TABLE OF CONTENTS PROGRAM……………………………………………………………………………………..5 PLENARY STEM CELL AND NUCLEAR BIOPHYSICS - NANOMECHANICAL ASPECTS OF DIFFERENTIATION ................... P1 BIOMEDICAL APPLICATIONS OF SCANNING ION CONDUCTANCE MICROSCOPY............................................. P2 NANOMEDICINE: NEW APPROACHES TO OLD PROBLEMS ............................................................................... P3 ENGINEERING CARBON NANOTUBE ARCHITECTURES ...................................................................................... P4 CELLULAR SENSING OF FORCE AND GEOMETRY THROUGH FORCE-DEPENDENT UNFOLDING AND ONCOGENE PHOSPHORYLATION........................................................................................................................ P5 INVITED BIOLOGICALLY-INSPIRED ENGINEERING AND MEMS FOR REALIZATION OF NANOMEDICINE ...................... I1 MULTI-FUNCTIONAL NANOSYSTEMS FOR TUMOR-TARGETED DRUG AND GENE DELIVERY ......................... I2 A NOVEL PCR BASED DNA MICRO-ANALYZER.................................................................................................. I3 SECOND HARMONIC GENERATION IN COPPER NANOPARTICLES ..................................................................... I4 MULTIMODAL CERAMIC NANOVECTOR ............................................................................................................. I5 INTEGRATED SYSTEMS FOR MANUFACTURING AT THE NANOSCALE .............................................................. I6 APPLICATION OF INNOVATIVE FLUIDICS APPROACHES FOR AIR AND LIQUID BASED BIOLOGICAL POINT DETECTORS.......................................................................................................................................................... I7 SYNTHESIS OF NANOSTRUCTURED SPINTRONIC MATERIALS USING PULSED LASER DEPOSITION ................. I8 SELF-ASSEMBLING OF AU AND AG NANOPARTICLES USING HYDROGEN BONDING ....................................... I9 NANOSCIENCE AND NANOTECHNOLOGY RESEARCH AT THE WILLIAM L. CLAY CENTER FOR MOLECULAR ELECTRONICS AT THE UNIVERSITY OF MISSOURI-ST. LOUIS........................................................................ I10 DENSITY FUNCTIONAL THEORY: FROM CONVENTIONAL BULK TO NANOPOROUS MATERIALS .................. I11 CONTRAST-ENHANCED RADIOTHERAPY OF CANCER ..................................................................................... I12 NANOMEDICINE IMPROVES DRUG SAFETY AND EFFICACY............................................................................. I13 CHEMICALLY RESPONSIVE NANOREACTOR MATERIALS FOR BIOLOGY AND MEDICINE ............................. I14 FIRST-PRINCIPLES STUDY OF BORON NANOSTRUCTURES: SHEETS AND NANOTUBES.................................. I15 FUNCTIONAL DENDRITIC MATERIALS AND ORGANIC-INORGANIC HYBRID MATERIALS ............................. I16
Transcript
TABLE OF CONTENTS PROGRAM……………………………………………………………………………………..5
PLENARY
STEM CELL AND NUCLEAR BIOPHYSICS - NANOMECHANICAL ASPECTS OF DIFFERENTIATION................... P1
BIOMEDICAL APPLICATIONS OF SCANNING ION CONDUCTANCE MICROSCOPY............................................. P2
NANOMEDICINE: NEW APPROACHES TO OLD PROBLEMS ............................................................................... P3
NANOENGINEERING OF AMINOSUGAR FUNCTIONALIZED GOLD NANOPARTICLES FOR SURFACE TARGETING
OF CANCER CELLS .............................................................................................................................................L9
SYNTHESIS AND IN-VITRO STUDIES OF GLYCOPROTEIN LABELED GOLD NANOCHAIN...............................L10
SIZE CONTROLLED SYNTHESIS OF MAGHEMITE NANOPARTICLES FOR BIOMEDICAL APPLICATIONS .......L11
BIOSENSOR DESIGN AND FABRICATION USING GOLD NANOPARTICLES .......................................................L12
DETECTION OF HIV-1VIRAL ENVELOPE SURFACE PROTEINS USING QUANTUM DOTS AND FÖRSTER
RESONANCE ENERGY TRANSFER (FRET) IN LIQUID CORE WAVEGUIDES.....................................................L13
PRODUCTION OF GOLD 198/199 NANOPARTICLES FOR POTENTIAL USE IN DIAGNOSIS AND TREATMENT OF
The shape and behavior of mammalian cells is defined by an interplay between extracellular signals (physical and chemical) and the cellular responses. In particular, external molecular-level geometry and forces have major effects on cell behavior (Vogel and Sheetz, Nature Rev. Mol. Cell Biol. 7:265, 2006). A prominent example is the rigidity response since transformed cells can often grow on soft agar whereas normal cells require rigid surfaces to grow, i.e. oncogenes are involved in defining cell mechanics (reviewed in Giannone and Sheetz, Trends Cell Biol., 16:213, 2006). Thus, a critical component for cancer is the ability to override the requirement for force production and rigidity response. For most mammalian cells there are relatively few types of motility that are evident from quantitative analyses of rapidly spreading fibroblasts (Dubin-Thaler et al., Biophys. J. 86:1794-1806, 2004). One motile phase that we have studied extensively involves periodic contractions (24 s period) in local regions of the leading edge of the cell (Giannone et al., Cell, 116:431-443, 2004). The periodic signal is carried radially from the cell edge toward the center and is part of a general mechanism for rigidity-directed movement and pathfinding. Another motile phase involves the movement of individual collagen fibers in a hand-over-hand fashion (Meshel et al., Nature Cell Biol. 7:157-164, 2005) where the geometry of the fiber is being sensed. Rigidity and geometry responses in these systems are dependent upon the cytoskeleton and force-dependent tyrosine phosphorylation through oncogenes (Sawada and Sheetz, J Cell Biol. 156:609-15, 2002; Tamada et al., Developmental Cell, 7:706-718, 2004) that appears to involve unfolding of cytoplasmic kinase substrates, particularly p130Cas (Sawada et al. ). Recent studies indicate that the cell rigidity response requires RPTPα and occurs preferentially at the leading edges of moving cells through forces of 10-20 pN generated by displacements of 50-100 nm (Jiang et al., Biophys J. 90:1804, 2006). The mechanism of rigidity response involves recruitment of Fyn kinase in a palmitoylation-dependent process and the phosphorylation of p130Cas at the leading edge (Kostic and Sheetz, Mol Biol Cell, 17:2684, 2006). A displacement mechanism for the rigidity response is postulated. We will discuss how cells organize motility tools in motile phases (Döbereiner et al., Phys. Rev. Letters. 93:108105-1-4, 2004) in a dialogue with the environment to define cell morphology and behavior over time.
