Person: KOCA, ATIF
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KOCA
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Publication Metadata only A new redox-active multisite ligand: synthesis, spectroscopy and electrochemistry of its mono and dinuclear complexes, and the interaction of (E,E)M (M = Ni) complex with Pd-II and Ag-I(PERGAMON-ELSEVIER SCIENCE LTD, 2004) ÖZKAYA, ALİ RIZA; Kandaz, M; Koca, A; Ozkaya, ARA novel redox active (E,E)-dioxime ligand, S,S-bis-[2(2'-ferrocenemethylaminobenzyl)]-dithioglyoxime (LH2), containing ferrocene and flexible aminobenzenesulfanyl-moieties on the periphery has been synthesized from 2-(2'-ferrocenemethylamino)benzenethiol. which was obtained by the reduction of 2,2-pyridylbenzothiazolidine with a large excess of NaBH4. Mononuclear (LH)(2)M (M = Ni-II, Cu-II, Co-II, Fe-II and Mn-II), homodinuclear (LH)(2)(UO2)(2)(OH)(2) and heterotrinuclear (LH)(2)MM'X-2(n) (M = Ni-II and M' = Pd-II, X = Cl-, n = 4 and M' = Ag-1, X = NO3-, n = 2) complexes have been obtained with the metal:ligand ratios of 1:2, 2:2 and 3:2. respectively. Flexible ferrocenemethylaminobenzenesulfanyl moieties bearing two different heteroatoms, -S and -N, on the periphery of the vic-dioxime serve as weak binding sites for Pd-II and Ag-I ions. The detection of H-bonding in all complexes except the uranyl complex by IR revealed square-planar MN4 coordination of the mono- and trinuclear complexes. The MN4 coordination of the Ni-II complex was also determined by the H-1 NMR spectroscopy. The structures of the complexes were characterized by elemental analysis, H-1 NMR, IR, MS, UV-Vis spectral and cyclic voltammetry. The voltammetric analyses of the complexes showed metal, ligand, and ferrocene based signals. The redox chemistry of the complexes exhibited both M-I and M-III oxidation states of the central metals of the complexes. (C) 2004 Published by Elsevier Ltd.Publication Metadata only Electropolymerization and Electrochemical Pesticide Sensor Application of Metallophthalocyanines Bearing Polymerizable Morpholin Groups(ELECTROCHEMICAL SOC INC, 2016) ÖZKAYA, ALİ RIZA; Ozen, Umit Ergin; Keles, Turgut; Biyiklioglu, Zekeriya; Koca, Atif; Ozkaya, Ali RizaIn this paper, new metallophthalocyanines (MPc) were synthesized by cyclotetramerization of 4-{[4-(2-morpholin-4-ylethoxy)benzyl]oxy}phthalonitrile. To increase potential application of MPcs, redox active Co(II), Mn(III) and Ti(IV)O metal centers were preferred. MPcs were decorated with redox active and electropolymerizable {[4-(2-morpholin-4-ylethoxy)benzyl]oxy} substituents in order to coat the complexes with electropolymerization. Synthesized MPcs were characterized with UV-Vis, IR, H-1-NMR, C-13-NMR and MS (ES+ and MALDI-TOF) spectroscopies and voltammetry and in situ spectroelectrochemistry techniques. Voltammetric and in situ spectroelectrochemical analyses indicated that all complexes gave metal based reduction processes in addition to the Pc based processes. During oxidation reaction, all complexes were coated on the glassy carbon electrode (GCE) surface with oxidative electropolymerization reactions. Redox active and conductive GCE/MPc electrodes were constructed with the electropolymerization of MPcs and these electrodes were tested as active pesticide sensors for eserine, parathion, diazinon and fenitrothion pesticides. CoPc did not interact with any pesticide compound while MnPc and TiOPc selectively sensed diazinon and eserine, respectively. (C) 2016 The Electrochemical Society. All rights reserved.Publication Metadata only Electrocatalytic hydrogen evolution reaction with metallophthalocyanines modified with click electrochemistry(PERGAMON-ELSEVIER SCIENCE LTD, 2015) ÖZKAYA, ALİ RIZA; Akyuz, Duygu; Dincer, Hatice; Ozkaya, Ali Riza; Koca, AtifCobalt and zinc phthalocyanines bearing terminal alkyne