Dissertations / Theses on the topic '030306 Synthesis of Materials'

High-pressure techniques have become increasingly important in the synthesis of ceramic and metallic solids allowing the discovery of new materials with interesting properties. In this research dense solid oxides have been synthesised at high pressures, and structural investigations have been conducted using x-ray and neutron diffraction. The perovskite LaPdO3 has been synthesised at pressures of 6{10GPa. Neutron diffraction studies have been carried out from 7{260K to investigate any structural distortions, particularly related to the possibility of charge order at low temperatures. No reduction in symmetry associated with charge ordering has been observed; the material appears to remain metallic with only one unique Pd site down to 7K. LaPdO3 adopts the GdFeO3-type Pbnm structure. The PdO6 octahedra exhibit a tetragonal distortion throughout the temperature range with a shortening of the apical Pd{O bonds of 2:5% relative to the equatorial bonds. Attempts to prepare analogues of the perovskite containing smaller rare earths have resulted in multi-phase samples, and further RPdO3 perovskites remain inaccessible although there is evidence for a small amount of the perovskite phase in the products of synthesis attempts with neodymium. Three new oxypnictide superconductors, RFeAsO1 xFx (R = Tb, Dy and Ho) have been synthesised at 7{12GPa. The materials are isostructural with other recently discovered iron arsenide superconductors and have Tc's of 52:8 K, 48:5K and 36:2K respectively, demonstrating a downturn in Tc in the series for smaller R. Systematic studies on TbFeAsO0.9F0.1 and HoFeAsO0.9F0.1 show negative values of dTc=dV in contrast to those reported for early R containing materials. Low-temperature neutron diffraction measurements on both materials, and synchrotron studies on HoFeAsO0.9F0.1 reveal no tetragonal to orthorhombic transitions as observed in early R-containing materials with lower doping levels. Magnetic reflections are evident but they are shown to be from R2O3 and RAs impurities with TN's of 5:5K for Tb2O3, 6:5K for HoAs and 1:7K < TN < 4K for Ho2O3. The implications of these results for superconductivity in the iron arsenides are discussed.

Chapter 1 contains a brief background into subjects such as Robin-Day classes, binary code, logic gates and electrochemistry in order to aid understanding of the rest of the chapter. The unique paradigm of Molecular Quantum Cellular Automata (MQCA) is presented along with the advantages it offers to traditional silicon based electronics. A summary of the existing modelled and synthesised MQCA systems is included along with an explanation of the characteristics required for materials to be suitable for MQCA. The subject of chapter 2 is cyclopentadiene cobalt cyclobutadiene complexes for the application of MQCA. The introduction examines the mechanism for the formation of cyclopentadiene cobalt cyclobutadiene complexes and the bonding in these compounds. A range of acetylenes were prepared for the formation of cyclopentadiene cobalt cyclobutadiene complexes were examined and characterised. Metal fragments including {Ru(dppe)2Cl} and AuPPh3Cl were attached to a cyclopentadiene cobalt cyclobutadiene core and these materials were characterised. The subject of chapter 3 is benzene based materials for the application of MQCA. 1,2,4,5-tetrakis(ferrocenylethynyl)benzene was prepared, characterised and the electrochemistry was examined for electronic communication between the ferrocene sites. A range of two metal centre compounds were examined for solubility and electrochemical stability with the view of preparing four metal centre compounds with a benzene core. The subject of chapter 4 is porphyrin based materials. This was the first area of work for this thesis and was discontinued. A brief summary of the synthetic work carried out is described, along with some literature work that was published whilst this work was being carried. Chapter 5 contains the experimental information for chapters 2-4.

Microcrystalline indium(III) selenide was prepared from a diphenyl diselenide precursor and a range of chloroindate(III) ionic liquids via a microwave-assisted ionothermal route. A mixture of nano- and micro-sized zinc(lI) selenide materials were also prepared using the same ionothermal procedure and chlorozincate ionic liquids. Influence of the reaction temperature and variation of the cation and the anion of the ionic liquid on the product morphology and composition were investigated. All products formed were characterised using PXRO, SEM and EOX. Additional characterisation was carried out using Raman spectroscopy and photoluminescence measurements. The investigation into the production of indium(III) selenide, zinc(II) selenide and gallium(III) selenide semiconductor materials using conventional heating methods was subsequently carried out and the products were characterized using SEM, EOX and ESI-MS. Electrochemical investigations into some of the stable homogeneous liquids that were formed between the chloroindatel chlorzincate ionic liquids with the diphenyl diselenide with conventional heating, have been carried out. An additional selenium precursor, selenium tetrachloride, was also investigated with the depositions analysed using SEM and EOX. Finally, the ternary compound copper indium selenide (CIS) has been prepared as nano- and micro-sized materials through colloidal synthesis using an indium(III) selenide precursor and copper(I) chloride via a microwave-assisted ionothermal route. The crystal structures of three intermediate structures were determined after formation through an ionothermal procedure utilising metal-containing imidazolium ionic liquids and a selenium precursor with conventional heating. A comparative study into the use of microwave irradiation over conventional heating with different ionic liquids on the stoichiometry of the resulting products was carried out. The influence of the reaction temperature, reaction time, order of addition of reagents and variation of ionic liquids on the final products was investigated, which have been characterized using PXRO, SEM and EOX. I

