Carbon is one of the most plentiful elements on the planet. From a materials perspective, carbon is unique because of the microstructurally distinct allotropes it forms. These include single and polycrystalline diamond, diamond-like carbon, glassy carbon, and graphite. All of these carbon materials are commonly used in electroanalysis, energy storage and conversion, separation, and chemical analysis, due to numbers of reasons, including low cost, high mechanical strength, wide usable potential range, rich surface chemistry, chemical inertness, and compatibility with a variety of solvents and electrolytes. For the optimal usage of carbon electrodes in electrochemistry, it is critical to fully understand and control the variables that impact background voltammetric current, capacitance, and heterogeneous electron-transfer kinetics at these materials. Over the years of carbon electrode usage in electrochemistry, much knowledge has been gained about the structure-function relationship at sp2- and sp3- bonded carbon electrodes. Nevertheless, as most of this knowledge pertains to aqueous electrolyte solution, there is still a significant gap about the properties of the electric double layer and the transport processes near the electrode interface in room temperature ionic liquids. The room temperature ionic liquids are solvent-free medium, composed purely of ions, with a melting point near or below room temperature. In electrochemistry, they are appreciated for several of their excellent properties, such as wide working potential window, moderate electrical conductivity, high thermal and chemical stability, negligible vapor pressure etc. As the RTILs does not contain any solvent, their interfacial structure at an electrified interface is significantly distinguished from the conventional Gouy-Chapman-Stern model describing the double layer in aqueous solutions. Additionally, also the redox analyte environment in RTILs is expected to different compared to those in aqueous solutions. The work in this dissertation thesis is focused on the electrochemical performance of microstructurally different carbon electrodes in aqueous electrolytes and room temperature ionic liquids. The physical, chemical and electronic properties of glassy carbon, boron-doped diamond, and tetrahedral amorphous carbon electrodes are discussed. Furthermore, the microstructure of carbon electrodes is correlated to the heterogeneous electron transfer rate constants of soluble inorganic and organic redox couples in aqueous electrolytes and room temperature ionic liquids. The attention was primarily focused on tetrahedral amorphous carbon electrode that can be doped with nitrogen, resulting in significant physical, chemical an electrochemical properties. Moreover, the electrode surface chemistry was alternated by an oxygen plasma modification and its effect on the electrochemical performance (background voltammetric current, capacitance and electron transfer kinetics), as well as potential surface damage was studied. Lastly, as it is believed that the nitrogen incorporated tetrahedral amorphous material possesses an equally superb properties compared to the boron doped diamond, both electrode materials were used for determination of endocrine disruption compounds, specifically estriol, estradiol and estrone, using high-pressure liquid chromatography with electrochemical detection. The detection figures of merit for both boron doped diamond and nitrogen-incorporated tetrahedral amorphous carbon thin-film electrodes were determined.
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