Modified Glassy Carbon Electrode Research Articles

Voltammetric Sensing of Bilirubin Based on Nafion/Electrochemically Reduced Graphene Oxide Composite Modified Glassy Carbon Electrode

A sensitive square wave voltammetric sensor for the quantification of bilirubin (BR) at the Nafion-electrochemically reduced graphene oxide (NF/ER-GO) hybrid composite modified conventional glassy carbon electrode was offered. The voltammetric oxidation conducts of bilirubin at the NF/ER-GO modified GC electrode were examined in acetone containing H2SO4 as the supporting electrolyte. The electrochemical conduct of BR on NF/ER-GO hybrid modified GC electrodes was explored by electrochemical impedance spectroscopy, cyclic voltammetry and square-wave voltammetry (SWV). The oxidation peak current response of BR achieved at the NF/ER-GO modified GC electrode was 3 times higher than that of the unmodified GC electrode. At specified conditions, the linear calibration curve for BR showed two good linear segments: the first linear segment increased from 2.0 μM to 20 μM and second linear segment increased up to 70 μM. The limit of detection was calculated as 0.84 μM using SWV. The results showed that the NF/ER-GO modified electrode can be applied to determine BR without interference from ascorbic acid and uric acid, while ensuring good sensitivity, selectivity, and reproducibility. Finally, the proposed sensor was successfully employed to detect bilirubin in human serum samples. Keywords: Bilirubin, voltammetry, graphene, biomolecule, serum analysis.

Graphene-Polyaniline Nanofiber Composite as Electrocatalyst for Oxygen Reduction Reaction in Alkaline Media

Here, we report a novel, cost effective, metal free electrocatalyst for oxygen reduction reaction. Graphene nanosheet (GNS) - polyaniline (PANI) nanofiber composite was prepared by simple chemical route using pre-synthesized GNS and PANI nanofibers. The GNS-PANI nanocomposite exhibited better electrochemical performance compared to GNS alone. The structural and morphological features of this composite were examined by microscopy, spectroscopy and electro-analytical techniques. The results confirmed that PANI nanofibers are homogeneously dispersed as well as interconnected with the GNS. This characteristic feature significantly enhances the charge transfer reactions at the interface. GNS-PANI nanocomposite modified glassy carbon (GC) electrode exhibited finite onset potential for oxygen reduction reaction with a 100 mV positive shift compared to GNS modified GC electrode in alkaline electrolyte. Koutecky–Levich (K-L) plot analysis revealed that the oxygen reduction reaction proceed virtually via 4 electron pathway. Thus, the present GNS-PANI nanocomposite may be a promising cathode material for fuel cell applications.

Detection of Cyanuric Acid Using Cu1.1Fe1.1S2 Modified Glassy Carbon Electrode by Voltammetry Method

Detection of Cyanuric Acid Using Cu<SUB>1.1</SUB>Fe<SUB>1.1</SUB>S<SUB>2</SUB> Modified Glassy Carbon Electrode by Voltammetry Method

A 3D Microfluidic Chip for Electrochemical Detection of Hydrolysed Nucleic Bases by a Modified Glassy Carbon Electrode

Modification of carbon materials, especially graphene-based materials, has wide applications in electrochemical detection such as electrochemical lab-on-chip devices. A glassy carbon electrode (GCE) modified with chemically alternated graphene oxide was used as a working electrode (glassy carbon modified by graphene oxide with sulphur containing compounds and Nafion) for detection of nucleobases in hydrolysed samples (HCl pH = 2.9, 100 °C, 1 h, neutralization by NaOH). It was found out that modification, especially with trithiocyanuric acid, increased the sensitivity of detection in comparison with pure GCE. All processes were finally implemented in a microfluidic chip formed with a 3D printer by fused deposition modelling technology. As a material for chip fabrication, acrylonitrile butadiene styrene was chosen because of its mechanical and chemical stability. The chip contained the one chamber for the hydrolysis of the nucleic acid and another for the electrochemical detection by the modified GCE. This chamber was fabricated to allow for replacement of the GCE.

Amperometric Determination of Quercetin in Some Foods by Magnetic Core/Shell Fe3O4@ZnO Nanoparticles Modified Glassy Carbon Electrode

In this paper, Fe3O4@ZnO core/shell magnetic nanoparticles (MNPs) have been synthesized by a simple method, to modify carbon paste/glassy carbon electrode and improve its efficiency for determination of quercetin. The synthesized MNPs were characterized by X-ray powder diffraction (XRD), transmission electronic microscope (TEM), and scanning electronic microscope (SEM). SEM and TEM results show that the prepared Fe3O4@ZnO MNPs are made of the spherical shape particles with an average size of about 15 nm. The electrochemical behavior of quercetin at the surface of modified electrode was investigated. Under the optimal conditions, a linearity range of quercetin was 7.9 × 10−7 to 6.1 × 10−5 mol/L (0.24–18.44 mg/L) with detection limit (S/N = 3) and sensitivity of 0.16 μmol/L (0.048 mg/L) and 0.04 μA/μM, respectively. The validated method was applied successfully for determination of quercetin in some foods and human breast milk.

Voltammetric Determination of Cr(VI) Using Gold Nanoparticles-modified Glassy Carbon Electrode

Gold nanoparticles-modified glassy carbon electrode was utilized in the present study to determine trace amount of Cr(VI). The steps employed in the present study were fabrication of gold nanoparticles colloids, modification of glassy carbon electrode using the gold nanoparticle colloids, and voltammetric determination of Cr(VI) using the modified electrode. The results of the present study indicate that 290μL of 0.1M NaBH4 was required to form gold nanoparticles colloids. Self assembly process was found to give better gold nanoparticles binding onto glassy carbon electrode compared to adsorption process as indicated by more gold nanoparticles attached onto the glassy carbon electrode. Modification of the glassy carbon electrode using gold nanoparticles increase sensitivity as indicated by good limit of detection (2.38 ng/L) with an acceptable linearity range within 0.050 – 0.250μg/L. The correlation coefficient and precision of the method were 0.9948 and 99.14%, respectively.

Determination of isoniazid content via cysteic acid/graphene modified glassy carbon electrode

The electrodeposited graphene (EGR) and cysteic acid (CA) composite (CA/EGR) was fabricated through an electrochemical method for the modification of glassy carbon electrode (GCE). The obtained detection linearity of isoniazid at the CA/EGR/GCE ranged from 0.1 to 200 μM with the detection limit of 0.03 μM (S/N= 3).

Simultaneous Determination of Epinephrine and Uric Acid at Poly (Guanine) Modified Glassy Carbon Electrode

Simultaneous Determination of Epinephrine and Uric Acid at Poly (Guanine) Modified Glassy Carbon Electrode

Electrocatalytic Oxidation and Determination of Insulin at Rhodamine B –Multi-walled Carbon Nanotubes Modified Glassy Carbon Electrode

The modified electrode surface was provided with the electropolymerization of the rhodamine B in the presence of carbon nanotube (CNT). The modified electrode offers dramatic improvements in the stability and sensitivity of voltammetric measurements of insulin compared to the bare and rhodamine B modified glassy carbon electrodes. The enhanced electrocatalytic activity towards insulin is indicated from lowering the potential of the oxidation process (starting around 0.75 vs. Ag/AgCl) and the substantially higher sensitivity over the entire potential range. A linear dynamic range (100–600nM) was achieved with a detection limit of 5nM. The accuracy of the modified electrode was indicated by insulin recovery test in the real samples as human plasma and pharmaceutical samples.

Ultra-Selective Dopamine Detection in an Excess of Ascorbic Acid and Uric Acid Using Pristine Palladium Nanoparticles Decorated Graphene Modified Glassy Carbon Electrode

In the present work, we report the electrochemical detection of dopamine (DA) by means of cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA) in the presence of excess ascorbic acid (AA) and uric acid (UA) using pristine palladium nanoparticles decorated graphene modified glassy carbon electrode (G/PdNPs-GCE). G/PdNPs nanocomposite was synthesized by preparing pristine PdNPs from its precursor palladium acetylacetonate, with morpholineborane as the reducing agent and subsequently assembled them on graphene nanosheets. The nanocomposite was characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), UV-Vis spectrophotometry and Fourier transform infrared spectroscopy (FTIR). CV, DPV and CA determination of DA showed distinct increase in the current with increasing concentration and a wide range of linearity. The catalytic material exhibited ultra selective detection of dopamine with a peak to peak separation of 90 and 149 mV for AA-DA and DA-UA oxidation respectively. The reduced overpotential for simultaneous oxidation of DA, AA and UA in DPV and CV is also a remarkable feature of the catalytic material. More importantly, the modified electrode exhibited clear and distinct peak for DA in CV and DPV even in the presence of 300 and 450 times excess of AA and UA respectively.

A Sensitive Amperometric Sensor for the Determination of Sophocarpine Based on Vertically Oriented Graphene Nanosheets Modified Glassy Carbon Electrode

We presented to fabricate the electrodeposition of the film of reduced graphene oxide (ERGO) with preferred vertical orientation on the glassy carbon electrode through pulse potential method (PPM). The ERGO film were characterized by electrochemical methods and scanning electron microscopy. For the first time, the electrodeposition of the film was applied to develop a highly sensitive electrochemical sensor for determination of sophocarpine. The electrochemical behavior of sophocarpine was then studied by cyclic voltammetry. The results revealed that the ERGO film can effectively increase response toward the oxidation of sophocarpine by greatly enhancing the oxidation peak currents and decrease the overpotential of sophocarpine. Under the selected conditions, the sensor showed good amperometric response for sophocarpine within a wide linear range from 1.0 × 10−6 to 1.0 × 10−4 mol L−1 and a low detection limit of 3.0 × 10−7 mol L−1. At the same time, the method was also successfully applied to the quantitative determination of sophocarpine in spiked human urine and its result was satisfactory.

Investigation of Direct Electrooxidation Behavior of NADH at a Chemically Modified Glassy Carbon Electrode

In this study, the composite material that made up polyglycine/3d-4f hybrid-metallic cyano-bridged mixed coordination polymers (CyMCP) was successfully decorated onto a glassy carbon rotating disk electrode (GC RDE) using electrodeposition. The voltammetric behavior of NADH showed typical direct electrooxidation characteristics on the modified GC electrode. Our polyglycine/CyMCP-modified GC RDE was able to measure the apparent heterogeneous electron transfer rate constant of NADH during its direct electrooxidation by preventing fouling effects on the working electrode, which would generally cause a decrease in the oxidative peak current of NADH. In addition, differential pulse voltammetry provided a large linear range between the oxidative peak current and the concentration of NADH from 2–1500 μM at the polyglycine/CyMCP/GC electrode. Finally, the apparent heterogeneous electron transfer rate constant (ksNADH) of NADH was determined to be 1.73 × 10−2 cm·s−1 using the polyglycine/CyMCP-modified GC RDE.

Non-Enzymatic Amperometric Determination of Glucose by CuO Nanobelt Graphene Composite Modified Glassy Carbon Electrode

We have successfully developed for the first time an electrochemical sensor for glucose by using a simple and effective design of growing CuO nanobelts graphene composites (CuO@G). The as prepared composites were characterized by X-ray diffraction studies (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The prepared composite material exhibits higher electrocatalytic activity for the oxidation of glucose compared to chemically reduced graphene (C rGO) and bare CuO nanobelts. The optimized protocol has linearity with current response for glucose concentration in the range 0.5-6.5 μmol L−1 and detection limits were found to be 0.05 μmol L−1 (3σ). The method exhibits good reproducibility and selectivity towards glucose in the presence of other electro active compounds that are normally present in blood serum like dopamine, ascorbic acid, uric acid and sodium chloride. The protocol has been successfully applied for glucose determination in clinic human blood serum samples.

Direct Electrochemistry and Electrocatalysis of Hemoglobin Immobilized on Eggshell Membrane Modified Glassy Carbon Electrode

Direct Electrochemistry and Electrocatalysis of Hemoglobin Immobilized on Eggshell Membrane Modified Glassy Carbon Electrode

Voltammetric determination of immunosuppressive agent, azathioprine, by using a graphene-chitosan modified-glassy carbon electrode

Electrodeposition of graphene-chitosan (GR-CS) composite onto glassy carbon electrode was done via a simple one-step strategy. Different methods were used for surface characterization which confirmed the presence of a nano-structure of graphene sheets. The modified electrode was highly efficient in azathioprine analysis by square-wave voltammetry. Reversibility of the redox couple of azathioprine was significantly improved at the surface of GR-CS modified electrode compared to the bare electrode. A linear range of 1.0 × 10−7 to 2.6 × 10−5 M of azathioprine was obtained with a sensitivity of 5.54 A/M and a detection limit of 4.7 × 10−8 M. The proposed sensor exhibited high reproducibility (RSD % = 5%) and repeatability (RSD % = 3.5%) and long-term storage stability. The modified electrode was applied successfully to the accurate determination of azathioprine in pharmaceutical and blood serum samples.

Manganese oxide nanoflakes/multi-walled carbon nanotubes/chitosan nanocomposite modified glassy carbon electrode as a novel electrochemical sensor for chromium (III) detection

In this research a nanocomposite containing chitosan (Chit) and maltiwalled carbon nanotubes (MWCNTs) was applied as platform for immobilization of electrodeposited manganese oxide (MnOx) nanostructures. First, glassy carbon (GC) electrode modified with thin film of Chitosan/MWCNTs nanocomposite. Then MnOx nanostructures was electrodeposited onto Chitosan/MWCNTs modified GC electrode using combination of constant potential step (0.6V) and cyclic voltammetry(0.3–0.6V) techniques. The XRD patterns and scanning electron microscope images indicated immobilization of uniformly MnOx nanoflakes with high crystallite onto MWCNTs/Chit film. The modified electrode shows a well-defined redox couple for Mn2+/MnO2 system. Charge transfer coefficient (α), electron transfer rate constant (ks) and surface concentration (Γ) were 0.394, 3.44s−1 and 3.3×10−11molcm−2, respectively. The modified electrode showed excellent electrocatalytic activity toward oxidation of chromium (III) at natural pH solutions. Cyclic voltammetry and hydrodynamic amperometery were applied as measuring techniques for chromium detection. Detection limit, sensitivity and linear concentration range of the sensor were, 0.3 (μM), 18.7nAμM−1 and 3μM to 200μM, respectively. Moreover, the sensor retained about 90% of its original response toward Cr(III) after storage three months in ambient condition. Furthermore, the sensor response toward different common interferences was negligible. Finally, the developed sensor was applied for the detection of Cr(III) in real samples with satisfactory results.

Methionine – Au Nanoparticle Modified Glassy Carbon Electrode: a Novel Platform for Electrochemical Detection of Hydroquinone

A high sensitive electrochemical sensor based on methionine/gold nanoparticles (MET/AuNPs) modified glassy carbon electrode (GCE) was fabricated for the quantitative detection of hydroquinone (HQ). The as-modified electrode was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The electrochemical performance of the sensor to HQ was investigated by using cyclic and differential pulse voltammetry, which revealed its excellent electrocatalytic activity and reversibility towards HQ. The separation of anodic and cathodic peak (∆Ep) was decreased from 471 mV to 75 mV. The anodic peak current achieved under the optimum conditions was linear with the HQ concentration ranging from 8 μM to 400 μM with the detection limit 0.12 μM (3σ). The as-fabricated sensor also showed a good selectivity towards HQ without demonstrating interference from other coexisting species. Furthermore, the sensor showed a good performance for HQ detection in environmental water, which suggests its potential practical application. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6477

Simultaneous Determination of Copper, Lead, and Cadmium Ions at a Mo6S9-xIx Nanowires Modified Glassy Carbon Electrode Using Differential Pulse Anodic Stripping Voltammetry

A novel electrochemical sensor based on a new kind of nanomaterials Mo6S9-xIx nanowires modified glassy carbon electrode (GCE) was constructed for simultaneous determination of cadmium(II), lead(II) and copper(II) using differential pulse anodic stripping voltammetry (DPASV). Various experimental parameters such as the modified amount, pH, deposition time and deposition potential were optimized. Under the optimal conditions, the stripping peak currents increase linearly with increasing concentrations of Cd(II), Pb(II) and Cu(II) ions in the ranges of 0.5∼150 μg · L−1, 1.5∼450 μg · L−1 and 0.8～240 μg · μg·L−1, 1.5∼450 μg·L−1 and 0.8∼240 μg·L−1, respectively. And the limits of detection (S/N = 3) are estimated to be 0.10 μg · L−1 for Cd (II), 0.45 μg·L−1 for Pb(II) and 0.20 μg·L−1 for Cu(II), which are two orders of magnitude lower than those obtained at the unmodified electrodes. Most importantly, the sensor has been successfully applied to the determination of trace metal ions in the tap water samples. This developed electrochemical sensor exhibits high sensitivity, good stability and reproducibility.

Design and evaluation of a highly sensitive nanostructure-based surface modification of glassy carbon electrode for electrochemical studies of hydroxychloroquine in the presence of acetaminophen

N,N′-bis[(E)-(1-pyridyl) methylidene]-1,3-propanediamine (PMPDA) self-assembled monolayer (SAM) was covalently prepared on a glassy carbon electrode (GCE). The electrode surface modification was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Then GC-PMPDA SAM modified electrode was used to investigate the electrochemical behavior of hydroxychloroquine (HQ) using CV, double potential step chronocoulometry and linear sweep voltammetry (LSV) techniques. Using these techniques, the diffusion coefficient (D), electron transfer coefficient (α) and exchanging current density (j0) for HQ were calculated. Furthermore the modified electrode was applied as a high sensitive biosensor for determination of HQ in the presence of acetaminophen (AC). The GC-PMPDA SAM modified electrode provides two linear responses for HQ in the presence of AC in the concentration ranges from 0.09 to 10.21μM and 10.21 to 98.29μM by differential pulse voltammetry (DPV). The detection limit (three times the signal blank/slope) was 4.65nM. Finally the modified electrode was satisfactorily used for determining of HQ in human body fluids.

Electroanalysis of Diazepam on Nanosize Conducting Poly (3-Methylthiophene) Modified Glassy Carbon Electrode

A glassy carbon electrode (GCE) was modified with nanosize poly (3-methylthiophene) (P3MT) and used for the sensitive voltammetric determination of diazepam. The cyclic voltammetric response of the bare GCE was compared with the P3MT modified electrode. Electrochemical impedance response of diazepam on modified GCE was studied by various concentrations of diazepam from 0.2 μM to 0.6 μM. The poly (3-methylthiophene) modified glassy carbon electrode (P3MT/GCE) can greatly enhance the peak currents and the detection sensitivity of diazepam under optimal conditions. The quantitative analysis of diazepam was made by the DPSV method. The experimental results showed that the peak current increased with the increase in concentration of diazepam. A calibration was made, which indicated the linear dependence of peak current with concentration (ip = 13.31Conc. + 0.4359R2 = 0.9948) in the range od determination and ot was found to be good between 0.2 and 1.07 μg/L. The limit of detection was 0.1μg/mL. The reproducibility of the stripping signal was realized in terms of relative standard deviation for 6 identical measurements and was found to be 2.6%. The effect of interference of different cations and anions on the oxidation of diazepam was studied. Real sample analysis of diazepam was also studied through DPSV.