A Boron Doped Diamond Electrode Modified with Nano‐carbon Black for the Sensitive Electrochemical Determination of Chlorogenic Acid

An electrochemical method was developed for the sensitive determination of chlorogenic acid using a boron doped diamond electrode (BDDE) modified with nano‐carbon black (nano‐CB). The active surface areas were found to be 0.059 and 0.146 cm² for the unmodified BDDE, and nano‐CB/BDDE, respectively. Compared with a BDDE, the nano‐CB/BDDE exhibited a well‐defined redox couple for chlorogenic acid. In addition, the plot of the peak current response changing from a square root to a linear dependence on scan rate is attributed to the transition from planar diffusion to surface behaviour. The anodic and cathodic peak separations (ΔE_p) were 97 mV and 14 mV at BDDE and nano‐CB/BDDE, respectively. The decrease in ΔE_p at the proposed electrode indicated that the process of chlorogenic acid was greatly accelerated. Square wave voltammetry (SWV) exhibited a dynamic range in which the current versus the concentration of chlorogenic acid were linear from 2.0×10^?8 to 2.0×10^?6 M with a LOD of 4.1×10^?9 M (based on 3S_b/m). The nano‐CB modified BDDE provided improved electrochemical behavior, high electrocatalytic activity, high sensitivity and good reproducibility.     

Two‐dimensional π‐conjugated metal‐organic framework with high electrical conductivity for electrochemical sensing

A two‐dimensional π‐conjugated metal‐organic framework (MOF) with long‐range delocalized electrons has been prepared and applied as modified electrode material without further post‐modification. The MOF (Cu₃(HHTP)₂) is composed of Cu(II) centers and a redox‐active linker (2,3,6,7,10,11‐hexahydroxytriphenylene, HHTP). Compared to most MOFs, Cu₃(HHTP)₂ displays higher electrical conductivity and charge storage capacity owing to the collective effect of metal ions and aromatic ligands with π–π conjugation. In order to confirm the superior properties of this material, the electrochemical detection of dopamine (DA) was conducted and the satisfactory results were obtained. The currents increase linearly with the concentration of DA in the range 5.0 × 10^?8 to 2.0 × 10^?4 M with a detection limit of 5.1 nM. Furthermore, Cu₃(HHTP)₂ presents high selectivity and applicability in serum samples for electrochemical DA sensing. Overall, this material has excellent potential as a promising platform for establishing an MOF‐based electrochemical sensor.     

An Electrochemical DNA Sensor Based on Electrodepositing Aluminum Ion Films on Stearic Acid‐Modified Carbon Paste Electrode and Its Application for the Detection of Specific Sequences Related to Bar Gene and CP4 Epsps Gene

An electrochemical DNA biosensor was fabricated by immobilizing DNA probe on aluminum ion films that were electrodeposited on the surface of the stearic acid‐modified carbon paste electrode (CPE). DNA immobilization and hybridization were characterized with cyclic voltammetry (CV) by using methylene blue (MB) as indicator. MB has a couple of well‐defined voltammetric redox peaks at the CPE. The currents of redox peaks of MB decreased after depositing aluminum ion films on the CPE (Al(III)/CPE) and increased dramatically after immobilizing DNA probe (ssDNA/Al(III)/CPE). Hybridization of DNA probe led to a marked decrease of the peak currents of MB, which can be used to detect the target single‐stranded DNA. The conditions for the preparation of Al(III)/CPE, and DNA immobilization and hybridization were optimized. The specific sequences related to bar transgene in the transgenic corn and the PCR amplification of CP4 epsps gene from the sample of transgenic roundup ready soybean were detected by differential pulse voltammetry (DPV) with this new electrochemical DNA biosensor. The difference between the peak currents of MB at ssDNA/Al(III)/CPE and that at hybridization DNA modified electrode (dsDNA/Al(III)/CPE) was applied to determine the specific sequence related to the target bar gene with the dynamic range comprised between 1.0×10^?7 mol/L to 1.0×10^?4 mol/L. A detection limit of 2.25×10^?8 mol/L of oligonucleotides can be estimated.     

