Electrochemical behavior of tartaric acid at CuGeO3 nanowire modified glassy carbon electrode

The electrochemical behavior of tartaric acid at the CuGeO₃ nanowire modified glassy carbon electrode has been investigated by cyclic voltammetry (CV). The results show that two pairs of semireversible electrochemical peaks are observed and can be assigned to the process of oxidation–reduction and adsorption–desorption of tartaric acid at the modified glassy carbon electrode, respectively. The intensity of the CV peaks increases linearly with the increase of the content of tartaric acid in the range of 0.01–5 mM and scan rate ranging from 25–200 mV s^?1. CuGeO₃ nanowire modified glassy carbon electrode exhibits good detection ability for tartaric acid in neutral solution with the detection limit of 8.9 and 7.7 μM for cvp1 and cvp2, respectively, at a signal-to-noise ratio of 3. The CuGeO₃ nanowire modified glassy carbon electrode has good reproducibility and stability.     

An amperometric glucose biosensor based on the immobilization of glucose oxidase on the CuGeO3 nanowire modified electrode

A new amperometric biosensor based on adsorption of glucose oxidase (GOx) at the CuGeO₃ nanowires (NW) modified glassy carbon electrode (GCE) is reported in this article. The properties of the biosensor were characterized by Fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS) and electrochemical techniques. The GCE modified with the CuGeO₃ NW/GOD showed excellent electrocatalytical response to the oxidation of glucose. Different parameters including GOx concentration, working potential and pH of supporting electrolyte that governed the analytical performance of the biosensor have been studied in detail and optimized. The biosensor was applied to detect glucose with a linear range of 0.5 to 7 mM. The biosensor exhibited excellent reproducibility and stability.     

The NADH Electrochemical Detection Performed at Carbon Nanofibers Modified Glassy Carbon Electrode

In this work, the capability of carbon nanofibers to be used for the design of catalytic electrochemical biosensors is demonstrated. The direct electrochemistry of NADH was studied at a glassy carbon electrode modified using carbon nanofibers. A decrease of the oxidation potential of NADH by more than 300 mV is observed in the case of the assembled carbon nanofiber‐glassy carbon electrode comparing with a bare glassy carbon electrode. The carbon nanofiber‐modified electrode exhibited a wide linear response range of 3×10^?5 to 2.1×10^?3 mol L^?1 with a correlation coefficient of 0.997 for the detection of NADH, a high specific sensitivity of 3637.65 (μA/M cm²), a low detection of limit (LOD=3σ) of 11 μM, and a fast response time (3 s). These results have confirmed the fact that the carbon nanofibers represent a promising material to assemble electrochemical sensors and biosensors.     

Fabrication of highly sensitive cysteine electrochemical sensor based on nanostructured compound and carbon nanotube modified electrode

This work describes the electrochemical behavior of copper(II)-bis[5-((4-ⁿ-decyloxyphenyl)azo)-N-(ⁿethanol)-salicylaldiminato]film immobilized on the surface of multiwall carbon nanotube glassy carbon electrode and its electrocatalytic activity toward the oxidation of L-cysteine. The surface structure and composition of the sensor was characterized by scanning electron microscopy. Electrocatalytic oxidation of L-cysteine on the surface of modified electrode was investigated with cyclic voltammetry, chronoamperometry and hydrodynamic amperometery methods and the results showed that the Cu-Schiff base film displays excellent electrochemical catalytic activities towards L-cysteine oxidation. The modified electrode indicated reproducible behavior and high level of stability during the electrochemical experiments.     

Selective determination of cysteine in the presence of tryptophan by carbon paste electrode modified with quinizarine

A sensitive and selective electrochemical method for the determination of L-cysteine was developed using a modified carbon paste electrode (MCPE) with quinizarine. Cyclic voltammetry was used to investigate the redox properties of this modified electrode at various solution pH values and at various scan rates. The apparent charge transfer rate constant, ks and transfer coefficient for electron transfer between quinizarine and carbon paste electrode (CPE) were calculated as 2.76 s^?1 and 0.6, respectively. This modified carbon paste electrode shows excellent electrocatalytic activity toward the oxidation of L-cysteine in a phosphate buffer solution (pH 7.0). The linear range of 1.0 × 10^?6 to 1.0 × 10^?3 M and a detection limit (3s) of 2.2 × 10^?7 M were observed in pH 7.0 phosphate buffer solutions. In differential pulse voltammetry, the quinizarine modified carbon paste electrode (QMCPE) could separate the oxidation peak potentials of L-cysteine and tryptophan present in the same solution, though at the unmodified CPE the peak potentials were indistinguishable. This work introduces a simple and easy approach to selective detection of L-cysteine in the presence of tryptophan. Also, the modified electrode was employed for the determination of L-cysteine in the real samples such as serum of blood and acetylcysteine tablet.     

