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Title from PDF of title page. / Document formatted into pages; contains 64 pages. / Thesis (M.E.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The ability of Mercuric Iodide (HgI2) to function as a highly efficient radiation detector at room temperature has generated great interest and has triggered further studies on this difficult material. This property is expected to enable significant enhancements to a far-ranging variety of applications and systems. HgI2 devices have shown superior performance at room temperature compared to elemental Si or Ge devices, which require to be cooled down to liquid nitrogen temperature when used as nuclear radiation detectors. While substantial studies have been conducted on single crystal HgI2, polycrystalline HgI2 remains a comparatively less studied form of this material. The primary use of HgI2 is as a direct radiation detector. It can also be used in applications with a scintillator intermediate to generate visible light from incident nuclear radiation. Hence its response to visible light can be used to study the electronic properties of HgI2 polycrystalline films. / ABSTRACT: The films are deposited on TEC-15 LOF glass with a Tin Oxide(Sn02) coating which acts as the growth surface. It also acts as the front contact with Palladium (Pd) being the back contact. Wire leads are attached to the palladium for electrical contact. The deposited films are circular in shape with a diameter of 2.5cm with thickness ranging from 50 to 600ìm. A maximum of 7 devices are contacted at various points on every film. For the measurements documented in this thesis, a tungsten-halogen lamp and an Oriel 1/4m grating monochromator are used as a light source. The incident flux on the sample is determined using a Si photodiode as reference. Device performance for both single crystal as well as polycrystalline films is documented. We have attempted to identify a set of optimum growth parameters using these measurements. / ABSTRACT: For a film to be considered favorably, not only should the individual devices show high quantum efficiencies and low dark currents, but the response of all devices on the same film should be uniform. A number of films are studied and the optimum film deposition conditions are commented upon. A powerful semiconductor device simulation tool, MEDICItm, is used to simulate the photoresponse of these films. The simulations are compared to the measurements and the transport and light absorption parameters of the polycrystalline films are determined. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

A commercial GC-AFS instrument has been developed and optimised for the speciation of organomercury. This instrument couples a GC oven to a modified atomic fluorescence detector via a ceramic pyrolyser. Organomercury compounds in dichloromethane solvent were directly injected through a Programmable Temperature Vaporiser Injector onto a DBl Megabore column. Once separated, the compounds eluted from the column and were atomised in the pyrolyser then detected by AFS. The direct injection technique, ceramic pyrolysis design and argon purged detector have improved previous instrument designs by enhancing and maintaining sensitivity. The instrumental limit of detection was determined to be 0.25 pg Hg absolute. Methods were developed for the extraction of methylmercury from a variety of marine samples. The techniques were validated using mussel homogenate and dogfish liver (IAEA 142, SRM 8044 and DOLT-2) certified reference materials. An interlaboratory comparision exercise was participated in and a method was developed for the detemination of methylmercury in Fucus sea plant (IAEA 140). A concentration of 0.63 ± 0.006 ng g-1 was reported. The material is now certified at 0.626 +0.139 ng g-1. Of all the participating laboratories, this was the closest result to the certified value. The instrument and methods were also applied to soil and sediment samples. Once again validation was performed with a CRM sediment, IAEA 356. Although this material has been reported to give positive artifact formation when using a steam distillation sample preparation procedure, good agreement and no artifects were observed upon analysis. A further contaminated land, an uncontaminated soil and sediment sample were also studied. For all the samples studied by GC-AFS total mercury measurements were also made following an appropriate digestion procedure and CV-AFS. A gas chromatograph was also coupled with ICP-MS and HPLC was coupled to CV-AFS as comparative techniques. Both approaches were optimised and validated with CRM's. The GC-ICP-MS had the advantage of providing additional element information and confirmed the presence of methylmercury bromide in the final mussel homogenate extract. The HPLC approach found to be much less sensitive than the GC techniques and also suffered from vapour generation interferences. The PTV injector was considered for large volume injection and thermal desorption techniques. Injector breakdown problems were overcome by optimising the conditions and solid phase adsorbent for cold splitless injection. A recovery of 70% was achieved for a 50 ul large volume injection of methylmercury chloride in DCM. This technique indicated the possibility that LVI may in the future offer increased method sensitivity.

