5
Archived Theses
0
DOIs Assigned
0%
DOI Rate
Discipline
β-karoten ve lutein ayrımı için grafen oksit ve türevi HPLC sabit fazlarının geliştirilmesi
Bu tez çalışmasında; gıda, çevre ve sağlık gibi farklı alanlarda uygulamaları bulunan grafen oksit ve türevlerinin sıvı kromatografisinde sabit faz olarak kullanımı için grafen oksit, Si-GO ve Si-GO-C18 materyallerinin sentezlenmesi, karakterizasyonlarının yapılması, β-karoten ve lutein moleküllerinin ayrımı için metotların geliştirilmesi ve bu metotların validasyonunun yapılması amaçlanmıştır. H2SO4 ve H3PO4 ile modifiye edilmiş Hummers metodu kullanılarak sentezlenen grafen oksit (GO), daha önce aminopropil silika üzerine kimyasal olarak bağlanarak Si-GO sabit fazı daha sonra bu sabit üzerine C18 bağlanarak Si-GO-C18 sabit fazı elde edilmiştir. Sentezlenen GO, Si-GO ve Si-GO-C18 materyallerinin karakterizasyonları UV-vis, FTIR, TEM ve SEM analizleri ile yapılmıştır. Yüksek okside elde edilen GO nano partikülleri FTIR analizine tabi tutularak grafen okside hidrofiliklik veren -OH ve -COOH grupları ile C=C, C=O ve epoksit (C–O–C) pikleri tespit edilmiştir. GO`de bulunan -OH ve -COOH piklerinin bir kısmının azalarak peptit bağının oluştuğu gözlenmiştir. Ayrıca Si-GO-C18 spektrumunda GO üzerine C18 bağlanmasını gösteren -CH titreşimleri tespit edilmiştir. Elde edilen GO ve sabit fazların TEM ve SEM görüntülerinin de FTIR analizini desteklediği görülmüştür. Elde edilen Si-GO ve Si-GO-C18 sabit fazlarının her ikisi de farklı kolonlara yüksek basınçta doldurulmuştur. Kolonlar sırasıyla metanol, saf su ve asetonitril ile yıkanarak analizlere hazır edilmiştir. Si-GO kolonu üzerinde β-karoten ve lutenin ayrımı için hem izo kritik hem de gradient ayırmalar yapılmış ve istenen ayrımların yapılamadığı görülmüştür. Ayrımları iyileştirmek için kemometrik dizayn yapılmış ve 21 farklı metot oluşturarak ayırma gücü ve tabaka sayıları hesaplanmıştır. Kemometrik tasarımın arzu edilirlik fonksiyonu (D) kullanılarak optimum metot parametreleri IPA mobil faz bileşimi %25, akış hızı 1,8 mL/dak ve sıcaklık 30°C olduğu belirlenmiştir. Optimum parametreleri belirlenen metodun validasyon çalışmaları için % bağıl standart sapma, % geri kazanım, LOD, LOQ ve R2 değerleri hesaplanmıştır. β-karoten ve lutein için %RSD değerlerinin 3,40 ve 2,76, geri kazanım değerlerinin %90 ve %93, LOD ve LOQ değerlerinin sırasıyla 0,27 ve 0,34 mg/L ile 0,09 ve 0,11 mg/L olduğu bulunmuştur. Si-GO-C18 kolonu kullanılarak metot tespit etme çalışmalarında hem izo kritik hem de gradient ayırmalar yapılmıştır. İzo kritik çalışmalardan istenen sonuç elde edilememiş ve gradient ayırmalardan Metot 6`nın β-karoten ve lutein ayrımı için uygun olduğu ayırma gücü ve tabaka sayıları hesaplanarak tespit edilmiştir. Metodun β-karoten ve lutein için %RSD değerlerinin 0,86 ve 1,09, geri kazanım değerlerinin %95 ve %80, LOD ve LOQ değerlerinin sırasıyla 0,26 ve 0,27 mg/L ile 0,80 ve 0,82 mg/L olduğu bulunmuştur.
