Person: ÖZKAYA, ALİ RIZA
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ÖZKAYA
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ALİ RIZA
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Publication Metadata only Tiyobis-naftol sübstitüe metalli ftalosiyanin bileşiklerinin elektrokimyasal, spektroelektrokimyasal ve elektrokatalitik özellikleri(2022-10-12) CENGİZ, ERHAN ŞÜKRÜ; ORMAN, EFE BATURHAN; ODABAŞ, ZAFER; ÖZKAYA, ALİ RIZA; Cengiz E. Ş., Akdağ Ö., Zayin Ö., Orman E. B., Odabaş Z., Özkaya A. R.Yakın gelecekte yaşanabilecek enerji kıtlığı nedeniyle çevre dostu ve sürdürülebilir enerji sistemlerine ihtiyaç duyulmaktadır. Yakıt pilleri; sürdürülebilir ve temiz enerji için umut vadeden, yüksek özgül enerji yoğunlukları, enerji dönüşüm verimlilikleri, düşükten sıfıra emisyonları ve yüksek güvenlikleri nedeniyle büyük ilgi görmüştür. Ayrıca metal-hava pilleri, özellikle teorik enerji yoğunluğu mevcut Li-iyon pillere göre çok daha yüksek olan Zn-hava pili, çok daha ucuz ve güvenli olmakla birlikte, gelecek vadeden sistemlerdir. Oksijen indirgeme reaksiyonu (ORR) elektrokatalizörleri, bu sistemlerin genel performansını ve verimliliğini belirler. Sonuç olarak değerli Pt bazlı malzemelere alternatif olarak uygun maliyetli ORR elektrokatalizörlerinin geliştirilmesi bu sistemlerin uygulanabilirliği açısından önemlidir.Ftalosiyanin (Pc) kompleksleri, yüksek redoks aktiviteleri, kimyasal ve ısıl kararlılıkları ve ayrıca karbon malzemelerle yüksek uyumlulukları nedeniyle sıklıkla araştırılan umut verici adaylardandır. Karbon malzemelerle olan kompozitleri, yukarıda belirtilen sistemlerin katotları için oldukça aktif ve değerlidir. Bu çalışmada, 1,1`-tiyobis(naftalen-2-oksi) sübstitüe Pc komplekslerinin redoks davranışları voltametrik ve eş-zamanlı spektroelektrokimyasal ölçümler ile incelenmiş ve ardından MPc-karbon kompozitleri ile modifiye edilen camsı karbon elektrotlar (GCE) ile ORR\" ye yönelik katalitik aktiviteleri değerlendirilmiştir.Publication Metadata only Electrochemical, Electrocatalytic Dioxygen Reducing and Dielectric Relaxation Properties of Non-Peripheral Tetra-2,3-dihydro-1H-inden-5-yloxy Substituted Phthalocyanines(ELECTROCHEMICAL SOC INC, 2015) ÖZKAYA, ALİ RIZA; Orman, Efe Baturhan; Altun, Selcuk; Odabas, Zafer; Altindal, Ahmet; Ozkaya, Ali RizaNovel metal-free and metallophthalocyanines were synthesized by cyclotetramerization of 3-(2,3-dihydro-1H-inden-5-yloxy)phthalonitrile and characterized. The redox properties of these compounds were investigated by cyclic voltammetry, square-wave voltammetry, controlled-potential coulometry and in situ spectroelectrochemistry in dimethylsulfoxide and dichloromethane. The compounds displayed metal and/or phthalocyanine ring-based reduction and oxidation processes. The color changes associated with these redox processes and electrogenerated anionic and cationic redox species were recorded with in situ electrocolorimetric measurements. The electrocatalytic performances of the compounds toward oxygen reduction reaction having vital importance for fuel cell applications were determined by hydrodynamic rotating disk and bipotentiostatic rotating ring-disk voltammetry measurements. The Vulcan XC-72/Nf/FePc modified glassy carbon electrode showed much higher catalytic performance toward oxygen reduction than those of the other modified ones. Furthermore, the field dependence of dielectric response and the conductivity of the samples were measured as a function of frequency and temperature. Dielectric relaxation behaviors of the phthalocyanines were also investigated. The ITO/ZnPc/Au sample showed the highest value of epsilon'(omega) as compared to the other samples. The analysis of the real and imaginary parts of the dielectric permittivity with frequency was carried out assuming a distribution of relaxation times as well as the scaling behavior of the dielectric loss spectra. (C) 2015 The Electrochemical Society. All rights reserved.Publication Metadata only Tiyobis Naftelen Köprülü Top Tipi Metalli Ftalosiyanin Bileşiklerinin Elektrokimyasal, Spektroelektrokimyasal ve Elektrokatalitik Özellikleri(2022-10-12) CENGİZ, ERHAN ŞÜKRÜ; ORMAN, EFE BATURHAN; ODABAŞ, ZAFER; ÖZKAYA, ALİ RIZA; Cengiz E. Ş., Akdağ Ö., Zayin Ö., Orman E. B., Odabaş Z., Özkaya A. R.Geçiş metali N4-makrosiklik komplekslerin, moleküler oksijeninin katalitik indirgenmesi için oldukça aktif olduğu uzun zamandır bilinmektedir. Bu ailedeki çeşitli elektrokatalizörler arasında, ftalosiyanin (Pc) kompleksleri, özellikle yüksek reversibillikteki ve zengin elektron transfer yeteneklerine sahip redoks-aktif metal merkezlere sahip olanları, yüksek aktiviteleri ve düşük maliyetleri ile umut vaat eden adaylardır. 