Dissertations / Theses on the topic 'Oxime Chemistry'

Chapter One reviews the literature, discussing the role of nucleophilic additions to oximes and their derivatives. This introduction is primarily concerned with the formation of new carbon–carbon bonds, this is achieved by the addition of organometallic reagents to the carbon–nitrogen double bond functionality of oximes and their derivatives.

Organophosphorus compounds (OPs) are used as pesticides, e.g. parathion, which is converted in the body to paraoxon, and chemical warfare nerve agents, such as sarin, soman, cyclosarin, VX, and tabun. Even small amounts of OP exposure can be fatal, depending on the toxicity of the compound. Great stocks of highly toxic chemical warfare nerve agents exit around the world and are considered a serious threat to national security and international stability. OPs exert their toxicity by covalent irreversible inhibition of acetylcholinesterase (AChE) that prevents the enzyme from hydrolyzing acetylcholine (ACh), a neurotransmitter in the central and peripheral nervous systems (CNS and PNS). Therefore, ACh accumulates in the cholinergic synapses throughout the body, which results in overstimulation of the ACh receptors. Removal of the phosphyl moiety from the OP-bound AChE active site has been a promising method to restore AChE’s catalytic activity. However, a secondary process called aging also occurs in the OP-AChE complex. Once aging occurs, currently available oximes are ineffective in removing the phosphyl moiety from the enzyme’s active site, and hence are ineffective as antidotes against the aged enzyme. Several families of alkylating and acylating agents including several classes of agents that combine alkylating moieties with known active site or peripheral cite (PAS) binding motifs were synthesized and evaluated. The general aim of the research was that successful alkylation or acylation of the phosphonate monoanion of aged AChE would produce neutral phosphyl complexes that would either spontaneously reactivate or would be reactivatable in the presence of oxime antidotes. Methoxylamine analogs of the oxime antidote 2-PAM were synthesized with the aim that methyl transfer to the aged AChE adduct would produce a neutral phosphyl AChE adduct simultaneously with 2-PAM in situ, and subsequent 2-PAM nucleophilic attack would reactivate the newly formed neutral phosphyl-AChE adduct. However, none of these 2-PAM analogs resurrected the activity of aged AChE. Another strategy for resurrecting the activity of aged AChE utilizes N-methylpyridiniums that are substituted at the 2-position with a beta-lactam moiety. For these compounds, opening of the electrophilic beta-lactam unmasks a nucleophilic amidine function which could putatively attack at phosphorus to expel the free enzyme. For this class of agents, only the active site directed compound that possessed the 5-CF₃ substituent showed possible resurrection of the activity of aged AChE, though activities in both the control and treated samples were low. Methyl transfers are common in Nature, and the natural transfer agent is S-adenosylmethionine, a sulfonium methyl donor. Consequently, the array of sulfonium compounds were evaluated on the expectation that they would bind to the AChE active site and transfer a methyl group to the phosphonate monoanion of the aged enzyme. Though high-affinity binding was noted for these compounds, none of these resurrected the activity of the aged AChE complex. Finally, several selected agents were evaluated on reactivating the initial OP-AChE complex before aging has occurred. It was observed that degraded samples of selected inhibitors are capable of reactivating initial complexes of sarin and soman inhibited AChE at low concentration that is an important character of efficient reactivators. However, the structure of reactivator is still unknown. Two major challenges still face researchers in the quest to design effective medicinal agents for counteracting poisoning by AChE-inhibiting nerve agents. The first is that there is no universal oxime antidote. Oximes that are effective against certain nerve agents are ineffective against others. The second is that, despite extensive efforts that span two generations, aged phosphyl-AChE adducts have never been reactivated. However, given the powerful tools of modern structural biology, medicinal chemistry and molecular biology, there is still hope that these considerable challenges can be met.

5-Acatylamino-l,2-benzoquinone 2-oxine [5-AcqoH] results from the direct nitrosation of 3-acatylaminophenol together with its isomer 3-acetylamino-l,4-benzoquinone 4-oxine [3-AcqoH]. The quinone oximic structure of the former has been indicated by i.r. and n.m.r. studies. In the case of 3-AcqoH this type of structure has been established by X-ray crystallography. Following a brief review of quinone oxinic complexes, a study of the synthesis, properties and structure of Cu(II), Ni(II), Co(III), and Mn(III) complexes of 5-AcqoH is presented. The complexes Ni(5-Acqo)2.nH2O (n = 2-6), Cu(5-Acqo)2, Co(5-Acqo)3, and Mn(5-Acqo)2, .H2O were prepared by the direct reaction of 5-AcqoH with the appropriate metal(II) chloride or by the nitrosation of 3-acetylaminophenol in the presence of the metal salt. Co(5-Acqo)3 was also prepared by the reaction of the ligand with Na3[Co(NO2)6]. The complex Na(Co(5-Acqo)2 (NO2)2 ], resulted from the nitrosation of Na3(Co(NO2)6] in the presence of 3-acetylaminophenol. Pyrolysis of Ni(5-Acqo)2.6H2O gave Ni(5-Acqo)2. The complexes Cu(5-Acqo)2 and Ni(5-Acqo)2.nH2O (n = 0, 2-6) reacted with pyridine and 2,2-dipyridyl to give adducts whereas the complexes of M(5-Acqo)3 (M = Co, Mn) showed no reaction with pyridine. Magnetochemical measurements, indicated that all complexes, [except Ni(5-Acqo)2], are magnetically dilute and hence monomeric. Ni(5-Acqo)2 complex has a subnormal magnetic moment due to association. The diamagnetism of Co(5-Acqo)3 and the low spin configuration of Mn(5-Acqo)3.H2O are indicative of the strong field character of the ligand. COSY, H- and C n.m.r. studies have shown that Co(5-Acqo)3 is a mixture of facial and meridial isomers. For all complexes i.r. studies indicate the involvement of the ring CO in bonding. Their electronic spectra show strong absorption in the u.v. region which tails into the visible but d - d transitions have been clearly Identified for Ni(5-Acqo)2.6H20 and Mn(5-Acqo)3 .H20. Reexamination of the reaction of several complexes of type M(Rqo)2 [M = Ni or Cu) with dimethyl acetylenedicarboxylate has confirmed the occurence of cycloaddition and the formation of oxazine. A metal-containing product, M(II)(butynedioate), and in some cases an additional organic product, l,4-benoxazin-2-one, have been isolated. Mechanistic appraisals for the 1,4-benoxazinone formation are presented and the structure of one has been elucidated by X-ray crystallography. The reaction of the new complex Cu(5-Acqo)2 with DMAD leads to analogous products. The reaction of the complexes M(l-nqo)2 [M = Cu, Ni) with methyl propiolate give the hydrated M(II)(propynoate)2 and oxazine.

Pyrrolo[1,2-a]pyrazine is one of the isomers of pyrolodiazine family. Pyrrolo[1,2-a]pyrazine possesses a bicyclic heteroaromatic structure that have 10 electrons. It has various biological importances in synthetic chemistry
therefore, many different approaches to generate this skeleton have been developed so far. In this study, our prior aim was to develop a new synthetic methodology for the formation of pyrrolo[1,2-a]pyrazine moiety. In the first part of this focus, the starting compound, methyl 2-(2-methoxy-2-oxoethyl)-1-(prop-2-yn-1-yl)-1H-pyrrole-3-carboxylate was successfully synthesized, then the conversion of the ester group at the lower arm to the amine group was carried out. Heteroatom cyclization catalyzed by CuI afforded the desired substituted pyrrolo[1,2-a]pyrazine structure. In the second part, it was aimed to synthesize new compounds with unusual structures which are not described in the literature
namely, as pyrrolo[1,2-a]pyrazine N-oxide. In this direction, first pyrrole was submitted to Vilsmeier-Haack reaction to attach a formyl group at C-2. Substitution reaction then effectively gave 1-(prop-2-yn-1-yl)-1H-pyrrole-2-carbaldehyde, which was a key molecule to synthesize the aldoxime. AuCl3 catalyzed cyclization of the corresponding oxime afforded pyrrolo[1,2-a]pyrazine N-oxide. In the next step, Sonogashira coupling reactions were carried out to obtain terminal alkynes (RC&equiv
CR'
) starting from 1-(prop-2-yn-1-yl)-1H-pyrrole-2-carbaldehyde. The aim of this part was to study the effect of aryl groups to the activated alkyl functional group by a metal catalyst. In this case, unexpected oxime-oxime transformation was observed, which is unprecedented in the literature

