Phd Degree / Doktora

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

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Asymmetric Synthesis of 5,6-Dihydro Derivatives
(Izmir Institute of Technology, 2014-09) Akçok, İsmail; Çağır, Ali; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
α,β-unsaturated lactone derivatives are very important structural core which are isolated from nature and shown as source for several biological activities. Biologically active styryl δ-lactones are well known α,β-unsaturated-δ-lactones. Up to date, many α,β- unsaturated-δ-lactones and their analogues have been isolated and synthesized, exhibiting promising anti-proliferative properties against different cancer cell lines. In this thesis, large scale asymmetric syntheses of (R)-4’-methylklavuzon and (R)- 2’-methylklavuzon were completed successfully. Also, syntheses of heteroatom functionalized naphthyl substituted novel α,β-unsaturated-δ-lactone (5,6-dihydro-2Hpyran- 2-one) derivatives, α,β-unsaturated-γ-lactone (furan-2(5H)-one) derivatives and 7- membered α,β-unsaturated lactone (6,7-dihydro-5H-oxepin-2-one) derivatives were accomplished. Development of a method for one-pot synthesis of 6-membered α,β-unsaturated- δ-lactone was also studied, and a new vinylogous aldol addition method was developed. By this method, new α,β-unsaturated methyl esters were prepared via dienolate formation starting with methyl buten-3-oate.
Characterization and Catalytic Applications of Hydrothermally Synthesized Poyoxotungstate Clusters Containing Organic-Inorganic Hybrid Materials
(Izmir Institute of Technology, 2019-07) Ece, Özlem; 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.
Characterization of Conjugated Polyelectrolytes for Nucleic Acid Sensing, Gene Delivery and Imaging
(01. Izmir Institute of Technology, 2022) Yücel, Müge; Yıldız, Ümit Hakan; Yıldız, Ümit Hakan; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
In this thesis, cationic derivatives of poly(3-alkylmethoxythiophene) (PT) which are a class of conjugated polyelectrolytes (CPE), have been synthesized. PT has been polymerized via FeCl3 oxidative polymerization, were treated in a set of solvents to elaborate coil conformation of polymer chain in different physicochemical environment. Spectroscopic and scattering techniques have ascertained that ethylene glycol is a good solvent for PT regarding Flory-Huggins theory. The smaller interaction parameter of PT with respect to ethylene glycol than water drives a thermodynamically driven ultra-small particle (Pdot) formation in aqueous phase by a rapid nanophase separation between PTrich ethylene glycol and PT-poor water phase. All CPEs have been then employed to prepare single polymer chain polymer dots (Pdot) by “nanophase separation” method. As a next step, Pdots have been characterized in terms of optical and colloidal properties that they possess in the backbone conformations altered by solvation effect. Regarding their colloidal characteristic, translocation of Pdot into cancerous cells was analyzed compared to healthy cells by 2D cell culture and co-culture studies. It has reported that Pdots have ability to penetrate through nuclear envelope in hepatocellular carcinoma whereas accumulate around nucleus of healthy liver cells in cytoplasm. Additionally, Pdots were studied in breast cancer cell lines to understand the behavior of Pdot staining in 2D cell culture of invasive and non-invasive breast cancer types. The findings suggest that Pdots are prone to penetrate into the invasive cancerous cells attributed to the greater deformations on nucleus membrane of triple negative breast cancer cells. In a next application, the enhanced photophysical property of PT exhibited in ethylene glycol media allows PT to be utilized as a fluorescent probe for determination of single nucleotide polymorphism by a non-amplification-based protocol. Fluorescence emission at specific wavelengths resulted from very distinct conformations of PT chain is the key elements for the SNP detection assay. The evaluation of optical data obtained from the probe with principal component analysis proves the separation of healthy individuals from patients with an overall 96% accuracy.
