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Alandering Of Li-Ion Electrodes And Its Im-Pact On The Final Capacity Of Lithium-Ion Cell
Svoboda, Lukáš
There is an effort to produce lithium-ion batteries with maximal density of energy, or higher capacity of cell with the same size. Calendaring of electrodes is important part of manufacturing of batteries. Its parameters, mainly the pressure of calendaring and with it related the final compression ratio of electrode layers, affect parameters of battery significantly. It is the process of pressing electrode material coated on current collector with certain pressure and it reduces its porosity and thickness. The aim of this article is determination of suitable level of calendaring that increases specific capacity, but does not reduce its cyclability.
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Study of intercalation properties of electrode materials based on expanded graphite
Vencelides, Lukáš ; Máca, Josef (referee) ; Libich, Jiří (advisor)
The diploma thesis deals with the issue of electrochemical cells and deals in detail with lithium-ion batteries. The thesis describes the history of development of lithium-ion batteries, basic information about lithium and basic types of electrochemical cells. The work is devoted in detail to the description of characteristics and operating principle of lithium-ion batteries with emphasis on the negative electrode and negative electrode materials. Of the negative electrode materials, both the most widely used material graphite and modern materials with a great potential for the future are described. In the measurement methods the work describes methods CV, GCPL and EIS. Great emphasis is placed on the explanation of the principle of the function of electrochemical impedance spectroscopy and its application in measurement of electrochemical properties of materials used in lithium-ion batteries. There is also described the procedure of calculation of diffusion coefficients using the results of electrochemical impedance spectroscopy. In the practical part, two methods are used to calculate the diffusion coefficients of lithium ions into the negative electrode made of expanded flake graphite using the results of a series of electrochemical measurements.
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Impedance spectroscopy characterization of perovskite solar cell materials
Křečková, Jitka ; Vanýsek, Petr (referee) ; Novák, Vítězslav (advisor)
The Master‘s thesis deals with the topic of perovskite solar cells with the main focus on the materials used for the active layer. In the introductory part, the electrical and optical properties of halide perovskites are described and specific examples of perovskite crystals are introduced. The description of impedance and photoimpedance measurement methods used for characterization of perovskite solar cells is also included in the thesis. The measurement of electrochemical impedance spectroscopy was conducted on four perovskite crystals and equivalent circuit was formed to fit the obtained data. Parameters of the circuit elements were acquired using the fitting method and were further evaluated in experimental part of this thesis.
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Development of Novel Electrochemical Methods Using Various Membrane Materials for Monitoring of Selected Anticancer Drugs and Phytochelatins
Skalová, Štěpánka ; Barek, Jiří (advisor) ; Labuda, Ján (referee) ; Trnková, Libuše (referee)
Present Ph.D. Thesis is focused on the development of electrochemical methods for determination of anticancer drugs using various types of membranes for their preliminary separation. Furthermore, this Thesis reports the study of transport mechanisms of heavy metals in the presence of phytochelatins across biological membranes. Sodium anthraquinone-2-sulphonate (AQS) was used as a model compound for its similar structure with anthraquinone-based (AQ-based) anticancer drugs (doxo/daunorubicin) and also due to its better availability. All these compounds can be easily electrochemically oxidized and/or reduced. Redox behaviour of AQS was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in a cathodic region on mercury meniscus modified (m-AgSAE) and polished silver solid amalgam (p-AgSAE) electrodes, Obtained results were used for the development of a micro-volume voltammetric cell (MVVC). Its applicability for voltammetric determination of anticancer drugs was verified by using doxorubicin (DX) as a model substance. The second part of this Thesis deals with therapeutic monitoring of anticancer drugs in the blood circulation of the patients. For pilot experiments, a liquid-flow system with dialysis catheter and amperometric detection was used. The flow rate of carrier...
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Preparation and Characterization of Fluoride Conversion Coatings on Biodegradable Magnesium Alloys
Drábiková, Juliána ; Hadzima, Branislav (referee) ; Brezinová,, Janette (referee) ; Ptáček, Petr (advisor)
The submitted work is aimed at the unconventional fluoride conversation coating preparation on the AZ31, AZ61, ZE10 and ZE41 magnesium alloys by their immersion in Na[BF4] molten salt. The influence of the preparation parameters (such as temperature and time) on the quality of the fluoride conversion coating is investigated. Methods of light and scanning electron microscopy were used for the evaluation of morphology, chemical composition and thickness of the coating. Short and long-term corrosion tests were executed to analyze the corrosion performance in simulated body fluid solution at 37 ± 2 °C with and without the fluoride conversion coating. The short-term behavior was evaluated by potentiodynamic tests, namely by the linear polarization. Long-term performance was assessed by electrochemical impedance spectroscopy or immersion tests. The coating preparation parameters influence on the character of the formed fluoride conversion coating was defined based on the obtained results. The next part of the thesis deals with the description of the possible mechanism of formation and kinetics of growth of the unconventional fluoride conversion coating on the selected AZ61 magnesium alloy. In this part, further detailed analyses were carried out to investigate the microstructure and chemical composition of the fluoride conversion coating using focused ion beam, transmission electron microscopy and X-ray photoelectron spectroscopy.
