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Special MNT Seminar - Friday, September 26, 2014, 3:00, 221 South Engineering

Ab Initio Electron Dynamics at Metal-Semiconductor Nanointerfaces, Professor Dmitri Kilin, Department of Chemistry, University of South Dakota

Photo-induced charge transfer at the interface of two materials is a fundamental process in (i) photovoltaic and (ii) photocatalytic applications. The photo-induced time-dependent electron dynamics are computed for different interfaces by a combination of ab initio electronic structure and time-dependent density matrix methodology. A dissipative equation of motion for the reduced density matrix for electronic degrees of freedom is used to study the phonon-induced relaxation of hot electrons in the simulated systems. Non-adiabatic couplings between electronic orbitals are computed on-the-fly along nuclear trajectories. Equations are solved in a basis set of orbitals generated ab initio from a density functional.  For an application to photovoltaic effect, one explores light-induced electric current in a model of a simplified photovoltaic cell composed of a Si nano-crystal co-doped with p-and n- type doping, interfacing with Au electrodes. Charge carrier dynamics induced by selected photo-excitations show that hole relaxation in energy and in space is much faster than electron relaxation. Use of the continuity equation for electric current allows us to identify substantial local currents at the Si/Au interfaces and small overall net charge transfer across the slab. For an application to photocatalytic water splitting, charge transfer dynamics is explored at the interface of supported metal nanocluster and liquid water. The metal cluster introduces new states into the band gap of semiconductor TiO2 surface, narrows the band gap of TiO2, and enhances the absorption strength. The H2O adsorption significantly enhances the intensity of photon absorption, which is due to the formation of metal-oxygen (water) coordination bonds at the interfaces. The metal cluster promotes the dissociation of water, facilitates charge transfer, and increases the relaxation rates of holes and electrons. Reported results help in understanding basic photophysical and protochemical processes contributing to harvesting solar energy by photovoltaics and photoelectrochemical water splitting.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Special MNT Seminar - Monday, October 20, 2014, 3:00, 271 Batcheller Technology Center

Ruga Mechanics of Folding Atomic-Layer Nanostructures, Professor Kyung-Suk Kim, Institute of Molecular and Nanoscale Innovation, Brown University

When one folds a thin solid film that is only a few atoms thick, such as graphene, the film properties can be controlled for various functions. For example, a simple compression of the folded film can change optical, electrical, wetting and adhesion characteristics of the film, and can be used for making multifunctional materials such as transparent electric circuits, self-cleaning surfaces, oil-spill cleaning cloths and self-adjusting friction grips. Such atomic-layer nanostructures can be folded and self-organized by nonlinear large deformation of soft material substrates. In particular, nano science and technology has enabled us to explore new functional properties of hierarchically ruga-structured materials through folding or wrapping thin atomic-layer structures with nanometer scale features. The Latin word ruga means a state of a “large-amplitude” wrinkle, crease, fold or ridge to form various 1-D or 2-D patterns. As multi-scale surface morphologies of rugae determine effective properties such as wetting, adhesion, friction, flexoelectric and optoelectronic properties, ruga state control is considered as a viable method for real-time regulation of effective material properties. It is found that graded or layered elastic properties of the substrate can provide diverse bifurcation paths of the attached atomic-layer deformation under lateral compression, producing various atomic-layer ruga states. Nonlinear mechanics of soft-material substrate enables us to construct ruga-phase diagrams. As an example, a mathematical analysis of sequential bifurcation processes of hyper-elastic neo-Hookean substrates is used to construct generic ruga-phase diagrams. When an atomically layered structure such as multi-layer graphene is folded by ruga control, nano-scale crinkles are generated. In general, nano-scale crinkle ridges are invisible to conventional AFM due to its peculiar flexoelectric properties. Here, a new invention of “Dual-Tip AFM Interferometer” (DT-AFMI) will be introduced, which makes the invisible visible. The DT-AFMI image reveals that the crinkle ridge of a multi-layer graphene has its ridge width less than 1.8nm. The nano-crinkle ridges have strong flexoelectric characteristics, and the crinkle ridge networks of the top graphene layer exhibit high molecular adsorptivity. Potential applications of such high molecular adsorptivity localized along the nano-ridges will be discussed as well.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Special MNT Seminar - Friday, November 7, 2014, 3:00, 221 South Engineering

Encapsulation of Solutes in Lipid Vesicles: Origins of Life Considerations, Dr. Tereza Pereira de Souza, Rowland Institute, Harvard University

In the past years we have investigated the entrapment of macromolecules inside vesicle by analyses of cryo-transmission electron microscopy of liposome populations created in the presence of ferritin, ribosomes and small macromolecular aggregates. And surprisingly, results reveal that the local (intra-liposomal) macromolecules concentration in these liposomes largely exceeds the bulk concentration. This seminar aims to summarize and discuss these results under the light of the origins of life scenario and synthetic biology, addressing question as: What is the minimal size of a minimal cell? Is the number of entrapped macromolecules inside vesicles homogeneous? Lipid compartments are frequently addressed as agents of confinement and protection, but could these compartments have a more active role in the pre-biotical scenario? In another words, does the formation of lipid compartments play a role in concentrating the "entrapped to be" macromolecules?

