Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 135-144).

L'objectif est la mise au point d'une méthodologie de synthèse des nanoparticules d'or en présence du chitosane sous rayonnement permettant l'obtention d'objet de taille homogène et contrôlée. Dans ce but, nous mettrons l'accent sur l'étude des interactions entre les ions Au(III) et le chitosane en solution avant irradiation. En effet, la coordination entre des unités de glucosamine et l'ion Au(III) favorise la réduction de Au(III) en Au(0) et la formation de nanoparticules d'or. Cela est démontré clairement par l'étude de l'influence du pH sur la formation de nanoparticule lors du vieillissement des solutions d'HAuCl4 en présence de chitosane. Ce phénomène a été avance pour expliquer tout au moins partiellement, le mécanisme de la réduction des ions Au(III) en présence du chitosane sous rayonnement. Il s'agissait de définir si le mécanisme de réduction des ions Au(III) en ions Au(0) suivait un processus classique tels qu'il a été décrit dans les travaux de Belloni et de Henglein, ou si la présence de chitosane influe sur ce processus. L'élaboration des nanoparticules d'or en présence du chitosane utilisé comme agent stabilisant a été réalisée sous irradiation par faisceau d'électrons ou par rayonnement gamma. L'influence des paramètres de synthèse (rapport du [GLA]/[Au(III)], conditionnement des échantillons, effet de la dose d'irradiation, effet du débit de dose, rôle d'un piégeur de radicaux ou d'électrons solvatés) a ensuite été évaluée sur les propriétés caractéristiques des solutions de nanoparticules d'or (taille, charge, résonance plasmon de surface). L'activité catalytique des nanoparticules synthétisées a été testée vis-à-vis de la réaction de réduction du 4-nitrophénol en 4-aminophénol par NaBH4.Mots-clés : or, nanoparticules, chitosane, coordination, irradiation, faisceau d'électrons, rayonnement gamma, 4-nitrophénol. / The goal of this work is to develop a methodology for the synthesis of gold nanoparticles in the presence of chitosan under radiation to obtain a homogeneous object and controlled size. To reach this purpose, we will focus on the study of interactions between the ions Au(III) and chitosan in solution before irradiation. Indeed, the coordination between units of glucosamine and Au(III) promotes the reduction of Au(III) to Au(0) and the formation of gold nanoparticles. This is clearly demonstrated by the influence of pH on the formation of nanoparticles upon aging of HAuCl4 solutions in the presence of chitosan. This formulation has been used to explain the mechanism of reduction of Au(III) in the presence of chitosan in radiation. It was to define whether the reduction mechanism of ion Au(III) ions Au(0) followed a conventional process such as those described by the work of Belloni and Henglein, or if the presence of chitosan affects this process. The development of gold nanoparticles in the presence of chitosan used as a stabilizing agent was produced by the electron beam and gamma radiation. The influence of the synthesis parameters (report [GLA]/[Au (III)], sample conditioning, effect of irradiation dose, dose rate effect, role of a radical scavenger) on the characteristic gold nanoparticles was then evaluated (size, charge, surface plasmon resonance). The catalytic activity of these nanoparticles was tested towards the reduction reaction of 4-nitrophenol to 4-aminophenol by NaBH4.Keywords: gold, nanoparticles, chitosan, coordination, irradiation, electron beam, gamma radiation, 4-nitrophenol.

