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Öğe Asidik ortamda paslanmaz çeliğin korozyonuna yeşil inhibitör olan Nikotinamidin etkisi(GAZI UNIV, FAC ENGINEERING ARCHITECTURE, 2023) Asan, GüldenPaslanmaz çelik tüm dünyada en çok kullanılan metallerden birisidir. Paslanmaz çeliğin asidik ortamda korozyon direnci düşük olduğu için ve endüstride asit kullanımı çok yaygın olduğundan paslanmaz çeliğin korozyondan korunması önem arz etmektedir. Bu çalışmada inhibitör olarak çevre dostu olan nikotinamid bileşiği paslanmaz çeliğin korozyondan korunmasında kullanıldı. Çalışmada öncelikle paslanmaz çeliğin 0,1 M HCl asit çözeltisinde elektrokimyasal davranışını belirlemek için dönüşümlü voltametri tekniği kullanıldı. Daha sonra 0,1 M HCl asit çözeltisinde Tafel polarizasyon yöntemi nikotinamid inhibitörü olmadığında, 500 ppm, 750 ppm ve 1000 ppm nikotinamid varlığında paslanmaz çeliğin korozyon davranışını tayin etmek için uygulandı. Bu 3 farklı derişimde inhibitör 0, 15, 30, 45 ve 60 dakikalık sürelerde bekletilerek her bir derişim için optimum süre tayini yapıldı. En yüksek inhibitör etkinliği 1000 ppm nikotinamid derişiminde 15 dakikalık bekletme süresinde % 96,8, süre kısıtlaması olmadığında 500 ppm nikotinamid derişiminde 60 dakikalık bekletme süresinde inhibitör etkinliği %96,6 olarak bulundu. Elde edilen sonuçlar gösterdi ki nikotinamid, paslanmaz çeliğin korozyondan korunmasında etkin bir şekilde kullanılabilir ve çevre dostu olması sebebiyle de korozyondan korunma sağlanırken çevreye ve canlılara zarar verilmemiş olur.Öğe Therapeutic Effects of Newly Synthesized Boron Compounds (BGM and BGD) on Hepatocellular Carcinoma(Humana Press Inc, 2021) Koldemir Gündüz, Meliha; Bülter Bolat, Melda; Kaymak, Güllü; Berikten, Derya; Köse, Dursun AliBoron has an important potential for facilitating biological activity and for use in pharmaceutical drug design. Boron glycine monoester (BGM) and boron glycine diester (BGD) compounds containing boron atoms were synthesized and investigated their cytotoxic, oxidative stress, and antimicrobial activities on the HepG2 cancer cell line. The cytotoxic activity of newly synthesized boron compounds on hepatocellular carcinoma was determined by the MTT method for 48 h. Antioxidant (CAT, GSH), lipid peroxidation (MDA), and enzyme activity (ACP, ALP) analyses were determined by spectrophotometric methods in HepG2 cells. Antimicrobial activity was determined by the disk diffusion method. After 48 h of BGM and BGD application to HepG2 cells, we found the IC50 values as 9.9 mM and 24 mM, respectively. While CAT and ACP enzyme activities decreased in all groups compared to the control, ALP enzyme activity did not change in the BGM group but increased in the BGD group. It was determined that the GSH level did not change in all groups, while the MDA level increased. It has been stated that these IC50 doses of BGM and BGD have antibacterial effects on Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 25922. Newly synthesized boron compounds, particularly BGM, with their cytotoxic, oxidative stress, and antimicrobial effects, could provide a new therapeutic approach for the treatment of hepatocellular carcinoma.Öğe Water-soluble polymeric particle embedded cryogels: Synthesis, characterisation and adsorption of haemoglobin(Walter De Gruyter Gmbh, 2021) Erol, Kadir; Bolat Bülter, Melda; Köse, Dursun Ali; Kaplan Can, HaticeMaking cryogels, which are among today's accepted adsorbents, more functional with different methods, has been one of the subjects spent overtime. In this study, water-soluble poly(maleic anhydride-alt-acrylic acid) polymer embedded in poly(2-hydroxyethyl methacrylate) cryogels. Copper ionswere then immobilised to this structure, and this polymer was used for adsorption of haemoglobin from aqueous systems. Adsorption interaction was carried out on an electrostatic basis, and approximately 448.62 mg haemoglobin/g polymer adsorption capacity value was obtained. Itwas found that the same material hasmanaged to maintain its adsorption ability by 90.3% even after the use of it five times in the adsorption/desorption cycle. The adsorption interaction was determined to be appropriate for the Langmuir model by isotherm studies. The change in Gibbs free energy value was calculated as -2.168 kJ/mol.