No description available.

La propolis est un produit de la ruche à base de résine de plantes et d’arbres mélangée à de la cire d’abeille. Elle est utilisée pour polir les murs de la ruche et la protéger contre les intrus provenant de l’extérieur. Elle contient un grand nombre de composés incluant les métabolites des plantes, alors elle est un ingrédient des médicaments naturels, des additifs alimentaires et des produits cosmétiques en raison de sa richesse en polyphénols qui lui confèrent ses propriétés anti-oxydantes, anti-inflammatoires et antibiotiques. La composition de la propolis est cependant complexe et très variable en raison de la région de provenance qui est étroitement liée aux résines utilisées par les abeilles. De plus, la présence de contaminants dans l’environnement, comme les pesticides et les éléments traces d’origine anthropique, incluant des métaux lourds, donne un risque d’exposition à ces substances en consommant la propolis ou les extraits de propolis. Plusieurs échantillons de propolis brute ainsi que des teintures commerciales et artisanales provenant du Canada, de la Roumanie et du Brésil ont été analysés. L’extraction des polyphénols totaux des échantillons bruts a été faite 3 fois dans l’éthanol (EtOH) 70 % (v/v) à 70 ̊C, et les teintures ont quant à elles été diluées dans l’EtOH 70 %. Les polyphénols totaux ont ensuite été analysés par spectroscopie moléculaire UV-Vis en utilisant la méthode de Folin- Ciocalteu. Des analyses chromatographiques préliminaires par la chromatographie liquide couplée à la spectrométrie de masse (LC-MS) ont permis de comparer des polyphénols et des pesticides dans deux sources de propolis du Québec, avec une grande similarité entre les deux extraits. Des échantillons bruts ainsi que des extraits éthanoliques et des teintures ont été analysés suite à l’ionisation par plasma à couplage inductif (ICP-MS) et la spectroscopie de fluorescence atomique à vapeur froide (CVAFS) pour déterminer des concentrations de certains éléments traces présents à l’état de trace incluant l’As, le Cd, le Pb et le Hg total. / Propolis is a honeybee product made of plant and tree resins mixed with beeswax. It is used to build and repair the walls of the hive and to protect it from outside invaders. It contains a large number of compounds including plant metabolites, and is thus used in natural medications, cosmetic products and as food additives due to its richness in polyphenols, which confer its antioxidant, anti-inflammatory and antibiotic properties. However, the composition of propolis is complex and highly variable because of the geographical location of the resins used by the bees. Furthermore, the presence of contaminants in the environment, such as pesticides and trace elements of anthropogenic origin, brings a risk of exposure to these substances when consuming the propolis. Various raw propolis samples as well as commercial and homemade tinctures from Canada, Romania and Brazil were analysed. The raw samples were extracted 3 times in 70 % EtOH (v/v) at 70 ̊C, whereas the tinctures were diluted in 70 % EtOH. The total polyphenol content was determined by UV-Vis spectroscopy using the Folin-Ciocalteu method. Preliminary chromatography analyses by LC-MS on two propolis samples from Québec showed that the detected polyphenols and pesticides in their extracts were very similar, with only a few compounds found exclusively in either one or the other sample. Several raw propolis samples, their extracts and some tinctures were analyzed by ICP-MS and CVAFS to determine trace concentrations of heavy metals including As, Cd, Pb and total Hg.

