Chemistry Commons^™

Applications Of Spectroscopic Ellipsometry In Corrosion Investigation, Ling-Jie Li, Yu-Ling He, Jing-Lei Lei, Sheng Tao Zhang

Journal of Electrochemistry

As a highly-sensitive and non-destructive in situ technique, spectroscopic ellipsometry has been widely applied in corrosion investigation to acquire the dynamic information of the “electrode-medium” interface during corrosion. This paper lays out some representative demonstrations in several established optical models used to interpret data obtained with spectroscopic ellipsometry in corrosion investigation. In addition, the latest trends in development of this technique are analyzed.

An Investigation Of Thin Films Formed On Zinc By Spectroscopic Ellipsometry, Juan Zuo, Ying Chen, Chang-Jian Lin, Andreas Erbe

Journal of Electrochemistry

The formation of natural oxide films on polycrystalline zinc surface, the growth of natural oxide films in different atmospheres, as well as the electrochemical process of metal zinc in alkaline carbonate solution, studied recently by using spectroscopic ellipsometry in our group, are introduced. The objective of this paper is to outline that the optical, electrical properties, the change and growth kinetics of zinc metal oxide film on the surface can be investigated by in-situ and ex-situ ellipsometry, which makes significant sense to evaluate the overall performance of zinc oxide layer.

Optimization Of Polymer Separation By Gradient Polymer Elution Chromatography, Gideon R. Liem, Linda Nien-Hwa Wang

The Summer Undergraduate Research Fellowship (SURF) Symposium

High Performance Liquid Chromatography (HPLC) has been a versatile separation method for polymers for many years. Analysis of different polymers by HPLC is typically done by utilizing the differential solubility of the polymers by mixing a good solvent and an anti-solvent in various compositions. This method is called Gradient Polymer Elution Chromatography (GPEC). While GPEC has been used extensively, it commonly uses a linear gradient to separate components. Linear solvent gradients consume a lot of solvent and take a relatively long time (> 30 minutes) to complete. The goal of this study is to develop a step gradient from a …

Development Of A Field-Portable Miniature Mass Spectrometer Designed For In-Situ Analysis And Ion Trap Miniaturization, Paul Isaac Hendricks

Open Access Dissertations

Chemical analysis by mass spectrometry has become the gold standard due to the sensitivity, selectivity, and short analysis times that are afforded by the method. Advances in miniaturized vacuum systems, mass analyzers, electronics, and ionization sources have allowed for the development of field-portable mass spectrometers. The performance of portable instruments has received much attention for their utility in the detection of illicit drugs, explosives, environmental contaminants, therapeutic drugs, and more recently, biological tissues. Furthermore, detection of the aforementioned compounds can be completed at atmospheric pressures and in the presence of complex matrices and sample surfaces when used in conjunction with …

Development Of Isotags For Nmr Based Metabolite Profiling And Applications, Fariba Tayyari

Open Access Dissertations

NMR spectroscopy is a powerful analytical tool for both qualitative and quantitative metabolite profiling analysis. However, accurate quantitative analysis of biological systems especially using one dimensional NMR has been challenging due to signal overlap. In contrast, the enhanced resolution and sensitivity offered by chemoselective isotope tags have enabled new and enhanced methods for detecting hundreds of quantifiable metabolites in biofluids using NMR spectroscopy or mass spectrometry. In this thesis we show improved sensitivity and resolution of NMR experiments imparted by 15N and 13C isotope tagging which enables the accurate analysis of plasma metabolites. To date, isotope tagging has been used …

Construction And Demonstration Of A Tandem Mass Spectrometer Based Instrument For Cold Ion Spectroscopy, James Gerhardt Redwine

Open Access Dissertations

A new instrument incorporating ion trap based tandem mass spectrometry and cold ion UV and UV-IR double resonance spectroscopy has been developed at Purdue University for the study of gas phase, biologically relevant ions. The instrument incorporates multiple quadrupole linear ion trap mass analyzers to prepare and isolate the precursor ions as well as to analyze the resultant photofragments. A 22-pole ion trap cooled to 5 K via a closed cycle helium cryostat is used to cool the ions for spectroscopic interrogation. Results show the vibrational and rotational temperature of a wide assortment of ions to be 12±2 K.

