Dissertations / Theses on the topic 'Selenites'

Thesis (Ph. D.)--West Virginia University, 2010.
Title from document title page. Document formatted into pages; contains ix, 106 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

The current work investigates the photocatalytic reduction of selenium (Se) ions, selenate Se(VI) and selenite Se(IV), from two perspectives: Se ion removal from water and wastewater and the formation of nano-Se compounds. Se ion pollution has become an environmental issue in recent years, and hence there is an urgent need for an efficient removal technique. In addition, there is increasing interest in the formation of nano-size semiconductors for niche applications. Since Se is a semiconductor, its formation onto the semiconductor TiO2 could lead to the discovery of new composite materials. The current study has successfully elucidated the mechanism of Se ions reduction by photocatalysis. Factors such as the simultaneous adsorption of the Se ions (the electron scavenger in this case) and a suitable organic compound (the hole scavenger), and the chemical properties of the hole scavenger were crucial for effective and efficient Se ions photoreduction. Optimum conditions in relation to pH, concentrations and types of hole scavenger were reported and discussed. It was also found that stoichiometric adsorption ratio of formate and selenate resulted to optimum photoreduction rate. A modified Langmuir-Hinshelwood kinetic model that considered the simultaneous adsorption of both solutes was derived. The current investigation has also seen the successful formation Se deposits of different morphologies onto the TiO2 particles. Discrete Se particles of various sizes in the nano-size range as well as a Se film were deposited onto the TiO2 particles under different initial experimental conditions. The Se-TiO2 composite semiconductor was explored for the removal of cadmium Cd2+ ions, which resulted in the formation of CdSe-TiO2 systems. The photoreduction of Se ions using silver-modified TiO2 showed the enhanced reduction of Se ions to Se2- in the form of H2Se gas. It is suggested that the H2Se gas generated from the current photoreduction process could be used as a safer and cheaper technique in the formation of Se-compounds such copper selenide, cadmium selenide and zinc selenide. All these compounds were widely used in optical and semiconducting devices.

Cette recherche concerne la synthese, le comportement thermique et l'etude magneto-structurale des selenites des elements de transition 3d. Les structures ainsi etudiees peuvent varier de la tridimensionnalite au systeme discret. Deux diselenites de fer(iii) et de chrome(iii), m#2(se#2o#5)#3, presentant un caractere tridimensionnel et un faible couplage antiferromagnetique ont ete prepares. Quatre nouveaux complexes: cu(hseo#3)#2(h#2o)#2 ; cu(hseo#3)#2(no#3)#2#2#-,2nh#4+,nh#4no#3 ; cu(hseo#3)#2cl#-,nh#4+ et cu(hseo#3)#2cu#xm(#1#-#x)cl#2(h#2o)#4 ont ete isoles. Ils ont une structure en couche derivant de celle du compose hote cu(hseo#3)#2, mais l'ecartement entre les feuillets est variable suivant le complexe. De plus, tous ces nouveaux complexes presentent une transition magnetique a basse temperature (ferromagnetisme faible ou metamagnetisme). L'introduction d'un ligand supplementaire, la 2,2'-bipyridine, reduit encore la dimensionnalite de ces systemes ; chaines (1d): cu(se#2o#5)(c#1#0h#8n#2),2h#2o et m(hseo#3)#2(c#1#0h#8n#2), ou zero-d: dimere cu(hseo#3)#2(c#1#0h#8n#2)#2 ou monomere cu(hseo#3)cl(h#2seo#3)(c#1#0h#8n#2)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O objetivo deste trabalho foi avaliar concentrações de selênio (selenato e selenito de sódio) no crescimento, produção e biofortificação de duas cultivares de repolho. Para isso foram realizados dois experimentos em casa de vegetação, em sistema hidropônico, no período de julho a novembro de 2014, na UNESP, campus Jaboticabal-SP. Os experimentos diferiram conforme a fonte de selênio (Se) utilizada (selenato e selenito de sódio). Em ambos os experimentos, avaliaram-se dois fatores, sendo: duas cultivares de repolho (‘Fênix’ e 'Red Dinasty’) e cinco concentrações de Se (0, 5, 15, 30 e 60 µmol L-1) na solução nutritiva. O delineamento experimental utilizado foi o de blocos casualizados, com esquema fatorial 2 x 5 e quatro repetições. As variáveis analisadas foram o teor e acúmulo de Se na raiz e cabeça de repolho, área, diâmetro, comprimento e densidade de raiz, produtividade de repolho, massa seca de raiz, caule e cabeça de repolho e o teor e acúmulo de nitrogênio, fósforo e enxofre na cabeça de repolho. As fontes selenato e selenito promoveram o crescimento das raízes de repolho devido aos aumentos verificados em área, diâmetro, comprimento e densidade de raiz, em baixas concentrações de Se aplicadas. O aumento da produção de massa seca de raiz provavelmente foi devido o maior crescimento da raiz, que foi influenciado pelo fornecimento de Se. A massa seca do caule foi diferente apenas entre as cultivares de repolho com aplicação de selenato ou selenito. O teor de nitrogênio apresentou diferenças apenas entre as cultivares quando utilizada a fonte selenito. Ambas as fontes de Se também proporcionaram aumentos na absorção de fósforo e enxofre quando baixas concentrações de Se foram fornecidas. Observou-se que a aplicação de até 16,77 e 7,54 µmol L-1 de Se com as fontes selenato e selenito, respectivamente, proporcionaram os maiores incrementos na produtividade do repolho, e mesmo com a redução da produtividade com concentrações acima destas, os valores foram maiores que o tratamento controle. Isso indica que o Se foi benéfico ao repolho, pois não reduziu a sua produção. Verificou-se que a biofortificação foi eficiente para ambas as cultivares de repolho, que absorveram e acumularam Se na cabeça de repolho em função do incremento de Se, tanto com selenato como selenito.
The objective of this research was to evaluate concentrations of selenium (sodium selenate and selenite) in the growth, production and biofortification of two cabbage cultivars. Two experiments were carried out in greenhouse under hydroponic system, from July to November, 2014, at UNESP, Jaboticabal-SP campus. The experiments differed according to the source of selenium (Se) used (sodium selenate and selenite). In both experiments two factors were evaluated: two cabbage cultivars ('Fênix' and 'Red Dinasty') and five concentrations of Se (0, 5, 15, 30 and 60 μmol L-1) in the nutrient solution. The experimental was a randomized block design, with 2 x 5 factorial and four replications. The variables analyzed were the content and accumulation of Se in the root and shoot cabbage, evaluating area, diameter, length, density and dry mass in the root, cabbage yield, stem and cabbage head, and the content accumulation of nitrogen, phosphorus and sulfur in the cabbage shoot. Selenate and selenite sources promoted the growth of cabbage roots due to increases in area, diameter, length and root density at low concentrations of Se applied. The increase in root dry mass production was probably due to higher root growth, which was influenced by the supply of Se. The dry mass of the stem was different only between the cabbage cultivars with application of selenate or selenite. The nitrogen content presented differences only among the cultivars when the selenite source was used. Both S sources also provided increases in phosphorus and sulfur absorption when low concentrations of if were provided. It was observed that the application of up to 16,77 and 7,54 μmol L-1 of Se with selenate and selenite sources, respectively, provided the greatest increases in cabbage yield, and even with the reduction of productivity with concentrations above these, the values were higher than the control treatment. These indicate that the Se was beneficial to the cabbage, since it did not reduce its production. It was verified that biofortification was efficient for both cabbage cultivars, which absorbed and accumulated Se in the cabbage head as a function of the increase of Se, with both selenate and selenite.

