Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of Fluorescent Carbon-Dots for Biological Imaging(01. Izmir Institute of Technology, 2021) Kavuranpala, Tuğçe; Özçelik, SerdarCarbon dots are called carbon quantum dots or carbon nanoparticles (NPCs), and their use has recently started to increase thanks to their good biocompatibility, unique optical properties, easy synthesis, and low toxicity. Different kinds of carbon sources and amine sources also used as different dopes of chemical create a different emission color of CDs under UV-lamp. In this study, our aim to provide a simple synthesis of carbon dots with high quantum efficiency and low toxicity for use in cell imaging. Nitrogen and sulfur-doped carbon dots were synthesized using citric acid and thiourea, and emission was obtained in the blue-green region. After the synthesized carbon dots were seeded to the A549 cell culture, intracellular viability and cell toxicity results showed that carbon dots did not affect cell viability at certain concentrations. Afterward, the carbon dots are combined with gold nanoparticles and it is aimed to attach the gold to the surface of the carbon dots. Our aim here is to increase the efficiency of carbon dots, which give an emission peak at 550 nm, thanks to gold nanoparticles. As a result of these studies, it was proved by DAPI staining that the carbon dot is directed to the nucleus of the cell. Since it does not create a toxic effect and is transported to the cell nucleus, it allows it to be used in intracellular drug transport and imaging processes in the next stages.Master Thesis A Computational Study of Excitation Dynamics on Semiconductor Surfaces(Izmir Institute of Technology, 2019) Kaya, Birnur; Sevinçli, Haldun; Özçelik, SerdarRecent experimental studies have shown that collodial quantum dots can be produced in large quantities and their optical properties can be tailored by controlling their composition, size and surface characteristics. Motivated by these studies, this thesis is devoted to the investigation of excitation dynamics on semiconductor surfaces, which are passivated with organic molecules. First, constructing a simplified model, excitation dynamics is investigated by computing time dependent occupations of frontier molecular orbitals for various scenarios regarding the values for the energy gap between the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO), as well as the coupling strengths. Second, the model is enhanced to address realistic systems. Passivation of ZnS surface with oleic acid (OA) is modeled using density functional theory based tight binding (DFTB) simulations. Extracting the Hamiltonian and overlap matrices, excitation dynamics is studied for Zn rich and S rich surfaces and different coverage ratios of surfaces. The excitation dynamics is compared and contrasted against the simplified model. Characteristic features are identified and typical decay rates are calculated for various molecular configurations. In addition to these, X-Ray diffraction spectra of quaternary ZnCdSSe nanoalloys have been investigated.Master Thesis Development of Mitochondria Targeted Gold Nanorods(Izmir Institute of Technology, 2019) Uçak, Hande; Özçelik, SerdarLung cancer has the largest number of lives for the global pattern of cancer death. However, the percentage of the cancer treatment is too low. Gold nanoparticles have a widely range in terms of biomedical applications in diagnosis, imaging because of their unique optical properties, simple synthesis techniques, biocompatibility and suitable for easy surface change. Redox reactions in the mitochondria generates a potential called as mitochondria membrane potential. The aim of the study is to design mitochondria targeted gold nanorods and to observe how the designed gold nanorods effects the mitochondria membrane potential by targeting the mitochondria on A549 and BEAS-2B cell lines. Gold nanorods were utilized by seed growth mediated method and the surface bioconjugation was performed with triphenyl phosphonium cation as a mitochondria targeted molecule. Poly (sodium-p-styrene sulfonate) was used to prevent aggregation during the bioconjugation process. Gold nanorods which had 30 nm x 10 nm in length and diameter depending on SEM images had well-defined absorption bands 513 nm and 774 nm in wavelength. Mito-pot analysis with the fluorescent intensity ratio and colocalization analysis with light intensity for targeting gold nanorods to mitochondria showed that the accumulation on mitochondria for TPP-GNR was higher than PSSGNR. TPP-GNR was more toxic than PSS-GNR for both of cell lines by investigations of MTT viability test. TPP-GNR targeted to mitochondria and it affected fundamental cellular functions in mitochondria. To concluded that accumulation on mitochondria was accomplished for TPP-GNR and the decreasing of mitochondria membrane potential was observed on this study.Master Thesis Development of Copper and Manganese Doped Ternary Colloidal Quqntum Dot Alloys(Izmir Institute of Technology, 2019) Yırtıcı, İlayda Melek; Özçelik, SerdarSemiconductor nanocrystals have great interest due to their unique optical properties such as the particle size and the alloy composition dependent spectra, photochemical and colloidal stability. They have wide range of potential applications like solar cells, light emitting diodes (LED) and bioimaging etc. In this thesis, colloidal ternary Cu doped and undoped ZnSxSe1-x nanoalloys were synthesized by modified one pot aqueous approach. TGA and MPA ligands were used as