Bishkek, Kyrgyzstan
Bishkek, Kyrgyzstan

Time filter

Source Type

Mulazimolu I.E.,University of Konya | Solak A.O.,Ankara University | Solak A.O.,Kyrgyz Turk Manas University
Analytical Methods | Year: 2011

In this study, electrochemical modification of a glassy carbon (GC) electrode with apigenin was carried out and the modified electrode was used for determination of copper(ii) (Cu(ii)) in soil samples. The GC was modified through the electrochemical polymerization of apigenin (PolyApi/GC) on the electrode surface in aqueous media. The electrode surface was modified with apigenin in phosphate buffer solution (PBS), pH 7, from 0 mV to +1400 mV potential ranges, using 100 mV s -1 sweep rate and 30 cycles by cyclic voltammetry (CV). The surface characterizations of this sensor electrode were performed by CV, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Britton-Robinson (BR) buffer solution at pH 5 was used for determination of Cu(ii) by differential pulse voltammetry (DPV). The detection limit was obtained as lower as 1.0 × 10 -11 M. By using this calibration curve, the amount of Cu(ii) was determined as 7.34 × 10 -7 M in soil samples. The results showed that pH, incubation time and interferences of some cations and anions were significant. © 2011 The Royal Society of Chemistry.


Oztekin Y.,Selcuk University | Oztekin Y.,Vilnius University | Ramanaviciene A.,Vilnius University | Ryskevic N.,Vilnius University | And 5 more authors.
Sensors and Actuators, B: Chemical | Year: 2011

This study reports the electrochemical modification of glassy carbon (GC) electrode surface with the electro-polymerized form of 1,10-phenanthroline monohydrate (PMH), the characterization of this polyphenanthroline modified electrode (PPMH/GC) and the electroanalytical application suitable for the determination of Cd(II) ions. The PPMH/GC electrode was characterized by cyclic voltammetry, chronoamperometry and atomic force microscopy and formation of polyphenanthroline layer grafted to surface of GC electrode was evidenced. Selectivity of PPMH/GC electrode towards heavy metal ions was investigated by square wave voltammetry. The PPMH/GC electrode was found to be suitable for selective determination of Cd(II) in the solutions containing the mixture of heavy metal ions and showed high stability and reproducibility. The analytical methodology was successfully applied for monitoring the toxic metal ions in real samples. © 2011 Elsevier B.V. All rights reserved.


Gupta V.K.,Indian Institute of Technology Roorkee | Gupta V.K.,Dr Rml Avadh University Faizabad | Yola M.L.,Sinop University | Yola M.L.,Hacettepe University | And 5 more authors.
Electrochimica Acta | Year: 2013

Sulfisoxazole (SO) was grafted to glassy carbon electrode (GCE) via the electrochemical oxidation of SO in acetonitrile solution containing 0.1 M tetrabutylammoniumtetra-fluoroborate (TBATFB). The prepared electrode was characterized by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), reflection-absorption infrared spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS). The ellipsometric thickness of SO nanofilm at the glassy carbon surface was obtained as 14.48 ± 0.11 nm. The stability of the SO modified GCE was studied. The SO modified GCE was also utilized for the determination of Cd(II) ions in water samples in the presence of Pb(II) and Fe(II) by adsorptive stripping voltammetry. The linearity range and the detection limit of Cd(II) ions were 1.0 × 10-10 to 5.0 × 10-8M and 3.3 × 10-11M (S/N = 3), respectively. © 2013 Elsevier Ltd. All rights reserved.


Ustundag Z.,Dumlupinar University | Caglayan M.O.,Cumhuriyet University | Guzel R.,Dicle University | Piskin E.,Hacettepe University | And 2 more authors.
Analyst | Year: 2011

The scope of this study is to modify a Surface Plasmon Resonance (SPR) sensor slide with isophthalic acid to evaluate the possible application on the detection of copper(ii) ions in aqueous media by total internal reflection ellipsometry. A gold sensor surface was modified by an electrochemical diazonium reduction modification method. The modified surfaces are characterized with cyclic voltammetry (CV) and ellipsometry. Isophthalic acid monolayer modified gold slides were used for in situ detection of aqueous Cu2+ solution with the SPR enhanced total internal reflection ellipsometry (SPRe-TIRE) technique. Layer formation, pH dependency of adsorption, sensor response of the SPRe-TIRE and isothermal kinetic parameters were examined. A high dependency on the number of CV cycles in the monolayer-multiple layer transition was observed. The suggested sensor gave a linear response over a wide range of Cu 2+ concentrations. It was also reported that adsorption on the SPRe-TIRE sensor gave Langmuir adsorption model behavior. © The Royal Society of Chemistry 2011.