Kadmis yra plačiai paplitęs aplinkos teršalas. Šis sunkusis metalas yra pavojingas žmonių sveikatai. Tuo tarpu cinkas ir selenas yra būtini elementai žmonėms ir gyvūnams. Todėl šio darbo tikslas buvo įvertinti kadmio, cinko ir selenito jonų ūmų poveikį baltymų sintezės sistemos ir jos komponentų bei ląstelių antioksidacinės sistemos aktyvumams laboratorinių pelių kepenyse. Tikslui pasiekti iškelti šie uždaviniai: įvertinti ūmų kadmio jonų poveikį baltymų sintezės sistemai pelių kepenyse, transliacijos sistemos komponentų – tRNR bei aminoacil-tRNR sintetazės – aktyvumams, metalotioneino koncentracijai pelių kepenyse, redukuoto glutationo koncentracijai ir lipidų peroksidacijai pelių kepenyse bei eritrocituose ir įvertinti cinko ir selenito jonų įtaką pelių baltymų sintezės ir antioksidacinėms sistemoms, esant ūmiam kadmio jonų poveikiui. Tyrimo rezultatai parodė, kad kadmio jonų poveikis baltymų sintezės procesui pelių kepenyse susijęs su tiesioginiu poveikiu šiame procese dalyvaujančių komponentų – tRNR bei aminoacil-tRNR sintetazės – aktyvumų pokyčiais. Be to, kadmio jonai keitė ląstelių antioksidacinės sistemos komponentų (redukuoto glutationo ir metalotioneino) koncentracijas ir aktyvino lipidų peroksidaciją pelių kepenyse. Cinko ir selenito jonai apsaugojo transliacijos ir antioksidacinę sistemas nuo toksinio kadmio jonų poveikio.
Cadmium is a widespread environmental pollutant. This heavy metal forms a serious hazard to the public health. Zinc and selenium are essential elements for humans and animals. So, the aim of present study was to evaluate the acute effects of cadmium, zinc, and selenite ions on the effectiveness of protein synthesis system and its components in the liver of laboratory mice as well as on the activity of cellular antioxidant system. The objectives of the study were to evaluate the effects of cadmium ions on the rate of liver protein synthesis, on the activities of components of translation machinery – tRNA and aminoacyl-tRNA synthetase, on the content of metallothionein in the liver, on the content of reduced glutathione and lipid peroxidation in the liver and red blood cells; to evaluate the influence of zinc and selenite ions on the protein synthesis system and antioxidative system of mice affected by cadmium ions. The obtained results showed, that the toxicity of cadmium ions on hepatic protein synthesis is related to the changes in activities of the key components of protein synthesizing system – tRNAs and aminoacyl-tRNA synthetases. Moreover, cadmium ions altered the content of antioxidant components (reduced glutathione, metallothionein) and activated liver lipid peroxidation. Mice pre-treatment with zinc and selenite ions prevented both translational machinery and antioxidative system against cadmium-induced disturbances.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
As informações sobre fontes de selênio (Se) em alface são incipientes na literatura, sobretudo, com relação ao limite entre biofortificação e toxicidade. Assim, o objetivo deste estudo foi determinar níveis críticos de Se na solução nutritiva e foliar, e a melhor fonte que aumente a biofortificação da alface hidropônica sem causar toxicidade. O delineamento experimental utilizado foi inteiramente casualizado representado por duas fontes de selênio, selenito de sódio (Na2SeO3) e selenato de sódio (Na2SeO4), dez concentrações de selênio (0; 2; 4; 6; 8; 16; 32; 64; 96; 128 μM) com quatro repetições por tratamento, totalizando 80 unidades experimentais. As concentrações adequadas estão entre 5,6 e 16 μM de selênio na forma selenato em solução nutritiva e teores foliares adequados de 10,2 a 41,8 mg kg-1 de selênio.
Information on sources of selenium (Se) in lettuce are scarce in the literature, especially with respect to the boundary between Biofortification and toxicity. The objective of this study was to determine critical levels of Se in the nutrient solution and leaf and the best source to increase biofortification of hydroponic lettuce without causing toxicity. The experimental design was completely randomized represented by two sources of selenium, sodium selenite (Na2SeO3) and sodium selenate (Na2SeO4) ten selenium concentrations (0. 2. 4. 6. 8. 16. 32. 64. 96. 128 M) with four replicates per treatment, totaling 80 experimental units. The concentrations are between 5.6 and 16 M selenium selenate form the nutrient solution and appropriate foliar 10.2 to 41.8 mg kg-1 of selenium.
CNPq: 132361/20159

O selênio durante a fase fetal e na lactação é de vital importância para o correto desenvolvimento dos sistemas imunológico, muscular e antioxidante dos potros. Existe pouca informação na literatura a qual seria a melhor fonte e o melhor momento para suplementar eqüino, assim como qual o grau de transferência placentária ou colostral. O presente estudo teve como objetivo avaliar a capacidade de transferência placentária e colostral de duas fontes dietéticas de selênio, utilizando como parâmetros os níveis plasmáticos de éguas e potros, e do colostro e do leite. Foram utilizadas 24 éguas gestantes, divididas em três grupos iguais e distribuídas seguindo um delineamento inteiramente casualizado. Grupo I suplementado por via oral com selenito de sódio como fonte inorgânica, grupo II suplementado por via oral com selenometionina como fonte orgânica, e grupo III controle, sem suplementação. A suplementação teve início no último terço da gestação até o sétimo dia pós-parto. Foram colhidas amostras de sangue das éguas, no dia do inicio do teste e no dia do parto, dos potros do nascimento e sétimo dia, e do leite no primeiro e sétimo dia pós-parto. A quantidade de selênio no colostro foi maior (p<0,05) no grupo suplementado com selenito de sódio (59,18 ± 14,5) quando comparada ao grupo do selenometionina (24,27 ±15,9). No plasma dos potros foi observada uma maior (p<0,05) presença de selênio naqueles animais do grupo suplementado com selenito de sódio (61,7 ± 34,4), quando comparada ao grupo do selenometionina (36,7 ± 17,3). Foi possível concluir que o selenito de sódio apresenta maior taxa de transferência placentária e colostral que o selenometionina, resultando em níveis colostrais e plasmáticos maiores, tanto nas éguas quanto nos potros.
Selenium is of vital importance for the correct development of immunologic, muscular and antioxidant systems of foals. There is not much information in literature about the best source and the best moment to supplement equines as well as to the level of placenta and colostrums transference. The objective was evaluate the capacity of placenta and colostrums transference of two dietetic sources of selenium, using plasma levels of mares and foals and colostrums and milk as parameters. Twenty four pregnant mares were studied, divided in three equal groups and distributed according to randomized design. Group I was supplemented with sodium selenite as inorganic source, group II was supplemented selenometionine as organic source, in equal quantities, from the beginning of the last third of gestation until the seventh day after birth and group III was control. The quantity of selenium in the colostrums was higher (p<0,05) in the group supplemented with sodium selenite (59,18 ± 14,5) when compared to the selenometionine group (24,27 ±15,9). In the plasma of foals it was observed a higher (p<0,05) presence of selenium than in those animals of the group supplemented with sodium selenite (61,7 ± 34,4) when compared to the selenometionine group (36,7 ± 17,3). The results of this study are that the sodium selenite presents higher taxe of placenta and colostrums transference than selenometionine, resulting in higher colostrums and plasmatic levels in mares and foals.

