Sukriye Ulubay Karabiberoğlu | Ege University (original) (raw)

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Papers by Sukriye Ulubay Karabiberoğlu

The electrochemical oxidation of 2,6-diaminopurine (2,6-DAP) was studied in pH 7.4 phosphate buff... more The electrochemical oxidation of 2,6-diaminopurine (2,6-DAP) was studied in pH 7.4 phosphate buffer solution on multiwall carbon nanotube modified glassy carbon electrode (MWCNT/GCE) over a temperature range of 20 to 50 • C using cyclic voltammetry. 2,6-DAP oxidation on MWCNT/GCE showed a well-defined and irreversible oxidation peak at about 0.72 V vs. Ag/AgCl at pH 7.4. The oxidation potential of 2,6-DAP linearly varied with pH over the range of 3.0 to 10.0 with a slope of -0.0547 V/pH, implying that 2 protons were accompanied by 2 electrons transferred in the electrochemical reaction. The activation energy, Ea, of oxidation reaction was found to be 33.10 ± 1.88 kJ/mol. The differential pulse voltammetric determination of 2,6-DAP was also studied. The peak currents increased linearly with increasing of the 2,6-DAP concentration range from 0.4 µ mol/L to 80 µ mol/L. The linear regression equation appeared as I p / µ A = -(1.66 ± 0.42) + (4.21 ± 0.11) [2,6-DAP]/ µ mol/L, R 2 = 0.9982, and the detection limit (S/N = 3) was 3 × 10 −7 ± 0.015 mol/L (n = 3). The electrocatalytic oxidation of 2,6-DAP on MWCNT/GCE showed that acid pretreated multiwall carbon nanotube can be used in new applications in electrochemical determinations of biologically important compounds.

Electrocatalytic reduction of oxygen at electrochemically deposited Pt ad-layer modified Au(111) ... more Electrocatalytic reduction of oxygen at electrochemically deposited Pt ad-layer modified Au(111) electrodes was studied in an O 2 -saturated NaOH (0.1 M) solution. The results were compared with those obtained by using a polycrystalline Pt electrode and another Pt-deposited electrode prepared by replacement with Cu on bare Au(111). Linear sweep voltammetry displayed a positive shift of the oxygen reduction potential by about 0.14 V compared to the bare Au(111) electrode. This shift was about 0.06 V compared to a Pt disk electrode. Tafel slopes gradually changed between 0.06 and 0.1 V/dec, from 0.075 to -0.10 V/dec, from lower to higher current density region. The Pt ad-layer clearly served as a catalyst for oxygen reduction via 4-electron transfer. In terms of the desired shift in reduction potential and increased current density, the best electrocatalytic activity was obtained with a 30-s electrodeposited Pt ad-layer modified Au(111) electrode.

Ethanol oxidation was studied on single-crystal Au(111) electrodes that were modified by platinum... more Ethanol oxidation was studied on single-crystal Au(111) electrodes that were modified by platinum, palladium, and cadmium metal ad-layers. The metal ad-layer modification was carried out by the underpotential deposition process, in which controlled amounts of Pt, Pd, and Cd were electrodeposited onto the substrate as submonolayer or monolayer coverage. The activity of the metal ad-layer modified Au(111) electrodes toward ethanol oxidation was studied in alkaline media, and recorded voltammograms were compared to those of bare single crystal Au(111) and polycrystalline gold and platinum disk electrodes. In terms of the desired shift in reduction potential and increased current density, the best electrocatalytic activity was obtained with a 30-s electrodeposited Pt ad-layer modified Au(111) electrode.

International Journal of …, 2011

Pt ad-atom Zn ad-atom Cd ad-atom Au(111) single crystal electrode Fuel cell a b s t r a c t The e... more Pt ad-atom Zn ad-atom Cd ad-atom Au(111) single crystal electrode Fuel cell a b s t r a c t The electrochemical oxidation of borohydride was investigated by using various ad-atom modified Au(111) electrodes in alkaline media in comparison to Au(111) single crystal, polycrystalline Au, Pt and Zn electrodes. The catalytic activity of gold towards borohydride oxidation has tended to increase in more alkaline media as reflected in the oxidation peak in the concentration range of NaOH (0.01e2.0 M) studied. Additional shift on the oxidation peak potential of borohydride on Pt and Zn ad-atom modified Au(111) electrodes was observed for both ad-atom modified electrodes to more negative potentials compared to that of bare electrodes, respectively. The ad-atom modified Au(111) electrodes surfaces do not only provide a superior electrical contact, but also accelerates electron transfer as proven by the increase in peak current and positive shift in the peak potential. (Z. Dursun).

