ahmet m önal - Academia.edu (original) (raw)
Papers by ahmet m önal
2011 Approval of the thesis: COLOR ENGINEERING OF π-CONJUGATED DONOR-ACCEPTOR SYSTEMS:
2011 Approval of the thesis: COLOR ENGINEERING OF π-CONJUGATED DONOR-ACCEPTOR SYSTEMS:
Free radical mediated interaction of ascorbic acid and
Electrochimica Acta, 2021
Abstract A series of new donor-acceptor-donor type fluorescent molecules incorporating thieno[3,4... more Abstract A series of new donor-acceptor-donor type fluorescent molecules incorporating thieno[3,4-c]pyrrole-4,6-dione (TPD) as the acceptor unit were synthesized. TPD acceptor unit was modified with polyhedral oligomeric silsesquioxanes (POSS) cages and integrated with thiophene and alkylenedioxythiophene derivatives (3,4-ethylenedioxythiophene (EDOT) and 3,4-propylenedioxythiophene (ProDOT)) using Stille coupling reaction. The monomers, T2-POSS, E2-POSS, and P2-POSS, were polymerized successfully via electrochemical and chemical polymerization techniques. As a fingerprint of D-A-D monomers, all monomers showed dual band characteristics due to intramolecular charge transfer. Soluble polymers exhibited reversible electrochromic responses electrochemically and chemically with fast switching times and high coloration efficiencies. E2-POSS and its polymer PE2-POSS exhibited the lowest oxidation potential and band gap values as compared to their thiophene and ProDOT analogs. Also, P2-POSS and its chemically obtained fluorescent polymer PP2-POSS-C represented high sensitivity towards Fe2+ and Fe3+ ions, which makes them potential candidates to be amenable for use in ion sensing.
Journal of The Electrochemical Society, 2020
Herein, we report the synthesis of titania supported Rh(0) nanoparticles (Rh0/TiO2) as electrocat... more Herein, we report the synthesis of titania supported Rh(0) nanoparticles (Rh0/TiO2) as electrocatalyst for hydrogen evolution reaction (HER) in acidic medium. Rhodium nanoparticles with an average particle size of 2.54 nm are found to be well-dispersed on TiO2 surface. Rh0/TiO2 with very low loading density (3.79 μg cm−2) was attached on the glassy carbon electrode (GCE) by drop-casting method. Electrocatalytic performance of modified GCE was investigated via linear sweep voltammetry (LSV) in 0.5 M aqueous H2SO4 solution after 2000 cycle treatment (Rh0/TiO2-2000) and it was found that Rh0/TiO2-2000 on GCE exhibits superior electrocatalytic activity (TOF: 11.45 s−1 at η = 100 mV, η 0:−28 mV, η 10 mA cm −2: −37 mV, j0: 0.686 mA cm−2 and Tafel slope: 32 Mv dec−1). More importantly, it provides outstanding long-term stability (10000 cycles) at room temperature for HER, which makes Rh0/TiO2-2000 a promising electrocatalyst for hydrogen generation.
Journal of Colloid and Interface Science, 2020
![Research paper thumbnail of Synthesis and electropolymerization of thieno[3,4-c]pyrrole-4,6-dione based donor-acceptor-donor type monomers](https://attachments.academia-assets.com/117682697/thumbnails/1.jpg)
](Journal of Electroanalytical Chemistry, 2020
European Polymer Journal, 2019
dioxepin-6-yl)-4,4-dioctyl-4H-silolo[3,2-b:4,5-b']dithiophene, was synthesized via palladium cata... more dioxepin-6-yl)-4,4-dioctyl-4H-silolo[3,2-b:4,5-b']dithiophene, was synthesized via palladium catalyzed Stille Coupling Reaction and then polymerized electrochemically in an electrolyte solution of 0.1 M lithium perchlorate dissolved in a mixture of dichloromethane and acetonitrile (1:1, v:v). Due to the presence of long alkyl chains on donor and acceptor units, the corresponding polymer was soluble in common organic solvents like tetrahydrofuran, toluene, hexane and dichloromethane. Polymer has both fluorescent and electrochromic properties. Fluorescent polymer emits a reddish pink at 585 nm when excited at 480 nm and the quantum yield was found as 14%. On the other hand, the electrochromic polymer film changed its color from purple to transmissive cyan with 0.65 s switching time upon moving from neutral state to oxidized state and the film has a coloration efficiency of 501 cm 2 /C as well as 60% optical contrast. The optical band gap of the polymer was also calculated as 1.83 eV with a maximum wavelength at 577 nm.
