Study On The Electrocatalysis Of Multi-wall Carbon Nanotube And Its Composite Material Modified Electrode

By immobilizing unique molecules, ions or polymers on the electrode surface with chemical or physical technique, chemically modified electrodes (CMEs) via functional design possess super electrochemical performances than the conventional ones. Currently, the application of new material as nano-material in fabrication chemically modified electrodes is a hotspot of investigation. It will develop the application of electroanalytical chemistry in the field of life science, environmental engineering and energy source industry etc. In the present thesis, we deploy a series of works on the preparation of cabon nanotube and its composite material modified electrodes and their electrocatalysis toward some pharmic, enviromental. energy source and biologic molecules.This thesis involves two parts. Part one is a review in literature. The structure, preparation and characteristic of carbon nanotube, especially the application of different types of cabon nanotube composite material modified electrodes in analytical determination are reviewed.Part two is a research report. The content is summarized as follows:1. The voltammetric behavior of urapidil has been investigated at a multi-wall carbon nanotube paste electrode (MWCNT-PE). In pH 6.8 Britton-Robinson buffer, urapidil produced an oxidation peak at 0.62 V (vs. SCE). The oxidation of urapidil was an irreversible two-electron and two-proton process with adsorptive character. Moreover, the oxidation of urapidil at MWCNT-PE was more sensitive with lower peak potential than that at the carbon paste electrode (CPE). Based on the voltammetric behavior of urapidil, a differential pulse voltammetric method was proposed for the determination of urapidil. The oxidation peak current of urapidil was linearly with its concentration in the range from 5.0×10^-8 to 2.0×10^-6 mol·L^-1 at open-circuit accumulation for 60s. The detection limit was 3.8×10^-8 mol·L^-1. The proposed method was employed to determine urapidil in urapidil tablets.2. The voltammetric behavior and electrochemical reaction mechanism of cisapride has been investigated at a multi-wall carbon nanotube paste electrode (MWCNT-PE) using cyclic and differential pulse voltammetry. In pH 6.09 Britton-Robinson buffer, cisapride produced a sensitive oxidation peak at +0.89 V (vs. SCE). The oxidation of cisapride was an adsorption-controlled irreversible two-electron and one-proton process. The peak current varied linearly with the concentration of cisapride in the range from 4.0×10^-8 to 2.0×10^-5 mol·L^-1 with the detection limit of 1.0×10^-8 mol·L^-1. The relative standard deviation (R.S.D.) of ten measurements was 3.68% for 2.0×10^-6 mol·L^-1 cisapride. The proposed method was employed in determining cisapride in cisapride tablets.3. A CM-MWCNT-GCE modified electrode has been fabricated by electrodepositing curcumin (CM) at the surface of multi-wall carbon nanotubes (MWCNT) modified glassy carbon electrode (GCE). The CM-MWCNT-GCE shows a well-defined two-electron and two-proton redox couple with the formal potential of 0.14 V (vs. SCE) that results from the electrochemical oxidation product of CM, a CM derivative in quinone form. It also shows good electrocatalytic activity toward the oxidation of hydrazine at a reduced overpotential as well as an increased peak current compared with those at CM modified GCE, MWCNT modified GCE or activated GCE. The catalytic rate constant K_cat is determined to be 6.26×10³ L·mol^-1·s^-1 by chronoamperometry. The calibration curve for hydrazine determination is linear in the range of 2-44μmol·L^-1 in pH 8.0 phosphate buffer by amperometry. The detection limit and the sensitivity are 1.4μmol·L^-1 and 22.9 nA·L·μmol^-1, respectively. The modified electrode is simple in preparation, and is of character of fast response, high sensitivity and good reproducibility for