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    Catalytic Properties of Hydrothermally Synthesized Flower-like NiO@Fe3O4
    (2020) Yetim, Nurdan Kurnaz
    In this study, flower-like NiO structures were synthesized by hydrothermal method. Then, Fe3O4 was doped onNiO that NiO structures gain magnetic properties. TEM (Transmission Electron Microscopy) and SEM(Scanning Electron Microscopy) were used to assess the morphology of the NiO structures. XRD (X-rayDiffraction) was used to evaluate the crystal structures of the NiO structures. Magnetic properties of the NiOstructures were investigated using VSM (Vibrating Sample Magnetometry). Catalysis properties of the producedstructures were assessed use of products as catalyst in the reduction of 4-nitrophenol (4-NP) was examined.Especially NiO and Fe3O4 were found to exhibit excellent catalytic performance for nitrophenol reduction, whileNiO@Fe3O4 magnetic microflowers were found to exhibit very low catalytic activity.
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    Enzyme immobilization on polymeric microspheres containing Schiff base for detection of organophosphate and carbamate insecticides
    (Elsevier, 2020) Nartop, Dilek; Yetim, Nurdan Kurnaz; Ozkan, Elvan Hasanoglu; Sari, Nursen
    In this study, polymeric microsphere including Schiff base TrisPS-pyr and TrisPS-pyr-Pt(II) were obtained by condensation reaction for improve the enzymatic properties of acetylcholinesterase (AChE) and detect harmful insects. Structures of the synthesized compounds were characterized by spectroscopic methods such as FT-IR, UV-Vis, SEM-EDX, GPC. Acetylcholinesterase enzyme was immobilized to these new polymeric microspheres and their properties such as activity, reusability and storage stability were investigated. In addition, the qualitative determination of carbamate [2,3-dihydro-2,2-dimethyl-7-benzofuranol N-methylcarbamate (carbofuran), 4-methylthio-3,5-xylyl methylcarbamate (methiocarb) and S-methyl-N- (methylcarbamoyl oxy) thioacetamide (methomyl)] and organophosphate [diethyl (dimethyl thiophosphoryl) succinate (malathion), O, S-dimethyl phosphoramidothioate acetyl (acephate) and chlorpyrifos methyl] insecticides by the immobilized enzyme was performed. The reason for the selection of these pesticides is because they are widely used to combat pests of agricultural products (hazelnut, corn, sugar beet, apple and tobacco) which are grown in our region. (C) 2019 Elsevier B.V. All rights reserved.
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    Magnetic dendrimer-encapsulated metal nanoparticles (Au, Ag): effect of dendrimerization on catalytic reduction of 4-nitrophenol
    (Springer, 2022) Yetim, Nurdan Kurnaz; Koç, Mümin Mehmet; Nartop, Dilek
    Magnetic nanoparticles (MNPs) and nanocomposites can be used in different applications including catalysis reactions and applications. Magnetic nanocomposites can be reused and magnetically filtrated after catalysis reaction. For this purpose, Fe3O4 MNPs were produced using the co-precipitation technique. Fe3O4 MNPs were coated with SiO2 shell, APTES and G2 PAMAM dendrimers and lastly doped with Au and Ag nanoparticles (Fe3O4@G2/Au/Ag) which has been examined for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 as a model reaction. Physical structures of the nanocomposites were characterized using SEM and TEM which illustrate that nanoparticles were in composite form. Chemical composition of nanostructures was confirmed using EDX and FTIR. Magnetic characteristics were checked using VSM. Dendrimerization and Au and Ag nanoparticle doping on catalytic and magnetic properties were deeply assessed. PAMAM dendrimer coating on Fe3O4 nanoparticles results in a slightly decreased magnetic saturation value and in the reaction rate of 4-NP reduction. Au and Ag embedding in PAMAM dendrimers slightly increases the reaction rate while reducing the overall magnetic saturation values of nanocomposites. [GRAPHICS] .
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    Novel polymeric microspheres: Synthesis, enzyme immobilization, antimutagenic activity, and antimicrobial evaluation against pathogenic microorganisms
    (John Wiley and Sons Inc., 2020) Nartop, Dilek; Demirel, Birtane; Güleç, Murat; Özkan, Elvan Hasanoğlu; Yetim, Nurdan Kurnaz; Sarı, Nurşen; Ağar, Güleray
    New polymeric microspheres containing azomethine (1a-1c and 2a-2c) were synthesized by condensation to compare the enzymatic properties of the enzyme glucose oxidase (GOx) and to investigate antimutagenic and antimicrobial activities. The polymeric microspheres were characterized by elemental analysis, infrared spectra (FT-IR), proton nuclear magnetic resonance spectra, thermal gravimetric analysis, and scanning electron microscopy analysis. The catalytic activity of the glucose oxidase enzyme follows Michaelis-Menten kinetics. Influence of temperature, reusability, and storage capacity of the free and immobilized glucose oxidase enzyme were investigated. It is determined that immobilized enzymes exhibit good storage stability and reusability. After immobilization of GOx in polymeric supports, the thermal stability of the enzyme increased and the maximum reaction rate (Vmax) decreased. The activity of the immobilized enzymes was preserved even after 5 months. The antibacterial and antifungal activity of the polymeric microspheres were evaluated by well-diffusion method against some selected pathogenic microorganisms. The antimutagenic properties of all compounds were also examined against sodium azide in human lymphocyte cells by micronuclei and sister chromatid exchange tests. © 2019 Wiley Periodicals, Inc.
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    Qualitative enzymatic detection of organophosphate and carbamate insecticides
    (Taylor & Francis Inc, 2020) Nartop, Dilek; Hasanoglu Ozkan, Elvan; Yetim, Nurdan Kurnaz; Sari, Nursen
    In this study, new polymers containing amides (TrisPS-Ntaa, andTrisPS-Ntaa-Fc) were synthesized by condensation reaction for qualitative identification of insecticides. The synthesized polymers, including amides were investigated by infrared spectroscopy (IR), scanning electron microscopy-energy dispersion X- ray spectrometry (SEM-EDX), and gel permeation chromatography (GPC). Then, acetylcholinesterase enzyme (AChE) was covalently immobilized on these polymers to improve properties (including activity, reusability, and storage stability). Accordingly, organophosphate (malathion, acephate, chlorpyrifos methyl) and carbamate (carbofuran, methiocarb, methomyl), which are used to prevent harmful organisms in some agricultural products were enzymatically determined based on their inhibitory activity on AChE.