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Scholz, Sunna [Verfasser]. "Qualifizierung eines Voltammetrie-Messsystems / Sunna Scholz." Berlin : Freie Universität Berlin, 2014. http://d-nb.info/104631291X/34.
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Scholz, Sunna Veronika [Verfasser]. "Qualifizierung eines Voltammetrie-Messsystems / Sunna Scholz." Berlin : Freie Universität Berlin, 2014. http://nbn-resolving.de/urn:nbn:de:kobv:188-fudissthesis000000095831-5.
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Rühling, Irina. "Anwendung voltammetrischer Verfahren in Kopplung mit der HPLC zur Charakterisierung redoxaktiver Wirkstoffe." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=957160879.
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Bestry, Joanna [Verfasser]. "Neue Konzepte in der Voltammetrie : tropfende Kohleelektrode und ionische Flüssigkeiten / Joanna Bestry." Berlin : Freie Universität Berlin, 2012. http://d-nb.info/1027815863/34.
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Channaa, Hanan [Verfasser]. "Neue Flüssigmetallelektrode als Alternative zur Quecksilberelektrode : Galinstan in der Voltammetrie / Hanan Channaa." Saarbrücken : Südwestdeutscher Verlag für Hochschulschriften, 2012. https://www.svh-verlag.de.
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Channaa, Hanan [Verfasser]. "Eine neuartige Metallelektrode als Alternative zur Quecksilberelektrode : Galinstan in der Voltammetrie / Hanan (geb. Zeyat) Channaa." Berlin : Freie Universität Berlin, 2008. http://d-nb.info/1023170396/34.
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BOUAZIZ, DJEMAI. "Etude de catalyseurs a base d'heteropolyanions en phase homogene et dans des matrices de polymeres : voltammetrie cyclique et spectroscopies." Paris 11, 1991. http://www.theses.fr/1991PA112165.
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Ce travail examine quelques-unes des larges possibilites offertes par les isopoly et heteropolyanions dans le domaine des etudes physicochimiques et de la catalyse redox ou chimique, homogene ou supportee. C'est ainsi que nous avons montre que des heteropolyanions judicieusement choisis, sont des substrats nouveaux pour l'etude des effets de solvants sur les potentiels redox d'espece anioniques. Par rapport aux seuls exemples connus de la litterature, les interactions entre solvants et les atomes d'azote de complexes hexacyano sont remplaces par des interactions avec des atomes d'oxygene. Les resultats s'interpretent parfaitement dans le cadre d'une approche fondee sur des interactions de type lewis, exprimees quantitativement par exemple, par les nombres accepteurs du gutmann. Par ailleurs, un aspect important de la reduction catalytique de l'oxygene par les heteropolyanions a ete aborde: il s'agit d'etudier la stabilite en presence du produit final, en l'occurrence l'eau oxygenee, d'heteropolyanions sous forme oxydee, ou sous forme reduite. Il a ete trouve que les heteropolyanions qui, sous forme oxydee, dont stables a l'eau oxygenee participent sous forme reduite a la catalyse de reduction de h#2o#2. Les constantes de vitesse de ce processus ont pu etre evaluees. Dans le cas de l'anion phosphotungstique qui reagit avec l'eau oxygenee, les conditions qui permettent de preparer des derives peroxy en conservant ou non la structure de keggin ont ete mises en evidence. Au cours de ce travail nous avons egalement montre comment il est possible de preparer des composites dans lesquels les oxometallates sont inclus dans des polymeres conducteurs. Ces composites, utiles pour les etudes et les applications des isopoly et heteropolyanions en catalyse, peuvent etre formes de maniere stable et reproductible. Il a ete possible de separer les proprietes de conduction du polymere de la fonction d'immobilisation d'oxometallate en faisant appel a des entites presentant des proprietes intrinseques d'echange d'anion. Enfin, la synthese et la stabilisation a l'interieur d'une matrice polymere d'especes labiles a ete montrees. Ainsi, l'etude electrochimique du decatungstate ou de derives peroxy, s'est trouvee facilitee, illustrant un des aspects importants des electrodes modifiees
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Koelsch, Magali. "Nanoparticules de TiO2 : contrôle structural, morphologique, dimensionnel et propriétés électrochimiques." Paris 6, 2004. http://www.theses.fr/2004PA066175.
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PRAT, NOYON EVELYNE. "Etude par voltammetrie cyclique et impedancemetrie, de reactions d'oxydation mettant en jeu les ions oxyfluoroaluminates en milieu cryolithique a 1000c." Paris 6, 1987. http://www.theses.fr/1987PA066588.
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Jbarah, Abdel Aziz. "Spectroelectrochemistry of Substituted Anilines." Doctoral thesis, Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601985.
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Die Elektrochemie und die Spektroelektrochemie von Nitroanilinen (ortho-, meta- und para- Isomere) und deren entsprechenden Diaminoverbindungen (ortho-, meta- und para-Phenylendiamin) wurden an zwei verschiedenen Elektroden (Platin und Gold) und in zwei Elektrolytlösungen (saure und neutrale Perchloratlösung) untersucht. Die erhaltenen Messergebnisse wurden als Referenz für die spektroelektrochemische Untersuchung von Polyvinylaminen mit o- oder p- Nitroanilinsubstituenten verwendet. Es wurden außerdem spektroelektrochemische Untersuchungen mit anderen Polyvinylaminen, die das Wurster Kationradikal oder Stilbene als Substituenten enthalten, durchgeführt. Die oxidative und reduktive Elektrochemie von drei Nitroanilinisomeren wurde in neutraler (0.1 M KClO4) und saurer (0.1 M HClO4) wässriger Elektrolytlösung mit zyklischer Voltammetrie und oberflächenverstärkter Ramanspektroskopie (Surface Enhanced Raman Spectroscopy SERS) untersucht. Die zyklischen Voltammogramme, die mit einer Goldelektrode in saurer Elektrolytlösung für o- und p-Nitroanilin aufgezeichnet wurden, zeigten die Bildung von o- und p-Phenylendiamin beim Potenzialdurchlauf in kathodischer Richtung. In neutraler Elektrolytlösung ist die Situation anders und die Endprodukte der elektrochemischen Reduktion dieser Isomere sind o- und p- Amino-N-phenylhydroxylamin. Aus den zyklischen Voltammogrammen, die mit Gold- und Platinelektroden bei anodischem Potenzialdurchlauf für diese Isomere in saurer und neutraler Elektrolytlösung aufgezeichnet wurden, erhält man folgende Reihenfolge für die Lage der Oxidationspotentiale m-Nitroanilin > p-Nitroanilin > o-Nitroanilin. Eine Sauerstoff-Gold-Adsorbat- Streckschwingung wurde zwischen 400 und 430 cm-1 in den SER-Spektren der drei isomeren Nitroaniline in beiden Elektrolytlösungen bei positiven Elektrodenpotenzialen beobachtet. Das SERS-Experiment zeigte auch eine senkrechte Orientierung der adsorbierten Nitroaniline zur Oberfläche der Goldelektrode. Für die isomeren Phenylendiamine wurde in beiden Elektrolytlösungen und mit beiden Elektroden im anodischen Durchlauf das gleiche Verhalten beobachtet. Das beim Ein- Elektronenübergang erhaltene Oxidationsprodukt (Radikalkation) reagiert im Fall von o- und m- Phenylendiamin über eine C-N-Kopplung mit einem weiteren Radikal zum Dimer (1.Schritt der Elektropolymerisation). p-Phenylendiamin