Phd Degree / Doktora

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

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Now showing 1 - 10 of 27
  • Doctoral Thesis
    Synthesis and Characterization of Novel Organometallic-Semicondutor Nanocomposit Photoelectrodes
    (Izmir Institute of Technology, 2022) Karabudak, Engin; Karabudak, Engin; Karabudak, Engin; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Studies on novel electrochemical catalyst synthesis for efficient oxygen evolution reaction (OER) attract the attention of researchers. In general, changing of synthesis method and the doping metal affect the electrochemical activities of BSCF. In this work, silver doped Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF-Ag) perovskite structure is shown to be a better electrocatalyst for oxygen evolution reaction (OER) due to its lower overpotential and extended durability. BSCF structure was synthesized by the EDTA-citric acid method. Appropriate amount of Ba(NO3)2 and EDTA were dissolved 0.1 M NH4OH solution. Nitrate salts of other metals were dissolved in distilled water, then mixed with prepared Ba(NO3)2 solution. The mixture was stirred at 70 °C until gelation occurred. The gelled samples obtained were baked in a drying oven at 250 °C for 24 h before being calcined at 1000 °C for 12 h. To achieve a current density of 10 mA cm−2, BSCF-Ag has required an overpotential of 0.36 V, which is very low compared to BSCF. To determine the stability of BSCF-Ag, continuous chronopotentiometry tests were carried out for 5 h and at a constant current density of 10 mA cm−2. BSCF-Ag was characterized by XRD, SEM, and XPS. Recent advances in inkjet printing technology for applications relating to heterogeneous catalysis are presented. Catalysts lie at the heart of most chemical reactions where raw materials are converted to value-added products. Therefore, synthesis and immobilization of active catalysts in the reactor are of great importance. Inkjet printing is an additive manufacturing technology introduced recently as a useful method for the fabrication and application of catalysts as a class of functional materials. Inkjet printing provides special features which can be tailored to the design of high-efficient catalytic processes. This thesis presents an overview of the technology along with developments and challenges associated with the combination of inkjet printing and heterogeneous catalysis, such as ink preparation, thin-film properties and real-life applications.
  • Doctoral Thesis
    Preparation of Nanostructured Interface by Polymer Grafting on Various Solid Substrates for Biosensor Applications
    (Izmir Institute of Technology, 2021) Özenler, Sezer; Yıldız, Ümit Hakan; Özenler, Sezer; Yıldız, Ümit Hakan; 04.01. Department of Chemistry; 01. Izmir Institute of Technology; 04. Faculty of Science
    This thesis presents the utilization, various applications, and characterization of the soft material-based coating formed on the gold surface with varying thickness and chemical properties resulting from the isocyanate-gold interaction. Theoretical calculations regarding the interaction of isocyanate with the gold surface revealed the character of the bond formed and the orientation of the functional groups on the surface. Results by X-ray photoelectron spectroscopy showed the tendency to shift to the high energy at N 1s and C 1s binding energies in the gold-interacting isocyanate group. In the next steps, the isocyanate-activated gold substrate was subjected to sequential incubation of 1,4-butanediol/hexamethylene diisocyanate, and thin-film formation was achieved by surface assisted (SurfAst) urethane polymerization. It was revealed with three different applications that a nano-porous polyurethane (PU) structure was formed on the gold substrate and could be postmodified by using SurfAst polymerization method. In the first application, modification with polyethylene glycol (PEG) was provided to obtain antifouling properties. The PEG-terminated PU structure on the gold surface was shown to reduce protein adhesion by approximately ten-fold. In the second application, SurfAst was applied on the 11-mercaptodecanoic acid incubated surface and grafting onto the poly (N-allyl-N-methyl-N-(3-((4-methylthiophen-3-yl)oxy)propyl) prop-2-en-1-aminium surface was characterized. As a result of PT grafting, PT nanowires with an average height of 100 nm, a width of 250 nm, and a length of 7 μm were obtained on the gold surface. In the last application, a soft nanogel was obtained by a reactive layer-layer (rLBL) coating method using the aza-Michael addition reaction of branched polyethyleneimine and polyester on the isocyanate functional surface. The mechanical and electrical permeability and coating properties of the nanogel layer were assessed. In conclusion, the high potential of isocyanate in surface activation has been demonstrated theoretically and experimentally. Effective modification of gold surfaces by polymer grafting with the SurfAst method and rLBL coating techniques has been achieved.
