Chemistry Commons^™

A Grand Unified Model For Liganded Gold Clusters, Wen Wu Xu, Beien Zhu, Xiao Cheng Zeng, Yi Gao

Xiao Cheng Zeng Publications

A grand unified model (GUM) is developed to achieve fundamental understanding of rich structures of all 71 liganded gold clusters reported to date. Inspired by the quark model by which composite particles (for example, protons and neutrons) are formed by combining three quarks (or flavours), here gold atoms are assigned three ‘flavours’ (namely, bottom, middle and top) to represent three possible valence states. The ‘composite particles’ in GUM are categorized into two groups: variants of triangular elementary block Au₃(2e) and tetrahedral elementary block Au₄(2e), all satisfying the duet rule (2e) of the valence shell, akin to …

Kinetics And Reaction Mechanisms For Methylidyne Radical Reactions With Small Hydrocarbons, Joao Marcelo Lamim Ribeiro

FIU Electronic Theses and Dissertations

The chemical evolution with respect to time of complex macroscopic mixtures such as interstellar clouds and Titan’s atmosphere is governed via a mutual competition between thousands of simultaneous processes, including thousands of chemical reactions. Chemical kinetic modeling, which attempts to understand their macroscopic observables as well as their overall reaction mechanism through a detailed understanding of their microscopic reactions and processes, thus require thousands of rate coefficients and product distributions. At present, however, just a small fraction of these have been well-studied and measured; in addition, at the relevant low temperatures, such information becomes even more scarce. Due to the …

The Tribology And Chemistry Of Phosphorus Containing Lubricant Additives, David W. Johnson

Chemistry Faculty Publications

Phosphate esters, thiophosphate esters and metal thiophosphates have been used as lubricant additives for over 50 years. Recently, phosphorus‐containing ionic liquids have emerged as a new class of lubricant additives. While the use of phosphorus compounds has been extensive, a detailed knowledge of how they work has been a much more recent development. In this chapter, the use of phosphate esters, thiophosphate esters, metal thiophosphates and phosphorus‐containing ionic liquids as antiwear or extreme pressure additives is discussed. The primary emphasis will be on how they form a protective film, which is both durable and reduces friction. The first part of …

In Situ Ion Exchange In A Micro-Porous Transition Metal Silicate Framework, Jason M. Lively

Masters Theses & Specialist Projects

Ion selectivity of minerals has traditionally been utilized in industry as a catalyst, metal separation, and environmental reclamation/sequestration tool. There is an increased interest in understanding ion selectivity mechanisms of micro-porous minerals and mineral-like structures and how they can be applied in various industries: environmental and, potentially, pharmaceutical. This study seeks to understand the ion exchange mechanisms in micro-porous zirconosilicates using time-resolved Raman spectroscopy and X-ray diffraction. The thesis material was exchanged with H+, Na+, K+, and Cs+ in order to better understand structural changes as well as the influence of the H+-bonding during the exchange process. It is hypothesized …

Metal-Organic Hybrid Nanocomposites For Energy Harvesting Applications, Thulitha Madawa Abeywickrama

Masters Theses & Specialist Projects

Various synthetic methods have been developed to produce metal nanostructures including copper and iron nanostructures. Modification of nanoparticle surface to enhance their characteristic properties through surface functionalization with organic ligands ranging from small molecules to polymeric materials including organic semiconducting polymers is a key interest in nanoscience. However, most of the synthetic methods developed in the past depend widely on non-aqueous solvents, toxic reducing agents, and high temperature and high-pressure conditions. Therefore, to produce metal nanostructures and their nanocomposites with a simpler and greener method is indeed necessary and desirable for their nano-scale applications. Hence the objective of this thesis …

Preface-Jes Focus Issue On Electrolysis For Increased Renewable Energy Penetration, B. Pivovar, M. Carmo, K. Ayers, X. Zhang, J. O'Brien

Mechanical & Aerospace Engineering Faculty Publications

(First paragraph) Today represents a particularly exciting time, as our planet’s energy system is undergoing major changes due to dramatically decreasing renewable energy prices and increasing societal concerns over greenhouse gas emissions, criteria pollutants (arsenic, mercury, NOx, particulate matter), and climate change. These factors are pushing society toward deep decarbonization of our energy system, perhaps the most challenging issue facing the planet today. Unfortunately, wind and solar energy, while both promising generation sources, come with intermittency challenges and have limitations in their abilities to impact industrial and transportation sector demands where fossil fuel energy carriers based on chemical bonds have …

