, Department of Chemical Engineering, Columbia University

    Thursday, March 5, 2020, 4 pm
    CFN, Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Mingzhao Liu

    Emission of CO2, a byproduct from many industrial processes and power plants, has increased with increasing energy demand and growing population. In this talk we will first give a brief summary of CO2 conversion by H2 [1,2], followed by discussing our recent efforts in converting CO2 by light alkanes. Using a combination of kinetic studies, in situ characterization and DFT calculations, we have identified several classes of catalysts that can activate both CO2 and light alkanes [3,4]. We will then discuss how to achieve net-reduction of CO2 using mass and energy balances in thermocatalysis and electrocatalysis [5]. Finally, we will propose reducing CO2 emission by alternative pathways for N2 transformation reactions, which are currently the most CO2-emitting chemical processes [6]. [1] S. Kattel, P. Liu and J.G. Chen, "Tuning Selectivity of CO2 Hydrogenation Reactions at the Metal/Oxide Interface", J. Am. Chem. Soc. 139 (2017) 9739. [2] S. Kattel, P.J. Ramírez, J.G. Chen, J.A. Rodriguez and P. Liu, "Active Sites for CO2 Hydrogenation to Methanol on Cu/ZnO Catalysts", Science, 355 (2017) 1296. [3] B. Yan, S. Yao, S. Kattel, Q. Wu, Z. Xie, E. Gomez, P. Liu, D. Su and J.G. Chen, "Active sites for tandem reactions of CO2 reduction and ethane dehydrogenation", PNAS, 115 (2018) 8278. [4] E. Gomez, S. Kattel, B. Yan, S. Yao, P. Liu and J.G. Chen, "Combining CO2 Reduction with Propane Oxidative Dehydrogenation over Bimetallic Catalysts", Nature Commun. 9 (2018) 1398. [5] B.M. Tackett, E. Gomez and J.G. Chen, "Net reduction of CO2 via its thermocatalytic and electrocatalytic transformation reactions in standard and hybrid processes", Nature Catalysis, 2 (2019) 381. [6] J.G. Chen, R.M. Crooks, L.C. Seefeldt, et al. "Beyond Fossil Fuel-Driven Nitrogen Transformations", Science, 360 (2018) 873. Jingguang Chen is the Department Chair and

  5. CFN Colloquium

    "Progress in Trapped Ion Quantum Computing"

    Presented by Prof. Jungsang Kim, Duke University

    Thursday, February 6, 2020, 4 pm
    CFN, Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Chang-Yong Nam

    Trapped ions are one of the leading candidates for realizing practically useful quantum computers. Introduction of advanced integration technologies to this traditional atomic physics research has provided an opportunity to convert a complex atomic physics experiment into a stand-alone programmable quantum computer. In this presentation, I will discuss the new enabling technologies that changes the perception of a trapped ion system as a scalable quantum computer, and the concrete progress made to date in this endeavor. Short Biography: Prof. Jungsang Kim's current research focus is practical realization of quantum computers. He received his B.S. degree from Seoul National University (1992) and his Ph.D. from Stanford University (1999), both in Physics. He worked at Bell Laboratories for five years, working on developing cutting-edge optical and wireless communication systems. He joined the Electrical and Computer Engineering department at Duke University in 2004, where he has worked on trapped ion quantum computing, high pixel-count imaging systems, and novel quantum device research. He has been serving as a principal investigator for many collaborative research projects on quantum computing and communications. In 2015, he co-founded IonQ, focusing on commercial development of ion trap based quantum computer.

  6. CFN Colloquium

    "From Materials to Quantum Devices and Back Again"

    Presented by Giulia Galli, University of Chicago & Argonne National Laboratory

    Thursday, January 16, 2020, 4 pm
    CFN, Bldg 735, 2nd Floor Seminar Room

    Hosted by: Deyu Lu

    We discuss computational strategies to predict materials with desired characteristics for quantum sensing and quantum computations, and the impact that quantum computers may have in revolutionizing materials simulations and hence materials design and innovation.

  7. CFN Colloquium

    "Looking at Silicates Through the Eyes of Surface Science: A Story of Struggle, Incompatibility, Compromise, Hope, ... and Curiosities"

    Presented by Dr. J. Anibal Boscoboinik, Brookhaven National Laboratory, Center for Functional Nanomaterials

    Thursday, December 12, 2019, 4 pm
    CFN, Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Deyu Lu

    Silicates are the most abundant materials in the earth's crust and are tremendously important in numerous applications. In catalysis, for example, they can be used as supports for active species, or as catalysts themselves in the case of their crystalline nanoporous Al-doped versions (a.k.a.: zeolites). While surface science techniques provide exquisite levels of chemical and electronic detail, this approach struggles with non-conductive materials like silicates due to their incompatibility with methods that require electron conductivity. A way to reach a compromise between the world of silicates and the world of surface science is to use ultra-thin films supported on conductive supports, which gives us hope to truly reach a detailed understanding of these materials. In this talk, I will discuss the work we are doing at the Center for Functional Nanomaterials in trying to understand silicates and zeolites, and I will often diverge into "curiosities" we found along the way. Most notably, confinement effects at the silicate/metal interface have resulted in fascinating properties far beyond our expectations.

  8. CFN Colloquium

    "Controlling Light Matter Interactions in Layered Materials with Conventional and Topological Band Structures"

    Presented by Prof. Ritesh Agarwal, University of Pennsylvania

    Friday, September 6, 2019, 4 pm
    CFN, Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Chang-Yong Nam

    Strongly confined electrical, optical and thermal excitations drastically modify material's properties and break local symmetries that can enable precisely tunable novel responses and new functionalities. We will discuss the effect of engineered plasmonic lattice on light matter interactions in 2D excitonic crystals to produce novel responses such as enhanced and tunable emission, Fano resonances and strong exciton-plasmon polaritons, which can be precisely controlled by geometry and applied fields to produce new device concepts. Our recent work on collective polaritonic modes and the formation of a complete polaritonic bandgap in few-layered excitonic semiconductors coupled to plasmons will also be presented along with our ability to control them via externally applied electric fields. We will also discuss our efforts to explore the optoelectronic properties of MoxW1-xTe2, which are type-II Weyl semimetals, i.e., gapless topological states of matter with broken inversion and/or time reversal symmetry, which exhibit unconventional responses to externally applied fields. We have observed spatially dispersive circular photogalvanic effect (s-CPGE) over a wide spectral region (0.2 - 2.0 eV range) in these materials. This effect shows exclusively in the Weyl phase and vanishes upon temperature induced topological phase change. Since the photon energy leads to interband transitions between different electronic bands, we use the density matrix formalism to describe the photocurrent response under chiral optical excitation with a spatially inhomogeneous beam. We will discuss how spatially inhomogeneous optical excitation and unique symmetry and band structure of Weyl semimetals produces CPGE in these systems. The effect of band inversion, Berry curvature and asymmetric carrier relaxation in this material system on the s-CPGE signal will also be discussed along with the implications for designing new optoelectronic devices. Short B

