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Öğe Comparative activation of pine pollen-derived carbon with KOH and CuCl2 for high-performance supercapacitor electrodes(Springer Heidelberg, 2025) Atalay, Funda Ersoy; Kaya, Harun; Korkmaz, Aydan Aksogan; Gokturk, Gunay; Guler, SeherBiomass-derived porous carbons have emerged as promising candidates for high-performance supercapacitor electrodes owing to their low cost, sustainability, and tunable physicochemical properties. In this work, pine pollen, an abundant and underutilized natural precursor, was converted into porous carbon via hydrothermal carbonization followed by chemical activation using KOH and CuCl2. A systematic comparison of these activation agents was conducted to elucidate their effects on structural, morphological, and electrochemical characteristics. KOH activation produced carbon with a high specific surface area of 2030.32 m2/g and a specific capacitance of 230 F/g at 5 A/g, while CuCl2 activation yielded carbon with a surface area of 736.8 m2/g and a capacitance of 176 F/g. After 5000 charge-discharge cycles, capacitance retention was 76% for the KOH-activated electrode and 93% for the CuCl2-activated counterpart. This study provides the first comprehensive insight into the role of activation chemistry in tailoring pine pollen-derived carbon for supercapacitor applications, demonstrating the potential of pine pollen as a sustainable and low-cost resource for advanced energy storage systems.Öğe Degenerate magnetic structures and antiferromagnetic phase transitions in \gamma-Mn alloys(Turkish Journal of Physics, 1996) Bayrı, Ali; Atalay, Funda Ersoy; Gencer, HüseyinAbstract: Manganese alloy systems, which have been studied experimentally, show a host of antiferromagnetic phase transitions. Developing a linearized theory for the clas¬sical Heisenberg model, we can solve the local distortion of model of spins around an impurity in non-collinear antiferromagnet. Since the alloying removes the degeneracy in non-collinear magnets, this theory is useful. Looking at the case of ?-Mn alloys, especially Mn3Pt, we can predict the experimentally observed phase transitions caused by alloying.Öğe Different Plant Sporopollenin Exine Capsules and Their Multifunctional Usage(Amer Chemical Soc, 2022) Atalay, Funda Ersoy; Culum, Ayse Asiye; Kaya, Harun; Gokturk, Gunay; Yigit, EmelSporopollenin exine capsules (SECs) are highly resistant to heat and various acids and bases. They are also cheap, highly porous, eco-friendly polymer biomaterials with stable microencapsulation capacity. Due to their strong and uniquely shaped exine layers, they can allow growth on metal oxide materials, as a biotemplate for use in different applications. In this study, first, a single SEC extraction method was applied to three different pollens from Pinus, Fraxinus excelsior, and Tilia. Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, and thermogravimetric/differential thermal analysis (TGA/DTA) measurements both before and after the extraction process were performed to observe changes in surface area, morphology, porous structure, and degradation properties. The protein content and removal were analyzed by elemental and spectrophotometric analyses. Then, SECs were loaded by passive and centrifuge loading for drug delivery, and the loading capacities were analyzed by Fourier transform infrared spectroscopy and spectrophotometry. The method was successful in opening the pores and maintaining the structural integrity of SECs. It was determined that the morphology and porosity affected the encapsulation efficiency. According to the loading capacities, Tilia SECs were the most efficient SECs for both loading methods. In addition, three different SECs were hydrothermally coated with cobalt and then heat-treated to obtain a metal oxide structure. A CO3O4 supercapacitor electrode constructed using CO3O4-F. excelsior SEC powder had the best surface area parameters. The electrode showed a maximum specific capacity of 473 F/g for over 3000 continuous cycles of galvanostatic charge-discharge (GCD).Öğe Electrode material development from natural specularite ore for supercapacitor applications(Springer Heidelberg, 2025) Kaya, Harun; Korkmaz, Aydan Aksogan; Guler, Seher; Atalay, Funda ErsoyNatural specularite ore was investigated as a sustainable and low-cost raw material for supercapacitor electrodes. This study provides new insight by demonstrating the direct conversion of an abundant iron ore into a functional nanostructured electrode (nano sp/NF) through a combined process of planetary ball milling, ultrasonic exfoliation in N, N-dimethylformamide, and hydrothermal treatment. The fabricated electrode exhibited a specific capacitance of 425 F/g at 20 A/g together with remarkable cycling stability over 10,000 charge-discharge cycles. These superior performances are associated with the enlarged surface area and porous architecture, which facilitate rapid ion transport and efficient Faradaic reactions. Overall, the findings highlight the originality of employing natural ores through environmentally friendly and scalable processing routes, offering a promising pathway toward next-generation energy storage electrodes.