Nonenzymatic Hydrogen Peroxide Electrochemical Sensor Based on Au‐HS/SO3H‐PMO (Et) Nanocomposite

A newly nonenzymatic sensor for hydrogen peroxide (H₂O₂) based on the (Au‐HS/SO₃H‐PMO (Et)) nanocomposite is demonstrated. The electrochemical properties of the as‐prepared nanocomposite were studied. It displayed an excellent performance towards H₂O₂ sensing in the linear response range from 0.20 µM to 4.30 mM (R=0.9999) with a sensitivity of 6.35×10² µA µM^?1 cm^?2 and a low detection limit of 0.0499 µM. Furthermore, it was not affected by electroactive interference species. These features proved that the modified electrode was suitable for determination of H₂O₂.     

Reduced Graphene Oxide|Carbon Ceramic Electrode Modified with CdS‐Hemoglobin as a Sensitive Hydrogen Peroxide Biosensor

A sensitive hydrogen peroxide (H₂O₂) biosensor was developed based on a reduced graphene oxide|carbon ceramic electrode (RGO|CCE) modified with cadmium sulfide‐hemoglobin (CdS‐Hb). The electron transfer kinetics of Hb were promoted due to the synergetic function of RGO and CdS nanoparticles. The transfer coefficient (α) and the heterogeneous electron transfer rate constant (k_s) were calculated to be 0.54 and 2.6 s^?1, respectively, indicating a great facilitation achieved in the electron transfer between Hb and the electrode surface. The biosensor showed a good linear response to the reduction of H₂O₂ over the concentration range of 2–240 µM with a detection limit of 0.24 µM (S/N=3) and a sensitivity of 1.056 µA µM^?1 cm^?2. The high surface coverage of the CdS‐Hb modified RGO|CCE (1.04×10^?8 mol cm^?2) and a smaller value of the apparent Michaelis? Menten constant (0.24 mM) confirmed excellent loading of Hb and high affinity of the biosensor for hydrogen peroxide.     

The hemoglobin-modified electrode with chitosan/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocomposite for the detection of trichloroacetic acid

A hemoglobin (Hb)-modified electrode based on chitosan/Fe₃O₄ nanocomposite coated glassy carbon has been constructed for trichloroacetic acid (TCA) detection. The structure of chitosan/Fe₃O₄ nanocomposite was investigated using energy-dispersive X-ray analysis (EDS) and X-ray diffraction (XRD) patterns. The electron transfer rate constant (k _s) of Hb was estimated for as high as 3.12 s^?1. The immobilized Hb exhibited excellent electro-catalytic activity toward the reduction of TCA. The response current regressed to the concentration of TCA within the range of 5.70 μM to 205 μM with a detection limit of 1.9 μM (S/N = 3).     

Direct Electrochemistry and Electrocatalysis of Hemoglobin Based on Nafion‐Room Temperature Ionic Liquids‐Multiwalled Carbon Nanotubes Composite Film

A robust and effective composite film combined the benefits of Nafion, room temperature ionic liquid (RTIL) and multi‐wall carbon nanotubes (MWNTs) was prepared. Hemoglobin (Hb) was successfully immobilized on glassy carbon electrode surface by entrapping in the composite film. Direct electrochemistry and electrocatalysis of immobilized Hb were investigated in detail. A pair of well‐defined and quasi‐reversible redox peaks of Hb was obtained in 0.10 mol·L^?1 pH 7.0 phosphate buffer solution (PBS), indicating that the Nafion‐RTIL‐MWNTs film showed an obvious promotion for the direct electron transfer between Hb and the underlying electrode. The immobilized Hb exhibited an excellent electrocatalytic activity towards the reduction of H₂O₂. The catalysis current was linear to H₂O₂ concentration in the range of 2.0×10^?6 to 2.5×10^?4 mol·L^?1, with a detection limit of 8.0×10^?7 mol·L^?1 (S/N=3). The apparent Michaelis‐Menten constant (K_m^app) was calculated to be 0.34 mmol·L^?1. Moreover, the modified electrode displayed a good stability and reproducibility. Based on the composite film, a third‐generation reagentless biosensor could be constructed for the determination of H₂O₂.     

