Person: KAHRAMAN, MEMET VEZİR
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KAHRAMAN
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MEMET VEZİR
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Publication 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.Publication 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, ZhumabayPublication 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, ZhumabayLight 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)).Publication 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, ZhumabayConventional 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.Publication 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.Publication 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.