Zwei Modellreaktionen wurden mit thermoresponsiven Nanoreaktoren untersucht. Die Reduktion von 4-Nitrophenol und von Kaliumhexacyanidoferrat(III) mit Natriumborhydrid. Die Nanoreaktoren bestehen aus einem Polystyrol Kern, umgeben von einer Hydrogel Schale aus Poly-(N-Isopropylacrylamid). Die Reaktionen werden auf der Oberfläche von Metall Nanopartikeln in der Hydrogel Schale katalysiert. In einer auf Gold- und Silberkatalysatoren fokussierten Literaturstudie zeigte sich, dass der geschwindigkeitsbestimmende Reaktionsschritt zwischen beiden Metallen variieren könnte. Kinetische Studien mit Silber haben gezeigt, dass ein erfolgreich auf Gold angewandtes Modell modifiziert werden muss um auf Silber anwendbar zu sein und haben gezeigt, dass sich die Kinetik der Reaktion auf beiden Metallen unterscheidet. Die weitere Analyse ergab die typische, nicht der Arrhenius Abhängigkeit folgende, Abhängigkeit der Reaktionsrate von der Temperatur und hat gezeigt, dass die Partitionierung der Reaktanden im Hydrogel für das kinetische Modell relevant ist. Die Reduktion von Kaliumhexacyanidoferrat(III) auf Gold hat gezeigt, dass elektrostatische Effekte hier eine maßgebliche Rolle spielen. Ein kinetisches Modell wurde erarbeitet, dass die relevanten Einflussfaktoren durch Hydrogel, Geometrie der Nanoreaktoren, diffusions- und elektrostatische Effekte miteinbezieht. Die gewonnenen Daten konnten mittels eines auf der Auswertung des stationären Zustands basierenden Modells erfolgreich gefittet werden. Hierbei wurde das komplexe Zusammenspiel von elektrostatischen Effekten, deren Abschirmung und Einfluss auf die Diffusion sowie die Reaktionsrate gezeigt. Mit wenigen physikalisch aussagekräftigen Fitparametern konnten alle beobachteten Effekte erfolgreich erklärt werden. Der Vergleich der Reduktion von 4-Nitrophenol und von Hexacyanidoferrat(III) zeigt hierbei die entscheidenden Faktoren sowohl für reaktions- als auch für diffusionskontrollierte Reaktionen in thermoresponsiven Hydrogelen. / Two model reactions were investigated with thermoresponsive core-shell nanoreactors, the reduction of 4-nitrophenol and of potassium hexacyanoferrate(III), both reduced with sodium borohydride. The nanoreactors comprise of a polystyrene core surrounded by a hydrogel shell of poly-N-isopropylacrylamide (PNIPAM) crosslinked with N,N’-methylenebisacrylamide. Metal nanoparticles are immobilized inside the hydrogel shell on the surface of which the model reactions are catalyzed. In the reduction of 4-nitrophenol, special emphasis is laid on the reduction on gold and silver catalysts. A literature review of mechanistic as well as kinetic studies reveals that the rate determining step may differ between the two catalyst metals. Kinetic investigations with a silver catalyst reveal that the kinetic model derived previously for gold catalysts needs to be modified for the kinetic analysis in this study, confirming a difference in the kinetics for both catalyst metals. The temperature dependent analysis reveals the typical non-Arrhenius dependency of the reaction rate and shows that the partition ratio of the reactants is relevant for the kinetics. The reduction of potassium hexacyanoferrate(III) on gold reveals that electrostatic effects play a major role in this reaction. A new kinetic model is derived, accounting the relevant influence factors of the hydrogel, the nanoreactor geometry, diffusional and electrostatic effects. With a stationary state approach the experimental data are fitted successfully, revealing the complex interplay of electrostatic effects, the screening thereof and the influence on diffusion and reaction rate. With only a few physically meaningful fit parameters all observed effects can be explained successfully. The comparison of the reduction of 4-nitrophenol and potassium hexacyanoferrate(III) highlights the decisive factors in both, reaction and diffusion controlled reactions inside thermoresponsive hydrogels.

The present work describes the development of a highly sensitive and selective molecularly imprinted electrochemical sensor for 4-nitrophenol detection. A glassy carbon electrode was modified with vyniltrimethoxisylane (VTMS) and multiwall carbon nanotubes (MWCNT). The introduced nanocomposite increased surface area and active sites for electron transfer. When the sillane is used on the synthesis, it is named MIS (molecularly imprinted silane) and NIS (non-imprinted silane) when the analyte is not on the synthesis. For those silane films characterization, it was used the scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and fourier transform infrared spectroscopy (FTIR). This sensor showed its best performance in 0.1 mol L-1 phosphate buffer solution, at pH 7.0. After optimizing the operational conditions, this sensor provided a linear response range for 4-NP from 0.1 up to 100 μmol L-1 and good parameters as LOD, LOQ and sensibility, 0.03 μmol L-1, 0.1 μmol L-1 and 1.4×10-2 A mol L-1 respectively. Furthermore, the MIS/PNP sensor exhibited good stability with adequate reproducibility and accuracy. / No presente trabalho é descrito o desenvolvimento de um sensor eletroquímico altamente sensível e seletivo baseado na tecnolgia dos Polímeros Impresso Molecularmente para detecção de 4-nitrofenol. Um eletrodo de carbono vítreo foi modificado com viniltrimetoxisilano (VTMS) e nanotubos de carbono de pardes múltiplas (MWCNT). O nanocompósito de carbono introduzido aumentou a área superficial e os locais ativos para transferência de elétrons. No método sol-gel quando um sillano é usado na síntese, é denominado MIS (Molecular Imprinted Silane) e NIS (non-imprinted Silane) quando o analito não está na síntese. Para a caracterização dos filmes de silanos utilizou - se a microscopia eletrônica de varredura (MEV), a análise termogravimétrica (TGA) e a espectroscopia de infravermelho por transformação de Fourier (FTIR). Este sensor apresentou o seu melhor desempenho em solução tampão fosfato 0,1 mol L-1, a pH 7,0. Depois de otimizado as condições operacionais, este sensor proporcionou uma faixa de resposta linear para o 4-nitrofenol de 0,1 a 100 μmol L-1 e bons parâmetros como limite de detecção, quantificação e sensibilidade de 0,03 μmol L-1, 0,1 μmol L-1 e 1,4×10-2 A mol L-1 respectivamente. Além disso, o sensor MIS/4-nitrofenol apresentou boa estabilidade com reprodutibilidade e precisão adequadas.

