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Articles 1 - 30 of 62
Full-Text Articles in Physical Sciences and Mathematics
Premade Nanoparticle Films For The Synthesis Of Vertically Aligned Carbon Nanotubes, Abdul Hoque, Ahamed Ullah, Beth S. Guiton, Noe T. Alvarez
Premade Nanoparticle Films For The Synthesis Of Vertically Aligned Carbon Nanotubes, Abdul Hoque, Ahamed Ullah, Beth S. Guiton, Noe T. Alvarez
Chemistry Faculty Publications
Carbon nanotubes (CNTs) offer unique properties that have the potential to address multiple issues in industry and material sciences. Although many synthesis methods have been developed, it remains difficult to control CNT characteristics. Here, with the goal of achieving such control, we report a bottom-up process for CNT synthesis in which monolayers of premade aluminum oxide (Al2O3) and iron oxide (Fe3O4) nanoparticles were anchored on a flat silicon oxide (SiO2) substrate. The nanoparticle dispersion and monolayer assembly of the oleic-acid-stabilized Al2O3 nanoparticles were achieved using 11-phosphonoundecanoic acid …
Electrochemical Studies Of Cobalt(Ii) Diphenylazodioxide Complexes, Lakshmi Balarama, Kylin A. Emhoff, Ahmed M.H. Salem, Jovana Hanna, Mohamed N. Alsabony, Mekki Bayachou, Jerry Mundell, W. Christropher Boyd
Electrochemical Studies Of Cobalt(Ii) Diphenylazodioxide Complexes, Lakshmi Balarama, Kylin A. Emhoff, Ahmed M.H. Salem, Jovana Hanna, Mohamed N. Alsabony, Mekki Bayachou, Jerry Mundell, W. Christropher Boyd
Chemistry Faculty Publications
The electrochemical behavior of the unusual cobalt(II) diphenylazodioxide complex salts [Co(az)4](PF6)2 1 and [Co(bpy)(az)2](PF6)2 2 has been studied by cyclic voltammetry. Each complex displays two quasireversible redox couples, which are proposed to correspond to a reduction of Co(II) to Co(I), followed by a ligand-based reduction. Irreversible reductions of 1 are observed at more negative potentials, and are proposed to arise from deposition of elemental Co and the decomposition of transiently formed Co(-I) species. Spectroelectrochemical experiments on both 1 and 2, involving electrolytic reduction followed by reoxidation, are consistent with …
Metal-Assisted Hydrolysis Reactions Involving Lipids: A Review, Dominique E. Williams, Kathryn B. Grant
Metal-Assisted Hydrolysis Reactions Involving Lipids: A Review, Dominique E. Williams, Kathryn B. Grant
Chemistry Faculty Publications
This report covers major advances in the use of metal ions and complexes to hydrolyze ester and phosphate ester lipid bonds. These metal-based Lewis acids have been investigated as catalysts to isolate fatty acids from biological sources, as probes to study phospholipid bilayer properties, as tools to examine signal transduction pathways, and as lead compounds toward the discovery of therapeutic agents. Metal ions that accelerate phosphate ester hydrolysis under mild conditions of temperature and pH may have the potential to mimic phospholipase activity in biochemical applications.
