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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Reactivity of rhodium-heteroatom bonds: from catalytic bond activation to new strategies for olefin functionalization

van Rooy, Sara Emily 05 1900 (has links)
Rhodium complexes bearing multidentate nitrogen donor ligands were investigated for their ability to promote alkyne and olefin functionalization reactions. This thesis work is comprised of two projects in which rhodium-heteroatom reactivity is investigated: P-H bond activation reactions and olefin functionalizations via rhodaoxetane intermediates. [Tp*Rh(PPh3)2] [Tp* = hydrotris(3,5-dimethylpyrazolyl)borate] and [Tp*Rh(cod)]2 (cod = cyclooctadiene) were evaluated for their activity in alkyne hydrophosphinylation in comparison to known catalysts for this reaction. [Tp*Rh(PPh3)2]and [Tp*Rh(cod)]2 were both shown to effect hydrophosphinylation of 1-octyne with diphenylphosphine oxide with high regioselectivity but moderate yields in comparison with Wilkinson's catalyst [C1Rh(PPh3)3]. [Tp*Rh(PPh3)2] was further shown to effect hydrophosphinylation of a range of aromatic and aliphatic alkynes with diphenylphosphine oxide, in each case exclusively providing the E-linear vinylphosphineoxide product. 1H and 31P NMR spectroscopy provided evidence that alkyne hydrophosphinylation in the presence of pyrazolylborate rhodium complexes follows an analogous mechanism to that proposed for this reaction catalyzed by [C1Rh(PPh3)3] or[C1Rh(cod)]2. The 2-rhodaoxetane [(TPA)Rhmec2_,-4u, 0-2-oxyethypr BPh4- (TPA = tris[(2-pyridal)methyl]amine) was investigated for its potential as an intermediate in proposed functionalization reactions of olefins. RTPA)Rh111(K2-C,0-2-oxyethyl)]+ BPh4- was prepared by two published methods with limited success. A third method involved the use of nitrous oxide to oxygenate [(12-ethene)(K4-TPA)Rh1]+ to RTPA)Rh1110(-2-C,0-2-oxyethyDr. Only a trace amount of [(TPA)Rhmoc2 -C,0-2-oxyethypr was observed in the 1I-1 NMR spectrum of this reaction mixture. Initial test reactions of [(TPA)Rhilioc2_C,0-2-oxyethypr combined with substrates (aniline, toluenesulfonamide, phenylboronic acid, or benzaldehyde) were inconclusive since the results were obscured by the impurity of the samples.
2

Reactivity of rhodium-heteroatom bonds: from catalytic bond activation to new strategies for olefin functionalization

van Rooy, Sara Emily 05 1900 (has links)
Rhodium complexes bearing multidentate nitrogen donor ligands were investigated for their ability to promote alkyne and olefin functionalization reactions. This thesis work is comprised of two projects in which rhodium-heteroatom reactivity is investigated: P-H bond activation reactions and olefin functionalizations via rhodaoxetane intermediates. [Tp*Rh(PPh3)2] [Tp* = hydrotris(3,5-dimethylpyrazolyl)borate] and [Tp*Rh(cod)]2 (cod = cyclooctadiene) were evaluated for their activity in alkyne hydrophosphinylation in comparison to known catalysts for this reaction. [Tp*Rh(PPh3)2]and [Tp*Rh(cod)]2 were both shown to effect hydrophosphinylation of 1-octyne with diphenylphosphine oxide with high regioselectivity but moderate yields in comparison with Wilkinson's catalyst [C1Rh(PPh3)3]. [Tp*Rh(PPh3)2] was further shown to effect hydrophosphinylation of a range of aromatic and aliphatic alkynes with diphenylphosphine oxide, in each case exclusively providing the E-linear vinylphosphineoxide product. 1H and 31P NMR spectroscopy provided evidence that alkyne hydrophosphinylation in the presence of pyrazolylborate rhodium complexes follows an analogous mechanism to that proposed for this reaction catalyzed by [C1Rh(PPh3)3] or[C1Rh(cod)]2. The 2-rhodaoxetane [(TPA)Rhmec2_,-4u, 0-2-oxyethypr BPh4- (TPA = tris[(2-pyridal)methyl]amine) was investigated for its potential as an intermediate in proposed functionalization reactions of olefins. RTPA)Rh111(K2-C,0-2-oxyethyl)]+ BPh4- was prepared by two published methods with limited success. A third method involved the use of nitrous oxide to oxygenate [(12-ethene)(K4-TPA)Rh1]+ to RTPA)Rh1110(-2-C,0-2-oxyethyDr. Only a trace amount of [(TPA)Rhmoc2 -C,0-2-oxyethypr was observed in the 1I-1 NMR spectrum of this reaction mixture. Initial test reactions of [(TPA)Rhilioc2_C,0-2-oxyethypr combined with substrates (aniline, toluenesulfonamide, phenylboronic acid, or benzaldehyde) were inconclusive since the results were obscured by the impurity of the samples.
3