of the Diploma Thesis In this Diploma Thesis, the electrochemical behavior of 4-nitrophenol (4-NP) was studied at a newly prepared large-surface carbon film electrode (ls-CFE) using techniques of DC voltammetry (DCV) and differential pulse voltammetry (DPV) with the aim to develop sensitive analytical methods for its determination. Voltammetric behavior of 4-NP was investigated in the region of anodic potentials, in dependence on the pH of the medium used (realized using Britton-Robinson buffer). The optimum pH values for the determination of 4-NP were chosen as follows: pH 3.0 (for DCV) and pH 7.0 (for DPV). During anodic oxidation of 4-NP on the ls-CFE at the concentration of the analyte of 1·10-4 mol/l, the passivation of the electrode surface occurred. Thus, it was decided to record series of measurements always at a new carbon film. Using the sample of 4-NP (at the concentration of 1·10-4 mol/l), the repeatability of the application of individual carbon films was tested, with obtained RSD values of 3.7% and 3.6% for DCV and DPV, respectively. Under optimum conditions, the calibration dependences of 4-NP were measured in the concentration range from 1·10-6 to 1·10-4 mol/l, with the limits of quantification (LQs) of 1.5·10-6 mol/l (for DCV at the ls-CFE) and 4.6·10-7 mol/l (for DPV at the...

Ce travail, sur la dépollution de l’eau par OVHC sur charbon actif (CA), étudie l'interaction oxydation - adsorption : comment l'oxydation sur charbon de produits aromatiques modifie ses propriétés et en particulier sa capacité d'adsorption et d'oxydation (désactivation). Divers charbons commerciaux, mais aussi issus de boues activées, ont été caractérisés avant et après oxydation : propriétés texturales, composition élémentaire (CHNSO), fonctions de surface, pH au point de charge nulle et allure des courbes ATG. Seule leur teneur en cendres semble différer notablement. Les charbons actifs de boues ont une surface spécifique bien moindre (de 90 à 265 m².g-1) et un taux de cendres supérieur à 50% qui en font de moins bons adsorbants. Cependant la présence de métal, notamment le fer, a un effet positif sur l'oxydation catalytique. L'étude comparative en oxydation catalytique de 4 CA commerciaux en grains montre une désactivation intense (qui augmente avec la concentration de polluant) sur les 3-4 premières utilisations, puis une stabilisation. Le charbon résultant est nettement moins adsorbant. Les CA S23 et F22 ainsi stabilisés ont ensuite été utilisés pour déterminer la cinétique d'oxydation catalytique apparente et intrinsèque du phénol, grâce à un modèle incluant la diffusion. La comparaison de l'OVHC de 4 polluants aromatiques seuls et en divers mélanges synthétiques met en évidence des effets de mélange significatifs: les polluants les plus réfractaires en oxydation catalytique se dégradent beaucoup plus vite en mélange (ex 4NP) et inversement, les polluants les plus oxydés, lorsqu'ils sont seuls en solution, voient leur cinétique diminuer lorsqu'ils sont mélangés aux autres polluants (ex phénol, 4chlorophénol). Le mélange tend donc à uniformiser les comportements particuliers. Enfin, les essais de faisabilité du procédé de régénération oxydante AD-OX ont été effectués sur des effluents industriels. La régénération du charbon actif comme adsorbant est moins limitée qu'avec des mélanges de phénols substitués. / This work, on water treatment by catalytic Wet Air Oxidation (CWAO) using activated carbon (AC), aimed to study the interaction between oxidation-adsorption phenomena: how the oxidation of aromatic compounds on AC can modify its properties and specially its adsorption and oxidation characteristics (deactivation). Various commercials AC, and AC produced from activated sludge, have been characterized before and after oxidation by according methods such as textural characterization, elemental analysis (CHNSO), functional groups on carbon surfaces analysis, pH of the point of zero charge (pHpzc) analysis and thermogravimetric analysis (TGA); however, only their ash level was significantly different. In addition, the sludge based AC (SBAC) have a specific surface range of 90 to 265 m².g-1, which is lower than commercial AC, and with an ash level over 50%. Consequently they are less good adsorbents. However, the presence of metal, e.g. iron, has a positive affect on catalytic oxidation. The comparative study of catalytic oxidation with 4 commercial AC, show a severe deactivation (which increase with the pollutant concentration) on the first 3-4 utilizations before stabilization. The residual AC is clearly poor adsorbent. After stabilization, 2 commercials AC, only S23 and F22 CA, were studied on catalytic oxidation of phenol in term of apparent and intrinsic kinetics with including the diffusion effect in the model. The CWAO of 4 pure aromatic pollutants, and their various synthetic mixtures, showed mixing effects significantly: the most oxidation catalytic refractory pollutants were degraded rapidly when they mixed (e.g. 4-nitrophenol) but the kinetic was slow down for the pure pollutant whereas, the most oxidised pollutants, for pure solution, have an oxidation kinetic slower than when they mixed with others pollutants (e.g. Phenol, 4-chlorophenol). Therefore, the mixture tends to standardize from the individual behaviour. In conclude, the feasibility study of the oxidative regeneration process (AD-OX) was performed on industrial waste water. The regeneration AC as adsorbent is less limited than with mixtures of substituted phenols.