Le bassin de la Garonne, deuxième plus grand bassin français de par sa superficie (52000 km2 au Mas d'Agenais), fait l'objet de pressions anthropiques liées aux activités humaines agricoles, domestiques et industrielles.<br />Le prélèvement des eaux de la Garonne et de ces principaux affluents sur une année hydrologique a permis de détecter des enrichissements significatifs pour un grand nombre d'éléments en trace métalliques (ETM : Pb, Cr, Ni, Cu, Zn...). Il s'avère que la plus part de ces éléments métalliques en quantité de trace (ppb) sont éventuellement transportés sous forme particulaire par les rivières. De nombreux arguments vont dans le sens d'une source majeure diffuse de pollution à l'origine de ces enrichissements : les pluies. Toutefois, certains enrichissements spécifiques liés à des activités industrielles locales sont observées (cas du Cr sur l'Agout). Les bilans des flux [entrée (pluies), sortie (exutoire)] ont mis en évidence le stockage de certains métaux, vraisemblablement dans les sols et les sédiments du lit de la Garonne.<br />Le suivi des flux d'éléments dissous majeurs (NO3-, Cl-, SO42-, Mg2+, Ca2+, K+, Na+) et plus spécialement des nitrates, en période de basses eaux estivales (50 m3/s), dans les eaux d'un tronçon de Garonne Toulousaine, a permis la caractérisation et la quantification des apports anthropiques spécifiques en NO3-, Cl-, K+ et Na+ liés à cette agglomération. Certains de ces éléments, nitrates et potassium, sont partiellement éliminés tout au long de ce tronçon. Cette consommation peut être attribuée à l'activité biologique qui se développe dans le lit de la Garonne (développement du biofilm) dans ces périodes critiques où les eaux sont plus anoxiques (moins oxygénées).<br />L'étude plus spécifique du devenir des nitrates dans une zone humide riveraine de la Garonne (site de Monbéqui) a mis en exergue les capacités de ces sites à éliminer ce composé azoté. Ces zones humides sont le théâtre de la rencontre entre les eaux de la Garonne et de la nappe, propice au développement de nombreux processus biogéochimiques. Nous avons identifié et quantifié de fortes consommations biologiques en nitrates dans les zones de mélange entre la Garonne et la nappe. Cela résulte des effets couplés de l'oxydation de la matière organique, de la respiration aérobie, de la dénitrification et de la réduction des oxydes et hydroxydes de Mn et de Fe. Au contraire, dans les zones de sortie de nappe vers la Garonne, il semblerait qu'il y ait nitrification de l'ammonium probablement originaire des profondeurs de la nappe et/ou des sols.

Emerging energy storage applications are driving the demand for Li-ion battery positive electrode materials with higher energy densities and lower costs. The recent production of complete pseudo-ternary phase diagrams of the Li-Mn-Ni-O system generated using combinatorial methods has provided a greater understanding of the impact of initial composition, synthesis temperature, and cooling rate on the phases that form in the final materials. This thesis focuses on the synthesis and characterization of gram-scale positive electrode materials in the Li-Mn-Ni-O system. Structural analysis of these samples has resulted in the production of partial pseudo-ternary phase diagrams focusing on the positive electrode materials region of the Li-Mn-Ni-O system at 800°C and 900°C in air for both quenched and slow cooled compositions. These bulk-scale diagrams support the observations of the combinatorial diagrams, and show similar layered and cubic structures contained within several single- and multi-phase regions. The phases that form at each composition are shown to be dependent on both the reaction temperature and cooling rate used during synthesis. The electrochemical characterization of two composition series near Li2MnO3, one quenched and one slow cooled, is presented. The quenched compositions exhibited reversible cycling at 4.4 V, voltage plateaus and small increases in capacity above 4.6 V, and large first cycle irreversible capacity losses at 4.8 V. In the slow cooled series, all but one composition exhibited initial capacities below 100 mAh/g which began to continually increase with cycling, with several compositions exhibiting capacity increases of 300% over 150 cycles at 4.9 V. In both series, analysis of the voltage and differential capacity plots indicated that significant structure rearrangements are taking place in these materials during extended cycling, the possible origins of which are discussed. Finally, high precision coulometry studies of one Li-deficient and two Li-rich single-phase layered compositions are discussed. These materials exhibit minimal oxidation of simple carbonate-based electrolyte when cycled to high potential, with the Li-deficient composition producing less electrolyte oxidation at 4.6 V vs. Li/Li+ than commercial Li[Ni1/3Mn1/3Co1/3]O2 at 4.2 V. The inherent inertness of this composition may make it suitable for use as a thin protective layer in a core-shell particle.

