Yazar "Bayrakci, Mevlut" seçeneğine göre listele
Listeleniyor 1 - 20 / 20
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe A new calix[4]azacrown ether based boradiazaindacene (Bodipy): Selective fluorescence changes towards trivalent lanthanide ions(ELSEVIER SCI LTD, 2013) Bayrakci, Mevlut; Kursunlu, Ahmed Nuri; Guler, Ersin; Ertul, SerefWe report on the synthesis and photophysical properties of a new calix[4]azacrown derivative, capped with two amide bridges, in the cone conformation bearing two boradiazaindacene (Bodipy) groups at the narrow rim. Its binding properties towards trivalent lanthanide ions such as La3+, Gd3+, Tb3+, Dy3+, Er3+ and Yb3+ were investigated by using spectroscopic techniques. With respect to fluorescence intensity changes upon trivalent lanthanide ion complexation, calix[4]azacrown ether based Bodipy showed higher selectivity towards Yb3+ ion over other ions. Presence of proximal two amide groups in calix[4] azacrown ether based Bodipy were observed to play an important role in exhibiting its lanthanide ion binding. (C) 2013 Elsevier Ltd. All rights reserved.Öğe An Application of a Schiff-Base Type Reaction in the Synthesis of a New Rhodamine-Based Hg(II)-Sensing Agent(Springer/Plenum Publishers, 2019) Cicekbilek, Fulya; Yilmaz, Bahar; Bayrakci, Mevlut; Gezici, OrhanA facile synthesis procedure, whereby 9-Anthraldehyde (AA) is coupled to aminated rhodamine (AR) via a Schiff base-type reaction, is reported. The applicability and performance of the obtained material (AA-AR) as a sensing agent was studied towards 16 metal cations (i.e. Li+, Na+, Ag+, Ca2+, Ba2+, Co2+, Cs+, Cu2+, Mg2+, Hg2+, Mn2+, Pb2+, Ni2+, Sr2+, Zn2+, Al3+). Among the studied metals, an extraordinary selectivity was observed for Hg2+, and the observed selectivity was found not to be influenced by the presence of other cations and some common anions (i.e. Br-, Cl-, I-, HPO42-, H2PO4-, NO3-, NO2-, ClO4-, AcO-, HSO4-, SO42-, Cr2O7-, CO32-, OH- and HCO3-). The material, AA-AR, exhibited such a high selectivity and sensitivity towards Hg2+ that it could be detected even by naked eyes. The Hg2+-sensing property of AA-AR was found not to be limited to colorimetric detections so that a high fluorescent nature of the compound was also observed upon binding Hg2+ ion. The detection limit, which is correspondent to fluorescence emission intensity, was found as 0.87 mu M. The underlying mechanism of sensing property was studied by using some spectroscopic techniques such as FT-IR, H-1-NMR, C-13-NMR, and UV-Vis. (Job-plot). In the final course of the experiments, the performance of AA-AR in cell-imaging was also studied, and even trace amounts of Hg2+ in living cells could be detected by the studied probe. Thus, the applicability of a new synthesis approach in producing a highly efficient new fluorescence sensor for the detection of Hg2+ ions is discussed in detail.Öğe An Application of a Schiff-Base Type Reaction in the Synthesis of a New Rhodamine-Based Hg(II)-Sensing Agent (vol 29, pg 1349, 2019)(Springer/Plenum Publishers, 2020) Cicekbilek, Fulya; Yilmaz, Bahar; Bayrakci, Mevlut; Gezici, Orhan[Abstract Not Available]Öğe Calixarene-engineered surfaces and separation science(SPRINGER, 2015) Gezici, Orhan; Bayrakci, MevlutAfter their discovery, calixarenes have attracted the attention of many researchers from various disciplines. This group of supramolecules has an increasing popularity and this is most probably related with the flexibility of calixarene chemistry. Owing to their multifunctional character and stability, calixarenes became important precursors in separation science to derive new-type of sorbents or stationary phases. Immobilization of calixarenes to a suitable solid support (e.g. silica, synthetic polymers, magnetite nanoparticles, etc.) is a very popular concept being used for this purpose, and various immobilization methodologies have been proposed in the literature. In the present work, some state-of-the-art researches and developments published in the past are reviewed in a collective manner, and thus fundamentals of calixarene-immobilization and the application of the obtained materials in sorption and high performance liquid chromatography are represented.