Chemistry Commons^™

First-Principles Studies On Physical And Chemical Properties Of Nanostructures, Menghao Wu

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

The physical and chemical properties of decorated graphene and graphene ribbons, single-layer III-V systems, three-dimensional carbon and BN foam, and transition-metal-molecular sandwich nanowires have been investigated by first-principle calculations and their potential applications have been predicted. First, it is shown that zigzag graphene nanoribbons (ZGNRs) can be converted into half metal when their edges are decorated by some chemical functional groups, and the half-metalicity is induced by chemical potential difference between two edges when one edge is decorated by electron-donating group like –OH and the other edge is decorated by electron-accepting group like –F, -NH₂, -N(CH₃) …

Quantum Mechanical And Molecular Mechanical Study Of Solvent Effects, Dejun Si

Department of Chemistry: Dissertations, Theses, and Student Research

Intermolecular interaction and solvent effects play important roles in determining physical and chemical properties of molecular systems, and must be considered in relevant quantum mechanical (QM) calculations. Due to the high computational cost, full and rigorous QM treatment of both solute and solvent molecules is impractical. Computationally efficient molecular mechanical (MM) methods can be used to describe solvent effects, and combined into QM methods to formulate QM/MM methods. Classical force field method and reaction-field method are the two most popular MM methods. However, the issue of effectively combining MM methods with high-level QM methods remains unsolved. This thesis presents several …

Preparation And Characterization Of Biomimetic Hydroxyapatite-Resorbable Polymer Composites For Hard Tissue Repair, Kristopher R. Hiebner

Department of Chemistry: Dissertations, Theses, and Student Research

Autografts are the orthopedic “gold standard” for repairing bone voids. Autografts are osteoconductive and do not elicit an immune response, but they are in short supply and require a second surgery to harvest the bone graft. Allografts are currently the most common materials used for the repair of segmental defects in hard tissue. Unlike autografts, allografts can cause an undesirable immune response and the possibility of disease transmission is a major concern. As an alternative to the above approaches, recent research efforts have focused on the use of composite materials made from hydroxyapatite (HA) and bioresorbable polymers, such as poly-L-lactide …

Effects Of Molecular Architecture On Fluid Ingress Behavior Of Glassy Polymer Networks, Matthew Blaine Jackson

Dissertations

This manuscript demonstrates the synthesis of glassy polymer network isomers to control morphological variations and study solvent ingress behavior independent of chemical affinity. Well-controlled network architectures with varying free volume average hole-sizes have been shown to substantially influence solvent ingress within glassy polymer networks. Bisphenol-A diglycidyl ether (DGEBA), bisphenol-F diglycidyl ether (DGEBF), Triglycidyl p-aminophenol (pAP, MY0510), Triglycidyl maminophenol (mAP, MY0610), and tetraglydicyl-4,4’-diamino-diphenyl methane (TGDDM, MY721) were cured with 3,3’- and 4,4’-diaminodiphenyl sulfone (DDS) at a stoichiometric ratio of 1:1 oxirane to amine active hydrogen to generate a series of network architectures with an average free volume hole-size (V_h) …

Exploration In Metallic Nitride Fullerenes And Oxometallic Fullerenes: A New Class Of Metallofullerenes, Mary Alice Mackey

Dissertations

Research groups around the world have taken an interest in the synthesis, purification, characterization, and functionalization of Metallic Nitride Fullerenes (MNFs) since their discovery in 1999. This dissertation details the discovery of another new class of molecules—Oxometallic Fullerenes (OMFs).

There are many groups worldwide doing research on MNFs, and there is a large database of published MNF research, but we have had a unique opportunity to fill a research void on OMFs as at present no one else is doing research on these molecules; herein we take molecules that we discover and perform seminal research relating to them. MNF research …

Free Volume Studies Of Various Polymeric Systems Using Positron Annihilation And Pvt-Eos Analyses, Mukul Kaushik

Dissertations

The glass transition phenomenon and free volume behavior below and above the glass transition temperature of various polymeric systems have been investigated. Several novel polymeric systems were considered for this study. Two generations of hyperbranched polyols, H40 and H20, were selected due to large number of hydroxyl groups on the periphery and within the bulk. The effect of hydrogen bonds and molecular weight was related with the glass transition and free volume behavior for the whole range of experimental temperature. The free volume behavior was experimentally studied using PVT and PALS to determine occupied volume, fractional free volume and number …

Design Of Covalently Dynamic Films And Coatings: Analysis Of Biocatalyzed Kinetic Behavior In Soft Condensed Matter, Pirro Cipi

