This thesis focuses on developing a new method to measure trace tellurium (Te) in different environmental samples such as lake waters, mine tailings and sediments. The developed technique is based on Hydride Generation Atomic Fluorescence Spectroscopy (HG-AFS), a technique that can measure low concentration of Te and also allows for Te speciation at low cost and high efficiency in various environmental samples. To validate the method that could be used to determine Te speciation in various types of environmental samples, a series of tests has been designed for finding the best conditions to measure Te(IV) using HG-AFS and obtain accurate and reliable results. Those tests include the stability of the signal, the acidity of the solution, the volatility of Te after digestion of solids, the reduction from Te(VI) to Te(IV), the detection limit of the technique, and the validity of two digestion methods under the optimum (HG-AFS) instrumental settings. An interference study including the most common elements in the Earth’s crust such as (Ni, Fe, Pb, Cr, Cu, Co, Zn, Mn and Mo) was also performed. The results of this study showed that Cu(II) can severely interfere with Te quantification decreasing the Te signal to almost zero. Therefore, different masking agents such as 8-hydroxyquinoline, 1,10-phenanthroline, urea and thiourea were tested to reduce and eliminate this interference.

No description available.

No description available.

Thesis (Ph. D.)--University of Iowa, 1923. / Reprinted from the Journal of the Optical society of America and review of scientific instruments, v. 10, no. 6, June, 1925.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Abstracted in Dissertation abstracts, v. 25 (1965) no. 10, p. 6020. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:29:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-03-15Bitstream added on 2014-06-13T20:38:23Z : No. of bitstreams: 1 silva_rr_me_araiq.pdf: 6153824 bytes, checksum: 99fdc68a43b515fbf9a4f98f2d7ce84b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho baseou-se no estudo da preparação de novos nanomateriais multifuncionais baseados em nanoestruturas 1D de telúrio (Te1D), as quais foram obtidas pela redução de óxido de telúrio através da síntese por modelagem assistida de protetores de colóide. Os protetores de colóide utilizados foram baseados em surfactantes iônicos e não iônicos, copolímeros em blocos ou carboidratos de cadeias lineares. Nanoestruturas de Te1D na forma de filamentos ou fios longos e flexíveis, ou ainda bastões rígidos, foram obtidas em dispersões aquosas estáveis. A morfologia e tamanho das nanoestruturas de Te1D foram dependentes da razão molar Te: H3PO2 e da natureza do protetor de colóide empregados. Novos nanobiocompósitos de Te1D foram obtidos pelo crescimento de nanoestruturas de Te1D em molde sólido formado pela rede tridimensional de nanofibras entrecruzadas de celulose bacteriana (CB-hidrogel). O arranjo das nanofibras de CB atua como barreira de difusão no controle da formação de nanoestruturas de Te1D. Além disso, a formação de nanofios de Te1D foi dependente da proporção mássica de telúrio/CB empregada. Nanopartículas de maghemita de diâmetro médio de 11 nm (-Fe2O3) foram obtidas pela oxidação de magnetita previamente sintetizada pelo método de coprecipitação de íons ferro em meio alcalino. As nanopartículas apresentaram perfil superparamagnético e foram funcionalizadas com camada de sílica (-Fe2O3@SiO2) pelo método modificado de Stöber. Novos nanocompósitos bifuncionais magneto-luminescentes foram obtidos pela associação de nanopartículas... / This work was based on the study of the preparation of novel nano multifunctional 1D nanostructures based on tellurium (Te1D), which were obtained by reduction of tellurium oxide at template synthesis by a colloid protector. The colloid protectors used were based on ionic and nonionic surfactants, block copolymers or carbohydrates of linear chains. Te1D nanostructures in the shape of filaments or wires long and flexible, or rigid rods were obtained in stable aqueous dispersions. The morphology and size of Te1D nanostructures were dependent to the molar ratio of Te:H3PO2 and the nature of the colloid protector employed. New Te1D nanobiocomposites were obtained by the growth of Te1D nanostructures into solid template of the intersecting three-dimensional network of bacterial cellulose nanofibers (BC-hydrogel). The arrangement of nanofibers CB acts as a diffusion barrier into control of the nanostructures Te1D formation. Moreover, the formation of Te1D nanostructure was dependent to the weight proportion between tellurium and CB employed. Maghemite nanoparticles with average diameter about 11 nm (-Fe2O3) were obtained by oxidation of magnetite previously synthesized by the coprecipitation method of iron ions in alkaline media. The nanoparticles exhibits a superparamagnetic profile and they were functionalized with a silica layer (SiO2@Fe2O3) by the modified Stöber method. New magneto-luminescent bifunctional nanocomposites were prepared by anchoring the visible emitter... (Complete abstract click electronic access below)