  9. CFN Colloquium

    "Water technologies by interface engineering"

    Presented by Dr. Seth B. Darling, Argonne National Laboratory

    Thursday, June 6, 2019, 4 pm
    CFN, Bldg 735, 2nd Floor, Seminar Room

    Hosted by: Chang-Yong Nam

    Driven by climate change, population growth, development, urbanization, and other factors, water crises represent the greatest global risk in the coming decades. Advances in materials represent a powerful tool to address many of these challenges. Understanding—and ultimately controlling—interfaces between materials and water are pivotal. In this presentation, Dr. Darling will lay out the challenges and present several examples of work in his group based on materials science strategies for addressing applications in water. In each instance, manipulation of interfacial properties provides novel functionality, ranging from selective transport to energy transduction to pollution mitigation.

  10. CFN Colloquium

    "Materials Innovation in Hybrid Nanocomposites, Nanofabrication, and Semiconductor Nanostructures by Atomic Layer Deposition"

    Presented by Chang-Yong Nam, Center for Functional Nanomaterials, Brookhaven National Laboratory

    Thursday, March 7, 2019, 4 pm
    Bldg 735, CFN, Seminar Room 2nd Floor

    Hosted by: Kevin Yager

    Atomic layer deposition (ALD), typically utilized for coating ultrathin conformal inorganic films for semiconductor device processing, is fundamentally enabled by the reaction specificity between vapor-phase organometallic precursors and chemical groups available on the substrate surface. The infiltration synthesis (IS), a recently developed ALD-derived method, expands the concept by driving precursors into the matrix of organic polymer substrates to form embedded inorganic molecules. This not only generates organic-inorganic hybrids with new materials functionalities but also provides non-conventional nanopatterning routes for inorganic nanostructures that can be directly integrated into electronic devices. In this talk, I will discuss our recent efforts of applying IS for developing organic-inorganic hybrids and semiconductor nanostructures with unique properties and enhanced device functionalities, such as hybrid nanopillars with the highest capacity to store/release elastic mechanical energy among engineering materials and wafer-scale-integrated, in-plane-aligned ZnO nanowire array phototransistors with ultrahigh UV sensitivity and usual superlinear photoconductivity. Also highlighted is the generation of metal oxide nanopatterns by combining IS with self-assembled block copolymer and lithographically patterned polymer templates, revealing important roles of selective interaction of organometallic precursors and chemical groups in the organic matrix on enabling IS. I will conclude the talk by briefly mentioning other potential applications of IS on improving energy and nanotechnologies, such as gas separation membranes, hybrid gravimetric vapor sensors, and next-generation lithography.

  11. CFN Colloquium

    "CANCELED - Fermi systems and quantum computing"

    Presented by Antonio Mezzacapo, IBM T.J. Watson Research Center

    Thursday, January 3, 2019, 4 pm
    CFN, Bldg 735, 2nd Floor Seminar Room

    Hosted by: Deyu Lu

    Solving correlated Fermi systems is a problem of ubiquitous importance in the fields of chemistry, materials science and fundamental interactions. Quantum computers can help addressing this type of challenges, provided that descriptions of Fermi systems are loaded onto a set of qubits. In this talk I will review methods to represent Fermi quantum states and interactions onto a set of qubits, how to optimize mapping procedures, and how these methods are used to perform computations on quantum hardware. I will then introduce connections between such mappings and stabilizer codes, showing that adequate encodings can account for the correction of single-qubit errors. Finally, I will show how the tools presented can have an impact on classical numerical methods.

  12. CFN Colloquium

    "Metamaterial, Metasurface and Plasmonic Optics"

    Presented by David Smith, Duke University

    Thursday, December 6, 2018, 2 pm
    Bldg 735, CFN Seminar Room, 2nd Floor

    Hosted by: Don Dimarzo / Mircea Cotlet

    In 2000, the demonstration of an artificially structured metamaterial with simultaneously negative permittivity and permeability—or a negative index metamaterial—stimulated widespread interest both in the fundamental properties of metamaterials as well as those of plasmonic materials. This interest has had an impact on virtually every aspect of optics and photonics research and technology. Nanostructured materials have the potential for unique and unprecedent photonic devices relevant to applications such as sensing, imaging, information storage and retrieval, processing, and many more. Our group has focused on several metasurface platforms as a means of investigating and demonstrating key concepts. While structuring of a surface or volume provides an important means of controlling the propagation of light with tremendous precision, the use of plasmonic nanostructures provides the means of actually interacting with the radiative dynamics of emitters and other sources, modifying density of states; enhancing or suppressing stimulated and spontaneous emission; modifying nonlinear scattering and harmonic generation; and so forth. The combination of tools available with metamaterials, metasurfaces and plasmonic materials—while still not yet fully exploited—lead to the opportunity for new inventive photonic devices with improved and flexible performance metrics. In this talk, I will describe our group's efforts in the areas of holographic metamaterials, and the need to go beyond holography for multifunctional optical devices. I will also describe the film-coupled nanoparticle platform we have developed over the years and discuss the capability of field enhancement in nanogaps to impact diverse applications such as lasing; ultrafast and ultrabright light sources; light absorbing surfaces; and controlled emission surfaces.

