The electrochemical oxidation of CoCl2(PPh3)2 was investigated in a mixture of acetonitrile and pentanol (1:1) at a platinum disk working electrode using Cyclic Voltammetry (CV) and Chronoamperometry. Elemental Analysis and Infrared Spectroscopy were used to characterise the synthesized compounds i.e. CoCl2(PPh3)2 and CoCl(PPh3)3. Cyclic Voltammetry was utilised for the examination of different working electrode materials that could be used for the anodic voltammetric studies of CoCl2 (PPh3)2, to characterise the reactants and products of each electrode reaction, to investigate the chloride binding ability to a CoCl(PPh3)3 complex, and to evaluate the electrocatalytic substitution of chloride by PPh3 from the complex CoCl2(PPh3)2. Use of ferrocene as an internal standard during the anodic studies of CoCl2(PPh3)2 was also evaluated. The number of electron involved in the electrode process, CoII to CoIII from CoCl2(PPh3)2 and diffusion coefficient of ferrocene in a mixture of acetonitrile and pentanol (1:1) were determined using Chronoamperometry. Ultraviolet-Visible (UV-Vis) and 31P Nuclear Magnetic Resonance (31P NMR) spectra were used to assist with the characterisation of the electrode reactions involved during oxidation of CoCl2(PPh3)2. / Dissertation (MSc (Chemistry))--University of Pretoria, 2008. / Chemistry / unrestricted

This master thesis deals with supercapacitors based on electrical double layer and proper carbon electrodes for this type of supercapacitors. In theoretical part of work is described theory of supercapacitors, energy storage principles and their properties. In the next part are described carbon materials, their properties and electrochemical methods of measurements that we used. In the experimental part is described preparation of electrodes, results and conclusion.

The diploma thesis deals with researching electrodeposition of silicon in anhydrous solutions. As electrolyte was used EC:DMC (1:1) with (C2H5)4NBF4, LiPF6 and LiClO4. Research was measured by cyclic voltammetry and XRD.

This work is focused on optimalisation of coposite materials for civil engineering. In the theoretical part of the project is introduction of the composite materials and materials which are used for their production. There are also concerned their properties and possible application areas. In conclusion of theoretical part this project is a summary of the possible use of composite materials. The practical part compares the characteristics of the different types of composites made in terms of conductivity and the rate of corrosion.

This thesis deals with the mixing of liquids issues. The simulation of structure for mixing of liquids and evaluation of parametres which have most significant influence on mixing of liquids was made with help of COMSOL programm. In the next section of thesis the quality of electrodes used for cyclic voltammetry made on LTCC by thick layer technology was determined. In the end of this thesis the 3D structure for mixing of liquids was made. The quality of mixing was controlled by cyclic voltammetry.

This work deals with the preparation of gold nanostructures for future usage in electrochemical sensors and biosensors, methods for their characterization and production. The emphasis is focused on the template-based electrodeposition method of gold and on study of the effect of manufacturing conditions on physical properties, mainly electrical and topological of nanostructures. Thesis is focused also on overall function and sensitivity of the gold nanostructured electrode.