groups (TA-CoPc and TA-ZnPc) were electrochemically characterized in order to determine their functionalities for practical usages as effective electrocatalysts. Observation of multi-electron and metal and/or ring based reduction reactions at low potentials indicated the worthy of these complexes as functional materials. Shifts of proton reduction potentials toward more positive values in solutions involving MPc indicated homogeneous electrocatalytic activities of the complexes for hydrogen evolution reaction (HER). For practical usage as heterogeneous electrocatalysts for HER, electrodes were constructed with a new electrode modification technique, click electrochemistry, with which TA-CoPc and TA-ZnPc complexes were bonded to azido functionalized polyaniline (PANI-N-3) electropolymerized on electrodes. The modified Glassy Carbon Electrode (GCE)/PANI-N-3/TA-CoPc and GCE/PANI-N-3/TA-ZnPc electrodes were characterized using voltammetric techniques and electrochemical impedance spectroscopy (EIS), then tested as heterogeneous electrocatalyst for HER. GCE/PANI-N-3/TA-CoPc electrodes especially decrease the over-potential of the bare electrode about 216 mV and increase the efficiency of the electrode about 32 fold at low pHs. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Publication Metadata only Electrochemical, Spectroelectrochemical, and Electrochromic Properties of Lanthanide Bis-Phthalocyanines(ELECTROCHEMICAL SOC INC, 2014) ÖZKAYA, ALİ RIZA; Orman, Efe Baturhan; Koca, Atif; Ozkaya, Ali Riza; Gurol, Ilke; Durmus, Mahmut; Ahsen, VefaVoltammetric, in-situ spectroelectrochemical, and in-situ electrocolorimetric characterization of octa-2,2,3,3-tetrafluoropropoxy-substituted lanthanide (III) bis-phthalocyanines [samarium(III) (SmPc2), europium (III) (EuPc2), gadolinium (III) (GdPc2), dysprosium( III) (DyPc2) and lutetium(III) (LuPc2)] were performed in solution and in the solid states as Langmuir-Blodgett (LB) films. The type of the central metal of the complexes slightly altered the potentials of the electron transfer reactions. Redox peaks shifted toward the negative potentials as a function of the decreasing metal ion size. All complexes gave three reduction and one oxidation reactions with in the whole potential window of the electrolyte system. Due to the p-p interaction of phthalocyanine rings around the lanthanide metal ions the complexes were easily reduced at even positive potentials. Assignments of the redox processes, spectra and color of the electrogenerated species of the complexes were determined with in-situ spectroelectrochemical, and in-situ electrocolorimetric measurements. Various colors recorded during the electron transfer reactions well reflected electrochromic characters of the complexes. For practical usage, LB thin films of the complexes were easily coated on the ITO electrodes and investigated as electrochromic materials. All complexes displayed three distinctive color alternatives as green, orange, and red for their different redox states. Electrochromic measurements indicated that the nature of the metal ions in the phthalocyanine cavity alters the basic electrochromic parameters of the complexes. LB films of DyPc2 and LuPc2 were especially found as ideal neutral and anodic coloring electrochromic materials with their short response times, and high optical and coulombic stabilities. (C) 2014 The Electrochemical Society. All rights reserved.Publication Metadata only A water-soluble multisite ionophore ligand bearing pyridine and aminothiophenol functionality. Synthesis, spectroscopy and electrochemistry of its complexes, and peripheral reactivity of the (E,E)M (M = Ni) complex with Pd2+ and Ag+(SPRINGER, 2004) ÖZKAYA, ALİ RIZA; Kandaz, M; Ozkaya, AR; Koca, AThe design, synthesis and coordination of a novel multisite vic-dioxime compound, LH2 containing flexible pyridine substituents and amitiophcnylsulfanyl moieties on the periphery, facilitating solubility in water as pyridinium hydrochloride salt are described. LH2 was prepared by the reaction between 2-(2-pyridylethylamino)-benzenethiol and (E,E)-dichloroglydioxime. Mononuclear [(E,E)M] (M = Ni-II, Cu-II. Co-II, Fe-II and Mn-II) and dinuclear uranyl (UO2II) complexes of LH2 were isolated and characterized with metal:ligand ratios of 1:2 and 2:2. respectively. The reaction of Na2PdCl4 . 