Self-assembly electrode based on silver nanoparticle toward electrogenerated chemiluminescence analysis of glucose

Electrogenerated Chemiluminescence (ECL) involves applying a certain electric potential to a chemical reaction, resulting in the oxidation or reduction of the substance which reacts to produce light. We determined the amount of glucose by its reaction to glucose oxidase (GO _X ) on the surface of the proposed modified electrode, which results hydrogen peroxide (H₂O₂) as side product. After that the reactions between luminol and H₂O₂ under oxidizing conditions generate dependent light which can be used to analyze. In the current article at first we proposed a convenient method to obtaining a self-assembly modified electrode. A nano based modified glassy carbon (GC) electrode (Glucose oxidase/Ag nanoparticles/cysteamine (CA)/p-aminobenzene sulfonic acid/GC electrode) was prepared, and the ECL behavior of luminol in the presence of glucose was examined. Compared to the bare GC electrode, the modified electrode incorporating glucose oxidase significantly enhanced the response of the ECL biosensor to glucose due to the enhanced specificity of the modified surface to enzymatic reaction, and the sensitivity of the luminol ECL reaction. Under optimal conditions, the electrode was established to respond linearly to glucose in the concentration range 5.0×10^?7 to 8.0×10^?3 mol/L, and the detection limit was established to be a glucose concentration of 4.0×10^?8 mol/L.     

Green synthesized Au–Ag bimetallic nanoparticles modified electrodes for the amperometric detection of hydrogen peroxide

Simple and eco-friendly electro deposition method was employed for the fabrication of Au–Ag bimetallic nanoparticles modified glassy carbon electrode. Nano Au–Ag film modified glassy carbon electrode surface morphology has been examined using atomic force microscopy. Electrodeposited Au–Ag bimetallic nanoparticles were found in the average size range of 15–50 nm. The electrochemical investigations of nano Au–Ag/1-butyl-3-methylimidazolium tetrafluoroborate-nafion film have been carried out using cyclic voltammetry and electrochemical impedance spectroscopy. The nano Au–Ag/1-butyl-3-methylimidazolium tetrafluoroborate-nafion film modified glassy carbon electrode holds the good electrochemical behavior and stability in pH 7.0 phosphate buffer solutions. The nano Au–Ag/1-butyl-3-methylimidazolium tetrafluoroborate-nafion modified glassy carbon electrode was successfully employed for the detection of H₂O₂ in the linear range of 1–250 μM in lab samples, and 1 × 10⁻³–2 × 10⁻² M in real samples, respectively.     

Amperometric biosensor for nitrite and hydrogen peroxide based on hemoglobin immobilized on gold nanoparticles/polythionine/platinum nanoparticles modified glassy carbon electrode

BACKGROUND: This paper describes a convenient and effective strategy to construct a highly sensitive amperometric biosensor for nitrite (NO₂^?) and hydrogen peroxide (H₂O₂). First, Pt nanoparticles (PtNPs) were electrodeposited on a glassy carbon electrode (GCE) surface, which promoted electron transfer and enhanced the loading of poly‐thionine (PTH). Subsequently, thionine (TH) was electropolymerized on the PtNPs/GCE, and gold nanoparticles (AuNPs) were assembled onto the PTH film to improve the absorption capacity of hemoglobin (Hb) and further facilitate electron transfer. Finally, Hb was immobilized onto the electrode through the AuNPs. RESULTS: Cyclic voltammetry (CV) and scanning electron microscopy (SEM) were used to characterize the fabrication process of the sensing surface. Under optimum conditions, the biosensors can be used for the determination of NO₂^? in the concentration range 70 nmol L^?1 to 1.2 mmo L^?1 and of H₂O₂ in the range 4.9 µmol L^?1 to 6.8 mmol L^?1. The detection limits (S/N = 3) were 20 nmol L^?1 and 1.4 µmol L^?1, respectively. CONCLUSION: The biosensor exhibits good analytical performance, acceptable stability and good selectivity. Copyright © 2011 Society of Chemical Industry     