Functionalized Carbon Nanotube Adsorption Interfaces For Electron Transfer Studies Of Galactose Oxidase, Mulugeta B. Wayu, Michael J. Pannell, Najwa Labban, William S. Case, Julie A. Pollack, Michael C. Leopold
Functionalized Carbon Nanotube Adsorption Interfaces For Electron Transfer Studies Of Galactose Oxidase, Mulugeta B. Wayu, Michael J. Pannell, Najwa Labban, William S. Case, Julie A. Pollack, Michael C. Leopold
Chemistry Faculty Publications
Modified electrodes featuring specific adsorption platforms able to access the electrochemistry of the copper containing enzyme galactose oxidase (GaOx) were explored, including interfaces featuring nanomaterials such as nanoparticles and carbon nanotubes (CNTs). Electrodes modified with various self-assembled monolayers (SAMs) including those with attached nanoparticles or amide-coupled functionalized CNTs were examined for their ability to effectively immobilize GaOx and study the redox activity related to its copper core. While stable GaOx electrochemistry has been notoriously difficult to achieve at modified electrodes, strategically designed functionalized CNT-based interfaces, cysteamine SAM-modified electrode subsequently amide-coupled to carboxylic acid functionalized single wall CNTs, were significantly more …
Halogen Bonding Interactions For Aromatic And Non-Aromatic Explosive Detection, Arjun K. A. Jaini, Lillian B. Hughes, Michael K. Kitimet, Kevin John Ulep, Michael C. Leopold, Carol A. Parish
Halogen Bonding Interactions For Aromatic And Non-Aromatic Explosive Detection, Arjun K. A. Jaini, Lillian B. Hughes, Michael K. Kitimet, Kevin John Ulep, Michael C. Leopold, Carol A. Parish
Chemistry Faculty Publications
Improved sensing strategies are needed for facile, accurate and rapid detection of aromatic and nonaromatic explosives. Density functional theory was used to evaluate the relative binding interaction energies between halogen-containing sensor model molecules and nitro-containing explosives. Interaction energies ranged from –18 to –14 kJ/mol and highly directional halogen bonding interactions were observed with bond distances ranging between 3.0 and 3.4 Å. In all geometry optimized structures, the sigma-hole of electropositive potential on the halogen aligned with a lone pair of electrons on the nitro-moiety of the explosive. The computational results predict that the strongest interactions will occur with iodine-based sensors …
Sintering-Induced Nucleation And Growth Of Noble Metal Nanoparticles For Plasmonic Resonance Ceramic Color, Nathan Dinh, Michael C. Leopold, Ryan Coppage
Sintering-Induced Nucleation And Growth Of Noble Metal Nanoparticles For Plasmonic Resonance Ceramic Color, Nathan Dinh, Michael C. Leopold, Ryan Coppage
Chemistry Faculty Publications
This study demonstrates the formation of nanoparticles (NPs) from metal salts within ceramic glazes, such that the use of this colorant technology is more accessible to artisans, employs less metal content, is less environmentally harmful, and allows for the use of traditional kilns. Gold NPs have been demonstrated to possess a specific, low material loading use as a ceramic glaze colorant via plasmon resonance. Pre-synthesized gold NPs that are added to ceramic glazes have been found to significantly change in size after firing in both reductive and oxidative atmospheres, but still maintain some size relationships and color properties. Unfortunately, it …
Oxidation Of Benzylic Alcohols And Lignin Model Compounds With Layered Double Hydroxide Catalysts, Justin K. Mobley, John A. Jennings, Tonya Morgan, Axel Kiefer, Mark Crocker
Oxidation Of Benzylic Alcohols And Lignin Model Compounds With Layered Double Hydroxide Catalysts, Justin K. Mobley, John A. Jennings, Tonya Morgan, Axel Kiefer, Mark Crocker
Chemistry Faculty Publications
Alcohol oxidation to carbonyl compounds is one of the most commonly used reactions in synthetic chemistry. Herein, we report the use of base metal layered double hydroxide (LDH) catalysts for the oxidation of benzylic alcohols in polar solvents. These catalysts are ideal reagents for alcohol oxidations due to their ease of synthesis, tunability, and ease of separation from the reaction medium. LDHs synthesized in this study were fully characterized by means of X-ray diffraction, NH3-temperature programmed desorption (TPD), pulsed CO2 chemisorption, N2 physisorption, electron microscopy, and elemental analysis. LDHs were found to effectively oxidize benzylic alcohols …