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Made available in DSpace on 2014-10-09T12:28:00Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:28Z (GMT). No. of bitstreams: 0 / O Reservatório Rio Grande, localizado na Região Metropolitana de São Paulo (RMSP), é um importante manancial de abastecimento de água dessa região. Foram analisadas amostras de água de fundo e de sedimentos coletadas nesse reservatório em 4 pontos, em 4 campanhas, de setembro de 2008 a janeiro de 2010, sendo estas quantificadas em relação à concentração de Hg total pela técnica de CV AAS. Em seguida, adaptou-se uma metodologia da literatura para quantificação de Hg orgânico em sedimentos, que consistiu na extração dos compostos organomercuriais com diclorometano em meio ácido e, posterior destruição dos compostos orgânicos com cloreto de bromo. A validação dessa metodologia, em termos de precisão e exatidão, foi realizada por meio da análise dos materiais de referência BCR CRM 580 e IAEA 405. Para avaliação dos mecanismos de metilação e desmetilação de Hg nesse ambiente, foram determinados os seguintes parâmetros físicos e químicos, in situ: pH, temperatura da água, potencial redox (EH), transparência e profundidade. Nos sedimentos foram determinados também a granulometria, carbono orgânico total, bactérias redutoras de sulfato, N total e P total, além de Co, Cu, Fe e Mn. A seleção destes parâmetros esteve relacionada diretamente a fatores que influenciam o comportamento do MeHg em sedimentos e sua zona de transição. Foram encontradas concentrações para Hg total variando entre 1,0 e 71,0 mg kg- 1 e de Hg orgânico entre <10,0 a 47,2 &mu;g kg-1 e taxas de metilação entre 0,06 e 1,4% em sedimentos, ao longo do reservatório. Discutiram-se também as diferentes condições de metilação e suas influências, ao longo do reservatório. Como estudo suplementar, avaliou-se a concentração de outros metais e elementos traço presentes nos sedimentos, por meio da técnica de ativação neutrônica. Foram quantificados os elementos As, Ba, Br, Co, Cr, Cs, Hf, Fe, Na, Rb, Sb, Sc, Zn e os elementos terras raras Ce, Eu, La, Lu, Nd, Sm, Tb e Yb. Os fatores de enriquecimento calculados em relação aos valores da crosta terrestre utilizando-se Sc como elemento normalizador apresentaram valores acima de 2,0 para os elementos As, Br, Sb, U e Zn. Verificou-se uma forte influência antrópica para alguns dos elementos analisados, principalmente nos pontos localizados na entrada do reservatório, que recebem descarga de efluentes domésticos e industriais dos rios que alimentam o reservatório. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Recently, the Parkin group has synthesized tris[(1-isopropylbenzimidazol-2-yl)dimethylsilyl]methane, [Tismᴾʳⁱᴮᵉⁿᶻ]H, a bulky tetradentate tripodal ligand, which upon deprotonation can coordinate to metal centers via three nitrogen donor atoms and a carbon bridgehead to form metal atrane compounds. The [Tismᴾʳⁱᴮᵉⁿᶻ] ligand has been previously shown to stabilize metal hydride complexes, for example [Tismᴾʳⁱᴮᵉⁿᶻ]MgH [Tismᴾʳⁱᴮᵉⁿᶻ]ZnH. However, no attempts had been previously made to employ this ligand to stabilize heavier Group 12 analogues of these complexes, namely the cadmium and mercury hydride derivatives. In addition, all [Tismᴾʳⁱᴮᵉⁿᶻ] complexes previously reported have employed metals in the first or second oxidation states. In this work, an investigation is undertaken to use the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand to stabilize rare examples of cadmium and mercury hydrides, as well as survey how this ligand binds to Group 13 and transition metals in a variety of oxidation states. In Chapter 1, a series of [Tismᴾʳⁱᴮᵉⁿᶻ] cadmium complexes are reported, including the novel cadmium hydride species [Tismᴾʳᴮᵉⁿᶻ]CdH, which is only the third terminal cadmium hydride species to be structurally characterized by X-ray diffraction. The reactivity of this complex has been probed, revealing the first detailed report of reactivity for a Cd-H bond, as well as the first comparison in relative reactivity between an analogous Cd-H and Zn-H bond. This reactivity of [Tismᴾʳⁱᴮᵉⁿᶻ]CdH includes the ability to insert CO₂ and CS₂, and the resulting cadmium formate and dithioformate complexes have been characterized and discussed, with the latter being the first structurally characterized example of a cadmium dithioformate complex. In addition, [Tismᴾʳⁱᴮᵉⁿᶻ]CdH can undergo hydride extraction to yield the ion pair {[Tismᴾʳⁱᴮᵉⁿᶻ]Cd}[HB(C6F5)₃], a rare example of trigonal monopyramidal cadmium complex. Finally, [Tismᴾʳⁱᴮᵉⁿᶻ]CdMe was synthesized, revealing a different coordination mode of the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand than in the analogous [Tismᴾʳⁱᴮᵉⁿᶻ]ZnMe. In Chapter 2, a series of [Tismᴾʳⁱᴮᵉⁿᶻ] mercury complexes are reported and compared with their cadmium analogues. This comparison revealed several notable differences between [Tismᴾʳⁱᴮᵉⁿᶻ] mercury and cadmium complexes, most notably that the M-O-Si bond angle in [Tismᴾʳⁱᴮᵉⁿᶻ]HgOSiPh₃ is bent, as opposed to the linear [Tismᴾʳⁱᴮᵉⁿᶻ]CdOPh₃ derivative. The synthesis and characterization of [Tismᴾʳⁱᴮᵉⁿᶻ]HgH, the first mercury hydride complex to be structurally characterized by X-ray diffraction, is also reported. This complex has been crystallized in both the κ⁴ and κ³-coordination mode of the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand, representing the first example of a [Tismᴾʳⁱᴮᵉⁿᶻ] compound to be structurally characterized in two coordination modes. In Chapter 3, the synthesis of Group 13 and transition metal [Tismᴾʳⁱᴮᵉⁿᶻ] complexes are reported. These compounds include the first examples of [Tismᴾʳⁱᴮᵉⁿᶻ]M(III) complexes, which reveal that trivalent Group 13 [Tismᴾʳⁱᴮᵉⁿᶻ]M halide compounds form charged ion pairs, whereas trivalent transition metal chloride compounds form six-coordinate octahedral complexes. The investigation into Group 13 [Tismᴾʳᴮᵉⁿᶻ] complexes also led to the structural characterization of [Tismᴾʳⁱᴮᵉⁿᶻ]In→InI₃, the first example of a [Tismᴾʳⁱᴮᵉⁿᶻ] compound with a metal-metal bond. A series of [Tismᴾʳⁱᴮᵉⁿᶻ]MCl (M = Mn, Fe, Co, Cu) complexes are reported and their metrical data compared, along with an investigation into the reactivity of [Tismᴾʳⁱᴮᵉⁿᶻ]NiBr, which led to spectroscopic evidence for a [Tismᴾʳⁱᴮᵉⁿᶻ]NiH complex. Finally, the gold complex [κ1-Tismᴾʳⁱᴮᵉⁿᶻ]AuPPh₃ is reported, which adopts a novel κ1-coordination of the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand.

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