National Repository of Grey Literature 29 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Optimization of the operational temperature of photoluminescence sensor field for detection of linear alcohols
Pokorný, Matěj ; Dian, Juraj (advisor) ; Červený, Václav (referee)
Chemical sensors are used to detect the presence of chemical substances using various physical quantities. Porous silicon, prepared by electrochemically etching the surface of crystalline silicon with a mixture of hydrofluoric acid and ethanol under appropriate conditions, is a porous material that contains nanocrystalline forms of silicon. Nanocrystalline silicon exhibits intense photoluminescence properties at room temperature, which strongly depend on the presence of chemical substances in its surroundings. The photoluminescence intensity of porous silicon is generally quenched in the presence of the analyte. The photoluminescence sensor response to the substances to be determined depends mainly on the concentration of the substance in question, but also on the operating conditions. Most critical is the operating temperature, which fundamentally affects the intensity of photoluminescence and the rate of sensor response when the analyte is added or removed from the system. The aim of this bachelor thesis was the preparation of porous silicon samples and their characterization by infrared (FTIR) and photoluminescence spectroscopy. These samples were tested as sensor elements of a photoluminescence sensor array for the detection of ethanol linear alcohol vapor. The main objective of the bachelor...
Optimization of the optical setup for chemiluminescence detection of natural products
Laho, Tomáš ; Dian, Juraj (advisor) ; Hraníček, Jakub (referee)
The content of the bachelor thesis was the implementation of a new luminescent apparatus and the study of chemiluminescence of luminol and beer samples of suitable age. The chemiluminescence of luminol was used in this work to determine its basic characteristics (spectrum, intensity of chemiluminescence, and its dependence on the composition of the reaction mixture) using a fiber spectrometer and, subsequently, verify the functionality of the assembled apparatus. This work aimed to realize an apparatus suitable for the chemiluminescence measurement of natural substances with potential use in the food industry. Luminol made it possible to observe intense chemiluminescence, thanks to which it was possible to optimize the measured signal. After successful optimization, there was an attempt to detect the chemiluminescent response in samples of artificially aged beer and compare the results obtained with those already published in the professional literature. In the presented bachelor thesis, the characteristics of luminol chemiluminescence were measured using a fiber spectrometer. Based on these results, the parameters of the new luminescent apparatus (size of slots, voltage on the photomultiplier) and the maximum values of chemiluminescence intensity for the correct operation of the apparatus were...
Application of (chir)optical analytical methods in the characterization of nonracemic helically chiral aromatics
Vilím, Vojtěch ; Hraníček, Jakub (advisor) ; Dian, Juraj (referee)
This master thesis is focused on preparation and characterization of thin layers for organic electronics forming a binary system, composed of achiral small conductive molecules (TIPS-pentacen) and chiral helicenes with various electronic density of their aromatic scaffold. Using organic electronics is innovative approach to manufacture electronic devices and compensate disadvantages of inorganic materials-based electronics. Induction of chirality into achiral organic electronics brings new possibilities for application in optical spintronics, optical quantum information processing and many others. Key words: thin layer, helicenes, circular dichroism, organic electronics
Optical characterization of supramolecular complexes of selected organic fluorophores with cyclodextrins
Haiklová, Simona ; Dian, Juraj (advisor) ; Červený, Václav (referee)
The content of this thesis is the optical characterization and determination of the strength of supramolecular interaction of selected organic fluorophores and cyclodextrins (CD) using the stability constant with optical methods: UV-Vis absorption and fluorescence. Two series of fluorophores differed in the presence of groups with two positive charges, and two types of cyclodextrins (-CD a -CD) with different cavity sizes were chosen for the study. Fluorophores with charged end groups can be efficiently bound by electrostatic interaction on solid surfaces of suitable chemical composition or thin films with an excess of negative charge and thus immobilized by a very strong interaction on a given support. These prepared surfaces or layers can then be used for the optical detection of chemical substances. The aim of this work was to determine the influence of cyclodextrin cavity size, the presence of a charged anchor, and solution pH on the supramolecular interaction of the studied systems and evaluate the application possibilities of the studied systems for optical chemosensors. In the presented thesis, the change in optical absorption and fluorescence intensity of four pairs of fluorophores: PRODAN, RhB, RhB-Si, DANSA, and their derivatives with a charged anchor was studied during supramolecular...
