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X-Ray Spectroscopy Of Nio And Nanodiamond At Ssrl, Jackson Earl 2018 Illinois State University

X-Ray Spectroscopy Of Nio And Nanodiamond At Ssrl, Jackson Earl

STAR (STEM Teacher and Researcher) Presentations

The first aspect of this research project focuses on investigating the surface chemistry of high pressure high temperature (HPHT) nanodiamond by using X-ray spectroscopy techniques at the Stanford Synchrotron Radiation Lightsource (SSRL). HPHT nanodiamond is being examined as a biosensing tool for electric field detection based on the fluorescent nitrogen vacancy center hosted within diamond. With use of the transition edge spectrometer (TES), a state-of-the-art X-ray fluorescence detector, we are able to probe the surface and bulk properties of diamond. Preliminary work using density functional theory (DFT) has been done, offering insight into ground state energies and electronic structure. DFT ...


Radical Chemistry In A Femtosecond Laser Plasma: Photochemical Reduction Of Ag+ In Liquid Ammonia Solution, Victoria K. Meader, Mallory G. John, Laysa M. Frias Batista, Syeda Ahsan, Katharine M. Tibbetts 2018 VCU

Radical Chemistry In A Femtosecond Laser Plasma: Photochemical Reduction Of Ag+ In Liquid Ammonia Solution, Victoria K. Meader, Mallory G. John, Laysa M. Frias Batista, Syeda Ahsan, Katharine M. Tibbetts

Chemistry Publications

Plasmas with dense concentrations of reactive species such as hydrated electrons and hydroxyl radicals are generated from focusing intense femtosecond laser pulses into aqueous media. These radical species can reduce metal ions such as Au3+ to form metal nanoparticles (NPs). However, the formation of H2O2 by the recombination of hydroxyl radicals inhibits the reduction of Ag+ through back-oxidation. This work has explored the control of hydroxyl radical chemistry in a femtosecond laser-generated plasma through the addition of liquid ammonia. The irradiation of liquid ammonia solutions resulted in a reaction between NH3 and OH·, forming peroxynitrite and ONOO−, and significantly reducing ...


3d Momentum Imaging Spectroscopy Probing Of Strong-Field Molecular And Surface Dynamics, Lin Fan 2018 Wayne State University

3d Momentum Imaging Spectroscopy Probing Of Strong-Field Molecular And Surface Dynamics, Lin Fan

Wayne State University Dissertations

Electron-ion coincidence measurements in combination with 3-dimensional (3D) momentum imaging can provide comprehensive 3D-momentum information to unravel multichannel photoionization/dissociation processes, and thus is an effective tool to investigate atomic/molecular dynamics. A camera-based 3D coincidence momentum imaging system and the velocity mapping imaging (VMI) based machine were introduced in Chapter 2. Studies of strong field dissociative single and double ionization of relatively large molecules camphor and 2-phenylethyl-N, N-dimethylamine (PENNA) were carried out and illustrated in Chapter 3. We demonstrated the main products of double ionization of PENNA were singlet diradicals. In Chapter 4, a novel angle resolved-photoemission spectroscopy based ...


Physicochemical, Spectroscopic Properties, And Diffusion Mechanisms Of Small Hydrocarbon Molecules In Mof-74-Mg/Zn: A Quantum Chemical Investigation, Gemechis Degaga 2018 Michigan Technological University

Physicochemical, Spectroscopic Properties, And Diffusion Mechanisms Of Small Hydrocarbon Molecules In Mof-74-Mg/Zn: A Quantum Chemical Investigation, Gemechis Degaga

Dissertations, Master's Theses and Master's Reports

In petroleum refining industries, the fracturing process allows for the cracking of long-chain hydrocarbons into a mixture of small olefin and paraffin molecules that are then separated via the energetically and monetarily demanding cryogenic distillation process. In an attempt to mitigate both energetic and capital consumptions, selective sorption of light hydrocarbons by tunable sorbents, such as metal-organic frameworks (MOFs), appears to be the most promising alternative for a more efficient gas separation process. MOFs are novel porous materials assembled from inorganic bricks connected by organic linkers. From a crystal engineering stand point, MOFs are advantageous in creating a range of ...


