44
Archived Theses
0
DOIs Assigned
0%
DOI Rate
Departman Tezleri
HAM PETROL İLE KİRLENMİŞ TOPRAKLARDAN PETROL PARÇALAYAN BAKTERİLERİN İZOLASYONU MOLEKÜLER KARAKTERİZASYONU VE PETROL BOZUNMA POTANSİYELLERİNİN BELİRLENMESİ
Bu çalışma, ham petrol ile kirlenmiş topraklardan petrol parçalayan bakterilerin izolasyonu, moleküler düzeyde karakterizasyonu ve petrol bozunma potansiyellerinin belirlenmesi amacıyla yapılmştır. Toprak örnekleri, Azerbaycan’dan temin edilerek ham petrol ile kontamine edilildikten sonra çalışmalar gerçekleştirilmiştir. Laboratuvar çalışmalarıyla bakteri izolasyonu prosedürüne uygun çalışmalarla izole edilen bakteriler, morfolojik ve biyokimyasal analizlerin ardından moleküler tanımlama amacıyla DNA izolasyonu ve PCR teknikleri ile incelenmiştir. Ayrıca bakterilerin petrol bozunumu üzerindeki etkileri spektrofotometrik ölçümler ile değerlendirilmiştir. Elde edilen bulgular, ekolojik açıdan sürdürülebilir biyoremediasyon yaklaşımlarında bu bakterilerin potansiyelini ortaya koymaktadır. Çalışmalar neticesinde biyoremediasyon potansiyeline sahip 5 bakterinin saf kültürleri elde edilmiştir. Karakterizasyon sonucu ham petrolü parçalayan mikroorganizmaların, pseudomonas neustonica, bacillus licheniformis, corynebacterium stations, sphingobactrrium soli, lysinibacillus fusoformis türlerine ait suşlar olduğu belirlenmiştir. Elde edilen bakteri suşlarının petrol degredasyon etkisini görmek amacıyla GC–MS analizleri yapıldı. Analizler sonucunda örneklerde toplam 10 farklı bileşik elde edilmiştir. Bu bileşikler arasında alifatik alkoller, ketonlar ve kısa zincirli karboksilik asitler yer almaktadır. Elde edilen Kovats indeks değerleri 810-1813 aralığındadır. Bu sonuçların literatürdeki referans değerlerle büyük ölçüde uyumlu olduğu belirlenmiştir. C2–C5 aralığındaki kısa zincirli organik asitlerin mikrobiyal metabolizmaya işaret ettiği anlaşılmıştır. Pseudomonas neustınica bakterisinin 99,79’luk benzerlik oranına göre petrol biyodegradasyonunda daha baskın bir rol oynadığı belirlenmiştir.
Gümüş oksalat sentezi ve nano gümüş hazırlanması
Bu çalışmada nano malzemelerin günümüzdeki yeri ve önemine parelel olarak, yeni nanoteknoloji teknikler, özellikle nano gümüş hazırlanması, karekterizasyonu, özellikleri ve kullanım alanları hakkında temel bilgiler verilmiştir. Nano gümüş hazırlanmasında kullanılan prekursör bileşiklerinin sentezi, kristallendirilmesi ve yapısal analizleri yapılmıştır. Gümüş oksalat (Ag2C2O4) hazırlanması sırasında karşılaşılan yeni tip pembe renkli gümüş oksalat kristallerinin yeni bir polimorf yapı olup olmadığı incelenmiştir. Bilinen gümüş oksalat yapısının tersine, yeni sentezlenen kristallerin renkli olması yani görünür bölgede belirgin ışık absorpsiyonu yapması HOMO-LUMO band eneji aralığında küçülme olduğuna işaret etmektedir. Optik mikroskop, FE-SEM, XRD, FT-IR ve TEM analizleri kullanılarak kristal ve partiküllerin yapısı araştırılmıştır. Hazırlanan pembe renkli yeni tür Ag2C2O4 kristallerinin fotokimyasal bozunması sonucunda 5-50 nm boyutlarında nano gümüş partiküllerinin oluşumu TEM mikroskopu ile gözlenmiştir.Anahtar Kelimeler: Nanoteknoloji, nano malzeme, gümüş oksalat, nano gümüş,fotokimyasal bozunma
İki yeni liyotropik sıvı kristal mezofazın incelenmesi: [Zn(H2O)6(NO3)2-C12EO10-CTAB-H20 and [Zn(H2O)6(NO3)2-C12EO10-SDS-H20
The transition metal aqua complex salts (TMS) can be dissolved in oligo (ethylene oxide) type non-ionic surfactants (CnH2n+1(CH2CH2O)mOH, denoted as CnEOm) with very high salt/surfactant ratios to form lyotropic liquid crystalline (LLC) mesophases. In this study we show that addition of charged surfactants, such as cethyltrimethylammoniumbromide (CTAB) or sodiumdodecylsulfate (SDS) results a new type of LLC in which the solubility of the salts in the LC mesophase of TMS: C12EO10 is enhanced. The LC phase of a [Zn(H2O)6](NO3)2:C12EO10 is hexagonal between 1.2 and 3.2 and cubic (liquid like) above 3.2 salt/ C12EO10 mole ratios. Addition of CTAB or SDS increases the same salt/surfactant mole ratio to 8.0-9.0, which is a record salt amount for a lyotropic liquid crystalline system. The mixed surfactant mesophases have birefringent hexagonal mesophase between 2.0 and 8.0 salt/C12EO10 mole ratios The new mixed surfactant systems can also accomodate high TMSs in the presence of excessive amounts of water (35.0 water:C12EO10 mole ratio).Both systems have similar thermal properties. Izotropisation Temperature (IT) values of the new