A Comparative Study of Thin-Film Coated Silicon Wafer Surfaces for Laser-Induced Breakdown Spectroscopic Analysis of Liquids
(01. Izmir Institute of Technology, 2021-07) Aras, Nadir; Yalçın, Şerife Hanım; 03.07. Department of Environmental Engineering; 04.01. Department of Chemistry; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
Laser-Induced Breakdown Spectroscopy, LIBS, is a relatively new atomic emission spectroscopic technique that shows rapid growth due to its many special peculiarities, like its ability to provide spectral signatures of all chemical species at the same time, in all environments of solid, liquid, or gas. Liquid sample analysis by LIBS is more troublesome compared to analysis of solids. Therefore, liquid analysis by LIBS requires some pretreatment steps to be applied before direct analysis of the samples. In the literature, a variety of approaches has been successfully applied and there is still plenty of room to improve methodologies used in the liquid-LIBS analysis. The main purpose of this thesis study was to perform studies for the development of a LIBS-TARGET for sampling liquids on it, after drying, by repetitive laser pulses. With this purpose, silicon wafer-based substrates with differing surface compositions; uncoated (crystalline silicon, c-Si), oxide-coated silicon, SiO2, and nitride coated silicon, Si3N4, were tested for several experimental parameters. Within the content of this study, a fast and accurate methodology for direct analysis of aqueous samples by LIBS is proposed. This methodology has two important attributes: one is the use of the non-metal substrate, silicon wafer, for the first time for direct analysis of aqueous samples dried on, and two is the use of high energy laser pulses focused outside the minimum focal point of a plano-convex lens at which relatively large laser beam spot covers the entire droplet area for plasma formation. Si-wafer-based substrates were used for both qualitative and quantitative analysis of Cd, Cr, Cu, Mn, and Pb elements, and analytical figures of merit were determined. The analytical performance of each substrate was evaluated from the experiments performed with aqueous standards and real water samples. Silicon nitride-coated substrate has shown superior properties in terms of enhancing the LIBS signal and as low as 11 pg detection limits for Pb were obtained.
A Computational Study on the Structures of Protonated Peptides
(Izmir Institute of Technology, 2014-07) Karaca, Sıla; Elmaci Irmak, Nuran; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
The reliable protein identification can be achieved by the knowledge of the structures and fragmentation mechanisms of gas-phase peptide fragment ions. Depending on the size and variety of amino acids in the peptide sequence, the probable structures of b-type fragments have been proposed as an acylium, a diketopiperazine, and an oxazolone structures. Recently, a macrocyclic structure has also been reported in the literature for larger b ions (b4 and greater). The macrocyclic structure is one of the problems for determining the correct sequence of peptides because original primary peptide structure is lost. Another problem is the unclear structure of the fragment ions depending on the peptide size and type. In such cases, the databases which are used with the MS/MS results will be insufficient to identify peptide/protein. In this thesis, the structures of peptide bn + ions having different size and type with a sequence of XAAAA, AAXAA and AAAAX (where A is Ala and X is Asn, Asp, Leu, Phe, Tyr or Cys) have been analyzed by using computational methods. The results showed that, the macrocyclic structure is more favorable than linear oxazolone structure for all b5 + ions studied in this work. The proton prefers to be on the oxygen atoms in the macrocycle while it likes to be on the nitrogen atom for the corresponding linear isomer. However, histidine containing b5 + ions do not obey this observation, for those, proton always is found on the nitrogen on the side chain of histidine. There is no significant position effect of amino acid residue for those b5 + ions, the energies of the most of the linear isomers with different position are very similar. Additionally, the proton affinity calculations have also been carried out to explain intensities of PX (where P is Pro and X is Ala, Phe, Asp, Trp or His) and AAAA fragment ions in the mass spectra. The results demonstrated that the mass spectrum consist of both PX and AAAA fragments were in competition with each other, this is explained by the proton affinity calculations.
