Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
Browse
10 results
Search Results
Master Thesis Synthesis of Polythiophene-Polyurethane Soft Nanoparticles for Bioimaging Applications(Izmir Institute of Technology, 2020) Karabacak, Soner; Yıldız, Ümit Hakan; Yıldız, Ümit Hakan; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn this study, synthesis of fluorescent polythiophene and polyurethane soft nanoparticles carrying them was carried out for bioimaging applications. Conjugated polythiophenes and polyurethane derivatives were obtained by changing their structural properties such as size, charge, and group, and were characterized by nuclear magnetic resonance, infrared spectroscopy, dynamic functional light scattering, fluorescent microscopy, methods. In the study, changing characteristics of polyurethane nanoparticle materials were investigated depending on the synthesis conditions. Synthesis of polyurethane nanoparticles was carried out by miniemulsion polymerization technique and synthesized as nanosphere to be more controllable on nanoparticle size, morphology and stability. The sizes of the polyurethane nanospheres varied in the range from 10 to 500 nm. Polyelectrolyte-polyelectrolyte complexation was investigated using cationic polythiophene-anionic polythiophene for use in bioimaging applications. Synthesized conjugated polythiophenes are divided into two groups as anionic and cationic polythiophenes. In this thesis, three kinds of cationic polythiophene synthesis are included, but poly (1,4-dimethyl-1- (3- ((4-methylthiophene-3-yl) oxy) propyl) piperazine-1-ium bromide) (PT4) was used as cationic conjugated polythiophene in the studies. Anionic polythiophene acetic acid (PTAA) was used as a counter-charged polythiophene. In addition to these studies, dual-mode imaging agents were prepared, consisting of PTAA as fluorescent agent and gadolinium metals as magnetic agent. The bioimaging studies continued under conditions imitating biological systems, and the potential of the proposed bioimaging agents was investigated.Master Thesis Modification of Gold Surface by Layer-By Reactive Coating of Polyester-Polyethyleneimine Based Gel(Izmir Institute of Technology, 2020) Yıldız, Ümit Hakan; Yıldız, Ümit Hakan; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyPolymeric gels defined as soft and solid-like systems that enable to retain a large volume of solvent and their high molecular weight provides long-term stability without crystallization. Therefore, the use of polymeric gels in the fields of energy and sensor technologies has become advantageous. In this thesis, the polymeric gel is successfully synthesized on the gold surface by Aza-Michael addition reaction of the polyester scaffold with a triple covalent bond and branched polyethyleneimine which is a secondary amine source. The polyester-polyethyleneimine based gel was generated on the isocyanate functionalized gold surface by using the grafting-to methodology. The morphology of the surface and thickness of the coating can be adjusted by layer-by-layer reactive coating on the gold surface of polymer structures. Electroactive properties are acquired for different application areas of the synthesized gels. To provide modular electron transfer, polyethyleneimine was modified with ferrocene carboxaldehyde prior to obtaining gel on the surface. The gel interface on the gold surface will increase the surface area and activity due to its three-dimensional structure and adjustable morphology. The number of the immobilized structures, the electroactive species in a unit area and electron transfer increases. The modified electrode surfaces coating yields and electroactivity examined with electrochemical methods, Cyclic Voltammetry and Electrochemical Impedance Spectroscopy. The morphological properties investigated by Atomic Force Microscopy. Additionally, polyester-based gels lithium-ion conductivity was investigated. Dissociation of lithium perchlorate in the gel and enhancing the conductivity was investigated. Indium tin oxide coated glasses were used as an electrode to characterize lithium ion conductivity.Master Thesis Fabrication of Polymer Nanofiber / Poly (3,4 Ethylene Dioxythiophene) / Metal Particle Hybrid Composite for Volatile Organic Compound Sensing Applications(Izmir Institute of Technology, 2020) Yıldız, Ümit Hakan; Yıldız, Ümit Hakan; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyThis study aims to produce polymer nanofiber / poly (3, 4 ethylene dioxythiophene) / metal particle hybrid composite as a bioelectronic interface for the detection of volatile organic compounds in human breath. The sensor platform consists of two layers: polymeric nanofiber structure and conductive layer. Polyurethane (PU), polycaprolactone (PCL) and poly L-lactide-co-?