Reactivity of rhodium-heteroatom bonds: from catalytic bond activation to new strategies for olefin functionalization

van Rooy, Sara Emily 05 1900 (has links)
Rhodium complexes bearing multidentate nitrogen donor ligands were investigated for their ability to promote alkyne and olefin functionalization reactions. This thesis work is comprised of two projects in which rhodium-heteroatom reactivity is investigated: P-H bond activation reactions and olefin functionalizations via rhodaoxetane intermediates. [Tp*Rh(PPh3)2] [Tp* = hydrotris(3,5-dimethylpyrazolyl)borate] and [Tp*Rh(cod)]2 (cod = cyclooctadiene) were evaluated for their activity in alkyne hydrophosphinylation in comparison to known catalysts for this reaction. [Tp*Rh(PPh3)2]and [Tp*Rh(cod)]2 were both shown to effect hydrophosphinylation of 1-octyne with diphenylphosphine oxide with high regioselectivity but moderate yields in comparison with Wilkinson's catalyst [C1Rh(PPh3)3]. [Tp*Rh(PPh3)2] was further shown to effect hydrophosphinylation of a range of aromatic and aliphatic alkynes with diphenylphosphine oxide, in each case exclusively providing the E-linear vinylphosphineoxide product. 1H and 31P NMR spectroscopy provided evidence that alkyne hydrophosphinylation in the presence of pyrazolylborate rhodium complexes follows an analogous mechanism to that proposed for this reaction catalyzed by [C1Rh(PPh3)3] or[C1Rh(cod)]2. The 2-rhodaoxetane [(TPA)Rhmec2_,-4u, 0-2-oxyethypr BPh4- (TPA = tris[(2-pyridal)methyl]amine) was investigated for its potential as an intermediate in proposed functionalization reactions of olefins. RTPA)Rh111(K2-C,0-2-oxyethyl)]+ BPh4- was prepared by two published methods with limited success. A third method involved the use of nitrous oxide to oxygenate [(12-ethene)(K4-TPA)Rh1]+ to RTPA)Rh1110(-2-C,0-2-oxyethyDr. Only a trace amount of [(TPA)Rhmoc2 -C,0-2-oxyethypr was observed in the 1I-1 NMR spectrum of this reaction mixture. Initial test reactions of [(TPA)Rhilioc2_C,0-2-oxyethypr combined with substrates (aniline, toluenesulfonamide, phenylboronic acid, or benzaldehyde) were inconclusive since the results were obscured by the impurity of the samples. / Science, Faculty of / Chemistry, Department of / Graduate
4

Macro-, Micro- and Nanospheres from Cellulose : Their Preparation, Characterization and Utilization

Carrick, Christopher January 2014 (has links)
The structure of a polymeric material has a great influence in many fundamental scientific areas as well as in more applied science, since it affects the diffusion, permeability, mechanical strength, elasticity, and colloidal properties of the materials. The results in this thesis demonstrate that it is possible to fabricate solid and hollow cellulose spheres with a cellulose shell and encapsulated gas, liquid or solid particles and with a sphere size ranging from a few hundreds of nanometres to several millimetres, all with a tailored design and purpose. The sizes of the different spheres have been controlled by three different preparation methods: large cellulose macrospheres by a solution solidification procedure, hollow micrometre-sized cellulose spheres by a liquid flow-focusing technique in microchannels, and nanometre-sized cellulose spheres by a membrane emulsification technique.  The spheres were then modified in different ways in order to functionalize them into more advanced materials. This thesis demonstrates how to control the cellulose sphere dimensions and the wall-to-void volume ratio, the elasticity and the functionality of the spheres as such, where they were prepared to be pH-responsive, surface specific and X-ray active. These modifications are interesting in several different types of final materials such as packaging materials, drug release devices or advanced in vivo diagnostic applications. In the more fundamental science approach, surface-smooth solid cellulose spheres were prepared for characterization of the macroscopic work of adhesion when a cellulose surface is separated from another material. Using these ultra-smooth macroscopic cellulose probes, it is possible to measure the compatibility and the surface interactions between cellulose and other materials which provide an important tool for incorporating cellulose into different composite materials. / <p>QC 20140829</p>
5