Made available in DSpace on 2014-06-11T19:25:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-10-05Bitstream added on 2014-06-13T18:53:36Z : No. of bitstreams: 1 stefanelo_jc_me_rcla.pdf: 1971755 bytes, checksum: f2545c6a190dc7a872bf14f2c2b4fce6 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho foi desenvolvido um dispositivo eletroluminescente (EL) constituído de um compósito híbrido (CH), formado por uma blenda polimérica e um material EL inorgânico. A blenda é composta por um polímero condutor, a poli(o-metoxianilina) (POMA) dopada com ácido tolueno sulfônico (TSA), e um polímero isolante, o poli(fluoreto de vinilideno-co-trifluoretileno) (P(VDF-TrFE)). A esta blenda é acrescentado um material EL inorgânico, o silicato de zinco dopado com Manganês (Zn2SiO4:Mn), formando assim, o compósito híbrido. O dispositivo foi construído depositando o compósito por drop casting sobre um substrato de óxido de estanho dopado com flúor (FTO) e após cristalização em uma estufa foi depositado um eletrodo de metal por evaporação à vácuo formando uma estrutura tipo “sanduíche”. Neste trabalho foram construídos dispositivos com eletrodo superior de Alumínio (Al) e Ouro (Au), denominados: FTO/CH/Al e FTO/CH/Au. O comportamento elétrico dos dispositivos de FTO/CH/Al foram analisados aplicando-se as teorias de Emissão Termoiônica, Emissão Schottky e Emissão Poole-Frenkel, o que tornou possível encontrar alguns parâmetros como: altura da barreira para a junção metal/CH, condutividade do CH e fator de retificação. O dispositivo de FTO/CH/Au foi caracterizado pela técnica de espectroscopia de impedância, sendo obtido também a altura da barreira para a junção metal/CH, a condutividade do CH, além da constante dielétrica do compósito e como variam esses dois últimos parâmetros com a temperatura. A aplicação das teorias de Emissão Termoiônica, Emissão Schottky e Emissão Poole-Frenkel produziram resultados semelhantes aos obtidos pela técnica de espectroscopia de impedância. Os espectros de luminescência apresentaram um pico em l = 528 nm com estabilidade temporal de emissão comparável a dos dispositivos inorgânicos puros. / In this work was developed an electroluminescent (EL) device made up with a hybrid composite (CH), that is formed by a polymeric blend and an inorganic EL material. The conductive polymer, poly(o-methoxyaniline) (POMA) doped with p-Toluene sulphonic acid (TSA), and an isolating polymer, the poly(vinylidenefluoride-co-trifluoroethylene) (P(VDFTrFE)), was used to make the polymer blend. An inorganic EL material, the zinc silicate manganese-doped (Zn2SiO4:Mn), was added to the blend, forming the hybrid composite. The composite was deposited by drop-casting over a Fluoride Tin Oxide substrate (FTO) and after the crystallization in an oven a metal electrode was deposited by vacuum evaporation, forming a type “sandwich” structure. In this work were constructed different devices. Aluminum (Al) and Gold (Au) were used as upper electrodes, therefore the device structures were: FTO/CH/Al and FTO/CH/Au. To analyze the electrical behavior of the FTO/CH/Al device was applied the theories of Thermionic Emission, Schottky Emission and Poole- Frenkel Emission. Using these theories was possible to obtain parameters such as; the barrier height from the metal/CH junction, CH conductivity and diode rectifier factor. The FTO/CH/Au device was characterized using the impedance spectroscopy technique. For this device was also possible to obtain the barrier height from the metal/CH junction, CH conductivity and CH dielectric constant. For the last two parameters the dependence with the temperature were also observed. The application of the theories of Thermionic Emission, Schottky Emission and Poole-Frenkel Emission produced similar results to that obtained by the impedance spectroscopy technique. The luminescence spectra, for the devices, showed a peak at l = 528 nm with emission stability in time that it is comparable of pure inorganic devices.