Conservation Approaches of Patina Formation on Marble and Travertine Surfaces in the Archaeological Sites
(Izmir Institute of Technology, 2017-07) Badur, Fulya; Böke, Hasan; Yalçın, Şerife Hanım; 02.01. Department of Conservation and Restoration of Cultural Heritage; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology; 02. Faculty of Architecture
Patina, which is formed on the stone surfaces of historical buildings and monuments as a result of aging, is considered as a value of the building in the conservation of cultural heritage studies. It should be conserved on calcareous stone surfaces whether or not it represents protective characteristics, since it provides information about previous times. Within this respect, the determination of mineralogical composition, and microstructural and chemical characteristics of patina are critical for the conservation decisions. The aim of this study is to determine the characteristics of yellow patina formation on marble and yellow travertine surfaces to constitute a conservation approach in the archaeological sites. In this study, XRD, FT-IR, SEM-EDX, LIBS and TGA were used to determine the characteristics of yellow patina formation on marble and yellow travertine surfaces in Aizanoi, Aphrodisias, Sardes and Hierapolis. Analysis results indicated that yellow patina is mainly composed of calcium oxalate (whewellite or weddelite) minerals. CaO, MgO, Al2O3, SiO2, P2O5, K2O, SO3, FeO and Na2O were observed on the chemical analyses of the same samples. The results of LIBS and SEM-EDX showed that Ca increases, and other elements decrease from surface to the sound inner parts of the stone due to calcium oxalate and gypsum precipitation and clay deposition on the surfaces. The calcium oxalate patina forms a homogeneous film layer on calcite crystals. It is most likely formed by the reaction of calcite and oxalic acid produced by the biological formations on stone surfaces. It is colorless in original. The yellow color may be related with the FeO and clay deposition on the stone surfaces. The outcomes of the study proved the presence of a protective yellow patina formation on yellow travertine surfaces against the weathering effects of water which cannot be distinguished by naked eye. This patina presents same characteristics with the yellow patina on marble surfaces which should be conserved. The results of this study show that the determination of yellow patina is critical to keep irreversible cleaning interventions away from surfaces especially for the monuments that yellow travertine is used as building materials.
Design, Construction and Optimization Studies of a Hydride Generation Laser-Induced Breakdown Spectrometric System, (hg-Libes), for the Determination of Toxic Elements in Aqueous Samples
(Izmir Institute of Technology, 2013-05) Ünal Yeşiller, Semira; Yalçın, Şerife Hanım; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
In this thesis study, design, construction and optimization of a continuous flow hydride generation laser-induced breakdown spectroscopic system, HG-LIBS, for the determination toxic and environmentally important elements: arsenic, selenium, lead, antimony, tin, bismuth, germanium and tellurium, has been performed. The HG-LIBS system, which has been constructed from its commercially available components, consisted of four main parts: a laser source, a hydride generation unit, a sample/plasma cell and a detection unit. In order to maximize LIBS emission signal, some instrumental parameters such as laser energy and detector gating parameters were investigated. Some chemical parameters such as acid/reductant concentration and flow rate, carrier gas type and flow rate, presence of pre-reducing/oxidizing agent that effect hydride generation efficiency and transportation of hydrides were also studied. Under optimized conditions detection limits of 0.2 mg L-1, 1.1 mg L-1, 1.0 mg L-1, 1.3 mg L-1 and 0.2 mg L-1 were obtained for Sn, As, Sb, Pb and Ge, respectively. No analytical signal could be detected from Se and Te elements with the system developed. The applicability of the HG-LIBS system for the determination of As, Sb, Pb and Ge in aqueous environments has been tested on several real water samples including tap water, drinking water and reference river water standard. Temporal variation of electron temperature and electron density values for tin and germanium hydride plasma was determined under argon and nitrogen environment. Electron temperatures were calculated by making use of neutral atomic lines in Boltzmann equation. Plasma electron density was evaluated from the Stark-broadened line shapes of Hα line at 656.3 nm. In order to investigate the main cause of increase in germanium signal under argon environment, physical plasma parameters were evaluated in argon and nitrogen gas mixtures. With this thesis study, the applicability of the HG-LIBS system for on-line monitoring of environmental pollutants has been shown.