Doctor of Philosophy
Department of Chemistry
Christer B. Aakeröy
Co-crystallization allows the manipulation of physical properties of a given compound without affecting its chemical behavior. The ability to predict hydrogen bonding interactions, provides means to the rational design of supramolecular architectures. It also makes it possible to select with a degree of accuracy, a few co-formers that have a high probability of forming co-crystals with a compound of interest, instead of blindly screening against a large number of candidates. To study the effects of changing electronic environment on the ability to form co-crystals, five symmetric dioximes of different hydrogen bond donating ability were synthesized with different functional groups on the carbon α to the oxime moiety. It was shown that the supramolecular yield increase with the positive MEP value on the donor site. In order to further explore this relationship between calculated MEP values and supramolecular selectivity three asymmetric ditopic donors containing phenol carboxylic acid and aldoxime groups were screened against a series of asymmetric ditopic acceptors. Nine crystal structures show that the supramolecular outcome can be predicted according to Etter’s rules by ranking donors and acceptors according to calculated MEP values. To explore the possibility of using the same approach with other hydrogen bond donors, three asymmetric ditopic donor ligands containing cyanooxime groups were synthesized and screened against a series of asymmetric ditopic acceptors. Nine out of ten times the supramolecular outcome could be predicted by MEP calculations 1-deazapurine exists in two tautomeric forms (1H and 3H) in aqueous solution, which have very different hydrogen bonding environments. The 3H tautomer forms a self-complementary dimer involving a donor and an acceptor site leaving a second acceptor site vacant. In order to stabilize this tautomer the molecule was screened against a of series hydrogen and halogen bond donors. Four out of five structures obtained showed 3H tautomer. The 1H tautomer is the geometric complement of urea. Therefore the molecule was screened against a series of N,N-diphenylureas and all five structures showed the 1H tautomer.

The work presented within this thesis can be separated into two distinct parts. The first investigates the direct synthesis of hydrogen peroxide from molecular hydrogen and oxygen using gold-palladium supported catalysts and caesium exchanged tungstophosphoric acid as an acidic additive. The direct synthesis of H2O2 presents an environmentally friendly alternative to the current industrial, anthraquinone process. However for the direct route to be viable a variety of issues must be addressed. Primarily catalytic selectivity towards H2O2 is a major concern for the majority of catalysts active for H2O2 synthesis, with the degradation of H2O2 through hydrogenation or decomposition reported for a number of catalysts within the literature. The use of acid either during catalyst preparation or as part of the reaction solution has previously been shown to improve selectivity towards H2O2. Furthermore acidic supports, including heteropolyacid, have been observed to produce catalysts with greater selectivity than those with a higher isoelectric point and in turn provide higher yields of H2O2. This work investigates the ability of caesium exchanged heteropolyacids to improve catalytic activity towards H2O2 when used in addition to Au-Pd supported catalysts, in particular 2.5 wt. % Au - 2.5 wt. Pd/TiO2. The second part of this work is concerned with the ammoximation of cyclohexanone to cyclohexanone oxime via the in-situ formation of H2O2, in a one-pot style process. The conditions associated with ammoximation of cyclohexanone that is the presence of elevated temperatures and basic conditions, are considered extremely harsh for H2O2 stability. The in-situ generation of H2O2 during the ammoximation of cyclohexanone to cyclohexanone oxime would yield significant reductions in overall costs of the ammoximation reaction. Primarily these costs are associated with the purchasing, transport, storage and dilution of H2O2. This work determines the feasibility of a one-pot ammoximation process via in-situ H2O2 formation. Firstly, reaction conditions are established for this process and following this the role of catalyst design in improving selectivity towards cyclohexanone oxime as well as cyclohexanone conversion for this reaction is studied.

C-terminal binding proteins (CtBPs) are transcriptional co-repressors involved in developmental processes, and also implicated in a number of breast, ovarian, colon cancers, and resistance against cancer chemotherapy. CtBP is a validated novel potential anti-cancer target. In this project we sought to develop potent and selective small-molecule inhibitors of CtBP. Using a combination of classical medicinal chemistry and modern computational approaches, we designed a potent inhibitor HIPP (hydroxyimino-3-phenylpropanoic acid) that showed an IC50 of 0.24 μM against recombinant CtBP. Further elucidation of the structure-activity relationship (SAR) of HIPP led to the design of more potent inhibitors 3-Cl HIPP (CtBP IC50 = 0.17 μM) and 4-Cl HIPP (CtBP IC50 = 0.18 μM). These compounds also showed inhibition in HCT-116 colon cancer cells with GI50 values ~ 1-4 mM. The compounds showed no off-target toxicity against a closely related protein. This is a starting point for the development of CtBP inhibitors as anti-cancer therapeutics. The second part of this dissertation focuses on C–H activation chemistry. C–H activation is the most atom-economical method of introducing complexity into a molecule, even at late stages of drug/product development. We have used solid-supported palladium nanoparticle catalyst (Pd-MWCNT) to investigate the scope of C–H activation reactions it can catalyse. Pd-MWCNT was found to efficiently catalyse N-chelation directed C-H activation reactions – halogenations, oxygenations and arylations. The turn-over numbers for these reactions were significantly higher than that of the reported homogenous catalyst. The added advantages of reuse/recyclability of catalyst, low contamination of metal in the final product make this catalyst very attractive on an industrial scale. This work serves as a foundation for the further development of Pd-MWCNT catalyst in late-stage synthesis of drugs and/or diversification of products.

A facile method for the direct conversion of oximes into carbonyl compounds by treatment with manganese triacetate is described. Manganese triacetate can be used for an effective and mild oxidizing agent for the regeneration of carbonyl compounds in good yield. Many functional groups are tolerated under reaction conditions.

La recherche sur le cancer se tourne vers le développement de la nanomédecine, c’est-à-dire l’utilisation de nanoparticules pour augmenter l'efficacité thérapeutique et réduire la toxicité du traitement. Dans ce contexte, ces travaux ont été consacrés à la conception de nano objets pour des applications en thérapie anticancéreuse. Ces systèmes ont été élaborés à partir d'un châssis moléculaire cyclodécapeptidique présentant plusieurs ligands peptidiques RGD ciblant l’intégrine αvβ3, récepteur transmembranaire jouant un rôle clé dans l’angiogenèse. Dans un premier temps, nous avons synthétisé plusieurs composés en faisant varier la structure du châssis peptidique afin de moduler la présentation des ligands RGD lors de leur interaction avec l’intégrine αvβ3. L’évaluation biologique in vitro des différents composés synthétisés suivi d’une étape de simulation de dynamique nous a permis de déterminer une présentation optimale des ligands RGD. Nous avons ensuite développé une nouvelle voie de synthèse combinant deux réactions orthogonales catalysées au cuivre permettant l’accès à ces vecteurs peptidiques avec de meilleurs rendements et avec un temps de synthèse réduit par rapport à la voie classique. Finalement, nous avons greffé les clusters de RGD sur des nanoparticules lipidiques, puis polymériques, afin d’apporter un élément de ciblage. Ces deux projets ont été réalisés à travers des collaborations, respectivement avec le laboratoire du Prof. Patrick Couvreur (nanoparticules de squalène) et avec le laboratoire du Dr Marie-Thérèse Charreyre (nanoparticules de copolymères NAM/NAS). Ces systèmes ont ensuite été étudiés in vitro pour des applications en thérapie et en imagerie
Cancer research is now taking advantage of nanomedicine that is to say the use of nanoparticles to increase treatment efficiency and reduce toxicity. In this context, this work has been devoted to the design and synthesis of nano objects for applications in cancer therapy. These systems are based on a cyclodecapeptidic molecular scaffold presenting several RGD peptidic ligands targeting the αvβ3 integrin, a transmembrane receptor playing a key role in angiogenesis. We first synthesized several compounds by modifying the structure of the peptidic scaffold in order to alter the presentation of the RGD ligands during their interaction with the αvβ3 integrin. Biological in vitro evaluation of the different synthesized compounds followed by dynamics simulation allowed us to identify an optimal presentation of the RGD ligands. We then developed a new synthesis combining two orthogonal copper-catalyzed reactions yielding those peptidic vectors with lower reaction times and better yields compared to the classic synthesis. We finally grafted the RGD clusters on lipidic, then polymeric nanoparticles to add targeting moieties. Both projects were realized through collaborations, respectively with Prof. Patrick Couvreur’s lab (squalene nanoparticles) and Dr. Marie-Thérèse Charreyre’s lab (NAM/NAS copolymers). Those systems were then evaluated in vitro for applications in therapy and imaging

