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    Effective Removing of Remazol Black B by the Polyacrylamide Cryogels Modified with Polyethyleneimine
    (Springer, 2022) Gun Gok, Zehra; Inal, Murat
    In this study, modified polyacrylamide (PAAm) cryogels with high dye holding capacity were synthesized with an easily and cheaply process and adsorption of Remazol Black B (RBB) with the synthesized materials was investigated. Firstly, PAAm cryogels were synthesized with free radical cryo-copolymerization method and they were modified with Hofmann reaction to form amine groups in the structure of the cyrogels. Then, to increase the removal efficiency of cryogels, polyethylenimine (PEI) molecules were crosslinked onto the cryogels via NH2 groups present in the PAAm gels modified by the Hofmann reaction. The original and modified cryogels were characterized with fourier transformed infrared spectroscopy, C-13 nuclear magnetic resonance spectroscopy, scanning electron microscopy and thermogravimetric analysis. The point of zero charge (pH(pzc)) of the modified cryogels was found to be 7.13 and RBB removing capabilities of PEI-modified PAAm cryogels were investigated at pH between 2 and 7. In addition, the adsorption treatments were performed at different process time, incubation temperature, initial dye concentration and adsorbent amount to find maximum removal capacity of the adsorbent. The modified cryogels adsorbed maximum amount of RBB at pH 2 and the sorption process reached equilibrium in 6 h. It was observed that the adsorption efficiency did not change much with the increase in temperature. The maximum RBB removal capacity of the modified cyrogels was determined to be 201 mg/g when the initial RBB concentration was 200 mg/L, treatment time was 6 h at pH 2. Moreover, the adsorption of RBB dye with the modified cryogels takes place with a second order kinetic and RBB dye adsorption data showed compliance with the Langmuir isotherm. The findings of the study expose that the obtained PEI-modified PAAm cryogels are a hopeful material for RBB removal in aqueous environment.
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    Öğe
    In situ synthesis of silver nanoparticles on modified poly(ethylene terephthalate) fibers by grafting for obtaining versatile antimicrobial materials
    (SPRINGER, 2020) Gun Gok, Zehra; Demiral, Ayse; Bozkaya, Ogun; Yigitoglu, Mustafa
    Because of having high mechanical properties and cheapness of PET textiles, functionalization of them for new properties is an active research area. In the present work, methacrylic acid (MAA)-grafted PET fibers (PET-g-MAA) were obtained by grafting of MAA monomers to PET surface for an antimicrobial material synthesis. The morphologies of the obtained graft copolymers were examined with a scanning electron microscopy (SEM), and the chemical modification after grafting was determined with Fourier-transform infrared spectroscopy (FTIR) analysis. Subsequently, silver ions were adsorbed onto the PET-g-MAA fibers surface and the adsorbed ions to the surface were reduced to silver nanoparticles (AgNPs) by UVC light. The morphology of fiber surfaces modified with MAA and coated with AgNPs was examined by SEM studies, and it was observed that AgNPs were disturbed along the fibers. The presence of silver on the surface was also confirmed by energy-dispersive X-ray spectroscopy (EDS) and energy dispersion X-ray fluorescence spectrometry (EDXRF). The crystalline structure of the original PET fiber, PET-g-MAA fiber and PET-g-MAA fiber modified with AgNPs was investigated by X-ray diffraction (XRD). The thermal properties of the obtained fibers were investigated by thermogravimetric analysis (TGA). The immobilization of AgNPs on the grafted fibers leads to a change on the patterns of TGA curves. The most significant change is the less weight reduction in the temperature range of 200-300 degrees C. Disk diffusion test was performed using Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 25,922) bacteria in order to investigate the antibacterial ability of the obtained fibers, and it was found that the fibers coated with AgNPs had antibacterial effect on both bacterial species. The cytotoxicity of the groups with the best antibacterial properties was determined by MTT test, and the synthesized material did not have cytotoxic effects on L929 fibroblast cells. The material obtained has the potential to be used in antimicrobial applications.
