Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

The syntheses, spectral and electrochemical characterization of new family electropolymerizable pyrrole, thiophene and mercaptopyrimidin substituted metallophthalocyanine (MPc) complexes are described. Tetraamino substituted chromium and manganese phthalocyanine complexes were also synthesized and characterized. The spectral and electrochemical results are comparable to literature reports. The complexes formed stable films when deposited on electrode surfaces. The MPc films were formed by electropolymerization, drop-dry method and self-assembling. Nickel hydroxide-like electrodes were formed by electrotransformation of nickel-tetra-4- (pyrrol-1-yl)phenoxy phthalocyanine polymer films to the corresponding PcNi-O-NiPc modified electrodes in alkaline solution. The thiophene, mercaptopyrimidine functionalized MPcs and amino group containing complexes formed good self-assembled monolayers (SAMs) on gold electrode. The electrode modification processes were reproducible. The conductivities of the electrode were dependent on the surface concentrations of the complexes as a function of electropolymerization scan numbers. The electrodes showed good catalytic responses toward L-cysteine, nitrite, nitric oxide (NO), glycine, phenol and its derivative and oxygen. The results also suggest that the presence of thio groups on the ring substituents lowers the oxidation potential of Lcysteine more compared to literature values. The stability of the amperometric responses toward the various analytes is used to diagnose the applicability of the materials for electroanalytical purposes. The limits of detection for L-cysteine, nitrite, NO and glycine were in the range of ~10⁻⁷ to 10⁻⁵ mol dm⁻³.

Some metallophthalocyanine complexes were synthesized and their catalytic activities towards the detection and quantification of the neurotransmitters dopamine, serotonin and histamine were investigated. The study of the possible interaction between these transmitter substances and the metallophthalocyanine complexes was undertaken. Dopamine, serotonin and histamine formed complexes with Iron (II) tetrasulfophthalocyanine. The rate and equilibrium constants obtained for the coordination are in the range of values reported in the literature for ligand coordination to iron phthalocyanine complexes. Carbon paste electrodes of millimetric diameters modified with Iron (II) tetrasulfophthalocyanine exhibited good electro catalytic activity towards the detection and analysis of dopamine and serotonin while at the same time eliminated the problem of interference posed by ascorbic acid in the electrochemical analysis of neurotransmitters. A detection limit of the order of 10-6 mol dm-3 was obtained for both dopamine and serotonin at the modified electrodes. Carbon paste ultra micro electrodes modified with iron (II) tetrasulfophthalocyanine were also used for the detection of dopamine and serotonin as well as the simultaneous determination of dopamine and ascorbic acid in a mixture. The detection limit obtained for dopamine at the ultra microelectrode was 4.2xlO-7 mol dm-3 The electrode kinetics of vitamin BI as well as the stability of the electrode towards its determination was improved upon by modifying carbon paste electrodes with manganese phthalocyanine. The modified electrodes were used for the analysis of vitamin BI in tablets.

No description available.

