 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
|
New Concepts in Molecular and Energy Transport within Carbon Nanotubes: Thermopower Waves, Stochastically Resonant Ion Channels, and Single Molecule Biosensors Charles and Hilda Roddey Associate Professor of Chemical Engineering Abstract Our laboratory has been interested in how carbon nanotubes can be utilized to illustrate new concepts in molecular and energy transfer. In the first example, we predict and demonstrate the concept of thermopower waves for energy generation. Coupling an exothermic chemical reaction with a thermally conductive CNT creates a self-propagating reactive wave driven along its length. We realize such waves in MWNT and show that they produce concomitant electrical pulses of high specific power >7 kW/kg. Such waves of high power density may find uses as unique energy sources. In the second system, we fabricate and study SWNT ion channels for the first time and show that the longest, highest aspect ratio, and smallest diameter synthetic nanopore examined to date, a 500 μm SWNT, demonstrates oscillations in electro-osmotic current at specific ranges of electric field, that are the signatures of coherence resonance, yielding self-generated rhythmic and frequency locked transport. The observed oscillations in the current occur due to a coupling between stochastic pore blocking and a diffusion limitation that develops at the pore mouth during proton transport. Lastly, I will discuss our work on biosensors based on SWNT fluorescence, which has advanced such that we can develop platforms to solve longstanding biological problems. Here, we develop an array of fluorescent SWNT that selectively record the discrete, stochastic quenching events that occur as H2O2 molecules are emitted from individual human epidermal carcinoma cells. We use this sensor array to map, for the first time, the H2O2 signaling pathway. Biographical Sketch Professor Michael S. Strano is currently the Charles and Hilda Roddey Associate Professor in the Chemical Engineering Department at the Massachusetts Institute of Technology. His research focuses on biomolecule/nanoparticle interactions and the surface chemistry of low dimensional systems, nano-electronics, nanoparticle separations, and applications of vibrational spectroscopy to nanotechnology. He received his B.S from Novel Subwavelength Coaxial Nanostructures with Optical, Solar and Biosensing Utility Professor Michael J. Naughton Evelyn J. and Robert A. Professor, and Chair Department of Physics Abstract We discuss a novel nanoscale platform offering utility in nanophotonics, photovoltaics, visual prosthetics, and biological and chemical sensing. As subwavelength optical waveguides, these nanostructures can be used in a range of nanoscale manipulations of light, including optical nanomicroscopy and lithography, high efficiency solar cells, high electrode-density retinal implants and discrete optical metamaterials. A modification of the basic structure enables the fabrication of highly sensitive “nanocavity” biochemical sensors and nanoscale bipolar neurostimulators. We will report on aspects of these applications, with emphasis on radial junction "nanocoax" thin film solar cells. This structure allows for a unique decoupling of the optical and electronic length scales in photovoltaic devices, enabling highly efficient charge extraction in ultrathin films with, paradoxically, highly efficient light collection. The nanocoax thus exhibits strong optical absorption across the visible, and state-of-the-art power conversion efficiency using PV thinner than carrier (electron and hole) diffusion lengths, suggesting a new path to high efficiency solar power. Biographical Sketch Mike Naughton is a Professor and Chairman and Evelyn J. and Robert A. Ferris Professor of Physics in the Department of Physics at Thiol-Protected Gold Nanoparticle Films as Part of a Multi-Array Chemical Vapor Detection System Jisun Im, Sandip K. Sengupta, Maor Baruch, James E. Whitten Department of Chemistry and Center for High-Rate Nanomanufacturing The Abstract Thiol-protected gold nanoparticle films have been investigated as the chemiresistive materials in that their resistance values increase upon exposure to analytes by swelling. The colloidal gold nanoparticle films have been prepared by spincoating, drop-casting and ink-jet printing. The ink-jet printing technique especially enables us to make reproducibly thin films for consistent and stable baseline resistance and the film thickness can be controlled by varying the number of passes through the printer. The photometer based on an LED and a photodiode detector was developed in order to monitor the thickness of the inkjet-printed film. Toward the goal of building a portable, battery-operated vapor sensor system, the multi-sensor array has been