This investigation is based on the topochemical modification of three set of phases: Sr₃Co₂O₅Cl₂, SrO(Sr(Ru_0.5M_0.5)O₃)n (M = Ti, Mn, Fe; n = 1, 2, ∞), and SrO(SrVO₃)n (n = 1, 2, ∞). The topochemical reduction of Sr₃Co₂O₅Cl₂ using sodium hydride as a solid state reducing agent results in the formation of a reduced phase containing cobalt centres with an average oxidation state of +2 and an overall composition of Sr₃Co₂O₄Cl₂. The resulting material adopts a structure containing double sheets of square-planar corner-sharing CoO2 units separated by rock salt SrCl layers. Variable-temperature diffraction measurements reveal that these sheets undergo a cooperative Jahn-Teller distortion at T ~ 200 K due to unevenly filled degenerate (d_xy, d_yz) orbitals. This material adopts a magnetic structure in which the moments within each sheet are ordered antiferromagnetically, but the sheets are aligned ferromagnetically. An investigation was carried on the reduction behaviour of Ru-doped Sr(Ru_xFe_1-x)O₃. It was found that the reduction was non-topochemical for values of x > 0.5. For values of 0 < x < 0.5, no single phase precursor material could be formed. For the material with x = 0.5, reduction with CaH₂ produced a new phase with composition Sr(Ru_0.5Fe_0.5)O₂. This material is the first reported instance of Ru²⁺ in an extended transition metal oxide. DFT calculations reveal that, while the iron centres adopt a high-spin configuration, the ruthenium centres are in an intermediate-spin S = 1 configuration. Resulting competing magnetic interactions lead to frustration and lack of ordering. In order to further study the reduction behaviour of extended transition metal oxides containing ruthenium, the reduction of Sr₂(Ru_0.5Fe_0.5)O₄ and Sr₃(Ru_0.5Fe_0.5)₂O₇ was performed using CaH₂ as a solid state reducing agent. In these cases, reduction leads to segregation of the materials into multiple phases adopting closely related structures that differ mainly in their oxygen content. In these materials, the ruthenium centres are preferentially reduced, such that starting from materials containing Ru⁵⁺ and Fe³⁺, materials containing Ru^(3-δ)+ and Fe³⁺ are produced. Similarly, the low-temperature oxidation using CuF₂ as a solid state fluoride source was performed on materials with composition Sr3(Ru0.5M0.5)2O7 (M = Ti, Mn, Fe). In the case of M = Mn and Ti, materials with composition Sr₃(Ru_0.5Fe_0.5)₂O₇F₂ are produced in which the ruthenium centres are oxidised to Ru⁶⁺. For the M = Fe material, oxidation results in partial exchange of O for F and a material with composition Sr₃(Ru_0.5Fe_0.5)₂O_5.5F_3.5 in which the ruthenium centres are oxidised from +5 to +5.5 while the iron centres remain in a +3 oxidation state. While fluorination of the M = Ti leads to increasing itinerant electronic behaviour, fluorination of the M = Mn and Fe materials induces a twisting of the MX₆ octahedra that enables magnetic order to emerge at low temperatures. Finally, reaction of the SrO(SrVO₃)n (n = 1, 2, ∞) series of phases with CaH₂ results in the formation of phases with composition SrO(SrVO₂H)_n (n = 1, 2, ∞), the first examples of stoichiometric oxyhydride materials. SrVO₂H is magnetically ordered at room temperature, while the n = 1 and n = 2 materials order at 170 K and 240 K respectively. The high magnetic ordering temperature arises from strong interactions between (d_xy, d_yz) orbitals in a manner analogous to the reduced iron-containing phases SrO(SrFeO₂)_n.

Due to their highly interesting electroactive properties, complexes based on the sulphur heterocycle DMIT have been studied extensively for several decades. The literature is abundant with materials exhibiting semiconducting and metallic properties and up to early 2000 there are eight examples of DMIT based superconductors. In the case of the DMIT complexes, previous work has been constrained to the variation of the transition metal and/or the counter-anion. The work herein concerns the synthesis of a novel series of electroactive ligands, similar to the well-known DMIT species. In contrast to the DMIT ligand, our target derivatives incorporate two thioether and two dithiolate environments as the overall chelating entity. The thioether functionalities are linked via suitable spacer groups and this feature should present a major advantage over traditional DMIT complexes, by adding solubility and synthetic versatility to the overall nature of the complex. In addition to the metal complexes based on DMIT ligands, charge transfer (CT) halogen adducts of these DMIT ligands and their synthetic intermediates are described, providing highly interesting and novel solid state structures and atom-to-atom inter- and intra-molecular interactions.