Electronic and optical properties of semiconducting nanocrystals, that can be engineered and manipulated by various ways like varying size, shape, composition, structure, has been a subject of intense research for more than last two decades. The size dependency of these properties in semiconductor nanocrystals is direct manifestation of the quantum confinement effect. Study of electronic and optical properties in smaller dimensions provides a platform to understand the evolution of fundamental bulk properties in the semiconductors, often leading to realization and exploration of entirely new and novel properties. Not only of fundamental interests, the semiconductor nanocrystals are also shown to have great technological implications in diverse areas. Besides size tunable properties, introduction of impurities, like transition metal ions, gives rise to new functionalities in the semicon-ductor nanocrystals. These materials, termed as doped semiconductor nanocrystals, have been the subject of great interest, mainly due to the their interesting optical properties. Among different transition metal doped semiconductor nanocrystals, manganese doped systems have drawn a lot on attention due to their certain advantages over other dopants. One of the major advantages of Mn doped semiconductor nanocrystals is that they do not suffer from the problem of self-absorption of emission, which quite often, is consid-ered detrimental in their undoped counterparts. The doped nanocrystals are known to produce a characteristic yellow-orange emission upon photoexcitation of the host that is relatively insensitive to the surface degradation of the host. This emission, originating from an atomic d-d transition of Mn2+ ions, has been a subject of extensive research in the recent past. In spite of the spin forbidden nature of the specific d-d transition, namely 6A1 −4 T1, these doped nanocrystals yield intense phosphorescence. However, one major drawback of utilizing this system for a wide range application has been the substantial inability of the community to tune the emission color of Mn-doped systems in spite of an intense effort over the years; the relative constancy of the emission color in these systems has been attributed to the essentially atomic nature of the optical transition involving localized Mn d levels. Interestingly, however, the Mn emission has a very broad spectral line-width in spite of its atomic-like origin. While the long (∼ 1 ms) emission life-time of the de-excitation process is well-studied and understood in terms of the spin and orbitally forbidden nature of the transition, there is little known concerning the process of energy transfer to the Mn from the host in the excitation step. In this thesis, we have studied the ultrafast dynamic processes involved in Mn emission and addressed the issues related to its tunability and spectral purity. Chapter 1 provides a brief introduction to the fundamental concepts relevant to the studies carried out in the subsequent chapters of this thesis. This chapter is started with a small preview of the nanomaterials in general, followed by a discussion on semiconducting nanomaterials, evolution of their electronic structure with dimensions and size as well as the effect of quantum confinement on their optical properties. As all the semiconducting nanomaterials studied in the thesis are synthesized via colloidal synthesis routes, a separate section is devoted on colloidal semiconducting nanomaterials, describing various ways of modifying or tuning their optical properties. This is followed by an introduction to the important class of materials “doped semiconductor nanocrystals”. With a general overview and brief history of these materials, we proceed to discuss about various aspects of manganese doped semiconductor nanocrystals in great details, highlighting the origin of the manganese emission and the associated carrier dynamics as well as different reported synthetic strategies to prepare these materials. The chapter is closed with the open questions related to manganese doped semiconductor nanocrystals and the scope of the present work. Chapter 2 describes different experimental and theoretical methods that have been employed to carry out different studies presented in the thesis. It includes common experimental techniques like UV-Vis absorption spectroscopy, steady-state and time-resolved photoluminescence spectroscopy used for optical measurements, X-ray diffraction, trans-mission electron microscopy and atomic absorption spectroscopy used for structural and elemental analysis. Experimental tools to perform special studies like transient absorption and single nanocrystal spectroscopy are also discussed. Finally, theoretical fitting method used to analyse various spectral data has been discussed briefly. Chapter 3 deals with the dynamic processes involved in the photoexcitation and emission in manganese doped semiconductor nanocrystals. For this study, Mn doped ZnCdS alloyed nanocrystal has been chosen as a model system. There are various radiative and nonrdiative recombination pathways of the photogenerated carriers and they often compete with