L’Héparane Sulfate (HS) est un polysaccharide linéaire hautement sulfaté largement présent à la surface des cellules ou dans la matrice extracellulaire des tissus animaux. L’HS est l'un des polymères les plus hétérogènes et présente une alternance de domaines fortement sulfatés (S) et faiblement sulfatés (A). L'exposition à la surface cellulaire de ces domaines SAS permet d'établir des interactions spécifiques avec des protéines basiques présentant des topologies de charges complémentaires, permettant la régulation de leurs activités biologiques. CXCL12, une protéine de la famille des chimiokines se liant aux chaînes d’HS, est l'unique ligand naturel du récepteur CXCR4. La signalisation CXCL12/CXCR4 est impliquée dans divers processus biologiques dont l'hématopoïèse, la réponse immunitaire et la migration des cellules cancéreuses et leur prolifération. La conception de glycoligands pouvant se lier spécifiquement à CXCL12 pourrait permettre de moduler son interaction avec son récepteur et donner accès à une substance thérapeutique innovante pour le traitement de plusieurs types de cancer. Nous avons ainsi imaginé la construction d’un ligand tridentate symétrique comportant une partie centrale de type fragment d’HS synthétique (dp4) dont les extrémités réductrice (ER) et non réductrice (ENR) seraient reliées à des ligands capables d'occuper une partie du site de liaison à CXCR4.Grâce à de précédents travaux sur l'IFN-γ, une cytokine se liant aux chaînes HS, notre laboratoire a déjà démontré que la préparation de mimes de SAS pouvait être obtenue en reliant deux fragments d’HS synthétiques (domaines S) par leur ER via des bras espaceurs de type PEG et de longueur différente pour mimer les domaines A. Afin d’adapter cette stratégie à la préparation de neutraligands de CXCL12 et d’une nouvelle génération de mimes de SAS, ce programme doctoral visait (i) à établir une stratégie générale de modification de l’ER et l’ENR de fragments d’HS, (ii) à établir des conditions efficaces de réactions de couplage pour (iii) synthétiser des ligands de CXCL12 ainsi que de nouveaux mimes de SAS. Nous avons sélectionné deux réactions orthogonales de couplage dans le panel de Chimie Click, à savoir la formation de triazole «CuAAC» et la «ligation oxime». Afin de déterminer la faisabilité de transformation des deux extrémités de fragments d’HS pour réaliser ces réactions de couplage, nous avons optimisé les conditions de ces modifications sur un disaccharide modèle dérivé du cellobiose. Tout d’abord, en utilisant la procédure de couplage thiol-ène décrite par notre équipe, nous avons introduit une amine sur l'ER de ce disaccharide et optimisé les conditions d’une séquence monotope transfert de diazo/CuAAC permettant la conversion sélective de cette amine en azoture puis son couplage avec des alcynes vrais. Cette séquence a également pu être appliquée à des acides aminés libres pour la préparation de dérivés organofluorés. Ensuite, l'installation d'un motif aldéhyde sur l’ENR du composé modèle a été obtenue par une séquence en trois étapes comportant une allylation décarboxylante de type Tsuji-Trost de la position O-4 de l'unité NR, une dihydroxylation de l’éther d’allyle obtenu et enfin une coupure oxydante du diol formé. En plus d'explorer la sélectivité de la coupure oxydante en faveur de diols vicinaux acycliques en présence de diols cycliques portés par le squelette saccharidique, nous avons également optimisé les conditions de la réaction de formation d’oximes pour obtenir une seconde procédure monotpe de coupure oxydante/formation d’oxime pour la modification rapide de l’ENR de fragments d’HS. Cette stratégie de fonctionnalisation sélective de l’ER et l’ENR d’oligosaccharides a été implémentée dans notre voie actuelle de synthèse de fragments d’HS : elle a été appliquée de manière représentative à un fragment tétrasaccharidique d’HS qui permettra la préparation de neutraligands de CXCL12 et de mimes de SAS
Heparan sulfate (HS) is a class of linear and highly sulfated polysaccharides widely present in animal tissues, onto the cell surface or into the extracellular matrix. HS is one of the most heterogeneous polymers and presents an alternation of highly sulfated domains (S domains) and weakly sulfated one (A domains). Exposition of those SAS domains at the cell surface permits the establishment of specific interactions with proteins displaying complementary charge topologies, leading to the regulation of their biological activities.CXCL12, a HS-binding protein, member of the chemokine family of pro-inflammatory mediators, is the unique natural ligand of CXCR4 receptor. CXCL12/CXCR4 signaling is involved in several biological processes, including hematopoiesis, immune response and cancer metastasis. The design of HS type ligands that could bind specifically to CXCL12 to block or modulate its interaction with its receptor should give access to therapeutic substance being able to modulate its activity and allow treatment of several cancer types. To this aim, we planed to construct a symmetric tridentate ligand of CXCL12 in which the reducing end (RE) and non-reducing end (NRE) of a short synthetic HS fragment (dp4) would be connected to ligands able to occupy part of the CXCR4 binding site. Thanks to previous investigation onto IFN-γ, a cytokine that binds tightly to HS chains, our lab already demonstrated that the preparation of SAS mimics should be reached by connecting two synthetic HS fragments (S domains) by their RE through a PEG-type spacer differing in length to mimic internal A domain. To adapt this strategy to the preparation of CXCL12 neutraligands and new type of SAS mimics, this PhD program aimed (i) to establish a general strategy of modification of the HS fragments RE and NRE, (ii) to setup efficient conditions of ligation reactions for (iii) the preparation of CXCL12 neutraligands as well as a second generation of SAS mimics. We selected our two orthogonal ligation reactions into the Click Chemistry panel: “the CuAAC” triazole formation and the “oxime ligation”. In order to setup the practicability of this strategy of transformation of the two HS fragments ends, we optimized reaction conditions onto model disaccharide derived from cellobiose. On one hand, by using thiol-ene coupling procedure reported by our lab, we introduced an amino group to the RE of this disaccharide and optimized reactions conditions of a one-pot diazotransfer reaction/CuAAC sequence, allowing the selective conversion of this amino group into azide and its coupling with alkyne derivatives. To demonstrate the robustness of this sequence, we applied it to the direct modification of free amino acids for the preparation of organofluorine derivatives. On the other hand, the installation of an aldehyde motif onto the NRE of the model compound was obtained via a three steps sequence involving a Tsuji-Trost decarboxylative allylation of the position O-4 of the NRE unit, dihydroxylation of the resulting allyl ether and finally oxidative cleavage of the formed diol. Besides exploring the possibility of the selectivity of the oxidative cleavage in favor of vicinal acyclic diols without affecting cyclic diols of the disaccharide backbone, we also optimized the reaction conditions of oxime ligation to obtain a second one-pot procedure of oxidative cleavage/oxime ligation for the rapid modification of the NRE of HS fragments. This strategy of functionalization of the RE and NRE of oligosaccharides was implemented into our current synthetic pathway of preparation of HS fragments: a tetrasaccharidic HS fragment was representatively modified using this strategy for the synthesis of CXCL12 neutraligands and SAS mimics