Dissertations

Reversibly adjusting surface and bulk properties of materials is advantageous to many applications and will vastly expand current polymer capabilities. A novel strategy was developed to render materials capable of “smart” surface and bulk properties with the aid of embedded biocatalyst and latent functional groups that are selectively activated in the presence of biocatalyst to undergo chemical transformation. The research presented herein focused on systematically characterizing the activity of lipase catalysts embedded in poly (alkyl methacrylate)s simultaneously with functionalized components, either as diffusing within the polymeric matrix or tethered to the matrix. Lipase activity, ester forming (synthetic) or ester breaking …

Influence Of Ionic Mobile Phase Additives With Low Charge Delocation On The Retention Of Ionic Analytes In Reversed Phase Hplc, Cesar Florez

Seton Hall University Dissertations and Theses (ETDs)

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Electrochemistry Of Pani/Metal Composites In Basic Solutions, Tamthinhan Quy

UNLV Theses, Dissertations, Professional Papers, and Capstones

Polyaniline (PANI) has been extensively investigated due to its unique conductivity, which is primarily dependent on the oxidation state of the material and the solution pH. PANI is an insulator when it is oxidized, and the solution pH exceeds four. Numerous attempts to extend PANI's conductivity to neutral and alkaline environments have been unsuccessful. However, our previous study has demonstrated that PANI/Pd composite is conductive and catalytically active in a basic solution, pH ∼ 12. Therefore, the conductivity and the electrochemical properties of PANI composites including PANI/Au, PANI/Pd and PANI/Pt were evaluated in basic solutions. The fundamental studies of PANI/metal …

Intragroup Separation Of Trivalent Lanthanides And Actinides For Neutron Capture Experiments In Stockpile Stewardship Sciences, Narek Gharibyan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Knowledge of low-energy cross sections for stable and unstable nuclei in neutron-, γ- and ion induced reactions is important in both the simulation and radiochemistry diagnosis of nuclear device performance. This dissertation explores extraction chromatography and ion chromatography methods for the intragroup separation of trivalent actinides and lanthanides in support of cross section measurements for isotopes of interest. For trivalent actinides, americium (Am(III)) and curium (Cm(III)), separation is necessary to assist in experiments related to the measurement of neutron capture cross section for ²⁴¹ Am and the production of ^{242 m} Am/^242g Am isomeric ratio. Extraction chromatography resins …

Spectroscopic Methods Of Process Monitoring For Safeguards Of Used Nuclear Fuel Separations, Jamie Lee Warburton

UNLV Theses, Dissertations, Professional Papers, and Capstones

To support the demonstration of a more proliferation-resistant nuclear fuel processing plant, techniques and instrumentation to allow the real-time, online determination of special nuclear material concentrations in-process must be developed. An ideal materials accountability technique for proliferation resistance should provide nondestructive, realtime, on-line information of metal and ligand concentrations in separations streams without perturbing the process. UV-Visible spectroscopy can be adapted for this precise purpose in solvent extraction-based separations.

The primary goal of this project is to understand fundamental URanium EXtraction (UREX) and Plutonium-URanium EXtraction (PUREX) reprocessing chemistry and corresponding UV-Visible spectroscopy for application in process monitoring for safeguards. By …

Direct Contact Pyrolysis Of Hydrocarbons: A Source Of Hydrogen And Interesting Carbon Formations, Peter G. Faught

UNLV Theses, Dissertations, Professional Papers, and Capstones

The work detailed in this document looks at a novel liquid metal supported catalytic system for the generation of hydrogen by decomposition of ethanol through direct contact pyrolysis. The hydrogen is produced at relatively low temperatures (500-600°C) and has carbon and water as co-products. It should be noted that CO is not observed as a product at these low temperatures. This is to be contrasted with the hydrogen produced at higher temperature from ethanol which does contain carbon monoxide. The presence of carbon monoxide in hydrogen complicates fuel cell operation and catalytic chemical processes. Thus, the lack of CO in …

Prevention Of Iron- And Copper-Mediated Oxidative Dna Damage By Neurotransmmitters And Related Compounds: Evidence For Metal Binding As An Antioxidant Mechanism, Carla Garcia

All Theses

An array of health concerns have been attributed to oxidative DNA damage from the hydroxyl radical (*OH), and the presence of the most biologically available metals iron and copper perpetuate the production of this radical through the Fenton and Fenton-like reactions, respectively. The concentrations at which flavonol and polyphenol antioxidants prevent 50% of DNA damage (IC50) were measured using gel electrophoresis assays upon Fe(II)/H2O2- and Cu(I)/H2O2-mediated DNA damage (Chapter 2). Results show that catechol- and gallol-containing antioxidants differ greatly in preventing DNA damage by Cu(I)/H2O2, compared to Fe(II)/H2O2, behavior that was explained using electron paramagnetic resonance spectroscopy. Semiquinone and other …

