LEE- Nano Bilim ve Nano Mühendislik-Yüksek Lisans
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ÖgeGraphene oxide/calcium titanate composite preparation for humidity sensing by quartz crystal microbalance(Graduate School, 2022-09-06)Humidity measurement has been taking attention since 1900s because of the fact that it is used in various aspects from weather forecasts to food and human safety, agricultural processes to mineral processing facilities. Therefore, there has been a growing requirement and extensive research on designing humidity sensors that are rapid, cost-effective, and highly sensitive. Although various methods have been developed, the Quartz Crystal Microbalance (QCM) is a very promising candidate, as it has excellent sensitivity to changes in mass with a nanogram level of detection and, an extensive measuring range. In addition, QCM sensors are stable and reliable in mild operation conditions and can be developed with low-cost. However, the quality and the properties of sensors are highly dependent on the additional sensitive layer. Thus, an additional sensing layer on the surface of QCM electrodes is required to improve the sensor performance including selectivity, sensitivity, response/recovery time and stability. The sensing layer is one of the most important parameters that affects sensing properties of QCM. In literature, there are numerous studies for using different single component containing materials as sensing layer for humidity measurement. On the other hand, the combination of two or more materials, composites, is necessary to obtain improved sensing properties. For humidity sensing, the composite material can be made either with an additional porous material to enhance the interactions with water molecules or with an additional humidity sensitive material to increase the overall humidity sensitivity. Graphene oxide, a two-dimensional material with excellent physical properties, is an excellent candidate for humidity measurement because of the hydrophilic groups on its surface that ensure the adsorption of water molecules. In addition, the use of an additional nanostructured material as calcium titanate can improve the sensitivity by increasing the surface area to volume ratio. In this thesis, the preparation and coating properties of graphene oxide/calcium titanate composite-based material was investigated for the first time in literature. GO was obtained from graphite powder by using a modified Hummer's method. Calcium titanate particles were synthesized by sol-gel method. After the production of two different materials separately, they blended to obtain the composite material. Characterization analyses were performed for optical, structural, and morphological properties of graphene oxide, calcium titanate and graphene oxide/calcium titanate composite materials. The obtained results confirm that a successful production of the composite material was achieved.
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ÖgeFabrication of multi-component superparamagnetic nanoparticles and magnetic heating performance for hyperthermia cancer therapy(Graduate School, 2021-02-16)Nowadays, cancer has become a major public health problem worldwide. It is known that 19.3 million new cancer cases and approximately 10 million cancer deaths occurred worldwide in 2020 alone. The TUIK 2020 report, the cancer is in second place with 80,186 people in Turkey ranking of causes of death. Traditional methods such as chemotherapy, radiotherapy and surgery do not give highly successful results in cancer stages that have spread in the body. These treatment methods carry fatal risks by damaging healthy tissues depending on the treatment method in the patient. For this reason, various treatment methods have been developed that are expected to affect only damaged tissue. Hyperthermia is one of the methods developed for this purpose. Multilayer functional superparamagnetic nanoparticles (NPs) are used in the method, which can be used in medical imaging and treatment applications. With these NPs, it is tried to develop the use of optical and magnetic methods for both diagnosis and treatment of cancer. Thanks to a dielectric shell coated on the NPs, its agglomeration can be prevented, and thanks to an organic shell coated on it, its properties such as biocompatibility and stability can be increased, as well as various molecule adhesion capabilities for treatment purposes can be given to the surfaces of the NPs. In addition to the magnetic properties of these NPs, it will be possible to heat them with the near infrared (NIR) laser to be applied due to their surface plasmon resonance properties. Basically in this method; It is aimed to; (a) reach the denaturation temperature (42ºC) of the cancer cells by applying an alternative magnetic field that will affect only the tumor area, and (b) the malignant cells are destroyed by heating while the other healthy tissues remain stable. In this way, the side effects that occur in traditional methods are tried to be minimized. The two most important factors determining the use of magnetic NPs in hyperthermia therapy are; (a) the applied NPs must have a high ability to heat the cancerous tissue to the desired temperature and (b) heating should be limited only to the cancerous tissue. These two factors can be achieved by having excellent magnetic properties that can reach the target temperature by using a small amount of NPs in the target tissue. For