Journal of Applied Polymer Science, 2018
An analogue of disubstituted 3,4-propylenedioxythiophenes, namely 3,3-bis(cyclohexylmethyl)-3,4-d... more An analogue of disubstituted 3,4-propylenedioxythiophenes, namely 3,3-bis(cyclohexylmethyl)-3,4-dihydro-2H-thieno[3,4b][1,4]dioxepin (ProDOT-CycHex 2), was synthesized and its electrochemical polymerization was carried out successfully in an electrolyte solution of 0.1 M tetrabutylammonium hexafluorophosphate dissolved in a mixture of acetonitrile and dichloromethane (3/1: v/v). The corresponding polymer called PProDOT-CycHex 2 has a reduced band gap of 1.85 eV and an electrochromic property: blue/ violet when neutralized and highly transparent when oxidized. Also, PProDOT-CycHex 2 film exhibited faster response time (0.7 s) and higher coloration efficiency (769 cm 2 /C) during oxidation when compared to its benzyl substituted analogue. V
Journal of colloid and interface science, Jan 22, 2018
Ruthenium(0) nanoparticles were successfully prepared on the surface of ceria (Ru/CeO) and used a... more Ruthenium(0) nanoparticles were successfully prepared on the surface of ceria (Ru/CeO) and used as catalysts on glassy carbon electrode (GCE) in oxygen evolution reaction (OER) from water electrolysis at room temperature. Ru/CeO on GCE exhibits high catalytic activity for OER in alkaline solution. It provides a low onset potential of 1.57 V vs. RHE and low overpotential of 420 mV vs. RHE to reach a current density of 10 mA cm. Ru/CeO on GCE shows no change in the onset potential value even after 6.1 h electrochemical measurement in OER.
Journal of colloid and interface science, Jan 20, 2018
Designing a cost-effective catalyst with high activity and stability for hydrogen evolution react... more Designing a cost-effective catalyst with high activity and stability for hydrogen evolution reaction (2H + 2e → H) is a big challenge due to increasing demand for energy. Herein, we report the electrocatalytic activity of glassy carbon electrodes with group 4 metal oxides (TiO, ZrO, HfO) supported ruthenium(0) nanoparticles in hydrogen evolution reaction. Electrochemical activity of modified electrodes is investigated by recording linear sweep voltammograms in 0.5 M HSO solution. The results of electrochemical measurements reveal that among the three electrodes the glassy carbon electrode with Ru/TiO (1.20% wt. Ru) exhibits the highest activity with a relatively small Tafel slope of 52 mV dec, the highest exchange current density of 0.728 mA cm, and the smallest overpotential of 41 mV at j = 10 mA cm. Furthermore, it demonstrates superior stability in acidic solution with an unaltered onset potential for long term electrochemical measurement.
Reactive and Functional Polymers, 2010
A novel terthienyl based fluorescent polymer bearing strong electron-withdrawing substituents dir... more A novel terthienyl based fluorescent polymer bearing strong electron-withdrawing substituents directly attached to the 3,4-positions of the central thiophene ring was synthesized by electrochemical polymerization of diethyl 2,5-di(3,4-ethylenedioxythiophen-2-yl)thiophene-3,4-dicarboxylate. The corresponding polymer was characterized by cyclic voltammetry, FT-IR and UV-vis spectroscopy. The polymer has a well-defined redox process (E p,1/2 = 0.74 V) and demonstrates a reversible electrochromic behavior; lilac in the neutral state and transparent sky blue in the oxidized state. Also, the polymer had low band gap (E g = 1.82 eV) and high redox stability (retaining 94.0% of its electro-activity after 500th switch). Moreover, the sensitivity of both the monomer and its polymer towards metal cations was investigated by monitoring the change in the fluorescence intensity. Among various common ions both the monomer and its polymer were found to be selective towards Cu 2+ and Cu + ions by quenching the fluorescence efficiency with a Stern-Volmer constant (K sv) of (1.4-1.6 Â 10 3 M À1) and (1.5-1.8 Â 10 2 M À1) for monomer and polymer solutions, respectively.