18-Π elektron sistemleri, reaktif oksijenin yapıya difüzlenebilmesi için gerekli gözenekliliği destekleyen ve yukarıda belirtilen sistemlerin katodu için yüksek iletkenlik sağlayan karbon malzemelerle mükemmel uyumluluk gösterir. Bu nedenle, Pc-karbon ikili kompozitleri gelecek vaat eden katot malzemeleri olarak kabul edilir. Bu projede, mononükleer formlarına göre daha yüksek katalitik aktivite göstermesi beklenen ikili metal merkezleri nedeniyle dört adet 1,1`-Tiyobis(naftalin 2-oksi) köprülü top tipi metaloftalosiyanin kompleksi seçilmiştir. Elektrokimyasal ve spektroelektrokimyasal özellikleri, döngüsel voltametri (CV) ve kare dalga voltametrisi (SWV) gibi elektrokimyasal tekniklerle belirlenmiştir. Bu aşamadan sonra elektrot modifikasyonu için karbon malzemelerle hazırlanan ikili kompozitler ve bunların ORR\"ye yönelik katalitik aktiviteleri hidrodinamik elektroanalitik yöntemlerle incelenmiştir.Publication Metadata only Coumarin-substituted manganese phthalocyanines: synthesis, characterization, photovoltaic behaviour, spectral and electrochemical properties(ROYAL SOC CHEMISTRY, 2014) ÖZKAYA, ALİ RIZA; Altun, Selcuk; Odabas, Zafer; Altindal, Ahmet; Ozkaya, Ali RizaThe synthesis and spectroscopic characterization of novel manganese(III) phthalocyanines bearing 7-oxy-4-(4-methoxyphenyl)-8-methylcoumarin or/and chloro groups have been achieved. The effect of alpha and beta substitution on the ligand-and metal-based reduction processes of the manganese phthalocyanine complexes and their interaction with dioxygen were investigated. The more effective interaction of the central metal of the beta coumarin substituted complex with dioxygen than that of its alpha substituted analogue was attributed to the hindrance of the interaction by the nonplanarity in the case of alpha substitution. Similarly, the aggregation tendency was lower in the case of alpha substitution. Among the fabricated coumarin-substituted manganese phthalocyanine donor layer and fullerene (C-60) acceptor based photovoltaic heterojunction devices, the one containing 8 exhibited the best performance. The effect of the thickness of the active Pc layer on solar cell parameters has also been investigated. A nearly thickness independent open circuit voltage was observed.Publication Metadata only High Electrochemical Versatility and Applicability with Metal Phthalocyanines Carrying Peripheral 2,3-dihydro-1H-inden-5-yloxy Substituents: Rich Redox Behavior, Oxygen Electrocatalysis and Electrochromism(ELECTROCHEMICAL SOC INC, 2018) ÖZKAYA, ALİ RIZA; Orman, Efe Baturhan; Odaba, Zafer; Ozkaya, Ali RizaThe presence of cobalt(II), iron(III) and manganese(III) in the peripherally 2,3-dihydro-1H-inden-5-yloxy substituted phthalocyanine (Pc) core enriched their redox character in non-aqueous media with additional reversible metal-based reduction and oxidation couples, compared to their metal-free and tin(IV) Pc analogues displaying only Pc ring-based redox processes. The existence of trace amount of dioxygen in the electrolyte system was observed to considerably influence the redox behaviors of FePc and MnPc. As a result of the enhanced interaction between dioxygen and the central metal, the FePc showed much higher catalytic performance for oxygen reduction reaction than those of the others. It was also nearly insensitive to the presence of methanol. The comparison with the Pt-based catalyst showed that it could be a good alternative to the platinum as cathode catalyst, especially in direct methanol fuel cells. Furthermore, the association of the redox processes of metal Pcs with distinct spectral and color changes pointed out the possibility of their application as electrochromic materials. Langmuir Blodgett film of Mn(Cl)Pc compound on the indium tin oxide glass behaved as ideal neutral and cathodic coloring material, displaying red to green and red to purple color changes between its cationic forms with fast response time and high optical stability. (C) 2018 The Electrochemical Society.Publication Metadata only Novel alpha-7-oxy-4-(4-methoxyphenyl)-8-methylcoumarin substituted metal-free, Co(II) and Zn(II) phthalocyanines: Photochemistry, photophysics, conductance and electrochemistry(ELSEVIER SCI LTD, 2012) ÖZKAYA, ALİ RIZA; Odabas, Zafer; Orman, Efe Baturhan; Durmus, Mahmut; Dumludag, Fatih; Ozkaya, Ali Riza; Bulut, MustafaNovel alpha-substituted metal-free. Co(II) and Zn(II) phthalocyanines, bearing four 7-oxy-4-(4-methoxyphenyl)-8-methylcoumarin moieties were synthesized. The compounds were characterized by elemental analysis, IR, UV vis, H-1 NMR, C-13 NMR and MALDI-TOF mass spectroscopies. The Zn(II) phthalocyanine compound showed J-type aggregation in non-coordinating solvents. The photophysical and photochemical properties of these compounds were described in different solvents. Direct current conductivity measurements of the films of Co(II) and Zn(II) phthalocyanines as a function of temperature showed that these compounds are semiconductors with the activation energies within the range of 0.40-0.84 eV. The variation of alternating current conductivity of the films with frequency was found to be represented by the function sigma(AC) = A omega(s). The results indicated that charge transport mechanism of the films can be explained by hopping. The redox properties of the compounds were also examined in dimethylsulfoxide and dichloromethane by voltammetry and in situ spectroelectrochemistry. The compounds displayed metal and/or phthalocyanine ring-based reduction and oxidation processes. The electrochemistry of a phthalocyanine compound forming a J-aggregated species has been investigated. It was found that some redox couples of the Zn(II) compound in dichloromethane is split due to the equilibrium between its aggregated and non-aggregated species. (C) 2012 Elsevier Ltd. All rights reserved.Publication Metadata only Synthesis, characterization and electrochemical properties of novel beta 7-oxy-4-(4-methoxyphenyl)-8-methylcoumarin substituted metal-free, Zn(II) and Co(II) phthalocyanines(PERGAMON-ELSEVIER SCIENCE LTD, 2012) ÖZKAYA, ALİ RIZA; Odabas, Zafer; Kara, Hatice; Ozkaya, Ali Riza; Bulut, MustafaNovel metal-free (4), Co(II) (5) and Zn(II) (6) phthalocyanines bearing four 7-oxy-4-(4-methoxyphenyl)-8-methylcoumarin substituents at peripheral (p) positions have been prepared by cyclotetramerization of 4-(4-(4-methoxyphenyl)-8-methylcoumarin-7-oxy)phthalonitrile. The compounds have been characterized by elemental analysis and IR, UV-Vis and MALDI-TOF mass spectroscopies. H-aggregation behaviour of the compounds has been investigated in different solvent media. Furthermore, the redox properties of the complexes were examined in dimethylsulfoxide and dichloromethane by voltammetry and in situ spectroelectrochemistry. In general, compounds 4 and 6 displayed ligand-based one-electron redox processes, while compound 5 showed both ligand- and metal-based processes, in addition to a couple corresponding to the reduction of the 7-hydroxy-4-(4-methoxyphenyl)-8-methylcoumarin substituents. Both electrochemical and in situ spectroelectrochemical data showed that the redox processes of these complexes are complicated by their high aggregation tendency. (C) 2012 Elsevier Ltd. All rights reserved.Publication Metadata only Synthesis, characterization, and electrochemical, spectroelectrochemical and electrical measurements of novel ball-type four 1,1 '-methylenedinaphthalen-2-ol bridged metal-free, zinc(II) and cobalt(II), and metal-free clamshell phthalocyanines(PERGAMON-ELSEVIER SCIENCE LTD, 2007) ÖZKAYA, ALİ RIZA; Odabas, Zafer; Altindal, Ahmet; Ozkaya, Ali Riza; Bulut, Mustafa; Salih, Bekir; Bekaroglu, OzerThe new ball-type bisplithalocyanines [metal-free 6, Zn(II) 7 and Co(II) 8] were synthesized from the corresponding 4,4'-[1,1'-methyl-enebis(naphthalene-2,1-diyl)]bis(oxy)di-phthalonitrile 4, which can be obtained from the reaction of 4-nitrophthalonitrile (2) with 1,1'-methylenedinaphthalen-2-ol 3. A novel clamshell type bisphthalocyanine 5 was synthesized from compound 4 and 4,5-bis(hexylthio)phthalonitrile 1. The novel compounds have been characterized by elemental analysis, UV/Vis, IR, H-1 NMR and MALDI-TOF Mass spectroscopies. The electrochemical and spectroclectrochernical measurements showed the formation of various mixed-valence oxidation and reduction species, due to the strong intramolecular interactions between the two phthalocyanine rings, especially in the ball-type phthalocyanines. The conduction properties of the compounds have been examined by d.c. and impedance spectroscopy