A Multi-Size Study Of Gold Nanoparticle Degradation And Reformation In Ceramic Glazes, Nathan Nl. Dinh, Luke T. Dipasquale, Michael C. Leopold, Ryan H. Coppage
A Multi-Size Study Of Gold Nanoparticle Degradation And Reformation In Ceramic Glazes, Nathan Nl. Dinh, Luke T. Dipasquale, Michael C. Leopold, Ryan H. Coppage
Chemistry Faculty Publications
Most traditional ceramic glazes employ high amounts of transition metal colorants that are toxic to the environment and can cause health issues in humans through surface leaching. Gold nanoparticles (Au-NPs) have been found to be environmentally friendly and non-toxic alternative metal colorant in ceramic glazes. The plasmon band observed with Au-NPs can result in vibrant solutions by manipulating NP size, shape, and concentration; however, the effects of traditional firing in both reductive and oxidative kilns on Au-NPs are poorly understood. Aside from ancient art processes whose mechanisms have not been fully explored, the use of Au-NPs as suspended ceramic glaze …
Versatile Sarcosine Biosensing Schemes Utilizing Layer-By-Layer Construction Of Carbon Nanotube-Chitosan Composite Films, Michael J. Pannell, Elizabeth E. Doll, Najwa Labban, Mulugeta B. Wayu, Julie A. Pollack, Michael C. Leopold
Versatile Sarcosine Biosensing Schemes Utilizing Layer-By-Layer Construction Of Carbon Nanotube-Chitosan Composite Films, Michael J. Pannell, Elizabeth E. Doll, Najwa Labban, Mulugeta B. Wayu, Julie A. Pollack, Michael C. Leopold
Chemistry Faculty Publications
Layer-by-layer composite films of carbon nanotubes (CNTs) within a chitosan matrix with sarcosine oxidase enzyme and capped with Nafion have been developed and optimized as a versatile 1st generation amperometric sarcosine biosensing platform that operates successfully both as an isolated sarcosine sensor as well as a functional component within a creatinine sensor. Accurate measurement of sarcosine in urine and creatinine in blood may help with early diagnosis of diseases such as prostate cancer and renal failure, respectively. In this study, each material within the film is systematically optimized toward sarcosine sensitivity, including a critical evaluation of different CNTs effect on …
Gold Nanoparticle Colorants As Traditional Ceramic Glaze Alternatives, Raef H. Lambertson, Christie A. Lacy, Samuel D. Gillespie, Michael C. Leopold
Gold Nanoparticle Colorants As Traditional Ceramic Glaze Alternatives, Raef H. Lambertson, Christie A. Lacy, Samuel D. Gillespie, Michael C. Leopold
Chemistry Faculty Publications
Historically, Roman stained glass has been a standard for high‐temperature color stability since biblical times but was not properly characterized as emission from nanoparticle plasmon resonance until the 1990s. The methods under which it was created have been lost, but some efforts have recently been made to recreate these properties using gold nanoparticle inks on glassy surfaces. This body of work employs gold nanoparticle systems ranging from 0.015% to 0.100% (wt/wt), suspended in a clear glaze body. The glazes are fired with traditional ceramic methods—in both gas reduction and electric oxidation kilns—in which nanoparticles are retained and can be imaged …
Catalyzed Synthesis Of Zinc Clays By Prebiotic Central Metabolites, Marcelo I. Guzman, Ruixin Zhou, Kaustuv Basu, Hyman Hartman, Christopher J. Matocha, S. Kelly Sears, Hajatollah Vali
Catalyzed Synthesis Of Zinc Clays By Prebiotic Central Metabolites, Marcelo I. Guzman, Ruixin Zhou, Kaustuv Basu, Hyman Hartman, Christopher J. Matocha, S. Kelly Sears, Hajatollah Vali
Chemistry Faculty Publications
How primordial metabolic networks such as the reverse tricarboxylic acid (rTCA) cycle and clay mineral catalysts coevolved remains a mystery in the puzzle to understand the origin of life. While prebiotic reactions from the rTCA cycle were accomplished via photochemistry on semiconductor minerals, the synthesis of clays was demonstrated at low temperature and ambient pressure catalyzed by oxalate. Herein, the crystallization of clay minerals is catalyzed by succinate, an example of a photoproduced intermediate from central metabolism. The experiments connect the synthesis of sauconite, a model for clay minerals, to prebiotic photochemistry. We report the temperature, pH, and concentration dependence …
