BNL Home
May 2017
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  1. Center for Functional Nanomaterials Seminar

    1:30 pm, CFN, Bldg 735, Conference Room A, 1st Floor

    Hosted by: 'Oleg Gang'

    Growth and self-assembly processes sometimes result, on laboratory timescales, in structures that are in thermal equilibrium, and sometimes result in structures that are "trapped" out of equilibrium. I will discuss examples of each. DNA "bricks" are nanometer-scale particles that self-assemble into equilibrium structures of about 1000 particles in size. Each particle in these structures is of a distinct type and has a defined spatial location. I will discuss the constraints that inter-particle interactions must satisfy in order to produce such equilibrium structures in high yield. I will also discuss the case of a two-component mixture of particles that can self-assemble into a nonequilibrium structure in which component types are intermingled in a manner similar to spins in a ferromagnet at a (static) critical point. I will argue that such "critical soft matter" could be self-assembled from DNA-coated colloids, and would have new and useful properties.

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  1. Center for Functional Nanomaterials Seminar

    1:30 pm, CFN, Bldg 735, Conference Room A, 1st Floor

    Hosted by: 'Chang-Yong Nam'

    In the last decade, organic electronics has promised a seemingly bright future for flexible and large area electronics. However, functional organic transistors are not realized yet due to the low carrier mobilities and downscaling issue of the organic layers. Vertical organic transistors are a viable solution to overcome these challenges because the short vertical channel can drive large output currents at low powers. In this presentation, two types of vertical organic transistors will be introduced: 1) permeable metal-base transistors (PMBTs) where a permeable metal-base is sandwiched by two semiconductor layers and 2) vertical organic Schottky barrier transistors (VOSBTs) where an organic Schottky barrier is modulated by the underlying gate electric field. In both types of transistors, a nano-porous electrode play a key role for the output current modulation. Understanding the effects of the pore size and density in the porous electrode on the modulation behavior enables the development of high gain PMBTs or VOSBTs with large current on/off ratio. A key advantage of the vertical device architecture is its direct integration with functional layers for novel sensor applications. By inserting optoelectronic, ferroelectric, or piezoelectric layers into the gate insulator of the VOSBT, a high efficiency infrared photodetector (optoelectronic VOSBT), flexible non-volatile memory (ferroelectric VOSBT), or a novel ultrasonic sensor (piezoelectric VOSBT) could be developed respectively. Further insertion of an organic light-emitting diode into the channel layer of the VOSBT resulted in novel light-emitting sensors such as infrared-to-visible up-conversion devices or ultrasonic-gated OLEDs that may enable pixel-less infrared or acoustic imaging in the future.

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  1. Center for Functional Nanomaterials Seminar

    1:30 pm, CFN, Bldg 735, Conference Room A, 1st Floor

    Hosted by: ''Fang Lu''

    Owing to advances in multilayer Laue lens (MLL) fabrication and the development of a high-stiffness and high-precision instrument, MLL-based microscope has matured for real scientific applications and has become available for user operation at the Hard X-ray Nanoprobe beamline (HXN) of National Synchrotron Light Source II (NSLS-II) with 15-nm spatial resolution. In addition to high resolution, a suite of techniques that employs various contrast mechanisms to simultaneously image elemental, structural and chemical variations on the nanoscale has been developed, enabling imaging capabilities that are not previously available. In this presentation, I'll focus on the development of multimodality imaging capability at the HXN. I'll show that by collecting fluorescence and far-field diffraction data together, absorption-, phase- and fluorescence-contrast images can be taken simultaneously, yielding additional information that any one of them alone cannot provide. Software packages have been developed to streamline the analysis in 2D and 3D cases. I'll present a few case studies to demonstrate how multimodality imaging can help understand the science. I'll also show the development of Bragg Ptychography technique, which allows the reconstruction of the strain field in crystalline samples with very high spatial resolution. The combination of high spatial resolution and multimodality imaging with hard x-rays creates a unique microscopy tool for material studies on the nanoscale and opens up a lot of exciting research opportunities in many areas of science.

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  1. Center for Functional Nanomaterials Seminar

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

    Hosted by: ''''Oleg Gang''''

    The creation of colloidal machines – that is, dynamic assemblies of colloidal components that perform useful functions – requires advances in our ability to rationally engineer the dynamics of active colloids operating outside of thermodynamic equilibrium. Owing to their small size (nanometers to microns), such machines must assemble spontaneously and operate autonomously in response to simple energy inputs due to chemical fuels or external fields. Achieving non-trivial dynamical behaviors and ultimately function demands the use of complex components, into which the desired behaviors can be effectively encoded. The challenge is conceptually similar to that of programmable self-assembly, whereby assembly information encoded in the building blocks directs their organization into a specific structure. Extending this approach to design colloidal machines will require control over particle organization in time as well as space – that is, over dynamics as well as structure. This talk will present recent work from our group on strategies for powering active colloidal systems and for programming these systems to perform increasingly complex tasks. By directing colloidal matter outside of equilibrium, we aim to create new materials and technologies with capabilities that rival those of living organisms.

  2. Center for Functional Nanomaterials Seminar

    1:30 pm, CFN, Bldg 735, Conference Room A, 1st Floor

    Hosted by: 'Matthew Sfeir'

    Analogues to thin-film solar photovoltaics (PV), a typical solar-fuel device consists of a hybrid inorganic-polymer composite that directly converts solar energy into H2 or liquid fuels, with inputs of sunlight, water and CO2 only. Once abundant and low-cost solar H2 is produced as a universal energy carrier, we can use it to convert synthetic or bio-fuels, upgrade petrochemical feedstock, improve combustion and produce ammonia. However, achieving such an efficient and flexible solar-fuel membrane is not trivial, particularly due to the instability of efficient semiconductor/liquid interfaces. In this talk, I will first discuss several key advances of protective coatings as a stabilization strategy. All technologically important semiconductors so far like Si and GaAs photocorrode. Although protective coatings are not prevalent in solid-state research, they are essential in the field of photoelectrochemistry. With protective coating strategies, a 10% efficient water-splitting prototype has been demonstrated. With modeling-inspired materials design, I will show a viable pathway beyond 20% efficiencies. Finally, I will discuss needs for basic research on photocatalytic processes at solid/liquid interfaces. Operando synchrotron x-ray photoelectron spectroscopy presents vast opportunities for understanding energetics of solid/liquid interfaces and for further controlling their photocatalytic processes. Understanding the change-transfer rate picture of solid/liquid interfaces promise cost-effective particle-based photocatalyst devices.

  3. CFN Colloquium

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

    Hosted by: ''TBD''

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  1. JUN

    1

    Thursday

    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

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

    Thursday, June 1, 2017, 4:00 pm

    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.

  2. JUL

    6

    Thursday

    CFN Colloquium

    "TBD"

    Presented by TBD

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

    Thursday, July 6, 2017, 4:00 pm

    Hosted by: 'TBD'