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Öğe Chemical composition of essential oils from Crocus ancyrensis (Herbert) Maw Spreading In Çorum (Türkiye) Region(Pamukkale University, 2023) Doğan, Hacer; Kayır, Ömer; Alver, Erol; Bilici, İbrahimAbstract: Crocus ancyrensis is a yellow-flowered Crocus species and is in the same family and genus with saffron. Although various studies have been conducted on the antioxidant capacity and essential oil content characterization of saffron (Crocus sativus), there is no literature information about the C. ancyrensis plant, which is known as Crocus among the people. The members of Crocus family contain many valuable components including antioxidants, phenolic compounds and essential oils. The essential oils obtained from this family is a complex mixture of more than 30 components, which are primarily terpenes and their derivatives. These mixtures are used in paint, medicine, and food applications especially in the cosmetics sector. In the study, the essential oils of the Crocus ancyrensis plant were extracted with the clevenger system and characterized by GC-MS analyses. As a result, 23 volatile components were identified. 2-Hexenal, 1-ethylbutyl Hydroperoxide, 2-nitro-Hexane, ?-Isophorone, ?-Isophorone, 2-Caren-10-al and Eugenol are found as the main components of Crocus ancyrensis plant extract. Due to the antioxidant, antimicrobial, antifungal, anticancer and odorant properties of some of the identified components, C. ancyrensis can be used as a medicinal aromatic plant in various fields, especially in the cosmetics and perfume industry.Öğe Chitosan based metal-chelated copolymer nanoparticles: Laccase immobilization and phenol degradation studies(Elsevier Ltd, 2017) Alver, Erol; Metin, Ayşegül ÜlküImmobilization improves the stability and reusability of enzymes. In this study, laccase, which is a green biocatalyst, was immobilized onto Cu (II)-chelated chitosan nanoparticles via adsorption and successfully applied to remove phenol from aqueous solution. Cu (II)-chelated chitosan-graft-poly (glycidyl methacrylate) nanoparticles were prepared using poly (ethylene imine), PEI, which is employed as both a spacer arm and metal chelator and used to immobilize laccase by coordination. Properties of chitosan based nanoparticles were characterized using FTIR, TGA, SEM and zeta-sizer analysis. The maximum laccase loading capacity of Cu (II)-chelated chitosan based nanoparticles (CHT-PGMA-PEI-Cu (II) NPs) was calculated as 65.75 ± 2.51 mg/g. This immobilized system exhibited broad pH and temperature profiles, and better stability and reusability than free enzyme; after eight cycles of continuous use, the activity of the immobilized enzyme remained above 50 ± 0.62%. The Km and Vmax values of free and immobilized laccase were 0.055 mM, 0.070 mM, and 0.19 U/mg, 0.14 U/mg, respectively. The catalytic efficiencies (Vmax/KM) of the free and immobilized laccase were 3.45 and 2.0, respectively. Feasibility of the laccase immobilized system in the removal of phenol was investigated in a batch system. The results showed that the CHT-PGMA-PEI-Cu (II) NPs have great potential for industrial applications. More than 96% of phenol was removed with laccase immobilized metal chelated NPs in the presence of mediator, ABTS, indicating that the metal-chelated chitosan based NPs is a promising support for both laccase immobilization and further applications in the removal of phenolic compounds. © 2017 Elsevier LtdÖğe Efficient removal of acidic dye using low-cost biocomposite beads(2013) Metin, Ayşegül Ülkü; Çiftçi, Hakan; Alver, ErolThe objective of this study is to prepare and characterize chitosan/zeolite biocomposite beads and utilize them as adsorbent for removal of anionic dye, Acid Black 194 (AB194). Characterization studies of biocomposite beads were carried out by using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDX). The ability of chitosan/zeolite biocomposite beads as an adsorbent for the removal AB194 from an aqueous solution has been investigated under various experimental conditions. Maximum adsorption capacity of biocomposite beads was calculated as 2140 