The …

Instrumentation, Applications And Fundamentals Of Plasma Ionization Of Organic Molecules From Surfaces, Joshua Scott Wiley

Open Access Dissertations

Various aspects of the interaction of low-temperature plasma (LTP) ambient ionization with organic molecules and surfaces are discussed. As an application, LTP-MS has been used for the analysis of pesticides directly from fruits and vegetables revealing low parts per billion limits of detection (LODs). Due to low power and gas requirements, a battery-operated and handheld LTP probe was developed for the point-and-shoot MS analyses. Handheld LTP was compared with large-scale LTP on a benchtop and miniature MS revealing similar LODs for both. Long-distance ion transport up to one meter was also demonstrated with flexible tubing for non-proximate sample interrogation. Fundamentals …

Development Of Quantitative Ft- Ir Methods For Analyzing The Cure Kinetics Of Epoxy Resins, Sang Ha Son

Open Access Dissertations

Epoxy thermosets are important engineering materials with applications in coating, adhesives, packaging and as structural components in a variety of advanced engineering products. The ultimate performance of polymer critically depends upon the details of the cure chemistry used to produce the thermoset. In order to better understand and monitor the cure chemistry, quantitative analysis of the FT-IR response has been developed for describing the epoxy-amine curing reaction as well as monitoring the hydrogen bonding that occurs in these systems The FT-IR analysis includes (i) quantitative deconvolution of complex peaks into individual spectral contributions, (ii) peak identification via DFT analysis and …

Silica Colloidal Crystals As Emerging Materials For The High-Throughput Sizing Of Proteins By Packed Capillary Electrophoresis, Nadine K. Njoya

Open Access Dissertations

Protein heterogeneity is currently one of the leading problems in formulation of therapeutic proteins. The effectiveness of therapeutic proteins is diminished when they exhibit heterogeneity due to aggregates and degradation by-products. Furthermore, guidelines set forth by the FDA require therapeutic proteins to have high stability as well as high purity. With development time on the order of years and costs incurred in the millions, pharmaceutical companies are investing more time in finding fast and efficient ways to screen for protein heterogeneity. Current methods such as native polyacrylamide gel electrophoresis (PAGE), size-exclusion chromatography (SEC) and capillary electrophoresis (CE) are time consuming, …

Utilizing Electron Microscopy And Spectroscopy Methods To Understand Water Structure And Water Doping, Lior Miller

Open Access Dissertations

Water is the second most common element in the universe and the most studied material on earth. Most of the studies concerning water are from the fields of chemistry and biology. Hence, the structure of water molecules and short range order and interactions are well characterized and understood. However, the collective arrangement of water molecules and the long range order are still missing. Understanding of this long range order in water is needed, as it is the key to many water activities.

To fill this gap, this study utilizes a new direct method for characterization of water in the vapor …

Spectroscopic Characterization Of The Water-Oxidation Intermediates In The Ru-Based Catalysts For Artificial Photosynthesis, Dooshaye Moonshiram

Open Access Dissertations

Utilization of sunlight requires solar capture, light-to-energy conversion and storage. One effective way to store energy is to convert it into chemical energy by fuel-forming reactions, such as water splitting into hydrogen and oxygen. Ruthenium complexes are among few molecular-defined catalysts capable of water splitting. Insight into the mechanism of their action will help to design future robust and economically feasible catalysts for light-to-energy conversion. Mechanistic insights about the design of such catalysts can be acquired through spectroscopic analysis of short-lived intermediates of catalytic water oxidation. Development of time-resolved approaches through stopped flow UV-Vis Spectroscopy to follow the catalysis of …

Top-Down Interrogation And Characterization Of Biological Macromolecules, Yang Gao

Open Access Dissertations

Analytical mass spectrometry has been widely applied in the field of biomolecule identification and characterization. It provides fast, accurate and robust information relevant to the molecular mass, composition and structure of the target analytes.

This thesis is focused on the top-down analysis of various macrobiomolecules, nucleic acids and proteins, in the context of ion/ion reaction and gas-phase unimolecular dissociation. The first part of the thesis deals with gas phase fragmentation behavior of chemically modified oligonucleotides. Factors, such as the observation time-scale, the ion type and the energy deposition method, are explored using a quadrupole/time-of-flight mass spectrometer. Novel fragmentation pathway associated …

Structural Analysis Of Carbohydrates By Mass Spectrometry, Chiharu Konda

Open Access Dissertations

Protein glycosylation is a highly frequent post-translational modification. Glycosylation is actively involved in intermolecular and intercellular binding events that are important to a wide range of biological functions such as immunity and fertility. The unique functions of glycans are directly related to their structures. In order to fully characterize the structure of an unknown glycan, 5 levels of structural information is needed: sugar unit identity, anomeric configuration, linkage types, sequence, and branching location. One of the grand challenges limiting the advance of glycosciences is the lack of sensitive tools for detailed glycan structural analysis. Tandem mass spectrometry (MS/MS) is a …

Mass Spectrometric Studies On The Primary Products Of Fast Pyrolysis Of Carbohydrates And The Molecular Structures Of Asphaltenes, And The Development Of A Rastering Probe For Laser-Induced Acoustic Desorption Into An Atmospheric Pressure Chemical Ionization Source, Matthew Robert Hurt

