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Öğe Boric Acid Containing Polyimide as a Route to Low Heat Releasing Materials(Walter De Gruyter Gmbh, 2009) Koytepe, Sueleyman; Seckin, TurgayBoric acid particles were successfully prepared by using an emulsion liquid membrane (water-in-oil-in-water, W/O/W emulsion) to control the size of particles as raw materials. All materials aggregated in aqueous suspension, but their subsequent dispersion on treatment with the polyimide precursor, poly (amic acid), was observed. Using a combination by dissolving the polyimide and mixing fatty acid surfactant coated boric acid particles; we have demonstrated the formation of nanocomposites with uniform nanoparticle dispersion. The influence of boric acid on heat releasing capacity was analyzed. Heat releasing capacity of composites was reduced compared to polyimide itself The microstructures and morphology of the as obtained samples were studied by X-ray diffraction (XRD), infrared spectra (IR), scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS) and thermogravimetric analysis (TGA).Öğe Chemistry and engineering of brush type polymers: Perspective towards tissue engineering(Elsevier, 2022) Acari, Idil Karaca; Sel, Evren; Ozcan, Imren; Ates, Burhan; Koytepe, Sueleyman; Thakur, Vijay KumarIn tissue engineering, it is imperative to control the behaviour of cells/stem cells, such as adhesion, proliferation, propagation, motility, and differentiation for tissue regeneration. Surfaces that allow cells to behave in this way are critical as support materials in tissue engineering. Among these surfaces, brush-type polymers have an important potential for tissue engineering and biomedical applications. Brush structure and length, end groups, bonding densities, hydrophilicity, surface energy, structural flexibility, thermal stability, surface chemical reactivity, rheological and tribological properties, electron and energy transfer ability, cell binding and absorption abilities for various biological molecules of brush-type polymers were increased its importance in tissue engineering applications. In addition, thanks to these functional properties and adjustable surface properties, brush type polymers are used in different high-tech applications such as electronics, sensors, anti-fouling, catalysis, purification and energy etc. This review comprehensively highlights the use of brush-type polymers in tissue engineering applications. Considering the superior properties of brush-type polymer structures, it is believed that in the future, it will be an effective tool in structure designs containing many different biomolecules (enzymes, proteins, etc.) in the field of tissue engineering.Öğe Immobilization of Xylanase onto Starch Nanoparticles: A Reusable and Robust Nanobiocatalyst for Juice Clarification(Wiley-V C H Verlag Gmbh, 2023) Dik, Gamze; Bakar, Busra; Ulu, Ahmet; Koytepe, Sueleyman; Ates, BurhanNanoparticles (NPs) have attracted interest recently as a promising support for the immobilization of enzymes.Xylanase (Xyl) has been utilized in the food industry for several purposes. To improve its stability and reusability,starch NPs (SNPs)are synthesized and assessed for Xyl immobilization for the first time. . The characterization results reveal that SNPs are successfully synthesized and Xyl@SNPs are effective as the immobilization carrier. The Xyl is immobilized on SNPs under optimized conditions leading to 91% immobilization efficiency. A shift in optimum pH (from 6.0 to 8.0) and temperature (from 70 to 60 degrees C) of Xyl is observed after immobilization. The Xyl@SNPs possess improve pH stability and thermal stability as well as operational stability. The Xyl@SNPs are easily reutilized and the residual activity is still higher than 62% after seven times. More importantly, the Xyl@SNPs have a lower Km value and enhance affinity for the substrate compared to the free Xyl. Additionally, the clarity of orange juice is increased by 76.0% by using Xyl@SNPs after 2 h incubation at 60 degrees C, pH 8.0. These positive results show promising support for the Xyl immobilization of SNPs, confirming that this immobilized enzyme-based strategy is an effective technique for rapid clarification of targeted juices.