fabricated and it contains five different chemiresistive films: three gold nanoparticle films, polypyrrole, and carbon nanotube film. The library has been built by measuring the resistance changes of the sensor array upon exposure to five different vapors. To differentiate analytes, the microprocessor performs the minimization of the sum of the squares from the established library. The multi-sensor array was then programmed to display the identification of the unknown analyte and its concentration on an LCD screen. Biographical Sketch Jisun Im is currently a Ph.D. candidate in Polymer Science Program of Department of Chemistry at the Surface Morphology and Texture of TiAlN/CrN Multilayer Coatings Dale A. Delisle and James E. Krzanowski Materials Science Program and Department of Mechanical Engineering Abstract Thin multilayer films of TiAlN/CrN have been proposed for the next generation of wear and oxidation-resistant tool coatings. In this study a series of TiAlN/CrN multilayer coatings were deposited by RF magnetron sputtering and characterized using TEM, SEM, XRD, XPS and EDS to quantify film composition, crystallinity, surface and grain morphology and texture. Films were deposited in a mixed Ar/N2 background with a substrate bias of -150 VDC to a thickness of approximately 1 micron. Bilayer periods were varied from 2 to 16 nm, and for comparison TiAlNCrN, TiAlN, TiN and CrN films were also deposited and characterized in the same manner. Cross-section TEM analysis confirmed the presence of the multilayer structure and the bilayer thickness. SEM examination of the multilayer films showed that the bilayer period had a direct impact on both the surface morphology and texture of the film. Films deposited with a 2 nm periodicity exhibited sharp, faceted column tops, where as the 16 nm period films showed rounded column ends. Film texture showed a slightly off-axis (200) fiber texture, and the strength of the texture was dependent on bilayer period. Machining studies are underway to examine tool life during dry turning of A2 tool steel. Biographical Sketch Dale A. Delisle is currently a Ph.D. candidate in the Materials Science program at the James E. Krzanowski is Professor of Mechanical Engineering at the Tribological Properties of Polyaromatic Thiols in Nanometer-Sized Contacts Yutao Yang and Marina Ruths Department of Chemistry The Abstract Interfacial phenomena such as wetting, adhesion, and friction strongly influence the performance of magnetic storage devices and micro / nano-electromechanical systems (MEMS and NEMS). Despite this importance, only limited information is available on the molecular level lubricating function of simple aromatic model systems and of the aromatics naturally present in oils. Self-assembled monolayers (SAMs) are commonly selected to be the common model systems for studying the ultrathin lubricating films in MEMS/ NEMS, and for investigations of tribological properties at the molecular level. One interesting group of model systems for modification of the properties of surfaces and interfaces in devices is SAMs containing aromatic moieties, where the monolayer structure is influenced by stronger and more complex intermolecular interactions than in the well known alkanethiol and alkylsilane SAMs. Friction force microscopy, a technique based on atomic force microscopy (AFM), was used to investigate the effects of molecular packing and adhesion strength on the friction of self-assembled monolayers of the aromatic compounds thiophenol, p-phenylthiophenol, and p-terphenyl thiol, on template-stripped gold surfaces. The adhesion between a monolayer-covered tip and substrate was controlled by immersing the sliding contacts in ethanol or in dry nitrogen gas. At low loads L, low adhesion (obtained in ethanol) resulted in a linear dependence of the friction force F on load, F =μL, whereas in nitrogen, the higher adhesion between the same monolayers gave a non-linear, apparently area-dependent friction. This nonlinear friction in the adhesive systems was well described by F = ScA, with the contact area, A, calculated for a thin, linearly elastic film confined between rigid substrates using the extended Thin-Coating Contact Mechanics (TCCM) model, and Sc being the critical shear stress, a constant for each monolayer system. With increasing molecular packing, a systematic decrease was found in the friction coefficient, μ, obtained in ethanol and the critical shear stress, Sc, obtained in nitrogen. Biographical Sketch Yutao Yang is a graduating PhD student in Polymer Science at UMass Lowell. He was trained as a chemical engineer in Gently Lifting Gold’s Herringbone Reconstruction by Tuning Adsorbate Chemistry April D. Jewell, Heather L. Tierney, Erin V. Iski, Ashleigh E. Baber, Darin O. Bellisario, E. Charles H. Sykes Department of Chemistry Abstract