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Öğe Active carbon/graphene hydrogel nanocomposites as a symmetric device for supercapacitors(Taylor & Francis Inc, 2016) Ates, Murat; Cinar, Damla; Caliskan, Sinan; Gecgel, Unal; Uner, Osman; Bayrak, Yuksel; Candan, IdrisActivated carbons (ACs) are successfully synthesized from Elaeagnus grain by a simple chemical synthesis methodology and demonstrated as novel, suitable supercapacitor electrode materials for graphene hydrogel (GH)/AC nanocomposites. GH/AC nanocomposites are synthesized via hydrothermal process at temperature of 180 degrees C. The low-temperature thermal exfoliation approach is convenient for mass production of graphene hydrogel (GH) at low cost and it can be used as electrode material for energy storage applications. The GH/AC nanocomposites exhibit better electrochemical performances than the pure GH. Electrochemical performance of the electrodes is studied by cyclic voltammetry, and galvanostatic charge-discharge measurements in 1.0 M H2SO4 solution. A remarkable specific capacitance of 602.36 Fg(1) (based on GH/AC nanocomposites for 0.4 g AC) is obtained at a scan rate of 1 mVs(1) in 1 M H2SO4 solution and 155.78 Fg(1) for GH. The specific capacitance was increased 3.87 times for GH/AC compared to GH electrodes. Moreover, the GH/AC nanocomposites for 0.2 g AC present excellent long cycle life with 99.8% specific capacitance retained after 1000 charge/discharge processes. Herein, ACs prepared from Elaeagnus grain are synthesized GH and AC supercapacitor device for high-performance electrical energy storage devices as a promising substitute to conventional electrode materials for EDLCs.Öğe Adsorption of Methylene Blue by an Efficient Activated Carbon Prepared from Citrullus lanatus Rind: Kinetic, Isotherm, Thermodynamic, and Mechanism Analysis(Springer International Publishing Ag, 2016) Uner, Osman; Gecgel, Unal; Bayrak, YukselBy using the activated carbon obtained from Citrullus lanatus rind by zinc chloride activation, methylene blue (MB) removal from aqueous solutions was studied, and the adsorption mechanism was solved through Weber-Morris intraparticle diffusion model, Bangham model, Boyd model, Fourier transform infrared spectra, and scanning electron microscopy. The effects of adsorption parameters (adsorbent concentration, temperature, initial dye concentration, and pH) were investigated. The equilibrium data of MB adsorption were described by applying the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The obtained results from adsorption isotherms indicated that Langmuir model is the best-fitted model with the maximum adsorption capacities of 231.48, 243.90, 244.50, and 259.74 mg/g at 25, 35, 45, and 55 degrees C, respectively. The analysis of the kinetic data by pseudo-first-order, pseudo-second-order, and Elovich models displayed that MB adsorption followed pseudo-second-order model. Also, the date obtained from intraparticle diffusion model, Bangham model, and Boyd model presented that intraparticle diffusion, pore diffusion, and film diffusion played significant role in MB adsorption. The thermodynamic studies demonstrated that MB adsorption onto the activated carbon obtained from C. lanatus rind was physical, spontaneous, feasible, and endothermic. Thus, the activated carbon prepared from C. lanatus rind has been an efficient adsorbent for MB removal from an aqueous solution.Öğe Adsorptive Removal of Rhodamine B with Activated Carbon Obtained from Okra Wastes(Taylor & Francis Inc, 2017) Uner, Osman; Gecgel, UEnal; Kolancilar, Hakan; Bayrak, YukselThis study aimed at preparing and optimizing an activated carbon (OAC) obtained from dry okra wastes by chemical activation with zinc chloride. Also, Rhodamine B removal performance from aqueous solution was analyzed by using this optimized activated carbon. The characterization of the resultant activated carbon, with a high surface area of 1044m(2)/g, was carried out using thermogravimetric analysis, Brunauer-Emmett-Teller model, t-plot, N-2 adsorption/desorption isotherms, density functional