Design, Synthesis, and Characterization of Porous Dendritic Polymers for Gas Sensor Applications
(01. Izmir Institute of Technology, 2024) Büyükçakır, Onur; Zeybek, Hüseyin; Büyükçakır, Onur; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
Polifenilen dendrimerler (PPD'ler), yüksek oranda dallanmış 3D küresel yapıları ile ayırt edilen makromoleküllerdir. PPD'ler genellikle merkezi çok fonksiyonlu bir çekirdek molekül etrafında fenil halkaları ve uç gruplara sahip dallarla inşa edilir. PPD'ler fizikokimyasal olarak kararlı ve sağlam yapılar sunan rijit, şekil değiştirmeyen fenil halkalarından oluşur. Bu karakteristik özellikleri PPD'leri ışık hasadı, organik elektronik, katalizörler gibi birçok uygulamada kullanılmak üzere umut verici bileşikler haline getirse de, katı haldeki gözeneksiz yapıları nedeniyle gaz ve enerji depolamada kullanımları sınırlıdır. Bu tez, fonksiyonel PPD'leri gözenekli dendritik polimerlere (PDendP'ler) dahil etmek için yeni bir modüler yaklaşım benimsemeyi amaçlamaktadır; bu yaklaşım, 'kalıcı-şekilli dendrimerleri' organik bağlayıcılarla polimerize ederek gerçekleştirilmektedir. Şekli bakımından kalıcı PPD'lerin monomer olarak kullanılması, PDendP'lerde yüzey alanlarının ve gözenekliliklerinin öngörülebilirliğini ve kontrol edilebilirliğini artıran yerel bir düzen sunar. Bu bağlamda, bu yaklaşım PDendP'lerde yapı ve işlevsellik üzerinde hassas moleküler kontrol sağlar. Bu tez, üç farklı PDendP hazırlamak için ditopik bir bağlayıcı kullanarak üç nesil PPD'nin polimerleştirilmesini önermiştir. Bu nedenle, yüzeyde bromo atomlarına sahip üç nesil PPD sentezlenmiş ve bu PPD'ler Suzuki eşleşme reaksiyonları yoluyla bağlayıcı olarak 1,4-bis(4,4,5,5-tetrametil-1,3,2-dioksaborolan-2-il)benzen kullanılarak polimerleştirilmiştir. PDendP'ler ve PPD'ler NMR, FT-IR, BET, TGA, XRD, SEM ve EDX dahil olmak üzere çeşitli analitik teknikler kullanılarak karakterize edilmiştir. Sentezlenen tüm polimerler, PDendP'lerin kemorezistör sensör uygulamaları için bir algılama malzemesi olarak potansiyelini araştırmak amacıyla etanol buharına maruz bırakılmıştır. Islak laboratuvar ortamındaki sonuçları güçlendirmek için hesaplamalı simülasyonlardan yararlanılmıştır.
Determination of Vitamin D by Sensor Technologies Based on Molecular Imprinted Polymers
(Izmir Institute of Technology, 2022-07) Ölçer, Yekta Arya; Eroğlu, Ahmet Emin; Demir, Mustafa Muammer; 04.01. Department of Chemistry; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
Vitamin D is an essential nutrient in the body; it plays important roles in human health. Both its lack and excess can have health risks. As a consequence, there is a great demand for development of simple and precise detection methods for vitamin D derivatives in different samples. Molecular imprinting polymers (MIPs) are artificial receptors that can recognize target molecules in solution. In this study, two different polymerization techniques were used to obtain MIP/NIP sorbents/films for the detection of vitamin D3. Firstly, molecular imprinted solid phase extraction (MISPE) method was proposed prior to HPLC-DAD analysis. Optimized parameters were as follows; sorbent amount of 5.0 mg for 5.0 mL of 1.0 mg/L vitamin D3 in 90:10 (v/v) ratio of H2O:MeOH solution, 5 hours sorption time and MeOH:HOAc ratio of 90:10 (v/v) as desorption solution. The accuracy of the method was verified with spike recovery test for PBS:MeOH in a ratio of 90:10 (v/v) and overall recovery was found as 85.1 (±4.3, n=3). In latter case, a quartz crystal microbalance (QCM) method was proposed for determination of vitamin D3. Electrochemical polymerization of poly(4-vinylpyridine) MIP/NIP films were achieved on gold working electrode by cyclic voltammetry (CV). Mass-transfer ability of the polymer films were analyzed by electrochemical impedance spectroscopy (EIS). The electrochemical QCM (eQCM) was used to develop thin polymer films on quartz crystals and vitamin D3 determination was achieved by QCM. In a preliminary test, as small a concentration as 0.0100 mg/L vitamin D was detected with the QCM method.