Fabrication Of Mineralized Collagen From Bovine Waste Materials By Hydrothermal Method As Promised Biomaterials, Faheem A. Sheikh, M. A. Kanjwal, Javier Macossay-Torres, Muneeb A. Muhammad, Travis Cantu, Ioannis S. Chronakis, N. A. M. Barakat, Hak Yong Kim

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Chemistry)

In the present study, we aimed to produce mineralized-collagen by hydrothermal process. A simple method not depending on additional foreign chemicals has been employed to isolate the mineralized-collagen fibers from bovine waste. The process of extraction involves the use of hydrothermal method from available bovine bones. The structural and morphological properties of the collagen fibers were characterized by using scanning electron microscopy and transmission electron microscopy. These results indicated well received collagen fibers, having a diameter less than 1 μm and with established mineral content in the individual fibers. The X-ray diffraction showed the crystalline feature of the obtained nano-compounds. …

Electrolyte Incorporation Into Composite Electrodes For Proton-Exchange Membrane Fuel Cells And Lithium-Ion Batteries, Jung Oh

All Dissertations

This dissertation describes research on the preparation and characterization of composite electrodes for use in proton-exchange membrane (PEM) fuel cells and lithium ion batteries. The general focus of the research was on high-surface-area carbon supports for platinum catalysts in fuel cells, and integration of electrolytes, particularly fluoropolymer electrolytes, into composite electrodes both batteries and fuel cells. Results are described for work in the following three specific topical areas.
1. Carbon nanofibers for use as platinum (Pt) catalyst supports in fuel cells were prepared by carbonization of electrospun acrylic fibers. The resulting carbon nanofibers were found to contain mainly micropores. Following …

Modification And Characterization Of Fluorescent Conjugated Polymer Nanoparticles For Single Molecule Detection, Yueli Zheng

All Dissertations

Single molecule tracking using fluorescent dye or nanoparticle labels has emerged as a useful technique for probing biomolecular processes. Considerable interest arises in the development of nanoparticle labels with brighter fluorescence in order to improve the spatial and temporal resolution of single molecule detection and to facilitate the application of single molecule detection methods to a wider range of intracellular processes. The McNeill laboratory recently reported that conjugated polymer nanoparticles exhibit fluorescence cross-sections roughly 10-100 times higher than other luminescent nanoparticles of similar size, excellent photostability (2.2×108 photons emitted per nanoparticle prior to photobleaching), and saturated emission rates roughly 100 …

Studies Toward The Development Of A Microelectrode Array For Detection Of Dopamine Through Redox Cycling, Anupama Aggarwal

Graduate Theses and Dissertations

Redox cycling is an electrochemical technique that cycles the reversible redox species between its oxidative states repeatedly on generator and collector electrodes. Two or more individually-addressable microelectrodes located close to each other allow redox cycling to be possible. Electrochemical behavior of a biologically important molecule, dopamine is examined under redox cycling conditions. To our knowledge, this is the first report on detection of physiological concentration of dopamine in presence of up to 100 times excess ascorbate with the use of redox cycling, without the involvement of polymer coating such as Nafion®.

Microfabrication was used to produce different geometries (parallel bands …

Dynamics And Catalytic Resolution Of Selected Chiral Organolithiums, Timothy Kum Beng

Graduate Theses and Dissertations

One of the most important developments of the last decade has been the emergence of new methods to dynamically resolve racemic organolithiums using stoichiometric amounts of the chiral ligand. When this concept is implemented successfully, it obviates the need for covalently attached chiral auxiliary based methods, asymmetric deprotonation, and asymmetric synthesis of a precursor stannane as ways to access enantioenriched organolithium compounds for use in asymmetric synthesis. Since certain electrophiles consume the chiral ligand, it is desirable to render this process catalytic in the chiral ligand.