Nanotechnology is expected to have a revolutionary impact on cancer diagnosis and therapy. In cancer therapy, targeting and localized delivery are the key challenges. To wage an effective war against cancer, we have to have the ability to selectively attack the cancer cells, while saving the normal tissue from excessive burdens of drug toxicity. Furthermore, newer generation of molecular therapies, such as gene therapy and siRNA, will require intracellular delivery strategies for effective outcomes. In this presentation, I will discuss the different nanotechnology platforms that we have developed over the last ten years for targeted drug and gene delivery to the tumor mass. Using biodegradable polymers, we have formulated nanocarriers for hydrophobic anticancer drugs such as paclitaxel and tamoxifen. These nanocarriers can be tuned to release their content either by slow diffusion or upon pH-responsive trigger. Recently, we have used these nanocarriers for combination drug delivery to overcome multidrug resistance in cancer. Gelatin-based nanocarriers are developed for tumor-targeted gene delivery. Using plasmid DNA encoding for soluble Flt-1 (VEGF-R1) receptor, we show enhanced transfection and therapeutic efficacy in human breast cancer xenograft model. Nanomemulsion are heterogenous liquid system comprising of oil droplets in the nanometer length scale surrounded by water. Using oils rich in polyunsaturated fatty acids (e.g., �-linolenic acid), we have developed nanoemulsions that can facilitate drug delivery across different biological barriers, such as the blood-brain barrier. In addition, these nanoemulsions can be used for combination magnetic resonance imaging (MRI) and drug delivery for image-guided cancer therapy. Lastly, we work on metal nanoparticles, primarily gold and iron oxide-gold core-shell nanosystems. Multifunctional gold nanoparticles allow for simultaneous imaging and gene delivery in cells. Superparamagnetic iron oxide-gold core-shell nanoparticles are used for magnetic cell separation, MRI contrast enhancement, and hyperthermia.
I 3
A NOVEL PCR BASED DNA MICRO-ANALYZER
Shantanu Bhattacharya
Birck Nanotechnology Center, Purdue University Email: [email protected]
A micro-fluidic assay to quickly analyze microscopic samples of DNA is being developed for field applications. It consists of a micro-PCR chamber, micropumps, and micro-heaters. Additional components of the device include gel electrophoresis micro-channels and solid core waveguide fluorescence collectors. We have investigated the surface dynamics of a novel polymer surface coating to achieve amplification of template with pico-gram level concentration. Confirmation of surface behavior with ATR FTIR has revealed the temporal transition of the coating surface from hydrophilic (immediately after oxygen plasma exposure) to hydrophobic (a process achieved by oxygen plasma treatment). This is indicated by a gradual methylation and dehyroxylation with post exposure relaxation time. Non specific binding of nucleic acids has been further evaluated on this surface with fluorescence characterization. The micro-pumps, PCR chamber and capillary electrophoresis have been designed fabricated and tested. A variety of physical processes like mixing, pumping and valving of fluids at the microscopic length scale needed at various points in the analyzer have been achieved. For fabrication of the device, a regime has been developed for bonding PDMS surfaces to a variety of substrates (silicon in the present case). The unique heater design formulated by our team for thermal cycling of the PCR micro-chamber has extremely short ramp-up and down times at a low operating power of 6-watts. We have successfully achieved a compression in the cycle time by a factor of ten from the conventional PCR system. One requirement of the DNA assay posed by its intended field applicability is the need for operating at low powers. One problem with the current capillary electrophoresis assays is a use of extraordinarily high DC voltages. We have developed a protocol of doping agarose gels with platinum nanoparticles which change the overall conductivity level. The doping process also increases the dielectric constant of agarose. Due to this effect we have observed an almost two fold increase in the mobility of nucleic acid stains. This provides us a future direction of using this conducting gel matrix for low voltage capillary electrophoresis. The stain resolution does not get altered due to the dopant. The successful development of our lab-on-a-chip device will have several advantages over conventional bench top systems, which primarily include an overall reduction in size, reduced use of reagents, decreased power requirements, increased speed and accuracy of analysis, and increased portability for field use. We envision this assay as a highly sensitive analyzer tool with a capability to pick-up trace samples with high accuracy.
I 4
SECOND HARMONIC GENERATION IN COPPER NANOPARTICLES
Manabendra Chandra and Puspendu K. Das
Department of Inorganic and Physical chemistryIndian Institute of Science
Our research activities address basic issues on growth and characterization of nanostructured materials and fabrication of devices using these materials. Pulsed Laser Deposition (PLD) is an excellent technique to grow nanostructures of starting from simple metals such as gold, silver, and platinum to complex materials such as high Tc oxide superconductors, ferroelectrics, high dielectrics, compound semiconductors, and polymers. Using PLD technique we have successfully grown various nanostructured materials on surfaces such as metals (Au, Ag, and Co), alloys (Fe-Ni), dielectrics (SrTiO3), and compound semiconductors (ZnO). My presentation will focus more on oxide based nanostructured spintronic materials for technological applications such as (1) electro-optic switches1, (2) ultra-sensitive magnetic field sensors2, (3) spin-polarized solar battery3, and (4) quantum-based logic and memory for high speed computationi. Spintronics, a new approach to electronics, is an emerging field based on the up and down spins of the charge carrier rather than on the electrons and holes as in traditional semiconductor electronics. We have grown high quality nanostructured spintronic materials such as Mn and Co doped ZnO dilute magnetic semiconductors (DMS) on various substrates at various conditions using PLD. The structural, electrical, optical, and magnetic properties of these nanostructured materials have been investigated using various characterization techniques such as X-ray diffraction, Raman spectroscopy, Atomic Force Microscope, and magto-transport measurement. Work partly supported by a National Science Foundation Grant # DMR-0321187 to Kartik Ghosh. References 1. S. A. Wolf, “Spintronics: A spin based Electronics vision for the future”, Science 294, 1488 (2001). 2. D.D. Awschalom and J.M. Kikkawa, “Electrical Spin and Optical Coherence in Semiconductors”, Physics Today 52, 33 (1999). 3. Igor Zutic, Jaroslav Fabian, and S. Das Sarma, “Proposal for a spin-polarized solar battery”, Appl. Phys. Lett. 79, 1558 (2001). 4. Semiconductor Spintronics and quantum computation” edited by D. Loss and N. Samrath, Springer Verlag, 2002.
HYDROGEN BONDING Keisaku Kimura*, Yang Yang, Hiroshi Yao, and Seiichi Sato
Graduate School of Material Science, University of Hyogo There is a considerably increasing interest in the field of nanometer-sized substances such as surface
modified nanoparticles, nanodiscs and nanowires due to their notable electronic and optical properties based on the quantum size effect. Designing and fabrication of macroscopic architecture using these nanometer-sized materials as a constructing block will be a next target in the coming nanotechnology era. There are many reports on the construction of two and three-dimensional superlattices made of metallic nanoparticles, because it will provide a peculiar performance based on collective electronic behaviors resulting from interparticle interactions between neighboring ordered particles. In order to construct super structure from nanoparticles, we can use inherent van der Waals attractive force, static coulombic forces, and hydrogen bonding force. Rapid evaporation of organic solvent on solid substrates is a commonly used strategy for providing a three-dimensional architecture from alkane thiol protected metallic nanoparticles. In this case, van der Waals attraction is a main force to bind particles. We have developed a new class of superlattices at an air/water interface by virtue of hydrogen bonding interactions under an equilibrium condition [K.Kimura, S.Sato, H.Yao, Chem.Lett., 2001, 372], contrast to regular lattices by spontaneous evaporation of organic solvent with van der Waals force.
Two metallic nanoparticles, gold and silver, were used to construct nanoparticle assemblies at an air/liquid or liquid/liquid interfaces. Three thiols were used as a surface modifier, dicarboxylic acid (mercaptosuccinic acid), amino acid (N-(2-mercaptopropionyl-glycine)), and tripeptide (glutathione reduced form). The formed powdered samples were re-dispersible several times in water without aggregation. The mean particle diameter was typically 3.5 nm (fwhm: 0.4 nm). The crystallization took place in 4-10 days in the presence of an appropriate amount of hydrochloric acid in a sealed vial giving numerous micrometer-sized nanoparticle crystals with clear crystal habit. Vapor diffusion technique was also used to form superlattices from polydisperse powders. Some examples are shown in the following figures.
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I 10
NANOSCIENCE AND NANOTECHNOLOGY RESEARCH AT THE
WILLIAM L. CLAY CENTER FOR MOLECULAR ELECTRONICS AT
Contrast-enhanced radiotherapy (CERT) utilizes previously neglected effects of x-rays absorbed by contrast agents. Resulting secondary ionizing radiation transfers significant energy and damages a limited volume. By concentrating contrast in a lesion, a lethal radiation dose can be delivered quickly to a tumor with minimal toxicity to nearby tissue. Therefore, CERT should safely create tumor debris and could be a useful adjuvant for immunotherapy. We wanted to evaluate toxicity and efficacy of CERT alone and combined with an immune modulator in parallel human and canine clinical studies. In addition, we sought to follow molecular response in tumor aspirates during treatment. Small lesions and post-operative tumor beds with positive resection margins were treated with one CERT dose alone. Locally advanced and metastatic spontaneous canine tumors were treated with one CERT dose followed by continuous infusion or intratumoral injection of hGMCSF immunotherapy for 3 days. Tumor aspirates were analyzed by RT-PCR using a panel of canine genes. We treated advanced cancers in 43 dogs using CERT without toxicity. There were no recurrences in the 13 post-operative tumor beds treated with CERT alone. Of 27 dogs treated with CERT plus hGMCSF, approximately 70% had significant local responses and immune infiltrates. There has been no evidence of anti-tumor immunity against distant disease. Thus far, there are 2 dogs without evidence of recurrence more than 1 year after treatment. Employing intratumoral injection of commercially available contrast agents, CERT has clinical efficacy with minimal toxicity when used alone or in combination with immunotherapy for advanced canine malignancies. Response was not associated with specific pathology or putative radiosensitivity.
I 13
NANOMEDICINE IMPROVES DRUG SAFETY AND EFFICACY
Hayat Onyuksel
Department of Biopharmaceutical Sciences and Bioengineering,
University of Illinois at Chicago, Chicago IL 60612
We present a gold nanoparticle (Au/NP) based FRET assay to monitor DNA hybridization and the cleavage of DNA by nucleases. The fluorescence of a fluorophore tagged ss-DNA increases by a factor of 80 when it binds to a complementary DNA while the addition of single-base mismatch DNA had no effect on the fluorescence efficiency. We present theoretical and experimental results on dye fluorescence quenching induced by gold nanoparticles of different particle sizes. Fluorescence spectra clearly show that the quenching efficiency decreases by increasing size of the gold nanoparticles or increasing the distance between dye and nanoparticles. The mechanism of size and distant dependence of fluorescence quenching has been discussed. Fluorescence signal enhancement is observed by a factor of 120 after the cleavage reaction in the presence of S1 nuclease. This method has several advantages as follows: i) it is several orders of magnitude more sensitive than the usual gel electrophoresis or HPLC technique and few orders of magnitudes more sensitive than UV assays; ii) one can use this technique for multiple targets DNA damage detection and iii) it is much faster and easier to detect. Our experimental observation paradigm for design of optical based molecular ruler strategies at distances more than double the distances achievable using traditional dipole-dipole Columbic energy transfer based methods. This long-range feature will allow the development of biosensors and homogeneous bioassays that are not possible by using general FRET process e.g. catalytic activities of many enzymes such as HIV proteases and matrix metalloproteiases (MMP) as well as the proteins involved in cellular apoptosis. Given the simplicity, speed, and sensitivity of this approach, the described methodology could easily be extended to a high throughput format and become a new method of choice in all applications that require an assay for DNA hybridization and cleavage. A compact, highly specific, inexpensive and user friendly optical fiber laser-induced fluorescence (LIF) sensor based on fluorescence quenching by nanoparticles has been developed to detect single-strand (ss) DNA hybridization as well as DNA cleavage in femtomolar level. Looking into the future, we expect these compact sensor developments will have important implications in the development of better biosensors and bioassay for application to pathogen detection, clinical analysis and biomedical research. Our observations also point toward the exciting possibility to perform spatially confined detection on array formats of biological recognition, for example, RNA/DNA hybridization or antibody-antigen recognition.
I 18
COMBUSTION SYNTHESIS OF ULTRA-HIGH SURFACE AREA
METAL FOAMS Steven F. Son
School of Mechanical Engineering, Purdue University
eering3, Medical Pharmacology and Physiology4, University of Missouri, Columbia,
MO 65201, USA UV photolysis of caged Ca2+ has been widely used to study the dynamics of Ca2+-dependent exocytosis from living cells. Traditionally this technique is integrated with patch-clamp techniques and/or carbon-fiber amperometry, which are labor-intensive and low-throughput. Using photolithography and other microfabrication techniques, we have developed devices with transparent indium-tin-oxide (ITO) electrodes to detect quantal catecholamine release from adrenal chromaffin cells. A 100 nm – thick ITO film was sputter-deposited onto glass coverslips, which was then patterned into working ITO electrodes (15 µm by 35 µm) using photolithography and wet-etching techniques. Bovine adrenal chromaffin cells were brought into contact with the working ITO electrodes for recordings. We initially tested cells whose plasma membrane was permeabilized with digitonin to allow loading of the Ca2+ cage NP-EGTA and Ca2+ indicator dyes from the bath solution. One complication of this approach is that photolysis of cage resulted in a large time-dependent background current at the electrochemical electrode. We therefore tested loading cells using acetoxymethyl (AM) ester derivatives of NP-EGTA and Fura-4F. Upon UV photolysis of caged Ca2+, a uniform rise of intracellular Ca2+ concentration within those cells lead to quantal release of oxidizable catecholamines measured amperometrically by the ITO electrodes beneath them. Simultaneously [Ca2+]i was monitored by the Ca2+ indicator dye. We observed a burst of amperometric spikes upon rapid elevation of intracellular Ca2+ concentration and a “priming” effect of sub-stimulatory [Ca2+]i on the response of cells to subsequent [Ca2+]
nclude that UV photolysis of caged Ca is a suitable stimulation technique for higheoughput studies of Ca2+-dependent exocytosis on microfabricated biochips. Supported b
L 5
A GLUCOSE BIOSENSOR ENCAPSULATED IN ERYTHROCYTES
Majed Grant
Department of Biological Engineering, University of Missouri-Columbia,
robes are based on a competitive binding
anoprobes displayed a sensitivity
f at least 0.5 mM below 5 mM and a sensitivity of at least 3 mM above 5 mM, which meets
ur initial requirements for an implantable glucose sensor.