Gupta V.K.,Indian Institute of Technology Roorkee | Yola M.L.,Sinop University | Yola M.L.,Hacettepe University | Atar N.,Dumlupinar University | And 3 more authors.
Electrochimica Acta | Year: 2013

Graphene oxide (GO) based glassy carbon (GC) electrode has been prepared. Firstly, p-nitrophenyl (NP) modified GC (NP/GC) electrode was prepared via the electrochemical reduction of its tetraflouroborate diazonium salt. After the formation of NP/GC electrode, the negative potential was applied to NP/GC electrode to reduce the nitro groups to amine. p-Aminophenyl (AP) modified GC (AP/GC) electrode was immersed into a graphene oxide solution containing 1-ethyl-3(3-(dimethlyamino)propyl)-carbodiimide. Hence, we constructed GO terminated AP modified GC (GO/AP/GC) electrode. NP/GC, AP/GC and GO/AP/GC electrodes were characterized sequentially using cyclic voltammetry (CV) in the presence of 1.0 mM of potassium ferricyanide in 0.1 M KCl. In addition, GO and GO/AP/GC surfaces were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The GO/AP/GC electrode was used for the analysis of Cd(II) and Cu(II) ions by adsorptive stripping voltammetry. The linearity range and the detection limit of Cd(II) and Cu(II) ions were 1.0 × 10-11-5.0 × 10 -10 M and 3.3 × 10-12 M (S/N = 3), respectively. © 2013 Elsevier Ltd. All rights reserved.


Mulazimoglu I.E.,Selcuk University | Ozkan E.,Selcuk University | Solak A.O.,Ankara University | Solak A.O.,Kyrgyz Turk Manas University
Energy Education Science and Technology Part A: Energy Science and Research | Year: 2012

Herein, electrochemical oxidation and grafting of quercetin, morin and rutin as important biological molecules has been studied with the cyclic voltammetry technique by using a glassy carbon electrode. Electrochemical studies have been performed potentiostatically within a one-compartment three-electrode cell at room temperature. Glassy carbon electrode was used as a working electrode and Pt was used as a wire counter electrode. Ag/Ag + (10 mM AgNO 3), non-aqueous reference electrode calibrated to the E 1/2 of ferrocene redox probe and Ag/AgCl/KCl (sat.), an aqueous reference electrode calibrated to the E 1/2 of Fe(CN) 6 3- redox probe respectively. The modification and surface characterizations were carried out in both aqueous and non-aqueous media. 0.1 M tetrabutylammonium tetrafluoroborate in acetonitrile was used in non-aqueous experiments, Britton-Robinson buffer solution (pH=2) and 0.1 M KCl solution were used in aqueous experiments. Before each experiment the solution was de-aerated by the bubbling of Argon to remove the oxygen effects from the experiment results. Surface modification experiments were performed in the +0.3 V and +2.8 V potential ranges with a scan rate of 0.1 V s -1 and 10 cycles for all molecules. The presence of quercetin, morin and rutin at the glassy carbon electrode surface was characterized by cyclic voltammetry, electrochemical impedance spectroscopy and atomic force microscopy. © Sila Science.


Gupta V.K.,Indian Institute of Technology Roorkee | Yola M.L.,Sinop University | Atar N.,Dumlupinar University | Ustundag Z.,Dumlupinar University | And 2 more authors.
Journal of Molecular Liquids | Year: 2014

A fuel cell is an electrochemical cell that converts a source fuel into an electrical current. It generates electricity inside a cell through reactions between a fuel and an oxidant, triggered in the presence of an electrolyte. Fuel cells have been attracting more and more attention in recent decades due to high-energy demands, fossil fuel depletions, and environmental pollution throughout world. In this study, different sized metallic and bimetallic nanoparticles (AuNPs, Fe@AuNPs, Ag@AuNPs) were synthesized on graphene oxide sheets and their electrocatalytic activities for methanol oxidation were investigated. All the catalysts were characterized by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical measurements are performed to compare the catalytic efficiencies of methanol oxidation. Experimental results demonstrated that graphene oxide-supported bimetallic nanoparticles enhanced electrochemical efficiency for methanol electro-oxidation with regard to diffusion efficiency, oxidation potential and forward oxidation peak current. Graphene oxide-supported Ag@AuNPs, in comparison to graphene oxide-supported Fe@AuNPs and AuNPs, showed the more efficiency for methanol electro-oxidation. © 2013 Elsevier B.V.