  13. CFN Colloquium

    "Intricacies of Halide Ion Movement in Mixed Halide Lead Perovskites"

    Presented by Prashant Kamat, Department of Chemistry & Biochemistry and Radiation Laboratory, University of Notre Dame

    Thursday, November 1, 2018, 4 pm
    Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Mircea Cotlet

    Metal halide perovskites have drawn significant attention because of their ability to deliver high efficiency solar cells. Mixed halide lead perovskites offer a useful strategy for continuous tuning of the semiconductor bandgap. For example, by varying the halide ion composition of methylammonium lead iodide/bromide (CH3NH3PbBr¬xI3-x (x=0 to 3)) it is possible to tune the bandgap between 1.55 eV and 2.43 eV. In addition to photovoltaic applications these mixed halide perovskites offer rich photophysical properties with applications in lasing and optoelectronic devices. An intriguing property of mixed halide lead perovskites (e.g.,CH3NH3PbI3-xBrx) is phase segregation to create iodide-rich and bromide- rich regions under visible irradiation. The halide ion movement in mixed halide films can be tracked from the changes in the photoluminescence and absorption spectra. Photoinduced segregation in mixed halide perovskite has a direct influence on decreasing the solar cell efficiency as segregated I-rich domains serve as charge recombination centers. The recovery of loss in the external quantum efficiency mirrors the dark recovery of the absorption showing the reversibility of the photoinduced halide segregation. Implication of such halide ion migration in mixed halide perovskite solar cell will be discussed. Related Readings 1. Manser, J. S.; Saidaminov, M. I.; Christians, J. A.; Bakr, O. M.; Kamat, P. V., Making and Breaking of Lead Halide Perovskites. Accounts of Chemical Research 2016, 49, 330-338. 2. Manser, J. S.; Christians, J. A.; Kamat, P. V. Intriguing Optoelectronic Properties of Metal Halide Perovskites. Chem. Rev. 2016, 116, 12956–13008. 3. Hoffman, J. B.; Schleper, A. L.; Kamat, P. V., Transformation of Sintered CsPbBr3 Nanocrystals to Cubic CsPbI3 and Gradient CsPbBrxI3–x through Halide Exchange. J. Am. Chem. Soc. 2016, 138, 8603–8611. 4. Draguta, S.; Sharia, O.

  14. CFN Colloquium

    "Superconducting proximity effect in two-dimensional semiconductor-superconductor structures"

    Presented by Javad Habani, Assistant Professor of Physics, New York University, Center for Quantum Phenomena

    Thursday, October 4, 2018, 4 pm
    Bldg 735, CFN, Seminar Room 2nd Floor

    Hosted by: Mingzhao Liu

    Progress in the emergent field of topological superconductivity relies on synthesis of new material combining superconductivity, low density, and spin-orbit coupling (SOC). Theory indicates that the interface between a one-dimensional semiconductor with strong SOC and a superconductor hosts Majorana-modes with nontrivial topological properties. We discuss the recent developments in epitaxial growth of Al on InAs nanowires was shown to yield a high quality superconductor-semiconductor system with uniformly transparent interfaces and a hard induced gap, indicted by strongly suppressed subgap tunneling conductance. We have developed a two-dimensional (2D) surface InAs quantum wells with epitaxial superconducting Aluminum, yielding a planar system with structural and transport characteristics as good as the epitaxial nanowires. The realization of 2D epitaxial superconductor-semiconductor systems represent a significant advance over wires, allowing extended networks via top-down processing. We present our recent developments in materials synthesis and growth of these density-controlled surface 2D electron-gases and demonstrate Josephson junctions with highly transparent contacts. These developments have lead to unprecedented control over proximity effect in semiconductors where electron densities can be tuned using a gate voltage. We discuss potential applications of this new material system that can serve as a platform for low power circuits, gate-based qubits as well as exploring topological superconductivity for computation.

  15. CFN Colloquium

    "Safe Li-Ion Battery Electrolytes: from Aqueous Electrolytes, Nonflammable Organic Electrolytes, to Solid State Electrolytes"

    Presented by Chunsheng Wang, University of Maryland

    Thursday, September 6, 2018, 4 pm
    Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Dong Su

    Li-ion batteries are the critical enabling technology for the portable devices, electric vehicles (EV), and renewable energy. However, the safety of current batteries still needs to be improved to satisfy these requirements. We investigated the electrochemical performances of three nonflammable electrolytes: water-in-salt electrolytes, all fluorinated organic electrolytes, and solid state electrolytes. The electrochemical stability window of these electrolytes, interface/interphase stability with anodes and high-voltage cathodes, and the interface/interphase resistance between electrodes and electrolytes were systematically studied. The critical issues limiting the performance of these safe electrolytes will be discussed.

  16. CFN Colloquium


    Presented by Amy M. Heintz, Ph.D., Battelle - Advanced Materials Applications

    Wednesday, June 6, 2018, 4 pm
    CFN, Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Matthew Sfeir

  17. CFN Colloquium

    "Engineering coherent defects in diamond"

    Presented by Nathalie P. de Leon, Princeton University, Department of Electrical Engineering

    Thursday, May 3, 2018, 4 pm
    CFN, Bldg 735, Seminar Room 2nd Floor

    Hosted by: Mingzhao Liu

    Engineering coherent systems is a central goal of quantum science and quantum information processing. Point defects in diamond known as color centers are a promising physical platform. As atom-like systems, they can exhibit excellent spin coherence and can be manipulated with light. As solid-state defects, they can be produced at high densities and incorporated into scalable devices. Diamond is a uniquely excellent host: it has a large band gap, can be synthesized with sub-ppb impurity concentrations, and can be isotopically purified to eliminate magnetic noise from nuclear spins. Specifically, the nitrogen vacancy (NV) center has been used to demonstrate basic building blocks of quantum networks and quantum computers, and has been demonstrated to be a highly sensitive, non-invasive magnetic probe capable of resolving the magnetic field of a single electron spin with nanometer spatial resolution. However, realizing the full potential of these systems requires the ability to both understand and manipulate diamond as a material. I will present two recent results that demonstrate how carefully tailoring the diamond host can open new opportunities in quantum science. First, currently-known color centers either exhibit long spin coherence times or efficient, coherent optical transitions, but not both. We have developed new methods to control the diamond Fermi level in order to stabilize a new color center, the neutral charge state of the silicon vacancy (SiV) center. This center exhibits both the excellent optical properties of the negatively charged SiV center and the long spin coherence times of the NV center, making it a promising candidate for applications as a single atom quantum memory for long distance quantum communication. Second, color centers placed close to the diamond surface can have strong interactions with molecules and materials external to the diamond, which makes them promising for nanoscale sensing and imaging. However, uncontrolled surface termin

  18. CFN Colloquium

    "From band gaps to bound excitons: disentangling optical transitions and localized emitters in TMDCs at nanoscale dimensions"

    Presented by Jim Schuck, Associate Professor of Mechanical Engineering at Columbia University

    Thursday, March 1, 2018, 4 pm
    CFN, Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Matthew Sfeir

    The emergence of two-dimensional (2D) monolayer transition metal dichalcogenides (ML-TMDC) as direct bandgap semiconductors has rapidly accelerated the advancement of room temperature, 2D optoelectronic devices. Optical excitations on the TMDCs manifest from a hierarchy of electrically tunable, Coulombic free-carrier and excitonic many-body phenomena. Investigating the fundamental interactions underpinning these phenomena presents challenges, however, due to a complex balance of competing optoelectronic effects and interdependent properties. We show how optical detection of bound- and free-carrier photoexcitations is used to directly quantify carrier-induced changes of the quasiparticle band gap and exciton binding energies [1]. Pushing to the nanoscale, we demonstrate that a model hybrid architecture, a nano-optical antenna and a ML-WSe2 nanobubble, activates the optical activity of BX states at room temperature and under ambient conditions. These results show that engineered bound-exciton functionality as, in this case, localized nanoscale light sources, can be enabled by an architectural motif that combines localized strain and a nano-optical antenna, laying out a possible path for realizing room-temperature single-photon sources in high-quality 2D semiconductors.