Öğe Combined voltammetric and spectroscopic investigation of binding interaction between nifedipine and human serum albumin on polyelectrolyte modified ITO electrode(PERGAMON-ELSEVIER SCIENCE LTD, 2013) Ozmen, Mustafa; Maltas, Esra; Patir, Imren Hatay; Bayrakci, MevlutThe binding interaction between the drug molecule, nifedipine (Nf), and the human serum albumin (HSA) on polyelectrolyte modified indium tin oxide (ITO) electrode has been investigated by the combination of electrochemical and fluorescence spectroscopy techniques. Surface modification has also been characterized by scanning electron microscopy (SEM) and Contact Angle (CA) measurements in each step. The cyclic voltammetry, electrochemical impedance parameters (peak potential difference (Delta E-p)), peak current difference (Delta I-p) and charge-transfer resistance (R-ct) indicate that nifedipine strongly interacted with human serum albumin molecule on the polyelectrolyte modified ITO electrode surface. Stern-Volmer quenching constant K-a is inversely correlated with the temperature, which indicates that the probable quenching mechanism of the nifedipine-human serum albumin binding reaction is initiated by complex formation. The results obtained from these techniques showed that Nf could bind to HSA. The binding constant (K-b) and the number of binding sites (n) of the drug with HSA at different temperatures were determined. At 298 K, K-b was found as 4.04 x 10(-3) and n was 1.08 for Nf-HSA. According to the van't Hoff equation, the thermodynamic parameters, Delta G, Delta H and Delta S, were obtained, showing the involvement of hydrophobic and electrostatic force in this interaction. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Fabrication of Langmuir-Blodgett thin films of calix[4]arenes and their gas sensing properties: Investigation of upper rim para substituent effect(ELSEVIER SCIENCE SA, 2014) Ozmen, Mustafa; Ozbek, Zikriye; Buyukcelebi, Sumeyra; Bayrakci, Mevlut; Ertul, Seref; Ersoz, Mustafa; Capan, RifatThis study reports the characterization and organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of calix[4] arene derivatives that contain different numbers of tert butyl groups on their upper rims. Surface pressure-area isotherms show that very stable monolayers are formed at the air-water interface. The LB films are deposited onto different substrates, which allowed us to characterize the films by contact angle measurements, quartz crystal microbalance (QCM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The results indicate that good quality, uniform LB films can be prepared with transfer ratios of over 0.95. Meanwhile, our QCM results show that the deposition of LB film layers depends heavily on the number of p-tert-butyl groups and calix[4]arene with four p-tert-butyl groups yields the highest slope with a mass value of 1145 ng per layer. Furthermore, our AFM and SEM studies reveal a dense surface morphology for all prepared LB films. The kinetic response of calix[4]arenes containing p-tert-butyl groups and without p-tert-butyl groups as an LB film to chloroform, benzene, toluene, and ethanol vapors were investigated as a function of time. After attaching tert-butyl groups onto the calix[4]arene structure, the response of LB film to chloroform vapor increased. LB films of compounds 1-4 yield a response to all vapors and more often select chloroform with a larger, faster, and more reproducible response. We thus conclude that these calix[4]arenes could be applied to research concerning vapor sensing devices operating at room temperature. (C) 2013 Elsevier B.V. All rights reserved.Öğe Humic-makeup approach for simultaneous functionalization of polyacrylonitrile nanofibers during electrospinning process, and dye adsorption study(TAYLOR & FRANCIS INC, 2016) Gezici, Orhan; Guven, Idris; Ozcan, Fatih; Ertul, Seref; Bayrakci, MevlutA useful methodology is represented to functionalize polyacrylonitrile nanofibers by using humic acid as a makeup agent in electrospinning process. Both morphology and surface chemistry of polyacrylonitrile nanofiber mats were understood to be influenced by incorporation of humic acid into the structure. Physicochemical changes were evidenced by Fourier transform infrared spectroscopy, scanning electron microscope, and surface charge measurements. Unlike some anionic dyes (i.e., methyl orange, methyl red, and Congo red), there was an enhancement in crystal violet (a cationic dye) adsorption after incorporation of humic acid. The Langmuir model fitted well to crystal violet data, and monolayer adsorption capacity was calculated as 81.6 mg/g (r(2) = 0.998).