A.A. Hathoot

Electrochemical copolymerization of 2-(4-amino phenyl)-6-methyl benzothiazole and aniline

Abstract Electropolymerization of 2-(4-amino phenyl)-6-methyl benzothiazole (ABT) has been carried out in acetonitrile. Potential sweep electrolysis of ABT at platinum electrode produced an electroactive polymeric film in acidic solutions. Electrocopolymerization of ABT with different ratios of aniline were performed. The compositions of the copolymers were found by using 1 H-NMR spectroscopy. Conductivity measurements have been carried out on the copolymer prepared by constant current electrolysis. The films produced vary in their properties depending on the initial ratio of ABT to aniline. Films grown from a solution containing ABT and aniline in the ratio 50:50 exhibited good electroactivity and conductivity.

Electrochemical synthesis and characterization of poly[8-(3-acetylimino-6-methyl-2,4-dioxopyran)- 1-aminonaphthalene] film electrodes in acidic aqueous medium

Abstract The electrooxidation of 8-(3-acetylimino-6-methyl-2,4-dioxopyran)-1-amino-naphthalene Schiff base in acidic aqueous solution containing 0.1 M H2SO4 yielded a polymer film on glassy carbon electrode. The electrooxidative polymerization process was studied by potential sweep electrolysis and controlled potential electrolysis. The film showed a reversible well-defined redox system in aqueous acidic solutions. The factors that affected the electroactivity of the film, such as scan repetition, number of cycles used for the film formation, concentration of sulphuric acid in the electrolytic medium and scan rate (ν) were studied in detail. The modified electrode was shown to decrease the overpotential for oxidation of some redox species, such as catechol, hydroquinone. In addition to the decrease in overpotential, there was also an increase in the current for the oxidation process. The electrode was stable chemically and electrochemically both in aqueous and organic solutions, making it excellent candidate for sensing and/or electrocatalytic applications.

Preparation of a novel conducting polymer by electropolymerization of thiophenylidine 8-naphthylamine Schiff-base

Abstract The Schiff-base resulting from the reaction of 3-thiophene carboxaldehyde with 1,8-diaminonaphthalene was isolated and characterized. The electropolymerization of Schiff-base was carried out in acetonitrile containing tetrabutyl ammonium tetrafluoroborate. The film coated electrode showed an electrochemical response. The stability of the redox response towards repetitive cyclic voltammetry was studied. The effect of number of sweep, scan rates and potential cyclic limits on the redox peaks of the obtained modified electrodes were investigated and explained. The resulting modified electrode behaves as an electrocatalyst for the electrode reaction of hydroquinone. The modified electrode is chemically and electrochemically stable both in aqueous solution and mixtures containing methanol, making it excellent candidate for sensing and/or electrocatalytic applications.

Electropolymerization of N-methacryloyloxy phthalimide monomer using sacrificial nickel anode and characterization of the resulting polymer

Abstract The electropolymerization of N-methylacryloyloxy phthalimide has been studied in DMF using a sacrificial nickel anode in the presence of tetrabutylammonium perchlorate as supporting electrolyte. The effect of different reaction parameters such as the type of electrolyte, concentration of monomer and electrolyte, current strength, the duration of electrolysis and the temperature of the reaction on the yield of the polymer and the rate of polymerization were studied. It was found that the nickel content in the obtained polymer depends on the concentration of the monomer. A mechanism of electropolymerization is suggested and confirmed by i.r., 1 H-NMR, thermal analysis and electrical conductivity measurements.

