Preparation And Application Of Electrochemical Biosensors Based On Carbon Nanotubes

There has been intense interest in carbon nanotubes because of their significant mechanical strength, high surface area, excellent electrical conductivity and good chemical stability. The subtle electronic porperties suggest that carbon nanotubes have the ability to promote electron transfer reaction when used as electrode material, which is promising as an immobilization substance. In order to develop a new potential application of MWNTs in the field of electrochemical biosensors, we have studied applitions of the MWNTs in this thesis. The content consists of following two parts. In part one, direct electron transfer of Myb between MWNTs modified electrode was discussed: MWNTs modified glass carbon electrode (GC) was immersed in Myb from its solution at pH 5.6 to form a Myb/MWNTs electrode. The progress of adsorbtion was minitored by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). When the Myb/MWNTs modified electrode was put into blank phosphate buffer solution at pH 7.0, a pair of well-defined and reversible CV peaks were observed at about –0.248V (vs. SCE), characteristic of Heme Fe (III)/Fe (II) redox couple. The Myb/MWNTs modified GC electrode can catalyse the electroreduction of O2, H2O2 and NO, with a significant lowering of overpotential. Thus based on Myb immobilized on MWNTs modified electrode, a novel reagentless NO, O2 and H2O2 biosensor was constructed, respectively. The experimental optimization was also studied in detail. In part two, the preparation of a new type of composite nano-material and its application was discussed: a new type of composite nano-material modified electrode was constructed by electrochemical deposition of gold and platinum nanoparticles to MWNTs modified electrode, respectively. The composite nano-material of gold nanoparticles attached to MWNTs (nano-Au/MWNTs) exhibited a good electrocatalytic activity and stability for the direct electron transfer between cyt. c and electrode surface. The highly dispersed platinum nanoparticles on MWNTs (nano-Pt/MWNTs) exhibited a good electrocatalytic activity for the reduction of NO, and showed a widely linear response to NO. The nano-Pt/MWNTs catalysts show high performance and good stability for the electro-oxidation of some organic molecules, such as methanol, formic acid, formaldehyde, which is the result of co-operation effect of nano-Pt and MWNTs.