capping agents for the synthesis of ZnSxSe1-x and Cu doped ZnSxSe1-x colloidal nanoalloys. The results showed that capping agents have an significant effect on optical properties of ZnSxSe1-x nanoalloys. Although the TGA capped nanoalloys have well-defined absorption bands rather than MPA capped ones, ZnSxSe1-x nanoalloys with TGA capping agent fluorescence peak was not observed. Therefore, the further study was continued with MPA capped ZnS xSe1-x ternary nanoalloys. Optical spectra demonstrated both absorption and PL spectra were shifted due to the adding of Cu dopant. Absorption peak shifted from 335 nm to 376 nm. Fluoroscence spectra also was redshift from 469 nm to 565 nm. Thus, we can conclude that, colloidal ternary nanoalloys optical properties can be tuned by using chemical doping. On the other hand, the optical and structural properties of binary ZnSe QDs, Mn and Cu doped ZnSe nanocrystals were investigated. We concluded that ZnSe and ZnS xSe1-x nanocrystals can be used to synthesize doped nanocrystals by chemical doping. We demonstrated that optical and structural properties of Cu and Mn doped ZnSe can be tuned by chemical doping.Master Thesis Molecular Beam Epitaxial Growth of Znse on (211)b Gaas(Izmir Institute of Technology, 2017) Yavaş, Begüm; Ateş, Serkan; Özçelik, SerdarThe Mercury Cadmium Telluride (Hg1-xCdxTe) play important role for infrared (IR) focal plane array application. It is grown on variety alternative substrates which are Si, Ge, GaAs or GaSb. When GaAs is compared with the others alternative substrate, it is more preferable due to having good surface polarity and also easily commercially available of high quality. When HgCdTe epilayer is grown directly on the GaAs substrate, there exist some dislocations in the epilayer due to large lattice mismatch between HgCdTe and GaAs substrate.The CdTe semiconductor is grown like a buffer layer to reduce dislocation in the HgCdTe epilayer grown on GaAs or other alternative substrate [1].The crystal quality of CdTe buffer layer directly affected HgCdTe epilayer. Therefore, CdTe needed to be low defect density.Because of %14.6 lattice mismatch between CdTe and GaAs [2], some defects are observed in CdTe buffer layer. ZnSe epilayer can be used to decrease lattice mismatch between CdTe and alternative substrate. When ZnSe interlayers are grown with high quality, CdTe affects positively. The aim of this theses is the growth of ZnSe epilayer films on (211) GaAs substrates by molecular beam epitaxy (MBE). The effect of growth temperature, VI/II flux ratio and deoxidation process with In and As were studied in this study. Crystal qualities of films were investigated by using X-ray diffraction. The surface morphology of ZnSe films were analyzed by atomic force microscopy and Nomarski microscopy. Vibrational phonon modes, thermal and elastic strains of ZnSe epilayer were observed by using Raman spectroscopy.Master Thesis Production and Characterization of Water Soluble Cdsete Based Core/Shell Nanocrystals and Their Applications in Bioimaging(İzmir Institute of Technology, 2009) Özdemir, Seda; Özçelik, SerdarIn recent years, nanotechnology has become one of the most intensively studied fields. At the nanometer scale, materials have unique electrical, optical, magnetic and chemical properties. They can be used for a wide variety of applications such as electrooptical devices, tagging and medical applications. The goal of this study was to produce water-dispersible alloyed CdSexTe1-x semiconductor nanocrystals, which are suitable to interact with biomolecules. CdSexTe1-x nanocrystals were synthesized by a single step aqueous synthesis method. Monodisperse, CdSexTe1-x nanocrystals with zinc blende structure were obtained in water. Synthesized nanocrystals emit in the range from 528 nm to 620 nm. CdSexTe1-x nanocrystals have 17% photoluminescence quantum yield, after the CdS shell coating the photoluminescence quantum yield increased up to 22%. MTT test and Trypan Blue tests were used to evaluate the toxicity of CdSexTe1-x nanocrystals. MTT measurements reveal that the MCF7 cancer cells are not affected by the nanocrystals at any dosage and exposure condition, but lethal effects are determined at the concentration of 1.0ug/ml for the PC3 cells. The BEAS 2B cells are very sensitive to the nanocrystals and do not proliferate at concentration of 0.5ug/ml. Confocal microscopy studies show that the nanocrystals has ability to penetrate to the cytoplasm of cells.Master Thesis Development of a Novel Electrocardiography Sensor Based on a Composite Silver Chloride Nanoparticles and Polyaniline(Izmir Institute of Technology, 2013) Taşcıoğlu, Didem; Özçelik, SerdarThe electrical activity of the heart is detected by electrodes attached to the surface of the skin. These electrodes detect bioelectrical signals in the human body. Physilogical status of heart condition especially cardiovascular diseases and disturbances in the cardiac rthym are recorded by electrocardiography (ECG). Despite the fact that the usage of disposable ECG electrodes in our country is substantial nearly as 70 million in 2010, these electrodes are not fabricated in Turkey. In the scope of this study, it was aimed to develop a novel sensor based on synthesized AgCl/Polyaniline nanocomposites for ECG electrodes. In this study, the production of silver chloride (AgCl) nanoparticles was achieved by the polyol method. ABS (Acrylonitrile butadiene styrene) was used as a supporting material of the ECG electrode. Synthesized AgCl nanoparticles were not easily adsorbed