Öğe Helical microtubules of nanostructured cobalt oxide for electrochemical energy storage applications(Biointerface Research Applied Chemistry, 2016) Atalay, Funda Ersoy; Kaya, Harun; Asma, Dilek; Bingol, AlperIn this study, Co3O4 nanostructured porous microtubes were prepared via chemical precipitation onto Aquaspirillum bengal bacteria in an aqueous solution. The morphological properties of the synthesized material were studied using a scanning electron microscopy (SEM). The diameter of the Co3O4 micro tubes is approximately 0.8 mu m, and the length is 4 mu m. The Brunauer-Emmett-Teller (BET) surface area was determined to be 87.07 m2/g. The nitrogen adsorption and desorption isotherm displayed properties associated with a typical type IV isotherm. The electrochemical properties of the produced material were studied using cyclic voltammetry (CV), long-term charge/discharge analysis and impedance spectroscopy (EIS).Öğe High-Performance Supercapacitor Electrode Based on NiFe Nanowire Networks/PEDOT:PSS(Elsevier, 2020) Atalay, Funda Ersoy; Sener, Melike; Kaya, HarunIn this work, the usage of electrochemically produced NiFe nanowires (NW) as an electrode active material for supercapacitors has been investigated. Different concentrations of NiFe NWs were dispersed on thin conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films by spin coating system. NiFe NW networks/PEDOT:PSS electrode was used as a positive electrode in the three-electrode cell. Electrochemical capacitive performance tests such as; electrochemical impedance spectroscopy, galvanostatic charge-discharge tests (GCD) and cyclic voltammetry (CV) were performed in 1 M Na2SO4 electrolyte. The CV curves of the designed electrodes have been found to be similar to the CV curves of the ideal supercapacitor and they have almost rectangular in shape. The specific capacitance of 2 mg NW mass loading was evaluated 332 F/g at a current density of 2 A/g from GCD measurements with excellent cyclability up to 5000 times. These good electrochemical performances arise from network structure of NiFe NW based electrode. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Influences of deposition time and pH on magnetic NiFe nanowires fabrication(Elsevier Science Sa, 2009) Atalay, Funda Ersoy; Kaya, Harun; Atalay, Selcuk; Tari, SueleymanIn this work, NiFe nanowires were grown into highly ordered porous anodic alumina oxide (AAO) templates by dc electrodeposition at various deposition times and pH values. During the deposition process some electrochemical bath parameters such as ion content, deposition voltage, and temperature of solution were kept constant. The morphological properties of the nanowire arrays were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the chemical composition was determined by examination of the energy dispersive X-ray (EDX) spectra, and the magnetic behavior of the arrays was determined by vibrating sample magnetometer (VSM). (C) 2008 Elsevier B.V. All rights reserved.Öğe Juglans Sporopollenin for High-Performance Supercapacitor Electrode Design(Amer Chemical Soc, 2020) Atalay, Funda Ersoy; Bingol, Alper; Kaya, Harun; Emre, Yildiz; Bas, Hatice Hande; Culum, Ayse AsiyeRecently, plant pollen has been used as a source of activated carbon to produce carbon-containing supercapacitor electrodes. However, in this study, pollen was used as a biotemplate with a completely different approach. As a biotemplate, pollen offers a wide range of varieties in terms of exterior, porosity, shape, and size. An electrode formed by the use of metal oxide grown on the pollen exine layer (sporopollenin microcapsules) as the active substance will inevitably exhibit good electrochemical capacitive properties. Juglans male flowers have been distinguished by dissection from anthers. Isolation of pollen grains from anthers was carried out using sieving from suitable sieves (45-200 mu m). Juglans sporopollenin exine microcapsules (SECs) were separated from the intine and protoplasm by acetolysis in combination with reflux. The solution containing SECs, metal ions, and Ni foam was put into a Teflon-lined hydrothermal container, and then, it was reacted at 120 degrees C for 15 h. The resulting precipitate, as well as the Ni foam, was heat-treated at 300 and 360 degrees C for 3 h in air. The raw pollen, chemically treated pollen, and cobalt-coated SEC (CoSEC) and CoSEC/Ni foam were characterized using scanning electron microscopy, Brunauer-Emmett-Teller surface area analysis, thermogravimetric analysis, and X-ray diffraction techniques. Two different types of supercapacitor electrode designs, with the use of exine microcapsules of Juglans sporopollenin, were performed for the first time. The maximum specific capacitance was up to 1691 F g(-1) at 5 A g(-1).Öğe Magnetic diffuse scattering in the frustrated square lattice(Turkish Journal of Physics, 1998) Bayrı, Ali; Atalay, Funda Ersoy; Gencer, HüseyinÖz: Başlık (İngilizce): Öz (İngilizce): Some of the first transition metal alloys show first order antiferromagnetic phase transition as a function of alloy concentration [1-5]. The antiferromagnetism of materials can be classified into three different class: type I, type II and type III. Although the neutron diffraction studies give information about the type of magnetism, they do not show the fluctuations of magnetic moment from the original direction. So in order to have some information about this fluctuations one must perform the magnetic diffuse scattering. Recently, we proposed that the square lattice may have a double-Q structure as well as single-Q [6]. We showed that the alloying may cause a first order antiferromagnetic phase transition. In order to show that this is the case we perform the magnetic diffuse scattering and give more evidences that the alloying play the dominant role in this phase transition.