hydrazine determination.4. A modified electrode has been fabricated by electrodepositing nickel(â…¡)-quercetin [Ni(â…¡)-Qu] complex on the surface of multi-wall carbon nanotube paste electrode [MWCNT-PE] in alkaline solution. The Ni(â…¡)-Qu-MWCNT-PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(â…¢)/Ni(â…¡) couple compared with Ni(â…¡)-MWCNT-PE and Ni(â…¡)-Qu-CPE. It also shows electrocatalytic activity toward the oxidation of methanol and other short chain aliphatic alcohols, such as ethanol, 1-propanol and 1-butanol. The catalytic peak current and peak potential decrease in exponential form with the increase of carbon number pf the chains. Kinetic parameters such as the election transfer coefficientα, rate constant K_s of the electrode reaction and the catalytic rate constant K_cat for oxidation of methanol are determined. And the stability and reproducibility of the Ni(â…¡)-Qu-MWCNT-PE are good for practical applications.5. A modified electrode Ni(â…¡)-Qu-MWCNT-IL-PE has been fabricated by electrodepositing nickel(â…¡)-quercetin [Ni(â…¡)-Qu] complex on the surface of multi-wall carbon nanotube ionic liquid paste electrode (MWCNT-IL-PE) in alkaline solution. The Ni(â…¡)-Qu-MWCNT-IL-PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(â…¢)/Ni(â…¡) couple compared with Ni(â…¡)-Qu-MWCNT-PE. It also shows good electrocatalytic activity toward the oxidation of glucose. Kinetic parameters such as the electron transfer coefficientα, rate constant K_s of the electrode reaction and the catalytic rate constant K_cat of the catalytic reaction are determined. Moreover, the catalytic current presents linear dependence on the concentration of glucose in the range from 5μmol·L^-1 to 2.8 mmol·L^-1, with a detection limit of 1.0μmol·L^-1 by amperometry. The modified electrode for glucose determination is of the property of simple preparation, good stability, fast response and enough sensitivity.6. A modified electrode Ni(â…¡)-BA-MWCNT-PE has been fabricated by electrodepositing nickel(â…¡)-baicalein [Ni(â…¡)-BA] complex on the surface of multi-wall carbon nanotube paste electrode (MWCNT-PE) in alkaline solution. The Ni(â…¡)-BA-MWCNT-PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(â…¢)/Ni(â…¡) couple compared with Ni(â…¡)-BA-CPE. It also shows good electrocatalytic activity toward the oxidation of hydrazine. Kinetic parameters such as the electron transfer coefficientα, rate constant k_s of the electrode reaction, the diffusion coefficient D of hydrazine and the catalytic rate constant K_cat of the catalytic reaction are determined. Moreover, the catalytic currents present linear dependence on the concentration of hydrazine from 2.5μmol·L^-1 to 0.2 mmol·L^-1 by amperometry. The detection limit and sensitivity are 0.8μmol·L^-1 and 69.9μA·L·mmol^-1, respectively. The modified electrode for hydrazine determination is of the property of simple preparation, good stability, fast response and high sensitivity.7. A nano-structured modified electrode Ni(â…¡)-BA-MWCNT-PE has been fabricated by electrodepositing nickel(â…¡)-baicalein [Ni(â…¡)-BA] complex on the surface of multi-wall carbon nanotube paste electrode (MWCNT-PE) in alkaline solution. The Ni(â…¡)-BA-MWCNT-PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(â…¢)/Ni(â…¡) couple compared with Ni(â…¡)-BA-CPE. It also shows good electrocatalytic activity toward the oxidation of glycine. The catalytic currents present linear dependence on the concentration of glycine from 20μmol·L^-1 to 1.0 mmol·L^-1 by amperometry. The detection limit and sensitivity are 9.2μmol·L^-1 and 3.92μA·L·mmol^-1, respectively. The modified electrode for glycine determination is of the property of simple preparation, fast response, good stability and high sensitivity. Moreover, some kinetic parameters such as the electron transfer coefficientα, rate constant K_s of the electrode reaction and the catalytic rate constant K_cat of the catalytic reaction are also determined.