| Since their discovery by Iijima in 1991, carbon nanotubes have been the focus of intensive study due to their excellent physical and chemical properties. Vertically aligned multiwalled carbon nanotubes (VACNTs) is an orientation of carbon nanotubes form. The large surface area, ideal porous structure, excellent mechanical properties, good conductivity and stable chemical properties make VACNTs as materials for preparation of nanocomposites, electrochemical sensors, and optical devices. Modification of VACNTs with metals or metal oxides will result in nanocomposites not only with the properties of individual components, but also with a good synergistic effect. In addition, the VACNTs simplify the fabrication of electrode and solve the problem brought by the conventional drop method. In this thesis, studies on the preparation and modification of vertically aligned carbon nanotubes electrodes and their application for electroanalytical chemistry were carried out, and some valuable results were obtained. The main points of this thesis are summarized as follows:1. The VACNTs was fabricated by chemical vapor deposition method. Its morphology of nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy. The VACNTs was applied for electrocatalysis of rutin oxidation, and the possible mechanism of electrocatalysis was discussed. The sensors of cyclic voltammetry and stripping differential pulse voltammetry exhibit an adsorption-controlled, reversible two proton and two electron transfer reaction for the oxidation of rutin. Under Britton-Robinson buffer solution (pH 5.0, 0.1 mol·L-1), it shows a high sensitivity of 8.05 A mol·L?1, a linear dependence on the concentration of rutin from 1.0×10-8 mol·L-1 to 1.0×10-5 mol·L-1, a remarkably low detection limit 5.0×-9 mol·L-1. The method was successfully applied to determine rutin in tablets with satisfied recovery. In addition, VACNTs electrode has excellent reproducibility, good stability and high selectivity etc., which is expected to be a highly sensitive electrochemical sensors for detection of rutin with broad prospect.2. The Pt-modified vertically aligned multiwalled carbon nanotubes (Pt/VACNTs) was fabricated by magnetron sputtering deposition. Its morphology was characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy. Electrochemical behavior of L-cysteine at the Pt/VACNTs electrode was investigated by cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The mechanism for the electrochemical reaction of L-cysteine at the Pt/VACNTs electrode in different pH phosphate buffer solution was also discussed. The Pt/VACNTs electrode exhibits a higher electrocatalytic activity towards the oxidation of L-cysteine than VACNTs electrode. At an applied potential of +0.45 V, it shows a linear dependence (R=0.999) on the concentration of L-cysteine from 1.0×10-6 mol·L-1 to 0.5×10-3 mol·L-1, a remarkably low detection limit of 0.5 mol·L-1 (signal/nose = 3) and an outstandingly high sensitivity of 132.62 A mmol·L?1, which was the highest value ever reported. Meanwhile, the Pt/VACNTs electrode is also highly resistant towards other amino acids, creatinine and urea, etc.. In addition, the sensor based on the Pt/VACNTs nanocomposite electrode was applied for the determination of L-cysteine in urea with satisfactory discovery, demonstrating its potential for practical application.
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