Magnetoelectrocatalysis is a physical, catalytic process. When magnetic microparticles are incorporated at an electrode surface, increases in current and system efficiency are observed. These enhancements have been observed in both homogeneous and heterogeneous systems. Here, the effects of magnetic fields on three separate, yet related, systems are analyzed: fundamental heterogeneous rate constants at modified electrodes, dye sensitized solar cells (DSSC), and manganese dioxide electrodes for supercapacitor applications. Previous studies of magnetic field effects on homogeneous systems utilized the cation exchange polymer Nafion and transition metal redox probes, such as tris(bipyridine)ruthenium(II) chloride. At electrodes modified with Nafion films, redox probes experience current enhancement in the presence of a magnetic field. This effect is attributed to increased self exchange, known as Dahms Ruff conduction or hopping between redox species. Here, the impacts of magnetic fields on heterogeneous electron transfer, the electron transfer between the redox probe and solid-state electrode, are demonstrated. A derivative of Nafion, TMODA Nafion is used to study the effect. For transition metal complex redox probes, peak splitting in cyclic voltammagrams are lower for magnetically modified electrodes as compared to analogous nonmagnetic films. The effects of magnetic modification of DSSCs are analyzed. DSSCs are photoelectrochemical cells (PECs) that convert incident light (photons) to electrical power (electrons). DSSCs, or Grätzel cells, are heterogeneous, excitonic devices which undergo multiple electron transfer reactions to complete this process. For studies here, magnetic modification of the electrodes occurs in the semiconductor layer. Enhancements in current density, fill factor, and power output are observed in variety of systems, both n-type and p-type, on glass and PET substrates, utilizing different magnetic microparticles. Lastly, the effects of magnetic fields on the electrochemistry of electrolytic manganese dioxide (EMD) electrodes are examined. Manganese dioxide is an abundant, naturally occurring oxide of manganese that is used ubiquitously in alkaline batteries. manganese dioxide; is a complex material, existing, as many transition metal oxides do, in several polymorphs, each with unique properties. For the studies here, the use of manganese dioxide as a capacitor material in mild aqueous systems is considered. In comparison to traditional electrochemical capacitors, manganese dioxide undergoes both non-faradaic and faradaic charge storage. Magnetic field effects look to exploit this faradaic, pseudocapacitant behavior as a mechanism for increasing this power source's energy and power density.

No description available.

Paper-based microfluidic devices have been a promising device platform for point-of-care diagnostic applications. It is known for its cost-effective and simple nature. Various analytes, such as metabolites, electrolytes, and pathogens, have been quantified in various applications. One of the key advantages of paper-based devices is the inherent property of capillary flow, which allows for the transport of fluids without the need for external pumping. However, since their discovery, applications of paper-based microfluidics have become increasingly complicated. Using expensive materials or complex surface modification to push the device's performance to its limits. Many have lost sight of what made paper-based microfluidic devices attractive in the first place. Despite these advances and recently reported devices having extremely low sensitivity, none have been commercialized, like the first testing strips. This thesis presents a novel material that can mimic the properties of paper. The proposed material can be easily printed onto carbon electrodes to form a printed microfluidic device. The fabrication process is cheap and scalable for mass production. Unlike existing devices, the proposed material allows for a completely new area of design and optimization. This technology successfully demonstrated that it could similarly transport fluids to paper and the electrochemical detection of glucose. The results show that the printed microfluidic devices could detect glucose with high sensitivity and low detection limits, making them potentially useful for medical diagnostics. The material was also integrated onto commercially available screen-printed electrodes and shown to improve performance. The composition of the material is flexible and capable of being tuned for specific needs. For example, semi-conductive microparticles can be integrated for an improvement in electrochemical performance. The results show that the printed microfluidic devices offer a cost-effective, easy-to-produce and reliable alternative to current methods, with potential application in point-of-care testing. / Thesis / Master of Applied Science (MASc) / This thesis presents a novel material that can mimic the properties of paper. The proposed material can be easily printed onto carbon electrodes to form a printed microfluidic device. The fabrication process is cheap and scalable for mass production. The material can transport fluids via capillary action much like paper can, and can also handle glucose detection using electrochemical methods. The results show that the printed microfluidic devices could detect glucose with high sensitivity and low detection limits, making them potentially useful for medical diagnostics. This technology, also successfully integrated other microparticles into its composition to boost its electrochemical performance and improve its sensitivity. This novel material offers a cost-effective, easy-to-produce, and reliable alternative to current methods, with potential application in point-of-care testing.

