Sharif Digital Repository

The electrochemical oxidation of thiocytosine on the surface of carbon-paste electrode modified with Schiff base (salophen derivatives) complexes of cobalt is studied. The effect of the substituents in the structure of salophen on the catalytic property of the modified electrode is investigated by using cyclic and differential pulse voltammetry. Cobalt (II)-5-nitrosalophen, because of its electrophilic functional groups, leads to a considerable enhancement in the catalytic activity, sensitivity (peak current), and a marked increase in the anodic potential of the modified electrode. The differential pulse voltammetry is applied as a very sensitive method for the detection of thiocytosine. The... 

A modified carbon-paste electrode (CPE) is prepared by incorporating thionine-nafion supported on multi-walled carbon nanotube (MWCNT). The electrochemical behavior of dopamine (DA) and ascorbic acid (AA) on the surface of the modified electrode is investigated by cyclic voltammetry (CV). The results show that thionine effectively immobilized in the matrix of the paste by using an appropriate mixture of nafion/MWCNT under the ultrasonic condition. On the other hand, presence of nafion enhances the stability of the thionine supported by MWCNT in the composite electrode and improves the reproducibility of the surface of the modified electrode under renewing process by polishing. The results of... 

A carbon-paste electrode (CPE) is modified by incorporating cobalt-5-nitrosalophen (CoNSal) and tetraoctylammonium bromide (TOAB). The mechanism of electrocatalytic oxidation of dopamine (DA) and ascorbic acid (AA) at the surface of the CoNSal-modified CPE containing various percents of TOAB is thoroughly investigated by cyclic and differential pulse voltammetry. In solutions of pH 5.0, in which all studies are performed, DA exists as the positively charged species whereas AA is mainly as the neutral form. Therefore, the favorable ionic interaction (electrostatic repulsion) between the cationic form of DA and the cationic surfactant (TOA+) caused increasing the overvoltage for DA and... 

The electrochemical behavior of captopril at the surface of a carbon-paste electrode (CPE) modified with cobalt-5-nitrolsalophen (CoNSal) is described. The prepared electrode shows an excellent electrocatalytic activity toward the oxidation of captopril, which is leading to marked lowering in the anodic overpotential and considerable improvement of sensitivity (anodic current). Whereas at the surface of unmodified electrode an electrochemical activity for captopril cannot be observed, a very sharp anodic wave with an anodic peak potential about 650 mV (versus Ag/AgCl) is obtained using the prepared modified electrode. This catalytic wave is assigned to mediating of Co(III)/Co(II) redox... 

A carbon-paste electrode (CPE) chemically modified with the cobalt(II)-4-methylsalophen (CoMSal) as a Schiff base complex was used as a highly sensitive and fairly selective electrochemical sensor for simultaneous, determination of minor mounts of ascorbic acid (AA) and cysteine. This modified electrode shows very efficient electrocatalytic activity for anodic oxidation of both AA and cysteine via substantially decreasing of anodic overpotentials for both compounds. The. mechanism of electrochemical oxidation of both AA and cysteine using CoMSal-modified electrode was thoroughly investigated by cyclic voltammetry and polarization studies. Results of cyclic voltammetry (CV) and differential... 

The voltammetric behavior of thioglycolic acid (TGA) was studied at a carbon paste electrode modified with cobalt phthalocyanine (CoPc). The CoPc-modified electrode shows high electrocatalytic activity toward oxidation of TGA, lowering substantially the overpotential of anodic reaction. Results of the cyclic voltammetry show that TGA undergoes a two-step oxidation (each step with one electron) resulting the dimer of thiol. Enhancement of the rate of electron transfer results in a near-Nernstian behavior of modified electrode to the concentration of TGA and makes it as a suitable potentiometric sensor for the detection of this compound. This electrode shows a near-Nernstian response in a wide...