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Interdisciplinary relations of physics and chemistry in science education
Konečný, Martin ; Valenta, Jan (advisor) ; Rusek, Martin (referee)
Title: Interdisciplinary relations of physics and chemistry in science education Abstract: This master's degree thesis deals with the topic of interdisciplinary relations of chemistry and physics in science education. According to the review, to conveniently integrate physics and chemistry the appropriate topics and approaches were selected. The thesis includes teaching materials and worksheets to the three topics (Evolution of the Universe and the Origin of Elements, Luminescence and Composition and Properties of Matter) that are suitable for integration of physics and chemistry. The teaching material "Evolution of the Universe and the Origin of the Elements" includes a study text for teachers and a shorter study text for pupils. The teaching material "Luminescence" is based on an independent research done by pupils with their own crafted UV-lamp, completed with the facts included in a powerpoint presentation. The teaching material "Composition and Properties of Matter" consists of three parts (The paraffin, The Candle and The Properties of Selected Organic Substances) and is designed for an independent research done by pupils. Listed study materials were checked by teachers during meetings and seminars. The thesis also includes an evaluation of listed study materials by an expert group of high school...
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Multiphoton absorption of ultrafast laser pulse
Zukerstein, Martin ; Trojánek, František (advisor) ; Schmoranzerová, Eva (referee)
Nonlinear optics is constantly developing and in terms of future applications very perspective field of physics. With high-intensity pulsed lasers we are able to study interesting phenomena in matter that we cannot observe with common sources of light. The aim of this thesis is a study of the multiphoton absorption of high-intensity pulses in diamond using z-scan technique. It theoretically describes this nonlinear phenomenon using quantum theory. The next section author took a measurement of the two-photon absorption and found the two-photon absorption coefficients in different samples. Diamond was chosen as the sample material. This material has absolutely unique properties that rank it highly in future applications for optoelectronic devices.
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Synthesis and properties of zinc hydroxide and zinc oxide nanosheets
Hynek, Jan ; Lang, Kamil (advisor) ; Kovanda, František (referee)
1 Abstract The structure of layered zinc hydroxide intercalated with dodecyl sulfate (LZH-DS) anions was studied in detail. LZH-DS was prepared by direct precipitation in water and formed different phases. The following phases of LZH-DS were prepared - "extended" phase (ex) by direct precipitation in water, "shrunk" (s) and "super-shrunk" (ss) phases via treatment of LZH-DS(ex) phase in methanol. The studies of the thermal behavior of LZH-DS(ex) revealed interstratification of intercalated DS anions. It is the first example of interstratification in layered hydroxides that are intercalated with long aliphatic alkyl chain anions. The experimental results were used for molecular dynamic modelling of the structures. Nanometric thin films were prepared by dip-coating and inkjet printing of ZnO nanosheets on glass plates. The side-by-side alignment of the ZnO nanosheets on the substrate resulted in thin, transparent, oriented ZnO surfaces with the high-energy {001} facets exposed. The method of nanosheet deposition affected the film morphology; the dip-coated films were smooth and nonporous, while the inkjet-printed films were rough and had a surface area in the range of approximately 100-160 m2 g-1 . The first-order rate constants for the photocatalytic degradation of 4-chlorophenol on the nanosheet-based films...
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Laser spectroscopy of semiconductor quantum dots
Pokorný, Martin
This work is focused on examining photoluminescent properties of InAs quantum dots (QDs) on GaAs substrate covered by GaAs1-xSbx strain reducing capping layer (SRL) prepared by Stranski-Krastanow method. We measured luminescence decay time of two samples with different concentration of Sb in this layer. We investigated the influence of temperature, intensity and wavelength of the excitation pulse on the luminescent decay time. We also compared the properties of the samples after excitation by 760 nm pulse and 850 nm pulse - the former one is energetically above the substrate band gap; in the second case we excited only the QDs and the wetting layer (WL). We consequently derived recombination and relaxation processes occurring inside InAs QDs and also the transport of charge carriers from the substrate and the WL into QDs. One part of this diploma thesis was to learn about the methods of measuring ultrafast photoluminescence and build the experimental set-up.
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Optical properties of thin film scintillators
Onderišinová, Zuzana
In the present work we studied Pr, Sc co-doped and Eu-doped Lu3Al5O12 thin epitaxial garnet layers prepared by liquid phase epitaxy (LPE) on Y3Al5O12 (YAG) and Lu3Al5O12 (LuAG) single crystalline substrates. In the process of growth BaO - BaF2 - B203 (Pr, Sc co - doped layers) and PbO - B2O3 (Eu - doped layers) fluxes were used. These materials are considered perspective scintillators with high density, fast scintillation response, high quantum efficiency and good chemical and mechanical stability. They are used in a number of applications in which high spatial resolution is required. The absorption, emission and excitation spectra of experimental samples were measured and investigated. Our attention was focused especially on the study of influence of Sc3+ ions on the emission properties of Pr3+ ions in epitaxial layers which mutually contain various amounts of concentrations of dopants. The Sc3+ ions do not show any radiative transitions in visible and UV spectral regions, but they increase the scintillation response of Pr3+ ions. This phenomenon is caused by overlappig of the Sc-related emission around 275 nm with the 4f-5d absorption band of Pr3+ centers. By measurement of radioluminescence this energy transfer from Sc3+ to Pr3+ activator centres was confirmed.