Synthesis, Characterization, and Mechanism Study of Carbon-Encapsulated Copper Nanoparticles

Leng, Weiqi 14 August 2015 (has links)
In this project, the synthesis of carbon encapsulated copper nanoparticles using sustainable bioproducts as raw material was systematically studied. The synthesis mechanism, process parameters, and functionalization of carbon encapsulated copper nanoparticles were well established. In a preliminary study, carbon encapsulated copper nanoparticles were successfully synthesized at 1000 ºC, 1h, 20 ºC/min, and 1800 sccm argon gas flow rate using BCL-DI lignin as the carbon source. Carbon encapsulated copper nanoparticles were mainly located at defect sites. Copper was found not tightly encapsulated by graphene shells. The carbon encapsulated copper nanoparticles were uniformly distributed. The conversion of copper ions into copper atoms occurred at above 300 ºC, with the company of decomposition of BCL-DI lignin into CO, CO2, and hydrocarbon gases. The growth of graphene layers was proposed to start above 300 ºC. TEM images illustrated the onset of growth of graphene at the edge of the surface at 400 ºC, and the formation of graphene bands at 500 ºC. Copper catalyst continued to facilitate the decomposition of lignin functional groups at 600 ºC. Further increasing the temperature retarded the degradation of lignin, while assisted the reconstruction of the defective sites of the graphene layers, producing higher quality products. Plastic film phase of lignin dominated on the synthesis of carbon encapsulated copper nanoparticles, while gaseous phase had little impact. The orthogonal experiment revealed that temperature played the most important role in the growth of graphene: high temperature was preferred in order to obtain less defective sites. The optimum synthesis parameters were suggested as 1000 °C, 30 min duration time, 20 °C/min temperature rising ramp, and 1200 sccm argon gas flow rate. Post heat treatment was proved to be a feasible way to improve the crystallinity of graphite. Amorphous carbon was removed or converted into crystalline graphite under heat and oxygen. FTIR spectra confirmed the covalent linkages between carbon encapsulated copper nanoparticles and N-methyl-2-pyrrolidone and polyvinylpyrrolidone, indicating a successful functionalization. This study has presented a homogeneous carbon encapsulated copper nanoparticles solution in water and ethanol, and paved ways for further functionalization of CECNs.
6

Development of Catalyst Systems for Regio- and Enantioselective Transformations of Amine and Ether C-H Bonds:

Yesilcimen, Ahmet Selman January 2022 (has links)
Thesis advisor: Masayuki Wasa / This dissertation describes the development of novel catalyst systems that could promote the regio- and enantioselective transformations of C-H bonds contained in N-alkylamines and ethers through Lewis acid-mediated hydride abstraction processes. The progress made in C-H functionalization of N-alkylamines and ethers that served as the intellectual foundation of this dissertation research are summarized in Chapter 1. Despite notable advances, the development of broadly applicable, enantioselective, and catalytic protocols to functionalize C-H bonds in N-alkylamines and ethers with high regio- and stereo-selectivity was regarded as an unsolved problem when we started this dissertation research. In an effort to overcome these fundamental limitations, we first identified a B(C6F5)3/Cu-PyBOX cooperative catalyst system for the enantioselective conversion of a-amino C-H bonds through the generation of an iminium by (F5C6)3B-catalyzed hydride abstraction process (Chapter 2). We then envisioned that in situ generated iminium ions could be further deprotonated to furnish an enamine intermediate, which may react with electrophilic species for a-amino C-H functionalization. The design and development of such a catalyst system were discussed in Chapter 3. Finally, we disclose enantioselective Cu–BOX-catalyzed hetero Diels-Alder reactions of enol ethers generated through Ph3C+-mediated oxidation of alkyl ethers. (Chapter 4). / Thesis (PhD) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
7

Stereoselective Functionalization of Carbonyl Compounds and N-Alkylamines Promoted by Cooperative Catalysts:

Chan, Jessica Zee January 2020 (has links)
Thesis advisor: Masayuki Wasa / This dissertation describes the development of cooperative catalyst systems for the functionalization of monocarbonyl compounds and stereoselective transformations of alpha-C–H bonds of N-alkylamines, inspired by the concepts of frustrated Lewis pairs (FLPs). Prior to this dissertation research, practical and broadly applicable C–C and C–heteroatom bond forming reactions involving the FLP complexes that provide synthetically desirable products with high enantioselectivity remained to be developed. Chapter 1 of this dissertation describes the recent advances in the transformations involving FLPs and B(C₆F₅)₃-catalyzed reactions. Inspired by the unique capability of FLP catalysts to activate otherwise unreactive molecules, and circumvent undesirable acid–base complexation, we have developed potent cooperative acid/base catalysts for C–C bond forming reactions of various monocarbonyl compounds and an appropriate electrophile, which will be discussed in Chapter 2. Another reactivity of FLPs to be explored has to do with the catalytic and enantioselective reactions of N-alkylamines, where two Lewis acid catalysts with potentially overlapping functions, work cooperatively to activate alpha-amino C–H bonds and promote the enantioselective C–C bond forming reaction between N-alkylamines and a nucleophilic species. In Chapter 3, B(C₆F₅)₃-catalyzed union of N-alkylamines and silicon enolates followed by the enantioselective B(C₆F₅)₃/Mg–PyBOX-catalyzed alpha-alkylation of N-alkylamines and alpha,beta-unsaturated compounds to form beta-amino carbonyl compounds will be described. In Chapter 4, B(C₆F₅)₃/Cu–PyBOX-catalyzed alpha-C–H alkynylation of N-alkylamines and the applications in late-stage functionalization and stereoselective synthesis will be discussed. / Thesis (PhD) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
8

FUNCTIONALIZATION OF SINGLE WALL CARBON NANOTUBES USING RF-PLASMA: THE ROLE OF DEFECTS IN SIDEWALL FUNCTIONALIZATION

JAYASINGHE, CHAMINDA 05 October 2007 (has links)
No description available.
9

Synthesis, characterization and anticancer effects of quantum dots in neuroblastoma and glioblastoma cell lines

Lasher, Sashca Yosima January 2018 (has links)
>Magister Scientiae - MSc / Introduction: Nanoparticles (NPs) are gaining increased popularity for cancer treatment, especially the multifunctional nanoparticles like Quantum dots (QDs) which have a wide range of applications in nanotheranostics, cell imaging and targeted drug delivery to cancerous tissue. QDs comprise of very tiny crystals of a semiconductor material (diameter: 2-10 nm) capable of producing bright, intensive and size-tuneable near-infrared fluorescence emissions. In particular, 3-mercaptopropionic acid -capped Cadmium Telluride Quantum Dots with a zinc sulphide shell (MPA-capped CdTe/ZnS QDs), are known to be very stable, highly photoluminescent, less toxic with long-lasting “fluorophore” effects, thus making them the preferred QDs for this study. Aims: To synthesize and characterize biocompatible MPA-capped CdTe/ZnS QDs to determine size range, polydispersity index (PdI), zeta (ζ) potential, photoluminescence (PL) spectra, stability in various milieus as well as to evaluate the effects of the synthesized QDs on the viability and morphology of neuroblastoma (NB) and glioblastoma (GB) cell lines using the WST-1 cell viability assay, imaging and cell cycle analysis. Materials and methods: MPA-capped CdTe/ZnS QDs were synthesized and analysed with the Zetasizer to determine ζ-potential, hydrodynamic (hd) size and PdI, while high resolutiontransmission electron microscopy (HR-TEM) was used to validate the hd size and elemental composition using energy dispersive X-ray (EDX) spectra. Pl absorption and emission spectra were obtained with a fluorometer and stability studies were done using UV-Vis spectroscopy, permitting further biological evaluation. A concentration range of 5-20μg/ml QDs was exposed to U87 and SH-SY5Y cancer cell lines to determine biological effects at different time points, using the WST-1 assay. Confocal fluorescence microscopy was used to establish uptake and cellular localization of the QDs, cell morphology was visualized with an inverted microscope while cell cycle distribution analysis was done using the C6 flow cytometer.
10

Multifunctional electrospun nanofibers incorporated with an anti-infection drug and immobilized with proteins

Zhou, Shufei 16 August 2010 (has links)
Electrospinning is a novel technique to fabricate non-woven fibers with sizes ranging from nano to micrometers. Polymers have been electrospun into nanofibers that can be developed into desirable materials with excellent biocompatibility and biodegradability for biomedical applications in wound healing and tissue regeneration. These nanofiber materials can be further functionalized to be loaded with bioactive molecules, including antibacterial agents, functional proteins that promote tissue reconstruction while protect host tissues from contamination. This study focuses on the development of multifunctional nanofibers that are incorporated with antibacterial drug(s) and immobilized with bioactive proteins. These nanofibers are potentially useful for wound care and tissue engineering scaffolding to provide both infection control and promotion of wound healing or tissue regenerations.

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