Dissertations / Theses on the topic 'Metal complexes and nanoparticles'
To see the other types of publications on this topic, follow the link: Metal complexes and nanoparticles.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Metal complexes and nanoparticles.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Zapiter, Joan Marie Diangson. "Transition Metal Complexes Anchored on Europium Oxide Nanoparticles." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/24786.
Full textAbstract:
Polypyridyl transition metal complexes containing ruthenium, rhodium and iridium centers are mainly studied due to their light absorbing and emitting properties. Lanthanide oxides such as europium oxide absorb light as well and exhibit strong luminescence and long lifetimes. The optical properties of these materials were significant especially in solar energy utilization schemes and optical applications. Energy transfer across a surface is important in several applications including phosphors and biomedical applications. Excited states of metal complexes with a carboxylate-containing ligand such as deeb = diethyl-2,2'-bipyridine-4,4'-dicarboxylate were studied on nanoparticle surfaces. In this work, [Rh(deeb)2Cl2](PF6), [Ir(deeb)2Cl2](PF6) and [Ir(deeb)2(dpp)](PF6)3 were synthesized using the building block approach. The metal complexes were characterized using 1H NMR spectroscopy, mass spectrometry, electronic absorption spectroscopy and electrochemistry. The 1H NMR spectra of the complexes were consistent with those of their ruthenium analogs. Mass spectra contain fragmentation patterns of the (M-PF6)+ molecular ion for [Rh(deeb)2Cl2](PF6) and [Ir(deeb)2Cl2](PF6), and (M-3PF6)3+ molecular ions for [Ir(deeb)2(dpp)](PF6)3. The electronic absorption spectrum of [Rh(deeb)2Cl2](PF6) shows a maximum at 328 nm, which is assigned as 1π→π*transition. The electronic absorption spectrum of [Ir(deeb)2Cl2](PF6) shows maxima at 308 nm and 402 nm, which are assigned as 1π→π* and metal-to-ligand charge transfer transitions, respectively. The [Ir(deeb)2(dpp)](PF6)3 complex exhibits peaks due to 1π→π* transitions at 322 nm and 334 nm. [Rh(deeb)2Cl2](PF6) has emission maxima from the 3LF state at 680 nm and 704 nm for the solid and glassy solutions at 77 K, respectively. [Ir(deeb)2Cl2](PF6) has emission maxima from the 3MLCT state at 538 nm in acetonitrile and 567 nm in the solid state at room temperature, with lifetimes of 1.71 μs and 0.35 μs, respectively. [Ir(deeb)2Cl2](PF6) has an unusually higher quantum yield than analogous compounds. [Ir(deeb)2(dpp)](PF6)3 has emission maxima from the 3IL state at 540 nm in acetonitrile and 599 nm in the solid state at room temperature, with lifetimes of 1.23 μs and 0.14 μs, respectively. Cyclic voltammetry of [Ir(deeb)2Cl2](PF6) and [Ir(deeb)2(dpp)](PF6)3 yield reversible and quasi-reversible couples corresponding to deeb ligand and Ir3+/+reductions, respectively. Attachment of the complexes were conducted by equilibration of complex solutions in acetonitrile with europium oxide nanoparticles. Europium oxide nanoparticles, which were synthesized by gas-phase condensation, have 11-nm diameters and exhibit sharp f-based luminescence in the visible and near IR regions. EDX, TEM, IR and reflectance spectroscopy measurements indicate substantial coating through various modes of attachment of the nanoparticle surface by the metal complexes while retaining the excited state properties of the metal complexes. Surface adsorption studies indicate monolayer coverage of the nanoparticle surface by the metal complexes, consistent with limiting surface coverages of previously reported analogous systems. Eu2O3 nanoparticles modified with [Rh(deeb)2Cl2]+ exhibit minimal to no energy transfer from emission spectra, and a reduction in the lifetime at 77K could be due to the rhodium complex preventing the excitation of Eu3+. Upon attachment of the Ir complexes [Ir(deeb)2Cl2]+ and [Ir(deeb)2(dpp)]3+ on as-prepared nanoparticles, Eu3+ luminescence was observed for nanoparticles modified with iridium complexes at room temperature, which could be due to energy transfer among other possibilities. Efficiencies of 68% and 50%, and energy transfer rate constants of 1.1 x 10-5 and 1.0 x 10-5 were calculated from lifetime data for [Ir(deeb)2Cl2]+ and [Ir(deeb)2(dpp)]3+ on Eu2O3 nanoparticles, respectively. Since iridium complexes are used as components of light-emitting diodes, europium oxide nanoparticles modified with iridium complexes have potential in optical applications which make studies of these compounds interesting.Master of Science
2
Kamras, Brian Leon. "Application-Focused Investigation of Monovalent Metal Complexes for Nanoparticle Synthesis." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1538771/.
Full textAbstract:
Over the last 20 years, there has occurred an increase in the number, scope, and impact of nanomaterials projects. By leveraging the Surface Plasmon Resonance of metallic nanoparticles for labelling, sensing, and treatment, researchers have demonstrated the versatile utility of these nanomaterials in medicine. The literature provides evidence of use of simple, well-known chemistry for nanomaterials synthesis when the focus is new applications of nanomaterials. A case in point, is the synthesis of metallic nanoparticles, whereby HAuCl4, CuCl2, Cu(acac)2, and AgNO3 are typically employed as nanoparticle precursors. Unfortunately, the use of these precursors limits the number of applications available to these materials - particularly for AuNPs in medicine, where the byproducts of nanoparticle synthesis (most often surface-adsorbed reductants, toxic stabilizers, and growth directors) cause nanoparticles to fail clinical trials. Despite the several thousand publications detailing the advancements in nanoparticle therapeutics, as of 2017, there were only 50 FDA-approved nanoparticle formulations. Less than 10 were based on metallic nanoparticles. This is a problem because many of these nanoparticle therapeutics demonstrate potent cell killing ability and labeling of cells. A solution to this problem may be the use of weakly coordinated, monovalent metal complexes, which require only one electron to reduce them to their metallic state. Further, by designing nanoparticle syntheses around these monovalent complexes, we can employ weaker, environmentally friendly stabilizers. This strategy also forgoes the use of exogenous reducing agents, because the monovalent complexes can be reduced and stabilized by one reagent. Herein we investigate the use of Au(Me2S)Cl, [Cu(MeCN)4]BF4, and AgBF4 with green stabilizers to synthesize a variety of nanomaterials. We find that a range of sizes of spherical particles, as well as a range of sizes of gold triangular prisms can be synthesized by using techniques that follow this strategy.
3
Luska, Kylie. "The catalytic application of ionic liquid-stabilized metal nanoparticles and molecular complexes." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110575.
Full textAbstract:
Ionic liquids (ILs) have gained considerable research attention as potential replacements for volatile organic chemicals (VOCs) based solvents due to their low vapour pressures and ability to be easily recovered and recycled. Research on ILs has revealed such novel properties as: high chemical and thermal stabilities, good gas solubilites, wide windows of electrochemical stability, good electrical conductivities, high ionic mobilities and immiscibilities with some organic solvents and water. The exploitation of these IL properties has expanded the application scope to include: analytics, catalysis, electrochemistry, nanotechnology, synthesis and separations. This thesis examined the use of ILs in the synthesis of metal nanoparticles (NPs) and molecular complexes, with their application in biphasic catalysis. Metal NPs were synthesized directly in imidazolium or phosphonium ILs, which act as a reaction solvent and an electrostatic NP stabilizer. ILs functionalized with a metal binding moiety (i.e. thiolate or phosphine), otherwise known as functionalized ILs (FILs), were also employed for the synthesis of NPs to enhance their stability by direct attachment of the IL moiety to the metal surface. Transition metal NPs embedded in an IL solvent provided highly effective and recyclable biphasic hydrogenation catalysts for the reduction of alkene and arene substrates. FILs were also employed as stabilizing species of molecular complexes used as biphasic hydroformylation catalysts of long-chain olefins. Important to all of these studies was the influence of the IL parameters (i.e. cationic headgroup, alkyl chain length, counter anion) on the properties of the metal NPs and molecular complexes (i.e. NP size, surface plasmon band, stability under catalytic conditions, catalytic activity and selectivity). ILs are shown to be a highly tunable class of compounds, which allow for control of the properties of metal species stabilized within an IL.Les liquides ioniques (LIs) ont fait l'objet d'une attention considérable en tant qu'alternatives potentielles aux solvants à base de composés organiques volatiles du fait de leur faible pression de vapeur saturante et de la facilité avec laquelle on peut les récupérer et les recycler. La recherche sur les LIs a par ailleurs révélé de nombreuses propriétés telles que : une grande stabilité chimique et thermique, de bonnes solubilités pour les gaz, une large fenêtre de stabilité électrochimique, une bonne conductivité électrique, une bonne mobilité ionique et une immiscibilité avec certains solvants organiques et l'eau. L'exploitation de ces propriétés ont étendues le champ des applications pour comprendre : la chimie analytique, la catalyse, l'électrochimie, la nanotechnologie, la synthèse et la purification. Cette thèse traite de l'utilisation des LIs pour la synthèse de nanoparticules (NPs) métalliques et de complexes, ainsi que de leur utilisation en catalyse biphasique. Des NPs métalliques ont été synthétisées directement dans les LIs à base de cations imidazolium ou phosphonium. Ces LIs jouent le rôle de solvant et de stabilisants électrostatiques pour les NPs. Des LIs fonctionnalisés avec une espèce ligante (i.e. un thiolate ou une phosphine), appelés LIs fonctionnalisés (LIFs), ont été employés pour la synthèse de NPs pour améliorer leur stabilité par attachement direct du LI à la surface métallique. Les NPs de métaux de transition ainsi obtenues sont très actives en catalyse biphasique d'hydrogénation des alcènes et des arènes et recyclables. Les LIFs ont également été employés comme ligands pour des complexes moléculaires utilisés en catalyse biphasique d'hydroformylation des oléfines à longue chaine. Au centre de cette étude, les paramètres moléculaires des LIs (i.e. le groupement cationique, la longueur de la chaine alkyle, le contre-ion) se sont révélés influer sur les propriétés des NPs métalliques et des complexes moléculaires (i.e. la taille des NPs, leur bande plasmon, leur stabilité en condition catalytique, leur activité catalytique et leur sélectivité). Les LIs constituent une classe de composés hautement versatiles, qui permettent le contrôle des propriétés des espèces métalliques qu'ils stabilisent.
4
Rogers, Nicola Jane. "The development of gold nanoparticles labelled with transition metal complexes for imaging applications." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5058/.
