| Chemically modified electrode originated in1970s and then became the most active frontier of electrochemistry and electroanalytical chemistry. Via this method, electrodes could be functionally designed. In this thesis, conducting nano-composites modified GCE were fabricated and characterized. Their electrochemical performance for the removal of m-nitroaniline, the reduction of bromate and the detection of mercury ions, was studied.M-nitraonilie was inert and slowed the co-polymerization rate. Both UV-Vis and FTIR confimed the generation of poly(aniline-co-m-nitroaniline). Based on this conclusion,m-nitaoanline polymerized onto PANI/CNE through cyclic voltammetry. M-nitaoaniline generated a passive film on bare GCE, which prevented its further polymerization. However, PANI chains had a lot of free radicals, which helped reduce the electrode’s inertness and made the continueous polymerization of m-nitraoniline, generating EPANI/EP(mNA). This method could be used to remove m-nitaoaniline from aquesous solutions.PANI has electrocatalytic activity. The prepared PANI/CNT composite had higher electrochemical performance than PANI, including higher redox currents, higher specific capacitance and lower peak separations. The results suggest that the bromate reduction and the reduction of PANI/CNT itself were almost sychronous and the obtained reduction current was the sum of the two. The peak current of bromate reduction increased linearly with bromate concentration, indicating an analyte diffusion process. The activation energy for bromate reduction was10.98kJ mol-1. Various initial bromate concentrations had different removal rates. After1hour, the removal rates were48.9%,30.1%and13.2%for10,50and100mg L-1bromate, respectively. Meanwhile, the electrocatalytic activity of PANI/CNT modified electrode declined along with the reduction processing for the doping of bromide ions into PANI.Phosphomolybdate (PMo12) is a kind of polyoxometalates with redox and electrocatalytic activity, which is similar with PANI. The loading of PMo12directly decides its electrochemical performance. This part studied the adsorption of PMo12onto a poly(diallyldimethylammonium chloride) functionalized reduced graphene oxide (rGO-PDDA) modified GCE. The rGO-PDDA electrode has a significantly increased loading of PMo12due to its large surface area. Besides, the presence of positively charged PDDA also favors the adsorption of negatively charged PMo12anions and enhances the stability of the modified electrode. CV showed that PMo12@rGO-PDDA/GCE exhibits high electrocatalytic performance and good stability for bromate reduction. A wide linear current versus bromate concentration response (0.02mM to10mM) was achieved with excellent sensitivity (454.3μAcm-2mM-1). Based on Koutecky-Levich equation, the kinetic parameters for the electrocatalytic reduction of bromate were evaluated and the proposed mechanism (six-electron reaction) was verified using rotating disk electrode method. The new form of PMo12modified electrode is therefore concluded to be potentially suitable candidate for bromate detection and also for its elimination from aqueous solutions by large scale electrolysis.Polystyrenesulfonate doped poly(hydroxymethyl3,4-ethylenedioxythiophene) stabilized gold nanoparticles (Au@PEDOT) were synthesized through chemical reduction of chloroauric with EDOT monomer as the reductant, and PEDOT formed from oxidation of EDOT and PSS as the stabilizers. The resultant Au@PEDOT nanoparticles were characterized by UV-Vis, SEM, EDX as well as cyclic voltammetry. GCE modified with these nanoparticles were assessed for Hg(II) detection in chloride media by the use of a solid-state Hg/Hg2Cl2process. Results show that this modified electrode is a reusable sensor for the determination of Hg(II) with high selectivity and sensitivity (limit of detection=0.05μM). Thus Au@PEDOT/GCE could be used as a mercury sensor at micro-Moore level.Graphene-gold nanocomposite (rGO-Au) modified GCE have been fabricated by a one-step electrodeposition method. The nanocomposites were characterized by SEM, EDX, Raman spectra as well as electrochemical methods, and were utilized for mercury(II) detection via anodic stripping voltammetry. The peak stripping current was linearly dependent on the concentration of Hg(II) over the range of1.0to150.0nM and high selectivity and sensitivity (limit of detection0.6nM) and excellent stability/reusability were achieved. The applicability to environmental samples was successfully demonstrated by the direct determination of Hg(II) in tap water samples with minimal sample pretreatment. |
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