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October 2017
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  1. CFN Colloquium

    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.

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  1. NOV

    2

    Thursday

    CFN Colloquium

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

    Presented by Jeffrey Elam, Argonne National Laboratory

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

    Thursday, November 2, 2017, 4:00 pm

    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.

  2. DEC

    7

    Thursday

    CFN Colloquium

    "Engineering functionality in colloidal semiconductor nanomaterials"

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

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

    Thursday, December 7, 2017, 4:00 pm

    Hosted by: '''Oleg Gang'''

    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.