A series of Fischer mono- and biscarbene complexes of the type [MLn{C=(XR)R'}] was synthesized and characterized. The redox behavior of the complexes was studied by different techniques, including cyclic voltammetry, spectroelectrochemistry, ESR and computational methods. Different transition metals (M) and carbene substituents (XR, R') were employed to compare both the effect of the central metal atom as well as the carbene substituent. Thienyl, furyl and ferrocenyl chromium(0) mono- and biscarbene complexes with ethoxy and amino substituents were electrochemically studied in CH2Cl2. Results were mutually consistent with computational data showing that the carbene double bond of all complexes is reduced pseudo reversibly to an anion radical, -Cr-C•. The Cr centers are oxidized in two successive one electron transfer steps to Cr(II) via the Cr(I) intermediate. For all ferrocenyl carbene complexes the Fe(II) is oxidized after the first oxidation of Cr. It was found that with respect to the aryl substituents the donating effect decreases from Fc>Fu>Th. Stabilization from the XR substituent, where XR = NHR, also resulted in lower redox potentials compared to their OEt analogues. The inclusion of ferrocene in the carbene substituent was done, as its redox activity and increased donating effect are well known. Mono- and biscarbene complexes with ethoxy and amino substituents of both chromium and tungsten were electrochemically studied. Again experimental data were supported by computational studies. Similar to the ethoxy chromium complexes, reduction of the W=C fragment to -W-C• was observed. However oxidation of the Fc group occurred first before the electrochemically irreversible oxidation process for W(0) involving a three electron-mediated process as seen in chronocoulometric analyses. The tungsten oxidation was restricted to a W0/II, consistent with computational studies, by the use of the electrolyte [NnBu4][B(C6F5)4]. The short-lived W(II) species were calculated to be stabilized by agostic CH···W interactions, similar to the chromium analogues. To extend linkers between the metal-carbene termini and investigate metal-metal interaction, biferrocenyl and 2,5-thienylbiferrocenyl tungsten(0) mono-and biscarbene complexes were synthesized and studied by spectroelectrochemistry. A metal-metal charge transfer transition between the tungsten carbonyl increment and the biferrocenyl / 2,5-thienylbiferrocenyl unit was confirmed by infrared spectroelectrochemical studies. The electronic interaction in the corresponding cationic species can be described as weakly coupled class II systems according to Robin and Day. The cymantrenyl moiety, Mn(η5-C5H4)(CO)3, provides an interesting alternative to ferrocene as an organometallic molecular tag, however the instability of the radical cation impairs its use. Improved stability of the cation, monitored by electrochemical measurements, was accomplished by substituting a carbonyl with a ferrocenyl Fischer carbene ligand resulting in Mn(I) oxidation occuring at lower potentials than ferrocenyl oxidation. These uncommon Fischer carbene complexes is the first organometallic multi-tags reported. The mono cationic species, [CpMn(CO)2{=C(OEt)Fc}][PF6], could be isolated and characterized with ESR analysis. Finally, transmetallation from the tungsten(0) Fischer carbene complexes yielded examples of rare acyclic alkoxy- and aminocarbene complexes of gold(I). Single x-ray structures for all complexes could be obtained including the novel ferrocenophane dinuclear biscarbene Au(I) complex. All structures display unsupported aurophilic interactions, while the bridging biscarbene shows a semi-supported Au-Au interaction. In the case of the furanyl/thienyl methoxy monocarbene complexes, extended Au-Au interactions result in oligomeric structures. Although this study is of a fundamental nature, it is imperative for the understanding and design of gold compounds with specific applications. / Thesis (PhD)--University of Pretoria, 2013. / gm2014 / Chemistry / unrestricted

The aim of this thesis is preparation of inverse model catalyst CeOx/Pt(111) and its investigation using combination of surface physics methods and electrochemistry. New electrochemical cell was designed and built for electrochemical experiments. CeOx/Pt(111) samples were prepared and studied in UHV using STM and XPS methods. After that, samples were transferred to the electrolyte environment and studied by means of cyclic voltammetry and AFM. For high surface coverage of CeOx, new reaction was observed. We have identified this reaction as a combination of the reduction of cerium(IV) oxide by interaction with hydrogen adsorbed on the Pt(111) surface and oxidation of cerium(III) oxide by dissociative adsorption of water molecules. Powered by TCPDF (www.tcpdf.org)

Title: Cobalt phthalocyanines as sensors for determination of thiol groups Annotation: The possibility of employment of cobalt phthalocyanine as a material for the modification of HOPG electrode for construction of a sensor for quantification of thiol groups was studied. Thiol groups are occurring in various biologically active substances (sulfur amino acids). The electrochemical behavior of cobalt tetraneopentoxy-phthalocyanine (CoTNPc) in the water/organic phase system was studied, and individual peaks of cyclic voltammogram of the compound were identified. The electrodeposition of CoTNPc on HOPG electrode was found as a suitable method for construction of the sensor for quantification of thiol groups. The reproducibility of fabrication of the sensor and its time-stability was studied. The calibration dependencies for model analytes (cysteine hydrochloride and homocysteine) were measured. Key words: thiols, phthalocyanines, amperometric sensor, cyclic voltammetry

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