The structure of the molecule-metal interface in alkane thiol-based Self-Assembled Monolayers (SAMs) is much more complex than first believed. Thiols lift the herringbone reconstruction of Au(111) and remove a significant fraction of the Au surface atoms. The etch pits formed by these Au atom vacancies are thought to be one of the weakest areas of the SAM films in terms of susceptibility to and degradation by oxidation. In an effort to tailor the molecule-metal interaction strength and prevent the formation of etch pits we have chosen to study the interaction and assembly of various organic molecules on Au(111) using a scanning tunneling microscope. Species investigated include thioethers (RSR’), selenoethers (RSeR’), and trialkylphosphines (PR3). The images in Figure 1 show examples of the three types of system under investigation. Figure 1: STM images of monolayer coverage of (A) dibutyl sulfide, (B) dibutyl selenide and (C) trimethylphosphine on Au(111). Scale bar = 10 nm. Biographical Sketch April D. Jewell received a B.S. in chemistry from Chemical Vapor Detection using Reduced Graphene Oxide and Carbon Nanotubes Sumedh P. Surwade, Vineet Dua, Srikanthrao Agnihotra, Srikanth Ammu, Sanjeev K. Manohar Department of Chemical Engineering The Abstract A lightweight, flexible chemiresistor using thin films of reduced graphene oxide and carbon nanotubes deposited on flexible substrates can reversibly detect a wide range of chemical warfare agents (CWAs). Chemically aggressive vapors like NO2, SO2 Cl2, etc., including simulants for explosives and nerve agents are detected in the 100 ppm to 250 ppb concentration range at room temperature, in ambient air, without the aid of a vapor concentrator. Biographical Sketch Sanjeev K. Manohar joined the Inductively Coupled Plasma Reactive Ion Etching of GaAs Materials Michael K. Connors and Jason J. Plant MIT Abstract This presentation will describe the development of a dry etch process, utilizing inductively coupled plasma reactive ion etching (ICP-RIE) of GaAs and AlGaAs materials, for the fabrication of ridge structures in slab-coupled optical waveguide semiconductor diode lasers and amplifiers. A commercial ICP-RIE tool used in this work produces very high density plasmas, resulting in very high etch rates (200°A/s) and anisotropic etch profiles. Exposure to such high density plasma requires active thermal management of the sample during etching for reproducible process control. Small area samples are typically processed on a carrier substrate, requiring the use of a removable thermal grease to enhance substrate-carrier thermal contact. A reduced etch rate (65°A/s), controllable etch depth process for small area samples has been developed that eliminates the need for thermal grease. Etched areas and sidewall profiles are smooth, and etch depth control is +/-2% of the desired target depth of ~1.25 µm. It was determined that etch system preparation is critical to ensuring a reproducible etch environment. Data will be presented to show the impact of tool use history on etch rate which has led to development of specific etch chamber conditioning procedures. Device processing details, including etch mask composition and pre-etch surface preparation have been optimized, contributing to the development of a reproducible device fabrication process. Finally, SEM images will be presented highlighting ridge profiles and etched surfaces of semiconductor laser and amplifier devices fabricated with the new dry etch process. Biographical Sketch Michael K. Connors received his B.S. in Biological Science and Environmental Science from the This work was sponsored by the Defense Advanced Research Projects Agency under Air Force contract number FA8721-05-C-0002. The opinions, interpretations, conclusions and recommendations are those of the author and are not necessarily endorsed by the United States Government. Accurate Co-Deposition of Multiple Materials from Multiple Sources R.R. Olson, R.M. Hartmann, G.L. Carpenter, P.P. Chow, J.M. Burkstrand SVTA, Inc. Abstract In depositing multiple component thin films where the film composition depends on the flux of arriving components, it is important to be able to monitor the deposition process. An optical deposition flux monitor based on Atomic Absorption Spectroscopy has been developed for monitoring co-deposition of materials from multiple sources. It provides independent monitoring of the different elements being deposited. As an optical technique, it provides this monitoring without physically shadowing the substrate, and with a minimum of in-vacuum components. An innovative high sensitivity optical design provides flux measurements equivalent to growth rates as low as 0.001 nm/s. Examples of monitoring deposition during MBE and during deposition of a CIGS PV thin film are shown. Biographical Sketch