|
|
Selective hydrogenation/Oxidation of CVD graphene using AFM
Přikryl, Vojtěch ; Švarc, Vojtěch (referee) ; Bartošík, Miroslav (advisor)
Graphene is a perspective material for utilization in electronics due to its high charge carrier mobility. However, in order to be applicable in practice the bandgap opening is necessary. One way of achieving this is modification of graphene by hydrogenation or oxidation. This work concerns the possibility of using AFM for local hydrogenation/oxidation of graphene depending on the bias voltage between the tip and the sample. The presence of hydrogenation/oxidation was examined by Kelvin probe force microscopy and Raman spectroscopy. The possibility of oxidation was proved but hydrogenation was not proved.
|
|
|
Raman spectroscopy teaching equipment
Indra, Zdeněk ; Sedlák, Petr (referee) ; Škarvada, Pavel (advisor)
This thesis examines the principle of the Raman phenomenon and the function of the Raman spectrometer in order to build a low-cost Raman spectrometer assembly for school laboratory teaching. The thesis lists the important parts of the device and describes their key features. Subsequently, the selection of each component is discussed and a basic experiment is performed to verify the principle of this spectrometer. In the final part, a low-cost Raman spectrometer is constructed and tested thanks to the knowledge gained.
|
|
|
Raman spectroscopy of biologically active species and antitumor drugs
Třeštíková, Liběna ; Vetterl,, Vladimír (referee) ; Vrána, Oldřich (advisor)
SERRS spektra of biological materials are very komplex, because they consist of signals from all molecules present in cells. In this text are presented SERRS spektra of antitumor drugs and its komplex with DNA. Experimental are rated on doxorubicin and another antitumor druha and on study of theirs potential by treatment for tumors. Doxorubicin belong to clase antracycline antibiotics and is used for stop of tumor cells reproduction. Scientists found still new ways, new drugs. SERRS is one of possibilities for study of this drugs and theirs interaction with DNA.
|
|
|
Molecular modelling - Structure and Properties of carbene-based catalyst
Kulovaná, Eva ; Hermanová, Soňa (referee) ; Richtera, Lukáš (advisor)
Pomocí molekulového modelování je možné předpovídat chování nových látek a napomáhá při jinak obtížné interpretaci experimentálních dat. Cílem práce byla predikce vybraných vlastností polymeračních katalyzátorů na bázi karbenů, predikce jejich struktur a spektrálních charakteristik a studie mechanismu polymerace za otevření kruhu laktidu. K ověření chování karbenů a jejich prekurzorů ve formě chloridů byly studovány vybrané charakteristiky molekuly. Byl proveden výpočet vybraných molekulových orbitalů a elektrostatických map. Následně pomocí počítačových programů byly získány teoretické vazebné délky a úhly vybraných imidazolových a imidazolinových sloučenin, karbenů a jejich možných produktů hydrolýzy. Data strukturně podobných, již charakterizovaných sloučenin, byla získána z CCDC (Cambridge Crystallographic Data Centre) a následně byla konfrontována s vypočítanými daty. Byla změřena infračervená a Ramanova spektra imidazolové soli a infračervené spektrum příslušného karbenu. Tato spektra byla konfrontována s napredikovanými. Pro lepší interpretaci spekter byla spočítána spektra možných produktů hydrolýzy. Následně byl studován mechanismus polymerace za otevření kruhu laktidu. Na základě spočítaných energií stacionárních bodů byl navržen nový mechanismus polymerace.
|
|
|
Preparation of graphene layers by various methods and characterization of their properties
Zahradníček, Radim ; Bartošík, Miroslav (referee) ; Lišková, Zuzana (advisor)
This bachelor's thesis deals with the production of graphene by different methods. Graphene was prepared by mechanical exfoliation and chemical methods. Graphene oxide (GO) was first prepared by modified Hummers method and disolved the solution in isopropyl alcohol. It was subsequently reduced by photoreduction, UV radiation and thermal reduction. Produced graphene samples were characterized using optical microscopy, electron microscopy, atomic force microscopy, Raman spectroscopy and X$-$ray photoelectron spectroscopy. Measurement results and evaluation of production quality of graphene are shown in this work.
|
|
|
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.