Characterization of electrodes modified with nanocomposites of cobalt tetraaminophenoxyphthalocyanine,reduced graphene and multi-walled carbon nanotubes

Abstract

Glassy carbon electrodes or plates were modified with nanocomposites consisting of cobalt tetraaminophenoxyphthalocyanine (CoTAPhPc), reduced graphene oxide nanosheets (rGONs) and multi-walled carbon nanotubes (MWCNTs). The modified electrodes were characterized using cyclic voltammetry, scanning electrochemical microscopy (SECM) and time-of-flight-secondary ion mass spectrometer (TOF-SIMS). The electrocatalytic activity of the modified electrode was tested for detection of L-cysteine. The presence of CoTAPhPc on sequential layers of MWCNT and rGONs resulted in improved detection currents compared to CoTAPhPc alone or when MWCNT/rGONs are mixed in CoTAPhPc–MWCNT/rGONs (mix)–glassy carbon electrode (GCE). CoTAPhPc–MWCNT–GCE (without rGONS) showed higher sensitivity toward l-cysteine as compared to the probes incorporating rGONs with a catalytic rate constant of 4.62?×?10⁴ M^?1s^?1 and a detection limit of 30?nM. The presence of rGONs improved the stability of the electrode.     

Electrocatalytic Oxidation and Direct Determination of L-Tyrosine by Square Wave Voltammetry at Multi-wall Carbon Nanotubes Modified Glassy Carbon Electrodes

The electrochemical behavior of L-tyrosine was investigated at a multi-wall carbon nanotubes modified glassy carbon electrode. L-tyrosine itself showed a poor electrochemical response at the bare glassy carbon electrode; however, a multi-wall carbon nanotubes film fabricated on the glassy carbon electrode can directly enhance the electrochemical signal of L-tyrosine when applying cyclic voltammetry and square wave stripping voltammetry without any mediator. Cyclic voltammetry was carried out to study the electrochemical oxidation mechanism of L-tyrosine, which shows a totally irreversible process and an oxidation potential of 671 mV at the modified electrode and 728 mV at the bare electrode, ΔE_p = 57 mV. The anodic peak current linearly increases with the square root of scan rate in the low range, suggesting that the oxidation of L-tyrosine on the multi-wall carbon nanotubes modified electrode is a diffusion-controlled process. The square wave stripping voltammetry currents of L-tyrosine at the multi-wall carbon nanotubes modified electrodes increased linearly with the concentration in the range of 2.0 × 10⁻⁶–5.0 × 10⁻⁴ mol L⁻¹. The detection limit was 4.0 × 10⁻⁷ mol L⁻¹. The method is simple, quick, sensitive and accurate.     

Electrochemical detection of L-cysteine using a glassy carbon electrode modified with a two-dimensional composite prepared from platinum and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles on reduced graphene oxide

We report on an electrochemical sensor for L-cysteine that consists of a glassy carbon electrode modified with a two-dimensional ternary nanocomposite prepared from platinum, magnetite, and reduced graphene oxide (referred to as Pt-Fe₃O₄/rGO). It was prepared by a solvothermal method and characterized by X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Electrochemical detection processes were investigated by cyclic voltammetry, amperometry, double potential step chronoamperometry and differential pulse voltammetry. The diffusion coefficient (7.41 × 10^?7 cm² s^?1) and reaction rate constant (9.96 × 10⁷ cm³ mol^?1 s^?1) were calculated via the Cottrell equation. The sensor, best operated in 0.1 M NaOH solution at a working voltage of 0.65 V vs. SCE, has a 10 μM detection limit and an analytical range that extends from 0.10 to 1.0 mM. The method is acceptably selective, stable, repeatable and reproducible due to the synergistic effect of the various components applied. The detection limit is 1.0 × 10^?5 M.