Full textAbstract:
13 nm and 100 nm citrate-stabilised gold nanoparticles are used as inert scaffolds for the assembly of multiple transition metal lumiphores, and thiol-appended ruthenium(II) and iridium(III) polypyridyl complexes have been synthesised for surface-attachment. The direct attachment of cationic lumiphores to citrate-stabilised gold colloids with negative zeta potentials, affords nanoparticle aggregation, due to loss of electrostatic stabilisation. In order to circumvent this problem, a surfactant pre-coating step has been implemented, and the following commercial surfactants have been evaluated: Triton™ X-100, TWEEN® 20, and Zonyl® 7950. Gold nanoparticles coated with Zonyl® 7950 fluorosurfactant can be functionalised with cationic lumiphores and colloidal stability is maintained even at high nanoparticle concentrations, i.e. 9 nM. The fluorosurfactant not only ensures colloidal stability, but also enhances the emission of the ruthenium(II) and iridium(III) complexes investigated. Importantly, the complexes attached on the resultant luminescent nanoprobes do not exhibit luminescence quenching from the gold nanoparticles. Imaging applications of the resultant luminescent nanoparticles have been demonstrated in in vitro cellular uptake studies and in blood flow particle tracking within the microvasculature. Furthermore, gold nanoparticles have been co-coated with lumiphores and both functional peptides, for targeted delivery in cells, and gadolinium(III) complexes, in order to realise imaging probes for both luminescence and MRI detection.
5
Yakushev, I. A., N. Y. Kozitsyna, O. N. Kondratyeva, M. N. Vargaftik, and I. I. Moiseev. "Mixed-Metal Palladium(II) Complexes: a Way from Heterometallic Carboxylates to Bimetallic Nanoparticles." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35239.
Full textAbstract:
The paper describes some chemical transformations of the mixed-metal palladium (II) complexes, including
interactions of binuclear complexes with pyridine, 1,10-phenanthroline and bipyridine; also described
thermal and reductive transformations of some binuclear and pentanuclear nitrogen-containing
complexes, in particular red-ox transformations in reductive media to yield mixed-metal nanomaterials.
For this nanomaterials and nanoalloys also provided HREM and TEM investigations.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35239
6
Thangwane, Selaelo Christabel. "Synthesis and characterization of substituted dithiocarbamates ligands and complexes as a source of metal (Pb, Ni & Co) sulphide nanoparticles." Thesis, Vaal University of Technology, 2017. http://hdl.handle.net/10352/396.
Full textAbstract:
M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology.Lead, nickel and cobalt dithiocarbamates complexes were synthesized using methanol and water as solvents. All complexes were refluxed at 60 °C, cooled at room temperature, washed with methanol to remove the impurities and dried under the fume hood. A combination of Fourier transformer infrared (FTIR), elemental analysis (EA) and thermogravimetric analysis (TGA) were used to characterize these complexes. There was shifting of bands from low to high frequencies of the dithiocarbamates complexes compared to benzimidazole derivatives. The absence of the N-H band and the presence of new C=S bands confirmed that the complexes can be used in the preparation of metal sulphide nanoparticles. Elemental analysis showed that there was a percentage mismatch for the complexes I, III, IV and V. Complexes II and VI calculated percentages were within the limits with the found percentages except for sulphur which was low. The TGA curves decomposed to form a mixture of metal and metal sulphides for complex I, II, III and IV except for complex VI which gave metal sulphide only. All benzimidazole complexes decomposed at higher temperatures and were considered as stable complexes. Lead sulphide (PbS) is an important group IV-VI metal chalcogenide semiconductor. It has a direct narrow band gap of 0.41 eV at 300K and a large excitonic Bohr radius of 18 nm. Lead sulphide absorption band can be tuned to anywhere between near IR to UV (0.4μm) covering the entire visible spectrum, while achieving the quantum confinement region. The synthesis of lead sulphide nanoparticles was conducted by varying the effect of the reaction conditions such as the type of capping agents and temperature. Lead dithiocarbamate complex derived from benzimidazole, [Pb(S2N2C8H5)2] was thermolysed in hexadecylamine (HDA) and trioctylphosphine oxide (TOPO) at different reaction temperatures (140, 160 and 180 °C) to produce HDA and TOPO capped PbS nanoparticles. The nanoparticles were characterized using X-ray diffraction (XRD) for structural analysis, transmission electron microscopy (TEM) for shape and size, Ultraviolet visible (UV/Vis) and Photoluminescence (PL) spectroscopy for optical properties. An increase in temperature gave a decrease in the sizes of the nanoparticles when using the HDA capped lead benzimidazole dithiocarbamate complex. The observed morphology was cubes. TOPO capped lead benzimidazole dithiocarbamate complex gave no specific trend when temperature was varied. A cross-like layer with quasi spherical particles on top was observed at 160 °C. At 180 °C, the cross-like layer decomposed into rods- like materials with quasi spherical particles on top for TOPO capped PbS nanoparticles. For lead 2-methylbenzimidazole [Pb(S2N2C9H7)2] dithiocarbamate complex, TOPO capped PbS produced agglomerated cubic morphology at low temperature but as the temperature was increased agglomerated cylindrical shapes were observed. HDA capped PbS produced polydispersed nanocubes which were increasing in size when the temperature was increased. Nanoparticles displayed a blue shift in band edges with good photoluminescence behaviour which was red shifted from their respective band edges all temperatures and capping agents. XRD confirmed the crystal structure of cubic phase (galena) of PbS at all temperatures except for HDA capped PbS nanoparticles at 140 °C from lead benzimidazole dithiocarbamate complex which confirmed the crystal structure of face-centred cubic phase of PbS nanoparticles. Nickel sulphide has much more complicated phase diagram than cobalt sulfides and iron sulfides. Their chemical composition has many crystalline phases such as α-NiS, β=NiS, NiS2, Ni3S2, Ni3S4, Ni7S6 and Ni9S8. Ni3S2 phase has shown potential as a low-cost counter electrode material in dye sensitised solar cells, while the α-NiS phase has been applied as a cathode Material in lithium-ion batteries. The synthesis of nickel sulphide nanoparticles was done by varying the effect of the reaction conditions such concentration and temperature. Nickel benzimidazole dithiocarbamate [Ni(S2N2C8H5)2] and nickel 2-methylbenzimidazole [Ni (S2N2C9H7)2] dithiocarbamates complexes were thermolysed in hexadecylamine (HDA) at different reaction temperatures (140, 160 and 180 °C) and precursor concentrations (0.30, 0.35 and 0.40 g) to produce HDA capped NiS nanoparticles. It was observed that increasing both temperature and precursor concentration increased the size of the nanoparticles. Anisotropic particles were observed for both complexes when varying precursor concentration and temperature. Nickel benzimidazole dithiocarbamate complex produced stable shapes (spheres and cubes) of nickel sulphide nanoparticles. Nickel 2-methylbenzimidazole dithiocarbamate complex produced a mixture of spheres, cubes, triangles and rods nickel sulphide nanoparticles at all concentrations. But when varying temperature, it only produced that mixture at 160 °C. The optical measurements supported the presence of smaller particles at all temperatures and concentrations. XRD showed the presence of C7OS8 and pure nickel as impurities. However, the crystal structure of cubic Ni3S4 was observed at low temperatures and an introduction of monoclinic NixS6 at high temperature (180 °C) when varying temperature for both complexes. When varying concentration using nickel benzimidazole dithiocarbamate complex, XRD showed the presence of NiSO4.6H2O impurities at high temperatures. At 160 °C a mixture of hexagonal NiS and cubic Ni3S4 was observed. At low temperatures only nickel as a metal was found as an impurity and the crystal structure of cubic Ni3S4 was observed. When nickel 2-methylbenzimidazole complex was used, C7OS8 and pure nickel were found as impurities but the crystal structure of cubic Ni3S4 was observed. Cobalt sulphide (CoS) belongs to the family of group II-IV compounds with considerable potential for application in electronic devices. They have a complex phase diagram and their chemical composition have many phases such as Co4S3, Co9S8, CoS, Co1-xS, Co3S4, Co2S3 and CoS2. The synthesis of cobalt sulphide nanoparticles was conducted by varying the effect of temperature on size and shape of the nanoparticles. Nickel benzimidazole dithiocarbamate, [Ni(S2N2C8H5)2] and nickel 2-methylbenzimidazole [Ni(S2N2C9H7)2] complexes were thermolysed in hexadecylamine (HDA) at different reaction temperatures (140, 160 and 180 °C) to produce HDA capped CoS nanoparticles. Cobalt benzimidazole dithiocarbamate complex produced close to spherical shapes nanoparticles at all temperatures. The images showed that as temperature was increased, the size of the particles decreased. All the main reflection peaks were indexed to face-centred cubic Co3S4 and there were some impurities of C7OS8 at all temperatures. The optical measurements supported the presence of smaller particles at all temperatures. Cobalt 2-methylbenzimidazole dithiocarbamate complex produced big and undefined morphology. The optical properties were also featureless and XRD only showed impurities of C7OS8. The impurity is thought to be generated from a side reaction between benzimidazole and carbon disulphide to give this persistent organic moiety.
7
Roffey, A. R. "Dithiocarbamate complexes as single source precursors to metal sulfide nanoparticles for applications in catalysis." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1437012/.
Full textAbstract:
Herein we report the solvothermal decomposition of a range of metal dithiocarbamate complexes for the synthesis of metal sulfide nanoparticles. Metal sulfides exist in a variety of structural phases, some of which are known to be catalytically active towards various processes. The aim of this work was to synthesise a variety of different metal sulfide phases for future catalysis testing, particularly the iron sulfide greigite (Fe3S4, a thiospinel containing Fe2+ and Fe3+) which is to be tested for CO2 reduction. A range of metal dithiocarbamate complexes were synthesised and Chapter 2 focusses on the synthesis of iron dithiocarbamates. Both iron(II) and iron(III) complexes were synthesised, the latter being a facile, open bench reaction producing a range of [Fe(S2CNRR’)3] complexes. Iron(II) bis(dithiocarbamates) are extremely air sensitive therefore carbonyl protected [Fe(S2CNRR’)2(CO)2] complexes were prepared for ease of use as precursors. The stability of the complexes was tested by TGA to ensure they were suitable precursors for metal sulfide synthesis, i.e. that the carbonyl ligands were sufficiently labile to leave the complexes before decomposition, which proved to be successful. In the following Chapter these iron dithiocarbamate complexes were solvothermally decomposed, but interestingly a combination of iron(II) and iron(III) precursors did not produce greigite as expected, but pyrrhotite (Fe7S8, containing only Fe2+). Systematic studies into the effect of decomposition temperature, precursor concentration and precursor type, on the phase and morphology of the resulting iron sulfide nanoparticles were performed on the iron(III) dithiocarbamate precursor. The phase was found to be highly dependent on both concentration and temperature. The use of a redox active additive, thiuram disulfide, on the decomposition was also investigated and found to have a significant effect, promoting the formation of the metastable greigite phase. Chapter 4 examines the nickel bis(dithiocarbamate) decomposition system to see if its behaviour was consistent with trends observed in the iron case. In general, similar trends were observed in the phase and morphology of the nickel sulfides when the decomposition parameters were varied, metastable phases were observed at lower temperature and higher concentration. The effect of thiuram disulfide on the system was greater, however, than in the iron case, whereby an additional nickel sulfide phase (NiS2) was observed at high concentration in the presence of this additive. Chapter 5 deals with a broader range of metal dithiocarbamate systems, to attempt to elucidate whether or not the trends seen for nickel and iron are universal for metal dithiocarbamate precursors. The Co, Cu, Zn and In dithiocarbamate systems were examined with and without thiuram disulfide, and some effect were seen on the phase of metal sulfide nanoparticle formed, but only at high concentration in the presence of the additive. Mixed-metal studies were performed to investigate the suitability of metal dithiocarbamates as precursors to ternary metal sulfides, and success was observed for iron-nickel, cobalt-nickel and iron-copper sulfides, though the iron-zinc and iron-indium systems only produced binary sulfides. The final Chapter looks into the metal dithiocarbamate decomposition mechanism in detail, using [Ni(S2CNiBu2)2] as a model system. NMR, in situ UV-vis, MS and powder XRD are all employed to probe the mechanism, in conjunction with XAS and computer modelling which was performed by others. The mechanism was found to rely heavily on an intermediate formed from amide exchange between the dithiocarbamate backbone and solvent amine, indicating the solvent plays an extremely significant role in the solvothermal synthesis of metal sulfides from dithiocarbamate precursors.
