Chemistry Commons^™

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 …

An Investigation Of The Requirements For Excimer Formation And Charge Stabilization In Model Pi-Stacked Assemblies, Brandon Uhler

Dissertations (1934 -)

Formation of -stacked excimers plays an important role in many systems, ranging from biological phenomena and polymer formation and function to photovoltaic devices and organic molecular electronics. In these systems, the geometrical reorganization of the ground state upon photoexcitation is still a subject of debate. In this work, we compare the dynamics of excimer formation and hole (charge) stabilization in fluorene and fluorene-based model systems. We use a variety of gas-phase methods to examine the spectroscopy and dynamics of these systems, including Two-Color Resonant Two-Photon Ionization (2CR2PI), Hole-Burning (HB), Laser Induced Fluorescence (LIF), and Dispersed Fluorescence (DF). In order to …

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 …

Nmr Studies Of Electrochemical Energy Storage Materials, Jing Peng

Dissertations, Theses, and Capstone Projects

Electrochemical energy storage materials constitute essential elements in the development of sustainable energy technologies. They are crucial for improving the efficiency of energy storage devices to facilitate the use of renewable resources. The increasing human demands for energy and limitation of fossil fuel stimulates the continued development of energy storage materials. Better understanding of their working mechanisms and electrochemical properties from a view of chemistry is quite necessary for improving the energy storage technology. In this work, Nuclear Magnetic Resonance (NMR) has been used as a powerful tool to characterize the solvation behavior and diffusion ability of some commonly used …

Photodynamic Killing Of Human Cancer Cells With Smart Photosensitizer Materials And An Endoscopic Implement For Singlet Oxygen Delivery, Mihaela N. Minnis

Dissertations, Theses, and Capstone Projects

The thesis describes progress on probe tips for a microoptic device for the precise delivery of the components necessary for photodynamic therapy (PDT) in a highly localized and controllable fashion. The thesis also summarizes results of a photosensitized oxidation study. The work focused on i) developing a photoactive fluoropolymer surface that will release sensitizer drug molecule for use in PDT, ii) designing new probe tips surfaces for use as sensitizer support for a microoptic PDT device, iii) exploring strategies for covalent attachment of sensitizers and model compounds to Teflon/PVA surfaces with the aim of being coupled with our microoptic device, …

Probing The Structure And Photophysics Of Porphyrinoid Systems For Functional Materials, Christopher D. Farley

Dissertations, Theses, and Capstone Projects

Porphyrins (Pors) and their many cousins, including phthalocyanines (Pcs), corroles (Cors), subphthalocyanines (SubPcs), porphyrazines (Pzs), and naphthalocyanines (NPcs), play amazingly diverse roles in biological and non-biological systems because of their unique and tunable physical and chemical properties. These compounds, collectively known as porphyrinoids, can be employed in any number of functional devices that have the potential to address the challenges of modern society. Their incorporation into such devices, however, depends on many structural factors that must be well understood and carefully controlled in order to achieve the desired behavior. Self-assembly and self-organization are key processes for developing these new technologies, …

Nanostructured Air Electrodes And Electrochemical Reaction Mechanism Studies For Sodium-Oxygen Batteries, Hossein Yadegari

Electronic Thesis and Dissertation Repository

Alkali metal-O₂ batteries, i.e. Li- and Na-O₂, are considered as the next generation of energy saving technologies with potential application in electric transportation. The high theoretical energy density in these cells is related to the use of high energy alkali metals as negative and oxygen as the positive electrode materials. The performance of alkali metal-O₂ cells is highly dependent on the positive electrode material, where oxygen reduction and evolution reactions take place. Besides, the primary products of oxygen reduction reaction in these cells are typically metal oxides, which are insoluble in nonaqueous electrolytes, resulting in accumulation …

Model Of The Formation Of Iron Oxide Nanoparticles By Irradiation In Aqueous Media, Thomas I. Sutherland

Electronic Thesis and Dissertation Repository

This thesis aims to develop the mechanistic understanding of the formation of iron oxide nanoparticles by γ-irradiation. Under irradiation water breaks down into a wide array of redox active species (H•, •OH, H₂O₂, •e^-_(aq)) uniformly throughout the solution. These species are capable of rapidly interconverting any soluble Fe^II and insoluble Fe^III species resulting in the formation of nanoparticles with a narrow size distribution. The initial concentration of Fe²⁺ in the solution, the solution pH, the presence of any radical scavengers, the temperature of the reaction, and the dose rate of …

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.