  • Doctoral Thesis
    Characterization and Catalytic Applications of Hydrothermally Synthesized Poyoxotungstate Clusters Containing Organic-Inorganic Hybrid Materials
    (Izmir Institute of Technology, 2019) Ece, Özlem; Çağır, Ali; Emirdağ Eanes, Mehtap; Eanes, Mehtap; Çağır, Ali; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Many scientists have been interested in hydrothermal synthesis and characterization of polyoxometalate clusters containing organic-inorganic hybrid materials recently because of having different applications in lots of fields, especially, using as catalysis in chemical reactions. In this study, three novel polyoxotungstate clusters were synthesized using hydrothermal method and catalytic activities of these three novel polyoxometalates and in addition two crystals previously synthesized in our group were studied. The first compound, [(4,4’-bpyH2)3][PCuW11O39] yellow crystals, crystallize in the space group P2(1)/n of the monoclinic system with four formula units in a cell. The crystal is a Keggin polyoxometalate and includes free 4,4’-bipyridine groups between the clusters. The second compound, (4,4’-bpyH2)[H2PW12O40]2.H2O colorless crystals, crystallize in the space group Ia-3 of the cubic system with twelve formula units in a cell. The crystal is a Keggin polyoxometalate and consists of two polyoxotungstate clusters, a free 4,4’-bipyridine group and a water molecule. The third and the last novel compound, (4,4’-bpyH2)4[H2P2W18O62]2 dark yellow crystals, crystallize in the space group P-1 of the triclinic system with four formula units in a cell. The crystal is a Wells-Dawson polyoxometalate and contains two polyoxotungstate clusters and free 4,4’-bipyridine groups between clusters. The catalytic study has been carried out using starch hydrolysis reactions by using hydrothermal synthesis and five different crystals were tried and conversion results were obtained. Starch samples converted to D-glucose with glucose yields above 90 wt.%. Catalyst reusability was performed for each crystal. No appreciable loss was observed in activity after five reaction cycles for each crystal.
  • Doctoral Thesis
    Proteomic Analyses of Biological Samples by Using Different Mass Spectrometric Strategies
    (Izmir Institute of Technology, 2018) Dinç, Melilke; Yalçın, Talat; Yalçın, Talat; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    The advent of soft ionization techniques MALDI and ESI have opened the doors of mass spectrometry to biological samples. Particularly protein research exploited this opportunity to the utmost that qualitative, quantitative, structural and distributional analyses of proteins have become achievable. Comparison of all expressed proteins belonging to two or more states is defined as differential proteomics and commonly performed either separating the proteins on a gel or separating the peptides in the mixture within a column. In this study, both of these methods were applied to a parasite that causes to the infectious disease, Leishmaniasis. Consequences of the disease become severe when parasite is multiplied in viscera rather than skin. Occurrence of different clinical manifestations is attributed to the variety in species however some species can cause to both such as L.infantum and L.tropica. The purpose of this study was to investigate this duality in L.infantum. Despite originating from two different species, cutaneous leishmaniasis isolates obtained from ten different patients exhibited considerably similar protein profiling on the gels however isolates belonging to five visceral leishmaniasis patients were discriminated from them with regards to protein abundances. Additionally, several differential proteins between cutaneous leishmaniasis and visceral leishmaniasis samples were determined by gel-free approach. Apart from that, another mass spectrometric strategy for the abovementioned distributional analysis namely mass spectrometry imaging was included in the last section. Herein, a method incorporating the application of enzyme with matrix was developed for easy sample preparation to on-tissue digestion and promising results were obtained for a start.
  • Doctoral Thesis
    Development of Colloidal Alloyed Nanocrystals for Quantum Dot Based Device Applications
    (Izmir Institute of Technology, 2018) Sevim Ünlütürk, Seçil; Özçelik, Serdar; Varlıklı, Canan; Özçelik, Serdar; Varlıklı, Canan; 04.01. Department of Chemistry; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Quantum dots (QDs) are very attractive luminescent semiconducting nanoparticles. In this study, our aim was to synthesize Cd and/or Zn based QDs with tunable optical properties by the particle size and the alloy composition. Colloidal water dispersible Mn-doped and nondoped ZnSxSe1-x QDs were synthesized by the one-pot aqueous method. Optical measurements indicate that photoluminescent properties are strongly depended on the capping agent. While MPA capped QDs showed an emission peak in the blue region, others did not show any photoluminescence at all. Mn doping up to 10% resulted in no significant effect on the optical spectra. However structural characterizations, EPR and XRD, supported that Mn ions were bounded to the 220 and 311 facets of QD. ZnxCd1-xSySe1-y quaternary nanoalloys were synthesized by using a modified two-phase approach for the first time in the literature. Optical properties of highly luminescent ZnxCd1-xSySe1-y nanoalloys were tuned from blue to yellow by the particle size, the alloy composition, and thickness of shell layer. The reactivity of the reactants, initial mole ratios, and other reaction parameters was adjusted to control alloy composition and alloy type: homogeneous and gradient. The reaction time controls the size of particles. The PL QE (up to 52%) and lifetimes (about 25 ns) were found similar regardless of core and core-shell nanoalloys. MicroPL measurements were carried out on ZnxCd1-xSySe1-y nanoalloys by fiber spectrometer integrated to confocal microscope. Photobleaching and blue-shifting, about 6 nm, were observed in the microPL spectra. Photobleaching times and rate constants obtained from single exponential decay curves showed that purification and exposure time are strongly effective. Additionally, the power the excitation light is essential that below 11 μW, photobleaching slows down, and at 2 μW there is no photobleaching. Scale-up methods with high-volume batch and flow reactor were used to synthesize CdTe and ZnxCd1-xSySe1-y QDs. LEFETs were fabricated with TUBITAK support in collaboration with Heidelberg University. PbS QDs were used as emitting material at the bottom contact top-gate unipolar LEFETs in which uniform electroluminescence was obtained.
