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Events: NanoSEC Seminars

  • Nonlinear Optics at Reduced Dimensions

    Guest: Prof. Hayk Harutyunyan, Department of Physics, Emory University
    Friday, April 10, 2015 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    When light interacts with low-dimensional systems, new optical new interesting phenomena can arise because of the reduced dimensionality. Classic examples include quantum dots with discrete electronic energy levels or plasmon resonances of metallic nanoparticles. In addition to the dimensionality or shape, the light-matter interaction can be further tuned by using optical nonlinearities. Typically, the induced polarization currents depend linearly on the intensity of the radiation field. However, when the linear relationship breaks down new interesting phenomena arise like frequency conversion or intensity dependent refractive index. We combine this new possibility with the interesting properties of low dimensional systems and use them for applications ranging from subdiffraction resolution imaging to on-chip frequency conversion.

  • TBD

    Guest: Sankar Nair, Professor of Chemical Engineering, Georgia Institute of Technology
    Friday, October 3, 2014 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

  • Micro Fabrication Advances Including Miniature Power Sources for Wireless Devices

    Guest: Paul Kohl, Professor of Chemical Engineering, Georgia Institute of Technology
    Friday, September 19, 2014 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    Power sources have become a critical enabling technology, especially for portable electronic devices. The goal is to have the smallest, lowest-cost power sources, which safely meet or exceed the mission lifetime. Our technology options include batteries and fuel cells. A critical component of these electrochemical devices is the ionic conducting electrolyte. Advances include electrolytes leading to dendrite-free lithium or silicon anodes for high energy density lithium batteries and low-cost, ambient temperature fuel cells. In addition, other microfabrication processing advances will be described such as the fabrication of ultra-low dielectric constant insulators and chemically amplified permanent dielectrics for integrated circuits and packages.

  • Some surprises in electronic transport through self-assembled-monolayer molecular junctions

    Guest: Professor Yonatan Dubi, Ben-Gurion University, Israel
    Thursday, July 31, 2014 11:00 am - 12:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    Dr. Dubi is one of the key players in developing theoretical means to understand the transport properties (electronic, heat and energy) at the nanoscale. His research results have been published in the most prestigious scientific journals, such as Nature, Rev. Mod. Phy., Phys. Rev. Lett.

  • Optical Metamaterials: Beyond the Linear Regime

    Guest: Prof. Wenshan Cai, School of Electrical and Computer Engineering, Georgia Institute of Technology
    Friday, April 18, 2014 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    Metamaterials are commonly viewed as artificially-structured media capable of realizing arbitrary effective parameters, in which metals and dielectrics are delicately combined to facilitate the index contrast and plasmonic response required for a particular purpose. We aim to drive beyond this limited vision and explore the use of optical metamaterials as a generalizable platform for optoelectronic information technology: Metals will provide tailored plasmonic behavior as before, but will serve double duty by providing electrical functions including voltage input, carrier injection/extraction, and heat sinking, and dielectrics will consist of functional elements such as Kerr materials, electrooptic polymers, and p-n junctions. In this talk I will discuss our preliminary results on several topics in this category, including the electrically induced harmonic generation and optical rectification of light in a perfect metamaterial absorber, the nonlinear spectroscopy and imaging from a chiral metamaterial, and the backward phase-matching in an optical metamaterial where the fundamental and frequency- doubled waves possess opposite indices of refraction.

  • Shaping Nanomedicines for Cancer Applications

    Guest: Prof. Efstathios (Stathis) Karathanasis, School of Medicine, Case Western Reserve University
    Friday, March 28, 2014 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    The Karathanasis Laboratory for Nanomedical Engineering focuses on translational cancer nanomedicine. Specifically, our research program exploit the engineerable nature of nanoparticle technology to develop clinically relevant therapeutic and imaging agents for hard-to-treat cancers based on the integration of nanotechnology, oncology, imaging science and cancer biology. Using robust in vitro, in silico and in vivo analyses, we study the relation between the physical characteristics of nanoparticles (size, shape, etc.) and the nanoparticle’s navigation through different biological processes to extract design parameters that improve the in vivo performance of nanoparticles. In addition to the development of contemporary therapeutic paradigms, our lab develops nanoparticle imaging agents for MRI, CT and molecular imaging to enable non-invasive in vivo interrogation at super-high resolutions and highly accurate diagnosis of disease.