wird nach dem ECE-Mechanismus (E = Elektronentransfer, C = chemische Reaktion) oxidiert, wobei die Ladungsübertragung in zwei Schritten erfolgt, gekoppelt mit Säure-Base-Reaktionen, was zur Bildung des Diimin führt. Aus den SERS-Messungen kann man schlussfolgern, dass m- und p-Phenylendiamin waagerecht zur Metalloberfläche über den Benzenring und die Stickstoffatome adsorbiert sind. Die Adsorption von o-Phenylendiamin erfolgt über die Stickstoffatome und mit schräger Orientierung zur Metalloberfläche. Die zyklischen Voltammogramme, die mit einer Goldelektrode in saurer und neutraler Elektrolytlösung von den Polyvinylaminen mit Nitroanilinsubstituenten aufgenommen wurden, zeigen dasselbe Verhalten wie Nitroanilinmonomere beim Potenzialdurchlauf in kathodischer Richtung. Die für diese Polymere im anodischen Durchlauf erhaltenen Zyklovoltammogramme unterscheiden sich von denen für die Monomere. Die Zahl der Adsorptionsplätze und die Adsorptionsstärke der Polyvinylamine verändern sich in Abhängigkeit vom Elektrodenpotential, vom Prozentsatz und der Art des aromatischen Substituenten am Polymerrückgrat und vom pH-Wert der LösungThe electrochemistry and spectroelectrochemistry of nitroanilines (ortho, meta, and para isomers) and their respective amino compounds (ortho-, meta- and paraphenylenediamines) have been investigated at two different electrodes (platinum and gold) and in two different electrolyte solutions (acidic and neutral perchlorate). The results of these investigations were used as a reference for the spectroelectrochemistry of polyvinylamines containing o- or p-nitroaniline substituents. Spectroelectrochemical investigations of polyvinylamine containing Wurster radical cation or stilbene as a substituent were also carried out. The oxidative and reductive electrochemistry of the three isomeric nitroanilines has been studied in neutral (0.1 M KClO4) and acidic (0.1 M HClO4) aqueous electrolyte solutions with cyclic voltammetry and Surface Enhanced Raman Spectroscopy (SERS). The cyclic voltammograms recorded with a gold electrode in acidic electrolyte solution showed formation of o- and p-phenylenediamine in the negative going potential scan for o- and pnitroaniline respectively. In neutral electrolyte solution the situation is different and the final products of electrochemical reduction of these isomers are o- and p-amino-Nphenylhydroxylamine. The order of increasing electrochemical oxidation potential is mnitroaniline > p-nitroaniline > o-nitroaniline as observed from cyclic voltammograms recorded with a gold and platinum electrodes and in the positive going potentials scan for these isomers in acidic and neutral electrolyte solutions. An oxygen-gold adsorbate stretching mode was detected between 400 to 430 cm-1 in SER-spectra of the three isomeric nitroanilines in both electrolyte solutions at positive electrode potentials. The SERS experiments showed also a perpendicular orientation of adsorbed nitroanilines on a gold electrode with respect to the metal surface. General trends are observed in the anodic scans of isomeric phenylenediamines at both electrodes and in both electrolyte solutions. The one-electron electrochemical oxidation product (radical cation) in case of o- and m-phenylenediamine go into fast C-N coupling between radicals to form dimers (the first step of electropolymerization). The pphenylenediamine is oxidized according to an ECE mechanism (E = electron transfer reaction, C = chemical reaction), which involved two charge transfer steps coupled with acidbase reactions to form diimine. As we deduced from SERS measurements, m- and p-phenylenediamine adsorbed in flat orientation with respect to the metal surface via benzene ring and nitrogen atoms, respectively. o-Phenylenediamine adsorption is taking place via nitrogen atoms and with tilted orientation with respect to the metal surface. The cyclic voltammograms recorded with a gold electrode in acidic and neutral electrolyte solutions of polyvinylamines containing o- or p-nitroaniline substituents exhibit the same features like nitroaniline monomers in the negative going potentials scan. The result observed in the anodic scan for these polymers are different from those observed for monomers. Adsorption site and strength of the polyvinylamine polymer varies according to the applied electrode potential, percentage and type of the aromatic substituent at the polymer backbone, and the pH of the medium
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BAGEL, OLIVIER. "Mise au point et etude d'une electrode serigraphiee recouverte par un film de nafion. Applications de la voltammetrie par echange d'ions aux dosages enzymatiques par affinite." Clermont-Ferrand 2, 1998. http://www.theses.fr/1998CLF22039.
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Au cours d'une immunoanalyse enzymatique, c'est le produit genere par l'enzyme utilisee comme marqueur qui doit etre sensiblement detecte. L'utilisation d'electrodes modifiees par un film de nafion, polymere polyanionique qui accumule selectivement les cations hydrophobes, permet d'exalter la detection electrochimique du produit enzymatique apres son accumulation dans le film de nafion. Ce concept implique d'une part un couple substrat/produit (s/p) de la phosphatase alcaline (ap), tel que s soit anionique (discrimine par le nafion) et p cationique (accumulation directe mais irreversible dans le nafion), et d'autre part une electrode modifiee par un film de nafion, a usage unique, produite en masse et de faible cout. Nous avons developpe une electrode serigraphiee a base d'une encre de graphite dont nous avons mis au point la formulation. La modification par du nafion est effectuee par depot de 1 l d'une solution diluee de nafion dans l'ethylene glycol pour constituer un film de 1,9 m. Un dosage indirect de l'ap a ete realise avec une limite de detection de 4 10##1#6 m. Apres avoir adapte a des micropuits de 200 l les electrodes serigraphiees et modifiees, nous avons realise deux types differents de dosages enzymatiques par affinite : l'immunoanalyse enzymatique de l'hormone hcg et le dosage de fragments d'adn de cytomegalovirus. Dans les deux cas, lorsque le marqueur enzymatique est l'ap, la detection electrochimique s'est revelee 16 fois plus sensible qu'une detection colorimetrique. Afin de modeliser le comportement de telles electrodes modifiees, nous avons etudie les processus d'accumulation et de diffusion d'especes cationiques dans un film de nafion. Nous avons montre pour deux molecules differentes que la constante de partage ainsi que le coefficient de diffusion evoluent avec l'epaisseur du film de nafion. La simulation mathematique de ces deux variations permet de prevoir l'epaisseur optimale de nafion pour obtenir un courant de pic maximal.
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Kubeil, Clemens [Verfasser], Andreas [Akademischer Betreuer] [Gutachter] Bund, and Alexander [Gutachter] Eychmüller. "Zum Einfluss elektrochemischer Doppelschichten auf den Stofftransport in nanoskaligen Elektrolytsystemen: : Leitfähigkeit von Nanoporen und Voltammetrie an Nanoelektroden / Clemens Kubeil ; Gutachter: Alexander Eychmüller, Andreas Bund ; Betreuer: Andreas Bund." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://d-nb.info/1126922226/34.