The oxygen stoichiometry of RuO_{2+atop -x} was investigated by thermogravimetric and isopiestic techniques, in the temperature range 200-800^oC. RuO_{2+atop -x} could be made hyperstoichiometric to a maximum of RuO_2.014 at 500^oC and hypostoichiometric to a maximum of RuO_1.9808 at 600^oC. Above 800^oC loss of ruthenium as the volatile species RuO₃(g) and RuO₄(g) prevented any reasonable determination of oxygen stoichiometry. Solid solutions were prepared in the Ru-V-O, Ru-Nb-O, Ru-W-O and Ru-Mo-O systems by solid state reaction. Complete solid solution was observed in the Ru-V-O system. Unit cell parameters were determined by X-ray powder diffraction for a range of compositions in the Ru-V-O system. Large deviations from the linearity predicted by Vegard's law were found for both a and c, e.g. at 5 wt.% vanadium a = 4.489, c = 3.089 and at 75 wt.% vanadium a = 4.592, c = 2.873. Conductivity of polycrystalline pressed pellets of RuO₂:VO₂ solid solutions was measured using a four point probe technique. All small vanadium concentrations conductivity increased with percent dopant i.e. resistivity decreased from 8.5 k Ω cm at 2 wt.% vanadium to 4.5 k Ω cm at 5 wt.% vanadium. Solid solutions containing 25-85 wt.% vanadium were found to be semiconducting and increasing amounts of vanadium in this range produced no significant change in resistivity. Solid solutions containing 95 wt.% vanadium showed a transition, at -13^oC, from metallic to semiconducting behaviour as the temperature was lowered. In the Ru-Nb-O, Ru-W-O and Ru-Mo-O systems only 5 wt.% dopant could be successfully incorporated into the RuO₂ lattice. On the basis of the Ru-V-O system however these materials are considered to be potentially good conductors. Resistor inks dilute in ruthenium could prove economically viable. The high vanadium containing materials may have potential as temperature sensitive electronic switching devices. The temperature programmed reduction of an RuO₂:VO₂ solid solution containing 25 wt.% vanadium showed that the onset of reduction occurred at a much higher temperature (234^oC) than for RuO₂ itself (63^oC). This suggests that vanadium containing solid solutions of RuO₂ are more resistant to reduction than RuO₂ itself, a much sought after property in the production of thick film resistors.

Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2008.
Title from PDF t.p. (viewed Oct. 7, 2009). Source: Dissertation Abstracts International, Volume: 70-02, Section: B, page: 1054. Adviser: Krishnan Raghavachari.

Three alkenes, (R/S)-2-phenyl-4-vinyl-4,5-dihydro-oxazole (11), (4R)-3-N-t-butoxycarbonyl-2,2-dimethyl-4-vinyloxazolidine (12) and (2R)-2-(N-t-butoxycarbonyl)aminobut-3-en-1-ol (13), have been prepared from (S)-serine and used in cycloaddition reactions with some common nitrile oxides, to investigate the effect of an allylic nitrogen at an α-chiral centre on π-facial selectivity. Alkene (11) was prepared in racemic form after an unexpected racemisation during its synthesis. Cycloaddition reactions with three nitrile oxides (benzonitrile oxide, ethoxycarbonylformonitrile oxide and bromonitrile oxide) furnished the isoxazoline/oxazoline adducts in poor to good yield. π-facial selectivity varied from 69.31 (BrCNO) to 82:18 (EtO_2CCNO) in favour of the (5R,4'S) erythro product. The stereoselectivity has been explained by both a steric transition state model and by the existence of a stereoelectronic contribution to the stability of the transition state. Alkene (12) afforded good yield of cycloadducts with the same three nitrile oxides, but only gave moderate π-facial selectivity (ca. 66:34); the (5R,4'S) erythro products were again favoured. The diastereomeric products were separated after partial deprotection of the β-amino-alcohol moiety (deacetonisation). The observed π-facial selectivity has been explained by a steric transition state model. The N-protected vinylamino-alcohol (13) has been reacted with benzonitrile oxide and ethoxycarbonylformonitrile oxide to give the corresponding cycloadducts in moderate yield. π-facial selectivity was poor, and the (5S,2'S) threo isomer was favoured. The reduction and reversal of π-facial induction has been explained by a hydrogen bonding interaction in the transition state. Two examples of chiral heterocyclic nitrile oxides (39) and (41) which correspond to the two heterocyclic alkenes have also been prepared, each of which represents a protected chiral β-amino-alcohol nitrile oxide.

Metal oxide nanoparticles (MONPs) are increasingly being incorporated in domestic and industrial products. They are expected to pass into waste water treatment facilities, and may inadvertently be applied in biosolids to agricultural soils. Very few nanotoxicity studies have been conducted in soils and the risk that MONPs pose to soil organisms are poorly understood. The aim of this study was to investigate the behaviour and effects of two MONPs with different solubilities on terrestrial organisms in soils. Exposure of earthworms to soils amended with up to 10,000 mg/kg nano-sized TiO2, a virtually insoluble nanomaterial, resulted in no adverse effects on earthworm population parameters such as survival or reproduction. Earthworms avoided nano-TiO2 amended soils, but only at nanoparticle concentrations higher than those expected for agricultural soils. The mechanisms resulting in the avoidance response, and nano-TiO2 transformations in soils, could not be further investigated because techniques to track nanoparticles in complex media are lacking. Subsequent studies focused on a sparingly soluble nanomaterial, nano-CuO, which releases Cu2+ ions as it dissolves. To identify nanoparticle-specific effects on organisms, the effects of the Cu2+ ions must be determined but little is known about the effect of nano-CuO on Cu2+ activity in soils. Tests revealed that Cu2+ activity in nano-CuO amended soils increased over a 56 d period, but were not comparable to those in soils amended with similar concentrations of micrometer-sized CuO or Cu(NO3)2, which are commonly used as treatments to control for the effects non-nanosized Cu in nanotoxicity tests. These results have implications for the design of experiments that test effects of dissolving particulates. A subsequent barley growth test demonstrated that there was no significant difference in plant growth or shoot Cu concentrations between soils amended with nano-CuO, micrometer-sized CuO or Cu(NO3)2 once growth was normalised to Cu2+ activity. These results demonstrate that release of metal ions can play an important role in toxicity of soluble metal-based nanoparticles and highlight the importance of direct measurement of potentially toxic products of nanoparticle dissolution. There was no evidence of nanoparticle-specific toxicity under the conditions studied either for earthworms exposed to nano-TiO2 or barley exposed to nano-CuO. The study highlighted some of the challenges of understanding the fate and effects of nanomaterials in soils, including the lack of techniques to track nanomaterials in complex media and the difficulty in designing toxicity tests that control for temporal changes to both nanoparticles and soils.
Les nanoparticules des oxydes de métaux (MONP) sont davantage incorporés dans les produits domestiques et industriels. Une importante proportion de ces nanoparticules est susceptible de se retrouver dans les usines de traitement d'eaux usées et d'être épandue sur les terres agricoles sous forme de biosolides. Dû au fait que peu de recherches sur la nanotoxicité ont été faites dans les sols, le risque que pose ces MONP aux organismes du sols est peu connu. Le but de cette étude est donc d'observer la réaction et les effets de deux MONP de solubilité différente dans des sols agricoles et artificiels. L'exposition des vers de terre dans des sols amendés avec jusqu'à 10,000 mg par kg de sol de nano-TiO2, un nanomatériel pratiquement insoluble, n'a causé aucun effet sur leur survie ou leur reproduction. Les vers de terre n'ont évité les sols modifiés de nano-TiO2, qu'à des concentrations de nanoparticules beaucoup plus élevées que celles attendues dans les sols agricoles. Les mécanismes impliqués dans la réponse d'évitement et les transformations de nanoTiO2 dans les sols n'ont pu être étudiés plus à fond par manque de techniques développées pour suivre les nanoparticules dans les médias complexes. Dans les recherches subséquentes, un nanomatériel de très faible solubilité, le nano-CuO, qui relâche des ions Cu2+ au fur et à mesure qu'il se dissout, a été choisi comme matériel d'intérêt. Afin d'identifier les effets spécifiques des nanoparticules sur des organismes, les effets du Cu2+ doivent être déterminés. Cependant, peu est connu sur l'activité du Cu2+ dans les sols traités avec des nano-CuO. Les recherches ont démontré que l'activité de Cu2+ a augmenté durant une période de 56 jours pour les sols amendés de nanoparticules de CuO mais cette augmentation ne s'est pas produite, à des concentrations égales, pour des sols enrichis de CuO de diamètre micrométrique ou même de sels de Cu(NO3)2 ; ces deux derniers traitements sont souvent utilisés comme tests contrôles lors d'études de nanotoxicité. Ces résultats ont des implications pour la conception des expériences pour évaluer les effets sur la dissolution des particules. Une étude ultérieure sur la croissance d'orge a démontré qu'il n'y avait aucune différence significative dans la croissance des plantes ou des concentrations de Cu dans les feuilles entre les sols modifiés avec du nano-CuO, CuO de taille micrométrique ou le Cu(NO3)2 une fois que les données furent normalisées en activité de Cu2+. Ces résultats ont démontré que la dissolution d'ions de métaux peut jouer un rôle important sur la toxicité des nanoparticules. Ils soulignent aussi l'importance de mesurer directement la concentration de produits de la dissolution de nanoparticules. Il n'y avait aucune évidence de toxicité spécifique aux nanoparticules sous les conditions étudiées pour les vers de terre soumis au nano-TiO2 ou pour l'orge soumis au nano-CuO. Cette étude a révélé certaines lacunes de compréhension dans le comportement du nanomatériel ajouté aux sols, des difficultés de tenir compte des changements temporels des nanoparticules et des sols ainsi que le manque de techniques disponibles pour suivre les nanoparticules dans les médias complexes.