A nutrição para matrizes de frangos de corte tem como objetivo maximizar a produção de ovos e a qualidade da progênie subsequente e é considerada essencial para a melhora da produção e qualidade dos ovos. Os nutrientes transferidos para os ovos são importantes para o crescimento e desenvolvimento fisiológico do embrião. O organismo animal sofre constantemente ação do estresse oxidativo e o selênio (Se) é considerado um eficiente antioxidante natural que é essencial para matrizes de frangos de corte. Este estudo foi conduzido com matrizes de frango de corte alimentadas com duas fontes de Se (selenometionina - orgânica e selenito de sódio - inorgânico) para avaliar o seu desempenho produtivo, as características reprodutivas, a concentração de Se no ovo bem como o desempenho e rendimento de carcaça da progênie subsequente. Foram utilizadas 216 matrizes AP95 Aviagen de 55 a 65 semanas de idade, em delineamento inteiramente casualizado, com dois tratamentos e 27 repetições de quatro aves cada. Para o experimento com a progênie, foram utilizados 520 pintinhos mistos em delineamento inteiramente casualizado em um fatorial 2 x 2 (duas fontes de Se da dieta das matrizes e duas fontes de Se para dietas de frangos de corte - selenito de sódio e selenometionina) com quatro tratamentos, 13 repetições de 10 aves cada. As matrizes alimentadas com Se orgânico melhoraram a produção de ovos em comparação com o Se inorgânico (p = 0,038; p = 0,044). A concentração do Se no ovo e na clara foi maior para Se orgânico em comparação com o inorgânico (p <0,001; p <0,001). As taxas de fertilidade, bem como mortalidade embrionária, não sofreram efeito significativo ao se comparar as duas fontes. Não foram observadas diferenças entre a altura de albúmen, unidade Haugh e espessura da casca para a qualidade do ovo. O peso do ovo e coloração da gema foram estatisticamente diferentes (p=0,001; p=0,026) para fonte inorgânica comprada com a orgânica. A resistência a quebra do ovo foi melhor estatisticamente (p=0,007) para fonte orgânica. Não foram observadas interações entre a dieta da progênie e a dieta materna para nenhum dos critérios avaliados. Não foram observados efeitos da dieta materna, assim como da dieta da progênie sobre o consumo de ração, ganho de peso corporal e rendimento de carcaça e cortes. No entanto, a taxa de conversão alimentar foi melhor (p = 0,017) em frangos de corte provenientes de matrizes alimentadas com selenometiona. Assim, a selenometionina melhorou a produção e qualidade de ovos e propiciou maior transferência de Se para o ovo, principalmente na clara. Além disso, melhorou a conversão alimentar da progênie, devido a sua melhor biodisponibilidade.
The nutrition for broiler breeders has the objective of maximizing egg production and the quality of subsequent progeny. It is essential to improve the egg production and egg quality. The nutrients transferred to the eggs are important for growth and physiological development embryo. The animal organism is constantly suffering by oxidative stress. Selenium (Se) is considered an efficient natural antioxidant and has shown to be essential for broiler breeders. This trial was conducted using broiler breeders fed with two different sources of Se (organic - selenomethionine and inorganic - sodium selenite) to determinate performance, reproductive characteristics, Se concentration in egg as well as performance and carcass yield of the subsequent progeny. It was used 216 AP95 Aviagen broiler breeders, from 55 to 65 weeks of age, in completely randomized design with two treatments and 27 replications of four birds each. For subsequent progeny, it was used 520 straght-run chicks in a completely randomized design in a 2 x 2 factorial (two sources of Se for broiler breeders diets and two sources of Se for broilers diets- sodium selenite and selenomethionine) with four treatments and 13 replications of 10 birds each. Broiler breeders fed with organic Se had improved egg production in comparison to inorganic Se (p=0.038; p=0.044). Se concentration in whole egg and white egg were higher for organic Se in comparison to inorganic Se (p<0.001; p<0.001). The fertility and embryonic mortality were not significant between Se sources. No difference were observed to albumin height, Haugh unit and shell thickness for egg quality. The egg weight and yolk color were statistically different (p = 0.001; p = 0.026) for inorganic source compering to organic. The egg breaking was statistically better (p=0.007) for organic source. For progeny, no interactions between broiler diet and the maternal diet were observed for any of the criteria measured. No effect of maternal diet as well as broiler diet differences were observed on feed intake, body weight gain and carcass yield and cuts. However, feed conversion ratio was improved (p=0,017) in broiler from breeders fed selenomethione. Thus, selenomethionine has improved the egg production and quality, and has been transferred to the egg mainly in the egg white. Also, selenomethionine has improved feed conversion ratio because has a higher bioavailability.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第17641号
農博第2003号
新制||農||1012(附属図書館)
学位論文||H25||N4762(農学部図書室)
30407
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 栗原 達夫, 教授 阪井 康能, 教授 平竹 潤
学位規則第4条第1項該当

Dans cette these, la synthese et l'etude de la reactivite de derives n-selenoacylamidines sont discutes. L'opportunite d'obtenir des heterodienes selenies stabilises a permis de realiser une etude comparative de leur comportement par rapport a leurs analogues soufres. La polarisabilite marquee des n-selenoacylamidines leur confere des proprietes nucleophiles et electrophiles prononcees. Celles-ci ont ete eploitees pour la preparation d'heterocyles selenazolines et selenazoles. Les heterodienes selenies reagissent plusvite et avec de meilleurs rendements que leurs analogues soufres en presence de dienophiles electrophiles. Ainsi, par reactions de cycloaddition 4 + 2, une variete d'heterocycles selenies a 6 chainons a ete isolee : 4h et 6h-1,3-selenazines. Sous conditions thermodynamiques douces, les 4h-1,3-selenazines cycloreversent pour conduire aux vinylogues de selenoamides correspondants. Ces heterodienes selenies dans lesquels l'atome d'azote est substitue par un carbone fonctionnalise, reagissent par reaction de diels-alder en presence de dienophiles acetyleniques pour fournir les 4h-1,3-selenopyranes fonctionnalises. Les seleno-1,3-pentadienes peuvent subir des reactions de cyclisations intramoleculaires, lorsque de l'oxygene est present dans le milieu reactionnel. Les selenophenes resultants peuvent etre isoles one pot ou a partir de chacun des intermediaires de la sequence reactionnelle. Une application originale dans le domaine des materiaux organiques illustre l'interet de leurs syntheses. Une interpretation theorique de la reactivite des heterodienes selenies n-selenoacylamidines et vinylogues de selenoamide est discute dans ce travail. Les calculs theoriques, realises par la methode pm3, ont mis en evidence un resserrement des niveaux des energies de leurs orbitales frontieres respectives (ho-1 et bv) qui rend compte de leur comportement vis a vis des reactions de cycloaddition. Le gain du gap energetique entre les orbitales frontieres suit l'ordre inverse de l'electronegativite des heteroatomes de la colonne via (o, s, se) presents en position 1 sur les heterodienes. Enfin, les n-selenoacylamidines apparaissent comme de bon precurseurs d'heterodienes oxygenes, soufres et azotes dont la variete ne depend que du nucleophile choisi. Cette particularite est relative au caractere electrophile des sels d'amidinium qui sont aisement accessibles par simple alkylation des n-selenoacylamidines.

GeₓSe₍₁₋ₓ₎ and AsₓSe₍₁₋ₓ₎ glasses have found use in many technological applications due to their excellent rheological properties and their wide IR transparency window. However, the low glass transition temperatures of these glasses leads to large changes in their properties, due to structural relaxation, over the weeks and months subsequent to their fabrication. Thus, obtaining a more thorough understanding of structural relaxation and its relation to the structure, composition, and processing of these glasses is important in furthering their use. Structural investigations, using NMR and Raman spectroscopies, performed on the GeₓSe₍₁₋ₓ₎ family of glasses show that the structure of these glasses is composed of two distinct microdomains. One corresponds to a rigid GeSe₂-like domain and the other corresponds to a floppy Se domain. These results are compared to other existing structural models for GeₓSe₍₁₋ₓ₎ glasses. Enthalpy measurements on both GeSe₉ and GeSe₄ optical fibers which were aged up to five years demonstrate that both compositions undergo a large amount of enthalpy relaxation in this time period. Raman spectroscopy performed concurrently with enthalpy measurements on the same GeSe₉ and GeSe₄ fibers shows that one of the structural changes taking place within the glass network is the conversion of edgesharing to corner-sharing tetrahedra in the GeSe₂-like phase. Moreover, the rate at which this conversion takes place is shown to be similar to the rate of enthalpy relaxation, suggesting that this structural change is one of the main mechanisms for structural relaxation in GeₓSe₍₁₋ₓ₎ glasses. Implementation of the Tool-Narayanaswamy-Moynihan (TNM) model as a hybrid computer model allowing the prediction of the four relaxation parameters Δh*, log(A), x, and β via optimization of simulated and experimental data was accomplished. It was found that a multi-rate version of the TNM model, which obtains an average set of model parameters via optimization of multiple experimental thermal histories simultaneously, was able to predict relaxation parameters for AsₓSe₍₁₋ₓ₎ glasses within the 2.10 ≤ ≤ 2.50 compositional domain, where is the average bond coordination of the glass network as defined by the Phillips and Thorpe constraints model. Above = 2.50, however, the model fails, due to a bimodal distribution of relaxation times within the glass structure contrary to the TNM model assumption of a unimodal distribution of relaxation times, thus rendering the model inapplicable. Muti-rate modeling of the GeₓSe₍₁₋ₓ₎ family of glasses was also attempted, however the TNM model also fails for this family of glasses due to the inherently bimodal distribution of relaxation times which arises from their bimodal structure.