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System for electroluminiscence defect detection of solar cells
Marčík, Silvestr ; Jandová, Kristýna (referee) ; Vaněk, Jiří (advisor)
The master thesis focuses primarily on issues of photovoltaic cells in terms of their defects. The introductory part deals with the history of photovoltaics, their introduction into practice and finally an explanation of the photoelectric effect itself. The thesis also describes photovoltaic cells themselves. It explains their principle, advantages, disadvantages and the creation of photovoltaic systems. A substantial part of the work is focused on the topic of detection of defects using luminescent methods. Subsequently, it describes procedural defects arising from the improper handling of already manufactured products. The final part deals with the main topic of the work, which is a detection using luminescence methods and it also mentions the non-luminescence method LBIC. The practical part of the master thesis contains the analysis of the current solution and of the subsequent proposal of solution using a low cost camera. It describes how to modify the camera, verify its spectral sensitivity using a spectrometer and measure the sensitivity of the CMOS sensor. The conclusion is focused on verifying the functionality of the proposed solution on different sources of infrared radiation and photovoltaic panels themselves.
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Bioapplications of novel nanostructured materials
Fučíková, Anna ; Valenta, Jan (advisor) ; Polívka, Tomáš (referee) ; Plášek, Jaromír (referee)
Title: Bioapplications of novel nanostructured materials Author: Anna Fučíková Department / Institute: Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University in Prague Supervisor of the doctoral thesis: Doc. RNDr. Jan Valenta, Ph.D., Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University in Prague Abstract: This work is aimed at development of new fluorescent labels based on silicon nanocrystals. Nanodiamonds and commercial CdSe quantum dots have been used as comparative materials. Silicon nanocrystals are relatively small (1-4 nm) compared to other studied nanomaterials. They are prepared by electro-chemical etching and their surface can be activated by various molecules which strongly influences luminescence properties. Luminescence quantum efficiency can be as high as 30 % and perfectly photostable even in biological environment. Si nanocrystals are biodegradable in a living organism within reasonable time scale and non-toxic. We are able to detect luminescence of single nanocrystals, even inside living cells, with use of our micro-spectroscopy apparatus. Nanodiamonds have weak luminescence; they are toxic at higher dosages and very stable in living bodies (without available technique how to remove them). Studied CdSe...
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Laser spectroscopy of semiconductor quantum dots
Pokorný, Martin ; Trojánek, František (advisor) ; Kuldová, Karla (referee)
This work is focused on examining photoluminescent properties of InAs quantum dots (QDs) on GaAs substrate covered by GaAs1-xSbx strain reducing capping layer (SRL) prepared by Stranski-Krastanow method. We measured luminescence decay time of two samples with different concentration of Sb in this layer. We investigated the influence of temperature, intensity and wavelength of the excitation pulse on the luminescent decay time. We also compared the properties of the samples after excitation by 760 nm pulse and 850 nm pulse - the former one is energetically above the substrate band gap; in the second case we excited only the QDs and the wetting layer (WL). We consequently derived recombination and relaxation processes occurring inside InAs QDs and also the transport of charge carriers from the substrate and the WL into QDs. One part of this diploma thesis was to learn about the methods of measuring ultrafast photoluminescence and build the experimental set-up.
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Study of semiconductors by methods of laser spectroscopy
Dzurňák, Branislav ; Trojánek, František (advisor) ; Oswald, Jiří (referee) ; Herynková, Kateřina (referee)
Title: Study of semiconductors by methods of time resolved laser spectroscopy: Luminescence spectroscopy of nanocrystalline diamond Author: Branislav Dzurňák Department: Department of Chemical Physics and Optics Supervisor: doc. RNDr. František Trojánek, Ph.D. Abstract: The PhD thesis is focused on optical properties of nanocrystalline diamond prepared by chemical vapour deposition method. Photoluminescence of nanocrystalline diamond samples and effects of ambient temperature, pressure, pH and UV irradiation on it are studied by laser spectroscopy. Results suggest the keyrole of water and air adsorbates which affect the energy states in the sub-bandgap region of diamond. Photoluminescence decay of samples of different surface termination and structure and its dependency on ambient pressure and temperature is studied by methods of ultrafast (picosecond and nanosecond scale) laser spectroscopy. Results are analysed by power-law decay function which fits well the luminescence decay curves and also describes the dynamics of charge carriers in states localised within the bandgap. The model of interaction of nanocrystalline diamond with air adsorbates is proposed. Non-linear optical properties of nanocrystalline diamond are also studied, namely the generation of second and third harmonic frequency. The thesis...
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