  19. CFN Colloquium

    "First principles modeling of electronic excitations: From basic understanding to materials applications"

    Presented by Deyu Lu, Center for Functional Nanomaterials, Brookhaven National Laboratory,

    Thursday, February 1, 2018, 4 pm
    Bldg 735, CFN, Seminar Room, 2nd Floor

    Hosted by: Mircea Cotlet

    Electronic excitations are fundamental physical processes. Spectroscopic information, such as absorption and emission spectra, from electron or photon probes is crucial for materials characterization and interrogation, especially in the context of in situ studies of materials or processes under operando conditions. When experimental data are supplemented by first principles atomic modeling and state-of-the-art data analytics tools, a coherent physical picture emerges containing atomic level details of materials and insights derived from spectral signatures, which eventually allows us to establish the mechanistic understanding of the intriguing structure-property-function relationship. In this talk, the significance of the first principles modeling of electronic excitations is highlighted with three examples. In the first example, we investigated the oxygen 1s core-level binding energy shift of bilayer silica films on Ru(0001) in the X-ray photoelectron spectroscopy (XPS) measurement. Our study revealed that the binding energy shift is an electrostatic effect caused by the interplay of the surface and interface dipole moments. In the second example, we applied ab intio X-ray absorption near edge structure (XANES) modeling for spinel lithium titanate (Li4/3Ti5/3O4), an appealing lithium ion battery material. We identified key spectral features as fingerprints for quantitative assessment of the structural transformation during lithiation. In the third example, we demonstrated that how machine learning algorithms can be combined with XANES modeling to predict the 3D structures of metal nanoparticles on-the-fly.

  20. CFN Colloquium

    "Engineering functionality in colloidal semiconductor nanomaterials"

    Presented by Dmitri Talapin, The University of Chicago, Department of Chemistry and James Franck Institute

    Thursday, December 7, 2017, 4 pm
    Bldg. 735, 2nd Floor Seminar Room

    Hosted by: Alexei Tkachenko

    Development of nanostructured materials has introduced revolutionary approaches for materials processing and electronic structure engineering. These materials can offer the advantages of crystalline inorganic solids combined with inexpensive solution-based device fabrication. I will discuss emerging advances in the surface chemistry of semiconducting nanostructures that are poised to enable advances in additive manufacturing of semiconducting and multifunctional materials. Specifically, I will discuss inorganic linkers that permit electronic coupling between the nanocrystals and new semiconducting "solders" that enable solution processing of high-quality inorganic semiconductors. I will also introduce a general chemical approach for photoresist-free, direct optical lithography of functional inorganic nanomaterials (DOLFIN). Examples of patterned materials include metals, semiconductors, oxides, and magnetic and rare earth compositions. No organic impurities are present in the patterned layers, which helps achieve good electronic and optical properties. The conductivity, carrier mobility, dielectric, and luminescence properties of optically patterned layers are on par with the properties of state-of-the-art solution-processed materials. The ability to directly pattern all-inorganic layers using a light exposure dose comparable to that of organic photoresists opens up a host of new opportunities for thin-film device manufacturing.

  21. CFN Colloquium

    "Synthesis, Characterization, and Applications of Nanocomposite Coatings with Tunable Properties Prepared by Atomic Layer Deposition"

    Presented by Jeffrey Elam, Argonne National Laboratory

    Thursday, November 2, 2017, 4 pm
    CFN, Bldg 735, 2nd Floor Seminar Room

    Hosted by: Chang-Yong Nam

    We have been developing atomic layer deposition (ALD) nanocomposite coatings comprised of conducting, metallic nanoparticles embedded in an amorphous dielectric matrix. These nanocomposite films have proved to be exceptional as resistive coatings in solid-state electron multipliers, as charge drain coatings, and as solar absorbing films in concentrated solar power. All of these applications demand tunable properties so that particular attributes of the film, such as electronic resistivity, can be precisely tailored for maximum efficiency. In our films, the properties are tuned by adjusting the ratio of metallic and dielectric components. For example, nanocomposite films comprised of W:Al2O3 are prepared using alternating exposures to trimethyl aluminum (TMA) and H2O for the Al2O3 ALD and alternating WF6/Si2H6 exposures for the W ALD. By varying the ratio of ALD cycles for the W and the Al2O3 components in the film, we can tune precisely the resistance of these coatings over a very broad range from 1012-105 Ohm-cm. We have used this strategy to synthesize a broad range of ALD nanocomposites combining different metals and dielectrics. These nanocomposite coatings have been utilized to functionalize capillary glass array plates and fabricate large-area microchannel plates suitable for application in large-area photodetectors. In addition, we have applied these films to serve as charge drain coatings in micro electro-mechanical systems (MEMS) devices for a prototype electron beam lithography tool, and obtained high-resolution electron beam patterns without charging artifacts. We have also used these nanocomposite coatings to infiltrate porous scaffolds resulting in selective solar absorbing coatings with high visible absorption and low IR emittance suitable for power tower receivers in concentrated solar power. Bio Sketch: Dr. Jeffrey Elam is a Senior Chemist and Group Leader at Argonne National Laboratory where he directs a program in atomic layer depositi

  22. CFN Colloquium

    "Applications of Model Nanocatalysts Prepared by Size-Selected Cluster Deposition"

    Presented by Michael White, BNL/Stony Brook U Chemistry

    Thursday, October 5, 2017, 4 pm
    Bldg. 735, Seminar Room 2nd Floor

    Hosted by: Mircea Cotlet

    Small clusters exhibit electronic and chemical properties that can differ significantly from that of the bulk and offer a unique opportunity for preparing novel catalysts whose reactivity can be modified at the atomic level. Here, we use mass-selected cluster deposition to prepare model "inverse" catalysts comprised of small metal oxide (MxOy: M = Ti, Nb, Mo, Ce, W) and sulfide (MxSy: M = Mo, W) clusters deposited on Cu and Au surfaces, respectively, for reactivity studies related to the water-gas-shift reaction (WGSR) and CO/CO2 activation. A key advantage of cluster deposition is that it allows control over cluster stoichiometry which provides a means of introducing oxygen/sulfur "vacancies" and varying the average cation oxidation state. Moreover, the use of well-ordered supports and size-selected clusters is ideally suited for computational modeling of structure and reactions using DFT electronic structure theory. Results will be presented for studies of water dissociation on oxide clusters deposited on Cu surfaces and CO2 binding on K-modified sulfide clusters, as well as very recent measurements using ambient pressure XPS (CSX-2 at NSLS-2) to explore the activity of (TiO2)n/Cu(111) surfaces for the water-gas-shift reaction.