this reason, the type of magnetic NPs used and their magnetic heating performance are of great importance. Studies on various NPs such as Fe3O4, MnFe2O4 are quite common, but it becomes impossible to compare the experimental results due to the different methods and different environmental conditions determined for NPs fabrication in the studies. Therefore, more research is needed to make hyperthermia treatment available. In the thesis, in the first part, Fe3O4, MgFe2O4, MnFe2O4 and SrFe12O19 NPs were synthesiszed as cores. Later, their outher surface was first coated with SiO2 layer, functionalized with amination, then decorated via Au NPs and consequently the outer surface of overall NPs will be coated via PEG. After each coating, the NPs have been characterized using FTIR, SEM and EDX. Heating process was carried out under AMF, using induction generator, in water and in agar according to the rate calculation of 0.1% (v/m) of the produced NPs. According to the results of the heating tests, among all samples, SrFe12O19 NPs showed the lowest and MgFe2O4 NPs showed the highest heating performance among all samples in the tests where different core types were compared. According to the heating results comparing the different coating stages, the aminated NPs gave the fastest warming result among the other coating stages. Comparing different coating steps, PEG coated samples gave the slowest heating result in the heating results. In addition, the heating performance of gold-coated samples, which is the previous coating step from PEG, is very close to that of PEG coated samples and gave the second lowest performance. As a result, our study has shown that different coating stages and NPs differences change the heating performance of superparamagnetic NPs. Although there are many studies of magnetic NPs in the literature, the effects of different types of magnetic NPs on the heating performance of different coating stages of these NPs were compared under standardized laboratory conditions. It is possible to say that this study, which is carried out with easily accessible and economical laboratory materials, is illuminating for future researches related to the subject.
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ÖgeSynthesis of folate receptor 1 targeted dye-conjugated peptides for use in positron emission tomography imaging systems(Graduate School, 2022-01-26)Nowadays, it is tried to find solutions for human beings to have a long and high-quality life, increase the number of studies in the field of health, and detect diseases that become difficult to treat with their progress. Cancer is one of the first causes of death statistics in official records in the world and Turkey. It is known that the diagnosis of cancer is difficult and takes time, and the number of cases continues to increase rapidly day by day. Because of the metabolism change in cancer cells, the cells continue to grow and divide instead of dying. Cancer factors; inherited mutations can be internal, such as hormones, or acquired environmental, such as carcinogens, radiation, infectious organisms, and lifestyle. By imaging the changes caused by cancer in cells, information about the stage of cancer can be obtained. Cancer researchers want to detect cells where cancers develop, identify biomarkers of cancers early, and create treatment plans for cancer. Proteins produced by tumor cells can be used as biomarkers to evaluate disease processes. Molecular imaging (MI) aims to combine patient and disease-specific molecular information and is an interdisciplinary area covering a wide range of sciences when is used in the diagnosis and treatment of diverse disease genres. For this purpose, targeted cell-specific chemical biomolecules are delivered to the organism by labeled radioactive isotopes. The imaging method to be utilized varies specifically according to the disease state. Positron emission tomography (PET), which has become more advanced with the integration of scanners such as computerized tomography (CT) used in the imaging of cancer, is one of the several imaging methods widely used in the diagnosis of cancer today. Since radioisotope imaging agents are required for imaging in PET devices, studies for their development are increasing day by day. Peptides are used as ligands/agents in imaging cancer imaging, thanks to their properties such as high selectivity and high affinity, ease of synthesis and chemical stability, quick removal from blood, and low immunogenicity/safety for cell surface proteins. Due to the metabolic rate of cancer cells, more folic acid is produced in these cells than in normal healthy body cells, and this uncontrolled increase has led to its use in cancer imaging studies. Peptide-based imaging agents are used for molecular imaging by binding to target cancer receptors such as Folate Receptor 1 (FOLR1) of tumor cells. Molecules that can bind to the FOLR1 receptor with high sensitivity and affinity were synthesized by the Solid Phase Peptide Synthesis (SPPS) method. The peptides KWGFR, KLWWN, KFLSW, KWIAG, KWSYW, KGWRN, and KSYFA were selected from the peptide library and successfully synthesized. Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC) was used to purify the peptides and Liquid Chromatography-Mass Spectrometry (LC-MS) was utilized for peptide characterization. Finally, the imaging agent will be obtained by conjugating the peptide-based signaling agent labeled with the 68Ga isotope.
