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Electrochemical Determination of Environmental Pollutants on the Nanomaterials Modified Electrode

Author: ChuLin
Tutor: ZhangXiaoLi
School: Shandong University
Course: Analytical Chemistry
Keywords: Chemical modified electrode Electrochemical determination Electrogenerated chemiluminescence Cyclic voltammetry Semi-derivative technique Scanning electron microscopy Transmission electron microscop
CLC: X830.2
Type: Master's thesis
Year: 2012
Downloads: 303
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Abstract


In chapter one of this thesis, we reviewed the chemically modified electrodes (CMEs) and its application in environmental analysis in the recent years. First, we gave a brief introduction about the CMEs with their classification, fabrication and application. Then, we gave a simple introduction of the nanoparticles and its application in the detection of the environmental pollutants. Finally, we collected, classified and gave a brief introduction of the recent progress and result in EC and ECL by using nanoparticles modified electrodes.In chapter two of this thesis, a novel method for simultaneous determination of nitrophenol isomers at nano-gold modified glassy carbon electrode has been developed. The gold nanoparticles were directly electrodeposited onto the glassy carbon electrode via a constant potential. The resulting electrode (nano-Au/GCE) was characterized with scanning electron microscopy (SEM). The electrochemistry response of nitrophenol isomers at the nano-Au/GCE was studied. The result indicated that o-, m-, and p-nitrophenol are separated entirely at nano-Au/GCE, and a semi-deriva-tive voltammetric technology was adopted to enliance the determination sensitivity. Under the optimum conditions, the linear relationships between the peak height and the concentration are obtained in the range of1.0×10-5-1.0×10-3mol L-for o-nitrophenol;7.5×10-6-2.0×10-3mol L-1for m-nitrophenol;1.0×10-5-1.0×10-3mol L-1for p-nitrophenol, respectively. The limit of detection (LOD) is8.0×10-6mol L-1for o-nitrophenol,5.0×10-6mol L-1for m-nitrophenol and8.0×10-6mol L-1for p-nitrophenol. Based on this, the modified electrode could be applied to direct simultaneous voltammetric determination of nitrophenol isomers in water samples without presepa-ration with higher sensitivity.In chapter three of this thesis, Nano-porous hydroxyapatite (HAp) modified electrode was fabricated by simply electrodepositing HAp onto the glassy carbon electrode (GCE), the resulting electrode (nano-HAp/GCE) was characterized with scanning electron microscopy (SEM).The electrochemical behavior of p -chlorophenol (p-CP) at nano-HAp/GCE was studied by cyclic voltammetry. The electrode displayed selective and enhanced clectroanalytical response towards p-CP, obviously because the nano-HAp/GCE exhibits large surface area, excellent electrocatalytic activity and particular adsorbability. After accumulation of4min for p-CP on nano-HAp/GCE, the peak height was linearly related to the concentration of p-CP in the range of1.0×10-8-1.0×10-7mol L-1. The detection limit was4.0×10-9mol L-1. Based on this, the modified electrode was successfully applied in water samples with high sensitivity.In chapter four of this thesis, a novel method for sensitive determination of chloride anion at multilayer nano-silver modified indium-tin oxide (ITO) electrode has been developed. The multilayer films were fabricated via self-assembly/electrochemical-assembly methods, in which the3-aminopropyltriethoxysilane (APTS) was used to modify ITO conducting glass, layer-by-layer (LBL) method was applied to prepare the multilayer films and poly (diallyldimethylammonium chloride)(PDDA) was employed as a bridging ligand. The resulting electrode (Ag/{PDDA/Ag}m/APTS/ITO) surface was characterized with SEM and UV-vis. The electrochemical behavior of Cl-at the Ag/{PDDA/Ag}m/APTS/ITO electrode was studied by cyclic voltammetry. The results indicated that the modified electrode exhibited substantial enhancement in electrochemical sensitivity for Cl-due to its large surface area and particular absorbability. After accumulation of3min for Cl-at Ag/{PDDA/Ag}m/APTS/ITO electrode, the peak height (Ag/Cl-) increased linearly with the concentrations of Cl-in the range of1.0×10-8mol L-1to1.0×10-6mol L-6. The detection limit was5.2×10-9mol L-1at3σ level. This modified electrode could be successfully applied in water samples with low cost and high sensitivity.In chapter five of this thesis, a novel electrochemical sensor for sensitive determination of herbicide paraquat (PQ) has been developed in this paper. The water-soluble and electroactive gold-grapheme (Au-GR) nanocomposites were synthesized in one pot. Ionic liquids (ILs) were designed to disperse the nanocomposites and increase the sensitivity for PQ. The obtained sensing surface based on Au-GR-ILs composites modified glassy carbon electrode (Au-GR-ILs/GCE) was characterized with scanning electron microscopy (SEM). The electrochemical behavior of PQ at Au-GR-ILs/GCE was studied by cyclic voltammetry and square wave voltammetry. The results indicated that the Au-GR-ILs/GCE exhibited substantial enhancement in electrochemical detection for PQ due to its large surface area, excellent electrocatalytic activity and particular adsorption capacity. After adsorption accumulation of10min for PQ at Au-GR-ILs/GCE, the peak height of PQ increased linearly with the concentration of PQ in the range of2.0×10-9mol L-1to1.0×10-7mol L-1. The detection limit was7.2×10-10mol L-1at3σ level. This sensor could be successfully applied to the determination of PQ in real samples with satisfactory results.In chapter six of this thesis, a novel and sensitive electrogenerated chemiluminescence (ECL) sensor for formaldehyde was developed with the amine-functionalized Ru(bpy)32+-doped silica nanoparticles (Ru-DSNPs) as ECL emitter. The uniform amine-functionalized Ru(bpy)32+-doped silica nanoparticles were characterized with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). This novel ECL sensor based on Ru-DSNPs showed significant advantages in sensitivity and stability due to:(1) a large number of Ru(bpy)3-+which were encapsulated in the silica shell maintained its electrochemical activities and generated strong electrochemiluminescence;(2) the exterior silica shell could effectively prevent the leakage of Ru(bpy)32+due to the strong electrostatic interaction between them. Besides, mercaptoacetic acid was used as the intermediate to conjugate the Ru-DSNPs with Au electrode leading to the more stable immobilization, which resulting in a good reproducibility and stability of ECL sensor. As formaldehyde can dramatically enhance the ECL emission from immobilized Ru-DSNPs, a simple ECL sensor for formaldehyde was developed with linear response range from1.0×10-8mol/L to1.0×10-6mol/L. The detection limit was6.0×10-9mol/L (S/N=3). Based on this, the sensor could be applied to determine directly the formaldehyde in real samples without pre-separation.

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CLC: > Environmental science, safety science > Environmental Quality Assessment and Environmental Monitoring > Environmental monitoring > General issues > Monitoring and analysis methods
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