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    Öğe
    Investigation of the in vitro antibacterial, cytotoxic and in vivo analgesic effects of silver nanoparticles coated with Centella asiatica plant extract
    (Ankara Univ, 2023) Bozkaya, Ogun; Ekici, Husamettin; Gun Gok, Zehra; Arat, Esra; Ekici, Seda; Yigitoglu, Mustafa; Vargel, Ibrahim
    In recent years, researchers have shown an increased interest in using medicinal plants for the synthesis of silver nanoparticles (AgNPs) having various therapeutic properties. Centella asiatica (CA), a medicinal plant, has been used to treat minor burn wounds, psoriasis, and hypertrophic wounds among many other pathological conditions. The current study aimed to synthesize CA coated AgNPs (CA-AgNPs) with appropriate biocompatibility and various therapeutic properties, including antimicrobial and analgesic activities. The synthesized CA-AgNPs were characterized by ultraviolet-visible (UV-Vis) spectroscopy, zeta potential measurements, and fourier transform infrared (FT-IR) spectroscopy. The formation of spherical CA-AgNPs was confirmed by a single surface plasmon resonance (SPR) peak emerging at 420 nm wavelength by UV-Vis. The average hydrodynamic diameter and zeta potential of the particles were found to be 29.5 nm and -24.5 mV, respectively. The FT-IR analyses showed that the AgNPs were coated and stabilized by bioactive compounds from the CA extract. MTT cytotoxicity assay revealed that CA-AgNPs at <= 1 mM concentrations exhibited biocompatibility for L929 fibroblast cells. The antimicrobial activity of CA-AgNPs was confirmed by significant inhibition of Staphylococcus aureus and Escherichia coli. In addition, the analgesic effect of CA-AgNPs was investigated for the first time in the literature by tail-flick and hot plate methods, and statistically significant results were obtained for both methods. Taken together, these results suggest that CA-AgNPs can be used as an effective antibacterial and analgesic agent in a variety of biomedical applications, including coating wound dressings.
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    Öğe
    Removal of anionic dyes with glycidyl methacrylate-grafted polyethylene terephthalate (PET) fibers modified with ethylenediamine
    (Springer, 2021) Bozkaya, Ogun; Gunay, Kubra; Arslan, Metin; Gun Gok, Zehra
    In this work, the epoxy groups of poly (ethylene terephthalate) PET copolymers grafted with glycidyl methacrylate (GMA) were modified with ethylenediamine (EDA) to form exclusive adsorbent for removal of congo red (CR) and acid violet7 (AV-7) in the aqueous environment. The graft copolymers (GMA-g-PET) were synthesized with different grafting yield by a radical polymerization process with using benzoyl peroxide (Bz(2)O(2)) as radical initiator. Amination of GMA-g-PET fibers using EDA was studied in different solvents, and maximum yield (w/w %) was obtained in the toluene. The grafted and modified fibers were analyzed by CHNS organic elemental analyzer, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance spectroscopy (C-13-NMR). By SEM analysis, the morphological changes have been shown after grafting. The chemical changes after grafting and addition of EDA to the fibers have been proven with FTIR, NMR and elemental analysis. The thermal properties of the grafted and aminated fibers were researched with thermogravimetric analysis and differential scanning calorimeter analysis. The removal of dyes by the EDA-GMA-g-PET fibers was investigated in aqueous medium at different conditions. Optimum conditions of different parameters such as pH of medium, graft yield of GMA on the fibers, adsorption duration, initial concentration of dye molecules and effect of graft yield on amination reaction were examined. The optimum pH of CR and AV-7 removal was found 5 and 3, respectively. The removal yield was found about 100% for both dyes while initial concentration of dyes was changed from 10 to 400 mg/L. Adsorbed dyes with the fibers were desorbed with 1 M NaOH at room conditions.
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    Öğe
    Synthesis of carrageenan coated silver nanoparticles by an easy green method and their characterization and antimicrobial activities
    (Springer, 2021) Gun Gok, Zehra; Karayel, Mine; Yigitoglu, Mustafa
    The aim of the present work was to synthesize carrageenan coated silver nanoparticles (CA-AgNPs) using carrageenan as reducing and stabilizing agent. For this purpose, 10 mL of 0.35% (w/v) carrageenan solution was mixed with 10 mL AgNO3 solution at different concentrations (1, 5 and 10 mM), and the resulting mixture was stirred at 100 degrees C at high speed for 2 h. The formation of CA-AgNPs was proven with the surface plasmon peaks observed at approximately 420 nm. The sizes and zeta potentials of CA-AgNPs were determined by Zeta-Sizer. Negative zeta potentials of CA-AgNPs indicated that the obtained AgNPs were stable. With scanning electron microscope (SEM) and transmission electron microscope analysis, it was seen that CA-AgNPs have spherical structure. According to the energy dispersion spectrometer analysis based on SEM images, it was observed that the samples were elementally composed of carbon, oxygen, sulfur, potassium and silver. The chemical structures of CA-AgNPs were determined by Fourier transform infrared spectroscopy, and it was proved that the carbonyl and OH groups of carrageenan were involved in formation and stabilizing of AgNPs, respectively. According to thermal gravimetric analysis, it has been observed that CA-AgNPs were thermally more stable than pure carrageenan. Antibacterial activity of CA-AgNPs against gram-positive and gram-negative bacteria was investigated with agar well diffusion and liquid test. It has been observed that CA-AgNPs synthesized with 1 mM AgNO3 did not have an antibacterial activity on Escherichia coli and Staphylococcus aureus. Inhibition zones of varying diameters were observed in the 5 mM and 10 mM S-AgNPs groups. The synthesized CA-AgNPs (5 and 10 mM) have the capacity to be used in wound dressing materials or topical agents applied to burns and wounds due to their antibacterial effects and stability.