Öğe Novel humic acid-bonded magnetite nanoparticles for protein immobilization(ELSEVIER SCIENCE BV, 2014) Bayrakci, Mevlut; Gezici, Orhan; Bas, San Zeki; Ozmen, Mustafa; Maltas, EsraThe present paper is the first report that introduces (i) a useful methodology for chemical immobilization of humic acid (HA) to aminopropyltriethoxysilane-functionalized magnetite iron oxide nanoparticles (APS-MNPs) and (ii) human serum albumin (HSA) binding to the obtained material (HA-APS-MNPs). The newly prepared magnetite nanoparticle was characterized by using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and elemental analysis. Results indicated that surface modification of the bare magnetite nanoparticles (MNPs) with aminopropyltriethoxysilane (APS) and HA was successfully performed. The protein binding studies that were evaluated in batch mode exhibited that HA-APS-MNPs could be efficiently used as a substrate for the binding of HSA from aqueous solutions. Usually, recovery values higher than 90% were found to be feasible by HA-APS-MNPs, while that value was around 2% and 70% in the cases of MNPs and APS-MNPs, respectively. Hence, the capacity of MNPs was found to be significantly improved by immobilization of HA. Furthermore, thermal degradation of HA-APS-MNPs and HSA bonded HA-APS-MNPs was evaluated in terms of the Horowitz-Metzger equation in order to determine kinetic parameters for thermal decomposition. Activation energies calculated for HA-APS-MNPs (20.74 kJ mol(-1)) and HSA bonded HA-APS-MNPs (33.42 kJ mol(-1)) implied chemical immobilization of HA to APS-MNPs, and tight interactions between HA and HA-APS-MNPs. (C) 2014 Elsevier B.V. All rights reserved.Öğe Phase Solubility Studies of Poorly Soluble Drug Molecules by Using O-Phosphorylated Calixarenes as Drug-Solubilizing Agents(AMER CHEMICAL SOC, 2012) Bayrakci, Mevlut; Ertul, Seref; Yilmaz, MustafaThis study is the first report on the solubilizing effect of O-phosphorylated calix[n]arenes that form complexes with neutral molecules such as nifedipine, niclosamide, and furosemide by host-guest complexation. These complexation studies were carried out by using the phase solubility technique. From the obtained results, it was observed that the solubility of guest molecules such as nifedipine, niclosamide, and furosemide was significantly increased in the presence of host molecules tetrakis-O-(diethoxyphosphoryl)-p-tert-butylcalix[4]arene (1), tetrakis-O-(diethoxyphosphoryl)-calix[4]arene (2), bis-O-(diethoxyphosphoryl)-p-tert-butylcalix[4]arene (3), bis-O-(diethoxyphosphoryl)-calix[4]arene (4), and octakis-O-(diethoxyphosphoryl)-p-tert-butylcalix[8]arene (5). The increase in solubility of drugs by the calixarene host 1 to 5 was most probably due to inclusion complexation between drug molecules and cavities of the calixarene skeleton similar to drug-cyclodextrin complexes.Öğe Preparation and gas sensing properties of Langmuir-Blodgett thin films of calix[n]arenes: Investigation of cavity effect(ELSEVIER SCIENCE SA, 2014) Ozmen, Mustafa; Ozbek, Zikriye; Bayrakci, Mevlut; Ertul, Seref; Ersoz, Mustafa; Capan, RifatCharacterization and organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of calix[n]arene (n=4, 6, 8) derivatives are reported in this work. Surface pressure-area isotherm graph shows that very stable monolayers are formed at the water surface. The results indicate that good quality, uniform LB films can be prepared with a transfer ratio of over 0.95. Calix[n]arene LB films have been characterized by contact angle measurements, quartz crystal microbalance (QCM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). LB film of calix[8]arene which has the largest cavity yields a gradient with a mass value of 773 ng per layer according to the QCM results. AFM and SEM images showed a dense surface morphology obtained for all samples. QCM system was used for the measurement of sensor response against chloroform, benzene, toluene and ethanol vapors. These LB film samples yield a response to all vapors with a large, fast, and reproducible due to the adsorption of vapors into the LB film structures. Among them, calix[8]arene LB film has higher sensitivity toward the organic vapors because of a large cavity size. This study can be concluded that the cavity size of calix[n]arene molecule could have an important role in the research area of room temperature vapor sensing devices. (C) 2014 Elsevier B.V. All rights reserved.