8
Tilbury, Rhys David. "Investigation into Electronic Interactions Between Tetrazolato Complexes and Metal Nanoparticles Synthesised via Laser Ablation." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/57109.
Full textAbstract:
Metal nanoparticles were generated by the Laser Ablation Synthesis in Solution approach, encapsulated and stabilised by a variety of ligands in solution. The encapsulation ligands were designed and synthesised to allow the attachment of phosphorescent transition metal complexes on their outer shell. This should facilitate energy transfer between the complex-centre excited state and the surface plasmon resonance of the core. This exploitation of the electronic structure of the nanoparticle surface has insinuations for a variety of photovoltaic applications.
9
Zalich, Michael Andrew. "Physical Properties of Magnetic Macromolecule-Metal and Macromolecule-Metal Oxide Nanoparticle Complexes." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/27528.
Full textAbstract:
Magnetic nanoparticles are of considerable interest owing to their potential applications in biotechnology and the magnetic recording industry. Iron oxides have received much attention owing to their oxidative stability and biocompatibility; however, other transition metals and their alloys are also under investigation. Cobalt has one of the largest magnetic susceptibilities of these materials, but it readily oxidizes upon exposure to air resulting in antiferromagnetic oxide. Hence, coating cobalt nanoparticles with an oxygen-impermeable sheath would confer numerous benefits. Cobalt nanoparticles were prepared by the thermolysis of dicobalt octacarbonyl in two block copolymer micellar systems, wherein the copolymers were precursors to graphite or silica. Subsequent heat treatment of the samples at 600-700oC was conducted to condense the polymer coating around the cobalt nanoparticles and form oxygen impervious graphite or silica sheaths.
Magnetic and structural characterization of these novel materials afforded pertinent information about their physical properties. Magnetic susceptometry indicated that the graphite coated cobalt nanoparticles resisted oxidation for over one year. The silica coated cobalt nanoparticles had high saturated specific magnetic moments, but the coatings were brittle and grinding the particles resulted in oxidation over time. Transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and energy-filtered TEM (EFTEM) were employed to study particle size and structural differences of the cobalt nanoparticles before and after heat treatment. The mean particle size and size distribution increased for the graphite coated cobalt particles, due to particle sintering at 700oC. In the silica coated cobalt nanoparticle system, the mean particle size increased when the sample was heat-treated at 600oC leading to a bimodal distribution. This bimodal distribution was explained by a fraction of the particles sintering, while others remained discrete. When the silica system was heat treated at 700oC, the particle size and size distribution remained similar to those of the pre-heat-treated sample, indicating that no sintering had taken place. The rapid pyrolysis of the polymer at 700oC may serve to lock the cobalt nanoparticles into a silica matrix, thus preventing them from coming into contact with one another and sintering. Several diffraction techniques (selected area electron diffraction (SAD), nano-beam electron diffraction (NBD) and x-ray diffraction (XRD)) were used to probe the crystal structure of graphite and silica coated cobalt nanoparticles, which was determined to be predominantly face-centered cubic.
Anisotropic magnetic nanoparticles (nanorods) have an increased magnetophoretic mobility over spherical magnetic nanoparticles with the same equatorial radius. This property makes them attractive candidates for in vivo biological applications. Anisotropic mixed ferrite nanoparticles were coated with a biocompatible hydrophilic block copolymer to render them dispersible in aqueous media. Polymer coated mixed ferrite particles exhibited magnetic properties similar to that of pure magnetite, as the total level of other transition metals in the nanoparticulate system was less than 5%. Electron energy loss spectroscopy (EELS) and (EFTEM) confirmed that the dominant elements in the mixed ferrite nanoparticles were iron and oxygen. Furthermore, HRTEM, SAD and XRD analyses indicated that the crystal structure for the mixed ferrite nanoparticles was inverse spinel. X-ray diffraction peaks at low angles for the coated mixed ferrite rods corresponded to poly(ethylene oxide) peaks, suggesting that the block copolymer employed as a dispersant was associated with the particles.Ph. D.
10
Eriksson, Kristofer. "Development and Applications of Surface-Confined Transition Metal Complexes : Heterogeneous Catalysis and Anisotropic Particle Surfaces." Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-88215.
Full textAbstract:
The main focus of this thesis has been directed towards developing novel surface-confined transition metal complexes for applications in heterogeneous catalysis and for the preparation of anisotropic particle surfaces. The first part describes the heterogenization of a homogeneous transition metal-based catalyst tetraphenyl cobalt porphyrin (CoTPP) on silicon wafers and on silica particles. The activity in hydroquinone oxidation for the silica particle-immobilized CoTPPs was found to be increased 100-fold compared to its homogeneous congener whereas the silicon wafer-immobilized CoTPPs achieved lower activity due to the formation of clusters of catalyst molecules on the support surface as detected with atomic force microscopy (AFM). The second part of this thesis describes the development and characterization of anisotropic particle-surfaces by electrochemical site-specific oxidation of surface-confined thiols. Reactive patches or gold gradients could be obtained on the particle surfaces depending on the type of working electrode used and on the electrolyte composition. The particle surface functionalities were characterized with X-ray photoelectron spectroscopy (XPS) and the particle-surface-confined patches and gradients were conjugated with proteins to obtain fluorescence for investigation using fluorescence microscopy. Gold-functionalized siliceous mesocellular foams were further demonstrated to be highly efficient and selective catalysts in the cycloisomerization of 4-alkynoic acids to lactones. The final part of this thesis describes the preparation and characterization of palladium nanoparticles heterogenized in the pores of siliceous mesocellular foam. The nanoparticles were analyzed with transmission electron microscopy (TEM) and found to have a size of 1-2 nm. Primary- and secondary benzylic- and allylic alcohols were oxidized by the heterogeneous palladium nanoparticles in high to excellent yields using air atmosphere as the oxygen source. The nanopalladium catalyst was used up to five times without any decrease in activity and the size of the nanoparticles was retained according to TEM.At the time of doctoral defence the following paper were unpublished and had a status as follows: Paper1: Manuscript; Paper 4: Manuscript
11
Atoini, Youssef. "New luminescent hybrid materials : synthesis and properties." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAF004/document.
Full textAbstract:
L'objectif de cette thèse est la synthèse, la caractérisation et l'étude de complexes métalliquesluminescents, en particulier de Pt (II), leurs propriétés d'agrégation en solution, mais également dansun espace confiné ainsi qu’en surface. L'incorporation de complexes de métaux de transition dans lastructure poreuse, et ainsi que leur dépôt à la surface de nanoparticules et dans un cadre métalloorganique(MOF), par greffage post-synthétique, ont été étudiés. Sont également étudiés lacorrélation entre les propriétés de films d’une série de complexes de Pt(II) avec leur morphologie,leur mobilité électronique et la simulation de leur structure auto-assemblée par diffraction auxrayons-X. Les propriétés de luminescence de complexes amphiphiles de Pt(II) sont améliorées àl’intérieur de nanoparticules de silice mesoporeuse par la création d’un d’espace confiné. Un effetsimilaire est observé par le dépôt de complexes de Pt(II) fonctionnalisés sur une surface denanoparticules d’or. La luminescence d’un cadre organométallique a été modifiée par greffage postsynthétiquede complexes d’Ir(III) et de Pt(II)The aim of this thesis is the synthesis, characterization and investigation of luminescent metalcomplexes, and in particular of Pt(II) compounds, their aggregation properties in solution but inconfined space as well. The incorporation of transition metal complexes in porous structure, and inparticular in a metal-organic framework (MOF), by post-synthesis grafting, have been investigated.Luminescence properties of amphiphilic Pt(II) complexes were enhanced inside mesoporous silicananoparticles by the creation of a confined space. Similar effect is observed by deposition offunctionalized Pt(II) complexes on gold nanoparticles surface. Luminescence of metal organicframework was tuned by post-synthetic grafting of Ir(III) and Pt(II) complexes
12
TRASATTI, Andrea. "New heteroscorpionate and macrocyclic ligands, related metal complexes and novel Gold nanoparticles: synthesis, structure analysis and biological studies." Doctoral thesis, Università degli Studi di Camerino, 2013. http://hdl.handle.net/11581/401702.
Full textAbstract:
The synthesis, the structural and the biological analysis of a series of new macrocyclic, heteroscorpionate ligands and related copper complexes are reported in the first two parts of this PhD thesis. In the third part the study of the internalization processes of new gold nanoparticles in the HeLa cells were showed. In the first part the coordination environment and the stability behavior of the new macrocyclic ligands 1,10-dithia-4,7-diazacyclododecane-3,8-dicarboxylic acid (NEC-SE), 1,10-dithia-4,7-diazacyclotridecane-3,8-dicarboxylic acid (NEC-SP), 1,10-dithia-4,7-diazacyclotetradecane-3,8-dicarboxylic acid (NEC-SB), 4-methyl-1,7-ditihia-4,10,13-triazacyclopentadecane-9,14-dicarboxylic acid (NEC-SN-Me) and of the corresponding Cu(II) complexes were investigated both in the solid state and in aqueous solution. The Cu2+ complexation constants for NEC-SE were determined in aqueous solution. The behavior of the copper complexes in presence of the strong copper chelating bioagent human serum albumin was also examined, to gain information on the stability of these compounds in biological fluids. The corresponding 64Cu(II) labeled complexes were produced in major98% radiochemical purity in collaboration with Prof. J. S. Lewis (Memorial Sloan-Kettering Cancer Center, NY). Rats were injected with complexes and were euthanized at 1, 4 and 24 h. All three complexes were cleared from the blood over the first hour following injection but there was poor clearance of this activity over 24 h. In the second section the syntheses by direct coupling of preformed side chain acid and amine components of new nitroimidazole and glucosamine conjugated heteroscorpionate ligands, namely 2,2-bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide (LMN) and 1,3,4,6-tetra-O-acetyl-2-{[bis(3,5-dimethyl-1H-pyrazol-1-yl)acetyl]amino}-2-deoxy-b-D-glucopyranose (LDAC), respectively, were reported. The related copper(II) complexes {[(LMN)2Cu]Cl2} and {[(LDAC)2Cu]Cl2} were prepared from the reaction of CuCl2*2H2O with LMN or LDAC in methanol solution. XAS and EXAFS were used to determine the local environment of the two copper(II) complexes. The new copper(II) complexes and the uncoordinated ligands were evaluated for their cytotoxic activity towards a panel of several human tumour cell lines. The results indicated that both copper(II) complexes show similar spectra of cytotoxicity and very low resistance factors (RF minus 2) against C13* ovarian cancer cells which have acquired resistance to cisplatin. In the last part only partial results were reported because the study is still in progress. This part of PhD work was carried out in collaboration with the research groups of Prof. Stellacci in the Department of Materials Science and Engineering, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland, during my abroad 6 months stage. The synthesis of a series of mixed-ligand gold nanoparticle (NPs) obtained varying the lengths of both the hydrophobic and hydrophilic ligand length were carried out. The synthesized NPs were studied using 1H-NMR (first and before the decomposition with potassium cyanide), TEM and GC-MS analysis. The NPs with a size between 4 and 10 nm were recovered using the fractionation by centrifugation, which is a technique that uses the principle that larger particles sediment faster than smaller ones. Confocal laser scanning microscopy (CLSM) and flow cytometry (FCM) were used to explore how the temperature of the system, the size of NPs and their shell composition affect the internalization processes in the analyzed cell.