mg/g. The increase in temperature resulted in a higher AB194 loading per unit weight of biocomposite beads. As an additional factor affecting the adsorption behavior of AB194, the effect of ionic strength was investigated, and the adsorption capacity of biocomposite beads significantly decreased. Four isotherm models were employed to elucidate the adsorption process. The most appropriate model for the equilibrium process was the Freundlich. The kinetic studies indicated that the adsorption of AB194 followed the pseudo-second-order kinetics. Thermodynamic calculations showed that the adsorption of reactive dye was a spontaneous and endothermic process. The obtained results indicate that chitosan/zeolite biocomposite beads as an adsorbent are promising for dye removal from wastewater. © 2013 American Chemical Society.Öğe Electrochemical copper (II) sensor based on chitosan covered gold nanoparticles(Kluwer Academic Publishers, 2014) Çiftçi, Hakan; Tamer, Uğur; Metin, Ayşegül Ülkü; Alver, Erol; Kizir, NevinThis study outlines a new sensing platform based on glassy carbon electrodes modified by gold nanoparticles (AuNPs) for the determination of heavy metal. A glassy carbon electrode was modified by chitosan stabilized AuNPs. AuNPs were prepared by reducing gold salt with a polysaccharide chitosan. Here, chitosan acted as a reducing/stabilizing agent. The AuNPs were characterized with UV-Visible absorption spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Chitosan covered AuNPs were immobilized on the glassy carbon electrode for the determination of Cu (II) in aqueous solutions. The electrochemical determination of Cu (II) ions was performed using the differential pulse voltammetry technique. Some parameters for Cu (II) determination, such as pH, preconcentration time and electrolysis potential of Cu (II), were optimized. The detection limit was calculated as 5 × 10-9 mol L-1 by means of the 3:1 current-to-noise ratio. The interference of Cr(III), Fe(II), Ni(II), Pb(II), Mg(II), Zn(II), Ba(II) ions was investigated and showed a negligible effect on the electrode response. Recovery studies were carried out using tap water. © 2014 Springer Science+Business Media Dordrecht.Öğe Fabrication and characterization of gold-nanoparticles/chitosan film: A scaffold for L929-fibroblasts(2013) Türk, Mustafa; Tamer, Uğur; Alver, Erol; Çiftçi, Hakan; Metin, Ayşegül Ülkü; Karahan, SiyamiThe objective of the present study was to fabricate a gold nanoparticle crosslinked chitosan (Ch/AuNPs) composite film simple and to evaluate its use as a carrier matrix for L929- fibroblasts. L929- fibroblasts were seeded either onto Ch or Ch/AuNPs scaffolds. The Ch/AuNPs scaffold exhibited a higher cell proliferation and growth rate. The cytotoxicity test determined trypan blue staining indicated that Ch scaffolds devoid of AuNPs expressed almost no toxicity while the Ch/AuNPs composite scaffolds expressed a very limited toxicity only at higher doses. The Ch/AuNPs scaffold promotes cell attachment, growth and proliferation with almost no cytotoxicity. © 2013 Informa Healthcare USA, Inc.Öğe Fibrous polymer-grafted chitosan/clay composite beads as a carrier for immobilization of papain and its usability for mercury elimination(Springer Verlag, 2016) Metin, Ayşegül Ülkü; Alver, ErolPapain, which is an industrially important enzyme, has been immobilized on fibrous polymer-modified composite beads, namely poly(methacrylic acid)-grafted chitosan/clay. Characterization studies have been done using FTIR and SEM analysis. Operating parameters such as pH and initial concentration of papain have been varied to obtain the finest papain immobilized polymer-modified composite beads. The immobilization capacity of composite beads has been determined as 34.47 ± 1.18 (n = 3) mg/g. The proteolytic activity of immobilized papain was operated using bovine serum albumin (BSA) and maximum velocity (Vmax) and Michaelis–Menten constant (Km) values of the free and immobilized enzymes were determined using Lineweaver–Burk and Eadie–Hofstee equations. Usability of papain immobilized polymer-modified composite beads as adsorbents for the elimination of mercury was investigated. The maximum removal capacity of PIPMC beads has been found to be 4.88 ± 0.21 mg Hg/g when the initial metal concentration and weight of polymer-modified composite beads were 50 mg/L and 0.04 g at pH 7, respectively. Mercury removal performance of the papain immobilized polymer-modified composite beads was investigated in conjunction with Cu (II), Zn (II) and Cd (II) ions. The mercury adsorption capacity of papain immobilized polymer-modified composite beads was a slight reduction from 1.15 to 0.89 mg/g in presence of multiple metal salts. © 2016, Springer-Verlag Berlin Heidelberg.