Direct Electrochemistry of Hemoglobin Entrapped in Composite Electrodeposited Chitosan‐Multiwall Carbon Nanotubes and Nanogold Particles Membrane and Its Electrocatalytic Application

Hemoglobin was entrapped in composite electrodeposited chitosan‐multiwall carbon nanotubes (MCNTs) film by assembling gold nanoparticles and hemoglobin step by step. In phosphate buffer solution (pH 7), a pair of well‐defined and quasireversible redox peaks appeared with formal potential at ?0.289 V and peak separation of 100 mV. The redox peaks respected for the direct electrochemistry of hemoglobin at the surface of chitosan‐MCNTs‐gold nanoparticles modified electrode. The parameters of experiments have also been optimized. The composite electrode showed excellent electrocatalysis to peroxide hydrogen and oxygen, the peak current was linearly proportional to H₂O₂ concentration in the range from 1×10^?6 mol/L to 4.7×10^?4 mol/L with a detection limit of 5.0×10^?7 mol/L, and this biosensor exhibited high stability, good reproducibility and better selectivity. The biosensor showed a Michaelis–Menten kinetic response as H₂O₂ concentration is larger than 5.0×10^?4 mol/L, the apparent Michaelis–Menten constant for hydrogen peroxide was calculated to be 1.61 μmol/L.     

Fabrication of Glucose Biosensor Based on Encapsulation of Glucose‐Oxidase on Sol‐Gel Composite at the Surface of Glassy Carbon Electrode Modified with Carbon Nanotubes and Celestine Blue

A simple procedure was developed to prepare a glassy carbon electrode modified with multi walled carbon nanotubes (MWCNTs) and Celestin blue. Cyclic voltammograms of the modified electrode show stable and a well defined redox couple with surface confined characteristic at wide pH range (2–12). The formal potential of redox couple (E′) shifts linearly toward the negative direction with increasing solution pH. The surface coverage of Celestine blue immobilized on CNTs glassy carbon electrode was approximately 1.95×10^?10 mol cm^?2. The charge transfer coefficient (α) and heterogeneous electron transfer rate constants (k_s) for GC/MWCNTs/Celestine blue were 0.43 and 1.26 s^?1, respectively. The modified electrode show strong catalytic effect for reduction of hydrogen peroxide and oxygen at reduced overpotential. The glucose biosensor was fabricated by covering a thin film of sol‐gel composite containing glucose oxides (GOx) on the surface of Celestine blue /MWCNTs modified GC electrode. The biosensor can be used successfully for selective detection of glucose based on the decreasing of cathodic peak current of oxygen. The detection limit, sensitivity and liner calibration rang were 0.3 μM, 18.3 μA/mM and 10 μM–6.0 mM, respectively. The accuracy of the biosensor for glucose detection was evaluated by detection of glucose in a serum sample, using standard addition protocol. In addition biosensor can reach 90% of steady currents in about 3.0 sec and interference effect of the electroactive existing species (ascorbic acid–uric acid and acetaminophen) was eliminated. Furthermore, the apparent Michaelis–Menten constant 2.4 mM, of GOx on the nano composite exhibits excellent bioelectrocatalytic activity of immobilized enzyme toward glucose oxidation. Excellent electrochemical reversibility of redox couple, high stability, technically simple and possibility of preparation at short period of time are of great advantages of this procedure for modification of glucose biosensor.     

Determination of Reduced Nicotinamide Adenine Dinucleotide Based on Immobilization of Tris(2,2′‐bipyridyl) Ruthenium(II) in Multiwall Carbon Nanotubes/Nafion Composite Membrane