Linker-free layer-by-layer self-assembly of gold nanoparticle multilayer films for direct electron transfer of horseradish peroxidase and H2O2 detection

Au nanoparticle (AuNP) multilayer films were fabricated by combining interfacial assembly and layer-by-layer assembly. The key point is that the procedure does not require assistance of organic linker molecules, thus providing a suitable platform for the modification of biological molecules. Direct electron transfer can easily take place between a glassy carbon electrode and horseradish peroxidase (HRP) molecules adsorbed on AuNP films. The current density of direct electron transfer was closely related to the layer number, m, and reached a maximum value for m = 4. The optimized HRP/AuNP multilayer film had a relatively rapid response and satisfactory selectivity for H₂O₂ detection. The linear range and the detection limit were 9.8 × 10⁻⁶ to 6 × 10⁻³ mol/L and ∼4.9 × 10⁻⁶ mol/L (S/N = 3), respectively.     

Electrochemical determination diethylstilbestrol by a single-walled carbon nanotube/platinum nanoparticle composite film electrode

Platinum nanoparticles (Pt_nano) were prepared and used in combination with single-wall carbon nanotube (SWNT) for fabricating electrochemical sensors with remarkably improved sensitivity toward diethylstilbestrol (DES). The glassy carbon (GC) electrode modified with SWNT/Pt_nano composite film exhibited excellent electrochemical behaviors toward the redox of DES. Compared with the bare GC electrode and SWNTs film modified GC electrode, the redox peak currents at the SWNTs/Pt_nano composite film modified GC electrode was enhanced greatly. The experimental parameters, which influence the peak current of DES, were optimized. Under optimal conditions, a linear response of DES was obtained in the range from 1.0 × 10⁻⁷ to 2.0 × 10⁻⁵ mol L⁻¹ (R = 0.997) and with a limit of detect (LOD) of 1.5 × 10⁻⁸ mol L⁻¹. The proposed procedure was successfully applied to determine the active ingredient in the DES tablet with satisfactory results.     

Electrochemical biosensor for detection of formaldehyde in rain water

BACKGROUD: This study describes the construction of an electrochemical formaldehyde biosensor based on poly(glycidyl methacrylate‐co‐3‐methylthienyl methacrylate)/formaldehyde dehydrogenase/polypyrrole [poly(GMA‐co‐MTM)/FDH/PPy] composite film electrode. Formaldehyde dehydrogenase (FDH) was chemically immobilized via the epoxy groups of the glycidyl methacrylate (GMA) side chain of the polymer. Formaldehyde measurements were conducted in 0.1 mol L^?1, pH 8 phosphate buffer solution (PBS) including 0.1 mol L^?1 KCl, 0.5 mmol L^?1 of NAD⁺ (cofactor of the enzyme) and 1 mmol L^?1 of 1,2‐napthoquinone‐4‐sulfonic acid sodium salt (NQS) as mediator with an applied potential of ? 0.23 V (vs. Ag/AgCl, 3 mol L^?1 NaCl). Analytical parameters of the biosensor were calculated and discussed. The biosensor was tested in rain water samples. RESULTS: Sensitivity was found to be 15 000 per mmol L^?1 (500 nA ppm^?1) in a linear range between 0.1 ppm and 3 ppm (3.3–100 µmol L^?1). A minimum detectable concentration of 4.5 ppb (0.15 µmol L^?1) (S/N = 3) with a relative standard deviation (RSD) of 0.73% (n = 5) was obtained from the biosensor. Response time of the biosensor was very short, reaching 99% of its maximum response in about 4 s. The biosensor was also tested for formaldehyde measurements in rain water samples. Formaldehyde concentrations in samples were calculated using the proposed biosensor with recovery values ranged between 92.2 and 97.7% in comparison with the colorimetric Nash method. CONCLUSION: The poly(GMA‐co‐MTM)/FDH/PPy) electrode showed excellent measurement sensitivity in comparison with other formaldehyde biosensor studies. Strong chemical bonding between the enzyme and the copolymer was created via the epoxy groups of the composite film. The proposed biosensor could be used successfully in rain waters without a pretreatment step. © 2012 Society of Chemical Industry     

Screen Printed Biosensor for Hydrogen Peroxide Based on Prussian Blue Modified Hydroxyapatite

A disposable and sensitive screen-printed carbon electrode for the determination of hydrogen peroxide (H₂O₂) was fabricated with Prussian blue-modified hydroxyapatite (PB@HAP). PB@HAP was incubated with horseradish peroxidase (HRP). The synergistic effect between HAP and PB facilitated the electron-transfer process and retained the bioactivity of HRP. The proposed biosensor effectively overcame the shortcomings of electron mediator leakage because hydroquinone was added to the base solution. The biosensor showed a low detection limit of 7 μmol/L. A linear calibration plot was obtained over the concentration range, 1–15 mmol/L; the Michaelis constant was 1.31 mmol/L, which indicated that the enzyme retained high bioactivity and excellent appetency toward H₂O₂. Additionally, the screen-printed biosensor exhibited the characteristics of strong anti-interference, high long-term stability and good reproducibility. Based on the above, PB@HAP has potential for applications in immunosensors and glucose sensors.     

Electroanalysis of ascorbic acid (vitamin C) using nano-ZnO/poly(luminol) hybrid film modified electrode

Electrochemical analysis of ascorbic acid (AsA) in physiological condition using a new hybrid film modified electrode is described. Electrochemical polymerization of luminol in 0.1 M H₂SO₄ solution was carried out using ZnO nanoparticles (ZnO-NPs) coated glassy carbon electrode (GCE) as working electrode. This hybrid film coated electrode noted as poly(luminol)/ZnO-NPs hybrid film modified GCE (PLu/ZnO-NPs/GCE). The atomic force microscope (AFM) and scanning electron microscope (SEM) studies were demonstrated that PLu/ZnO-NPs hybrid film covered the electrode surface and the ZnO-NPs particle sizes were <100 nm. The visible blue colored organic–inorganic (PLu/ZnO-NPs) hybrid films were observed on the electrode surface. Electrochemical studies proved that PLu/ZnO-NPs hybrid film modified electrode is electroactive in the pH range from 1 to 11 and the poly(luminol) (PLu) redox peak was pH dependent with a slope of ?53 mV/pH. The PLu/ZnO-NPs modified electrodes electroactivity also investigated by catalyzing the oxidation of AsA, demonstrating its great potential applications in electroanalysis of AsA. The resulting, AsA electrochemical sensor exhibited a wide linear response range (from 1 × 10^?6 to 3.6 × 10^?4 M, r² = 0.9989), lower detection limit (1 × 10^?6 M) and fast response time (3 s) for AsA determination. Our results show that PLu/ZnO-NPs hybrid film provides a novel and efficient platform for the oxidation of AsA and realizing efficient electrocatalysis and that the materials have potential applications in the fabrication of electrochemical sensors. Analysis of commercial vitamin C samples using PLu/ZnO-NPs hybrid film modified electrode was demonstrated and the obtained results are good agreement with the labeled amount.     

Nanostructured manganese oxide–chitosan-based cholesterol sensor

Manganese oxide nano-rod (nano-MnO₂) was prepared by simple oxidation method. To fabricate nanocomposite film (nano-MnO₂/CT) onto glassy carbon electrode (GCE), nano-MnO₂ was homogeneously dispersed in chitosan (CT). Cholesterol oxidase (ChOx) was immobilized onto nano-MnO₂/CT by physisorption. Modified electrode was characterized by Fourier transform infrared, X-ray diffraction, cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and electrochemical impedance spectroscopy techniques. Prepared ChOx/nano-MnO₂/CT/GCE bioelectrode exhibited 0.03–11.66 mM linearity and 2.07 × 10^?3 mM limit of detection for cholesterol. Biosensing characteristics of modified bioelectrode were superior than other electrodes modified with metal oxide nanoparticles, reported in the literature.     