Activation Effect Of Nano-Carbon Derived From Co2 On Lead Electrode In Sulfuric Aqueous Solution, Yu-Qiao Song, Hua Zhu, Guang-Jin Zhao, Wen-Long Wu, Shou-Bin Zhou, Di-Hua Wang

Journal of Electrochemistry

Serious sulfation of the negative plate is one of the most popular reasons of the early failure of lead-acid battery. Addition of nano-carbon was proved to be effective for recovering the sulfated electrode and the property of the carbon material always plays an important role. In this work, a new kind of nano-carbon material with high electrical conductivity and good adsorption capability for heavy metal cations, which is electrochemically prepared from CO₂ in molten carbonates, was tested as activation additive for the sulfated lead electrode by cyclic voltammetry and SEM measurements. The results showed that the as-prepared carbon can …

Prospects Of D-Π-A Structured Porphyrins And Their Photoelectrochemical Application, Shuang-Shuang Liu, Jian-Feng Lu, Ming-Kui Wang

Journal of Electrochemistry

Porphyrins and their metalloderivatives are a class of compounds exhibiting a wide variety of interesting and highly useful properties, such as chlorophyll. Porphyrins are particularly interesting in photoelectrochemical applications due to their structural similarity to chlorophylls in natural photosynthetic systems, as well as their strong and tunable absorption properties. Recently, various porphyrins have been extensively studied for their applications in solar cells, photocatalytic hydrogen production, optical information storage and others. This review will focus on the unique physical and chemical properties of D-π-A structured porphyrins, and their photovoltaic performances in dye-sensitized solar cells. A brief discussion in the future development …

Preparations And Photoelectrochemical Properties Of Phosphate Modified Rgo-Biobr Nanocomposites, Shuang-Ying Chen, Zhi-Jun Li, Xu-Liang Zhang, Kang Hu, Rui Yan, Li-Qiang Jing

Journal of Electrochemistry

The RGO-BiOBr nanocomposites have been successfully synthesized by a hydrothermal process, and then modified with phosphorous acids. The photoelectrochemical properties of the fabricated RGO-BiOBr nanocomposite films were studied. The results indicate that the photocurrent densities of RGO-BiOBr were much larger compared with those of the bare BiOBr, and interestingly, the photocurrent densities were further improved after phosphate modification. Based on the analyses of the produced hydroxyl radical amounts, the enhanced photocurrent densities could be attributed to the introduction of RGO and to the formed negative fields of modified phosphate groups, which are favorable for electrons to be transferred and for …

Special Issue: Photoelectrochemistry And New Types Of Solar Cells, Chang-Jian Lin, Yong-Fang Li

Journal of Electrochemistry

Human society has been facing a global energy problem and gigantic challenge, due to the continually increasing energy demand to support economic growth, the gradual depletion of fossil fuels, and the greenhouse effect caused by fossil fuel combustion. Promoted development of various renewable energies becomes one of the most common issues and hot topics in the world. Photovoltaic technology is most attractive and has been fastest developing as a green and renewable energy in solar applications. The Sun shines on the Earth, thus providing around 3 × 1024 J of green energy per year, if covering only around 0.1% of …

Cathode Buffer Layer For Improving Photovoltaic Performance Of Planar P-I-N Perovskite Solar Cells, Xiao-Dong Liu, Yong-Fang Li

Journal of Electrochemistry

Organic/inorganic hybrid metal halide perovskite semiconductor materials have drawn great attention for the application in solar cells in recent years because of their combined superior photoelectrical properties of inorganic semiconductors (with high dielectric constant and high charge carriers mobility) and organic semiconductors (with good solution processability and high absorbance). The power conversion efficiency (PCE) of the organometal halide perovskite solar cells (pero-SCs) based on CH₃NH₃PbI₃ has been increased dramatically in a few years from 3.8% to a certified 22.1%, primarily owing to the development of new interfacial materials, careful optimization of morphology, and perovskite crystallization …

Application Of Metal-Organic Frameworks In Dye-Sensitized Solar Cells, Ya-Feng Li, Qing-Qing Sun, Ming-Deng Wei

Journal of Electrochemistry

To assemble dye-sensitized solar cells (DSSCs) with high efficiencies, their photoanodes should have large specific surface area to establish a large adsorption amount of dyes and good light-harvesting ability. From this point of view, it will be an interesting topic to explore the application of metal-organic frameworks (MOFs) in the field of DSSCs due to their huge specific surface area. This paper introduces the application of MOFs in photovoltaic devices briefly, and then summaries our approaches in using MOFs in the study of DSSCs, including the pre-treatment and the post-treatment of photoanode, the preparation of photoanode materials and the light …