measurements as function of temperature and frequency. D.c. conductivity, measured between 290 and 480 K, is thermally activated with the activation energy ranging between 0.62 and 0.84 eV. The a.c. results gave a power law behaviour, sigma(a.c.) = A(T)w(s), in which the frequency exponent s decreases with temperature for 6, 7 and 8. The bulk resistance of the samples was derived from complex impedance spectra. It was found that the bulk resistance shows a typical negative temperature coefficient of resistance, decreasing with a rise in temperature, like that of a semiconductor. (c) 2006 Elsevier Ltd. All rights reserved.Publication Metadata only Synthesis and electrochemical, in situ spectroelectrochemical, electrical and gas sensing properties of ball-type homo- and hetero-dinuclear phthalocyanines with four [1a,8b-dihydronaphtho[b]naphthofuro[3,2-d]furan-7,10-diyl] bridges(ELSEVIER SCIENCE SA, 2010) ÖZKAYA, ALİ RIZA; Odabas, Zafer; Koc, Imran; Altindal, Ahmet; Ozkaya, Ali Riza; Salih, Bekir; Bekaroglu, OezerThe new mono-nuclear Fe(II) 2 and ball-type homo-dinuclear Fe(II)-Fe(II) 3 phthalocyanines have been synthesized from the corresponding 4,4'-(1a,8b-dihydronaphtho[b]naphthofuro[3,2-d]-furan-7,10-diyl)bis(oxy)diphthalonitrile 1 while ball-type hetero-dinuclear Fe(II)-Co(II) phthalocyanine 4 was synthesized from 2. The compounds have been characterized by elemental analysis, UV-vis, IR and MALDI-TOF-mass spectroscopies. The redox behaviours of the complexes were identified by controlled-potential coulometry, cyclic voltammetry and differential pulse voltammetry measurements on Pt in dimethylsulfoxide containing tetrabutylammonium perchlorate. The assignments of the redox processes and the understanding of the interactions between the metal phthalocyanine units in 3 and 4 were achieved by the combined evaluation of the voltammetric and in situ spectroelectrochemical outcomes. Complex 3 showed ring-based mixed-valence behaviour as a result of the considerable interaction between the phthalocyanine rings. On the other hand, the interactions between the two metal phthalocyanine units of 4 were found to be much weaker than those in 3. The potential application of molecular organic semiconductors needs the control adjustment of conductivity. Ac and dc conductivity measurements were performed with the applied external electric filed. At high frequency, the conduction follows the universal power law and conduction mechanism can be explained by classical hopping barriers mechanism for the system. (C) 2010 Elsevier B.V. All rights reserved.Publication Metadata only Novel ball-type homo- and hetero-dinuclear phthalocyanines with four 1,1 '-methylenedinaphthalen-2-ol bridges: Synthesis and characterization, electrical and gas sensing properties and electrocatalytic performance towards oxygen reduction(ELSEVIER SCIENCE SA, 2010) ÖZKAYA, ALİ RIZA; Odabas, Zafer; Altindal, Ahmet; Ozkaya, Ali Riza; Salih, Bekir; Bekaroglu, OzerThe new mono-nuclear Fe(II) phthalocyanine 2 and ball-type homo-dinuclear Fe(II)-Fe(II) phthalocyanine 3 were synthesized from the corresponding 4,4'4-[1,1'-methylenebis-(naphthalene-2,1-diyl)]bis(oxy)diphthalonitrile 1, and then ball-type hetero-dinuclear Fe(II)-Co(II) phthalocyanine 4 was synthesized from 2. The novel compounds have been characterized by elemental analysis, UV/vis, IR and MALDI-TOF mass spectroscopies. Electrocatalytic activity of the high-surface area carbon, Vulcan XC-72R (VC) and Nation (NI) supported complexes towards oxygen reduction was investigated and compared by surface cyclic voltammetry and rotating ring-disk electrode experiments in acidic medium. The VC/Nf/2 and especially VC/Nf/3 modified glassy carbon electrodes showed high catalytic performance, producing water as the main product through the direct four-electron path. A.c. and d.c. measurements were performed on spin coated 2-4 films as a function of temperature (290-436 K). The d.c. results showed an activated conductivity dependence on temperature. The a.c. results gave a temperature dependent frequency exponent s. Gas sensing properties of the films for the volatile organic compounds (VOCs) (toluene, chloroform, ethanol and carbontetrachloride) were also investigated in the temperature range from 290 to 436K. It was observed that the operating temperature had a considerable effect on sensing characteristics of 3 but not 4. (C) 2009 Elsevier B.V. All rights reserved.