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Graphical abstract The electrochemical detection of L-cysteine based on a two-dimensional Pt-Fe₃O₄/reduced graphene oxide modified glassy carbon electrode has a detection limit of 1.0 × 10^-5 M in the range of 0.10 - 1.0 mM due to the synergistic effect of each component.

     

Employing Label‐free Electrochemical Biosensor Based on 3D‐Reduced Graphene Oxide and Polyaniline Nanofibers for Ultrasensitive Detection of Breast Cancer BRCA1 Biomarker

A label‐free DNA biosensor based on three‐dimensional reduced graphene oxide (3D‐rGO) and polyaniline (PANI) nanofibers modified glassy carbon electrode (GCE) was successfully developed for supersensitive detection of breast cancer BRCA1. The results demonstrated that 3D‐rGO and PANI nanofibers had synergic effects for reducing the charge transfer resistance (R_ct), meaning a huge enhancement in electrochemical activity of 3D‐rGO‐PANI/GCE. Probe DNA could be immobilized on 3D‐rGO‐PANI/GCE for special and sensitive recognition of target DNA (1.0×10^?15–1.0×10^?7 M) with a theoretical LOD of 3.01×10^?16 M (3S/m). Furthermore, this proposed nano‐biosensor could directly detect BRCA1 in real blood samples.     

木犀草素在离子液体修饰电极上的电催化氧化及其测定

用1-丁基-3-甲基咪唑六氟磷酸盐([BMIM]PF₆)疏水性离子液体修饰玻碳电极,在0.2 mol/L磷酸盐缓冲溶液(pH为4.0～8.0)中,运用循环伏安法（CV）和差示脉冲溶出伏安法(DPSV)研究了木犀草素在修饰电极上的电化学行为,建立了测定木犀草素含量的新方法。 实验结果表明,该修饰电极上木犀草素氧化、还原峰电位均负移,峰电流增大。 在-0.2～0.7 V电位区间,pH=7.0的磷酸盐缓冲溶液体系中,木犀草素在修饰电极表面发生的是受吸附控制的准可逆等电子等质子电极反应,电子转移系数α=0.5,吸附量为4.6×10-10 mol/cm²;木犀草素氧化峰电流与其浓度在1.0×10^-10～1.6×10^-8 mol/L范围内呈良好的线性关系,检出限达到3.2×10^-11 mol/L,回收率为98.7%～102.0%;该法操作简单、快速、灵敏、准确;可用于野菊花中类黄酮的测定。     

Detection of Aeromonas hydrophila DNA oligonucleotide sequence using a biosensor design based on Ceria nanoparticles decorated reduced graphene oxide and Fast Fourier transform square wave voltammetry

A new strategy was introduced for ssDNA immobilization on a modified glassy carbon electrode. The electrode surface was modified using polyaniline and chemically reduced graphene oxide decorated cerium oxide nanoparticles (CeO₂NPs-RGO). A single-stranded DNA (ssDNA) probe was immobilized on the modified electrode surface. Fast Fourier transform square wave voltammetry (FFT-SWV) was applied as detection technique and [Ru(bpy)₃]^2+/3+ redox signal was used as electrochemical marker. The hybridization of ssDNA with its complementary target caused a dramatic decrease in [Ru(bpy)₃]^2+/3+ FFT-SW signal. The proposed electrochemical biosensor was able to detect Aeromonas hydrophila DNA oligonucleotide sequence encoding aerolysin protein. Under optimal conditions, the biosensor showed excellent selectivity toward complementary sequence in comparison with noncomplementary and two-base mismatch sequences. The dynamic linear range of this electrochemical DNA biosensor for detecting 20-mer oligonucleotide sequence of A. hydrophila was from 1 × 10⁻¹⁵ to 1 × 10⁻⁸ mol L⁻¹. The proposed biosensor was successfully applied for the detection of DNA extracted from A. hydrophila in fish pond water up to 0.01 μg mL⁻¹ with RSD of 5%. Besides, molecular docking was applied to consider the [Ru(bpy)₃]^2+/3+ interaction with ssDNA before and after hybridization.     