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Osipovich, Nikolai P., Sergei K. Poznyak, Vladimir Lesnyak, and Nikolai Gaponik. "Cyclic voltammetry as a sensitive method for in situ probing of chemical transformations in quantum dots." Royal Society of Chemistry, 2016. https://tud.qucosa.de/id/qucosa%3A36419.
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The application of electrochemical methods for the characterization of colloidal quantum dots (QDs) attracts considerable attention as these methods may allow for monitoring of some crucial parameters, such as energetic levels of conduction and valence bands as well as surface traps and ligands under real conditions of colloidal solution. In the present work we extend the applications of cyclic voltammetry (CV) to in situ monitoring of degradation processes of water-soluble CdTe QDs. This degradation occurs under lowering of pH to the values around 5, i.e. under conditions relevant to bioimaging applications of these QDs, and is accompanied by pronounced changes of their photoluminescence. Observed correlations between characteristic features of CV diagrams and the fluorescence spectra allowed us to propose mechanisms responsible for evolution of the photoluminescence properties as well as degradation pathway of CdTe QDs at low pH.
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Trippé, Gaëlle. "Du macrocycle complexant à l'electrode modifiée : synthèse et propriétés." Angers, 2001. http://www.theses.fr/2001ANGE0028.
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Plusieurs récepteurs moléculaires de cations métalliques, associant l'unité tétrathiafulvalène à un site complexant ont été synthétisés. L'optimisation structurale par rapport aux systèmes initiaux concerne à la fois : le site électroactif (l'utilisation d'un squelette bis-pyrrolo TTF permet ainsi d'éviter les problèmes d'isomérisation Z/E rencontrés dans les dérivés rétrathio TTF) ; l'unité complexante (la préparation de macrocycles variant tant par leur taille (chaîne polyoxaéthylène) que par leur nature (chaîne polyéther, diaza-tétraoxa-18-couronne, dioxocyclame) doit permettre le piégeage d'autres cations métalliques). Ces synthèses ont pu être menées à bien en utilisant des techniques de haute-pression ou de haute-dilution. Les propriétés complexantes de ces molécules hôtes ont été évaluées à l'aide de différentes méthodes (spectrométrie de masse, RMN, spectroscopie UV-visible et voltammétrie cyclique). On peut notamment souligner les propriétés complexantes sans précédent en série TTF, d'un de ces récepteurs à l'égard de Ba2+ et Pb2+. Le caractère modulable des constantes de complexation en fonction du potentiel électrochimique appliqué a pu être démontré par voltammétrie cyclique. . . . .Several molecular receptors of metallic cations, associating the tetrathiafulvalene unit to a chelating site have been synthesized. The design optimization, in relation to the basic systems concerns : the redox site (the choice of a bis-pyrrolo TTF skeleton avoids the Z/E isomerization problems met with the tetrathio TTF derivatives) ; the chelating unit (the preparation of macrocycles varying by their size (polyoxaethylene chains) or by their nature (polyether chain, diazacrown, dioxocyclam) should allow trapping of other cations. These syntheses have been carried our using high-pressure or high-dilution techniques. Complexation properties of these host molecules have been determined using different methods (mass spectrometry, NMR, UV-visible spectroscopy and cyclic voltammetry). Unprecedented properties in the TTF receptors family, for the complexation of Ba2+ and Pb2+, have been found. The switchable character of metal chelation, as a function of the applied electrochemical potential, has been demonstrated by cyclic voltammetry. . .
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Chivot, Jacques. "1) la chronopotentiometrie par redissolution chimique : 2) electrochimie en milieu biphasique." Paris 6, 1988. http://www.theses.fr/1988PA066671.
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Lu, Min. "Voltammetric sensing." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:d99bedee-8055-45a9-a6f6-6066af80d13d.
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Electrochemical analysis using mercury electrodes has been a prominent methodology since the beginning of voltammetry, however, due to its toxic nature their use is being slowly phased out in favour of environmentally friendlier alternatives. In this thesis, carbon electrodes feature heavily as a means to provide a cheaper and non-toxic approach to voltammmetric sensing. Pulse techniques have been used for the sensitive detection of commonly studied analytes, including antimony and iron. A simple fabrication of a vibrating electrode is presented by modifying a commercially available vibrating toothbrush with platinum foil as a means to enhance mass transport for electroanalytical work. Finally, pH determination at carbon electrodes is investigated. Carbon electrodes have been proposed as a simple sensor for pH determination by exploiting the pH sensitive nature of surface quinone groups intrinsic within carbon edge-plane like sites. Using this approach, both EPPG and GC electrodes are suggested as new materials for pH determination and can be used in aqueous solutions over the pH range 1.0 to 13.0, as a cheap and simple alternative to the classic glass electrode.
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Tait, Russell John, and mikewood@deakin edu au. "Development and application of a microelectrode based scanning voltammetric detector." Deakin University. School of Physical and Chemical Sciences, 1991. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20060720.100447.
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A large part of the work presented in this thesis describes the development and use of a novel electrochemical detector designed to allow the electrochemical characterisation of compounds in flowing solution by means of cyclic voltammetry. The detector was microprocessor controlled, which provides digital generation of the potential waveform and collection of data for subsequent analysis. Microdisk working electrodes are employed to permit both thermodynamic and kinetically controlled processes to be studied under steady-state conditions in flowing solutions without the distortion or hysteresis normally encountered with larger sized electrodes. The effect of electrode size, potential scan rate, and solution flow rate are studied extensively with the oxidation of ferrocene used as an example of a thermodynamically controlled process and a series of catecholamines as examples of a kinetically controlled process. The performance of the detector was best demonstrated when used as a HPLC post-column detector. The 3-dimensional chromatovoltammograms obtained allow on-line characterisation of each fraction as it elutes from the column.
The rest of the work presented in this thesis involves the study of the oxidative degradation pathway of dithranol. The oxidative pathway was shown to involve a complex free radical mechanism, dependent on the presence of both oxygen and, in particular light. The pathway is further complicated by the fact that dithranol may exist in either a keto or enol form, the enol being most susceptible to oxidation. A likely mechanism is proposed from studies performed with cyclic voltammetry and controlled potential electrolysis, then defined by subsequent kinetic studies.
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Lefèvre, Guillaume. "Etude mécanistique de réactions de couplage catalysées par des complexes du cuivre et du fer." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00833319.
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L'utilisation de complexes du cuivre et du fer comme catalyseurs de réactions de couplage est d'un grand intérêrt en synthse organique du fait de leur faible coût et de leur basse toxicité. Dans cette thse sont étudiés dans un premier temps les mécanismes de formations de liaisons C-N et C-O catalysés par des complexes du cuivre. Ensuite, le rôle réel du fer dans la catalyse de la formation de liaisons C-N est étudié. Deux exemples de formation de liaisons C-C ferrocatalysées sont enfin étudiés: un couplage de Kochi entre un halogénure aromatique et un réactif de Grignard, ainsi qu'une réaction de cyclisation radicalaire. La voltammétrie cyclique, les modélisations théoriques par calculs DFT ainsi que les spectroscopies de RMN et de RPE ont été utilisés comme outils d'investigation.
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MacKnight, Eric. "An Autonomous, On-Site Sampling / Analyzing System for Measuring Heavy Metal Ions in Ground Water." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1226769402.