Porous silicon based optical sensors of chemical species for gas phase
Liška, Jiří ; Dian, Juraj (advisor) ; Červený, Václav (referee)
Title: Porous silicon-based optical sensors of chemical species for gas phase Author: Bc. Jiří Liška Department: Department of Inorganic Chemistry Supervisor: doc. RNDr. Juraj Dian, CSc. Abstract: Porous silicon is a nanostructured material, which is a suitable material for che- mical sensors due to its optical properties, especially photoluminescence and its quenching depending on the chemicals in the environment. Optical sensors based on porous silicon are the most studied group of sensors and have been successfully used for the detection of chemicals in both liquid and gas phases. In addition, the surface of porous silicon can be modified by a number of techniques, thereby modifying the recognition properties. In the case of combining multiple sensor elements of different properties, it is possible to measure multiple responses in the photoluminescent sensor array. The objectives of this thesis are: 1. Extension of electrochemical characterisation of initial silicon substrates using vol- tammetric techniques under different lighting conditions during the experiment, preparation of porous silicon samples from different types of crystalline silicon sub- strates (p-type, n-type), crystallographic orientation and doping degree. 2. Functionalisation of porous silicon surface with new chemical compounds by...
Cluster studies in molecular beams
Profant, Václav ; Dian, Juraj (advisor) ; Kužel, Petr (referee)
In the present work we study properties of clusters of small heteroatomic molecules with biological relevance by several experimental methods based on molecular beams. In the rst experiment structure and dynamics of size-selected charged pyrrole clusters have been studied by means of molecular beam scattering experiment. Small neutral P yn clusters were produced in Py/He expansions and larger mixed P ynArm clusters in Py/Ar expansions, and the scattering experiment with a secondary beam of He atoms was used to select the neutral clusters of dierent sizes. The complete size-selected fragmentation patterns for the neutral dimer to tetramer after an electron impact ionization at 70 eV from the measurements of the angular and velocity distributions at dierent fragment masses. In second experiment photolysis of size selected pyrrole, imidazole and pyrazole clusters has been investigated. Comparison with the photolysis of an isolated molecules and between studied systems has been made. Clusters were photolyzed at 243 and 193 nm and the kinetic energy distributions of the H-photofragments have been measured and analyzed. Finally the mass spectra of the fragments after multiphoton ionization have been measured. The signicant inuence of the cluster environment to the photolytic behavior was observed and discussed.
Application of modern analytical methods for the study of selected boron coordination compounds
Hrušková, Helena ; Jelínek, Ivan (advisor) ; Dian, Juraj (referee)
This thesis is focused on the study of boron coordination compounds, specifically boron pyrogallol and 2,3-dihydroxynaphthalene ligand complexes. In the introductory part of the work are discussed the properties of boron compounds, their preparation, the possibility of separation by capillary electrophoresis and methods of structural characterization. In the first part of the thesis, the methods of preparation of complexes are discussed and for each complex the optimal yield response is chosen. The resulting products were studied by low resolution mass spectrometry. In the second part of the thesis, structures of complexes, including their modeling in the Gaussian program, were described more precisely. Furthermore, the complexes were characterized by high resolution mass spectrometry. The complexes were also studied by 11 B, 1 H and 1 H COSY NMR and IR spectroscopy. The third part was devoted to the separation of these substances from the mixture after the reaction. CE-UV and CE-MS techniques were used for this purpose. To convert the results, the separation method was developed in ammonium formate buffers that are compatible with both instruments. The equilibration between complexes and ligands was also monitored by CE-UV. A special chapter is the study of pyrogallol autooxidation by UV-VIS and...

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