Öğe Synthesis, characterization and antibacterial application of silver nanoparticle embedded composite cryogels(Elsevier, 2020) Erol, Kadir; Bolat Bülter, Melda; Tatar, Demet; Nigiz, Cengiz; Köse, Dursun AliWater treatment applications; they consist of processes that desalination, softening, removals of dissolved organic matter, color, particle and microorganism. In traditional treatment processes, microorganisms cause thick film layer on the membrane to be used and not enough treatment. Silver nanoparticles (AgNPs), known to stop bacterial growth due to their superior antibacterial properties even at low concentrations due to their contact with microorganisms, are used for water disinfection. Membrane production with a combination of AgNPs and polymers has started to attract attention in recent years due to advanced optics, conductivity and antibacterial properties. The ability of AgNP to exhibit its antibacterial effect depends on the property of this material to be homogeneously dispersed in the polymer. In this study, Poly(2-hydroxyethyl methacrylate-glycidyl methacrylate), Poly(HEMA-GMA), cryogels were synthesized as solid support. In order to gain antibacterial properties to synthesized cryogels, AgNPs of different sizes were embedded in cryogels. These structures have been used as a kind of antibacterial filter in the purification of water obtained from natural sources used as drinking and using water in the local region. Particle Size analysis was used to determine the size of synthesized AgNPs. Swelling test, Scanning Electron Microscopy (SEM), Elemental Analysis, Fourier Transform Infrared Spectroscopy (FT-IR), and surface area (BET) analysis were performed for characterization of cryogels. (C) 2019 Elsevier B.V. All rights reserved.Öğe The effect of 2D-MoS2 doped polypyrrole coatings on brass corrosion(Elsevier B.V., 2020) Asan, Gülden; Asan, Abdurrahman; Çelikkan, HüseyinConductive polymers have an important potential against the corrosion applications because they arehighly resistant to chemicals besides they have homogeneous coating properties and transport metals tomore noble regions. However, the major disadvantage of conductive polymers such as polypyrrole (PPy)is their low mechanical strength. In this study, the doping effect of MoS2into the PPy coatings by theelectropolymerization of polypyrrole (PPy) and exfoliated MoS2on the corrosion of brass was investi-gated. The corrosion protection of these coatings were determined by measuring the corrosion rates withTafel polarization method in 0.1 M H2SO4media. PPy and MoS2doped PPy (MoS2@PPy) coatings weresuccessfully obtained by the use of chronoamperometry technique in 0.2 M H2C2O4solutions with 0.2 Mpyrrole and various concentrations of MoS2. It was observed that MoS2@PPy coatings were homoge-neously coated without and with all MoS2concentrations on the metal surface and well adhered to thebrass surface, but MoS2@PPy coating with 25 ppm MoS2showed the best corrosion protection. Thesurface and chemical characterizations of the coatings were performed by SEM-EDSÖğe Askorbik asitin MoS2 esaslı elektrotla elektrokimyasal tayini(Ahmet Yesevi Üniversitesi, 2017) Asan, Gülden; Çelikkan, HüseyinBu çalışmada, grafen, grafen oksit ve MoS iki boyutlu nanotabakalarına ayrılmak suretiyle 10 farklı kaplama süspansiyonu hazırlanmıştır. Hazırlanan kaplama süspansiyonlarıyla damlatarak-kaplama yöntemi kullanılarak camsı karbon elektrot modifikasyonu gerçekleştirilmiştir. Farklı kompozisyonlarda hazırlanan modifiye elektrotlar ile askorbik asit (AA) tayini için elektrokatalitik duyarlık incelenmiştir. Ölçümler diferansiyel puls voltametrisi (DPV) tekniği ile gerçekleştirilmiştir. Elektrotun modifikasyonu yapılarak 2,8 kata kadar duyarlıkta artış sağlanmıştır. MoS2'ün AA'ya karşı bir katalitik etkinliğinin görüldüğü bu çalışmada, AA'ya karşı duyarlık 7,26 µA mM-1, doğrusal çalışma aralığı 27 µM - 1100 µM aralığında ve gözlenebilme sınırı da 8,1 µM olarak bulunmuştur. Modifiye elektrotla gerçekleştirilen gerçek numune analizinde ortalama % 5,05 bağıl hatayla AA tayini gerçekleştirilmiştir. Hazırlanan MoS2'ün tabaka kalınlığı atomik kuvvet mikroskobu (AFM) cihazıyla ölçülmüş ve modifiye elektrot yüzeyi taramalı elektron mikroskobu (SEM) ile görüntülenmiştirÖğe Synthesis of new homoconduritols and homoaminoconduritols(Elsevier Ltd, 2016) Kaya, Özgür; Şengül, Mehmet Emin; Menzek, Abdullah; Şahin, Ertan; Gür, Berna(1R*,2R*,4R*,5S*,7S*,8S*)-Methyl 3,6-dioxatetracyclo[6.1.0.0(2,4).0(5,7)]nonane-9-carboxylate (10) and (1S*,2S*,4R*,7R*,8S*)-methyl 3-oxatricyclo[5.1.0.0(2,4)]oct-5-ene-8-carboxylate (11) were synthesized starting from methyl 1,3,5-cycloheptatriene-7-carboxylate. By ring opening of epoxide 11 with CH3OH, isomeric products including (1S*,2S*,4R*,7R*,8S*)-methyl 3-oxatricyclo[5.1.0.]oct-5-ene-8-carboxylate (12) were formed. Homoconduritol F derivatives were obtained from reactions such as epoxidation, cis-hydroxylation and ring opening of 12. Homoaminoconduritol B-1, B-2, and F-2 derivatives were synthesized from the corresponding reactions of 11. Ring opening of ene-epoxide 11 with NaN3 gave azidoalcohol as the sole product. Homodiaminoconduritol A-2,3 and B-2,3 derivatives were also synthesized from ring opening with NaN3 and catalytic hydrogenation reactions of both bis-epoxide 10 and ene-epoxide 11. The formations of the products are discussed. (C) 2016 Published by Elsevier Ltd.
