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Sensoric properties of organic N-type semiconductors and their air stability
Saska, Pavel ; Vala, Martin (referee) ; Salyk, Ota (advisor)
Hydrogen has been for some time discussed as a successor to fossil fuels whose stocks are constantly running low. One of the crucial requirements for the possible usage of hydrogen as an energy carrier is our ability of reliable detection. In context with development of organic electronics there occurred a possibility to use derivatives of diketopyrrolopyrroles as sensing materials of hydrogen sensors. Derivatives of diketopyrrolopyrrole are organic pigments that behave as semiconductors. Their analogues with pyridyl side group are due to free electron pairs of nitrogen atoms sensitive to hydrogen. The problem of organic N-type semiconductors is in general their instability on the air. This thesis is focused on testing of hydrogen sensors with active layer made from derivatives of diketopyrrolopyrrole and judging their stability on the air.
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Study of electrolyte influence on diaphragm discharge stability and efficiency
Němcová, Lucie ; Krčma, František (referee) ; Kozáková, Zdenka (advisor)
This thesis is focused on so-called diaphragm discharge, which is one kind of electric discharges in liquid, which belongs among so-called AOP´s techniques, still more used for water cleaning in the present. One of effectiveness and stability indicators of diaphragm discharge is generation of hydrogen peroxide. In theoretical part, detail principle description of electric discharge in liquid is situated. Further, properties of electrolyte are introduced and general spectrophotometric method of obtained sample determination is described. In experimental part, a full procedure of experiment is introduced. Next part containing results and discussions introduces particular results of individual measurements and their reasons. Final chapter is the end, which forms total summary and evaluation of all results. By the application of all chosen electrolytes in solution at diaphragm discharge formation of hydrogen peroxide has appeared. Inorganic and organic electrolytes were used. As inorganic electrolytes following salts were selected – solutions of halogenides, next sodium nitrate as a representative of nitrates, potassium dihydrogenphosphate as a representative of phosphates, etc. Representative of organic electrolytes was citric acid. The value of initial conductivity of electrolytes had the main influence on hydrogen peroxide formation. Electrolytes potassium dihydrogenphosphate and sodium sulphate the great influence on effectiveness and stability of the diaphragm discharge. Their rate constants reached maximum value by the application of solution with initial conductivity of approximately 400 mikrosiemens, particularly 0.0492 mmol/l.min and 0.048 mmol/l.min. On the contrary, low values of rate constant were achieved in electrolyte ammonium chloride at around the same initial conductivity – 0.0269 mmol/l.min. During experiments stainless steel and platinum electrodes were used. It was found that kind of electrode material hadn’t influence on generation of hydrogen peroxide. Hydrogen peroxide was formed only in the cathode space.
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Electrolytic properties of hyaluronan solutions
Suchá, Šárka ; Smilek, Jiří (referee) ; Chytil, Martin (advisor)
This batchelor thesis deals with electrolytic properties of hyaluronan in aqueous solutions. In this study measuring of conductance, acid-base and conductrometric titration, and UV-VIS spectroscopy were used. The measuring of conductance was made on the solutions of different concentrations of hyaluronic acid and of different ionic strength. Acid-base titrations were performed in water solution and conductometric titrations were performed in 0,3mmol.dm–3 solution of sodium chloride. UV-VIS spectra of hyaluronic acid were measured in solution with addition of acid, base and in buffer solution. Values of pKa obtained from the above mentioned measurements was between 2,8–6,5.
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Study of sensoric properties of organic semiconductors
Saska, Pavel ; Šedina, Martin (referee) ; Salyk, Ota (advisor)
Compounds based on diketopyrrolopyrrole are organic pigments that behave as semi-conductors. Their analogues with pyridyl side group are due to their sensitivity to hydrogen potentially useful as hydrogen sensors. The aim of this work was to examine properties of sensors with an active layer of diketopyrollopyrolle derivatives. The sensors were tested on an apparatus built for this purpose at FCH VUT in Brno. More specifically, changes to conductivity of these sensors in the presence of hydrogen under various conditions were studied.
