Study And Application Of Chemically Modified Electrodes And Biosensors

The chemically modified electrodes have been a most burgeoning and one of the most flourish research realms in the electrochemistry and electroanalytic chemistry since it was developed in the middle of 70's . It was for the moment widely applied in many cases such as life sciences , environmental science , analytic science and material science . The mediators modified on the surfaces of electrodes can realize the electrocatalytic reactions by accelerating electron transferring between redox centers and the electrode surface . The carriers immobilizing the mediators have a great influence on the electrochemistry activities of the mediators , The electrocatalysis of the modified electrodes is an enormous impetus for its development and was widely used in the slow electron transferring processes which isn't easily realized , for example , the electrocatalysis of biomolecules , organic compounds and inorganic ions.In our papers,host-guest inclusion complexes were prepared with organic coordination-agents and cation coloring-agents as the guests according to the molecular recognition of P - cyclodextrin and they were successfully used to fabricate the functional modified electrodes for the following analytical measurements: 1. The inclusion complex of P - cyclodextrin cross-linking polymer ( 3 ~ CDP) with pyridylazo-resorcinol(PAR) was prepared and it was intermingled into the carbon pastes to make carbon paste electrodes. The determined Co2+ was selectively separated by its complexing reaction with the inclusion compounds . The experiment results showed that P - cyclodextrin cross-linking polymer effectively reducing the running -off of the the organic coordination-agents (PAR) in the acidic and basic solution by the inclusion effect and greatly improved sensitivity and stability . 2. The mediators and enzymes were coimmobilized on the electrodes to fabricate Hi02 biosensors by supermolecular force between insoluble 3 -cyclodextrin cross-linking polymer and toludine blue 0 and condensing effect of glutaraldehyde .In addition,during the course of fabricating biosensors , mediators were immobilized on the surface of the modified electrodes by adsorption, electrodeposition and electropolymerization to catalize bioactive molecules such as ascorbic acid , hydrazine and hydrogen peroxide: 1. Chitosan layer was modified on the electrodes , which adsorbed and accumulated negatively charged [Fe(CN)6]3" by electrostatic interaction because chitosan molecules is positively charged in low pH solution due to the protonated ammo group in chitosan molecules , otherwise this kind of crude macromolecules materials can effectively eliminate the interference from big molecules and positively charged substances and improve the electrocatalytic oxidation capacity on the ascorbic acid . 2. A new type mixed silver/nickel hexacyanoferrate film was electrodeposited onto the electrode surface .The Ag+ in this film increased the stability of the film and this film showed significant catalytic effect on the oxidation of hydrazine . 3. The water-soluble electron transferring mediator neutral red(NR) formed a compact and stable film by electropolymerizing on the graphite electrodes , which efficiently decreased the running-off of the mediators .A gelatin layer was covered on the surface of HRP layer followed by the cross-linking of glutaraldehyde to avoid the deactivation of part of immobilized enzyme and at the same time improved the stability , sensitivity and the lifetime of the HbO: biosensor .