After completing his PhD in Electrical Engineering at the University of Minnesota, Rolf spent 13 years in various roles at Physical Electronics, Perkin Elmer including Product Manager for Auger electron spectroscopy, and Manager of the analytical lab in Munich Germany. His experience also includes roles at Keithley Instruments in Cleveland Ohio, and FSI International in product management and marketing positions. Rolf joined SVT Associates in 2008 where he focuses on marketing MBE and other thin film deposition equipment. Professor Samuel Thomas Department of Chemistry Abstract It is currently not possible to exert real-time, dynamic control over the sign and magnitude of contact electrification. This gap in knowledge and capability is an important problem because it limits the effectiveness of technologies such as anti-static materials, and prevents the development of new technologies that could use the large electric fields generated by contact electrification. This talk will present a strategy for controlling contact electrification using a combination of photoreactive acrylic polymers and light. Both irreversible (photolysis of o-nitrobenzyl esters) and reversible (isomerization of azobenzene and spiropyran) photoreactions dynamically modulate the sign and rate of charge separation by contact electrification. Consistent with empirical predictions, photochromic polymers tended to charge positively upon irradiation with UV light, whereas polymers with nitrobenzyl esters tended to charge negatively. Biographical Sketch Samuel Thomas has been Assistant Professor of Chemistry at Engineering and Atomic-Scale Characterization of Bimetallic Pd Alloys Ashleigh E. Baber, Heather L. Tierney, Timothy J. Lawton, E. Charles H. Sykes Department of Chemistry Abstract Dissociation of molecular hydrogen on the surfaces of Pd-based alloys is a key step in a number of energy-related technologies, including CO2 conversion and hydrogen separation. Low temperature scanning tunneling microscopy is used to study the atomic and electronic structure of Pd/Au{111} and Pd/Cu{111}, as well as H2 dissociation on these alloys. Our results indicated that H2 dissociation and subsequent H spillover was facile on Pd/Cu at 400 K, but that no H was found under the same H2 flux on a Pd/Au sample with identical atomic composition and geometry. The local density of states (LDOS) of individual Pd atoms in both surface and subsurface sites of Au and Cu{111} was examined and it was found that Pd atoms displayed a LDOS very similar to the surrounding atoms, except for a small electronic depletion at the band edge of the surface state. The geometric composition of Pd/Au alloys was varied via temperature control in order to form nano-sized Pd islands on Au{111}, which have an increased interaction with hydrogen as compared to surface or subsurface Pd atoms. These results demonstrate the powerful influence of Pd atoms on the catalytic activity when alloyed with an inert substrate. Biographical Sketch Ashleigh Baber graduated from Randolph-Macon Woman’s College in Atomic Scale Studies of Chiral Metal Surfaces Timothy J. Lawton, Ashleigh E. Baber, Vladimir Pushkarev, Andrew J. Gellman, E. Charles H. Sykes Department of Chemistry Abstract Synthesis of chiral reagents and separation of chiral compounds play key roles in the multibillion-dollar pharmaceutical industry. Currently, almost all of this chemistry is performed homogeneously. However, it has been demonstrated that heterogeneous reactions on surfaces modified by chiral reagents yield chiral products enantioselectively. There is a growing body of data revealing the enantioselective properties of naturally chiral metal surfaces. From the perspective of enantioselective chemistry, the most important results are those revealing enantiospecific adsorption, desorption, and reaction energetics. The best understood system is R-3-methylcyclohexanone adsorbed on the Cu(643)R&S surfaces which has been studied by Gellman and coworkers who demonstrated enantiospecific separations. This talk will include study of a curved copper single crystal that presents an almost infinite number of surface facets. The gradients of terrace widths and step/chiral kink densities available on these curved crystals provide an ideal test bed for quantifying many aspects of enantiospecific adsorption and reaction as well other structure sensitive reactions. Biographical Sketch Timothy Lawton is a second year graduate student in Prof. Charles Sykes’s physical chemistry group. His research focuses on studying surfaces and single molecule interactions via scanning tunneling microscopy (STM). Before Tufts, he received his B.S. in Chemistry from Worcester Polytechnic Institute in Detachable Plastic Co-Extruded Remote Phosphor for Dr. Miguel Galvez Osram Sylvania Abstract Coextruded remote