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KAHRAMAN, MEMET VEZİR

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Fen - Edebiyat Fakültesi

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KAHRAMAN

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MEMET VEZİR

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Now showing 1 - 10 of 11

Open Access
Fluorimetric reusable polymeric sensor for hydrogen sulfide detection
(2023-02-01) ÇUBUK, SONER; KAHRAMAN, MEMET VEZİR; Ünaldı A. Ş., Çubuk S., Çiğil A. B., Kahraman M. V.
In this study, with the help of reactive monomers, crosslinkers, and photoinitiator that detect H2S in various matrices, an H2S sensitive fluorescence sensor polymerizes under ultraviolet (UV) light was developed. To this goal, a polymeric membrane was prepared, and the characterization of the membrane was carried out with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods. Afterward, appropriate conditions were identified, the excitation wavelength was determined as 370 nm, and the emission wavelength was determined as 425 nm. It was established that the fluorescence intensity of the prepared polymeric membrane decreased in the presence of H2S. A detailed analysis was executed to determine the sensor's most suitable pH value and time. It was found that the optimum pH was 8.0, and the optimal duration was 15 s. It has been calculated that the linear range of the developed method is 2.19× 10–8– 6.25× 10–7 M, and the detection limit (LOD) is 7.37× 10–9 M. The effect of some possible interfering ions was investigated, and it determined that the sensor had excellent selectivity. In addition, the sensor used to determine H2S can be used at least 100 times. The recovery percentages were 102.1%–103.2%, and 104.6%, using tap water samples. In terms of providing reliable, fast results, high sensitivity, reusable, low cost, and ease of use, the developed fluorimetric sensor, compared to standard methods, has become more advantageous.
Open Access
Synthesis of 4-Acryloylmorpholine- based Hydrogels and Investigation of their Drug Release Behaviors
(SOC BRASILEIRA QUIMICA, 2013) KAHRAMAN, MEMET VEZİR; Efe, Hulya; Bicen, Merve; Kahraman, Memet Vezir; Kayaman-Apohan, Nilhan
In this study, hydrogels based on an amphiphilic, water soluble, bisubstituted and biocompatible acrylamide derivative, namely 4-acryloylmorpholine (4-AcM), were prepared. 4-AcM based hydrogels with different compositions were synthesized by photopolymerization from the mixtures of poly(ethylene glycol) diacrylate (PEG-DA) and poly(2-hydroxy ethyl methacrylate) (HEMA), and characterized by Fourier transform infrared spectroscopy (FTIR). Gel percentage and equilibrium swelling ratios were determined. Images obtained by scanning electron microscopy (SEM) confirmed porous structure of the hydrogels. Ciprofloxacin. HCl was chosen as a model drug in order to understand the drug loading and release behaviors of the hydrogels. As 4-AcM content increased, higher drug release was observed. On the other hand, the increase in crosslinking density due to PEG-DA content resulted in the swelling decrease of the hydrogel and reduced the diffusion of the drug.
Open Access
Photo and thermal crosslinked poly(vinyl alcohol)-based nanofiber membrane for flexible gel polymer electrolyte
(2022-02) KAHRAMAN, MEMET VEZİR; Kassenova, Nazym; Kalybekkyzy, Sandugash; Kahraman, Memet Vezir; Mentbayeva, Almagul; Bakenov, Zhumabay
Open Access
Electrospun 3D Structured Carbon Current Collector for Li/S Batteries
(MDPI, 2020-04-14) KAHRAMAN, MEMET VEZİR; Kalybekkyzy, Sandugash; Mentbayeva, Almagul; Yerkinbekova, Yerkezhan; Baikalov, Nurzhan; Kahraman, Memet Vezir; Bakenov, Zhumabay
Light weight carbon nanofibers (CNF) fabricated by a simple electrospinning method and used as a 3D structured current collector for a sulfur cathode. Along with a light weight, this 3D current collector allowed us to accommodate a higher amount of sulfur composite, which led to a remarkable increase of the electrode capacity from 200 to 500 mAh per 1 g of the electrode including the mass of the current collector. Varying the electrospinning solution concentration enabled obtaining carbonized nanofibers of uniform structure and controllable diameter from several hundred nanometers to several micrometers. The electrochemical performance of the cathode deposited on carbonized PAN nanofibers at 800 degrees C was investigated. An initial specific capacity of 1620 mAh g(-1) was achieved with a carbonized PAN nanofiber (cPAN) current collector. It exhibited stable cycling over 100 cycles maintaining a reversible capacity of 1104 mAh g(-1) at the 100th cycle, while the same composite on the Al foil delivered only 872 mAh g(-1). At the same time, 3D structured CNFs with a highly developed surface have a very low areal density of 0.85 mg cm(-2) (thickness of -25 mu m), which is lower for almost ten times than the commercial Al current collector with the same thickness (7.33 mg cm(-2)).
