This thesis presents findings realising two main objectives. The first aim is to investigate the electrochemical detection of nanomaterials with an emphasis on silver nanoparticles. The second goal is to employ silver nanoparticles in electroanalysis to aid in the detection of other analytes. First, the detection of silver nanoparticles was demostrated through two different electrochemical methods, stripping voltammetry and 'nano-impacts'. For stripping voltammetry, the potential of metallic nanoparticles oxidation was quantified by various new analytical expressions for peak potential. For the novel method of 'nano-impacts', individual silver nanoparticles were successfully detected in an optically opaque suspension. Then, a comparison between the two techniques was achieved via the oxidation of silver nanoparticles with different capping agents. Strong capping agent effects was found for stripping voltammetry and one may markedly underestimate the amount of silver nanoparticle present on the electrode surface. The electrochemical sizing of nanoparticles via 'nano-impacts' remained unaffected by the capping agent effect. Amidst the study on the various types of capping agent, it was discovered that cetyltrimethylammonium bromide (CTAB) is electroactive due to the oxidation of its bromide content. This inspired the use of 'nano-impacts' to detect the presence of large CTAB micelles which self-assembled at concentrations above the critical micelle concentration. Next, various types of silver nanoparticles were applied to different electroanalytical systems to aid in the measurement of other analytes. (a) Small silver nuclei, remaining after the oxidative stripping of an electrode modified by silver nanoparticle suspension drop casting, allowed subsequent signal enhancement (at least a factor of three) in anodic stripping voltammetry of silver ions. (b) The thermodynamic favourable formation of silver halide complexes allowed the silver nanoparticle modified electrode to analyse the halide content of a solution. Hence, a proof-of-concept for an electrochemical sensor based on silver nanoparticle modified electrode for chloride ions was established. This might be applied to the pre-screening of cystic fibrosis, a genetic disease detrimental to many infants' lives. (c) Another key halide in human body, iodide ions, was also measured using a related concept. The level of iodide ions in synthetic human urine was determined. Last, the strong affinity of silver to thiol groups also warranted a study devoted to their interaction through electrochemical and spectroscopic measurements. It was found that there is no general mechanism for silver-thiol interaction and each thiol must be treated as a separate entity.

Since their introduction to the United States in the 1970s, the invasive silver carp (Hypothalmichthys molitrix) has migrated into the native waters of 16 states with populations in the Mississippi, Missouri, Ohio and Illinois River systems expanding at exponential rates in the past decade. As this species advances towards Lake Michigan, the threat of their invasion into the Laurentian Great Lakes is becoming very real. Silver carp are opportunistic, capable of rapid and extensive dispersal. They have the potential to compete with native species for critical habitat and food, which are very important limiting resources in all freshwater systems. Understanding their diet and habitat selection could be helpful for predicting their expansion and impacts in systems they invade. In order to fully understand habitat selection, 77 silver carp were implanted with ultrasonic transmitters during Spring 2008 and Spring 2009 in Pools 26 (N=24) and 27 (N=53) of the Mississippi River. Fish were located monthly to assess macrohabitat use. To determine if phytoplankton availability was influencing habitat selection, environmental chlorophyll a (used as a surrogate for phytoplankton abundance) was quantified monthly at silver carp detection sites and at randomly generated points from all macrohabitats. 240 silver carp were sacrificed to analyze foregut chlorophyll a concentrations (Pool 26 N=141; Pool 27 N=99); chlorophyll a concentrations in the river at fish locations were measured. This allows us to determine utilization of available phytoplankton resources. Silver carp were detected mostly in channel border wing dike areas with island side channel also being a popular macrohabitat. Chlorophyll a concentrations in the river were higher in areas where carp were detected compared to random sites across all macrohabitat types (Ksa=1.28 p=0.080). There was no significant relationship between foregut chlorophyll a concentrations and what was available in the environment, suggesting silver carp are using resources similarly across all habitats. Given that this species accumulated high concentrations of phytoplankton in their guts even in areas of low phytoplankton concentrations, they may be able to successfully invade areas with scarce phytoplankton resources.