Öğe Preparation and characterization of activated carbon from tomato, pepper, and eggplant wastes by two-step KOH activation(Taylor & Francis Inc, 2026) Yavuz, Bahar; Aksogan Korkmaz, Aydan; Kaya, Harun; Guler, Seher; Atalay, Funda ErsoyThis study investigates the morphological, structural, and chemical properties of activated carbons synthesized from common lignocellulosic agricultural wastes such as tomato, pepper, and eggplant residues. A two-step chemical activation method was employed. In the first step, the biomass was carbonized at 500 degrees C for 1 h to produce biochar. In the second step, the activation process was conducted at 800 degrees C for 1 h using different biochar:KOH impregnation ratios (1:1, 1:2, 1:3). The surface area of the resulting porous carbonaceous materials was determined by BET analysis, while their morphological features were examined by Scanning Electron Microscopy (SEM). Structural and chemical properties were characterized using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The highest surface area values of activated carbons (2070-2254 m2/g) were obtained with a biochar:KOH weight ratio of 1:3. SEM images revealed the formation of a well-developed porous structure as a result of oxidation-reduction reactions. XRD analysis indicated the presence of graphite-like amorphous structures. FTIR spectra confirmed the presence of various surface functional groups, including C = C, C = O, C-H, C-C, and C-O. These findings demonstrate that widely available and low-cost agricultural wastes can serve as effective, environmentally friendly, and sustainable precursors for the production of activated carbon.Öğe The role of clustering for antiferromagnetic phase transitions in \gamma-Mn alloys(Turkish Journal of Physics, 1996) Gencer, Hüseyin; Bayrı, Ali; Atalay, Funda ErsoyThe role of clustering for antiferromagnetic phase transitions in ?-Mn alloysÖğe Sol-gel synthesis of TiO2 on Co3O4-coated sporopollenin exine microcapsules (SECs) and photocatalytic performance of new semiconductor heterojunction material(Springer Heidelberg, 2022) Yilmaz, Hatice Caglar; Atalay, Funda Ersoy; Kaya, Harun; Erdemoglu, SemaIn this study, a new approach was developed to prepare mesoporous hybrid TiO2/Co3O4 coated on Juglans sporopollenin exine microcapsules (SECs). TiO2 was synthesized on Co3O4-coated SECs used as substrate, by sol-gel method. The obtained semiconductor/semiconductor hetero-junction hybrid materials were characterized with X-ray diffractometry (XRD), UV-Vis absorption spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), particle size distribution, specific surface area, and zeta potential measurements. Photocatalytic performances of hybrid materials were tested for Reactive Black 5 dye under both UV and visible light. Equilibrium pH of the solution containing 10 mg/L Reactive Black 5 dye and 0.1% wt/v TiO2/Co3O4 was around 4.7. After irradiation in the solar box, more than 98% of the Reactive Black 5 was photocatalytically degraded within 60 min.Öğe Structural and electrochemical evaluation of ball-milled natural specularite ore for supercapacitor applications(Elsevier Science Sa, 2026) Korkmaz, Aydan Aksogan; Kaya, Harun; Guler, Seher; Atalay, Funda ErsoyThe widespread availability, high theoretical specific capacitance, and low cost of transition metal oxides, such as iron, make them promising candidates for electrode materials in energy storage applications. Among these nanostructured iron oxides, hematite is a highly preferred material for supercapacitor anodes due to its low cost, non-toxicity, high abundance, and the availability of various oxidation states. This study investigates the unique characteristics of natural (raw) specularite ore, also known as mica hematite, as a supercapacitor electrode material. We employed manual grinding and ball milling methods to reduce the particle size of specularite ore. The sample's morphological, chemical, and structural characteristics were analyzed using XRF, DTA/TGA, XRD, BET, and SEM/EDX, revealing its distinct properties that set it apart from other materials. The electrochemical properties of the specularite ore, ground to the nanoscale using a ball mill, were rigorously evaluated through cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. The results showed that the specularite electrode exhibited pseudo-capacitive characteristics, with a specific capacitance of 80.6 F g-1 and a stable initial capacitance of 50 F g-1 after 1000 cycles. These findings have significant implications for the practical use of specularite in energy storage applications.Öğe Synthesis of NiO Nanostructures Using Cladosporium cladosporioides Fungi for Energy Storage Applications(Sage Publications Ltd, 2016) Atalay, Funda Ersoy; Asma, Dilek; Kaya, Harun; Bingol, Alper; Yaya, PinarIn this work, we produced nickel oxide nanostructures that show high electrochemical capacitive behaviour, using fungus - one of the most common life forms in nature. Cladosporium cladosporioides fungi are particularly attractive biotemplates due to their tubular structures. The nanostructured porous microtubes were prepared by chemical precipitation onto fungi. The morphological properties of the biosynthesized NiO microtubes were studied by transmission electron microscope (TEM). The Brunauer-Emmett-Teller (BET) surface area was found to be 119.72 m(2) g(-1) with an average pore size distribution of 7.5 nm. A maximum capacitance value of 334 F g(-1) was observed at 0.8 A g(-1), and a capacitance retention of approximately 95% was obtained after 1000 cycles.
