High-performance electrochemical sensor based on electrodeposited iron oxide nanoparticle: catecholamine as analytical probe

In this paper, we report the synthesis and electrocatalytic activity of electrodeposited Fe₂O₃ nanoparticles modified on a glassy carbon electrode as highly sensitive sensors for determination of catecholamines. Results showed that the Fe₂O₃ nanoparticles on a glassy carbon electrode exhibit excellent catalytic activity toward catecholamines oxidation, including levodopa, dopamine, and epinephrine, resulting in a marked lowering in the peak potential and considerable improvement of the peak current as compared to the electrochemical activity at the bare glassy carbon electrode. The electrochemical characterizations of catecholamines were performed using cyclic voltammetry, chronoamperometry, and differential pulse voltammetry techniques. The electrocatalytic currents increase linearly with the levodopa, dopamine, and epinephrine concentrations in the ranges of 0.0625–1000, 0.25–1500, and 0.125–1000 µM, respectively, and the detection limits (3σ) were 24 ± 2, 14 ± 2, and 12 ± 2 nM, respectively.     

Graphene sheet for improving the electrocatalytic activity of a benzofuran derivative modified electrode for determination of epinephrine in the presence of serotonin

A nanocomposite system based on coumarin derivative and graphene sheet was used to prepare a new electrochemical sensor. The objective of the mentioned nanocomposite was to investigate novel electrochemical properties enabling the quantification of epinephrine (Ep). Cyclic voltammetry was used to study the redox properties of the mentioned modified electrode at different scan rates. Henceforward, the electrocatalytic oxidation of Ep at the surface of the modified electrode was considered. The data has shown excellent catalytic activity of the modified electrode for the electrooxidation of Ep, which leads to a reduction of overpotential for more than 238 mV. According to differential pulse voltammetry (DPV), the oxidation of Ep showed a dynamic range between 0.1 and 1000.0 μM and the detection limit (3s) of 0.011 μM. Besides, DPV was used for the determination of Ep at the mentioned modified electrode in the presence of serotonin.     

Electrochemical determination of vitamin C in the presence of uric acid by a novel TiO2 nanoparticles modified carbon paste electrode

<正>The electrochemical behavior of vitamin C(ascorbic acid or AA) is investigated on the surface of a carbon-paste electrode modified with TiO_2 nanoparticles and 2,2'-(1,2 butanediylbis(nitriloethylidyne))-bis-hydroquinone(BBNBH).The prepared modified electrode showed an efficient catalytic role in the electrochemical oxidation of AA,leading to remarkable decrease in oxidation overpotential and enhancement of the kinetics of the electrode reaction.This modified electrode exhibits well-separated oxidation peaks for AA and uric acid(UA).The modified electrode is successfully applied for the accurate determination of AA in pharmaceutical preparations.     

Nanomolar determination of hydrazine by TiO2 nanoparticles modified carbon paste electrode

In the present paper, the use of a novel carbon paste electrode modified by N,N′(2,3-dihydroxybenzylidene)-1,4-phenylene diamine (DHBPD) and TiO₂ nanoparticles prepared by a simple and rapid method for the determination of hydrazine (HZ) was described. In the first part of the work, cyclic voltammetry was used to investigate the redox properties of this modified electrode at various solution pH values and at various scan rates. A linear segment was found with a slope value of about 48 mV/pH in the pH range 2.0–12.0. The apparent charge transfer rate constant (k _s) and transfer coefficient (α) for electron transfer between DHBPD and TiO₂ nanoparticles-modified carbon paste electrode were calculated. In the second part of the work, the mediated oxidation of HZ at the modified electrode was described. It has been found that under optimum condition (pH 8.0) in cyclic voltammetry, a high decrease in overpotential occurs for oxidation of HZ at the modified electrode. The values of electron transfer coefficients (α) and diffusion coefficient (D) were calculated for HZ, using electrochemical approaches. Differential pulse voltammetry exhibited a linear dynamic range from 1.0 × 10⁻⁸ to 4.0 × 10⁻⁶ M and a detection limit (3σ) of 9.15 nM for HZ. Finally, this method was used for the determination of HZ in water samples, using standard addition method.     

Electrocatalytic oxidation of hydrazine with alizarin red S as a homogenous mediator on the glassy carbon electrode

Electro-catalytic oxidation and detection of hydrazine on a glassy carbon electrode,at pH 6.0,was studied by using alizarin red S as a homogeneous mediator.The overall number of electrons involved in the catalytic oxidation of hydrazine and that involved in the rate-determining step were four and one,respectively.The interfering effect of some cations,anions and organic compounds were examined.Peak current for this process varied linearly with the square root of the scan rate.The kinetic parameters,such as ...     

Electrochemical and theoretical study of novel functional porous graphene aerogel-supported Sm2O3 nanoparticles for supercapacitor applications

Journal of Solid State Electrochemistry - A graphene aerogel cross-linked by p-phenylenediamine (PPDA) composite with Sm2O3 nanoparticles (AP.Sm) was synthesized as a novel nanocomposite via a...     

Self-assembled monolayers of organosulfur derivative on gold nanoparticles as electrochemical sensor for determination of isoprenaline

In this paper, the use of molecular self-assembled monolayers of 5-(1,3-dithiolan-2-eyl)-3-methyl banzen-1,2-diol (DMD) on gold nanoparticles was described (DMD-AuNPs). The redox properties of modified electrode at various scan rates were investigated by cyclic voltammetry. A pair of well-defined quasi-reversible redox peaks of DMD were obtained at the modified electrode. Dramatically enhanced electrocatalytic activity was exemplified at the DMD-AuNPs, as an electrochemical sensor to investigate the electro-oxidation of isoprenaline (IP). With this modified electrode, the oxidation potential of the IP was shifted about 235 mV toward a less positive potential value than that of an unmodified electrode. The values of electron transfer coefficients (α = 0.5), catalytic rate constant (ks = 9.2 s^?1) and diffusion coefficient (D = 8.9 × 10^?5 cm² s^?1) were calculated for IP. The response of catalytic current with IP concentration showed a linear relation in the range from 0.5 to 800 µM with a detection limit of 0.21 µM. Finally, this modified electrode was used for the determination of IP in IP injections.     

尿酸和叶酸存在下改性碳纳米管糊电极上多巴胺电催化氧化(英文)

A chemically modified carbon paste electrode (CPE), consisting of 2,2'-[ (1E)- (1,2- phenylenebis (azanylylidene)] bis (methanylylidene)]bis (benzene-1,4-diol) (PBD) and multiwalled carbon nano-tubes (CNTs), was used to study the electrocatalytic oxidation of dopamine using cyclic voltamme-try, chronoamperometry, and differential pulse voltammetry (DPV). First, the electrochemical be-havior of the modified electrode was investigated in buffer solution. Then the diffusion coefficient, electrocatalytic rate constant, and electron-transfer coefficient for dopamine oxidation at the sur-face of the PBD-modified CNT paste electrode were determined using electrochemical approaches. It was found that under optimum conditions (pH = 7.0), the oxidation of dopamine at the surface of such an electrode occurred at about 200 mV, lower than that of an unmodified CPE. DPV of dopa-mine at the modified electrode exhibited two linear dynamic ranges, with a detection limit of 1.0 μmol/L. Finally, DPV was used successfully for the simultaneous determination of dopamine, uric acid, and folic acid at the modified electrode, and detection limits of 1.0, 1.2, and 2.7 μmol/L were obtained for dopamine, uric acid, and folic acid, respectively. This method was also used for the determination of dopamine in a pharmaceutical preparation using the standard addition method.     

Simultaneous determination of iodate and periodate by kinetic spectrophotometric method using principal component artificial neural network

A kinetic spectrophotometric method for the simultaneous determination of iodate and periodate in mixtures was proposed. The method was based on the reaction of periodate and iodate with pyrogallol red in sulfuric acid media. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of pyrogallol red at 470 nm. Kinetic data collected at 470 nm were processed by principle component artificial neural network (PC-ANN) method. The constructed model was able to predict the concentration of two species in the range of 0.1?C15.0 and 0.1?C17.0 ??g/mL for iodate and periodate, respectively. The proposed method was applied to the simultaneous determination of iodate and periodate in several real samples with satisfactory results.