  23. CFN Colloquium

    "First-Principles Theory of Epitaxial Film Growth"

    Presented by Shangbai Zhang, Department of Physics, Applied Physics, & Astronomy, Rensselaer Polytechnic Institute

    Thursday, September 7, 2017, 4 pm
    CFN, Bldg 735, Seminar Room 2nd Floor

    Hosted by: Deyu Lu

    First-principles studies often rely on the assumption of equilibrium, which can be a poor approximation, e.g., for epitaxial growth. Here, we propose a general effective chemical potential (μ ¯) approach for non-equilibrium systems. It incorporates growth kinetics into the chemical potential, while maintaining its correct equilibrium limits. In studying molecular beam epitaxy (MBE), we divide the process into three stages: pre-nucleation, nucleation, island growth, and focus our efforts on the first two. For the pre-nucleation stage, we solve the rate equations for small clusters on the surface, which serve as the feedstock for the growth, and find that μ ¯ is determined by the most probable, rather than by the lowest-energy, clusters. While this finding contradicts the equilibrium theory (which is in favor of the lowest-energy state), it reinforces the fundamental principle of statistic mechanics. In the case of Bi2Se3, μ ¯ is found to be highly supersaturated. As μ ¯ determines the nucleation barrier for the nucleation stage, this supersaturation leads to a high nucleus concentration and small-sized islands, in qualitative agreement with experiment.

  24. CFN Colloquium

    "Materials Chemistry via Electrochemistry: Electrochemical Synthesis of Semiconductor Electrodes and Catalysts for Use in Solar Energy Conversion"

    Presented by Kyoung-Shin Choi, Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53796

    Thursday, June 1, 2017, 4 pm
    CFN, Bldg 735, 2nd Floor Seminar Room

    Hosted by: Mingzhao Lu

    Harvesting energy directly from sunlight as nature accomplishes through photosynthesis is a very attractive and desirable way to solve the energy challenge. Many efforts have been made to find appropriate materials and systems that can utilize solar energy to produce chemical fuels. One of the most viable options is the construction of a photoelectrochemical cell that can directly utilize solar energy to drive chemical reactions (e.g. reduction of water to H2, reduction of CO2 to carbon-based molecules). For successful construction of photoelectrochemical cells, simultaneous developments of photoelectrodes, which will efficiently capture photons to generate and separate electron-hole pairs, and catalysts, which will facilitate the use of photogenerated electrons and holes for desired interfacial charge transfer reactions, are necessary. Furthermore, optimally interfacing photoelectrodes and catalysts is critical because the photoelectrode/catalyst interface can govern the overall efficiency of the integrated photoelectrode system. Our research group has been developing new electrochemical synthesis conditions to produce semiconductor electrodes and catalysts with precisely controlled compositions and architectures. In this seminar, we will discuss synthesis and properties of a few promising photoelectrode and catalyst systems for use in solar energy conversion. New synthesis strategies to improve photon absorption, charge transport properties, and catalytic properties will be presented. We will also discuss various strategies to increase the overall utility and efficiency of the photoelectrochemical cells, which include our new results on electrochemical and photoelectrochemical biomass conversion.

  25. CFN Colloquium


    Presented by TBD

    Thursday, May 11, 2017, 4 pm
    CFN, Bldg 735, 2nd Floor Seminar Room

    Hosted by: TBD

  26. CFN Colloquium

    "Darkening Pt Nanocrystals for Photocatalysis"

    Presented by Yugang Sun, Department of Chemistry, Temple University

    Thursday, April 27, 2017, 4 pm
    CFN Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Fang Lu

    Platinum (Pt) nanocrystals are commonly used in chemical reactions because of their unusual catalytic activity, for example, photocatalytic water splitting of water. In a typical design, Pt nanocrystals can accept photo-excited electrons from light absorbers such as semiconductor quantum dots (QDs) to catalyze hydrogen evolution reaction (HER) [1]. Charge transfer from QDs to Pt nanocrystals is very inefficient, and shuttle molecules (e.g., methyl viologen) or other shuttle species are necessary to facilitate the charge transfer [2]. In addition to receiving energetic electrons from semiconductor QDs, Pt nanocrystal can also absorb visible light to generate energetic electrons (or hot electrons), which can directly reduce reactive species or migrate across a metal/semiconductor Schottky barrier to the conduction band of a semiconductor. Different from the widely studied plasmonic metal nanocrystals (e.g., Au, Ag), the efficiency of generating hot electrons in the weakly absorbing Pt nanocrystals is very low. We found that depositing Pt nanocrystals on spherical glass beads (i.e., SiO2 particles) could significantly enhance the visible absorption coefficient of the Pt nanocrystals. For example, in SiO2@Pt nanocrystals@TiO2 core-shell nanostructures, the enhancement in visible absorption enables the efficient generation of energetic electrons in photoexcited Pt nanocrystals, which can easily transfer to the TiO2 surface layer to drive HER and many other chemical reactions [3].

  27. CFN Colloquium

    "Catalysis at Shell - Challenges & Opportunities for Energy"

    Presented by Carl Mesters, Shell, Shell Technology Center in Houston

    Thursday, April 6, 2017, 3 pm
    Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Dario Stacchiola

    Energy is vital to our daily lives. It helps us produce food, fuel transport and power communication channels across the world. Over the coming decades, more people will gain access to energy and enjoy higher standards of living. But these developments could place greater pressure on our world's resources, such as energy, fresh water and food. At the same time, climate change remains a serious concern. At Shell, we use human ingenuity, innovation and technology to unlock the energy our customers need to power their lives in the years ahead, while aiming to limit our impact on the environment. In this seminar we will discuss examples in the area of catalysis that are relevant to meet these challenges in energy. C.V: Carl Mesters joined Shell in 1984 and currently works from the Shell Technology Center in Houston. He has been active in catalysis and process R&D across many areas, including selective catalytic reduction of NOx, ethylene oxide, gas-to-liquids, catalytic dewaxing, aromatic hydrogenation, xylene isomerization, etc. resulting in more than 70 patents filed. In 2005 he was appointed Shell's Chief Scientist for Chemistry & Catalysis. Today's main topics are in 'Gas to Chemicals' and 'long range R&D'. Carl has been Chairman of the Catalysis Society of the Royal Dutch Chemical Society. He holds a degree in Physical and Inorganic Chemistry from the University of Utrecht, the Netherlands, where he also completed a research Ph.D.