theory, elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and the point of zero charge. Furthermore, the effects of operating conditions (contact time, initial concentration, adsorbent dosage, temperature, and pH) on Rhodamine B adsorption onto OAC were investigated. Langmuir model was determined to be the best adsorption process, and the maximum adsorption capacity was calculated to be 321.50mg/g at 25 degrees C. Also, the intraparticle diffusion and boundary layer diffusion were involved in RhB adsorption onto OAC. Moreover, OAC adsorption curves of Rhodamine B followed pseudo second-order model. At 25 degrees C, Gibbs free energy, enthalpy, and entropy obtained from thermodynamic studies were determined to be -27.87kJ/mol, 13.03kJ/mol, and 0.15kJ/mol K, respectively. These thermodynamic values revealed that Rhodamine B adsorption onto OAC was feasible, endothermic, physical, and spontaneous.Öğe Antioxidant Activity of Rumex conglomeratus P. Collected from Turkey(Asian Journal Of Chemistry, 2013) Kilic, Ismail; Yesiloglu, Yesim; Bayrak, Yuksel; Gulen, Sezer; Bakkal, TahirPlants contain a wide variety of free radical scavenging molecules, such as flavonoids, anthocyanins, carotenoids, dietary glutathionine, vitamins and endogenous metabolites and such natural products are rich in antioxidant activities. Rumex conglomeratus P. is widely spread in Turkey and used as an anticonstipate in traditional medicine. In this study, the antioxidant activity of water extract of R. conglomeratus was evaluated using different antioxidant tests. In addition, carotenoid content and proline level of R. conglomeratus were also determined. The results were compared with natural and synthetic antioxidants. The results showed that R. conglomeratus contained naturally occuring antioxidant components and possessed antioxidant activity which may be attributed to its radical scavenging and metal chelating activities. It was concluded that R. conglomeratus might be a potential source of antioxidants.Öğe Application of a Bio-waste Einkorn (Triticum monococcum L.) Husks Adsorbent for Removal of Metanil Yellow and Methylene Blue from Aqueous Media with Equilibrium, Kinetic, and Thermodynamic Studies(Springer Int Publ Ag, 2024) Kocabiyik, Baris; Bayrak, YukselIn this study, the activated carbon (TmAC) with a high surface area and appropriate pore distribution was produced from einkorn (Triticum monococcum L.) husks by using ZnCl2 with chemical activation method. The efficiency of the obtained activated carbon on the adsorption of anionic (metanil yellow) and cationic (methylene blue) dyestuffs from aqueous solutions was investigated in more detail. In addition, the surface characterization of activated carbon was performed using thermogravimetric analysis-differential thermal analysis (TGA-DTA), elemental analysis, scanning electron microscopy (SEM) images, Brunauer-Emmett-Teller (BET) specific surface areas, N-2 adsorption-desorption isotherms, pore volumes, pore size distributions, and Fourier-transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) spectra. The highest surface area of activated carbon was measured as 1321 m(2) g(-1) at the carbonization temperature of 500 degrees C by using impregnation ratio (w/w = 2.0). Batch method was used in adsorption experiments. The parameters affecting the adsorption studies such as adsorbent concentration, initial dye concentration, adsorption time, temperature, and pH were investigated. The adsorption mechanisms of metanil yellow (MY) and methylene blue (MB) on activated carbon were explained by using isotherms (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich), kinetic models (pseudo-first-order and pseudo-second-order), and the thermodynamic parameters (Gibbs free energy, enthalpy, and entropy).