|
|
|
Preparation and characterization of MoS2 thin films
Tomková, Renáta ; Zahradníček, Radim (referee) ; Bartoš, Miroslav (advisor)
This thesis deals with topological insulators, which are described by the quantum spin Hall effect, as well as on semiconductors, where the band structure of semiconductors and more specifically mentioned unipolar transistor MOSFET is explained. There are also mentioned primarily 2D materials and in particular of MoS2. Topic focuses on its structure, the electric properties, the use and preparation by using micromechanical exfoliation. In the last chapter it is described how to prepare MoS2 structures and their analysis. Structural properties of this material were measured by the AFM and Raman spectroscopy. The experimental part there are illustrative photograph of MoS2 taken with an optical microscope and spatial structures created by AFM.
|
|
|
Metabolism of Bacterial Cells and the Effect of Stress on Biosynthesis of PHA
Kučera, Dan ; Kráčmar, Stanislav (referee) ; Ondrejovič,, Miroslav (referee) ; Obruča, Stanislav (advisor)
This thesis deals with the study of polyhydroxyalkanoate biosynthesis as a microbial product with the potential to replace current conventional plastics made from petroleum. The dissertation thesis is elaborated in the form of a discussed set of already published publications, which are then part of the thesis in the form of appendices. The work builds on relatively extensive knowledge in the field of polyhydroxyalkanoate production and brings new facts and possible strategies. Various possibilities of analysis of polyhydroxyalkanoates using modern methods were tested in this work, which brings especially speed, which can be crucial in real-time evaluation of production biotechnological process. Raman spectroscopy has proven to be a very promising technique for rapid quantification of PHA. Furthermore, the work deals with valorisation of waste of food and agricultural origin. Emphasis is placed on methods of detoxification of lignocellulose hydrolysates. In this context, adsorption of inhibitors to lignin was first used as an alternative to other detoxification techniques. Due to detoxification, selected production strains Burkholederia cepacia and B. sacchari were able to utilize softwood hydrolyzate for PHA production. In the next part of the work was also tested the possibility of using chicken feathers as a complex source of nitrogen. Evolutionary engineering was also used as a possible strategy to eliminate the inhibitory effect of levulic acid as a microbial inhibitor that results from the hydrolysis of lignocellulosic materials. Adaptation experiments were used to develop strains exhibiting higher resistance to levulic acid and the ability to accumulate a higher 3HV copolymer from the original wild-type C. necator strain. Another promising approach tested in the work was the use of extremophilic microbial strain, which leads to a reduction in the cost of biotechnological production. Selected Halomonas species have shown high potential as halophilic PHA producers. The final part of the thesis was devoted to the selection of the production strain with regard to the properties of the resulting PHA. The Cupriavidus malaysiensis strain was selected to produce a P(3HB-co-3HV-co-4HB) terpolymer which revealed significant differences in material properties over P3HB.
|
|
|
Luminescence of semiconductors studied by scanning near-field optical microscopy
Těšík, Jan ; Klapetek, Petr (referee) ; Křápek, Vlastimil (advisor)
This work is focused on the study of luminescence of atomic thin layers of transition metal chalkogenides (eg. MoS2). In the experimental part, the work deals with the preparation of atomic thin layers of semiconducting chalcogenides and the subsequent manufacturing of plasmonic interference structures around these layers. The illumination of the interference structure will create a standing plasmonic wave that will excite the photoluminescence of the semiconductor. Photoluminescence was studied both by far-field spectroscopy and near-field optical microscopy.
|
|
|
Utilization of physico-chemical and spectroscopical methods in study on microbial extremofiles
Dobešová, Kateřina ; Enev, Vojtěch (referee) ; Sedláček, Petr (advisor)
The aim of this bachelor thesis is the determination od polyhydroxyalkanoates in the cells of extremophille bacterie, preformed by several methods. The chosen bacterium was Schlegelella thermodepolymerans DSM 15 344 Thermogravimetric analysis, infrared spectroscopy with Fourier transformation, and Raman spectroscopy were used in this thesis. The TGA method was used for the determination of extracellular and intracellular water in samples. The FTIR method was used in order to observe the amount od PHA, but aslo to observe the physical properties of the polymer in the sample, specifically to determine either amorphous or crystalline featuers of this polymer. Raman spectroscopy was used in oder to confirm the presence of PHA in the samples. All results e´were compared eith the results accomplished by gas chromatografy.
|
guest ::