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Chami, Zoubida. "Addition de radicaux aryles generes electrochimiquement sur les olefines." Paris 7, 1988. http://www.theses.fr/1988PA077031.
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Reaction d'electrosynthese des liaisons carbone-carbone: addition de radicaux aryles produits par electrochimie-reduction des derives aromatiques halogenes sur des doubles liaisons olefiniques. Etudes theorique et experimentale. Discussion de la regioselectivite des reactions
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Bilal, Salma. "Electrochemical Synthesis and Spectroelectrochemical Characterization of Novel Conducting Poly(o-phenylenediamine-co-o-/m-toluidine)." Doctoral thesis, Universitätsbibliothek Chemnitz, 2007. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200701705.
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In den vergangenen Jahren löste die Nachfrage nach hochwertigen organischen Werkstoffen die Suche nach neuen Materialien mit maßgeschneiderten Eigenschaften für mögliche technische An-wendungen aus. In der vorliegenden Arbeit wurde ein Ansatz entwickelt, neue organische Materia-lien zu synthetisieren, wobei die Untersuchung der Copolimerisation von o-Phenylendiamin (OPD) mit o-Toluidin (OT) und m-Toluidin (MT) in wässriger Schwefelsäure im Vordergrund stand. Da-bei fand die zyklische Voltammetrie sowohl bei der elektrochemischen Synthese als auch für die Charakterisierung der Homo- und Copolymere auf einer Goldelektrode Anwendung. Die Copoly-mere wurden aus gemischten Monomerlösungen synthetisiert, die unterschiedliche OPD-Konzentrationen sowie eine konstante OT- oder MT-Konzentration aufwiesen. Die Voltammogr- amme zeigten ein unterschiedliches Verhalten für die verschiedenen OPD-Konzentrationen bei der Zugabe. Die Mischung der Monomerlösungen mit geeigneten Konzentrationen ergab ein Copolym- er mit einem großen potenziell nutzbaren Bereich der Redoxaktivität relativ zu den korrespondiere- nden Homocopolymeren. Die Homopolymere Poly-o-toluidin (POT) und Poly-m-toluidin (PMT) zeigten ähnliche elektrochemische Eigenschaften. Es wurden jedoch Unterschiede in den Eigensch- aften zwischen den OT- und MT-Copolymeren mit OPD beobachtet, die möglicherweise auf eine Abweichung in den Monomereinheiten und der Ausrichtung entlang der Copolymerkette zurückzu- führen sind. Die Copolymerisation der OPD wird offenbar gefördert, wenn OT statt MT als einer der Comonomere verwendet wird. Weiterhin wurde der Einfluss der Vorschubgeschwindigkeit (dE/dt) und des pH-Wertes auf die elektrochemische Aktivität untersucht. Die Copolymere waren oberflächengebunden, elektrisch aktiv und zeigten sogar bei einem pH-Wert = 8,0 bei Poly(OPT-co-MT) bzw. 9,0 bei Poly(OPT-co-OT) eine gute elektrochemische Aktivität. Die Messungen der in situ Leitfähigkeit unterstützte die Herausbildung eines neuen Stoffes (Copolymer), da die Copo-lymere Elektrodenpotenzialbereiche für eine maximale Leitfähigkeit besitzen, die sich völlig von jenen der Homopolymere unterscheiden. Die Leitfähigkeitswerte der Copolymere lagen zwischen den Werten der Homopolymere. Die in situ UV-Vis spektroelektrochemischen Untersuchungen der Copolymerisation von OPD mit OT und MT bei konstanter potenzieller Polymerisation auf mit Indiumzinnoxid (ITO) be-schichteten Glaselektroden zeigten, dass ein Kopf-Schwanz-verknüpfter p-Aminodiphenylamin (PPD)-Typ eines gemischten Dimers/Oligomers, der wahrscheinlich aus der Dimerisation der Kati-onenradikalen von OPD und OT oder MT resultiert, vorwiegend zu Beginn der Elektropolyme- risation der Mischlösungen entsteht. Ein Absorptionspeak bei λ = 497 nm in den UV-Vis-Spektren wurde diesen Zwischenprodukten zugeordnet. Es erfolgte eine Identifizierung der charakteristi-schen UV-Vis- und Raman- (λ = 647,1 nm) Eigenschaften der Copolymere, synthetisiert mit ver-schiedenen Zugabekonzentrationen auf ITO-beschichtetem Glas bzw. auf Goldelektroden, sowie eine Diskussion ihrer Abhängigkeit vom Elektrodenpotenzial. Die spektroelektrochemischen Er-gebnisse zeigten, dass die Hauptkette des Copolymers wahrscheinlich aus einer Mischung aus Co-polymerketten mit unterschiedlichen Monomergehalten und einer signifikanten Anzahl an Block-segmenten besteht. Die Eigenschaften der Copolymere erwiesen sich als sehr sensibel gegenüber der OPD Zugabekonzentration, so dass eindeutige Änderungen in den elektrochemischen und spektroelektrochemischen Eigenschaften der Stoffe aus Mischlösungen durch bloße Variierung der OPD-Konzentration bei der Zugabe beobachtet werden konnten. Die FT-IR-Spektralanalyse der Copolymere deutet auf die Anwesenheit von sowohl OPD- als auch OT- oder MT-Einheiten und daher auf die Copolymerbildung während der Elektrolyse der Misch-lösungen aus OPD und OT oder MT hin. Die zyklischen Strukturen des Phenazintyps erhöhen sich im Copolymer mit steigender OPD-Konzentration bei der ZugabeIn recent years the demand for advanced organic materials has sparked the search for new materials with tailored properties for possible technological applications. In the present study an attempt has been made to synthesize new organic conducting materials by exploring the possibility of the copolymerisation of o-phenylenediamine (OPD) with o-toluidine (OT) and m-toluidine (MT) in aqueous sulfuric acid. Cyclic voltammetry was used both for the electrochemical synthesis and characterization of the homopolymers and copolymers on a gold electrode. The copolymers were synthesized from mixed solutions of the monomers having different concentrations of OPD and a constant concentration of OT or MT. The voltammograms exhibited different behavior for different concentrations of OPD in the feed. Mixing of the monomer solutions with appropriate concentrations resulted in a copolymer that shows an extended useful potential range of the redox activity relative to the corresponding homopolymers. The homopolymers poly(o-toluidine) (POT) and poly(m-toluidine) (PMT) show similar electrochemical properties. However, differences were observed in the properties between the copolymers of OT and MT with OPD that could be due to the variation in the monomer units and orientation along the copolymer chains. The copolymerization of OPD seems to be more facilitated if instead of MT, OT is present as one of the comonomers. The effect of scan rate and pH on the electrochemical activity was studied. The copolymers were surface confined, electroactive and showed good electrochemical activity even at pH 8.0 and pH 9.0 in case of poly(OPD-co-MT) and poly(OPD-co-OT), respectively. In situ conductivity measurements further suggest the formation of new material (copolymer) because the copolymers have electrode potential regions for maximum conductivity completely different from those of the homopolymers. The conductivity values of the copolymers were between the conductivities of the homopolymers. In situ UV-Vis spectroelectrochemical studies of the copolymerization of OPD with OT and MT at constant potential polymerization on indium tin oxide (ITO) coated glass electrodes reveal that head to tail coupled p-aminodiphenylamine (PPD) type of mixed dimers/oligomers, presumably resulting from the dimerization of OPD and OT or MT cation radicals, are predominantly formed during the initial stages of the electropolymerization of the mixed solutions. An absorption peak at λ = 497 nm in the UV-Vis spectra was assigned to these intermediates. Characteristic UV-Vis and Raman (λex = 647.1 nm) fea-tures of the copolymers synthesized with different feed concentrations on ITO coated glass and gold electrodes, respectively, have been identified and their dependencies on the electrode potential are discussed. Spectroelectrochemical results reveal that the copolymer backbone probably consist of a mixture of copolymer chains with different monomer contents and has significant number of block segments. The properties of the copolymers were found to be very sensitive to the OPD feed concentration and clear variations in the electrochemical and spectroelectrochemical properties of the materials from mixed solutions can be observed just by varying the concentration of OPD in the feed. FT-IR spectral analysis of the copolymers suggests the presence of both OPD and OT or MT units and thus formation of copolymer during the electrolysis of mixed solutions of OPD and OT or MT. The phenazine type cyclic structures increase in the copolymer with increasing OPD concentration in the feed
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Luscombe, Darryl L., and mikewood@deakin edu au. "Studies with voltammetric microdisk electrodes." Deakin University. School of Sciences, 1991. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20051201.153433.