Direct electrochemistry of horseradish peroxidase on graphene-modified electrode for electrocatalytic reduction towards H2O2

Graphene was synthesized by a chemical method to reduce graphite oxide and well characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD) and Fourier transform infrared (FTIR) spectra. Horseradish peroxidase (HRP) immobilized on a graphene film glassy carbon electrode was found to undergo direct electron transfer and exhibited a fast electron transfer rate constant of 4.63 s⁻¹. The HRP-immobilized electrode was investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The CV results showed that the modified electrode gave rise to well-defined peaks in phosphate buffer, corresponding to the electrochemical redox reaction between HRP–Fe(III) and HRP–Fe(II). The obtained electrode also displayed an electrocatalytic reduction behavior towards H₂O₂. The new H₂O₂ sensor shows a linear range of 0.33–14.0 μM (R² = 0.9987) with a calculated detection limit of 0.11 μM (S/N = 3). Furthermore, the biosensor exhibits both good operational storage and storage stability.     

A novel hydrogen peroxide biosensor based on Au-graphene-HRP-chitosan biocomposites

Graphene was prepared successfully by introducing -SO₃⁻ to separate the individual sheets. TEM, EDS and Raman spectroscopy were utilized to characterize the morphology and composition of graphene oxide and graphene. To construct the H₂O₂ biosensor, graphene and horseradish peroxidase (HRP) were co-immobilized into biocompatible polymer chitosan (CS), then a glassy carbon electrode (GCE) was modified by the biocomposite, followed by electrodeposition of Au nanoparticles on the surface to fabricate Au/graphene/HRP/CS/GCE. Cyclic voltammetry demonstrated that the direct electron transfer of HRP was realized, and the biosensor had an excellent performance in terms of electrocatalytic reduction towards H₂O₂. The biosensor showed high sensitivity and fast response upon the addition of H₂O₂, under the conditions of pH 6.5, potential −0.3 V. The time to reach the stable-state current was less than 3 s, and the linear range to H₂O₂ was from 5 × 10⁻⁶ M to 5.13 × 10⁻³ M with a detection limit of 1.7 × 10⁻⁶ M (S/N = 3). Moreover, the biosensor exhibited good reproducibility and long-term stability.     

Carbon nanotube-modified glassy carbon electrode for anodic stripping voltammetric detection of Uranyle

A multi-wall carbon nanotube (MWNT) modified glassy carbon electrode (GCE) is described for the measurement of trace levels of uranium by anodic stripping voltammetry. In a pH 4.4 NaAc-Hac buffer containing 0.010 mol L⁻¹ Mg(NO₃)₂, UO₂ ²⁺ was adsorbed onto the surface of a MWNT film coated glassy carbon electrode and then reduced at −0.40 V vs. Ag/AgCl. During the positive potential sweep the reduced uranium was oxidized and a well-defined stripping peak appeared at +0.20 V vs. Ag/AgCl. Low concentrations of Mg²⁺ significantly enhanced the stripping peak currents since they induced UO₂ ²⁺ to adsorb at the electrode surface. The response was linear up to 1.2 × 10⁻⁷ mol L⁻¹ and the relative standard deviation at 2.0 × 10⁻⁸ mol L⁻¹ uranium was 5.2%. Potential interferences were examined. The attractive behavior of the new “mercury-free” uranium sensor holds promise for on-site environmental and industrial monitoring of uranium.     