  • How to start a small business

    Guest: Dr. Stefan Schulze
    Friday, March 8, 2013 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

  • Patents and copyrights for a researcher

    Guest: Dr. Gennaro J. Gama
    Thursday, March 7, 2013 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

  • Entrepreneurship for a researcher

    Guest: Dr. Christopher Hanks
    Friday, February 22, 2013 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

  • Write a good research paper

    Guest: Prof. Zhengwei Pan
    Friday, February 15, 2013 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

  • Give a good presentation

    Guest: Prof. Jason Locklin
    Friday, February 8, 2013 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

  • Preparation of a Ph. D. Student

    Guest: Prof. Yiping Zhao
    Friday, February 1, 2013 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

  • Fabrication, Electrokinetics, and Applications of Carbon Nanotube Membranes

    Guest: Prof. Ji Wu, Department of Chemistry, Georgia Southern University
    Friday, November 30, 2012 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    Recently carbon nanotube (CNT) membrane has been a subject of intensive research activities due to their unique attributes, such as i) a dramatically enhanced fluid flow, ii) functional chemistry at the CNT tip entrance for effective chemical and biological separations, and iii) electrically conductive carbon nanotubes allowing for efficient electrochemical functionalization and electro-osmosis pumping.1-5 Meanwhile, the estimated overall costs of drug addiction and abuse in the United States alone exceed half a trillion dollars annually as reported by National Institute on Drug Abuse (NIDA). Classical transdermal patches for drug addiction and abuse treatments like nicotine patch can only provide constant dosing rates. However many drug abuse and addiction treatments demands variable dosing rates. Herein, a relatively low-cost microtoming method has been developed to fabricate carbon nanotube (CNT) membranes in large scale. The tips of CNT membranes were functionalized using an efficient electrochemical grafting method, following by a series of chemical coupling reactions. It was demonstrated that Ionic mobilities through CNT cores are enhanced by a factor of ~4 with a significant rectification seen for large anion/cation mixtures. High electro-osmotic flows of ~3 cm/s-V is seen for ~ 1nm single walled CNTs and ~0.15 cm/s-V for ~ 7nm multi-walled CNTs. The enhanced electrophoretic and electro-osmotic phenomenon of CNT membranes have been successfully applied to a programmed transdermal nicotine patch that can provide therapeutically useful fluxes ranging from high (1.30.65 μmol/hr-cm2) and to low (0.330.22 μmol/hr-cm2) for efficient smoking cessation treatments (in vitro (human skin) & in vivo (hairless guinea pig)).

    Bio: Dr. Ji Wu is an assistant professor of chemistry at Georgia Southern University, Statesboro, GA. He has been working as a postdoctoral scholar in University of Kentucky with research focus on the fabrication, electro-kinetics and applications of carbon nanotube membranes from 2007-2012. He received his PhD degree in Inorganic and Materials Chemistry from Texas Christian University in 2007, following his Advisor, J. L. Coffer. His PhD research was on erbium-doped semiconducting nanomaterials such as silicon and germanium nanowires. He also earned a Masters’ degree in Organometallic Chemistry from Anhui University (Hefei, China) in 2000. He has contributed over 20 publications on peer-reviewed journals, such as Nature Nano., PNAS, Nano Letters, Advanced Materials, J. Pharm. Sci. etc.