For more information, contact Sylvio May, 701-231-7048, sylvio.may [at] ndsu [dot] edu

Special MNT Seminar - Monday, November 10, 2014, 3:30, Sudro 27

Transdermal Therapeutic Systems: Structure, Function and Exelon(r) as a Convincing Example, Prof. Dr. Alfred Fahr, Department of Pharmaceutics, Friedrich-Schiller-University Jena, Germany

Transdermal Therapeutic Systems (TTS) have made their way over the last decades as an alternative to oral formulations not only for circumvention of the first pass effect as for example delivering nitroglycerine, but also for maintaining steady plasma level values and for reducing serious side effects during therapy. A very good example for the latter case is the Exelon TTS(r) with its active ingredient rivastigmine, which is used in therapies against Alzheimer's disease.

For more information, contact Sylvio May, 701-231-7048, sylvio.may [at] ndsu [dot] edu

Special MNT Seminar - Monday, December 15, 2014, 3:00, 221 South Engineering

Elasticity-Based Mechanism for Collective Motion in Natural and Artificial Swarms,  Dr. Cristián Huepe, Department of Applied Mathematics, Northwestern University

Collective motion is one of the simplest forms of self-organization in systems of active components such as cell colonies, bird flocks, fish schools, or groups of autonomous robots.  Its emergence in fluid-like swarms with aligning interactions has been the focus of much research activity. In this talk, I will introduce a different model for collective motion, consisting of self-propelled particles connected by linear springs without explicit aligning dynamics. In this system, a simple elasticity-based mechanism drives the particles to self-organize by cascading self-propulsion energy towards lower-energy modes. Given its ubiquity, this mechanism could play a relevant role in various natural and artificial swarms.

For more information, contact Thomas Ihle, 701-231-7045, thomas.ihle [at] ndsu [dot] edu

Special MNT Seminar - Monday, February 16, 2015 (time and location TBA)

Engineering Persister-Specific Antibiotics with Synergistic Antimicrobial Functions,  Professor Gerard Wong, Department of Bioengineering, Department of Chemistry & Biochemistry, California Nanosystems Institute, UCLA

For more information, contact Sylvio May, 701-231-7048, sylvio.may [at] ndsu [dot] edu

Special MNT Seminar - Wednesday, April 1, 2015, 3:00, 271 Batcheller Technology Center

Structure, Dynamics and Properties of Block Polymer Dispersions, Professor Frank S. Bates, Department of Chemical Engineering and Materials Science, University of Minnesota

Block copolymers belong to a broad class of amphiphilic compounds that includes soaps, lipids and nonionic surfactants. These macromolecules assemble into micelles with molecular dimensions on the order of 5 to 50 nm in size when mixed with excess solvent that preferentially solvates one block type. This presentation will explore two different aspects of block copolymer micelle formation. The fundamental thermodynamic and kinetic factors that control micelle shape and dynamics will be discussed based on small-angle x-ray and neutron scattering (SAXS and SANS) experiments and cryogenic transmission and scanning electron microscopy results. Although the structural features displayed by amphiphilic block copolymers resemble those associated with the self-assembly of lipids and simple surfactants (e.g., spherical and cylindrical micelles and vesicles) a macromolecular architecture leads to remarkably different dynamic properties, linked to a vanishingly small critical micelle concentration. As a consequence, molecular exchange is rapidly extinguished with increasing molecular weight resulting in non-ergotic behavior. These concepts have been exploited in developing a recently commercialized technology that provides immense improvements in the fracture toughness of thermosetting epoxy plastics, which also will be described.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Special MNT Seminar - Monday, April 20, 2015 (time and location TBA)

TBA, Professor Alfredo Alexander-Katz, Department of Materials Science and Engineering, MIT

For more information, contact Alexander Wagner, 701-231-9582, alexander.wagner [at] ndsu [dot] edu

Special MNT Seminar - Friday, April 24, 2015 (time and location TBA)

TBA, Professor Christos Likos, Faculty of Physics, University of Vienna

For more information, contact Alan Denton, 701-231-7036, alan.denton [at] ndsu [dot] edu

Special MNT Seminar - Tuesday, May 5, 2015, 3:00, 271 Batcheller Technology Center

A Robust Nonlinear Block Copolymer Nanoreactor-Based Strategy to Monodisperse Hairy Nanocrystals with Precisely Controlled Dimensions, Compositions and Architectures, Professor Zhiqun Lin, School of Materials Science and Engineering, Georgia Institute of Technology