在3,4-二羟基肉桂酸介质中以多壁碳纳米管为传感器电催化检测L-半胱氨酸(英文)

A highly sensitive electrochemical sensor was prepared for the determination of L-cysteine using a modified multiwall carbon nanotubes paste electrode in the presence of 3,4-dihydroxycinnamic acid(3,4-DHCA) as a mediator, based on an electrocatalytic process. The results indicate that the electrode is electrocatalytically efficient for the oxidation of L-cysteine in the presence of 3,4-DHCA. The interaction between the mediator and L-cysteine can be used for its sensitive and selective determination. Using chronoamperometry, the catalytic reaction rate constant was calculated to be 2.37 × 102 mol–1 L s–1. The catalytic peak current was linearly dependent on the L-cysteine concentration in the range of 0.4–115 μmol/L. The detection limit obtained by linear sweep voltammetry was 0.25 μmol/L. Finally, the modified electrode was examined as a selective, simple, and precise new electrochemical sensor for the determination of L-cysteine in real samples.     

Electrochemical preparation of a novel type of C-dots/ZrO2 nanocomposite onto glassy carbon electrode for detection of organophosphorus pesticide

A selective, sensitive novel electrochemical sensor for detection of methyl parathion on the preparation of a carbon dots (C-dots)/ZrO₂ nanocomposite was developed. The C-dots/ZrO₂ nanocomposite was fabricated using electrochemical deposition onto a glassy carbon electrode and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and cyclic voltammetry. The optimum parameters such as effect of pH, accumulation time, accumulation potential, scan rate, effect of amount of C-dots and effect of amount of ZrO₂ were investigated. The C-dots/ZrO₂ modified glassy carbon electrode allowed rapid, selective determination of methyl parathion in rice samples by adsorptive stripping voltammetry. The stripping response was highly linear over the methyl parathion concentrations ranging from 0.2 ng mL^?1 to 48 ng mL^?1, with a detection limit of 0.056 ng mL^?1. This novel electrochemical nanocomposite-based electrochemical sensor was successfully applied for the detection of methyl parathion in rice samples.     

Preparation of L-Cys–Au colloid self-assembled nanoarray electrode based on the microporous aluminium anodic oxide film and its application to the measurement of dopamine

A novel method for fabricating a nanoarray electrode combining the template technique with the self-assembled approach was developed. The glassy carbon electrode was modified with the Au nanoarray using micropores of aluminum anodic film as template. Then, the Au nanoarray electrode was self-assembled with L-cysteine (L-Cys) and gold colloid, respectively. In order to evaluate the electrochemical characteristics of L-Cys–Au colloid self-assembled nanoarray electrode, was chosen as molecule probe and cyclic voltammetry was used. In addition, the functional nanoarray electrode was applied to measuring dopamine (DA). The resulting L-Cys–Au colloid self-assembled nanoarray electrode demonstrated that the linear calibration range extended over three orders of magnitude of DA concentrations (1.0 × 10⁻⁹–1.0 × 10⁻⁶ mol/L) and the detection limit was 5.0 × 10⁻¹⁰ mol/L.     

Electrochemical oxidation determination and voltammetric behaviour of 4-nitrophenol based on Cu2O nanoparticles modified glassy carbon electrode

Cu₂O nanoparticles (nano-Cu₂O) modified glassy carbon electrode (GCE) was fabricated and used to investigate the electrochemical behaviour of 4-nitrophenol (4-NP) by cyclic voltammetry (CV), chronoamperometry (CA), chronocoulometry (CC) and differential pulse voltammetry (DPV). Compared with GCE, a remarkable increase in oxidation peak current was observed. It indicates that nano-Cu₂O exhibits remarkable enhancement effect on the electrochemical oxidation of 4-NP. Under the optimised experimental conditions, the oxidation peak currents were propotional to 4-NP concentration in the range from 1.0?×?10^?6 to 4.0?×?10^?4?mol?L^?1 with a detection limit of 5.0?×?10^?7?mol?L^?1 (S/N?=?3). The fabricated electrode presented good repeatability, stability and anti-interference. Finally, the proposed method was applied to determine 4-NP in water samples. The recoveries for these samples were from 94.60% to 105.5%.     