Electrochemistry and Electrocatalysis of Hemoglobin on 1‐Pyrenebutanoic Acid Succinimidyl Ester/Multiwalled Carbon Nanotube and Au Nanoparticle Modified Electrode

A biocompatible nanocomposite film was fabricated for hemoglobin (Hb) molecules immobilization. This film consists of multiwalled carbon nanotubes (MWNTs), 1‐pyrenebutanoic acid, succinimidyl ester (PASE), hemoglobin (Hb) and Au nanoparticles (AuNPs). Herein, PASE molecules physically adsorbed onto MWNTs, and its groups then covalently bond with Hb. AuNPs were then linked with Hb/PASE/MWNTs via electrostatic adsorption force. UV‐visible adsorption spectra, Fourier transform infrared spectra, scanning electron microscope and electrochemical impedance spectroscopy have characterized the film. Cyclic voltammetry (CV) scans showed that in the film Hb has well‐defined redox reaction, with the formal potential (E°) at about ?0.27 V (vs. Ag/AgCl). Herein, differential pulse voltammetry (DPV) was employed to electrochemically detect the Hb in the film with a detection limit of 9.3×10^?8 M. The proposed method was also succeeded for Hb detection in clinical blood samples. Furthermore, the Hb in the film showed good electrocatalytic activities to the reduction of H₂O₂, TCA, NaNO₂ and O₂.     

Enzyme Immobilization and Direct Electrochemistry Based on a New Matrix of Phospholipid‐Monolayer‐Functionalized Graphene

A new nanocomposite material for enzyme immobilization and subsequent direct electrochemistry and electrocatalysis was developed by using 1,2‐dimyristoyl‐sn‐glycero‐3‐phospho‐(1‐rac‐glycerol)‐phospholipid‐monolayer‐membrane‐modified graphene (DMPG‐G). Microperoxidase‐11 (MP11) was chosen as a model enzyme to investigate the composite system. Owing to the improved conductivity and biocompatible microenvironment, MP11 that was immobilized in the matrix of the DMPG‐G nanocomposite (DMPG‐G‐MP11) effectively retained its native structure and bioactivity. DMPG‐G‐MP11‐modified glassy carbon electrode (DMPG‐G‐MP11/GCE) exhibited a pair of well‐defined quasi‐reversible redox peaks of MP11 and showed high electrocatalytic activity towards hydrogen peroxide (H₂O₂). The linear response of the developed biosensor for the determination of H₂O₂ ranged from 2.0×10^?6 to 4.5×10^?4 M with a detection limit of 7.2×10^?7 M . This biosensor exhibited high reproducibility and long‐term storage stability. The promising features of this biosensor indicate that these lipid–graphene nanocomposites are ideal candidate materials for the direct electrochemistry of redox proteins and that they could serve as a versatile platform for the construction of a third‐generation biosensor.     

Direct Electrochemistry and Electrocatalysis of the Hemoglobin Immobilized on Diazonium‐Functionalized Aligned Carbon Nanotubes Electrode

