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An enhanced theoretical approach for accurate measurements of the optical and energy characteristics of semiconducting materials
Allaham, Mohammad M. ; Košelová, Zuzana ; Sobola, Dinara ; Fohlerová, Zdenka ; Knápek, Alexandr
The absorption coefficient is an important optical property in characterizing semiconducting materials. It plays a significant role in studying optical characteristics, electrical structure, energy band structure, and the creation/annihilation of excitons when a semiconducting material absorbs electromagnetic radiation. In this study, an enhanced theoretical model will be introduced and applied to characterize thin films prepared from UPR4 (unsaturated polyester resin) single-component epoxy resin, which is important to study the charge flow at the interface of tungsten-UPR4 composite field emission cathodes.
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Enzyme-Based Impedimetric Biosensor dotted with gold nanoparticles
Košelová, Zuzana ; Fohlerová, Zdenka
This research delves into the realm of biosensor improvement through the utilization of gold nanoparticles (Au NPs). The primary objective is to assess the impact of differentsized Au NPs on sensor performance, specifically investigating whether 100 nm or 20 nm nanoparticles prove more favourable to enhancement. Moreover, we aim to inspect the biosensor's response to varied concentrations of Au NPs, unravelling the involved collaboration between nanoparticle size, concentration, and overall sensor properties. This modification of commercial electrodes with Au NPs, could be way for enhancing surface area and enzyme immobilization. Notably, the investigation also explores the potential drawbacks associated with increasing nanoparticle concentration and offers insights into optimizing biosensor design. It has been observed that while 20 nm Au NPs slightly decreased impedance values at higher glucose concentrations, 100 nm Au NPs, conversely, exhibited an increase in capacitive behaviour. Equally crucial is the parameter chosen for constructing the calibration curve. From impedance values at low frequencies of alternating voltage, such as 2 Hz, a lower Limit of Detection (LOD) is obtained. However, the analysis of Rct in the case of 20 nm Au NPs reveals a broader range of glucose concentrations falling within the calibration area. Through a comprehensive analysis of electrochemical behaviour, impedance, and charge transfer resistance, we endeavour to provide contributions to the improvement of biosensor technologies.
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Design of an experiment to investigate the influence of the frequency of mechanical vibrations on the structure of a solder joint
Podolák, Šimon ; Košelová, Zuzana (referee) ; Otáhal, Alexandr (advisor)
The main goal of this bachelor's thesis is to study the influence of vibrations on the structure of solder joints, specifically SAC305 solder paste droplets. The thesis consists of three parts: theoretical, practical, and evaluation of results. The theoretical part focuses primarily on solder joints and the phenomena surrounding them, such as diffusion, voids, crystal morphology, and others. It also describes vibrations and everything related to them, including ultrasound and its use in the field of soldering. The practical part deals with designing workstations for creating individual samples, specifically without vibrations, with 5 kHz vibrations, and with ultrasonic vibrations. This is followed by the process of preparing the samples and modifying them to a state suitable for microscopic examination. The final part involves evaluating the results obtained and comparing the samples with each other.
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Formation of the solidification structure of a solder alloy during passing an electric current
Šrajer, Michal ; Košelová, Zuzana (referee) ; Skácel, Josef (advisor)
The bachelor thesis is devoted to the topic of soldering alloys, monitoring its structure and its formation during solidification. The first part of the thesis deals with the theoretical analysis of alloys, crystallization and explanation of the techniques and terminology used. This is followed by a practical part in which the process of sample formation and subsequent work with them is described. The next chapter of the practical part deals with the investigation of the structure of the given solder alloy samples.
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Functional Tungsten-based thin films and their characterization
Košelová, Zuzana ; Horáková, L. ; Sobola, Dinara ; Burda, Daniel ; Knápek, Alexandr ; Fohlerová, Z.
Anodizing is a technique by which thin oxide layers can be formed on a surface. Thin oxide layers have been found to be useful in a variety of applications, including emitters of electrons. Tungsten is still a common choice for cold field emitters in commercial microscopy applications. Its suitable quality can be further improved by thin film deposition. Not only the emission characteristic can be improved, but also the emitter operating time can be extended. Tungsten oxide is known for its excellent resistance to corrosion and chemical attack due to its stable crystal structure and strong chemical bonds between tungsten and oxygen atoms. Many techniques with different advantages and disadvantages have been used for this purpose. Anodization was chosen for this work because of the controllable uniform coverage of the material and its easy availability without the need for expensive complex equipment. The anodizing process involves applying an electrical potential to tungsten while it is immersed in an electrolyte solution. This creates a thin layer of tungsten oxide on the surface of the metal. The thickness and properties of the resulting oxide layer can be controlled by adjusting the anodization conditions, such as the electrolyte solution, voltage, and the duration of the process. In this work, H3PO4 was used as the electrolyte to test whether these tungsten oxide layers would be useful for electron emitters, for use in electron guns and other devices that require high-quality electron emitters. The properties were evaluated using appropriate techniques. In general, anodization of tungsten to form thin layers of tungsten oxide layers is a promising technique for producing high quality electron emitters.