Le sélénium et le tellurium partagent des propriétés chimiques communes et appartiennent à la colonne des éléments chalcogènes de la classification périodique des éléments. Ces métalloïdes ont des propriétés physico-chimiques remarquables et ils ont été utilisés dans un grand nombre d'applications dans le domaine des hautes technologies (électronique, semi-conducteurs, alliages). Ces éléments, qui se retrouvent généralement sous formes d'oxyanions, sont extrêmement solubles dans l'eau et présentent une forte toxicité. Leur libération dans l'environnement est donc d'un enjeu capital. Différentes méthodes physico-chimiques ont été développées pour la récupération de ces metalloïdes, en particulier pour le sélénium. Néanmoins, ces méthodes requièrent un équipement lourd et couteux et ne sont pas très recommandables sur le plan écologique. Le traitement biologique est donc une bonne alternative pour la récupération de Se et de Te provenant des effluents pollués. Cette approche réside dans la bioréduction des différents oxyanions sous formes métalliques. Ceux-ci sont moins toxiques et d'intérêts commerciales notables surtout lorsqu'ils se présentent sous forme nanométrique. L'utilisation de micro-champignons comme microorganismes catalyseur de la réduction de Se et de Te a été démontrée dans cette étude. La réactivité du champignon responsable de la pourriture blanche, Phanerochaete chrysosporium en présence de sélénite et de tellurite a été évaluée, ainsi que son application potentielle pour le traitement des eaux contaminées et la production de nanoparticules. La présence de Se et de Te a une influence importante sur la croissance et la morphologie du champignon. Il s'avère que P. chrysosporium est très sensible à la présence de sélénites. La synthèse de Se° et de Te° sous forme de nanoparticules piégées dans la biomasse fongique a été observée, ainsi que la formation de nano-composites Se-Te lorsque le champignon était cultivé simultanément en présence des deux métalloïdes. L'usage potentiel de biofilm fongiques pour le traitement des effluents semi-acides (pH 4.5) contenant du Se et du Te a été suggéré. De plus, le traitement en mode continu de sélénite dans un réacteur à biofilm fongique granulaire a été évalué. Le réacteur a montré un rendement d'élimination du sélénium en régime permanent de 70% pour differentes conditions opératoires. Celui-ci s'est montré efficace pendant une période supérieure à 35 jours. La bonne sédimentation du biofilm granulaire facilite la séparation du sélénium de l'effluent traité. L'utilisation du biofilm granulaire contenant du sélénium élémentaire comme bio-sorbant a également été étudiée. Cet adsorbant hybride s'est montré prometteur pour l'immobilisation du zinc présent dans les effluents semi-acides. La plupart des recherches effectuées se sont focalisées sur l'utilisation des biofilms granulaires. Toutefois, la croissance du champignon suite à l'exposition à des concentrations différentes de sélénites a également été étudiée. Des micro-électrodes à oxygène et un microscope confocal à balayage laser ont été utilisées pour évaluer l'effet du sélénium sur la structure des biofilms fongiques. Quel que soit le mode de croissance de P. chrysosporium, le mécanisme de réduction du sélénite semble être toujours le même tout en menant à la formation de sélénium élémentaire. Cependant, l'architecture des biofilms et l'activité en oxygène sont influencées par la présence de sélénium
Selenium (Se) and tellurium (Te) are particular elements, they are part of the chalcogens (VI-A group of the periodic table) and share common properties. These metalloids are of commercial interest due to their physicochemical properties, and they have been used in a broad range of applications in advanced technologies. The water soluble oxyanions of these elements (i.e., selenite, selenate, tellurite and tellurate) exhibit high toxicities, thus their release in the environment is of great concern. Different physicochemical methods have been developed for the removal of these metalloids, mainly for selenium. However, these methods require specialized equipment, high costs and they are not ecofriendly. The biological treatment is a green alternative to remove Se and Te from polluted effluents. This remediation technology consists on the microbial reduction of Se and Te oxyanions in wastewater to their elemental forms (Se0 and Te0), which are less toxic, and when synthesized in the nano-size range, they can be of commercial value due to their enhanced properties. The use of fungi as potential Se- and Te-reducing organisms was demonstrated in this study. Response of the model white-rot fungus, Phanerochaete chrysosporium, to the presence of selenite and tellurite was evaluated, as well as their potential application in wastewater treatment and production of nanoparticles. The presence of Se and Te had a clear influence on the growth and morphology of the fungus. P. chrysosporium was found to be more sensitive to selenite. Synthesis of Se0 and Te0 nanoparticles entrapped in the fungal biomass was observed, as well as the formation of unique Se-Te nanocomposites when the fungus was cultivated concurrently in the presence of Se and Te. Potential use of fungal pellets for the removal of Se and Te from semi-acidic effluents (pH 4.5) was suggested. Moreover, the continuous removal of selenite in a fungal pelleted reactor was evaluated. The reactor showed to efficiently remove selenium at steady-state conditions (~70%), and it demonstrated to be flexible and adaptable to different operational conditions. The reactor operated efficiently over a period of 35 days. Good settleability of the fungal pellets facilitated the separation of the selenium from the treated effluent. The use of elemental selenium immobilized fungal pellets as novel biosorbent material was also explored. This hybrid sorbent was promising for the removal of zinc from semi-acidic effluents. The presence of selenium in the fungal biomass enhanced the sorption efficiency of zinc, compared to Se-free fungal pellets. Most of the research conducted in this study was focused on the use of fungal pellets. However, the response of the fungus to selenite in a different kind of growth was also evaluated. Microsensors and confocal imaging were used to evaluate the effects of selenium on fungal biofilms. Regardless of the kind of fungal growth, P. chrysosporium seems to follow a similar selenite reduction mechanism, leading to the formation of Se0. Architecture of the biofilm and oxygen activity were influenced by the presence of selenium

The Gram negative bacterium Thauera selenatis is able to respire with selenate as the sole terminal electron acceptor, utilising a periplasmic selenate reductase enzyme to reduce selenate to selenite. Previous characterisation of this enzyme has shown that it is a heterotrimeric molybdo-enzyme (SerABC) of the dimethylsulfoxide reductase family, containing a Mo-bis molybdopterin guanine dinucleotide co-factor, Fe-S clusters and a b-type haem (Schroder et al., 1997, J Biol Chem, 272: 23765-68, Dridge et al., 2007, Biochem J, 408: 19-28). In order to elucidate the electron transport pathway to selenate reductase, and how it can generate a proton motive force, detailed study was required. Firstly, the redox potential of the b-haem of SerC was determined by optical redox titration to be +234 mV. The serC gene was cloned and expressed heterologously in E. coli, but the protein was incorrectly folded into inclusion bodies, and attempts to refold and reconstitute SerC with haem were unsuccessful. A profile of c-type cytochromes in T. selenatis was undertaken, and characterisation of a number of cytochromes was carried out. Two cytochromes were purified, cytc7 and cytc4, and cytc4 was shown to be able to donate electrons to SerABC in vitro. Protein sequence was obtained by N-terminal sequencing and LC-MS/MS, and assigned cytc4 to the cytochrome c4 family of dihaem cytochromes. Redox potentiometry combined with UV-visible and electron paramagnetic spectroscopy showed that cytc4 is a dihaem cytochrome with a redox potential of +282 mV and both haems are predicted to have His-Met ligation. To investigate the role of membrane bound cytochromes in selenate respiration, PCR with degenerate primers amplified a partial gene coding for quinol: cytochrome c oxidoreductase (QCR). A microplate growth method was developed to monitor growth of T. selenatis under reproducible conditions, and used to analyse the effect of respiratory chain inhibitors on growth under different conditions. Aerobic metabolism was unaffected by QCR inhibitors, while nitrite reduction was totally inhibited, linking nitrite reduction to the generation of a proton motive force by the QCR. The QCR inhibitor myxothiazol partially inhibited selenate respiration, showing that some electron flux is via the QCR, but total inhibition of selenate respiration was achieved by combining myxothiazol with the more general inhibitor 2-n-heptyl-4-hydroxyquinoline N-oxide (HQNO). These data suggest that electron transfer to selenate reductase occurs via a branched pathway, in which one route is inhibited by myxothiazol and the other by HQNO. Electron transfer via a QCR and a dihaem cytochrome c4 is a novel route for a member of the dimethylsulfoxide reductase family of molybdo-enzymes.

