Person: KOCA, ATIF
Loading...
Email Address
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
KOCA
First Name
ATIF
Name
14 results
Search Results
Now showing 1 - 10 of 14
Publication Metadata only Photoelectrochemical Performance of Cd0.8Zn0.2SxSe1-x Photoelectrodes Fabricated by Electrodeposition Method(2022-01-25) BUDAK, ÖZLEM; UĞUZ NELİ, ÖZLEM; KOCA, ATIF; Budak Ö., Uğuz Neli Ö., Koca A.Publication Metadata only New asymmetric bisthiocarbohydrazones and their mixed ligand nickel(II) complexes: Synthesis, characterization, crystal structure, electrochemical-spectroelectrochemical property, antimicrobial and antioxidant activity(PERGAMON-ELSEVIER SCIENCE LTD, 2021) KOCA, ATIF; Kaya, Yeliz; Ercag, Ayse; Uguz, Ozlem; Koca, Atif; Zorlu, Yunus; Hacioglu, Mayram; Tan, Ayse Seher BirteksozNew asymmetric isatin bisthiocarbohydrazone ligands were synthesized by the condensation of 3,5-dibromosalicylaldehyde, 3,5-dichlorosalicylaldehyde and 3-bromo-5-chlorosalicylaldehyde with isatin monothiocarbohydrazone. New mixed ligand Ni(II) complexes were synthesized from these ligands using triphenylphosphine (PPh3) as a secondary ligand. The synthesized ligands and complexes were characterized by elemental analysis, FT-IR, H-1 NMR, UV-Vis spectroscopy and mass spectrometry techniques, along with conductivity measurements. The ligands bind to the Ni(II) ion as ONS donors. The fourth coordination site is completed by the secondary ligand PPh3. The single crystal structures of one ligand and one complex were also resolved by X-ray crystallography. The electrochemical responses of the ligands and their complexes were determined and the results were evaluated to illustrate the influence of the substitution of different groups on the ligands. While the free ligands only give one oxidation peak, two oxidation peaks are observed for the Ni(II) complexes. Complexation of the ligands with the Ni(II) ion considerably affected the in-situ spectroelectrochemical responses of the ligands. Finally, the in vitro antioxidant and antimicrobial activities of the synthesized compounds were determined.Publication Open Access Crystal structures, antioxidant, electrochemical and in-situ spectroelectrochemical properties of new bisthiocarbohydrazones and their Ni(II) complexes(2023-05-01) UĞUZ NELİ, ÖZLEM; KOCA, ATIF; KAYA Y., ERÇAĞ A., Uğuz Ö., Zorlu Y., KOCA A.© 2023 Elsevier B.V.Four new isatin bisthiocarbohydrazone ligands (H2L1, H2L2, H2L3, H2L4) were synthesized by the condensation of salicylaldehyde, 5-bromosalicylaldehyde, 5-chlorosalicylaldehyde and 5-nitrosalicylaldehyde with isatin monothiocarbohydrazone, respectively. The mixed ligand Ni(II) complexes {[NiL1(P)], [NiL2(P)], [NiL3(P)] and [NiL4(P)]} containing triphenylphosphine (P: triphenylphosphine, PPh3) of these bisthiocarbohydrazone ligands were synthesized. The synthesized compounds were characterized by elemental analysis, FT-IR, 1H NMR, UV–Vis spectroscopy techniques and conductivity measurements. In the complexes, the bisthiocarbohydrazone ligands coordinate to nickel through ONS mode. The complexes are diamagnetic and exhibit square planar geometry. The crystal structures of two ligands, H2L1 and H2L3, and two complexes, [NiL1(P)] and [Ni3(L3)2(P)2], whose single crystals were obtained, were determined by single crystal X-ray diffraction technique. The crystal structure of [NiL1(P)] complex is monomeric and compatible with the structure of the solid complex. A new trinuclear Ni(II) complex, [Ni3(L3)2(P)2], was obtained by the crystallization of monomeric solid [NiL3(P)] complex in a different solvent mixture. Redox properties of bisthiocarbohydrazone ligands (H2L1-H2L4) bearing S1 or S2 substituents and their nickel(II) complexes {[NiL1(P)]-[NiL4(P)]} were