Development of Chitosan Based Biofoams
(Izmir Institute of Technology, 2020) Olcay Kurt, Aybike Nil; Polat, Mehmet; Polat, Hürriyet; Polat, Mehmet; Polat, Hürriyet; 04.01. Department of Chemistry; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
Chitosan is a preferred bio-foam material used in many research fields such as tissue engineering and drug delivery due to its unique structural features (wide pH stability, nontoxic-biocompatible-biodegradable, anti-inflammatory, antimicrobial). However, chitosan foams are mechanically too weak to maintain the desired shape until newly formed tissue natures. A wound infection and serious tissue necrosis, endanger human's lives. So, a dressing is required to protect loss of fluids and proteins from the wound area and prevents any bacterial invasion replacing the function of skin temporarily. Therefore controlled drug release from a wound dressing is necessary with a biocompatibility and enough mechanical strength. The aim of this study was the synthesis of mechanically durable - dual porosity chitosan bio-foams to provide a controlled drug release. For this purpose, oil droplets formed in a chitosan solution were used as templates to produce micropores that also contain vancomycin (a model antibiotic-hydrophylic) and curcumin (a model anti-inflammatory-hydrophobic) in the walls of the chitosan matrix with large structural voids. An anionic surfactant, sodium dodecyl sulfate (SDS) alone, was used as a crosslinking agent which was a new approach. Then the structures were characterized by SEM, FTIR, mechanical tests and BET analysis. The chitosan foams have dual pore structures. 1) The intrinsic micro pores that the walls of chitosan matrix have with different morphology that depends on the oil phase. 2) The structural voids that the chitosan matrix have, present even in the absence of an oil phase that depends on the experimental conditions. The mechanical strength of the foams were found to be much higher (up to 250 kPa) compare to the foams produced in literature and suggested to be suitable to use for wound dressing applications. The drug release mechanism of foams were found to depend on the conditions used for foam development and the released kinetics were presented with a mathematical model.
Development of Clustering and Classification Strategies for the Determination of Geographical Origin of Honey by Using Atomic and Molecular Spectrometry
(Izmir Institute of Technology, 2011) Yersel, Müşerref; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
Honey is a natural, nutritious and healthy food produced by honeybees from the nectar of plants. The classification of honey based on geographical origin is of great interest since the quality of honey depends on its chemical composition and geographical origin. In this study, it is aimed to develop classification models using elemental and molecular composition of honey samples via atomic and molecular spectrometry. For this purpose, honey samples from different regions of Turkey were collected from producers and they were scanned with Fourier Transform infrared spectrometer equipped with attenuated total reflectance (FTIR-ATR) accessory, and fluorescence spectrophotometer (synchronous fluorescence mode and 3D excitation emission mode). Afterwards, any clustering of the samples based on their regions was investigated using principal component analysis (PCA) and hierarchical cluster analysis (HCA) and soft independent modeling of class analogies (SIMCA). Finally, inductively coupled plasma mass spectrometry was applied to determine the metal concentrations (Mg, Al, Mn, Fe, Co, Ni, Cu, Zn, Sr, Ba) in honey samples and then the same classification methods were performed to compare the results. In conclusion, molecular spectrometry gave better classification results based on geographical origin compared to the results obtained with atomic spectrometry. Molecular spectrometry is more advantageous for the classification of honey samples in the case of saving time, saving chemicals and ease of usage.