Electrophilic Activation Of Silicon–Hydrogen Bonds In Catalytic Hydrosilations, Mark C. Lipke, Allegra L. Liberman-Martin, T. Don Tilley

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Hydrosilation reactions represent an important class of chemical transformations and there has been considerable recent interest in expanding the scope of these reactions by developing new catalysts. A major theme to emerge from these investigations is the development of catalysts with electrophilic character that transfer electrophilicity to silicon by Si-H activation. This type of mechanism has been proposed for catalysts ranging from Group 4 transition metals to Group 15 main group species. Additionally, other electrophilic silicon species, such as silylene complexes and η3-H2SiRR′ complexes, have been identified as intermediates in hydrosilation reactions. In this Review, different types of catalysts are …

Lubricants For Turbine Engines, David W. Johnson

Chemistry Faculty Publications

The lubricant systems used in turbine engine applications are discussed with respect to the particular problems associated with aircraft applications. After initially describing the relevant specifications, the typical basestocks are described along with some common degradation schemes. The additive systems, including antioxidants, anti-foaming agents, and anti-wear additives needed to achieve the typical specifications, are described along with their mechanism of action and degradation mechanisms. The methods used for the monitoring of lubricant health, including in-line and offline methods, are also discussed. Finally, future changes in specifications, basestocks, and additives are discussed with respect to new, high-performance bearing materials.

Revisiting The Fenceplot For The Maxwell Construction Of A Van Der Waals Fluid, Carl W. David

Chemistry Education Materials

An earlier published plot intended to better explain the Maxwell construction of the vapor pressure construct for van der Waals fluids is improved using Inkscape.

Insights From Molecular Dynamics On Substrate Binding And Effects Of Active Site Mutations In Delta1-Pyrroline-5-Carboxylate Dehydrogenase, Bogdan F. Ion, Mohamed M. Aboelnga, James W. Gauld

Chemistry and Biochemistry Publications

The NAD+-dependent enzyme, 1-pyrroline-5-carboxylate dehydrogenase (P5CDH), has an important role in proline and hydroxyproline catabolism for humans. Specifically, this aldehyde dehydrogenase is responsible for the oxidation of both L-glutamate- -semialdehyde (GSA) and 4-erythro-hydroxy-L-glutamate- -semialdehyde (4-OH-GSA) to their respective L-glutamate product forms. We have performed a detailed molecular dynamics (MD) study of both the reactant and product complex structures of P5CDH to gain insights into ligand binding (i.e., GSA, 4-OH-GSA, NAD+, GLU) in the active site. Moreover, our investigations were further extended to examine the structural impact of S352L, S352A, and E314A mutations on the deficiency in the P5CDH enzymatic activity. …

Verwiebe's "3-D" Ice Phase Diagram Reworked, Carl W. David

Chemistry Education Materials

The two dimensional phase diagrams of the various forms of ice are difficult to read and understand. A ``3D'' versions appearing ~80 years ago helps understanding of the phases and their inter-conversion into other phases.

Using In Situ Liquid Single Photon Ionization Mass Spectrometry (Spi-Ms) To Probe Lithium Polysulfide Electrolyte In Motion, Aala M. Al Hasan, Jiachao Yu, Juan Yao, Vijayakumar Murugesan, Manjula Nandasiri, Xiao-Ying Yu

STAR Program Research Presentations

The solid-liquid (s-l) interface is the most common interface encountered in electrochemical systems. The s-l interface has wide applications in energy storage, catalysis, and material sciences. In situ studies of chemical reactions taking place on the s-l interfaces can further our understanding of electron transfer and link to real-world device functions under challenging conditions. Direct probing of the solid electrode and liquid electrolyte interface has been realized using a vacuum compatible electrochemical microfluidic reactor, system for analysis at the liquid vacuum interface (SALVI) with time-of-flight secondary ion mass spectrometry (ToF-SIMS). Most recently, the electrochemical version of SALVI was integrated to …

Comparative Analysis Of In Situ Fibronectin Using Tof-Sims, Spi-Ms, And Dropdesi-Ms In A Microfluidic Reactor, Shannon Fasing, Xiao-Ying Yu, Juan Yao, Jiachao Yu

