Chemistry / Kimya
Permanent URI for this collectionhttps://hdl.handle.net/11147/4072
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Article Citation - WoS: 2Reduction of Carbon Dioxide During the Synthesis of Metal Nano-Particles in Water(Elsevier Ltd., 2003) Polat, Hürriyet; Cohen, H; Meyerstein, D; Rusonik, I.An effort was made to synthesize "carbon-free" metal (Fe-0, Co-0, Ni-0) nano-particles via the reduction of their salts with BH4- in aqueous solutions. Surprisingly it was found that when the synthesis is carried out in the presence of CO2, e.g., in aerated solutions, the CO2 is catalytically reduced by BH(4)(-)on the surface of the metal particles. Carbon-free metals can be prepared by reduction under an inert atmosphere. Thus metal surfaces might have acted as catalysts for CO2 fixation, probably via the initial formation of carbon clusters, in the reductive atmosphere in the prebiotic era. (C) 2003 Elsevier B.V. All rights reserved.Article Citation - WoS: 13Citation - Scopus: 15Synthesis of Poly-2 Methacrylate-Montmorillonite Nanocomposite Via in Situ Atom Transfer Radical Polymerization(Cambridge University Press, 2008) Oral, Ayhan; Shahwan, Talal; Güler, ÇetinThe poly-2-hyroxyethyl methacrylate (PHEMA)/clay nanocomposite was synthesized by in situ atom transfer radical polymerization (ATRP) from initiator moieties immobilized within the silicate galleries of the clay particles. To produce organically modified montmorillonite (MMT) that has ATRP initiator moiety, a new catalyst that consists of quaternary ammonium salt moiety and an initiator moiety was synthesized. This initiator was intercalated into the interlayer spacing of the MMT. The polymerization reaction was carried out in a mixed solvent system consisting of methyl ethyl ketone and 1-propanol at 50 °C, using the initiator that has been already synthesized with a copper bromide catalyst. The 2, 2′-bipyridyl (bpy) complex was used as ligand. The products were characterized via Fourier transform infrared, nuclear magnetic resonance (1H NMR, 12C NMR), transmission electron microscopy, x-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. © 2008 Materials Research Society.Article Citation - WoS: 31Citation - Scopus: 346-Bicycloaryl Substituted (s)- and (r)-5,6 Asymmetric Synthesis, and Anti-Proliferative Properties(Elsevier Ltd., 2009) Kasaplar, Pınar; Yılmazer, Özgür; Çağır, Ali(R)-Goniothalamin, is a member of styryl lactones, possesses selective cytotoxicity against cancer cell lines. In this work, replacement of styryl substituent with 2-naphthyl and 3-quinoyl gave new analogues which may have less conformational changes compared to the lead compound. Anti-proliferative tests indicated that 2-naphthyl substituted (R)-5,6-dihydro-2H-pyran-2-one has slightly better cytotoxicity than (R)-goniothalamin. To clarify the effect of 2-naphthyl substituent additional aryl substituted (R)-5,6-dihydro-2H-pyran-2-ones have been synthesized enantioselectively and tested against PC-3 and MCF-7 cell lines.Article Citation - WoS: 2Citation - Scopus: 2Polarized Absorption Spectra of Highly Oriented Two-Dimensional Aggregates of Tetrachlorobenzimidazolocarbocyanine in Thin Films(Elsevier Ltd., 2008) Özçelik, Serdar; Gülen, DemetReaching a control on the mesoscopic morphology and internal molecular arrangement of cyanine aggregates is an important step for realization of devices with tailor-made optical properties. Despite a wealth of research, understanding of the relationship between molecular organization, excitonic states and dynamics of aggregates is still preliminary. To this end, we have employed polarized absorption spectroscopy to investigate the relationship between internal molecular organization and excitonic states of J-aggregates in 1,1′,3,3′tetraethyl-5,5′,6,6′-tetrachlorobenzimidazolocarbocyanine (TTBC) thin films in poly-vinyl alcohol (PVA). Angular dependence of the UV-vis spectra has been measured at 11 different orientations between the electric field polarization and the macroscopic alignment axis. Aggregate spectral response consisted of an asymmetrically split Davydov pair of bands exhibiting opposite polarization: an H-band (505 nm, Lorentzian-like, polarized along the macroscopic film axis) and a J-band (594 nm, one-dimensional J-aggregate like band shape, polarized perpendicular to the macroscopic film axis). The polarized absorption observations were found to be consistent with a herringbone model for which the internal molecular arrangement, the excited state structure and dynamics have recently been detailed by us upon interpretation of isotropic absorption data in ionic aqueous solution.Article Citation - WoS: 4Citation - Scopus: 6Absorption Spectrum of Monomeric Pseudoisocyanine: a New Perspective and Its Implications for Formation and Spectral Response of J-Aggregates in Solution and in Thin Films(Elsevier Ltd., 2008) Gülen, Demet; Özçelik, SerdarWe argued against the current spectral assignment for absorption spectrum of monomeric PIC which is widely accepted since the pioneering works of Scheibe and Jelley [G. Scheibe, Angew. Chem. 49 (1936) 563; E.E. Jelly, Nature 138 (1936) 1009]. A new spectrum is presented along with its conceptual basis. The hypothesized spectrum attributes the previous 0-0 (≈525 nm) and 0-1 (≈490 nm) assignments, respectively, to intermediates acting as the precursor of J-aggregates and to the 0-0 transition of monomeric PIC and brings the spectrum in accord with the seemingly universal spectral fingerprint of cyanines. The hypothesis is used to analyze and interpret the temperature dependence of the UV-vis absorption of PIC aggregates in saline aqueous solution by incorporating the J-band