Abstract

An electrochemiluminescence (ECL) method for reduced nicotinamide adenine dinucleotide (NADH) was proposed by immobilizing tris(2,2′‐bipyridyl) ruthenium(II) (Ru(bpy)₃ ²⁺) in multiwall carbon nanotubes (MWCNTs)/Nafion composite membrane that was formed on glassy carbon electrode surface. The electrochemical and ECL behaviors of the immobilized Ru(bpy)₃ ²⁺ were investigated. The cyclic votammogram of the modified electrode in pH 7.0 phosphate buffer solution showed a couple of redox peaks at +1190 and +1060 mV at 100 mV/s. The composite film had a more open structure and a large surface area allowing faster diffusion of Ru(bpy)₃ ²⁺. The presence of MWCNTs resulted in the improved ECL sensitivity and longer‐term stability of the modified electrode. The modified electrode showed a linear response to NADH in the concentration range of 1.0×10^?6 to 1.6×10^?5 M with a detection limit of 8.2×10^?7 M.     

Electrochemical Behavior of a Glassy Carbon Electrode Chemically Modified with Nickel Pentacyanonitrosylferrate in Presence of Sulfur Compounds

The glassy carbon electrode was modified with a nickel pentacyanonitrosylferrate film by electrodeposition of Ni and subsequent derivatization with NaPCNF. The film was characterized by XPS and electrochemical methods. Cyclic voltammetry of the NiPCNF onto the GC shows a redox couple (Fe^III/Fe^II) with E°′ of 538 mV (I_pa/I_pc around 1) and ΔE_p of 93 mV in 0.5 mol L^?1 KNO₃, with a diffusion‐controlled process. There was a decrease of anodic peak currents of the film in the presence of sulfide and 2‐propanethiol due to a precipitation reaction on the film surface by nucleophilic attack.     

A Four‐Electron Sulfur Electrode Hosting a Cu2+/Cu+ Redox Charge Carrier

The elemental sulfur electrode with Cu²⁺ as the charge carrier gives a four‐electron sulfur electrode reaction through the sequential conversion of S?CuS?Cu₂S. The Cu‐S redox‐ion electrode delivers a high specific capacity of 3044 mAh g^?1 based on the sulfur mass or 609 mAh g^?1 based on the mass of Cu₂S, the completely discharged product, and displays an unprecedently high potential of sulfur/metal sulfide reduction at 0.5 V vs. SHE. The Cu‐S electrode also exhibits an extremely low extent of polarization of 0.05 V and an outstanding cycle number of 1200 cycles retaining 72 % of the initial capacity at 12.5 A g^?1. The remarkable utility of this Cu‐S cathode is further demonstrated in a hybrid cell that employs an Zn metal anode and an anion‐exchange membrane as the separator, which yields an average cell discharge voltage of 1.15 V, the half‐cell specific energy of 547 Wh kg^?1 based on the mass of the Cu₂S/carbon composite cathode, and stable cycling over 110 cycles.     

Improved Voltammetric Response of L‐Tyrosine on Multiwalled Carbon Nanotubes‐Ionic Liquid Composite Coated Glassy Electrodes in the Presence of Cupric Ion

L ‐Tyrosine can exhibit a small anodic peak on multiwalled carbon nanotubes (MWCNTs) coated glassy carbon electrodes (GCE). At pH 5.5 its peak potential is 0.70 V (vs. SCE). When an ionic liquid (i.e., 1‐octyl‐3‐methylimidazolium hexafluorophosphate, [omim][PF₆]) is introduced on the MWCNT coat, the peak becomes bigger. Furthermore, in the presence of Cu²⁺ ion the anodic peak of L ‐tyrosine increases further due to the formation of Cu²⁺‐L ‐tyrosine complex, while the peak potential keeps unchanged. Therefore, a sensitive voltammetry based on the oxidation of Cu²⁺‐L ‐tyrosine complex on MWCNTs‐[omim][PF₆] composite coated electrode is developed for L ‐tyrosine. Under the optimized conditions, the anodic peak current is linear to L ‐tyrosine concentration in the range of 1×10^?8–5×10^?6 M, and the detection limit is 8×10^?9 M. The modified electrode shows good reproducibility and stability. In addition, the voltammetric behavior of other amino acids is explored. It is found that among them tryptophan (Trp) and histidine (His) can also produce sensitive anodic peak under same experimental conditions, and their detection limits are 4×10^?9 M and 4×10^?6 M, respectively.     