systems go down with increasing salt and charged surfactant concentrations. The mesophases are stable at high salt concentrations in the presence of high CTAB or SDS concentration in the expense of the stability of the LLC mesophase. The IT values changes from around 80oC down to 32oC with increasing composition of the LLC mesophase. The new mesophase have 2D or 3D hexagonal structure that responds to water content of the phase. A 3D hexagonal phase transforms to 2D hexagonal phase with the evaporation of excess water in both [Zn(H2O)6](NO3)2:C12EO10-CTAB-H2O and [Zn(H2O)6](NO3)2:C12EO10-SDS-H2O systems. The new mesophases were investigated using POM (Polarised optical microscope), and a hot stage under the POM, XRD (X-ray Diffraction), FT-IR (Fourier Transform Infrared Spectroscopy) and Raman techniques. These new LLC systems are good candidates for metal containing mesostructured material synthesis due to their high salt content.
Model NOx depolama malzemesi olan Fe-Ba/Al2O3 malzemesinin yapısal ve NOx alım özellikleri
The composition effect of iron on the nature of the nitrogen oxides species and nitrogen oxide storage properties of barium oxide supported alumina was investigated. Nitrate-loaded samples were further treated at elevated temperatures in order to monitor the thermally induced structural changes.For the as prepared samples, the surface distribution and the thermal stability of the deposited barium nitrates were found to depend strongly on the interaction with the iron containing domains and the support material. It was observed that deposited nitrates have different thermal stability in iron containing samples. Besides, XRD data revealed that barium aluminate formation at elevated temperatures was diminished to a certain extent in the presence of iron. Moreover, the presence of iron depressed the gamma to alfa phase transformation temperature of alumina.FTIR experiments revealed that nitrogen dioxide adsorption at 323 K leads to the formation of nitrites for all of the samples at the initial introduction. In addition, iron containing samples indicate nitrosyl formation as well. With further doses, nitrite bands were converted into nitrate signals. Nitrogen dioxide adsorption on the samples containing Fe resulted in the accentuation of the surface/bidentate nitrates. Temperature dependent FTIR experiments showed that bulk nitrates were thermally more stable than the surface nitrates. TPD profile for barium/alumina sample was also found to be in line with the FTIR results, indicating that the high-temperature decomposition of bulk nitrates were in the form of nitric oxide and oxygen while the surface nitrates decomposed at lower temperatures and mostly as nitrogen dioxide.
Katman-katman kaplama yöntemiyle Au ve Ag nanoparçacıkları içeren ultra-ince filmlerin hazırlanması ve karakterizasyonu
The main objective of this thesis is to investigate the layer-by-layer deposited polyelectrolyte and polyelectrolyte/metal nanoparticle films by using X-ray Photoelectron (XPS) and Optical Spectroscopy (UV-Vis).Within this purpose, in the first part of the study, layer-by-layer deposited single and oppositely charged bilayered films are investigated by XPS. To extract additional information in the molecular level, the samples are analyzed while applying an external voltage bias. It is shown that applying external electrical stimuli to a single polyelectrolyte layer coated Si/SiO2 system responds to the change in the polarity by molecular rearrangements, evidenced by the changes only in the intensity of the corresponding ?N+(1s) peak.In the second part of the study, metal nanoparticle (Au and/or Ag) incorporated polyelectrolyte films are investigated by optical spectroscopy. Within this frame, multilayer gold and silver nanaoparticle/polyelectrolyte films are prepared both separately and in bimetallic form. In order to get further understanding about the optical responses of single type of metal nanoparticle incorporated systems, several experimental approaches are followed. These approaches also enable us to control and manipulate the optical properties of these compact structures.The last part focuses on incorporation of metallic ions into layer-by-layer assembled polyelectrolyte matrices through ion-exchange method. It is shown that metal ions can be incorporated and subsequently reduced within this polymer matrix by UV or X-ray irradiation and can also form nanoparticles.