Zeitschrift für Naturforschung B, 1998
Tricarbonyl(η6-cyclooctatetraene)metal(0) complexes of the group 6 elements were prepared by usin... more Tricarbonyl(η6-cyclooctatetraene)metal(0) complexes of the group 6 elements were prepared by using the procedures described in the literature with some minor modifications and identified by IR and NMR spectroscopy. Their electrochemical behavior was studied by using cyclic voltammetry in dichloromethane solution containing 0.1 M tetrabutylammonium tetrafiuorob-orate as supporting electrolyte. Their oxidation and reduction potentials were measured and discussed in terms of the frontier energy levels in connection with the UV-Visible electronic ab sorption spectral data. In order to elucidate the mechanism of electrooxidation of the complexes, constant potential electrolysis was performed for one representative example, tricarbonyl(η6-cyclooctatetraene)chromium(O). The IR monitoring of the reaction showed that it is gradually converted to hexacarbonylchromium(O) upon electrolysis at constant potential.
Polymer International, 2009
BACKGROUND: Microsphere and/or hollow sphere formation of methyl‐substituted polyaniline derivati... more BACKGROUND: Microsphere and/or hollow sphere formation of methyl‐substituted polyaniline derivatives was investigated via chemical polymerization where different sets of conditions were examined. It was found that a variety of parameters (e.g. types and concentrations of monomer and oxidant, polymerization time, solvent with and without acid) have a crucial influence on the morphology of the resulting polyaniline derivatives.RESULTS: Structures with desired morphologies (with or without microspheres and hollow spheres) may be obtained in a controlled manner by changing the parameters. Moreover, the electrochemical and optical properties of the polymers in the presence of acid and/or base were investigated via cyclic voltammetry and UV‐visible and electron spin resonance spectroscopic techniques. It is noteworthy that the morphologies of microspheres and/or hollow spheres remained unchanged after repeated acid and base treatments.CONCLUSION: Micro/hollow spherical structures were suc...
Organic Electronics, 2010
2011 Approval of the thesis: COLOR ENGINEERING OF π-CONJUGATED DONOR-ACCEPTOR SYSTEMS:
2011 Approval of the thesis: COLOR ENGINEERING OF π-CONJUGATED DONOR-ACCEPTOR SYSTEMS:
Free radical mediated interaction of ascorbic acid and
Electrochimica Acta, 2021
Abstract A series of new donor-acceptor-donor type fluorescent molecules incorporating thieno[3,4... more Abstract A series of new donor-acceptor-donor type fluorescent molecules incorporating thieno[3,4-c]pyrrole-4,6-dione (TPD) as the acceptor unit were synthesized. TPD acceptor unit was modified with polyhedral oligomeric silsesquioxanes (POSS) cages and integrated with thiophene and alkylenedioxythiophene derivatives (3,4-ethylenedioxythiophene (EDOT) and 3,4-propylenedioxythiophene (ProDOT)) using Stille coupling reaction. The monomers, T2-POSS, E2-POSS, and P2-POSS, were polymerized successfully via electrochemical and chemical polymerization techniques. As a fingerprint of D-A-D monomers, all monomers showed dual band characteristics due to intramolecular charge transfer. Soluble polymers exhibited reversible electrochromic responses electrochemically and chemically with fast switching times and high coloration efficiencies. E2-POSS and its polymer PE2-POSS exhibited the lowest oxidation potential and band gap values as compared to their thiophene and ProDOT analogs. Also, P2-POSS and its chemically obtained fluorescent polymer PP2-POSS-C represented high sensitivity towards Fe2+ and Fe3+ ions, which makes them potential candidates to be amenable for use in ion sensing.