Open Access
Fabrication of UV-Crosslinked Flexible Solid Polymer Electrolyte with PDMS for Li-Ion Batteries
(MDPI, 2020-12-23) KAHRAMAN, MEMET VEZİR; Kalybekkyzy, Sandugash; Kopzhassar, Al-Farabi; Kahraman, Memet Vezir; Mentbayeva, Almagul; Bakenov, Zhumabay
Conventional carbonate-based liquid electrolytes have safety issues related to their high flammability and easy leakage. Therefore, it is essential to develop alternative electrolytes for lithium-ion batteries (LIBs). As a potential candidate, solid-polymer electrolytes (SPEs) offer enhanced safety characteristics, while to be widely applied their performance still has to be improved. Here, we have prepared a series of UV-photocrosslinked flexible SPEs comprising poly(ethylene glycol) diacrylate (PEGDA), trimethylolpropane ethoxylate triacrylate (ETPTA), and lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) salt, with the addition of polydimethylsiloxane with acrylated terminal groups (acryl-PDMS) to diminish the crystallinity of the poly(ethylene glycol) chain. Polysiloxanes have gained interest for the fabrication of SPEs due to their unique features, such as decrement of glass transition temperature (T-g), and the ability to improve flexibility and facilitate lithium-ion transport. Freestanding, transparent SPEs with excellent flexibility and mechanical properties were achieved without any supporting backbone, despite the high content of lithium salt, which was enabled by their networked structure, the presence of polar functional groups, and their amorphous structure. The highest ionic conductivity for the developed cross-linked SPEs was 1.75 x 10(-6) S cm(-1) at room temperature and 1.07 x 10(-4) S cm(-1) at 80 degrees C. The SPEs demonstrated stable Li plating/stripping ability and excellent compatibility toward metallic lithium, and exhibited high electrochemical stability in a wide range of potentials, which enables application in high-voltage lithium-ion batteries.
Open Access
Covalent immobilization of acetylcholinesterase on a novel polyacrylic acid-based nanofiber membrane
(WILEY, 2018-04) OGAN, AYŞE; Cakiroglu, Bekir; Cigil, Asli Beyler; Ogan, Ayse; Kahraman, M. Vezir; Demir, Serap
In this study, polyacrylic acid-based nanofiber (NF) membrane was prepared via electrospinning method. Acetylcholinesterase (AChE) from Electrophorus electricus was covalently immobilized onto polyacrylic acid-based NF membrane by demonstrating efficient enzyme immobilization, and immobilization capacity of polymer membranes was found to be 0.4 mg/g. The novel NF membrane was synthesized via thermally activated surface reconstruction, and activation with carbonyldiimidazole upon electrospinning. The morphology of the polyacrylic acid-based membrane was investigated by scanning electron microscopy, Fourier Transform Infrared Spectroscopy, and thermogravimetric analysis. The effect of temperature and pH on enzyme activity was investigated and maxima activities for free and immobilized enzyme were observed at 30 and 35 degrees C, and pH 7.4 and 8.0, respectively. The effect of 1 mM Mn2+, Ni2+, Cu2+, Zn2+, Mg2+, Ca2+ ions on the stability of the immobilized AChE was also investigated. According to the Michaelis-Menten plot, AChE possessed a lower affinity to acetylthiocholine iodide after immobilization, and the Michaelis-Menten constant of immobilized and free AChE were found to be 0.5008 and 0.4733 mM, respectively. The immobilized AChE demonstrated satisfactory reusability, and even after 10 consecutive activity assay runs, AChE maintained ca. 87% of its initial activity. Free enzyme lost its activity completely within 60 days, while the immobilized enzyme retained approximately 70% of the initial activity under the same storage time. The favorable reusability of immobilized AChE enables the support to be employable to develop the AChE-based biosensors.
Open Access
Thioether functional chain extender for thermoplastic polyurethanes
(SPRINGER, 2015-06) ÇAKMAKÇI, EMRAH; Altintas, Zerrin; Cakmakci, Emrah; Kahraman, M. Vezir; Kayaman-Apohan, Nilhan
In this study, a novel three functional chain extender (TATATRIOL) was synthesized from the reaction of 1,3,5-tri(prop-2-en-1-yl)-1,3,5-triazinane-2,4,6-trione (TATA) with 2-sulfanylethanol. Then new thermoplastic polyurethanes (TPUs) were synthesized by a one-step bulk polymerization from the reaction of 1,1'-methanediylbis(4-isocyanatocyclohexane) (H12MDI), a poly(ethylene adipate) based polyester polyol and a chain extender. Butane-1,4-diol (BD) and the newly synthesized monomer, TATATRIOL, were used as chain extenders. The effects of TATATRIOL on the properties of the TPU were investigated and compared to those of the TPU prepared with BD. The TPUs which derived from the sulfur containing chain extender displayed lower modulus and high elongation at break values than the analogous TPUs derived from BD. Moreover sulfur containing TPUs exhibited higher thermal stability.