  • Multiscale Material from Atom Modeling and Simulation to Continuum

    Guest: Xianqiao Wang, College of Engineering, University of Georgia
    Friday, November 2, 2012 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    For several decades continuum theory has been a dominating theoretical framework for the analysis of materials and structures. This approach to predict material deformation and failure, by implicitly averaging atomic scale dynamics and defect evolution spatially and temporally is valid only for large system. It is realized that as technologies extend to the nanometer range, continuum mechanics at this new arena is questionable. Whereas atomic-scale modeling and simulation methods, e.g., molecular dynamics (MD), have provided a wealth of information for nano systems by elucidating the atomistic mechanisms that govern deformation and rupture of chemical bonds, these methods can only handle problems limited in length/time scales. Yet, ultimately we aim at the design and manufacture of synthetic and hierarchical material systems or structures in which the organization is designed and controlled on length scales ranging from nano to micro, even all the way to macro. Therefore multiscale modeling, from atom to continuum, is inevitably needed.

    This talk presents an atom-based continuum (ABC) theory coupling with thermal, mechanical and electrical mechanism, aiming at a seamless transition from the atomistic to the continuum description of multi-element crystalline solids (which has more than one kind of atom in the unit cell). By accounting for the upgraded Nosé-Hoover thermostat and Lorentz force, we put forth a novel way to appreciate the full benefit of coupling the thermal, mechanical and electromagnetic fields at nano/micro scale. Contrary to many multiscale approaches, ABC theory proposed here is naturally suitable for the multi-physics analysis of multi-element crystals. Taking both efficiency and accuracy into consideration, we adopt a cluster-based summation rule for atomic force calculations in the finite element formulations. When coarse mesh is used, the majority of the degrees of freedom can be eliminated, hence, the computational cost can be reduced, accompanying the decrease of the accuracy of the simulation results. When the finest mesh is used, any lattice site is a finite element node, and the model becomes identical to a full-blown MD model, which is the standard model manifesting the discrepancies or accuracies of others by comparisons. It is possible to envision that the use of this new method in support of diverse applications, ranging from the exploitations of critical physical phenomena such as crack extension, phase transformation, and dislocation initiation at nano scale to the energy harvesting and design of bone materials at micro scale.

    Bio: Dr. Xianqiao Wang is currently an Assistant Professor of College of Engineering at University of Georgia. He received his B.S. and M.S. degree in engineering mechanics from Hunan University (China) in 2004 and 2007, respectively. He obtained his Ph.D. degree in mechanical engineering from the George Washington University in 2011. After graduation, he joined the Mechanical and Aerospace Engineering Department at the George Washington University as a Research Assistant Professor. His main research areas are multiscale material modeling and simulation, computational nanomechanics, biomechanics, coupled physics analyses of nanomaterials, microcontinuum field theory, energy harvesting, and material design.

  • Embedded Metal Nanoparticles as Light-Driven, Localized Heaters for in-situ Materials Processing

    Guest: Laura Clarke, Department of Physics, NC State University
    Friday, October 19, 2012 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    When metal nanoparticles are excited by light resonant with the particle’s surface plasmon, non-radiative relaxation efficiently generates heat in the immediate region surrounding the particle. Such photothermal heating has been extensively explored in solution environments for applications such as cancer treatment and drug delivery. In contrast, use of and understanding of photothermal heating in solids, such as nanoparticle-polymer composites, has been limited. However, such photothermal effects could facilitate in situ thermal processing of polymeric materials via externally-controllable light excitation. The spatial specificity and temperatures achieved can potentially be used for triggering phase transitions, cross-linking, or driving region-specific chemical reactions inside the existing material. Anisotropic particles enable further tuning of the plasmonic frequency and polarization-controlled heating. By embedding fluorophores in the composite, a sensitive relative fluorescence approach can be utilized to dynamically monitor the average temperature within the sample as it is thermally processed. With modest light intensities and dilute nanoparticle concentrations, controllable temperature changes of several hundred degrees Celsius have been achieved.