The main purpose of the work reported in this thesis was to investigate and characterise the deep levels in zinc selenide crystals grown from the vapour phase at Durham, and by the CVD technique at AWRE, Aldermaston. The methods of TSC, TSL and DLTS were applied to samples of Durham-grown and CVD ZnSe. The study revealed the presence of traps at 0.14-0.16,0.23, 0.26, 0.30-0.31, 0.45, -0.60 and 0.70 eV in Durham-grown material, whereas the CVD material was found to contain trapping levels at 0.10, 0.20 and 0.27-0.28 eV. The 0.10 eV level in CVD ZnSe is ascribed to the Na acceptor. The traps occurring at 0.26-0.31 eV in both materials are thought to be due to a vacancy-impurity complex. Examination of the CVD material using the EBIC technique in an SEM revealed that the conductivity was limited by electrically-active grain boundaries which were shown to obey a simple potential barrier model. Cathodoluminescence studies showed that the emission bands at 465 nm (edge emission) and 630 nm (copper-red) were quenched at the grain boundaries. A relationship between the absorption coefficient at 10.6 ym and the intensity of the copper-red emission was demonstrated, which has important implications in the production of low absorption zinc selenide for laseroptics.

Doctor of Philosophy
Department of Chemistry
Viktor Chikan
Ever depleting sources of fossil fuel has triggered more research in the field of alternate sources of energy. Over the past few years, CdSe nanoparticles have emerged as a material with a great potential for optoelectronic applications because of its easy exciton generation and charge separation. Electronic properties of CdSe nanoparticles are highly dependent on their size, shape and electronic environment. The main focus of this research is to explore the effect of different electronic environments on various spectroscopic properties of CdSe nanoparticles and link this to solar cell performance. To attain that goal, CdSe quantum dots (QDs) and nanorods (NRs) have been synthesized and either doped with metal dopants or embedded in polymer matrices. Electronic properties of these nanocomposites have been studied using several spectroscopic techniques such as absorption, photoluminescence, time-resolved photoluminescence, confocal microscopy and wide field microscopy. Indium and tin are the two metal dopants that have been used in the past to study the effect of doping on conductivity of CdSe QDs. Based on the photoluminescence quenching experiments, photoluminescence of both indium and tin doped samples suggest that they behave as n-type semiconductors. A comparison between theoretical and experimental data suggests that energy levels of indium doped and tin doped QDs are 280 meV and 100 meV lower than that of the lowest level of conduction band respectively. CdSe nanorods embedded in two different polymer matrices have been investigated using wide field fluorescence microscopy and confocal microscopy. The data reveals significant enhancement in bandedge luminescence of NRs in the vicinity of a conjugated polymer such as P3HT. Photoactive charge transfer from polymers to the surface traps of NRs may account for the observed behavior. Further study shows anti-correlation between bandedge and trap state emission of CdSe NRs. A recombination model has been proposed to explain the results. The origin of traps is also investigated and plausible explanations are drawn from the acquired data.

Solvothermal (and ionothermal) synthesis has been used in this work to prepare novel group 13 selenide materials. The new phases were characterised using single crystal and powder X-ray diffraction, spectroscopic methods (infrared and UV-Vis diffuse reflectance spectroscopy) and thermal analysis (thermogravimetric and elemental analysis). Other characterisation methods used include SQUID magnetometry and the measurement of optical properties. The effect of the structure directing organic molecule on the inorganic structure was investigated in this thesis, with a variety of novel materials synthesised. A family of one-dimensional chains have been prepared. The first, composed of fused four-membered rings, was found in [NH4][InSe2] (using 3,5-lutidine) and in a number of phases prepared with bicyclic superbases. The second chain-type, composed of fused four- and five-membered rings was found in [C6H16N2][Ga2-xInxSe3(Se2)] (0 < x < 2) and [C7H14N3][In2Se3(Se2)]. These chains contain a (Se2)2- perselenide bond, which was previously unreported for solvothermally prepared group 13 selenides. The third chain type, found in [C7H13N2][InSe(Se2)] and [C9H17N2][InSe(Se2)], contains fused five-membered rings. More complex one-dimensional ribbons were also prepared with superbases. Many two-dimensional layered phases have been prepared in this work. [NH4][InSe2], which contains supertetrahedral clusters, generates a second harmonic generation response. A novel phase which incorporated a transition metal into the structure has been found for [Mn(C6H14N2)3][H2O][(C6H14N2)2MnIn3(SH)2Se4.89(Se2)0.12]2. The novel hybrid gallium selenides, [Ga6Se9(C6H14N2)4][H2O] and [C6H14N2][Ga4Se6(C6H14N2)2] were also isolated. The novel layers in [C7H10N][In3Se5], contain a new octahedral building-block. A further layered material, [C8H12N][In3Se4.85(Se2)0.15] was prepared, where disorder of selenium was observed. Using weakly basic pyridine and its related methyl-substituted isomers (lutidines and picolines), a three-dimensional framework [C5H6N][In9Se14], was prepared and its ion-exchange capabilities studied. Further framework materials prepared in this work include: [enH2][NH4][In7Se12], [C6H14N2][(C6H12N2)2NaIn5Se9] and [In14Se21(Se2)3]6-. Using an ionothermal route, the known three-dimensional framework, [In33Se56]13- was prepared. The first indium selenide prepared using an ionic liquid, in this case, 1-ethyl-3-methyl-imidazolium bromide (EMIm-Br).

Orientador: Solange Maria de Almeida
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Avaliou-se o efeito radioprotetor do selenito de sódio nas células secretoras das glândulas submandibulares de ratos, por meio da análise ultraestrutural. Foram utilizados 57 ratos subdivididos em quatro grupos experimentais: controle, irradiado, selenito de sódio e selenito de sódio/irradiado. Os animais, pertencentes aos grupos irradiado e selenito de sódio/irradiado, foram submetidos a 15 Gy de radiação gama na região de cabeça e pescoço. Nos animais correspondentes aos grupos selenito de sódio e selenito de sódio/irradiado foi administrado 0,5 mg/kg de peso de selenito de sódio por via intraperitonial 24 horas antes da irradiação e nos grupos controle e irradiado, injetou-se solução salina. As glândulas submandibulares foram removidas após 4, 8, 12, 24, 48 e 72 horas da irradiação. Os resultados mostraram que a radiação causou danos, desde o primeiro tempo, nas células secretoras, sendo maior para as células serosas. Os danos intensificaram-se até o período de 12 horas, com início do processo de reparo no tempo de 24 horas, sem recuperação completa nos últimos tempos avaliados. O grupo selenito de sódio também apresentou alterações celulares nos tempos estudados, porém com menor dano em relação ao causado pela radiação. Foram observados vacuolização, lise de inclusões citoplasmáticas e alterações nucleares. O grupo selenito de sódio/irradiado apresentou maior semelhança com o grupo controle que os outros grupos tratados durante todos os tempos estudados. Foi concluído que, apesar das alterações observadas no grupo selenito de sódio, o selenito de sódio possui ação radioprotetora nas células secretoras das glândulas submandibulares
Abstract: The radioprotective effect of sodium selenite in the secretory cells of submandibular glands of rats was assessed by ultrastructural analysis. A total of 57 rats were used, which were divided into four experimental groups: control, irradiated, sodium selenite and sodium selenite/irradiated. The animals belonging to the irradiated and sodium selenite /irradiated groups were submitted to 15 Gy of gamma radiation at the head and neck. The animals in the sodium selenite and sodium selenite/irradiated groups received intraperitoneal injections of sodium selenite, 0.5mg/kg of body weight, at 24 hours before irradiation; the control and irradiated groups received injection of saline solution. The submandibular glands were removed at 4, 8, 12, 24, 48 and 72 hours after irradiation. The results demonstrated that the radiation induced damages to the secretory cells, especially the serous cells, since the first period. The damages were increased up to the 12- hour period, with onset of the repair process at 24 hours, without complete recovery at the last periods. The sodium selenite group also presented cellular alterations in the study periods, yet with less damage compared to that caused by radiation. There was vacuolization, lysis of cytoplasmic inclusions and nuclear alterations. The sodium selenite/irradiated group was more similar to the control group than the other groups treated at all study periods. It was concluded that, despite the alterations observed in the sodium selenite group, the sodium selenite has a radioprotective action on the secretory cells of submandibular glands
Doutorado
Radiologia Odontologica
Doutor em Radiologia Odontológica