each other. We have studied the dynamics of all possible pathways of carrier relaxation, viz. excitonic recombination, surface state emission and Mn d-d transition. The main highlight of this chapter is the determination of the time-scale to populate surface states and the Mn d-states after the photoexcitation of the host. Employing femtosecond pump-probe based transient absorption study we have shown that the Mn dopant states are populated within sub-picosecond of the host excitation, while it takes a few picoseconds to populate the surface states. Keeping in mind the typical life-time of the excitonic emission (∼ a few ns), the ultra-fast process of energy transfer from the host to the Mn ions explains why the presence of Mn dopant ions quenches the excitonic as well as the surface state emissions so efficiently. Chapter 4 presents a study of manganese emission in ZnS nanocrystals of different sizes. By varying the size of the ZnS host nanocrystal, we show that one can tune the Mn emission over a limited range. In particular, with a decrease in host size, the Mn emission has been observed to red-shift. We have attributed this shift in Mn emission to the change in the ratio of surface to bulk dopant ions with the variation of the host size, noting that the strength of the ligand field at the Mn site should depend on the position of the Mn ion relative to the surface due to a systematic lattice relaxation in such nanocrystals. The ligand field affects the emission wavelength directly by controlling the splitting of the t2 and e levels of Mn2+ ions. The surface dopant ions experience a strong ligand field due to distorted tetrahedral environment which leads to larger splitting of these t2 and e states. We further corroborated these results by performing doping concentration dependent emission and life-time studies. In Chapter 5 addresses two fundamental challenges related to manganese photolumines-cence, namely the lack of a substantial emission tunability and presence of a very broad spectral width (∼ 180-270 meV). The large spectral width is incompatible with atomic-like manganese 4T1 −6 A1 transition. On the other hand, if this emission is atomic in nature, it should be relatively unaffected by the nature of the host, though it can be manipulated to some extent as discussed in Chapter 3. The lack of Mn emission tunability and spectral purity together seriously limit the usefulness of Mn doped semiconductor nanocrystals. To understand why the Mn emission tunability range is very limited (typically 565-630 nm) and to understand the true nature of this emission, we carried out single nanocrystal imaging and spectroscopy on Mn doped ZnCdS alloyed nanocrystals. This study reveals that Mn emission, in fact, can vary over a much wider range (∼ 370 meV) and exhibits widths substantially lower (∼ 60-75 meV) than reported so far. We explained the occur-rence of Mn emission in this broad spectral range in terms of the possibility of a large number of symmetry inequivalent sites resulting from random substitution of Cd and Zn ions that leads to differing extent of ligand field contributions towards the splitting of Mn d-levels. The broad Mn emission observed in ensemble-averaged measurements is the result of contribution from Mn ions at different sites of varying ligand field strengths inside the NC. Chapter 6 presents a synthetic strategy to strain-engineer a nanocrystal host lattice for a controlled tuning of the ligand field effect of the doped Mn sites. It is realized synthesizing a strained quantum dot system with the structure ZnSe/CdSe/ZnSe. A larger lattice parameter of CdSe compared to that of ZnSe causes a strain field that is maximum near the interface, gradually decreasing towards the surface. We control the positioning of Mn dopant ions at different distances from the interface, thereby doping Mn at different predetermined strain fields. With the help of this strain engineering, we are able to tune Mn emission across the entire range of the visible spectrum. This strain induced tuning of Mn emission is accompanied by life-times that is dependent on the emission energy which has been explained in terms of perturbation effect on the Mn center due to the strain generated inside the quantum dot. The spectacular emission tuning has been explained by modelling the quantum dot system as an elastic continuum containing three distinct layers under hydrostatic pressure. From this modelling, we found that the strain is max-imum at the interface and decreases continuously as one goes away from the interface. We also show that the Mn emission maximum red shifts with increasing distance of the dopants from the maximum strained region. In summary, we have performed a study on the photophysical processes in manganese doped semiconductor nanocrystals. We have emphasized in understanding of different dynamic processes associated with the manganese emission and tried to understand the true nature of manganese emission in a nanocrystal. This study has brought out some new aspects of manganese emission and opened up possibilities to tune and control manganese emission by proper design of the host material.

