ghasem karim-nezhad

In this research project, a simple electrochemical method was presented with the easy conversion of the electrode surface into a nano-sized and porous structure. The nanoporous was deposited on the surface of glassy carbon electrode by chronoamperometric method by applying potential. The proposed electrode was used to measure acyclovir drug. Under optimal conditions a significant improvement in the electrochemical behavior of acyclovir was observed on the surface of the modified electrode compared to the unmodified electrode. The detection limit of 0.13 μM and the linear range of 1.99 to 19.6 μM were obtained for the determination of acyclovir at the surface of modified electrode using differential pulse voltammetric method in phosphate buffer. Satisfactory results were obtained in the determination of acyclovir with the modified electrode in blood serum samples.

The present study aims to introduce a highly sensitive electrochemical sensor for quantification of trace amounts of Sumatriptan (SUM) in biological fluids. To immobilize a stable nano film of β-cyclodextrin (β-CD) on a glassy carbon electrode (GCE), electropolymerization of monomer was carried out within 0.1 M phosphate buffer with pH 6.0 utilizing cyclic voltammetry to yield polymerized β-CD (pβ-CD). The morphological characterization of pβ-CD/GCE was examined by Field emission scanning electron microscopy (FESEM). The electrochemical redox action of SUM on pβ-CD/GCE was scrutiny studied by cyclic voltammetry and chronocoulometry. The electrochemical parameters including the electron transfer coefficient (α), the standard heterogeneous rate constant (ks), the surface area of the electrode (A), the electron transfer number (n), and the surface coverage (Γ) were estimated to be 0.38, 1.23×10-3 cm s-1, 0.06 cm2, 1, 1.07×10-8 mol cm-2, respectively. At optimized criteria, a substantial enhancement was attained toward the electrooxidation of SUM on the developed electrode compared to the bare GCE, resulting in wide linear ranges of 0.0622.47µM and 2.4752.1µM with a low detection limit of 27 nM. The developed sensor was successfully employed for quantification of SUM in human blood serum and urine samples with good selectivity and acceptable recoveries, proving its utility for further applications as a sensitive and reliable sensor.

Developing simple yet efficient sensors for drug-abuse detection is highly required from both human health and medical aspects. In this work, a glassy carbon electrode modified by a thin layer of poly L-arginine (P-L-Arg/GCE) was fabricated by electropolymerization of L-arginine monomer using cyclic voltammetry (CV) and then it was used for determination of Methadone (MET). The surface characteristics of the P-L-Arg/GCE was examined by scanning electron microscopy and electrochemical impedance spectroscopy. To study the electrochemical responses of MET on P-L-Arg/GCE and bare GCE, cyclic and differential pulse voltammetric techniques were employed. For P-L-Arg/GCE, a considerable enhancement in electrooxidation signal of MET was observed compared to bare electrode. The influence of various determinant parameters on P-L-Arg/GCE performance was studied. At optimized conditions, using DPV technique, the electrooxidation peak current was linear to MET concentration in the ranges of 0.49-2.98 µM and 2.98-11.9 µM with a detection limit of 0.32 µM. The utility of P-L-Arg/GCE was successfully validated by analyzing MET in serum and urine samples, representing its potential application for real samples analysis.

In this study, a novel and convenient electrochemical sensor was fabricated by using dripping well-dispersed graphene oxide nanosheets, electropolymerization of poly glycine (p-Gly) and in situ plating of metallic copper nanoparticle film methods, successively. This sensor was further employed to investigate the electrochemical behavior of hydrazine. Scanning electron microscopy and energy dispersive X-ray spectrometry were used for the characterization of the prepared film. Anodic peak potential of hydrazine oxidation at the surface of modified electrode shifts by about 150 mV toward negative values compared with that on the bare electrode. The kinetic parameters such as the electron transfer coefficient (α) and charge transfer rate constant (k) for the oxidation of hydrazine was determined utilizing cyclic voltammetry (CV). The diffusion coefficient (D) of hydrazine was also estimated using chronoamperometry. The dynamic detection range of this sensor to hydrazine was 5- 60 and 80- 150 µM at the modified electrode surface using an amperometric method. The detection limit and quantitation are 5.33 µM and 17.77 µM, respectively. A new voltammetric method for determination of hydrazine was erected and shows good sensitivity and selectivity, wider linear relationship, very easy surface update and good stability.