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Szyrokyj, Natalka L. "Microelectrode studies for voltammetric analysis." Thesis, University of Salford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366051.
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Rees, Neil V. "Innovations in voltammetry." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408686.
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Wildgoose, Gregory G. "Modified electrode voltammetry." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432263.
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Adra, Mahmoud. "Voltammetry using microdevices." Thesis, University of Bath, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428375.
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Limon, Petersen Juan Gualberto. "Weakly supported voltammetry." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:c14f972c-8653-41c2-b2d1-b080e691e4dc.
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This thesis is concerned with dynamic electrochemical experiments with different concentrations of supporting electrolyte. Normally supporting electrolyte is added to a solution in order to avoid undesirable effects as migration and potential drop in solution. However, in the present thesis we focus on the study and understanding of such effects as the concentration of supporting electrolyte decreases. First a theoretical treatment is proposed, based on numerical simulation using the Nernst-Planck- Poisson system of equations. The theoretical treatment is compared with previous works as electroneutrality, the differences between both models are explained. The model is also compared with theoretical results to validate the theoretical treatment. Experimental results of chronoamperometry and cyclic voltammograms are compared with theoretical results obtaining remarkable agreement. Is noteworthy that to the best of the author’s knowledge this is the first time that experimental dynamic voltammetry under weakly supported conditions has been successfully modeled by a theoretical treatment. The electrochemical reaction of a non-charged electroactive species is presented for the system ferrocene/ferrocenium in acetonitrile in which the oxidized and reduced species are soluble in solution, the reaction is studied at different concentrations of supporting electrolyte. Comparison is presented between theoretical simulations and experimental results, for which potential drop in solution is studied. Then systems involving charged electroactive species are treated, in these cases the decrease of supporting electrolyte influence the mass transport of the electroactive species due to migration, comparison between different experimental systems as hexaammineruthenium (III)/(II), cobaltoceniun/cobaltocene and hexacyanoferrate (III)/(II) are presented in comparison with theoretical simulations. More complex mechanistic paths are also investigated, such as deposition and stripping, in which it is established that the level of support required to achieve ‘diffusion only’ voltammetry is on dependence of the concentration of amalgamated electroactive species prior to the stripping step. Comparison between theoretical simulation and experimental results of the deposition and stripping of thallium at a mercury hemisphere are presented, and found to be in good agreement for either chronoamperometry and cyclic voltammetry Simulations are also presented showing the necessary required amount of supporting electrolyte required to achieve ‘diffusion only’ cyclic voltammetry. This is obtained by comparison between diffusion only software and the simulation described in the present thesis. The required amount of supporting electrolyte is shown to depend on the concentration of the electroactive species and supporting electrolyte in the media, the electrode radius, the diffusion coefficient of species and the scan rate. Finally, the cyclic voltammetry in weakly supporting media is used to obtain mechanistic information, by using the migration of electroactive species to differentiate the mass transport of electroactive species to the electrode. The two single electron reductions of anthraquinone in acetonitrile is presented, and the comproportionation mechanistic path is observed in weakly supported media, diffusion only voltammetry is normally unable to present whether this mechanism path takes place, due to the similarity in diffusion coefficients of the electroactive species. In contrast in weakly support conditions the diffusion controlled comproportionation mechanistic path is observed experimentally and constraints for the rate constant are discussed.
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Bartlett, Thomas. "Nano-impact voltammetry." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:05ca3e7f-fea4-4d93-9f57-e86a2c397d1f.
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This thesis introduces new concepts to the study of nanoparticles by nano-impact voltammetry. Utilising the special chemistries of metal halide and metal oxide nanoparticles, the use of the nano-impact technique is expanded beyond quantitative sizing towards the study of the in-situ synthesis and detection of nanoparticles, reversible agglomeration behaviour and the fabrication of nanoelectrode arrays. Nano-impact voltammetry is also demonstrated to be an informative tool for the tracking of chemical and photochemical conversion reactions of metal halide nanoparticles and for the mechanistic determination of metallic nanoparticle growth during synthesis. The use of forced convection to gain improvements in the detection limit achievable for the direct-impact of metallic nanoparticles is also reported. Initially, the work reported herein looks at the direct-impact voltammetry of previously unstudied nanomaterials; mercury(I) chloride, silver bromide and bismuth oxide. The first sizing of metal halide nanoparticles is reported as well as a method for synthesising particles through the electrolytic induced implosion of a nanoscale metal halide layer on a liquid electrode. The "upper-limit" of the nano-impact technique is also quantified through the use of silver bromide and silver nanoparticles with diameters approaching 100 nm successfully studied. Next, bismuth oxide nanoparticles are studied by the nano-impact method to probe the reversible agglomeration of particles. By reducing impacting bismuth oxide nanoparticles at the electrode, bismuth deposits are shown to result and can be imaged by scanning electron microscopy. Through the analysis of these deposits, in combination with nanoparticle tracking analysis, experimental evidence for the voltammetrically induced de-agglomeration of nanoparticles is proposed. In the subsequent chapter, nano-impact voltammetry is employed in the study of photochemical reactions. First, the photochemical reduction of silver bromide nanoparticles to silver nanoparticles is followed both by ultra-violet visible spectroscopy and nano-impacts, allowing mechanistic determination of the conversion process. Second, the nano-impact technique is used in combination with ultra-violet visible spectroscopy and transmission electron microscopy for the mechanistic determination of the photochemical Ostwald ripening of silver nanoprisms from silver nanoseeds. Finally, the inter-play between nano-impacts and electrode arrays is reported. Through the electrolysis of impacting silver bromide nanoparticles, it is shown that a functional silver nanoelectrode array can be formed. The formed nanoelectrode array is characterised by the electrocatalytic reduction of hydrogen peroxide. The lowest reported detection limit for silver nanoparticles is also reported, through the combination of a random array of microelectrodes and a specially developed, custom built, and characterised wall-jet flow cell.