Made available in DSpace on 2015-03-26T13:53:35Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2372218 bytes, checksum: c684476e0801238a67fe879e90544505 (MD5) Previous issue date: 2007-08-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The dusty from the siderurgical industry (PD) it is an industrial solid residue originating from the processes of the metallurgy of the ore of manganese (Mn). This material contains significant concentration of Mn. The responsible industrial unit for the production of approximately 2000 ton/month of PD's is Rio Doce Manganês (RDM), company of the group of the Company is Worth of Rio Doce (CVRD), nowadays, Company is Worth. PD's were characterized chemically (stage 1) and soon afterwards, appraised as source of Mn for soy plants (Glicine max L.), of the variety it Conquers and eucalyptus plants (Eucalyptus globulus), of the hybrid Urograndis, vegetation home (stage 2). Para the stage 1 of the research, they were chosen ten materials of PD's collected in the industrial units of Barbacena/MG, Ouro Preto/MG, Salvador/Ba and Corumbá/MS, respectively. The samples of PD's were analyzed according to the lixiviação procedures and solubilization of solid residues (ABNT NBR 10005 and 10006, 2004). The tenors of metals of PD &#769;s were quantified through espectrofotometry in optic emission with plasma coupled induced (ICP-OES) and espectrofotometry for atomic absorption (AAS). Soon afterwards, the experiment was accomplished vegetation home (stage 2), being used samples of two Latossolos (LVa), a loamy one (TG) and other sandy (TM), of the cities Viçosa/MG and Three Marias/MG, respectively. As sources of Mn, were appraised samples of PD's in natura originating from five industrial units of RDM/CVRD and two prepared fertilizers starting from PD's: the sulfate of manganese (SM-PD) and the oxide of manganese (OM-PD). it was included as treatment controls another fertilizer sulfate of commercial manganese (SM- with). The materials were applied in equivalent amount to the doses 0,0; 2,5; 5,0; 7,5 and 30,0 mg kg-1 of Mn, except for applied OM-PD just in the doses 2,5 and 30,0 mg kg-1 of Mn. The plants were collected and droughts in greenhouses with ventilation forced of hot air. Soon afterwards, they were determined the tenors of P, Mn, Zn, Ass, Faith, Cr, Ni, You and If, with xiextraction of nítric acid and percloric (3:1), for espectrofotometry of optical emission with plasma coupled induced (ICP-OES). The data were submitted to the analysis of multiple lineal regression, being evaluated the production of the mass of dry matter, concentration and accumulation of the chemical elements in the aerial part and roots of the soy plants and eucalyptus. The results obtained with the extracts solubilizados (stage 1), they presented tenors of The, Pb, If, Hg, Mn, Faith and Al in values above the maximum limits established by ABNT (I Enclose G, ABNT NBR 10004, 2004). on the other hand, the tenors of metals found in the leached extracts didn't result in high values, second referred her norm. There was not significant answer with the sources of applied Mn in the treatments, in what he/she concerns the production of the mass of dry matter of the soy plants and eucalyptus (stage 2). there also was not, accumulation of heavy metals in the fabrics of the same ones in levels that represented any risk to his/her development. PD's in natura made available Mn to the cultivated plants, in amounts comparable to liberated them to SM-PD, OM-PD and the SM-COM. It is ended that, so much PD's in natura, as for the materials produced starting from PD's (SM-PD and OM-PD) they were efficient as sources of Mn to the soy plants and eucalyptus cultivated vegetation home. The obtained results indicate that the use of PD can be viable, as source of Mn for the industry of fertilizers. / O Pó de Despoeiramento (PD) é um resíduo sólido industrial proveniente dos processos da metalurgia do minério de manganês (Mn). Este material contém concentração significativa de Mn. A unidade industrial responsável pela produção de aproximadamente 2000 toneladas/mês de PD s é a Rio Doce Manganês (RDM), empresa do grupo da Companhia Vale do Rio Doce (CVRD), atualmente, Companhia VALE. Os PD s foram caracterizados quimicamente (etapa 1) e em seguida, avaliados como fonte de Mn para plantas de soja (Glicine max L.), da variedade Conquista e plantas de eucalipto (Eucalyptus globulus), do híbrido Urograndis, em casa de vegetação (etapa 2). Para a etapa 1 da pesquisa, foram escolhidos dez materiais de PD s coletados nas unidades industriais de Barbacena/MG, Ouro Preto/MG, Salvador/Ba e Corumbá/MS, respectivamente. As amostras de PD s foram analisadas segundo os procedimentos de lixiviação e solubilização de resíduos sólidos (ABNT NBR 10005 e 10006, 2004). Os teores de metais dos PD &#769;s foram quantificados por meio de espectrometria em emissão ótica com plasma acoplado induzido (ICP-OES) e espectrometria por absorção atômica (AAS). Em seguida, foi realizado o experimento em casa de vegetação (etapa 2), utilizando-se amostras de dois Latossolos (LVa), um argiloso (TG) e outro arenoso (TM), das cidades Viçosa/MG e Três Marias/MG, respectivamente. Como fontes de Mn, foram avaliadas amostras dos PD s in natura proveniente de cinco unidades industriais da RDM/CVRD e dois fertilizantes preparados a partir dos PD s: o sulfato de manganês (SM-PD) e o óxido de manganês (OM- PD). Foi incluído como tratamento controle um outro fertilizante sulfato de manganês comercial (SM-Com). Os materiais foram aplicados em quantidade equivalente às doses 0,0; 2,5; 5,0; 7,5 e 30,0 mg kg -1 