-caprolactone (PLLCL) were selected to form polymeric nanofibers with electrospinning. For electrospinning process, solutions of polyurethane (PU) (25wt%) in DMF, polycaprolactone (PCL) (20wt%) in DCM (4) -DMF (1) and poly L-lactide-co-?-caprolactone (PLLCL) (10wt%) in DCM (9) -DMF (1) are prepared. PU, PCL and PLLCL polymer solutions are subjected to 25 kV, 29kV and 25 kV electrical potential, respectively, to produce electrospinning fibers. Poly(3,4-ethylenedioxythiophene) (PEDOT) and multi-walled carbon nanotubes (MWCNTs) are used to produce conductive layers on PU, PCL and PLLCL polymer nanofibers. The produced sensor platforms are tested by the electrochemical station, which records the electrical current change over time. The sensing mechanism is assumed to be the adsorption of VOCs to the conductive PEDOT and CNT layer, thus blocking the electron current on the PEDOT and CNT network and causing resistance change. More clearly; swelling of the polymer structure in the sensor causes destruction in the upper layer and micro-dimensional cracks in the PEDOT and CNT network, increasing resistance to electron flow and decreasing current. Organic volatile compounds (acetone, toluene, ethanol, isopene etc.) are detected from ppm to ppb range and reproducible and reliable responses are recorded.Master Thesis A Novel Approach for Fabrication of Free-Standing Conductive Network: Pedot: Pss Based Bendable Chemo and Photoresistor(Izmir Institute of Technology, 2019) Mutlu, Mustafa Umut; Demir, Mustafa Muammer; Mutlu, Mustafa Umut; Yıldız, Ümit Hakan; Yıldız, Ümit Hakan; Demir, Mustafa Muammer; 03.09. Department of Materials Science and Engineering; 04.01. Department of Chemistry; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyElectrospinning is a simple and versatile technique for the fabrication of polymeric nanofibrous substrate with high surface to volume ratio. Besides high surface to volume ratio, their dimensional stability and flexibility make it a perfect candidate for conductive network for various sensor applications. Free-Standing conductive network can be fabricated by deposition of PEDOT:PSS or MWCNT through bendable nanofibrous substrate. As a simple example for sensor applications, the moving object has been sensed through the electrostatic interactions between fibers and object. The sensing range has been found to be 1-5 cm above the surface of fabric. By the controlled combination of conductive polymers and electrospun polymer nanofibers effective device miniaturization has been provided without loss of performance. The noncontact motion sensor platform has unique flexibility and light weight holding a potential for wearable sensor technology. For another application as a wearable electronics, the controlled combination of conductive network and light-matter interaction provides opportunities to fabricate photo-resistor exhibits broad band response 400 to 1600 nm that holding promises for ultra-thin sensors used in telecommunication. As a final example, we report the effect of gold and iron oxide nanoparticles on the selectivity and sensitivity of MWCNT or PEDOT:PSS based chemiresistor responsive to VOCs. The interplay between conductive layer by gold and iron oxide nanoparticles resulted a significant conductivity improvement that affecting selectivity which is governed by the interaction between electron-donating VOCs and NP doped conductive layer due to variation in charge carrier densities in conductive layer lattice.Master Thesis Ultra-Porous Interconnected Hydrogel Structures for Tissue Engineering Applications(Izmir Institute of Technology, 2018) Yıldız, Büşra; Arslan Yıldız, Ahu; Yıldız, Ümit Hakan; Yıldız, Ümit