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Study of properties of electrolytically modified NaCl solutions.
Brázda, Lukáš ; Mika, Otakar Jiří (referee) ; Mašek, Ivan (advisor)
This work concentrates on the study of properties of NaCl solutions, prepared by electrolysis and their using for disinfection of water. Then it is focused on reporting on possibality for corrosin of metals, whice are used in water distribution. For study was used 0,25 mol/l, 0,1 mol/l, 0,05 mol/l NaCl solutions and input direct-current voltage for electrolysis was 6V a 12 V. During the electrolysis pH and conducitivity were measured. After the end of electrolysis free active chlorine and chlorides were determined on the time. For electrolysis was used diaphragm.
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Hydrochemistry of underground waters in Chynov cave
LUTZ, Vojtěch
This thesis deals with the evaluation of hydrochemical characteristics of groundwater (dripping water) in The Chýnov Cave and the subsequent statistical processing of the results. There were followed three sampling points, which were irregularly distributed in the cave system. Bicarbonates occured as the dominant anions in the dripping water. The dominant cation was calcium. Water can therefore be classified as bicarbonate - calcium. This corresponds with the expectations for The Chýnov cave location. There were also detected enhanced concentrations of nitrates and sulphates at sampling site Štola - this has long-term character and influences the quality of the underground stream of The Chýnov cave, which is directly connected to spring "Rutický" (source of drinking water for the town of Chýnov). Although a protective zone is declared over the whole territory of Rutice water resources, there is increased amount of nitrates and sulphates which probably has anthropogenic character and it comes from applied fertilizer and mineralization processes in arable land in the close surrounding of the National Natural Monument: The Chýnov cave.
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Evaluation of quality and the renewal of surface water in the area affected by surface coal mining.
VLÁŠEK, Ondřej
The aim of the study was to evaluate the parameters of quality and renewal of surface water in the area affected by surface brown-coal mining. Selected streams were monitored on the Great pokrusnohorska dump, and streams unaffected by dumps. Values of pH, conductivity, alkalinity, oxygen saturation and temperature were measured, and quantitative and qualitative samples of macrozoobethos were taken too. The dump?s water are characterized by high concentrations of dissolved solids and alkalinity. Species diverzity of these waters is lower and is affected not only by chemical compositon of the water, but also by the character of the bottom substrate.
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Identification of point sources of surface water pollution and their quantification in selected catchments in the Šumava Mountains.
TOMKOVÁ, Zdeňka
An evaluation of chemical parameters of surface waters proceed in the three small basin areas in Šumava Mountains, in the area of Svatý Tomáš highlands, during the year 2009: Bukový (woods), Mlýnský (semi{--}intensive and drained pasture, part of Pasečná village) and Horský stream (wetlands, woods, mowed meadows, a part of Svatý Tomáš village). The aim was to chart the three main periods during the year. The spring sampling (the 12th May) should illustrate the beginning of growing season with higher water flow rates. The summer sampling (the 21st July) is the period on the top of growing and touristic season, seasonal works in wood and especially in agriculture (grazing and mowing meadows). The last sampling (the 21st October) represents the season at the end of growing season, generally with the lowest flow rates in the stream, the end of touristic season and the end of full{--}area grazing. Already during the field research, involving the water sampling and conductivity measurement, there were some inflows with increased concentrations of dissolved solids found. Whereas in Bukový stream, as has been assumed, these inflows didn´t more or less occur, in Horský stream they had, relatively surprisingly but significantly, appeared immediately in headwater area. The elevated concentrations of dissolved solids occurred in Mlýnský stream in the whole area of basin, as has been assumed regarding to drainage and full{--}area grazing. One year monitoring proved the advantage of water quality evaluation using simple measurement of conductivity in field. High water conductivity in field was subsequently confirmed by laboratory analysis of selected ions. On the basis of identification of point sources of pollution, the recommendation improving present condition was suggested.
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