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    Effect of Solid State Grinding on Properties of PP/PET Blends and Their Composites with Carbon Nanotubes
    (JOHN WILEY & SONS INC, 2010) Köysüren, Özcan; Yeşil, Sertan; Bayram, Göknur
    In this study, it was aimed to improve electrical conductivity and mechanical properties of conductive polymer composites, composed of polypropylene (PP), poly(ethylene terephthalate) (PET), and carbon nanotubes (CNT). Grinding, a type of solid state processing technique, was applied to PP/PET and PP/PET/CNT systems to reduce average domain size of blend phases and to improve interfacial adhesion between these phases. Surface energy measurements showed that carbon nanotubes might be selectively localized at PET phase of immiscible blend systems. Grinding technique exhibited improvement in electrical conductivity and mechanical properties of PP/PET/CNT systems at low PET compositions. Ground composites molded below the melting temperature of PET exhibited higher tensile strength and modulus values than those prepared above the melting temperature of PET. According to SEM micrographs, micron-sized domain structures were obtained with ground composite systems in which PET was the minor phase.
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    Electrospun Nanofibers Prepared with CdTe QDs, CdTeSe QDs and CdTe/CdS Core-Shell QDs
    (2018) Başlak, Canan; Köysüren, Özcan; Kuş, Mahmut
    In this study, a novel method is used to prepare water-soluble CdTe, CdTeSe quantum dots (QDS) and CdTe/CdS core-shell QDs by using Te, Se, NaBH4, and CdCl2 as precursors. Electrospinning method is used to obtain polyvinyl alcohol (PVA)/QDs composite nanofibers. A series of PVA/QDs nanofiber mats with three different QDs content are prepared. Transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) have been used to characterize QD nanoparticles. In addition, for characterization of the composite nanofibers, scanning electron microscopy (SEM) and atomic force microscopy (AFM) have been used. QDs have a good dispersed crystalline structure with an average crystalline size between 2-4 nm. Morphology analyses reveal that the composite nanofibers with an average diameter ranging from 50 to 250 nm are prepared using the electrospinning technique.
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    New Amperometric Cholesterol Biosensors Using Poly(ethyleneoxide) Conducting Polymers
    (TAYLOR & FRANCIS INC, 2013) Yıldız, Hüseyin Bekir; Demirkol, Dilek Odacı ; Sayın, Serkan; Yılmaz, Mustafa; Köysüren, Özcan; Kamacı, Musa
    Accumulation of cholesterol in human blood can cause several health problems such as heart disease, coronary artery disease, arteriosclerosis, hypertension, cerebral thrombosis, etc. Therefore, simple and fast cholesterol determination in blood is clinically important. In this study, two types of amperometric cholesterol biosensors were designed by physically entrapping cholesterol oxidase in conducting polymers; thiophene capped poly(ethyleneoxide)/polypyrrole (PEO-co-PPy) and 3-methylthienyl methacrylate-co-p-vinyl benzyloxy poly(ethyleneoxide)/polypyrrole (CP-co-PPy). PEO-co-PPy and CP-co-PPy were synthesized electrochemically and cholesterol oxidase was immobilized by entrapment during electropolymerization. The amperometric responses of the enzyme electrodes were measured by monitoring oxidation current of H2O2 at +0.7 V in the absence of a mediator. Kinetic parameters, such as Km and Imax, operational and storage stabilities, effects of pH and temperature were determined for both entrapment supports. Km values were found as 1.47 and 5.16 mM for PEO-co-PPy and CP-co-PPy enzyme electrodes, respectively. By using these Km values, it can be observed that ChOx immobilized in PEO-co-PPy shows higher affinity towards the substrate.
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    Triggered Release in Lipid Bilayer-Capped Mesoporous Silica Nanoparticles Containing Spion Using an Alternating Magnetic Field
    (ROYAL SOC CHEMISTRY, 2012) Bringas, Eugenio; Köysüren, Özcan; Quach, Dat V.; Mahmoudi, Morteza; Aznar, Elena; Roehling, John D.; Marcos, M. Dolores; Martinez Manez, Ramon; Stroeve, Pieter
    We report here the on-command cargo controlled delivery using an alternating magnetic field (AMF) from magnetic silica mesoporous supports capped with a lipid bilayer.