Öğe Binary nanocomposites of reduced graphene oxide and cobalt (II, III) oxide for supercapacitor devices(Taylor & Francis Ltd, 2022) Ates, Murat; Yoruk, Ozan; Bayrak, YukselIn this study, a simple and one-step cost-effective preparation of rGO/Co3O4 nanocomposite was given out in different monomer concentrations of [rGO]o/[Co3O4]o= 1:1; 1:2; 1:5 and 1:10. The electroactive materials were characterized by many techniques, such as FTIR-ATR, XPS, TGA-DTA, Raman, BET surface analysis, GCD, SEM-EDX, XRD, TEM, CV, and EIS analysis. A symmetric supercapacitor applying rGO/Co3O4 nanocomposite as positive and negative electrodes was taken in the potential window between 0.0 and 0.8 V as the highest specific capacitance of Csp= 115.35 Fxg-1 at 2 mVxs-1 for [rGO]o/[Co3O4]o= 1:2. Furthermore, the highest energy (E) and power densities (P) were obtained as E= 20.16 Whxkg-1 at 40 mA and P= 26.140 kWxkg-1 at 10 mA for [rGO]o/[Co3O4]o= 1:2 by GCD method, respectively. As a result, rGO/Co3O4 nanocomposite at different monomer concentrations showed an easy synthesis, a sustainable approach, and a high electrochemical performances for energy storage devices.Öğe Design and assembly of supercapacitor based on reduced graphene oxide/TiO2/polyaniline ternary nanocomposite and its application in electrical circuit(Springer, 2022) Yoruk, Ozan; Bayrak, Yuksel; Ates, MuratSupercapacitor devices are used as energy storage technology for electrical circuits. Graphene, metal oxide, and conducting polymers are used as electroactive materials to enhance energy, power density, and cycle life. The present study uses TiO2 and rGO materials, which are added to polyaniline (PANI). The nanocomposite structure can be observed using different initial feed ratios of rGO, TiO2, and aniline monomer as [rGO](o)/[TiO2](o)/[ANI](o) =1:5:1, 1:5:2, 1:5:3, 1:5:4, and 1:5:5. Fourier transform infrared-attenuation-transmission reflectance, scanning electron microscopy-energy-dispersive X-ray analysis, Brunauer-Emmett-Teller surface area, thermal-gravimetric analysis (TGA-DTA), X-ray diffraction (XRD), Raman spectroscopy, X-ray photon spectroscopy, and transmission electron microscopy analysis are conducted. Electrochemical performances of a ternary nanocomposite material are carried out by cyclic voltammetry, galvanostatic charge-discharge measurements, and electrochemical impedance spectroscopy (EIS). According to results, rGO/TiO2/PANI nanocomposite shows much better performance than its individual components in terms of specific capacitance, energy density, power density, and cycle life. The highest specific capacitance is obtained as C-sp = 692.87 F/g at 2 mV/s for [rGO](o)/[TiO2](o)/[ANI](o) =1:5:4. A new real circuit model of LRS (CR1)(QR(2)) is adopted to our device, which supplies enough energy to the light LED lamp (1.8 V) for 3 min. As a result, rGO/TiO2/PANI nanocomposite may be used as a promote candidate for energy storage systems. [GRAPHICS] .Öğe The effect of carbonization temperature, carbonization time and impregnation ratio on the properties of activated carbon produced from Arundo donax(ELSEVIER SCIENCE BV, 2018) Uner, Osman; Bayrak, YukselActivated carbons from Arundo donax were obtained by varying impregnation ratio, carbonization time, and carbonization temperature via chemical activation method. By operating impregnation ratio as 1.5 and carbonization temperature as 400 degrees C, the activated carbons with the highest surface areas were produced. Under this operating condition, the surface areas were measured to be 1784, 1781, and 1785 m(2)/g when the carbonization times were 60, 90, and 120 min, respectively. N, adsorption-desorption isotherms are generally Type I and Type IV isotherm mixtures, but when sufficient thermal energy at carbonization process is given and the chemical activation ratio is increased, N-2 adsorption-desorption isotherms are more likely to resemble Type IV isotherms. Also, H4 type hysteresis in the N-2 adsorption-desorption isotherms proves that activated carbons have micromesopore structures, and the pore shapes are usually cylindrical. Moreover, the resultant activated carbons were characterized by using pore size distributions, elemental analysis, SEM and FTIR.Öğe Investigation on the Antioxidant Activity of Roots and Stem of Colchicum turcicum L.