Öğe Metallo-supramolecular materials based on terpyridine-functionalized polyhedral silsesquioxane(Wiley, 2014) Koytepe, Sueleyman; Demirel, Maruf Hursit; Gultek, Ahmet; Seckin, TurgayIn this study, novel metallo-supramolecular materials based on terpyridine-functionalized polyhedral silsesquioxane were synthesized from 4 '-chloro-2,2 ':6 ',2 ''-terpyridine and amino-group-functionalized polyhedral oligomeric silsesquioxane. The obtained terpyridine-functionalized polyhedral silsesquioxanes were converted to metallo-supramolecular hybrid materials by coordination polycondensation reaction with Co(II) or Cu(II) ions. The supramolecular polymers created were characterized by means of structure, morphology and stimuli-responsive performance employing scanning electron microscopy, amperometric techniques and UV-visible and Fourier transform IR spectroscopy. UV-visible and cyclic voltammetry studies showed that both the optical and electrochemical properties of metallo-supramolecular materials are affected by the substituent at the pyridine periphery. The supramolecular polymers obtained exhibited electrochromism during the oxidation processes of cyclic voltammogram studies. As a result, these terpyridine-functionalized polyhedral silsesquioxanes are good candidates for electronic, opto-electronic and photovoltaic applications as smart stimuli-responsive materials. (c) 2013 Society of Chemical IndustryÖğe Preparation and Catalytic Properties of a Ru(II) Coordinated Polyimide Supported by a Ligand Containing Terpyridine Units(Springer, 2009) Seckin, Turgay; Ozdemir, Ismail; Koytepe, Sueleyman; Gurbuz, NevinThe synthesis of terpyridine-based polyimide catalysis for hydrosilylation reaction is outlined in this work. 5,5''-Bis(bromomethyl)-2,2':6',2''-terpyridine was polymerized with the corresponding diimide derivatives of dianhyrides to give polyimides utilizing the terpyridine unit in the main chain. The synthesis of polyimides containing Ru(II) complexes in the side chain is described. Condensation polymerization is used to synthesize the macromolecular backbone and, as a result, the Ru(II) complex was attached via coordination chemistry. The material design emphasizes the relationship between the molecular structure and supramolecular organization of these polymers. It demonstrates that terpyridyl complexes remain a versatile functionality for constructing supramolecular assemblies. The terpyridine unit may enhance the electron carrier mobility of the polymers, while the incorporation of ruthenium complexes into a conjugated polymer significantly changes the catalytic properties of the resulting polymers. The prepared polyimide-supported catalyst provides superior catalytic activity (70-79%), selectivity and stability in the hydrosilylation of acetophenone. The catalyst can be easily isolated from the reaction product, which benefits recycling. The catalysts were reused for four experiments.Öğe Preparation and Characterization of Nano TiO2-Hydroquinone-Doped Al Composites and Investigation of Theirs Wear Properties(Maik Nauka/Interperiodica/Springer, 2023) Emre, Fatma Bilge; Koytepe, Sueleyman; Bahce, ErkanIn this study, the preparation of nanoporous-TiO2-doped Al composites with improved mechanical properties and wear resistance was carried out. For this purpose, nanosized TiO2 structures were first synthesized using the hydrothermal synthesis method. The size distribution, morphology, and chemical structure of the obtained TiO2 particles were investigated by particle size analyzer, SEM, XRD, and FTIR spectroscopy techniques. At the same time, TiO2 structures containing hydroquinone (Hq) at different rates (5, 10, and 15%) were prepared in order to ensure homogeneous TiO2 distribution during the formation of Al matrix composites and to prevent oxidation that may occur during composite casting. TiO2-Al composite structures were obtained by doping the synthesized pure TiO2 nanoparticles and TiO2 nanoparticles containing hydroquinone in different ratios to the Al matrix structure. The obtained composite structures were examined structurally by FTIR and XRD spectroscopy techniques. Then, the thermal properties of the composite structures obtained were examined by TGA analysis. Morphological properties, microstructure, and surface elemental distribution of the composite structure were investigated by SEM and EDX techniques. The abrasion properties of the obtained TiO2 added Al composite structures were investigated using SiC papers (200-400-600 and 800-1200 mesh). As a result, it was observed that the doped TiO2 nanoparticles reduced surface deformation during abrasion.