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1,330 full-text articles. Page 48 of 49.

Tuning Quantum Dots Optical Properties By Temperature And Concentration Modulation, Amber Sexton 2010 Syracuse University

Tuning Quantum Dots Optical Properties By Temperature And Concentration Modulation, Amber Sexton

Syracuse University Honors Program Capstone Projects

Quantum dots have recently been awarded attention due to their tunable optical and spectroscopic properties. The optical and spectroscopic behavior of quantum dots was investigated as a function of mean particle size. Manipulation of the reaction conditions and constituents impact the controllability of size and surface conditions. Therefore, synthesis of CdSe and CdS semiconductor nanoparticles with tunable particle size were created using temperature, time, and composition as variables. Analytical techniques used to characterize the nanoparticles included fluorescence and electronic absorption. The effect of temperature, aside from changing the size of the particle, also eliminated defects on the surface and caused ...


Aqueous Raft Synthesis Of Stimuli-Responsive, Amphiphilic Block Copolymers And Self-Assembly Behavior In Solution And Incorporation Into Lbl Films, Matthew Grady Kellum 2010 University of Southern Mississippi

Aqueous Raft Synthesis Of Stimuli-Responsive, Amphiphilic Block Copolymers And Self-Assembly Behavior In Solution And Incorporation Into Lbl Films, Matthew Grady Kellum

Dissertations

Of all the living radical polymerization techniques, reversible addition– fragmentation chain transfer (RAFT) polymerization is arguably the most versatile in terms of the reaction conditions (e.g. temperature and solvent selection), monomer selection (e.g. neutral, anionic, cationic, and zwitterionic), and purification. Since the introduction of RAFT in 1998, the McCormick research group and others including the Lowe, Sumerlin, and Davis research groups have synthesized a wide range of (co)polymers with predetermined molecular weights, low polydispersities, and advanced architectures utilizing aqueous RAFT (ARAFT) polymerization. These research groups have also studied how various block copolymers exhibit stimuli-responsive behavior due to ...


Rational Design Of Self-Assembled Nanostructures Based On Polymers Synthesized Via Aqueous Reversible Addition-Fragmentation Chain Transfer Polymerization, Stacey Kirkland York 2010 University of Southern Mississippi

Rational Design Of Self-Assembled Nanostructures Based On Polymers Synthesized Via Aqueous Reversible Addition-Fragmentation Chain Transfer Polymerization, Stacey Kirkland York

Dissertations

Recent advances in reversible addition-fragmentation chain transfer (RAFT) polymerization have allowed the rational, bottom-up design of biorelevant assemblies. Utilizing foresight, polymers can be tailored to self-assemble into nano-, micro-, and macroscopic structures. Given the size scale on which rationally-designed polymers can be tailored, they hold significant promise in the biomedical field. For example, nanoscale materials can be designed to carry small-molecule and gene therapeutics while macroscopic structures can be tailored for cell growth scaffolds. The design process begins by selecting monomers, chain transfer agents, and reaction conditions which will yield the desired polymer architecture and composition.

The work herein builds ...


Synthesis, Characterization, And Deuterium Labeling Of Polyamides Studied By Nuclear Magnetic Resonance Spectroscopy, Christopher Allen Lange 2010 University of Southern Mississippi

Synthesis, Characterization, And Deuterium Labeling Of Polyamides Studied By Nuclear Magnetic Resonance Spectroscopy, Christopher Allen Lange

Dissertations

The synthesis, characterization, and deuterium labeling of polyamides have been investigated. In Chapter II, selective deuterium labeling of various polyamides was demonstrated via a facile method which does not require organic solvent or catalyst. Quantitative solution-state NMR analysis showed deuterium incorporation at the carbon alpha to the carbonyl ranged from 20-75%. Incorporation in ε-caprolactam increased with repeated treatments. Isotopic shift effects for the deuterated materials were additive for all sites within experimental error.

In Chapter III, the effect of stoichiometric imbalances on the polymerization of poly(dodecamethylene terephthalamide)was investigated. Molecular weight was varied by polymerizing the monomer salt with ...


Structure-Property Relationships In The Formation Of Polyphenylsulfone Molecular Composites And Nanocomposites, Paul Joseph Jones 2010 University of Southern Mississippi

Structure-Property Relationships In The Formation Of Polyphenylsulfone Molecular Composites And Nanocomposites, Paul Joseph Jones

Dissertations

As the constituent phases in a polymer composite approach the molecular level, specific phenomena occur that can lead to significant changes in material properties when only minimal quantities of the additive are incorporated into the polymer matrix. Molecular composite and nanocomposites are state-of-the-art polymeric materials that contain nanostructured additives effectively dispersed within polymer matrices. The properties of molecular composites and nanocomposites are directly related to the interactions of the nanostructured additive and the polymer matrix. Subtle changes to the nanostructured additive can have profound effects on the ultimate properties of the composite material. Therefore, understanding the structure-property relationships in these ...


Investigation Of Novel Quasiliving Polyisobutylene Chain-End Functionalization (Quenching) Methods, David Lee Morgan 2010 University of Southern Mississippi

Investigation Of Novel Quasiliving Polyisobutylene Chain-End Functionalization (Quenching) Methods, David Lee Morgan

Dissertations

This volume recounts efforts toward the development and understanding of chain functionalization techniques involving the direct addition of nucleophiles to quasiliving polyisobutylene (PIB). Nucleophiles included in the study were sterically hindered organic bases, (di)sulfides, N-substituted pyrroles, and alkoxybenzenes. A kinetic investigation of the end-quenching of TiCl4-catalyzed quasiliving PIB with sterically hindered amines was used to determine the mode of interaction with TiCl4 and the active species responsible for -proton abstraction. 2,5-disubstituted-N-hydropyrroles formed pyrrole-TiCl3 adducts that were active in formation of exo-olefin chain ends; whereas, with other sterically hindered amines, only an equilibrium fraction of the amine that did ...


Nanomaterials From Biologically Active Molecules: Self-Assembly And Molecular Recognition, Min Yu 2010 University of Southern Mississippi

Nanomaterials From Biologically Active Molecules: Self-Assembly And Molecular Recognition, Min Yu

Dissertations

This dissertation describes the development of molecular assemblies and molecular recognition of phospholipids (PLs) that exhibit potential applications in emerging nanotechnologies. It consists of two parts: (1) structural features of PLs responsible for recognition of synthetic copolymers, and (2) design, synthesis and analysis of magnetic nanotubes obtained from PLs with a common theme of colloidal synthesis served as a platform for film formation and nano-assemblies of nanotubes. Poly(methyl methacrylate/n-butyl acrylate) (p-MMA/nBA) colloidal particles that were stabilized by 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) PLs were synthesized, and upon the particle coalescence, PL stratification resulted in the formation of surface localized ...


Multi Stimuli-Responsive Copolymers Obtained From Colloidal Dispersions, Fang Liu 2010 University of Southern Mississippi

Multi Stimuli-Responsive Copolymers Obtained From Colloidal Dispersions, Fang Liu

Dissertations

This dissertation describes the design, synthesis, and development of multi stimuli-responsive random copolymers that exhibit collective responsiveness to temperature, pH or electromagnetic radiation. New colloidal particles of poly(N-(DL)-(1- Hydroxyymethyl) propylmethacrylamide/n-butyl acrylate) (p(DL-HMPMA/nBA) and poly(2-(N,N′-dimethylamino)ethyl methacrylate/n-butyl acrylate) (p(DMAEMA/nBA)) were synthesized, which upon coalesce to form solid continuous films. The presence of lower glass transition (Tg) nBA components not only facilitate film formation, but also provide sufficient free volume for polymer chain rearrangements. These studies showed that coalesced films exhibit 3D dimensional changes upon external stimuli, which are ...


Classification, Synthesis And Characterization Of Pyridyl Porphyrin Frameworks, Lucas D. DeVries 2010 University of Nebraska at Lincoln

Classification, Synthesis And Characterization Of Pyridyl Porphyrin Frameworks, Lucas D. Devries

Student Research Projects, Dissertations, and Theses - Chemistry Department

CLASSIFICATION, SYNTHESIS AND CHARACTERIZATION OF PYRIDYL PORPHYRIN FRAMEWORKS

Lucas D. DeVries, M.S. University of Nebraska, 2010 Adviser: Wonyoung Choe

Structural analysis of a solid-state material is vital because the structure often determines the physical (or chemical) properties of the material. An understanding of the relationship between structural components and bulk properties can be used to design materials with specific properties. To achieve such understanding, two things are required: a rigorous structural analysis method and a study of the properties of materials with noteworthy structural features.