Development of Colloidal Alloyed Nanocrystals for Quantum Dot Based Device Applications
(Izmir Institute of Technology, 2018-06) Sevim Ünlütürk, Seçil; 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.
Development of Genetic Algorithm Based Classification and Cluster Analysis Methods for Analytical Data
(Izmir Institute of Technology, 2009) Öztürk, Betül; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
In this study genetic algorithm based classification and clustering methods were aimed to develop for the spectral data. The developed methods were completely achieved hybridization of nature inspired algorithm (genetic algorithms, GAs) to other classification or clustering methods. The first method was genetic algorithm based principal component analysis (GAPCAD), and the second was genetic algorithm based discriminant analysis (GADA). Both methods were performed to achieve the best discrimination between the olive oil and vegetable oil samples. The classifications of samples were examined directly from their spectral data obtained from using near infrared spectrometry, Fourier transform infrared (FTIR) spectrometry, and spectrofluorometry. The GA was used to optimize the performance of classification or clustering techniques. on training set in order to maximize the correct classification of acceptable and unacceptable samples or samples of dissimilar properties and to reduce the spectral data by wavelength selection. After GA optimization the classification results of training set were controlled by validation set. Lastly, the success of both algorithms was compared to the results of PCA and SIMCA.
Development of New Chemometrics Approaches To Determine Physical and Chemical Properties of Crude Distillation Unit Products Based on Molecular Spectroscopy
(01. Izmir Institute of Technology, 2022-12) Meşe Sezen, Ayten Ekin; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
Crude distillation units are the first processing units of crude oils based on fractional distillation. The properties of the petroleum products obtained from refinery units are frequently analyzed to ensure that the off-spec product cannot be obtained and that the process is working under the desired conditions. This study aims to develop a method based on multivariate data analysis to determine physical and chemical properties of petroleum samples as an alternative to time-consuming and conventional analytical methods. Four different petroleum products obtained from CDU for years were selected and used in this study, which are heavy and light diesel, heavy and light straight run naphtha. Four different spectroscopic methods which are UV-Vis, Fluorescence, FT-NIR and FTIR-ATR spectroscopy, were performed and compared. Multivariate calibration models were developed using Partial least Squares (PLS) and Genetic Inverse Least Squares (GILS) algorithms. For heavy and light diesel, predictive performance of three different spectroscopic methods were compared and for heavy diesel UV-Vis spectroscopy, for light diesel FT-NIR spectroscopy was selected for most of the parameters. Developed models by fluorescence analysis of light diesel samples conducted with two different measurement modes and synchronized fluorescence spectral data has resulted in better models compared to total fluorescence spectra. Studies with straight run naphtha samples were obtained from three different refineries and prediction performances were compared. All obtained model results indicates that developed methodology can be used in routine operations instead of conventional analytical methods.