  • Shed Light on Nanomaterials for Solar Energy Conversion and Cancer Therapy

    Guest: Jin Zhong Zhang, Department of Chemistry and Biochemistry, University of California Santa Cruz
    Friday, September 28, 2012 3:00 pm - 4:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    Nanomaterials are of strong interest for both fundamental and technological purposes. At the fundamental level, nanomaterials possess novel physical and chemical properties that differ from those of bulk matter due to quantum confinement effects and exceedingly larger surface-to-volume ratio. These novel properties are highly promising for applications in emerging technologies such as solar cells and biomedicine. Our lab has been actively engaged in the study of optical and dynamic properties of nanomaterials for solar energy conversion and biomedical applications. One example is hydrogen generation from water splitting based on novel semiconductor nanostructures with improved properties. We also design and characterize metal nanostructures for chemical sensing based on surface enhanced Raman scattering (SERS) and biomedical imaging and therapy. An example is hollow gold nanospheres that have demonstrated outstanding photophysical properties for photothermal ablation therapy of cancer both in vitro and in vivo, due to their unique structural and optical characteristics.

  • Paramyxovirus, Host Kinases and Therapies

    Guest: Professor Biao He, GRA Distinguished Investigator
    Friday, April 20, 2012 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    Paramyxovirus family includes many important human and animal pathogens. Virus is a parasite of host cells: it requires host cellular proteins for survival and efficient replication. Our work focuses on investigating the interface of virus and host cells. We have identified host kinases that are important for virus replication. We have been exploring targeting host kinases as novel anti-viral therapies. Understanding virus and host cell interactions is also important for developing effective vaccines, a proven method for preventing viral infections. We have taken advantages of knowledge generated from our basic research to develop novel therapies for virus infection as well as for cancer.

  • Overcoming Pancreatic Cancer Chemoresistance as a Therapeutic Challenge

    Guest: Professor Rajgopal Govindarajan, Department of Pharmaceutical and Biomedical Sciences, University of Georgia College of Pharmacy
    Friday, March 9, 2012 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    Gemcitabine, a nucleoside analog drug, is the current standard of care for the treatment of pancreatic cancer. Its effects are suboptimal partly due to cellular mechanisms limiting its transport, activation, and overall efficacy. Nonetheless, novel therapeutic approaches are presently under study to circumvent gemcitabine resistance in pancreatic cancer. Specifically, microRNA (miRNA) control of gemcitabine chemoresistance will be discussed. With these new approaches come additional challenges to be addressed. The presentation summarizes the determinants of chemoresistance in the gemcitabine cytotoxicity pathways, provides an overview of miRNA investigational approaches for
    overcoming chemoresistance, and discusses new challenges presented. Understanding the future directions of the field may assist in the successful development of novel treatment strategies for enhancing chemotherapeutic efficacy in pancreatic cancer.

  • Gene Delivery for Protein Drug Discovery and Gene Therapy

    Guest: Professor Dexi Liu, Department of Pharmaceutical and Biomedical Sciences, University of Georgia College of Pharmacy
    Friday, March 2, 2012 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    Discovery of protein drugs has been one of the major focuses in biotechnology. Conventional approach involves expression of the candidate protein in cultured cells, isolation of the expressed protein from cell extracts or medium, and assessment of its therapeutic activity by injecting the protein into an animal. This talk will describe a new approach toward identification of a therapeutic protein or for protein drug discovery. The strategy involves the development of gene delivery method to allow expression of the candidate gene directly in animals bearing a disease, thereby bypassing the need for preparation and administration of protein into animals. The talk will center around recent progress in development of synthetic carriers and physical method for gene delivery. The advantage and disadvantages of the delivery
    systems, and their potential for gene therapy will also be discussed.