The impact of dissolved trace metals on aquatic ecosystems and human health is controlled by sorption, i.e., binding to the surfaces of environmental particles. Since many environmental particles are coated with highly reactive substances, and since discrepancies in trace metal sorption behavior persist between oxides developed in the laboratory and environmental oxide phases, it was hypothesized that the physical form of oxide coatings may influence the chemical properties of the coated particle. Therefore, relationships between the physical forms of several different Fe(III) oxide coatings and the Cu(II) sorption behavior of the coated solids were investigated in comparison with the component phases and natural sedimentary materials. Goethite (alpha-FeOOH) was coated onto quartz and kaolinite grains. Coating method and thickness were varied. Physical properties of the coated solids were probed using multipoint N2 (g) adsorption and desorption analysis (BET), The morphology of the particles was studied by scanning electron microscopy (SEM), and the uniformity of oxide distribution on the grain surfaces was assessed by energy-dispersive X-ray (EDS) analysis. Chemical properties were investigated via batch Cu(II) adsorption/desorption experiments. Goethite physical form was found to vary with coating method and substrate mineralogy. Cu(II) sorption (uptake and release of dissolved Cu from goethite-coated particles) depended on the coating method, substrate, and thickness of the coating. Analysis of these variations indicated physical changes in the form of the coating, interactions between goethite and substrate, and changes in the surface chemical properties of one or both solid phases (goethite and substrate). The combined physical and chemical alterations in the properties of the solids produced distinct behavior in each of the laboratory-prepared solids studied. A parallel set of experiments was conducted on three geologically related sedimentary materials. Several physical and chemical differences were observed between crude kaolin and a cleaned reference kaolinite. One laboratory-prepared goethite coating matched a surface soil at precipitation-dominated Cu loadings, and another coated solid matched a subsurface material at all Cu loading ranges sampled. These results suggest that more complex laboratory-prepared sorbent phases may better reflect trace metal sorption properties of environmental particles.

The transition metal carbonyls [Re2(CO)10], [Mn2(CO)10] and [Ru(CO)3(PPh3)2], and elemental iodine have been reacted with Xe(OSeF5)2. The products have been fully characterised by a combination of mass spectrometry, infrared spectroscopy 19F, 13C and 31P{1H} (where appropriate) NMR spectroscopies. Further characterisation of the novel compounds Xe(OSeF5)2, [Re(CO)5(OSeF5)] and [Mn(CO)5(OSeF5)] by EXAFS spectroscopy is reported. An extensive review of the halogen oxide fluorides has been carried out and attempts were made to synthesise a range of fluorides and oxide fluorides of bromine. The bromine fluorides [BrF2][AsF6], [BrF4][Sb2F11], K[BrF4] and Cs[BrF6] were successfully characterised using EXAFS spectroscopy. The compound Cs[BrOF4] has been synthesised and the application of EXAFS spectroscopy has yielded internal bond parameters. The area of fluorosulphate chemistry has been reviewed and reactions have been carried out between the superacid HSO3F and a range of transition metal carbonyl complexes and Ti, Hf and Zr derivatives. The complexes produced were characterised using mass spectrometry, infrared spectroscopy and 1H, 13C, 13C{1H} and 19F NMR spectroscopies. The protonation of the carbonyl clusters [Ir4(CO)12], [Os3(CO)12] and [Ru3(CO)12] by HSO3F was investigated. The systems are found to be the same as those previously observed for the superacid AHF.

A detailed study has been carried out to investigate the dissolution characteristics of unstabilized and stabilized CrO₂ particles. It has been found that on contact of CrO₂ with aqueous solutions, it dissolves by disproportionation reaction to HCrO₄ and Cr2O₃. XPS study has shown that stabilization of CrO₂ particles with bisulfite solution leads to the formation of Cr2O₃. However, because of agglomeration of the CrO₂ particles due to their magnetic properties, not all of the surface is completely stabilized. The electrokinetic characteristics of Cr(IV) and Cr(III) oxides in aqueous solutions have been investigated. Experiments suggest that sulfite ions chemisorb strongly on Cr₂O₃ particles. Experiments have also been carried out to study the adsorption of sodium dodecyl sulfate (SDS) on Cr₂O₃ particles. With increasing SDS concentration, Cr₂O₃ becomes less positively charged and ultimately negatively charged when the surfactant concentration exceeds 10⁻³ M. This suggests that SDS specifically adsorbs onto the oxide.

Le motif spiroacétal constitue une partie du squelette de nombreux produits naturels possédant des activités biologiques variées. Récemment, de nouveaux spiroacétals de synthèse incorporant un hétéroatome supplémentaire en bêta du carbone spiranique et possédant des activités biologiques intéressantes, ont été décrits. Nous avons mis au point une synthèse efficace et modulable de spiroacétals originaux possédant des hétéroatomes (oxygène, soufre, azote) en position 4 et 10 du squelette 1,7-dioxaspiro[5.5]undécane. Elle repose sur une étape clé de déprotection-spirocyclisation d'une cétone masquée obtenue par substitution nucléophile du 1,3-dichloropropanone O-benzyloxime par des précurseurs issus du solkétal. Ainsi nous avons préparé les motifs 4,10-dioxa-, 4,10-dithia-, 4-thia-10-oxa-, 10-aza-4-thia- et 10-aza-4-oxa-1,7-dioxaspiro[5.5]undécanes, pour lesquels une étude structurale complète a été effectuée par RMN. Une première approche du motif 4,10-diaza- est également présentée