Photochemical Properties And Structure-Activity Relationships Of RuIi Complexes With Pyridylbenzazole Ligands As Promising Anticancer Agents, Dmytro Havrylyuk, David K. Heidary, Leona Nease, Sean Parkin, Edith C. Glazer
Photochemical Properties And Structure-Activity Relationships Of RuIi Complexes With Pyridylbenzazole Ligands As Promising Anticancer Agents, Dmytro Havrylyuk, David K. Heidary, Leona Nease, Sean Parkin, Edith C. Glazer
Chemistry Faculty Publications
Ruthenium complexes capable of light‐triggered cytotoxicity are appealing potential prodrugs for photodynamic therapy (PDT) and photoactivated chemotherapy (PACT). Two groups of (polypyridyl)RuII complexes with 2‐(2‐pyridyl)benzazole ligands were synthesized and investigated for their photochemical properties and anticancer activity to compare strained and unstrained systems that are likely to have different biological mechanisms of action. The structure–activity relationship was focused on the benzazole‐core bioisosterism and replacement of coligands in RuII complexes. Strained compounds rapidly ejected the 2‐(2‐pyridyl)benzazole ligand after light irradiation, and possessed strong toxicity in the HL‐60 cell line both under dark and light conditions. In contrast, unstrained Ru …
Enzyme–Free Uric Acid Electrochemical Sensors Using Β–Cyclodextrin Modified Carboxylic Acid Functionalized Carbon Nanotubes, Mulugeta B. Wayu, Margaret A. Schwarzmann, Samuel D. Gillespie, Michael C. Leopold
Enzyme–Free Uric Acid Electrochemical Sensors Using Β–Cyclodextrin Modified Carboxylic Acid Functionalized Carbon Nanotubes, Mulugeta B. Wayu, Margaret A. Schwarzmann, Samuel D. Gillespie, Michael C. Leopold
Chemistry Faculty Publications
Carboxylic acid-functionalized multi-walled carbon nanotubes (COOH-MWCNT) were modified via ultrasonication with β-cyclodextrin (β-CD) to obtain a COOH-MWCNT:β-CD nanocomposite material for the purpose of developing an enzyme-free electrochemical sensor for uric acid—a clinically relevant molecule implemented in pregnancy-induced hypertension diagnosis. The nanocomposite material is deposited onto glassy carbon electrodes and subsequently capped with layers of Nafion and Hydrothane polyurethane. The surface morphology and electronic structure of the nanocomposite material were characterized using UV–Vis, TEM, and FTIR. The performance of the electrochemical sensor was measured through direct injection of UA during amperometry. With the high surface area of the COOH-MWCNT in concert …
Electropolymerization Of B–Cyclodextrin Onto Multi–Walled Carbon Nanotube Composite Films For Enhanced Selective Detection Of Uric Acid, Mulugeta B. Wayu, Luke T. Dipasquale, Margaret A. Schwarzmann, Samuel D. Gillespie, Michael C. Leopold
Electropolymerization Of B–Cyclodextrin Onto Multi–Walled Carbon Nanotube Composite Films For Enhanced Selective Detection Of Uric Acid, Mulugeta B. Wayu, Luke T. Dipasquale, Margaret A. Schwarzmann, Samuel D. Gillespie, Michael C. Leopold
Chemistry Faculty Publications
An amperometric uric acid (UA) sensor incorporating a multi-walled carbon nanotubes (MWCNT) network in Nafion and electropolymerized β-cyclodextrin (β-CD) layer is investigated. The electrochemical sensor is comprised of a glassy carbon electrode modified with Nafion-MWCNT nanocomposite film, a β-CD polymer inner selective layer, and a Hydrothane polyurethane (HPU) outer selective coating. The surface morphology and electronic structure of the electrode material are characterized using transmission electron microscopy (TEM), scanning electron microscope (SEM), and Fourier transform infrared (FTIR) spectroscopy. The electrocatalytic activity of the sensor is studied using cyclic voltammetry (CV), chronocoulometry (CC) and differential pulse voltammetry (DPV). Analytical performance of …
Layered Xerogel Films Incorporating Monolayer Protected Cluster Networks On Platinum Black Modified Electrodes For Enhanced Sensitivity In 1st Generation Uric Acid Biosensing, Mulugeta B. Wayu, Michael J. Pannell, Michael C. Leopold
Layered Xerogel Films Incorporating Monolayer Protected Cluster Networks On Platinum Black Modified Electrodes For Enhanced Sensitivity In 1st Generation Uric Acid Biosensing, Mulugeta B. Wayu, Michael J. Pannell, Michael C. Leopold
Chemistry Faculty Publications
