Abstract
M.Sc. (Chemistry)
The electrochemical behaviour and detection of phenols such as o-nitrophenol (o-NP) and p-nitrophenol (p-NP) and also 2-chlorophenol (2-CP) and 3-chlorophenol (3-CP), has been studied on a gold nanoparticle - nickel dimethylglyoxime complex (N(II)DMG) modified glassy carbon electrode (GCE). The electrode was prepared by drop coating nickel dimethylglyoxime complex on a GCE followed by the electrodeposition of gold nanoparticle. Each step in the electrode modification was characterised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and high resolution scanning electron microscopy (HRSEM). There two redox probes hexacyanoferrate (III) - hexacyanoferrate(II) ion ([Fe(CN)6]3−/4− ) and hexaammineruthenium (III) chloride – hexaammineruthenium (II) chloride [Ru(NH3)6 ]2+/3+ were applied to verify the suitability of the modified electrode (i.e. GCE/NiDMG-AuNP) with satisfactory results.
The results showed that nickel dimethylglyoxime complex/gold nanoparticles electrode had improved conductivity, reversibility and electron transfer rate in selected redox probe than the unmodified GCE. The GCE/NiDMG-AuNP electrode was used in the determination of o-NP and p-NP in water. Under the optimal conditions, detection limits of 0.58 μM and 0.103 μM were calculated for o-NP and p-NP respectively. The GCE/NiDMG-AuNP electrode was applied to real water sample and the effects of interferences were studied. Photoelectrochemical analysis was done with p-NP with substantial results.
The GCE/NiDMG-AuNP electrode was also used to investigate the electrochemical behaviour of 2-CP and 3-CP by Cyclic Voltammetry (CV) and differential pulse voltammetry (DPV). The results demonstrated that the GCE/NiDMG-AuNP exhibited remarkable enhancement effects towards 2-CP and 3-CP. Under the optimized conditions, the oxidation peak currents displayed a good linear relationship to concentration in the ranges from 0.5 to 30 μM for 2-CP and 0.5 to 35 μM for 3-CP, with detection limits of 0.097 and 0.093 μM, respectively. This sensor was successfully used in the detection 2-CP and 3-CP of real water samples with good results.