simulations within frenkel exciton formalism. Its implications for aggregate formation kinetics are given on the basis of current spectroscopic evidence. The hypothesis readily answers several long-standing questions: Why compared to many other cyanines at least an order of magnitude higher dye concentration is needed to form J-aggregates of PIC? Why are there no precursors, since aggregation is expected to be a consecutive process? A large number of observations on steady-state and time-resolved spectral properties, and aggregation kinetics in solution/thin films are likely to find reasonable explanations within this hypothesis.Article Citation - WoS: 12Citation - Scopus: 12Modification of Metal/Semiconductor Junctions by Self-Assembled Monolayer Organic Films(Elsevier Ltd., 2009) Yakuphanoğlu, Fahrettin; Okur, Salih; Özgener, HüseyinTwo new metal/molecule/semiconductor contacts, Au/n-Si/TDA/Au and Au/p-Si/ODM/Au, were fabricated to understand effect of organic compounds, tridecylamine and octadecylmercaptan self-assembled monolayer (SAM) films, on electrical charge transport properties of the metal/semiconductor junctions. The morphology of the organic monolayers deposited on Si substrates was investigated by atomic force microscopy. The molecular coverage of ODM deposited on p-Si is poorer than that of TDA on n-Si substrate. The ideality factors of the p-Si/ODM and n-Si/TDA diodes were found to be 1.66 and 1.48, respectively. The electrical results show that the tridecylamine monolayer passivated junction has a lower ideality factor. The ideality factor indicates clear dependence on two different type functional groups R-SH (Thiol) and R-NH2 (Amin) groups and it increases with different functional groups of organic molecule. The barrier height φb value of the n-Si/TDA diode is smaller than that of p-Si/ODM diode, as a result of chain length of the SAM organic molecules. The interface state density Dit values of the diodes were determined using conductance technique. The n-Si/TDA diode has the smaller interface state density according to p-Si/ODM diode. We have evaluated that the organic molecules control the electronic parameters of metal/semiconductor diodes and thus, organic modification helps to get one step closer towards to new organic assisted silicon based microelectronic devices.Article Citation - WoS: 63Citation - Scopus: 73Near Infrared Spectroscopic Determination of Olive Oil Adulteration With Sunflower and Corn Oil(Taiwan Food and Drug Administration, 2007) Özdemir, Durmuş; Öztürk, BetülDetermination of authenticity of extra virgin olive oils has become very important in recent years due to the increasing public concerns about possible adulterations with relatively cheap vegetable oils such as sunflower oil. This study was focused on the application of near infrared (NIR) spectroscopy in conjunction with multivariate calibration to identify the adulteration of olive oils. NIR transmittance measurements were made on pure olive oil and olive oil adulterated with varying concentrations (4-96%, v/v) of sunflower and corn oil in two sets of 26 binary and ternary mixtures. Multivariate calibration models were generated using genetic inverse least squares (GILS) method and used to predict the concentration of adulterants along with the concentration of olive oil in the samples. Over all, standard error of predictions ranged between 2.49 and 2.88% (v/v) for the binary mixtures of olive and sunflower oil and between 1.42 and 6.38% (v/v) for the ternary mixtures of olive, sunflower and corn oil.Other Erratum: Optical Transition Rates of a Meso-Substituted Thiacarbocyanine in Methanol-In Reverse Micelles (journal of Luminescence (2005) 113 (1-8)(Elsevier Ltd., 2005) Özçelik, Serdar; Atay, N. ZeynepThe correct correspondence information for the first author is: Serdar Özçelik Chemistry Department, Izmir Institute of Technology, Urla-35430 Izmir, Turkey E-mail address: serdarozcelik@iyte.edu.tr Tel.: +90 232 750 7557 fax: +90 232 750 7509Article Citation - WoS: 8Optical Transition Rates of a Meso-Substituted Thiacarbocyanine in Methanol-In Reverse Micelles(Elsevier Ltd., 2005) Özçelik, Serdar; Atay, N. ZeynepWe report the photophysical properties of 3,3′-diethyl-5,5′-dichloro-9-phenylthiacarbocyanine (DDPT) in methanol-in-oil (m/o) reverse micellar systems which form methanol droplets stabilized with anionic surfactant aerosol-OT (AOT) in n-heptane. The fluorescence quantum yield of DDPT is enhanced by a factor of 17 in the methanol droplet in comparison with bulk methanol. The fluorescence lifetimes of DDPT in m/o reverse micelles are prolonged up to 2.2 ns with increasing molar ratio of methanol to surfactant (w0=[MeOH]/[AOT]), whereas the fluorescence lifetime of DDPT in bulk methanol is 75 ps. The non-radiative rate constants of DDPT in the droplets are decreased by a factor of 40, resulting in a remarkable enhancement in quantum yields, indicating that internal motions of DDPT in the droplets are significantly reduced due to strong electrostatic interactions between the positively charged DDPT and the negatively charged sulfonate head-groups of AOT and the spatial confinement induced by the reverse micellar structure.Article Citation - WoS: 25Citation - Scopus: 20Rhodium-Catalyzed Carbonylative Arylation of Alkynes With Arylboronic Acids: an Efficient and Straightforward Method in the Synthesis of 5-Aryl(Royal Society of Chemistry, 2006) Aksın, Özge; Dege, Nurcan; Artok, Levent; Türkmen, Hayati; Çetinkaya, Bekir5-Aryl-2(5H)-furanones can be synthesized by the Rh-catalyzed reactions of arylboronic acids with internal alkynes under a CO atmosphere.
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