A simple and efficient electrochemical method is utilized to functionalize aligned carbon nanotubes (ACNTs) by the electrochemical reduction of 4‐carboxyphenyl diazonium salt. Thus hemoglobin (Hb) molecules were covalently immobilized on the diazonium‐ACNTs surface via carbodiimide chemistry. Direct electrochemistry and bioelectrocatalytic activity of the immobilized Hb were then investigated by cyclic voltammetry (CV) and amperometry techniques. It is showed that the Hb film on the diazonium‐ACNTs electrode had well‐defined redox peaks with a formal potential (E°) at ?312 mV (vs. Ag/AgCl), and the Hb‐ACNTs electrode displayed good electrocatalytic activity to H₂O₂ reduction. Owing to the high Hb covering on the ACNTs surface (Γ*=2.7×10^?9 mol cm^?2), the catalytic current were significantly improved when compared to the current measured at an Hb‐tangled carbon nanotubes electrode. The Hb‐ACNTs electrode exhibited high sensitivity, long‐term stability and wide concentration range from 40 μM to 3 mM for the amperometric detection of H₂O₂. The heterogeneous reaction rate constant (k_s) was 0.95±0.05 s^?1 and the apparent Michaelis–Menten constant (K was 0.15 mM.     

A Highly Sensitive and Selective Enzymatic Biosensor Based on Direct Electrochemistry of Hemoglobin at Zinc Oxide Nanoparticles Modified Activated Screen Printed Carbon Electrode

A sensitive enzymatic biosensor has been developed for the detection of hydrogen peroxide (H₂O₂), nitrite ( ) and trichloroacetic acid (TCA) by using hemoglobin (Hb) immobilized on activated screen printed carbon electrode (ASPCE) and zinc oxide (ZnO) composite. A pair of well defined redox peaks is observed with a heterogeneous electron transfer rate constant (K_s) of 5.27 s^?1 for Hb at ASPCE/ZnO. The biosensor exhibits the detection of H₂O₂, TCA and in the concentration range of 0.5–129.5 µmol L^?1, 2.5–72.5 mmol L^?1 and 0.2–674 µmol L^?1 with the detection limit of 0.083 µmol L^?1, 0.12 mmol L^?1 and 0.069 µmol L^?1, respectively.     

Application of NiMoO4 Nanorods for the Direct Electrochemistry and Electrocatalysis of Hemoglobin with Carbon Ionic Liquid Electrode

In this paper NiMoO₄ nanorods were synthesized and used to accelerate the direct electron transfer of hemoglobin (Hb). By using an ionic liquid (IL) 1‐butylpyridinium hexafluorophosphate (BPPF₆) modified carbon paste electrode (CILE) as the basic electrode, NiMoO₄ nanorods and Hb composite biomaterial was further cast on the surface of CILE and fixed by chitosan (CTS) to establish a modified electrode denoted as CTS/NiMoO₄‐Hb/CILE. UV‐vis and FT‐IR spectroscopic results showed that Hb in the film retained its native structures without any conformational changes. Electrochemical behaviors of Hb entrapped in the film were carefully investigated by cyclic voltammetry with a pair of well‐defined and quasi‐reversible redox voltammetric peaks appearing in phosphate buffer solution (PBS, pH 3.0), which was attributed to the direct electrochemistry of the electroactive center of Hb heme Fe(III)/Fe(II). The results were ascribed to the specific characteristic of NiMoO₄ nanorods, which accelerated the direct electron transfer rate of Hb with the underlying CILE. The electrochemical parameters of Hb in the composite film were further carefully calculated with the results of the electron transfer number (n) as 1.08, the charge transfer coefficient (α) as 0.39 and the electron‐transfer rate constant (k_s) as 0.82 s^?1. The Hb modified electrode showed good electrocatalytic ability toward the reduction of trichloroacetic acid (TCA) in the concentration range from 0.2 to 26.0 mmol/L with a detection limit of 0.072 mmol/L (3σ), and H₂O₂ in the concentration range from 0.1 to 426.0 µmol/L with a detection limit of 3.16×10^?8 mol/L (3σ).     

An Organic Sol‐Gel Film as Modifier to Construct Biosensor

A new amperometric biosensor for hydrogen peroxide (H₂O₂) was developed by adsorbing hemoglobin (Hb) on an organic sol‐gel film. The organic sol‐gel was prepared using resorcinol and formaldehyde as monomers. This sol‐gel film shows a biocompatible microenvironment for retaining the native activity of the adsorbed Hb. The direct electron transfer between Hb and electrode is achieved. Hb adsorbed on the film shows an enzyme‐like catalytic activity for the reduction of H₂O₂. The reduction peak currents are proportional linearly to the concentration of hydrogen peroxide in the range of 6×10^?8 to 3.6×10^?6 M, with a detection limit of 2.4×10^?8 M (S/N=3). This research enlarges the applications of organic sol‐gel materials in biosensor field.     