Öğe Removal of Phosphate Anions from Aqueous Solutions by Using Macrocyclic Receptors-Based Polyether, Lactone and Lactam Derivatives(TAYLOR & FRANCIS INC, 2011) Ertul, Seref; Bayrakci, Mevlut; Yilmaz, MustafaIn this study, the phosphate anions extraction efficiency of a series of receptors-based lactones 1a-d, 2, and 3, polyethers 4 and 5, lactam derivatives 6a-b, 7a-b, and 8a-d towards phosphate anion was evaluated by solvent extraction. It was observed that compounds 7a-b exhibited higher affinity toward phosphate ions than the other receptors. The extraction of phosphate anions by these compounds 7a-b indicates that the partially protonated amino groups play the major role for the formation of hydrogen bonds and electrostatic interactions at low pH. Furthermore, the effect of the polyethylene linkage and cavity of crown moieties on anion extraction was investigated. To evaluate the selectivity of receptors 6a-b and 7a-b, we also examined the retention of phosphate anions in the presence of Cl-, [image omitted], and [image omitted] anions at pH 1.5.Öğe Solubilizing effect of the p-phosphonate calix[n]arenes towards poorly soluble drug molecules such as nifedipine, niclosamide and furosemide(SPRINGER, 2012) Bayrakci, Mevlut; Ertul, Seref; Yilmaz, MustafaThis article reports the solubilization of the practically water insoluble drug molecules such as nifedipine, niclosamide and furosemide by guest:host inclusion complexation with p-phosphonates calix[n]arenes as drug soluble agent. This complexation studies were carried out by using the phase solubility technique. From the obtained results, it was observed that the solubility of drug molecules was significantly increased in the presence of calix[n]arene host molecules. The increase in solubility of drugs by the calix[n]arene was most probably due to inclusion complexation between drug molecules and cavities of the calixarene skeleton similar to drug:cyclodextrin complexes.Öğe Synthesis and application of novel magnetite nanoparticle based azacrown ether for protein recognition(POLYMER SOC KOREA, 2013) Bayrakci, Mevlut; Maltas, Esra; Yigiter, Sengul; Ozmen, MustafaThis article is the first report showing the human serum albumin (HSA) binding studies by using a new magnetite nanoparticle containing azacrown ether moieties via solid-liquid extraction process. The structure of the newly prepared magnetite nanoparticle was clarified by using attenuated total reflectance (ATR) infrared spectroscopy, scanning electron microscopy (SEM), UV-vis and elemental analysis. Analytic results indicated that modification of the surface of the magnetite nanoparticles with azacrown ether derivative was successfully carried out. The protein binding studies exhibited that the modified magnetite nanoparticles could be efficiently used for the binding of the human serum albumin (HSA) in aqueous solutions via non-covalent interaction between crown ether cavity and amino group of the protein.Öğe Synthesis and characterization of Cu(II), Cd(II) and Hg(II) complexes with Schiff bases(ASIAN JOURNAL OF CHEMISTRY, 2007) Demir, Ibrahim; Akkaya, Mustafa; Bayrakci, Mevlut; Pekacar, A. IhsanTwo new Schiff base have been synthesized by the condensation 1,2-diaminoethane (HL) and 1,4-diamino butane (HL) with isonitroso-p-chloroasetafenon. The complexes of copper(II), cadmium(II) and mercury(II) with HL and HL were prepared. The ligands and their metal complexes were characterized by spectroscopic techniques.Öğe Synthesis and Spectroscopic Studies of Novel Rhodanine Azo Dyes: An Excellent Selective Chemosensor for Naked-eye Detecting of Cu2+ Ion(SLOVENSKO KEMIJSKO DRUSTVO, 2012) Ceylan, Abdullah; Bas, Salih Zeki; Bayrakci, Mevlut; Ertul, Seref; Uysal, AhmetThis study is first report on the synthesis of novel rhodanine based azo dyes and their fluorogenic and chromogenic sensing behaviors with metal ions (Li+, Na+, K+, Rb+, Pb2+, Ni2+, Zn2+, Cu2+) by using UV-vis and fluorescence spectroscopy techniques. The results of spectroscopic experiments for rhodanine based azo dye 1a exhibited excellent selectivity for Cu2+ over the other metal ions. Furthermore, anti-bacterial studies of rhodanine azo dyes were performed towards some selected bacteria via microbroth dilution method. Obtained results showed that rhodanine ionophore 1a showed strong antibacterial activity against S. aureus.