Tableau d'honneur de la Faculté des études supérieures et postdoctorales, 2016-2017
Les zéolithes étant des matériaux cristallins microporeux ont démontré leurs potentiels et leur polyvalence dans un nombre très important d'applications. Les propriétés uniques des zéolithes ont poussé les chercheurs à leur trouver constamment de nouvelles utilités pour tirer le meilleur parti de ces matériaux extraordinaires. Modifier les caractéristiques des zéolithes classiques ou les combiner en synergie avec d'autres matériaux se trouvent être deux approches viables pour trouver encore de nouvelles applications. Dans ce travail de doctorat, ces deux approches ont été utilisées séparément, premièrement avec la modification morphologique de la ZSM-12 et deuxièmement lors de la formation des matériaux de type coeur/coquille (silice mésoporeuses@silicalite-1). La ZSM-12 est une zéolithe à haute teneur en silice qui a récemment attiré beaucoup l’attention par ses performances supérieures dans les domaines de l'adsorption et de la catalyse. Afin de synthétiser la ZSM-12 avec une pureté élevée et une morphologie contrôlée, la cristallisation de la zéolithe ZSM-12 a été étudiée en détail en fonction des différents réactifs chimiques disponibles (agent directeur de structure, types de silicium et source d'aluminium) et des paramètres réactionnels (l'alcalinité, ratio entre Na, Al et eau). Les résultats présentés dans cette étude ont montré que, contrairement à l’utilisation du structurant organique TEAOH, en utilisant un autre structurant, le MTEAOH, ainsi que le Al(o-i-Pr)3, cela a permis la formation de monocristaux ZSM-12 monodisperses dans un temps plus court. L’alcalinité et la teneur en Na jouent également des rôles déterminants lors de ces synthèses. Les structures de types coeur/coquille avec une zéolithe polycristalline silicalite-1 en tant que coquille, entourant un coeur formé par une microsphère de silice mésoporeuse (tailles de particules de 1,5, 3 et 20-45 μm) ont été synthétisés soit sous forme pure ou chargée avec des espèces hôtes métalliques. Des techniques de nucléations de la zéolithe sur le noyau ont été utilisées pour faire croitre la coquille de façon fiable et arriver à former ces matériaux. C’est la qualité des produits finaux en termes de connectivité des réseaux poreux et d'intégrité de la coquille, qui permet d’obtenir une stéréosélectivité. Ceci a été étudié en faisant varier les paramètres de synthèse, par exemple, lors de prétraitements qui comprennent ; la modification de surface, la nucléation, la calcination et le nombre d’étapes secondaires de cristallisation hydrothermale. En fonction de la taille du noyau mésoporeux et des espèces hôtes incorporées, l'efficacité de la nucléation se révèle être influencée par la technique de modification de surface choisie. En effet, les microsphères de silice mésoporeuses contenant des espèces métalliques nécessitent un traitement supplémentaire de fonctionnalisation chimique sur leur surface externe avec des précurseurs tels que le (3-aminopropyl) triéthoxysilane (APTES), plutôt que d'utiliser une modification de surface avec des polymères ioniques. Nous avons également montré que, selon la taille du noyau, de deux à quatre traitements hydrothermaux rapides sont nécessaires pour envelopper totalement le noyau sans aucune agrégation et sans dissoudre le noyau. De tels matériaux avec une enveloppe de tamis moléculaire cristallin peuvent être utilisés dans une grande variété d'applications, en particulier pour de l'adsorption et de la catalyse stéréo-sélective. Ce type de matériaux a été étudié lors d'une série d'expériences sur l’adsorption sélective du glycérol provenant de biodiesel brut avec des compositions différentes et à des températures différentes. Les résultats obtenus ont été comparés à ceux utilisant des adsorbants classiques comme par exemple du gel de sphères de silice mésoporeux, des zéolithes classiques, silicalite-1, Si-BEA et ZSM-5(H+), sous forment de cristaux, ainsi que le mélange physique de ces matériaux références, à savoir un mélange silicalite-1 et le gel de silice sphères. Bien que le gel de sphères de silice mésoporeux ait montré une capacité d'adsorption de glycérol un peu plus élevée, l'étude a révélé que les adsorbants mésoporeux ont tendance à piéger une quantité importante de molécules plus volumineuses, telles que les « fatty acid methyl ester » (FAME), dans leur vaste réseau de pores. Cependant, dans l’adsorbant à porosité hiérarchisée, la fine couche de zéolite silicalite-1 microporeuse joue un rôle de membrane empêchant la diffusion des molécules de FAME dans les mésopores composant le noyau/coeur de l’adsorbant composite, tandis que le volume des mésopores du noyau permet l’adsorption du glycérol sous forme de multicouches. Finalement, cette caractéristique du matériau coeur/coquille a sensiblement amélioré les performances en termes de rendement de purification et de capacité d'adsorption, par rapport à d'autres adsorbants classiques, y compris le gel de silice mésoporeuse et les zéolithes.
Zeolites as microporous crystalline materials have shown competence and versatility in a huge number of applications. Their unique properties have persuaded researchers to constantly look for novel pathways to get the most out of these extraordinary substances. Modifying the properties of classical zeolites or combining them synergistically with other materials are found to be two viable techniques to attain efficient zeolitic materials with improved characteristics. In this dissertation, these two approaches were separately used to study, first, the morphological modification of ZSM-12 and second, the formation of mesoporous silica@silicalite-1 core-shell materials. ZSM-12 is a high silica zeolite which has recently attracted much attention owing to its superior performance in adsorption and catalysis. In order to synthesize ZSM-12 with high purity and controlled size and morphology, the crystallization behavior of ZSM-12 zeolite was thoroughly studied by screening different commercially available chemical sources (structure-directing agents, silicon and aluminum source types) and compositions (alkalinity and Na, Al and water contents). The results presented in this study showed that, in contrast to TEAOH organic template, using MTEAOH and Al(o-i-Pr)3 could lead to the formation of mono-sized ZSM-12 single crystals in a shorter time. Alkalinity and Na+ contents were found to be playing the major roles. Following the second approach, zeolitic core-shell composites with a polycrystalline silicalite-1 shell, enclosing a mesoporous silica microsphere core (particle sizes of 1.5, 3 and 20-45 μm) in either pure form or loaded with metal guest species, were synthesized. Seeded growth technique was used as one of the reliable ways for the synthesis of such a material. The quality of the final products in terms of the pore network connectivity and shell integrity, which, together, ensure the shape-selective capability, was studied by varying synthesis parameters, such as core pre-treatments which include surface modification, seeding and calcination steps and the number of secondary hydrothermal crystallization steps. Depending on the core size and the presence of guest species, the quality of the seeding step was found to be influenced by the surface modification technique used, i.e., mesoporous silica microspheres which contain guest species need an additional treatment of chemical functionalization of the external surface with species such as APTES, rather than using a simple surface modification with ionic polymers. It was also shown that depending on the core size, two to four short hydrothermal treatments are required to fully cover the core, with no aggregation and core dissolution. Such materials with a molecular sieve crystalline shell can be used in a wide variety of applications, particularly for shapeselective adsorption and catalysis purposes. Selective adsorption capability of the final product was investigated by conducting a series of batch glycerol adsorption experiments from crude biodiesel with different compositions at different temperatures. Glycerol content of the purified biodiesel by using the core@shell material was compared to those purified by using conventional adsorbents including bare mesoporous silica gel spheres, classical zeolites, e.g., silicalite-1, pure siliceous β-zeolite (Si-BEA) and ZSM-5(H+) crystals as well as a physical mixture of the constitutive materials, i.e., equally mixed silicalite-1 and silica gel spheres. Although mesoporous silica gel spheres showed slightly higher glycerol adsorption capacity, the study revealed that the mesoporous adsorbents tended to trap a significant number of bulkier molecules, such as FAMEs, in their large pore networks (dpore> 6 nm). However, the silicalite-1 shell provided a microporous membrane which hindered the diffusion of FAME into the mesopores while the composite adsorbents benefited from large pore volume of mesoporous silica as core compartment, allowing a multi-layer glycerol adsorption. This feature of the synthesized core@shell material considerably enhanced the dry washing performance in terms of purification yield and adsorption capacity, in comparison to other conventional adsorbents including mesoporous silica gel and classical zeolites.

Thesis (Ph. D.)--University of Oregon, 2000.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 91-93). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Deng,Yulin; Committee Member: Hsieh, Jeffery S.; Committee Member: Nair, Sankar; Committee Member: Singh, Preet; Committee Member: Yao, Donggang. Part of the SMARTech Electronic Thesis and Dissertation Collection.