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SMV-2023-06: Development of test specimens for SEM
Matějka, Milan ; Krátký, Stanislav ; Meluzín, Petr ; Košelová, Zuzana ; Chlumská, Jana ; Horáček, Miroslav ; Kolařík, Vladimír ; Knápek, Alexandr
The study focuses on the research and development of precise calibration samples featuring relief structures. These samples are designed for calibrating parameters in scanning electron microscopes (SEM). The testing patterns enable the verification and calibration of magnification, orthogonality, and geometric distortion. The preparation of calibration specimens utilizes micro lithographic techniques tailored for silicon processing and other relevant technological procedures.
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SMV-2023-05: DI2023
Matějka, Milan ; Krátký, Stanislav ; Meluzín, Petr ; Košelová, Zuzana ; Chlumská, Jana ; Horáček, Miroslav ; Kolařík, Vladimír ; Knápek, Alexandr
The research focuses on the investigation and development of precise calibration samples with relief structures. These samples are designed for calibrating parameters in scanning electron microscopes (SEM). Test patterns allow verification of the imaging quality through microscopic techniques such as overall magnification, field of view size, resolution, deformation in lateral axes, and other geometric distortions. Precision lithographic techniques and other methods derived from silicon processing technologies in the semiconductor industry are employed for sample preparation. The development has been directed towards optimizing the recording of etching masks before transferring the image onto a monocrystalline silicon substrate.
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Diffusion Behavior of Analyte Molecules in a Nanoporous Matrix Created from Polystyrene Nanoparticles
Košelová, Zuzana
This study investigates the diffusion behavior ofanalyte molecules in a nanoporous matrix of polystyrene particles.Two approaches, steady-state current and potential stepchronoamperometry were employed to calculate diffusioncoefficients and compare the effect of nanoporous matrices withdifferent diameter of pores and different method ofimmobilization of enzyme. Pores were created with close packingof polystyrene nanoparticles. The covalent and cross-linkingimmobilization were used to immobilize the enzyme.Chronoamperometric measurement was applied to detect analyte.The study found that the presence of nanoporous matricesimmobilized on p-lysine affects diffusion. The potential stepchronoamperometry method showed the improvement ofdiffusion. This study provides insight into the diffusion behaviorof analyte molecules in nanoporous matrices, which can be usefulin optimizing the design of amperometric biosensors.
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Verify the possibility of plasma treatment of printed circuit boards for subsequent surface treatment
Brokeš, Josef ; Košelová, Zuzana (referee) ; Otáhal, Alexandr (advisor)
This thesis deals with the regeneration and cleaning of printed circuit boards with emphasis on the use of plasma technology. Various surface cleaning methods, including manual cleaning, industrial washing and plasma treatment, were investigated and their effect on the subsequent quality of the paintwork. A systematic analysis of the effect of plasma treatment on the paint quality and functionality of the plates is also carried out, including an investigation of the possibility of regenerating older plates. This study provides a basis for further research and development in this area. The thesis also presents the design and implementation of a prototype plasma developer device for integration into a production line.
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Nanoporous Enzyme-Based Impedimetric Biosensor
Košelová, Z.
The ordered nanopores surfaces has been studied in the field of biosensors for the detection of affinity interactions such as antigen-antibody or nucleic acid hybridization. Nanopores are frequently fabricated by anodic oxidation of aluminium. This method is practically simple method of highly ordered pore formation, but is not suitable for massive production. The principle of detection is usually based on the degree of pore blockage by biomolecular interaction that allows a sensitive electrochemical response. Here we show the development and characterization of the nanopore-based enzymatic biosensor for the detection of analytes. We performed and tested the concept of the simple and versatile method of nanopores formation on the electrode using non-conductive polystyrene nanoparticles. The variability in pore size was modulated by nanoparticles diameter (40 and 80 nm). We measured response of our designed biosensor using electrochemical impedance spectroscopy in presence of redox mediator at low potential. The smaller diameter of nanopores increases charge transfer resistance. Biosensors with 80 nm nanoparticles had behaviour similar to reference without nanoparticles, therefore the pore was too wide for this design. The limit of detection from Rct showed to be at most 0.01 mM for every sample type. This proposed biosensor contributes to the basic knowledge about nanopores sensors, and it could have a potential, for example, in the development of ―point of care‖ devices.
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