Preparation of Cu (II) imprinted polymer electrode and its application for potentiometric and voltammetric determination of Cu (II)

The Cu (II) imprinted polymer glassy carbon electrode (GCE/Cu-IP) was prepared by electropolymerization of pyrrole at GCE in the presence of methyl red as a dopant and then imprinting by Cu²⁺ ions. This electrode was applied for potentiometric and voltammetric detection of Cu²⁺ ion. The potentiometric response of the electrode was linear within the Cu²⁺ concentration range of 3.9 × 10^?6 to 5.0 × 10^?2 M with a near-Nernstian slope of 29.0 mV decade^?1 and a detection limit of 5.0 × 10^?7 M. The electrode was also used for preconcentration anodic stripping voltammetry and results exhibited that peak currents for the incorporated copper species were dependent on the metal ion concentration in the range of 1.0 × 10^?8 to 1.0 × 10^?3 M and detection limit was 6.5 × 10^?9 M. Also the selectivity of the prepared electrode was investigated. The imprinted polymer electrode was used for the successful assay of copper in two standard reference material samples.     

Electrocatalytic Nitrite Reduction to Nitrogen Oxide by a Synthetic Analogue of the Active Site of Cu‐Containing Nitrite Reductase Incorporated in Nafion Film

The electrocatalytic reduction of nitrite to NO by [CuMe₂bpa(H₂O)(ClO₄)]⁺ ( 1 ), which is a model for the active site of copper‐containing nitrite reductase, incorporated in Nafion film was investigated. The Cu complex in the Nafion matrix exhibits an intense band at 267 nm and a broad band around 680 nm, assigned to d–d and ligand field transitions, respectively. The 77‐K EPR spectrum of 1 in the Nafion matrix reveals the typical axial signals (g_//=2.28, g =2.08, A_//=13.3 mT) of a tetragonal Cu²⁺ chromophore. The redox potential, which is related to the Cu⁺/Cu²⁺ couple, was ?146 mV (ΔE=72 mV) at pH 5.5. The redox reaction of 1 in Nafion was not dependent on pH and was a diffusion‐controlled process. The electronic structure and redox properties of 1 in the negatively charged polymer matrix were almost the same as those in aqueous solution. In the presence of nitrite, an increase in the cathodic current was observed in the cyclic voltammogram of 1 in the Nafion matrix. The current increase was dependent on the nitrite concentration and pH in solution. Upon reaching ?400 mV, a linear generation of NO was observed for the 1 /Nafion film coated electrode. The relationship between the rate of NO generation and the nitrite concentration in solution was analyzed with the Michaelis–Menten equation, where V_max=45.1 nM s^?1 and K_m=15.8 mM at pH 5.5. The Cu complex serves the function of both the catalyst and electron transport in the Nafion matrix. The sensitivity of the electrode was estimated to be 3.23 μA mM^?1 in the range of 0.1–0.4 mM nitrite.     

Nucleic Acid Biosensor for Detection of Human Immunodeficiency Virus Using Aquabis(1,10‐phenanthroline)copper(II) Perchlorate as Electrochemical Indicator

The electrochemical behavior of aquabis(1,10‐phenanthroline)copper(II) perchlorate [Cu(H₂O)(phen)₂]·2ClO₄, where phen=1,10‐phenanthroline, on binding to DNA at a glassy carbon electrode (GCE) and in solution, was described. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) results showed that [Cu(H₂O)(phen)₂]²⁺ had excellent electrochemical activity on the GCE with a couple of quasi‐reversible redox peaks. The interaction mode between [Cu(H₂O)(phen)₂]²⁺ and double‐strand DNA (dsDNA) was identified to be intercalative binding. An electrochemical DNA biosensor was developed with covalent immobilization of human immunodeficiency virus (HIV) probe for single‐strand DNA (ssDNA) on the modified GCE. Numerous factors affecting the probe immobilization, target hybridization, and indicator binding reactions were optimized to maximize the sensitivity and speed of the assay. With this approach, a sequence of the HIV could be quantified over the range from 7.8×10^?9 to 3.1×10^?7 mol·L^?1 with a linear correlation of γ=0.9987 and a detection limit of 1.3×10^?9 mol·L^?1.     