13
Arnedo-Sanchez, Leticia. "Lanthanide and transition metal complexes as building blocks for supramolecular functional materials." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF047.
Full textAbstract:
Cette thèse porte sur les complexes de coordinations basés sur les métaux de transitions et les lanthanides en tant qu'éléments clés pour créer des matériaux fonctionnels. Précisément, des matériaux contenant des propriétés de détection, d'auto assemblage et optique ont été conçus et optimisés. En plus d'une brève introduction sur la photophysique, les gels supramoléculaires et les nanoparticules métalliques, un résumé sur les différents instruments et techniques employés pour ces travaux est inclus. Le chapitre 3 décrit la synthèse et la caractérisation de complexe de lanthanide anionique. Des techniques analytiques, tels que la spectroscopie d'émission ou la cristallographie à rayon X ont été employé pour caractériser ces différents complexes. Dans le chapitre 4, l'étude de complexes métalliques luminescents se focalise sur les complexes de métaux de transition, et plus précisément sur les complexes d'iridium(lll). Une famille de complexes d'iridium(lll) bi-cyclométallés neutres qui montre une intense émission rouge sous photo ou electro excitation est étudié. Le chapitre 5 présente la conception et le développement d'une nouvelle famille de gelators à faible poids moléculaire, basée sur des terpyridines perfluorés.La morphologie ainsi que les propriétés mécaniques et thermodynamique de ces metallogels sont étudiées. Le chapitre 6 présente une nouvelle sonde colorimétrique, composée de nanoparticules d'or fonctionnalisées avec des complexes de Zn aminoterpyridinique via des liaisons thiol est décrite pour la détection de pyrophosphateThis thesis deals with coordination compounds based on transition metals and lanthanides as key components of functional materials. Besides a brief summary of photophysics, supramolecular gels and metal nanoparticles, an overview of the instruments and techniques employed in this work is included. This thesis is further divided into four chapters focused on optically active metalcomplexes (chapters 3 and 4), stimuli responsive metallogels (chapter 5) and functionalized nanomaterials for sensing applications (chapter 6). In chapter 3, the synthesis and characterization of anionic lanthanide complexes is reported. Analytical techniques, emission spectroscopy and X-ray crystallography were employed to characterize these complexes. ln chapter 4, the study of light emitting metal complexes is extended to transition metal complexes, in particular to iridium (lll) complexes. A family of neutral bis-cyclometallated iridium (lll) complexes that exhibit an intense red emission under photo- or electro-excitation is studied. ln chapter 5 the design and investigation of a new family of low molecular weight gelators based on perfluorinated terpyridines is reported. The morphology and mechanical and thermodynamical properties of these metallogels is studied. Chapter 6 studies the excellent cooperation between coordination compounds and nanomaterials to yield optical sensors. A new colorimetric sensor for pyrophosphate consisting of gold nanoparticles acting as reporting units functionalized with a thiol-modified aminoterpyridine-Zn complex is described
14
Santos, Jonnatan Julival dos. "Ouro: um metal multifuncional. Estudo das propriedades eletrônicas e espectroscópicas de suspensões e filmes de nanopartículas de ouro aplicados a sensoriamento." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-16012014-081808/.
Full textAbstract:
Nanopartículas de ouro são \"blocos de construção\" muito versáteis para a preparação de novos nanomateriais híbridos funcionais. Suas propriedades físico-químicas permitem a criação de sistemas capazes de absorver luz, transportar elétrons ou, ainda, interagir com moléculas e biomoléculas. Nesta tese foram estudados os fatores que influenciam o Espalhamento Raman Intensificado pela Superfície (SERS), visando o aumento da sensibilidade da técnica pela formação de compósitos com nanopartículas magnéticas, além de explorar a estratégia de montagem coordenativa para a preparação de nanomateriais híbridos contendo complexos de rutênio visando o desenvolvimento de sensores para moléculas e/ou íons moleculares. Assim, foi demonstrado como é possível aumentar o sinal de espalhamento Raman obtido em pelo menos 30%, através do controle da relação número de moléculas/ nanopartícula de ouro. Ou seja, verificou-se que a melhor relação sinal ruído foi alcançado com cerca de 16 mil moléculas de fenantrolina por nanopartícula de ~42 nm, gerando espectros mais definidos e sem a presença de bandas indesejáveis, por exemplo associadas aos agentes estabilizantes. Essa propriedade das nanopartículas de ouro foi potencializada por meio da associação com nanopartículas superparamagnéticas de óxido de ferro gerando substratos SERS sensíveis, reprodutíveis, de preparação simples e baratos. A interação entre as nanopartículas de ouro e as nanopartículas superparamagnéticas foram monitoradas por espectroscopia eletrônica no ultravioleta-visível, microscopias eletrônicas de varredura e de transmissão e microscopias de campo escuro e hiperespectral. Verificou-se que as nanopartículas interagem fortemente entre si gerando materiais supramoleculares que podem ser atraídas e concentradas utilizando-se um imã, para a realização de medidas de espectroscopia Raman/SERS. Essa nova metodologia e substrato SERS possibilitaram a quantificação de azul de metileno e de fenantrolina em concentrações na faixa de 5x10-9 a 5x10-11 mol dm-3. De fato, foi observado um aumento do sinal Raman de até 60 vezes, quando comparado ao sinal sem a concentração magnética. Finalmente, a interação das nanopartículas de ouro com três diferentes clusters trigonais de acetato de rutênio (ou, simplesmente, clusters de rutênio) simétricos, com os ligantes 4-cianopiridina, 4,4\'-bispiridina e trans-1,2-bis(4-piridil)etileno como substituintes axiais foi explorado para a preparação de polímeros de coordenação funcionais. Os clusters de rutênios foram caracterizadas por espectroscopia eletrônica no ultravioleta-visível, eletroquímica e espectroeletroquímica. A seguir os clusters de rutênio foram utilizados como \"réguas molecular\", explorando a diferença de tamanho e o fato delas funcionarem como \"moléculas-pontes\", para a realização de estudos de acoplamento plasmônico, acompanhando-se tal fenômeno por espectroscopia eletrônica no ultravioleta-visível. A interação entre as nanopartículas de ouro e os clusters de rutênio puderam ser estudadas por espectroscopia de ressonância plasmônica de superfície (SPR), onde foi investigado o processo de formação de filmes por meio da técnica. Estes foram caracterizados por espectroscopia Raman utilizando lasers de excitação de 532 e 785 nm, onde foram observados as bandas vibracionais dos clusters de rutênio e as contribuições ressonante, eletromagnética e de transferência de cargana intensificação Raman. Esses nanomateriais híbridos foram ainda imobilizados sobre eletrodos de vidro condutor e utilizados como sensores eletroquímicos para detecção de nitrito na faixa de concentrações entre 0,5x10-6 e 1x10-3 mol dm-3.Gold nanoparticles are \"building blocks\" very versatile for the preparation of new functional hybrid nanomaterials . Their physicochemical properties allow the creation of systems capable of absorbing light, electron transportation, or even interact with molecules and biomolecules. In this thesis we studied the factors that influence the surface enhanced Raman scattering (SERS), in order to increase the sensitivity of the technique by forming composites with magnetic nanoparticles, as well as explore the coordinative assembly strategy for the preparation of hybrid nanomaterials containing complexes ruthenium for the development of sensors for molecules and/or molecular ions . Thus, it was shown how is possible to increase the Raman signal obtained by at least 30 % just controlling the relative number of molecules/gold nanoparticle. That is, it was found that the best signal to noise ratio was achieved with about 16 thousand of molecules per nanoparticle ~ 42 nm, more defined and generating spectra without the presence of undesirable bands, for example, associated with stabilizers. This property of gold nanoparticles was enhanced by association with superparamagnetic nanoparticles of iron oxide generating sensitive SERS substrates, reproducible, with simple preparation methodology and inexpensive. The interaction between the gold nanoparticles and superparamagnetic nanoparticles were monitored by electronic spectroscopy in the ultraviolet -visible, scanning electron microscopy and transmission electron microscopy and dark field and hyperspectral microscopy. It was found that the nanoparticles interact strongly which can be attracted and concentrated using a magnet for the realization of Raman spectroscopy measurements / SERS. This new methodology, and SERS substrate, allowing the quantification of methylene blue concentrations and phenantroline in the range of 5x10-9 to 5x10-11 mol dm-3. In fact , we observed an increase in the Raman signal up to 60 times when compared to the signal without the magnetic concentration. Finally, the interaction of gold nanoparticles with three different clusters trigonal ruthenium acetate (or simply ruthenium clusters) symmetrical with the ligand 4- cyanopyridine, 4,4\'-bispiridina and trans-1,2-bis(4-pyridyl) ethylene axial been explored as substituents for the preparation of functional coordination polymers. Ruthenium Clusters were characterized by electron spectroscopy in the ultraviolet-visible, electrochemical and spectroelectrochemical. After that, the ruthenium clusters were used as \"molecular rulers\", exploring the size difference and the fact that they can act as \" molecules-bridges \" for studies of plasmon coupling, following up this phenomenon by electronic spectroscopy in the ultraviolet - visible. The interaction between the gold nanoparticles and ruthenium clusters could be studied by spectroscopy, surface plasmon resonance (SPR), where it investigated the process of formation of films by the technique. These were characterized by Raman spectroscopy using laser excitation of 532 and 785 nm, which were observed vibrational bands of ruthenium clusters and contributions resonant electromagnetic and transfer cargana Raman enhancement. These hybrid nanomaterials were also immobilized on glass electrodes and conductive used as electrochemical sensors for the detection of nitrite concentrations in the range of 0.5 x10-6 to 1x10-3 mol dm-3.