investigated with cyclic voltammetry and in situ spectroelectrochemistry. Voltammetric analyses indicated that all ligands exhibited four quasi-reversible reduction and one irreversible oxidation process. Complexation of the ligands with Ni(II) cation decreased the number of the reduction processes and caused these processes to have more negative potentials. Significant spectral changes were also observed in the in situ spectroelectrochemical analysis due to electron transfer reactions. In addition, electrochemical responses of monosubstituted salicylaldehyde derivative isatin bisthiocarbohydrazone ligands and their nickel(II) complexes were compared with their disubstituted derivatives.Publication Metadata only Fabrication of Azide-Functionalized Reduced Graphene Oxide Bearing and ZnPc Decorated Cd0. 6Zn0.2Ni0.2S0.2Se0.8 Photoelectrode and Its Photoelectrochemical Properties /(2022-01-23) UĞUZ NELİ, ÖZLEM; KOCA, ATIF; BUDAK, ÖZLEM; Uğuz Neli Ö., Budak Ö., Varol D. E., Keskin B., Koca A.Publication Metadata only Simultaneous electrochemical deposition of nickel cobalt oxide-reduced graphene oxide composites for high performance asymmetric supercapacitors(Elsevier Ltd, 2021) KOCA, ATIF; Budak Ö., Uğuz Ö., Koca A.In this work, a one-step electrodeposition approach was applied for nanosheets fabrication of binder free nickel cobalt oxide (NCO) and NCO-reduced graphene oxide (NCO-rGO) composites on the nickel-foam substrate by repetitive cyclic voltammetry (rCV). The NCO-rGO hybrids were firstly fabricated on Ni foam surface with the reduction of GO and electrodeposition of NCO simultaneously. Interaction of NCO particles with rGO sheets increased the conductivity of the composite and consequently facilitated the electron transfer rate. Electrochemical measurements proved that specific capacitance and cyclic performance of as-prepared materials were improved with the synergistic effect of rGO in the hybrid structure. The optimized NCO-rGO electrode exhibited a specific capacitance of 1916.5 F g−1 at 1 A g−1 with superior stability of 95.6% at a high current density of 10 A g−1 even after 3000 cycles. To explore its practical applications, an asymmetric supercapacitor (ASC) based on NCO-rGO as a positive electrode and rGO as a negative electrode was constructed, which exhibited a prominent specific energy of 45.22 Wh kg−1 at 400 W kg−1. As a result, NCO-rGO hybrid structure as the functional electrode material for the supercapacitors with remarkable electrochemical performance were obtained, thanks to the increased conductivity and decreased mass by removing binders. © 2021 Elsevier LtdPublication Metadata only Photoelectrochemical performance of thermally sulfurized CdxZn1-xS photoanode: Enhancement with reduced graphene oxide support(PERGAMON-ELSEVIER SCIENCE LTD, 2020) ÖZKAYA, ALİ RIZA; Ayaz, RanaMuhammad Zunain; Akyuz, Duygu; Uguz, Ozlem; Tansik, Irem; Sarioglu, Cevat; Karaca, Fatma; Ozkaya, Ali Riza; Koca, AtifIn this study, photoelectrochemical performance of reduced graphene oxide (RGO)-CdxZn1-xS compos-ites, which were synthesized through a novel two-steps thermal sulfurization process by using elemental sulfur, was reported. This is the first time that the two-step thermal sulfurization process with elemental sulfur for the preparation of photoanode based on RGO-CdxZn1-xS. The electrodes exhibited high photostability and photocurrent response in the presence of visible light. The presence of RGO in CdxZn1-xS as electron collector and transporter increased the photocurrents approximately 40%. Among the RGOCdxZn1-xS composites, RGO-CdS photoanode yielded an extremely high photocurrent density of 6.5 mAcm(-2) with the rate of hydrogen production rate of 551.1mmolh(-1)cm(-2). This