Direct Electrochemistry of Catalase at a Gold Electrode Modified with Single‐Wall Carbon Nanotubes

The direct electrochemistry of catalase (Ct) was accomplished at a gold electrode modified with single‐wall carbon nanotubes (SWNTs). A pair of well‐defined redox peaks was obtained for Ct with the reduction peak potential at ?0.414 V and a peak potential separation of 32 mV at pH 5.9. Both reflectance FT‐IR spectra and the dependence of the reduction peak current on the scan rate revealed that Ct adsorbed onto the SWNT surfaces. The redox wave corresponds to the Fe(III)/Fe(II) redox center of the heme group of the Ct adsorbate. Compared to other types of carbonaceous electrode materials (e.g., graphite and carbon soot), the electron transfer rate of Ct redox reaction was greatly enhanced at the SWNT‐modified electrode. The peak current was found to increase linearly with the Ct concentration in the range of 8×10^?6–8×10^?5 M used for the electrode preparation and the peak potential was shown to be pH dependent. The catalytic activity of Ct adsorbates at the SWNTs appears to be retained, as the addition of H₂O₂ produced a characteristic catalytic redox wave. This work demonstrates that direct electrochemistry of redox‐active biomacromolecules such as metalloenzymes can be improved through the use of carbon nanotubes.     

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%.     

Simultaneous Determination of Dopamine and Ascorbic Acid Using the Nano‐Gold Self‐Assembled Glassy Carbon Electrode

Electrochemical behavior of dopamine (DA) was investigated at the gold nanoparticles self‐assembled glassy carbon electrode (GNP/LC/GCE), which was fabricated by self‐assembling gold nanoparticles on the surface of L ‐cysteine (LC) modified glassy carbon electrode (GCE) via successive cyclic voltammetry (CV). A pair of well‐defined redox peaks of DA on the GNP/LC/GCE was obtained at E_pa=0.197 V and E_pc=0.146 V, respectively. And the peak separation between DA and AA is about 0.2 V, which is enough for simultaneous determination of DA and AA. The peak currents of DA and AA were proportional with their concentrations in the range of 6.0×10^?8–8.5×10^?5 mol L^?1 and 1.0×10^?6–2.5×10^?3 mol L^?1, with the detection limit of 2.0×10^?8 mol L^?1 and 3.0×10^?7 mol L^?1 (S/N=3), respectively. The modified electrode exhibits an excellent reproducibility, sensibility and stability for simultaneous determination of DA and AA in human serum with satisfactory result.     

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.     

Electrochemical and Spectroscopic Studies on the Interaction of Gallocyanine with DNA

The interaction of gallocyanine (GC) with double‐stranded DNA (dsDNA) in pH 3.5 Tris‐HCl buffer solution was investigated by electrochemical methods and spectrophotometric methods as well. In the potential scan range of ‐0.25 ? +0.18 V(vs. SCE), GC had a couple of well‐defined redox peaks at ‐0.022 V and ‐0.069 V on a cyclic voltammogram at the scan rate of 100.0 mV/s, respectively. After the addition of dsDNA into the GC solution, the redox‐peak currents decreased obviously and the peak potentials shifted positively. The results demonstrated that GC binding to DNA was caused by intercalation. Electrochemical parameters such as the electron number (n), the charge transfer coefficient (α) and the electrochemical reaction standard rate constant (k_s) were calculated and compared in the absence and presence of dsDNA. Almost unchanged values of the electrochemical parameters after adding dsDNA showed that non‐electroactive complexes were formed when GC interacted with DNA. The results indicated that the decrease of the redox‐peak currents was caused by the decrease of the free concentration of GC in the reaction solution. The binding constant and binding ratio were investigated by spectrophotometric methods. DNA concentration can be determined by the decrease of the peak current of GC. The linear range for dsDNA was in the range of 1.45 × 10^?7 ? 1.45 × 10^?6mol/Land 1.45 × 10^?6 ? 1.45 × 10^?5 mol/L, respectively with the linear regression equation as Δi_P (10^?7 A) = 0.037 + 0.018C (10^?7mol/L), and Δi_P (10^?7 A) = 0.25 + 0.041C (10^?6mol/L), respectively, and the detection limit (3σ) was 1.13 × 10^?7 mol/L.     