In this thesis, the author reviews 44 pyridyl porphyrin frameworks in an effort to ...


Development Of A Scanning Angle Total Internal Reflection Raman Spectrometer, Kristopher J. McKee, Emily A. Smith 2010 Iowa State University

Development Of A Scanning Angle Total Internal Reflection Raman Spectrometer, Kristopher J. Mckee, Emily A. Smith

Chemistry Publications

A scanning angle total internal reflection (SATIR) Raman spectrometer has been developed for measuring interfacial phenomena with chemical specificity and high axial resolution perpendicular to the interface. The instrument platform is an inverted optical microscope with added automated variable angle optics to control the angle of an incident laser on a prism/sample interface. These optics include two motorized translation stages, the first containing a focusing lens and the second a variable angle galvanometer mirror. The movement of all instrument components is coordinated to ensure that the same sample location and area are probed at each angle. At angles greater ...


Dual-Action Hygienic Coatings: Benefits Of Hydrophobicity And Silver Ion Release And Surface Analysis, Niall Stobie, Brendan Duffy, John Colreavy, Patrick McHale, Steven Hinder, Declan McCormack 2010 Dublin Institute of Technology

Dual-Action Hygienic Coatings: Benefits Of Hydrophobicity And Silver Ion Release And Surface Analysis, Niall Stobie, Brendan Duffy, John Colreavy, Patrick Mchale, Steven Hinder, Declan Mccormack

Articles

Coatings that demonstrate reduced attachment of crystalline precipitates and the medical device colonising Staphylococcus epidermidis were prepared by the immobilisation of silver doped perfluoropolyether–urethane siloxane thin films on glass substrates. The presence of stratified hydrophobic perfluoropolyether groups protects the coating surface from the attachment of crystalline hydrophilic species such as chlorides and phosphates, whilst silver ion release inhibited attachment of S. epidermidis and subsequent biofilm formation in vitro. The release of silver ions protects the perfluoro groups from the hydrophobic interactions of S. epidermidis cells, which can reduce the hydrophobicity of the protective coating. These coatings also exhibited significant ...


Investigation Of Deactivation Of Transition Metal Oxide Catalysts Supported On Γ-Al2o3 During Catalytic Oxidation Of Some Oxygen Containing Vocs In A Tubular Reactor, Hosein Afshary 2010 University of Tabriz

Investigation Of Deactivation Of Transition Metal Oxide Catalysts Supported On Γ-Al2o3 During Catalytic Oxidation Of Some Oxygen Containing Vocs In A Tubular Reactor, Hosein Afshary

Hosein Afshary

It is necessary to decrease the emission of Volatile organic compound ( VOCs ) to air and among of all destructive techniques used for decreasing these compounds, Catalytic Oxidation is considered a suitable technique but deactivation of catalysts through catalytic processes is one of the major problems and most be studied. In this Project, at First, gamma alumina supported metal oxide catalysts were made and also industrial Pt catalyst was prepared. Then structure of these catalysts was studied using XRD, SEM and FT-IR techniques. These techniques approved the nanostructure of catalysts. The amount of supported metals in each catalyst was determined by ...


Microscopic Formulation Of The Zimm-Bragg Model For The Helix-Coil Transition, A. V. Badasyan, A. Giacometti, Y. S. Mamasakhlisov, V. F. Morozov, Albert S. Benight 2010 Portland State University

Microscopic Formulation Of The Zimm-Bragg Model For The Helix-Coil Transition, A. V. Badasyan, A. Giacometti, Y. S. Mamasakhlisov, V. F. Morozov, Albert S. Benight

Chemistry Faculty Publications and Presentations

A microscopic spin model is proposed for the phenomenological Zimm-Bragg model for the helix-coil transition in biopolymers. This model is shown to provide the same thermophysical properties of the original Zimm-Bragg model and it allows a very convenient framework to compute statistical quantities. Physical origins of this spin model are made transparent by an exact mapping into a one-dimensional Ising model with an external field. However, the dependence on temperature of the reduced external field turns out to differ from the standard one-dimensional Ising model and hence it gives rise to different thermophysical properties, despite the exact mapping connecting them ...


