| Summary: | 碩士 === 國立臺北科技大學 === 化學工程研究所 === 102 === Part I
Herein, we report a novel and sensitive method for high electro catalytic determination of Hydroquinone (HQ) and Catechol (CC). It was found that these two compounds could be completely separated on the electrode during cyclic voltammetry (CV) and differential pulse voltammetry (DPV) under optimal conditions. DPV provided larger peak potential separations and higher response sensitivities to HQ and CC compared to CV. Differential pulse voltammetry takes advantage of the linear relationship between the peak current and the concentration for the simultaneous determination of the concentrations of HQ and CC. The use of Pt/ZrO2-RGO/GCE in association with differential pulse voltammetry shows that with HQ the cathodic peak current increases linearly with an increase in the concentration of HQ, ranging from 1-1000μM, in the presence of 40μM CC. A detection limit of 0.4μM (S/ N = 3) can be achieved. At the same period, the anodic current has a linear relationship to the concentration of CC, from 1-400μM, with a detection limit of 0.4μM (S/N = 3) in the presence of 40μM HQ. In addition, the Pt/ZrO2-RGO/GCE composite modified electrode was used successfully for simultaneous determination of the concentration of Hydroquinone (HQ) and Catechol (CC) in wastewater samples with satisfactory recoveries. These results demonstrate that the composite modified electrode is a promising material for use in electrochemical sensing and electrocatalytic applications.
Part II
Electrochemical synthesis of mixed-valence Mn/Cu complexes has been successfully performed using graphene oxide (GO) and multi-walled carbon nanotubes (MWCNT) as a conductive and steric hybrid nanotemplate. Morphology of the MnCu/MWCNT/GO exhibits compact and nanoporous structure due to high conductivity and high steric space of MWCNT/GO nanotemplate, providing a mixed-valence hybrid composite of copper manganese oxide (CuMn2O4), tenorite (CuO), and hausmannite (Mn3O4). It is electroactive, pH-dependent, and stable in the electrochemical system. It shows eletrocatalytic activity to glucose oxidation with high current response and low overpotential. Both CV and LSV techniques show the same anodic peak (Epa = +0.05 V) for glucose oxidation. Particularly, DPV shows lower oxidation peak potential (Epa = -0.05 V) due to suitable control of pulse parameters. Voltammetric response of MnCu/MWCNT/GO hybrid composite shows linear correlation between current response and glucose concentration estimated with sensitivity of 49.1, 58.6, and 59.3 μA mM-1 cm-2 for using CV, LSV, and DPV techniques, respectively. It shows linear concentration range of 0–32 mM with a detection limit of 1×10-6 M (S/N ≧ 3). Coimmobilization and activity of Mn/Cu complexes can be effectively enhanced by MWCNT and GO, performing an active hybrid nanocomposite for glucose sensing.
Part III
Carbon paset electrode was electrocatalytically active for dopamine (DA), ascorbic acid (AA) and uric acid (UA) oxidation. The electrocatalytic oxidation current developed from the anodic peak of the redox couple. Electrochemical impedance spectra (EIS) was applied to monitor the whole process of the electrode modification. EIS can give useful information of the impedance changes on the electrode surface between each step. We have studied the surface morphology of composite film using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The cyclic voltammetry (CVs) has been used for the measurement of electroanalytical properties of analytes. The sensitivity values of carbon paset electrode was higher than bare electrode. Finally, the differential pulse voltammetry (DPV) has been used for the detection of mixture analytes at carbon paset electrode. We simulated more complex system if AA, DA and UA were present simultaneously.
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