Papers by Keyword: Fluorescence

Abstract: Some modern methods of surface contamination detection use the principle of luminescence for their function. This thesis aims at introducing the principle of the method that is available for the measurement of surface contamination, thesis deals with an innovative surface-detection device using UV-VIS luminescence spectroscopy. In the work is presented the industrial use of the detection of oil contaminants. Another specialized topic is the field of forensic practice - dactyloscopy, where the possible use of the principle of UV-VIS luminescence spectroscopy, the Recognoil device as a possible and effective method of ensuring dactyloscopic traces is proved.

Abstract: This research presents a new perspective on optical biosensors based on zinc oxide nanoparticles. The widely known and successfully applied nanostructured material is modified by the dopant - the green phosphor Terbium, which embedded in the structure of zinc oxide and makes a significant contribution to the fluorescent response of the material in both the UV and visible spectral regions. The effect of various dopant concentrations on the fluorescence of nanostructures was studied; the nanostructures were examined by SEM.

Abstract: Fluorescence polarization and emission spectra of Rhodamine 6G solution with gold nanoparticles have been studied. It is found that the emission intensities tend to be low when the gold nanoparticles are added into the solution partly due to the energy transfer from the Rhodamine 6G to gold nanoparticles. The fluorescence polarization increases as the concentration ratio of the gold and Rhodamine 6G is more than 124 and decreases as the ratio is about 1115. The enhancement and reduction of fluorescence polarization values are understood as the shortening of the fluorescence lifetime and a temperature effect from the heating of gold nanoparticles, respectively.

Abstract: X-ray diffraction (XRD) is a commonly used technology to identify crystalline phases. However, care must be taken with the combination of XRD configuration and sample. Copper (most commonly used radiation source) is a poor match with iron containing materials due to induced fluorescence. Magnetite and maghemite are analysed in different configurations using copper or cobalt radiation. Results show the effects of fluorescence repressing measures and the superiority of diffractograms obtained with cobalt radiation. Diffractograms obtained with copper radiation make incontestable phase identification often impossible. Cobalt radiation on the other hand yields high quality diffractograms, making phase identification straightforward.

Abstract: In-situ realtime method that can monitor the target bacteria should be used to determine the real situation of the bacteria in deep parts of heaps in heap bioleaching plants. This study suggest to apply flow cytometry technology to in-situ realtime monitoring of target bacteria. Flow cytometry is a method that can rapidly quantify the bacterial cells in bacterial suspension based on the detection of lights that are emitted from bacterial cells. In this study, we estimated the possibility of the application of flow cytometry to the selective detection of target bacteria. The bacterial culture solution that had been diluted by water including other bacteria was provided for fluorescence spectral analysis and scattered light analysis that were functions of flow cytometry. Our target bacteria could be selectively detected by those analyses in this study, therefore, it was shown that the flow cytometry could be useful for detecting target bacteria selectively. Because the measurement principle of flow cytometry is quite simple, it can be expected to be installed into deep heaps through the monitoring wells and determine the dominance of target bacteria in-situ and realtime in the future.

Abstract: The polymer blend electrolytes composed of poly (ethyl methacrylate)(PEMA) and Poly (vinyl acetate)(PVAc) as host polymer and lithium perchlorate (LiClO₄) as a salt are synthesized by solvent casting technique. The polymer membranes with different wt% of PEMA and PVAc are subjected to AC impedance analysis for the investigation of ionic conductivity. The maximum ionic conductivity of 3.541 X 10^{- 5}Scm^{- 1} at 303K is reported for PEMA/PVA_C (70/30wt%) –LiClO₄ (8wt%) polymer blend electrolyte system.The complexation has been confirmed by XRD and FTIR techniques. The glass transition temperature (T_g) of the blend polymer electrolytes has been obtained from DSC measurements. The SEM micrographs show the surface morphology of the prepared samples. The electrochemical stability of the sample exhibiting high conductivity has been carried out using linear sweep voltammetry (LSV) and cyclic voltammetry (CV) measurements. The potential window has been found to be-2.5 to +2.5 V. The lithium transference number evaluated using chronoamperometry technique results in a value of 0.90. The dielectric behavior of the solid polymer blend electrolytes has been analyzed as a function of frequency and temperature. The dc conductivity values obtained from the conductance spectra match the ac impedance results. The photoluminescence spectra that contain information about the local free volume of the prepared samples justify the conductivity results. The two and three dimensional images of the maximum ionic conducting sample exhibit numerous micropores.

Abstract: Cadmium based quantum dots (Cd QDs) is well established and extensively used for various applications, but found limiting usage in bioimaging application, due to its high toxicity and insolubility in aqueous solution. Passivation and/or encapsulation of the Cd QDs with a non-toxic and biocompatible polymer are common practice to overcome the drawback. In our work, CdSe is synthesized as a core and encapsulated with ZnS to produce a hydrophobic colloidal core/shell CdSe/ZnS QD. Then, a biocompatible PEGylated amphiphilic polymer as matrices is used to encapsulate CdSe/ZnS QD for converting it into water dispersible property which required for in-vitro imaging applications. The cell viability and cellular uptake of the biocomposite were studied against cancerous and non-cancerous cells. Also, peak of emission spectrum was recorded to determine the photostability of this biocomposites under continuous UV light illumination up to 100 minutes.

Abstract: A novel photochromic diarylethene was successfully synthesized, which is named 1-[2-methyl-5-phenyl-3-thienyl]-2-[2-methyl-5-(3-aldehyde-4-methoxy)-3-thienyl] perfluorocyclopentene. The compound showed good photochromic behavior. Upon irradiated with UV/vis lights, the color of the compound could be changed between colorless and blue, accompanied by a fluorescence switch between the open-ring isomer and closed-ring isomer.

Abstract: A new unsymmetrical photochromic diarylethene 1-[2-cyano-1, 5-dimethyl-4-pyrryl] -2-[2-methyl-5-(1, 3-dioxolane)-3-thienyl] perfluorocyclopentene has been synthesized, and its properties including photochromism, kinetics and fluorescence have been investigated in detail. The results showed that its photochromic behaviors could be modulated by UV/Vis light, changing from colorless to blue in acetonitrile solution.

Abstract: Currently electroluminescent devices, operated by alternating current (AC-EL) on film, paper or textile are based on a capacitor with one transparent electrode and one generally non-transparent, highly conductive electrode and a light-emitting dielectric layer in-between. The light-emitting pigments are mostly based on doped zinc sulfide. Currently available commercial products contain encapsulated pigments dispersed in organic solvents. Those dispersions allow AC-EL-devices illuminating solitary in the colors white, green, blue-green, blue and orange. Blending those pigments leads to numerous new colors however, always linked to loss of brightness in the final device. In this research work the combination of fluorescent organic and inorganic dyestuffs with inorganic EL-phosphors was investigated. The AC-EL-devices were all based on textile materials; all dispersions were free of organic solvents. Special focus was directed to the concentration of dyes in an additional layer within the EL-capacitor as well as the thickness and particularly the positioning of the layer. In the result colors were achieved, which cannot be found by blending the phosphors, such as yellow and red. In addition, depending on the type of added fluorescent dyestuff layer, the brightness could be increased substantially.