Hakan; Arslan Yıldız, Ahu; 04.01. Department of Chemistry; 03.01. Department of Bioengineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyTissue engineering aims to repair and regenerate tissue and organs with functional defects. The most significant developments in tissue engineering emerging as modification of the scaffold used to mimic native extracellular matrix (ECM) and support cell proliferation and differentiation. Hydrogel-based biomaterials are one of the most utilized materials as scaffold providing excellent chemical, physical/biophysical properties, high biocompatibility and functionality necessary for the applications in tissue engineering. In this study, Gelatin methacryloyl hydrogel (GelMA) and Gelatin-urethane hydrogels (GelatinK) are successfully synthesized as scaffold material for tissue engineering applications. Gelatin is modified with methacrylic anhydride for GelMA polymer and with 2-isocyanatoethly methacrylate for GelatinK polymer. The hydrogels of these two novel polymer are produced with photopolymerization reactions in aqueous media using Irgacure 2959 as redox initiator. Hydrogels are freeze-dried to remove solvent in the gel matrix and then they immersed in distilled water to reach equilibrium swelling ratio. The swelling capacity of GelMA hydrogels ranges between 1200 and 300% whereas GelatinK hydrogels has swelling capacity in between 1900-380%. Also, morphology of the hydrogels were investigated with Scanning Electron Microscopy (SEM). GelMA hydrogels has pore sizes between 142-14 µm while GelatinK hydrogels has between 160-56 µm pore sizes. The cell viability assay were also conducted using GelMA and GelatinK hydrogels. The results showed that both hydrogels provide high viability as compared to 2D control assay.Master Thesis Detection of Dna Methylation of Multiple Tumor Supressor P16ink4a Gene by Polythiophene Based Optical Sensor(Izmir Institute of Technology, 2018) Kaya, Hakan; Yıldız, Ümit Hakan; Elmacı Irmak, Nuran; Yıldız, Ümit Hakan; Elmacı Irmak, Nuran; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyDNA methylation is epigenetic events commonly occurs in mammalian genome starting from formation of embryo to the end of life. Especially, hypermethylation in tumor suppressor genes, corresponds the cancer growth and detection of DNA methylation in these genes crucial for the diagnosis of cancer. Water soluble polythiophenes are frequently used for the detection of biomolecules through the optoelectronic properties. In this study, detection of DNA methylation of multiple tumor suppressor p16INK4A gene via polythiophene based optical sensor was achieved. Newly designed, synthesized and characterized poly(1-(3-((4-methylthiophen-3-yl) oxy) propyl)-1,4diazabicyclo [2.2.2] octan-1-ium bromide) was used during characterization of DNA sequences and detection of DNA methylation. The target sequence position is +137 to +156 in p16INK4A gene which have three potential CG dinucleotide to be methylated. Detection of DNA methylation based on sodium bisulfite treatment, complementary sequence of unmethylated ssDNA and the conformational change of water soluble polythiophene. In our fluorometric analysis, unmethylated sequence/complementary successfully hybridized and dsDNA Io/I ratio is under the 1.40 while the methylated sequence/complementary hybridization failed due to different base content and remain as ssDNA and, Io/I ratio is higher than 1,60. The novelty of work is detection mechanism is PCR and FRET free with a range of 300 ng to 700 ng sample requirement. Characterization of homopurines, homopyrimidines, methylated and unmethylated sequence with cationic polythiophenes also accomplished. PolyG (10), polyG (20) and polyA (10) yielded a no signal in UV-VIS region while the polyA (20) yielded a 100 nm red shift. Furthermore, PolyC (10), PolyC (20), PolyT (10), PolyT (20) yielded three vibrionic peaks at 505 nm, 545 nm and 595 nm with different intensities and unique isosbestic points. All 10 bases long homopyrimidine and homopurine have a unique quencher character with cationic polythiophene. Lastly, conformational change of polythiophene investigated with computational methods and heptamer used as a model.Master Thesis Green Synthesis of