As part of a larger study on the amenability of chiral organolithiums to a …

Spatial And Temporal Variations In The Air-Sea Carbon Dioxide Fluxes Of Florida Bay, Christopher Michael Dufore

USF Tampa Graduate Theses and Dissertations

The flux of CO2 between the ocean and the atmosphere is an important measure in determining local, global, and regional, as well as short term and long term carbon budgets. In this study, air-sea CO2 fluxes measured using a floating chamber were used to examine the spatial and temporal variability of CO2 fluxes in Florida Bay. Measurements of dissolved inorganic carbon and total alkalinity obtained concurrently with chamber measurements of CO2 flux allowed calculation of ΔpCO2 from flux measurements obtained at zero wind velocity. Floating chamber measurements of ΔpCO2 were subsequently coupled with wind speed data to provide a simple …

Using Lectinmicroarrays To Identify Regulatory Mechanisms For Mammalian Glycosylation, John F. Rakus

Chemistry Faculty Research

Glycosylation involves the post-translational addition of carbohydrates to protein molecules and is an intricate and indispensable biochemical process. Study of this complicated network of interactions is hindered by the lack of a coding template analogous to the genetic code, and by the vast structural complexity inherent to carbohydrate polymers. We use lectins (non-enzymatic carbohydrate-binding proteins of non-immunological origin) as microarray probes to identify carbohydrate features expressed on cellular surfaces. Specifically, we utilized lectin microarray technology to investigate the differences in carbohydrates expressed by the cell lines of the Nation Cancer Institute’s NCI-60 panel. Our investigation identified tissue-specific expression differences in …

Electroless Plating Silver Without Pd Activation On Polyamide Fabrics And Its Properties, Yun Meng, Ya-Ping Zhao, Zai-Sheng Cai

Journal of Electrochemistry

Silver was deposited on the surface of polyaniline coated polyamide fabrics by electroless plating without using conventional palladium chloride solution as activator．Effects of electroless plating conditions such as the concentrations of silver nitrate, reducing agent glucose, complexing agent ammonium hydroxide, sodium hydroxide in the bath, as well as the depositing time and bath temperature on the rate of metal deposition and the square resistance were studied. Optimum electroless plating conditions were: 30℃, 50 min, with silver nitrate 12 g/L, ammonium hydroxide 100 ml/L, glucose 2.8 g/L, sodium hydroxide 8 g/L. Meanwhile, effects of the intermediate polyaniline layer on the metal …

Preparation And Application Of Nano-Nio As Anode In Lithium-Ion Batteries, Cheng-Dong Bai, Jia-Jia Chen, Qi Zhang, Ming-Sen Zheng, Quan-Feng Dong

Journal of Electrochemistry

In this work, the nano-NiO material was prepared by hydrothermal method. The surface morphologies and electrochemical properties of nano-NiO material were investigated. The special nano-NiO material with porous surface assembling honeycombs(100-200nm) was obtained by using surface active agents. The discharge capacity of nano-NiO electrode up to 2385.7 mAh/g was achieved at current density of 0.1A/g in the first circle,while 1100mAh/g could be maintained after 100 circles. At current density of 2.0A/g, the discharge capacity of 600 mAh/g was obtained. And when the current density was reduced to 0.1A/g, the discharge capacity was restored to 1050 mAh/g. The nano-NiO electrode exhibited …

Brief Introduction Of Organic Electrochemistry, Huan Wang, Jia-Xing Lu

Journal of Electrochemistry

Organic electrochemistry is a very useful tool for organic synthesis, not only because of the selective introduction or removal of electrons from organic molecules, but also for its green process. In this paper, electroorganic synthesis has been introduced from the systems, research methods and technologies to the characterization. Most of organic compounds could be electrochemically oxidized or reduced. Here, taking C=C compounds as an example, several kinds of electrochemical organic synthesis reactions are discussed, such as electrochemical addition, electrocatalytic dimrization, electropolymerization, etc. Electroorganic synthesis has been industrialized since 1960s. In this paper, electrosynthesis of adiponitrile was used as an example …

Corrosion Behaviors Of 316 Stainless Steel Weldment Studied By Array Reference Electrodes, Wang-Huo Yang, Rong-Gang Hu, Chen-Qing Ye, Wei Hang, Ning Li, Chang-Jian Lin

Journal of Electrochemistry

The array reference electrodes were developed to in situ measure the potential distributions of the welded 316 stainless steel in 12% FeCl3 solution, combined with metallographic analysis, polarization curve, EIS measurement and Kelvin volta potential imaging. It was indicated that the weld zone of metal suffered a serious preferential corrosion when immersed in the environment due to the distinct changes of structure and composition during the welding process. With time prolonging, the corrosion potential of the welding zone was negatively shifted to a maximum value, and then declined gradually. At 45 min immersion, the corrosion development from welding zone to …

Superhydrophilic/Superhydrophobic Surface Constructions On Titanium And Their Effects On Anti-Bacterial Properties, Guo-Wei Wang, Qiao-Ling Huang, Ren Hu, Chang-Jian Lin, Hao Wang, Li-Hai Zhang, Pei-Fu Tang

