Series
STAMI-GTPN Distinguished Lecture Series

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Event Series
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Associated Organization(s)

Publication Search Results

Now showing 1 - 5 of 5
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    Designer Colloidal Nanocrystal Materials for Electronic and Optical Applications
    ( 2019-03-12) Kagan, Cherie R.
    Semiconductor and plasmonic nanocrystals are known for their size and shape dependent photo-luminescence and localized surface plasmon resonances, respectively. In this talk, I will describe the use of semiconductor and plasmonic nanocrystals as building blocks of mesoscale materials for semiconductor electronics and optoelectronics and plasmonic optical metamaterials. Chemical exchange of the long ligands used in nanocrystal synthesis with more compact ligand chemistries brings neighboring nanocrystals into proximity and increases interparticle coupling. In semiconductor nanocrystal solids, we show strong electronic coupling in combination with doping allows us to control the carrier type and concentration to design high mobility n- and p-type materials. I will give examples where n- and p-type nanocrystal solids are used to construct field-effect transistors and integrated circuits and solar photovoltaics. In metal nanocrystals, ligand-controlled coupling allows us to tailor a dielectric-to-metal phase transition seen by a 1010 range in DC conductivity and a dielectric permittivity ranging from everywhere positive to everywhere negative across the whole range of optical frequencies. We realize a "diluted metal" with optical properties not found in the bulk metal analog, presenting a new axis in plasmonic materials design and the realization of optical properties akin to next-generation metamaterials. We harness the properties of metal nanocrystals by using nanoimprint lithography to print large-area metamaterials on glass and plastics with widely tailorable optical properties that are used to realize near-infrared optical devices.
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    Ionic Liquid/Block Polymer Nanocomposites: Remarkably Versatile, Functional Materials
    (Georgia Institute of Technology, 2017-02-10) Lodge, Timothy P.
    Ionic liquids are an emerging class of solvents with an appealing set of physical attributes. These include negligible vapor pressure, impressive chemical and thermal stability, tunable solvation properties, high ionic conductivity, and wide electrochemical windows. In particular, the non-volatility renders ionic liquids practical components of devices, but they require structure-directing agents to become functional materials. Block polymers provide a convenient platform for achieving desirable nanostructures by self-assembly, with lengthscales varying from a few nanometers up to several hundred nanometers. Furthermore, ionic liquids and polymer blocks can be selected to impart exquisitely tunable thermosensitivity, by exploiting either upper or lower critical solution transitions (UCSTs and LCSTs). In selected cases, it is also possible to prepare photoreversible and photopatternable systems. Overall, by combining designed block polymers and ionic liquids we have demonstrated materials with superior performance for a remarkably diverse set of applications. These include micelles for extraction, nanoreactors for catalysis, gate dielectrics in organic transistors, electrochromic and electroluminescent gels, and membranes for gas separation, ion batteries, and fuel cells.
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    Interface and Interphase in Polymeric Multilayer Materials
    (Georgia Institute of Technology, 2016-11-09) Baer, Eric
    Lessons from biology have revealed that natural materials systems have hierarchical structures that are specifically designed to accommodate a unique spectrum of required properties. These systems always have many scale levels that are bound together by interfacial coupling or adhesion. Micro/nanolayered coextrusion processing is highly suited to apply these lessons of scale, interaction and architecture. Three examples will be discussed emphasizing scale in photonic applications with high refractive index contrast, interfacial phenomena in amorphous systems, and polymer solid state structure and morphology obtained by confined crystallization. With different amorphous polymers, the degree of segmental interdiffusion has been quantitatively correlated with the thickness of the interphase region. This enables the establishment of relationships between adhesion and various degrees of miscibility. Finally, unique single crystal with lamellar orientation during confined crystallization, will be discussed which allows the development of high barrier packaging systems.
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    Applications for New Nanolayered Composite and Membrane Filters
    (Georgia Institute of Technology, 2016-11-08) Baer, Eric
    The fundamental discoveries with polymer micro/nanolayered and fibrillar systems are being “translated” into new novel products. Three examples will be described in detail. First the development of graded index lenses, which are copies of mamalian lenses for application in telescopic systems, will be outlined. This will be followed by describing new capacitors with much higher storage and use temperature characteristics. Finally, new membrane filters will be described that are specifically designed for the removal of water droplets out of gasoline. The lecture series will be concluded by indicating additional applications currently under consideration.
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    Layered and Fibrillar Polymeric Systems by NanoExtrusion Forced Assembly
    (Georgia Institute of Technology, 2016-11-07) Baer, Eric
    Recently, numerous new synthetic approaches have been used to develop macromolecular materials that “self-assemble” into nano-scale morphologies. This lecture addresses another approach – the solventless “forced-assembly” of extrudable synthetic polymers down to the nano-scale. Numerous commercial films currently available, used primarily in food packaging, have only a few layers. These films have a desirable mix of end-use characteristics. Layer-multiplying devices permit polymers with dissimilar solid state structures and properties to be combined into unique microlayer and nanolayer systems with thousands of layers. Studies of these layered polymer composites down to the nano-scale have revealed unique properties which are only achievable when the layers are thin enough to produce synergistic combinations of key properties of the constituent components. Recently, a new highly flexible continuous process for creating unique nanofibers by a related solventless co-extrusion methodology will also be described with particular emphasis on membrane filters for gaseous and liquid separation systems.