This work deals with the preparation of liquid electrolytes from different types of aprotic solvents with the aim of their application as electrolytes in electrochemical supercapacitors. Different sorts of aprotic solvents have been chosen, in which the following forms of salts were used: LiBF4, LiClO4,LiPF6. In the next part of the work, the properties of these solvents were measured and the best electrolyte, according to the biggest possible capacity of the system, was chosen. In the theoretical part of this work, the physical principle of supercapacitors and their propeties are described. It deals with electrolytes, their division and with the properties that are appropriate for supercapacitors. The experimental part of the work describes the process of preparation of the samples of electrodes, electrolytes and the techniques of measuring their capacities.

Lead-acid accumulators are the oldest and most common type of secondary cells. There are still some problems to solve. Grid corrosion in sulphuric acid is one of them, which reduced lifetime of lead-acid accumulators. The first part of work is focusing on a general theoretic description of lead – acid accumulators. Following is a description of the workstation and method of measuring. The final part of the text is measuring on an experimental cell.

This thesis deals with diagnostic fuel-cell parameters using electrochemical impedance spectroscopy. The document begins with brief explanation of fuel-cell operation and its basic principles. Thesis continues with description of fuel-cell voltage generation and influence of charge dual-layer on impedance. After that electrochemical impedance spectroscopy, signals used for perturbation and evaluation of impedance spectrum using Bode a Nyquist plot is described. Next part explains measurement of impedance spectrum using potentiostat in combination with lock-in amplifier or frequency response analyzer. Practical part of thesis is dedicated to electric circuit design of EIS module and software designed for automatic measurement of impedance spectrum. Last part shows results of EIS module testing.

Nowadays, nanostructures fixed on solid substrates and colloidal nanoparticles permeate through all areas of human life, in area of sensors and detection as well. This dissertation thesis deals with the fabrication of nanostructures on the surface of planar electrodes via self-ordered nanoporous template of aluminum trioxide. The nanofabrication, as one of many possible techniques, is used to increase the active surface area of electrodes by creating unique surface types with specific properties. These electrodes are very perspective in the applications, such as biomolecules electrochemical detection and measurement. The transformation of aluminum layer into non-conductive nanoporous template in the process of anodic oxidation is a fundamental technique employed to obtain the array of nanostructures in this thesis. The fabrication of high quality nanoporous membranes with narrow pore size distribution on various types of metallic multilayers is one of the key experimental parts in this work. Several problems associated with the production of the thin-film systems, including the dissolving the barrier oxide layer, are discussed and solved. Another part of this work deals with the use of nanoporous membrane as a template for the production of metallic nanostructures via electrochemical metal ions deposition directly into the pores. The obtained nanostructures as nanowires, nanorods or nanodots are characterized by the scanning electron microscopy and energy-dispersive or wavelength X-ray spectroscopy. The electrode surface, modified by gold nanostructures suitable for the detection of biomolecules, has been chosen for the electrochemical measurements, due to the gold biocompatibility. The nanostructured electrodes were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The effect of nanostructured surface geometrical parameters, including the size of the electrochemically active area, on the results of electrochemical measurements has been observed and compared to flat gold electrodes. Two model biomolecules, namely guanine and glutathione, have been chosen for the study of potential application of these nanostructures in biosensors.

The aim of this master’s thesis is electrochemical characteristics evaluation of magnesium alloys. The theoretical part describes the properties of magnesium and its alloys and their corrosion characteristics. In the experimental part are presented results of corrosion resistance measurement of two types of wrought magnesium alloys. It was AZ31 and AZ61 magnesium alloys, which were measured in Hank’s solutions with addition of ions Ca2+ and Mg2+ (SBF+) and without addition of the ions (SBF). The solution temperature during the measurement was 37 ± 1 °C. The experiments were used electrochemical impedance spectroscopy (EIS) and potentiodynamic tests using linear polarization (LP). EIS measurements were done in times of 5 minutes, 1, 2, 4, 8, 12, 24, 48, 72, 96 and 168 hours. Potentiodynamic tests were only short-term and they started after 5 minutes of stabilization. Both methods were used for measuring the electrochemical characteristics of polished and ground surface of the samples. The most important measurement results were polarization resistance, corrosion potential and corrosion current density. The electrochemical measurements are used to estimate the chemical composition influence and alloy’s structure of the corrosion resistance.