The shape and behavior of mammalian cells is defined by interplay between extracellular signals (physical and chemical) and the cellular responses. In particular, external molecular-level geometry and forces have major effects on cell behavior (Vogel and Sheetz, Nature Rev. Mol. Cell Biol. 7:265, 2006). A prominent example is the rigidity response since transformed cells can often grow on soft agar whereas normal cells require rigid surfaces to grow, i.e. oncogenes are involved in defining cell mechanics (reviewed in Giannone and Sheetz, Trends Cell Biol., 16:213, 2006). Thus, a critical component for cancer is the ability to override the requirement for force production and rigidity response. For most mammalian cells there are relatively few types of motility that are evident from quantitative analyses of rapidly spreading fibroblasts (Dubin-Thaler et al., Biophys. J. 86:1794-1806, 2004). One motile phase that we have studied extensively involves periodic contractions (24 s period) in local regions of the leading edge of the cell (Giannone et al., Cell, 116:431-443, 2004). The periodic signal is carried radially from the cell edge toward the center and is part of a general mechanism for rigidity-directed movement and pathfinding. Another motile phase involves the movement of individual collagen fibers in a hand-over-hand fashion (Meshel et al., Nature Cell Biol. 7:157-164, 2005) where the geometry of the fiber is being sensed. Rigidity and geometry responses in these systems are dependent upon the cytoskeleton and force-dependent tyrosine phosphorylation through oncogenes (Sawada and Sheetz, J Cell Biol. 156:609-15, 2002; Tamada et al., Developmental Cell, 7:706-718, 2004) that appears to involve unfolding of cytoplasmic kinase substrates, particularly p130Cas (Sawada et al. ). Recent studies indicate that the cell rigidity response requires RPTP� and occurs preferentially at the leading edges of moving cells through forces of 10-20 pN generated by displacements of 50-100 nm (Jiang et al., Biophys J. 90:1804, 2006). The mechanism of rigidity response involves recruitment of Fyn kinase in a palmitoylation-dependent process and the phosphorylation of p130Cas at the leading edge (Kostic and Sheetz, Mol Biol Cell, 17:2684, 2006). A displacement mechanism for the rigidity response is postulated. We will discuss how cells organize motility tools in motile phases (Döbereiner et al., Phys. Rev. Letters. 93:108105-1-4, 2004) in a dialogue with the environment to define cell morphology and behavior over time.
Research in the Nanomaterials and Biomaterials Laboratory (NBL) at the University
of Missouri-Columbia focuses on synthesis, characterization, and application of novel
nanostructured materials and biomedical materials with advanced properties. Our research
interests integrate a variety of materials, including ceramics, polymers, thin films, nanotubes,
nanowires, and composites, within the general context of materials science, mechanical
engineering, electrical engineering, and tissue engineering. The key rationale of our research
is that 1) materials and systems with nanoscale structures and components exhibit novel and
significantly improved physical, chemical, and biological properties, and 2) the systematic
organization of matter on the nanometer length scale is a key feature of biological systems.
Some of our current research results include: Horizontal Growth of Nanotubes and
Nanowires; Development of Nanotube and Nanofiber Reinforced Composites;
Nanocomposites as Hard Tissue Implants or for Hard Tissue Engineering.
L 17
SCANNING ION CONDUCTANCE MICROSCOPY REVEALS
CLUSTERED PUNCTATE DEPRESSIONS AND VALLEYS IN THE
PLASMA MEMBRANE DURING STIMULATION OF EXOCYTOSIS
FROM CHROMAFFIN CELLS
Wonchul Shin1,2 and Kevin D. Gillis1,2,3
Biological Engineering1, Dalton Cardiovascular Research Center2, and Medical Pharmacology and Physiology3, University of Missouri, Columbia, MO 65211, USA
The rate and extent that vesicles lose their spherical shape and collapse into the surface membrane upon exocytosis is controversial. We used Scanning Ion Conductance Microscopy (SICM) to image changes in surface membrane morphology upon stimulation of exocytosis from bovine adrenal chromaffin cells. SICM is an excellent scanning probe microscopy technique to scan living cells because the pipette probe does not touch and thus deform the membrane surface. We used a distance modulation method of SICM to continuously image cells before and during stimulation with a depolarizing bath solution containing an elevated K+ concentration. We found clustered punctate depressions (100 – 600 nm wide by 40 – 100 nm deep) in some cells, whereas others exhibited extended valley-type structures (widths of > 1000 nm). We observed punctate depressions in 9 out of 56 experiments and valleys or other large morphological changes in 36 out of 56 experiments. Depressions were not seen if Ca2+ was excluded from the depolarizing bath solution. Images that contained punctate depressions were clustered in groups of 2-4 depressions. The average distance between depressions was 0.93 µm for 3x3 µm image sizes and 1.12 µm for 5x5 µm images. Monte Carlo simulations demonstrated that a random clustering of depressions would have mean separations of ~1.56 and 2.6 µm, respectively for 3x3 and 5x5 µm image sizes. Combination of SICM with fluorescent tags of vesicle membrane proteins will be necessary to determine if the depressions indeed reflect sites of exocytosis and if the disappearance of depressions is due to flattening of fused membrane on the cell surface or re-uptake into the cell. Supported by NIH NS40453.
L 18
DEVELOPMENT OF AN OPTICAL NANOBIOSENSOR FOR
DETECTION OF PRRS
R Cody Stringer1, Sheila Grant1, Susan Schommer2, Daniel Hoehn1
1Dept. of Biological Engineering, University of Missouri, Columbia, MO. 2Dept of
Veterinary Pathobiology, University of Missouri, Columbia, MO
Integrin mediated mechano-transduction in vascular smooth muscle cells (VSMC) plays an important role in arteriole physiological functions, such as establishing the basal myogenic tone and regulation of vascular resistance. To understand the mechanism of integrin-mediated VSMC mechano-transduction, we used an atomic force microscope (AFM)
to apply defined pulling forces on VSMC (isolated from rat cremaster arteriole, 70-100 µm diameter) through integrin-fibronectin (FN) adhesions. AFM probes were configured with
fused borosilicate beads (2 µm diameter) at the tip. After coating with FN, the AFM bead tip was brought into contact with VSMC to form adhesions, and step increases of up-ward (z-axis) pulling force (800~2000 pN) were then applied to VSMC through the bead. VSMC responded to the applied force by developing a counterbalancing downward force, however, without an apparent increase of intracellular calcium concentration. Similar force-generating response was also observed in VSMC pre-loaded with BAPTA. Immunofluorescent microscopy studies indicated that FN-coated beads induced clustering of a variety of integrins and formation of actin filament network around the bead. Treatment of the cells with the actin filament depolymerizing compound (cytochalasin D) blocked the VSMC mechanical response, whereas an actin filament stabilizing compound (jasplakinolide) enhanced the VSMC mechanical response. Further studies with ML-7, a specific blocker for myosin light chain kinase (MLCK), also abolished the cellular force response. Similar pulling experiments with other extracellular matrix proteins (collagen I, vitronectin, or laminin) failed to induce a mechanical response of VSMC, however, beads coated with these proteins were able to form similar cytoskeletal connections on VSMC. Collectively, these results suggested that the VSMC mechanical response could be mediated by specific FN-related cell signaling, and that the response was actin and MLCK dependent.
