Physical Sciences and Mathematics Commons^™

Vapor Liquid Solid Growths Of Germanium And Gallium Antimonide Nanowires, Ralph Alvarez, Esmeralda Arreola, Michael Oye, Meyya Meyyappan

STAR Program Research Presentations

Determining the optimal growth parameters for germanium (Ge) and gallium antimonide (GaSb) nanowires is the focus of this research. Given the fact that nano materials behave differently from their bulk counterparts we are researching some variables that influence nanowire diameter and length such as temperature, ramp rate, gas flow rate, and catalyst particle size. Based on the nano material size which is typically a few 10s of nanometers wide, these nano materials can be engineered to take advantage of their optical properties. Specifically the infrared (IR) response of Ge and GaSb nanowires are directly controllable based on their geometry. Fine …

Effects Of Ambient Gases On Icf Target Capsules, Bryan Chambers, Steve Letts, Michael Stadermann

STAR Program Research Presentations

We researched how the chemical and physical properties of a plasma polymer fuel capsule change as they are exposed to ambient gases. The fuel capsules contain the deuterium fuel inside them, they serve as the outer shell for the fuel and act as a ablator for the process. If they are reactive or diffusive with the atmosphere this can change their mass and effect the outcome of the fusion shots performed at the National Ignition Facility where High Powered Lasers are incident upon a gold hohlraum containing a capsule. We discovered that nitrogen and water vapor diffuse into the material …

Characterization Of Uranium Species In Sediments Under Iron And Sulfate Reducing Conditions Using Synchrotron-Based Techniques, Don Q. Pham, John Bargar

STAR Program Research Presentations

Uranium is one of the most common and problematic contaminants at legacy Department of Energy sites. Groundwater contamination is particularly problematic because it occurs at depth, is present in large volumes, and cannot be easily accessed for clean-up. One method of remediation being investigated is the bioreduction of soluble U(VI) to insoluble U(IV) complexes through the in-situ stimulation of metal-reducing bacteria. Understanding the structure of these uranium complexes can help us determine their fate and stability in groundwater and map out the biological process of uranium reduction by metal-reducing bacteria. In this study, we used the synchrotron-based techniques, X-ray absorption …

Exploring Methods For Earthquake Prediction: The Effects Of Water On The Flow Of Stress-Activated Electric Currents In Igneous Rocks, Aaron M. Jahoda, Friedemann T. Freund

STAR Program Research Presentations

Much of the devastation and damage of earthquakes can be attributed to the fact that they occur suddenly and without much warning, which limits the ability of people to evacuate and/or properly prepare. One method, however, that might be used to predict seismic events is the generation of electric currents in rocks when stresses are applied. It is observed in this research that the application of direct force onto samples of igneous rock causes the rocks to generate a measurable current, which is attributed to positive-hole charges moving within the oxygen sub-lattice. Because large and changing forces are acted upon …

Spectroscopic Properties Of Lanthanide (Iii) Compounds In Aqueous And Ionic Media, Orissa A. Burghard, Sayandev Chatterjee, Zheming Wang, Samuel A. Bryan

STAR Program Research Presentations

Lanthanide containing materials are receiving increasing attention due to their wide range of potential applications including bioanalytical imaging, dye-sensitized solar cells, nano-biotechnology and catalysis. The unique spectroscopic properties (intense and sharp emission bands with high color purity and high quantum efficiency) of lanthanides make them strong candidates for use as bio-markers or selective detectors. The attractiveness of lanthanides as future imaging agents as well as recent interest in their potential use in biological media has increased the need to understand the behavior of lanthanides in the presence of other ions or in ionic media.

The complexity of the biological media …

Thermal-Initiated Hydroxyethyl Methacrylate Functionalization Of Multiwalled Carbon Nanotubes, Greg Curtzwiler, Philip Costanzo, Ray Fernando, Jeffrey E. Danes, Keith Vorst

Chemistry and Biochemistry

Multiwalled-carbon nanotubes (MWCNTs) were functionalized via thermoinitiated free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) using benzoyl peroxide. Tip sonication was used during the polymerization reaction to separate agglomerated nanotubes. The functionalization was confirmed by control experiments and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Differential scanning calorimetry indicated that the addition of poly(HEMA)-MWCNTs to a two-component polyurethane coating will have little effect on the glass transition temperature of the coating. The poly(HEMA)-functionalized MWCNTs formed large colloidal structures of highly dispersed nanotubes in both the nonsheared and sheared coatings as determined by atomic force microscopy. This study determined a quick …

Direct Imaging Of Two-State Dynamics On The Amorphous Silicon Surface, S. Ashtekar, Gregory E. Scott, J. Lyding, M. Gruebele

Chemistry and Biochemistry

Amorphous silicon is an important material, amidst a debate whether or not it is a glass. We produce amorphous Si surfaces by ion bombardment and vapor growth, and image discrete Si clusters which hop by two-state dynamics at 295 K. Independent of surface preparation, these clusters have an average diameter of ~5 atoms. Given prior results for metallic glasses, we suggest that this cluster size is a universal feature. The hopping activation free energy of 0.93 ± 0.15 eV is rather small, in agreement with a previously untested surface glass model. Hydrogenation quenches the two-state dynamics, apparently by increasing surface …

Better Biomolecule Thermodynamics From Kinetics, Kiran Girdhar, Gregory Scott, Yann R. Chemla, Martin Gruebele

Chemistry and Biochemistry

Protein stability is measured by denaturation: When solvent conditions are changed (e.g., temperature, denaturant concentration, or pH) the protein population switches between thermodynamic states. The resulting denaturation curves have baselines. If the baselines are steep, nonlinear, or incomplete, it becomes difficult to characterize protein denaturation. Baselines arise because the chromophore probing denaturation is sensitive to solvent conditions, or because the thermodynamic states evolve structurally when solvent conditions are changed, or because the barriers are very low (downhill folding). Kinetics can largely eliminate such baselines: Relaxation of chromophores, or within thermodynamic states, is much faster than the transition over activation …

Microfluidic Paper-Based Analytical Devices: From Pocket To Paper-Based Elisa, Andres W. Martinez

Chemistry and Biochemistry

Microfluidic paper-based analytical devices (microPADs) began as a simple idea with an ambitious goal. The idea was to make microfluidic devices out of paper instead of plastic or glass. The goal was to develop low-cost and portable paper-based diagnostic devices to improve healthcare in developing countries. Over the past 6 years, many developments have been made in the emerging field of paper-based microfluidic devices. Reviewing the development of these devices in the Whitesides group at Harvard University (Cambridge, MA, USA) can provide some insight into the future of the field and encourage scientists from a variety of backgrounds to contribute …