(Asian Journal Of Chemistry, 2014) Kilic, Ismail; Yesiloglu, Yesim; Bayrak, YukselWater and acetone extracts from Colchicum turcicum L. were investigated for their antioxidant and radical scavenging activities in four different assays, namely, total antioxidant activity, 1,1-dipenyl-2-picryl-hydrazyl (DPPH) free radical scavenging, hydrogen peroxide scavenging and ferrous chelating activities. Antioxidant activity, ferrous chelating and hydrogen peroxide scavenging activities of C. turcicum extracts showed dose dependence and increased with concentration of C. turcicum extract. At the same concentration (100 mu g/mL), water extract of C. turcicum (WECT) and acetone extract of C. turcicum (AECT) showed 53 and 48 % inhibition of lipid peroxidation of linoleic acid emulsion, respectively. On the other hand, butylated hydroxyanisole, butylated hydroxytoluene and ascorbic acid indicated inhibitions of 77, 71 and 59 % on the peroxidation of linoleic acid emulsion, respectively, at 50 mu g/mL. Also, the total phenolic content in both water extract of C. turcicum and acetone extract of C. turcicum were determined as catechol equivalents. The total phenolics content of water and acetone extracts were determined by the Folin-Ciocalteu procedure and 0.454 and 2.172 mg catechol equivalent of phenols was detected in 1 g water extract of C. turcicum and acetone extract of C. turcicum.Öğe Kinetic and Thermodynamics of Remazol Brilliant Blue R Adsorption(Asian Journal Of Chemistry, 2013) Bayrak, Yuksel; Uzgor, ResmiyeOrange peel, an agricultural solid waste abundantly available in Turkey, was utilized as a precursor for preparation of activated carbon via sulphuric acid chemical activation. The orange peel activated carbon (OPAC) is used for the removal of remazol brilliant blue R from aqueous solution. Research concerning the effects of pH, adsorbent dose, initial dye concentration and temperature are presented and discussed. Kinetic and thermodynamic parameters of adsorption were calculated.Öğe Kinetics and Thermodynamics of Cr(VI), Cu(II), and Ni(II) Adsorption on Activated Carbon Prepared from Rice Hulls(Taylor & Francis Inc, 2013) Bayrak, Yuksel; Topallar, Harika; Karagoz, Buse; Kilic, IsmailFirst, activated carbon was prepared by various ammonium compounds such as NH4NO3, NH4Cl, NH4Br, NH4I, NH4HCO3, and (NH4)(2)HPO4. The pore properties such as surface areas, pore volumes and pore sizes of them were compared under same activation conditions (600 degrees C, 5g of rice hull, 20g of ammonium compound, within a half-hour activation time). The highest surface area by Brunauer-Emmett-Teller (BET) method was obtained as 456.7667m(2)g(-1) by ammonium nitrate compared to other ammonium compounds, and then the kinetics and thermodynamics of Cr(VI), Cu(II), and Ni(II) ions removal from aqueous solutions on this activated carbon were studied. The adsorption data was found to follow second order kinetic model to explan the kinetics of Cr(VI), Cu(II), and Ni(II) ions adsorption, and rate constants were evaluated with the help of this kinetic model. Activation energy and other activation thermodynamic parameters (S, H, and G) were determined by means of the rate constants at different temperatures. Equilibrium data were fitted to the Langmuir and Freundlich adsorption isotherms. Freundlich isotherm best fits the experimental results. Thermodynamic parameters such as K-C, G, H, and S were also calculated. The positive value of S and negative values of G showed the spontaneous of this adsorption system, while the positive value of H pointed out this is an endothermic process.Öğe Preparation and characterization of mesoporous activated carbons from waste watermelon rind by using the chemical activation method with zinc chloride(Elsevier, 2019) Uner, Osman; Gecgel, Unal; Bayrak, YukselWaste watermelon rind was analyzed as a precursor for preparing activated carbons by using a one-step chemical activation process by zinc chloride. The effects of activation parameters, i.e., carbonization temperature, impregnation ratio, and impregnation time on the properties of the final products were tested in detail. The resultant activated carbons were characterized using elemental analysis, the Brunauer-Emmet-Teller method, pore property