STAR Program Research Presentations

Fibronectin is an important biomolecule due to its role in cell differentiation, growth, kinesis, and adhesion. Such biological responses are mediated through membrane recognition and signaling; where fibronectin is found. Studying the outer molecular surface of fibronectin allows deeper insight into the microbiological reactions that occur during these processes. In situ mass spectrometry analysis in aqueous solution accurately represents fibronectin’s chemical components, made possible by a vacuum compatible microfluidic reactor, SALVI (System for Analysis at the Liquid Vacuum Interface). SALVI was paired with the analytical tools: time-of-flight secondary ion mass spectrometer (ToF-SIMS), single photon ionization mass spectrometer (SPI-MS) and drop …

Synthesis And Applications Of Lanthanide Sulfides And Oxides, Christopher Marin

Department of Chemistry: Dissertations, Theses, and Student Research

This dissertation focuses on two of the key fields where lanthanides find ready application: as optically active materials with a focus on the lanthanide sulfides, and as catalytic materials with a focus on cerium oxide.

The lanthanide sulfides have attracted considerable interest for their potential as solar energy conversion materials, pigments, infrared window materials, and phosphor host media. However, applications of these materials remain limited due to their synthetic difficulty along with their not well understood properties compounded by both their difficulty in manufacturing as well as in simulating largely due to the need to take into account f-shell electrons. …

Conformational Dynamics And Stability Associated With Magnesium Or Calcium Binding To Dream In The Regulation Of Interactions Between Dream And Dna Or Presenilins, Khoa Ngoc Pham

FIU Electronic Theses and Dissertations

Downstream regulatory element antagonist modulator (DREAM) is involved in various interactions with targets both inside and outside of the nucleus. In the cytoplasm, DREAM interacts with the C-terminal fragments of presenilins to facilitate the production of β-amyloid plaques in Alzheimer’s disease. In the nucleus, Ca²⁺ free DREAM directly binds to specific downstream regulatory elements of prodynorphin/c-fos gene to repress the gene transcription in pain modulation. These interactions are regulated by Ca²⁺ and/or Mg²⁺ association at the EF-hands in DREAM. Therefore, understanding the conformational dynamics and stability associated with Ca²⁺ and/or Mg²⁺ binding to DREAM …

Aqueous Photochemistry Of Glyoxylic Acid, Alexis J. Eugene, Sha-Sha Xia, Marcelo I. Guzman

Chemistry Faculty Publications

Aerosols affect climate change, the energy balance of the atmosphere, and public health due to their variable chemical composition, size, and shape. While the formation of secondary organic aerosols (SOA) from gas phase precursors is relatively well understood, studying aqueous chemical reactions contributing to the total SOA budget is the current focus of major attention. Field measurements have revealed that mono-, di-, and oxo-carboxylic acids are abundant species present in SOA and atmospheric waters. This work explores the fate of one of these 2-oxocarboxylic acids, glyoxylic acid, which can photogenerate reactive species under solar irradiation. Additionally, the dark thermal aging …

A Direct Mechanism Of Ultrafast Intramolecular Singlet Fission In Pentacene Dimers, Eric G. Fuemmeler, Samuel N. Sanders, Andrew B. Pun, Elango Kumarasamy, Tao Zeng, Kiyoshi Miyata, Michael L. Steigerwald, X.-Y. Zhu, Matthew Y. Sfeir, Luis M. Campos, Nandini Ananth

Publications and Research

Interest in materials that undergo singlet fission (SF) has been catalyzed by the potential to exceed the Shockley–Queisser limit of solar power conversion efficiency. In conventional materials, the mechanism of SF is an intermolecular process (xSF), which is mediated by charge transfer (CT) states and depends sensitively on crystal packing or molecular collisions. In contrast, recently reported covalently coupled pentacenes yield ∼2 triplets per photon absorbed in individual molecules: the hallmark of intramolecular singlet fission (iSF). However, the mechanism of iSF is unclear. Here, using multireference electronic structure calculations and transient absorption spectroscopy, we establish that iSF can occur via …

Binding Of Oxygen To Human Hemoglobin Within The Erythrocyte Using Icam Spectrophotometry, Kyle K. Hill

Department of Chemistry: Dissertations, Theses, and Student Research

Many of the spectrophotometric techniques used to determine the properties of intracellular human hemoglobin cannot be utilized due to the turbidity of erythrocyte suspensions. An Integrating Cavity Absorption Meter, or ICAM, allows for absorption measurements of strongly scattering samples in the visible-light region of the spectrum. The spectrum of oxygenated hemoglobin within erythrocytes is significantly different from the absorption spectrum of oxygenated hemoglobin in solution. Studies of the oxygen binding to hemoglobin in erythrocytes allowed the four sequential binding constants (Adair constants) to be determined and compared with those of hemoglobin in solution. The Adair constants for hemoglobin in solution …

Is The Maxwell Construction Correct In Predicting The Van Der Waals Fluid's Vapor Pressure?, Carl W. David

Chemistry Education Materials

The Maxwell construction yields a pressure value which traditionally been associated with the vapor pressure. Here, the question is answered whether or not the two phases represented by the construct are indeed in equilibrium.

