The Application Of Chitosan Modified Electrode In The Field Of Electrochemical-Sensor

Chitosan is derived from chithin( a naturally occurring polysaccharide found in insects, arthropods and crustaceans) by deacetylation, and its special structure make it demonstrate unique exchange, chelation and adsorption abilities towards many metal cations, organic substances and so on, which allow it to be widely used in chemistry. Now chitosan has not only been used as a matrix for cell and enzyme immobilization, but also developed into membrane material of electrode for preparation of chemical sensors and biosensors. because of its excellent membrane-forming ability, high permeability toward water, good adhesion, high mechanical strength, biocompatibility, nontoxicity, safe and biodegradable materials presented in nature. In this thesis, a glassy carbon electrode coated with chitosan matrix has been recommended as a novel stereoselective electrode (SSE) based on the recognizing ability of chitosan matrix for chiral molecule, and by chitosan matrix immobilized enzyme achieving direct electron transfer (DET) reaction between enzyme and modified electrode.Stereoselective electrode based on chitosan matrix for chiral molecules with cyclic structure. The enantioselective response of SSE to three chiral compounds with cyclic structure and mechanism of discriminating enantiomers have been investigated. The electrochemical enantioselectivity Rl/d of ascorbic acid, norepinephrine and tryptophan on the SSE was found to be 1.48, 1.56 and 1.67, respectively. The enantioselectivity of chitosan membrane for chiral molecules was further demonstrated by chronocoulometry, which showed that the enantioselectivity of SSE is mainly due to the difference in the electron-transfer interaction caused by an acceleration and retardation of the mass transfer of l- and d-enantiomer in chitosan matrix.The direct electrochemistry of Glucose oxidase (GOD), Horseradish Peroxidase (HRP) is studied on the chitosan modified electrode. GOD, HRP was encapsulated in chitosan matrix and immobilized on a glassy carbon electrode, achieving direct electron transfer (DET) reaction between enzyme and electrode without any nano material. The characters of enzyme in chitosan modified films were investigated by cyclic voltammetry. The results showed that GOD, HRP in the films retained the essential features of its native structure because of chitosan's special structure and ability, two pair of well-defined and quasi-reversible cyclic voltammetric peaks were appeared. They both exhibited a linear relationship between catalytic current and concentration of glucose, H₂O₂ in certain range.