|
|
Lead-based relaxor ferroelectrics by Raman scattering
Rafalovskyi, Iegor ; Hlinka, Jiří (advisor) ; Deluca, Marco (referee) ; Dubroka, Adam (referee)
Title: Lead-based relaxor ferroelectrics by Raman scattering Author: Iegor Rafalovskyi Institute: Institute of Physics of the Czech Academy of Sciences Supervisor: Ing. Jiří Hlinka, Ph.D., Department of Dielectrics, Institute of Physics of the Czech Academy of Sciences Abstract: The following work is dedicated to measurement and analysis of Raman scat- tering spectra of different perovskite ferroelectrics, mainly lead-based relaxors in the form of bulk and thin films. Investigation of single crystal MPB composition PMN-0.32PT has shown that procedure of zero-field heating of previously field-cooled sample leads to sta- bilization of heterophase pattern with 10-100 µm parallel stripes of alternating tetragonal and rhombohedral (rhombohedral-like) phases. Another point of interest investigated in PMN-0.32PT is rhombohedral to tetragonal phase transition induced by electric field. The domain structure with 90-degree domain walls has been observed in relaxor based composition PFN-0.38PT. Adjacent domains were investigated by polarized Raman scat- tering to confirm their structure and symmetry. Relaxor ferroelectric PSN has shown totally different behavior in polarized Raman spectra if studied in the form of single crystal or epitaxial thin film. The normalized cross-polarized intensity of 810 cm−1 band measured in...
|
|
|
Spectroscopic Study of miRNA Structure and Interactions
Homolka, Radim ; Štěpánek, Josef (advisor) ; Maloň, Petr (referee)
MiRNA are short RNA molecules that mediate post-transcriptional regulation of gene expression by binding to a target mRNA. In this thesis, some structural properties and thermodynamic parameters (melting temperature, enthalpy ∆H and entropy ∆S changes connected with the transition between particular conformations) of oligonucleotides simulating complex of miRNA and mRNA, were characterized by using spectroscopic methods and a gel electrophoresis. Temperature dependences of UV and Raman spectra were measured, the results treated by means of a factor analysis, and the abovementioned thermodynamic parameters determined by a fit to a feasible model. The outputs have demonstrated the capability of the used methods to determine thermodynamic and structural properties of non-canonical RNA complexes. Powered by TCPDF (www.tcpdf.org)
|
|
|
Characterization of proteins of 2'-5' oligoadenylate pathway by means of vibrational spectroscopy
Víšová, Ivana ; Kopecký, Vladimír (advisor) ; Bednárová, Lucie (referee)
The work concerns to structural characterization of two important proteins of 2'-5' oligoadenylate pathway participating in an immune response of organism to a viral infection. Studied proteins were ankyrin domain of mouse RNase L, the C-terminal part of human phosphodiesterase 12 and the complete human phosphodiesterase 12. The proteins were characterized by Raman spectroscopy, infrared spectroscopy, electronic circular dichroism, dynamic light scattering and in addition by two non-spectroscopic methods- differential calorimetry and electrophoresis. For each protein the secondary structures, thermal stability, weight of oligomers and generally a basic characterization by above mentioned methods were provided.
|
|
|
PFM and Raman spectroscopy of selected dielectric materials
Borodavka, Fedir ; Gregora, Ivan (advisor) ; Baumruk, Vladimír (referee) ; Hehlen, Bernard (referee)
Title: PFM and Raman spectroscopy of selected dielectric materials Author: Fedir Borodavka Institute: Department of Dielectrics, Institute of Physics of the Academy of Sciences, Na Slovance 2, 182 21, Prague 8, Czech Republic Supervisor: Ing. Ivan Gregora, CSc. Training institute: Department of Dielectrics, Institute of Physics of the Academy of Sciences, Na Slovance 2, 182 21, Prague 8, Czech Republic Consultants: RNDr. Stanislav Kamba, CSc. and RNDr. Vladimír Vorlíček, CSc. Abstract: The thesis is devoted to a detailed investigation of dielectric materials using Raman spectroscopy and PFM microscopy techniques. Phonon properties of a newly synthesized guanylurea(1+) hydrogen phosphite single crystals have been studied. A tentative assignment of the observed Raman peaks has been done and the sets of A′ MIX, A′ TO and A′′ TO mode frequencies have been determined. Phonon behaviour of BiMnO3 ceramics, obtained from Raman spectra, has been char- acterized. After comparing the factor group analysis with the Raman spectra it has been concluded that the material has a centrosymmetric C2/c structure and is not ferroelectric. Lattice modes of the complex La1/2Na1/2TiO3 single crystal have been investigated. We have numerically analysed the intensity behaviour of the sharp peak at 455 cm−1 on heating and...
|
|
|
Mineralogical analysis of historical paintings
Čermáková, Zdeňka ; Hradil, David (advisor) ; Kanický, Viktor (referee) ; Artioli, Gilberto (referee)
Historical painted works of art have a very complex inner structure. The period painting technique led to the execution of a ground layer followed by several layers of underpainting and a top paint layer, over which a layer of glaze has been applied to increase the resistance to external wear. Each of these colour layers is composed of a dye or a pigment (or their mixture) bound by organic binder. Throughout the history, pigments were commonly prepared from minerals, either extracted from natural deposits or created artificially. In these heterogeneous layers containing both inorganic and organic components, undesirable degradation changes either driven by processes taking place directly in the colour layer or influenced by external agents may occur. Mineralogical approach, which focuses primarily on the structure of studied pigments, helps in the clarification of the occurring processes, in the determination of conditions leading to degradation as well as in the identification of original/degradation phases. Furthermore, it can be profitably applied in the micro- analysis of mineral pigments present in tiny micro-samples obtained from works of art, contributes to the artwork's provenance/authorship studies and the determination of regional provenance of the employed mineral pigments. This Ph.D....