Öğe Synthesis and trivalent lanthanide ion complexation studies of new macrocyclic receptors based lactam ionophores(SPRINGER, 2014) Gullu, Fadime; Bayrakci, Mevlut; Kursunlu, Ahmed Nuri; Yigiter, Sengul; Ertul, SerefThis study is the first report on the design, synthesis and photophysical properties of three new macrocyclic receptors based receptors containing two amide bridges. Their binding properties towards trivalent lanthanide ions such as La3+, Gd3+, Tb3+, Dy3+, Er3+ and Yb3+ were investigated by using spectroscopic techniques. With respect to emission intensity changes upon trivalent lanthanide ion complexation, macrocyclic receptors based lactam ionophores showed higher selectivity towards Yb3+ and/or Er3+ ion over other ions. Presence of proximal two amide groups in macrocyclic lactam receptors having different cavity size were observed to play an important role in exhibiting its lanthanide ion binding.Öğe Synthesis of new water-soluble phosphonate calixazacrowns and their use as drug solubilizing agents(SPRINGER, 2012) Bayrakci, Mevlut; Ertul, Seref; Yilmaz, MustafaThis study presents the selective chloromethylation of calix[4](aza)crown ethers 2a-c, using chloromethyl n-octyl ether and SnCl4 in chloroform at room temperature in good yield for the first time. Chloromethylated products 2a-c are used as key intermediates to synthesize new water-soluble p-phosphonato calix[4](aza)crown ethers 5a-c. Liquid-liquid phase extraction and phase solubility studies with poor water soluble drug molecules such as nifedipine, niclosamide and furosemide are performed to evaluate their binding properties. Among the studied drugs, furosemide was the most effectively dissolved drug by p-phosphonato calix[4](aza)crown ethers 5a-c in water.Öğe Synthesis of tetra-substituted calix[4]arene ionophores and their recognition studies toward toxic arsenate anions(PERGAMON-ELSEVIER SCIENCE LTD, 2013) Bayrakci, Mevlut; Yigiter, SengulThe article displays the synthesis of a family of novel tetra-substituted calix[4]arene ionophores bearing furyl, phenyl, and pyridyl units in the cone conformation. In the synthesis, the lower rims of calix[4]arene scaffold were modified in order to establish the influence of the molecular structure of calixarene on recognition of toxic anions as arsenate by liquid-liquid extraction process. In addition, the effects of solvent, solution conditions (mainly pH), and counter ions (Cl-, NO3-, and SO42-) on the extraction abilities of the ionophores were studied. From the liquid-liquid phase extraction studies, it was observed that the structures of the tetra-substituted calix[4]arenes influenced the extraction percentage of selected toxic anion. Also, thermodynamic parameters, such as the free energy (Delta G degrees) and enthalpy (Delta H degrees) indicated an exothermic nature of extraction and a spontaneous and favorable process. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Synthesis, Characterization, and Spectroscopic Properties of a Symmetrical Schiff Base Ligand and its Bimetallic Complexes(TAYLOR & FRANCIS INC, 2011) Bayrakci, Mevlut; Ertul, Seref; Bas, Salih Zeki; Demir, IbrahimThis article presents the synthesis of new Schiff base ligand and preparation of its transition metal complexes with copper (II), nickel (II), zinc (II), and cobalt (II). Furthermore, absorption and fluorescence properties of ligand and its metal complexes are investigated. The effect of the solvents, such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol, methanol, 1,4-dioxane on fluorescence properties of metal complexes, are performed and obtained results are summarized. All of the structures were characterized by using spectroscopic techniques.Öğe Transportation of Poorly Soluble Drug Molecules from the Organic Phase to the Aqueous Phase by Using Phosphorylated Calixarenes(AMER CHEMICAL SOC, 2011) Bayrakci, Mevlut; Ertul, Seref; Yilmaz, MustafaThis study is the first report on the extraction of poorly soluble drug molecules such as nifedipine, niclosamide, and furosemide from the organic phase to the aqueous phase by water-soluble p-phosphonate calix[n]arene receptors via a liquid-liquid phase extraction process. These water-soluble calixarene derivatives were easily obtained from the reaction between their corresponding chloromethylated derivatives and trimethyl phosphite. From the liquid-liquid phase extraction studies, it was observed that the size of the p-phosphonate calix[n]arenes changed the extraction percentage of selected drug molecules.