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Nakagawa, Yasue. "Protein electrochemistry : applications of sonovoltammetry, microelectrode voltammetry and solid-state voltammetry." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325772.
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Oxley, J. E. "Voltammetric studies in non-aqueous media." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484380.
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Owens, Dale Spencer. "Voltammetry in flowing streams." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/27054.
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Helfrick, John C. "Cyclic square wave voltammetry." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/30681.
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Fietkau, Nicole. "New directions in voltammetry." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442948.
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Davies, Trevor J. "Voltammetry at heterogeneous electrodes." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427873.
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Atcherley, Christopher Wade. "Voltammetric Measurements Of Tonic And Phasic Neurotransmission." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/338965.
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To understand how the brain functions and what disruptions underlie neurological diseases and disorders, analytical methods are needed that can succeed in the complexity of the native brain environment. To make a measurement in functioning, live tissue, these methods must be selective for specific analytes in a matrix that has over 1000 different chemical species, be able to measure chemical changes on multiple timescales (10-3 s to 104 s), have a high spatial resolution (μm), and be sensitive (pM to μM). The work described within, details the development and application of a voltammetric method, fast-scan controlled adsorption voltammetry (FSCAV) that is capable of monitoring baseline levels of serotonin and dopamine, as well as monitoring changes on multiple time scales with high sensitivity and selectivity. Because FSCAV is performed using a carbon-fiber microelectrode, the same sensor can be used for fast-scan cyclic voltammetry to monitor rapid (phasic) changes of dopamine and serotonin in the extracellular space. Thus a single-sensor strategy for measuring tonic and phasic concentrations of these important neurotransmitters is developed and used to elucidate important insight into the differences of serotonin and dopamine regulation. Additionally it is revealed that dopamine exhibits a coaction between tonic and phasic signaling where serotonin does not. Using this approach, a method for evaluating pain processing in a preclinical model is developed, which reveals an important relationship between chronic pain and dopamine signaling. Furthermore, a mathematical model to describe mass-transport limited adsorption is developed and used to determine the diffusion coefficient of both dopamine and serotonin in situ. The work described within details an important advancement in neuroanalytical methodology that will provide new insights both short-term and long-term for studying fundamental chemical mechanisms of neurotransmission.
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Al-Gamdy, Ahmad H. "Adsorptive stripping voltammetric determination of reactive dyes." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/15294.
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The present study was mainly devoted to evaluate the applicability of differential pulse adsorptive stripping voltammetry (DPAdSV) for the determination of ultra-trace concentration levels of a range of reactive dyes. The studied reactive dyes were found to adsorb effectively onto the hanging mercury drop electrode (HMDE). This applied electroanalytical method was primarily based on the nonelectrolytic accumulation (adsorption) of the analyte of interest (reactive dye), followed by a cathodic reduction scan measurement. Consequently, the adsorptive stripping voltammograms of the analysed reactive dyes exhibited several useful electrochemical signals, corresponding to the cathodic reduction of the anthraquinone, azo and halo-striazine groups.
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Hardcastle, J. L. "Novel voltammetric methods in heavily passivating media." Thesis, University of Oxford, 2002. http://ora.ox.ac.uk/objects/uuid:7ef17e49-dd12-4c3b-b2a0-b94605ccb1fa.
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The work contained in this thesis demonstrates that the introduction of power ultrasound into electrochemical systems can broaden the scope of techniques such as anodic stripping voltammetry. Analysis is facilitated by the well-documented phenomena associated with ultrasound, cavitation and acoustic streaming. Cavitation is caused by the collapse of voids created by ultrasonic compression and rarefaction of the solution and results in both localised high temperatures and pressures in the bulk solution and microjetting on the surface. Precise mechanistic details are still open to debate but there is evidence to suggest that shear forces at the interface when the electrode is flushed are responsible for removing organic material (particularly large species such as proteins) facilitating continuous cleaning and activation of the surface. Acoustic streaming has been shown to give diffusion layer thicknesses of the order of 1-10 μm depending on solvent and ultrasound power. The increased mass transport at such low diffusion layer thicknesses results in shorter preconcentration periods in electrochemical stripping voltammetry, greater sensitivity and a correspondingly lowered detection limit. Often ultrasound has been applied to highly passivating systems where conventional silent electroanalysis fails with the effect of transforming invisible or tiny voltammetric signals into large and quantitative responses suitable for sensitive and accurate analytical purposes. In Section IIthe relative contributions of acoustic streaming and cavitationally induced microjetting to the sonovoltammetric response is assessed. Chronoamperometry at insonated electrodes of both micro and macro dimensions, and differential pulse voltammetry (DPV) were used to explore the frequency and violence of cavitational events and the nature of the diffusion layer prevailing under steady-state electrolysis. The results lead to a physical model of an insonated electrode which may be described as a steady diffusion layer a few microns thick brought about by acoustic streaming which is occasionally and randomly punctuated by a cavitational event. The frequency and violence of the event is dependent on the solvent and ultrasound power, except at very short electrode-to-horn separation where the cavitational contribution becomes substantial. Section II concentrates on the implementation of the technique with applications to the detection of heavy metals in biofluids. In Chapter 4 sonoelectroanalysis is applied to the detection of copper bound within human blood protein and whole blood. It is shown that the enhancement of square wave anodic stripping peaks observed in ceruloplasmin and whole blood is not simply due to mass transport enhancement and cavitational cleaning effects alone but also the liberation of copper from the active sites in which it is bound prior to preconcentration. The results of a quantitative determination of total copper in two samples of whole blood were 1300 μg L-1 and 620 μg L-1, verified by independent blind analysis using atomic absorption spectroscopy (AAS). The need for rapid analysis of environmental samples can also be fulfilled using sonoelectroanalysis. In Chapter 5 fish gill mucus is used as a non-destructive biomarker for the detection of heavy metals by sono-square wave anodic stripping voltammetry (sono-SWASV). A quantitative assessment of copper content yielded values of 16 μgL-1 and 21 μgL-1 which compared favourably with independent blind analysis by AAS. The potential of the technique for detection of other heavy metals for example lead, was also demonstrated. Lead poisoning is recognized as a major environmental health risk and in Chapter 6 quantitative analysis of lead in artificial saliva from a realistic sputum volume, 220 μL, introduced to acetate buffer is investigated. An insonated preconcentration obviates the need for lengthy or degradative sample pretreatment by liberating the lead from the glycoproteins and other materials to which it binds in solution. Quantitative depassivation of the electrode surface by cavitational shearing maintained the analytical signal throughout the experiment where under silent conditions the signal diminished to zero with time. The detection limit in the analyte is 0.25 μg L-1. Following this proof of concept, Chapter 7 goes on to apply the technique to the quantitative determination of lead and cadmium in real human saliva. Close agreement between lead concentration determined by sono-SWASV and independent and blind ICP-MS is reported for human saliva samples with detection limits of 0.5 μg L-1 lead and 1 μg L-1 cadmium in saliva. Section IV harnesses the benefits of acoustic emulsification. Power ultrasound is capable of forming droplets of micron dimensions with lower energy consumption than conventional emulsifiers. Chapter 8 