  • Doctoral Thesis
    Synthesis, Physicochemical Characterization, and Biosensing Applications of Gold Nanoparticles
    (Izmir Institute of Technology, 2018) Üçüncü, Melek; Özçelik, Serdar; Özçelik, Serdar; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Cancer is one of the leading diseases that cause death all around the world. In Turkey, lung cancer is the most common type of cancer type in men and it is the fifth in women. Unfortunately, the percentage of treatment of lung cancer is too low. Gold nanoparticles (AuNPs) are widely used in the biotechnology as imaging, diagnosis, and therapeutic agents because of their unique properties such as plasmon resonance, easy synthesize, biocompatibility, and facile surface modification. In this study, it is aimed to design gold nanoparticles as biosensors for lung cancer cells. For this purpose, different sizes (5-40 nm) of Au nanoparticles were synthesized and their uptake and distribution into the lung cancer cells were investigated. The results of the study revealed that cellular uptake of gold nanoparticles are high for the size of 20 and 40 nm. The optimal visibility into the cells was achieved by using DIC microscopy in which the particles uptaken into the cytoplasm and localized at around nucleus of cells. In the second part of the study, surfaces of 20 and 40 nm particles were conjugated with RGD peptides and their distribution and light scattering properties were investigated in living cells by using dark-field microscopy. Due to the receptor-mediated endocytosis, RGD-AuNPs showed different distribution within the cells. These results indicate that the RGD conjugated Au nanoparticles exhibits much higher light scattering properties than non-conjugated nanoparticles. In addition to this, synthesized Au nanoparticles were conjugated with nucleus-localized peptide (NLS) and directed to the nucleus of cancerous (A549, H358) and healthy (BEAS2B) lung cells. The nucleus targeting properties of the NLS conjugated particles were also investigated to understand if there is any cell line selectivity. The internalizations of peptide conjugated Au nanoparticles into cell lines were visualized in living cells by using DIC microscopy. NLS conjugated AuNPs internalized into nucleus of A549 and H358 cancer cells. Although NLS conjugated AuNPs present inside the cytoplasm of BEAS2B cells, they did not localize into the nucleus of normal cell lines.
  • Doctoral Thesis
    Development of Novel Solid Phase Extraction (spe) Sorbents and Solid Phase Microextraction (spme) Fiber Coatings for Determination of Endocrine Disrupting Compounds (edcs)
    (Izmir Institute of Technology, 2017) Demirkurt, Merve; Eroğlu, Ahmet Emin; Eroğlu, Ahmet Emin; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    This thesis is composed of four chapters. In the first part of the study, molecularly imprinted polymer (MIP) was prepared as SPE sorbent for selective determination of BPA prior to HPLC DAD analysis. The adsorption capacity and selectivity of imprinted polymers were investigated. To improve the MISPE method, the parameters including pH of sample solution, adsorption time, amount of sorbent, desorption solvent were examined. The extraction efficiency of BPA imprinted polymer was investigated by using the spiked samples of ultrapure, drinking and tap water. The second part of the thesis was about determination of estrogen hormones. For this purpose, amino modified silica and molecular imprinted silica were prepared and their SPE performances were compared. The proposed methodology was validated through the analysis of real water samples. The preparation of MIP nanoparticles encapsulated in electrospun polystyrene fibers as the SPME fiber coating was the subject of the third part of the thesis. Developed fibers were used for selective extraction and analysis of parabens in water samples. The optimization parameters affecting the extraction and desorption of parabens were investigated. The validity of the proposed method was verified via spike recovery tests. Finally, fibers having amino functionality prepared by the sol-gel based electrospinning process were used for determination of BPA. The effect of solution pH, extraction time, agitation speed and ionic strength on the extraction performance were investigated. Validity was checked via the application of the proposed methodology on real samples.