Studies various nanostructured materials have gained considerable interest within the past several decades. This novel class of materials has opened up a new realm of possibilities, both for the fundamental comprehension of matter, but also for innovative applications. The size-dependent effect observed for these systems often lies in their interaction with the surrounding environment and understanding such interactions is the pivotal point for the investigations undertaken in this thesis. Three families of nanoparticles are analyzed: semiconductor quantum dots, metallic silver nanoparticles and rare-earth oxide nanomaterials. The radical scavenging ability of cerium oxide nanoparticles (CeO2) is quite controversial since they have been labeled as both oxidizing and antioxidant species for biological systems. Here, both aqueous and organic stabilized nanoparticles are examined in straightforward systems containing only one reactive oxygen species to ensure a controlled release. The apparent absence of their direct radical scavenging ability is demonstrated despite the ease at which CeO2 nanoparticles generate stable surface Ce3+ clusters, which is used to explain the redox activity of these nanomaterials. On the contrary, CeO2 nanoparticles are shown to have an indirect scavenging effect in Fenton reactions by annihilating the reactivity of Fe2+ salts. Cadmium selenide quantum dots (CdSe QD) constitute another highly appealing family of nanocolloids in part due to their tunable, size-dependent luminescence across the visible spectrum. The effect of elemental sulfur treatment is investigated to overcome one of the main drawbacks of CdSe QD: low fluorescence quantum yield. Herein, we report a constant and reproducible quantum yield of 15%. The effect of sulfur surface treatment is also assessed following the growth of a silica shell, as well as the response towards a solution quencher (4-amino-TEMPO). The sulfur treated QD is also tested for interaction with pyronin Y, a xanthene dye that offers potential energy and electron transfer applications with the QD. Interaction with the dye molecule is compared to results obtained with untreated quantum dots, as well as CdSe/ZnS core shell examples. In another chapter of this thesis, the catalytic potential of silver nanoparticles is addressed for the grafting of polyhydrosiloxane polymer chains with various alkoxy groups. A simple one-pot synthesis is presented with silver salts and the polymer. the latter serves as a mild reducing agent and a stabilizing ligand, once silver nanoparticles are formed in-situ. We evaluate the conversion of silane into silyl ethers groups with the addition of several alcohols, whether primary, secondary or tertiary, and report the yields of grafting under the mildest conditions: room temperature, under air and atmospheric pressure.

La síntesi d'òxids de metalls de transició per dipòsit de capes atòmiques (ALD) està contribuint al desenvolupament de nanomaterials, estructures i dispositius que són difícils d'aconseguir mitjançant tècniques de dipòsit tradicionals i tenen característiques prometedores per a diverses àrees d'aplicació com a energia, electrònica i salut. És important desenvolupar processos d'ALD més robustos per òxids de metalls de transició, ampliant la biblioteca de composicions i facilitant la seva integració amb altres materials. El principal objectiu d'aquesta tesi és contribuir al desenvolupament de processos d'ALD per fabricar capes primes basades en òxids de metalls de transició i recobriments conformals, i entendre la importància de la reactivitat entre els precursors metalorgànics i la superfície del substrat per guiar possibles aplicacions. En particular, els esforços s'han centrat en els següents aspectes: 1. Explorar un nou precursor de cobalt (β -heteroarilalquenolato de cobalt) per dipositar capes de Co3O4 per ALD. La introducció de lligands heteroarilo i grups CF3-, en comparació amb els precursors comercials, ofereix una major estabilitat del precursor i una manipulació segura en condicions ambientals. Les condicions de dipòsit d'ALD s'han investigat a fons optimitzant la durada del pols del precursor, la temperatura de dipòsit i la dependència de l'espessor de la capa amb el nombre de cicles d'ALD. Es mostra que aquesta química afavoreix la formació de capes primes d'ALD Co3O4 i recobriments conformals quan es combinen amb ozó com a oxidant. 2. Comparar la idoneitat d'un precursor heterobimetàl.lic de Gd-Fe versus fonts metalorgàniques separades de Gd i Fe per dipositar capes primes d'òxids ternaris magnètics de GdxFeyOz. El nou complex heterobimetàl.lic de Gd-Fe, que conté una relació estequiomètrica de 1Gd: 1Fe, facilita l'estabilització epitaxial de capes primes de GdFeO3 en substrats monocristal·lins de SrTiO3 quan es combina amb ozó. Alternativament, busquem l'oportunitat de sintetitzar òxids ternaris de GdxFeyOz utilitzant precursors separats de Gd i Fe sintetitzats a mida: un guanidinato de gadolini i un cetoiminato de ferro coordinat a N i O. El comportament del cetoiminat de ferro s'ha comparat amb el ferrocè, disponible comercialment. La reactivitat de cada precursor s'ha provat amb aigua i ozó com a agents oxidants. Es mostra que la química del precursor afecta tant la composició com a la cristal·linitat de les capes dipositades. S'han avaluat les propietats magnètiques dels sistemes d'òxid GdxFeyOz resultants. 3. Investigar la influència dels tractaments amb plasma (N2, H2O) en nanotubs de carboni (CNTs) en el posterior dipòsit de recobriments conformales de Fe2O3 per ALD. S'ha demostrat que la funcionalització de la superfície dels CNT és essencial per obtenir més llocs d'ancoratge per aconseguir la desitjada homogeneitat del recobriment. L'agent oxidant ozó també juga un paper clau. S'han dut a terme mesures electroquímiques en els nanocompòsits Fe2O3@CNTs per correlacionar la funcionalització de la superfície i la qualitat de la capa d'ALD Fe2O3 amb el rendiment electroquímic. Això obre noves oportunitats per a la fabricació d'ànodes més eficients per supercondensadors.
La síntesis de óxidos de metales de transición por depósito de capas atómicas (ALD) está contribuyendo al desarrollo de nanomateriales, estructuras y dispositivos que son difíciles de lograr mediante técnicas de depósito tradicionales y tienen características prometedoras para diversas áreas de aplicación como energía, electrónica y salud. Es importante desarrollar procesos de ALD más robustos para óxidos de metales de transición, ampliando la biblioteca de composiciones y facilitando su integración con otros materiales. El principal objetivo de esta tesis es contribuir al desarrollo de procesos de ALD para fabricar películas delgadas basades en óxidos de metales de transición y recubrimientos conformales, y arrojar luz sobre la reactividad entre los precursores metalorgánicos y la superficie del sustrato para guiar posibles aplicaciones. En particular, los esfuerzos se han centrado en los siguientes aspectos: 1. Explorar un nuevo precursor de cobalto (β -heteroarilalquenolato de cobalto) para depositar películas de Co3O4 por ALD. La introducción de ligandos heteroarilo y grupos CF3-, en comparación con los precursores comerciales, ofrece una mayor estabilidad del precursor y una manipulación segura en condiciones ambientales. Las condiciones de depósito de ALD se han investigado a fondo optimizando la duración del pulso del precursor, la temperatura de depósito y la dependencia del espesor de la película con el número de ciclos de ALD. Se muestra que esta química favorece la formación de películas delgadas de ALD Co3O4 y recubrimientos conformados cuando se combinan con ozono como oxidante. 2. Comparar la idoneidad de un precursor heterobimetálico de Gd-Fe versus fuentes metalorgánicas separadas de Gd y Fe para depositar películas delgadas de óxido ternario magnéticos de GdxFeyOz. El novedoso complejo heterobimetálico de Gd-Fe, que contiene una relación estequiométrica de 1Gd: 1Fe, facilita la estabilización epitaxial de películas delgadas de GdFeO3 en sustratos monocristalinos de SrTiO3 cuando se combina con ozono. Alternativamente, buscamos la oportunidad de sintetizar óxidos ternarios de GdxFeyOz utilizando precursores separados de Gd y Fe sintetizados a medida: un guanidinato de gadolinio y un cetoiminato de hierro coordinado con O, N. El comportamiento del cetoiminato de hierro se ha comparado con el ferroceno, disponible comercialmente. La reactividad de cada precursor se ha probado con agua y ozono como agentes oxidantes. Se muestra que la química del precursor afecta tanto a la composición como a la cristalinidad de las películas depositadas. Se han evaluado las propiedades magnéticas de los sistemas de óxido GdxFeyOz resultantes. 3. Investigar la influencia de los tratamientos con plasma (N2, H2O) en nanotubos de carbono (CNTs) en el posterior depósito de recubrimientos conformales de Fe2O3 por ALD. Se ha demostrado que la funcionalización de la superficie de los CNTs es esencial para obtener más sitios de anclaje para lograr la deseada homogeneidad del recubrimiento. El agente oxidante ozono también juega un papel clave. Se han llevado a cabo medidas electroquímicas en los nanocompuestos Fe2O3@CNTs para correlacionar la funcionalización de la superficie y la calidad de la capa de ALD Fe2O3 con el rendimiento electroquímico. Esto abre nuevas oportunidades para la fabricación de ánodos más eficientes para supercondensadores.
The synthesis of transition metal oxides by atomic layer deposition (ALD) is contributing to the development of nanomaterials, structures and devices that are difficult to achieve by traditional deposition techniques and hold promising characteristics for various application areas such as energy, electronics and health. Research on developing more robust ALD processes for transition metal oxides, expanding the library of compositions and facilitating their integration with other materials are thus of great relevance. The main objective of this thesis is to contribute to the development of ALD processes of transition metal oxide-based thin films and conformal coatings, and to shed light on the relevant reactivity between the metalorganic precursors and substrate surfaces to guide potential applications. In particular, the efforts have been focused on the following aspects: 1. Explore a novel cobalt precursor (β-heteroarylalkenolate Cobalt) to deposit ALD Co3O4 films. The introduction of heteroaryl moieties and CF3- groups, compared to commercial precursors, offers higher precursor stability and safe handling at ambient conditions. ALD deposition conditions have been thoroughly investigated by optimizing precursor pulse length, deposition temperature and film thickness dependence on the number of ALD cycles. It is shown that this chemistry favors the formation of ALD Co3O4 thin films and conformal coatings when combined with ozone as oxidant. 2. Compare the suitability of a heterobimetallic Gd-Fe precursor versus separate metalorganic sources of Gd and Fe to deposit magnetic GdxFeyOz ternary oxide thin films. The novel heterobimetallic single-source Gd-Fe complex which contains 1Gd:1Fe stoichiometric ratio, facilitates the epitaxial stabilization of GdFeO3 thin films on SrTiO3 single crystal substrates when combined with ozone. Alternatively, we seek the opportunity to synthesize GdxFeyOz ternary oxides from separate Gd and Fe precursors, with different precursor chemistries, via the supercycle approach. For that, it has been explored the use of two tailor-made precursors: a fully N-coordinated gadolinium guanidinate and a mixed O,N- coordinated iron ketoiminate. The behavior of the iron ketoiminate has been compared to the commercially available ferrocene. The reactivity of each precursor has been tested with water and ozone as co-reactants. It is shown that the precursor chemistry affects both the composition and crystallinity of the deposited films. Magnetic properties of the resultant GdxFeyOz oxide systems have been evaluated. 3. Investigate the influence of plasma treatments (N2, H2O) for carbon nanotubes (CNTs) on the subsequent deposition of conformal Fe2O3 coatings by ALD. It has been demonstrated that surface functionalization of the CNTs is essential to obtain more anchoring sites for achieving desirable coating homogeneity and that the ozone co-reactant plays a key role on it as well. Electrochemical measurements on the Fe2O3@CNTs nanocomposites have been carried out to correlate surface functionalization and ALD Fe2O3 layer quality with the electrochemical performance. This opens new opportunities for the fabrication of more efficient anodes for supercapacitors.