acoustic emulsification is employed in the detection of vanillin (4-hydroxy-3-methoxybenzaldehyde) in vanilla essence using ethyl acetoacetate as a novel electrochemical and sonoelectrochemical solvent. Contrasting with silent voltammetry, ultrasound facilitates emulsification and extraction of vanillin in the extract permitting an analytical square wave voltammetric signal to be obtained. Close agreement with a blind analysis of the samples using HPLC-UV is observed with a limit of detection in the biphasic medium of 0.020 mM. In Chapter 9 acoustic emulsification is utilized in the solvent extraction of copper. Ultrasonic emulsification of an aqueous phase containing copper ions with the N-benzoyl-N-phenyl-hydroxylamine ligand in an organic ethyl acetate phase was shown to facilitate the extraction of copper into the organic phase at 25°C. Subsequent emulsification with 1 M acid "back-extracts" or "re-strips" the copper into the aqueous phase prior to analysis via sono-SWASV. The technique necessarily removes contaminants present in the test solution since these will prefer to remain in the initial aqueous phase, or will transfer to the organic phase but are unlikely to be doubly transferred into the "clean" final aqueous phase. In Chapter 10 the technique is applied to the analysis of copper in the soft drink "Ribena® Light" with a detection limit of 2 μg L-1 and copper in blood with a detection limit of 0.16 μg L-1. In the latter case the analysis required a sample volume of 100 μL suggesting that a pinprick test may be feasible. Finally in Section V, the analysis of copper in the presence of surfactants is investigated. Surfactant adsorption has been shown to have a passivating effect on the electrode surface during anodic stripping voltammetric measurements. Effluent, both industrial and domestic, is commonly contaminated with surfactant and electroanalysis of heavy metals is frequently precluded. It is therefore desirable to formulate a new analytical strategy in waste water. This is facilitated by controlled experiments with known amounts of anionic, cationic or neutral surfactant which also provides an ideal model system for comparing the techniques introduced in earlier Chapters. "Direct" sonoelectroanalysis in the medium of interest is compared with biphasic sono-solvent double extraction and both are appraised in the light of novel sonotrode technology. This thesis concludes that sonoelectroanalysis is a powerful and versatile analytical tool that can be employed in an expanding range of applications. The examples given herein are pertinent to the major fields of medical diagnosis and the assessment of environmental pollution. They demonstrate that sonoelectroanalysis is a viable alternative to conventional analytical techniques which have the disadvantages of more lengthy sample pretreatment and cost.
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Baxter, R. I. "Voltammetric studies of some important antihistamine drugs." Thesis, Queen's University Belfast, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374204.
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Brimecombe, Rory Dennis. "Voltammetric analysis of pesticides and their degradation." Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1015724.
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Amitraz is a formamide acaricide used predominantly in the control of ectoparasites in livestock and honeybees. Amitraz hydrolysis is rapid and occurs under acidic conditions, exposure to sunlight and biodegradation by microorganisms. The main hydrolysis product of amitraz, 2,4-dimethylaniline, is recalcitrant in the environment and toxic to humans. An electrochemical method for the determination of total amitraz residues and its final breakdown product, 2,4-dimethylaniline, in spent cattle dip, is presented. Cyclic voltammetry at a glassy carbon electrode showed the irreversible oxidation of amitraz and 2,4-dimethylaniline. A limit of detection in the range of 8.5 x 10⁻⁸ M for amitraz and 2 x 10⁻⁸ M for 2,4-dimethylaniline was determined using differential pulse voltammetry. Feasibility studies in which the effect of supporting electrolyte type and pH had on electroanalysis of amitraz and its degradants, showed that pH affects current response as well as the potential at which amitraz and its degradants are oxidised. Britton-Robinson buffer was found to be the most suitable supporting electrolyte for detection of amitraz and its degradants in terms of sensitivity and reproducibility. Studies performed using environmental samples showed that the sensitivity and reproducibility of amitraz and 2,4-dimethylaniline analyses in spent cattle dip were comparable to analyses of amitraz and 2,4-dimethylaniline performed in Britton-Robinson buffer. In addition, the feasibility qf measuring amitraz and 2,4-dimethylaniline in environmental samples was assessed and compared to amitraz and 2,4-dimethylaniline analyses in Britton-Robinson buffer. Amitraz and 2,4-dimethylaniline were readily detectable in milk and honey. Furthermore, it was elucidated that 2,4-dimethylaniline can be metabolised to 3-methylcatechol by Pseudomonas species and the proposed breakdown pathway is presented. The biological degradation of amitraz and subsequent formation of 2,4-dimethylaniline was readily monitored in spent cattle dip. The breakdown of amitraz to 2,4-dimethylaniline and then to 3-MC was monitored using cyclic voltammetry.
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Gelis, Laurence. "Reactivite electrochimique des halogenures de trifluoromethyle." Paris 7, 1988. http://www.theses.fr/1988PA077064.
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Etude par voltammetrie lineaire et par coulometrie, du mecanisme d'oxydoreduction des halogenures de trifluoromethyl sur une electrode de carbone dans le dmf. La deuxieme partie decrit les essais de trifluoromethylation de differents substrats organiques (aldehyde, styrene)
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Wellington, Geoffrey R. "Novel aspects of hydrodynamic voltammetry." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334277.
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Hutchings, M. J. "Voltammetry of metal dialkyldithiophosphate systems." Thesis, Cardiff University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372342.
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Meng, Luwen. "Hydrodynamically modulated voltammetry in microreactors." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288480.
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This thesis describes modulated methods using both voltammetric and microfluidic perturbations to study mechanisms of electrolysis reactions. The initial chapters provide an overview of applications and research development in the fields of micro-engineering and electrochemistry, including microfabrication methodology, electrochemical detection techniques and analysis methods. Some typical electrochemical reactions have been studied for different kinds of industrial applications. Also hydrodynamic modulation methods have been investigated. The result chapters begin in Chapter 3 with detailed investigation of various electrochemical reactions by using cyclic voltammetry (CV) and large amplitude Fourier transformed alternating current voltammetry (FTACV) under microfluidic conditions. Single electron transfer reactions with different kinetics were studied first by using potassium ferrocyanide and ferrocenecarboxylic acid (FCA). Dual electron transfer reactions with different pathways were investigated by using 2,5-dihydroxybenzoic acid for one step oxidation and N,N,N',N'-tetramethyl-para-phenylene-diamine (TMPD) for two consecutive one-electron step oxidation. An irreversible reaction was explored by using borohydride solution. Examples of homogeneous reaction mechanisms were studied by using the combinations of Fe(CN)64-/L-cysteine or TMPD/ascorbic acid. The current response of all the electrolysis reactions except single electron transfer reactions was first reported under microfluidic conditions with FTACV, which has shown sensitive with the change of volume flow rates and the substrate concentrations when homogeneous reactions are involved. The linear relationships between peak current and volume flow rates or substrate concentrations can be obtained in every harmonic component. In chapter 4, the modulated technique was applied to microfluidic hydrodynamic systems. A range of electrolysis mechanisms including single electron transfer reactions, dual electron transfer reactions, irreversible reaction and homogeneous reactions were studied under hydrodynamic modulated conditions. The system showed rapid response with the change of volume flow rates during one measurement. The linear relationships between peak current and flow rates, as well as substrate concentrations, can be obtained simultaneously in one scan, which reveals a promising approach to get more information in a short-time measurement. Chapter 5 demonstrated a new protocol by forcing an oscillation of the electrochemical active solution flowing. Analysis of transition time and its effect on limiting current are presented to begin exploration of this new tool for supporting researchers on understanding redox mechanisms. A short simulated study was carried out to help better understand the mechanism under different hydrodynamic conditions.
