California NanoSystems Institute
CNSI
Text Size: A A A A

June 03, 2008

Gautam Mukhopadhyay
Indian Institute of Technology-Bombay
Physics


Streaming Video
  

On Scattering and Absorption of EM Radiation by Coated Ellipsoidal Nanoparticles
The scattering and absorption of electromagnetic radiation has been well studied for spherical particles within Mie theory; and for ellipsoidal particles using quasi-electrostatic approximations. Generalizations of these for particles with isotropic coating are also straight forward. However, a thin coating is invariably anisotropic, and therefore expected to show optical properties somewhat different from the case of isotropic coating. In this talk, I shall describe the theory for anisotropically coated ellipsoidal metallic nanoparticles. I shall use quasi-electrostatic approach and show that the there can be strong resonant coupling between the plasmon of the core with the molecular frequency of the coating. This is illustrated through the extinction spectrum for an arbtrary coated ellipsoid. If time permits, I shall discuss the scattering properties as well. This effect can be utilized, for instance, for sensors applications.

May 27, 2008

Hideo Ohno
Tohoku University
Research Institute of Electrical Communication


Streaming Video
  

Ferromagnetic III-V Semiconductors
Ferromagnetism in Mn-doped GaAs and InAs semiconductors is hole-induced [1-3] and thus magnetism can be manipulated by changing its carrier concentration by electric field [4, 5]. It has also been shown that spin-current flowing along with the electrical current in these materials exerts torque on localized Mn spins, resulting in, for example, current induced domain wall motion [6-8]. This presentation reviews the recent developments on ferromagnetic III-V semiconductors. Remaining issues particularly room-temperature ferromagnetism reported in various semiconductors will be discussed.

May 20, 2008

Junji Kido
Yamagata University
Research Group for Organic Electronic Materials and Devices


Streaming Video
  

Development of High Performance Organic Light-Emitting Devices for Lighting Application
Organic light-emitting devices (OLEDs) are expected to be the next generation flat panel displays and have been commercialized for mobile phones and car audios. In addition, the performance of white-light-emitting OLEDs have been steadily improved and, today, they are considered to be the light source of the next generation. In this talk, the recent development of high performance OLEDs will be discussed.

Approaches towards the high efficiency and long operating lifetime are introduced. High quantum efficiencies can be obtained by using phosphorescent emitters such as iridium complexes. It is important to use wide-energy-gap materials as the host and carrier transport materials to confine the triplet excited energy of the phosphorescent emitter. We synthesized a variety of wide gap materials and succeeded to fabricate extremely high efficiency OLEDs. External quantum efficiency (QE) of 25-30% was achieved for blue, green and red OLEDs, which correspond to the internal QE of nearly 100%. By using carrier transport materials with high carrier drift mobility, power efficiencies of over 50 lm/W for sky blue, and 130 lm/W for green can be obtained.

Device lifetime has been significantly improved by using tandem structure, called multiphoton structure, due to the reduced drive voltages. For a fluorescent multiphoton OLED, lifetime of over 1 million hours, which is more than 100 years, with the initial luminance of 100 cd/m2 was achieved. Internal QE of over 140% was reached by combining phosphorescent emitters and the multiphoton devices. Regarding the long-life OLEDs, we recently developed a simple method to fabricate OLEDs having graded organic/organic interfaces to improve lifetime. The newly developed method employs the in-line vacuum evaporator, which was developed in our laboratory. Operating lifetime for the device with the graded structure appears to be longer than that of the conventional hetero-junction structure. By combining the above techniques, OLEDs can be extremely efficient and possess extremely long lifetime. Luminaires using high performance white OLEDs have been developed.

May 13, 2008

Keith Hodgson
Stanford University Chemistry


Streaming Video
  

Photon Science and the Coming Revolution Enabled by X-ray Free Electron Lasers
Much of our understanding of structure and function of objects on the nanoscale - from drugs interacting with their biological targets to the behavior of materials as they superconduct at even higher temperatures - comes from "seeing the invisible". X-rays enable us to determine the arrangement of individual atoms and study structures. Today's state of the art x-ray synchrotron sources provide exquisite detail for such studies but lack the brightness to investigate materials as they undergo movements on the atomic scale. This will all change within 2 years with the beginning of operation of the world's first x-ray free electron laser (called LCLS at Stanford) whose peak brightness will surpass today's sources by about 10 billion! This lecture will first illustrate how such x-ray laser radiation will be produced and provide a brief overview of LCLS. The science LCLS will enable - from studying chemistry in "real time" to the imaging of large, non-crystalline nanostructured materials will also be discussed.