Electrochemical Characterization of Pyrocatechol Sulfonephthalein-Modified Glassy Carbon Electrode and Separation of Electrocatalytic Responses for Ascorbic Acid and Dopamine Oxidation

A pyrocatechol sulfonephthalein- (PS-) modified glassy carbon (PS/GC) electrode has been prepared by adsorption of PS on a glassy carbon electrode surface. Cyclic voltammograms of the PS/GC electrode indicate the presence of a couple of well-defined redox peaks, and the formal potential shifts in the negative direction with increasing solution pH. The relation between formal potential,E^0′, and solution pH can be fit to the equationE^0′(mV) = −51.4 pH + 538.7. The PS/GC electrode shows high electrocatalytic activity toward ascorbic acid oxidation, with an overpotential ca. 380 mV less than that of the bare electrode and a drastic enhancement of the anodic currents. The electrocatalytic reaction rate constant (k), which was decreased with increasing concentration of H₂A, was determined using rotating disk electrode measurements. The values ofkwas also affected by the solution pH. The electrode can also separate the electrochemical responses of ascorbic acid and dopamine. The separation between the anodic peak potentials of ascorbic acid and dopamine is more than 50 mV by the differential pulse voltammetry.     

Cu(II) Hexacyanoferrate(III) Modified Carbon Paste Electrode; Application for Electrocatalytic Detection of Nitrite

Copper hexacyanoferrate (CuHCF) film‐modified carbon paste electrode (CPE) has been prepared from various electrolytic aqueous solutions using consecutive cyclic voltammetry. The cyclic voltammograms showed the direct deposition of CuHCF films from the mixing of Cu²⁺ and Fe(CN)₆^3? ions and each time with one of the six cations: H⁺, Na⁺, K⁺, NH₄⁺, Mg²⁺, and Al³⁺. The CuHCF film showed a single redox couple that exhibited a cation effect (Na⁺, K⁺, Mg²⁺, and NH₄⁺) and anion effect (Cl^?, NO₃^?, SO₄^2?, ClO₄^?, and BrO₃^?) in the cyclic voltammograms. Voltammetric studies have indicated that in presence of nitrite, the cathodic peak current of CuHCF increases, followed by a decrease in the corresponding anodic current. This indicated that nitrite was reduced by the redox mediator immobilized on the electrode surface via an electrocatalytic mechanism. The process of reduction and its kinetics were investigated by using cyclic voltammetry, differential pulse voltammetry, chronoamperometry and chronocoulometry techniques. The electrocatalytic ability about 800 mV can be seen. The rate constant of the catalytic reduction of nitrite was found to be 7.9×10⁵ cm³ mol^?1 s^?1. Linearity range obtained was 5×10^?5?8.4×10^?3 by cyclic voltammetry and 8×10^?6?1.3×10^?3 and 4×10^?3?2×10^?2 by differential pulse voltammetry.     

Amperometric Biosensor for Hydrogen Peroxide Based on Electrodeposited Sub-micrometer Gold Modified Glassy Carbon Electrode

IntroductionAmperometricbiosensorofhydrogenperoxideisofpracticalimportancebecauseofitswideapplicationsinchemical,biological,clinical,environmentalandmanyotherfields.Forimprovementofsensor抯quality,vari-ouskindsofchemicalmodificationmethodshavebeendevelopedforreducingredoxoverpotentialsofH2O2atelectrodesurfaces,increasingthedetectionsensitivity,linearrange,stabilityandlivetime.Ithasbeenshownthattheuseofsub-micrometersizedmetalparticlessuchasPt-blackcansignificantlyimprovethequalityofthebiosens…