  • Rational Engineering of Nanowire Crystal Structure and Superstructure

    Guest: Professor Michael A. Filler, School of Chemical & Biomolecular Engineering, Georgia Institute of Technology
    Friday, February 24, 2012 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    Semiconductor nanowires promise exciting advances in fields as diverse as optoelectronics, photonics, quantum computing, and energy harvesting. The physical properties of these materials, and nanostructures in general, are intimately connected to their structure, which must be controlled with atomic-level precision. This remains a challenging task in many systems and stems from an inadequate chemical understanding of common synthetic routes. This presentation will provide an overview of our recent efforts to bridge this knowledge gap. In particular, realtime in-situ infrared spectroscopy measurements coupled with post-growth electron microscopy demonstrate the important, and as of yet unrecognized, role of transient surface chemistry during vapor-liquid-solid nanowire growth. Our findings indicate that covalently bonded hydrogen atoms are directly responsible for the planar defects (e.g. twinning boundaries) and growth direction transitions (e.g. <111> vs. <112>) that are frequently observed for Si nanowires. We subsequently leverage this fundamental knowledge to create complex semiconductor superstructures via temporal modulation of growth chemistry. For example, the use of “molecular masks,” which either allow or prevent conformal epitaxy, enables the fabrication of diameter-modulated nanowires with user-defined periodicity. These and other newly developed synthetic strategies open a number of new avenues to rationally engineer the crystal structure and properties of nanoscale semiconductors.

  • First-Principles Computational NanoBio Technology

    Guest: Professor Seung Soon Jang, Georgia Institute of Technology
    Friday, February 3, 2012 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    In this presentation, I will discuss about how the first-principles computational methods (quantum mechanics and molecular dynamics simulation) can make contributions to the nanobio technology: understanding of the given nanoscale systems and design of new systems. The first part is the nanostructured polymer membranes for fuel cell technology in which the first-principles methods were used to establish understandings of the relationship between the nanostructures of material and the proton transport properties. First, the hydrated nafion membrane is discussed for the structure-property relationship, and then a new molecular architecture designed from such relationship is presented. In the second part of this presentation, I will talk about the nanoscale molecular electronics such as molecular switch showing an electromechanical switching behavior. In this part, the first-principles methods predict the probable molecular configurations of molecular electronic device and its corresponding electron transport properties. For the last part of my talk, I will present the nanostructured biomaterials such as hydrogel in which a hydrophilic polymer network confines significant amount of water. To develop a good hydrogel with desirable properties in terms of mechanical and transport properties, the molecular mechanisms for mechanical deformation and molecular diffusion are investigated using the first-principles.The bottom line of my talk is how the multiscale first-principles computational methods can work together to investigate the nanoscale systems and help design new material based on the structure-property relationship for better desirable properties.

  • Statistical Mechanics of Molecular Structure Formation Processes in Theory and Application

    Guest: Professor Michael Bachmann, Department of Physics and Astronomy, UGA
    Friday, January 27, 2012 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    Folding and aggregation of molecules, as well as the adsorption of soft organic matter to solid inorganic substrates belong to the most interesting challenges in studies of structure formation and function of complex macromolecules. The substantially grown interest in the understanding of basic physical mechanisms underlying these processes is caused by their impact in a broad field that ranges from the molecular origin of the loss of biological functionality as, for example, in Alzheimer's disease, to the development of nanotechnological applications such as biosensors. A key factor that noticeably contributed to the accelerated development of the field has been the rapid increase of available computational resources and with it the development of efficient simulation strategies. In this talk, I am going to review different modeling approaches that aim at a theoretical understanding of properties of molecular structures. This includes mesoscopic and microscopic models for the folding of polymers and proteins, for aggregation, and for technologically particularly interesting hybrid systems of soft and solid condensed matter.