value of photocurrent density is almost 89% of its theoretical value. This is the maximum attained photocurrent density with superior stability in comparison with related literature. (c) 2020 Elsevier Ltd. All rights reserved.Publication Metadata only Hybrid photoelectrochemical-photocatalytic hydrogen evolution reaction with reduced graphene oxide-binary metal chalcogenide composites(WILEY, 2021) KOCA, ATIF; Uguz, Ozlem; Koca, AtifIn this study, a novel hybrid photoelectrochemical (PEC)-photocatalytic (PC) hydrogen evolution reaction (H-PEC@PC@HER) reactor was developed, in which, the PC and PEC hydrogen evolution reactions were simultaneously performed to maximize the light absorption and investigated the synergetic interactions between these processes. Solvothermally synthesized reduced graphene oxide (RGO)-Cd0.60Zn0.40S-Pt composite was used as the functional photocatalyst for these reactions in H-PEC@PC@HER reactor. The illumination of the RGO-Cd0.60Zn0.40S-Pt photocatalyst and photoanode was provided at the same time, thus while some of the incoming light was absorbed by the RGO-Cd0.60Zn0.40S-Pt photocatalyst, the light passing without being absorbed was also absorbed by the photoanode. Consequently, the utilization of the solar light spectrum was maximized with the PC reaction of RGO-Cd0.60Zn0.40S-Pt powder and PEC reaction of RGO-Cd0.60Zn0.40S-Pt photoanode. The results showed that the hydrogen production rate in the H-PEC@PC@HER increased ca. 8.2% with respect to that of the single PC reaction. It was observed that the hydrogen production rate in the H-PEC@PC@HER system enhanced with time due to the enhancing PEC reaction in the residual Na2S/Na2SO3 electrolyte. When compared with the results in fresh electrolyte, the photocurrent density of the RGO-Cd0.60Zn0.40S-Pt photoelectrode increased from 1.0 to 1.41 mA/cm(2) in the residual Na2S/Na2SO3 electrolyte with a reported enhancement of 17.4% in the photocurrent density. It was proposed that S2O32- ions produced with the PC reaction were used as the hole-recleavaging reagent of the RGO-Cd0.60Zn0.40S-Pt photoelectrode in the PEC system.Publication Open Access A detailed experimental and computational study of Cd complexes with pyridyl-based thiazolyl hydrazones(2022-11-01) UĞUZ NELİ, ÖZLEM; KOCA, ATIF; Kokanov S. B. , Filipovic N. R. , Visnjevac A., Nikolic M., Novakovic I., Janjic G., Hollo B. B. , Ramotowska S., Nowicka P., Makowski M., et al.Interest in Cd complexes has been growing in recent years. Cd complexes are considered a potential solution in the search for novel antibiotics that can fight antimicrobial resistance. In addition, Cd complexes draw attention to material chemistry. The main objective of this work was to prepare the first Cd(II) complexes with anionic forms of pyridine-based thiazolyl hydrazone (THs) ligands HLS2 [(E)-4-(4-methoxyphenyl)-2-(2-[pyridine-2-ylmethylene]hydrazinyl)thiazole] and HLS3 [(E)-2-(2-[pyridine-2-ylmethylene]hydrazinyl)-4-(p-tolyl)thiazole] and perform their structural and spectroscopic characterization, as well as stability in solution and upon heating. Studies related to their biological activities and possible electrochromic applications are also being conducted. Complexes [Cd(HLS2)(2)] (1) and [Cd(HLS3)(2)] (2) have been characterized by a single-crystal X-ray diffraction and computational analysis of intermolecular interactions responsible for their solid-state structures was performed. Thermal stability of 1 and 2 in the solid-state was analyzed by TGA/MS, where as their solution stability was determined by the spectrophotometric titration method. Electrochemical and in situ UV-Vis spectroelectrochemical analyses of 1 and 2 were carried out to determine redox mechanisms and the