In this research, a glassy carbon electrode was coated with a thin layer of multi-walled carbon nanotubes in the presence of the surfactant and subsequently was electro-polymerized with Poly-L-arginine (P-L-Arg). The prepared electrode was used as an effective sensor for the quantitative detection of Rutin (Ru). The fabricated electrode exhibited good electrochemical performance with low electron transfer resistance. The electrochemical behavior of Ru at the prepared electrode was also investigated by cyclic voltammetry and differential pulse voltammetry techniques. For modified glassy carbon electrode, the transfer coefficient (α), the number of electrons involved in the rate-determining step (nα) and electron transfer rate constant (ks) calculated. Under the favorable conditions, a linear relationship between the oxidation peak current and concentration of Ru was obtained in the range from 0.1 µM to 10 µM with a detection limit of 0.048 µM and with the extraordinary high sensitivity value of 6.3767, µA/µM was obtained. Interference and stability studies showed that satisfactory detection results are achieved using this electrode. The proposed electrode was successfully applied for the determination of Ru in human blood serum samples.

A simple and selective carbon paste electrode has been developed for the electrochemical determination of acyclovir (ACV). This electrode was designed by incorporation of multiwalled carbon nanotubes (MWCNTs) and ZnO nanoparticles into the carbon paste matrix, and then poly (o-aminophenol; OAP) film were subsequently electropolymerized on it. The surface structure of nanoparticles were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Surface morphology and electrochemical properties of the prepared nanocomposite modified electrode were investigated by SEM and cyclic voltammetry (CV). The calibration graph was linear over the concentration range 0.089 to 7.96 μg mL-1 for ACV determination with a detection limit of 0.067 μg mL-1. The proposed electrode was successfully applied for ACV determination in pharmaceutical formulations with satisfactory results.

In this paper, a sensitive and convenient electrochemical sensor based on stacked cysteic acid film and gold nanoparticles (AuNPs) composite modified glassy carbon electrode (GCE) was developed for the determination of Methadone (MET). Electrochemical investigation of the modified electrode is achieved using cyclic voltammetry (CV), differential pulse voltammograms (DPV) and field emission scanning electron microscopy. The effective surface areas of AuNPs/cysteic acid/GCE increased for about 4-fold larger than that of the unmodified GCE. The kinetic parameters of the electron transfer coefficient (α) and number of electrons involved in the rate determining step (nα) for the oxidation of MET were determined utilizing CV. The designed modified electrode was revealed linear responses in the ranges of 0.024 to 4.45 μM and 4.45 to 12.67 μM with a limit of detection (LOD) of 0.014 μM (S/N=3). Excellent recovery results were obtained for determination of MET in spiked human blood plasma and urine samples at the modified electrode.

In the present study, silver oxyfluoride modified silver electrode was employed to electrocatalytic oxidation of isoniazid. The process of oxidation and its kinetics were established by using cyclic voltammetry, chronoamperometry and amperometry techniques. The modified electrode shows a stable and linear response in the concentration range of 3×10−4 to 2.1×10−3 mol L-1 with a correlation coefficient of 0.9953. The overall number of electrons involved in the catalytic oxidation of isoniazid was found 4 electrons. The diffusion coefficient of 3.11×10−5 cm2 s-1 for isoniazid was also estimated using chronoamperometry study. It has been shown that using the silver oxyfluoride modified silver electrode, isoniazid can be determined by amperometry method with limit of detection of 3.85 µmol L–1. The method was successfully applied for analysis of isoniazid in solid pharmaceutical formulations. The results of the analysis suggest that the proposed method has promise for the routine determination of isoniazid in the products examined.

The electrocatalytic oxidation of formaldehyde and acetaldehyde on copper chloride modified copper electrode in alkaline solution was investigated. The process of oxidation and the kinetics have been investigated using cyclic voltammetry, chronoamperometry, and steady-state polarization measurements. The results show that the (ClCu)2O film on the electrode behaves as an efficient catalyst for the electrooxidation of two species in alkaline medium. The CV changes observed indicate that the modifide electrode has a good catalytic activity for the oxidation of formaldehyde and acetaldehyde. The transfer coefficient (α), the number of electrons involved in the rate-determining step (nα) and the catalytic rate constant (k) for modified electrode were calculated.