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Mizzon, Giulia. "Bioelectrochemistry by fluorescent cyclic voltammetry." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:6a1134dd-c24d-4e60-ac83-936a6918131f.
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Understanding the factors influencing the ET characteristics of redox proteins confined at an electrochemical interface is of fundamental importance from both pure (fundamental science) and applied (biosensory) perspectives. This thesis reports on progress made in the emerging field of coupled electrochemical characterization and optical imaging in moving the analysis of redox-active films to molecular scales. More specifically the combination of cyclic voltammetry and wide-field Total Internal Reflection (TIRF) microscopy, here named ‘Fluorescent Cyclic Voltammetry’ (FCV), was applied to monitoring the response of surface-confined redox active proteins at submonolayer concentrations. The combined submicrometre spatial resolution and photon capture efficiency of an inverted TIRF configuration enabled the redox reactions of localized populations of proteins to be directly imaged at scales down to a few hundreds of molecules. This represents a 6-9 orders of magnitude enhancement in sensitivity with respect to classical current signals observed in bioelectrochemical analysis. Importantly, measurements of redox potentials at this scale could be achieved from both natural and artificially designed bioelectrochemical fluorescent switches and shed fundamental light on the thermodynamic and kinetic dispersion within a population of surface confined metalloproteins. The first three chapters of this thesis provide an overview of the relevant literature and a theoretical background to both the rapidly expanding fields of electroactive monolayers bioelectrochemistry and TIRF imaging. The initial design and construction of a robust electrochemically and optically addressable fluorescent switch, crucial to the applicability of FCV is reported in chapter 5. The generation of optically transparent, and chemically modifiable electrode surfaces suitable for FCV are also described. Chapter 6 describes the response of the surface confined azurin-based switch. Analysis of the spatially-resolved redox reaction of zeptomole samples in various conditions enables the mapping of thermodynamic dispersion across the sampled areas. In chapter 7 the newly developed FCV detection method was extended to investigate more complex bioelectrochemical systems containing multiple electron transferring redox centres and responding optically at different wavelengths. This approach provides a platform for spectral resolution of different electrochemical processes on the same sample. Finally in chapter 8 an electrochemical procedure is proposed for investigating the kinetic response of redox proteins using a fundamentally new methodology based on interfacial capacitance. In using variations in the surface chemistry to tune the rate of electron transfer, the approach was shown to be a robust and facile means of characterising redox active films in considerably more detail than possible through standard electrochemical methodologies. Ultimately, it can be applied to probe dispersion within protein populations and represents a powerful means of analysing molecular films more generally.
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Ho, I.-Pin. "Instrumentation for Multi-Electrode Voltammetry." PDXScholar, 1990. https://pdxscholar.library.pdx.edu/open_access_etds/1141.
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When metal pollutants exist in natural water, their toxicity is dramatically dependent on the chemical species. Numerous sophisticated techniques and instruments have been developed to detect metal pollutants at very low concentration levels. However, one important factor is often ignored, i.e., rarely is species determination required. Electrochemical (EC) methods have the particular advantage of being, in principle, a species-sensitive method rather than an element-sensitive method for the study of metal speciation in natural waters.
The goal of this research was to develop an instrument using the EC technique for speciation and general voltammetric studies. It was accomplished by designing a flow-through EC cell containing multi-electrodes to which various fixed potentials over a selected range were applied. A special potentiostat was designed to supply a selected potential to each electrode in the cell. Potential control was provided by placing a combined counter-reference electrode at circuit ground and connecting each working electrode to the inverting input of a current follower which had a potential applied to its non-inverting input from two digital-to-analog converters and a resistor network. Integrating current followers were used for measuring signal currents generated by the electrolytes samples on each electrode. A multiplexing circuit, including an analog-to-digital converter, was used to fulfill data acquisition. These circuits were interfaced to a computer and the readout was a pseudo-voltammogram which is a plot of amperometric currents versus various applied fixed potentials on each electrode. Details of the instrumentation, software, and some initial results are described.
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Ward, Kristopher R. "Voltammetry of electrochemically heterogeneous surfaces." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:18190ffe-94d7-4d5a-90c8-f65568124280.
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In this thesis, mathematical modelling is used to theoretically investigate the electrochemical behaviour of surfaces which can be broadly classified as being ‘electrochemically heterogeneous’. Simulated voltammetry is used in the exploration of a number of specific systems as listed below. The cyclic voltammetry of electrodes composed of two different electroactive materials that differ in terms of their electrochemical rate constants towards any given redox couple. The effect of the distribution of the two materials was investigated and the occurrence of split peak cyclic voltammetry where two peaks are observed in the forward sweep, was studied. The technique was specifically applied to the modelling of highly-ordered pyrolytic graphite (HOPG). The steady-state voltammetry of a conducting spherical particle resting on an insulating supporting surface. An algebraic expression that completely describes the voltammetric waveform in the limit of irreversible kinetics was developed. The cyclic voltammetry of the EC′ (catalytic) mechanism at a regularly distributed array of hemispherical particles on an insulating supporting surface. Particular attention was paid to the ‘split-wave’ phenomenon, where two peaks are observed in the forward scan of a cyclic voltammogram and the conditions under which these peaks are resolvable were elucidated. The linear sweep voltammetry of micro- and nano-particle modified electrodes and other electrodes of partially covered and non-planar geometry. It was demonstrated that the apparent electrochemical rate constant of the reaction and thus the peak position of the voltammetry is dependent only on the relative electroactive surface area of the particles on the surface and not upon their shape or distribution. This has wide reaching implications as it can be used to explain some instances of a purported nano-catalytic effect without appeal to altered properties at the nanoscale. The linear sweep voltammetry of the interior of a partially electroactive cylindrical pore. Four limiting cases were observed and fully characterised. The linear sweep voltammetry of porous surfaces. It was established that if the pores are less than a certain threshold depth, then a porous surface will also display an apparent catalytic effect that is dependent on the relative electroactive surface area (including the area in the interior of the pores).
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Steiger, George Edward. "Voltammetric investigation of rhenium and technetium tricarbonyl prophyrins." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/26947.
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Amberson, Julie Ann. "Voltammetric study of dihydroxamic acids and their complexes." Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317065.
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Chamsi, Antoine Y. "Voltammetric determination of some antioxidants and other species." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/32899.
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Voltammetric procedures have been developed for the determination of four antioxidants, hydroquinone, butylated hydroxytoluene, butylated hydroxyanisole and n-propyl gallate. The methods are based on the electrochemical oxidation of these antioxidants at a glassy carbon electrode in 1 M acetate buffer in 90% methanol. The mechanism of the oxidation is discussed. These methods are applicable with good precision to quality control applications in the range 1 to 1000 μg ml-1.
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Maunier-Morin, Marie-Christine. "Oxydation électrocatalytique de l'éthanol sur le platine et l'or : effets de structure, étude des mécanismes sur le platine par voltammétrie à potentiel programme et par spectroscopie infrarouge de réflexion." Poitiers, 1988. http://www.theses.fr/1988POIT2308.
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