Amperometric uric acid (UA) biosensing schemes incorporating networks of alkanethiolate‐protected gold nanoparticles, monolayer protected clusters (MPCs), and platinum black (Pt‐B) electrode modification through the layer‐by‐layer construction of xerogels are investigated. MPC doping and Pt‐B augmentation are implemented within hydroxymethyltriethoxysilane xerogel bilayers at platinum electrodes. The first xerogel adlayer is doped with an MPC network and houses uricase for the enzymatic reaction required for first‐generation schemes. Polyluminol–aniline and polyurethane are used as selective/stabilizing interfacial layers. The sensing performance with and without Pt‐B and/or MPC doping is assessed by amperometry with standardized UA injections. The use of each individual material results in …
Electrochemical Characterization Of Self-Assembled Monolayers On Gold Substrates Derived From Thermal Decomposition Of Monolayer-Protected Cluster Films, Michael C. Leopold, Tran T. Doan, Melissa J. Mullaney, Andrew F. Loftus, Christopher M. Kidd
Electrochemical Characterization Of Self-Assembled Monolayers On Gold Substrates Derived From Thermal Decomposition Of Monolayer-Protected Cluster Films, Michael C. Leopold, Tran T. Doan, Melissa J. Mullaney, Andrew F. Loftus, Christopher M. Kidd
Chemistry Faculty Publications
Networked films of monolayer-protected clusters (MPCs), alkanethiolate-stabilized gold nanoparticles, can be thermally decomposed to form stable gold on glass substrates that are subsequently modified with self-assembled monolayers (SAMs) for use as modified electrodes. Electrochemical assessment of these SAM-modified gold substrates, including double-layer capacitance measurements, linear sweep desorption of the alkanethiolates, and diffusional redox probing, all show that SAMs formed on gold supports formed from thermolysis of MPC films possess substantially higher defect density compared to SAMs formed on traditional evaporated gold. The density of defects in the SAMs on thermolyzed gold is directly related to the strategies used to assemble …
Synthesis And Flammability Testing Of Epoxy Functionalized Phosphorous-Based Flame Retardants, Vladimir Benin, Xuemei Cui, Alexander Morgan, Karl Seiwert
Synthesis And Flammability Testing Of Epoxy Functionalized Phosphorous-Based Flame Retardants, Vladimir Benin, Xuemei Cui, Alexander Morgan, Karl Seiwert
Chemistry Faculty Publications
Several potential new phosphorus-containing flame retardant molecules were evaluated for heat release reduction potential by incorporation of the molecules into a polyurethane, generated from methylene diphenyl diisocyanate and 1,3-propane diol. The heat release reduction potential of these substances was evaluated using the pyrolysis combustion flow calorimeter (PCFC). The polyurethanes were prepared in the presence of the potential flame retardants via solvent mixing and copolymerization methods to qualitatively evaluate their potential reactivity into the polyurethane prior to heat release testing. The functionality of the flame retardants was epoxide based that would potentially react with the diol during polyurethane synthesis. Flammability testing …
Structure-Function Relationships Affecting The Sensing Mechanism Of Monolayer-Protected Cluster Doped Xerogel Amperometric Glucose Biosensors, Luke T. Dipasquale, Nicholas G. Poulos, Jackson R. Hall, Aastha Minocha, Tram Anh Bui, Michael C. Leopold
Structure-Function Relationships Affecting The Sensing Mechanism Of Monolayer-Protected Cluster Doped Xerogel Amperometric Glucose Biosensors, Luke T. Dipasquale, Nicholas G. Poulos, Jackson R. Hall, Aastha Minocha, Tram Anh Bui, Michael C. Leopold
Chemistry Faculty Publications
A systematic study of the structure–function relationships critical to understanding the sensing mechanism of 1st generation amperometric glucose biosensors with an embedded nanoparticle (NP) network is presented. Xerogel-based films featuring embedded glucose oxidase enzyme and doped with alkanethiolate-protected gold NPs, known as monolayer protected clusters (MPCs), exhibit significantly enhanced performance compared to analogous systems without NPs including higher sensitivity, faster response time, and extended linear/dynamic ranges. The proposed mechanism involves diffusion of the glucose to glucose oxidase within the xerogel, enzymatic reaction production of H2O2 with subsequent diffusion to the embedded network of MPCs where it is oxidized, an event …