Cerium oxide (Ceria) at nano scale has gained significant attention due to its numerous technological applications. Ceria in both doped and undoped forms are being explored as oxygen sensor, catalysis, protective coating against UV and corrosion, solid oxide fuel cell (SOFC) electrolyte and newly discovered antioxidant for biomedical applications. Therefore, there is an imminent need of a technology which can provide a cost effective, large scale manufacturing of nanoceria and its subsequent consolidation, specially using thermal spray. This dissertation aims to develop a scientific understanding towards the development of pure and doped ceria- based coating for a variety of technological applications, from SOFC applications to corrosion resistant coating. Atmospheric plasma spray (APS) and solution precursor plasma spray (SPPS) techniques for the fabrication of nano ceria coating were investigated. For feedstock powder preparation, a spray drying technique was used for the agglomeration of cerium oxide nano particles to achieve high density coating. Deposition efficiencies and coating porosity as a function of processing parameters were analyzed and optimized using a statistical design of experiment model. The coating deposition efficiency was dependent on the plasma temperature and vaporization pressure of the ceria nanoparticles. However, low standoff distance and high carrier gas flow rate were responsible for the improved density upto 86 [plus or minus] 3%.An alternative novel SPPS technique was studied for a thin film of cerium oxide deposition from various cerium salt precursors in doped and undoped conditions. The SPPS process allows controlling the chemistry of coating at a molecular level. The deposition mechanism by single scan experiments and the effect of various factors on coating microstructure evolution were studied in terms of splats formation. It was found that the precursor salt (nitrate of cerium) with lower thermal decomposition temperatures was suitable for a high density coating. The high concentration and low spray distance significantly improve the splat morphology and reduced porosity (upto 20%). The feasibility of the trivalent cations (Sm 3+ and Gd 3+) doping into cerium oxide lattice in high temperature plasma was discussed and experimentally studied. XRD analysis revealed the nano crystalline characteristic of the coating and lattice expansion due to doping. The extensive transmission electron microscopy, Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and thermo gravimetric were conducted to evaluate the precursors, and coating microstructure. Due to facial switching between Ce4+ and Ce3+ oxidation state, the cerium oxide surface becomes catalytically active. Thus, the APS ceria coatings were investigated for their applicability under extreme environmental conditions (high pressure and temperature). The air plasma sprayed coated 17-4PH steel was subjected to high pressure (10 Kpsi) and temperature (300 oF) corrosive environment. The coated steel showed continuous improvement in the corrosion resistance at 3.5 wt% NaCl at ambient temperature for three months study whereas, high pressure did not reveal a significant role in the corrosion process, and however, one needs to do further research. The ceria coated steel also revealed the improvement in corrosion protection (by 4 times) compared to the bare steel at low pH, 300 oF and 4000 Psi environment. This study projects the importance of cerium oxide coatings, their fabrication, optimization and applications.
ID: 031001377; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: Sudipta Seal.; Title from PDF title page (viewed May 21, 2013).; Thesis (Ph.D.)--University of Central Florida, 2012.; Includes bibliographical references (p. 171-182).
Ph.D.
Doctorate
Materials Science Engineering
Engineering and Computer Science
Materials Science and Engineering

Engineered nanoparticles are defined as having a dimension that is between one and one hundred nanometres. With toxicology studies reporting various degrees of toxicity the need to investigate nanoparticle fate and behaviour is vital. Monodispersed engineered nanoparticles were synthesised in-house to produce suitable materials to examine such processes. Iron oxide nanoparticles (5 nm) and citrate coated silver nanoparticles (20 nm) were subjected to different conditions of pH, ionic strength and different types of commercially available natural organic matter. Changes in particle size and aggregation were examined using a multi-method approach. Results showed that the natural organic matter was able to absorb onto nanoparticle surfaces and improve their stability when subjected to changes in pH and ionic strength, where they would normally aggregate. The presence of higher concentrations of NOM in some cases promoted aggregation due to bridging. This work also concluded that silver nanoparticles could be produced in the presence of NOM without additional stabilisers and that they themselves were stable. This work has demonstrated that engineered nanoparticles could remain stable within a range of environmental conditions, and thus raise future pollution concerns.