Catalysis letters, 2009

Oxygen reduction was studied on palladium, cadmium and zinc ad-atom modified single crystal Au el... more Oxygen reduction was studied on palladium, cadmium and zinc ad-atom modified single crystal Au electrodes. The electrodes were modified by underpotential deposition process and their activity towards oxygen reduction was studied in alkaline media by voltammetry. The reduction peaks obtained were compared with those of bare Au , Pd disc and bulk deposited Cd electrodes. Enhanced catalytic activity of the Au(111) electrode in the presence of Pd, Cd and Zn ad-layer can be attributed to a change in surface charge and energy by ad-layer formation. In oxygen saturated medium a well defined sharp reduction peak was observed at -0.12 V for 1/5 ML Pd ad atom modified Au(111) electrode while it was positioned at -0.18 V on a Pd disk electrode. The best shift in reduction peak potential was obtained with 2/5 ML Pd ad atom modified Au(111) electrode with similar current density of Pd disc electrode.

Talanta, 2010

Cu nanoparticles have been electrochemically incorporated polypyrrole film that was used for modi... more Cu nanoparticles have been electrochemically incorporated polypyrrole film that was used for modification of the glassy carbon electrode surface. The performance of the electrode has been characterized by cyclic voltammetry and atomic force microscopy. The electrode has shown high electrocatalytic activity towards the oxidation of dopamine (DA) and uric acid (UA) simultaneously in a phosphate buffer solution (pH 7.00). The electrocatalytic oxidation currents of UA and DA were found linearly related to concentration over the range 1 × 10 −9 to 1 × 10 −5 M for UA and 1 × 10 −9 to 1 × 10 −7 M for DA using DPVs method. The detection limits were determined as 8 × 10 −10 M (s/n = 3) for UA and 8.5 × 10 −10 M (s/n = 3) for DA at a signal-to-noise ratio of 3.

The electrochemical oxidation of 2,6-diaminopurine (2,6-DAP) was studied in pH 7.4 phosphate buff... more The electrochemical oxidation of 2,6-diaminopurine (2,6-DAP) was studied in pH 7.4 phosphate buffer solution on multiwall carbon nanotube modified glassy carbon electrode (MWCNT/GCE) over a temperature range of 20 to 50 • C using cyclic voltammetry. 2,6-DAP oxidation on MWCNT/GCE showed a well-defined and irreversible oxidation peak at about 0.72 V vs. Ag/AgCl at pH 7.4. The oxidation potential of 2,6-DAP linearly varied with pH over the range of 3.0 to 10.0 with a slope of -0.0547 V/pH, implying that 2 protons were accompanied by 2 electrons transferred in the electrochemical reaction. The activation energy, Ea, of oxidation reaction was found to be 33.10 ± 1.88 kJ/mol. The differential pulse voltammetric determination of 2,6-DAP was also studied. The peak currents increased linearly with increasing of the 2,6-DAP concentration range from 0.4 µ mol/L to 80 µ mol/L. The linear regression equation appeared as I p / µ A = -(1.66 ± 0.42) + (4.21 ± 0.11) [2,6-DAP]/ µ mol/L, R 2 = 0.9982, and the detection limit (S/N = 3) was 3 × 10 −7 ± 0.015 mol/L (n = 3). The electrocatalytic oxidation of 2,6-DAP on MWCNT/GCE showed that acid pretreated multiwall carbon nanotube can be used in new applications in electrochemical determinations of biologically important compounds.