Quantitative Analysis Of Heavy Metals In Children’S Toys And Jewelry: A Multi-Instrument, Multi-Technique Exercise In Analytical Chemistry And Public Health, Lauren E. Finch, Margot M. Hillyer, Michael C. Leopold
Quantitative Analysis Of Heavy Metals In Children’S Toys And Jewelry: A Multi-Instrument, Multi-Technique Exercise In Analytical Chemistry And Public Health, Lauren E. Finch, Margot M. Hillyer, Michael C. Leopold
Chemistry Faculty Publications
For most chemistry curricula, laboratory-based activities in quantitative and instrumental analysis continue to be an important aspect of student development/training, one that can be more effective if conceptual understanding is delivered through an inquiry-based process relating the material to relevant issues of public interest and student career trajectories. Laboratory experiences that actively engage students in this manner can be difficult to identify and execute. A special topics, project-based laboratory module is presented here that utilizes multiple techniques and instruments to investigate toxic metal content (lead, cadmium, and arsenic) in children’s toys and toy jewelry. The module effectively illustrates a considerable …
Functional Layer-By-Layer Design Of Xerogel-Based 1st Generation Amperometric Glucose Biosensors, Nicholas G. Poulos, Jackson R. Hall, Michael C. Leopold
Functional Layer-By-Layer Design Of Xerogel-Based 1st Generation Amperometric Glucose Biosensors, Nicholas G. Poulos, Jackson R. Hall, Michael C. Leopold
Chemistry Faculty Publications
Xerogel-based first-generation amperometric glucose biosensors, constructed through specific layer-by-layer assembly of films featuring glucose oxidase doped xerogel, a diffusion-limiting xerogel layer, and capped with both electropolymerized polyphenol and blended polyurethane semipermeable membranes, are presented. The specific combination of xerogels formed from specific silane precursors, including propyl-trimethoxysilane, isobutyl-trimethoxysilane, octyl-trimethoxysilane, and hydroxymethyl-triethoxysilane, exhibit impressive dynamic and linear ranges of detection (e.g., ≥24–28 mM glucose) and low response times, as well as significant discrimination against common interferent species such as acetaminophen, ascorbic acid, sodium nitrite, oxalic acid, and uric acid as determined by selectivity coefficients. Additionally, systematic electrochemical and contact angle studies of …
Heat Release Of Polyurethanes Containing Potential Flame Retardants Based On Boron And Phosphorus Chemistries, Vladimir Benin, Bastien Gardelle, Alexander Morgan
Heat Release Of Polyurethanes Containing Potential Flame Retardants Based On Boron And Phosphorus Chemistries, Vladimir Benin, Bastien Gardelle, Alexander Morgan
Chemistry Faculty Publications
Using a polyurethane of methylene diphenyl isocyanate and 1,3-propane diol, several new non-halogenated aromatic boron and phosphorus flame retardants were evaluated for heat release reduction potential using the pyrolysis combustion flow calorimeter (PCFC). The polyurethanes were prepared in the presence of the potential flame retardants via solvent mixing and copolymerization methods, and were then analyzed via spectroscopic methods to determine if the flame retardant was still present in the final product. PCFC testing on the resulting products showed that the flame retardant molecule can have different effects on heat release depending upon how it is mixed into the polyurethane. Some …
Determination Of Corrosion Inhibitor Lubricity Improver In Jet Fuel By Liquid Chromatography-Electrospray Ionization Mass Spectrometry, David W. Johnson, Milissa Flake, Ryan Adams
Determination Of Corrosion Inhibitor Lubricity Improver In Jet Fuel By Liquid Chromatography-Electrospray Ionization Mass Spectrometry, David W. Johnson, Milissa Flake, Ryan Adams
Chemistry Faculty Publications
Military jet fuel (JP-8) is very similar to commercial jet fuel (Jet A) except for the presence of three additives, fuel system icing inhibitor, corrosion inhibitor–lubricity improver (CI-LI), and antistatic additive, which are added to improve characteristics of JP-8. Of particular interest is the CI-LI additive; the most common active ingredient is a dimer of linoleic acid. This article focuses on quantification of the active ingredient in the CI-LI additive by liquid chromatography–mass spectrometry (LC–MS). This method will allow the determination of CI-LI content in military jet fuel samples.