Spectrophotometric determination of fenoprofen calcium drug in pure and pharmaceutical preparations. Spectroscopic characterization of the charge transfer solid complexes

Simple, accurate and robust spectrophotometric method was developed for determination of fenoprofen calcium drug (FPC). The proposed method was based on the charge transfer (CT) reaction of FPC drug (as n-electron donor) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,4,6-trinitrophenol (picric acid, PA) or 1,2,5,8-tetrahydroxyanthraquinone (Quinalizarin, QZ) (as π-acceptors) to give highly colored charge transfer complexes. Different variables affecting the reaction such as reagent concentration, temperature and time have been carefully optimized to achieve the highest sensitivity. Beers law was obeyed over the concentration ranges of 2-60, 0.6-90 and 4-30μgmL-1 using DDQ, PA and QZ CT reagents, respectively, with correlation coefficients of 0.9986, 0.9989 and 0.997 and detection limits of 1.78, 0.48 and 2.6μgmL-1 for the CT reagents in the same order. Elucidation of the chemical structure of the solid CT complexes formed via reaction between the drug under study and π-acceptors was done using elemental, thermal analyses, IR, 1H NMR and mass spectrometry. X-ray diffraction was used to estimate the crystallinity of the CT complexes. Their biological activities were screened against different bacterial and fungal organisms. The method was applied successfully with satisfactory results for the determination of FPC drug in fenoprofen capsules. The method was validated with respect to linearity, limit of detection and quantification, inter- and intra-days precision and accuracy. The proposed method gave comparable results with the official method.

Simultaneous and selective electrochemical determination of hydroquinone, catechol and resorcinol at poly(1,5-diaminonaphthalene)/glassy carbon-modified electrode in different media

The electrochemical behavior of phenolic isomers hydroquinone (HQ), catechol (CC) and resorcinol (RC) was examined in poly(1,5-diaminonaphthalene)/glassy carbon-modified electrode (P1,5-DAN/GC M.E.) by cyclic voltammetry (CV), square wave voltammetry (SWV) and chronoamperometry (CA) techniques in perchloric acid (HClO4) and phosphate buffer solution (PBS, pH 7.0). P1,5-DAN/GC M.E. was investigated for simultaneous determination of HQ, CC and RC in single, binary and ternary systems. Oxidation peak potentials were negatively shifted with increasing oxidation peak current for HQ, CC and RC at P1,5-DAN/GC M.E. compared with bare GC electrode. The obtained results illustrate that the former electrode exhibits better performance towards the three isomers in PBS rather than in HClO4 solution. The catalytic currents for different concentrations of HQ, CC and RC showed good relationship in the range of 0.1–100 μM for all analytes and low detection limits (LOD) of 0.034, 0.059 and 0.14 μM for them, respectively, in a ternary system in PBS at pH 7.0. This method has been practically applied for the detection of these isomers in tap water with acceptable results.

Electrocatalytic oxidation of ethanol at Pd, Pt, Pd/Pt and Pt/Pd nano particles supported on poly 1,8-diaminonaphthalene film in alkaline medium

An ethanol oxidation reaction (EOR) in alkaline medium was carried out at palladium (Pd) or platinum (Pt) nanoparticles/poly 1,8-diaminonaphthalene (p1,8-DAN) composite catalyst electrodes. Pd and Pt were incorporated onto a p1,8-DAN/GC electrode by a cyclic voltammetry (CV) strategy. The obtained Pd/p1,8-DAN/GC, Pt/p1,8-DAN/GC, Pt/Pd/p1,8-DAN/GC and Pd/Pt/p1,8-DAN/GC modified electrodes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and cyclic voltammetry (CV) techniques. Electrode surface areas (ESAs) of the obtained catalysts were calculated by carbon monoxide (CO) adsorption using differential electrochemical mass spectroscopy (DEMS). The electrocatalytic oxidation of ethanol (EtOH) at the catalyst electrodes was considered in 0.5 M NaOH solutions by CV and chronoamperometric techniques. The catalyst electrodes significantly enhanced the catalytic efficiency for EOR compared to a bare glassy carbon (GC) electrode. Bimetallic catalyst electrodes demonstrate improved catalytic activity, superior durability and higher tolerance to (CO) poison generated in the development of EOR compared with Pd/p1,8-DAN and Pt/p1,8-DAN catalysts, giving priority to Pt/Pd/p1,8-DAN/GC electrodes. Viability parameters, such as NaOH and EtOH concentrations, scan rate and upper potential limits, were examined and analyzed. This study suggests that the prepared catalysts have pronounced potential applications in direct EOR in fuel cells.