  • Doctoral Thesis
    Design and Synthesis of Rhodamine Based Fluorescent and Colorimetric Sensors for the Detection of Gold Ions
    (Izmir Institute of Technology, 2017) Karakuş, Erman; Emrullahoğlu, Mustafa; Emrullahoğlu, Mustafa; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    The usage of chemosensors for the detection of heavy and transition metal ions is prevalent. Because these metal ions play crucial roles in living systems and have extremely toxic effects on the environment. Among these metal ions, gold species have interesting biological properties and uses. They play important roles in biological systems and often have significant impacts on human health. For instance, gold based drugs have long been used in the treatment of rheumatoid arthritis and other autoimmune diseases. In addition, gold nanoparticles function as carriers for drugs and gene delivery systems. Gold ions, on the other hand, are potentially toxic to humans. Because of their reactive nature, ionic gold species can interact with proteins, DNA and other biomolecules and disturb a series of cellular processes, leading to serious health problems. Detection of gold ions can be performed by spectroscopic methods such as atomic absorption and atomic emission spectroscopy and inductively-coupled plasma spectrometry that required complicated sample preparation steps, and sophisticated instrumentation. In contrast to these highly expensive and time consuming methods, fluorogenic or chromogenic methods can be good alternatives for the detection of these species that provides high analyte sensitivity and selectivity, visual simplicity, instantaneous response, as well as real time monitoring. The rhodamine scaffold is an ideal template for the construction of metal ion chemosensors because they have large molar extinction coefficient, long excitation and emission wavelengths, high fluorescence quantum yields, good water solubility, and the potential for colorimetric and turn-on fluorescent detection. In this thesis work, we focus on design and synthesis of novel rhodamine based molecules for the detection of gold ions. Moreover, we investigate the photophysical properties of synthesized molecules in the absence and presence of gold ions in both synthetic samples and living cells.
  • Doctoral Thesis
    Proteomic Studies and Its Application To Biological Samples Using Mass Spectrometry
    (Izmir Institute of Technology, 2017) Güray, Melda Zeynep; Karakaya, Hüseyin Çağlar; Yalçın, Talat; Yalçın, Talat; Karakaya, Hüseyin Çağlar; 04.03. Department of Molecular Biology and Genetics; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Mass spectrometry (MS) is a powerful analytical tool with its application in the field of biological sciences for identification of proteins, defining post-translational modifications, studying protein expression and protein interactions. This thesis presents MS analyses of proteins for defining modifications observed during sample preparation and identification of proteins isolated from clinical samples and microorganisms. The first part of the thesis includes proteomic analysis of antimony resistant L. tropica. The results clearly indicated that the generation of antimony resistance by parasites, either in host organism or in vitro, causes alteration of protein expression levels, and the mechanism of antimony resistance in host organism and in vitro conditions follow different strategies. In the second part of the study, proteomic analysis of Bence Jones proteins isolated from urine of multiple myeloma patients was performed. Gel electrophoresis and MS analysis revealed that the proteins from different patients with different nephrotoxicity have different tendencies to form multimeric structures and contained different type of light chain. In the third part, it was shown that precipitation of proteins in acetone causes +98 u mass artifacts on proteins when analyzed by MS. The parameters affecting the formation of modification was studied and it was revealed that this modification is dependent on solution pH, incubation time and temperature. In the last part, aspartic acid and glutamic acid containing synthetic peptides were shown to be methylated upon incubation in acidified methanol solution. MS analysis revealed that the reaction is dependent on temperature and time and is affected by the type of acid included in methanol solution. All in all, this thesis provides a comprehensive study of proteins by mass spectrometry for identification of proteins from different sources, as well as defining protein modifications observed as artifacts during sample handling in proteomic workflows.
  • Doctoral Thesis
    Synthesis of Vinylallenols Via Palladium-Caralyzed Arylation Reactions of (z)-2,4 Oxiranes With Organoborons
    (Izmir Institute of Technology, 2016) Ziyanak, Fırat; Artok, Levent; Ziyanak, Fırat; Artok, Levent; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Allenes are important functional groups especially in synthetic organic chemistry. Due to their unique reactivity and high level of chirality transfer, allenes can be used as building blocks in the synthesis of complex molecules. In recent decades transition-metal catalyzed synthesis of allenes with organometallic reagents has become attractive method. For the synthesis of functionalized allenes, addition of different nucleophiles with the help of various transition metals to propargylic compounds bearing a leaving group has been mostly used. Transition metals are crucial for these reactions for shifting them from SN2 to SN2’ for the formation of allenes. Within the context of this research, a novel palladium-catalyzed arylation reactions of (Z)-2,4-enyne oxiranes with organoborons have been investigated. As a result of the 1,5-substitution reaction, aryl-substituted vinylallenes bearing a hydroxyl group on the allylic position (7-aryl-3,5,6-trien-2-ol) were obtained in high yields and diastereoselectivities. We were able to also disclose that Diels-Alder adducts could be obtained with excellent endo and facial selectivities when the vinylallen types of this study were reacted with dienophiles.