Cette thèse a été réalisée initialement dans le cadre du projet Stockage Thermique Appliqué à l’extension de Production d’énergie Solaire thermodynamique (STARS) soutenu par l'Agence De l'Environnement et de la Maîtrise de l'Energie (ADEME).L’objectif du projet est de développer une solution de stockage thermique adaptée à la technologie Fresnel à génération directe de vapeur avec une zone de stockage de chaleur latente. Dans une unité de stockage latent, le nitrate de sodium (NaNO3) a été choisi comme matériau à changement de phase (MCP) et l’acier faiblement allié a été envisagé comme matériau de structure du conteneur et de l’échangeur thermique. La contribution de la thèse se positionne au niveau de l’étude de la corrosion et de la durabilité des matériaux de structure (conteneur et échangeur) en contact avec le MCP. L’objectif est de déterminer une loi de vitesse de corrosion qui permettrait de dimensionner les parois de l’échangeur et de développer des protocoles utilisant les techniques électrochimiques afin de suivre in-situ l’état de la corrosion au sein de l’unité de stockage. Les travaux présentés dans ce manuscrit portent sur l’étude expérimentale de la corrosion de l’acier dans le nitrate de sodium fondu à 340°C en fonction des paramètres expérimentaux tels que la présence d’impuretés (oxydes, chlorures), l’atmosphère gazeuse et le cyclage thermique. L’étude par mesures gravimétriques met en évidence la formation d’une couche de corrosion protectrice en surface de l’acier et la production de nitrite de sodium (NaNO2) par la réaction de corrosion. Cette couche constituée principalement de Fe2O3 (insoluble dans NaNO3 fondu) a été caractérisée par différentes méthodes d’analyse de surface (DRX, XPS). L’évolution de l’épaisseur de la couche de corrosion obtenue par cette technique montre une cinétique de corrosion logarithmique dans NaNO3 pur et une cinétique linéaire en présence d’une teneur importante en impuretés chlorures (10 mol%). L’étude électrochimique a apporté des indications sur le comportement du fer (et de l’acier) dans NaNO3 fondu. En combinant ces données avec les observations expérimentales issues des essais de corrosion nous avons pu proposer un mécanisme réactionnel pour la corrosion de l’acier en milieu nitrate fondu. L’étude par spectroscopie d’impédance électrochimique a permis de valider le mécanisme réactionnel proposé. A l’aide de ce mécanisme, les paramètres cinétiques puis la valeur du courant de corrosion ont été déduits par simulation des diagrammes d’impédance. L’analyse de la variation du courant de corrosion en fonction du temps permet de calculer l’épaisseur de la couche de corrosion et de la comparer à celle obtenue par gravimétrie. Un bon accord entre les valeurs obtenues par différentes techniques a été observé.Au cours de ce travail, nous avons également montré la possibilité d’utiliser les techniques électrochimiques pour l’instrumentalisation des installations industrielles afin de suivre in-situ l’évolution de la composition du MCP et l’état d’avancement de la corrosion de l’acier.Enfin, ce travail a montré que l’acier faiblement allié est adapté pour être utilisé dans une unité de stockage latent avec le nitrate de sodium comme matériau à changement de phase. / This thesis was originally performed as part of the STARS project (Stockage Thermique Appliqué à l’extension de Production d’énergie Solaire thermodynamique) which was supported by ADEME (l'Agence De l'Environnement et de la Maîtrise de l'Energie). The objective is to develop a thermal storage system using latent heat from a phase change material (PCM) in order to match with Fresnel technology using direct steam generation. Sodium nitrate (NaNO3) has been selected as PCM and low-alloy steel has been considered as candidate material to build the container and the heat exchanger of a latent heat storage system. The contribution of this thesis is to provide better understanding of the corrosion of the candidate material in contact with the PCM. This thesis aims to determine a corrosion rate law which helps design the thickness of the heat exchanger’s wall and to develop protocols using electrochemical technics to follow in-situ corrosion process in the latent heat storage system. The work presented in this manuscript focuses on experimental study of corrosion of low-alloy steel in molten NaNO3 (340°C) in function of different parameters: presence of impurities (oxides, chlorides), atmosphere and thermal cycling. Gravimetric measurements reveal the formation of a protective corrosion layer on the steel’s surface and the production of sodium nitrite (NaNO2) by corrosion reaction. The corrosion layer consisting mainly of Fe2O3 (insoluble in molten NaNO3) was characterized by surface analytical methods (XRD, XPS). Variation of the thickness of corrosion layer obtained by gravimetric methods shows logarithmic kinetics in pure NaNO3 and linear kinetics in the presence of 10mol% of impurity chlorides. Electrochemical study has provided indications on the iron (and steel) behavior in molten NaNO3. By combining results of this study with experimental observations from gravimetric study, we were able to propose a corrosion mechanism of the steel in molten NaNO3. This mechanism was then validated by electrochemical impedance spectroscopy study. Kinetics parameters and value of corrosion current were deduced by the simulation of impedance diagrams using the proposed mechanism. The thickness of corrosion layer was calculated by analyzing the variation of the corrosion current with time. These values present a good agreement with values obtained by gravimetric study.In this work, we also show the possibility of using electrochemical measurements at industrial scale to follow in-situ the evolution of the PCM's composition and the corrosion state. Finally, this work has shown that low-alloy steel is suitable for using in a latent heat storage system with NaNO3 as phase change material.

The corrosion susceptibility of selected metallic materials frequently employed in prosthetic dentistry has been examined with electrochemical methods. Results have been compared with data derived from breakthrough potential measurements performed with these materials before. Mostly agreement and/or close correlation were found, discrepancies are discussed and tentatively assigned to the different experimental conditions.