Aus CdTe- und Edelmetallnanopartikeln werden 3-dimensionale Netzwerkstrukturen aufgebaut, welche durch einen überkritischen Trocknungsprozess zu hochporösen, weitverzweigten Halbleiter-Metall-Nanokompositen, sogenannten Aerogelen, umgewandelt werden. Zunächst werden Thiol-stabilisierte CdTe- und Edelmetallnanopartikel im wässrigen Milieu hergestellt und deren Morphologie und optischen Eigenschaften umfangreich mittels UV-Vis-Spektroskopie, Fluoreszenzspektroskopie und -lebensdauermessung, ICP-OES, TEM, STEM-EDX und AFM charakterisiert. Als Metallkomponente kamen Gold-, Palladium- sowie bimetallisch gemischte Gold-Palladium-Nanopartikel zum Einsatz. Die Gelierung der Nanopartikellösungen erfolgt durch Vermischen der Kolloide und anschließender kontrollierter Destabilisierung mithilfe einer Xe-Dampflampe oder der Zugabe von Wasserstoffperoxid. Neben einer mechanistischen Beschreibung der Gelbildungsmethoden wurden die resultierenden Hydrogele und die aus der überkritischen Trocknung erhaltenen Aerogele bezüglich Zusammensetzung, Morphologie und optischen Eigenschaften mithilfe von TEM und REM jeweils gekoppelt mit EDX-Analyse, Stickstoff-Porosimetrie, diffuser Reflexionsspektroskopie, Fluoreszenzspektroskopie und Fluoreszenzlebensdauermessungen untersucht. Weiterhin wird die UV-Vis-Spektroskopie als Methode zur Konzentrationsbestimmung von Gold in Lösungen kolloidaler Gold-Nanopartikel validiert. Dabei wird die Absorption der Kolloide bei einer Wellenlänge von 400 nm als Maß verwendet. Die NP-Lösungen werden anhand der Parameter Partikelgröße, Oberflächenfunktionalität und der Oxidationsstufe des enthaltenen Goldes variiert. / 3-dimensional network structures are formed combining CdTe and noble metal nanoparticles. A supercritical drying process allows production of highly porous and widely branched semiconductor-metal nanohybrids, so-called aerogels. Primarily, thiol-capped CdTe and noble metal nanoparticles are synthesized in aqueous media and their morphology and optical properties are studied extensively using UV-Vis and fluorescence spectroscopy, time-resolved fluorescence spectroscopy, ICP-OES, TEM, STEM-EDX and AFM. The metal entity involves gold and palladium nanoparticles as well as bimetallic mixed Au/Pd nanoparticles. After mixing of the different colloids gelation is induced by a controlled destabilization process using a Xenon lamp irradiation or the addition of hydrogen peroxide. Gelation techniques are described mechanistically. Resulting hydrogels and aerogels which are obtained by supercritical drying approach are characterized concerning composition, morphology and optical properties using TEM and SEM each coupled with EDX, nitrogen porosimetry, diffuse reflection spectroscopy, fluorescence spectroscopy and time-resolved fluorescence spectroscopy. Moreover, the UV-Vis spectroscopy is validated as a method to determine the gold concentration in gold nanoparticle solutions using the colloids absorbance at 400 nm as a measure. Gold nanoparticle solutions are varied concerning the parameters particle size, surface functionality and oxidation state of contained gold.

Made available in DSpace on 2017-07-21T18:53:11Z (GMT). No. of bitstreams: 1 dissertacao parcial.pdf: 389132 bytes, checksum: 1072407aabab8f91b6ea13999acc01d4 (MD5) Previous issue date: 2009-02-06 / Pectinases, a group of enzymes that degrade pectic substances and break glycosidic linkages, are produced by fungi, yeasts and bacteria, but are also in plants in general and fruit in particular.In the juice industry the pectinolytic enzymes are added to increase the efficiency of the process, decrease the viscosity and reduce the time of filtration. The pectin methylesterase, PME, hydrolyzes the methyl ester groups, forming carboxyl groups in pectin chain, releasing methanol end H3O+. Therefore, its knowledge is vital in order to control the effectiveness of the treatment. The purpose of this study was to determine the optimum conditions of the activity of the pectin methylesterase in industry preparations, proposing a potentiometric procedure for determining the PME activity and compare the data with those obtained by traditional potentiometry and Uv-Vis, evaluate the efficacy of this method in determining the residual activity exogenous of PME in mango juice. The activity of PME in the three commercial samples, Pectinex 100L Plus, Panzym Univers and Panzym Clears, was determined by potentiometry, Uv-Vis spectroscopy, with the bromophenol blue indicator, and the action of alcohol oxidase with acetyl acetone. The reaction consisted of 5.00 mg.mL-1 apple pectin, 0.100 mol.L-1 sodium chloride and 50 μL commercial pectinolytic