analysis, N-2 adsorption/ desorption isotherms, Fourier transform infrared spectroscopy, the point of zero charge, Boehm titration method and scanning electron microscopy. The maximal Brunauer-Emmett-Teller surface area of the resultant activated carbon, produced by using the impregnation (ZnCl2/dried watermelon rind) ratio of 2/1 at the carbonization temperature of 700 degrees C with the residence time of 60 min, was 1156 m(2)/g. Upon using the impregnation ratio of 3/1 at the carbonization temperature of 600 degrees C with the residence time of 60 min, the maximal total pore volume, which also contains the highest mesopore volume, was 1.41 cm(3)/g. (C) 2015 The Authors. Published by Elsevier B.V. on behalf of King Saud University.Öğe Preparation of Rice Hull-Based Activated Carbon with Ammonium Nitrate(Asian Journal Of Chemistry, 2013) Kilic, Ismail; Bayrak, Yuksel; Topallar, Harika; Karagoz, BuseThe present study deals with the preparation of rice hull-based activated carbon with ammonium nitrate. The obtained carbon was activated at temperatures between 400 and 900 degrees C. The rice hull-activated carbon presented a BET surface area of 456.77 m(2) g(-1) and a pore volume of 0.2406 cm(3) g(-1) at 600 degrees C. The adsorption and desorption average pore widths by BET method were found as 2.727 and 2.725 nm, respectively, whereas the Barret-Joyner-Halenda (BJH) adsorption and desorption average pore widths were 4.015 and 4.446 nm, respectively. Thus, it was found that rice hull-based activated carbon consisted of mesopores predominantly. These experimental results indicated the potential use of rice hull as a precursor in the activated carbon preparation process with ammonium nitrate. Moreover, the adsorption-desorption isotherm and the adsorption potential of the activated carbon that prepared at the optimum conditions were evaluated.Öğe Reduced graphene oxide/Titanium oxide nanocomposite synthesis via microwave-assisted method and supercapacitor behaviors(Elsevier Science Sa, 2017) Ates, Murat; Bayrak, Yuksel; Yoruk, Ozan; Caliskan, SinanIn this paper, graphene oxide (GO) was firstly synthesized by modification of Hummers method from the literature. Secondly, reduced graphene oxide (rGO)/Titanium oxide (TiO2) nanocomposites were synthesized with different wt/wt % of GO/TiO2 (1:1; 1:2; 1:5 and 1:10) by microwave-assisted method. By treating GO and GO/TiO2 nanocomposites in a microwave oven, reduced graphene oxide (rGO) and rGO/TiO2 materials could be obtained within power of 180 Win 10 min. The weight ratio of rGO and TiO2 was used to obtain the optimum conditions for nanocomposite materials. The rGO/TiO2 nanocomposite active materials were characterized by cyclic voltammetry (CV), Fourier-transform infrared - Attenuated total reflectance (FTIR-ATR), scanning electron microscopy-energy dispersion X-ray (SEM-EDX), thermogravimetry (TGA), differential thermal analyzer (DTA) and electrochemical impedance spectroscopy (EIS) analysis. Thirdly, supercapacitors were fabricated as a symmetric device with two electrode configuration. The device performances were tested by CV, galvanostatic constant current (CC), and EIS measurements. TGA analysis indicated that the thermal stability of the nanocomposites improved from rGO (40% at 892.8 degrees C) to nanocomposite as the initial feed ratio of [GO](o)/[TiO2](o) = 1/10 as (94% at 949.3 degrees C) increased. The result show that the as-prepared symmetrical rGO/TiO2 nanocomposite on the two-electrode system displays very high specific capacitance of 524.02 F/g at 2 mV/s for [GO](o)/[TiO2](o) = 1/5 with a high energy density of E = 50.07 Wh/kg at 2 mV/s for [GO](o)/[TiO2](o) = 1/1 and high power density of P = 58.6 kW/kg at a the scan rate 1000 mV/s for [GO](o)/[TiO2](o) = 1/1. Additionally, the symmetric electrode shows good cycling stability with a retention value of 6.6% for [GO](o)/[TiO2](o) = 1/1 after 1000 cycles. These good results suggest us that rGO/TiO2 nanocomposite which is obtained by microwave-assisted method has a great potential as an electrode material for supercapacitor applications. The equivalent circuit model of R-s(C-dl(RctW)) was used to explain parameters of solution resistance, double layer capacitance (Cdl), charge transfer resistance (R-ct), Warburg impedance (W). Theoretical and experimental values support with each other. (C) 2017 Elsevier B.V. All rights reserved.