Multi-Technique Quantitative Analysis And Socioeconomic Considerations Of Lead, Cadmium, And Arsenic In Children's Toys And Toy Jewelry, Margot M. Hillyer, Lauren E. Finch, Alisha S. Cerel, Jonathan D. Dattelbaum, Michael C. Leopold
Multi-Technique Quantitative Analysis And Socioeconomic Considerations Of Lead, Cadmium, And Arsenic In Children's Toys And Toy Jewelry, Margot M. Hillyer, Lauren E. Finch, Alisha S. Cerel, Jonathan D. Dattelbaum, Michael C. Leopold
Chemistry Faculty Publications
A wide spectrum and large number of children’s toys and toy jewelry items were purchased from both bargain and retail vendors and analyzed for arsenic, cadmium, and lead metal content using multiple analytical techniques, including flame and furnace atomic absorption spectroscopy as well as X-ray fluorescence spectroscopy. Particularly dangerous for young children, metal concentrations in toys/toy jewelry were assessed for compliance with current Consumer Safety Product Commission (CPSC) regulations (F963-11). A conservative metric involving multiple analytical techniques was used to categorize compliance: one technique confirmation of metal in excess of CPSC limits indicated a “suspect” item while confirmation on two …
Science Classics, Mark Masthay
Science Classics, Mark Masthay
Chemistry Faculty Publications
An essay on the impact of the works in the Imprints and Impressions: Milestones in Human Progress, an exhibition of rare books from the collection of Stuart Rose. Exhibition was held Sept. 29-Nov. 9, 2014, at the University of Dayton.
Phosphate Esters, Thiophosphate Esters And Metal Thiophosphates As Lubricant Additives, David W. Johnson, John E. Hils
Phosphate Esters, Thiophosphate Esters And Metal Thiophosphates As Lubricant Additives, David W. Johnson, John E. Hils
Chemistry Faculty Publications
Phosphate esters, thiophosphate esters and metal thiophosphates have been used as lubricant additives for over 50 years. While their use has been extensive, a detailed knowledge of how they work has been a much more recent development. In this paper, the use of phosphate esters and thiophosphate esters as anti-wear or extreme pressure additives is reviewed with an emphasis on their mechanism of action. The review includes the use of alkyl phosphates, triaryl phosphates and metal containing thiophosphate esters. The mechanisms of these materials interacting with a range of iron and steel based bearing material are examined.
Conversion Of Iodide To Hypoiodous Acid And Iodine In Aqueous Microdroplets Exposed To Ozone, Elizabeth A. Pillar, Marcelo I. Guzman, Jose M. Rodriguez
Conversion Of Iodide To Hypoiodous Acid And Iodine In Aqueous Microdroplets Exposed To Ozone, Elizabeth A. Pillar, Marcelo I. Guzman, Jose M. Rodriguez
Chemistry Faculty Publications
Halides are incorporated into aerosol sea spray, where they start the catalytic destruction of ozone (O3) over the oceans and affect the global troposphere. Two intriguing environmental problems undergoing continuous research are (1) to understand how reactive gas phase molecular halogens are directly produced from inorganic halides exposed to O3 and (2) to constrain the environmental factors that control this interfacial process. This paper presents a laboratory study of the reaction of O3 at variable iodide (I–) concentration (0.010–100 μM) for solutions aerosolized at 25 °C, which reveal remarkable differences in the reaction intermediates …
Structure, Theoretical Studies And Coupling Reactions Of Some New Cyclic Boronic Esters, Andrew Kuttler, Sravanthi Durganala, Albert Fratini, Alexander Morgan, Vladimir Benin
Structure, Theoretical Studies And Coupling Reactions Of Some New Cyclic Boronic Esters, Andrew Kuttler, Sravanthi Durganala, Albert Fratini, Alexander Morgan, Vladimir Benin
Chemistry Faculty Publications