Development of Novel Anticounterfeiting Technologies Using Heavy Metal Free Nanoparticles
(Izmir Institute of Technology, 2021-07) Taşcıoğlu, Didem; Özçelik, Serdar; Demir, Mustafa Muammer; 04.01. Department of Chemistry; 03.09. Department of Materials Science and Engineering; 01. Izmir Institute of Technology; 03. Faculty of Engineering; 04. Faculty of Science
Counterfeiting, the act of illegally copying a product, document or currency, is a growing problem and causes economic losses. Anticounterfeiting technology uses fluorescent inks that are invisible to the naked eye in daylight, but become visible under UV light. However, these inks have problems such as fading when exposed to sunlight or room light for a long time and disappear completely over time. This is due to the relevant inks are made using organic dyes that fade. The inks used in anticounterfeiting application preventing copying of secure documents such as banknotes, passports and ID cards must be health-friendly and chemically and optically stable for years. All of the existing security materials and equipments for ID cards, driver's licenses, passports, banknotes used in our country are imported. In this study, our aim is to create a new generation of security materials and codes to combat counterfeiters and to verify the generated security codes in a simple, efficient and fast way. In this study, it is aimed to produce nanoparticles, which do not contain heavy metals and show optical stability for a long time, emitting in visible region, on the basis of the security codes created. For this purpose, water and solvent-based nanoparticles synthesized which are non-toxic should have a long-term optical stability. The synthesized nanoparticles act like a pigment in security codes. The photoluminescence (emission color) of the security codes can be adjusted by size and chemical composition of nanoparticles. In this study, colloidally monodispersed and highly photoluminescent InP based nanoparticles were synthesized by the hot-injection approach under an inert atmosphere. In addition, a protective shell (ZnS, ZnSe) coating methods have been applied to provide optical stability to InP nanoparticles. Moreover, carbon-based nanoparticles with high optical stability and being dispersible in water were synthesized using the bottom-up method. Security codes that cannot be detected in daylight have been created on different subtrates (paper, polymer, glass, etc.) by using screen printing and inkjet printing methods, which are well known printing methods using the synthesized nanoparticles. In addition, the authenticity of the security codes was checked using a commercial fiber optic based spectrometer (Ocean Optics spectrometer) and a handy hand-held optical device called the Quantag sensor developed by Quantag Nanotechnologies. Thus, a verification method that can be distinguished by a simple detection device is proposed. The synthesized nanoparticles were furthermore dispersed in a polymer solution to create random droplet and droplet/fiber patterns by electrospinning method. Thus, unique and inimitable security codes detectable under UV light were created which may be used in the fight against counterfeiting. To check the authenticity of the original security codes created; images collected with a simple smartphone microscope and a database was created in which the original patterns were recorded. The originality of the random patterns obtained was checked by comparing it with the patterns recorded in the database. In addition, the spectral information of the particle from the droplet/fiber pattern obtained was determined with a simple hand-held device (Ocean Optics optical spectrometer). Thus, by reading spectral information from the pattern, the spectral signature of the nanoparticles was determined and thus a second-step security was created. In this way, a two-stage anticounterfeiting technology that is impossible to imitate has been developed. As a conclusion, it is believed that the security codes developed in this study will pave the way for the commercialization of quantum labeling technology.
Development of Novel Functionalized Solid Phase Extraction (spe) Sorbents and Solid Phase Microextraction (spme) Fiber Coatings for Analytical Applications
(Izmir Institute of Technology, 2011) Boyacı, Ezel; Eroğlu, Ahmet Emin; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
In the first part of the study, amino-, mercapto- and bifunctional silica-based solid phase extraction (SPE) sorbents were developed, characterized and utilized for sorption and speciation of inorganic As(III)/As(V). Critical parameters on sorption and desorption of species were investigated. The proposed methodology was validated through the analysis of a standard reference material. The subsequent studies were concentrated on the transfer of the experience gained during the modification of silicate surface for preparation of SPE sorbents to the preparation of SPME coatings. The second part of the thesis includes the development, characterization and use of solid phase microextraction (SPME) fibers for the speciation of inorganic and organometallic arsenic compounds. SPME fiber coatings have been prepared by two routes, namely, sol-gel synthesis and nanoparticle immobilization. Fibers having amino functionality synthesized through the sol-gel process were used in the speciation of As(III), As(V), monomethyl arsonic acid (MMA) and dimethyl arsinic acid (DMA). HPLC-HGAAS or HPLC-ICPMS was used in the measurements. Speciation of arsenic compounds was also realized using SPME fibers modified with zero valent iron nanoparticles embedded into an agarose matrix. The detection of the solid phase microextracted analytes was realized by HPLC-ICPMS. Prepared fibers have shown superior extraction for arsenicals. The effect of several parameters on the extent of extraction of arsenic species; namely, solution pH, extraction time, agitation speed and ionic strength were investigated. Validity was checked via the application of the proposed methodology on real samples (tap water, bottled water and geothermal water, urine samples) and standard reference materials.