Öğe INVESTIGATION THE PERFORMANCE OF CHITOSAN BASED COMPOSITE BEADS ON REMOVAL OF ANIONIC DYE (AY-204)(Yildiz Technical Univ, 2015) Alver, Erol; Metin, Aysegul Ulku; Ciftci, HakanThe aim of this study is to investigate the utility of chitosan/zeolite composite beads as adsorbent for removal of anionic textile dye, Acid Yellow 204. It was investigated the influence of parameters such as pH, time, zeolite content in the composite structure, electrolyte concentration, dye concentration and sorbent dosage on the efficiency of dye removal. It was determined that the adsorption capacity increased significantly with decreasing pH Langmuir and Freundlich isotherm models were applied to the experimental data to determine the adsorption mechanism. and The Langmuir isotherm model was determined to be more consistent with the experimental data. It was observed that the reaction kinetics is suitable for the pseudo-second-order.Öğe İyonotropik jelleşme yöntemi ile hazırlanan kitosan nanopartiküllerde hapsetme (enkapsülasyon) ile anyonik boyaların uzaklaştırılma ve hapsedilen boyanın nanopartikülde depolanma etkinliğinin araştırılması(Gümüşhane Üniversitesi, 2018) Alver, Erolİyonotropik etkileşim ile kitosan nanopartiküller anyonik boya (Fast Green FCF) içeren çözelti ortamında hazırlandı. Boya hapsedilmiş kitosan nanopartiküller SEM ve Zeta-sizer ile karekterize edildi. Kitosan nanopartikül içerisine hapsedilen boyanın sulu ortamdan uzaklaşmasında etkili parametreler ve nanopartiküller içerisinde hapsolma kararlılığı farklı pH çözeltilerinde araştırıldı. Fast Green FCF'nin sulu ortamdan % 90'nın üzerinde bir etkinlikle uzaklaştırılması sağlandı. Kitosan nanopartikül içerisine hapsedilen boya miktarı ise 1140 mg/g kitosan olarak belirlendiÖğe Methylene blue adsorption on magnetic alginate/rice husk bio-composite(Elsevier, 2020) Alver, Erol; Metin, Aysegul Ulku; Brouers, FrancoisMagnetic alginate/rice husk (m-ALG/RH) bio-composite beads prepared with ionotropic gelation method and used for methylene blue (MB) removal. Structural analysis of magnetic alginate/rice husk composite beads was performed using FTIR, SEM-EDS and TGA techniques. The accomplishment of magnetic alginate/rice husk composite beads as an adsorbent for the removal methylene blue was investigated from aqueous solution. Maximum experimental adsorption capacity of the bio-composite beads was calculated as 274.9 mg/g. The various process parameters such as pH, temperature and initial MB concentration optimized. It was determined that pH no significant effect on dye removal efficiency of beads while temperature and ionic strength caused a decrease on removal efficiency. The various isotherm models were applied for determine the adsorption mechanism and Freundlich isotherm model is more compatible with the experimental data. The kinetic studies showed that the adsorption of methylene blue can be well described by the fractal Brouers-Sotolongo kinetic model. The thermodynamic calculations indicated that methylene blue adsorption was a spontaneous and exothermic nature. The results showed that the magnetic alginate/rice husk bio-composite as low-cost and eco-friendly adsorbent can be effectively used for cationic dye removal steps in the environmental engineering applications. (C) 2020 Elsevier B.V. All rights reserved.