15
Bräuer, Björn. "Synthesis of bis(oxamato) transition metal complexes and Ni nanoparticles and their structural, magnetic, optical, and magneto-optical characterization." Doctoral thesis, Universitätsbibliothek Chemnitz, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200800928.
Full textAbstract:
Im Rahmen dieser Arbeit werden ein- und mehrkernige Cu(II)- und Ni(II)-bis(oxamato)-Komplexe im Hinblick auf ihre magneto-optischen Eigenschaften gezielt hergestellt und strukturell charakterisiert. Über ladungs- und übergangsmetallinduzierte Abweichungen vom allgemeinen in der Literatur beschriebenen Reaktionsverhalten wird berichtet.
Aus Elektronenspinresonanz-Untersuchungen wird die Spindichteverteilung in den einkernigen Cu(II)-Komplexen abgeleitet. Die Beeinflussung dieser durch die Koordinationsgeometrie sowie die Auswirkungen auf die Superaustausch-Wechselwirkung werden diskutiert und mit Ergebnissen der Dichtefunktionaltheorie (DFT) verglichen. Dreikernige bis(oxamato)-Komplexe werden erstmals durch Spin-Coating auf Si(111)-Substraten aufgebracht und mit Hilfe der spektroskopischen Ellipsometrie sowie der Ramanspektroskopie untersucht und mittels DFT-Berechnungen ausgewertet. Magneto-optische Kerr-Effekt-Untersuchungen werden an dünnen Schichten dieser Komplexe sowie Phthalocyaninen durchgeführt.
Zum Vergleich werden die magnetischen und magneto-optischen Eigenschaften von Ni-Nanopartikeln in verschiedenen organischen Matrizen untersucht. Mit Hilfe der Photoelektronenspektroskopie wird das Oxidationsverhalten dieser studiert und es werden Rückschlüsse auf Ladungstransferprozesse zwischen den Matrizen und den Nanopartikeln gezogen.
16
Escárcega, Bobadilla Martha Verónica. "Organometallic compounds and metal nanoparticles as catalysts in low environmental impact solvents." Doctoral thesis, Universitat Rovira i Virgili, 2011. http://hdl.handle.net/10803/9114.
Full textAbstract:
Durant les darreres dècades, el disseny de processos en el marc de la química sostenible ha anat creixent de forma exponencial. La recerca constant de processos mes benignes amb el medi ambient ha implicat un gran esforç per obtenir millors rendiments mitjançant l'activació de llocs específics, i possant especial èmfasi amb el control de la quimio-, la regio- i la enantioselectivitat, punts crucials per a l'economia atómica. En aquest sentit, els dissolvents juguen un paper crític, i com podrà veure's al llarg d'aquesta memòria..Aquesta Tesi s'enfoca en l'ús de mitjans de reacció alternatius i sostenibles, com són els líquids iònics (ILs), el diòxid de carboni supercrític (scCO2) i la barreja de ambdós dissolvents, amb l'objectiu de disminuir l'ús de dissolvents orgànics convencionals i la seva aplicació en els següents processos catalítics: hidrogenació asimètrica, reacció de Suzuki d'acoblament creuat C-C, reacció d'alquilació al·lílica asimètrica i la hidrogenació de arens.
In the last decades, the design of processes in the framework of the sustainable chemistry has been exponentially growing. The constant searching of cleaner processes has led to a lot of effort to obtain higher yields by activation of specific sites, and improving chemo-, regio- and enantio-selectivities, which are crucial from a point of view of an atom economy strategy. In this sense, solvents play a critical role.
This PhD thesis focuses on the use of alternative sustainable reaction media such as ionic liquids (ILs), supercritical carbon dioxide (scCO2) and mixtures of both solvents in different catalytic processes, with the aim of decreasing the use of conventional organic solvents applied in the following catalytic reactions: homogeneous and supported rhodium catalysed asymmetric hydrogenation, biphasic palladium catalysed Suzuki C-C cross-coupling, homogeneous palladium catalysed asymmetric allylic alkylation, and ruthenium and rhodium nanoparticles catalysed arene hydrogenation were tested.
17
Mefford, Olin Thompson. "Physical Properties of Macromolecule-metal oxide nanoparticle complexes: Magnetophoretic Mobility, Size, and Interparticle Potentials." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28133.
Full textAbstract:
Magnetic nanoparticles coated with polymers hold great promise as materials for applications in biotechnology. In this body of work, magnetic fluids for the treatment of retinal detachment are examined closely in three regimes; motion of ferrofluid droplets in aqueous media, size analysis of the polymer-iron oxide nanoparticles, and calculation of interparticle potentials as a means for predicting fluid stability. The macromolecular ferrofluids investigated herein are comprised of magnetite nanoparticles coated with tricarboxylate-functional polydimethylsiloxane (PDMS) oligomers. The nanoparticles were formed by reacting stoichiometric concentrations of iron chloride salts with base. After the magnetite particles were prepared, the functional PDMS oligomers were adsorbed onto the nanoparticle surfaces.
The motion of ferrofluid droplets in aqueous media was studied using both theoretical modeling and experimental verification. Droplets (~1-2 mm in diameter) of ferrofluid were moved through a viscous aqueous medium by an external magnet of measured field and field gradient. Theoretical calculations were made to approximate the forces on the droplet. Using the force calculations, the times required for the droplet to travel across particular distances were estimated. These estimated times were within close approximation of experimental values.
Characterization of the sizes of the nanoparticles was particularly important, since the size of the magnetite core affects the magnetic properties of the system, as well as the long-term stability of the nanoparticles against flocculation. Transmission electron microscopy (TEM) was used to measure the sizes and size distributions of the magnetite cores. Image analyses were conducted on the TEM micrographs to measure the sizes of approximately 6000 particles per sample. Distributions of the diameters of the magnetite cores were determined from this data. A method for calculating the total particle size, including the magnetite core and the adsorbed polymer, in organic dispersions was established. These estimated values were compared to measurements of the entire complex utilizing dynamic light scattering (DLS). Better agreement was found for narrow particle size distributions as opposed to broader distributions.
The stability against flocculation of the complexes over time in organic media were examined via modified Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations. DLVO theory allows for predicting the total particle-particle interaction potentials, which include steric and electrostatic repulsions as well as van der Waals and magnetic attractions. The interparticle potentials can be determined as a function of separation of the particle surfaces. At a constant molecular weight of the polymer dispersion stabilizer, these calculations indicated that dispersions of smaller PDMS-magnetite particles should be more stable than those containing larger particles. The rheological characteristics of neat magnetite-PDMS complexes (i.e, no solvent or carrier fluid were present) were measured over time in the absence of an applied magnetic field to probe the expected properties upon storage. The viscosity of a neat ferrofluid increased over the course of a month, indicating that some aggregation occurred. However, this effect could be removed by shearing the fluids at a high rate. This suggests that the particles do not irreversibly flocculate under these conditions.Ph. D.
18
Manrique, Salas Ester. "Development of new transition metal complexes for their use in sustainable catalytic processes and as antitumoral agents." Doctoral thesis, Universitat de Girona, 2018. http://hdl.handle.net/10803/668830.
Full textAbstract:
In this thesis we present the synthesis and characterization of different
types of ruthenium complexes containing N-donor ligands together with
monodentate ligands, along with their complete characterization through
spectroscopic and electrochemical techniques. The complexes have been
evaluated as catalysts for olefin epoxidation and nitrile hydration in
2/1
homogeneous phase. On the other hand, taking into account the importance and
advantages of the heterogeneous catalysis, we have carried out the
immobilization of some of these complexes on silica-type supports and
magnetic nanoparticles and we have evaluated their catalytic activity,
comparing them with the analogous homogeneous systems, and have been reused
for several runs maintaining high values of selectivity for the epoxide. Some
of the complexes together with other complexes previously synthesized in our
research group, have been tested as antitumoral agentsEn aquesta tesi es presenta la síntesi de diferents tipus de complexos de ruteni i manganès que contenen lligands N-donadors en combinació amb altres lligands monodentats, i la seva completa caracterització mitjançant tècniques espectroscòpiques i electroquímiques. Els complexos han estat avaluats com a catalitzadors en epoxidació d'olefines i hidròlisi de nitrils en fase homogènia. Per altra banda, tenint en compte la importància i els avantatges de la catàlisi heterogènia, s’ha dut a terme la immobilització d’alguns d’aquests complexos sobre suports tipus sílice i nanopartícules magnètiques i se n'ha avaluat l'activitat catalítica, comparant-los amb els anàlegs en fase homogènia, i s'han pogut reutilitzar durant diversos cicles mantenint alts valors de selectivitat per l'epòxid. Alguns dels complexos, juntament amb d'altres sintetitzats anteriorment al grup de recerca, han estat avaluats com agents antitumorals
19
HONEMANN, YVONNE CARINA. "DESIGN, CHARACTERIZATION AND APPLICATION OF HETEROGENEOUS SILICA SUPPORTED CATALYSTS, BASED ON PD NANOPARTICLES AND METAL SINGLE SITES (RH, CU)." Doctoral thesis, Università degli Studi di Milano, 2013. http://hdl.handle.net/2434/214937.
Full textAbstract:
The immobilization of metal NPs and metal single sites on silica support materials offers an interesting approach to heterogeneized catalysts for a multitude of different reactions.
Selective hydrogenation reactions of prochiral substrates, such as
(hetero-)aromatics, can be catalyzed by heterogeneized “hybrid catalysts” of the type RhI-Pd0/SiO2, consisting of silica-supported PdNPs and chiral Rh(I) phosphine single sites. These new “hybrid catalysts” were reported in the recent years, revealing the synergetic effect between Pd and Rh. Regarding the hydrogenation of benzene/toluene, it could be shown that RhI-Pd0/SiO2 are 4 times more active than Pd0/SiO2. In particular, the scope of this work was the extension of the “hybrid catalysts” by the use of chiral phosphine ligands. PdNPs were immobilized onto various mesoporous silica supports, having an ordered (e.g. MCM-41, SBA-15) or a non-ordered (e.g. Davisil B, Davison 62) structure, both in powdery form and as monoliths. Different immobilization methods were tested (impregnation, ionic exchange, CVD), whereupon CVD proved to be a promising procedure, giving high Pd loadings up to 1.95 wt % (expected: 2 wt %). Moreover, this method was suitable for both powdery silica materials and silica monoliths.
Silica-supported chiral Cu(I) complexes of the type [CuI(PC-L*)]CF3SO3/SiO2 can be applied in the asymmetric cyclopropanation of -methyl styrene with ethyl diazoacetate (EDA). Regarding the different mesoporous ordered- and non-ordered silica supports (MCM-41, SBA-15, Davisil B, Aerosil, basic silica), SBA-15 turned out to be the most-suitable one, giving excellent Cu loadings up to 1.79 wt %. The application of the [CuI(PC-L*)]CF3SO3/SiO2 catalysts gave the cyclopropanes in high yields (83 %). In this context, the recyclability of [CuI(PC-L*)]CF3SO3/SiO2 could be proven.