This dissertation describes research on the synthesis and characterization of extended heptazine–based, graphite–like carbon nitride materials (CNx), as well as molecular heptazine (C6N7) derivatives. Spurred on by recent triazine to heptazine conversion studies, a structural examination was performed on an amorphous nitrogen–rich carbon nitride material formed via the rapid and exothermic self-propagating decomposition of a triazine (C3N3) precursor, trichloromelamine (TCM). The thermally stable and insoluble CNxHy product was determined to be composed of heptazine repeat units. This conclusion was supported by 13C solid state NMR and isolation of molecular heptazine anions after base hydrolysis (structural deconstruction) of the CNxHy material. Modifications to the decomposition of TCM were explored. Introduction of a solid template (NaCl or silica) led to morphological changes in the TCM–CNx product, observed by scanning electron microscopy. It was found that the sodium salts, NaBr and NaN3, led to chloride exchange with TCM. The use of mixtures of NH4Cl and NaN3 also showed changes in the morphology of the material, while leading to slight changes in the IR spectra. A series of reactions between NaBH4 and TCM yield novel thermally stable boron carbon nitride (BCN) materials. Reactions between TCM and Li2C2 or aromatic organic solids led to CNx materials with increased carbon contents. Crystalline metal–heptazine precipitates were generated by cation exchange reaction with the base hydrolysis product of TCM–CNx, potassium cyamelurate. A structure solution was attempted for the crystalline copper cyamelurate salt, KCu[C6N7O3]·4H2O. Neutral molecular heptazines were also synthesized; these species included 2,5,8–tribromo–s–heptazine (TBH), 2,5,8–triphenyl–s–heptazine (TPH), 2,5,8–tris(diisopropylamino)–s–heptazine (TAmH), and 2–bis(trimethylsilyl)amido–5,8–dichloroheptazine (DCAH). These materials were sublimable and showed interesting optical absorption and emission properties. A polymeric heptazine material was synthesized by thermal decomposition of DCAH. Several attempts were made to synthesize polymeric materials from heptazine precursors. Extended solids with C6N8 and C9N7 stoichiometry were made through solid state metathesis reactions between trichloroheptazine and either lithium nitride or lithium carbide. Powder X–ray diffraction indicated that salt formation was occurring during these reactions and products had the desired stoichiometry by elemental analysis. It was generally observed that CNx materials containing excess carbon displayed increased thermal stability when compared to pure CNx.

The search for new materials for hydrogen storage is important for the development of future hydrogen energy applications. In this Thesis, it is shown that new materials with interesting properties can be synthesized by the reaction of hydrogen with various nanocarbon precursors. The thesis consists of two parts. The first part is devoted to studies of hydrogen storage in some metal-organic frameworks (MOFs) and nanostructured carbon materials, while the second part describes synthesis of new materials by the reaction of hydrogen gas with various carbon materials (i.e. fullerene C60, single-walled carbon nanotubes (SWCNTs), and fullerene C60 encapsulated inside SWCNTs (C60@SWCNTs)). Hydrogen adsorption was measured for a set of Zn- and Co-based MOFs at near ambient temperatures. MOFs synthesized using different metal clusters and organic connecting ligands allowed to study effects of different surface area, pore volume, and pore shapes on hydrogen storage parameters. Hydrogen adsorption values in the studied MOFs correlated well with surface area and pore volume but did not exceed 0,75wt.%. Therefore, new methods to improve the hydrogen storage capacity in MOFs were investigated. The addition of metal catalysts was previously reported to improve significantly hydrogen storage in MOFs. In this thesis the effect of Pt catalyst addition on hydrogen adsorption in MOF-5 was not confirmed. Contrary to previous reports, hydrogen adsorption in MOF-5 mixed/modified with Pt catalysts had fast kinetics, correlated well with surface area, and was on the same level as for unmodified MOF-5. New nanostructured carbon materials were synthesized by the reaction between fullerene C60 and coronene/anthracene. Despite negligible surface area these materials adsorbed up to 0,45wt.% of hydrogen at ambient temperatures. The reaction of fullerene C60 with hydrogen gas was studied at elevated temperatures and hydrogen pressures. In situ gravimetric monitoring of the reaction was performed in a broad temperature interval with/without addition of metal catalysts (i.e. Pt and Ni). The reaction resulted in synthesis of hydrogenated fullerenes C60Hx (with x≤56) followed by fullerene cage fragmentation and collapse upon prolonged duration of hydrogen treatment. Possible mechanisms of C60 hydrogenation and fragmentation were discussed. It is demonstrated that reaction of SWCNTs with hydrogen gas at elevated temperatures and hydrogen pressures can be used for nanotube opening, purification from amorphous carbon, side-wall hydrogenation, and partial unzipping of SWCNTs. Some graphene nanoribbons (GNRs) were synthesized as the result of SWCNTs unzipping. A surprising ability of hydrogen to penetrate inside SWNTs and to react with encapsulated fullerene C60 was demonstrated.
Sökandet efter nya material för vätelagring är viktigt för utveckling av framtida väteenergitillämpningar. I denna avhandling visas att nya material med intressanta egenskaper kan syntetiseras genom reaktion av väte med olika nanokolprekursorer. Avhandlingen består av två delar. Den första delen ägnas åt studier av vätelagring i vissa metall-organiska fackverk (så kallade MOFs) och nanostrukturerade kolmaterial medan den andra delen beskriver syntes av nya material genom reaktion av vätgas med olika kolmaterial (dvs. fulleren C60, enkelväggiga kolnanorör (SWCNTs) och fulleren C60 kapslat i SWCNTs (C60 @ SWCNTs)). Väteadsorptionen mättes för ett antal Zn- och Co-baserade MOFs vid rumstemperatur. MOFs syntetiserades med hjälp av olika metallkluster och organiska ligander för att studera effekterna av olika yta, porvolym och porformer på vätelagringsparametrarna. Väteadsorptionsvärden i de studerade MOFs korrelerade väl med yta och porvolym, men översteg inte 0,75wt.%. Därför undersöktes nya metoder för att förbättra kapaciteten för vätelagring i MOFs. Tillsättning av metallkatalysatorer har tidigare rapporterats avsevärt förbättra vätelagring i MOFs. I denna avhandling kunde effekten av en tillsats av Pt-katalysator på väteadsorption i MOF-5 inte bekräftas. I motsats till tidigare rapporter hade väteadsorption i MOF-5 blandad/modifierad med Pt-katalysatorer snabb kinetik och korrelerade väl med arean, men var på samma nivå som för omodifierad MOF-5. Nya nanostrukturerade kolmaterial syntetiserades genom reaktion mellan fulleren C60 och coronene/antracene. Trots försumbar yta adsorberade dessa material upp till 0,45wt.% väte vid rumstemperatur. Reaktionen av fulleren C60 med vätgas studerades vid förhöjda temperaturer och vätetryck. In situ gravimetrisk övervakning av reaktionen utfördes i ett brett temperaturintervall med/utan tillsats av metallkatalysatorer (dvs. Pt och Ni). Reaktionen resulterade i syntes av hydrogenerade fullerener C60Hx (med x≤56) följt av fragmentering och kollaps av fullerenstrukturen vid förlängd varaktighet av vätebehandlingen. Möjliga mekanismer för hydrering och fragmentering av C60 diskuteras. Det har visats att reaktionen mellan SWCNTs och vätgas vid förhöjda temperaturer och vätetryck kan användas för öppning av nanorör, borttagning av amorft kol, funktionalisering av sidoväggar och partiell "blixtlåsöppning" av SWCNTs. Reaktionen kan också syntetisera grafen-nanoband (GNRs) som en följd av att SWCNTs öppnas på längden. En överraskande stor förmåga för väte att tränga in i SWNT och där reagera med inkapslade fullerenmolekyler C60 demonstrerades.