>Magister Scientiae - MSc / Prostate cancer, commonly referred to as adenocarcinoma of the prostate, is the leading cause of cancer death in men in 46 countries, and it was estimated that by the end of 2018 there would approximately be 1.3 million new cases of prostate cancer worldwide. Currently, the Food and Drug Administration (FDA) approved biomarker for prostate cancer disease diagnostics Prostate Specific Antigen (PSA) is not specific to the disease itself but extends to other cases such as Benign Prostate Hyperplasia (BPH) a condition in which the prostate grows uncontrollably. This biomarker is then detected in blood samples via conventional methods which require a qualified individual to operate and are often time consuming. Examples of these methods are spectrophotometry and High Performance Liquid Chromatography (HPLC). Hence, a more efficient biomarker and method of detection is needed for prostate cancer disease diagnostics, as early detection of the disease means early treatment, which could ultimately save lives. Currently, an emerging biomarker for prostate cancer known as Alpha-Methyl CoA Racemase (AMACR) has shown to be more specific to the disease with advantages such as being a non-invasive biomarker. AMACR has been reported to be present in urine, and thus may be detected via a non-invasive method. This study proposed an economical, non-invasive electrochemical biosensor for the rapid detection of AMACR based on mercaptosuccinic acid capped tungsten telluride (MSA-WTe3) quantum dots (QDs). Nanomaterial has shown promise in terms of increasing the sensitivity and specificity of sensors. MSA-WTe3 QDs was successfully synthesized using easy, inexpensive method and was studied by various techniques such as High Resolution Transmission Electron Microscopy (HR-TEM) where the size was confirmed to be within the nanometer scale and was reported to be 2.65 nm with a good crystallinity. X-ray diffraction (XRD) confirmed the structural properties and chemical composition of the QDs and it is reported that the QDs are rich in both tellurium and tungsten and comprise of a hexagonal structure. Scanning Electron Microscopy (SEM) confirmed the successful immobilization of aptamer sequence specific to AMACR onto the electrode surface by showing a distinct conformational change when aptamers were introduced to the QDs under study. This study reports the successful detection of AMACR using an MSA-WTe3 QDs based aptasensor immobilized onto a screen printed glassy carbon electrode, with a detection limit of 0.35651 ng/mL and a limit of quantification calculated to be 1.08033 ng/mL.

Philosophiae Doctor - PhD / Immunosensors are affinity ligand-based biosensor solid-state devices in which the immunochemical reaction is coupled to a transducer. The specificity of the molecular recognition of antigens by antibodies to form a stable complex is the basis of the immunosensor on the electrode. The development of such a sensor requires a better design and preparation of an optimum interface between the biomolecules and the detector material. The immunosensors were developed based on Polyaniline derivative composite. Novel water soluble PdTe quantum dots (QD) was synthesized and characterized by different physical techniques such as UV-Visible (UV-VIS), Fluorescence Spectroscopy (PL), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). The electroactivity of such synthesized quantum dots was studied by cyclic voltammetry in aqueous media. The synthesis of poly(2,5- dimethoxyaniline)-multi wall 'carbon nanotubes nanocomposite was carried out by electropolymerization in situ of 2,5-dimethoxyaniline - multi wall carbon nanotubes (PDMA-MWCNT) from aqueous dispersion containing acid-treated multi wall carbon nanotubes (MWCNT) and 2,5-dimethoxyaniline subsequently modifying a glassy carbon electrode in acid media. An undoped PDMA was also prepared for control. The composite for this work, consists of layer-by-layer method to form a multilayer film of QDs and PDMA-MWCNT. The method used was as follows; the drop coating of quantum dots followed by electrodeposition of poly(2,5- dimethoxyaniline )-carbon nanotubes onto surface of glassy carbon. The PDMA-CNT was characterized by UV-Visible (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The electrochemical characterisation of PDMA-CNT was carried out using cyclic voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The composite (QDs-PDMA-MWCNT) was also characterized using above mentioned techniques. The electrochemical immunosensor for fumonisin a mycotoxin was prepared by dropcoating of mycotoxins antibody onto the composite modified glassy carbon electrode. The response profiles of fumonisins sensors system were obtained from electrochemical impedance spectroscopy (EIS) measurements. The fumonisin immunosensor was used for the detection of fumonisins in certified com reference materials. For comparison reasons, analysis of such mycotoxins was carried out by using conventional analytical method enzyme-linked immunosorbent assay (ELISA). The EIS response of FBI immunosensor (GCEIPT-PDMA-MWCNT/anti-Fms-BSA) gave a linear range of 7 to 49 ng L-I and the corresponding sensitivity and detection limits were 0.0162 ka L ng-I and 0.46 pg L-I, respectively. Hence the limit of detection of GCEIPT-PDMA-MWCNT immunosensor for fumonisins in com certified material was calculated to 0.014 and 0.011 ppm for FBI, and FB2 and FB3, respectively. These results are lower than those obtained by ELISA, a provisional maximum tolerable daily intake (PMTDI) for fumonisins (the sum of FBI, FB2, and FB3) established by the Joint FAO / WHO expert committee on food additives and contaminants of 2 ug kg" and the maximum level recommended by the U.S. Food and Drug Administration (FDA) for protection of human consumption (2-4 mg L-I).

No description available.