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Effects of detergents on activity, thermostability and aggregation of immobilized lipases
Bančáková, Anna ; Voběrková, Stanislava (referee) ; Hermanová, Soňa (advisor)
Predmetom tejto diplomovej práce bolo štúdium vplyvu detergentov na aktivitu, termostabilitu a agregáciu voľnej a imobilizovanej formy komerčného preparátu lipázy izolovanej z mikroskopickej huby Rhizopus arrhizus. Teoretická časť obsahuje ucelenú rešerš popisujúcu štruktúru, mechanizmus účinku a priemyselný význam spomínanej hydrolázy spolu s popisom chemických účinkov detergentov, pričom dôraz bol kladený predovšetkým na skupinu neionogénnych detergentov s názvom tweeny. V experimentálnej časti bol študovaný efekt tweenov na rozpustnej a imobilizovanej forme RA lipázy. Imobilizácia spočívala v priamej adsorpcii enzýmu na neupravený nosič. Ako nosič bol použitý oxidovaný grafén ošetrený tweenom (tween 20, 60, 80). Aktivita enzýmu bola stanovená spektrofotometricky za pomoci substrátu p-nitrofenyl laurátu. Zvýšenie aktivity voľnej lipázy (104 % oproti maximálnej hodnote) bolo zaznamenané pri použití tweenu 20 o koncentrácii vysoko nad hodnotou kritickej micelárnej koncentrácie (10 mmol•dm-3). Na základe štúdie imobilizačných podmienok, boli nastavené ideálne parametre pre dosiahnutie účinnej imobilizácie v spojení s čo najvyššou lipolytickou aktivitou (koncentrácia enzýmu 0,1 mg•ml-1, fosfátový tlmivý roztok pH 7,2, koncentrácia tweenu 10,8 mmol•dm-3, čas imobilizácie 1 hodina). Obe formy lipázy vykazovali maximálnu aktivitu pri 35 °C. Optimálne pH sa u imobilizovanej lipázy posunulo na hodnotu 8, v porovnaní s voľnou formou, ktorej pH optimum bolo stanovené na 9. Tepelná stabilita vykazovala približne rovnaký priebeh u oboch foriem skúmanej hydrolázy. Avšak v prípade štúdia stability enzýmu pri dlhodobej úschove bolo po imobilizácii zistené výrazné zlepšenie tohto parametru.
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The oxygen modification of the graphene structures for biosensors
Mikerásek, Vojtěch ; Bartošík, Miroslav (referee) ; Mach, Jindřich (advisor)
The bachelor thesis deals with the modification of CVD graphene by oxygen atoms. The theoretical part describe the structure of graphene oxide and its physical properties. Methods of production of this material and its use in biosensors are also described. The practical part describes the preparation of monolayer graphene on a silicon wafer. The main attention was paid to the oxidation of graphene by atomic oxygen and its modification in oxygen plasma. The samples were measured during process of oxidation at individual time intervals using XPS.
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Photocatalytic water splitting by oxide semiconductors modified with graphen/graphenoxide
Marek, Jiří ; Čáslavský, Josef (referee) ; Cihlář, Jaroslav (advisor)
This master thesis deals with the topic of alternative production of hydrogen as the energy carrier of the future. The primary focus is on the production of hydrogen based on photocatalytical water splitting in the presence of semiconductor materials (especially modified and unmodified TiO2). The aim of the thesis is a synthesis of nanostructured oxide, graphene/graphene oxide particles and its composites, and a study of its structures and photocatalytical properties regarding photolysis of water. Products of the syntheses are described from the point of view of phase composition, surface area and photocatalytical activity. The main output of the thesis is a discussion of the influence of alkaline complex forming reagents on the hydrothermal low-temperature synthesis of biphasic TiO2, and a study of the influence of graphene/graphene oxide modification on photocatalytical activity of biphasic TiO2.