The Role Of Defects On The Optical, Electronic, And Magnetic Properties Of Iron-Sulfur Solids, Alyssa Ruth Landin 2018 University of Colorado at Boulder

The Role Of Defects On The Optical, Electronic, And Magnetic Properties Of Iron-Sulfur Solids, Alyssa Ruth Landin

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Solids composed of iron and sulfur are earth abundant and nontoxic, and can exhibit interesting and technologically important optical, electronic, and magnetic phenomena. Troilite (hexagonal FeS) is predicted to exhibit large room temperature magnetoelectricity and may exhibit high temperature superconducting properties, and pyrite (cubic FeS2) is a promising candidate for photovoltaic

applications. However, defects naturally occur within both of these solids. Troilite contains Fe deficiencies with atomic formula Fe(1-x)S, while pyrite contains sulfur deficiencies with the atomic formula FeS(2-x). The Fe-S phase diagram is congested in these regions of slight non-stoichiometries, and even when the atomic ...


Using Semiconductor Nanocrystals To Drive Redox Enzymes With Light, Hayden Tyler Hamby 2018 University of Colorado at Boulder

Using Semiconductor Nanocrystals To Drive Redox Enzymes With Light, Hayden Tyler Hamby

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Nanocrystals are an emergent strategy for providing electrons to redox enzymes for catalysis. In this dissertation I present my work on the investigation of how nanocrystals can be used to drive active site chemistry of two different enzymes. In the first project I present for the first time the direct coupling of cadmium sulfide nanorods (CdS NRs) to a CO2 reduction enzyme for the creation of new carbon-carbon bonds using light. Under optimal conditions, the maximum turnover frequency (TOFmax) for CO2 reduction is similar to that obtained in the native system where the native electron donor ferredoxin ...


Core Ion Structures In Co2- And N2o-Based Cluster Anions Studied By Infrared Photodissociation Spectroscopy, Michael Thompson 2018 University of Colorado at Boulder

Core Ion Structures In Co2- And N2o-Based Cluster Anions Studied By Infrared Photodissociation Spectroscopy, Michael Thompson

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

The interactions of anionic species with other molecules opens up new avenues to study the process of bond formation or charge transfer. Gas phase clusters are a useful tool for studying such systems in the absence of competing effects in condensed phase. Cluster ions can be studied as model analogues to more complex condensed phase systems. The majority of this thesis focuses on gas phase cluster ions of the form [M(CO2)n] (M=Bi, Sn, Mn, Fe). These clusters consist of a charged molecular anion surrounded by weakly bound “solvent” CO2 species. IR photodissociation spectroscopy is used ...


Electron Enhanced Atomic Layer Deposition (Ee-Ald) For Room Temperature Growth Of Gallium Nitride, Silicon, And Boron Nitride Films, Jaclyn Kelly Sprenger 2018 University of Colorado at Boulder

Electron Enhanced Atomic Layer Deposition (Ee-Ald) For Room Temperature Growth Of Gallium Nitride, Silicon, And Boron Nitride Films, Jaclyn Kelly Sprenger

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Electron enhanced atomic layer deposition (EE-ALD) can drastically reduce the temperatures required for film growth through electron stimulated desorption (ESD) of surface species. The desorption process creates highly reactive “dangling bond” surface sites. Precursors can then adsorb efficiently on the dangling bonds. EE-ALD enables deposition of thin films on thermally sensitive substrates and growth of laminate materials where alloying would occur at traditional processing temperatures.

We have demonstrated the EE-ALD of polycrystalline GaN, BN, and amorphous Si at room temperature (27˚C). Film growth was performed using alternating exposures of the appropriate precursors and low energy electrons (~100 eV). X-ray ...


Excited-State Dynamics Of Semiconductor Nanocrystals: Trapped-Hole Diffusion And Electron-Transfer Kinetics In Cds And Cdse Nanorods, James Keller Utterback 2018 University of Colorado at Boulder

Excited-State Dynamics Of Semiconductor Nanocrystals: Trapped-Hole Diffusion And Electron-Transfer Kinetics In Cds And Cdse Nanorods, James Keller Utterback

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Colloidal semiconductor nanocrystals have many remarkable properties—such as exceptionally tunable excited states and surface chemistry—that have led to an enthusiastic interest in using them for optoelectronic applications such as solar-energy conversion. Such technologies require control over the generation, separation, and extraction of photoexcited electrons and holes. However, the interpretation of experimentally measured excited-state decay curves is challenging because they typically exhibit complicated shapes that are elusive to simple kinetic models. To understand the principles that govern electron and hole relaxation dynamics in these complex systems, models rooted in fundamental physical phenomena are needed. This dissertation describes efforts to ...