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Simple Electrochemical DNA Biosensor for Detection of DNA Damage Caused by UV Radiation
Arustamian, Daria ; Vyskočil, Vlastimil (advisor) ; Dejmková, Hana (referee)
Ultraviolet (UV) radiation is a common DNA damaging agent. Major DNA lesions, such as cyclobutane pyrimidine dimers (CPDs) and pyrimidine-(6-4)-pyrimidone (6-4PPs) photoproducts, are carcinogenic and mutagenic. UV induced DNA damage was investigated using a simple electrochemical DNA biosensor based on an ultra-trace graphite electrode (UTGE) and low molecular weight doble-stranded DNA (dsDNA) from salmon sperm. Biosensor was prepared using adsorption of dsDNA on a surface of the UTGE and then used to detect UV-induced DNA damage. Effects of UV radiation were investigated using a combination of several electrochemical technics: square-wave voltammetry (SWV) for direct monitoring of DNA base oxidation and cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), as non-direct methods, using redox-active indicator [Fe(CN)6]4-/3- . CV and EIS, which allow characterization of electrode surface, were used to optimize preparation of the dsDNA/UTGE biosensor. Prepared dsDNA/UTGE biosensor was exposed to UV radiation using UV lamp with two set wavelengths: UVC of 254 nm and UVA of 365 nm. UVC radiation was used to damage DNA. Relative signal decrease was 50% after 20 minutes of exposure to UVC radiation. UVA radiation was used to compare effects of different types of UV radiation. Obtained...
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Electrochemical corrosion characteristics of Mg-Zn systems prepared by powder metallurgy
Kotek, Jakub ; Hadzima, Branislav (referee) ; Fintová, Stanislava (advisor)
The diploma thesis deals with evaluation of electrochemical corrosion characteristics of Mg-Zn systems prepared by powder metallurgy in SBF solution. The main aim of the thesis is to analyze the influence of chemical composition, achieved structure and parameters of the process of production of Mg-Zn systems on their electrochemical corrosion characteristics. The basic electrochemical properties of the prepared materials will be evaluated by electrochemical impedance spectroscopy. In order to clarify the mechanism of corrosion of materials, the immersion tests will be used, accompanied by metallographic observations.
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Detection of Oxidative Stress Using Electrochemical DNA Biosensors
Jurečková, Zuzana ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
Presented Diploma Thesis is focused on the development, characterization, and utilization of simple and inexpensive electrochemical DNA biosensor for the detection of DNA damage caused by oxidative stress. The initial part of the work is devoted to preparation and characterization of a large-surface carbon film electrode (ls-CFE) modified with carbon nanotubes (CNT/ls-CFE). Carbon nanotubes improve electrochemical properties of the transducer and increase the amount of adsorbed DNA on the electrode surface. Testing of the electrode surface modified with multiwalled carbon nanotubes (MWCNT) was performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using a redox system [Fe(CN)6]4-/3- and using square wave voltammetry without any redox indicator. Carbon nanotubes have proved to be unsuitable material for our type of biosensor, but it can be used inanalytical chemistry for the determination of electroactive substances. The second part of this Thesis deals with the application of the prepared DNA biosensor for the detection of DNA damage by oxidative stress. The biosensor based on the ls-CFE was chosen for this purpose, having several advantages, such as its fast preparation, a simple mechanical renewal of the electrode surface, a good reproducibility of measurements,...
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The Use of a Simple Electrochemical DNA Biosensor for the Determination of Environmental Pollutants and Investigation of Their Interaction with DNA
Blašková, Marta ; Vyskočil, Vlastimil (advisor) ; Zima, Jiří (referee)
The interaction between three selected representatives of environmental pollutants - naphthalene, anthracene, and 2-aminoanthracene - and DNA was investigated using an electrochemical DNA biosensor based on a glassy carbon electrode (GCE) and low molecular weight DNA from salmon sperm (DNA/GCE). The interactions with DNA were monitored using square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). For naphthalene, there was no DNA damaging interaction observed. In the case of anthracene, the formation of an intercalation complex [DNA-anthracene] was observed. However, its formation does not cause DNA strand breaks. The formation of similar intercalation complex was observed for 2-aminoanthracene [DNA-2-aminoanthracene], where we suppose on the basis of the results obtained that the intercalation of 2-aminoanthracene into the DNA double helix induces a tension and subsequent formation of single-strand breaks, which cause that the fragments of DNA fall away from the electrode surface. The intercalative interaction of DNA with anthracene a 2-aminoanthracene was used in the development of electrochemical methods for determination of these compounds at the GCE and DNA/GCE. At the development of the methods, DC voltammetry (DCV) and differential pulse voltammetry (DPV) were used....
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Novel Electrochemical Biosensor for the Detection of DNA Damage Based on a Large-Surface Carbon Film Electrode
Jurečková, Zuzana ; Vyskočil, Vlastimil (advisor) ; Zima, Jiří (referee)
Presented Bachelor Thesis is focused on the development and utilization of a simple and inexpensive electrochemical DNA biosensor for the detection of DNA damage caused by chemical carcinogens. A large-surface carbon film electrode (ls-CFE), having several advantages, such as its fast preparation, a simple mechanical renewal of the electrode surface, a good reproducibility of measurements, an absence of problems connected with "electrode history", and simple chemical modification, was used for its preparation. The initial part of the work is devoted to the investigation of the composition of a carbon ink suspension, which was optimized and tested using a [Fe(CN)6]4-/3- redox system by cyclic voltammetry (CV), further to the optimization of the DNA biosensor (DNA/ls-CFE) preparation and to its characterization, which was performed using two electrochemical techniques - CV and electrochemical impedance spectroscopy (EIS). The second part of this Thesis deals with the application of the newly prepared DNA biosensor for the detection of DNA damage by model chemical carcinogens. The direct interaction of DNA with fluorene and 2-aminofluorene (2-AF) was investigated using CV and EIS at the DNA/ls-CFE. The obtained results confirmed that the interaction of DNA with fluorene and 2-AF causes DNA damage,...
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