Direct electrochemistry of hemoglobin on graphene/Fe3O4 nanocomposite-modified glass carbon electrode and its sensitive detection for hydrogen peroxide

Graphene/Fe₃O₄ nanocomposite was prepared for the immobilization of hemoglobin (Hb) to improve the electron transfer between Hb and glass carbon electrode (GCE). The characterization of nanocomposites was described by transmission electron microscopy, Fourier transform infrared, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The electrochemistry of Hb on the graphene/Fe₃O₄-based GCE was investigated by cyclic voltammetry and amperometric measurement. The modified electrode showed a wide linear range from 0.25 μmol/L to 1.7 mmol/L with a correlation coefficient of 0.9967. The detection limit of the H₂O₂ biosensor was estimated at 6.0?×?10^?6?mol/L at a signal-to-noise ratio of 3.     

Synthesis and Characterization of Co3O4/Multiwalled Carbon Nanotubes Nanocomposite for Amperometric Sensing of Hydrazine

Co₃O₄ nanoparticles (NPs) were synthesized and decorated on the multi‐walled carbon nanotubes (MWCNTs) through a simple hydrothermal procedure. The deposited Co₃O₄ NPs on the sidewalls of MWCNTs were found to be cubic crystal structure and homogenously dispersed with a narrow particle size distribution centered at around 6 nm. The Co₃O₄/MWCNTs nanocomposite was then utilized for the electrochemical detection of hydrazine, and exhibited a high sensitivity of 34.5 µA mM^?1, a low detection limit of 0.8 µM (S/N=3), a wide linear range of 20 µM to 1.1 mM along with a short response time of less than 5 s.     

Hydrogen Peroxide Biosensor Based on the Electrochemistry of the Myoglobin‐TATP Composite Film

Abstract

Direct electrochemistry of the myoglobin‐triacetone triperoxide (Mb‐TATP) composite on carbon paste (CP) electrode is reported. This electrode gives a well‐defined and quasi‐reversible cyclic voltammogram for the Mb Fe^III/Fe^II redox coupled with the formal potential (E?′) of ?0.302 V (vs. Ag/AgCl) in pH 6.92 phosphate buffer. Electronic and vibrational spectroscopies show that the Mb in the composite retains a structure similar to its native form. The enzymatic reactivity to the reduction of H₂O₂ has been studied for the Mb‐TATP film. The analytical performances have been obtained with the linear range of 78.32–1135.64 µM, the detection limit of 55 µM (S/N=3), and the apparent Michaelis‐Menten constant (K _m) of 662.8 µM. This H₂O₂ biosensor based on the electrocatalysis of the immobilized Mb presents a higher stability within two weeks.     

Hemoglobin‐Titanate Composite Based Biosensor for the Amperometric Determination of Hydrogen Peroxide in Acidic Medium

A hemoglobin‐titanate composite based biosensor was chosen for determination of H₂O₂ in an acidic medium. CV results of the Hb‐titanate modified pyrolytic graphite electrode showed a pair of well‐defined, quasi‐reversible redox peaks centered at ?246 mV (vs. Ag/AgCl) in a pH 5.0 HAc‐NaAc buffer solution. The modified electrode exhibited good electrocatalytic response for monitoring H₂O₂ and had a large linear detection range from 20 μM to 3.2 mM with a detection limit of 8 μM (S/N=3) and a sensitivity of 29.7 mA M^?1 cm^?2 in the pH 5.0 solution. The biosensor also possessed good long term storage stability.     