Öğe Removal of Reactive Dye from Aqueous Solution by Activated Carbon(Asian Journal Of Chemistry, 2013) Bayrak, Yuksel; Uzgor, ResmiyeThis study investigates the potential use of activated carbon prepared from orange peel for the removal of remazol brilliant blue R (RBBR) dye from aqueous solution. The effects of different system variables, solution pH (from 4 to 10), solution temperature (from 25 to 55 degrees C), adsorbent dose (from 0.1 to 1 g) and contact time (from 15 to 75 min) were studied. The maximum dye removal was reached at 75 min. The results showed that as the amount of the adsorbent increased, the percentage of dye removal increased accordingly. Sorption isotherms were analyzed by Langmuir, Freundlich, Redlich-Peterson, Tempkin and Dubinin-Radushkevich models at different temperatures of 25, 35, 45 and 55 degrees C. The maximum adsorption capacity obtained from Langmuir equation was 26.15 mg g(-1). Furthermore, adsorption kinetics of remazol brilliant blue R were studied and the rate of adsorption was found to conform to pseudo-second-order kinetics with a good correlation (R-2 > 0.85) with intraparticle diffusion as one of the rate determining steps. The results of this study showed that activated carbon developed from orange peel could be employed as effective and low-cost materials for the removal of dyes from aqueous solution.Öğe Removal of Remazol Black B Textile Dye from Aqueous Solution by Adsorption: Equilibrium and Thermodynamic Studies(Taylor & Francis Inc, 2013) Bayrak, Yuksel; Uzgor, ResmiyeThe use of low-cost, easy obtained, high-efficiency, and eco-friendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from aqueous solution. This study investigates the potential use of activated carbon prepared from orange peel for the removal of Remazol Black B (RB) dye from aqueous solution. It was seen that the removal of RB increased with increasing solution pH (4-10), solution temperature (25-55 degrees C) and adsorbent dose (0.1-1g/20mL). The maximum dye removal was reached at 90 minutes. Adsorption isotherms were analyzed by Langmuir and Freundlich models at different temperatures of 25 degrees C, 35 degrees C, 45 degrees C, and 55 degrees C, and the results were discussed in detail. Moreover, the thermodynamics of adsorption were also studied. It was found that the values of standard free energy (G degrees) were negative for activated carbon. The values of standard enthalpy (H degrees) and entropy (S degrees) were found to be positive, and the obtained results were interpreted in detail. Activated carbon developed from orange peel can be attractive options for dye removal from diluted industrial effluents since test reaction made on simulated dyeing aqueous solution show better removal percentage of RB.Öğe rGO/CuO/PEDOT nanocomposite formation, its characterisation and electrochemical performances for supercapacitors(Taylor & Francis Ltd, 2019) Ates, Murat; Garip, Alpay; Yoruk, Ozan; Bayrak, Yuksel; Kuzgun, Ozge; Yildirim, MuratSupercapacitor properties of rGO, CuO, PEDOT and rGO/CuO at [rGO](o)/[CuO](o) = 1:1; 1:1.5; 1:2 and rGO/CuO/PEDOT nanocomposite at [rGO](o)/[CuO](o)/[EDOT](o) = 1:1:1; 1:1:3; 1:1:5 were investigated using chemical reduction of GO and in-situ polymerisation process. SEM-EDX, HRTEM, BET surface area analysis confirm the nanocomposite formations. Nanocomposite materials are also analysed through FTIR-ATR, Raman, TGA-DTA, GCD, CV and EIS. The highest specific capacitance of C-sp = 156.7 F/g at 2 mV/s is determined as rGO/CuO/PEDOT at [rGO](o)/[CuO](o)/[EDOT](o) = 1:1:5. In addition, two-electrode supercapacitor device for rGO/CuO/PEDOT at [rGO](o)/[CuO](o)/[EDOT](o) = 1:1:5 are found to provide a maximum specific energy (E = 14.15 Wh/kg at 20 mA) and specific power (P = 24730 W/kg at 50 mA), electrical serial resistance (ESR = 13.33 omega) with good capacity retention after 3000 cycles. An equivalent circuit model of LR1(CR2)(QR3) is proposed to interpret the EIS data. The supercapacitor performance of the rGO/CuO/PEDOT nanocomposite electrode indicates the synergistic effect of hybrid supercapacitors.