Orientador: Sidney José Lima Ribeiro / Banca: Osvaldo Novais de Oliveira Junior / Banca: Cid Bartolomeu de Araujo / Resumo: Este trabalho baseou-se no estudo da preparação de novos nanomateriais multifuncionais baseados em nanoestruturas 1D de telúrio (Te1D), as quais foram obtidas pela redução de óxido de telúrio através da síntese por modelagem assistida de protetores de colóide. Os protetores de colóide utilizados foram baseados em surfactantes iônicos e não iônicos, copolímeros em blocos ou carboidratos de cadeias lineares. Nanoestruturas de Te1D na forma de filamentos ou fios longos e flexíveis, ou ainda bastões rígidos, foram obtidas em dispersões aquosas estáveis. A morfologia e tamanho das nanoestruturas de Te1D foram dependentes da razão molar Te: H3PO2 e da natureza do protetor de colóide empregados. Novos nanobiocompósitos de Te1D foram obtidos pelo crescimento de nanoestruturas de Te1D em molde sólido formado pela rede tridimensional de nanofibras entrecruzadas de celulose bacteriana (CB-hidrogel). O arranjo das nanofibras de CB atua como barreira de difusão no controle da formação de nanoestruturas de Te1D. Além disso, a formação de nanofios de Te1D foi dependente da proporção mássica de telúrio/CB empregada. Nanopartículas de maghemita de diâmetro médio de 11 nm (-Fe2O3) foram obtidas pela oxidação de magnetita previamente sintetizada pelo método de coprecipitação de íons ferro em meio alcalino. As nanopartículas apresentaram perfil superparamagnético e foram funcionalizadas com camada de sílica (-Fe2O3@SiO2) pelo método modificado de Stöber. Novos nanocompósitos bifuncionais magneto-luminescentes foram obtidos pela associação de nanopartículas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work was based on the study of the preparation of novel nano multifunctional 1D nanostructures based on tellurium (Te1D), which were obtained by reduction of tellurium oxide at template synthesis by a colloid protector. The colloid protectors used were based on ionic and nonionic surfactants, block copolymers or carbohydrates of linear chains. Te1D nanostructures in the shape of filaments or wires long and flexible, or rigid rods were obtained in stable aqueous dispersions. The morphology and size of Te1D nanostructures were dependent to the molar ratio of Te:H3PO2 and the nature of the colloid protector employed. New Te1D nanobiocomposites were obtained by the growth of Te1D nanostructures into solid template of the intersecting three-dimensional network of bacterial cellulose nanofibers (BC-hydrogel). The arrangement of nanofibers CB acts as a diffusion barrier into control of the nanostructures Te1D formation. Moreover, the formation of Te1D nanostructure was dependent to the weight proportion between tellurium and CB employed. Maghemite nanoparticles with average diameter about 11 nm (-Fe2O3) were obtained by oxidation of magnetite previously synthesized by the coprecipitation method of iron ions in alkaline media. The nanoparticles exhibits a superparamagnetic profile and they were functionalized with a silica layer (SiO2@Fe2O3) by the modified Stöber method. New magneto-luminescent bifunctional nanocomposites were prepared by anchoring the visible emitter... (Complete abstract click electronic access below) / Mestre

No description available.

No description available.

Made available in DSpace on 2014-10-09T12:31:38Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:05Z (GMT). No. of bitstreams: 1 02286.pdf: 3044750 bytes, checksum: 753f2e5a876a0a848f90cf7bcb06b0e5 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP