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Öğe A New Redox Mediator (Cupric-Neocuproine Complex)-Modified Pencil Graphite Electrode for the Electrocatalytic Oxidation of H2O2: A Flow Injection Amperometric Sensor(Wiley-V C H Verlag Gmbh, 2020) Emir, Gamze; Dilgin, Yusuf; Apak, ResatThis paper introduces the cupric-neocuproine complex ([Cu(Nc)(2)](2+)) as a new redox mediator for the electrocatalytic oxidation of H2O2. For this purpose, [Cu(Nc)(2)](2+) was modified onto a disposable pencil graphite electrode (PGE) surface by using Nafion (Nf) as a cation-exchange membrane for the effective adsorption of complex. The modified electrode was prepared by immersing Nf-adsorbed PGE into [Cu(Nc)(2)](2+) complex solution (0.40 mM of Cu2+ and 0.80 mM of Nc prepared at pH 4.76 in 0.10 M acetate buffer). SEM images and EDX spectra of electrodes were presented for the elucidation of their surface morphologies. Cyclic voltammetric results showed that H2O2 was electrocatalytically oxidized at [Cu(Nc)(2)](2+)/Nf/PGE, because both the increase in current and the potential shift to a more negative direction were observed for oxidation of H2O2 at [Cu(Nc)(2)](2+)/Nf/PGE in comparison to bare PGE. Then, the electrocatalytic activity of [Cu(Nc)(2)](2+)/Nf/PGE toward H2O2 oxidation was utilized for amperometric determination of H2O2 in flow injection analysis (FIA) system. Flow injection (FI) amperometric studies showed two linear calibration ranges (1.0-1000.0 mu M (R-2=0.9958) and 1000.0-10000.0 mu M (R-2=0.9902) with a detection limit of 0.4 mu M H2O2 which is considered good for electroanalytical determinations, especially for electrocatalytic oxidation. To test the applicability of the developed FI amperometric hydrogen peroxide sensor, H2O2 contents of some relevant samples were determined.Öğe A novel enzyme-free FI-amperometric glucose biosensor at Cu nanoparticles modified graphite pencil electrode(Elsevier, 2020) Ayaz, Selen; Karakaya, Serkan; Emir, Gamze; Dilgin, Didem Giray; Dilgin, YusufIn this work, graphite pencil electrode (GPE) was modified with Cu nanoparticles (CuNPs) for enzyme-free flow injection (FI) amperometric detection of glucose. To modify electrode, CuNPs were electrodeposited onto GPE surface by recording 10 successive cyclic voltammograms (CVs) of 2.0 mM Cu(NO3)(2) in 100 mM KNO3. The electrochemical characterizations of the electrodes were realized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry techniques. The SEM images and EDX spectra of the pencil leads were recorded to investigate the surface morphologies of the electrodes. Then, the electrochemical response of both unmodified GPE and CuNPs/GPE towards electrochemical oxidation of glucose was performed by recording CVs in the supporting electrolyte consisted of 100 mM NaOH and 100 mM KCl. CVs recorded at GPE showed that the electron transfer rate of glucose is relatively slow and oxidation of glucose irreversibly observed with very low current at a high positive potential (+ 0.70 V). On the other hand, glucose oxidized at more negative potential value ( + 0.45 V) than that of unmodified GPE with a view of sharp peak at CuNPs/GPE. These results show that CuNPs/GPE exhibits excellent electrocatalytic activity and high electrochemical response towards oxidation of glucose because electron transfer rate of glucose was remarkably enhanced by modification of GPE with CuNPs. In the flow injection (FI) amperometric experiments, + 0.45 V and 2.5 mL/min were used as optimal values for applied potential (E-ap) and flow rate (f(r)), respectively. A linear calibration curve was obtained in the range from 0.10 to 400 mu M glucose with a detection limit and sensitivity of 0.04 mu M and 0.830 mu A mu M-1 cm(-2), respectively. The selectivity of glucose sensor was tested in the presence of various interferences. At last step, constructed glucose biosensor was successfully tested on some real glucose samples.Öğe A Self-Powered Enzymatic Glucose Sensor Utilizing Bimetallic Nanoparticle Composites Modified Pencil Graphite Electrodes as Cathode(Springer, 2024) Emir, Gamze; Dilgin, Yusuf; Sahin, Samet; Akgul, CahitEnzymatic biofuel cells (EBFC) are promising sources of green energy owing to the benefits of using renewable biofuels, eco-friendly biocatalysts, and moderate operating conditions. In this study, a simple and effective EBFC was presented using an enzymatic composite material-based anode and a nonenzymatic bimetallic nanoparticle-based cathode respectively. The anode was constructed from a glassy carbon electrode (GCE) modified with a multi-walled carbon nanotube (MWCNT) and ferrocene (Fc) as a conductive layer coupled with the enzyme glucose oxidase (GOx) as a sensitive detection layer for glucose. A chitosan layer was also applied to the electrode as a protective layer to complete the composite anode. Chronoamperometry (CA) results show that the MWCNT-Fc-GOx/GCE electrode has a linear relationship between current and glucose concentration, which varied from 1 to 10 mM. The LOD and LOQ were calculated for anode as 0.26 mM and 0.87 mM glucose, respectively. Also the sensitivity of the proposed sensor was calculated as 25.71 mu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu$$\end{document}A/mM. Moreover, the studies of some potential interferants show that there is no significant interference for anode in the determination of glucose except ascorbic acid (AA), uric acid (UA), and dopamine (DA). On the other hand, the cathode consisted of a disposable pencil graphite electrode (PGE) modified with platinum-palladium bimetallic nanoparticles (Nps) which exhibit excellent conductivity and electron transfer rate for the oxygen reduction reaction (ORR). The constructed EBFC was optimized and characterized using various electroanalytical techniques. The EBFC consisting of MWCNT-Fc-GOx/GCE anode and Pt-PdNps/PGE cathode exhibits an open circuit potential of 285.0 mV and a maximum power density of 32.25 mu W cm-2 under optimized conditions. The results show that the proposed EBFC consisting of an enzymatic composite-based anode and bimetallic nanozyme-based cathode is a unique design and a promising candidate for detecting glucose while harvesting power from glucose-containing natural or artificial fluids.Öğe Amperometric nonenzymatic glucose biosensor based on graphite rod electrode modified by Ni-nanoparticle/polypyrrole composite(Elsevier Inc., 2021) Emir, Gamze; Dilgin, Yusuf; Ramanaviciene, Almira; Ramanavicius, ArunasThis study reports non-ezymatic electrocatalytic amperometric glucose biosensor based on a graphite rod electrode (GRE) modified with biomimetic-composite consisting of Ni nanoparticles (Ni-NPs) and polypyrrole (Ppy) prepared by 1 cycle electro polymerization of pyrrole monomer (Ni-NPs/Ppy(1)/GRE). During the modification of GRE, the electropolymerization of pyrrole and the electrodeposition of Ni-NPs onto GRE surface were consequentially performed by potential cycling. Surface morphology of Ni-NPs/Ppy(1)/GRE electrode was evaluated by atomic force microscopy and scanning electron microscopy based imaging, and electrochemical characterization of electrodes was performed by electrochemical impedance spectroscopy and cyclic voltammetry. Cyclic voltammograms recorded in the presence of glucose show that Ni-NPs/Ppy(1)/GRE at + 500 mV vs Ag/AgCl exhibits efficient electrocatalytic oxidation activity towards glucose, while the oxidation of glucose was not observed at a bare GRE. Amperometric sensing of glucose was performed by Ni-NPs/Ppy(1)/GRE at constant + 450 mV vs Ag/AgCl electrode potential in 0.10 mol L−1 NaOH. Ni-NPs/Ppy(1)/GRE-based sensor, which was characterized by a wide linear glucose determination range between 1.0 and 1000 µmol L−1 with a limit of detection of 0.4 µmol L−1 and a sensitivity of 2873 µA mmol−1 L cm−2. The applicability of here reported Ni-NPs/Ppy(1)/GRE-based sensor has been demonstrated by the determination of glucose concentrations in real samples.Öğe Aromatik sülfonik asit grubu boyar madde modifiye kalem grafit elektrot kullanarak sülfürün elektrokatalitik tayini(Çanakkale Onsekiz Mart Üniversitesi, 2018) Emir, Gamze; Dilgin, YusufBu tez çalışmasında; aromatik sülfonik asit grubu boyar maddelerinden kalmagit (Clm), kromotropik asit (Cta), tropeolin (Trp), pirokatekol viyole (Pcv) ile elektropolimerizasyon ve adsorpsiyon olmak üzere iki farklı yöntem kullanılarak modifiye kalem grafit elektrotlar (PGE) hazırlanmış ve bu elektrotlarda sülfürün elektrokimyasal yükeltgenmesi voltammetrik ve amperometrik teknikler kullanılarak incelenmiştir. Bu modifiye elektrotlardan, Pcv ve Clm modifiye PGE'ler sülfürün yükseltgenmesine iyi bir elektrokatalitik etkinlik gösterirken, Trp ve Cta modifiye PGE'lerle sülfürün elektrokatalitik yükseltgenmesine beklenen düzeyde bir yanıt alınamamıştır. Clm ve Pcv modifiye PGE'lerde sülfürün elektrokatalitik yükseltgenmesine bağlı amperometrik tayini, daha önceki çalışmalarda PGE için geliştirilen fotoelektrokimyasal akış hücresi kullanılarak akışa enjeksiyon analiz (FIA) sisteminde gerçekleştirilmiştir. FI amperometrik çalışmalarda uygulama potansiyeli, akış hızı Poli-Clm/PGE için +250 mV ve 2,0 ml/dk ve Pcv/PGE için +100 mV ve 2,0 ml/dk olarak optimize edilmiştir. Bu şartlarda, sülfürün doğrusal derişim aralıkları, Poli-Clm/PGE için 0,1–500 µM (R2 = 0,9989) ve Pcv/PGE için 0,25-250 µM (R2= 0,9993) olarak belirlenmiş ve gözlenebilme sınırı (LOD) sırasıyla 0,03 µM ve 0,07 µM olarak hesaplanmıştır. Geliştirilen FI amperometrik sülfür sensörü için girişim ve girişim giderilmesi çalışmaları gerçekleştirlmiştir. FI amperometrik sülfür sensörünün gerçek örneklere uygulanabilirliğini test etmek için, belirli derişimde sülfür ilave edilmiş deniz suyu ve çeşme suyu örneklerinde sülfürün FI amperometrik yanıtları kaydedilmiş ve %98-104 arasında geri kazanımı sağlanmıştır. Tüm bu sonuçlara göre, sülfürün aromatik sülfonik asit boyar maddeleriyle modifiye PGE'lerde elektrokatalitik yükseltgenmesine bağlı hassas, seçici, doğru, hızlı, tek kullanımlı ve ekonomik bir FI amperometrik sülfür sensörü geliştirilmiştir.Öğe Electrocatalytic oxidation and flow injection analysis of formaldehyde at binary metal oxides (Co3O4-NiO and CuO-Co3O4) modified pencil graphite electrodes(Springer, 2021) Emir, Gamze; Karakaya, Serkan; Ayaz, Selen; Dilgin, Didem Giray; Dilgin, YusufIn this work, a highly efficient performance of bimetallic thin films as their oxide forms (Co3O4-NiO and CuO-Co3O4) modified on pencil graphite electrodes (PGEs) was presented for electrocatalytic oxidation of formaldehyde. In addition, a sensitive and selective amperometric determination of formaldehyde in flow injection analysis system have been first performed using binary transition metal oxides modified PGEs. Co3O4-NiO and CuO-Co3O4 films were electrochemically deposited on the PGE surface using cyclic voltammetric procedures. The recorded cyclic voltammograms in the presence of formaldehyde in 0.10 M NaOH containing 0.10 M KCl showed that the prepared binary transition metal oxides modified PGEs exhibited a higher electrocatalytic activity than single metal oxide thin films modified PGEs towards oxidation of formaldehyde. The linear responses based on electrocatalytic oxidation of formaldehyde were determined as 2.5-5000 mu M and 0.25-1000 mu M for Co3O4-NiO/PGE and CuO-Co3O4/PGE, respectively. Moreover, limit of detections and sensitivities were estimated as 0.73 mu M and 81.8 mu A mM(-1) cm(-2) and 0.09 mu M and 166 mu A mM(-1) cm(-2) for Co3O4-NiO/PGE and CuO-Co3O4/PGE, respectively. The results from real sample studies proved that the fabricated FI-amperometric sensors enable high applicability towards determination of formaldehyde in real water samples.Öğe Flow Injection Analysis of Sulfide at a Calmagite-Modified Pencil Graphite Electrode(Taylor & Francis Inc, 2018) Emir, Gamze; Dilgin, YusufIn this study, a new approach is proposed for low cost, sensitive, rapid, and selective detection of sulfide based on its electrocatalytic oxidation at a calmagite-modified pencil graphite electrode. The calmagite-modified pencil graphite electrode was prepared through electropolymerization in which five successive cyclic voltammograms of 0.10 mM monomer on a pencil graphite electrode were recorded in pH 2.0 Britton-Robinson buffer containing 0.10M NaNO3. Cyclic voltammograms of the prepared polycalmagite-modified pencil graphite electrode show that the peak potential of sulfide shifted from +420 mV at an unmodified pencil graphite electrode to +250 mV at the proposed electrode. The results show that a polycalmagite-modified pencil graphite electrode exhibits good electrocatalytic response to the oxidation of sulfide. Flow injection analysis of the sulfide at the polycalmagite-modified pencil graphite electrode was performed under optimized conditions using a home-made electrochemical flow cell constructed specially for the pencil graphite electrode. The anodic peak currents obtained from flow injection amperometric curves at +250 mV in pH 9.0 Britton-Robinson buffer containing 1.0M KCl show that the polycalmagite-modified pencil graphite electrode gave a linear range of 0.10-500.0 mu M and a detection limit of 0.03 mu M. The modified electrode was successfully applied to determine sulfide in real samples, and the method was also verified with recovery studies.Öğe Flow-Injection Amperometric Determination of Glucose Using Nickel Oxide-Cobalt (II,III) Oxide and Nickel Oxide-Copper Nanoparticle Modified Pencil Graphite Electrodes(Taylor & Francis Inc, 2022) Ayaz, Selen; Karakaya, Serkan; Emir, Gamze; Usakligil, Nihan; Dilgin, Didem Giray; Dilgin, YusufThis study features an enzyme-free amperometric determination of glucose with flow injection analysis (FIA) using pencil graphite electrodes (PGEs) modified with nickel oxide-cobalt (II,III) oxide (NiO-Co3O4/PGE) and nickel oxide-copper nanoparticle (NiO-CuNPs/PGE). Both modified PGEs exhibited excellent electrocatalytic activity toward oxidation of glucose in strong alkaline media since they enhanced the peak current compared with the bare PGE and single metal oxide- or metal nanoparticle-modified PGEs. Flow-injection (FI) amperometry showed the linear response range, the limit of detection and sensitivity for NiO-Co3O4/PGE and NiO-CuNPs/PGE were 1.0-1000 mu M, 0.23 mu M and 586 mu A mM(-1) cm(-2), and 0.10-250 mu M, 0.03 mu M and 949 mu A mM(-1) cm(-2), respectively. Glucose was determined in real samples with good accuracy and precision.Öğe Pyrocatechol Violet Modified Graphite Pencil Electrode for Flow Injection Amperometric Determination of Sulfide(Korean Electrochemistry Soc, 2020) Emir, Gamze; Karakaya, Serkan; Dilgin, YusufIn this study, pyrocatechol violet (Pcv) is proposed for the first time as an efficient electrocatalyst for oxidation of sulfide and flow injection analysis (FIA) of sulfide. A graphite pencil electrode (GPE) was modified with Pcv via immersion of the GPE into 0.01 M Pcv solution for 15 min. Cyclic voltammograms (CVs) demonstrated that Pcv/GPE exhibits a good electrocatalytic performance due to shift in the potential from +400 at bare GPE to +70 mV at Pcv/GPE and obtaining an enhancement in the peak current compared with the bare GPE. A linear range between 0.25 and 250 mu M sulfide with a detection limit of 0.07 mu M was obtained from the recorded current-time curves in Flow Injection Analysis (FIA) of sulfide. Sulfide in water samples was also successfully determined using the proposed FI amperometric methods.