Öğe Non-enzymatic sensing of glucose using a glassy carbon electrode modified with gold nanoparticles coated with polyethyleneimine and 3-aminophenylboronic acid(Springer-Verlag Wien, 2016) Çiftçi, Hakan; Alver, Erol; Çelik, Filiz; Metin, Ayşegül Ülkü; Tamer, UğurA non-enzymatic electrochemical method was developed for sensing glucose by using a glassy carbon electrode modified with 3-aminophenylboronic acid (APBA) immobilized on polyethyleneimine (PEI)-coated gold nanoparticles. The modified electrode was characterized by TEM, zeta potential measurements and UV-Vis spectroscopy. Its analytical performance was evaluated in pH 9 solution by potentiometry. The respective calibration plot, established at open circuit potential (vs. Ag/AgCl) covers the 0.5–50 mM glucose concentration range, which makes it suitable for blood glucose assays. The detection limit is 0.025 mM, and no interference is caused by ascorbic acid, dopamine, and uric acid. Effects of other carbohydrates such as fructose, galactose and saccharose were also investigated. The electrode was used to determine glucose in human serum samples and the results agreed well with those obtained with commercial amperometric enzymatic sensors. [Figure not available: see fulltext.] © 2016, Springer-Verlag Wien.Öğe One step effective removal of Congo Red in chitosan nanoparticles by encapsulation(Elsevier B.V., 2017) Alver, Erol; Bulut, Mehmet; Metin, Ayşegül Ülkü; Çiftçi, HakanChitosan nanoparticles (CNPs) were prepared with ionotropic gelation between chitosan and tripolyphosphate for the removal of Congo Red. The production of chitosan nanoparticles and the dye removal process was carried out in one-step. The removal efficiency of Congo Red by encapsulation within chitosan from the aqueous solution and its storage stability are examined at different pH values. The influence of some parameters such as the initial dye concentration, pH value of the dye solution, electrolyte concentration, tripolyphosphate concentration, mixing time and speed on the encapsulation is examined. Congo Red removal efficiency and encapsulation capacity of chitosan nanoparticles were determined as above 98% and 5107 mg Congo Red/g chitosan, respectively. © 2016 Elsevier B.V.Öğe Quantification of Phenolic Component by LC-HESI-MS/MS and Evaluation of Antioxidant Activities of Crocus Ancyrensis (Ankara cigdemi) Extracts Obtained with Different Solvents(WILEY-V C H VERLAG GMBH, 2023) Kayır, Ömer; Doğan, Hacer; Alver, Erol; Bilici, İbrahimIn this study, Crocus ancyrensis was extracted from different parts of the plants with various solvents and their antioxidant activities and phenolic contents were investigated in detail for the first time. The highest amount of total phenolic substance in all parts of the plant was determined in the stigmaless flower. In the DPPH and FRAP methods, the highest antioxidant activity was obtained from the water extraction from the plant. Rutin is the highest detected by LC MS/MS. Stigmaless flower extract in all solvents is attributed to the component that contributes the most to antioxidant capacity. p-hydroxy benzoic acid was detected as the highest phenolic component after rutin. When the antioxidant activity results were examined, it was determined that the highest activity was in the water extract. As a result, it is evaluated that rutin and p-hydroxybenzoic acid in the plant contribute to the antioxidant capacity.Öğe Synthesis and Characterization of Chitosan/Polyvinylpyrrolidone/Zeolite Composite by Solution Blending Method(Springer New York LLC, 2014) Alver, Erol; Metin, Ayşegül Ülkü; Çiftçi, HakanPolymer/clay composites have been studied for several decades; in the study, polymer/zeolite composite beads have been prepared by a simple solution blending method using chitosan, polyvinylpyrrolidone and zeolite particles as organic and inorganic components, respectively. Different techniques, such as SEM, FTIR spectroscopy, and thermogravimetry have been used to characterize the composite beads. Chitosan/polyvinylpyrrolidone/zeolite (CH/PVP/Z) beads are expected to have a potential as an adsorbent for wastewater treatment. To investigate its applicability, copper (II) was selected as a model compound. The results showed that the composite beads had effective loading capacity and it is a promising adsorbent for heavy metal removal. © 2014, Springer Science+Business Media New York.