A research project submitted to the University of the Witwatersrand, Faculty of Humanities, Wits School of Education, in partial fulfilment of the requirements for the degree of Master of Science in Science Education. November 2014 / This study was on the investigation of the effectiveness of the Sci-Bono outreach programme in the teaching of electrochemistry at grade11. Two aspects were used to measure effectiveness. The first aspect was a change in learners’ ability to answer questions before and after intervention. The second aspect was the programme’s ability to eliminate common misconceptions in electrochemistry. A sample of five schools was used in the study. At each school a pre-test was given to learners before intervention and a similarly structured and equally difficult task was given after intervention as a post-test. The marks for each learner were compared and the results for each school were analysed using a Wilcoxon signed rank test and a paired data test. Results from both methods of analysis reflected significant improvement in learners’ ability to answer questions after intervention at all five schools that made the sample of the research. A question by question analysis was also done to check a change learners’ ability to answer specific questions. Improvement in answering particular questions differed significantly, pointing out that certain concepts had been grasped better than others. Interviews were held with both learners and their teachers. These interviews were held to try and determine the extent to which misconceptions had been identified and eliminated. Pre-tests and post-test analysis reflected that one common misconception, where learners define oxidation and reduction in terms of addition and removal of oxygen was completely eliminated. Learner interviews however reflected a 75% success rate in the elimination of the misconception. Analysis of pre-tests and post-test results also showed a 75% success rate in the elimination of a misconception of the second misconception, where learners take an oxidising agent as a substance that has been oxidised and a reducing agent as a substance that has been reduced, compared to 76% from analysis of the learners’ interview results. Teacher interview results also reflected that the Sci-Bono outreach programme is to a high degree able to eliminate common misconceptions electrochemistry. From lesson observation and teacher interviews another misconception came to light. The misconception held by some learners is that ‘the oxidation number is the number of oxygen atoms in the molecule of a compound.’ This misconception was also tackled. During teachers’ interviews it emerged that all host teachers perceive the Sci-Bono Subject Matter Experts as effective in eliminating the identified common misconceptions in electrochemistry. The researcher is convinced that the Sci-Bono outreach programme improves the learners’ ability to answer questions in electrochemistry and that they address misconceptions in their teaching. The intervention however does not completely eliminate common misconceptions in electrochemistry. The Sci-Bono outreach programme is thus only effective to a certain extent in the teaching of electrochemistry at grade 11. The study also revealed that the teachers at schools expect the Sci-Bono Subject Matter Experts to have better pedagogical skills and they also expect them to bring scarce resources when they visit schools. They expect them to be able to tackle all formal and informal experiments covered in the grade11 curriculum. They believe that, in addition to enabling the elimination of misconceptions, the practicals carried out by the Sci-Bono SMEs also enhance understanding and provide practical skills to learners.

Thesis (doctoral)--Lunds universitet, Malmö, 1981. / Includes the author's five published papers. Extra t.p. with thesis statement inserted.

Conducting diamond electrodes provide unique advantages for electrochemistry such as a wide potential window, low baseline current, chemical inertness and resistance to fouling. De Beers boron-doped diamond electrodes, manufactured by chemical vapour deposition and containing varying amounts of boron, were therefore investigated in order to determine their suitability for future electrochemical applications. These electrodes were initially characterised using techniques such as SEM, LA-ICP-MS, Raman spectroscopy and XPS. The electrochemical behaviour of these electrodes was investigated in two redox systems (potassium iron (III) cyanide and cerium (III) sulphate) and two biological systems (dopamine and ascorbic acid). These results were compared against that of the conventional glassy carbon electrode. Porous boron-doped diamond, a novel electrode material, was used for the electrochemical detection of thyroid hormones (L-T3 and L-T4). These hormones have never previously been investigated using a boron-doped diamond electrode. The De Beers boron-doped diamond electrode was found to outperform the conventional glassy carbon electrode, which fouled very easily, in the detection of dopamine. Peak separation between dopamine and the interfering ascorbic acid was attained at a pretreated boron-doped diamond electrode. The feasibility of detecting thyroid hormones using a porous boron-doped diamond electrode was demonstrated, and the electrode material was patented. / Dissertation (MSc (Chemistry))--University of Pretoria, 2006. / Chemistry / unrestricted