BNL Home
September 2016
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  1. Center for Functional Nanomaterials Seminar

    11 am, CFN, Bldg. 735, Conference Room A - 1st floor

    Hosted by: 'Dario Stacchiola'

    The study of surface structure and interface phenomena is an interdisciplinary research area, involving materials synthesis, characterization, performance evaluation and theoretical calculations. The performance at the surface of functional materials is of paramount relevance for many applications: in catalysis, sensors, corrosion-resistant materials and microelectronic devices. Progress in nanomaterials and catalysis stands on three pillars: 1) synthesis of nanomaterials, including the preparation of hierarchically dispersed nano-particles; 2) theoretical studies of materials that enable experimental results to be understood; and 3) advanced, in situ characterization during actual operation (operando methodology). An interdisciplinary approach fosters knowledge-based design of functional materials (e.g., catalysts). Our research focuses on catalysis, where the understanding of the structure-property relationships at the molecular level provides rational basis for the development of catalysts with improved performance and stability. We will present our research on operando methodology to understand structure-properties on supported oxide catalysts, addressing the state of the catalyst during activation and deactivation processes. In this seminar, we summarize the use of operando Raman methodology to assess the molecular basis of catalyst activation-operation-deactivation, mainly focused on alkane oxidative dehydrogenation and ammoxidation reactions. The transversal operando approach places it at the junction between fundamental catalytic chemistry and applied chemical engineering. We will present data about fundamental computational chemistry study on catalysts structure/performance; but also engineering operando to honeycomb shaped working catalysts, and design of operando cells for these applications.

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  1. CFN Colloquium

    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.

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  1. Center for Functional Nanomaterials Seminar

    11 am, CFN, Bldg 735, Conference Room A, 1st Floor

    Hosted by: ''Oleg Gang''

    Directed self-assembly (DSA) of block copolymers (BCPs) has become a promising patterning technique for advanced node hole shrink process due to its material-controlled CD uniformity and process simplicity. In practice, multiple patterning and self-aligned via (SAV) processes have been implemented in semiconductor manufacturing to address resolution issue. In this talk, DSA of lamella-forming BCP was evaluated as a candidate for forming SAV, which requires the DSA process to support structures from circular via to lines and spaces. The basic process flow is similar to general graphoepitaxy method. The morphologies of the DSA vias derived from lamellar BCPs were found to be less sensitive to the BCP coating thickness compared to the cylindrical BCP system of similar L0. This implies that lamellar BCP may provide a larger process window and higher tolerance for local pattern density variation. The profile and the thickness of the residual PS layer of DSA structures were studied using Monte Carlo simulation and FIB cross-section SEM. Furthermore, a series of defectivity study using the lamellar system will be discussed, including film stack, DSA, and etch process fine-tuning. Finally, the benefits and challenges of implementing DSA for via process will be discussed.

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  1. OCT

    3

    Monday

    Center for Functional Nanomaterials Seminar

    "Extending the Capabilities of Scanning Probe Microscopy: The Path towards Robust, Quantitative, Multidimensional Atomic Resolution Imaging with Chemical Selectivity"

    Presented by Udo D. Schwarz, Yale University, New Haven, CT

    2 pm, CFN, Bldg. 735 - Seminar Room, 2nd floor

    Monday, October 3, 2016, 2:00 pm

    Hosted by: 'Percy Zahl'

    Despite the evolution of scanning probe microscopy (SPM) into a powerful set of techniques that image surfaces and map their properties down to the atomic level, significant limitations in both imaging and mapping persist. Currently, typical SPM capabilities qualitatively record only one property at a time and at a fixed distance from the surface. Furthermore, the probing tip's apex is chemically and electronically undefined, complicating data interpretation. To overcome these limitations, we have started to integrate significant extensions to existing SPM approaches. First, we expanded noncontact atomic force microscopy with atomic resolution to three dimensions by adding the capability to quantify the tip-sample force fields near a surface with picometer and piconewton resolution [1, 2]. Next, we gained electronic information by recording the tunneling current simultaneously with the force interaction [3] and introduced a new operating scheme called tuned-oscillator atomic force microscopy that substantially improved imaging robustness and therefore sample throughput and user friendliness [4]. Finally, we will illustrate how the tip chemistry, tip asymmetry, and tip-sample distance influence the recorded interactions – and thus the information one can gain from images –, ultimately allowing to selectively image specific atomic species [3, 5]. During the talk, applications to various model systems including oxides, metals, ionic crystals, and layered materials will be presented. [1] B. J. Albers et al., Nature Nanotechnology 4, 307 (2009). [2] M. Z. Baykara et al., Advanced Materials 22, 2838 (2010). [3] M. Z. Baykara et al., Physical Review B 87, 155414 (2013). [4] O. E. Dagdeviren et al, Nanotechnology 27, 065703 (2016). [4] H. Mönig et al., ACS Nano 7, 10233 (2013). Host: Percy Zahl

  2. OCT

    6

    Thursday

    Center for Functional Nanomaterials Seminar

    "Reversed Nanoscale Kirkendall Effect in Au-InAs Hybrid Nanoparticles"

    Presented by Anatoly I. Frenkel, Department of Materials Science and Engineering, Stony Brook University / Chemistry Department, Brookhaven National Laboratory

    11 am, Bldg 735, Conference Room A

    Thursday, October 6, 2016, 11:00 am

    Hosted by: ''Eric Stach''

    Metal-semiconductor hybrid nanoparticles (NPs) have synergistic properties that have been exploited in photocatalysis, electrical, and optoelectronic applications. Rational design of hybrid NPs requires the knowledge of the underlying mechanisms of diffusion of the metal species through the nanoscale semiconductor lattice. One extensively studied process of diffusion of two materials across the nanoparticle surface is known as the nanoscale Kirkendall effect. There, an atomic species A with the lower diffusion rate enters the nanocrystal slower than the B species diffusing from the nanocrystal outward. As a result, voids are formed in B, providing an interesting avenue for making hollow nanocrystals. We used time-resolved X-ray absorption fine-structure spectroscopy, X-ray diffraction and electron microscopy to monitor the diffusion process of Au atoms through InAs nanocrystals in real time. In this system the diffusion rate of the inward diffusing species (Au) is faster than that of the outward diffusion species (InAs), which results in the formation of a crystalline metallic Au core surrounded by an amorphous, oxidized InAs shell with voids in it. These observations indicate that in hybrid Au-InAs NPs the rarely observed "reversed nanoscale Kirkendall effect" is in play. It presents a potentially new way to synthesize unique nanoscale core-shell structures.

  3. OCT

    6

    Thursday

    CFN Colloquium

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

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

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

    Thursday, October 6, 2016, 4:00 pm

    Hosted by: '''Mircea Cotlet'''

  4. NOV

    7

    Monday

    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

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

    Monday, November 7, 2016, 4:00 pm

    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.