A subcutaneous injection of sodium selenite (30 umol/kg body weight) in 10â day old rats produced a cataract within 72 hours. Lens opacification was preceded by a 15% decrease in ATP content. Lens ATP did not fully recover to control concentrations by 11 days postâ injection. A moderate correlation existed between lens weight and total ATP content in control lenses
Master of Science

As results we can said that were investigated optical properties of ZnSe thin films, deposited by CSVS method at different physical and technological condensation regimes. Established physical and technological deposition regimes with optimal parameters for using as window layers of the heterojunction tandem solar cells and in optoelectronic devices. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/4075

Organoselenium reagents have found varied applications throughout organic chemistry. Like many transition metals selenium can occupy a variety of oxidation states, giving access to a range of redox processes. It may also be bound covalently to organic frameworks that offer the possibility of straightforward catalyst design and tuning for enantio- and stereoselectivity. Hence selenium offers access to a unique niche of reactivity, however, the use of organoselenium compounds as catalysts, or to perform enantioselective transformations, is still an under-exploited area. The work described herein presents investigations towards the syntheses of chiral organic selenides and diselenides and their applications to enantioselective processes. Catalyst design was centred around cyclic C2-symmetric organic frameworks such as binaphthalene, 2,5-disubstituted tetrahydroselenophenes, dihydroselenepines and dihydroselenocines. The effectiveness of these reagents in a variety of catalytic processes was tested. Transformations included oxidative processes such as allylic and propargylic C–H oxidation to afford α,β-unsaturated alcohols; Lewis base catalysed halolactonisations; Corey-Chaykovsky epoxidations; and conjugate reactions of alkenylselenonium(IV) species. During the course of these investigations novel conditions for a palladium-catalysed cross-coupling of aryl electrophiles and organic selenolates were developed enabling the facile synthesis of asymmetric diaryl- and arylalkyl- selenides. The dealkylation of arylalkylselenides was further investigated to enable an alternative route to diselenides.

Conselho Nacional de Desenvolvimento Científico e Tecnológico
The aim of this study was to evaluate the utilization of a standard treatment with diminazene aceturate against the infection caused by T. evansi, associated to sodium selenite and vitamin E. In vitro tests showed trypanocidal effect related to the treatment with diminazene aceturate and sodium selenite, but vitamin E had no harmful effect on the trypanosomes. In vivo experiments utilized a total of 72 adult outbreed females rats, separated into 9 groups (A, B, C, D, E, F, G, H and I), 8 animals each. Group A was the uninfected group; groups B to I were infected with 0.2 mL of blood containing 106 trypanosomes. Parasitemia was estimated daily by microscopic examination of blood smears. Group B served as positive control; group C was treated with diminazene aceturate; group D with sodium selenite; group E with vitamin E; group F received an association of diminazene aceturate and sodium selenite; group G received an association of diminazene aceturate and vitamin E; group H received an association of diminazene aceturate, sodium selenite and vitamin E, and group I received an association of sodium selenite and vitamin E. Diminazene aceturate was administrated in a single dose on the 3rd day post infection (PI). Sodium selenite and vitamin E were administered at the 3rd and 23rd day PI. In vivo tests showed increase of longevity in groups treated with diminazene aceturate associated with sodium selenite (groups F and H). No difference was found between groups C and E, thus the vitamin E did not increase the efficacy of treatment against T. evansi when associated to diminazene aceturate. The curative efficacy of treatments was 37.5, 87.7, 37.7 and 75% to the groups C, F, G and H, respectively. Other treatments showed no efficacy. The sodium selenite when combined with chemotherapy may represent an alternative in the treatment of trypanosomosis.
O objetivo deste estudo foi avaliar a utilização de um tratamento padrão contra a infecção causada pelo T. evansi, baseado na utilização do aceturato de diminazeno associado ao selenito de sódio e a vitamina E. Os testes in vitro mostraram um efeito tripanocida relacionados ao tratamento com aceturato de diminazeno e selenito de sódio; contudo a vitamina E não gerou nenhum efeito nocivo sobre o tripanossomas. Experimentos in vivo utilizaram um total de 72 fêmeas adultas de ratos, separados em 9 grupos (A, B, C, D, E, F, G, H e I), com 8 animais cada grupo. O grupo A serviu como grupo não infectado; grupos de B a I foram infectados com 0,2 mL de sangue contendo 106 tripanossomas. A parasitemia foi estimada diariamente por exame microscópico de esfregaços sanguíneo. O grupo B serviu como controle positivo; grupo C, tratado com aceturato de diminazeno; grupo D, com selenito de sódio; grupo E, com vitamina E; grupo F, recebeu uma associação de aceturato de diminazeno e selenito de sódio; grupo G, associação de aceturato de diminazeno e vitamina E; grupo H, associação de aceturato de diminazeno, selenito de sódio e vitamina E; e por fim o grupo I o qual recebeu uma associação de selenito de sódio e vitamina E. O aceturato de diminazeno foi administrado em dose única no 3º dia pós-infecção (PI). Selenito de sódio e vitamina E foram administradas no 3º e 23º dias PI. Os testes in vivo mostraram aumento da longevidade nos grupos tratados com aceturato de diminazeno associado ao selenito de sódio (grupos F e H). Não foi encontrada diferença entre os grupos C e E, portanto, a vitamina E não aumentou a eficácia do tratamento contra T. evansi quando associado ao aceturato de diminazeno. A eficácia curativa dos tratamentos foi de 37.5, 87.7, 37.7 e 75% para os grupos C, F, G e H, respectivamente. Os demais tratamentos não mostraram eficácia. Assim, podemos sugerir que o selenito de sódio, quando combinado com a quimioterapia pode representar uma alternativa no tratamento da tripanossomose.

The sizes, shapes, relaxed atomic positions, eigenvalues, and total energies are calculated for selected ultra-small CdSe clusters using SIESTA, a software package for electronic structure calculations and molecular dynamics simulations of molecules and solids. The properties of these bare clusters with small numbers of constituent atoms are studied using density functional theory (DFT) for energy calculations and the conjugate gradient approximation as well as simulated annealing type of molecular dynamics techniques in relaxing the structure to find the lowest energy configurations.The ab-initio norm-conserving pseudopotentials, the exchange-correlation approximation, and parameters used in the computations by Siesta software is verified using FHI98PP, a package used to generate and test the ab-initio norm-conserving pseudopotentials. The initial position of the atomic co-ordinates is determined using ancillary software written in Matlab.
Department of Physics and Astronomy

