الفهرس 
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Abstract
PDAN/GC modified electrode was fabricated by electropolymerization of 1.5×10-3 M 1,5-diaminonaphthalene from aqueous solution containing 1 M HClO4, at GC electrode surface using consecutive cyclic voltametry for 15 cycles between 0 and 0.8 V at 0.02 V/s versus Ag/AgCl as a reference electrode and platinum electrode as auxiliary electrode. After that NiNPs/PDAN/GC modified electrode was fabricated by dispersing nickel nanoparticles into polymer film pores by soaking the polymer film modified electrode for 30 minutes in aqueous solution of 1.0 M NiCl2.6H2O. Finally, the last modified electrode was activated by anodic polarization for 30 cycle in 0.1 M NaOH at 0.05 V/s from 0.0 to 0.7 V vs. Ag/AgCl. The cyclic voltametric studies showed stable redox behavior at 0.480 / 0.390 corresponding to the Ni (III) / Ni (II) couple in 0.1M NaOH aqueous solution. NiNPs/PDAN/GC modified electrode showed enhanced electrocatalytic behavior towards NADH electrooxidation in 0.1 M NaOH. Upon addition 10-2 M NADH, there was a significant increasing in the anodic peak current and decreasing in the cathodic peak current. Different parameters affecting NADH electrooxidation were studied such as effect of scan rate, effect of NADH concentration, effect of NaOH concentration, interfering with different ions and effect of electrode material. It was observed that as the NADH concentration increases, the peak height increases linearly for concentration ranges between 0.3×10-3 M to 7×10-3 M, 0.1×10-3 M to 1×10-3 M and 0.1×10-4 M to1.5×10-4 M for CV, SWV and DPV techniques respectively. It could be assumed that this increase is due to the presence of a diffusion –controlled process that appears to play an important role at low NADH
Summary
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concentrations. The current of NADH oxidation response was found to be greatly dependent upon NaOH concentration. NADH can be oxidized with increased solution alkalinity with greatly enhanced oxidation current. In presence of 10-2 M NADH, by increasing the scan rate, Ipa increased with a good linear relationship holding between the square root of scan rate (υ 1/2 ) and Ipa, confirming a diffusion-controlled process. NiNPs/PDAN/GC modified electrode exhibits stability for 5 days from its preparation, after that it showed variation in response as the current peak value starts to decrease and an increase in potential peak was also observed. The study showed that NiNPs/PDAN/GC modified electrode exhibited highly electrocatalytic activity towards the oxidation of NADH. It can be used for analyze NADH with high stability, reproducibility, sensitivity and selectivity with low detection limit of 0.378×10-6 M, 0.122×10-6 M and 0.02×10-6 M for CV, SWV and DPV techniques respectively, overcoming bare electrode problems in NADH detection, that are represented in high overpotential for oxidation, fouling with oxidation products and interfering with other ions and foreign species in the solution such as K+, NH4+, SO42- and urea. On the other hand PDAN/GC was tested for HQ and CT detection in 0.03 M H2SO4 and showed a good electrochemical performance on the oxidation peaks separation for the two dihydroxybenzene isomers compared with bare GC. The effect of acid type and acid concentration on the electrochemical oxidation of these compounds were studied. Also scan rate and interfering species such as dopamine, glucose and ascorbic acid were studied. The effect of concentration of both HQ and CT was studied using both CV and SWV techniques.