Gold Nanoparticles Electrodeposited on Ordered Mesoporous Carbon as an Enhanced Material for Nonenzymatic Hydrogen Peroxide Sensor

A facile and controllable electrodeposition method was developed to directly attach gold nanoparticles (GNPs) on ordered mesoporous carbon (OMC). The GNPs on OMC substrate were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectrometer (XPS), respectively. A nonenzymatic hydrogen peroxide (H₂O₂) sensor was fabricated on GNPs‐OMC/GCE. The sensor demonstrated a fast amperometric response (2.5 s), a wide linear range toward H₂O₂ concentrations between 2.0×10^?6 and 3.92×10^?3 M (R=0.999), and a low detection limit of 0.49 µM (S/N=3). Moreover, it exhibited good reproducibility and long‐term stability. The excellent electrocatalytical activity might be attributed to the synergistic effect of OMC and GNPs.     

Direct Electrochemistry and Electrocatalysis of Hemoglobin/ZnO‐Chitosan/nano‐Au Modified Glassy Carbon Electrode

The highly efficient H₂O₂ biosensor was fabricated on the basis of the complex films of hemoglobin (Hb), nano ZnO, chitosan (CHIT) dispersed solution and nano Au immobilized on glassy carbon electrode (GCE). Biocompatible ZnO‐CHIT composition provided a suitable microenvironment to keep Hb bioactivity (Michaelis‐Menten constant of 0.075 mmol L^?1). The presence of nano Au in matrix could effectively enhance electron transfer between Hb and electrode. The electrochemical behaviors and effects of solution pH values were carefully examined in this paper. The (ZnO‐CHIT)‐Au‐Hb/GCE demonstrated excellently electrocatalytical ability for H₂O₂. This biosensor had a fast response to H₂O₂ less than 4 s and excellent linear relationships were obtained in the concentration range from1.94×10^?7 to 1.73×10^?3 mol L^?1 with the detection limit of 9.7×10^?8 mol L^?1 (S/N=3) under the optimum conditions. Moreover, the stability and reproducibility of this biosensor were evaluated with satisfactory results.     

Hydrogen Peroxide Biosensor Based on Immobilization of Hemoglobin on Au@Ag Nanoparticles Modified Carbon Ionic Liquid Electrode

A hydrogen peroxide (H₂O₂) biosensor based on the combination of Au@Ag core‐shell nanoparticles with a hemoglobin‐chitosan‐1‐butyl‐3‐methyl‐imidazolium tetrafluoroborate (Hb‐CHIT‐BMIM×BF₄) composite film was prepared. UV‐vis spectroscopy and transmission electron microscopy confirmed a core‐shell nanostructure of Au@Ag nanoparticle was successfully obtained. Cyclic voltammetric results showed a pair of well‐defined redox peaks appeared with the formal potential (E^O′) of ‐0.301 V (versus Ag/AgCl reference electrode) and the peak‐to‐peak separation (ΔE_p) was 84 mV in 0.1 M phosphate buffer solutions. Due to the synergetic effect of Au@Ag core‐shell nanoparticles and Hb‐CHIT‐BMIM×BF₄, the biosensor exhibited good electrocatalytic activity to the reduction of H₂O₂ in a linear range from 1.0 × 10^?6 to 1.0 × 10^?3 M with a detection limit of 4 × 10^?7 M (S/N = 3). The apparent Michaelis‐Menten constant (K_M) was estimated to be 4.4 × 10^?4 M, showing its high affinity. Thus, the study proved that the combination of Au@Ag core‐shell nanoparticles and Hb‐CHIT‐BMIM×BF₄ is able to open up new opportunities for the design of enzymatic biosensors.     