Open Access Dissertations

Mass spectrometry (MS) has proven invaluable in the field of mixture analysis and structural elucidation. Tandem mass spectrometry (MS/MS) utilizing collision-activated dissociation (CAD) has become the technique of choice for structural elucidation of unknown analytes in mixtures. When coupled with gas chromatography (GC) or high performance liquid chromatography (HPLC), it allows for trace level analysis of mixture components. In spite of the utility of mass spectrometry in complex mixture analysis, it does have limitations. Traditional GC/MS methods used for the analysis of fast pyrolysis products cannot be used to analyze the primary products, thus limiting the knowledge that can be …

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

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 …

Approaches For Improved Positional Proteomics, Yanjie Jiang

LSU New Orleans Theses and Dissertations

Positional proteomics is emerging as an attractive technique to characterize protein termini, which play important biological roles in cells. Even with the advances in past decades, there still are areas for improvement. This thesis focuses on improving data quality and assignment confidence in positional proteomics.

A novel workflow was designed for the large-scale identification of protein N-terminal sequences. 4-sulfophenyl isothiocyanate (SPITC) is used for N-termini sulfonation; Upon higher energy collisional dissociation (HCD), SPITC peptides in electrospray ionization ESI generate predominately y-type ion series; such simplification of spectra enables the identification of N-termini with high fidelity. The presence of b_{1 …}

Io3- And I- Sorption From Groundwater By Layered Double Hydroxides, Abbey Rickelmann, Emily Campbell, Natasha Pence, Tatiana Levitskaia, Sayandev Chatterjee, Frances Smith

STAR Program Research Presentations

Several subsurface water plumes are found at the Hanford U.S. DOE site. These plumes contain many different types of hazardous components including radioactive iodate (IO₃^-) and iodide (I^-), which may have deleterious health effects. To selectively uptake IO₃^- and I^-, inorganic layered double hydroxide (LDH) compounds were synthesized and tested. LDHs are mixed transition metal hydroxides that contain positively charged layers that undergo anion exchange. When LDHs are submerged in the plume water, they can selectively uptake IO₃^- and I^- and remove them from the plume. Raman spectroscopy …

Development Of Colloid Displacement Lithography Platforms For Sensor Applications, Mahesh Thugu

Masters Theses & Specialist Projects

In this work, Poly (diallyldimethylammonium) chloride - (PDDA) was used as a base layer for developing colloid displacement lithography platforms for sensor applications. Previous work shows that glass coated with PDDA and exposed to gold acts as a good platform for colloid displacement lithography. However, for actual sensor applications, electrical isolation of individual sensor sections must be achieved. This is attempted by laying down a 40 μm stripe of PDDA on a cleaned substrate and coating that stripe with gold colloid. The size of 40 μm or less in width is set as the target to fit within the scan …

Reinventing Aromatic Substitution: A Novel Look, Quang Nguyen

Masters Theses & Specialist Projects

Electrophilic aromatic substitution (EAS) and directed ortho-metalation (DoM) involve the direct substitution of an arene hydrogen. A major drawback involving EAS is the necessity for harsh forcing conditions for the reaction to proceed. Catalysts such as Lewis acids FeBr₃ and AICI₃ for the introduction of halogens and acyl groups, respectively, are each highly toxic and corrosive. Textbook preparations of aryl iodides classicaly involved the use of iodine and nitric acid. This approach affords only modest yields and does not provide regiospecific substitution of most substituted aromatics because most contain ortho/para directors which afford mixtures of …

Analyses Of Multivitamins In Nutraceuticals By Reverse Phase Hplc With Dad, Elsd And Ms, Hsiang-Chi Huang

All Theses

ABSTRACT
Vitamins are essential to human beings and support long-term healthy lifestyle. They exist widely in food, but in small amount. Hence, dietary supplements and fortified food products are more and more popular in the nutritional markets. According to the Infant Formula Act of 1980, the range of each of the nutrients should fall within a specific range or above the required minimum, so there is an increasing interest of accurate measurement of vitamins, particularly the B-group vitamins. However, traditional methods for vitamin B analyses are time-consuming and often in poor accuracy. As a result, rapid and reliable analytical methods …

Optimization Of Sample Preparation In Matrix-Assisted Laser Desorption/Ionization (Maldi) Mass Spectrometry Of Macromolecules, Evgenia Akhmetova