de Mn, com exceção do OM-PD aplicado apenas nas doses 2,5 e 30,0 mg kg -1 de Mn. As plantas foram coletadas e secas em estufas com ventilação forçada de ar quente. Em seguida, determinaram-se os teores de P, Mn, Zn, Cu, Fe, Cr, Ni, Ti e Se, com ixextração de ácido nítrico e perclórico (3:1), por espectrometria de emissão óptica com plasma acoplado induzido (ICP-OES). Os dados foram submetidos à análise de regressão linear múltipla, avaliando-se a produção da massa de matéria seca, concentração e acúmulo dos elementos químicos na parte aérea e raízes das plantas de soja e eucalipto. Os resultados obtidos com os extratos solubilizados (etapa 1), apresentaram teores de As, Pb, Se, Hg, Mn, Fe e Al em valores acima dos limites máximos estabelecidos pela ABNT (Anexo G, ABNT NBR 10004, 2004). Por outro lado, os teores de metais encontrados nos extratos lixiviados não resultaram em valores elevados, segundo a referida norma. Não houve resposta significativa com as fontes de Mn aplicadas nos tratamentos, no que diz respeito à produção da massa de matéria seca das plantas de soja e eucalipto (etapa 2). Não houve também, acúmulo de metais pesados nos tecidos das mesmas em níveis que representassem qualquer risco ao seu desenvolvimento. Os PD s in natura disponibilizaram Mn às plantas cultivadas, em quantidades comparáveis às liberadas ao SM-PD, OM- PD e o SM-Com. Conclui-se que, tanto os PD s in natura, quanto aos materiais produzidos a partir dos PD s (SM-PD e OM-PD) foram eficientes como fontes de Mn às plantas de soja e eucalipto cultivadas em casa de vegetação. Os resultados obtidos indicam que o uso do PD pode ser viável, como fonte de Mn para a indústria de fertilizantes.

The past few decades have witnessed an almost exponential increase in interest in the field of metal organic frameworks (MOFs), which can be evidenced from the large number of scientific articles being published routinely in this area. The MOFs are crystalline hybrid materials built via the judicial use of inorganic metal ions and organic linkers, thereby bridging the gap between purely inorganic and organic materials. The structural versatility and the potential tunability of the MOFs imparts unique physicochemical and thermomechanical properties, which have rendered them immensely useful in the branches of chemistry, material science, physics, biology, nanotechnology, medicine as well as environmental engineering. The MOFs have been shown to be promising as materials for gas storage and separation, sensors, ferroelectric and non-linear optical materials, magnetism, catalysis, drug delivery etc and researchers have been devising strategies to utilize the MOFs to tackle a number of global challenges of the twenty-first century. A survey of the literature reveals that the linear organic linkers, 1,4- benzenedicarboxylic acid (BDC) and 4,4’-biphenyldicarboxylic acid (BPDC), have been the organic linkers of choice for the construction of stable, porous and multifunctional MOFs. The aim of this thesis has been to monitor the effect that the presence of a functional group in between the benzene rings of the BPDC would have on the overall structures and the properties of the MOFs. Thus, as part of the investigations, the preparation of the MOF compounds using 4,4’-sulfonyldibenzoic acid (SDBA) and 4,4’- azodibenzoic acid (ABA) have been accomplished. Along with the conventional hydrothermal and solvothermal synthetic techniques, the liquid-liquid biphasic reaction method was also utilized for the synthesis of some of the compounds. The structures of the compounds were ascertained from single crystal X-ray diffraction technique. Proton conductivity studies were performed on Mn based porous MOFs using AC impedance spectroscopy. The ferroelectric behavior in a Co based porous MOF was established using dielectric and polarization vs electric field measurements. The labile nature of the lattice solvent molecules was established utilizing single crystal X-ray diffraction studies and water sorption experiments. In addition, the site selective substitution in a homometallic MOF and the subsequent conversion to a mixed-metal spinel oxide upon thermal decomposition, have also been studied. Chapter 1 of the thesis is a brief overview of the metal organic framework compounds and summarizes the various important structures that have been reported in literature and the interesting properties that they exhibit. In chapter 2, the proton conductivity behavior, solvent mediated single crystal to single crystal (SCSC) and related structural transformations in a family of Mn and Co based porous MOFs with SDBA have been presented. Also presented are the results of the site selective substitution of Mn by Co in a homometallic Mn based MOF and it’s subsequent decomposition to CoMn2O4 spinel oxide nanoparticles. In chapter 3, the syntheses, structures and the magnetic properties of the pentanuclear Mn5 based MOF compounds with SDBA have been presented. The role of the time and the temperature in the formation of the compounds has also been presented. In chapter 4, the dehydration/rehydration mediated switchable room temperature ferroelectric behavior, the single crystal to single crystal solvent exchange studies and selective gas sorption behavior in an anionic Co based MOF with SDBA has been discussed. In chapter 5, the use of the liquid-liquid biphasic synthetic route in the formation of Zn and Cd based MOFs with ABA has been discussed. Structural transformations between the one dimensional Zn based compounds and the heterogeneous catalytic studies using the Cd based compounds have also been presented.