  • Imaging and mapping brain architectures

    Guest: Professor Tianming Liu, Department of Computer Science, UGA
    Friday, January 20, 2012 4:00 pm - 5:00 pm
    Location: Riverbend Research South Laboratory Auditorium

    Understanding and mapping the organizational architecture of the brain has been of keen interest for centuries. With the advancements of modern imaging techniques, the pace of scientific discoveries of principles underlying the evolution, development, and organization of brain architectures has been accelerated. This talk will present our recent efforts in discovering general principles of structural, connectional and functional brain architectures by applying macro-scale neuroimaging and micro-scale bioimaging techniques and computational methods. The applications of these discovered principles in neuroscience, medicine and computer science will also be showcased and discussed.

  • Micro/Nanofluidic Physics in Bio- and Energy-Systems

    Guest: Professor Rui (Jim) Qiao, Department of Mechanical Engineering, Clemson University
    Friday, December 2, 2011 4:00 pm - 5:00 pm
    Location: Riverbend Research South Auditorium

    Micro/nanofluidics deal with interfacial and transport phenomena at micro/nanoscale, and they received significant attention in the last two decades largely due to their potential applications in biochemical fields. While the significant promise (aka hype) of micro/nanofluidics is yet to be
    realized as envisioned in the 1990s, the importance of micro/nanofluidic physics in practical technologies is widely recognized. Here we present two examples in which micro/nanofluidics physics play a central role in determining the viability and performance of a technology. In the first case, we examine ink-jet based bio-manufacturing, in which cells are delivered with high spatial resolution by ink-jets. While the viability of this technique has long been doubted, we show that, using scaling analysis and computer simulations, cell experiences strong but very brief
    shearing, which can explain the apparent success of the technique. By elucidating the flow physics underlying the printing process, we identify the mechanisms responsible for cell damage and suggest methods for alleviating the cell damage during printing. In the second case, we examine the capacitive electrical energy storage using supercapacitors. We show that simple interfacial physics are behind the anomalous enhancement of capacitance in sub-nanometer pores. We show that a fundamentally new regime of fluid transport emerges in the next-generation supercapacitors based on hierarchical nanomaterials, and exciting opportunities exist in harnessing the new flow physics in these materials.

  • Strain Effect Analysis on the Thermoelectric Figure of Merit in Si/Ge Nanocomposites

    Guest: Professor Gang Li, Department of Mechanical Engineering, Clemson University
    Friday, October 21, 2011 7:00 pm - 8:00 pm
    Location: Riverbend Research South Auditorium

    Thermoelectric (TE) energy conversion is a technology that converts thermal energy to electrical power and vice versa. Thermoelectric technology has significant advantages over other energy conversion technologies due to its compactness, high reliability and zero emissions of noise and pollutants. However, the energy conversion efficiency in existing thermoelectric devices is typically low. Since early 1990s, many studies have shown that higher energy conversion efficiency is achievable by reducing the phonon
    thermal conductivity of TE materials using nanostructured thermoelectric materials. While the future of the technology is promising, the performance of state-of-the-art nanostructured materials is still much less than that of the conventional energy conversion techniques. In this work, we suggest that, by utilizing the different responses of electron and phonon transport to mechanical strains, the efficiency of
    nanocomposite TE materials can be further improved through mechanical tuning. We perform computational analysis to investigate strain effect on the thermoelectric figure of merit in n-type Ge nanowire-Si host nanocomposite materials. The Seebeck coefficient and electrical conductivity of the Si/Ge nanocomposites are calculated by an analytical model derived from the Boltzmann transport equation (BTE) under the relaxation-time approximation. The effect of strain is incorporated into the BTE through strain induced energy shift and effective mass variation calculated from the deformation potential theory and a degenerate kp method. Strain effect on phonon thermal conductivity in the nanocomposites is computed through a model combining the strain dependent lattice dynamics and the ballistic phonon BTE. Electronic thermal conductivity is computed from electrical conductivity by using the Wiedemann-
    Franz law. Normal and shear strains are applied in the transverse plane of the Si/Ge nanocomposites. Thermoelectric properties including electrical conductivity, thermal conductivity, Seebeck coefficient and dimensionless figure of merit are computed for Si/Ge nanocomposites under these strain conditions.

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