A Third‐Generation Hydrogen Peroxide Biosensor Based on Horseradish Peroxidase Immobilized in Carbon Nanotubes/ SBA‐15 Film

A new third‐generation biosensor for H₂O₂ assay was developed on the basis of the immobilization of horseradish peroxidase (HRP) in a nanocomposite film of carbon nanotubes (CNTs)‐SBA‐15 modified gold electrode. The biological activity of HRP immobilizing in the composite film was characterized by UV‐vis spectra. The HRP immobilized in the nanocomposite matrix displayed excellent electrocatalytic activity to the reduction of H₂O₂. The effects of the experimental variables such as solution pH and working potential were investigated using steady‐state amperometry. Under the optimal conditions, the resulting biosensor showed a linear range from 1 µM to 7 mM and a detection limit of 0.5 µM (S/N=3). Moreover, the stability and reproducibility of this biosensor were evaluated with satisfactory results.     

A Novel Hydrogen Peroxide Biosensor Based on the PDDA‐GNPs/MWNTs Nanocomposite Matrix

A novel nanocomposite designed by the assembly of the positively charged poly(diallyldimethylammonium chloride) protected gold nanoparticles (PDDA‐GNPs), and the negatively charged multi‐walled carbon nanotubes (MWCNTs) on ITO electrode via electrostatic interaction, was used as a supporting matrix for immobilizing hemoglobin (Hb) to develop a high‐performance hydrogen peroxide (H₂O₂) biosensor. The cyclic voltammetrys of immobilized Hb showed a pair of well‐defined and quasi‐reversible redox peaks with the formal potential of ‐0.205V (vs. SCE) and the peak‐to‐peak potential separation of 44 mV at a scan rate of 100 mV×s^?1 in 0.1 mol×L^?1 pH 7.0 PBS. Under the optimized experimental conditions, a linearity range for determination of H₂O₂ was from 2.0 × 10^?6 to 5.2 × 10^?4 mol×L^?1 with a correlation coefficient of 0.9994 (n = 37) and a detection limit of 8.4 × 10^?7 mol×L^?1. The biosensor displayed excellent electrochemical and electrocatalytic response to the reduction of H₂O₂, high sensitivity, long‐term stability, good bioactivity and selectivity.     

Preparation,Characterization and Electrochemical Application of Graphene‐metallic Nanocomposites

Three different Graphene‐Metallic (Graphene‐Me) nanocomposites – Graphene‐Silver (Graphene‐Ag), Graphene‐Gold (Graphene‐Au) and Graphene‐Platinum (Graphene‐Pt) nanocomposites – were prepared and characterized. The electrochemical performances of these nanocomposites were tested by incorporating them with glassy carbon paste electrode (GCPE) and used them in biofuel cells (BFC) and as amperometric xanthine biosensor transducers. Present work contains the first application of Graphene‐Au and Graphene‐Ag nanocomposite in BFCs and also first application of these Graphene‐Me nanocomposites in xanthine biosensors. Considering BFC, power and current densities were calculated as 2.03 µW cm^?2 and 167.46 µA cm^?2 for the plain BFC, 3.39 µW cm^?2 and 182.53 µA cm^?2 for Graphene‐Ag, 4.43 µW cm^?2 and 230.15 µA cm^?2 for Grapehene‐Au and 6.23 µW cm^?2 and 295.23 µA cm^?2 for Graphene‐Pt nanocomposite included BFCs respectively. For the amperometric xanthine biosensor linear ranges were obtained in the concentration range between 5 µM and 50 µM with the RSD (n=3 for 30 µM xanthine) value of 4.28 % for plain xanthine biosensor, 3 µM and 50 µM with the RSD (n=3 for 30 µM xanthine) value of 9.37 % for Graphene‐Ag, 5 µM to 20 µM with the RSD (n=3 for 5 µM xanthine) value of 9.00 % and 30 µM to 70 µM with the RSD (n=3 for 30 µM xanthine) value of 8.80 % for Grapehene‐Au and 1 µM and 70 with the the RSD (n=3 for 30 µM xanthine) value of 2.59 % for Grapehene‐Pt based xanthine biosensors respectively.