Journal of The Electrochemical Society, 2020
Herein, we report the synthesis of titania supported Rh(0) nanoparticles (Rh0/TiO2) as electrocat... more Herein, we report the synthesis of titania supported Rh(0) nanoparticles (Rh0/TiO2) as electrocatalyst for hydrogen evolution reaction (HER) in acidic medium. Rhodium nanoparticles with an average particle size of 2.54 nm are found to be well-dispersed on TiO2 surface. Rh0/TiO2 with very low loading density (3.79 μg cm−2) was attached on the glassy carbon electrode (GCE) by drop-casting method. Electrocatalytic performance of modified GCE was investigated via linear sweep voltammetry (LSV) in 0.5 M aqueous H2SO4 solution after 2000 cycle treatment (Rh0/TiO2-2000) and it was found that Rh0/TiO2-2000 on GCE exhibits superior electrocatalytic activity (TOF: 11.45 s−1 at η = 100 mV, η 0:−28 mV, η 10 mA cm −2: −37 mV, j0: 0.686 mA cm−2 and Tafel slope: 32 Mv dec−1). More importantly, it provides outstanding long-term stability (10000 cycles) at room temperature for HER, which makes Rh0/TiO2-2000 a promising electrocatalyst for hydrogen generation.
Journal of Colloid and Interface Science, 2020
Journal of Electroanalytical Chemistry, 2020
European Polymer Journal, 2019
dioxepin-6-yl)-4,4-dioctyl-4H-silolo[3,2-b:4,5-b']dithiophene, was synthesized via palladium cata... more dioxepin-6-yl)-4,4-dioctyl-4H-silolo[3,2-b:4,5-b']dithiophene, was synthesized via palladium catalyzed Stille Coupling Reaction and then polymerized electrochemically in an electrolyte solution of 0.1 M lithium perchlorate dissolved in a mixture of dichloromethane and acetonitrile (1:1, v:v). Due to the presence of long alkyl chains on donor and acceptor units, the corresponding polymer was soluble in common organic solvents like tetrahydrofuran, toluene, hexane and dichloromethane. Polymer has both fluorescent and electrochromic properties. Fluorescent polymer emits a reddish pink at 585 nm when excited at 480 nm and the quantum yield was found as 14%. On the other hand, the electrochromic polymer film changed its color from purple to transmissive cyan with 0.65 s switching time upon moving from neutral state to oxidized state and the film has a coloration efficiency of 501 cm 2 /C as well as 60% optical contrast. The optical band gap of the polymer was also calculated as 1.83 eV with a maximum wavelength at 577 nm.
Journal of Applied Polymer Science, 2018
An analogue of disubstituted 3,4-propylenedioxythiophenes, namely 3,3-bis(cyclohexylmethyl)-3,4-d... more An analogue of disubstituted 3,4-propylenedioxythiophenes, namely 3,3-bis(cyclohexylmethyl)-3,4-dihydro-2H-thieno[3,4b][1,4]dioxepin (ProDOT-CycHex 2), was synthesized and its electrochemical polymerization was carried out successfully in an electrolyte solution of 0.1 M tetrabutylammonium hexafluorophosphate dissolved in a mixture of acetonitrile and dichloromethane (3/1: v/v). The corresponding polymer called PProDOT-CycHex 2 has a reduced band gap of 1.85 eV and an electrochromic property: blue/ violet when neutralized and highly transparent when oxidized. Also, PProDOT-CycHex 2 film exhibited faster response time (0.7 s) and higher coloration efficiency (769 cm 2 /C) during oxidation when compared to its benzyl substituted analogue. V
Journal of colloid and interface science, Jan 22, 2018
Ruthenium(0) nanoparticles were successfully prepared on the surface of ceria (Ru/CeO) and used a... more Ruthenium(0) nanoparticles were successfully prepared on the surface of ceria (Ru/CeO) and used as catalysts on glassy carbon electrode (GCE) in oxygen evolution reaction (OER) from water electrolysis at room temperature. Ru/CeO on GCE exhibits high catalytic activity for OER in alkaline solution. It provides a low onset potential of 1.57 V vs. RHE and low overpotential of 420 mV vs. RHE to reach a current density of 10 mA cm. Ru/CeO on GCE shows no change in the onset potential value even after 6.1 h electrochemical measurement in OER.