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Study on interactions between lipase and carbon-based support
Hamrlová, Romana ; Voběrková, Stanislava (referee) ; Hermanová, Soňa (advisor)
Tématem diplomové práce je imobilizace lipáz a konkrétně studium interakcí mezi lipázou a nosičem na bázi uhlíku. Lipáza izolovaná z kmene Rhizopus arrhizus byla adsorbována přímo na různé typy grafen oxidu (a1, a, b, c a d) a na grafen oxid typu a1 modifikovaný poly(ethylenglykolem), PEG-a1. Enzym adsorbovaný na nosič a1 byl následně sesítěn pomocí glutaraldehydu a vzorek byl označen jako GA(RA-a1). Vliv hydrofobního charakteru povrchu nosiče na účinnost imobilizace byl potvrzen vyšší úchovou počáteční aktivity enzymu imobilizovaného na více hydrofobním nosiči (nižší koncentrace polárních skupin) i při vyšší koncentraci rozpustného enzymu v roztoku. Stanovení enzymové aktivity bylo provedeno spektrofotometricky za použití p-nitrofenyl laurátu (p-NPL) jako substrátu. Pro imobilizovaný a volný enzym byly stanoveny základní biochemické a kinetické parametry. Optimální pH kovalentně imobilizovaného enzymu bylo posunuto do více kyselého oblasti (pH 7-8) ve srovnání s volným enzymem, kdy bylo optimum dosaženo při pH 9. Tepelná stabilita imobilizovaného enzymu byla výrazně zlepšena v případě vzorku GA(RA-a1), kde bylo aplikován glutaraldehyd po adsorpci enzymu na nosič. Sesíťování adsorbovaného enzymu pomocí glutaraldehydu vedlo ke zlepšení tepelné stability vzorku, a to pravděpodobně v důsledku intermolekulárních kovalentních vazeb. Na základě měření stability enzymu při teplotě 4 C ve fosfátovém pufru bylo prokázáno značné zlepšení úchovy lipolytické aktivity imobilizovaného vzorku oproti volnému enzymu. Volný enzym ztratil více než 84 % své původní aktivity za 42 dní, zatímco imobilizovaný enzym na nosiči c si zachoval 100 % své původní aktivity. Nejlepší stabilitu enzymu při úchově měl nosič c, když si po 180 dnech stále zachoval 87 % své původní aktivity.
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Biomimetic polymer/graphene layered nanocomposites
Dostalík, Petr ; Ondreáš, František (referee) ; Zbončák, Marek (advisor)
This batchelot thesis deals with preparation of biomimetic polymer/graphene layered nanocomposites. In order to prepare nanocomposites, it was first necessary to prepare a suitable graphene material. The Tour-Marcan method was chosen for its preparation, in which the effect of oxidation time on the structure of the resulting graphene/graphite oxide was investigated. From the result of structural analysis was evaluated, that after 4 hours of oxidation structure of graphite was intercalated, oxygen groups were formed (mainly expoxy groups) and inter-layer spacing increased to form graphite oxide (GO). Extension of oxidation time did not lead to major changes in struture of GO. Nanocomposites were prepareted by solution-casting method. The polar polymer – polyvinyl alcohol (PVAl) was used as a matrix with assumption of strong interaction between GO a PVAl. In order to promote GO intercalation, an ultrasonic dispersant was used in the process of nanocomposite preparation, the effect of which was manifested by an increase in the inter-layer GO distance in nanocomposites. It has been observed that the inter-layer spacing of GO and PVA1 is affected by the concentration of the individual components in the nanocomposites, suggesting a possible modification of the PVA1 crystalline structure. Structural analysis revealed that GO layers in composite were oriented in one direction.