Theoretical Study Of Photoelectrochemical Reactions And Ec-Sers On Spr Metallic Electrodes Of Silver And Gold, Yuan-Fei Wu, Ran Pang, Meng Zhang, Jian-Zhang Zhou, Bin Ren, Zhong-Qun Tian, De-Yin Wu

Journal of Electrochemistry

At present photoelectrochemistry has received much concern back to nanostructures of noble metals from semiconductor electrodes. This is due to the surface plasmon resonance (SPR) effect of metallic nanostructures, which can effectively convert the far-field light to the near-field light and concentrate the photonic energy to the local surface area with high energy density. Thus, the different enhancement mechanisms, such as the local optical field enhancement, the formation of light generated hot carriers (hot electron-hole pairs), or the photothermal effect, have been proposed in literatures. On the basis of the SPR enhancement effect, the surface-enhanced Raman spectroscopy (SERS) can be …

Photoelectrochemical Water Splitting Cells: Methods For Improving Performance Of Electrodes And Recent Progress On Photocathodes, Kai-Jian Zhu, Wen-Jun Luo, Zhong-Jie Guan, Xin Wen, Zhi-Gang Zou, Wei Huang

Journal of Electrochemistry

Photoelectrochemical water splitting can convert solar energy into hydrogen which is an ideal way to utilize and store solar energy. A p-n tandem cell is considered as the most promising solar water splitting cell due to its high theory conversion efficiency, low cost and photoelectrode material flexibility. However, solar conversion efficiency of a tandem cell is still low in the experiment because of poor performance in a single photoelectrode. In this review, we have introduced some effective approaches to improve the performances of photoelectrodes by reducing recombination of photogenerated carriers in the bulk or on the surface, and suppressing back …

Solvent Effect On The Anticorrosive Properties And Active Coating Area Of A Long Alkyd Varnish, Saadawy M., Abd-El-Nabey B.A., Gomaa A.Z., Ashour M.

Journal of Electrochemistry

The effects of solvent nature and composition on the anticorrosive properties of a long alkyd varnish after different days of immersion in 0.5 mol•L^-1 NaCl were studied using electrochemical impedance spectroscopy. The protection efficiencies of the long alkyd varnishes containing different solvents increased with increasing the volatility of solvent or the composition of a given volatile solvent, which was confirmed with the observations using scanning electron microscopy and energy-dispersive X-Ray spectroscopy. The delaminated area, the area where the organic coating is detached from the metal surface leaving it unprotected, was found to decrease by increasing the volatility of solvent.

WoX/Pedot:Pss Double-Layered Hole-Transport Layers For Efficient And Stable Planar Heterojunction Perovskite Solar Cells, Wen-Yuan Qiao, Qiang Guo, Cong Li, Shuang Ma, Fu-Zhi Wang, Song-Yuan Dai, Zhan-Ao Tan

Journal of Electrochemistry

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a commonly used hole-transport material in the perovskite solar cells (PerSCs) structure of perovskite/fullerene planer heterojunction, but it also has a negative effect on the stability of device because of its acidity which will corrode metal oxide transparent electrodes. In this work, a WO_x hole-transport layer with high work function was inserted into the PEDOT: PSS and FTO to enhance the stability and photovoltaic performance. The inserted WO_x layer not only can avoid direct contact between PEDOT:PSS and FTO, but also can further reduce the contact barrier between the electrode interface. We studied the effect …

A Novel Flexible Dye-Sensitized Solar Cell Based On Pt Networks Counter Electrode, Zi-Jie Xu, Fa-Yin Zhang, Xiao-Dan Hong, Wen-Xi Guo, Xiang-Yang Liu, Chang-Jian Lin

Journal of Electrochemistry

Flexible dye-sensitized solar cells (DSSCs) have received widespread attentions in recent years because of their ease of fabrication, low production cost, relatively high chemical stability and flexibility. We report the fabrication of ZnO DSSCs based on the highly flexible, conducting, catalytic and transparent Pt networks counter electrode, and the performance of this solar cell was characterized by SEM, XRD, polarized fluorescence microscope, motor, I-V test station and electrochemical workstation. Compared to Pt nanofiber arrays (NFs), Pt networks not only show a better conductivity, but also exhibit superior transparency and catalytic activity. Furthermore, Pt networks electrode could be constructed on arbitrary …