Photocatalytic Properties Of G-C3n4–Tio2 Heterojunctions Under Uv And Visible Light Conditions, Rachel Fagan, Declan Mccormack, Steven J. Hinder, Suresh Pillai

Articles

Graphitic carbon nitride (g-C3N4) and titanium dioxide (TiO2) were chosen as a model system to investigate photocatalytic abilities of heterojunction system under UV and visible light conditions. The use of g-C3N4 has been shown to be effective in the reduction in recombination through the interaction between the two interfaces of TiO2 andg-C3N4. A simple method of preparing g-C3N4 through the pyrolysis of melamine was employed, which was then added to undoped TiO2 material to form the g-C3N4–TiO2 system. These materials were then fully characterized by X-ray diffraction (XRD), Brunauer Emmett Teller (BET), and various spectroscopic techniques including Raman, X-ray photoelectron …

Photocatalytic Reduction Of Fumarate To Succinate On Zns Mineral Surfaces, Ruixin Zhou, Marcelo I. Guzman

Chemistry Faculty Publications

The reductive tricarboxylic acid (rTCA) cycle is an important central biosynthetic pathway that fixes CO₂ into carboxylic acids. Among the five reductive steps in the rTCA cycle, the two-electron reduction of fumarate to succinate proceeds nonenzymatically on the surface of photoexcited sphalerite (ZnS) colloids suspended in water. This model reaction is chosen to systematically study the surface photoprocess occurring on ZnS in the presence of [Na₂S] (1–10 mM) hole scavenger at 15 °C. Experiments at variable pH (5–10) indicate that monodissociated fumaric acid is the primary electron acceptor forming the monoprotic form of succinic acid. The following …

Xiao Cheng Zeng Bibliography (April 2016), Xiao Cheng Zeng

Xiao Cheng Zeng Publications

397 articles sorted by topics

Novel Mitochondrial Complex I Inhibitors Restore Glucose-Handling Abilities Of High-Fat Fed Mice, Darren Martin, Siobhan Leonard, Robert Devine, Clara Redondo, Gemma Kinsella, Conor Breen, Victoria Mceneaney, Mary Rooney, Tim Munsey, Richard Porter, Asipu Sivaprasadarao, John Stephens, John Findlay

Articles

Metformin is the main drug of choice for treating type 2 diabetes, yet the therapeutic regimens and side effects of the compound are all undesirable and can lead to reduced compliance. The aim of this study was to elucidate the mechanism of action of two novel compounds which improved glucose handling and weight gain in mice on a high-fat diet. Wildtype C57Bl/6 male mice were fed on a high-fat diet and treated with novel, anti-diabetic compounds. Both compounds restored the glucose handling ability of these mice. At a cellular level, these compounds achieve this by inhibiting complex I activity in …

Enhancing The Photovoltaic Efficiency Of A Bulk Heterojunction Organic Solar Cell, Swapnil Ashok Sahare

Masters Theses & Specialist Projects

Active layer morphology of polymer-based solar cells plays an important role in improving power conversion efficiency (PCE). In this thesis, the focus is to improve the device efficiency of polymer-based solar cells. In the first objective, active layer morphology of polymer-solar cells was optimized though a novel solvent annealing technique. The second objective was to explore the possibility of replacing the highly sensitive aluminum cathode layer with a low-cost and stable alternative, copper metal. Large scale manufacturing of these solar cells is also explored using roll-to-roll printing techniques.

Poly (3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl (PCBM) were used as the …

Characteristic Length Scales Of The Secondary Relaxations In Glass-Forming Glycerol, Sudipta Gupta, Eugene Mamontov, Niina Jalarvo, Laura Stingaciu, Michael Ohl

Faculty Publications

We investigate the secondary relaxations and their link to the main structural relaxation in glass-forming liquids using glycerol as a model system. We analyze the incoherent neutron scattering signal dependence on the scattering momentum transfer, Q , in order to obtain the characteristic length scale for different secondary relaxations. Such a capability of neutron scattering makes it somewhat unique and highly complementary to the traditional techniques of glass physics, such as light scattering and broadband dielectric spectroscopy, which provide information on the time scale, but not the length scales, of relaxation processes. The choice of suitable neutron scattering techniques depends …