Thesis (Ph. D.)--University of California, San Diego, 2006.
Title from first page of PDF file (viewed October 11, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 116-126).

Nitrogen-rich materials are of increasing interests for the development of a wide variety of applications. These compounds are prime candidates for ligands used in the complexation of metals since they possess several lone pairs. Resulting complexes have also exhibited a wide variety of interesting properties, ranging from magnetism to gas absorption to energetic properties. This thesis describes the synthesis and characterisation of new metallic complexes with the known energetic ligands: hydrazine and H3bta, as well as that of a new nitrogen-rich compound: H4ttp. Chapter 2 outlines a series of chains bridged by hydrazine and their potential as initiatory compounds. Mononuclear lanthanide H3bta complexes are presented in Chapter 3. The development of the new nitrogen-rich, tetrazole-based H4ttp ligand is described in Chapter 4. This new ligand was used to synthesise various lanthanide complexes through hydrothermal reactions.

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

Inorganic framework materials, with structures based on arsenate As04 tetrahedra and a variety of additional trigonal, tetrahedral or octahedral units have been synthesised by hydrothermal methods. The framework topologies of these materials have been characterised by single crystal X-ray diffraction; additional techniques, including thermogravimetric analysis and SQUID magnetoinetry, have been used to assess properties ofsome materials. Iron arsenates with 2D and 3D framework topologies are reported; these include structures templated by piperazine; 1,4-diaminobutane, DABCO, Fe2As207·2H20 and LiFeAs040H. The boron arsenic system has been investigated using a molten salt technique and a variety of alkali metal templates. A total of ten boroarsenate materials have been characterised, including [Cs2CBAs030H)s(As04)2] [(CsCI4)]CI, which is templated on both anions and cations and a family of materials XBAs04F ex = Cs, Rb, NHt). Hydrothermal techniques have been used to produce arsenate frameworks in combination with molybdenum, zinc and scandium. Two 'zinc arsenate materials with new framework topologies have been synthesised; a chiral framework with 16-ring channels and a 2D layer framework, both with caesium templates. Five scandium arsenate frameworks have been synthesised and are characterised; three have the same basic framework structure but with differing amine templates. Further new compounds have been synthesised by evaporating solutions of ainines with metal chloride or arsenate covnter-ions; these include three arsenate DABCO structures and a related phosphate DABCO material. Zinc chloride, cobalt chloride and hydrated manganese chloride salts with piperazinium counter-ions were also synthesised. Hydrothermal syntheses with vanadium reagents resulted in the formation of five new structures - a vanadium arsenate; a vanadium oxalate; a nickel vanadate cluster cap'ped by 2,2bipyridyl and isostructural nickel and cobalt metavanadates, NiV20 6·H20 and CoV206·H20. Powder neutron diffraction was used to show the isostructural,materials possessed differing magnetic cells. During investigations into copper arsenate framework materials, four new copper halide coordination polymers were discovered. Two materials with tetramethylammonium (TMA) templates - CU2Br3(TMA) and CU2I3(TMA) - and a DABCO templated structure CU2Ch(DABCO) share a common stoichiometry but were shown to possess different structural motifs. A fourth material discovered, CU7I7(DABCOhs, forms a· complex 3D organic-inorganic hybrid framework.

Synthesis of controlled quality and quantity of nanostructured materials form the basis of future nanotechnology building blocks. The understanding of fundamental properties, creation of complex hierarchical nanostructured materials and development of nanotechnologies are research areas which follow closely after the synthesis of nanomaterials. First and foremost, the key growth parameters of vapour-phase synthesis were identified so as to control the growth of nanomaterials with desired physical dimensions and chemical compositions. The synthesized nanomaterials were characterised using various chemical and structural analysis techniques in a complementary fashion. In addition, various self-assembly growth techniques were used to engineer the growth of complex nanostructures. The use of lithography; photolithography and ion beam lithography to generate micro to nano dimension catalyst patterns proved to be a valuable guide for selective growth of nanowires, whilst the use of zinc oxide polyhedron crystals and grain-boundary textured Cu templates have successfully produced a variety of interesting hierarchical nanostructures. Essentially, the templates act as a structure directing medium to intercede the growth in a confined manner. Success in the growth of one-dimensional single-crystal nanowires is the focus of interest since they offer the potential to answer fundamental questions about the effect of dimensionality on physical properties and are expected to play a central role in applications ranging from molecular electronics to scanning microscopy probes. Finally, with the availability of nanostructures in desirable crystal structures and chemical compositions, studies on their physical properties and phenomena were performed. Interesting properties such as the wettability and electrical properties were investigated. In particular, silicon carbide nanowire flowers show remarkable surface hydrophobicity and elasticity attributed to the unconventional multi-directional assembly of nanowires. The zinc oxide nanowires, on the other hand, exhibit superior electrical conductivity due to their clean surfaces and perfect crystallinity nature.

The studies covered in this dissertation concentrate on the various forms of diamond films synthesized by chemical vapor deposition (CVD) method, including microwave CVD and hot filament CVD. According to crystallinity and grain size, a variety of diamond forms primarily including microcrystalline (most commonly referred to as polycrystalline) and nanocrystalline diamond films, diamond-like carbon (DLC) films were successfully synthesized. The as-grown diamond films were optimized by changing deposition pressure, volume of reactant gas hydrogen (H2) and carrier gas argon (Ar) in order to get high-quality diamond films with a smooth surface, low roughness, preferred growth orientation and high sp3 bond contents, etc. The characterization of diamond films was carried out by metrological and analytical techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and Raman spectroscopy. The results of characterization served as feedback to optimize experimental parameters, so as to improve the quality of diamond films. A good understanding of the diamond film properties such as mechanical, electrical, optical and biological properties, which are determined by the qualities of diamond films, is necessary for the selection of diamond films for different applications. The nanocrystalline diamond nanowires grown by a combination of vapor-liquid-solid (VLS) method and CVD method in two stages, and the graphene grown on silicon substrate with nickel catalytic thin film by single CVD method were also investigated in a touch-on level.