  28. CFN Colloquium

    "Tricking Block Copolymers into Forming New Morphologies"

    Presented by Kevin Yager, CFN / BNL

    Thursday, March 16, 2017, 4 pm
    CFN, Bldg 735, 2nd Floor Seminar Room

    Hosted by: Oleg Gang

    Block copolymer self-assembly allows the rapid formation of nanostructures over wide areas. Yet, the range of possible patterns is fairly limited. I will present emerging strategies for constructing three-dimensional nanostructures whose shapes and symmetries go beyond those of the bulk equilibrium diblock copolymer phase diagram. Photo-thermal methods are used to accelerate assembly, and control block copolymer ordering and orientation. Self-assembly is known to be pathway-dependent, which can be exploited to select a particular nano-pattern. Ordered layers can be stacked to yield new lattice symmetries. This multi-layered ordering can be performed in a responsive mode, where each self-assembled layer templates the ones that follow. Taken together, these new motifs point towards the ability to construct designed, multi-functional 3D nanostructures.

  29. CFN Colloquium

    "The emergence of hybrid-perovskites for low-cost, high-efficiency optoelectric devices"

    Presented by Aditya D. Mohite, Los Alamos National Laboratory

    Thursday, December 1, 2016, 4 pm
    CFN, Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Matthew Sfeir

    Hybrid (inorganic-­-organic) perovskites have demonstrated an extraordinary potential for clean  sustainable  energy  technologies  and  low-­-cost  optoelectronic  devices  such  as  solar  cells; light emitting diodes, detectors, sensors, ionic conductors etc. In spite of the unprecedented  progress  in  the  past  six  years,  one  of  the  key  challenges  that  exist  in  the  field today is the large degree of processing dependent variability in the structural and physical  properties.  This  has  limited  the  access  to  the  intrinsic  properties  of  hybrid  perovskites and led to to multiple interpretations of experimental data. In addition to this, the stability and reliability of devices has also been strongly affected and remains an open question,  which  might  determine  the  fate  of  this  remarkable  material  despite  excellent  properties. In this talk, I will describe our recently discovered approach for thin-­-film crystal  growth  as  a  general  strategy  for  growing  highly  crystalline,  bulk-­-like  thin-­-films  of  both three-­-dimensional (3D) and layered two-­-dimensional (2D) hybrid perovskites that overcomes the above issues by allowing access to the intrinsic charge and energy transport processes  within  the  perovskite  thin-­-films  and  results  in  reproducible  and  stable  high  performance optoelectronic devices.

  30. CFN Colloquium

    "The role of chemical and steric environment of active sites on catalytic activity"

    Presented by Prof. Dr. Johannes A. Lercher, Department of Chemistry Technische Universität München, Garching, Germany / Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, WA, Germany

    Monday, November 7, 2016, 4 pm
    CFN Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Mircea Cotlet

    Understanding the elementary steps in acid-base and metal catalyzed organic transformations is a key for sustainable chemical conversions. Solid acids and bases with nano-pores such as zeolites act as solid Brønsted and Lewis acids, widely used as catalysts with well-defined acid-base sites and a well-defined reaction space around the sites. Within the pores of molecular sieves reacting molecules are constrained in a reaction space, which can be subtly adjusted via direct synthesis, as well as via the addition of cations, oxidic clusters or organic fragments. The impact of such changes on mono- and bimolecular reactions such as elimination reactions of alcohols, cracking and alkylation of hydrocarbons are discussed for gas and liquid phase reactions. Experimental methods to define the state of the reacting molecules combined with detailed kinetic analysis and theory will be used to explain the principal contributions of the interactions and the confinement to determine reaction rates. It will be discussed how reaction rates and pathways can be tailored using the space available for a transition state and the chemical constituents around the active site.

  31. CFN Colloquium

    "Crystal Microstructure and Dynamics by Bragg Coherent X-ray Diffraction"

    Presented by Ian Robinson, Condensed Matter Physics & Materials Science, Brookhaven National Laboratory

    Thursday, October 6, 2016, 4 pm
    Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Mircea Cotlet

  32. CFN Colloquium

    "Billions and Billions of molecules: Exploring chemical space for functional molecular materials"

    Presented by Alan Aspuru-Guzik, Department of Chemistry and Chemical Biology, Harvard University

    Thursday, September 8, 2016, 4 pm
    CFN, Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Qin Wu

    Many of the challenges of the twenty-first century are related to molecular processes such as the generation and storage of clean energy, water purification and desalination. These transformations require a next generation of more efficient, chemically stable, and non-toxic materials. Chemical space, the space of all possible synthesizable molecules, is practically infinite and promises to have relevant candidate functional molecules to address these challenges. One of the main goals of my research group is to develop understanding and tools for the exploration chemical space in order to accelerate the discovery of organic materials. Our design cycle is sped up by the constant interaction of theoreticians and experimentalists, the use of high-throughput computational techniques, machine learning, and the development of specialized big data tools. We have had recent successes in theoretically predicting and experimentally confirming in record times top performers in the areas of organic electronics, organic flow batteries and organic light-emitting diodes. In this talk, I will discuss what I consider are the key factors related with a successful high-performance screening approach as illustrated by these three different applications. I will end by discussing the future prospects and challenges associated with developing appropriate metrics for the cartography of chemical space.

  33. CFN Colloquium

    "Graphene Synthesis and Devices"

    Presented by Dr. James Tour, Rice University

    Thursday, June 2, 2016, 11 am
    CFN, Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Dmitri Zakharov

    An in-depth look at numerous methods to make graphene, ranging from single-crystal sheets that grown in precise hexagonal arrays to growth of graphene in air at room temperature using lasers, and 2- and 3-D hybrid graphene nanotube structures. Use of the graphene materials in composites will be discussed. Many of the devices made and their transitions to industry will be shown. These devices include fuel cells, water splitting systems, batteries, supercapacitors and more.