Electroanalytical study of sulphadiazine at solid electrodes. Determination in pharmaceutical preparations

An electroanalytical study of the sulphadiazine oxidation process at solid electrodes using different voltammetric techniques was carried out. Limiting current is diffusion-controlled in the concentration range studied. dpv at a glassy carbon electrode allows the determination of sulphadiazine within the range 1.5 × 10⁻⁵−6.0 × 10⁻⁵ mol l⁻¹. The dpv method was applied to determine sulphadiazine in a commercial pharmaceutical preparation.     

Two Nanostructured Polymers: Polyaniline Nanofibers and New Linear-dendritic Matrix of Poly(citric acid)-block-poly(ethylene glycol) Copolymers for Environmental Monitoring in Novel Biosensors

In this work two phenol biosensors, one based on polyaniline nanofibers (PNFs) and the other based on the newly created and introduced linear-dendritic matrix of poly(citric acid)-block-poly(ethylene glycol) copolymers (PCA-PEG-PCA), were chemically modified with horseradish peroxidase (HRP) enzyme. These phenol biosensors showed an oxidation peak at 0.55 V. The amperometric response for biosensors based on PNFs showed a linear response range from 2.5 × 10^?6 to 2.5 × 10^?5 mol/L, with a detection limit of 2.5 µM phenol. Also, the amperometric response for a biosensor based on PCA-PEG-PCA showed a linear response range from 2.5 × 10^?6 to 4 × 10^?5 mol/L, with a detection limit of 1.5 µM phenol.     

Determination of epigallocatechin‐3‐gallate with a high‐efficiency electrochemical sensor based on a molecularly imprinted poly(o‐phenylenediamine) film

An electrochemical molecularly imprinted polymer (MIP) sensor for detecting the existence of epigallocatechin‐3‐gallate (EGCG) in tea and its products was successfully developed on the basis of a glassy carbon electrode modified with an electropolymerized nonconducting poly(o‐phenylenediamine) film. The properties of the electrode were characterized by cyclic voltammetry, differential pulse voltammetry, and infrared spectroscopy. The template molecules could be rapidly and thoroughly removed by methanol/acetic acid. The linear response range for EGCG was 5.0 × 10^?7–1.0 × 10^?4 mol/L, and the limit of detection was as low as 1.6 × 10^?7 mol/L. The prepared MIP sensor could discriminate between EGCG and its analogs. In addition, satisfactory results were obtained in the detection of real tea samples. The results of our investigation indicate that the MIP sensor was useful for the determination of EGCG with excellent selectivity, high sensitivity, repeatability, and reproducibility. This MIP sensor provides the potential for monitoring the variation of EGCG content during the industrial processes and for predicting the quality of tea and its products. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Arsenic detection by nanogold/conducting‐polymer‐modified glassy carbon electrodes

This article discusses the results for the development of a nanogold‐particle/polyaniline‐modified glassy carbon electrode for the detection of arsenic(III) in water. A thin polyaniline film was electropolymerized onto a glassy carbon electrode. The gold nanoparticle was then deposited onto the polyaniline‐coated glassy carbon electrode via potential step electrolysis from 1.1 to 0 V versus Ag/AgCl/NaCl (saturated) for 45 s from a 0.5M H₂SO₄ solution containing 0.1 mM NaAuCl₄ in the absence and presence of a 0.1 mM KI additive. The surface of the modified electrode was examined with scanning electron microscopy. Cyclic and anodic stripping voltammetry of arsenic(III) was performed on the modified electrode. The thus modified nanogold‐particle/polyaniline‐modified glassy carbon electrode prepared in the presence of the I^? (KI) additive showed a high sensitivity in detecting arsenic(III) in water, and with stripping voltammetry, a limit of detection of 0.4 ppb arsenic was obtained, which is much lower than the arsenic guideline limit of the World Health Organization. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1306–1311, 2007     

Micropatterning of active enzyme with a high-resolution by scanning electrochemical microscopy coupled with a nanometer-sized carbon fiber disk tip