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ÖgeDevelopment of interlayer based thin-film nanofibrous composite membranes adjusted by functionalized carbon nanotubes for effectual water purification(Graduate School, 2022-01-20)Drinkable water supply is one of the fundamental human prerequisites all over the world. Due to the population expansion, the changes in the global climate, and water degradation, The requirement for freshwater increases with time around the world. Based on the reported calculations, except for 2.5% of existence global water, which is classified in the potable water range for humans, 70% of the remaining freshwater (FW) is frozen. Due to recent reports, more than 700 million people worldwide have not been accessed clean water. Ascribed to the severe FW demands, which have been observed in some developing countries and sub-Saharan African countries, the water treatment technologies must be enforced in these overwhelmed countries. Nanoscience and nanotechnology are other novel solutions to water treatment technology problems. Ascribed to nanomaterials properties, including high aspect ratio, reactivity, adjustable pore volume, hydrophilic, hydrophobic, and electrostatic interactions, they have been utilized in numerous types of applications. Multiple types of batteries, optics, fuel cells, sensors, electrics, thermoelectric devices, pharmaceuticals, and cosmetics are some industries that have used nanomaterials to improve their products. Moreover, nanotechnology has been performed in economically unconventional water sources, resolving contaminant-free water for humans, and suggesting many solutions to alleviate needs with regard to reducing scarcity or removing contamination. For example, there are filters that remove pesticides from drinking water using nanochemistry. At the same time, due to the multidisciplinary feature of membrane technology and essential advantages of membrane science technology, such as being clean energy, the ability of energy-saving, high-quality products, and system versatility, it has been applied in multiple applications. The power of membrane technology to replace other purification systems, including distillation and ion exchange systems, has been distinguished as other membrane technology's benefits. Furthermore, because of the forward osmosis (FO) and nanofiltration (NF), membranes' excellent features such as energy conversion, low-cost procedure, and high water recovery ability have received much more attention in wastewater treatment, water purification, and brackish water desalination over the last decade. The electrospinning device generally consists of a high voltage power supply, a supply unit, and a grounded collector. The feed solution is sent to the feed end by a pump. An electric field is created by a high-voltage power supply connected to the supply terminal. As the applied voltage increases, the electrical forces overcome the viscoelastic forces of the solution at the feed end. After a critical voltage, a jet formation is observed at the supply end. The bubbler solution diffuses in the electrical field and accumulates randomly on the collecting plate in microscopic diameter fibers. The solvent in the solution evaporates before or after the fibers are collected in the container. Among the factors affecting the nanofiber production by electrospinning method are the type of polymer to be obtained, conductivity and dielectric properties, the solvent used, the viscosity of the feed solution, the distance between the feed unit and the collector, the feed rate (flow rate), the voltage used. More than 100 polymers can be electrospinning, and the most preferred among these polymers in nanofiber membrane construction are; polyacrylonitrile (PAN), poly(ethylene oxide) (PEO), polystyrene (PS), Nylon-6, poly(vinyl alcohol) (PVA), poly(ε-caprolactone) (PCL) and polycarbonate. PVA is a water-soluble, non-toxic, and biocompatible polyhydroxy polymer with high chemical resistance and thermal stability among these polymers. It is known that PVA easily interacts with other organic and inorganic materials. However, PVA's applications are limited due to its hydrophilic nature. Therefore, it must be modified to minimize dissolution, mainly used in aqueous applications such as filtration and adsorption. Chemical crosslinking of PVA nanofibers with dialdehydes, dicarboxylic acids, or dianhydride is advantageous in becoming insoluble in all solvents and increasing their thermal and chemical properties. Polymeric thin-film composites are essential types of compounds applied in various practical applications, including surface coatings and modifications, adsorption and immobilization, membrane technologies, and low surface energy interfaces. Also, the inherent internal concentration polarization (ICP), which causes osmotic driving force's decline, is another major problem of conventional TFC membranes which has been challenged for several years. Moreover, biological fouling is another disadvantage that limits the conventional TFC membranes' performance in multiple usages. Due to the biological fouling of TFC type membranes, microorganisms and micropollutants, which require reproduction, easily stick to the membrane's surface and cause a significant reduction of FO