Neste trabalho foi testada a eficiência antimicrobiana de um nanocompósito de prata preparado a partir da modificação da resina comercial Lewatit VPOC1800 (contendo grupos sulfônicos) para três espécies de bactérias (Staphylococcus aureus, Pseudomonas aeruginosa e Escherichia coli.) cuja estrutura e composição das camadas externas da parede celular são distintas. Em termos da susceptibilidade aos biocidas essa diferença pode significar um fator importante de estudo. A avaliação da atividade biocida foi feita através de experimento que estimou a zona de inibição proporcionada pela atividade da resina sobre as bactérias estudadas. A resina mostrou eficiência biocida que aparentemente não é afetada pelas diferenças morfológicas das bactérias estudadas. Uma série de teste em batelada foi realizado com o intuito de se verificar a massa da resina e o tempo de contato ideal com a solução a ser descontaminada, chegando aos valores de 0,2g e 1minuto. As diferentes concentrações bacterianas utilizadas no estudo não influenciaram na atividade antimicrobiana da resina. Um estudo em coluna foi realizado para se averiguar o ponto de saturação do compósito, observando-se que a curva de ruptura da resina segue um tendência exponencial crescente igual a todas as espécies estudas, atingindo a saturação em aproximadamente 2250 mL / In this work, the bactericidal action of silver nanocomposite, prepared from the modification of the commercial resin Lewatit VPOC1800 (containing thiol group), was tested in three species of bacteria (Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli). The cellular structure and composition of those bacteria are different, influencing their reaction to the biocides, thus being an important factor of study. The evaluation of the biocidal activity was made through experiments that esteemed the area of inhibition in proportion to the activity of the resin on the target bacteria to be studied. The resin showed bactericidal activity on all the bacteria studied. Seemingly, the morphologic differences did not affect the bactericidal activity. A test series was performed with the intention of verifying the mass of the resin and the ideal time of contact with the solution to achieve descontamination. Values of 0,2g for 1min were observed. The different bacterial concentrations used in the study did not influence in the bactericidal activity of the resin. A study in column was accomplished to discover the point of saturation of the composite. We observed that the curve of rupture of the resin follows an exponential growth tendency, being the same for all the species studies, reaching the saturation in approximately 2250 mL

No description available.

No description available.

Candelaria, situated in central western Nevada, along the western margin of the Great Basin, is a large and predominantly low grade, epigenetic disseminated- and vein-type Ag deposit, of Early Cretaceous age. It represents the eroded, deeply oxidised and fault-disrupted root of extensive stratiform quartz-dolomite stockworked and sericite-dolomite-altered zones of medium temperature pyrite-dominated Ag(-Pb-Zn-Sb-As±Cu±Au) sulphide-sulphosalt mineralisation, which is hosted by receptive sedimentary and igneous rocks within structurally favourable zones in a district-scale tectonic pinchout, and which is genetically associated with Cordilleran granodiorite porphyry hypabyssal magmatism (diking), of high K calc-alkaline affinity. The mineralisation occurs along and directly beneath the Pickhandle allochthon, a serpentinite-sheathed volcanic-sedimentary tectonic méange which forms a local 'sole' plate to the regionally extensive Golconda allochthon, which was emplaced onto the edge of continental North America during the Early Triassic Sonoma orogeny. Mineralisation occurred where an irregularity in the Pickhandle thrust plane, caused by thickening of the méange, effected locally deeper truncation of the parautochthonous foreland sequence in its footwall - chiefly marine sediments of the Lower Triassic Candelaria Formation - against the deformed cherts of the Ordovician basement (Palmetto complex), to form a structural trap. Within this trap, mineralisation is hosted mainly by carbonaceous, carbonate- and phosphate-rich (and trace metal-rich) black shales at the base of the Candelaria Formation and by dolomite-quartz-altered serpentinites at the base of the Pickhandle allochthon. Stable isotope data (O, H, S) point to a predominantly magmatic source for the hydrothermal fluids and ore sulphur, a source most likely to be the parent pluton to the granodiorite porphyry dikes. More ore metals were also of igneous origin (mass balance calculations rule out Candelaria member 1 as the chief metal source).

Master of Science / Department of Physics / Christopher M. Sorensen / An easier, cheaper and scalable method to obtain silver nanoparticles, AgNPs, directly from the bulk material has been obtained. Two different solvents were tried, water and ethylene glycol, the coating agent was polyvinylpyrrolidone, PVP, and two different silver sizes were used, micron size powder and silver shots, millimeter size. It was seen that changing the size of bulk silver, the temperature of reaction, the amount of oxygen, the concentration of PVP and its molecular weight all had an important influence in the synthesis of nanoparticles. Different morphologies could be obtained when these parameters were adjusted ranging from spheres to triangles and hexagons. A complex mechanism is proposed: during the first step, bulk silver is oxidized by oxygen in solution, forming a thin layer of oxidized silver on the surface. Then, PVP acts as a reducing agent at the oxidized surface, where silver becomes Ag⁰ again. At the same time that PVP reduces the oxidized silver back to metallic silver; it coordinates with the silver atoms acting as a protecting agent. That coordination between PVP and silver pulls out the atoms and produces a detachment of silver atoms from the bulk surface. These silver-PVP complexes in solution later combine to form silver nanospheres and evolve to rods first and then triangles and hexagon with longer reaction time.