We developed a new method for fabrication of nanometer-sized carbon fiber disk electrodes and applied them to micropattern active horseradish peroxidase (HRP) with a high-resolution by scanning electrochemical microscopy (SECM). In order to pattern active HRP, except for active HRP micropatterns predesigned other regions on a HRP-immobilized substrate was deactivated by a reactive species generated at the electrode as the tip of SECM held at 1.7 V through oxidation of Br⁻ in 0.20 mol/L phosphate buffer (PB) containing 2.5 × 10⁻² mol/L KBr and 2.0 × 10⁻³ mol/L BQ (pH 7.0). The micropatterns of active HRP were characterized using the feedback mode of SECM in PB containing 2.0 × 10⁻³ mol/L BQ and 2.0 × 10⁻³ mol/L H₂O₂, when the tip potential was held at −0.2 V.     

Fabrication of CeO2 nanoparticles modified glassy carbon electrode and its application for electrochemical determination of UA and AA simultaneously

A glassy carbon electrode modified with CeO₂ nanoparticles was constructed and was characterized by electrochemical impedance spectrum (EIS) and cyclic voltammetry (CV). The resulting CeO₂ nanoparticles modified glassy carbon electrode (CeO₂ NP/GC electrode) was used to detect uric acid (UA) and ascorbic acid (AA) simultaneously in mixture. This modified electrode exhibits potent and persistent electron-mediating behavior followed by well-separated oxidation peaks towards UA and AA with activation overpotential. For UA and AA in mixture, one can well separate from the other with a potential difference of 273 mV, which was large enough to allow the determination of one in presence of the other. The DPV peak currents obtained in mixture increased linearly on the UA and AA in the range of 5.0 × 10⁻⁶ to 1.0 × 10⁻³ mol/L and 1.0 × 10⁻⁶ to 5.0 × 10⁻⁴ mol/L, with the detection limit (signal-to-noise ratio was 3) for UA and AA were 2.0 × 10⁻⁷ and 5.0 × 10⁻⁶ mol/L, respectively. The proposed method showed excellent selectivity and stability, and the determination of UA and AA simultaneously in serum was satisfactory.     

A Novel Amperometric Sensor for Salicylic Acid Based on Molecularly Imprinted Polymer-Modified Electrodes

A novel electrochemical MIP-sensor for salicylic acid (SA) has been synthesized firstly by electropolymerizing o-phenylenediamine on glassy carbon electrode in presence of template molecule (salicylic acid). The response of the sensor to SA is investigated by square wave voltammetry (SWV). The linearity is obtained over a concentration range of 6 × 10^?5 ～ 1 × 10^?4 mol/L (R² = 0.9961). And the detection limit of SA is about 2 × 10^?5 mol/L. The sensor exhibits good selectivity for salicylic acid by virtue of the interaction between molecularly imprinted binding sites and the template.     

Amperometric bienzyme glucose biosensor based on carbon nanotube modified electrode with electropolymerized poly(toluidine blue O) film

The amperometric bienzyme glucose biosensor utilizing horseradish peroxidase (HRP) and glucose oxidase (GOx) immobilized in poly(toluidine blue O) (PTBO) film was constructed on multi-walled carbon nanotube (MWNT) modified glassy carbon electrode. The HRP layer could be used to analyze hydrogen peroxide with toluidine blue O (TBO) mediators, while the bienzyme system (HRP + GOx) could be utilized for glucose determination. Glucose underwent biocatalytic oxidation by GOx in the presence of oxygen to yield H₂O₂ which was further reduced by HRP at the MWNT-modified electrode with TBO mediators. In the absence of oxygen, glucose oxidation proceeded with electron transfer between GOx and the electrode mediated by TBO moieties without H₂O₂ production. The bienzyme electrode offered high sensitivity for amperometric determination of glucose at low potential, displaying Michaelis-Menten kinetics. The bienzyme glucose biosensor displayed linear response from 0.1 to 1.2 mM with a sensitivity of 113 mA M⁻¹ cm⁻² at an applied potential of −0.10 V in air-saturated electrolytes.