|
|
|
Non-resonant Raman Spectroscopic Study of Guanine Quadruplex Structures
Golan, Martin ; Mojzeš, Peter (advisor) ; Mašek, Vlastimil (referee)
Parts of human telomere sequences containing at least 4 guanine subsequences show the ability to form intrastrand quadruplexes of remarkable conformational diversity. Former studies using conventional Raman spectroscopy have revealed that the sequence G3(TTAG3)3 at milimolar concentrations in phosphate buffer solution doped with Na+ ions (ionic strength 150 mM) adopts antiparallel conformation regardless of the length of standing at room temperature or annealing, whereas K+ ions cause gradual transition to "3+1" or even parallel conformation. On the other hand, measurements carried out upon sequence AG3(TTAG3)3 at similar concentrations using Photonic Crystal Fibre-enhanced Raman Spectroscopy (PCFRS) suggest that in the respective presence of both Na+ and K+ (ionic strength 100 mM), a parallel structure is adopted. The hereby presented work employs conventional Raman spectroscopy and Drop Coating Deposition Raman spectroscopy to examine the sequence AG3(TTAG3)3 at concentrations ranging from units to hundreds of milimoles in strands. It concludes that the structure adopted in the presence of Na+, resp. K+ ions is antiparallel, resp. "3+1", and doesn't change over time despite both long standing and annealing. Two hypotheses about the cause of the differences between the results obtained by PCFRS and...
|
|
|
The Study of the Molecular Structure of Various Forms of Conducting Polymers using FTIR and Raman Spectroscopies
Morávková, Zuzana ; Trchová, Miroslava (advisor) ; Baumruk, Vladimír (referee) ; Matějka, Pavel (referee)
In this Thesis, the structure of thin films formed by a conducting polymer, polyaniline, was studied using mainly infrared and Raman spectroscopies. That led to the study of aniline oligomers. The oligomers play a key role in the formation of thin films and nanostructures of polyaniline. Furthermore, the Thesis deals with the carbonization of various forms of polyaniline (granular polyaniline base, thin films of polyaniline salt, multi-wall carbon nanotubes coated with polyaniline salt or base, polyaniline nanotubes/nanorods prepared in the presence of ethanol). The two topics, aniline oligomers and carbonization of polyaniline, are connected by a paper concerning the carbonization of microspheres formed during oxidation of aniline in alkaline medium. Optical microscopy, transmission and scanning electron microscopy, UV-Vis spectroscopy, spectroscopic ellipsometry, wide angle X-ray scattering and thermogravimetric analysis were used.
|
|
|
Biologically important non-canonical structures of nucleic acids in complexes with cationic porphyrins
Palacký, Jan ; Mojzeš, Peter (advisor) ; Setnička, Vladimír (referee) ; Víglaský, Viktor (referee)
Guanine quadruplexes are a class of unusual nucleic acids conformations based on stacked planar guanine tetrads stabilized via Hoogsteen pairing and cation coordination. They are implicated in numerous cellular processes including replication, recombination or transcription. Guanine quadruplexes are widespread within the human genome but their occurrence is highest in the single stranded guanine-rich regions at telomeres. Telomeric guanine quadruplexes are gaining growing interest due to their ability to inhibit the activity of the telomerase enzyme, which is responsible for the proliferation of tumor cells. Specifically, we investigated the conformational polymorphism of the human core telomeric sequence G3(TTAG3)3 conditioned by the concentration of DNA, metal cations (K+ , Na+ ) and/or annealing. Raman spectroscopy was employed as the primary method for this study because, unlike common spectroscopic methods, it allowed us to monitor the quadruplex structure at very high DNA concentrations mimicking molecular crowding conditions in the cell. We demonstrate that the G3(TTAG3)3 quadruplex switch between the antiparallel and parallel strand alignment as a function of nucleoside and potassium concentration. In addition, we demonstrate that cationic porphyrins can be used as sensitive probes of the quadruplex...
|
|
|
The Study of the Molecular Structure of Various Forms of Conducting Polymers using FTIR and Raman Spectroscopies
Morávková, Zuzana
In this Thesis, the structure of thin films formed by a conducting polymer, polyaniline, was studied using mainly infrared and Raman spectroscopies. That led to the study of aniline oligomers. The oligomers play a key role in the formation of thin films and nanostructures of polyaniline. Furthermore, the Thesis deals with the carbonization of various forms of polyaniline (granular polyaniline base, thin films of polyaniline salt, multi-wall carbon nanotubes coated with polyaniline salt or base, polyaniline nanotubes/nanorods prepared in the presence of ethanol). The two topics, aniline oligomers and carbonization of polyaniline, are connected by a paper concerning the carbonization of microspheres formed during oxidation of aniline in alkaline medium. Optical microscopy, transmission and scanning electron microscopy, UV-Vis spectroscopy, spectroscopic ellipsometry, wide angle X-ray scattering and thermogravimetric analysis were used.
|
|
|
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.
|
guest ::