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.
Includes bibliographical references (p. 49-50).
I have investigated electrical properties of arrays of lead selenide (PbSe) nanocrystals (NC's) of approximately 6nm diameter. The films become substantially more conducting when annealed at 400K, although no chemical changes of the capping layer occur at this low temperature. There is no evidence based on TEM images of annealed and unannealed films that the interparticle spacing changes at 400K. The dependence of the conductance on the voltage applied to a gate separated from the sample by 350nm of SiO2 was also measured. At 77K and 150K, a U-shaped curve is observed with a minimum in conductance near zero gate voltage, indicating that both electrons and holes are injected. At 294K, the conductance falls monotonically with increasing gate voltage, indicating injection of holes only. I calculate the electron and hole mobilities, [mu]e and [mu]h at 77K and 150K and find effective mobilities 10 orders of magnitude smaller than those of bulk PbSe at 77K.
by Maria C. Schriver.
S.B.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2000.
Includes bibliographical references.
Semiconductor quantum dots or nanocrystals have size dependent optical and electronic properties that arise from quantum confinement. While the quantum size effect is reasonably well understood, the effect of abrupt interface between the nanocrystal and its dielectric environment is not. In this thesis we study how the dielectric environment affects the quantum dot electronic structure, the optical absorption ~ross-section, charge separation, and transport in cadmium selenide colloidal quantum dots. The electronic states and optical absorption cross-section are found to be less sensitive to changes in the dielectric environment than predicted from theory unless screening from the ligand shell is taken into account. The absolute absorption cross section is measured as a function of quantum dot size; excellent agreement with theory is obtained for absorption far above the band edge. Three-dimensional close packed solids of quantum dots are predicted to act as model artificial solids. Optical absorption measurements indicate that the electronic states of CdSe quantum dots separated by 11 angstroms or more are essentially uncoupled. Photoconductivity measurements suggest that photoexcited quantum confined excitons are ionized by the applied field with a rate that depends on both the size and surface passivation of the quantum dots. The charge generation efficiency decreases with increasing temperature as non-radiative and radiative recombination pathways increasingly compete with charge separation. A simple tunneling model for the initial charge separation step is presented that qualitatively reproduces both the size and surface dependence of the photoconductivity as a function of applied electric field. Finally, we report observations of amplified spontaneous emission from quantum dot solids. The stimulated emission is tunable with quantum dot size and does not sensitively depend upon surface passivation. These measurements demonstrate the feasibility of nanocrystal quantum dot lasers and amplifiers.
by Catherine A. Leatherdale.
Ph.D.

Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2009.
Thesis Advisor(s): Karunasiri, Gamani. Second Reader: Smith, Craig. "December 2009." Description based on title screen as viewed on January 28, 2010. Author(s) subject terms: Zinc Selenide, photodetectors, ultraviolet, Schottky, responsivity, current-voltage, depletion region, bandgap, melanoma, dark current, forward biased, reverse biased. Includes bibliographical references (p. 39-40). Also available in print.

Since the discovery of graphene, a new era of physics called "Two Dimensional (2D)Materials" has emerged. Group IV and Group III Selenides such as SnSe and InSe arepromising members of the 2D family. Structure of Group IV selenides is unique and highlysensitive to pressure and temperature. To further tweaking their properties by structuralchanges, thorough understanding of how the structure relates to the electronic bands is veryimportant. Based on the results from DFT calculations, I carefully analyzed electronic bandstructures of layered SnSe with various interlayer stacking. The first part of this dissertationdiscussed the possible stacking-dependent indirect-direct transition of bilayer SnSe.By further analysis, these results reveal that the directionality of interlayer interactionsdetermine the critical features of their electronic band structures. Further, it demonstratedthat such changes can be achieved by substitutional chemical doping. Using a multi-scalemodeling approach by combining the result of DFT and Boltzmann Transport Theory, Idiscussed the electron transport properties of co-doped SnSe, a class of thermodynamicallyand dynamically stable structures. The second part discussed on charge transfer across InSe/Gas interface, which showsbi-polar transport properties. This finding is in a good agreement with the recent experimentalobservations. Fundamental understanding of charge transfer in few-layer InSe /gasinterfaces at the atomic level is expected to pave the path for designing gas sensing devices.

Several solvothermal synthetic methods have been developed to produce novel low-dimensional magnetic materials and determine their structure-properties relationships. Two main classes of compounds were investigated, including iron selenides and transition metal formate-chlorides.

Chapter 2 details the development of the first solution-based synthetic route to superconducting iron (II) selenide. Samples were found to retain superconducting properties only when air and water were rigorously excluded from the synthesis.

Chapter 3 presents the synthesis, structure, and magnetic properties of two new mixed-valence compounds with infinite ∞¹(FeSe ₂) tetrahedral chains separated by Fe-amine complexes. The use of different Fe-amine complexes allows for tuning of the magnetic properties without changing the general structural motif.

Chapters 4 and 5 report the first members of the transition metal chloride-formate family of compounds, which contain linear zig-zag chains of octahedrally coordinated metal atoms linked by μ₂-Cl and syn-syn formate bridges. These compounds order antiferromagnetically and exhibit metamagnetic transitions.

Chapter 6 describes a related set of transition metal formate-chloride compounds that are comprised of helical chains of edge-sharing M²⁺ -centered octahedra. These compounds undergo 3D ferrimagnetic ordering at low temperature, and are rare examples of homospin topological ferrimagnets.