The field of drug delivery is developinq rapidly and is gaining the attention of scientists and the pharmaceutical Industry. Serious challenges in designing drug delivery systems are that many new drug entities such as cancer drugs are water-insoluble. Hyperbranched polymers, most notably dendrimers, are a class of macromolecules whose unique properties such as their degree of branching, multi-valency and defined molecular shape make them suitable as new scaffolds for drug delivery. Dendrimers can offer two different environments which are very important in drug delivery, namely the interior and the outer surface. The outer surface represents molecular features such as solubility where the terminal groups are located, and its interface with the surrounding medium. When a hydrophilic substituent is introduced into the surface (the periphery) the dendrimer becomes hydrophilic and water-soluble. The interior of these water soluble dendrimers gives a hydrophobic environment to the incorporated organic molecule. Having a hydrophobic interior and a hydrophilic surface makes dendrimers potentially very good drug delivery vehicles. The primary aim of this investigation was to synthesise a suitable water soluble dendritic material which was able to encapsulate the non-polar drugs (water insoluble dye) in a lower generation; the idea was that the large branching unit could the encapsulate drugs at lower generation. The selection of building blocks for the preparation of dendritic material was very important. In this project, the monomer selected to build the dendritic macromolecule was 3,5-dihydroxybenzyl alcohol, and initially ethyl 6- bromohexanoate as a branching unit. The cores used were 4,4- dihydroxybiphenyl and 1,1, 1-tris (4-hydroxy-phenyl) ethane; in the later stage of this project, physical and chemical properties of dendrimers such as solubility at different pH, maximum solubility at pH 7.4, Absorptivity of the molecules, and finding their CMC using dye-encapsulatlon, surface tension, and molar conductivity were investigated. The first part of this investigation was the synthesis of dendritic macromolecules achieved by attaching first and second generation dendrons to 4,4-dihydroxybipnenyl and 1,1, 1-tris(4-hydroxyphenyl) ethane, and then hydrolysis prior to measurement of their physical-chemical properties. Some of the products had properties that could improve the solubility of a water insoluble dye by encapsulation. Their critical micelle concentration was found by surface tension measurement and was verified by two other analytical techniques (molar conductivity and dye encapsulation). Study of physico-chemical results and molecular modelling of these compounds revealed that they have a potential to be used in drug delivery systems, although further modification of structure would improve their properties for this purpose.

Chapter 1 gives a brief review of oxychalcogenide materials and their properties, particularly those with structures similar to systems discussed in the later chapters. Particular attention is paid to the structural and magnetic properties of La2O2Fe2OSe2-type materials, work on which is presented in chapters 3–5. These oxychalcogenides, along with ZrCuSiAs-related materials, are of interest due to their potentially interesting magnetic and conducting properties. In particular they are close relatives of the LaOFeAs superconductors. Chapter 2 describes the synthetic and analytical techniques used in this project. The theory behind the powder diffraction techniques used throughout is described, and information on specific methodology used in the data collections and analysis of this work is given. SQUID magnetometry is also discussed. Chapter 3 discusses the variable temperature structural and magnetic properties of La2O2Mn2OSe2 and Pr2O2Mn2OSe2, as well as those of the newly prepared material Ce2O2Mn2OSe2. These materials are observed to undergo a phase transition on cooling revealed by a change in the thermal expansion of the c cell parameter, and show evidence for the static disorder of oxide ions from the [Mn2O]2+ plane below this temperature. Pr2O2Mn2OSe2 is also shown to undergo a further transition on cooling below 36 K to an orthorhombic unit cell. Neutron diffraction data have also shown that the Mn2+ moments in these materials order with an AFM1 structure on cooling below ~180 K. Chapter 4 describes the study of both La2O2Fe2OS2 and La2O2Fe2OSe2 by variable temperature neutron powder diffraction. These materials have been demonstrated to order with an AFM3 structure on cooling below ~100 K, which is coincident with a subtle structural change observed in the thermal expansion of the a cell parameter. The unexpected adoption of the AFM3 magnetic structure is discussed in relation to structurally similar iron-based superconductors. Chapter 5 presents the synthesis of several new La2O2Fe2OSe2-type materials, and the magnetic structure of La2O2Co2OSe2. The stability range over which these materials form is discussed with respect to the size of the metal ions present. A comparison of the structural properties of all the A2O2M2OSe2 materials is given and the various magnetic structures they adopt discussed. Chapter 6 reports the synthesis of a new family of transition metal oxychalcogenides (β La2O2MnSe2). Their structure has been solved from laboratory X ray diffraction data, using a combination of charge-flipping and direct methods, and confirmed by neutron diffraction. Variable temperature structural properties are discussed and show these materials undergo a phase transition on cooling associated with ordering of transition metal ions. SQUID magnetometry and neutron powder diffraction have both demonstrated these materials order antiferromagnetically at low temperatures. Chapter 7 describes the synthesis of two new ZrCuSiAs-related transition metal containing oxychalcogenides: Ce2O2FeSe2 and La2O2ZnSe2. The structure solution of Ce2O2FeSe2 by charge-flipping is reported, alongside the determination of the magnetic structure from neutron powder diffraction data collected at 12 K. The variable temperature structural properties of La2O2ZnSe2 are also reported.

This thesis has mainly focused on the electrochemical synthesis of ammonia at atmospheric pressure using three different catalyst types (nitride, spinel and perovskite). Attention also has been given to developing new electrolyte materials based on oxide-carbonate composites, with the aim of exploring their application in ammonia synthesis at low operating temperature (< 500 °C). Ammonia was synthesised from H₂ and N₂ using an electrolyte supported cell based on LiAlO₂-(Li/Na/K)₂CO₃ as electrolyte, Ag-Pd as anode and either nitride (e.g. Co₃Mo₃N) or spinel (CoFe₂O₄) as cathode. The maximum rate of ammonia formation (3.27 x 10⁻¹⁰10 mol s⁻¹ cm⁻² at 450 °C and 0.8 V) was obtained when Co₃Mo₃N was used as a cathode. Ammonia was also synthesised from H₂ and N₂ in an electrolytic cell based on Sm-doped ceria-carbonate composite (SDC-(Li/Na/K)₂CO₃) as an electrolyte, NiO-SDC as anode and perovskite oxide La₀.₆Sr₀.₄Fe₀.₈Cu₀.₂O₃-δ (LSFCu) catalyst as a cathode. The maximum rate was found to be 5.39 x 10⁻⁹ mol s⁻¹ cm⁻² at 450 °C and 0.8 V. Ammonia was also synthesised successfully from water vapour (3% H₂O) and nitrogen, using a new electrolyte material based on Ca and Gd co-doped ceria-carbonate composite (CGDC-(Li/Na/K)₂CO₃). Perovskite oxide Sm₀.₅Sr₀.₅CoO₃-δ (SSCo) was used as an anode and either spinel or perovskite based catalysts were used as cathodes. The maximum rate of ammonia formation (4.0 x 10⁻¹⁰ mol s⁻¹ cm⁻² at 375 °C and 1.4 V) was attained with a La₀.₇₅Sr₀.₂₅Cr₀.₅Fe₀.₅O₃-δ (LSCrF) cathode. Ammonia was synthesised directly from air and water vapour (3% H₂O) in a symmetrical cell composed of LSCrF as electrodes (cathode and anode) and CGDC-(Li/Na/K)₂CO₃ composite as electrolyte. The maximum rate was found to be 1.94x10⁻¹¹ mol s⁻¹ cm⁻² at 375 °C with an applied voltage of 1.2 V.