Open Access
Molecularly imprinted nanoparticles with recognition properties towards diphtheria toxin for ELISA applications
(2022-11-01) KAHRAMAN, MEMET VEZİR; Alkanlı S. S. , Dal Yöntem F., Yaşar M., Güven C., Kahraman M. V. , Kayaman Apohan N., Aktaş Z., Öncül M. O. , Ünlü A., Akçakaya H.
Plastic antibodies can be used for in vitro neutralization of biomacromolecules with different fragments due to their potential in separation, purification, chemical sensor, catalysis and drug production studies. These polymer nanoparticles with binding affinity and selectivity comparable to natural antibodies were prepared using functional monomer synthesis and copolymerization of acrylic monomers via miniemulsion polymerization. As a result, the in vitro cytotoxic effect from diphtheria toxin was reduced by MIPs. In vitro imaging experiments of polymer nanoparticles (plastic antibodies) were performed to examine the interaction of diphtheria toxin with actin filaments, and MIPs inhibited diphtheria toxin damage on actin filaments. The enzyme-linked immunosorbent assay (ELISA) was performed with plastic antibodies labeled with biotin, and it was determined that plastic antibodies could also be used for diagnostic purposes. We report that molecularly imprinted polymers (MIPs), which are biocompatible polymer nanoparticles, can capture and reduce the effect of diphtheria toxic and its fragment A. HIGHLIGHTS Macromolecules can be imprinted by using their fragments as template molecules. MIPs gain an affinity for the template molecule by covalent binding, non-covalent interactions or ligand interactions, as well as the ability to bind, release and recognize the template molecule.
Open Access
Yüksek Hidrofilik Polietilen İmin Kaplamaların Hazırlanması Ve_x000D_ Karakterizasyonu
(2019-07-31) ARMAN KANDIRMAZ, EMİNE; Aslı BEYLER ÇİĞİL;Emine ARMAN KANDIRMAZ;Hatice BİRTANE;Memet Vezir KAHRAMAN
Bu çalışmada süperhidrofilik bir kaplama hazırlanması planlanmış ve bu amaçla polietilen imin (PEI),silanlanmış cam yüzey üzerine modifiye edilmiştir; bu cam yüzeyin karakterizasyonları, X-ışını fotoelektronspektroskopisi (XPS), Geçirgenlik spektrumu ve temas açısı ölçümleri ile yapılmıştır. İlk olarak, cam örnekleripiranha çözeltisinde (sülfürik asit:hidrojen peroksit, 7:3) temizlenerek hidroksil fonksiyonelleştirilmiş daha sonra3-glisidiloksipropiltrimetoksisilan (GPTMS) kullanılarak silanlanmıştır. Epoksi modifiye cam örnekleri dahasonra polietilen imin (PEI) çözeltisine daldırılmış ve amin grubu modifiye edilen cam örnekler başarıylahazırlanmıştır. Sonuç olarak GPTMS'nin cam yüzeyine modifikasyonunun başarılı bir şekilde gerçekleştirildiğiXPS ile kanıtlanmıştır. Polietilen imin ile cam yüzeyinin modifikasyonundan sonra, XPS ile amino grubuoluşumu belirlenmiştir. Yüzey hidrofilikliği, su temas açısı (WCA) ölçümleriyle belirlenmiştir. Hiç işlemgörmemiş cam yüzeyin su temas açısı 73,6° olarak ölçülmüş ve amin grupları ile modifiye edilen cam yüzeyin sutemas açısı değeri 11,7° olarak ölçülmüştür. PEI modifiye edilen kaplamanın süperhidrofilik olduğubelirlenmiştir.
Open Access
Facile application of terahertz spectroscopy in UV-coated and phase change material loaded MPS
(2023-05-01) KAHRAMAN, MEMET VEZİR; Aytan E., Aytekin Y. S., Aytan T. A., Esenturk O., Kahraman M. V.
In this study, capability of Terahertz (THz) spectroscopy for determination of thermal properties of phase change materials (PCM) in an acrylated polyurethane coating investigated. Spherical shaped mesoporous silica materials (MPSs) are prepared as a template for stearic acid (SA). SA was impregnated into MPSs for investigate its PCM properties. Surface of MPSs was modifed with 3-(Trimethoxysilyl)propyl methacrylate (MEMO) to add acrylate functionality to form covalently bond to polyurethane (PU)-based composite UV matrix to avert leakage problem. Finally, this resin was photopolymerized and its change in thermal properties was determined by both conventional Diferential Scanning Calorimetry (DSC) and THz. DSC results show that the heating process phase change enthalpy is measured between 20.83 J/g and 136.80 J/g, and the freezing process phase change enthalpy is found between 13.55 J/g and 181.13 J/g by DSC. The thermal properties of phase changing behavior of the sample were also analyzed by Terahertz Time Domain Spectroscopy (THz-TDS). Besides the phase changes THz spectroscopy has shown the temperature dependent variation in the host matrix, also fnal PCM sample. Comparison of the data suggest that THz Spectroscopy is a fairly strong technique for characterization of phase changing materials even in very complex resin environment and it is a strong complementary technique especially following the temperature dependent properties close to room temperature.