Simple Room-Temperature Preparation Of High-Yield Large-Area Graphene Oxide, Huang Nay Ming 2010 University of Malaya

Simple Room-Temperature Preparation Of High-Yield Large-Area Graphene Oxide, Huang Nay Ming

Huang Nay Ming

Graphene has attracted much attention from researchers due to its interesting mechanical, electrochemical, and electronic properties. It has many potential applications such as polymer filler, sensor, energy conversion, and energy storage devices. Graphene-based nanocomposites are under an intense spotlight amongst researchers. A large amount of graphene is required for preparation of such samples. Lately, graphene-based materials have been the target for fundamental life science investigations. Despite graphene being a much sought-after raw material, the drawbacks in the preparation of graphene are that it is a challenge amongst researchers to produce this material in a scalable quantity and that there is ...


Highly Active Heterogeneous Palladium Nanoparticle Catalysts For Homogeneous Electrophilic Reactions In Solution And The Utilization Of A Continuous Flow Reactor, Wenyu Huang, Jack Hung Chang Liu, Pinar Alayoglu, Yimin Li, Cole A. Whitman, Chia-Kuang Tsung, F. Dean Toste, Gabor A/ Somorjai 2010 University of California - Berkeley

Highly Active Heterogeneous Palladium Nanoparticle Catalysts For Homogeneous Electrophilic Reactions In Solution And The Utilization Of A Continuous Flow Reactor, Wenyu Huang, Jack Hung Chang Liu, Pinar Alayoglu, Yimin Li, Cole A. Whitman, Chia-Kuang Tsung, F. Dean Toste, Gabor A/ Somorjai

Wenyu Huang

highly active heterogeneous Pd-nanoparticle catalyst for the intramolecular addition of phenols to alkynes was developed and employed in a continuous flow reaction system. Running the reaction in flow mode revealed reaction kinetics, such as the activation energy and catalyst deactivation, and provides many potential practical advantages.


Vinyl Cations Substituted With Β Π-Donors Have Triplet Ground States, Arthur Winter, Daniel E. Falvey 2010 University of Maryland - College Park

Vinyl Cations Substituted With Β Π-Donors Have Triplet Ground States, Arthur Winter, Daniel E. Falvey

Arthur Winter

Computations at the CASPT2, CBS-QB3, and B3LYP levels of theory demonstrate that β-substitution of vinyl cations with π-donors switches the ground state of these ions from the familiar closed-shell singlet state to a carbene-like triplet state similar to the electronic state of triplet phenyl cations. Although the parent vinyl cation is a ground-state singlet species with a very large energy gap to the lowest energy triplet state, substituting the β hydrogens with just one strong π-donor (e.g., NH2, NMe2, OMe) or two moderate π-donors (e.g., F, OH, Ar, vinyl) makes the triplet state the computed ground electronic state ...


Furan Hydrogenation Over Pt(111) And Pt(100) Single-Crystal Surfaces And Pt Nanoparticles From 1 To 7 Nm: A Kinetic And Sum Frequency Generation Vibrational Spectroscopy Study, Christopher J. Kliewer, Cesar Aliaga, Marco Bieri, Wenyu Huang, Chia-Kuang Tsung, Jennifer B. Wood, Kyriankos Komvopoulos, Gabor A. Somorjai 2010 University of California - Berkeley

Furan Hydrogenation Over Pt(111) And Pt(100) Single-Crystal Surfaces And Pt Nanoparticles From 1 To 7 Nm: A Kinetic And Sum Frequency Generation Vibrational Spectroscopy Study, Christopher J. Kliewer, Cesar Aliaga, Marco Bieri, Wenyu Huang, Chia-Kuang Tsung, Jennifer B. Wood, Kyriankos Komvopoulos, Gabor A. Somorjai

Wenyu Huang

Sum frequency generation surface vibrational spectroscopy and kinetic measurements using gas chromatography have been used to systematically study the adsorption and hydrogenation of furan over Pt(111) and Pt(100) single-crystal surfaces and size-controlled 1.0-nm, 3.5-nm and 7.0-nm Pt nanoparticles at Torr pressures (10 Torr of furan, 100 Torr of H2) to form dihydrofuran, tetrahydrofuran, and the ring-cracking products butanol and propylene. As determined by SFG, the furan ring lies parallel to all Pt surfaces studied under hydrogenation conditions. Upright THF and the oxametallacycle intermediate are observed over the nanoparticle catalysts under reaction conditions. Butoxy increases in ...


