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Gold nano systems for the detection of molecules using surface-enhanced Raman scattering (SERS)
Benešová, Markéta ; Bernatová,, Silvie (referee) ; Skoumalová, Petra (advisor)
This diploma thesis was focused on the production and use of gold nanosystems to enhance Raman scattering. Metal nanoparticles, when interacting with electromagnetic radiation, form so-called localized plasmons, which can enhance Raman scattering. SERS (surface-enhanced Raman scattering) is a non-destructive analytical technique used in this work to measure the concentration and chemical changes in the rhodamine B molecule. Rhodamine B was subjected to photocatalytic degradation using two types of photocatalysts before measurement: TiO2-(H) and TiO2-(H)-Ag. The quantitative dependence of rhodamine B photodegradation on the presence of photocatalysts in a given period time was sought using photodegradation processes. The results of measurements using the SERS method were compared with the results obtained by UV-VIS spectroscopy. From the measured data, it was found that the photocatalysts significantly accelerate the photodegradation processes, because the Raman signal of rhodamine B decreased, while the signal decrease was most pronounced for the catalyst with added TiO2-(H)-Ag, less prominent but still statistically significant signal decrease was observed for the TiO2-(H) catalyst. In the control sample without the addition of photocatalyst, no decrease in signal was observed. In the next phase of the thesis, a sandwich immunoassay was designed that uses SERS to detect E. coli bacteria or other specific microorganisms in the sample. The first component of the sandwich immunoassay is gold nanoparticles, which carry a so-called Raman reporter, which has a clear Raman response in the spectrum, and gold nanoparticles amplify this signal, and antibodies, thanks to which the particles specifically bind to the microorganism. Another component is either gold layered slides or magnetic nanoparticles, which are modified with antibodies and serve to immobilize microorganisms. This system can be a fast and very accurate way to identify a given microorganism in a sample.
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Enhancement of detection limits in Laser-Induced Breakdown Spectroscopy (LIBS) using nanoparticles
Képeš, Erik ; Prochazka, David (referee) ; Sládková, Lucia (advisor)
This bachelor's thesis describes the options of ehnancing the detection limits of laser-induced breakdown spectroscopy (LIBS). It summarizes different modifications of the classical LIBS apparatus, which are used by methods double-pulsed LIBS (DPLIBS), Townsend effect plasma sectroscopy (TEPS), resonance enhanced LIBS (RELIBS), spark discharge LIBS (SDLIBS), flame-enhanced LIBS (FELIBS), and new ways of sample preparation, such as are used in the method nanoparticle enhanced LIBS (NELIBS). It briefly describes the mechanisms, which are used by each method to reduce the detection limit and it contains an overview of obtained enhancements against the classical method LIBS. It deals with the method nanoparticle enhanced LIBS in more detail and experimentally verifies and studies the effects of nanoparticles of different types and sizes on the emission spectrum of the method LIBS.
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Plasmonically active electrochemical electrodes based on tungsten disulfide nanotubes decorated with gold nanoparticles
Salajková, Zita ; Daňhel,, Aleš (referee) ; Ligmajer, Filip (advisor)
When an electromagnetic wave illuminates metal nanostructure under right circumstances, it can couple to the motion of electrons and thus give rise to so-called LSPR. When these collective oscillations non-radiatively decay, they excite charge carriers that can have, for a short moment of time, highly non-thermal energy distribution. These so-called "hot" electrons and holes can then take part in photochemical applications, e.g. in reactions on photoactive electrodes where hot electrons act as catalysts. Gold nanoparticles seem to be a good candidate for fabrication of such electrodes because they exhibit resonantly enhanced absorption due to plasmon excitation in the visible and near infrared spectral range, which could make the solar energy harvesting more efficient. In this work we present electrohemical experiments that should help to clarify the underlying principles of photochemical reactions involving hot electrons. Our model system consists of indium tin oxide electrodes covered with tungsten disulphide nanotubes that were previously decorated by gold nanoparticles. By comparing the results of chronoamperometric measurements on individual components of this system it was shown that excitation of plasmonic nanoparticles indeed leads to photocurrents and that electrochemical methods can serve as a valuable tool for analysis of photochemical reactions catalyzed by hot electrons.
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Photoelectrochemical properties of titanium dioxide doped by metals
Vičarová, Monika ; Drbohlavová, Jana (referee) ; Dzik, Petr (advisor)
This thesis deals with the optimization of materials and processes for making layers of titanium dioxide enriched with metal nanostructured aggregates. These layers have a plasmonic effect in visible light radiation. Gold-doped titanium dioxide thin films were applied to the FTO glass substrate by spin-coating method and calcined at 450 ° C for 30 minutes. Two forms of titanium dioxide and two different gold precursors were used to make the layers. The structure of the layers was observed by optical and SEM microscopy. The photoelectrochemical properties of the prepared layers were studied by electroanalytical methods linear sweep voltammetry and chronoamperometry.
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Functionalized nanostructures
Váňa, Rostislav ; Kvapil, Michal (referee) ; Kolíbal, Miroslav (advisor)
This thesis deals with functionalized nanoparticles. In the first part there are mentioned materials suitable for a functionalization, the usage of functionalized nanoparticles in medicine and biochemistry and detection methods of changes of optical properties. In the second part changes of optical properties after functionalization are investigated by spectroscopic ellipsometry and FTIR spectroscopy.