Yeni nesil membran üretimi ve meyve suyu endüstrisinde uygulamaları
When membrane processes are compared to conventional processes, they have significant advantages for instance, providing decrease in operation time and cost with saving nutritious components and sensory parameters in food production plants. Especially, in fruit juice industry, UF membranes are utilized for clarification by eliminating big molecules like suspend proteins, fat and polysaccharides, which leads turbidity. Although, UF membranes have many advantages like its affordable cost, higher film forming ability, excellent mechanical properties, and superior chemical and thermal resistance, it has a major drawback leading the fouling of the membrane. To get rid of this problem, many researchers focused on the modification of membrane surface to both increase hydrophilicity and enhance antifouling characteristics. In this study, PSF/PEI (20wt%, 2wt%) UF membranes and PSF/PEI (17wt%, 2wt%) MF membranes were prepared with the addition of different concentrations of TiO2 and Al2O3 nanoparticles (0.01, 0.03, 0.05 wt %) using phase inversion method to alter the structural and morphological properties of membranes. Turbid apple and pomegranate juice samples supplied from Döhler Inc. (Karaman, Turkey) were clarified by using cross flow membrane filtration system and dead-end filtration system at 5.4 bar trans-membrane pressure, respectively. Prepared nanocomposite membranes were characterized by using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), water-contact angle porosity and pure water flux. To investigate fouling resistance of nanocomposite membranes flux recovery ratio (FRR), flux decay ratio (DR), relative flux reduction (RFR) values were also calculated. In addition, clarified apple and pomegranate juice samples were characterized in terms of color, turbidity, total soluble solid, total antioxidant capacity (ABTS radical scavenging method and DPPH radical scavenging method) and total phenolic content. Total monomeric anthocyanin pigment content of pomegranate juice was also determined. The clarified juices obtained using new generation nanocomposite membranes were compared with the clarified product juice samples supplied from Döhler Inc. Membrane characterization and fruit juice characterization results demonstrated that fabricated new generation nanocomposite membranes were effective in apple and pomegranate juice clarification. Among these fabricated new generation nanocomposite membranes, the ones prepared with the addition of 0.01% of TiO2 UF membrane and prepared with the addition of 0.05% Al2O3 MF membrane exhibits superior performance in terms of clarification of apple juice and pomegranate juice, respectively.
Solüsyondan proses edilebilir çubuk yapısında moleküler yarı iletkenler ve alan etkili transistör uygulamaları
The structural design and synthetic development of novel n-channel organic semiconductors have attracted considerable scientific and technological attention in order to understand the fundamentals of charge-transport mechanisms in organic (opto)electronics. Although large number of n-channel semiconductors have been reported in the literature over the past few decades, solution-processable and air-stable n-channel semiconductors are still scarce. Herein, we report the design, synthesis, single crystal structures, optoelectronic properties, solution-processed thin-film morphologies/microstructures, and organic field effect characteristics of two molecular indeno[1,2-b]fluorenes containing (triisopropylsilyl)ethynyl groups in the 2,8-positions functionalized with carbonyl and dicyanovinylene moieties in the 6,12-positions. Inclusion of electron-withdrawing carbonyl, dicyanovinylene, and (triisopropylsilyl)ethynyl groups to indeno[1,2-b]fluorene cores create fully acceptor type -conjugated structures, 2,8-(triisopropylsilyl)ethynyl-indeno[1,2-b]fluorine-6,12-diones (TIPS-IFDK) and 2,8-(triisopropylsilyl)ethynyl-indeno[1,2-b]fluorine-6,12-bis(dicyanoviynlene) (TIPS-IFDM). HOMO/LUMO energies of the new compounds are -5.77/-3.65 eV and -5.84/-4.18 eV for TIPS-IFDK and TIPS-IFDM, respectively. Slightly increased optical band gaps of 2.12 eV (for TIPS-IFDK) and 1.66 eV (for TIPS-IFDM) compared to previously developed donor-acceptor type indenofluorenes could be attributable to their acceptor type -conjugated structures. Solid-state arrangements and intermolecular - interactions of TIPS-IFDK and TIPS-IFDM were examined via single single-crystal X-ray diffraction (XRD) analysis. The new semiconductors exhibited 1-D columns in the solid-state. OFETs in top-contact/bottom-gate transistor geometry utilizing TIPS-IFDM semiconductor layer fabricated via solution-shearing possessed n-channel charge transporting characteristics with an air-stable electron mobility 0.02 cm2 (V s)-1 and Ion/Ioff ratios of 107. However, TIPS-IFDK exhibited three orders of magnitude lower electron mobility in OFETs because of less effective - interactions and the poor crystallinity in thin-film phase, and TIPS-IFDK based OFETs did not exhibit ambient stability. Electronic effects of (trialkylsilyl)ethynyl grops substitutions on frontier molecular orbitals were reavealed by DFT calculations. To the best of our knowledge, TIPS-IFDM is the first example of a solution-processable, air-stable n-type molecular semiconductor functionalized with (trialkylsilyl)ethynyl groups along the long molecular axis. Our results clearly provide a novel molecular design approach for the development of easily synthesizable, solution-processable semiconductors for ambient-stable n-channel organic field-effect transistors and potentially various organic (opto)electronic technologies.