Velocity-Map Imaging Photoelectron Spectroscopy Of Small Molecular Anions, Allan Maple de Oliveira 2018 University of Colorado at Boulder

Velocity-Map Imaging Photoelectron Spectroscopy Of Small Molecular Anions, Allan Maple De Oliveira

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Gas phase anion photoelectron spectroscopy presents an opportunity for investigating molecules that are inaccessible by other experimental techniques, by providing data on the structure, reactivity and energetics of short-lived radicals and transition state species. Our recent development of a novel, plasma entrainment source of cold, weakly-bound anions opens a door to new exotic species to be investigated. In this thesis, I explore the capabilities of photoelectron spectroscopy and its application to small exotic molecular anions, while further developing and employing the novel dual-valve ion source.

The thesis begins with a brief history of photoelectron spectroscopy, followed by a description of ...


Development And Characterization Of Improved Red Fluorescent Protein Variants, Premashis Manna 2018 University of Colorado at Boulder

Development And Characterization Of Improved Red Fluorescent Protein Variants, Premashis Manna

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Aequorea victoria-based green fluorescent proteins and their blue, cyan and red counterparts offer unprecedented advantage as biological markers owing to their genetic encodability and straightforward expression in different organisms. Fluorescent proteins are characterized with complex photo-kinetics due to the presence of light-induced non-fluorescent or dark states which are responsible for their fluorescence intermittency or 'blinking'. We developed time- and frequency-domain techniques for probing the kinetics involving dark state conversion (DSC) and ground state recovery (GSR) in red fluorescent proteins (RFPs). Ensemble-level DSC and GSR kinetics in FPs were presented in the context of their single molecule fluorescence behaviors. Although ...


A Kinetic Study Of Novel Gas-Phase Reaction Pathways For Pyruvic Acid And Hydrogen Halides With Hox Radicals., Jonathan Richard Church 2018 University of Colorado at Boulder

A Kinetic Study Of Novel Gas-Phase Reaction Pathways For Pyruvic Acid And Hydrogen Halides With Hox Radicals., Jonathan Richard Church

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Hydroperoxy (HO2) and hydroxyl (OH) radicals are known to play important roles in both combustion and atmospheric chemistry. Although less reactive than hydroxyl radicals, HO2 has been found to be important to the ignition process in combustion systems and has been found in greater concentrations than that of OH in the troposphere. In this work, gas-phase reactions between HO2 and hydrogen halides (HX, X=F, Cl, Br, I) are examined due to the catalytic effect halides can have in the ozone destruction process, as well as their ability to inhibit flame speeds under combustion settings. During the ...


Analytical Modeling And Numerical Simulations Of Time Delays In Attosecond Streaking Of One- And Two-Photon Ionization, Cory Scott Goldsmith 2018 University of Colorado at Boulder

Analytical Modeling And Numerical Simulations Of Time Delays In Attosecond Streaking Of One- And Two-Photon Ionization, Cory Scott Goldsmith

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

The generation of attosecond-duration (1 as = 10-18 s) coherent light through the process of high-order harmonic generation has opened the perspective for probing fundamental processes, such as photoionization, on the natural timescale of electron dynamics in matter. One probing technique is the attosecond streaking method, in which the momentum of the photoelectron is measured as a function of the time delay between the ionizing, attosecond extreme ultraviolet (XUV) pulse, and a weak, femtosecond near-infrared (NIR) pulse which streaks the momentum of the photoelectron, known as a streaking trace. The observed trace contains time information about the photoionization process in ...


Water Dynamics And The Effect Of Static And Alternating Electric Fields, Mohammadmahdi Shafiei Alavijeh 2018 Virginia Commonwealth University

Water Dynamics And The Effect Of Static And Alternating Electric Fields, Mohammadmahdi Shafiei Alavijeh

Theses and Dissertations

Having a net dipole moment, water molecules tend to align with an external electric field. The re-orientation of water molecules to align with the field direction can result in structural and dynamic changes in liquid water. Studying these changes can help us to understand the role of an E-field in many biological systems, chemical reactions, and many technological advancements.

In short, the application of static electric fields causes molecules to stay aligned with the field, so, fewer hydrogen bonds break, and molecules have slower dynamics. This type of field can be used when the mobility of water molecules needs to ...


Physical Chemistry Of Gas-Liquid Interfaces: Foreword, Jennifer Faust 2018 The College of Wooster

Physical Chemistry Of Gas-Liquid Interfaces: Foreword, Jennifer Faust

All Faculty Articles

Physical Chemistry of Gas-Liquid Interfaces, the first volume in the Developments in Physical & Theoretical Chemistry series, addresses the physical chemistry of gas transport and reactions across liquid surfaces. Gas-liquid interfaces are all around us, especially within atmospheric systems such as sea spray aerosols, cloud droplets, and the surface of the ocean. Because the reaction environment at liquid surfaces is completely unlike bulk gas or bulk liquid, chemists must readjust their conceptual framework when entering this field. This book provides the necessary background in thermodynamics and computational and experimental techniques for scientists to obtain a thorough understanding of the physical chemistry ...