May 06, 2008

Xiaowei Zhuang
Harvard University
Chemistry/Chemical Biology/Physics


Streaming Video
  

Nanoscopic Imaging of Biomolecules and Cells
My research lab develops optical imaging techniques to monitor the behavior of individual biological molecules and complexes in vitro and in live cells. The lab's current research is focused on three major directions: (1) to develop super-resolution optical imaging techniques that allow imaging of cells and tissues with molecular-scale resolution, (2) to probe how biomolecules function, especially how proteins and nucleic acids interact, using single-molecule approaches; (3) to develop live-cell imaging techniques and to investigate virus-cell interactions. In this talk, I will focus on the first two topics.

April 29, 2008

Belinda Seto
National Institute of Health (NIH)
National Institute of Biomedical Imaging and Bioengineering (NIBIB)


Streaming Video
  

Promise of Nanomedicine
The application of nanotechnology in biomedical research has advanced our understanding of biological processes at the molecular level. These molecular interactions and their regulation underpin the basis of human biology and pathogenesis of diseases. The seminar will focus on the National Nanotechnology Initiative, the NIH nanomedicine initiative and nanotechnology program at the National Institute of Biomedical Imaging and Bioengineering.

April 22, 2008

Caroline Ross
Massachusetts Institute of Technology
Materials Science and Engineering


Streaming Video
  

Magnetic Rings for Memory and Logic
Magnetic data storage devices, including magnetic random access memories and patterned media, are based on thin film magnetic nanostructures. Magnetic multilayer thin film rings present a particularly interesting geometry, and their rich behavior offers opportunities for development of multibit magnetic memories and programmable, non volatile logic devices. A single layer magnetic ring can adopt a variety of stable and metastable magnetic states characterized by different numbers of domain walls, and the behavior of a multilayer ring is further complicated by magnetostatic and exchange interactions between the individual magnetic layers. In this study, rings with nanoscale to micron scale dimensions are made using electron beam lithography and self-assembled block copolymer lithography. We will describe the behavior of single layer, multilayer and exchange-biased magnetic rings, including control of the chirality of the magnetization direction, and magnetotransport measurements made on electrically contacted rings that show voltage signals of 1000s of percent, and we will discuss how these structures may be used in multibit memory cells and logic devices.

April 08, 2008

Taekjip Ha
University of Illinois at Urbana-Champaign
Physics and Biophysics


Streaming Video
  

Extreme Sports with Nature's Nano-Machines, in singulo
Single molecule measurement techniques have revolutionized biological inquiries by providing previously unobtainable data on elementary molecular processes. However, most studies thus far have been limited to single isolated molecules even though these molecules do not function in isolation in the cell. To emulate the cellular conditions better, more complex systems with multiple components need to be looked at. This requires major improvements in measurement and analysis techniques which is a subject of this talk. I will present our attempts to develop 'extreme in vitro single molecule techniques' in order to maximize information content in single molecule analysis.
April 01, 2008

Gerard Wong
University of Illinois at Urbana-Champaign
Materials Science and Engineering


Streaming Video
  

Molecular 'hole punchers' in bionanotechnology: From HIV cell penetrating peptides to femtosecond movies of water structure in confined geometries
The TAT protein transduction domain (PTD) of the Human Immunodeficiency Virus (HIV-1) can cross cell membranes with unusual efficiency, and has many potential biotechnological applications. In this seminar, we elucidate the pore-forming mechanism of HIV TAT cell penetrating peptides using synchrotron x-ray diffraction. We also examine the transport of water through pores and other confined geometries, which are notoriously difficult to access experimentally at molecular time-scales and length-scales simultaneously. Using 3rd generation synchrotron sources, it is possible to combine spectroscopy and diffraction in an inelastic x-ray scattering (IXS) experiment. We show that it is possible to do experiments in the frequency and momentum domains, and reconstruct water dynamics in nanoscopic geometries at sub-Angstrom spatial and 50 femtosecond temporal resolution.