Silica monoliths are very advantageous and thus gladly used as support material: Besides their easy handling, they allow to work in flow conditions without packing a reactor. Within this work, silica monoliths were grafted and subsequently applied in the dehydration of fructose to 5-hydroxymethylfurfural (HMF). It was shown that the reaction works in batch as well as in flow, both homogeneously (using the sole unsupported grafting agent) and heterogeneously (using blank or grafted silica monoliths).
20
Upadhyay, Prabhat Kumar. "Design, Synthesis, and Characterization of Aqueous Polymeric Hybrid Composites and Nanomaterials of Platinum(II) and Gold(I) Phosphorescent Complexes for Sensing and Biomedical Applications." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822788/.
Full textAbstract:
The two major topics studied in this dissertation are the gold(I) pyrazolate trimer {[Au(3-R,5-R’)Pz]3} complexes in aqueous chitosan polymer and phosphorescent polymeric nanoparticles based on platinum(II) based complex. The first topic is the synthesis, characterization and optical sensing application of gold(I) pyrazolate trimer complexes within aqueous chitosan polymer. A gold(I) pyrazolate trimer complex, {[Au(3-CH3,5-COOH)Pz]3}, shows high sensitivity and selectivity for silver ions in aqueous media, is discussed for optical sensing and solution-processed organic light emitting diodes (OLEDs) applications. Gold(I) pyrazolate trimer complexes are bright red emissive in polymeric solution and their emission color changes with respect to heavy metal ions, pH and dissolved carbon dioxide. These photophysical properties are very useful for designing the optical sensors. The phosphorescent polymeric nanoparticles are prepared with Pt-POP complex and polyacrylonitrile polymer. These particles show excellent photophysical properties and stable up to >3 years at room temperature. Such nanomaterials have potential applications in biomedical and polymeric OLEDs. The phosphorescent hybrid composites are also prepared with Pt-POP and biocompatible polymers, such as chitosan, poly-l-lysine, BSA, pnipam, and pdadmac. Photoluminescent enhancement of Pt-POP with such polymers is also involved in this study. These hybrid composites are promising materials for biomedical applications such as protein labeling and bioimaging.
21
Tambosi, Reem. "Stress and toxicity of metal in photosynthetic bacteria : multi-scale study of the effects and the targets of metal ions and nanoparticles Silver and Copper Acute Effects on Membrane Proteins and Impact on Photosynthetic and Respiratory Complexes in Bacteria Silver Effect on Bacterial Cell Membrane Structure Investigated by Atomic Force and Scanning Electron Microscopes Cadmium and Copper Cross-tolerance. Cu+ alleviates Cd2+ toxicity, and both cations target heme and chlorophyll biosynthesis pathway in Rubrivivax gelatinosus Additive effects of metal excess and superoxide, a highly toxic mixture in bacteria." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASL070.
Full textAbstract:
L’usage intensif des métaux et des ions métalliques dans l'industrie et l'agriculture représente une menace sérieuse pour l'environnement et pour tous les êtres vivants en raison de la toxicité aiguë de ces ions. Cependant, cela peut aussi être un outil prometteur. En effet, les ions comme les nanoparticules d'argent sont très utilisés dans diverses applications médicales, industrielles et sanitaires. L'effet antimicrobien de ces nanoparticules est en partie lié aux ions Ag⁺ libérés et à leur capacité à interagir avec les membranes bactériennes. L'objectif de ce projet est d'étudier l'interaction entre un objet biologique (les bactéries) et des objets physiques (métaux), pour comprendre l'impact des métaux sous différentes formes (ions, nanoparticules et nanostructures) sur les cellules bactériennes en utilisant différentes approches: de physiologie, biochimie, génétique et de biologie cellulaire. Nous avons utilisé comme modèles biologiques, principalement la bactérie photosynthétique pourpre Rubrivivax (R.) gelatinosus, mais aussi Escherichia coli; et pour les objets physiques, nous avons utilisé l'argent comme métal principal mais aussi d'autres métaux (cuivre, cadmium et nickel) à titre de comparaison. Les principaux objectifs de ce travail sont: 1- d'étudier l'impact et les mécanismes de toxicité de ces ions métalliques / NPs sur les métabolismes bactériens respiratoire et photosynthétique. 2- Identifier des gènes bactériens impliqués dans la réponse à un excès d'ions Ag⁺. 3- Etudier l'internalisation et l'interaction des ions métalliques et des NP au sein des membranes biologiques. Ainsi, nous avons pu identifier, à la fois in vitro et in vivo, des cibles spécifiques d'ions Ag⁺ et Cu²⁺ dans la membrane des bactéries. Cela inclut des complexes impliqués dans la photosynthèse, mais également des complexes de la chaine respiratoire. Il a été démontré que les ions Ag⁺ et Cu²⁺ ciblent spécifiquement une bactériochlorophylle exposée au solvant dans les antennes de collecte de lumière du photosystème de la bactérie. Ceci présente également, à notre connaissance, la première preuve directe de dommages induits par des ions Ag⁺ sur les protéines membranaires impliquées dans ces métabolismes. Par ailleurs, nous avons également réalisé une étude comparative par microscopie (AFM/ MEB) de l'effet de l'Ag⁺ en solution ou des Ag-NPs synthétisés dans notre laboratoire, sur la morphologie des cellules bactériennesThe extensive use of metal ions in industry and agriculture represents a serious threat to the environment and to all living being because of the acute toxicity of these ions. However, it can also be a promising tool, silver ions and nanoparticles are some of the most widely used metals in various industrial and health applications. The antimicrobial effect of these nanoparticles is in part related to the released Ag⁺ ions and their ability to interact with bacterial membranes. The goal of this project is to study the interaction between biological subject (the bacteria) and physical objects (metals), and more specifically to understand the impact of metals in different forms (ions, nanoparticles and nanostructures) on the growth of the bacterial cells using different approaches : physiology, biochemistry, genetics and cell biology. We used as biological models, principally the purple photosynthetic bacterium Rubrivivax (R.) gelatinosus, but also Escherichia coli; and for physical objects, we used silver as main metal but also other metals (copper, cadmium and nickel) for comparison. The main objectives are: 1- to study the impact and the mechanisms of toxicity of these metallic ions/NPs on the bacterial respiratory and photosynthesis metabolisms. 2- To identify the bacterial genes involved in response to excess silver. 3- To study the internalization and interaction of metals ions and NPs within biological membranes. The results showed that we were able to identify, both in vitro and in vivo, specific targets of Ag⁺ and Cu²⁺ ions within the membrane of bacteria. This include complexes involved in photosynthesis, but also complexes involved in respiration. Ag⁺ and Cu²⁺ were shown to specificaly target a solvent exposed bacteriochlorophyll in the light harvesting antennae of the photosystem. This also presents, in our knowledge, the first direct evidence of silver ions damages to membrane proteins involved in these metabolisms. We also carried out a microscopy (AFM/ SEM) comparative study of the effect of Ag⁺ ions or Ag-NPs synthesized in our laboratory, on the bacterial cell morphology
22
Carrara, Serena. "Towards new efficient nanostructured hybrid materials for ECL applications." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAF016/document.
Full textAbstract:
Cette thèse vise à développer de nouveaux matériaux hybrides pour les applications en électrochimiluminescence. Les propriétés électrochimiluminescentes de nouveaux complexes de Pt(II) et d’Ir(III) ont été explorés comme alternative aux marqueurs existants. En plus, la combinaison de complexes et de carbon nanodots portant des groupes primaires ou tertiaires à la surface comme espèces coréactives a abouti à une stratégie intéressante pour éliminer la TPrA. Les carbon nanodots dans un systéme lié par liaison covantent avec complexes métalliques sont non seulement un support innocent pour les espèces actives d’ECL, mais agissent également comme coréactif, se révélant être une plateforme auto-améliorante en ECL. Enfin, un véritable immunoessai pour la détection des marqueurs cardiaques a été mis au point avec une sensibilité et une stabilité accrues pour les applications de détection biologique et biomédicale. La même technologie peut alors être appliquée à une variété d’autres analytes, ouvrant ainsi le site à d’autres dosagesThis doctoral dissertation aim to develop new hybrid materials for ECL applications. In the field of metal complexes, the electrochemiluminescent properties of new Pt(II) and Ir(III) complexes were investigated as alternative of existing complexes. Passing to nanomaterials, the combination of labels and NCNDs bearing primary or tertiary groups on the surface as alternative co-reactant species resulted an interesting strategy to eliminate the toxic TPrA. In particular, NCNDs in covalently linked system with metal complexes is not only an innocent carrier for ECL active species, but act also as co-reactant in the ECL process, revealing itself an ECL self-enhancing platform. Finally, a real immunoassay for cardiac marker detection has been built with enhanced sensitivity and stability, which is of fundamental importance for biological and bio-medical detection applications. The same technology can be applied to a variety of other analytes opening the venue to other assays
23
Rico, Santacruz Marisa. "Band gap control in hybrid titania photocatalysts." Doctoral thesis, Universidad de Alicante, 2014. http://hdl.handle.net/10045/42201.
Full text
24
DeVries, Gretchen Anne. "Divalent metal nanoparticles." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44387.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.Includes bibliographical references.
Metal nanoparticles hold promise for many scientific and technological applications, such as chemical and biological sensors, vehicles for drug delivery, and subdiffraction limit waveguides. To fabricate such devices, a method to position particles in specific locations relative to each other is necessary. Nanoparticles tend to spontaneously aggregate into ordered two- and three-dimensional assemblies, but achieving one-dimensional structures is less straightforward. Because of their symmetry, nanoparticles lack the ability to bond along specific directions. Thus, the technological potential of nanoparticles would be greatly enhanced by the introduction of a method to break the interaction symmetry of nanoparticles, thus inducing valency and directional interparticle interactions. When a nanoparticle is coated with a mixture of two different ligands, the ligands have been shown to phase-separate into ordered domains encircling or spiraling around the core. Topological constraints inherent in assembling two-dimensional vectors (e.g., ligands) onto a sphere (the core of the nanoparticle) dictate the necessary formation of two diametrically opposed defect points within the ligand shell. The molecules at these points are not optimally stabilized by intermolecular interactions and thus these sites are highly reactive. By functionalizing the polar singularities with a third type of molecule, we generate divalent nanoparticles with "chemical handles" that can be used to direct the assembly of the particles into chains. For example, taking inspiration from the wellknown interfacial polymerization synthesis of nylon, we place carboxylic acid terminated molecules at the polar defect points and join the newly bifunctional nanoparticles into chains by reacting them with 1,6-diaminohexane through an interfacial reaction.