L 20
IMMOBILIZATION OF PEPTIDES ON QUANTUM DOTS FOR THE
DEVELOPMENT OF A PROTEASE BIOSENSOR
Craig Weilbaecher, Darcy Lichlyter, and Sheila Grant Biological Engineering, University of Missouri-Columbia
Due to their special features at nanoscale, carbon nanotubes could enter the human
body via certain way. The growing use of carbon nanotubes in practical applications, hence,
prompts a necessity to study the potential health risks of carbon nanotubes. A numerical
study is performed here to investigate the size effect of carbon nanotubes on the bulk
modulus of a lipid bilayer by using the constant surface tension molecular dynamics
simulation procedure. It is found that the size effect is not monotonic with the increase of
nanotube length. An explanation is given based on the atomic interaction between the
nanotube and bilayer involved in the model system.
M 9
HIGHLY CONDUCTIVE AND TRANSPARENT ZNALO THIN FILM
FOR ORGANIC LIGHT EMITTING DIODES
R. K. Gupta, C. Vera, L. Fadiga, K. Ghosh, and P. Kahol Department of Physics, Astronomy, and Materials Science, Missouri State University,
Springfield, Missouri-65897, USA
Organic light emitting diodes (OLEDs) have attracted much attention for use in the
next generation of display technology. In these devices transparent conductive oxide (TCO)
layer is used as anodes. Although indium tin oxide (ITO) is most widely used as TCOs,
indium is relatively scarce element in the earth’s crust so the cost for production of ITO is
relatively high. In this communication we are reporting the preparation, and characterization
of thin films of Zn0.99Al0.01O. Highly conductive and transparent thin films of Zn0.99Al0.01O
were deposited on the quartz substrate using pulsed laser deposition (PLD) technique. The
target for the PLD was prepared by the standard solid state reaction method. The electrical
and optical properties of these films have been compared with that of ITO and pure ZnO. It
has been observed that the ZnAlO film has transparency comparable to that of pure ZnO and
ITO. The Hall measurements of these films have been carried out at room temperature.
Different parameters such as type of majority carriers, carrier concentration, and mobility
have been calculated. The carrier concentration of ITO, ZnO and ZnAlO was 2.74 × 1020,
1.72 × 1019 and 1.37 × 1020 per cm3 respectively. Al-doped ZnO could be an excellent
transparent conducting electrode for future optoelectronic devices.
M 10
MICROWAVE PLASMA-ASSISTED CHEMICAL VAPOR
DEPOSITION REACTOR: INSTRUMENTATION AND
IMPLEMENTATION FOR CARBON-BASED MATERIALS FOR
ELECTRONIC DEVICES AND BIOSENSING APPLICATIONS*
S. Gupta1, G. P. Vierkant2,, and R. E. Giedd2
1Department of Electrical and Computer Engineering, University of Missouri-Columbia, MO 65211, 2Department of Physics and Materials Science and Center for Applied Science and
Engineering, Missouri State University, Springfield, MO 65897 Email: [email protected]
Chemical vapor deposition techniques prove to be extremely valuable for the
deposition of a variety of technological important materials for diverse applications. One of its variants - Microwave Plasma-assisted Chemical Vapor Deposition (MPACVD) provides invaluable capabilities to synthesize a gamut of carbon-based materials utilizing advanced process control of growth parameters including plasma, power, feedstock gases and their ratio, substrate temperature and so forth. MPACVD growth of carbon-based materials such as diamond offers an excellent alternative to existing silicon technology which is usually limited by intrinsic thermal, mechanical, and electrical properties. While extensive carbon material research has been performed over the last two decades, growth mechanism including nucleation, synthesis, and doping are not yet fully understood. This work will present and discuss the (a) assembly and testing of an ASTeX PDS-18 MPACVD unit for synthesizing advanced carbon materials; poly-/micro-/nanocrystalline diamond films; (b) upgrade of system hardware and software to leverage modern computing and control capabilities while maintaining process safety and performance; and last but not the least (c) process optimization to study growth mechanism and their influence on structure properties with a view to establish microscopic structure-property correlation. Specifically, boron-doped diamond (BDD) will be presented as a case study being used for diverse technological applications such as electronic devices, N/MEMS, and electrochemical microelectrodes for sensing.
*This work is financially supported by ONR Grant while one of the authors (SG) was at the Missouri State University, Springfield. #The other authors (GPV) is a graduate student who conducted his master’s thesis in Materials Science and defended in June, 2006 under the guidance of corresponding author (SG) and REG is a director of the center-CASE. *This work is submitted on behalf of Graduate student by his advisor.
M 11
NANOSCALE SURFACE CHARACTERIZATION WITH NONLINEAR
PARAMETER IDENTIFICATION
Siddharth Hazra, Brian Mann
Mechanical and Aerospace engineering, University of Missouri-Columbia, MO, USA.
Unconventional energy generation is becoming more important due to disappearing
natural resources and an increased concern for cleaning the environment. Direct energy conversion techniques that convert thermal and/or mechanical energy into electricity without the need for an intermediate fluid (as in the case of Rankine cycle based generators) are ideally suited for such remote applications. Thermoelectric power generators are direct energy conversion technologies that are attracting significant attention due to enhanced material properties and their ability to be scaled to very small dimensions.
Electricity can be generated if one junction of two electrically dissimilar materials is heated and the other junction is cooled (each junction is called a thermocouple). The performance of such a thermoelectric generator can be characterized by the maximum energy conversion efficiency, and is known to be dependent on the thermocouple material properties and the hot and cold temperatures.
To demonstrate this, we fabricated a device, where a clean glass substrate was coated with sputtered platinum film and a dispersed thermite (CuO nanorods/nano-Al). A schematic of this device is shown in figure 1. Two Pt-Al junctions were formed by soldering Al wire on the Pt films. An impact initiation was utilized to trigger a thermite reaction which produced heat in one junction. Due to a temperature differential, between two junctions, a voltage was generated, which was recorded using a data acquisition card (DAQ) and LabVIEW program. A voltage pulse of about 0.3 V peak and 126 microsecond width at FWHM was generated using one platinum strip (Figure 2). From the generated voltage value, the Seebeck coefficient of platinum is calculated to be approximately 17 µV/°C. In the present research, large temperature differential was used unlike the small temperature differential [1, 2] used by existing thermoelectric power generators.
0 200 400 600 800 1000-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Voltage generated by seebeck effect
Volta
ge (V
)
Time (µS)
Voltage output
Figure 1. Schematic of a device for thermo-
Thermites Platinum films
electric power generation using a thermite reaction. References: 1. Buist, Richard J.; Lau, Paul G., International Conferen1997. 2. Ichiro Matsubara, Ryoji Funahashi, Tomonari TakeucKazuo Ueno, Appl. Phys. Lett., vol. 78, p. 3627-3629, 200
Figure 2 Voltage generated using onePt strip.Figure Error! No text of specified
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hi, S1.
style in document..4
n Thermoelectrics, Vol. 16, p. 551-554,
atoshi Sodeoka, Tadaaki Shimizu, and
M 15
LIGHT WAVEGUIDES WITH AN AQUEOUS CORE AND AN ULTRA
LOW REFRACTIVE INDEX NANOPOROUS SILICA CLADDING
Korampally Venumadhav, Manor Rosalynn, Othman Maslina, Kwon Jae and
Gangopadhyay Shubhra
Department of Electrical and Computer Engineering, University of Missouri, Columbia, Missouri 65211
Email: [email protected] We present a novel chip based light waveguide system capable of guiding light
through aqueous solutions with minimal losses. The waveguide system comprises of an
aqueous core and an ultra low refractive index nanoporous silica cladding for efficient light
containment. The system comprises of channels etched in silicon and anodically bonded to
glass. These channels are later coated with nanoporous silica layer following our novel
coating method to form the cladding. The waveguide relies on total internal reflection within
the channels for light propogation. We have observed a tremendous increase in light
collection ability with our system compared to the control system with no nanoporous silica
coating.
