Modified Glassy Carbon Research Articles

A Selective Electrochemical Sensor Based on a Modified-Glassy Carbon Electrode Using f-MWCNTs-Polydopamine for Ciprofloxacin Detection

An electrochemical sensor was designed and prepared based on a modified-glassy carbon electrode using f-MWCNTs and dopamine. The dopamine is electropolymerized to form a layer of polydopamine on the surface of functionalized carbon nanotubes. Various techniques, including FE-SEM, EDS, elemental mapping, FT-IR, AFM, XRD, and Raman spectroscopy, were used to investigate different prepared catalyst features. Using cyclic voltammetry and EIS techniques, the proposed sensor's potency for ciprofloxacin detection was examined and proved. In the next step, in the DPV technique, different parameters affecting the selectivity and the sensitivity of detection, including pH, pre-concentration potential and time, MWCNTs suspension drop size, and cycle number in the electropolymerization stage, were optimized. Two linear dynamic ranges from 0.075 to 10 μM and from 10 to 100 μM were obtained for ciprofloxacin detection in the optimum condition and using the DPV technique. The detection limit was calculated to be 0.04 μM, and repeatability and reproducibility were found to be 3.2 and 3.3%, respectively. Afterward, the sensor's selectivity against common interfering agents was checked out, and the sensor proved to be highly selective for ciprofloxacin detection. Ciprofloxacin was determined in human plasma and urine samples with desired results at the final stage. The sensor proved to be a trustable tool for ciprofloxacin measurement in clinical and industrial applications.

Synthesis of chitosan-grafted poly-acrylic acid (CTS-g-PAA) hydrogel and its potential application in biosensors for signal enhancing and bioanalysis.

Nowadays, hydrogels have been attracted a lot of interest due to their immense potential in different fields such as biomedicine and biotechnology. Biodegradable and biocompatible pH-sensitive chitosan-grafted polyacrylic acid (CTS-g-PAA) hydrogel was synthesized by grafting an acrylic acid monomer onto chitosan at the presence of methylene bisacrylamide as a cross-linking agent and ammonium persulphate as an initiator. FT-IR spectroscopy and scanning electron microscopy (SEM) were used to analyze the properties of the obtained hydrogel. The synthesized hydrogel is suitable for the delivery of many hydrophilic drugs or species. Using a multi-walled carbon nanotube modified-glassy carbon electrode (CNT-GCE), the loading and release conditions of Nile Blue (NB) as an electroactive compound were evaluated utilizing the differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The effect of various parameters on the electrochemical signal of NB was investigated, and the optimal conditions for the efficient performance of hydrogel to delivery of NB were obtained. The electrocatalytic current values show linear dependence to NB concentration in the range of 0.098 – 0.971 μM while the detection limit of this electrochemical platform was 12.3 nM. The unique proposed hydrogel with the electroactive NB has a broad range of possible applications in biosensors for signal enhancement and bioanalysis.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10854-021-06939-7.

Polyaniline nanoconical array on carbon nanofiber for supersensitive determination of nitrophenol

The polyaniline nanoconical array coated carbon nanofibers (PANI-array@CNF) were successfully fabricated by the polymerization of aniline monomers on the surface of the carbonized electrospun polyacrylonitrile fibers at low temperature. The morphology and electrochemical activity of the PANI-array@CNF are much dependent on the polymerization time and feeding speed of ammonium persulfate. In contrast with CNFs, the specific surface area and pore volume of the PANI-array@CNF become larger. Compared to commercial PANI powder, the oxidation/reduction response of PANI-array@CNF is dramatically enhanced due to the abundant active sites of the PANI nanoconical array perpendicular to the CNF surface. The PANI-array@CNF modified-glassy carbon electrode (PANI-array@CNF/GCE) exhibits outstanding electrochemical response to the reduction of o-nitrophenol (o-NP), m-nitrophenol (m-NP) and p-nitrophenol (p-NP). The PANI-array@CNF/GCE delivers a super-high detection sensitivity for individual analysis of nitrophenol isomers, with the limit of detection down to 0.5 nM for o-NP, 1.0 nM for m-NP and 1.5 nM for p-NP. In addition, the fabricated sensor has been successfully applied for the simultaneous determination of o-NP and p-NP in lake and tap water samples. The PANI-array@CNF based sensor has good repeatability, high stability and excellent selectivity. It demonstrates a great potential for highly sensitive determination of nitrophenols in environmental pollution system.

Solar Exfoliated Graphene Oxide: A Platform for Electrochemical Sensing of Epinephrine

Introduction:In this study, solar exfoliated graphite oxide modified glassy carbon electrode was used for the anodic oxidation of epinephrine in a phosphate buffer medium at pH7. The modified electrode showed fast response and sensitivity towards Epinephrine Molecule (EP). The electrode was characterized electrochemically through Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV). Area of the electrode enhanced three times during modification and studies reveal that the oxidation process of EP occurs by an adsorption controlled process involving two electrons. The results showed a detection limit of 0.50 ± 0.01μM with a linear range up to 100 μM. The rate constant calculated for the electron transfer reaction is 1.35 s-1. The electrode was effective for simultaneous detection of EP in the presence of Ascorbic Acid (AA) and Uric Acid (UA) with well-resolved signals. The sensitivity, selectivity and stability of the sensor were also confirmed.Methods:Glassy carbon electrode modified by reduced graphene oxide was used for the detection and quantification of epinephrine using cyclic voltammetry and differential pulse voltammetry.Results:The results showed an enhancement in the electrocatalytic oxidation of epinephrine due to the increase in the effective surface area of the modified electrode. The anodic transfer coefficient, detection limit and electron transfer rate constant of the reaction were also calculated.Conclusion:The paper reports the determination of epinephrine using reduced graphene oxide modified glassy carbon electrode through CV and DPV. The sensor exhibited excellent reproducibility and repeatability for the detection of epinephrine and also its simultaneous detection of ascorbic acid and uric acid, which coexist in the biological system.

Biosensor design using an electroactive label-based aptamer to detect bisphenol A in serum samples

A new and simple procedure was applied to detect bisphenol A (BPA) based on a BPA aptamer and its complementary strand (Comp. Str.). An electrode was modified with a mixture of carboxylated multiwalled carbon nanotubes and chitosan. The Comp. Str. was immobilized on a modified-glassy carbon electrode (GCE) surface via covalent binding. After the incubation of the aptamer with the electrode surface, it could interact with the Comp. Str. In the presence of BPA, its aptamer will interact with the analyte, resulting in some changes in the configuration and leading to separation from the electrode surface. Due to the attached ferrocene (Fc) group on the 50 head of the aptamer, the redox current of Fc has reduced. This aptasensor can sense the level of BPA in the linear range of 0.2-2 nM, with a limit of detection of 0.38 nM and a sensitivity of 24.51 lA/μM. The proposed aptasensor showed great reliability and selectivity. The acceptable selectivity is due to the specificity of BPA binding to its aptamer. The serum sample was used as a real sample; the aptasensor was able to effectively recover the spiked BPA amounts. It can on-site monitor the BPA in serum samples with acceptable recoveries.

One-pot synthesis of cerium doped 3D ZnO nano-flowers modified on glassy carbon electrode as portable electro-chemical sensing platform for sensitive detection of methotrexate as an anticancer drug

• Cerium doped ZnO nano-flowers were characterized by XRD, SEM and EDX. • Ce 3+ -ZnO nano-flowers was used for modified glassy carbon electrode. • This modified electrode was used for the determination of methotrexate. Ce-doped ZnO catalysts were synthesized for the first time with simplistic hydrothermal method and characterized by XRD, SEM and EDX. The impact of cerium amount (0, 6 and 12%) on the structure and morphology of Ce-doped ZnO catalyst was investigated. According to the findings, the as-synthesized Ce-doped ZnO has nano-flower structures, big pore volumes and high surface area. In addition, an electro-chemical sensor has been constructed based on Ce-doped ZnO nano-flowers modified-glassy carbon electrode. Electro-chemical detection of methotrexate that is used as an anticancer medicine is conducted by the modified electrode. Electro-chemical methods for examining electro-chemical behaviors of methotrexate on the modified electrode surfaces have been chronoamperometry, cyclic voltammetry, and differential pulse voltammetry. This research findings demonstrated the synergetic impact of Ce-doped ZnO nano-flowers on the oxidation of methotrexate via declining oxidation over-potential and enhancing oxidation peak current. When instrumental and experimental conditions have been optimized, the suggested electro-chemical sensor has been used to measure methotrexate in the range between 0.01–500.0 μM with a detection limit of 6.3 nM. Sensitiveness and functionality of the suggested electro-chemical sensor toward methotrexate have been explored by analyzing pharmaceutical ampoules, which was accompanied by acceptable outcomes.

CoFe2O4/reduced graphene oxide/ionic liquid modified glassy carbon electrode, a selective and sensitive electrochemical sensor for determination of methotrexate

In this work, an electrochemical sensor based on CoFe2O4/reduced graphene oxide (rGO) and ionic liquid modified-glassy carbon electrode is fabricated. The modified glassy carbon electrode is used for electrochemical determination of methotrexate, as an anti-cancer drug. Cyclic and differential pulse voltammetry are used as electrochemical techniques to study the electrochemical behavior of methotrexate on the surface of the modified electrode. The results of our study showed that CoFe2O4/IL-rGO nanocomposite has synergetic effect on the oxidation of methotrexate, by decreasing the oxidation overpotential and increasing the oxidation peak current. After optimization of the experimental and instrumental conditions, using the proposed electrochemical sensor, methotrexate can be measured in the range of 0.05–7.5nmolmL–1 with a limit of detection of 0.01nmolmL–1. Relative standard deviation for five replicates measurements of 2.0nmolmL–1 methotrexate was 4.5%. The selectivity and applicability of the proposed electrochemical sensor toward methotrexate were investigated using analysis of pharmaceutical tablets with satisfactory results.

Electrochemical Determination of Dopamine with Ruthenium(III)-Modified Glassy Carbon and Screen-Printed Electrodes

ABSTRACTHere is reported for the first time the application of sodium bis[N-2-oxyphenyl-5-bromosalicylideneiminato-ONO]ruthenate(III) as a mediator with multiwalled carbon nanotubes and Nafion at glassy carbon and screen-printed electrodes for the determination of dopamine in the presence of ascorbic acid. Electrochemical studies were performed using cyclic voltammetry, differential pulse voltammetry, and flow injection amperometry. In flow injection mode, the flow rate was 0.4 mL min−1, the injection volume 250 µL, and the operation potential 0.05 V vs. Ag/AgCl. In 0.1M pH 7.5 phosphate buffer, the sensor provided a linear dynamic range up to 50 mg L−1 dopamine with a detection limit of 0.11 ± 0.04 mg L−1. The sensor was used for the determination of dopamine in ampoules of dopamine hydrochloride by cyclic voltammetry, differential pulse voltammetry, and flow injection amperometry.

Sensitivity Control of Label‐free DNA Hybridization Detection Based on Poly(thionine)‐Modified Glassy Carbon and Gold Electrodes

Poly(thionine) (PTH)‐modified glassy carbon (PTH‐S/GCE and PTH‐D/GCE) and gold (PTH‐S/Au) electrodes were prepared for the label‐free detection of DNA hybridizations and their performances in terms of sensitivity and selectivity were compared. Single‐strand probe DNA (pDNA) was immobilized on the PTH films via covalent bonding between the amine (−NH2) group of PTH and the phosphate (PO43−) group at the 5' end of the pDNA. The PTH oxidation current was decreased because of the increase in the stiffness of PTH films. The current was further decreased after the duplex was formed by the hybridization of the target complementary DNA (cDNA). The pDNA/PTH‐S/GCE, pDNA/PTH‐D/GCE, and pDNA/PTH‐S/Au sensors showed excellent sensitivities of ca. 2.1, 55, and 1.9 μA/cm2/nM, respectively, and the detection limits (S/N = 3) were ca. 40.6, 1.5, and 45 pM, respectively, for the hybridization of target cDNA.

Label-Free Detection of DNA Hybridization by Using Charge Perturbation on Poly(thionine)-Modified Glassy Carbon and Gold Electrodes

Simple and label-free electrochemical sensors for the detection of DNA hybridization were developed based on charge perturbation of poly(thionine)-modified glassy carbon and gold electrodes (PTH/GCE and PTH/Au). Probe DNA (pDNA) was immobilized on PTH films via covalent bonds between the amine (-NH2) group of the PTH and the phosphate (PO43−) group at the 5′ end of the pDNA. The immobilized single-strand pDNA decreased the oxidation current of [Fe(CN)6]4− as a result of electrostatic repulsion by the negatively charged PO43- backbone of the pDNA. The current was further decreased subsequent to duplex formation by the hybridization of target complementary DNA (cDNA) due to increased electrostatic repulsion. Both sensors demonstrated excellent selectivity, stability, and the sensitivity of 1.27 and 58.6 μA·cm−2·pM−1 with detection limits of 0.47 and 0.20 pM, respectively, for cDNA hybridization.

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.

Electrocatalytic oxidation of hydrazine at poly(4,5-dihydroxy-1,3-benzenedisulfonic acid) multiwall carbon nanotubes modified-glassy carbon electrode: Improvement of the catalytic activity

A stable electroactive thin film of poly(4,5-dihydroxy-1,3-benzenedisulfonic acid) was electrochemically deposited at the surface of multiwall carbon nanotubes-glassy carbon electrode. The electrocatalytic oxidation of hydrazine has been studied at the surface of the modified electrode using cyclic voltammetry, chronoamperometry and linear sweep voltammetry as diagnostic techniques. The modified electrode exhibits good electrocatalytic activity for the oxidation of hydrazine with a good sensitivity. Linear calibration range was in the wide concentration range of 10–3540 μM hydrazine with a detection limit of 1.8 μM and a sensitivity of 85.3 nA/μM. A Tafel plot, derived from voltammograms, indicated a one-electron transfer process to be the rate-limiting step and the overall number of electrons involved in the catalytic oxidation of hydrazine was found to be four. The influences of potentially interfering substances were studied. The diffusion coefficient of hydrazine was also evaluated. Finally, the proposed modified electrode was used for the determination of hydrazine in spiked water samples.

Electrocatalytic Oxidation of Hydrazine at Poly(4,5-Dihydroxy-1,3-Benzenedisulfonic Acid) Multiwall Carbon Nanotubes Modified-Glassy Carbon Electrode: Improvement of the Catalytic Activity

Electrocatalytic Oxidation of Hydrazine at Poly(4,5-Dihydroxy-1,3-Benzenedisulfonic Acid) Multiwall Carbon Nanotubes Modified-Glassy Carbon Electrode: Improvement of the Catalytic Activity

DNA Hybridization Detection by Charge Perturbation Through DNA At Poly(thionine)-Modified Glassy Carbon and Gold Electrodes

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Highly Sensitive Determination of Hg(II) Using Self-Assembled Monolayer of 4-Pyridineethanthiol on Gold Nanoparticles Modified-Glassy Carbon Electrode Pretreated by Exclusively Cathodic Polarization

Highly Sensitive Determination of Hg(II) Using Self-Assembled Monolayer of 4-Pyridineethanthiol on Gold Nanoparticles Modified-Glassy Carbon Electrode Pretreated by Exclusively Cathodic Polarization

Electrochemical study of anthraquinone groups, grafted by the diazonium chemistry, in different aqueous media-relevance for the development of aqueous hybrid electrochemical capacitor

The cyclic voltammetry behavior of anthraquinone (AQ) modified-glassy carbon and carbon powder-based composite electrodes was investigated as a function of the solution pH. The modification of glassy carbon electrode and carbon powder was performed by electrochemical and chemical reduction of the diazonium ions, respectively. The modification was performed by using 1-diazoanthraquinone and 2-diazoanthraquinone as anthraquinone precursor and yielded materials that differ in the point of attachment of the anthraquinone moieties. Cyclic voltammetry measurements were performed in several aqueous solutions in a pH range from 0.5 to 14 and the apparent redox potential and the anthraquinone surface concentration were determined. The shape of the cyclic voltammogram is affected by the solution pH. A well-defined cyclic voltammogram is observed for the AQ-modified glassy carbon based composite electrode in alkaline electrolyte whereas the electrochemical response for the carbon powder-based composite electrodes is more complex. On the other hand, the opposite is true in acidic media as a well-defined cyclic voltammogram is seen for the composite electrode. The amount of electrochemically addressable AQ molecules was found to depend on the solution pH. The relevance of the results for the use of anthraquinone-modified carbon in electrochemical capacitor is discussed.

Simple flow injection for screening of total antioxidant capacity by amperometric detection of DPPH radical on carbon nanotube modified-glassy carbon electrode

An amperometric flow injection (FI) method suitable for evaluation of ‘total antioxidant capacity’ (TAC) is presented. In this method, a carrier stream of a solution of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) continuously flows through an electrochemical cell, furnished with a carbon nanotube modified-glassy carbon electrode (CNT/GC) as the working electrode. At the applied voltage of 0.05V (vs. Ag/AgCl), DPPH• is reduced resulting in a constant electric current. For measurement of the TAC, a sample zone containing antioxidant(s) is injected into the carrier stream therein reduction reaction of DPPH• occurring within the sample zone. The decreased amount of the radical in the sample zone leads to a drop of the amperometric signal at the CNT/GC electrode. We have also compared the performance of the CNT/GC electrode to the unmodified GC electrode using cyclic voltammetry. The sensitivity of the CNT/GC electrode was more than twenty five times greater than the bare GC electrode. The study of the sweep rate dependence showed that the cathodic and anodic current of 0.1mM DPPH solution varied linearly (r2=0.998) with the square root of the scan rate, from 0.02 to 0.12Vs−1. These results demonstrated that the CNT/GC electrode is appropriate for the quantitation of antioxidants via amperometric detection of the residual concentration of non-reacted DPPH•. We obtained linear calibrations for all the antioxidants tested including gallic acid, catechin, quercetin, caffeic acid and Trolox. The system offers rapid sample throughput (45samplesh−1) and good precision of 3.2% R.S.D., for 20μL-injection of 2.5μM Trolox (n=30). This method was applied to evaluate the TAC of extracts of some Thai indigenous vegetables.

Study of Factors Affecting the Performance of Voltammetric Copper Sensors Based on Gly‐Gly‐His Modified Glassy Carbon and Gold Electrodes

AbstractThis paper reports a study of the factors affecting the analytical performance of gold and glassy carbon electrodes modified with the tripeptide Gly‐Gly‐His for the detection of copper ions. Gly‐Gly‐His is attached to a glassy carbon (GC) surface modified with 4‐carboxyphenyl moieties or a gold surface modified with 3‐mercaptopropionic acid by the reaction of the N‐terminal amine group of the peptide with the carboxylic acid groups of the monolayer via carbodiimide activation. X‐ray photoelectron spectroscopy was used to characterize the steps in the biosensor fabrication. It was found that the analytical performance of a sensor prepared with Gly‐Gly‐His on a GC electrode was similar to that on a gold electrode under the same conditions. The performance was greatly enhanced at higher temperature, no added salt during copper accumulation and longer accumulation time within a pH range of 7–9. Interference studies and investigations of stability of the Gly‐Gly‐His sensor are reported. Analysis of natural water samples show that the sensors measure only copper ions that can complex at the sensor surface. Strongly complexed copper in natural water is not measured. Despite greater stability of diazonium salt derived monolayers on carbon surfaces compared with alkanethiols self‐assembled monolayers on gold, the stability of the sensors was essentially the same regardless of the modification procedure.

ChemInform Abstract: Surface‐Modified Glassy Carbon Electrodes Obtained by Electrochemical Treatment. Its Effect on Ru(bpy)2+ 3 Adsorption and the Electron‐Transfer Rates of the Fe2+/Fe3+ Couple.

AbstractA modified glassy carbon (MGC) electrode, obtained by cycling the electrode between ‐500 and +1860 mV (vs.

Studies of surface-modified glassy carbon electrodes obtained by electrochemical treatment: Its effect on Ru(bpy) 2+3 adsorption and the electron transfer rates of the Fe 2+/Fe 3+ couple

Glassy carbon electrodes were treated electrochemically by cycling the electrode between - 500 and 1860 mV (vs. SCE) in 1 M H 2SO 4 at a sweep rate of 150 mV/s. The modified glassy carbon (MGC) electrode surfaces obtained have been characterized by cyclic and step potentiostatic techniques. The redox reactions of the surface functionalities attributed to the quinone-like structures of these MGC electrodes are slow and exhibit apparent diffusion control. Thus, when a given catalytic effect depends on the redox state of the surface, it will also depend on the time scale of the experiment. The conditions for obtaining reproducible MGC electrodes are given. Cyclic voltammetric studies show that Ru(bpy) 2+ 3 adsorbs strongly on MGC electrodes while the adsorption is negligible on freshly polished electrodes. The adsorption fits the Temkin isotherm, giving the value of the repulsive interaction between the molecules. The value of †G = −39.6 kJ mol was calculated for the process. A specific interaction between the bipyridyl moieties and the surface functionalities is proposed. Appreciable photocurrents are observed for Ru(bpy) 2+ 3 adsorbed on a MGC electrode which may lead to future applications. On the other hand, by measuring the formal heterogeneous rate constants ( k s) for Fe 2+/Fe 3+ it is possible to show how the catalytic efficiency of MGC depends on the degree of modification of its surface.