Resumen (Castellano) El aumento del consumo de energía global junto con las preocupaciones ambientales ha generado mucho interés por las fuentes de energía alternativas y limpias, como la energía solar fotovoltaica. Los investigadores en la comunidad fotovoltaica han estado buscando formas de reducir costos mientras mantienen o aumentan las eficiencias. Una mejor comprensión de los materiales implicados es esencial para el rápido desarrollo de nuevas tecnologías. Las películas delgadas I-III-VI2 ofrecen sistemas prometedores para lograr células solares de alta eficiencia a un costo menor. De hecho, al adaptar la composición de los compuestos, es posible cambiar la banda prohibida del material para captar la luz solar de manera más eficiente. Esta tesis se centra en la preparación y caracterización del material de la capa absorbente, especialmente las películas delgadas nanocristalinas y la consideración de las características estructurales y eléctricas de dicha capa principal absorbente de células. La tesis examina cómo las diferentes técnicas de preparación y uso del material podrían afectar las propiedades del películas delgadas sintetizadas. Películas delgadas CuInSe2 y CuInS2 se depositaron sobre sustratos de vidrio ITO usando la técnica de electrodeposición en solución acuosa. Las películas electrodepositadas se caracterizaron por difracción de rayos X (XRD), microscopía electrónica de barrido (SEM) y análisis de rayos X de energía dispersiva (EDS). Se investigaron los efectos de recocido sobre los precursores electrodepositados. La estructura de calcopirita de CuInSe2/CuInS2 mostró una mejora de la cristalinidad después del tratamiento posterior de selenización/sulfurización en atmósfera Se/S, respectivamente. Los estudios de XRD y SEM revelaron una mejora de la calidad cristalina de las películas de CIS después de los tratamientos térmicos. Las propiedades ópticas de las películas delgadas recocidas CuInSe2-Se y CuInSe2-S se han estudiado para determinar el efecto del proceso de recocido en diferentes ambientes de selenio y azufre. Además, modificamos el CuInxCryGa1-x-ySe2 de cobre indio, donde x = 0.4, y = (0.0, 0.1, 0.2, 0.3) la capa de superestrato por el proceso de recubrimiento por centrifugado. CuInxCryGa1-xySe2 donde x = 0.4, y = (0.0, 0.1, 0.2, 0.3) nanopartículas han sido sintetizadas en primer lugar usando un método hidrotermal químico húmedo que se basa en un proceso térmico sin vacío sin ningún proceso de selenización adicional. Introduciendo diferentes fuentes de metal en un autoclave con etilenamina como solvente, se obtuvieron nanopartículas de CIGS a diferentes temperaturas en un rango de 190-230 °C. Los resultados de la difracción de rayos X (XRD) confirmaron la formación de una estructura de calcopirita CuInxCryGa1-x-ySe2 tetragonal. Finalmente, se estudió el efecto de la temperatura de recocido en los materiales tipo Kesterita (como el Cu2ZnSnS4) que son materiales de muy bajo costo y que no dañan el medio ambiente. Estudiamos el crecimiento de las películas delgadas cuaternarias Cu2ZnSnS4 (CZTS) de kesterita mediante un depósito electroquímico de un solo paso seguido de un recocido a baja temperatura. La influencia de diferentes atmósferas de recocido a tiempos de recocido constantes (t = 45 min) y parámetros de control de preparación fijos; es decir, concentración de la solución de materiales de partida (sales de metales precursores), tiempo de deposición y potencial de electrodeposición. Se estudiaron las propiedades estructurales, de composición, morfológicas y ópticas, así como las propiedades fotoelectroquímicas.
Abstract Increasing global energy consumption together with environmental concerns has led to much interest in alternative, cleaner sources of energy such as solar photovoltaic. Researchers in the solar cell community have been looking for ways to reduce costs while maintaining or increasing already high efficiencies. A fundamental understanding of the materials under consideration is essential to rapid development of new technologies. The I-III-VI2 thin films offer promising systems for achieving high efficiency solar cells at lower costs. In fact, by tailoring the chemistry of the compounds it is possible to change the bandgap of the material in order to collect sunlight more efficiently. First of all, this thesis focuses on absorber layer material preparation and characterization, especially nanocrystalline thin films and consideration of both structural and electrical characteristics of such main cell absorber layer.The thesis examines how different preparation techniques and material usage could affect the properties of the synthesized thin films (absorber layer). In this study CuInSe2 and CuInS2 thin films were deposited onto ITO glass substrate using the electrodeposition technique in aqueous solution. The electrodeposited films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS). The annealing effects on the electrodeposited precursors were investigated. The chalcopyrite structure of CuInSe2/CuInS2 showed an enhancement of crystallinity after subsequent selenization/sulfurization treatment in Se/S atmosphere, respectively. XRD and SEM studies revealed a dramatic improvement of the crystalline quality of CIS films after annealing treatments. The optical properties of annealed CuInSe2-Se and CuInSe2-S thin films have been studied in order to determine the effect of annealing process in different selenium and sulfur atmosphere. In the second step we modified copper indium CuInxCryGa1-x-ySe2 where x=0.4, y= (0.0, 0.1, 0.2, 0.3)superstrate layer by spin coating process. CuInxCryGa1-x-ySe2 where x=0.4, y= (0.0, 0.1, 0.2, 0.3) nanoparticles have been synthesized firstly using a wet chemical hydrothermal method that is based on a non-vacuum thermal process without any additional selenization process. Introducing different metal sources in an autoclave with ethylenediamine as solvent, CIGS nanoparticles were obtained at different temperatures range 190-230°C. The X-ray diffraction (XRD) results confirmed the formation of a tetragonal CuInxCryGa1-x-ySe2 chalcopyrite structure. Finally, we turned again to the study of the annealing temperature effect onKesterite materials but this time in those of very low-cost materials and environmentally friendly Cu2ZnSnS4. We studied the growth of quaternary Cu2ZnSnS4 (CZTS) kesterite thin films by a single step electrochemical deposition followed by annealing at low temperature. The influence of different annealing atmospheres at constant annealing times (t = 45 min) and fixed preparation controlling parameters; i.e., starting materials (precursor metal salts) solution concentration, time of deposition and electrodeposition potential. Structural, compositional, morphological, and optical properties, as well as photoelectrochemical properties were studied.
Resum (Valencià) L'augment del consum d'energia global juntament amb les preocupacions ambientals ha generat molt d'interès per les fonts d'energia alternatives i netes, com ara l'energia solar fotovoltaica. Els investigadors de la comunitat fotovoltaica han estat buscant formes de reduir costos mentre mantenen o augmenten les eficiències. Una millor comprensió dels materials implicats és essencial per al ràpid desenvolupament de noves tecnologies. Les pel·lícules primes I-III-VI2 ofereixen sistemes prometedors per aconseguir cèl·lules solars d'alta eficiència a un cost menor. De fet, en adaptar la composició dels compostos, és possible canviar la banda prohibida del material per captar la llum solar de manera més eficient. Aquesta tesi se centra en la preparació i caracterització del material de la capa absorbent, especialment les pel·lícules primes nanocristal·lines i la consideració de les característiques estructurals i elèctriques d'aquesta capa principal absorbent de cèl·lules. La tesi examina com les diferents tècniques de preparació i ús del material podrien afectar les propietats del pel·lícules primes sintetitzades. Pel·lícules primes CuInSe2 i CuInS2 es van dipositar sobre substrats de vidre ITO usant la tècnica d'electrodeposició en solució aquosa. Les pel·lícules electrodepositadas es van caracteritzar per difracció de raigs X (XRD), microscòpia electrònica de rastreig (SEM) i anàlisi de raigs X d'energia dispersiva (EDS). Es van investigar els efectes de recuit sobre els precursors electrodepositados. L'estructura de calcopirita de CuInSe2/CuInS2 va mostrar una millora de la cristal·linitat després del tractament posterior de selenització/sulfurització en atmosfera de Se o S, respectivament. Els estudis de XRD i SEM van revelar una millora de la qualitat cristal·lina de les pel·lícules de CIS després dels tractaments tèrmics. Les propietats òptiques de les pel·lícules primes recuites CuInSe2-Es i CuInSe2-S s'han estudiat per determinar l'efecte del procés de recuit en diferents ambients de seleni i sofre. A més, modifiquem el CuInxCryGa1-x-ySe2 de coure indi, on x = 0.4, i = (0.0, 0.1, 0.2, 0.3) la capa d'superstrat pel procés de recobriment per centrifugat. CuInxCryGa1-x-ySe2 on x = 0.4, i = (0.0, 0.1, 0.2, 0.3) nanopartícules han estat sintetitzades en primer lloc fent servir un mètode hidrotermal químic humit que es basa en un procés tèrmic sense buit sense cap procés de selenización addicional. Introduint diferents fonts de metall en un autoclau amb etilenamina com solvent, es van obtenir nanopartícules de CIGS a diferents temperatures en un rang de 190- 230 °C. Els resultats de la difracció de raigs X (XRD) van confirmar la formació d'una estructura de calcopirita CuInxCryGa1-x-ySe2 tetragonal. Finalment, es va estudiar l'efecte de la temperatura de recuit en els materials tipus kesterita (com el Cu2ZnSnS4) que són materials de molt baix cost i que no danyen el medi ambient. Vam estudiar el creixement de les pel·lícules primes quaternàries Cu2ZnSnS4 (CZTS) de kesterita mitjançant un dipòsit electroquímic d'un sol pas seguit d'un recuit a baixa temperatura. La influència de diferents atmosferes de recuit a temps de recuit constants (t = 45 min) i paràmetres de control de preparació fixos; és a dir, concentració de la solució de materials de partida (sals de metalls precursors), temps de deposició i potencial d'electrodeposició. Es van estudiar les propietats estructurals, de composició, morfològiques i òptiques, així com les propietats fotoelectroquímiques
Kamal Abdelhamied Saber, S. (2018). Synthesis and characterization of some nano-selenides and their applications in solar cells [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/107389
TESIS

Cataract disease affects millions of people worldwide. It is characterized by the accumulation of light-scattering bodies within the lens that reduce visual acuity. Cataracts are effectively treated surgically, but at great expense, costing Medicare $3.4 billion in 1997. Development of an alternative therapy for this disease would provide medical and economic benefits. We have investigated a novel antioxidant, the superoxide scavenger Mn(III)-salophen, as a therapeutic agent in the selenite cataract model. Mn(III)-salophen has been shown to protect E. coli colonies against oxidative stress but was untested in a eukaryotic system. A total dose of 300 mmol/kg, given IP in four equal 75 mmol/kg doses spaced four hours apart, protects 75% of neonatal rats from nuclear cataract development five days after selenite injection. Selenite is toxic through its reaction with the endogenous antioxidant glutathione (GSH). The reduction of selenite to selenide through an intermediate, selenodiglutathione (GSSeSG) leads to generation of superoxide radical, one of several toxic oxygen species that can damage the lens. Mn(III)-salophen causes an in vitro preservation of the lifetime of GSSeSG by interrupting the reduction of selenite. We have established that the reduction of GSSeSG to selenide does not use GSH as a reducing agent, but rather depends upon electrons generated in the earlier reduction of selenite to selenodiglutathione. These electrons can be intercepted by known one-electron scavengers, arresting the metabolism of GSSeSG. Extensive proteolysis of lens crystallins and loss of calcium homeostasis occur in cataractous lenses from a rat treated with sodium selenite. The visual protection with Mn(III)-salophen is accompanied by a partial loss of the calcium homeostasis, a net increase in sodium, and calpain-mediated proteolysis of à -crystallins similar to lenses from animals treated with selenite alone. Although preservation of alpha-crystallins may contribute to the greater transparency in the protected lens, generalized à -crystallin proteolysis is insufficient for cataract formation. From these experiments we propose that Mn(III)-salophen minimizes the oxidative stress imposed upon the cell by interfering with the metabolism of selenodiglutathione. This allows the cell to compensate for the loss of cation homeostasis and prevents aggregation of proteolyzed crystallins into cataracts.
Ph. D.