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Articles 1 - 18 of 18
Full-Text Articles in Physical Sciences and Mathematics
Polymeric Carbon Nanocomposites - Preparation, Characterization, And Properties, Lucia Veca
Polymeric Carbon Nanocomposites - Preparation, Characterization, And Properties, Lucia Veca
All Dissertations
Excellent thermal properties of carbon nanomaterials such as carbon nanotubes and newly discovered graphene make them the filler of choice for the development of thermal management materials. Graphene has been viewed as “ unrolled single-walled carbon nanotube and as a wonder material with many superlatives to its name ” thus there is an excessive interest in developing new synthetic routes towards large scale production of high quality graphene nanosheets.
In this dissertation, we report different methods that could further exfoliate the commercially available expanded graphite to nanometer sized carbon structures, “carbon nanosheets ”, for their use in highly thermal conductive …
Synthesis, Modification Of Mesoporous Carbons And Their Application In Polymer Electrolyte Membrane Fuel Cells, Bing Liu
All Dissertations
Mesoporous carbon materials of carbon xerogel (CX) and silica-templated carbon (MC) were synthesized and explored as catalyst supports alternative to the most-commonly-used carbon black (CB) support, for polymer-electrolyte-membrane fuel cell (PEMFC) application. Pt catalyst was loaded on these carbons and electrodes were fabricated from them. These Pt-loaded carbon supports were characterized with XRD, TEM, ex-situ and in-situ cyclic voltammetry, etc. The fabricated electrodes were evaluated in single-cell testing in comparison with commercial CB-supported Pt catalyst fabricated electrodes. The experimental results showed that CX-supported Pt catalyst had close or better performance than that of CB-supported Pt, possibly due to CX's 3-D …
Synthesis And Development Of Novel Fullerene-Based Structures For Photovoltaics, Electronic Applications And Mri Contrast Agents, Manuel Chaur
All Dissertations
Metallic nitride endohedral metallofullerenes (EMFs) are one of the most interesting types of metallofullerenes due to their high yields and interesting electronic properties. The synthesis of these compounds allows the encapsulation of different metals inside fullerenes making it possible to combine the properties of the metal with those of the fullerene. Their interesting electrochemical and optical features make them potential candidates for several applications such as molecular electronics, biomedical imaging, non-linear optical devices, and magnetic resonance imaging (MRI) agents. This thesis reports the synthesis of novel metallic nitride EMFs based on Gd, Nd, Pr, Ce and La. These families of …
Synthesis And Characterization Of Metallic, Core-Shell And Composite Nanoparticles, Amar Kumbhar
Synthesis And Characterization Of Metallic, Core-Shell And Composite Nanoparticles, Amar Kumbhar
All Dissertations
ABSTRACT
Silver nanoparticles exhibit size, shape and the surrounding dielectric medium dependent optical properties (scattering and absorption) in the visible spectral region. These optical properties can be explained in terms of the collective oscillation of the 'free conduction band electrons' or 'surface plasmons' induced by an external electromagnetic field. Dipole and Quadrupole Plasmon resonances have been observed for silver particles less than 100nm in diameter prepared using various synthetic techniques. However higher order resonances have been elusive due to lack of experimental techniques to prepare colloidal solutions of large silver nanoparticles in the size range above 100nm. Controlled hydrogen reduction …
Development Of A Fluorescent Probe For Determination Of Water Transport In Subcellular Organelles, Adriana Chaurra-Arboleda
Development Of A Fluorescent Probe For Determination Of Water Transport In Subcellular Organelles, Adriana Chaurra-Arboleda
All Dissertations
Water transport has been widely studied in a variety of cells and isolated membranes. However, the intrinsic complexity related with the study of intracellular processes has delayed the development of an analytical technique for the study of water transport in subcellular compartments of living cells. This study represents the development and application of a ratiometric fluorescent probe to study water transport in endocytic organelles of intact living cells. The probe is based on the use of a D2O-sensitive fluorophore, Lucifer yellow dextran (LY-dex), together with a D2O-insensitive fluorophore, Alexa fluor 546 dextran (AF546-dex), used as an …
Synthesis And Characterization Of Magnetic Solids Containing Periodic Arrays Of Transition Metal Oxide Nanostructures, Wendy Queen
Synthesis And Characterization Of Magnetic Solids Containing Periodic Arrays Of Transition Metal Oxide Nanostructures, Wendy Queen
All Dissertations
The ultimate goal of the research presented in this dissertation was to explore new systems containing low–dimensional magnetic nanostructures in hopes of finding new extended solids exhibiting novel magnetic properties due to the confined magnetic lattices. The scope of this research is threefold: 1) to explore new solids containing low–dimensional magnetic nanostructures in the A–M–X–O system, where A is an alkali or alkalinendash;earth metal cation, M is a first–row transition metal cation, and X is P, As, or V, 2) to characterize these new materials and, through chemical substitution, fine tune (and optimize) magnetic and electronic properties of solids that …
Hydrothermal Crystal Growth Of Tetravalent And Pentavalent Metal Oxides, James Mann
Hydrothermal Crystal Growth Of Tetravalent And Pentavalent Metal Oxides, James Mann
All Dissertations