Metal Nanoparticles and Their Applications as Plasmonic Substrates(Izmir Institute of Technology, 2018) Elveren, Beste; Arslan Yıldız, Ahu; Yıldız, Ümit Hakan; Arslan Yıldız, Ahu; Yıldız, Ümit Hakan; 04.01. Department of Chemistry; 03.01. Department of Bioengineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyGold nanoparticles (GNPs) have been widely used in diagnostic, tissue engineering, and drug delivery fields, in the last decades. Generally, reducing gold salts to zero valent gold has been accomplished by harsh chemicals and strong reducing agents, which cause toxicity and eventually limiting the bioapplications. Green synthesis is a newly developing methodology to synthesize GNPs. Especially natural products and plants extracts are commonly preferred for green synthesis based on their natural content. Biological molecule-capped GNPs, are more biofriendly and biocompatible nano-materials that can be used for varied applications.1-3 Sensor applications; varying from biosensing to environmental analysis, are an important field that GNPs were intensively utilized.4-5 Cyanide ion (CN-) has been considered as one of the main pollutants of water, because of its rapid discharge. CN- is currently being used in industry such as; polymer synthesis6, noble metal mining7, pest control8, plastics production etc., at large scale. However, there is an unmet need for CN- detection and monitoring. Colorimetric detection of CN- that utilizes GNPs has been done by several researchers.9-10 However, in all these studies reduction of GNPs were done by strong reducing agents. Green synthesis of GNPs eliminates the toxic side-products that can be harmful to both environment and human health. To overcome this problem green synthesized GNPs were used to establish the sensor platform, which can be further employed for CN- detection. Oxidation of GNPs in the presence of cyanide molecules is a direct-forward, colorimetric and optical method that requires no toxic chemicals; therefore it is a greener approach towards CN- detection in water resources.Master Thesis Development of Gold Nanoparticle-Based Plasmonic Assay Platform for Esherichia Coli Detection(Izmir Institute of Technology, 2017) Erdoğan, Duygu; Yıldız, Ümit Hakan; Arslan Yıldız, Ahu; Yıldız, Ümit Hakan; Arslan Yıldız, Ahu; 04.01. Department of Chemistry; 03.01. Department of Bioengineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyThe traditional methods for pathogen detection have long detection time and insufficient sensitivity. Optical methods can overcome these drawbacks. There are solution based nanoparticle growth in the literature to enhance a surface sensitivity for biosensing applications. In this project, surface refractive index (RI) sensitivity was enhanced on solid support via gold growth to develop a label free, simple and costeffective methodology for bacteria screening. The gold nanoparticles (GNPs) were grown on solid support by using 20 μl of HAuCl4 / 80 μl of NH2OH at varied incubation times. Firstly, about 20 nm GNPs were synthesized and immobilized on polystyrene surfaces. Then, these GNPs were utilized as seed particles, and grown on solid support. During GNPs growth, a red shift in the plasmonic wavelength was observed. Morphological characterization showed that almost uniform gold growth could be achieved. The plasmonic platform sensitivity was validated by varied concentrations of sucrose, ethanol and BSA solutions, showing that the plasmonic platform gave a response to any small RI change. Next, two different E.coli bacterial strains’ adsorption was tested. Adsorption screenings for about 107 E.coli DH5-alpha cells/ml and 107 E.coli BL21(DE3) cells/ml in Phosphate Buffer Saline were made on growth gold surfaces. Further, E.coli BL21(DE3) containing milk and apple juice were also adsorbed on these gold surfaces with a 30 min incubation time. The results showed that these gold surfaces exhibit higher binding kinetics for bacteria. Therefore, the proposed LSPR-based label free methodology can be an alternative to the bacteria screening in water or food samples.Master Thesis Fabrication of Thin Layer Polymer-Based Biointerphase for Biosensing Application(İzmir Institute of Technology, 2016) Yücel, Müge; Yıldız, Ümit