Nanocrystals exhibit a wide range of unique properties (e.g., electrical, optical, and optoelectronic) that depend sensitively on their size and shape, and are of both fundamental and practical interest. Breakthrough strategies that will facilitate the design and synthesis of a large diversity of nanocrystals with different properties and controllable size and shape in a simple and convenient manner are of key importance in revolutionarily advancing the use of nanocrystals for a myriad of applications in lightweight structural materials, optics, electronics, photonics, optoelctronics, magnetic technologies, sensory materials and devices, catalysis, drug delivery, biotechnology, and among other emerging fields. In this talk, I will elaborate a general and robust strategy for crafting a large variety of functional nanocrystals with precisely controlled dimensions (i.e., plain, core/shell, and hollow nanoparticles) by capitalizing on a new class of unimolecular star-like block copolymers as nanoreactors. This strategy is effective and able to produce organic solvent-soluble and water-soluble monodisperse nanoparticles, including metallic, ferroelectric, magnetic, luminescent, semiconductor, and their core/shell nanoparticles, which represent a few examples of the kind of nanoparticles that can be produced using this technique. The applications of these functional nanocrystals in energy-related applications (i.e., solar cells and photocatalysis) will also be discussed.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Past MNT Seminars

Special MNT Seminar - Wednesday, March 19, 2014, 3:00-4:00, 271 Batcheller Technology Center

Revealing Protein Dynamics by Integrating Molecular Dynamics Simulations with Neutron Scattering Experiments, Dr. Liang Hong, Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, Web: http://cmb.ornl.gov/people/liang

Protein, the engine of life, carries out most functions in living things on the earth through characteristic modulation of its three-dimensional structure over time. Understanding the microscopic nature of the protein internal motion and its connection to the function and structure of the biomolecule is a central topic in biophysics, and of great practical importance for drug design, study of diseases, and the development of renewable energy, etc. Under physiological conditions, protein exhibits a complex dynamics landscape, i.e., a variety of diffusive and conformational motions occur on similar time and length scales. This variety renders difficult the derivation of a simplified description of protein internal motions in terms of a small number of distinct, additive components. This difficulty is overcome by our work using a combined approach of Molecular Dynamics (MD) simulations and the state-of-the-art Neutron Scattering experiments. Our approach enables quantitative characterization of distinct protein motions, furnishing an in-depth understanding of the connection between protein structure, dynamics, energy landscape and function.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Special MNT Seminar - Thursday, March 27, 2014, 3:30-4:30, 271 Batcheller Technology Center

Single Molecule Bioelectronics, Dr. Yongki Choi, Department of Physics and Astronomy, University of California Irvine

Nanoscale electronic devices like field-effect transistors have long promised to provide sensitive, label-free detection of biomolecules.  In particular, single-walled carbon nanotubes have the requisite sensitivity to detect single molecule events, and have sufficient bandwidth to directly monitor single molecule dynamics in real time.  Our recent work has demonstrated this premise by monitoring the dynamic, single-molecule processivity of three different enzymes: lysozyme, protein Kinase A, and DNA polymerase I.  With all three enzymes, single molecules were electronically monitored for 10 or more minutes, allowing us to directly observe rare transitions to chemically inactive and hyperactive protein conformations.  The high bandwidth of the nanotube transistors further allow every individual chemical event to be clearly resolved, providing excellent statistics from tens of thousands of turnovers by a single enzyme. Besides establishing values for processivity and turnover rates, the measurements reveal variability, dynamic disorder, and the existence of intermediate states.  Initial success with the three enzymes indicates the generality and attractiveness of the nanotube devices as a new tool to complement existing single molecule techniques.  Furthermore, our focused research on transduction mechanisms provides the design rules necessary to further generalize this architecture.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Special MNT Seminar - Monday, March 31, 2014, 3:00-4:00, 271 Batcheller Technology Center

Directed Assembly of Colloidal Particles at Liquid Crystal Interfaces, Dr. Mohamed Amine Gharbi, University of Pennsylvania

