Browsing by Subject "Fluorescence spectroscopy."
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Item Open Access Chemical characterization of Sinopean archaeological common ware(Bilkent University, 2004) Özal, Tuğba ArzuChemical characterization of archaeological common wares is important in order to make quantitative explanations about history and trade relations of nations. Chemistry uses a microscopic point of view by applying spectroscopic methods rather than macroscopic studies that archaeologists usually deal in the structural analysis. The present study is done on the common ware samples which were made of raw clays from Demirci, Sinop, Black Sea Coast of Turkey, because of the geopolitical importance of this region having trade routes. Elemental and mineralogical analyses of the clay-originated common ware samples found in the archaeological excavations and of the clay taken from Demirci region, which locates at almost 15 km southern of Sinop, were made. While the elemental compositions of the samples were obtained by the spectroscopic method, X-Ray Fluorescence (XRF), the mineral structures were investigated by Powder XRay Diffraction (PXRD) and Fourier Transform Infra Red (FT-IR) spectroscopic method. Furthermore, the characteristic reactions (dehydroxylation, decomposition, transformation) that the clays experienced between the temperatures 50 and 1000 o C were determined by Thermal Gravimetric Analysis (TGA). Characterizations of the Sinopean samples were made and the similarity and differences between other samples from different regions were investigated. Besides the provenance characterization, the distinctions between the production and firing techniques were observed. In addition to the experimental studies, chemometric techniques using statistical methods such as the standard clustering method and principal component analysis (PCA) was also applied to identify the groupings in the set of samples. As a result of this study, it is observed that the raw clays and ceramic samples have minerals of montmorillonite, quartz, feldspars, pyroxene, calcite and hematite at different amounts. From the mineralogical and elemental data, it is concluded that the color variations are resulted from the calcium element occurring in pyroxene mineral. In the light colored samples, amount of this element and mineral is high whereas it is low in red colored ones. From the interpretation of elemental data by statistical methods, it is observed that a classification among the Demirci samples is possible according to the function of the pottery. In addition, classification among ceramics from two different regions is possible by the interpretation of chemical analysis, even though the ceramics have the same morphological properties of the same period.Item Open Access Physical integration of chemical logic gates(Bilkent University, 2012) Öztürk, ŞeymaRecent research in molecular logic gates produced molecular equivalence of highly complex digital designs. Advanced data processing at the molecular level requires a considerable degree of integration (concatenation) between molecular logic gates. So far, almost all the integration reported in the literature has been “virtual”, meaning that the outputs at various channels are determined first and then an integrated set of logic gates is proposed to be operating on inputs to produce those outputs. Nevertheless, there is no doubt that at some point there has to be methods to physically connect one molecular logic gate to the other one, for a rational design and implementation. In this study, we synthesized a few derivatives of the well known fluorophore “Bodipy” and then proposed two methodologies to concatenate separately existing and functioning Bodipy-based chemical logic gates. In one instance, we coupled a photochromicity-based AND gate to an ion-responsive Bodipy-based AND gate, making use of the modulation of inner filter effect. In the other example, we coupled two ion-responsive Bodipy-based AND gates through the increased efficiency of energy transfer and “click” chemistry. We are certain that these methodologies are highly promising and our studies are in progress to demonstrate more complex examples of physical integration.Item Open Access Selective manipulation of ICT and PeT processes in styryl-Bodipy derivatives : applications in molecular logic and fluoerescence sensing of metal ions(Bilkent University, 2010) Selçuk, SencerRecent developments in the Bodipy chemistry, provided new opportunities for modification of this chromophore which, in turn, using appropriate metal-ligand pairs, allowed the control and manipulation of PeT and ICT mechanisms. Exploiting these mechanisms, we demonstrated that photophysical properties of Bodipy can be shaped as desired using metal cation modulators to obtain absorbance signals in accordance with a digital half-adder circuit. In addition, another Bodipy derivative with a simple and rational design, shown to have emission signals equivalent to AND operation in Boolean logic. A molecular threeinput AND gate was also synthesized taking the advantage of differential binding affinities of metal cations for different ligands. Our work proves that, with careful design, photophysical properties of a single chromophore can be modified as desired. Hence molecular logic gates, and even molecules performing more complex logic operations can be obtained using metal cations as non-annihilating logic inputs.Item Open Access Solid state emissive bodipy dyes with bulky substituents as spacers and a sensitive and selective ratiometric near IR fluorescent probe for zinc ions based on the distyryl-bodipy fluorophore(Bilkent University, 2010) Özdemir, TuğbaDyes having solid state fluorescence are playing an important role for organic light emitting devices (OLED), optoelectronic devices and photoelectric conversion. However, emissive solids are not common because of the quenching resulting from the packing. With these considerations, we have synthesized and characterized novel boradiazaindacene BODIPY-based dye with bulky substituents (3,5-di-tert-butylphenyl) to prevent π-π stacking of the chromophore. We have succesfully demonstrated that by simple modulation of BODIPY core with very bulky groups lead us to have a bright emissive compounds in solid state. In the second part of this research, we developed BODIPY based near-IR dye as a selective, ratiometric and water-soluble fluorophore for Zn (II) cation. We functionalized the versatile BODIPY from its 3 and 5 positions for long wavelength emission the zinc selective chemosensor.Item Open Access Synthesis and characterization of novel ion sensor based on 2, 6-functionalized BODIPY structure(Bilkent University, 2012) Uyar, Taha BilalLatest developments in chemistry of BODIPY make available synthesis of novel BODIPY based fluorescent chemosensors. Therefore, the design of novel chemosensors is attracting great attention in recent years. In this study, we functionalized 2 and 6 positions of BODIPY choromophore to understand that binding of different metal ions how affect the absorption and emission spectrums of BODIPY. We used three metal ions which are important in environment and biological systems and these are Hg (II), Zn (II) and Ca ions. Binding of these metal ions to azo crown ether is which attached BODIPY caused large changes in absorption and emission spectrums according to photoinduced electron transfer (PET) and internal charge transfer (ICT) mechanism.