3H(2)O and AgNo3 in DMF with the mononuclear complex, (LH)(2)Ni, resulted in the formation of the heterotrinuclear complexes [Pd2Ni(LH)(2)]Cl-4 and [Ag2Ni(LH)(2)](NO3)(2). The complexes were characterized by elemental analysis, H-1-n.m.r., u.v.-vis. spectroscopy, i.r., and MS (LSIMS). The redox properties of the complexes were studied by cyclic voltammetry.Publication 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 Enhanced hydrogen production with photo-induced phase transformation and cocatalyst loading(WILEY, 2019) ÖZKAYA, ALİ RIZA; Akyuz, Duygu; Ozkaya, Ali Riza; Koca, AtifIn this study, reduced graphene oxide (RGO)-Cd(1 - x)ZnxS nanocomposites have been synthesized with the solvothermal method in one pot. Moreover Pt, Ru, and Rh nanoparticles have been loaded on the RGO-Cd(1 - x)ZnxS nanocomposites as cocatalysts with the aim of increasing the photocatalytic (PC) performance for hydrogen evolution reaction. The structure of Cd(1 - x)ZnxS blend transforms from cubic to hexagonal structure during the PC hydrogen evolution reaction (PCHER) at the room temperature. This photo-induced phase transformation (PIPT) enhances not only the hydrogen evolution rate, but also the stability of the photocatalysts. Interestingly, RGO triggers the PIPT process only during the PCHER under solar light illumination. On the other hand, the loading of Pt, Ru, and Rh cocatalysts do not affect the PIPT process. However, they enhance the PC and photoelectrochemical (PEC) hydrogen production activity of RGO-Cd(1 - x)ZnxS photocatalyst. PEC performance increases about 5.5 times when Pt (5%) and RGO are added to the Cd0.60Zn0.40S catalyst. RGO-Cd0.60Zn0.40S including 1.5% Rh photocatalyst reaches a remarkable PC hydrogen production rate of 135 mu molh(-1) with QE of 23.3% at 460 nm. Therefore, Rh cocatalyst appears as a good alternative to Pt.Publication Metadata only Electrochemical pesticide sensors based on electropolymerized metallophthalocyanines(ELSEVIER SCIENCE SA, 2017) ÖZKAYA, ALİ RIZA; Akyuz, Duygu; Keles, Turgut; Biyiklioglu, Zekeriya; Koca, AtifNew metallophthalocyanines (MPcs) were designed with redox active Co(II) (CoPc(ma)), Cl-Mn(III) (Cl-MnPc(ma)), and Ti(IV)O (TiOPc(ma)) metal centers and morpholin and amino bearing substituents (ma). While redox active metal centers enhanced redox activity of the complexes, redox active and electropolymerizable [2-(4-{[(1E)-(4-morpholin-4-ylphenyl)methylene]amino}phenyl)ethoxy] substituents triggered the coating of MPcs with the oxidative electropolymerizations. Voltammetry and in situ spectroelectrochemistry techniques were used for the electrochemical characterizations of MPcs. All complexes gave metal based reduction processes in addition to the Pc based processes. Moreover, all complexes were coated on GCE with the oxidations of morpholin and amino moieties of the substituents, thus redox active and conductive GCE/MPc(ma) electrodes were constructed. Modified electrodes were investigated as the potential pesticide sensors. Changing the metal center of the complexes significandy altered their sensing activities. While all complexes showed interaction abilities for chlorophyros, fenitrothion, and methomyl. GCE/CoPc(ma) electrode sensed fenitrothion with good selectivity and sensitivity. A linear range for the fenitrothion sensing