M 16
MIC COMBUSTION WAVEFRONT VELOCITY IN ELASTOMERIC
MICROCHANNELS
Mike Kraus, Steve Apperson, Rajesh Shende, Raj Thiruvengadathan, Andrey
Bezmelnitsyn, Shubhra Gangopadhyay
Department of Electrical and Computer Engineering, University of Missouri, Columbia, Missouri 65211
In the defense sector there is an urgent need for miniaturization of critical components of a weapon system that would benefit from advances of reduced size and weight integration. Systems include sensors, data transmission, computers and other microprocessor-driven devices, displays, global positioning system devices, etc. The silicon MOSFET, the workhorse of the semiconductor industry, is an integral part of many of the critical systems. A scaled down version of the device in Si technology would increase the packaging density of the chips employed in all the applications and could contribute greatly in fulfilling the needs. Scaling of silicon MOSFET dimensions is facing several challenges set by the limits of optical lithography and short channel effect (SCE). The classical single gate MOSFET has almost reached its minimum channel length limit imposed by gate oxide tunneling. Several non-classical models have been proposed to extend the scalability of MOS devices by reducing the SCE, including double gate [1], Pi-gate [2], and cylindrical surrounding or wrap around gate MOSFET [3, 4]. True scaling, however, can be realized only when there is a reduction of not only the channel length but the overall size of transistors. Because of the advantages in its integration with existing technology, Silicon (Si) MOSFET with nano scale channel and wrap-around-gate (WAG) has become a subject of active research. The WAG MOSFETs have been shown to have the best control over SCE and significantly improved carrier transport properties over conventional devices because of reduced scattering and better gate control [5]. Significant improvement of current density has been reported in nano-channel WAG devices as compared to its planer gate counterpart. We report on the fabrication and analysis of a silicon nano-channel WAG MOSFET. The SOI MOS device with 50 nm channel diameter is shown in Figure 1. It was fabricated using interferometric lithography in combination with conventional I line lithography. The experimental characteristics of the device and planar MOSFETs were compared with theoretical simulation results based on semi-empirical carrier mobility models. Enhancement of current density in the device can be attributed to higher longitudinal mobility achieved through the suppression of transverse electric field [4]. The right hand side of the figure shows the associated schematic diagram of the n-channel Si WAG MOSFET used in simulations with a diameter of 50 nm, a length of 2 microns. The plots in Figure 2 represent the I-V characteristic curves of the device, showing that drain current increases as the gate voltage moves toward positive value. We further analyze the device and presents mechanisms to further increase the channel current density and show the characteristics of a nano-scale inverter based on this WAG MOSFET. The inverter with WAG MOSFETs has been found to be superior to inverters with planar MOSFETs in terms of reduced power
M 21
consumption and rise time. Figure 3 presents the input-output characteristic of the inverters designed with WAG and planner MOSFETs. It clearly demonstrates the advantages of the nano inverter with smaller transition width (TW) and lower
Figure 1 SEM pictures of a slab gate and nanowire gate structures (left) and the three
dimensional view of the nchannel nanowire MOSFET (right).
Figure 2 Variation of drain current with drain tosource voltage as a function of gate voltage.
Figure 3 I/O Characteristics of planar and nanowireinverters comparing transition widths. Inset shows thenMOS inverter circuit.
switching voltage. The WAG inverter simulation setup and results, such as the power consumption and the transient response of planar MOS inverter and nanowire MOS inverter will be detailed in the full version of the paper, including influences on such parameters due to the channel length and diameter. References 1. Y. Taur, “An Analytical Solution to a Double-Gate MOSFET with Undoped Body,” IEEE Electron Device Lett., vol. 20. no. 5, pp. 245-247, May 2000. 2. J.-T. Park, J. P. Collinge and C. H. Diaz, “Pi-gate SOI MOSFET,” IEEE Electron Device Lett., vol. 22, no 8, pp. 405-406, August 2001. 3. D. Jiménez, B. Iñíguez, J. Suñé, L. F. Marsal, J. Pallarès, J. Roig, and D. Flores, “Continuous Analytic I–V Model for Surrounding-Gate MOSFETs,” IEEE Electron Device Lett., vol. 25, no. 8, August 2004 4. A. K. Sharma, S. H. Zaidi, S. Lucero, S. R. J. Brueck, and N. E. Islam, “Mobility and transverse electric field effects in channel conduction of wrap-around-gate nanowire MOSFETs,” IEE Proceedings - Circuits, Devices and Systems, volume 151, issue 5, p. 422-430, October 2004. 5. E. Leobandung, G. Gian, G. Lingjie, and S. Y. Chao, “Wire-channel and wrap-around-gate metal-oxide semiconductor field-effect transistors with a significant reduction of short channel effects,” J. Vac. Sci. Technol. B, 5, (6), p. 2791, 1997.
M 22
SELF ASSEMBLY OF OXIDE NANO-STRUCTURES USING PULSED
LASER DEPOSITION
Matthew W. Summers, Ram Gupta, Pawan Kahol, Kandiah Manivannan, and Kartik
Ghosh
Department of Physics, Astronomy, and Materials Science, Missouri State University,
Due to growing interest in Copper Oxide based Energetic Materials, a more cost effective method of preparing Copper Oxide for use in Energetic Materials was sought. Previous methods of preparing Copper Oxide for use in Energetic Materials have relied on Copper Ethoxide as the primary precursor. Materials prepared by this method have been demonstrated to have extremely good energetic properties with burn rates in excess of 2000 m/s. However, despite the very good energetic properties of the material produced by this method of synthesis the extremely high cost of Copper Ethoxide (~ $675/ 100g Copper Ethoxide) has limited the practical applications of material prepared by this method. Therefore a new method preparing Copper Oxide utilizing a less expensive precursor material was sought. Experimentation has revealed Copper Oxide can be formed using a sol-gel method which utilizes Copper(II) Chloride as the primary precursor. The relatively affordable cost of Copper(II) Chloride (~ $9.60/ 100g Copper(II) Chloride) makes this method an attractive alternative to Copper Ethoxide preparation. FTIR of Copper Oxide prepared by the Copper(II) Chloride method has shown that extremely pure Copper Oxide can be prepared by this method of synthesis. Because this method utilizes a sol-gel process it is believed surfactant templating can be used in the preparation of Copper Oxide to increase the porosity of the resulting material, leading to better energetic properties. Several samples were prepared utilizing various concentrations P-123 surfactant. Burn rate measurement of the resulting Copper Oxide, combined with aluminum nano-particle fuel has been shown to produce burn rates in excess of 1300 m/s. This burn-rate far exceeds the expected burn-rate of ~700 m/s for typical Copper Oxide nano-particles. This seems to indicate the surfactant templating method was successful in increasing the porosity of the resulting Copper Oxide. However, TEM was unable to confirm the formation of porous structures. Although Copper Oxide prepared by the Copper(II) Chloride method of preparation currently performs at a level below similar material prepared by the Copper Ethoxide method, early results have shown Copper Oxide prepared by the Copper(II) Chloride method is suitable for energetic purposes. It is hoped that with further refinement Copper Oxide prepared by the Copper(II) Chloride method will be able to perform on a level comparable to materials prepared by the current Copper Ethoxide method at a much more affordable cost.
