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Preparation Techniques and Characterization of Electrodes with Nanostructured Surface
Hrdý, Radim ; Trnková, Libuše (referee) ; Janderka,, Pavel (referee) ; Hubálek, Jaromír (advisor)
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.
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Application of metal and semiconductor nanostructures for biodetection
Kejík, Lukáš ; Skládal, Petr (referee) ; Kolíbal, Miroslav (advisor)
The master’s thesis deals with two applications of gold discoidal nanostructures exhibiting plasmon resonance for biodetection. The first approach considers the detection of changes in the phase on plasmonic antennas using coherence-controlled holography microscope. It was found that the steepness of the phase is increasing with the illumination wavelength when plasmon resonance is excited in larger antennas. The sensitivity of the phase to refractive-index changes of the surrounding media was observed when the largest response was given by antennas in resonance with wavelength of illumination. Next part deals with plasmon resonance detection by means of optical spectroscopy combined with voltametry which characterizes the electrochemical activity. Changes in resonance wavelength induced by the presence of SSC buffer were observed, although this influence seems to diminish in time. Conducted experiments have also shown that oxygen-plasma cleaning is not suitable for sample surface cleaning because of oxidation of metals including gold as well.
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Low temperature fuel cells
Skibik, Petr ; Barath, Peter (referee) ; Sedlaříková, Marie (advisor)
This work deals with making of catalyst materials with used nickel and commercial carbons that is appropriate for using in low temperature H2-O2 fuel cell. This thesis is described the methods of preparation electrode materials, its consistence and making electrode for the measure. This thesis is compared catalyst activity of nickel materials with platinum materials and poor commercial carbons. The samples were measured by voltammetric method by potentiostat Autolab with used the software GPES and the software FRA for impedance spectroscopy.
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Optimization of electrochemical sensor for detection in microvolume
Gajdoš, Libor ; Pekárek, Jan (referee) ; Prášek, Jan (advisor)
This thesis describes optimization and modification of standard thick-film electrochemical sensor to be able to be used for detection in microvolumes. In the theoretical part, the thick film technology is described. The work is then focused on the wettability of surfaces followed by introduction to electrochemistry and electro-analytical methods. In the experimental part, screen-printing of various types of thick film pastes on ceramic substrates for determination of their wettability and the following modification of the sensors with thick-film paste and with Parylene vaporization can be found, as well as the basic electrochemical measurements in microvolume using the modified sensor. Finally the results are summarized in conclusion.
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The electrochemical sensors with 3-D structure of electrodes
Štekovič, Michal ; Hrdý, Radim (referee) ; Adámek, Martin (advisor)
Miniature electrochemical sensors can be produced by thick-film technology. The optimal properties of thick-film electrode system, the production technology optimization of thick-film sensors and the adjustment of optimal technological properties are main problems of sensor design. An area of working electrode and an electrode topology design is the important parts in design of electrode system optimization. The rules for optimization of electrode systems in classical electrochemistry exist. The design of standard thick-film electrode construction is limited (2-D construction, substrate dimensions, resolution, paste parameters …). Therefore rules for classical electrode systems cannot be used fully in this case and larger electrode area can be making by 3D structure only. One of resolutions is unconventional method. The increase of working electrode surface by unconventional method – ball and wire bonding is discussed in this work.
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Study of MnOx properties using RRDE
Podal, Pavel ; Vondrák, Jiří (referee) ; Novák, Vítězslav (advisor)
This master thesis deals with qualifications of the catalytic materials for positive electrode low-temperature fuel cells. The teoretical part focuses on the physical and chemical properties of low-temperature fuel cells. There are described methods of hydrodynamic RDE and RRDE. RRDE study utilizes methods linear and cyclic voltammetry for qualifying performance of catalytic materials and presentation of results. The practical part describes the preparation various types of carbon materials. There are monitored the oxygen reduction using RRDE. Catalytic materials are evaluated: CV, stability, kinetic parameters, creation of intermediate H2O2 and kinetics of electrode reactions.
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Multichannel instrumentation for electrochemical measurement from sensor array
Žák, Jaromír ; Kizek, René (referee) ; Hubálek, Jaromír (advisor)
The work deals with n-channel system enabling many sample analysis at sort time from sensor array using electrochemical methods. The 8x12 sensor arrays are formed from 3 electrodes system created on PCB which can be used for heavy metal analysis and toxic substances determination. The control unit switches each 3 electrode sensor to 8 channel precise potentiostat which was designed for electrochemical analysis with current sensitivity below 10 pA. The potentiostat can synchronize with control unit. Developed system is able to measure up to eight single inputs and may be simply converted to measure other nonchemical values. Measured data will be sent to user-friendly application in computer and analyzed or saved consequently.
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The lead detection in solders
Macháň, Ladislav ; Prášek, Jan (referee) ; Adámek, Martin (advisor)
This work deals with issues of lead detection in solder irons used in electrotechnics. The general aim is to study principles of quantitative heavy metal detection by the electrochemical methods, optimal method selection and construction of detecting instrument.
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Reactivity and controll of properties of metallic materials
Tkacz, Jakub ; Šoukal, František (referee) ; Zmrzlý, Martin (advisor)
This thesis is focused on corrosion protection of magnesium alloys AZ 91. Very important is material corrosion in some environments and last but not least surface treatment as grinding, polishing and etching. Theoretical part of this thesis is about magnesium and magnesium alloy. It focuses on properties, in order to determine the best procedure for corrosion protection. It characterize material corrosion- for example corrosion in special environment (atmosphere, water, etc.) or elektrolyte corrosion. Big part of theoretical part is focused on electrochemistry, in particular kinetic aspects (Tafel diagrams, corrosion current, etc.) and potentiostatic testing, where are observed properties of material in relation to potential: corrosion potential Ecorr, brakedown potential Ebd and repassivation potential Erp. This work present preparing, utilization and positive or negative aspects of corrosion protection. Metallography is important too since metallographical preparation is crucial for the research on the material. Described metallography procedures are mounting, grinding, polishing, etching and interpretation. Experimental part of this thesis is in particular about corrosion properties of magnesium alloy AZ 91. It focuses on calculation of corrosion rate in defferent environments. Principle is mass defekt of the alloy. The environments are: destilled water, hot service water and 3% NaCl solution (like sea water). Last but not least are important. procedure manipulation with materials. Very important are choice and composition of solutions, etching time, choice of polishing cloth, lubricant solution and good pressure. Beacuse of this aspects can be show corrosion action of environments on magnesium alloy AZ 91 by photographies.
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Fabrication of Nanowires into Porous Alumina by Electrolysis
Staňo, Michal ; Čechal, Jan (referee) ; Škoda, David (advisor)
This thesis deals with preparation of metal nanowires based on electrodeposition from aqua solution of metallic salts into porous dielectric aluminium oxide templates. The theoretical part covers various bottom-up methods of nanowire preparation using a template, electrochemistry and electrodeposition overview. The Experimental part is focused on the nanowire (Ag, Cu, Ni-H) preparation by means of direct current and alternating current electrodepositon and geometrical characterization of fabricated nanowires by scanning electron and atomic force microscopy. Defects of commercially available and prepared porous alumina templates are mentioned. Branching and coalescence of nanowires are briefly discussed as well.
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