An Effective Method For The Preparation Of High Temperature Stable Anatase Tio2 Photocatalysts, Rachel Fagan, Declan Mccormack, Suresh Pillai, Damian Synnott

Articles

An efficient, rapid and straightforward method for the preparation of nitrogen and fluorine (N, F) codoped high temperature stable anatase using a microwave pre-treatment is reported. Using a single source, ammonium fluoride (NH₄F) for both nitrogen and fluorine, effective doping of the precursor titanium isopropoxide (TTIP) was possible. These samples were characterised for their structural and optical properties using X-ray diffraction (XRD), Fourier transform IR (FTIR), Raman spectroscopy and UV-vis spectroscopy. In terms of the anatase to rutile transition enhancement using a novel microwave assisted technique, the sample prepared in a composition of 1:8 TiO₂: NH …

Study Of Infrared Emission Spectroscopy For The B 1Δg- A 1Πu And B ′1Σg +- A 1Πu Systems Of C2, Wang Chen, Kentarou Kawaguchi, Peter F. Bernath, Jian Tang

Chemistry & Biochemistry Faculty Publications

Thirteen bands for the B¹Δ_g-A¹Π_u system and eleven bands for the B′¹Σ_g ⁺-A¹Πu system of C₂ were identified in the Fourier transform infrared emission spectra of hydrocarbon discharges. The B′¹Σ_g ⁺ v = 4 and the B¹Δ_g v = 6, 7, and 8 vibrational levels involved in nine bands were studied for the first time. A direct global analysis with Dunham parameters was carried out satisfactorily for the B¹Δ_g-A¹Π_u system except for a …

Efficient Bimolecular Mechanism Of Photochemical Hydrogen Production Using Halogenated Boron-Dipyrromethene (Bodipy) Dyes And A Bis(Dimethylglyoxime) Cobalt(Iii) Complex, Randy Pat Sabatini, Brian M. Lindley, Theresa M. Mccormick, Theodore Lazarides, William Brennessel, David W. Mccamant, Richard Eisenberg

Chemistry Faculty Publications and Presentations

A series of Boron-­dipyrromethene (Bodipy) dyes were used as photosensitizers for photochemical hydrogen production in conjunction with [Co^III(dmgH)2pyCl] (where dmgH = dimethylglyoximate, py = pyridine) as the catalyst and triethanolamine (TEOA) as the sacrificial electron donor. The Bodipy dyes are fully characterized by electrochemistry, x-­‐ray crystallography, quantum chemistry calculations, femtosecond transient absorption and time-­‐resolved fluorescence, as well as in long-­‐term hydrogen production assays. Consistent with other recent reports, only systems containing halogenated chromophores were active for hydrogen production, as the long-­‐lived triplet state is necessary for efficient bimolecular electron transfer. Here, it is shown that the photostability of …

Phase Transition Enthalpy Measurements Of Organic And Organometallic Compounds. Sublimation, Vaporization And Fusion Enthalpies From 1880 To 2015. Part 1. C1 − C10, William Acree, James Chickos

Chemistry & Biochemistry Faculty Works

A compendium of phase change enthalpies published in 2010 is updated to include the period 1880–2015. Phase change enthalpies including fusion, vaporization, and sublimation enthalpies are included for organic, organometallic, and a few inorganic compounds. Part 1 of this compendium includes organic compounds from C1 to C10. Part 2 of this compendium, to be published separately, will include organic and organometallic compounds from C11 to C192. Sufficient data are presently available to permit thermodynamic cycles to be constructed as an independent means of evaluating the reliability of the data. Temperature adjustments of phase change enthalpies from the temperature of measurement …

Unraveling A Generic Growth Pattern In Structure Evolution Of Thiolate-Protected Gold Nanoclusters, Wen Wu Xu, Yadong Li, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Precise control of the growth of thiolate-protected gold nanoclusters is a prerequisite for their applications in catalysis and bioengineering. Here, we bring to bear a new series of thiolateprotected nanoclusters with a unique growth pattern, i.e., Au₂₀(SR)₁₆, Au₂₈(SR)₂₀, Au₃₆(SR)₂₄, Au₄₄(SR)₂₈, and Au₅₂(SR)₃₂. These nanoclusters can be viewed as resulting from the stepwise addition of a common structural motif [Au₈(SR)₄]. The highly negative values of the nucleus-independent chemical shift (NICS) in the center of the tetrahedral Au4 …