Taner B.,Selcuk University | Deveci P.,Selcuk University | Ozcan E.,Selcuk University | Solak A.O.,Kyrgyz Turk Manas University | Solak A.O.,Ankara University
Journal of Inclusion Phenomena and Macrocyclic Chemistry | Year: 2012

A new calix[4]pyrrole functionalized vic-dioxime, 3-(4-methyl-9,9,14,14,19, 19-hexaethylcalix[4]pyrrole)benzoaminoglyoxime (LH 2) was synthesized from anti-chloroglyoxime and 3-aminophenyl-calix[4]pyrrole at room temperature. The mononuclear complexes {nickel(II), copper(II) and cobalt(II)} of this vic-dioxime ligand were prepared and their structures were confirmed by elemental analysis, IR and UV-Vis spectrophotometry, magnetic susceptibility; the MS, 1H and 13C NMR spectra of the LH 2 ligand and its Ni(II) complex were also recorded. The experimental results indicated that the ligand:metal ratio was 2:1 in the cases of Ni(II), Cu(II) and Co(II) complexes as is with most vic-dioximes. Electrochemical properties of the ligand, and its complexes were investigated in DMSO solution by cyclic voltammetry at 200 mV s -1 scan rate. © 2012 Springer Science+Business Media B.V.


Oztekin Y.,Vilnius University | Oztekin Y.,Selcuk University | Ramanaviciene A.,Vilnius University | Yazicigil Z.,Selcuk University | And 3 more authors.
Biosensors and Bioelectronics | Year: 2011

This study reports direct electron transfer (DET) from immobilized glucose oxidase (GOx) via grafted and electropolymerized 1,10-phenanthroline monohydrate (PMH). The layer of poly-1,10-phenanthroline (PPMH) was gained via electrochemical deposition, which was used to create the PPMH-modified GC-electrode (PPMH/GC-electrode). Further, the GOx was immobilized on the PPMH/GC-electrode. The effect of surface-modification by the PPMH on the electron-transfer between enzyme and electrode-surface and some other electrochemical/analytical-parameters of newly designed enzymatic-electrode were evaluated. The PPMH/GC-electrode showed superior DET to/from flavine adenine dinucleotide cofactor of GOx, while some redox-compounds including ferrocene and K 3[Fe(CN) 6] were completely electrochemically inactive on the PPMH/GC-electrode. It was also found that the resulting GOx/PPMH/GC-electrode functioned as a " direct response type" glucose-biosensor. The biosensor showed excellent selectivity towards glucose and demonstrated good operational-stability. According to our best knowledge, this study is the first scientific report on electrochemical-polymerization of PMH on the GC-electrode in non-aqueous media followed by its application in the design of glucose-biosensor. © 2010 Elsevier B.V.


Yola M.L.,Sinop University | Yola M.L.,Hacettepe University | Atar N.,Dumlupinar University | Ustundag Z.,Dumlupinar University | And 2 more authors.
Journal of Electroanalytical Chemistry | Year: 2013

In this study, gold nanoparticles (AuNPs) with the diameters of maximum 25 nm were self-assembled onto the surfaces of p-aminothiophenol functionalized graphene oxide (ATPGO) sheets simply by mixing their aqueous dispersions. The prepared graphene oxide (GO), ATPGO and AuNPs-ATPGO composites were characterized by a transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), reflection-absorption infrared spectroscopy (RAIRS), the X-ray diffraction (XRD) method and Raman spectroscopy. The electrochemical determination of quercetin (QR) has been studied using square wave voltammetry (SWV) on glassy carbon electrode (GCE) modified with AuNPs-ATPGO composite (AuNPs-ATPGO/GCE). QR gave rise to a single oxidation peak in the potential interval from 200 to 600 mV in 0.1 M acetate buffer (pH 5.5). The well-defined peaks were observed at the optimized instrumental parameters for SWV such as frequency, amplitude and potential increments. The developed method was validated according to the ICH guideline and found to be linear, sensitive, specific, precise and accurate. The linearity range of QR was 1.0 × 10-12-1.0 × 10-11 M with the detection limit (S/N = 3) of 3.0 × 10-13 M under optimum conditions. The validated method was applied successfully for the determination of QR in pharmaceutical preparations. © 2013 Elsevier B.V. All rights reserved.

Loading Kyrgyz Turk Manas University collaborators
Loading Kyrgyz Turk Manas University collaborators