Over the past two hundred years synthetic growth of crystals has become vital to the technological advancement of our society. A variety of crystal growth techniques have been developed during this time, with each having its own nuances. These differences have enabled the growth of a wide spectrum of crystalline materials that can be used for many applications which include solid state lasers, semiconductors, and communication devices. Despite these techniques there are entire classes of materials which have thus far proved quite difficult to prepare as single crystals. In particular, crystal growth of the tetravalent and pentavalent metal oxides has …
Synthesis Of Complex Fluorides For Optical Applications, Seth Stepleton
Synthesis Of Complex Fluorides For Optical Applications, Seth Stepleton
All Dissertations
Large single crystals of alkali metal fluorides are desirable for many reasons. Fluoride laser crystals have a wide transmission range and on account of their low phonon energies, many efficient laser emissions have been obtained from 285 nm to 4.34 µm.1,2 Inorganic fluoride single crystals feature large bandgaps, very wide optical transmittance ranges from vacuum-ultraviolet (VUV) to mid-IR wavelength regions, lower refractive indices than those of oxides, and typically lower phonon energies (which drastically reduce multiphonon relaxation rates of rare earth ions).3
The main goal of this work was to investigate the hydrothermal synthesis of alkali metal fluorides. Melt techniques …
Understanding The Antioxidant Mechanism Of Inorganic Selenium, Oxo- Sulfur, And Polyphenol Compounds, And The Biological Implications Of Functionalized Nanoparticles, Ria Ramoutar
All Dissertations
Inorganic selenium, oxo-sulfur, and polyphenol compounds are found in foods and dietary supplements, and are recognized for their nutritional benefits and their potential to treat or prevent diseases caused by oxidative stress. In our experiments to determine the effects of inorganic selenium compounds on iron-mediated DNA damage, Na2SeO33 and SeO2 exhibit antioxidant and pro-oxidant activities depending on concentrations of both the compound and hydrogen peroxide. Additional experiments demonstrate that iron coordination is a novel mechanism responsible for the observed activities. In similar experiments, oxo-sulfur compounds prevent Cu+/ H2O2-mediated DNA damage significantly …
Synthesis Of Polymers Featuring Novel Diphosphines, Eleanor Tennyson
Synthesis Of Polymers Featuring Novel Diphosphines, Eleanor Tennyson
All Theses
This report details the synthesis of functionalized platinum-based metallopolymers featuring m-terphenyl-scaffolded and light-harvesting phosphine ligands. Substituents placed on both the phosphine and pendant alkynyl units can enhance the optical activity of the metallopolymers depending on their inherent properties. The presence of the platinum metal atom can be exploited to increase conductivity of the molecule and promises to be a unique and valuable modification for polymers to be used in light emitting diodes and photovoltaics. Light-harvesting phosphines prepared in the course of the metallopolymer development have also been used to prepare luminescent polyelectrolytes that prove valuable for well-defined composite film formation …
Phenomenological Investigation Of The Effectiveness Of A Cooperative Problem-Based Laboratory And A Metacognitive Problem-Solving Exercise, Todd Gatlin
All Theses
Problem-solving has been described by many as the most important goal of chemistry teaching and learning. Solving real problems requires not only cognitive abilities but also a regulation of those abilities-metacognition. In fact, metacognition is recognized as having considerable impact on problem-solving success and learning. Recent research focused on the development of interventions designed to enhance the use of metacognition. The main objective of this study was to determine 'how' and 'why' two interventions were effective in increasing students' metacognitive use, and problem-solving abilities. Therefore, this study represents the qualitative portion of a sequential explanatory mixed-methods study; Qualitative evidence was …
Development Of Improved Torsional Potentials In Classical Force Field Models Of Poly (Lactic Acid), James Mcaliley
Development Of Improved Torsional Potentials In Classical Force Field Models Of Poly (Lactic Acid), James Mcaliley
All Dissertations
In this work, existing force field descriptions of poly (lactic acid), or PLA, were improved by modifying the torsional potential energy terms to more accurately model the bond rotational behavior of PLA. Extensive calculations were carried out using density functional theory (DFT), for small PLA molecules in vacuo, and also using DFT with a continuum model to approximate the electronic structure of PLA in its condensed phase. From these results, improved force field parameters were developed using a combination of the OPLS and CHARMM force fields. The new force field, PLAFF2, is an update to the previously developed PLAFF model …
Organocuprate Mediated Syntheses Of O, And N-Heterocycles, Fenghai Guo
Organocuprate Mediated Syntheses Of O, And N-Heterocycles, Fenghai Guo
All Dissertations
ABSTRACT
The δ-lactone moiety comprises structural subunits in a number of natural products. Highly substituted δ-lactones are important both in synthetic applications and also as naturally occurring compounds. We have reported a one-pot procedure for the synthesis of trans-4,5-disubstituted tetrahydropran-2-ones from 3-hydroxy-3,6-dihydropyran-2-one involving sequential cuprate mediated allylic substitution and 1,4-conjugate addition reactions. We have now examined the same protocol for synthesis of 4,5,6-trisubstituted δ-lactones.