  34. CFN Colloquium

    "Manipulating Light on Chip"

    Presented by Michal Lipson, Columbia University, NY

    Thursday, May 19, 2016, 11 am
    CFN, Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Chuck Black

    Photonics on chip could enable a platform for monolithic integration of optics and microelectronics for applications of optical interconnects in which high data streams are required in a small footprint. This approach could alleviate some of the current bottlenecks in traditional microelectronics. In this talk I will review the challenges and achievement in the field of Silicon Nanophotonics and present our recent results. Using highly confined photonic structures, much smaller than the wavelength of light, we have demonstrated ultra-compact passive and active silicon photonic components that enhance the electro-optical, mechanical and non-linear properties of Silicon. Based on the ability to dynamically modulate light on the same time scale as the time of flight we have demonstrated novel GHz structures for a variety of applications including all-optical synchronized RF oscillators and optical isolators on a silicon chip. Michal Lipson is the Higgins Professor of Electrical Engineering at Columbia University, New York, NY. Her research focuses on novel on-chip Nanophotonics devices. She has pioneered several of the critical building blocks for silicon photonics including the GHz silicon modulators. Professor Lipson's honors and awards include 2010 Macarthur fellow, NYAS Blavatnik award, OSA Fellow, IBM Faculty Award, and NSF Early Career Award. More information on Professor Lipson can be found at

  35. CFN Colloquium

    "2-dimensional zeolites for catalysis and separations"

    Presented by Michael Tsapatsis, University of Minnesota

    Friday, March 11, 2016, 11 am
    Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Anibal Boscoboinik

    It is only recently that single-unit-cell thick zeolite nanosheets (2-dimensional zeolites; AIChE Journal 60(7), 2374-2381 (2014) ) with intact crystal and micropore structure were shown to be possible. The structural integrity and unprecedented purity and uniformity of these microporous nanosheets, open exciting possibilities for technological breakthroughs in molecular sieve membrane fabrication, synthesis of hierarchical catalysts and polymer-zeolite nanocomposites. Moreover, zeolite nanosheets enable for the first time zeolite pore mouth adsorption and catalysis to be studied by traditional uptake methods as well as surface science techniques. However, along with the exciting possibilities, challenges abound. For example, the in-plane dimensions of the existing nanosheets are in the sub-micrometer range limiting potential applications and processability as thin films. Moreover, the two exfoliated zeolites currently available are only a small fraction of zeolite topologies one would like to have available for a representative set. Earlier attempts to exfoliate other layered zeolites, including certain layered silicates and aluminophosphates with microporous layers, did not preserve the crystallographic order of the layers. Synthesis of high aspect ratio zeolite and other crystalline nanoporous nanosheets, methods to characterize their structure and properties, along with their processing and assembly to create membranes and catalysts will be the focus of this talk.

  36. CFN Colloquium

    "Breakthrough water filtration membrane technology based on nanofibers"

    Presented by Ben Hsiao, Distinguished Professor of Chemistry, Co-founding Director, Innovative Global Energy Solutions Center, Director, Center for Advanced Technology in Integrated Electric Energy Systems, Stony Brook University

    Thursday, February 18, 2016, 11 am
    Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Dmytro Nykypanchuk

    The fabrication of nanofibers (diameter from 1- 100 nm) can be accomplished by using a variety of methods, including electro-spinning and a combination of chemical/mechanical processes, especially for cellulose, as a form of green sustainable resource material. Non-woven nanofiber mats have unique properties, such as interconnected pores, a very large surface-to-volume ratio, and a high capacity for surface modifications, making such scaffolds useful for fabrication of high throughput separation membranes. Directed water channels in the barrier layer are formed through the formation of interface between the cross-linked nanofibers and the polymer matrix, while the gap thickness (less than 1 nm) may be regulated by physical interactions or chemical bonding. In the present context, advances in electro-spinning and fundamental studies on cellulose microfibrils (or nanocelluloses) by means of synchrotron x-ray scattering have provided us with new insight to use the fibrous format with varying pore sizes for applications from micro-filtration via ultra-filtration to nano-filtration and reverse osmosis. We have taken advantage of unique breakthroughs in chemical modifications and physical scale-up transformations to drastically improve filtration membrane development with predesigned properties. This technology has led to a revolutionary design of highly permeable filtration membranes with significantly higher flux (or lower energy) than commercial membranes. Biography: Prof. Hsiao served as Chair of the Chemistry Department and held Vice President for Research and Chief Research Officer positions at Stony Brook. His research is focused on the development of new nanostructured polymers for energy, environmental and health applications. Recently, Hsiao and his research team have demonstrated a breakthrough technology using nanofibrous materials, such as natural cellulose nanofibers, for water purification. This technology has led to a

  37. CFN Colloquium

    "In-situ XAS, TXM and RIXS experiments"

    Presented by Frank de Groot, Debye Institute of Nanomaterials Science, Utrecht University, Netherlands

    Thursday, October 1, 2015, 11 am
    Bldg 735, Seminar Room, 2nd Floor

    Hosted by: Deyu Lu

    New developments in in-situ x-ray absorption (XAS), transmission x-ray microscopy (TXM) and resonant inelastic x-ray scattering (RIXS) will be discussed. A brief introduction is given of x-ray absorption spectroscopy, including the multiplet interpretation of XAS spectral shapes [1,2]. Nanoscale chemical imaging of catalysts under working conditions is possible with transmission x-ray microscopy. We have shown that TXM can image a catalytic system under relevant reaction conditions and provides detailed information on the morphology and composition of the catalyst material in situ [3]. The 20 nanometer resolution combined with powerful chemical speciation by XAS and the ability to image materials under reaction conditions opens up new opportunities to study many chemical processes. I will discuss the present status of in-situ TXM, with an emphasis on the abilities of the 10+ nm resolution TXM technique in comparison with 0.1 nm STEM-EELS [4,5]. Hard X-ray TXM allows the measurement of chemical images and tomographs under more realistic conditions, using a capillary reactor at 10 bar Fischer-Tropsch conditions [6]. The second part of the talk deals with resonant inelastic x-ray scattering (RIXS), In 2p3d RIXS one scans through the 2p XAS edge and measures the optical excitation range. As an example, the RIXS spectra of CoO will be discussed. The experimental resolution of 100 meV at ADRESS allows the detailed observation of the electronic structure. First-principle theoretical modelling was performed for the ground state and multiplet analysis for the RIXS experiments. The implications for measurements on coordination compounds (cobalt carboxylates) and cobalt nanoparticles is discussed, in particular the comparison with optical spectroscopy [7]. Related to the RIXS measurements is the analysis of Fluorescence yield (FY) detected x-ray absorption spectra (XAS), including the intrinsic deviations of the FY-XAS spectral shape from