Ordered mesoporous materials have attracted much attention recently for use in a wide range of applications. The oxidising materials, ceria (CeO₂) and CGO (Ce₀.₉Gd₀.₁O[subscript(2-δ)]) have both been synthesised with ordered mesopores, but a method for the simple fabrication of these materials in high yields with crystalline pore walls has not yet been reported in the literature. This thesis details the development of the vacuum impregnation method for the synthesis of ordered mesoporous materials with emphasis on ceria and CGO. Using the vacuum impregnation method both materials were successfully prepared. The materials exhibited the porous single crystal morphology in high yields, with unusual crystallographic features. Nitrogen physisorption, transmission electron microscopy (TEM), TEM tomography and temperature programmed studies were employed. Temperature programmed studies showed the materials to be catalytically active at lower temperatures than traditionally-prepared ceria. Photovoltaic studies showed that the materials exhibited efficient exciton quenching. The observation of nanowire extrusion during the synthetic procedure assisted in the postulation of a mechanism for product formation in the vacuum impregnation method. The vacuum impregnation method was subsequently shown to be applicable to the synthesis of other materials, with encouraging results presented for ordered mesoporous carbon and Zr₀.₈₄Y₀.₁₆O[subscript(2-δ)]. The syntheses of ordered mesoporous La₀.₈₅Sr₀.₁₅GaO[subscript(3-δ)] and La₀.₇₆Sr₀.₁₉CoO[subscript(3-δ)] were unsuccessful.

-4Scm-1 whereas the hexamethyl was insulating. This was proposed to be due to differing stacking characteristics. The properties of the ternary salts were proved to be intrinsic and not solvent induced. The failure of the amphiphilic dipyrrylmethene to complex with TCNQ was proposed to be due to steric hindorance which encumbers the close approach of the TCNQ. The Langmuir film of the dipyrrylmethene was shown to undergo re-orientation on the subphase. The L-B film of a picolinium TCNQ charge transfer salt was shown not to under go a molecular re-orientation due to the increase in the area of the hydrophobic aliphatic chains.

Natural and synthetic zeolites have been the focus for extensive research owing to their many applications and huge potential number of new topologies. The work presented here represents the first major study into the formation of zeotypical materials incorporating BeO4 and T5+O4 (T5+ = As or P) tetrahedra and a large number of new structures have been produced. These novel materials have been synthesised via hydrothermal procedures and characterised via Single Crystal X-ray Diffraction, supported by Powder X-ray Diffraction, Thermogravimetric Analysis, Magic Angle Spinning Nuclear Magnetic Resonance and Electron Dispersive Spectroscopy. The berylloarsenates produced encompass the entire range of dimensionality, from cluster structures such as Na3.5[AsO4(BeF3)(BeF2)]•0.4H2O to the novel three dimensional framework [Hbis( 2-ethylhexyl)amine, NH4] [(AsO4)3(AsO3OH)Be3(BeOH)] and include analogues of known zeolite topologies; MER, AFI and WEI. Four completely novel fully connected three-dimensional zeolitic topologies are also reported with one already being assigned the Framework Type code of BOZ. These new topologies represent the most structurally complicated zeolites known and are remarkable in their high calculated internal pore volume. The berylloarsenates are supported by parallel research into the beryllophosphates which has produced unusual new structures of low dimensionality such as the one dimensional chain Na2[(BeO2OH)(PO2)]•H2O as well as structural analogues of the berylloarsenate structures including [H-pyridine][(BeO4)2BeO3(OH2)P3(OH)] which exhibits the AFI topology. These structures could potentially be used in catalysis, ion exchange and due to their low framework density, gas storage. A short investigation into other beryllate chemistry is also presented which includes the novel two dimensional structures Na[BeGeO3(OH)] and Ba[BeGeO3(OH)] which significantly contribute to the sparse field of beryllogermanates. This section also contains the first structural characterisation of Sr[Be(OH)4], a vital species in beryllium solution chemistry.

Inorganic framework materials, with structures based on arsenate and phosphate, AsO4 and PO4, tetrahedra and a variety of octahedral metal units, such as hafnium, niobium and iron, have been synthesised and fully characterised. These materials have been synthesised by solvothermal techniques and the principal analytical technique to characterise the resulting single crystals has been Single Crystal X-ray Diffraction. Supporting analysis was carried out, using techniques such as Powder and Neutron Diffraction, Thermogravimetric Analysis, Electron Dispersive Spectroscopy and Infrared Spectroscopy. Of the hafnium arsenates and phosphates that have been synthesised, several are fluorinated and one is templated, such as Hf2F2(H(PO4)2)(NH4)2 and [Hf2F8(AsO4)][DABCO-H2](NH4) respectively. Similar layered frameworks have also been characterised and reported for titanium, zirconium and niobium. These structures all offer ion exchange potential, due to their ammonium cations and/or water molecules. The hydrogen iron phosphates that are discussed include two novel frameworks and one material which offers an improved model for the mineral lipscombite, Fe1.34(PO4)OH0.96. One of the new frameworks presented, (NH4)3Fe3(HPO4)6, offers particularly interesting potential applications as a high capacity battery material via lithium exchange reactions. The hydrothermal synthesis of two novel hydrated sodium tungstate structures is also discussed. One of these materials was found to contain a very high H : Na ratio, resulting in strong hydrogen bonding and a densely packed framework, which may be of interest in the field of high density liquids.