The rich functionalities(i.e. the epoxide, olefin and ester functional groups) in ,δ-epoxy-α,β-enoates provide opportunities for SN2-epoxide opening, allylic substitution, and 1,4-conjugated addtion. The opening of the epoxide with AcCl, AcBr, and benzoyl chloride afforded the -acetoxy--halo-,-enoates …
Fundamental Aspects Of Small Molecules And Macromolecules On Poly(Ethylene Terephthalate) Capillary-Channeled Polymer Fibers, Christine Straut
Fundamental Aspects Of Small Molecules And Macromolecules On Poly(Ethylene Terephthalate) Capillary-Channeled Polymer Fibers, Christine Straut
All Dissertations
Stationary phases and adsorbents are continually being developed to enhance separations in high performance liquid chromatography (HPLC). Polymeric stationary phases have gained popularity due to their ability to be employed over a large pH range and because they are more chemically robust when compared to silica based phases. Capillary-channeled polymer (C-CP) fibers are an alternative to traditional porous packed bed beads. These fibers have a unique geometry with increased the surface area/volume ratios when compared to cylindrical fibers. Very unique characteristics are realized in the use of the C-CP fibers, including drastically reduced backpressures and selection of solute-surface interaction through …
Synthesis Of Ionic Liquid Monomers Using Fluorinated Sulfonyl Imide Anions And The 1,3-Dialkylimidazolium Cation, Thomas Hickman
Synthesis Of Ionic Liquid Monomers Using Fluorinated Sulfonyl Imide Anions And The 1,3-Dialkylimidazolium Cation, Thomas Hickman
All Dissertations
With their unique material and solvent properties, ionic liquids have seen an amazing, exponential increase in interest. After a brief introduction of select areas of interest for these compounds, this thesis mainly focuses on the development of novel polyfunctional ionic liquids and polymeric ionic liquids.
One of the preferred anions for ionic liquids is the bis((trifluoromethyl)sulfonyl) imide anion, first introduced by our group in 1982. It shows excellent thermal stability and the desired resonance delocalization of a negative charge for ionic liquids. A series of monofunctional, difunctional, and multi-functional bis(perfluoroalkylsufonyl)imides, along with 1,3-dialkylimidazolium cations were prepared by direct methylation of …
Specific And Non-Specific Binding Of Proteins And Nucleic Acids On Chemically Modified Reticulated Vitreous Carbon Electrodes, Hemangi Shedge
Specific And Non-Specific Binding Of Proteins And Nucleic Acids On Chemically Modified Reticulated Vitreous Carbon Electrodes, Hemangi Shedge
All Theses
Proteins and nucleic acids play major roles in many important biological processes. Specific and rapid detection of these biomolecules is important for early and precise diagnosis of various genetic diseases and other medical conditions. However, accurate and inexpensive detection of proteins and nucleic acids has always been a challenge. One of the obstacles is their non-specific adsorption on the sensor surface which leads to the conformational changes in the proteins, sometimes causing their denaturation. The non-specific adsorption on the surface also leads to sensor fouling which induces changes in the availability of active sensor surface for detection of analytes and …
Investigation Of Photophysical And Photochemical Processes In Conjugated Polymer Nanoparticles By Single Particle And Ensemble Spectroscopy, Craig Szymanski
Investigation Of Photophysical And Photochemical Processes In Conjugated Polymer Nanoparticles By Single Particle And Ensemble Spectroscopy, Craig Szymanski
All Dissertations
Single molecule imaging has emerged as a powerful tool in a range of applications, but the field is limited by a lack of fluorescent probes with sufficient brightness and photostability for many demanding applications such as tracking of single biomolecules in cells and tissues at video rate with 1 nm spatial resolution. Conjugated polymers hold great promise as a solution to these issues, with a high density of π electrons and variety of chemistries, allowing efficient and tunable absorption of light. This dissertation describes the development and characterization of a novel type of nanoparticle composed of conjugated polymer called CPdots. …
Ratiometric Single-Nanoparticle Oxygen Sensors For Biological Imaging, Changfeng Wu, Barbara Bull, Kenneth Christensen, Jason Mcneill
Ratiometric Single-Nanoparticle Oxygen Sensors For Biological Imaging, Changfeng Wu, Barbara Bull, Kenneth Christensen, Jason Mcneill
Publications
It makes sense: Conjugated polymer nanoparticles doped with a platinum porphyrin dye exhibit bright phosphorescence that is highly sensitive to the concentration of molecular oxygen. The small size, extraordinary brightness, excellent sensitivity, and ratiometric emission, together with the demonstration of single-particle sensing and cellular uptake, indicate the potential of the nanoparticle sensors for quantitative mapping of local molecular oxygen concentration.