İki yarı iletken içeren mezoyapılı ince filmlerin faz davranışı ve sentezi: Meso-CdS-TİO2
Mesostructured [Cd(H2O)4](NO3)2 - titania - P123((PEO)20(PPO)70(PEO)20, PEO = -OCH2CH2-, PPO = -OCH(CH3)CH2-) materials have been investigated by changing the [Cd(H2O)4](NO3)2 and titania content of the structures. This has been achieved by making thick samples by casting and thin film samples by spin coating of a butanol solution of [Cd(H2O)4](NO3)2, P123, nitric acid and Ti(OC4H9)4. The film samples are named as meso-xCd(II)-yTiO2, where x is theCd(II)/P123 and y is TiO2/P123 mole ratios. Increasing the titania amount in the media has transformed the samples from LC-like to soft and then to rigid mesostructured materials. Changing the amount of [Cd(H2O)4](NO3)2 salt in the media only influenced the mesostructure, such that no change on the mechanical properties is observed. However, the synthesis of rigid mesostructured titania materials required controlled humidity. The rigid film samples were prepared first by spin coating and then by aging under a 50% humidity oven.The mesostructure remains stable upon H2S reaction, in the soft and rigid materials region. However, only rigid samples stand to removal of nitrates from the media that is important to keep the CdS nanoparticles stable in or on the pore walls of mesostructured film samples. The phase behavior of the meso-Cd(II)-TiO2, the structural properties of the meso-xCdS-yTiO2 samples, coordination and elimination of the NO3- ions and the particle size of the CdS nanocrystallites were investigated using diffraction (XRD), spectroscopy (FT-IR, Raman and UV-Vis absorption, EDS)and microscopy (POM, SEM, and TEM) techniques.
Yakın kızıl ötesi emisyonu olan tetrastiril-bodipy yapısındaki ışık hasatı yapan enerji trasnfer kasetlerinin sentezi ve karakterizasyonu
Light harvesting antenna systems are being used to harvest light through its antenna units. Using these systems, light is channeled into an acceptor chromophore and much more concentrated energy is obtained in acceptor unit with a specific wavelength. In this study, we have rationally designed and synthesized two different novel Förster-type light harvesting energy transfer cassettes which have large stokes shifts and emit in near-IR region. The first cassette has four boradiazaindacene (BODIPY) as donor groups and one tetrastyryl-BODIPY as an acceptor group. The second cassette has four distyryl-BODIPY units as donor groups and one tetrastyryl-BODIPY as an acceptor group. Click chemistry is successfully used to combine donor and acceptor groups to each other. Efficient energy transfer from donor groups to acceptor group in both cassettes was observed and characterized using emission spectrum, quantum yields and lifetimes. Energy transfer efficiencies and rate of energy transfer were calculated and it is demonstrated that there is more efficient energy transfer in cassette that has better overlap in donor emission and acceptor absorption spectrum which is in accordiance with expected behaviour for Förster-type of energy transfer cassettes.