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Characterization of graphene electrical properties on MEMS structures
Brodský, Jan ; Pekárek, Jan (referee) ; Gablech, Imrich (advisor)
This work presents basic properties of graphene, methods for its synthesis and methods for its characterization by Raman spectroscopy, two-point probe, four-point probe and van der Pauw measurements. The experimental part of this work describes the process of graphene oxide, reduced graphene oxide and graphene sample preparation and measurement of its current-voltage characteristic by two-point probe method. Subsequently, sample annealing in vacuum furnace is described in this work. The annealing is important for acquiring good electrical contact between the 2D material and electrodes. Sample analysis by Raman spectroscopy is performed. The last chapters of this work describe design and fabrication of MEMS structure. Such structure serves for characterization of graphene and other 2D materials.
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Verification of properties of concretes with nanoparticles
Pacltová, Klára ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
This diploma thesis deals with the influence of addition of carbon nanoparticles on cement composites. The theoretical part of the diploma thesis is focused on the research of information about carbon nanoparticles, more precisely about carbon nanotubes and graphene oxide. There are summarized methods of dispersing carbon nanotubes and their effects on cement composites. The practical part follows the theoretical part of the research. In the first phase, the correct technique of graphene oxide dispersion was verified. Subsequently, the effects of graphene oxide on the mechanical properties of cement mortars were verified. In the final phase of the diploma thesis, the knowledge gained from the previous part was verified on concrete samples.
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Electrochemical preparation of graphene oxide and its utilization in LiFePO4 composites
Krejčí, Pavel ; Chladil, Ladislav (referee) ; Čech, Ondřej (advisor)
This work deals with issues of application of the graphene material in the field of electrochemical energy storage. It includes basic graphene properties, the overview of methods for the production of lithium-iron-phosphate/graphene composites and results of different research approaches. The general aim is to present growing opportunity of application of graphene based composites in the electrochemical energy storage field. In the experimental part of this work, a electrochemical exfoliation of graphite and a production of LFP/G composites with different amount of graphene material and with different types of graphene material are carried out. This work includes also x-ray diffraction spectroscopy measurements and the evaluation of impacts of graphene additives on final properties of the electrochemical energy storage.
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Modification of capillary wall by graphene for separation applications
Ptáčková, Aneta ; Lochman, Lukáš (advisor) ; Kučera, Radim (referee)
CHARLES UNIVERSITY FACULTY OF PHARMACY IN HRADEC KRÁLOVÉ Department of Pharmaceutical Chemistry and Pharmaceutical Analysis Candidate: Aneta Ptáčková Supervisor: PharmDr. Lukáš Lochman, Ph.D. Title of thesis: Modification of capillary wall by graphene for separation applications Capillary electrophoresis (CE) is a highly efficient separation method. Substances are separated due to their different mobility in an electric field. The CE modes of operation can be modified in different ways, e.g. capillary electrochromatography or micellar electrokinetic capillary chromatography. Modification of the inner wall of the capillary is believed to help improve separation efficiency and selectivity. Graphene is carbon with a hexagonal structure in form of two-dimensional sp2 single-atom-thick sheets. Graphene seems to be a suitable material for separation application due to its excellent properties such as large surface area and affinity to aromatic ring through π-π interactions. Our work is focused on the modification of the capillary wall by graphene. One of the methods of capillary wall modification is the Layer-by-Layer method via layering of differently charged substances bounded by electrostatic forces. Another method is chemical coating employing covalent interactions. Different combinations of polymers...
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The oxygen modification of the graphene structures for biosensors
Mikerásek, Vojtěch ; Bartošík, Miroslav (referee) ; Mach, Jindřich (advisor)
The bachelor thesis deals with the modification of CVD graphene by oxygen atoms. The theoretical part describe the structure of graphene oxide and its physical properties. Methods of production of this material and its use in biosensors are also described. The practical part describes the preparation of monolayer graphene on a silicon wafer. The main attention was paid to the oxidation of graphene by atomic oxygen and its modification in oxygen plasma. The samples were measured during process of oxidation at individual time intervals using XPS.
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