Orientador: Marisa Saenz Leme / Banca: Wilma Peres Costa / Banca: Denise Aparecida Soares de Moura / Resumo: Os recrutamentos militares foram uma realidade na Capitania de São Paulo, desde o século XVIII. Os conflitos na Bacia do Prata, na busca de delimitar as fronteiras da América portuguesa e espanhola, exigiram a organização de uma estrutura militar no Brasil. Para sediar essa estrutura foi escolhida a referida Capitania. A união de interesses, de segmentos da elite paulista e da Coroa portuguesa, possibilitou a consolidação da militarização da Capitania ao longo da segunda metade do século XVIII. Todavia, a dinamização da economia e da sociedade paulista, a partir das últimas décadas do século XVIII e início do XIX, entrou em conflito com a militarização ali desenvolvida. O presente trabalho buscou analisar as diferenças entre os recrutamentos realizados em São Paulo nesses dois momentos, focando as relações entre a sociedade e o Estado na organização e manutenção da estrutura militar. / Abstract: The military recruitment had been a reality in São Paulo, since the 18th century. The conflicts at the Silver Drainage Basin, in search to delimit the Portuguese and Spanish America borders, they had demanded to orgazine the military structure in Brazil. Hosting this structure São Paulo Captainship was chosen. The union of interests, segments of São Paulo’s elite and the Portuguese Crown, made it possible the militarization of Captainship consolidation throughout the second half of 18th century. However, the joining of the economy and the paulista society, from the last decades from the 18th and beginning of 19th century, it got in conflict with the militarization developed there. The current paper searched to analyze the differences between the recruitment fulfilled in São Paulo at these two moments, focusing the relations between the society and the State over the organization and maintenance of the military structure. / Mestre

Neste trabalho foi testada a eficiência antimicrobiana de um nanocompósito de prata preparado a partir da modificação da resina comercial Lewatit VPOC1800 (contendo grupos sulfônicos) para três espécies de bactérias (Staphylococcus aureus, Pseudomonas aeruginosa e Escherichia coli.) cuja estrutura e composição das camadas externas da parede celular são distintas. Em termos da susceptibilidade aos biocidas essa diferença pode significar um fator importante de estudo. A avaliação da atividade biocida foi feita através de experimento que estimou a zona de inibição proporcionada pela atividade da resina sobre as bactérias estudadas. A resina mostrou eficiência biocida que aparentemente não é afetada pelas diferenças morfológicas das bactérias estudadas. Uma série de teste em batelada foi realizado com o intuito de se verificar a massa da resina e o tempo de contato ideal com a solução a ser descontaminada, chegando aos valores de 0,2g e 1minuto. As diferentes concentrações bacterianas utilizadas no estudo não influenciaram na atividade antimicrobiana da resina. Um estudo em coluna foi realizado para se averiguar o ponto de saturação do compósito, observando-se que a curva de ruptura da resina segue um tendência exponencial crescente igual a todas as espécies estudas, atingindo a saturação em aproximadamente 2250 mL / In this work, the bactericidal action of silver nanocomposite, prepared from the modification of the commercial resin Lewatit VPOC1800 (containing thiol group), was tested in three species of bacteria (Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli). The cellular structure and composition of those bacteria are different, influencing their reaction to the biocides, thus being an important factor of study. The evaluation of the biocidal activity was made through experiments that esteemed the area of inhibition in proportion to the activity of the resin on the target bacteria to be studied. The resin showed bactericidal activity on all the bacteria studied. Seemingly, the morphologic differences did not affect the bactericidal activity. A test series was performed with the intention of verifying the mass of the resin and the ideal time of contact with the solution to achieve descontamination. Values of 0,2g for 1min were observed. The different bacterial concentrations used in the study did not influence in the bactericidal activity of the resin. A study in column was accomplished to discover the point of saturation of the composite. We observed that the curve of rupture of the resin follows an exponential growth tendency, being the same for all the species studies, reaching the saturation in approximately 2250 mL

As part of a worldwide effort to develop efficient catalysts for use in organic chemistry and in the synthesis of highly valuable molecules, work performed during the course of my stay in St Andrews has focused on the design and synthesis of new group 11 metal complexes for their applications in catalysis. The aim of this work was to develop new, active and stable, easy to synthesise group 11 complexes and investigate their catalytic activity as well as to try to understand their mode of action. Two different types of complexes were explored in order to develop more active catalysts: the neutral N-Heterocyclic carbene metal complexes and the cationic derivatives. More than 20 new catalysts were developed and their reactivity studied in different catalytic reactions. New hydroxide and tert-butoxide copper(I) or silver(I) complexes were developed and compared to the common NHC metal systems. Overall, the neutral NHC-metal catalysts showed to be highly active in a broad range of applications: in the methylation of amines using CO₂ as a C1 source, in a multicomponent reaction (A³ coupling) and in dual catalysis (hydrophenoxylation). Additionally, mechanistic studies were undertaken to obtain a greater understanding of these transformations and to possibly lead to the design of new generations of catalyst. Regarding the cationic NHC metal complexes, a straightforward methodology was developed leading to a library of highly stable catalysts. Bis-NHC, mixed NHC/ phosphine as well as NHC/pyridine species were efficiently synthesised using thermal or microwave heating, in high purity and yields. In addition, the effect of the presence of two different or identical ligands on catalytic reactivity was investigated in the 3+2 cycloaddition and in the alkynylation of ketones. Insight into the catalytic cycle was obtained via mechanistic studies. These showcased the release of one ligand during the catalytic cycle and the crucial role of this ligand displacement in generating the catalytically relevant active species. The results highlight the importance of understanding the reactivity of catalyst in order to develop new and improved ones.