Öğe Preparation of pyridoxine-based polyurethane modified sensors and their use in simultaneous determination of Cu(II) - Co(II) ions(Elsevier, 2024) Savan, Ebru Kuyumcu; Kazici, Dilek; Ozcan, Imren; Bayram, Songuel; Koytepe, SueleymanIn this study, pyridoxine-based polyurethane-modified electrodes were prepared to simultaneously and sensitively measure copper (Cu(II)) and cobalt (Co(II)) ions in complex matrix samples. For the production of the electrodes, firstly, the synthesis of pyridoxine-based polyurethane structures was carried out. In these syntheses, the polymer structure was diversified by using different isocyanates. Polyethyleneglycol-200 (PEG), pyridoxine (B6), and beta- cyclodextrin ( beta- CD) groups were used as the source of polyol. The synthesized polyurethane structures were characterized by different instrumental techniques and used in gold electrode surface modification. Modified sensor surfaces were examined by scanning electron microscopy and atomic force microscopy techniques. The prepared modified sensors were used for the simultaneous detection of Cu(II) and Co(II) ions using the differential pulse voltammetry technique. The limit of detection (LOD), limit of quantitation (LOQ), and R 2 values for Cu(II) ions were calculated as 8.81 mu M, 29.4 mu M, and 0.993, respectively. LOD, LOQ, and R 2 values for Co(II) ions were calculated as 9.84 mu M, 32.8 mu M, and 0.9935, respectively. For repeatability, the relative standard deviation (RSD %) of the prepared simultaneous sensors was determined as 1.54 and 1.71 for Cu(II) and Co(II), respectively. As a result, Cu(II) and Co(II) ions were measured independently and simultaneously with high sensitivity. According to these results, it is predicted that pyridoxine-based polyurethane-modified sensors may be suitable for the simultaneous detection of Cu(II) and Co(II) in medical, food, and agricultural samples.Öğe Preparation, Characterization, and Properties of Novel Polyimide-SiO2 Hybrid Composites Based on Bipyridine for Low Dielectric Applications(Taylor & Francis Inc, 2015) Koytepe, Sueleyman; Kucuk, Ilhan; Seckin, Turgay; Adiguzel, H. IbrahimNovel low dielectric polyimide-SiO2 hybrid materials containing bipyridine were prepared with three-step sol-gel process from poly(amic acid)s. (3-Aminopropyl)triethoxysilane as coupling agent was used to increase the intrachain chemical bonding between the polyimide and SiO2 groups. The thermal, dielectric, and physical properties of the hybrid materials were investigated and correlated with the porous structure. The glass transition temperatures of all the hybrids were found to be higher than polyimides. The effect of SiO2 groups on the porous structure and dielectric properties was investigated. The dielectric constant of the hybrid materials was observed a decrease from 3.30 to 2.15 with increased SiO2 amount.Öğe Simultaneous Electrochemical Detection of Estradiol and Testosterone Using Nickel Ferrite Oxide Doped Mesoporous Carbon Nanocomposite Modified Sensor(Electrochemical Soc Inc, 2020) Tanrikut, Emrullah; Ozcan, Imren; Sel, Evren; Koytepe, Sueleyman; Savan, Ebru KuyumcuEstradiol levels in women are related to lung, uterine (endometrial), ovarian and breast cancers, although the exact mechanism of cancer development is not fully understood. A new cost-effective sensor was fabricated by incorporating conductive NiFe2O4 metal oxide into the electrochemical sensitive platform of mesoporous carbon (MC) derived from cotton to measure estradiol determination by electrochemical methods. A new modified GCE/NiFe2O4-MC electrode, which exhibits electrocatalytic activities, was created by dropping NiFe2O4-MC onto the glassy carbon electrode (GCE) surface using the drop casting technique to detect the electroactive estradiol molecule. Estradiol was determined electrochemically by using the square wave voltammetry technique with a detection limit of 6.88 nM in 20.0-566 nM linear range in phosphate buffer solution at pH 7.4 with this novel modified GCE/NiFe2O4-MC electrode, that has the best electron transfer rate. The simultaneous determination of estradiol in the presence of testosterone was successfully performed in 0.1 M tetrabutylammonium tetrafluoroborate supportive electrolyte solution prepared in acetonitrile, an anhydrous medium. Real sample applications were carried out to prove the applicability and precision of the novelty-produced electrode. The amount of estradiol in tablet samples was obtained satisfactorily with high recovery values by standard addition method. (C) 2020 The Electrochemical Society (ECS). Published on behalf of ECS by IOP Publishing Limited.
