Phd Degree / Doktora

Permanent URI for this collectionhttps://hdl.handle.net/11147/2869

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2012 - 20163

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Department: search.filters.department.Thesis (Doctoral)--İzmir Institute of Technology, ChemistryPublisher: search.filters.publisher.İzmir Institute of Technology

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Now showing 1 - 3 of 3
  • Doctoral Thesis
    Development of Solid Phase Microextraction (spme) Fibers for Various Analytical Applications: (i) Selenium Speciation in Waters. (ii) Separation and Determination of Triclosan and Triclocarban in Waters
    (İzmir Institute of Technology, 2016) Ziyanak, Esen; Eroğlu, Ahmet Emin
    In the first part of this study, four selenium species namely selenite, selenate, selenomethionine and selenocystine in water samples were tried to be separated using single solid phase microextraction (SPME) fiber on the same chromatographic run. Bare silica fibers were immersed into agarose matrix containing nano zerovalent iron (nZVI), ceria (CeO2) or zirconia (ZrO2). After characterization of fibers sorption/desorption parameters were optimized and standard reference materials were used to validate the proposed method. Direct mode of SPME method was used to extract the analytes prior to their separation with HPLC and detection with ICPMS. The optimum conditions for the extraction of selenium species with nZVI-agarose fibers are obtained as extraction pH: 4.0, agitation speed: 700 rpm, extraction time: 60 min, desorption matrix: 10.0 mM citrate solution, desorption time: 30 min, solution temperature: 25 °C, ionic strength: no NaCl addition. In the second part of this study, same fibers were used to separate triclosan (TCS) and triclocarban (TCC) using HPLC-DAD. Among all fibers prepared, nZVI-agarose modified fibers demonstrated the best extraction performance. The optimum conditions for the extraction of TCS and TCC with nZVI-agarose fibers are obtained as extraction pH: 5.0 and 7.0, agitation speed: 400 rpm, extraction time 60 min, desorption matrix: % 90 methanol - %10 water (adjusted to pH 3.0 with acetic acid), desorption time: 30 min, ionic strength: no NaCl addition.
  • Doctoral Thesis
    Design and Synthesis of Boron-Dipyrromethene (bodipy) Based Fluorescent and Colorimetric Sensors for the Detection of Gold and Mercury Ions
    (İzmir Institute of Technology, 2016) Üçüncü, Muhammed; Emrullahoğlu, Mustafa
    The identification and quantification of heavy metal ions such as gold and mercury species in synthetic samples and living cells have crucial importance for scientific research. Even at very low concentrations, heavy metal ions can cause mortal consequences. Hence, there is a huge need for the development of new, sensitive, and selective methods to detect biologically active molecules, heavy metal ions, and anions that have significant effects on humans or animals. Up to now, trace metal analyses have been performed by classical spectroscopic methods such as atomic absorption and emission spectroscopy and inductively coupled plasma mass spectrometry. However, these methodologies require sophisticated devices and must be preceded by complicated sample preparation steps. In contrast to these time-consuming and expensive methods, fluorogenic and chromogenic methods that have high analyte sensitivity and selectivity and easy sample preparation steps and that use cheaper instrumentation have become important alternatives in recent years. There are many organic dye molecules that act as signaling units for fluorogenic-sensing strategies such as rhodamine derivatives, fluorescein, coumarin, and BODIPY. For this thesis, we chose the BODIPY core as a signal reporter unit because of such unique properties as long excitation/emission wavelengths, high molar absorption coefficients and fluorescence quantum yields, and wide pH range for the sensing event. Also, BODIPY dyes can be easily derivatized from their various positions so that they produce an important advantage over other florophore molecules. The main purpose of this thesis is to design and synthesize new BODIPY derivatives that bear highly selective and sensitive receptor units towards gold and mercury ions. In addition, to investigate the photophysical properties of designed molecules in the absence and presence of targeted metal ions in both synthetic samples and living cells.
  • Doctoral Thesis
    Synthesis and Control of Exciton Dynamics in Cdte, Cdte/Cds and Znxcd1-Xte Colloidal Nanocrystals
    (İzmir Institute of Technology, 2012) Eral Doğan, Leyla; Özçelik, Serdar
    The aim of this study is to synthesize cadmium-based semiconductor colloidal nanocrystals and to control their exciton dynamics by tuning the size and composition of the nanocrystals (NCs). CdTe, CdTe/CdS binary, and ZnxCd1-xTe ternary semiconductor NCs are prepared by wet chemistry. The reactions are thoroughly optimized to enhance the optical properties. The optical properties of CdTe and CdTe/CdS are tuned by the size of the NCs by adjusting the reaction (the growth) time. Coating CdTe NCs with CdS layer enhances the photoluminescence quantum yields up to 45%. ZnxCd1-xTe ternary nanoalloys were synthesized by varying the initial mole ratios of metals (Zn/Zn+Cd) and the growth time. The size and the composition-tunable ZnxCd1-xTe nanoalloys exhibit highly luminescent optical properties. When the amount of initial Zn precursor is low, the nanoalloys have Cd-rich and Zn-poor internal crystal structure. However, at higher amount of Zn precursor, the nanoalloys have Zn-rich and Cd-poor core exhibiting gradient composition. The exciton interactions and dynamics are investigated as a function of the size of CdTe/CdS, and the composition and the size of ZnxCd1-xTe nanoalloys. The exciton interaction yields amplification in the output signal at the threshold of 1015 photon/cm2s per laser pulse. The exciton lifetimes are in the range of picoseconds to nanoseconds. The decay associated spectra are affected by the laser power, size and composition of the NCs. As the laser power increases new excitonic states are created especially in ZnxCd1-xTe nanoalloys. Multiexcitons were created in the NCs depending on the laser power. Small NCs exhibit stronger exciton-exciton interactions under high laser power compared to larger NCs. However larger NCs have lesser exciton density, therefore reducing the exciton-exciton interactions.