Structural And Chemical Consequences Of High Oxygen Coverages On Rh(111), Rachael Gabrielle Farber 2018 Loyola University Chicago

Structural And Chemical Consequences Of High Oxygen Coverages On Rh(111), Rachael Gabrielle Farber

Dissertations

Partial oxidations of small molecules over metal surfaces are central to many heterogeneously catalyzed reactions. However, the identity of the actual surface species that promote or hinder these reactions has remained elusive for a variety of reasons. Recently, the understanding of the role of surface oxides in catalytic activity has changed. Instead of being thought of as poisons, they are now believed to be effective promoters of selective catalysis.

Rhodium (Rh) effectively promotes oxidation reactions and is a benchmark system for models of heterogeneously catalyzed chemistry. For this reason, Rh(111) was chosen as the model system for this dissertation ...


Modeling Nonadiabatic Dynamics At Molecule-Metal Interfaces, Wenjie Dou 2018 University of Pennsylvania

Modeling Nonadiabatic Dynamics At Molecule-Metal Interfaces, Wenjie Dou

Publicly Accessible Penn Dissertations

The coupled electronic-nuclear dynamics at molecule-metal interfaces are fundamental processes that underlie many distinct areas of science: from electrochemistry, chemisorption, heterogeneous catalysis, quantum dots, all the way to molecular conduction. Simulating these coupled dynamics at molecule-metal interfaces is very challenging, due to the breakdown of the Born-Oppenheimer approximation and the inclusion of a manifold of electrons from the metal. Two methods are presented to investigate these nonadiabatic dynamics: a) In the outer sphere regime (weak electronic coupling between molecule and metal), a surface hopping approach is developed to treat nuclear motion classically with electronic motion captured by hopping between different ...


Quantum Chemical Analysis Of Stable Noble Gas Cations For Astrochemical Detection, Carlie M. Novak 2018 Georgia Southern University

Quantum Chemical Analysis Of Stable Noble Gas Cations For Astrochemical Detection, Carlie M. Novak

University Honors Program Theses

The search for possible, natural, noble gas molecules has led to quantum chemical, spectroscopic analysis of NeCCH+, ArNH+ ArCCH+, and ArCN+. Each of these systems have been previously shown to be a stable minimum on its respective potential energy surface. However, no spectroscopic data are available for laboratory detection or interstellar observation of these species, and the interstellar medium may be the most likely place, in nature, where these noble gas cations are found. The bent shape of NeCCH+ is confirmed here with a fairly large dipole moment and a bright C -- H stretching frequency at 3101.9 cm-1 ...


Applications Of Molecular And Quantum Mechanical Methods For Studying The Chemical Reactions Of Inorganic And Organic Systems, Yi-Jung Tu 2018 Wayne State University

Applications Of Molecular And Quantum Mechanical Methods For Studying The Chemical Reactions Of Inorganic And Organic Systems, Yi-Jung Tu

Wayne State University Dissertations

Computational studies can assist chemists to interpret experimental observations and to predict the properties and behaviors of molecules. The work presented in this dissertation applies different computational methods to study the molecular properties and reaction paths for various inorganic and organic systems. The second and third chapters discuss the force field development using “Gaussian Electrostatic Model (GEM)” and its amenability for use in the AMOEBA force field. The forth and fifth chapters discuss the density functional theory (DFT) studies of photodissociation behaviors for inorganic molecules. The sixth chapter explores the oxidation mechanisms of ascorbic acid and its antioxidant properties in ...


Photofragment Imaging Fast Ion Beams, Michael D. Johnston Jr. 2018 University of Massachusetts Amherst

Photofragment Imaging Fast Ion Beams, Michael D. Johnston Jr.

Doctoral Dissertations

Metal-containing ions have been the subject of much research due to their roles in catalytic activation and small cluster chemistries. However, they can be difficult to study both experimentally and theoretically, and new approaches are needed. The goal of the research described here is to characterize the electronic structures and thermodynamics of metal-containing ions using gas-phase spectroscopy experiments performed on a powerful new instrument. Presented in the following chapters are the details of a recently built velocity map imaging mass spectrometer that is capable of imaging the photofragments of trap-cooled (≥7K) ions produced in a versatile ion source. This instrument ...


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