Colloidal particles organize spontaneously at fluid interfaces owing to a variety of interactions to form well-organized structures that can be exploited to synthesize advanced materials. While the physics of colloidal assembly at isotropic interfaces is well understood, the mechanisms that govern interactions between particles at complex fluid interfaces are not yet clearly established. In particular, nematic and smectic liquid crystal materials offer important degrees of freedom that can be used to direct particles into new structures. In this work, I report the behavior of solid micrometric beads with homeotropic anchoring confined at interfaces of liquid crystal films. First, I will detail the behavior of spherical solid particles at planar nematic liquid crystal (NLC) interfaces. Subsequently, I will report the behavior of particles at more complex NLC interfaces. I will review how the competition between anchoring conditions, liquid crystal elasticity, and topology of curved surfaces is responsible for the formation of new ordered structures in a self-assembly process. Second, I will report the behavior of silica beads confined at interfaces of thin smectic films. I study the interactions and self-assembly of these particles in both supported and free standing films. When particles are captured in thin membranes, they induce distortions of the smectic interface to satisfy wetting properties at particle boundaries, leading to capillary interactions. These forces compete with elastic ones induced by the distortion of the smectic layers. The resulting potential drives assembly of the spheres into new different structures. Recent progress in understanding the mechanism of particle self-organization is presented.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Special MNT Seminar - Thursday, April 3, 2014, 3:30-4:30, 271 Batcheller Technology Center

Imaging of Complex Biological Systems at the Sub-Cellular, Cellular and Multicellular Levels, Dr. Alexander Khmaladze, University of Michigan

Non-invasive nature of optical microscopy enables researchers to study a great variety of materials under conditions approaching or similar to their "natural" environment. This is especially relevant to live biological specimens, which can be studied both in-vitro and in-vivo, providing a unique insight into the dynamic processes occurring in the live organisms. In recent years, the emphasis has been shifting towards the technologies that combine several different imaging techniques to study a particular system. Each technique then allows measuring a partially overlapping set of parameters, leading to deeper understanding of the processes occurring within that system. This talk presents several imaging and spectroscopic techniques, namely dual-wavelength digital holographic microscopy, hyperspectral coherent anti-Stokes Raman imaging and spontaneous Raman spectroscopy. I will show how these techniques proved to be useful to answer specific questions, and also how they can be applied to solve a wide range of problems in physics, chemistry, biology and medicine. Moreover, by combining them, a single objective, such as a comprehensive study nanoparticles entry into cells and tissues, can be achieved. Due to interdisciplinary nature of these research topics, they are particularly well suited for involving researchers with various scientific backgrounds and interests. This research also provides rich opportunities for students to explore and gain knowledge in optical design, software programming, mathematics and nano-biology.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Special MNT Seminar - Tuesday, April 8, 2014, 3:30-4:30, 271 Batcheller Technology Center

Macromolecules on Lipid Membranes: Brownian Motion, Conformational Dynamics, and Local Perturbations, Dr. Eugene Petrov, Max Planck Institute of Biochemistry, Department of Cellular and Molecular Biophysics, Martinsried, Germany

Interaction of polymer molecules and colloidal particles with lipid membranes is one of the important problems of the modern bio-inspired soft matter physics. Its understanding provides an insight into mechanisms of interaction of biological macromolecules with cell membranes. What is the effect of the lipid membrane on the conformational dynamics and Brownian motion of membrane-bound polymer molecules? How lipid diffusion and phase separation in the membrane are affected by local perturbations induced by macromolecules? In my talk I will address these and other related questions using my recent results for model membrane systems and macromolecular structures including DNA, DNA origami, fd-virus, and artificial FtsZ-based membrane cortex. Experimental results obtained using fluorescence video-microscopy, fluorescence correlation spectroscopy, and single-particle tracking will be compared with Monte Carlo simulations and theoretical models. I will discuss implications for understanding important biological issues such as anomalous diffusion in cell membranes, effect of the membrane cytoskeleton on cold-shock resistance of organisms, and spontaneous DNA uptake by living cells

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Special MNT Seminar - Wednesday, November 20, 2013, 4:00-5:00 PM, 148/154 Research 1

Manipulating Conjugated Polymer Structure and Chemistry: Creating Active Materials for Applications in Electronics and Energy Storage/Conversion, Dr. Michael Freund, Department of Chemistry, University of Manitoba

Conjugated polymers are an exciting class of materials that hold great promise in emerging electronic and energy applications. The excitement surrounding the field has resulted from the tremendous possibilities presented by merging the vast knowledge base of synthetic organic chemistry and polymer science with critically important areas of electronic materials and solid-state physics. This rapidly growing field presents opportunities for revolutionizing material science and electronics in ways we are just beginning to imagine. Despite this great promise, significant obstacles remain for widespread use and technological impact of these materials. For example, unlike most common industrial polymers, conjugated polymers are relatively insoluble and are not compatible with thermal processing. This is largely due to strong inter-chain interactions that also limit molecular weight and in turn mechanical properties as well as thermal reactivity and volatility of dopants. This presentation will discuss approaches that have been developed in our laboratory to overcome many of these issues. The versatility of these approaches will be illustrated with examples of nanocomposites and porous structures with enhanced properties. In addition, new work on the development of conducting polymer nanocomposites designed for electronics and energy applications will be discussed.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu


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Materials and Nanotechnology program
Phone: (701) 231-6456
Fax: (701) 231-6524

Last Updated: Monday, December 15, 2014 8:38:36 AM