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, 2017-12) Demirkurt, Merve; 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.
Development of Novel Sorbents for the Determination of Mercury in Waters by Cold Vaporatomic Absorption Spectrometry
(Izmir Institute of Technology, 2011) Erdem, Arzu; Eroğlu, Ahmet Emin; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
Mercury is one of the most toxic heavy metal ions to all living organisms. A novel solid support with selective functional groups was developed for mercury sorption from waters prior to its determination by cold vapor atomic absorption spectrometry. The support was prepared by immobilization of several functional groups (amino, mercapto, etc.) on silica. Among the sorbents developed, 3-MPTMS-silica has been shown to be an efficient material for the sorption of mercury species due to its selectivity. Sorption experiments were performed to optimize the necessary parameters and conclusively, sorption pH of 7.0, reaction temperature of 25 oC, sorbent amount of 10.0 mg and shaking time of 30 min were applied throughout the study. Various mineral acids, organic acids, oxidizing agents and sulfur- or nitrogen-containing ligands were tried for the elution of mercury species and 2.0 M TGA was found to offer the maximum desorption. The validity of the method was checked via spike sorption experiments with four different types of water; namely, ultra pure, bottled drinking, tap and sea water. The method worked efficiently (>95%) for all types of water. Permeable reactive barriers, such as zero-valent iron and zero-valent copper were also applied for the removal of mercury species. Similar optimization parameters with 3-MPTMS-silica were also obtained for both sorbents. The method validation was also performed and although sea water is a heavy matrix, high uptake results were achieved for both sorbents.
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, 2016-07) Ziyanak, Esen; Eroğlu, Ahmet Emin; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
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.
The Effects of Engineered Silica Nanoparticles on the Cellular Behaviours of Human Hepatocellular Carcinoma Cell Lines
(Izmir Institute of Technology, 2018-07) Tüncel Çerik, Özge; Özçelik, Serdar; Atabey, Safiye Neşe; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
Physicochemical properties of the silica nanoparticles have vital roles in determining the physiological behaviours of the cells. Applications of nanoparticle treatments have some outcomes as a response of the cells in living systems as mitochondrial disruption, oxidative stress, reactive oxidative species (ROS) generation, altered cell cycle regulation and DNA damage. In this study 10 and 100 nm sized SiNPs were prepared and physicochemically characterized in the second part. Well characterized silica nanoparticles were used to assess the cytotoxicity and genotoxicity of the hepatocellular carcinoma cell lines as HuH-7 and SK-HEP-1 and lymphocytes. The cell cycle analysis was performed for engineered SiNPs to elucidate the DNA damage in the third part. In the fourth part mitochondrial responses of the cells were determined by real time confocal microscopy at single cell level. An image analysis method for evaluating the cellular responses by mitochondrial staining was developed. DCF stained cells were analyzed in order to assess the production of ROS in the cells. Localization of the SiNPs were determined by lysosomal and mitochondrial staining. Pearson correlation coefficients of the images were used for evaluating the colocalization of organelles with SiNPs. Lastly, diffusion coefficients of the SiNPs in the cells were determined by quantitative confocal microscopy. The SiNPs were found as non-toxic up to 200 μg/ml for 5 days. The SiNPs did not induce the formation of micronuclei in lymphocytes. The SiNPs were not cause an arrest in cell cycle progression. Mitochondrial potentials were not changed after SiNP exposure as well. They were mostly internalized at 30 minutes in both cell line in lysosomal parts without increasing ROS in the cells. It can be concluded that the SiNPs can be safely used for targeted delivery of organic compounds, biological molecules or drugs in medicine, and may be utilized as a probe system in biological studies.

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