enzyme for a volume of 30 mL. In all experiments the enzyme deesterification showed first-order kinetics, with increased activity at pH 4.0 to 4.5 and 45 ºC, whereas the complete inactivation occurred at 75 ºC for 10 minutes, in the three industrial preparations. The thermal inactivation of the PME of Pectinex 100L Plus and Panzym Clears preparations occurred under the same conditions, when the activity was measured by the procedures of ΔVNaOH / Δttime or of ΔpH/ Δttime. The activity of PME in industrial preparations at 25 °C and pH 4.5, determined by UV-Vis spectroscopy with bromophenol blue indicator, showed good correlation with the activity determined by the procedures by potentiometry. The stability of the indicator in the pectin solution allows its use to determine the PME activity in samples in which the optimum pH is located in acid band. The release of methanol as measured by alcohol oxidase, followed by the reaction with acetyl acetone to determine the formaldehyde, showed good agreement with the results of the enzyme activity measuring procedures used in this research. The inactivation of residual PME in mango juice occurred at 75 ºC for 20 minutes of exposure in the procedure ΔVNaOH / Δttime and 10 minutes of exposure during the procedure ΔpH/ Δttime. The residual activity of PME in 70 °C for 10, 20 and 30 minutes of exposure in the presence of juice was higher than in the control, indicating its protective effect. The procedure of ΔpH/ Δttime shows good correlation with other methods, with the advantage of precise and direct measures of [H+], excusing a series of reagents and high costs materials. / As pectinases, um grupo de enzimas que degradam substâncias pécticas e rompem ligações glicosídicas, são produzidas por fungos filamentosos, leveduras e bactérias, mas encontram-se também em plantas em geral e em frutas, em particular. Na indústria de sucos as enzimas pectinolíticas são adicionadas para aumentar o rendimento do processo, diminuir a viscosidade e reduzir o tempo de filtração. A pectina metilesterase, PME, hidrolisa os grupos metil éster, formando grupos carboxilícos na cadeia da pectina, produzindo metanol e H3O+.Portanto, é fundamental o seu conhecimento, a fim de controlar a eficiência do tratamento. O objetivo deste trabalho foi determinar as condições ótimas da atividade da PME presente em preparações industriais, propor um procedimento potenciométrico para determinação da atividade da enzima e comparar os dados com os obtidos por potenciometria tradicional e Uv- Vis, avaliar a eficiência do método proposto na determinação da atividade residual da PME exógena no suco de manga. A atividade da PME nas três amostras comerciais, Pectinex 100L Plus, Panzym Univers e Panzym Clears, foi determinada por potenciometria, espectroscopia Uv-Vis, com o indicador azul de bromofenol, e pela ação do álcool oxidase com acetil acetona. A reação consistiu de 5,00 mg.mL-1 de pectina de maçã, 0,100 mol.L-1 de cloreto de sódio e 50 μL de enzima pectinolítica comercial para um volume de 30 mL. Em todos os experimentos a desmetoxilação enzimática mostrou uma cinética de primeira ordem, com maior atividade em pH 4,0 a 4,5 e 45 ºC, sendo que a inativação completa ocorreu a 75 ºC por 10 min, nas três preparações industriais. A inativação térmica da PME das preparações Pectinex 100L Plus e da Panzym Clears ocorreu sob mesmas condições, quando a atividade foi medida pelos procedimenos de ΔVNaOH / Δttempo ou de ΔpH/ Δttempo. A atividade da PME nas preparações industriais a 25 ºC e pH 4,5, determinada por espectroscopia Uv-Vis com o indicador azul de bromofenol, apresentou boa correlação com a atividade determinada pelos procedimentos por potenciometria. A estabilidade do indicador em solução com a pectina permite a sua utilização para determinar a atividade da PME em amostras nas quais o pH ótimo localiza-se na faixa ácida. A liberação do metanol medida pela álcool oxidase, seguida da reação com a acetil acetona para determinar o formaldeído, mostrou boa concordância com os resultados dos procedimentos de medida de atividade enzimática utilizados neste trabalho. A inativação da PME residual em suco de manga ocorreu na temperatura de 75 ºC por 20 min de exposição no procedimento ΔVNaOH / Δttempo e durante 10 min de exposição pelo procedimento ΔpH/ Δttempo. A atividade residual da PME a 70 ºC por 10, 20 e 30 min de exposição em presença do suco foi maior do que no controle, indicando o seu efeito protetor. O procedimento da ΔpH/ Δttempo apresenta boa correlação com os demais métodos, com a vantagem de medidas precisas e diretas da [H+], dispensando uma série de reagentes e materiais de custos elevados.