The transport of elements by streams from headwater regions to the sea is influenced by landscape characteristics. This thesis focuses on the influence of landscape characteristics (e.g. proportion of wetland/forest coverage) on temporal and spatial variations of Fe, Mn, S and trace elements (As, Co, Pb) in streams located in northern Sweden, a boreal region characterized by coniferous forests and peat wetlands. Water samples from a network of 15 streams revealed a different hydrogeochemistry in forested catchments compared to wetland catchments. The temporal variation was dominated by spring flood, when concentrations of Fe, Mn and trace elements increased in forested headwaters. However, in streams of wetland catchments concentrations decreased, but Pb concentrations were higher in comparison to other streams. Both Fe and Pb showed positive correlations with wetland area, while Co correlated with forest coverage. The anthropogenic contribution of As and Pb appear to be larger than the supply from natural sources. During spring flood SO42- decreased in most streams, although concentrations increased in streams of wetland catchments. Concentrations of SO42- were higher in streams of forested catchments than in wetland dominated streams, the former being net exporters of S and the latter net accumulators. Isotope values of stream water SO42- (δ34SSO4) were close to that of precipitation during spring flood, indicating that the major source of S is from deposition. The results show that, although emissions of anthropogenic S have been reduced, there is still a strong influence of past and current S deposition on runoff in this region. In conclusion, wetlands are key areas for the hydrogeochemistry in this boreal landscape. The findings emphasize the importance of understanding stream water chemistry and element cycling from a landscape perspective. This may be important for predicting how boreal regions respond to environmental disturbances such as climate change.

Subject of this diploma thesis is analysis of selected heavy metals in soils which are exposed to long-time cause of contaminants from metallurgical industry in localities Třinec and Ostrava. For assessment of the contamination, indexes for evaluation of soils were chosen. Those indexes are focusing mainly on rate of enrichment of the soils by selected heavy metals and resulting ecological and possibly health risk for human organism. Within every location, 26 samples were extracted, while every sample extract location, were selected to map the level of pollution around metallurgical plants in the most complex way. The analysis of the samples was done by techniques F-AAS and AMA 254 and established metals were mercury, lead, copper, chrome, nickel, manganese and zinc.

In the last few years a renewed interest has reappeared in materials that were highly investigated in the 50s-70s, like manganese perovskites, spinel chalcogenides and vanadium oxides. The first two classes of materials are nowadays intensively studied due to the colossal magnetoresistance effect, which is the magnetoresistance associated with a ferromagnetic-paramagnetic transition. Vanadium oxides are known to form many compounds and most of them undergo metal-to-insulator phase transitions, with a high increase in the electrical conductivity (MIT). Many technological applications derive from the variation of the physical properties around the phase transition temperature. Although many efforts have been done in order to understand their electronic structures and to elucidate the MIT mechanisms, the vanadium oxides are still matter of debate in science.The present study has been performed in order to understand the electronic structure of these very intriguing materials. The role of different dopants that induce strong changes in the electronic and magnetic properties has been investigated making use of two spectroscopic techniques, namely X-ray photoelectron and X-ray emission spectroscopy.

No description available.