This thesis presented a detailed research work on diamond materials. Chapter 1 is an overall introduction of the thesis. In the Chapter 2, the literature review on the physical, chemical, optical, mechanical, as well as other properties of diamond materials are summarised. Followed by this chapter, several advanced diamond growth and characterisation techniques used in experimental work are also introduced. Then, the successful installation and applications of chemical vapour deposition system was demonstrated in Chapter 4. Diamond growth on a variety of different substrates has been investigated such as on silicon, diamond-like carbon or silica fibres. In Chapter 5, the single crystalline diamond substrate was used as the substrate to perform femtosecond laser inscription. The results proved the potentially feasibility of this technique, which could be utilised in fabricating future biochemistry microfluidic channels on diamond substrates. In Chapter 6, the hydrogen-terminated nanodiamond powder was studied using impedance spectroscopy. Its intrinsic electrical properties and its thermal stability were presented and analysed in details. As the first PhD student within Nanoscience Research Group at Aston, my initial research work was focused on the installation and testing of the microwave plasma enhanced chemical vapour deposition system (MPECVD), which will be beneficial to all the future researchers in the group. The fundamental of the on MPECVD system will be introduced in details. After optimisation of the growth parameters, the uniform diamond deposition has been achieved with a good surface coverage and uniformity. Furthermore, one of the most significant contributions of this work is the successful pattern inscription on diamond substrates by femtosecond laser system. Previous research of femtosecond laser inscription on diamond was simple lines or dots, with little characterisation techniques were used. In my research work, the femtosecond laser has been successfully used to inscribe patterns on diamond substrate and fully characterisation techniques, e.g. by SEM, Raman, XPS, as well as AFM, have been carried out. After the femtosecond laser inscription, the depth of microfluidic channels on diamond film has been found to be 300~400 nm, with a graphitic layer thickness of 165~190 nm. Another important outcome of this work is the first time to characterise the electrical properties of hydrogenterminated nanodiamond with impedance spectroscopy. Based on the experimental evaluation and mathematic fitting, the resistance of hydrogen-terminated nanodiamond reduced to 0.25 MO, which were four orders of magnitude lower than untreated nanodiamond. Meanwhile, a theoretical equivalent circuit has been proposed to fit the results. Furthermore, the hydrogenterminated nanodiamond samples were annealed at different temperature to study its thermal stability. The XPS and FTIR results indicate that hydrogen-terminated nanodiamond will start to oxidize over 100ºC and the C-H bonds can survive up to 400ºC. This research work reports the fundamental electrical properties of hydrogen-terminated nanodiamond, which can be used in future applications in physical or chemical area.

L'objectif de la thèse est de synthétiser et de caractériser les matériaux photoluminescents qui présentent de la luminescence extrinsèque et intrinsèque. Pour les matériaux luminescents extrinsèques, l'objectif était de régler la couleur d'émission de terres rares par deux méthodes: la méthode conventionnelle du dopage / codopage par un ion de terre rare et une nouvelle méthode appelée la réduction contrôlée des dopants. Le dopage a été effectué pour les ions tels que Eu2+, Eu3+ dopés dans la matrice M2Ga2SiO7 (M: Sr, Ca). Mais une telle méthode présente des inconvénients, à savoir pour réaliser le contrôle de la couleur d'émission qui nécessite soit un changement du réseau hôte pour le dopage, soit le dopage par au moins deux ions de terres rares. Ainsi, une nouvelle technique appelée réduction contrôlée de dopants a été mis en oeuvre, où la couleur d'émission est provient d’un contrôle précis du rapport Eu3+/Eu2+. Cette approche a été illustrée par la réduction progressive du matériau SrAl2O4: Eu3+ qui passe d’un luminescence rouge à une luminescente verte, en passant par le jaune selon le rapport Eu3+/Eu2+. L'autre partie de la thèse est axée sur la luminescence intrinsèque de certains qui provient de la présence de défauts intrinsèques. Le composé stannate tels que Mg2SnO4 a été utilisé comme un exemple pour illustrer ce genre de luminescence intrinsèque. Ce matériau présente une autre caractéristique intéressante puisqu’il phosphoresce dans le blanc tout en ayant une luminescence dans l’IR
The objective of the thesis is to synthesize and characterize the photoluminescent materials which exhibit extrinsic and intrinsic luminescence. For extrinsic luminescent materials, the objective was to tune the emission color of such rare earth doped materials via two methods: the conventional method Doping/Codoping by a rare earth ion and a new method called Controlled Reduction of Dopants. Doping was carried out for the rare earth ions such as Eu2+, Eu3+ doped gallates M2Ga2SiO7 (M:Sr,Ca) phases. But such method have drawbacks i.e. to achieve the control over the emission color either a change of the host lattice is required for doping or minimum of two rare earth ions are required for codoping. So a new technique called Controlled Reduction of Dopants was setup, where the emission color is tuned on the basis of the change of the oxidation state of the rare earth ion doped in the phase. This approach was illustrated with the progressive reduction of the red phosphor SrAl2O4:Eu3+ to green phosphor SrAl2O4:Eu2+ to target yellow luminescence. The other part of the thesis is focused upon self activated or intrinsic luminescent materials which show luminescence due to the intrinsic defects present in them. Stannates such as Mg2SnO4 was used as an example to illustrate this kind of intrinsic luminescence. This material exhibits another interesting character of exhibiting the both white long lasting luminescence and IR luminescence

Control of solid state ordering in conjugated small molecules is paramount to the continued development and implementation of organic materials in electronic devices. However, there exists no reliable method on which to predicatively determine how a change to the molecular structure will impact the solid-state packing. As such, the molecule must be synthesized before its solid-state packing can be definitively evaluated. However, once the packing structure of a material is known there exist both qualitative structure- function relationships derived from the literature, as well as quantitative computational methods that can be employed to suggest if a material will perform well in a given device. This type of bottom-up strategy is used in Chapter 2 to design and synthesize a high performance material for organic field effect transistors. A core molecule is synthesized, and through rigorous optimization of pendant and solubilizing groups a material with exceptional solid-state packing is developed and its performance in an organic field effect transistor is discussed. Chapter 3 discusses the use of conjugated organic molecules in conjunction with inorganic materials to develop hybrid organic/inorganic materials. A scalable synthesis is developed so derivatives can be rapidly synthesized and their properties evaluated. Two classes of materials are developed and synthesized: tetracene-based ligands for quantum dots and diammonium-substituted anthracene and tetracene derivatives for 2D-perovskites. Initial results for both classes of materials are presented. Chapter 4 discusses the topochemical photopolymerization of heptacene [4+4] dimers. Multiple derivatives were synthesized in order to give the ideal alignment of molecules in the crystal, followed by irradiation of crystals to give crystal templated polymerization. In Chapter 5, triarylmethane derivatives are synthesized and their performance as radiochromic sensors is evaluated. Chapter 6 involves the development of a robust synthetic scheme toward a difficult to attain π- extended regioisomer of pyrene. Photophysical characterization reveals that the direction of π-extension from the pyrene core has a profound effect on electron delocalization.