(cont.) Furthermore, we perform a full kinetic and thermodynamic characterization of the molecularly defined polar defect points. We demonstrate that the rate of place-exchange at these points is significantly faster than it is elsewhere in the ligand shell. We also determine the equilibrium constant and standard free energy of the place-exchange reaction at the polar defect sites and demonstrate that the reaction is strongly affected by the molecular environment, i.e. the composition of the ligand shell.
by Gretchen Anne DeVries.
Ph.D.
25
Kumar, Sachin. "Electrocatalysis at Metal Nanoparticles." Miami University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1218138524.
Full text
26
Chui, Yu-hang, and 崔宇恒. "Molecular simulations of metal nanoparticles." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29288733.
Full text
27
Rogers, S. M. "Designing metal nanoparticles for catalysis." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1560408/.
Full textAbstract:
The sol-immobilisation method, in which metal nanoparticles are ‘preformed’ (stabilised by the polymer, polyvinyl alcohol) before they are anchored to a support material, was adapted in order to prepare monometallic Au/TiO2 and Pd/TiO2 catalysts, with tailored properties. Varied temperature and solvent environments (H2O, mixed H2O:EtOH and EtOH) were employed during colloidal metal formation, generating metal particles with distinct characteristics (metal particle diameter and available metal sites). The metal nanoparticle properties in the resulting catalysts were fully characterised using a range of spectroscopic (XAFS, IR and UV-Vis) and imaging techniques (TEM and HAADF STEM). It was determined that the preparation of metal nanoparticles at −30°C, in a mixed H2O:EtOH solvent afforded the smallest average particle diameter, regardless of the choice of metal (2.0 nm for Au, 1.4 nm for Pd). However, when prepared at 1°C in H2O, a higher population of small Au (< 5 atoms) or Pd clusters (< 20 atoms) existed, compared with any other environment. The performance of the catalysts were tested in three different reactions; Au/TiO2 for the oxidation of glycerol, and Pd/TiO2 for the hydrogenation of furfural and pnitrophenol. For the two former reactions, it was established that metal particle size is not the only factor influencing performance; the highly active isolated metal clusters, as well as the solvent-PVA-metal interaction, are considered very important factors, and are discussed. Understanding colloidal metal formation, including nucleation and growth phenomena, is vital in the future design of metal nanoparticle properties, and was investigated by means of in situ XAFS. A continuous flow method of nanoparticle synthesis was first explored and developed, before a synchrotron based experiment was performed to monitor the nanoparticle generation (colloidal reduction) in a range of reactors fabricated from different materials (silicon/glass, PTFE and PEEK).
28
Martinsson, Erik. "Nanoplasmonic Sensing using Metal Nanoparticles." Doctoral thesis, Linköpings universitet, Molekylär fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-111841.
Full textAbstract:
In our modern society, we are surrounded by numerous sensors, constantly feeding us information about our physical environment. From small, wearable sensors that monitor our physiological status to large satellites orbiting around the earth, detecting global changes. Although, the performance of these sensors have been significantly improved during the last decades there is still a demand for faster and more reliable sensing systems with improved sensitivity and selectivity. The rapid progress in nanofabrication techniques has made a profound impact for the development of small, novel sensors that enables miniaturization and integration. A specific area where nanostructures are especially attractive is biochemical sensing, where the exceptional properties of nanomaterials can be utilized in order to detect and analyze biomolecular interactions. The focus of this thesis is to investigate plasmonic nanoparticles composed of gold or silver and optimize their performance as signal transducers in optical biosensors. Metal nanoparticles exhibit unique optical properties due to excitation of localized surface plasmons, which makes them highly sensitive probes for detecting small, local changes in their surrounding environment, for instance the binding of a biomolecule to the nanoparticle surface. This is the basic principle behind nanoplasmonic sensing based on refractometric detection, a sensing scheme that offers real-time and label-free detection of molecular interactions. This thesis shows that the sensitivity for detecting local refractive index changes is highly dependent on the geometry of the metal nanoparticles, their interaction with neighboring particles and their chemical composition and functionalization. An increased knowledge about how these parameters affects the sensitivity is essential when developing nanoplasmonic sensing devices with high performance based on metal nanoparticles.
29
Bahadory, Mozhgan Solomon Sally. "Synthesis of noble metal nanoparticles /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2901.
Full text
30
Brayshaw, Simon Keith. "Metal complexes bearing pendant alkynes and metal complexes of N-heterocyclic carbenes." University of Western Australia. School of Biomedical and Chemical Sciences, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0017.
Full textAbstract:
This thesis is comprised of two parts. The first part describes the synthesis of cyclopentadienyltungsten complexes containing a pendant alkyne group (I), and the subsequent photo-induced intramolecular coordination of the alkyne, forming complexes such as II. Compounds containing intramolecularly coordinated alkynes are rare, and this is the first example using cyclopentadiene as the core ligand. The second part describes the synthesis and structural characterisation of a number of novel metal complexes containing N-heterocyclic carbene ligands, some containing particular functionality for taylored applications. New methods were used to form complexes of rhodium, iridium, silver and gold (eg. III, IV). Structural and spectroscopic properties of the complexes were correlated with electronic characteristics of the ancillary ligands. A number of rhodium and iridium complexes (eg. IV) derived from imidazolium-linked cyclophanes were synthesised and structurally characterised. Complexes of N-heterocyclic carbenes with pendant ionic groups were synthesised, and a preliminary examination of their catalytic activity in water was performed. N-Heterocyclic carbenes complexes containing an electron withdrawing nitro group were synthesised and the effect of the nitro group on metal-ligand bonding was examined.
31
Barron, Andrew Ross. "Transition metal aluminohydride complexes." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/37935.
Full text
32
Alem, Nassreen. "Zeolite encapsulated metal complexes." Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239055.
Full text
33
Jasim, Naseralla. "Transition metal bifluoride complexes." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323538.
Full text
34
Buha, Jelena. "Nonaqueous syntheses of metal oxide and metal nitride nanoparticles." Phd thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2008/1836/.
Full textAbstract:
Nanostructured materials are materials consisting of nanoparticulate building blocks on the scale of nanometers (i.e. 10-9 m). Composition, crystallinity and morphology can enhance or even induce new properties of the materials, which are desirable for todays and future technological applications. In this work, we have shown new strategies to synthesise metal oxide and metal nitride nanomaterials.
The first part of the work deals with the study of nonaqueous synthesis of metal oxide nanoparticles. We succeeded in the synthesis of In2O3 nanopartcles where we could clearly influence the morphology by varying the type of the precursors and the solvents; of ZnO mesocrystals by using acetonitrile as a solvent; of transition metal oxides (Nb2O5, Ta2O5 and HfO2) that are particularly hard to obtain on the nanoscale and other technologically important materials.
Solvothermal synthesis however is not restricted to formation of oxide materials only. In the second part we show examples of nonaqueous, solvothermal reactions of metal nitrides, but the main focus lies on the investigation of the influence of different morphologies of metal oxide precursors on the formation of the metal nitride nanoparticles. In spite of various reports, the number and variety of nanocrystalline metal nitrides is marginally small by comparison to metal oxides; hence preformed metal oxides as precursors for the preparation of metal nitrides are a logical choice. By reacting oxide nanoparticles with cyanamide, urea or melamine, at temperatures of 800 to 900 °C under nitrogen flow metal nitrides could be obtained. We studied in detail the influence of the starting material and realized that size, crystallinity, type of nitrogen source and temperature play the most important role. We have managed to propose and verify a dissolution-recrystallisation model as the formation mechanism. Furthermore we could show that the initial morphology of the oxides could be retained when ammonia flow was used instead.Nanostrukturierte Materialien sind Materialien, die aus nanopartikulären Baueinheiten in der Größenordnung von Nanonmetern (d.h. 10-9 m) bestehen. Zusammensetzung, Kristallinität und Morphologie können die natürlichen Eigenschaften dieser Materialien verbessern oder zusätzliche Eigenschaften erzeugen, die für heutige und zukünftige Anwendungen und Verfahren wünschenswert sind. In dieser Arbeit präsentieren wir neue Strategien zur Synthese von Nanopartikeln der Metaloxide und Metalnitride. Im einführenden Teil wird die nichtwässrige Synthese von Metaloxidnanopartikeln beschrieben. Uns gelang die Darstellung von In2O3 Nanopartikeln, deren Größe und Form wir durch die Wahl des Prekursors und des Lösemittels deutlich beeinflussen konnten; von ZnO Mesokristallen durch den Einsatz von Acetonitril als Lösemittel; von Übergangsmetalloxiden (Nb2O5, Ta2O5 and HfO2), die besonders schwer im Nanomaßstab zu erhalten sind und von anderen, technisch relevanten Materialien. Die Möglichkeiten der solvothermalen Synthese sind nicht mit der Darstellung von Oxidmaterialen erschöpft. Im zweiten Teil zeigen wir einige Beispiele nichtwässriger, solvothermaler Synthese von Metalnitriden auf; das Hauptaugenmerk liegt aber auf einer Betrachtung der Einflüsse der Morphologie von Metaloxidnanopartikelprekursoren auf die Bildung der Metalnitridnanopartikel. Die Anzahl und Vielfalt bekannter nanokristalliner Metalnitride ist verschwindend klein im Vergleich zu den Metaloxiden, die in der Fachliteratur etabliert sind und demzufolge einen reichen Baukasten an Prekursoren zur Darstellung von Metalnitriden liefern. Durch die Reaktion von Metaloxidnanopartikeln mit Cyanamid, Urea oder Melamine bei Temperaturen von 800 bis 900 °C unter Stickstofffluss konnten Metalnitride erhalten werden. Eine detaillierte Studie der Reaktionsbedingungen und des Reaktionsablaufs zeigte auf, dass Größe und Kristallinität der Metaloxide, die Art der Stickstoffquelle und die Temperatur die entscheidenden Faktoren sind und legte eine Auflösungs-Rekristallisation als Modelmechanismus dieser Art Reaktion nahe. Darüber hinaus konnte gezeigt worden, dass die anfängliche Morphologie des Oxids unter einem Ammoniafluss beibehalten werden konnte.
35
Warne, Barnaby. "Nanoparticles prepared from reactive metal surfactants." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311430.
Full text
36
Gaskell, Christine V. "Tailored metal nanoparticles for selective catalysis." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/44554/.