Journal of Electrochemistry

The microbial infection of biomaterials often causes clinic problems and sometimes even leads to the prosthesis failure. It is, therefore, important to prevent the biomaterials from bacterial contamination. This can be done by using anti-bacteria drugs. However, this method causes physiological burdens to the patients and does not always work. To stop the contamination from the just beginning is believed to be a better choice. The first step for infection is the attachment of bacteria on the material. In this work, the thin TiO₂ nanotubes array films were constructed with totally different wettabilities showing either superhydrophobic or superhydrophilic. The …

Microemulsion Preparation And Electrochemical Characterization Of Pt/C, Ptir/C Electrocatalysts, Ya-Ping Zeng, Sheng Sui

Journal of Electrochemistry

The Pt/C electrocatalysts were prepared by three different systems and the PtIr/C electrocatalysts were prepared with four different Ir contents. The samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), cyclic voltammetry (CV), potentiostatic and potentiodynamic polarizations measurements. The experimental results confirmed that the electrocatalyst particles prepared by the microemulsion method were well distributed on XC-72R supports with the active particle sizes of 5～10nm and good electrocatalysts activity. The Pt85Ir15/C electrocatalysts showed the highest overall electrochemical activity in unitized regenerative fuel cell.

The Electrochemical Properties Of Cathode Materials LimXV3-XO8, Hui Yang, Gang-Gang Zhao, Juan Li

Journal of Electrochemistry

The cathode material of LiM_xV₃-xO₈ was fabricated by sol-gel method using citric acid as a chelating agent and doping transition metal ions M (Mn, Ti, Co and Ni). The structure, morphology and electrochemical proprieties of the LiMxV3-xO8 samples were investigated by XRD, TGA/DTA, SEM, charge-discharge and CV measurements. The results showed that different calcining temperatures result in different structures and morphologies, which lead to different discharge capacities. The specific discharge capacity of the sample calcined at 500℃ for 6 h was up to 300.4 mAh/g in the first cycle, and the capacity decreased with the …

Electrocatalytic Determination Of 15 Kinds Of Phenolic Compounds By Novel Gold Nanoparticles-Modified Glassy Carbon Electrode, Yan-Ping Cui, Wei-Xing Wang, Chang-Zhu Yang, Wen-Hong Pu

Journal of Electrochemistry

A gold nanoparticles modified glassy carbon electrode (Au/GCE) was used to detect 15 kinds of phenolic compounds. In the cyclic voltammetry measurements, the peak currents of phenolic compounds at Au/GCE were all increased as compared with GCE and planar gold electrodes, and the oxidation potentials were determined by the activity of analytes. Besides, electrocatalysis of salicylic acid was studied at Au/GCE. The results showed that, there was a good linear relationship between the oxidation current and the concentration of salicylic acid, and the current sensitivity was 1.8 fold higher than that obtained on GCE. Trace phenolic compounds determination could be …

Electrochemical Behaviors Of Hydroquinone On Polypyrrole/Stab-Nammt/Gc Electrode, Rong Li, Jian Xiong, Wei-Qiong Zhu, Yuan-Yuan Han, Jin Xu, Xiao-Ying He

Journal of Electrochemistry

The PPy/STAB-MMT/GC electrode was made using montmorillonite modified by STAB and polypyrrole (PPy). The electrochemical behaviors of hydroquinone on the PPy/STAB-MMT/GC electrode were researched by cyclic voltammetry and square wave stripping voltammetry (SWSV). The results showed that the electrode reaction occurred on the hydroquinone electrode was controlled by diffusion in PBS (pH=6.0). The number of electron transfer was equal to the number of protons (n=m=1) with the effective area of PPy/STAB-MMT/GC electrode Aeff=0.031 cm². Under the optimized conditions, the linear response of peak current in SWSV with the concentration of hydroquinone in a range of 8.0×10^-6~8.0×10 …

A Brief Review Of Research Progress In The Development Of Engineering Models For Lithium Ion Batteries, Da-Wei Wang, Dong-Jiang Li, Jun Li, Yong Yang

Journal of Electrochemistry

Lithium ion battery has become an important and popular electrochemical device for energy storage.Suitable evaluation and understanding of electrochemical performance and state of charge play a key role in the applications of lithium ion batteries.Construction and utilization of engineering modeling for lithium ion batteries is an effective way to fulfill this target.In this paper,engineering models of lithium ion batteries based on electrochemical reaction,ionic diffusion and migration are introduced.The emphasis is placed on the development of engineering models by the introduction of side reaction,phase transition,stress and energy.The applications of engineering models in such simulations as charge-discharge,concentration distribution,current distribution,state of charge,stress and …