Hakan; Yıldız, Ümit Hakan; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyThis study aims to fabricate polymer-carbon nanotube composite as a bioelectronic interface for sensing volatile organic compounds (VOCs) in exhaled breath. Sensor platform is made of two layers i) polymeric membranes and ii) conducting layer. Poly(vinylidene fluoride) (PVDF), polystyrene (PS), and poly(methyl methacrylate) (PMMA) are selected as model polymers that are processed by electrospinning to utilize polymeric membranes. Multi-walled carbon nanotubes (MWCNTs) are used to fabricate conducting layer on top of PVDF, PS, PMMA polymer membranes. Aqueous solution of well-dispersed MWCNTs are obtained by several purification and filtration steps and conductivity of working MWCNT solution is adjusted about 120 μS/cm for whole study. This solution is further used to impregnate PVDF, PS, PMMA membrane. The PVDF-MWCNT, PS-MWCNT and PMMA-MWCNT sensor platforms are tested by electrochemical station that recording electrical resistivity change by time. All sensors platforms, made of three polymeric membranes-MWCNT, are found to be a responsive upon applying the toluene and acetone vapor. The sensing mechanism is hypothesized as the adsorption of VOCs onto the conducting CNT layer blocking electron stream on CNT network and causing resistivity change. The sensitivity of PVDF-MWCNT sensing platform is exceedingly higher with respect to other two candidates due to solvent vapor- polymeric membrane interactions. This contribution changes sensor platform characteristics and make them quite sensitive to trace amount of VOCs. Acetone and toluene are detected from ppm to ppb range and reproducible responses are recorded. As a result, acetone and toluene, biomarkers of diabetes and lung cancer, can be differentiated with produced sensor.Master Thesis Glucose Biosensor Applicatiın of Electrospun Polyvinyl Alacohol (pva) Fibers(Izmir Institute of Technology, 2016) Berber, Emine; Yıldız, Ümit Hakan; Demir, Mustafa Muammer; Demir, Mustafa Muammer; Yıldız, Ümit Hakan; 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 TechnologyElectrospinning is a simple and versatile technique for the fabrication of polymeric nanofibrous membranes with high surface to volume ratio. Besides the large surface area of the fibrous membranes, their dimensional stability and flexibility allows the immobilization of biomolecules on to the nanofiber surfaces. Therefore, electrospun nanofibers have been extensively used in enzyme electrodes. This thesis examines the glucose biosensor application of electrospun polyvinyl alcohol (PVA) nanofibers – carbon nanotube (CNT) nanocomposite membranes. By manipulating the structural design and the composition of the nanocomposite membranes, glucose sensing efficiency of the five different enzyme electrodes a) Glucose oxidase (GOx) immobilized PVA electrospun electrode, b) Glucose oxidase (GOx) immobilized PVA electrospun electrode containing multi-walled carbon nanotube (MWCNT), c) Glucose oxidase (GOx) immobilized PVA electrospun electrode containing Poly(diallyldimethylammonium chloride) (PDDA) functionalized multi-walled carbon nanotube (MWCNT) d) Glucose oxidase (GOx) immobilized PVA electrospun electrode containing Poly(diallyldimethylammonium chloride) (PDDA) functionalized single-walled carbon nanotube (SWCNT), e) Interfacially cross-linked PVA electrospun electrode containing Poly(diallyldimethylammonium chloride) (PDDA) functionalized multi-walled carbon nanotube (MWCNT) were comperatively studied. PVA electrospun nanofibers were fabricated by using electrospinning technique. Morphology and average diameter of the fibers were characterized by using Scanning Electron Microscopy (SEM). Average diameter for the neat PVA electrospun fibers were 115 nm. Carbon nanotubes were oxidatively functionalized by acid treatment and addition of functional groups after acid treatment was proved by using Raman Spectroscopy. Glucose sensing activities of the electrodes were amperometrically measured at an applied voltage -0.5 V (vs. Ag/AgCl) in 0.1M phosphate buffer solution (PBS pH 7). Glucose detection sensitivies of the electrodes were calculated as 19.6, 27.7, 67.5, 44.4, 4.0 μA mM-1cm-2 respectively.