The present report describes the X-ray structural and theoretical studies of some new pinacolboronate esters, and it also outlines the use of the target structures in Suzuki coupling reactions to produce new aromatic or heteroaromatic esters and amides. X-ray structural analysis of the studied compounds revealed that the pinacolborane ring's position with respect to the benzene ring varies, depending on the particular environment. An ortho-positioned carboxylic ester (methyl ester) causes a nearly perpendicular orientation of the pinacolborane unit with respect to the benzene ring, whereas an ortho-positioned amide (N,N-dimethylamide) causes the pinacolborane unit to orient itself nearly coplanar. A plausible …
Characterization By Nmr Of Reactants And Products Of Hydrofluoroether Isomers, Cf3(Cf2)3och3 And (Cf3)2c(F)Cf2och3, Reacting With Isopropyl Alcohol, Howard Knachel, Vladimir Benin, William E. Moddeman, Janine C. Birkbeck, Thomas A. Kestner, Tayna L. Young
Characterization By Nmr Of Reactants And Products Of Hydrofluoroether Isomers, Cf3(Cf2)3och3 And (Cf3)2c(F)Cf2och3, Reacting With Isopropyl Alcohol, Howard Knachel, Vladimir Benin, William E. Moddeman, Janine C. Birkbeck, Thomas A. Kestner, Tayna L. Young
Chemistry Faculty Publications
The 3M Company product Novec™ 71IPA DL, a mixture of methoxyperfluorobutane, methoxyperfluoroisobutane and 4.5 wt.% isopropyl alcohol, has been found to be very stable at ambient temperature, producing fluoride at the rate of ~1 ppm/year. Our earlier kinetic and theoretical studies have identified the reaction mechanism. This paper identifies the 1H and 19F NMR chemical shifts, multiplicities, and coupling constants of reactants and the major products that result from aging the mixture in sealed Pyrex NMR tubes for periods up to 1.8 years at temperatures from 26 °C to 102 °C. Chemical shifts and coupling constants of fluorine …
Interaction Between Lubricants Containing Phosphate Ester Additives And Stainless Steels, David W. Johnson, Matthew Bachus, John E. Hils
Interaction Between Lubricants Containing Phosphate Ester Additives And Stainless Steels, David W. Johnson, Matthew Bachus, John E. Hils
Chemistry Faculty Publications
One way to improve fuel efficiency in today’s jet aircraft engines is to create an environment for higher operating temperatures and speeds. New and improved lubricants and bearing materials must be developed to remain stable in these elevated operating temperatures. Three lubricants, with varying amounts of tricresyl phosphate added as an anti-wear/extreme pressure additive were tested on two different stainless steels at varying temperatures ranging from 300 °C to 350 °C in vacuum. Significant decomposition of the lubricant base-stocks and the phosphate ester additive did occur in most of the trials resulting in the formation of carboxylic acids and phenols. …
Monolayer-Protected Nanoparticle Doped Xerogels As Functional Components Of Amperometric Glucose Biosensors, Michael Hartley Freeman, Jackson R. Hall, Michael C. Leopold
Monolayer-Protected Nanoparticle Doped Xerogels As Functional Components Of Amperometric Glucose Biosensors, Michael Hartley Freeman, Jackson R. Hall, Michael C. Leopold
Chemistry Faculty Publications
First-generation amperometric glucose biosensors incorporating alkanethiolate-protected gold nanoparticles, monolayer protected clusters (MPCs), within a xerogel matrix are investigated as model systems for nanomaterial-assisted electrochemical sensing strategies. The xerogel biosensors are comprised of platinum electrodes modified with composite films of (3-mercaptopropyl)trimethoxy silane xerogel embedded with glucose oxidase enzyme, doped with Au225(C6)75 MPCs, and coated with an outer polyurethane layer. Electrochemistry and scanning/transmission electron microscopy, including cross-sectional TEM, show sensor construction, humidity effects on xerogel structure, and successful incorporation of MPCs. Analytical performance of the biosensor scheme with and without MPC doping of the xerogel is determined from direct glucose injection during …