Öğe Spectroscopic studies on the antioxidant activity of ellagic acid(Pergamon-Elsevier Science Ltd, 2014) Kilic, Ismail; Yesiloglu, Yesim; Bayrak, YukselEllagic acid (EA, C14H6O8) is a natural dietary polyphenol whose benefits in a variety of diseases shown in epidemiological and experimental studies involve anti-inflammation, anti-proliferation, anti-angiogenesis, anticarcinogenesis and anti-oxidation properties. In vitro radical scavenging and antioxidant capacity of EA were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe2+) chelating activity and ferric ions (Fe3+) reducing ability. EA inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45 mu g/mL concentration. On the other hand, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), alpha-tocopherol and ascorbic acid displayed 69.8%, 66.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, EA had an effective DPPH center dot scavenging, ABTS(center dot+) scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe3+) reducing power and ferrous ions (Fe2+) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, alpha-tocopherol and ascorbic acid as references antioxidant compounds. These results' suggested that EA can be used in the pharmacological, food industry and medicine because of these properties. (C) 2014 Elsevier B.V. All rights reserved.Öğe Supercapacitor performances of RuO2/MWCNT, RuO2/Fullerene nanocomposites(Wiley, 2019) Ates, Murat; Kuzgun, Ozge; Yildirim, Murat; Yoruk, Ozan; Bayrak, YukselIn this study, RuO2/Fullerene and RuO2/MWCNT nanocomposites were synthesized to use as an electroactive materials in symmetric supercapacitor device performances. The materials were examined via Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), thermo-gravimetric analysis (TGA-DTA), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The RuO2/MWCNT and RuO2/Fullerene nanocomposite electrodes show good electrochemical performances. For instance, the highest specific capacitance of RuO2/Fullerene and RuO2/MWCNT electrodes reaches C-sp = 3895.11 and 1662.19F/g at 1mV/s within the potential range of 0.8 V in 1 M H2SO4 solution. RuO2/MWCNT and RuO2/Fullerene nanocomposites have good cycle stability similar to 100% specific capacitance at [RuO2](o)/[MWCNT](o) = 1:1; 2:1 and [RuO2](o)/[Fullerene](o) = 2:1, respectively. The different equivalent circuit models of LR(1)Q(C1R2) and LR1(Q(1)R(2))(Q(2)R(3)) were used to interpret EIS data.Öğe Symmetric supercapacitor device applications of rGO / Co3O4 / polypyrrole nanocomposites(Springer Heidelberg, 2022) Ates, Murat; Yoruk, Ozan; Bayrak, YukselSymmetric supercapacitor electrode design and synthesis of micro-nano structured metal oxide (Co3O4) and polypyrrole with reduced graphene oxide (rGO) have played an important role in supercapacitor investigations. The characterizations of rGO/Co3O4/PPy nanocomposites were given by FTIR-ATR, SEM-EDX, TGA-DTA, BET surface, and porous analysis and Four-point probe analysis. The symmetric rGO/Co3O4/PPy supercapacitor devices were presented in different initial feed ratios of [rGO](o)/[Co3O4](o)/[Py](o) = 1:5:1; 1:5:2; 1:5:5 and 1:5:10 for 2 M and 6 M KOH solutions. The highest specific capacitances, energy and power densities of C-sp = 896 F x g(-1), E = 31.75 Wh x kg(-1) and P = 11,705 W x kg(-1) for [rGO](o)/[Co3O4](o)/[Py](o) = 1:5:10 in 2 M KOH solution and C-sp = 1370 F x g(-1) for [rGO](o)/[Co3O4](o)/[Py](o) = 1:5:5 and E = 31.43 Wh x kg(-1) and P = 11,600 W x kg(-1) for [rGO](o)/[Co3O4](o)/[Py](o) = 1:5:1 in 6 M KOH solution. The lowest capacitance retention was obtained as 3.69% in 2 M KOH solution for [rGO](o)/[Co3O4](o)/[Py](o) = 1:5:1 after 1000 cycle charge/discharge performances by CV method. Symmetric supercapacitor of rGO/Co3O4/PPy should open up new opportunities for the next-generation high-performance supercapacitors.