Electrocatalytic reduction of oxygen at electrochemically deposited Pt ad-layer modified Au(111) ... more Electrocatalytic reduction of oxygen at electrochemically deposited Pt ad-layer modified Au(111) electrodes was studied in an O 2 -saturated NaOH (0.1 M) solution. The results were compared with those obtained by using a polycrystalline Pt electrode and another Pt-deposited electrode prepared by replacement with Cu on bare Au(111). Linear sweep voltammetry displayed a positive shift of the oxygen reduction potential by about 0.14 V compared to the bare Au(111) electrode. This shift was about 0.06 V compared to a Pt disk electrode. Tafel slopes gradually changed between 0.06 and 0.1 V/dec, from 0.075 to -0.10 V/dec, from lower to higher current density region. The Pt ad-layer clearly served as a catalyst for oxygen reduction via 4-electron transfer. In terms of the desired shift in reduction potential and increased current density, the best electrocatalytic activity was obtained with a 30-s electrodeposited Pt ad-layer modified Au(111) electrode.

Ethanol oxidation was studied on single-crystal Au(111) electrodes that were modified by platinum... more Ethanol oxidation was studied on single-crystal Au(111) electrodes that were modified by platinum, palladium, and cadmium metal ad-layers. The metal ad-layer modification was carried out by the underpotential deposition process, in which controlled amounts of Pt, Pd, and Cd were electrodeposited onto the substrate as submonolayer or monolayer coverage. The activity of the metal ad-layer modified Au(111) electrodes toward ethanol oxidation was studied in alkaline media, and recorded voltammograms were compared to those of bare single crystal Au(111) and polycrystalline gold and platinum disk electrodes. In terms of the desired shift in reduction potential and increased current density, the best electrocatalytic activity was obtained with a 30-s electrodeposited Pt ad-layer modified Au(111) electrode.

International Journal of …, 2011

Pt ad-atom Zn ad-atom Cd ad-atom Au(111) single crystal electrode Fuel cell a b s t r a c t The e... more Pt ad-atom Zn ad-atom Cd ad-atom Au(111) single crystal electrode Fuel cell a b s t r a c t The electrochemical oxidation of borohydride was investigated by using various ad-atom modified Au(111) electrodes in alkaline media in comparison to Au(111) single crystal, polycrystalline Au, Pt and Zn electrodes. The catalytic activity of gold towards borohydride oxidation has tended to increase in more alkaline media as reflected in the oxidation peak in the concentration range of NaOH (0.01e2.0 M) studied. Additional shift on the oxidation peak potential of borohydride on Pt and Zn ad-atom modified Au(111) electrodes was observed for both ad-atom modified electrodes to more negative potentials compared to that of bare electrodes, respectively. The ad-atom modified Au(111) electrodes surfaces do not only provide a superior electrical contact, but also accelerates electron transfer as proven by the increase in peak current and positive shift in the peak potential. (Z. Dursun).

Catalysis letters, 2009

Oxygen reduction was studied on palladium, cadmium and zinc ad-atom modified single crystal Au el... more Oxygen reduction was studied on palladium, cadmium and zinc ad-atom modified single crystal Au electrodes. The electrodes were modified by underpotential deposition process and their activity towards oxygen reduction was studied in alkaline media by voltammetry. The reduction peaks obtained were compared with those of bare Au , Pd disc and bulk deposited Cd electrodes. Enhanced catalytic activity of the Au(111) electrode in the presence of Pd, Cd and Zn ad-layer can be attributed to a change in surface charge and energy by ad-layer formation. In oxygen saturated medium a well defined sharp reduction peak was observed at -0.12 V for 1/5 ML Pd ad atom modified Au(111) electrode while it was positioned at -0.18 V on a Pd disk electrode. The best shift in reduction peak potential was obtained with 2/5 ML Pd ad atom modified Au(111) electrode with similar current density of Pd disc electrode.

Talanta, 2010

Cu nanoparticles have been electrochemically incorporated polypyrrole film that was used for modi... more Cu nanoparticles have been electrochemically incorporated polypyrrole film that was used for modification of the glassy carbon electrode surface. The performance of the electrode has been characterized by cyclic voltammetry and atomic force microscopy. The electrode has shown high electrocatalytic activity towards the oxidation of dopamine (DA) and uric acid (UA) simultaneously in a phosphate buffer solution (pH 7.00). The electrocatalytic oxidation currents of UA and DA were found linearly related to concentration over the range 1 × 10 −9 to 1 × 10 −5 M for UA and 1 × 10 −9 to 1 × 10 −7 M for DA using DPVs method. The detection limits were determined as 8 × 10 −10 M (s/n = 3) for UA and 8.5 × 10 −10 M (s/n = 3) for DA at a signal-to-noise ratio of 3.