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Study On Nano-materials Modified Electrochemical Sensors And Their Applications In Harmful Substances Detection

Posted on:2015-03-07Degree:DoctorType:Dissertation
Country:ChinaCandidate:M WuFull Text:PDF
GTID:1268330431959101Subject:Analytical Chemistry
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Currently, environmental pollution problems such as air pollution, marine pollution, and urban environmental issues are more and more serious around the world. Electrochemical analysis method with the advantages of simple, cheap, sensitive, rapid and easy-to-green miniaturization, etc., it is widely used in the detection of environmental pollutants, such as water quality monitoring, drug analysis and environmental monitoring.In this paper, we mainly focused on the development establishment of new electrochemical sensors for detecting Sudan Ⅰ, phenol, sulfite, nitrite, heavy metals and other substances based on efficient, rapid, sensitive and convenient advantages of nano-metarials modified electrodes. These proposed methods were employed to real samples and the experimental results were satisfied. The detailed profile in this dissertation is shown as follows.1. Electrochemical detection of Sudan Ⅰ using a multi-walled carbon nanotube/chitosan composite modified glassy carbon electrodeA simple and sensitive electrochemical method was developed to determine Sudan Ⅰ by cyclic voltammetry and differential pulse voltammetry using a glassy carbon electrode modified with a chitosan/carbon nanotube composite. In cyclic voltammetry, Sudan Ⅰ exhibited a well-defined oxidation peak located at0.72V at the multi-walled carbon nanotube (MWCNT)/chitosan-modified GCE. The determination conditions, including pH, scan rate, and chitosan:MWCNT mass ratio at the modified electrode, were optimized. Under the optimum experimental conditions, Sudan Ⅰ could be linearly detected by differential pulse voltammetry with a detection limit of3.0×10-8mol/L.2. Simultaneous electrochemical determination of hydroquinone and catechol based on three-dimensional Graphene/MWCNTs/BMIMPF6nanocomposite modified electrodeA three-dimensional (3-D) carbon electrode was fabricated in the form of1-D multiwalled carbon nanotubes (MWCNTs) and2-D graphene (GR), using ionic liquid 1-butyl-3-methylimidazolium (BMIMPF6) to improve the dispersibility and stability of the3-D carbon electrode. This GR/MWCNTs/BMIMPF6modified glassy carbon electrode (GCE) was a highly sensitive electrochemical sensor for the simultaneous determination of hydroquinone (1,4-dihydroxybenzene, HQ) and catechol (1,2-dihydroxybenzene, CT). The GR were characterised using a transmission electron microscope (TEM). The electrochemical behaviours of HQ and CT at the GR/MWCNTs/BMIMPF6/GCE were investigated using cyclic voltammetry (CV) and differential pulse voltammetry. The chemically modified electrode displayed excellent electrochemical catalytic activities towards HQ and CT. Linear relationships between the values of the oxidation peak current and the concentration of HQ and CT were obtained in the ranges of0.5μmol/L to2.9mmol/L and0.2μmol/L to0.66mmol/L with detection limits (S/N=3) of0.1μmol/L and0.06μmol/L, respectively. This GR/MWCNTs/BMIMPF6/GCE showed many advantages in terms of stability, sensitivity, facility and economy.3. Simultaneous electrochemical determination of sulfite and nitrite using a gold nanoparticle/graphene-chitosan modified electrodeA highly sensitive electrochemical sensor for the simultaneous determination of SO32-and NO2-based on a glassy carbon electrode(GCE) modified with graphene(GR)-chitosan(CS) and gold nanoparticles(AuNPs) has been developed. The GR and GR-CS/AuNPs GCEs were characterised using a transmission electron microscope (TEM). The electrochemical behaviours of SO32-and NO2-at the GR-CS/AuNPs GCE were investigated using cyclic voltammetry (CV). The chemically modified electrode displayed excellent electrochemical catalytic activities towards sulphite and nitrite. Linear relationships between the values of the oxidation peak current and the concentration of SO32-and NO2-were obtained in the ranges of5μmol/L to0.41mmol/L(R=0.9986) and1μmol/L to0.38mmol/L(R=0.9940) with detection limits(S/N=3) of1μmol/L and0.25μmol/L, respectively. This GR-CS/AuNPs GCE showed many advantages in terms of stability, sensitivity, facility and economy. The proposed method was employed to example real samples with recoveries of97.2to102.6%. 4. Electrochemical detection of Cd2+and Pb2+in Chinese herbals using graphene/Bi composites modified glassy carbon electrodeThe GR/Bi GCE modified electrode was prepared by drop-coating graphene (GR) on the glassy carbon electrode and electrodeposition of Bi on the surface of GR. The electrochemical behaviors of Cd2+and Pb2+were studied on GR/Bi GCE with square wave stripping voltammetry. The results showed that this modified electrode had good electro-catalytic activity to Cd2+and Pb2+, and their linear ranges at the modified electrode were both from0.01to85μM with low detection limits of0.01μM. This GR/Bi GCE was of good stability, reproducibility and sensitivity. It was used for the simultaneous determination of Cd2+and Pb2+in medicine and the results were satisfied.5. Simultaneous electrochemical determination of Ascorbic Acid, Dopamine and Uric Acid using a palladium nanoparticle/Graphene/Chitosan Modified ElectrodeA palladium nanoparticle/graphene/chitosan/glassy carbon electrode (PdNPs/GR/CS GCE) was prepared and characterized. This chemical modified electrode displayed excellent eletrochemical catalytic activities towards ascorbic acid (AA), dopamine (DA) and uric acid (UA) compared with bare GCE, PdNPs/GCE and GR/CS GCE by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). All oxidation potentials of AA, DA and UA at the PdNPs/GR/CS GCE shifted negatively and the peak currents were much larger than other electrodes. DPV was used for simultaneous determination of AA, DA and UA in their mixture, and the peak potential separations between AA and DA, DA and UA, AA and UA were252mV,144mV and396mV, respectively. The limits of detection (S/N=3) for AA, DA and UA were20μM,0.1μM and0.17μM, respectively. This PdNPs/GR/CS GCE showed many merits in stability, sensitivity, facility and economy.
Keywords/Search Tags:Electrochemical sensors, Graphene, Sudan I, Hydroquinone, Catechol, Sulfite, Nitrite, heavy metal ions
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