<p>ZnO nanoparticles in the size range 2.5–7 nm have been synthesised by a wet chemical method where ZnO particles were grown in basic zinc acetate solution. The optical band gap increases when the size of the particles decreases. An empirical relation between the optical band gap given from absorption measurements, and particle size given from XRD measurements has been developed and compared to other similar relations found in the literature.</p><p>   Time resolved UV-Vis spectroscopy has been used to follow the growth of particles in situ in solution. The data show that the growth mechanism not can be described by a simple Oswald ripening approach and nor by an exclusive agglomeration of smaller clusters into larger particles. The growth mechanism is more likely a combination of the proposed reaction themes. The data also reveal that particle formation do not demand a heating step for formation of the commonly assumed initial cluster Zn₄O(CH₃COO)₆.</p><p>   Steady state fluorescence has been studied as a function of particle size during growth in solution. These measurements confirm what is found in the literature in that the visible fluorescence is shifted to longer wavelengths and loses in intensity as the particles grow. Some picosecond spectroscopy has also been done where the UV fluorescence has been investigated. From these measurements it is apparent that the lifetime of the fluorescence increases with particle size.</p><p>    The phonon spectrum of ZnO has been studied with Raman spectroscopy for a number of different particle sizes. From these measurements it is clear that there is a strong quenching of the phonons due to confinement for the small particles, and the only clearly observed vibration is one at 436 cm^-1 which intensity strongly increases with particle size.   </p>

In the past decade, tremendous progress has been made in organic field effecttransistors. Fused oligothiophenes and anthracene molecules are fascinatingmacromolecules having unique optoelectronic properties. These compounds are successfully employed as active components in optoelectronic devices including field effect transistors. Our goal is to design and synthesize conjugated molecular materials, which are highly functionalized through structural modifications in order to enhance their electronic, photonic, and morphological properties. The main desire is to synthesize novel organic fused-arenes having efficient charge carrier mobilities, as well as to optimize optical properties for organic field effect transistors (OFETs). Novel series of fused arene molecules of 9,10-di(thiophen-3-yl)anthracene (1), trans-2,5-(dianthracene-9- vinyl)thiophene (2), trans-5,5’-(dianthracene-9-yl)vinyl)- 2,2’-bithiophene (3), 5,5’-di(2 thiophene)-2,2’-bithiophene (4) , 9,10-(divinyl)anthracene core with 1- phenylcarboxypyrene (6) and polymers of poly(anthracene-co-bithiophene) (5) and poly(anthracene) (7) have been synthesized as promising materials for organic field effect transistors (OFETs). These compounds were confirmed and characterized by 1H-NMR, FT-IR, and elemental analysis. Their optical, thermal, and electronic properties were investigated using UV-Vis and photoluminescence spectroscopy, and thermogravimetric analysis respectively. Future studies will focus on evaluating OFETs performance of these material.

ZnO nanoparticles in the size range 2.5–7 nm have been synthesised by a wet chemical method where ZnO particles were grown in basic zinc acetate solution. The optical band gap increases when the size of the particles decreases. An empirical relation between the optical band gap given from absorption measurements, and particle size given from XRD measurements has been developed and compared to other similar relations found in the literature.    Time resolved UV-Vis spectroscopy has been used to follow the growth of particles in situ in solution. The data show that the growth mechanism not can be described by a simple Oswald ripening approach and nor by an exclusive agglomeration of smaller clusters into larger particles. The growth mechanism is more likely a combination of the proposed reaction themes. The data also reveal that particle formation do not demand a heating step for formation of the commonly assumed initial cluster Zn4O(CH3COO)6.    Steady state fluorescence has been studied as a function of particle size during growth in solution. These measurements confirm what is found in the literature in that the visible fluorescence is shifted to longer wavelengths and loses in intensity as the particles grow. Some picosecond spectroscopy has also been done where the UV fluorescence has been investigated. From these measurements it is apparent that the lifetime of the fluorescence increases with particle size.     The phonon spectrum of ZnO has been studied with Raman spectroscopy for a number of different particle sizes. From these measurements it is clear that there is a strong quenching of the phonons due to confinement for the small particles, and the only clearly observed vibration is one at 436 cm-1 which intensity strongly increases with particle size.