phosphor plastic shell has been engineered to create white LED light sources with uniform light distribution along the plastic shell to create an LED light tube. The plastic technology is well known and accuracy in the plastic thickness is fairly simple to achieve. This tight tolerance in the thickness significantly contributes to the colour consistency of the plastic emitting surface but also colour consistency from lamp to lamp. The light source is made of blue LEDS so that lamp construction utilizing detachable remote phosphors brings flexibility on lamp manufacturing by having a single blue light source crowned with a detachable remote phosphor shell with specified CCT and CRI. Biographical Sketch Dr. Galvez has spent 20 years working for Osram Sylvania in computer simulation for high intensity discharges, raytracing and lately in the research of detachable remote phosphor for new LED light sources applied to distributed lighting and high density LED light kernels greater than 3000 lumens. Practical Electron Beam Analysis – All Applications, No Theory (Unless You Ask)! Joe Geller Geller Microanalytical Laboratory, Inc. 426e Abstract So, you may have heard about SEM, EPMA, Auger, and EDAX. Well we’re presenting backwards. I’ll review lots of interesting problems in the material science, semiconductor, medical industry……. and their solutions. If asked, I might divulge what kind of instrumentation was used for the analysis. Biographical Sketch Joe Geller is the President of Geller MicroAnalytical Lab in Topsfield, MA., which was started in 1985. Prior to that he was in charge of applications and demonstrations for JEOL (USA) in Joe has a B.S. from the Rochester Institute of Technology and an MBA from Salem State College. Emerging SEM Technology to Advance Energy Research Natasha Erdman, Naoki Kikuchi, Regina Campbell, and Vernon E. Robertson JEOL USA, Inc. Abstract High resolution Field Emission Scanning Electron Microscopes (FEG-SEMs) have proven to be very powerful tools for current and future applications in energy related research. Increased interest and developments in such areas as solar thin films, oil shale, catalysis and fuel cell research require sub-nm resolution SEMs with a versatile set of detectors as well as advanced sample preparation and handling techniques, such as argon ion polishing and FIB (focused ion beam). Over the last few years JEOL has introduced several advanced technologies in FEG-SEMs: new LABe low angle backscatter detector allows unprecedented imaging of specimens at both high and ultra-low kVs; application of specimen bias (Gentle Beam mode) allows examination of charging specimens without need for additional coating; and the use of STEM detectors in SEM allow observation of sub-nm size features. Furthermore, the JEOL Cross-section Polisher (CP), a defocused Ar+ ion beam specimen preparation device, allows preparation of well-polished cross sections of various materials without smearing, strain, mechanical deformation or other common artifacts. We will discuss incorporation of both advanced sample preparation and handling techniques and newest SEM detectors and imaging capabilities to study various aspects associated with energy resources. Examples will include solar thin films, catalysis, oil shale, nuclear materials and others. Biographical Sketch Dr. Erdman is an SEM/FIB Product Manager at Jeol Self-Assembled Monolayers of Functionalized C60 Fullerenes Prof. Karsten Pohl Department of Physics and Materials Science Program Abstract Structured organic thin films are relevant for many emerging technologies like optoelectronic molecular devices, energy conversion, and biosensors. The structural arrangement of molecules forming self-assembled monolayers (SAMs) is a consequence of molecular shape, and the competing molecule-substrate and intermolecular interactions. We will present a STM/DFT study of the self-assembly of C60 functionalized with alkyl chains of various lengths (F-C60) on compact metal surfaces. We find that the molecule surface interaction drives the selection of particular molecular conformations resulting in diverse SAM structures as a function of the alkyl chain lengths. The SAM structures are ranging from zigzag to linear arrays of C60 cages. These results show that C60s can be assembled in 2D and non-compact molecular arrays with a unit cell symmetry and size controllable via appropriate chemical functionalization and surface selection. Biographical Sketch Karsten Pohl is Associate Professor of Physics at UNH and a member of the Materials Science Program and the Center for High-rate Nanomanufacturing. His work explores molecular and stress relaxation driven self-assembly processes yielding to novel nano-materials and the electronic properties of reduced dimensional systems. He received a Ph.D. in Physics from the |