Size Effect Of Ruthenium Nanoparticles In Catalytic Carbon Monoxide Oxidation, Sang Hoon Joo, Jeong Y. Park, J. Russell Renzas, Derek R. Butcher, Wenyu Huang, Gabor A. Somorjai 2010 University of California - Berkeley

Size Effect Of Ruthenium Nanoparticles In Catalytic Carbon Monoxide Oxidation, Sang Hoon Joo, Jeong Y. Park, J. Russell Renzas, Derek R. Butcher, Wenyu Huang, Gabor A. Somorjai

Wenyu Huang

Carbon monoxide oxidation over ruthenium catalysts has shown an unusual catalytic behavior. Here we report a particle size effect on CO oxidation over Ru nanoparticle (NP) catalysts. Uniform Ru NPs with a tunable particle size from 2 to 6 nm were synthesized by a polyol reduction of Ru(acac)3 precursor in the presence of poly(vinylpyrrolidone) stabilizer. The measurement of catalytic activity of CO oxidation over two-dimensional Ru NPs arrays under oxidizing reaction conditions (40 Torr CO and 100 Torr O2) showed an activity dependence on the Ru NP size. The CO oxidation activity increases with NP size, and ...


Seedless Polyol Synthesis And Co Oxidation Activity Of Monodisperse (111)- And (100)-Oriented Rhodium Nanocrystals In Sub-10 Nm Sizes, Yawen Zhang, Michael E. Grass, Wenyu Huang, Gabor A. Somoraji 2010 University of California - Berkeley

Seedless Polyol Synthesis And Co Oxidation Activity Of Monodisperse (111)- And (100)-Oriented Rhodium Nanocrystals In Sub-10 Nm Sizes, Yawen Zhang, Michael E. Grass, Wenyu Huang, Gabor A. Somoraji

Wenyu Huang

Monodisperse sub-10 nm (6.5 nm) sized Rh nanocrystals with (111) and (100) surface structures were synthesized by a seedless polyol reduction in ethylene glycol, with poly(vinylpyrrolidone) as a capping ligand. When using [Rh(Ac)2]2 as the metal precursor, (111)-oriented Rh nanopolyhedra containing 76% (111)-twinned hexagons (in 2D projection) were obtained; whereas, when employing RhCl3 as the metal precursor in the presence of alkylammonium bromide, such as tetramethylammonium bromide and trimethyl(tetradecyl)ammonium bromide, (100)-oriented Rh nanocubes were obtained with 85% selectivity. The {100} faces of the Rh nanocrystals are stabilized by chemically adsorbed ...


Corrosion Protection Of Aa 2024-T3 Aluminium Alloys Using 3, 4-Diaminobenzoic Acid Chelated Zirconium-Silane Hybrid Sol-Gels, P.C. Rajath Varma, John Colreavy, John Cassidy, Mohamed Oubaha, Colette McDonagh, Brendan Duffy 2010 Dublin Institute of Technology

Corrosion Protection Of Aa 2024-T3 Aluminium Alloys Using 3, 4-Diaminobenzoic Acid Chelated Zirconium-Silane Hybrid Sol-Gels, P.C. Rajath Varma, John Colreavy, John Cassidy, Mohamed Oubaha, Colette Mcdonagh, Brendan Duffy

Articles

Organic-inorganic polymers formed by hydrolysis/condensation reactions of alkoxide precursors, such as organically modified silanes (Ormosils) have found applications as electronic, optical and protective coatings. Such coatings possess important characteristics such as chemical stability, physical strength and scratch resistance. Further performance improvement is achieved through the incorporation of zirconium and titanium based nanoparticles, also formed through the sol-gel process. However due to the inherent difference in the reactivity of the precursors, the hydrolysis of each precursor must be carried out separately before being combined for final condensation. Zirconium precursors are commonly chelated using acetic acid or acetyl acetonate prior to ...


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