Studies On The Carbon Nanotubers And Its Composite Materials In The Electroanalytical Chemistry

Since the discovery of carbon nanotubes (CNT) in the early 90s, much attention has been paid to them. The one-dimensional tubular structure of CNT has greatly stimulated studies of this novel material in the field of physics, chemistry and material science. Depending on their atomic structure, CNT behave electronic properties suggest that CNT have the ability to promote electron-transfer reactions. In a recent review, attention has been paid that the CNT composite material has electronic, adsorption, mechanical and thermal properties. With the further development of CNT and nanotechnology, studies on preparation, properties and application of CNT and its composite materials have still been a hot topic attracting lots of researchers in the world.In the chapter one, the systemtic aspects, the preparation of CNT, the structure of CNT, the modification of CNT and its application were described in detail.In the second section, the carboxylic group-functionalized carbon nanotubeswere prepared successfully. A synthesized single stranded DNA (ssDNA) was covalently immobilized on gold electrodes that had been modified by carboxylic group-functionalized carbon nanotube which had been activated using EDC and NHS. Differential pulse voltammetry was used to detect DNA with an electroactive indicator of daunomycin which could bind to double stranded DNA effectively. The detection limit is found to be 2.54 × 10^-10 mol/L. Additionally, Ferrocenecarboxaldehyde labeled DNA probes were prepared. Binding events were monitored by electrochemical signal of ferrocenecarboxaldehyde. The method also has the advantage of low-cost, simplified detection and high sensitivity.In the third section, the catalyst of platinum-decorated carbon nanotubes (CNT-Pt) were prepared by a chemical reduction method. Graphite electrode which had been modified by CNT-Pt were constructed (IME). Electrocatalytical behaviors and analytical detection for hydrogen peroxide (H₂O₂) have been studied on these modified electrodes. An amperometric cholecterol biosensor based on the enzymeelectrode with CNT-Pt modified on graphite surface (ChOx/CNT-Pt/IME) has been fabricated. The cholesterol oxidase (ChOX) in gelatin is cross-linked by the use of Sol-gel. Compared with normal other electrodes, the ChOx/CNT-Pt/IME showed more favorable analytical properties, with advantages of short response time, high sensitivity and good stability. In addition, glucose oxidase (GOD) immobilized on the surface of the carbon nanotube modified glassy carbonelectrode (GOD/CNT-Pt/ GC) can undergo effective and stable direct electron transfer reaction. The cyclic voltammetric results indicate that the GOD/CNT-Pt/ GC electrode exhibits a pair of well-defined and nearly symmetrical redox peaks in 0.1 mol/ L phosphate buffer solution. The method presented here can be easily extended to obtain the direct electrochemistry of other redox enzymes or proteins.In the last section, the composite material of nano-meter titanium dioxide decorated carbon nanotubes (CNT-T1O2) were prepared by acid sol method. A sensitive amperometric sensor for the determination of H2O2 has been constructed. Horseradish peroxidase was successfully immobilized on CNT-TiO2 modified glassy carbonelectrode (GOD/CNT-T1O2/GC). Phenylhydrazine was chosen as the electron mediater in the system. The experimental results showed that the sensor displayed excellent electrocatalytical response to the reduction of H2O2. What's more, a novel inhibition based biosensor of HRP for phenylhydrazine detection is described. The response of the sensor is based on the electrocatalytic current redox by inhibitory effect of phenylhydrazine on HRP sensor. The performance of the sensor and the optimum experimental conditions are studied. And the sensor exhibited a better stability and reproducibility.