Full textAbstract:
The development of clean, sustainable chemical processes is a key priority towards meeting the growing demand for synthetic functional chemicals, while balancing rapidly depleting natural resources. The selective oxidation (selox) of crotyl alcohol to crotonaldehyde and the selective hydrogenation of benzyl cyanide to phenylethylamine are two specific systems for which, it is proposed, new heterogeneous catalysts and deeper mechanistic insight will improve. In this thesis the rational design of palladium catalysts is investigated for these systems, via synthesis of palladium nanoparticles with tailored morphology and palladium-gold nanoparticles with tuneable surface composition. Pd icosahedra, nanorods and nanocubes were synthesised and characterised extensively to confirm the size and morphology of the nanoparticles. Pd icosahedra are revealed to be three times more active for crotyl alcohol selox than the nanocubes, and ten times faster than the nanorods, while maintaining good selectivity. An Au-shell, Pd-core structure was synthesised, progressively annealed to induce alloying and characterised using various in situ spectroscopies. Surface Au was found to enhance crotyl alcohol selox activity and selectivity towards crotonaldehyde, in accordance with model predictions. An optimum crotonaldehyde yield was obtained for an Au40Pd60 surface alloy. By employing in situ and time-resolved spectroscopies the active site of Pd selox catalysts is examined, and the role of oxygen in this system and the catalyst’s kinetic behaviour is defined. Reversible redox cycling of the catalyst dependent on its environment was observed, and it was possible to identify PdOx as the active catalytic species responsible for selectively oxidising crotyl alcohol to crotonaldehyde, with high temperatures suppressing catalytic selectivity. Systematic characterisation of an industrial carbon supported Pd catalyst, used in nitrile hydrogenation, reveals potential sources of deactivation including surface poisoning by CN species. Solutions to improve catalyst performance are proposed using the knowledge acquired from the nanoparticle catalysts’ studies.
37
Steven, Christopher R. "Plasmonic metal nanoparticles : synthesis and applications." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27939.
Full textAbstract:
Plasmonic metal nanoparticles are widely exploited in academia and industry for use in various assay types. In collaboration with an industrial partner, BBI Solutions, the work here details investigations into the production and use of the plasmonic nanoparticles. The work was split into two themes. The first of these was flow chemistry of nanoparticles, covering a microfluidic assay platform and continuous colloid production. In chapter one, a novel microfluidic assay platform was developed which facilitated the transfer of multiple, sequential bench-top procedures into a single device. This allowed the rapid detection of a sugar binding protein to be demonstrated. The microfluidic system included all pre-detection steps involved in employing the specific aggregation of functionalised silver nanoparticles. Straightforward detection of the protein was demonstrated at concentrations lower than those achieved using comparable methods in the literature. In the second chapter, a novel bench-top scale continuous reactor for the production of gold nanoparticles was developed. It was found that the continuous stirred tank reactor was generally unsuitable for this synthesis. A laminar tubular reactor was more successful but fouling of the reactor material was a significant obstacle to production of good quality colloid. In both cases, nanoparticles produced in a batch synthesis were of more consistent quality. This suggested that further work was needed to develop a competitive continuous production method. The second research theme was development of a novel nanoparticle assembly assay, based on DNA assembly. In chapter three it was found that current tools for the understanding of dynamic DNA structure were limited. This led to the first use of an existing coarse grain model to determine thermodynamic properties of DNA assembly. Analysis showed that the results were comparable with the best simulation models shown in the literature, while being generated much more quickly and at less computational expense.
38
Aksomaityte, Gabriele. "Synthesis of metal and metal oxide nanoparticles in supercritical fluids." Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523001.
Full text
39
Tejpal, Jyoti. "The use of metal and metal oxide nanoparticles against biofilms." Thesis, De Montfort University, 2016. http://hdl.handle.net/2086/13114.
Full textAbstract:
The persistence of biofilms in hospital settings are associated with Healthcare Associated Infections (HCAI), causing increased morbidity, mortality and healthcare costs. The resistance of biofilms against commonly used hospital disinfectants has been well reported. Metal and metal oxide nanoparticles (NP) such as silver (Ag), copper (Cu), zinc oxide (ZnO) and copper oxide (CuO) exhibit antimicrobial properties against various pathogens. Methods: Biofilm formation of Pseudomonas aeruginosa and Staphylococcus aureus in a Centre for Disease Control (CDC) biofilm reactor and a 96 well plate was compared. A three stage approach including Minimum Biofilm Reduction Concentration (MBRC), R2 values and log(10) reductions was used to assess the efficacy of Ag and ZnO NPs both alone and in combination against P. aeruginosa and S. aureus biofilms. Atomic Absorption Spectroscopy (AAS), Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) was used to further assess the antimicrobial ability of the metal and metal oxide NPs. The prevention of P. aeruginosa and S. aureus adherence on Ag and ZnO thin film coating on silicon (Si) surfaces was also investigated, as well as icaC, ebpS and fnbB gene expression in S. aureus biofilms. Results: The CDC biofilm reactor demonstrated to be the most effective method for P. aeruginosa and S. aureus biofilm production in comparison to 96 well plates, with lower standard errors of the mean (SE) and higher replicability. Individual MBRC of ZnO and Ag NPs in suspension were 256 and 50 µg/ml for P. aeruginosa and 16 and 50 µg/ml for S. aureus respectively. The concentrations in combination were reduced by at least a half, with concentrations of 32/25 µg/ml of ZnO/Ag NPs in suspension resulting in a significant (p ≤0.05) reduction of 3.77 log(10) against P. aeruginosa biofilms and 8/12 µg/ml of ZnO/Ag NPs in suspension resulted in a 3.91 log(10) (p ≤0.05) against S. aureus biofilms. Both combinations showed an additive effect. Time point analysis confirmed that a 24 hour treatment is vital for any significant (p ≤0.05) antimicrobial activity. AAS data suggested that the Ag+ ions quenched Zn2+ ions, therefore the antimicrobial efficacy of the combination is mainly due to Ag+ ions. Damage of the biofilms from Ag and ZnO NPs was observed in the SEM imaging and energy dispersive X-ray (EDX) analysis confirmed the adherence of Zn and Ag within the biofilms. CLSM imaging showed dead (red) cells of P. aeruginosa and S. aureus biofilms throughout the depth of the biofilm. P. aeruginosa formation was reduced by 1.41 log(10) and 1.43 log(10) on Ag and ZnO thin film coatings respectively. For S. aureus, a reduction of 1.82 log(10) and 1.65 log(10) was obtained for Ag and ZnO coating respectively. Only low levels of ribonucleic acid (RNA) were achieved so no further gene analysis could occur. Conclusion: Reductions of ≥3 log(10) were observed for P. aeruginosa and S. aureus biofilm treatment with ZnO/Ag NP suspensions. It can be concluded that the ZnO/Ag NP suspensions had greater antimicrobial activity than Ag and ZnO coated surfaces owing to large concentrations of Ag+ and Zn2+ ions acting upon the biofilms. The slower release of ions from coated surfaces suggest an inadequate concentration of ions in the media, which are therefore unable to prevent biofilm formation as rapidly as NP suspensions, however provide a sustained release of ions over time. The results from this investigation propose that Ag and ZnO NPs in suspension could be a potential alternative to disinfectants for use in nosocomial environments against P. aeruginosa and S. aureus biofilms.
40
Anderson, Amanda E. "Strategic immobilisation of catalytic metal nanoparticles in metal-organic frameworks." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/10816.
Full textAbstract:
This thesis describes the synthesis, characterisation and catalytic testing of multifunctional immobilised metal nanoparticle in metal-organic framework (MOF) materials. Combining the activity of metal nanoparticles with the porosity and Lewis acidity of metal-organic frameworks provides a single catalytic material which can perform multi-step reactions. Strategies to immobilise the metal nanoparticles within the metal-organic frameworks have been investigated. Immobilisation has been achieved by applying three different methodologies. First, deposition of metal nanoparticle precursors within mesoporous MOFs is discussed. Chapter 3 shows the effectivity of the double solvents deposition technique to achieve dispersed and small nanoparticles of around 2.7 nm. The best system combined Pd nanoparticles with MIL-101(Cr). This system was further investigated in tandem reductive amination catalysis, discussed in Chapter 4, to investigate the activity and selectivity provided by these multifunctional catalysts. Another immobilisation technique was performed by coating Pd decorated SiO2 spheres with a MOF layer. Using this technique, MOF was grown cyclically in solution, providing tuneable shell thicknesses of MOF on the metal nanoparticle decorated oxide spheres. While the homogeneity of the MOF shell needs more optimisation, it was determined that the surface charge on the spheres played an important role in the growth of MOF in the desired location. Finally, the third immobilisation technique is the core-shell growth of MOF on colloidal metal nanoparticles. Polymer-capped metal nanoparticles with well-defined shapes were synthesised and characterised. From here, the optimisation of conditions for core-shell growth of UiO-66 and MIL-100(Sc) were investigated. Conditions which provided the desired core-shell morphology were found for both MOF types. These materials were then subsequently used in tandem reductive amination catalysis and a more straightforward styrene hydrogenation. It was shown that the metal nanoparticles remain active catalysts within either MOF shell and the MOF shell stabilises the metal nanoparticle and acts as a Lewis acid catalyst.
41
Humphrey, Elizabeth Rebecca. "Tris(pyrazolyl)borate metal complexes : new ligands and metal-metal interactions." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340301.
Full text
42
Zhao, Ningfeng Eichhorn David M. "Cyano-substituted polypyrazolylborate metal complexes." Diss., Click here for available full-text of this thesis, 2005. http://library.wichita.edu/digitallibrary/etd/2005/d019.pdf.
Full textAbstract:
Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry."December 2005." Title from PDF title page (viewed on February 8, 2007). Thesis adviser: David Eichhorn. Includes bibliographic references (leaves 123-128).
43
Rao, Sumitrananda N. R. "Novel adsorbents using metal complexes." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/10200.
Full text
44
Felsher, Dave. "Electrowinning of metal - DETA complexes." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33329.
Full textAbstract:
Sludges formed by lime treatment of acidic mine effluents are a widespread environmental hazard. One treatment option is to recover the toxic and potentially valuable contained metals. A method has been reported to selectively recover the metals by leaching with a complexing agent, diethylenetriamine (DETA). In this thesis a novel method has been developed to recover metals from the metal---DETA complexes by direct electrowinning. Copper was studied initially as a test system due to the relative ease with which it is recovered in conventional sulphate electrowinning. The main industrial interest, and hence the main focus of the work, is in the nickel---DETA system. For both metals, initially batch tests were run to determine acceptable electrowinning conditions. These were followed by recycle tests to simulate a potential process flowsheet. In the nickel-DETA system the effects of pH, nickel concentration, temperature, and DETA to nickel ratio on current efficiency were determined.Recycle tests for copper showed that a steady DETA concentration was achieved after ca. six hours. In the case of nickel, the system seemed to continually deteriorate. A pH range of 4.6 to 4.8 maximized the current efficiency, due to a competition between hydrogen formation at low pH and increased complex stability at high pH. Both increasing Ni concentration and temperature increased the current efficiency, while increasing the DETA to nickel ratio lowered it.
45
Tovilla, Cao-Romero Jorge Alberto Francisco. "Molecular recognition with metal complexes." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436343.
Full text
46
Harrison, Simon. "Metal-arene complexes and clusters." Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280332.
Full text
47
Jones, P. "Studies of chiral metal complexes." Thesis, Bucks New University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373593.
Full text
48
Blackwell, Elizabeth Sarah. "Fluxionality in organonitrogen metal complexes." Thesis, University of Exeter, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332328.
Full text
49
Harrison, Stephen Anthony. "Novel chiral cyclopentadienyl metal complexes." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442873.
Full text
50
Veighy, Clifford Robert. "Novel cyclopentadienyl transition metal complexes." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327366.
Full text