Label-Free Detection of DNA Hybridization Based on MnO2 Nanoparticles

Abstract

Nano-MnO₂/chitosan composite film modified glassy carbon electrode (MnO₂/CHIT/GCE) was fabricated and a DNA probe was immobilized on the electrode surface. The immobilization and hybridization events of DNA were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The EIS was applied to the label-free detection of the target DNA. The human immunodeficiency virus (HIV) gene fragment was successfully detected by this DNA electrochemical sensor. The dynamic detection range was from 2.0 × 10^?11 to 2.0 × 10^?6 mol/L, with a detection limit of 1.0 × 10^?12 mol/L.     

Highly Sensitive Electrochemical Sensor for Determination of Vitamin D in Mixtures of Water‐Ethanol

This paper describes the electrochemical determination of vitamin D₂ (ergocalciferol) and D₃ (cholecalciferol) in mixed organic/water solvent, using a glassy carbon electrode (GCE). The mixing ratio of organic/water solvent has an important influence on the electrocatalytic response of D vitamins on the surface of the glassy carbon electrode. Well‐defined peaks for Vitamin D₂ and D₃ were observed in a 40 % ethanol/60 % water solution with lithium perchlorate as the support electrolyte. This study demonstrated that the glassy carbon electrode is highly sensitive for the determination of vitamin D₂ and D₃, with a limit of detection of 0.13 and 0.118 µmol L^?1, respectively. No significant interference was seen for vitamins A, E and K in the detection of vitamin D.     

Novel Designing of Chemically Modified Electrode (CME) of the Bio-MOF-1 for the Detection of Dopamine Based on Inhibition of [Ru(bpy)3]2+/DBAE System

Metal organic frameworks (MOFs) have attracted extensive attention in electrochemical research fields due to their high surface area and controlled porosity. Current study is design to investigate the ECL performance of the chemically modified electrode (CME) based on the bio-MOF-1, a porous zinc-adenine framework, which loaded ruthenium complex and employed for the detection of dopamine (DA). The composite material [Ru(bpy)₃]²⁺@bio-MOF-1 (Ru-bMOF) modified carbon glassy electrode (Ru-bMOF/GCE) exhibited an excellent ECL performance having a linear co-efficient response (R²=0.9968) for 2-(dibutyl amino) ethanol (DBAE), a classical ECL co-reactant was obtained over a concentration range of 1.0×10⁻⁹ M to 1.0×10⁻⁴ M in 0.10 M pH=6.0 phosphate buffer solution (PBS). Furthermore, DA was detected based on its inhibition effect on [Ru(bpy)₃]²⁺/DBAE system. Compared to traditional analytical methods, this method has various advantages such as simple electrode preparation, quick response, high reproducibility (RSD<2.0 %), low limit of detection (LOD=1.0×10⁻¹⁰ mol/L). This chemical investigated modified electrode had exploited potential for detection of DA.     

Detection of acetaminophen using cyclic voltammetry on MnFe2O4/polyaniline

A novel sensing material, MnFe₂O₄/polyaniline (PANI), was fabricated by doping PANI to MnFe₂O₄ on a modified glassy carbon electrode (GCE). This sensing material was characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and high‐resolution transmission electron microscopy (HR‐TEM). Using a cyclic voltammetry electrochemical‐sensing method, we tested MnFe₂O₄/PANI, and an acetaminophen concentration of 0.0625–5 mM was recorded. Furthermore, the sensor responses were 2.05–22.44. The detection limit was 2.23 × 10^?7 M. Strong selectivity was observed for MnFe₂O₄/PANI, which is a possible sensing mechanism.     

Fabrication of CeO2 Nanoparticle Modified Glassy Carbon Electrode for Ultrasensitive Determination of Trace Amounts of Uric Acid in Urine

The preparation of a glassy carbon electrode modified by CeO2 nanoparticles was described, which was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. In pH 6.0 buffer, the CeO2 nanoparticle modified electrode （CeO2 NP/GC） gave an excellent electrocatalytic activity for the oxidation of uric acid （UA）. The catalytic current of UA versus its concentration had a good linear relation in the range of 2.0 × 10^-7-5.0 × 10^- 4 mol/L, with the correlation coefficient of 0.9986 and detection limit of 1.0 ×10^-7 mol/L. The modified electrode can be used for the determination of UA in urine, which can tolerate the interference of ascorbic acid up to 1000-fold. The method was simple, quick and sensitive.