M 24
SYNTHESIS AND CHARACTERIZATION OF COPPER OXIDE
BASED NANOENERGETIC COMPOSITES
Rajagopalan Thiruvengadathan, Rajesh V. Shende, Paul Koch, Steven Apperson,
Andrey V. Bezmelnitsyn and Shubhra Gangopadhyay
Department of Electrical and Computer Engineering, University of Missouri, Columbia, MO
In order to realize high combustion rates, it is essential to enhance the interfacial
contact between oxidizer copper oxide (CuO) nanorods and fuel Aluminum (Al)
nanoparticles. Enhanced interfacial contacts will ensure faster thermite reactions. We show
that self-assembly processes can facilitate homogeneous distribution of fuel nanoparticles
around the oxidizer, thereby leading to enhanced interfacial contacts.
Copper oxide nanorods were synthesized by inorganic condensation method using
polyethylene glycol (PEG) surfactant as a template. The structural properties of CuO
nanorods were determined using X-ray diffraction, transmission electron microscopy and
Fourier transform infrared spectroscopy. Al nanoparticles were assembled around CuO
nanorods employing poly (4-vinylpyridine) (P4VP). The pyridyl group in this polymer
provides the binding sites to enable assembling of the Al nanoparticles around the oxidizer
nanorods. The energetic performance of such self-assembled composite is superior in
comparison with that of a composite prepared without self-assembly. Our results reveal that
the combustion speeds of self-assembled composite is 2100 ± 100 m/s.
M 25
FIELD-EFFECT TRANSISTORS BASED ON SINGLE NANOWIRES
OF CONDUCTING POLYMERS
Adam K. Wanekaya,* Mangesh A. Bangar,# Minhee Yun+, Wilfred Chen,#
Nosang V. Myung# and Ashok Mulchandani#
Chemistry Department, Missouri State University, Springfield MO 65897 #Department of Chemical and Environmental Engineering and Center for Nanoscale Science
and Engineering, University of California, Riverside, CA, 92521 + Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh,
We report the electronic characteristics of field-effect transistors based on single
conducting polymer nanowires. The 100 nm-wide and 2.5 micron-long conducting polymer
nanowire field-effect transistors were turned “on” and “off” by electrical or chemical signals.
A large modulation in the electrical conductivity of up to three orders of magnitude was
demonstrated as a result of varying the electrochemical gate potential of these nanowires.
Single conducting polymer nanowire field-effect transistors show higher electrical
performance than field-effect transistors based on conducting polymer nanowire electrode
junctions and thin films in terms of their transconductance (gm) and on/off current (Ion/Ioff)
ratio. Furthermore, the performance of the single conducting nanowire field-effect
transistors was found to be comparable to the silicon nanowire field-effect transistors. These
results imply that it is possible to tune the sensitivities of these conducting polymer
nanowires by simple control of the electrolyte/liquid ion gate potentials. Based on these
findings, we demonstrated the ability to tailor the sensitivities of sensors based on single
conducting polymer nanowires.
M 26
LATTICE FRINGE SIGNATURES OF EPITAXY ON NANOTUBES Jinfeng Wang and P. Fraundorf
Physics and Astronomy and Center for Molecular Electronics, University of Missouri-St.Louis (63121), St.Louis, MO, USA
Email: [email protected] Carbon nanotubes are of increasing interest for nanotechnology applications in general [1, 2]. They are also interest as supports for heterogeneous catalysts [3], for example in fuel cell applications. Carbon nanotubes also have advantages for electron microscopy, because their near-cylindrical symmetry and propensity of lie perpendicular to the electron beam makes data acquisition and interpretation much simpler than for single crystal supports. We show here that, with help from recent work on the theory of lattice fringe visibility, that the crystallographic relationship between catalyst nanocrystals and their nanotube supports (Fig.1) can sometimes be inferred from a single lattice fringe image. If the relationship is epitaxial, one might conversely decorate tubes in order to determine the chirality of their outer sheet. We illustrate this with a specific case: Growth of FCC metals on (0002) graphite surfaces and/or grapheme sheets. The theory is easily extended to growth of other lattice types. Application to experimental images of Pt fuel cell catalyst crystals, on carbon nanotube supports, illustrates the strategy. According to diffraction data in the literature, epitaxy of FCC Pd on single crystal graphite (0002) planes typically takes place with parallel to in the growth direction, and parallel to in the plane of the substrate. This fully specifies the expected fringe distributions.
Pd)111( graphite)0002(
Pd]112[ graphene]0.01[
The bottom up view of such a 65 Pd-atom nanocrystal on grapheme is shown in Fig. 4. Here for simplicity we have approximately positioned two of every three bottom-layer Pd atoms directly over a carbon atom, with the result that one of every three is over the center of a cyclohex graphene ring. The actual transitional alignment of the nanoparticle should have little effect on metal fringe visibility, provided that contrast from the underlying carbon does not obscure the metal lattice. Because the Pd lattice azimuth is now fixed with respect to top graphene sheet of the underlying nanotube, the fringe visible will be fully specified by the projected position for a given top sheet chirality. The result is illustrated at the bottom of Fig. 5 for armchair, zigzag, and “15 degree” chiral top-layer orientations, in sequence. As a fringe benefit, epitaxial “decoration” of carbon nanotubes will in principle make routine determination of top-layer tube chirality. Of course, prepartation of nanotube surfaces sufficiently clean and flat for epitaxial decoration may not be trivial. Reference [1] M.S.Dresselhaus et al., Science of Fullerenes and Carbon Nanotubes, Academic Press, New York, 1996. [2] H. Dai, Surface Science 500,218 (2002). [3] P. N. Rylander, Catalytic Hydrogenation in Organic Synthesis, Academic Press, New York, London, 1979.
M 27
PLASMA NANOCOATED DIAMOND NANOPARTICLES FOR HEAT
TRANSFER NANOFLUIDS Q.S. Yu,1 Y. J. Kim,1 C. Wilson,2 K. Park,2 H.B. Ma 2
1 Center for Surface Science and Plasma Technology, Department of Chemical
Engineering, University of Missouri-Columbia, Columbia, MO65211 2 Department of Mechanical and Aerospace Engineering, University of Missouri-
As a part of the Alliance for Collaborative Research in Alternative Fuel Technology
(ALL-CRAFT) our group studies the formation and properties of nanoscale pore structures in
activated carbon with the goal of storing methane at low pressures. To study the pore
structure of activated carbon we employ various methods including small/ultra-small angle x-
ray scattering (SAXS/USAXS), methane and nitrogen adsorption isotherms, electron
microscopy, and cellular automata modeling. By assuming a two phase model with
uncorrelated spherical pores we show that the pore size distribution (PSD) obtained from
methane and nitrogen adsorption is in excellent agreement with SAXS/USAXS data. We also
show that data obtained from probabilistic cellular automata modeling of the pore formation
process yields data that is consistent with both SAXS/USAXS and methane and nitrogen
adsorption. Finally, we show that many of our carbon samples have desirable properties for
methane storage.