Graduate Theses and Dissertations

New method for the matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and Fourier transform mass spectrometry (MALDI-FTMS) analysis of low molecular weight polyvinyl acetate (PVAc) was developed and then applied to the characterization of commercially available chewing gum. The optimization of MALDI analysis of PVAc was achieved by investigating the influence of sample preparation variables such as the choice of solvent and choice of matrix-analyte ratio. It was demonstrated that the use of ethyl acetate as a solvent and 2,5-Dihydroxybenzoic acid as a matrix yielded the highest signal intensity for the pure polymer sample. The application of TOF technique did not …

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 …

Surface Tethered Pamam Dendrimers On Controlled Pore Glass As Color Release Sensors For Phosphates, Chang Liu

Master's Theses

Poly(amidoamine) dendrimer (PAMAM) are highly branched macromolecules with reactive amine groups in their interior and exterior. PAMAM dendrimers were attached to controlled pore glass (CPG) surfaces in order to create new functionalized surfaces and used as platforms for UV-vis and fluorescent sensing of phosphate substrates via indicator displacement assays (IDA).

CPG surfaces were first modified with different sized PAMAM dendrimers (generation 3.0, 4.0, and 5.0), then reacted with two strong metal-chelators: aminofunctionalized terpyridine (synthesized from 2,2’:6’,2’’-terpyridine) and Nα-Nα-bis(carboxymethyl)-L-lysine (Lys-NTA). First of all, Cu(II) metal ion binding capacities were measured on the surfaces. Second, two terminal group density tests, amine assay …

Effect Of Leaving Ligands Of Platinum(Ii) Diamine Complexes On Dna And Protein Residues, Ramya Kolli

Masters Theses & Specialist Projects

Platinum compounds are widely used drugs in cancer treatments. Although DNA is the biological target, reaction of platinum compounds with proteins is also potentially significant. Our objective is to study the effects of leaving ligands on the relative reactivity between 5'-GMP (guanosine 5' phosphate), a key DNA target, and N-Acetyl - L-Methionine (N-AcMet), a key protein target. We have used NMR spectroscopy to monitor reactions with N-AcMet and 5'-GMP added to a platinum complex to see which products are formed preferentially. Previous research showed that both a non-bulky complex such as [Pt(en)(D₂O)₂]²⁺ [en=ethylenediamine], and a …

Study Of Immobilizing Cadmium Selenide Quantum Dots In Selected Polymers For Application In Peroxyoxalate Chemiluminescence Flow Injection Analysis, Christopher S. Moore

Electronic Theses and Dissertations

Two batches of CdSe QDs with different sizes were synthesized for immobilizing in polyisoprene (PI), polymethylmethacrylate (PMMA), and low-density polyethylene (LDPE). The combinations of QDs and polymer substrates were evaluated for their analytical fit-for-use in applicable immunoassays. Hydrogen peroxide standards were injected into the flow injection analyzer (FIA) constructed to simulate enzyme-generated hydrogen peroxide reacting with bis-(2,4,6-trichlorophenyl) oxalate.

Linear correlations between hydrogen peroxide and chemilumenscent intensities yielded regression values greater than 0.9750 for hydrogen peroxide concentrations between 1.0 x 10^-4 M and 1.0 x 10^-1 M. The developed technique’s LOD was approximately 10 ppm. Variability of the prepared …

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. …

Polymers For Dna Binding, Sue Yuan Li

Seton Hall University Dissertations and Theses (ETDs)

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Separation Of Tc From U And Development Of Metallic Tc Waste Forms, Edward Mausolf

UNLV Theses, Dissertations, Professional Papers, and Capstones

The isotope Technetium-99 (⁹⁹Tc) is a major fission product of the nuclear industry. In the last decade, approximately 20 tons of 99Tc have been produced by the US nuclear industry. Due to its long half-life (t_1/2 = 214,000 yr), beta radiotoxicity, and high mobility as pertechnetate [TcO₄]^-, Tc represents long-term concern to the biosphere. Various options have been considered to manage ⁹⁹Tc. One of them is its separation from spent fuel, conversion to the metal and incorporation into a metallic waste form for long-term disposal. After dissolution of spent fuel in nitric …

An Electrochemical Impedance Spectroscopic Study Of Cuf2/Moo3/C Cathode Composites, Yue-Li Shi, Nan Wu, Ming-Fang Shen, Jia-Qun Dong, Quang-Chao Zhuang, Li Jiang

Journal of Electrochemistry

Composite electrode of CuF₂/MoO₃/C was fabricated through high energy mechanical milling. The properties of CuF₂/MoO₃/C were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM), galvanostatic charge-discharge measurements, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the grain sizes of CuF₂ and MoO₃ after milling were 200 ~ 300 nm, and the initial discharge capacity of CuF₂/MoO₃/C was 647 mAh·g^-1 at room temperature and at a current density of 10 mA·g^-1. However, the …