on the surface of ABS. We develop a synthetic chemistry to perform simultaneous synthesis of AgCl nanoparticle and polymerization of aniline on surface of ABS. Polyaniline acts as a chemical linker between the nanoparticle and ABS surface in the same batch reactor. The synthesized composite based on polyaniline and AgCl nanoparticles completely covers the surface of ABS. To evaluate electrodes, we fabricated a disposable ECG electrode and compared it with the disposable electrodes that are commercially available. The electrocardiography data indicated that the fabricated electrodes were demonstrated a performance which is comparable with the commercial electrodes. The results demonstrate that a novel ECG electrodes can be manufactured based on this new composite material and method develop in our laboratory.Master Thesis Synthesis and Characterization of Monodispere Silica Based Functional Nanoparticles for Multi-Purpose Applications(Izmir Institute of Technology, 2009) Altın, Burcu; Özçelik, SerdarThe Stöber method was performed to tune the size of monodisperse silica nanoparticles in the range of 10 to 500 nm. It was observed that increasing amount of reactants favors the formation of larger particles A Stöber method in the presence of L-lysine as a catalyst instead of ammonia was developed to prepare well-ordered, highly monodisperse silica nanoparticles based on the hydrolysis and condensation of TEOS. The effect of medium temperature, amounts of L-lysine, TEOS, octane and dye on the size of particle was investigated. It was found that L-arginine increased the size of particles. The amount of TEOS was determined to be 50.0 mmol to obtain the smallest size of particle. The mole of L-lysine slightly altered the size of particles, however the surface of particles was substantially covered by L-lysine. The presence of octane does not change the size of particles. The amount of dye molecule Rhodamine B isothiocyanate (RBITC) does not alter the size of nanoparticles. We showed that temperature plays important role tuning the particle size from 5.0 nm to 80.0 nm.MTT assay indicates no cytotoxicity of the silica particles against MCF-7 (human breast cancer cell lines) and PC-3 (human prostate cancer cell lines) cancer cell lines. The particles enter to the cells within 5 minutes with a concentration of 0.1.g/mL. We propose that these particles can be used in the field of bioimaging and drug delivery.Master Thesis Development of Semiconductor Nanocrystals for Biotechnological Applications(Izmir Institute of Technology, 2008) Ünlü, Caner; Özçelik, SerdarSemiconductor nanocrystals are very useful tools in biological applications because of their unique optical properties. In this study, synthesis and characterization of CdTe / CdS and CdSexS1-x nanocrystals were carried out. CdSexS1-x nanocrystals were synthesized by a modified two phase method. Highly luminescent (Quantum yied . %80) , monodisperse and face centered cubic CdSexS1-x nanocrystals were obtained in toluene. The size of nanoparticles varies from 3.5 to 3.7 nm Ligand exchange was performed on CdSexS1-x nanocrystals and luminescent water soluble CdSexS1-x nanocrystals were obtained. CdTe / CdS nanocrystals were synthesized in one step and and one pot by a modified method. Face centered cubic, luminescent (Quantum yield . 30%) and monodisperse CdTe / CdS nanocrystals with different sizes in a size range from 4.7 to 9.3 nm were obtained in water. Toxicity of CdTe / CdS nanocrystals was determined by MTT test. The lethal concentrations were respectively 1.0 and 15 .g/ml for PC3 and MCF7 cells. Confocal microscopy shows that the nanoparticles enter to the cytoplasm of cells.Master Thesis Synthesis, Characterization of Cdsxse1-X Quantum Dots and Evaluation of Their Real-Time Motions in Live Cells(Izmir Institute of Technology, 2011) Ünal, Gülçin; Özçelik, SerdarThe use of quantum dots as fluorescent labels in bioimaging is the most intensively studied subject. The aim of this study is to elucidate locations of quantum dots and track their motions in real time through confocal microscopy and to evaluate influence of surface chemistry on diffusions of quantum dots in live cells. In this study, trioctylphosphine oxide (TOPO) capped CdSxSe1-x quantum dots were synthesized and then TOPO molecules were exchanged with 3-mercaptopropionic acid and N-acetyl-Lcysteine to make quantum dots water dispersible for cellular imaging. Human lung adenocarcinoma epithelial cells (A549) and human bronchial epithelial cells (BEAS-2B) were incubated 1 hour with CdSxSe1-x quantum dots with a concentration range of 1-10 g/mL. Localizations and real time motions of quantum dots were tracked by a spinning disc confocal microscope. The center of fluorescent spots of quantum dots was determined by 2D Gaussian fitting with a sub-pixel resolution (<100nm/pixel). The mean square displacements, diffusion coefficients and trajectories in which quantum dots made motions were analyzed by the software ImageJ with a plug in Spot Tracker. Confocal images showed that both MPA and NAC cappped quantum dots were observed in the cytoplasm of cells. Trajectories of quantum dots in cellular environment demonstrated that the quantum dots performed various types of motions in live cells. Unimodal, trimodal and multimodal distribution histograms of the diffusion coefficeints were obtained for different capping agents (MPA and NAC) and cell types (A549 and BEAS-2B). We conclude that the surface chemistry regulates the motion of the quantum dots in the cellular environment.