Person: KAHRAMAN, MEMET VEZİR
Loading...
Email Address
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
KAHRAMAN
First Name
MEMET VEZİR
Name
13 results
Search Results
Now showing 1 - 10 of 13
Publication Metadata only alpha-Amylase immobilization on functionalized nano CaCO3 by covalent attachment(WILEY-V C H VERLAG GMBH, 2012) KAHRAMAN, MEMET VEZİR; Demir, Serap; Gok, Sevda Burcu; Kahraman, Memet VezirIn this study, a-amylase was immobilized on glutaraldehyde activated silanized calcium carbonate nanoparticles by a using covalent binding method. The surface modified nano calcium carbonate (CaCO3) were characterized using FTIR and SEM. Immobilization yield was found as 199.43 mg/g of calcium carbonate nanoparticles. The maximum activity was observed at pH 6.5. The immobilized enzyme had a higher activity at elevated temperature (5090 degrees C) than the free one. Reuse studies demonstrated that the immobilized enzyme could reuse 25 times while retaining 18.2% of its activity. Free enzyme lost its activity completely within 15 days. Vmax values for the free and immobilized enzymes were calculated as 10 and 0.35 mg/mL/min, respectively.Publication Metadata only Nanodiamond-containing polyethyleneimine hybrid materials for lead adsorption from aqueous media(WILEY, 2019) KAHRAMAN, MEMET VEZİR; Cigil, Asli Beyler; Urucu, Oya Aydin; Kahraman, Memet VezirThis study describes the preparation of new surface-modified nanodiamond (ND) particles containing urethane-based hybrid materials by photopolymerization of aliphatic urethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate monomers, and their usage for lead adsorption from aqueous media. ND and synthesized surface-modified ND were characterized by atom transfer radical addition Fourier transform infrared spectroscopy (ATR-FTIR) and scanning transmission electron microscopy analysis. Crosslinked adsorbent nanocomposites were then treated with polyethylene imine and all adsorbent nanocomposites were characterized by ATR-FTIR, scanning electron microscopy, thermogravimetric analysis, and contact angle measurements. The metal ion binding capacity of the surfaces of the nanocomposites containing high amine content was investigated. The effects of the percentage of functional monomer, pH, and contact time on adsorption, and the interaction of foreign metal ions have been tested. Optimum contact time was found to be 7 h at pH 5. The adsorption capacity of the synthesized nanocomposite adsorbent for lead (II) was determined as 17.12 mg g(-1). Langmuir and Freundlich isotherms were used to determine the adsorption behaviors and Langmuir isotherm model was found to be the most suitable model (R-2: 0.9988). The amount of adsorption of Pb (II) ions of UV curable adsorbent film prepared in river water samples was investigated. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48241.Publication Metadata only Thermal, optical and electrical properties of UV-curing screen-printed glass substrates(SPRINGER, 2019) ARMAN KANDIRMAZ, EMİNE; Cigil, Asli Beyler; Kandirmaz, Emine Arman; Birtane, Hatice; Kahraman, Memet VezirIn this study, the hydroxyl functionality of the polyaniline surface was obtained using hydroxyethyl methacrylate and acrylated with isocyanatoethyl methacrylate. Coating formulation being curable with UV was designed by mixture of acrylated PANI (a-PANI) (0-5wt%), polyethylene glycol diacrylate, trimethylolpropane triacrylate, hydrolyzed 3-(methacryloxy) propyl trimethoxysilane (hydMEMO) and photoinitiator. The hybrid composite formulation has been printed on the glass surface with the method of screen printing. The chemical structure and the properties of thermal, electrical and surface obtained products were determined with ATR-FTIR, goniometer, current-voltage meter, scanning electron microscopy (SEM) and thermogravimetric analysis. ATR-FTIR results have shown that all materials were clearly produced. SEM results have revealed that PANI was dispersed at the composite in a stable manner. The conductivity value of the conductive line printed with F5a-PANI was found to be 3.7x10(-3)S. The best electrical results have presented that PANI has been beneficial for conductive line, and thus, screen printing was a convenient method for printing conductive lines.Publication Metadata only Preparation and Characterization of Thermally Conductive Thermoplastic Polyurethane/h-BN Nanocomposites(WILEY, 2014) ÇAKMAKÇI, EMRAH; Cakmakci, Emrah; Kocyigit, Ciler; Cakir, Selma; Durmus, Ali; Kahraman, M. VezirPublication 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 Metadata only Alpha-Amylase Immobilization on Epoxy Containing Thiol-Ene Photocurable Materials(KOREAN SOC MICROBIOLOGY & BIOTECHNOLOGY, 2013) ÇAKMAKÇI, EMRAH; Cakmakci, Emrah; Danis, Ozkan; Demir, Serap; Mulazim, Yusuf; Kahraman, Memet VezirThiol-ene polymerization is a versatile tool for several applications. Here we report the preparation of epoxide groups containing thiol-ene photocurable polymeric support and the covalent immobilization of alpha-amylase onto these polymeric materials. The morphology of the polymeric support was characterized by scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) coupled with SEM was used to explore the chemical composition. The polymeric support and the immobilization of the enzyme were characterized by FTIR analysis. SEM-EDS and FTIR results showed that the enzyme was successfully