Journal of colloid and interface science, Jan 20, 2018
Designing a cost-effective catalyst with high activity and stability for hydrogen evolution react... more Designing a cost-effective catalyst with high activity and stability for hydrogen evolution reaction (2H + 2e → H) is a big challenge due to increasing demand for energy. Herein, we report the electrocatalytic activity of glassy carbon electrodes with group 4 metal oxides (TiO, ZrO, HfO) supported ruthenium(0) nanoparticles in hydrogen evolution reaction. Electrochemical activity of modified electrodes is investigated by recording linear sweep voltammograms in 0.5 M HSO solution. The results of electrochemical measurements reveal that among the three electrodes the glassy carbon electrode with Ru/TiO (1.20% wt. Ru) exhibits the highest activity with a relatively small Tafel slope of 52 mV dec, the highest exchange current density of 0.728 mA cm, and the smallest overpotential of 41 mV at j = 10 mA cm. Furthermore, it demonstrates superior stability in acidic solution with an unaltered onset potential for long term electrochemical measurement.
Reactive and Functional Polymers, 2010
A novel terthienyl based fluorescent polymer bearing strong electron-withdrawing substituents dir... more A novel terthienyl based fluorescent polymer bearing strong electron-withdrawing substituents directly attached to the 3,4-positions of the central thiophene ring was synthesized by electrochemical polymerization of diethyl 2,5-di(3,4-ethylenedioxythiophen-2-yl)thiophene-3,4-dicarboxylate. The corresponding polymer was characterized by cyclic voltammetry, FT-IR and UV-vis spectroscopy. The polymer has a well-defined redox process (E p,1/2 = 0.74 V) and demonstrates a reversible electrochromic behavior; lilac in the neutral state and transparent sky blue in the oxidized state. Also, the polymer had low band gap (E g = 1.82 eV) and high redox stability (retaining 94.0% of its electro-activity after 500th switch). Moreover, the sensitivity of both the monomer and its polymer towards metal cations was investigated by monitoring the change in the fluorescence intensity. Among various common ions both the monomer and its polymer were found to be selective towards Cu 2+ and Cu + ions by quenching the fluorescence efficiency with a Stern-Volmer constant (K sv) of (1.4-1.6 Â 10 3 M À1) and (1.5-1.8 Â 10 2 M À1) for monomer and polymer solutions, respectively.
Zeitschrift für Naturforschung B, 1998
Tricarbonyl(η6-cyclooctatetraene)metal(0) complexes of the group 6 elements were prepared by usin... more Tricarbonyl(η6-cyclooctatetraene)metal(0) complexes of the group 6 elements were prepared by using the procedures described in the literature with some minor modifications and identified by IR and NMR spectroscopy. Their electrochemical behavior was studied by using cyclic voltammetry in dichloromethane solution containing 0.1 M tetrabutylammonium tetrafiuorob-orate as supporting electrolyte. Their oxidation and reduction potentials were measured and discussed in terms of the frontier energy levels in connection with the UV-Visible electronic ab sorption spectral data. In order to elucidate the mechanism of electrooxidation of the complexes, constant potential electrolysis was performed for one representative example, tricarbonyl(η6-cyclooctatetraene)chromium(O). The IR monitoring of the reaction showed that it is gradually converted to hexacarbonylchromium(O) upon electrolysis at constant potential.
Polymer International, 2009
BACKGROUND: Microsphere and/or hollow sphere formation of methyl‐substituted polyaniline derivati... more BACKGROUND: Microsphere and/or hollow sphere formation of methyl‐substituted polyaniline derivatives was investigated via chemical polymerization where different sets of conditions were examined. It was found that a variety of parameters (e.g. types and concentrations of monomer and oxidant, polymerization time, solvent with and without acid) have a crucial influence on the morphology of the resulting polyaniline derivatives.RESULTS: Structures with desired morphologies (with or without microspheres and hollow spheres) may be obtained in a controlled manner by changing the parameters. Moreover, the electrochemical and optical properties of the polymers in the presence of acid and/or base were investigated via cyclic voltammetry and UV‐visible and electron spin resonance spectroscopic techniques. It is noteworthy that the morphologies of microspheres and/or hollow spheres remained unchanged after repeated acid and base treatments.CONCLUSION: Micro/hollow spherical structures were suc...
Organic Electronics, 2010