with GCE/CoPc(ma) electrode was observed between 1.20 mu moldm(-3) and 42.0 mu moldm(-3) concentrations. Moreover, sensitivity and LOD of the electrode were found as 0.26 Acm(-2) M-1 and 0.46 mu moldm(-3) respectively. Although GCE/TiOPc(ma) electrode also sensed fenitrothion with a good selectivity, the linear range of this sensing was very narrow. GCE/Cl-MnPc(ma) electrode sensed all pesticides with similar voltammetric responses, thus its selectivity is poorer than the others, although it has good sensitivity for the pesticides.Publication Metadata only Metal ion sensing multi-functional differently octasubstituted ionophore chiral metallophthalocyanines: Synthesis, characterization, spectroscopy, and electrochemistry(ELSEVIER SCI LTD, 2007) ÖZKAYA, ALİ RIZA; Kandaz, Mehmet; Cetin, H. Sinan; Koca, Atif; Ozkaya, Ali RizaMulti-functional, differently octasubstituted ionophore chiral metallophthalocyanines (MPc's where M = Ni, Cu, Co and Zn), bearing reactive functionalities on the periphery, propane 1,2-diolsulfanyl moieties, which facilitated solubility in polar solvents and metal ion binding, were prepared from the corresponding anhydrous metal salts and differently substituted 4-(1,2-propanediolsulfanyl)-5-chlorobenzene-1,2-dicarbonitrile compound. The reactivity of the peripheral groups of the synthesized We's towards several metal ions was determined spectrophotometrically resulting in the formation of polynuclear phthalocyanine complexes. In all ionophore phthalocyanines, peripheral 1,2-propanediolsulfanyl moieties serve as exocyclic binding sites for a number of metal ions for further reactions after phthalocyanine formation, and also provide solubility of the phthalocyanines in protic solvents. The newly synthesized ligand and MPc's were characterized by elemental analysis, FTIR, H-1 NMR, C-13 NMR, MS (El and FAB), UV/Vis and Atomic Absorption Spectroscopy. The electrochemical behaviours of the complexes have also been investigated. Electrochemical studies reveal that cobalt phthalocyanine indicated two metal-based and three ligand-based redox processes while nickel phthalocyanine and copper phthalocyanine showed three ligand-based reduction and one ligand-based oxidation processes. (c) 2006 Elsevier Ltd. All rights reserved.Publication Metadata only Photocatalytic-electrocatalytic dual hydrogen production system(PERGAMON-ELSEVIER SCIENCE LTD, 2016) ÖZKAYA, ALİ RIZA; Aydemir, Mehmet; Akyuz, Duygu; Agopcan, Burag; Sener, M. Kamm; Albayrak, Fatma Karaca; Sarzoglu, Ceuat; Koca, AtifIn this paper, in order to produce efficient and low cost hydrogen by using alternative energies with simple ways; a photocatalytic electrocatalytic dual hydrogen production system (PEHPS) which combined discontinuous photocatalytic and electrocatalytic systems in one continuous dual system was designed and optimized. In the photocatalytic chamber of PEHPS, nano-sized Cd(1-x)ZnxS/Pt photocatalysts were utilized. The synthesized Cd(1-x)ZnxS/Pt photocatalysts were characterized with scanning electron microscopy (SEM), X-Ray Diffraction (XRD) and diffuse reflectance UV Vis spectroscopy. The most active photocatalyst having CdZnS2 core and 10% Pt shell showed 24.0 mLg(-1) h(-1) (963.6 gmol g 1 h(-1)) hydrogen evolution rate with 4.01% solar energy conversion efficiency (SECE%). S2O3-2 produced in the photocatalytic chamber of PEHPS was used as redox species in the electrocatalytic chamber. This process decreased the cell potential of water electrolysis from 2.50 V to 1.70 V on glassy carbon electrodes. Moreover, usage of electro-polymerized metallophthalocyanines (Poly-MPc) as cathode active electrocatalyst, the over-potential of cathode of the electrocatalytic chamber for hydrogen reduction reaction decreased by 0.230 V. (C) 2015 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.