Nox depolama-indirgeme kataliz işleminin BaOx/ Pt(111) ve BaOx/ TiO2/ Pt(111) model katalizörleri yardımıyla möleküler düzeyde anlaşılması
In this work, formation and decomposition pathways of of Ba(NO3)2 on BaO-BaO2 /Pt(111) surfaces were investigated at the molecular level for different BaO-BaO2coverages starting from small 2D islands of 0.5 MLE (MLE: monolayer equivalent) to thick multilayers of 10 MLE via temperature-programmed desorption (TPD), and X-ray Photoelectron Spectroscopy (XPS) and Low Energy Electron Diffraction (LEED). BaOxoverlayers with a surface coverage of ~ 1 MLE reveal long range ordering with (2×2) and/or (1×2) structures while BaOx films with a surface coverage of1.5 MLE yields a BaO(110) termination and thicker films ( ? 5 MLE) were observed to be amorphous. Saturation of thick (10 MLE) BaOxoverlayers with NO2 leads to the formation of nitrates. Nitrate thermal decomposition was demonstrated to proceed through nitrite intermediates. In TPD experimentstwo major pathways fornitrate decomposition were observed: 1) nitrate decomposition yielding only NO evolutionat ~650 K, and 2) nitrate decomposition withNO + O2evolutionat ~700 K. This multi-step decomposition behavior was explained by BaO2 formation during the first stage. The influence of the BaOxdepositionmethod on the morphology of the BaOx overlayers were established: when a thick BaOx layer is prepared using NO2 for Ba oxidation, BaOx overlayer efficiently wets the Pt(111) substrate forming a well-dispersed film. On the other hand, ifa thick BaOx layer is heated in O2 (to 873 K), BaOx overlayer agglomerates into 3D clusters, resulting in the formation of exposed (uncovered) Pt sites. BaOxoverlayers with uncoveredPt sitescan be ?cured? by nitration ? thermal decomposition procedures. When the BaOx layer coverage is below 2.5 MLE, nitrate decomposition temperature is observed at significantly lower temperatures, demonstrating the catalytic influence of the Pt sites facilitating the nitrate decomposition. It is proposed that initially, Ba(NO3)2 decomposes at the boundary/peripheral sites of the Pt/BaOx interface, followed by the nitrate decomposition originating from 2D BaOx islands, and eventually from the 3D BaOx agglomerates.Catalytic deactivation of TiO2-promoted NOx-storage reduction (NSR) catalysts due to thermal aging effects was investigated using a BaO/TiO2/Pt(111) model catalyst system. At room temperature, metallic Ba overlayers on TiO2/Pt(111) was found to be very reactive towards oxide ions on TiO2/Pt(111) resulting in the formation of BaOx and partial reduction of TiO2. Ba films adsorbed on TiO2/Pt(111) that are further oxidized in O2 at 523 K lead to BaO and BaO2 surface domains which can efficiently adsorb both NO2 and CO2. Thermal treatment of BaO-BaO2/TiO2/Pt(111) surface at T ? 300 K leads to a monotonic decrease in the surface Ba/Ti atomic ratio indicating the diffusion of BaO-BaO2 domains into the underlying TiO2 framework. Solid state reactions between BaOx and TiO2 particularly within 473-873K facilitate the formation of BaTiO3/Ba2TiO4/BaxTiyOz overlayers. After oxidation at higher temperatures (T > 873 K), surface becomes Ba-deficient and the enrichment of the surface with the Ti4+ sites results in a TiO2-terminated surface. Diffusion of BaOx into the TiO2 matrix and the enrichment of the surface with Ti sites drastically suppress the NO2 and CO2 adsorption/storage capacity of the model NOx storage system. These results reveal a direct evidence for the structural changes associated with the thermal deactivation of TiO2-promoted NSR catalysts.Key Words: NSR, model catalyst, BaO thin films, TiO2 thin films, NO2, UHV, BaOx / Pt(111), BaOx/ TiO2/ Pt(111), XPS, TPD, LEED.
Fe ile zenginleştirilmiş NOx depolama malzemesi olan BaO/Al2O3 sistemlerinin kükürt toleransı
Ternary mixed oxide systems in the form of BaO/FeOx/Al2O3 were studied with varying compositions as an alternative to the conventional NOx storage materials (i.e. BaO/Al2O3). NOx uptake properties of the freshly prepared samples, sulfur adsorption and NOx storage in the presence of sulfur were investigated in order to elucidate the sulfur tolerance of these advanced NOx storage systems in comparison to their conventional counterparts.
Fotodinamik terapi için potansiyel foto duyarlaştırıcı olan tetrastiril-boradiazaindasen
Photodynamic therapy (PDT) is a novel methodology for a wide range of treatments of cancerous and noncancerous diseases. Success of treatment and photodynamic action is highly dependent the performance of PDT agents. Therefore, PDT agents with unique photophysical properties are required in clinical applications. There are several photosensitizers in literature and some are available. However, most of them less than ideal due to limitations such as low molar absorptivity and photo stabilities.In this study, we synthesized near-IR tetrastyryl-Bodipy derivatives as photosensitizers. These sensitizers have strong absorption in therapeutic region and are good photo-generator of singlet oxygen. They are promising for photodynamic therapy with their favorable properties.