influence of the substituents and electrolytes on their redox responses. The antioxidant capacity of both complexes was tested in antioxidant assays, while their antimicrobial activity was tested against five Gram-positive and four Gram-negative bacteria, as well as against three fungi. The obtained results indicate their potent antioxidant capacity. The antimicrobial activity of investigated compounds on almost all tested bacterial strains was stronger than that of the standard antibiotic erythromycin. The results of docking studies indicate that the minor groove DNA is the possible biological target of 1 and 2.Publication Metadata only Metal chalcogenide based photocatalysts decorated with heteroatom doped reduced graphene oxide for photocatalytic and photoelectrochemical hydrogen production(PERGAMON-ELSEVIER SCIENCE LTD, 2019) ÖZKAYA, ALİ RIZA; Akyuz, Duygu; Ayaz, Rana Muhammad Zunain; Yilmaz, Seda; Uguz, Ozlem; Sarioglu, Cevat; Karaca, Fatma; Ozkaya, Ali Riza; Koca, AtifHeteroatom (N, B and P) doped reduced graphene oxide (RGO)-metal chalcogenide nanocomposites (RGO-Cd0.60Zn0.40S) were prepared by the solvothermal method, and then they were characterized with X-ray diffraction, Raman spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, UV-Vis diffuse reflectance spectroscopy and photoluminescence techniques. Doping of RGO with heteroatoms of N, B and P increased charge-transfer capability of nanocomposites and thus, improved both photocatalytic and photoelectrochemical hydrogen production activities of them. N-doped RGO-Cd0.60Zn0.40S photocatalyst exhibited the highest photocatalytic hydrogen production rate (1114 mu molh(-1) g(-1)) in photocatalytic (PC) system amongst other and it was 1.5 times higher than that of RGO-Cd0.60Zn0.40S photocatalyst. Having a current density of 0.92 mAcm(-2), photoelectrochemical hydrogen production activity of N-RGO-Cd0.60Zn0.40S electrode was found to be 3 times higher than RGO-Cd0.60Zn0.40S photoelectrode without any applied bias potential under visible light irradiation in photoelectrochemical system. In general, these results clearly showed that heteroatom doping of RGO led to promising materials for renewable hydrogen production in the photocatalytic and photoelectrochemical systems. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Publication Metadata only Simultaneous electrodeposition of electrochemically reduced graphene oxide-binary metal chalcogenide composites to enhance photoelectrochemical performance(PERGAMON-ELSEVIER SCIENCE LTD, 2021) KOCA, ATIF; Uguz, Ozlem; Budak, Ozlem; Koca, AtifIn this study, a facile and one-step simultaneous electrodeposition of the composite thin films bearing binary metal chalcogenides (CdxZn1-xS (x = 0.0, 0.2, 0.5, 0.8, 1.0)) and electrochemically reduced graphene oxide (RGO) was carried out via repetitive cyclic voltammetry (rCV). Then their photoelectrochemical (PEC) performances were investigated under the solar light irradiation to find out the optimized composition of the composites. Immobilization of Cd1-xZnxS nanoparticles among the RGO sheet with the rCV confined the Cd1-xZnxS nanoparticles between the RGO sheets, which prevented leakage of these particles from the electrode surface and contributed to the increase of active sites for the PEC reaction. PEC results showed that increasing x from 0 to 0.8 in CdxZn1-xS composition boosted the photocurrent density, reaching from 25 mA cm(-2) to 438 mA cm(-2). Incorporation of RGO to the structure increased the conductivity and prevented the photocorrosion of Cd0.8Zn0.2S, thus, RGO(0.25)-Cd0.8Zn0.2S enhanced the photocurrent density from 0.44 mA cm(-2) (as-synthesized Cd0.8Zn0.2S) to 1.38 mA cm(-2). (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.