membranes' stability and durability. In order to break the trade-off between permeability and selectivity of TFC membranes and obtain membranes with balanced permeability and rejection performance and excellent durability, triple-layered thin film composite (TFC) forward osmosis (FO) membranes fabricated by introducing an interlayer on the porous electrospun membranes before interfacial polymerization (IP) procedure. Introducing an interlayer on the electrospun substrate overcomes the conventional TFC membranes' limitations and causes synthesizing controlled polyamide (PA) layer and improving the IP process. Carbon nanotubes (CNTs), cellulose nanocrystal, and cadmium hydroxide nano-strands are some of the nanomaterials that have been introduced as an interlayer in TFC types of membranes. The adopted interlayers develop the barrier selective layer's structure and control the IP procedure. Due to the CNT's ideal characteristics, such as large specific surface area (SSA) and excellent mechanical stability, CNTs are distinguished as superior nanomaterials that have been performed as interlayers in TFC membranes. Triple-layered TFC membranes with CNT interlayer enhance the PA layer formation with defect-free and ultrathin structure and promote the membrane's permeation ability, even rejecting monovalent and divalent ions. The membranes were utilized in this research are thin-film nanofibrous composite membranes with hydrolyzed multi-walled carbon nanotubes (MWCNTs) as an interlayer. First of all, MWCNTs had been acid-treated in the presence of sulfuric (H2SO4) and nitric (HNO3) acids. Secondly, the different amounts of hydrolyzed MWCNTs were dispersed in the distilled water using ultrasonication and then introduced as an interlayer onto the porous polyacrylonitrile (PAN) electrospun membranes by vacuum filtration procedure. Finally, TFC membranes were prepared to utilize the IP procedure. In this study, MPD and TMC solutions had been performed as aqueous and organic phases to begin the IP proceeding. The prepared membranes had been tested in dead-end filtration systems to investigate the membranes' performance in salt rejections. Also, these interlayer-based TFC membranes had been applied in the dye removal from industrial wastewaters and compared to the conventional TFC type of membranes in their filtration performance.
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ÖgeFormation and structural properties of water induced structures at graphene/mica and graphene/CrxO/glass interfaces(Graduate School, 2021-10-08)Water behavior at interfaces has great importance. Especially molecularly thin layer water or nanoconfined water. Nanoconfined water properties are different from bulk ones. Studying nanoconfined water properties have fundamental importance in biology, material science, nanofluidics, tribology, and corrosion. Nanoconfiment materials are carbon nanotubes and layered two-dimensional materials or Van der Waals crystals. In this thesis, we studied water interaction behavior with graphene/water/CrxOy/glass and graphene/mica systems. For this purpose, we needed the following devices: Optic microscope with the isolated system, PVD system, graphene heater, and materials like CVD-grown graphene, muscovite mica, soda-lime glass, and chromium granulates. Firstly, we started with graphene/water/CrxOy/glass system. We did thermal evaporation of chromium using PVD system that was assembled in our laboratory. As a substrate, we used soda lime microscope slide glass(INTROLAB). Chromium thin-film on glass samples was produced. The thickness of thin-film chromium was varied. We transferred CVD-grown graphene onto chromium thin-film glass with the wet transfer method, then annealed it in a tube furnace around 450°C degrees under atmospheric ambient conditions for approximately 40 minutes. As soon as annealing finished we quickly transferred produced sample into a container full of silica gels to preserve from environmental humidity. We reduced humidity within enclosed boxes in which an Optical light microscope stayed for study samples under controlled humidification. We took optic data before, during, and after the humidification process. Secondly, our second system for research was graphene/water/mica. Again as in the graphene/water/CrxOy/glass system, we used CVD-grown graphene and V2grade muscovite mica(Ted Pella). Using scotch tape we cleavage mica several times then CVD-grown graphene was transferred onto it using the wet transfer method. We preserve graphene/mica samples in a container full of silica gels. We studied them with two methods: First under the optic microscope in the isolated box and second using the graphene heater. We reduced humidity to 9% in the isolated box using silica. In the case of the graphene heater, we managed to heat up nearly 200°C. We observed fractal in graphene/CrxOy/glass system but due to non-homogeneous deposition of chromium fractal formation was inconsistent. In case of graphene/mica system observation of de/rewetting process was not possible even though we reduce humidity. The graphene heater was functional, the reason that we couldn't use it was a poorer resolution of the graphene/mica system. Otherwise, observation de/rewetting graphene/water/mica with the optic microscope is challenging.