In the recent studies thiocyanate-containing metal complexes are considered to be the most investigated systems. Such complexes exhibit specific properties which could be applied in various fields such as catalysis, photochemistry, biochemistry, pharmacology and etc. The complexes of mercury(II) and iron(III) thiocyanates are of interest since they are widely applied for analysis in the clinical or industrial laboratories. As a result these complexes received great attention, due to the fascinating properties in designing new materials with inorganic and organic ligands. Dealing with such complex system, accurate prediction of the synthesized compound properties is challenging. For this reason, researchers analyze how the replacement of certain group, modification, molar ratio of the mixed ligands and etc. may influence the structure and properties of the obtained complex. Molecular structure, vibrational and electronic spectra of aqueous mercury(II) thiocyanate and iron(III) monoisothiocyanate solutions (at the pH ~ 2) were analyzed in the dissertation by means of Raman and UV-VIS spectroscopies and quantum chemical calculations. The structure, coordination number and vibrational assignments of the titled complexes were determined. The influence of different solvation models upon spectral properties was estimated. The excited state analysis of iron(III) monoisothiocyanate was performed. / Metalų tiocianatų chemija yra ypatingai sparčiai besivystanti tyrimų kryptis. Dėl specifinių metalų tiocianatų savybių šie junginiai plačiai taikomi katalizinėje chemijoje, biochemijoje, farmakologijoje, fotochemijoje ir pan. Vieni iš plačiausiai nagrinėjamų pereinamųjų metalų tiocianatų kompleksų yra geležies ir gyvsidabrio tiocianatai. Pastaruoju metu mokslininkai bando susintetinti kompleksinius geležies ir gyvsidabrio tiocianatų junginius, turinčius neorganinį ir organinį ligandus, kurie pasižymi specifinėmis savybėmis tokiomis kaip: liuminescencija, magnetizmas, katalizinis aktyvumas ir pan. Tačiau, siekiant susintetinti junginius su norimomis fizikinėmis ir cheminėmis savybėmis, reikalingos žinios apie kompleksų struktūras, kompleksavimo ypatybes ir visą tai įtakojančius veiksnius molekuliniame lygmenyje. Disertacijoje analizuota tirpių gyvsidabrio(II) tiocianatų ir geležies(III) monoizotiocianato kompleksų (esant pH ~ 2) molekulinė struktūra, virpesiniai ir elektroniniai spektrai taikant Ramano ir UV-RŠ spektroskopines analizes bei kvantinius skaičiavimus. Nustatyti kompleksų koordinacijos skaičiai ir struktūros, atlikti funkcinių grupių signalų priskyrimai, įvertinta solvatacijos įtaka kompleksų spektrinėms savybėms ir išanalizuoti geležies(III) monoizotiocianato komplekso elektroniniai perėjimai sužadintoje būsenoje.