covalently attached to the polymeric support. The immobilization efficiency and enzyme activity of alpha-amylase were examined at various pH (5.0-8.0) and temperature (30-80 degrees C) values. The storage stability and reusability of immobilized alpha-amylase were investigated. The immobilization yield was 276 +/- 1.6 mg per gram of polymeric support. Enzyme assays demonstrated that the immobilized enzyme exhibited better thermostability than the free one. The storage stability and reusability were improved by the immobilization on this enzyme support. Free enzyme lost its activity completely within 15 days. On the other hand, the immobilized enzyme retained 86.7% of its activity after 30 days. These results confirm that alpha-amylase was successfully immobilized and gained a more stable character compared with the free one.Publication Metadata only Immobilization of alpha- amylase on aminated polyimide membrane: Preparation, characterization, and properties(WILEY-V C H VERLAG GMBH, 2014) ÇAKMAKÇI, EMRAH; Cakmakci, Emrah; Cigil, Asli Beyler; Danis, Ozkan; Demir, Serap; Kahraman, Memet Vezir-amylase was covalently immobilized on functionalized polyimide (PI) membranes via glutaraldehyde (GA) activation. 3,3,4,4-Benzophenonetetracarboxylic acid dianhydride (BTDA) and 4,4-oxydianline (4,4-ODA) based polyimide membranes were obtained via thermal imidization. Free amine groups on the surface of the polyimide membranes were generated by the amination reaction of polyimides with hexamethylenediamine (HMDA). Surface-aminated membranes were subjected to enzyme immobilization after GA activation. Immobilization efficiency and enzyme activity of -amylase was examined at various pH (3.0-8.0) and temperature (15-80 degrees C). The storage stability and reusability of immobilized -amylase were investigated. Immobilization yield was found as 359.53mg per gram of modified polyimide films. Enzyme assays demonstrated that the immobilized enzyme exhibited better thermo stability than the free one. The storage stability and reusability improved by the immobilization on this enzyme support. Free enzyme lost its activity completely within 15 days. On the other hand, the immobilized enzyme retained 79.98% of its activity after 30 days. These results confirmed that -amylase was successfully immobilized and gained more stable character compared to the free enzyme.Publication Metadata only Polymeric nanoparticles for selective protein recognition by using thiol-ene miniemulsion photopolymerization(TAYLOR & FRANCIS LTD, 2020) KAHRAMAN, MEMET VEZİR; Yasar, Merve; Dal Yontem, Fulya; Kahraman, M. Vezir; Apohan, Nilhan Kayaman; Aktas, Zerrin; Oncul, Mustafa Oral; Akcakaya, HandanThe fabrication of molecularly imprinted nanoparticles (MIP-NPs) specific for myoglobin by using thiol-ene photopolymerization in miniemulsion was described. Allyl derivatives of phenylalanine as a functional monomer was synthesized and copolymerized with acrylic monomersviaminiemulsion polymerization to produce NIP-NPs with approximately 74 nm number average particle diameter. FTIR and(1)H-NMR analysis confirmed the synthesis of functional monomer. MIP-NPs were prepared in the existence of myoglobin as a template protein. Morphological investigations exhibited that the particle size of the MIP-NPs, increased compared to the corresponding NIPs and the mean particle diameter by number was measured as 141 nm with narrow distribution. NIP-NPs that were polymerized without myoglobin were found to have less affinity to the target protein. In addition, the rebinding ability of MIP-NPs was much bigger than that of the corresponding NIPs. ELISA results showed that MIPs interact particularly with the myoglobin and show little affinity for BSA in competitive binding experiments.Publication 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, SerapIn 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.Publication Metadata only Thermal and Phase Change Material Properties of Comb-Like Polyacrylic Acid-Grafted-Fatty Alcohols(TAYLOR & FRANCIS INC, 2018) KAHRAMAN, MEMET VEZİR; Basturk, Emre; Kahraman, Memet VezirPoly(acrylic acid)-graft-fatty alcohol are synthesized from the esterification of polyacrylic acid with octadecanol and docosanol. The characterization of poly(acrylic acid)-graft-fatty alcohol was performed by attenuated total reflection-Fourier transform infrared spectroscopy. The thermal stability performances and phase change behaviors of poly(acrylic acid)-graft-fatty alcohol were examined by using thermogravimetric analysis system and differential scanning calorimetry. The results indicate that the poly(acrylic acid)-graft-fatty alcohol polymeric phase change materials possess good phase change properties and provide a suitable working temperature range. The heating process phase change enthalpy is measured between 112 and 122J g(-1), and the freezing process phase change enthalpy is found between 118 and 126J g(-1). The decomposition of poly(acrylic acid)-graft-fatty alcohol polymeric phase change materials started at 177 degrees C and reached a maximum of 380 degrees C. All of the obtained poly(acrylic acid)-graft-fatty alcohol polymeric phase change materials improved latent heat storage capacity in comparison with the pristine poly(acrylic acid) polymer. With the obtained results we conclude that, these materials promise a great potential in thermal energy storage applications. [GRAPHICS]