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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...
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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...
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Photoluminescence sensor field applied for detection of chemical compounds in gas mixtures
Liška, Jiří ; Dian, Juraj (advisor) ; Broncová, Gabriela (referee)
Title: Photoluminescence sensor field applied for detection of chemical compounds in gas mixtures Author: Jiří Liška Department: Department of Analytical Chemistry Supervisor: doc. RNDr. Juraj Dian, CSc. Abstract Porous silicon is a nanostructured material that can be prepared by galvanic etching of silicon in the presence of hydrofluoric acid. The properties of this material can be influenced by way of preparation or by the chemical modification of the surface. Porous silicon has many extraordinary properties as compared to macrocrystalline silicon; the most important one for chemical sensing is the visible photoluminescence at room temperature. In the presence of organic and inorganic analytes in the gas phase, the photoluminescence of the material is quenched. This phenomenon can be used for chemical sensors of chemical compounds in the gas phase. These sensors are very sensitive and give reasonable results for organic compounds. Photoluminescence sensor field uses for measurement several sensor elements with the modified surface. It is possible to use this method for the identification and determination of gaseous organic compounds. The aim of this thesis was: 1. the preparation of porous silicon samples, 2. the modification of surface with different methods, 3. the characterization of samples with FTIR...
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Electrochemical etching of silicon
Vrzal, Pavel ; Voborný, Stanislav (referee) ; Šamořil, Tomáš (advisor)
The electrochemical etching is very used technique for semiconductor materials modification. Different structures which find applications in many fields (biotechnology, nanotechnology or electronics) can be prepared by this technique. The task of bachelor’s thesis was preparation of porous silicon using electrochemical etching. At first, a study dedicated to porous Si was carried out. Experimental part of this work deals with a design of etching cell which was used for preparation of porous silicon by electrochemical etching. In addition, the porous Si was prepared by metal assisted chemical etching. Subsequently, created structures were analyzed by scanning electron microscopy. Photoluminescence properties of porous silicon were studied as well.
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Preparation and characterization of silicon-based materials
Šlechta, Miroslav ; Dian, Juraj (advisor) ; Jelínek, Ivan (referee)
Title: Preparation and characterization of silicon-based materials Author: Miroslav Šlechta Department: Department of Chemical Physics and Optics Supervisor: doc. RNDr. Juraj Dian, Csc., Department of Chemical Physics and Optics Abstract: Porous silicon is nanostructured material based on silicon. He was prepared by anodic etching of crystalline silicon in hydrofluoric acid. Physical and chemical properties of porous silicon nanocrystals resulting from the dimensions, which range from units to tens of nanometers. For nanostructured silicon compared to crystalline silicon, exhibit unique properties that depend on the degree of quantum dimensional phenomena and phenomena on its large internal surface. Suitable choice of the silicon substrate, particularly in terms of conductivity and crystallographic orientation, and technological conditions (in particular electrolyte composition, the etching time and current density) can be prepared nanostructured materials of different pore sizes - macroporous, mesoporous and microporous silicon and varying representation Si-O and Si-H bonds. Morphology and chemical composition of the surface of porous silicon allows to think of it as a suitable material for a range of applications - particularly chemical sensors and biosensors, optoelectronics and biomedical applications....
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Morfology and surface chemical composition of porous silicon prepared at various conditions
Konečný, Martin ; Dian, Juraj (advisor) ; Herynková, Kateřina (referee)
Title: Morfology and surface chemical composition of porous silicon prepared at various conditions Author: Bc. Martin KONEČNÝ Author's e-mail: konecmar@seznam.cz Department: Department of Chemical Physics and Optics Supervisor: Doc. RNDr. Juraj Dian, CSc. Supervisor's e-mail: Juraj.Dian@mff.cuni.cz Abstract: Porous silicon is a silicon-based material prepared mainly by anodic etching of crystalline silicon in hydrofluoric acid. Physical and chemical properties of porous silicon are governed by structures with sizes of the order of ones to tens of nanometers. Properties of nanostructure material are affected - as compared to macroscopic counterparts - by quantum confinement effect and enormous internal surface. According to type of silicon substrate (type of dopant, conductivity, crystallographic orientation) and technological conditions a material with different mean size of pores (macro-, meso- and nanoporous silicon) and surface chemical composition (different ratio of Si-O and Si-H bond) can be prepared. Morphology and surface chemical composition predestinated application potential of porous silicon for sensors of chemical species by taking advantage of strong sensitivity of physical properties of silicon nanocrystals - especially of photoluminescence - on the chemical state of a surface. Detection of...
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Electrochemical etching of silicon
Vrzal, Pavel ; Voborný, Stanislav (referee) ; Šamořil, Tomáš (advisor)
The electrochemical etching is very used technique for semiconductor materials modification. Different structures which find applications in many fields (biotechnology, nanotechnology or electronics) can be prepared by this technique. The task of bachelor’s thesis was preparation of porous silicon using electrochemical etching. At first, a study dedicated to porous Si was carried out. Experimental part of this work deals with a design of etching cell which was used for preparation of porous silicon by electrochemical etching. In addition, the porous Si was prepared by metal assisted chemical etching. Subsequently, created structures were analyzed by scanning electron microscopy. Photoluminescence properties of porous silicon were studied as well.
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Electrochemical etching of silicon
Vrzal, Pavel ; Voborný, Stanislav (referee) ; Šamořil, Tomáš (advisor)
The electrochemical etching is very used technique for semiconductor materials modification. Different structures which find applications in many fields (biotechnology, nanotechnology or electronics) can be prepared by this technique. The task of bachelor’s thesis was preparation of porous silicon using electrochemical etching. At first, a study dedicated to porous Si was carried out. Experimental part of this work deals with a design of etching cell which was used for preparation of porous silicon by electrochemical etching. In addition, the porous Si was prepared by metal assisted chemical etching. Subsequently, created structures were analyzed by scanning electron microscopy. Photoluminescence properties of porous silicon were studied as well.
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