  38. CFN Colloquium Series

    "Water at Interfaces: Adsorption, Reactions, Wetting"

    Presented by Miguel Salmeron, Lawrence Berkeley Laboratory

    Tuesday, April 17, 2012, 11 am
    Bldg. 735 - Seminar Room, 2nd Floor

    Hosted by: Jerzy Sadowski

    The molecular nature of solid-liquid interfaces and the processes that take place there is an important and fascinating area of research. Surface chemistry and catalysis, wetting, fluid flow in pipes, electrochemistry, and batteries are areas impacted by the chemistry of interfaces. I will present results on the formation and growth of wetting films on surfaces, diffusion and reactions using Scanning Probe Microscopies (Tunneling, Force), in vacuum and in wet environments, as well as x-ray based spectroscopies (XPS, XAS). With them can obtain a detailed picture at the most fundamental level of understanding of interface phenomena. Most recently, we developed novel techniques to extend our research to the solid-liquid interface during application of electric fields, which provide fundamental information in the electrochemistry area.

  39. CFN Colloquium Series

    "Scale Bridging Simulations for Soft Matter – Extension to Materials for Organic Electronics"

    Presented by Kurt Kremer, Max Planck Institute for Polymer Research, Germany

    Tuesday, November 8, 2011, 11 am
    Building 735 - Seminar Room, 2nd floor

    Hosted by: Mark Hybertsen

    Despite the long history of organic electronics, there has been only very little understanding how the chemistry of a particular compound relates to the properties of the final device. The main difficulty is that processes at all length scales equally contribute to the final efficiency. In solar cells, for example, the global morphology (micro- and nanometers) assists percolation of charges to the electrodes; the local molecular arrangement (on the Angstrom and nm scale) facilitates charge hopping, increasing the charge mobility. Finally, the electronic structure is tuned to achieve efficient photon harvesting, as well as creation, diffusion and dissociation of excitons. Theory and simulation on different length scales can help to understand these fundamental processes by linking self-organizing, structural, and electronic properties together.

  40. CFN Colloquium Series

    "Self-Assembly of Nanoparticles"

    Presented by Nicholas Kotov, University of Michigan, Ann Arbor

    Tuesday, October 11, 2011, 11 am
    Bldg. 735 - Seminar Room, 2nd Floor

    Hosted by: Oleg Gang

    Self-organization of nanoparticles (NPs) and nanoscale objects in general represents one of the most dynamic areas of modern science. Better understanding of these phenomena is important from both fundamental and practical perspectives because nanoparticle self-organization processes: (1) identify similarities between biological and non-biological nanoscale species; (2) lead to unusual optical properties from different combinations of nano- and microscale features; (3) can potentially simplify manufacturing of electronic, photonic, and sensing devices. Over a period of last decade we demonstrated that intricate 1D, 2D, and 3D systems from CdTe, CdS, Au, ZnO NPs could be formed. It was achieved by exercising fine degree of control over attractive and repulsive interactions between the NPs. Pivotal roles in expanding the variety of self-assembled structures were attributed to factors determining anisotropy of the force fields around NPs: geometry of the NP facets, crystal lattice, dipole moments, distribution of a stabilizer, and intrinsic chirality of the NP cores. Rationalization of the topology of the self-assembled structures (Figure 1) in the framework of different contributions to the force fields, such as electrostatic, dipolar, hydrophobic forces, and hydrogen bonding will be presented. Fine tuning of the interactions also resulted in dynamic NP assemblies capable of restructuring in response to different media parameters. The analysis of the self-assembly processes for NPs also revealed surprising analogies with self-organization behavior of biological macromolecules. The idea of NP-protein analogy can also extended not only to geometry but to biological functions of proteins. Latest data on the design of inorganic biomimetic inhibitors, enzymes, and cellular signaling agents based on inorganic NPs will be presented. Advantages and limitations of protein replications by nanocrystals will be discussed.

  41. CFN Colloquium

    "Photovoltaics Research at IBM"

    Presented by Supratik Guha, IBM Research

    Tuesday, September 20, 2011, 11 am
    Bldg. 735 - Seminar Room, 2nd Floor

    Hosted by: Mark Hybertsen

    In my talk I will describe some of the ongoing research in three different areas of photovoltaics at IBM. Concentrator photovoltaics, which has not yet benefitted from the economies of scale that silicon photovoltaics has, can offer significant advantages over flatpanels in regions with high direct normal incidence, and also has the potential to be mass manufactured cheaply using readily available materials and components. I will describe some of the work at IBM in building high concentration photovoltaic systems. In the second area, earth abundant thin film PV, I will describe our research on fabricating solar cells using the material copper-zinc-tin-sulfide (CZTS), a compound with readily available, cheap and non toxic components that may turn out to be a viable alternative to CIGS and CdTe without the toxicity and availability issues that are associated with them. This is a less mature material compared to CdTe or CIGS however, and the challenge currently is to demonstrate cells with high efficiencies. I will describe results from vacuum deposited materials that now have achieved efficiencies of 8.4% and higher. Finally, if time permits, I will describe some of our work on silicon nanowire solar cells, which while demonstrating higher light absorption and even slightly higher efficiencies compared to their planar counterparts, have so far not demonstrated any significant advantage with respect to their potential—I will present data and discuss the reasons behind this.

  42. Monthly CFN Colloquium Series Seminar

    "Functional Hybrid Nanomaterials and their Applications"

    Presented by Ulrich Wiesner, Cornell University

    Monday, January 10, 2011, 9:30 am
    Bldg. 735 - Conf Rm A

    Hosted by: Dmytro Nykypanchuk

    This talk will describe the synthesis, characterization and processing of block copolymer based composites. It is structured according to the degree of order achieved in the resulting materials, moving from amorphous to polycrystalline to single crystal-type materials. By using thermodynamic principles established for block copolymers and mixtures with nanoparticles, well-defined nanostructured morphologies are obtained at all these levels of structural order. Thermal processing of the polymer-inorganic hybrids results in nanoporous materials with uniform pores and hexagonal as well as bicontinuous cubic pore structures. These concepts are applied to amorphous nanostructured aluminosilicates and non-oxide type ceramics stable up to 1500C, polycrystalline nanostructured transition metal oxides and metals, as well as nanostructured, porous single crystal silicon and metal thin films (~10-100nm) with epitaxial growth relation to the substrate. The various chemical approaches will be discussed in detail. Perspectives will be given in the context of nanomaterials for applications ranging from microelectronics to energy generation and storage.