A route to C-glycosides and C-disaccharides with functionalised linkages has been investigated. This convergent strategy involves cycloaddition of selected alkenes and sugar derived nitrile oxide moieties. The resultant 2-isoxazolines can be modified and subsequently ring opened to afford compounds with carbonyl or amino containing linkages. The alkenes selected for study were two w-unsaturated monosaccharide derivatives: 5,6-dideoxy-1,2-O-isopropylidene-a-D-xylo-hex-5-enofuranose and methyl 5,6-dideoxy-2,3-O-isopropylidene-a-D-lyxo-hex-5-enofuranoside. Styrene, oct-1-ene and methylenecyclohexane were also studied as models. Four sugar based nitrile oxides were investigated in cycloadditions to these alkenes, based on D-glucose, D-galactose, D-mannose and L-fucose. Three complementary cycloaddition procedures were developed and evaluated: the dehydration of 2,6-anhydro-1-deoxy-1-nitroalditols, the hypochlorite-mediated oxidative dehydrogenation of pyranosyl oximes, and the dehydrochlorination of a pyranosyl hydroximoyl chloride. The oximes and hydroximoyl chloride compounds were synthesised from the corresponding pyranosylnitromethanes. Reactions involving the sugar oximes typically resulted in variable yields of the by-product furazan N-oxide (furoxan) in addition to the cycloadducts, depending on the dipolarophile reactivity. In contrast, uniformly high yields of cycloadducts (70-90%) were obtained from the nitromethyl compounds and hydroximoyl chloride with a range of dipolarophiles; little or no nitrile oxide dimerisation was observed in these reactions.

The work of this thesis focuses on three perovskite-based compounds: YSr2Cu3−xCoxO7+δ cuprates, Gd2BaCo2O5+δ related phases and Sr2SnO4 Ruddlesden-Popper structures. Both YSr2Cu3−xCoxO7+δ and Gd2BaCo2O5+δ are cathode material candidates for solid oxide fuel cells (SOFCs). Doping of Sr2SnO4 aims to enhance the ionic conductivity of the parent phase and explore the phases as a potential SOFCs electrolyte material. The cobalt content in the layered perovskite YSr2Cu3−xCoxO7+δ has been increased to a maximum of x = 1.3. A slight excess of strontium was required for phase purity in these phases, yielding the composition Y1−ySr2+yCu3−xCoxO7+δ (where y = 0.03 and 0.05). The potential of Y1−ySr2+yCu3−xCoxO7+δ (where x = 1 to 1.3) as a cathode material for a solid oxide fuel cell has been explored through optimisation of processing parameters, AC impedance spectroscopy and DC conductivity measurements. The stability of Y0.95Sr2.05Cu1.7Co1.3O7+δ with commercial electrolytes has been tested along with the stability under CO2. This material exhibits a significant improvement in properties compared to the parent member, Y0.97Sr2.03Cu2CoO7+δ, and is compatible with commercially available doped ceria electrolytes at 900 °C. Energetics of Ln2BaCo2O7 (Ln = Gd, Nd, Ce) materials consisting of a layer of LnBaCo2O5+δ (Ln = Gd, Nd) and a fluorite layer (CeO2 or Ln2O3, Ln = Gd, Nd) have been studied using DFT calculations. Various reactions including binary oxides and double perovskites were taken into an account for the formation energy calculations. Phases favourable in DFT calculations were observed also in PXRD patterns of the materials prepared by a solid state synthesis. DFT prediction has been also used in the work with Ruddlesden-Popper phases. The structures of experimentally prepared Nb- and Ta-doped Sr2SnO4 phases were investigated using high resolution diffraction methods. The conductivity of single phased materials was studied by AC impedance spectroscopy. A significant improvement in conductivity was observed in Sr2Sn1−xTaxO4 compounds with x = 0.03 and 0.04. The origin of the enhancement has been studied using different techniques such as solid state Sn-NMR, UV-vis and NIR spectroscopy methods and it tends to be explained by an ionic contribution.

This diploma thesis deals with the optimalization of synthesis of gold nanoparticles and their surface modification allowing their use as contrast agents for in vivo imaging by CT. Gold nanoparticles were prepared by the Turkevich method and characterized by TEM, DLS, MADLS and UV -Vis. Their surface was functionalized with polyethylene glycol containing a thiol group forming a bond with the Au atoms in the surface of gold nanoparticles. The terminal end of the polymer was methylated or containing an aminooxy group forming an orthogonal bond with hyaluronic acid using click-chemistry. The eligibility for in vivo application of the prepared nanoparticles was verified with stability and cytotoxicity tests. The nanoparticles modified by methylated polyethyleneglycol were injected intravenously into a mouse and their application potential as contrast agents were verified by CT.

Au cours des dix dernières années, les hétérostructures à base de matériaux oxyde ont été grandement étudiées comme potentiel systèmes d’application pour le nanoélectronique. Parmi eux, les ferroélectriques (FE) sont particulièrement intéressants comme support pour ces applications technologies. En effet, leur polarisation électrique spontanée, aisément réversible par application d’un champ électrique en fait de bons candidats pour le stockage de données non-volatile. Renverser la polarisation nécessite un contact avec une électrode, ainsi les hétérostructures de films mince de FE avec électrodes métalliques ont été grandement étudiées. A l’interface entre les deux matériaux, les charges libres de l’électrode permettent d’écranter les charges de surfaces, détrimentales au maintien de la polarisation au sein du film FE. Avec des électrodes d’oxyde métalliques, un déplacement ionique à l’interface électrode/FE va d’avantage favoriser cet écrantage, plaçant l’interface au cœur du processus d’écrantage. Cependant, malgré d’importantes découvertes théoriques, les données expérimentales sont rares et le comportement exact de l’interface électrode/FE est seulement partiellement maitrisée. Une plus grande compréhension est indispensable pour une intégration correcte des films FE dans des dispositifs nanométriques. Dans cette thèse, des techniques basées sur la spectroscopie de photoémission sont utilisées pour sonder l’interface enfouie d’une hétérostructure électrode/BaTiO₃/électrode, dans le cas de deux électrodes différentes : l’oxyde métallique SrRuO₃ et le métal cobalt. Nous avons acquis des informations sur le comportement de l’interface et sa réponse au renversement de la polarisation. Ce travail est un nouveau pas vers une plus grande maitrise des phénomènes physiques gouvernant le comportement de l’interface entre électrodes le ferroélectrique BaTiO₃, en termes de propriété électronique, de cinétique et de fatigue. Les expériences présentées couplent des techniques d’analyses de pointes, où l’utilisation de rayons X durs et l’application de champs électriques in situ ont rendus possible la difficile tâche de sonder des interfaces enfouies en condition de fonctionnement
In the past decade, oxide-based heterostructures have been studied extensively as potentially attractive systems for applications in nanoelectronics. Among them, ferroelectric materials raised interest as potential support for those technological applications. Indeed, their spontaneous electric polarization easily switched by applying an electric field makes them a good basis for non-volatile data storage. Switching the polarization requires a metallic contact with an electrode, thus heterostructures of ferroelectric thin films with metallic electrodes have been widely studied. At the interface between those two materials, free charges of the electrode help screening the polarization induced surface charges detrimental to maintaining proper polarization in the ferroelectric thin film. With metallic oxide electrodes, an ionic displacement at the electrode/ferroelectric interface will help the screening. However, despite important theoretical discoveries, direct experimental data is scarce and further understanding of the interface behavior is crucial for a proper integration of ferroelectric films in functioning nanometer sized devices. In this thesis, photoemission spectroscopy based techniques are used to probe the buried interface of an electrode/BaTiO₃/electrode heterostructure, for two different electrodes: the metallic oxide SrRuO₃ and the Co metal. We acquired information on the behavior of the interface and its response to polarization switching. This work is a new step towards a complete understanding on the behavior of the interface between electrodes and the BaTiO₃ ferroelectric, in device-like heterostructures, in terms of electronic properties, kinetic, and fatigue. The experiments presented combined state of the art characterization techniques, where the use of hard X-rays and in situ bias application made it possible to resolve the difficult task of probing buried interfaces in working conditions