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Synthesis of spherical gold nanoparticles for biomedical applications
Gablech, Evelína ; Adam, Vojtěch (referee) ; Drbohlavová, Jana (advisor)
Tato práce se zabývá syntézou sférických zlatých nanočástic pro biomedicínské aplikace. Zlaté nanočástice byly syntetizovány ekologicky nezávadnými metodami, kterým je věnována i značná část rešerše. Cílem bylo nasyntetizovat stabilní koloidní zlaté nanočástice vhodné pro různé biomedicínké aplikace zejména, pro in vivo a in vitro zobrazovací metody, kterých přehled je take obsažen v teoretické části práce. Také byl proveden test cytotoxicity, jelikož částice mají být použitelné pro in vivo aplikace. Částice byly dale charakterizovány metodami SEM, DLS a UV-VIS.
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Functionalization of gold nanoparticles for imaging
Jakubechová, Jana ; Pekárková, Jana (referee) ; Drbohlavová, Jana (advisor)
The diploma thesis deals with synthesis of gold nanoparticles and their surface functionalization suitable for in vitro imaging. In this view there are requirements for optical properties such as stability, monodispersity and no presence of cytotocxicity. In order to fulfill these demands the synthesis by Turkevich method with surface modification by glutathione and polytethylenglycol was performed. Analytical methods such as DLS, SEM and Zeta potential measurement were utilized to characterize the physical and chemical properties of synthesized gold nanoparticles. Finally, MTT assay was performed to evaluate toxicity of gold nanoparticles using HEK 293 cell line.
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Characterization of semiconducting nanowires
Novotný, Karel ; Grym, Jan (referee) ; Kolíbal, Miroslav (advisor)
This diploma thesis is focused on characterization of semiconductive nanowires. Theoretical part of thesis deals with basic physical properties of TiO2 and a search of selected properties of titanium dioxide nanostructures is preseted. The experimental part describes several spectroscopic measurements carried out with complex of TiO2 nanowires. The influence of gold nanoparticles (deposited on the nanowire surface) on sample properties is also tested. The final part of thesis is devoted to methodology for measurement of electrical properties. These experiments are carried out only with one nanowire. Focused electron beam induced deposition (resp. Focused ion beam induced deposition) and electron lithography are utilized.
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Analysis of one-dimensional structures using Kelvin Probe Force Microscopy
Kovařík, Martin ; Bartošík, Miroslav (referee) ; Kolíbal, Miroslav (advisor)
This bachelor's thesis deals with the use of Kelvin probe force microscopy (KPFM) for analysis of 1D nanostructures, namely germanium nanowires and tungsten disulfide (WS2) nanotubes. First part of this thesis is dedicated to the possibility of gold nanoparticles detection on germanium nanowires and also to the analysis of relevance of the KPFM method to measurements performed at various humidity. Second part deals with the measurement of surface potential changes on WS2 nanotubes induced by interaction with light. We have concluded, that relative surface potential changes can be measured at various humidity. This conclusion is also applied to study the interaction of WS2 nanotubes with monochromatic light. The experiment has revealed, that when exposed to light with defined wavelength, nanotubes coated with gold nanoparticles show opposite surface-potential changes as compared to pristine nanotubes, which indicates different physical processes under way.
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Preparation Techniques and Characterization of Electrodes with Nanostructured Surface
Hrdý, Radim ; Trnková, Libuše (referee) ; Janderka,, Pavel (referee) ; Hubálek, Jaromír (advisor)
Nowadays, nanostructures fixed on solid substrates and colloidal nanoparticles permeate through all areas of human life, in area of sensors and detection as well. This dissertation thesis deals with the fabrication of nanostructures on the surface of planar electrodes via self-ordered nanoporous template of aluminum trioxide. The nanofabrication, as one of many possible techniques, is used to increase the active surface area of electrodes by creating unique surface types with specific properties. These electrodes are very perspective in the applications, such as biomolecules electrochemical detection and measurement. The transformation of aluminum layer into non-conductive nanoporous template in the process of anodic oxidation is a fundamental technique employed to obtain the array of nanostructures in this thesis. The fabrication of high quality nanoporous membranes with narrow pore size distribution on various types of metallic multilayers is one of the key experimental parts in this work. Several problems associated with the production of the thin-film systems, including the dissolving the barrier oxide layer, are discussed and solved. Another part of this work deals with the use of nanoporous membrane as a template for the production of metallic nanostructures via electrochemical metal ions deposition directly into the pores. The obtained nanostructures as nanowires, nanorods or nanodots are characterized by the scanning electron microscopy and energy-dispersive or wavelength X-ray spectroscopy. The electrode surface, modified by gold nanostructures suitable for the detection of biomolecules, has been chosen for the electrochemical measurements, due to the gold biocompatibility. The nanostructured electrodes were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The effect of nanostructured surface geometrical parameters, including the size of the electrochemically active area, on the results of electrochemical measurements has been observed and compared to flat gold electrodes. Two model biomolecules, namely guanine and glutathione, have been chosen for the study of potential application of these nanostructures in biosensors.
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