Project supported by: National Science Foundation (EEC-0438469), University of
Missouri, Midwest Research Institute, Argonne National Laboratory, U.S. Department of
Education (GAANN), and U.S. Department of Energy (W-31-109-Eng-38)
M 30
COHERENCE EFFECTS IN ELECTRON DIFFRACTION FROM
PRESOLAR GRAPHENES E. Mandell, P. Fraundorf
Department of Physics and Astronomy and Center for Molecular Electronics University of Missouri – St. Louis, St. Louis, Missouri 63121
This set of analyses examines how coherence effects for coordinated atom-thick structures evidence themselves in diffraction. It also provides an example where this effect may be occurring in nature, through the examination of carbonaceous materials condensed from meteorites. For atom-thick structures, these coherence effects may be seen in diffraction, and they provide additional structural information beyond simple lattice periodicities [1]. The target here is unlayered graphene in the core of a subset of the isotopically heavy (i.e. with 12C/13C < solar=89), micron-sized, ultramicrotomed graphite spherules from the Murchison meteorite (Fig. 1) [2]. These presolar particles are characterized by “graphite onion” rims (with a concentric arrangement of 0.34[nm] (002) graphite layers) surrounding the spherical cores of interest. The core is comprised primarily of atom-thick graphene “flakes” [3, 4], as shown e.g. by the presence of graphite (hk0) ordering in electron diffraction, with no sign of the 0.34[nm] (002) graphitic layering characteristic of graphite, amorphous carbon, multi-wall carbon nanotubes, and most solid non-diamond carbon phases (Fig. 1). While flat-sheet diffraction models for graphene sheets fit experimental data from the cores reasonably well, systematic differences arise. For example, we have applied Warren models [5] for single-sized flat sheets, two sheet sizes, and a log-normal size distribution of flat sheet sizes to fit the experimental data. Each of these left the extra scattering at the graphene peaks and on the leading (low-frequency) edge unresolved. Also, the same residual effects were seen in experimental diffraction patterns from different spherules. One explanation for these differences is the coherence effect that results from coordination between adjacent graphene sheets. Fig. 2 contains a model faceted nanocone and the three dimensional reciprocal lattice structure corresponding to the (110) lattice spacing for each sheet. Of interest are the intersections of the harmonics, where the triple intersections serve to slightly broaden or shift the location of the (110) peak, and where the double intersections (where two rel-rods nearly touch) result in a satellite peak. For clarity, Fig. 3 shows a modeled azimuthally-averaged diffraction profile for two adjacent facets and a single facet, or flat sheet. If the angle between the facets is changed, these coherence spikes will also move, as the preferential foreshortening of the molecule is altered, or the intersections of corresponding rel-rods in reciprocal space occur at different spatial frequencies. Using a least squares, splined, fitting routine that uses Debye diffraction models for flat sheets, we compare the systematic differences that arise when fitting experimental data to those calculated for assemblages of randomly-oriented graphene, or faceted structures (Fig. 4) [6]. Visually, we see the similar inability of the flat sheet model to fit the amount of scattering at the (100) and (110) peaks in both the experimental data and the model ensemble of randomly-oriented graphene. The flat-sheet model also falls short on the leading edge of the graphene spacings in both cases. Thus, the inability of the flat sheet model to fit core electron diffraction may be due to coherence effects arising from inter-sheet relationships.
M 31
References: 1. J. M. Cowley, Acta. Cryst. 14, 920 (1961) 2. S. Amari, E. Zinner, and R.S. Lewis, Meteoritics 30, 679 (1995). 3. T. Bernatowicz, et. al., Astrophysical Journal 472, 760 (1996). 4. P. Fraundorf and M. Wackenhut, Ap. J. Lett. 578, L153 (2002). 5. B.E. Warren, Phys. Rev 59(9), 693 (1941). 6. B.E. Warren, X-Ray Diffraction, Addison-Wesley/Dover, New York (1969/1990).
Figure 1: A presolar graphite spherule with a Figure 2: A picture of atom positions for a faceted core-rim structure, and a diffraction pattern carbon nanocone consisting of five flat faces, and from the core. The (002) graphite spacing is the corresponding reciprocal lattice structure for absent in diffraction. (110) periodicity.
Figure 3: A comparison of Debye diffraction patterns for one and two facets of the faceted nanocone. Observe the occurrence of a satellite peak due to the orientation of the facets.
Figure 4: Debye flat sheet models fitted to experimental data and an ensemble of randomly-oriented flat sheets. Similarities in differences may arise, simply from coherence
M 32
PULSED POWER GENERATION USING THE RELEASED HEAT OF
NANO-ENGINEERED THERMITES 1Maruf Hossain and 1,2Shubhra Gangopadhyay
1Department of Electrical and Computer Engineering, University of Missouri, Columbia, Missouri 65211
Email: [email protected] Unconventional energy generation is becoming more important due to disappearing
natural resources and an increased concern for cleaning the environment. Direct energy conversion techniques that convert thermal and/or mechanical energy into electricity without the need for an intermediate fluid (as in the case of Rankine cycle based generators) are ideally suited for such remote applications. Thermoelectric power generators are direct energy conversion technologies that are attracting significant attention due to enhanced material properties and their ability to be scaled to very small dimensions.
Electricity can be generated if one junction of two electrically dissimilar materials is heated and the other junction is cooled (each junction is called a thermocouple). The performance of such a thermoelectric generator can be characterized by the maximum energy conversion efficiency, and is known to be dependent on the thermocouple material properties and the hot and cold temperatures.
To demonstrate this, we fabricated a device, where a clean glass substrate was coated with sputtered platinum film and a dispersed thermite (CuO nanorods/nano-Al). A schematic of this device is shown in figure 1. Two Pt-Al junctions were formed by soldering Al wire on the Pt films. An impact initiation was utilized to trigger a thermite reaction which produced heat in one junction. Due to a temperature differential, between two junctions, a voltage was generated, which was recorded using a data acquisition card (DAQ) and LabVIEW program. A voltage pulse of about 0.3 V peak and 126 microsecond width at FWHM was generated using one platinum strip (Figure 2). From the generated voltage value, the Seebeck coefficient of platinum is calculated to be approximately 17 µV/°C. In the present research, large temperature differential was used unlike the small temperature differential [1, 2] used by existing thermoelectric power generators.
Figure 1. Schematic of a device for thermoelectric
0 200 400 600 800 1000-0.05
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0.05
0.10
0.15
0.20
0.25
0.30
0.35
Voltage generated by seebeck effect
Volta
ge (V
)
Thermites Platinum films
Voltage output
power generation using a thermite reaction. References: [1] Buist, Richard J.; Lau, Paul G., International Con
554, 1997. [2] Ichiro Matsubara, Ryoji Funahashi, Tomonari T