L’utilisation de dioxygène lors de la délignification des pâtes à papier permet une réduction considérable des coûts de production et de l’impact environnemental du procédé de blanchiment. Seulement, le taux de délignification est limité par le fait qu’une partie de la lignine résiduelle n’est pas réactive vis-à-vis du dioxygène et que la cellulose est partiellement dépolymérisée au cours du procédé. L’utilisation de catalyseur pourrait permettre d’améliorer l’efficacité et la sélectivité de la délignification au dioxygène comme le suggèrent certaines études. Le complexe cuivre(II)-phénanthroline présente des résultats prometteurs en termes d’efficacité, mais entraîne une dégradation importante de la cellulose. Différents ligands polypyridiniques ont été étudiés dans ces travaux, afin de trouver un complexe du cuivre(II) présentant une affinité forte vis-à-vis de la lignine et faible vis-à-vis de la cellulose. Les complexes formés ont été caractérisés par spectroscopie UV/Vis et voltammétrie cyclique et étudiés comme catalyseurs de l’oxydation de différents substrats : un composé modèle de lignine non phénolique et des substrats lignocellulosiques (un modèle de cellulose, un modèle de lignine native et une pâte kraft industrielle). Les résultats ont montré que la nature même du ligand a un effet important sur l’activité catalytique du complexe de Cuivre (II) lors de l’oxydation du composé modèle de lignine. En revanche, les complexes actifs présentent une activité faible lors de la délignification d’une pâte kraft et oxydent fortement les hydrates de carbone. Ce manque de sélectivité ne permet pas une application pour la production de pâte à papier mais oriente l’utilisation de ce type de catalyseur dans de nouvelles applications n’ayant pas les mêmes contraintes sur le degré de polymérisation de la cellulose. / Dioxygen delignification considerably reduces the operating cost of the bleaching process and decreases the environmental impact of the bleaching effluent. Unfortunately the performance of dioxygen delignification is limited since part of the residual lignin is not reactive toward dioxygen while cellulose depolymerisation occurs. Studies suggested that dioxygen delignification could be improved thanks to the use of catalysts such as copper(II)–phenanthroline type complexes which have shown promising results on delignification efficiency. However cellulose was also more degraded. Different polypyridinyl ligands have been studied in this work, in an attempt to find copper(II) complexes that have more affinity toward lignin and less toward cellulose. Complexes have been characterised by UV/Vis spectroscopy, cyclic volammetry, and they were studied for the catalysed oxidation of various substrates: a non phenolic lignin model compound and lignocellulosic substrates (a model of cellulose, a model of native lignin and an industrial kraft pulp). It has been shown that the nature of the ligand had a significant effect on the catalytic activity of Cu(II) complexes in the oxygen oxidation of the lignin model compound. However, the active complexes only show a limited activity during the delignification of a kraft pulp and oxidize carbohydrates. This lack of selectivity prevents from an industrial application for paper pulp production but may be useful for the design of products with fewer constraints on cellulose polymerization degree.

Philosophiae Doctor - PhD / A highly dispersive gold nanoparticle-dotted 4-nitrophenylazo functionalised graphene nanocomposite (AuNp/G/PhNO2) was successfully synthesised and applied in enhancing sensing platform signals. Three label-free electrochemical immunosensors for the detection of deoxynivalenol mycotoxin (DON) based on the systematic modification of glassy carbon electrodes (GCE) with AuNp/G/PhNO2 was effectively achieved. General electrochemical impedance method was employed for the sensitive and selective detection of DON in standard solutions and reference material samples. A significant increase in charge transfer resistance (Rct) of the sensing interface was observed due to the formation of insulating immune-complexes by the binding of deoxynivalenol antibody (DONab) and deoxynivalenol antigen (DONag). Further attachments of DONab and DONag resulted in increases in the obtained Rct values, and the increases were linearly proportional to the concentration of DONag. The three immunosensors denoted as GCE/PDMA/AuNp/G/PhNH2/DONab, GCE/Nafion/[Ru(bpy)3]2+/AuNp/G/PhNH2/DONab and GCE/Nafion/[Ru(bpy)3]2+/G/PhNH2/DONab have detection range of 6 – 30 ng/mL for DONag in standard samples. Their sensitivity and detection limits were 43.45 ΩL/ng and 1.1 pg/L; 32.14ΩL/ng and 0.3 pg/L; 9.412 ΩL/ng and 1.1 pg/L respectively. This result was better than those reported in the literature and compares reasonably with Enzyme Linked Immunosorbent Assay (ELISA) results. The present sensing methodology represents an attractive alternative to the existing methods for the detection of deoxynivalenol mycotoxin and other big biomolecules of interest due to its simplicity, stability, sensitivity, reproducibility, selectivity, and inexpensive instrumentation. And they could be used to develop high-performance, ultra-sensitive electrochemiluminescence, voltammetric or amperometric sensors as well.