Koruyucu ve elektrik gücü sağlayıcı askeri kıyafetlere yönelik malzeme seçeneklerinin değerlendirilmesi
Ballistic vests used in military applications are usually made out of layers of various materials and then combined to form a solitary conservative vest. Contrasted with bygone eras, functionality and productivity of ballistic vests have improved to a critical sum. ANSYS was explicitly used to compute such finite element analysis and the initial segment of the postulation dealt with the determination of material used for the first/front layer of the vest. Since nowadays all ballistic vests almost use Kevlar and epoxy layers in the material formation of the vest, the similar material candidates were chosen for this research as well. Practically, the only choice of material that had to be decided is for the front layer of the vest since many different materials can be used in that regard. Silicon Carbide (SiC) was picked on the grounds that it demonstrated the least deformation and least stress compared to other materials that were tested in ANSYS. In total; three materials were tested and evaluated respectively were Silicon Carbide, Boron Carbide (BC) and Alumina (Al2O3). In order to prove the protection of the ballistic vest design and its reliability in the ballistic sense, 6 (six) flawless shots were fired at certain points on the vest, based on American NIJ standards. In short, the thesis examines the protection of ballistic protective vests from serious military injuries during combat and the development of a hybrid solution that will provide the vest with a new function to provide the power needs of the equipment the soldier will need during combat. In addition, a novel idea is proposed to the literature by adding the fourth layer into the FEA based examined ballistic vest.
Omega-3 yağ asitlerinin nişasta nanopartiküllerle stabilize edilmiş emülsiyonlar içine enkapsüle edilmesi
The main purpose of the thesis is to produce starch nanoparticles to be used as an emulsion stabilizer. In the first part of the thesis, starch nanoparticles were produced via acid hydrolysis and the starch nanoparticles were characterized in terms of morphological properties and size, crystallinity and structural properties. Pickering emulsions were prepared in two different oil fractions (Φ0.6 and Φ0.8) with different oils (sunflower and corn oil). To determine the starch nanoparticle which provides the best emulsion stability, emulsions were prepared with addition of 2% (mg starch/g emulsion) starch nanoparticles. Emulsions were stored for 30 days at room conditions and phase separation was visually examined. The most stable emulsion was prepared with corn oil at Φ0.6 oil fraction when the starch nanoparticle (%2) produced with a 1:3 starch:H2SO4 ratio and 3 days hydrolysis (1:3 (3)) was used as stabilizer. In the second part of the thesis, omega-3 fatty acids were encapsulated in Pickering emulsions. Flaxseed oil was selected as the omega-3 fatty acid source. The emulsions were prepared using flaxseed oil at a Φ0.2 oil fraction with the addition of 3% starch nanoparticles (1: 3 (3)). The emulsions were stored for 15 days at 25±1°C. Changes in the emulsions during storage were examined in terms of physical stability, peroxide number, pH, particle size, and zeta potential. Pickering emulsions stabilized with starch nanoparticles to encapsulate omega-3 fatty acids made flaxseed oil more resistant to primary oxidation.