Fabrications Of Three Copper Sulfide Counter Electrodes And Their Influences On Photovoltaic Properties In Qdsscs, Xiao-Dan Hong, Zi-Jie Xu, Fa-Yin Zhang, Yu-Peng Li, Mei-Dan Ye, Chang-Jian Lin, Wen-Xi Guo

Journal of Electrochemistry

Quantum dot-sensitized solar cells (QDSSCs) have attracted intensive attention in scientific and industrial fields due to their high molar extinction coefficient, spectral tunability by particle size, ease of fabrication, and low cost. In the past years, semiconductor metal sulfides have attracted extensive attention because of their attractive physical and chemical properties for potential applications in many fields，such as PbS, CuS, CoS and CdS. In particular, copper sulfides have become a promising candidate for counter electrode materials in QDSSCs for their outstanding electrochemical and catalytic properties. In order to explore more stable and efficient copper sulfide counter electrode materials, in this …

Hydrothermal One-Step Synthesis Of Layered Nickel/Cobalt Double Hydroxide With Using Shape-Directing Agent And Homogeneous Precipitating Agent, Li-Wei Zhu, Yun-Hai Yan, Hui Jia, Run-Fen Liang

Journal of Electrochemistry

Nickel/cobalt double hydroxide (Ni/Co-DH) has been prepared by facile hydrothermal one-step synthesis method using hexamethylene tetramine (HMT) as a homogeneous precipitating agent and cetyltrimethylammonium bromide (CTAB) as a shape-directing agent. With the hydrolysis of HMT and the use of CTAB, the Ni/Co-DH could be synthesized without additional alkali source, and in the meantime, the Ni/Co-DH exhibited a controlled mesopore size of 13.4 nm and a large BET surface area of 93.6 m² •g^-1 . The X-ray diffraction (XRD) pattern displays that the Ni/Co-DH existed as a mixture of α-Ni(OH)₂-β-Co(OH)₂. The scanning electron microscope (SEM) …

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. …

Development Of Novel Anode Materials For Lithium Ion Batteries, Mike A. Nieradko

Electronic Thesis and Dissertation Repository

This thesis focuses on the development of new anodes for Li ion batteries. Aluminium has been long considered as promising anode material for Li ion batteries because of its low cost, abundance, and low toxicity. Aluminium undergoes alloying with lithium through intermetallic LiAl formation which offers a relatively high theoretical capacity of 993 mAh/g compared to 372 mAh/g for graphite that is currently the principal anode material in commercial Li ion batteries. However, despite intensive research, all aluminium-based anodes tested so far suffered from rapid capacity fading and failure within first few cycles. Furthermore, there is insufficient understanding of the …

Alamethicin In Lipid Bilayers: Combined Use Of X-Ray Scattering And Md Simulations, Jianjun Pan, D. Peter Tieleman, John F. Nagle, Norbert Kučerka, Prof. Stephanie Tristram-Nagle Ph.D.

John Copeland Nagle

We study fully hydrated bilayers of two di-monounsaturated phospholipids diC18:1PC (DOPC) and diC22:1PC with varying amounts of alamethicin (Alm). We combine the use of X-ray diffuse scattering and molecular dynamics simulations to determine the orientation of alamethicin in model lipids. Comparison of the experimental and simulated form factors shows that Alm helices are inserted transmembrane at high humidity and high concentrations, in agreement with earlier results. The X-ray scattering data and the MD simulations agree that membrane thickness changes very little up to 1/10 Alm/ DOPC. In contrast, the X-ray data indicate that the thicker diC22:1PC membrane thins with added …

Photo-Isomerizable Self-Complementary Hydrogen Bond Arrays, Iamnica Janic Linares Mendez

Electronic Thesis and Dissertation Repository

This thesis exploits the use of a photochromic system in a self-complementary hydrogen bond array; i.e. the azo group, -N=N. The novelty of the approach described in this thesis resides in the double function of the azo group within the array: as a hydrogen bond acceptor site and as an element that promotes a structural change capable of disrupting the complexation equilibrium when irradiated with light.

The photo-isomerizable self-complementary hydrogen bond arrays presented are obtained by a general and practical synthetic method from inexpensive starting materials. Their self-complementary recognition was corroborated by ¹H NMR dilution experiments and single crystal …