Electrochemical Analyses Based On Fenton-type Reaction On Electrode Surface

This thesis described the basic principle,classification,preparation and research progress of electrochemical sensors.The preparation and application of conductive polymer-modified electrode as well as the origin and reaction mechanism of Fenton-type reaction were also briefly introduced.Glassy carbon electrodes modified with poly(thionine)(PTH)and poly(azure A)(PAA)were fabricated,respectively.The quantitative detections of reduced glutathione(GSH),F-and Bcl-2 antigen were achieved based on Fenton-type reaction on electrode surface.The main contents are listed as follows.1.The polymerization of electro-active dye thionine was performed on glassy carbon electrode surface by using a two-step cyclic voltammetric scan.Copper ions were immobilized based on the chemical bonding to form PTH-Cu2+ modified film on the electrode surface,which was characterized by scanning electron microscopy,XPS and electrochemical measurements.Hydroxyl radicals,OH,that were derived from the Fenton-type reaction between Cu2+ and H2O2 could effectively oxidize PTH,leading to the great enhancement of the cathodic peak current of the dye polymer during the cyclic voltammetry scan.The addition of GSH inhibited the reduction of PTH on the electrode surface,resulting in the decrease of the cathodic peak current.Under the optimized conditions,the cathodic peak current change was found to be proportional to the logarithm of the GSH concentration from 10 nM to 1 mM with a detection limit of 2.5 nM estimated at a signal-to-noise ratio of 3.The proposed electrochemical sensor was successfully employed for the determination of GSH in real samples with satisfactory results.2.PTH-modified glassy carbon electrode was prepared by using a two-step cyclic voltammetric scan.Ferrous ions(Fe2+)were immobilized on the electrode surface based on the complex interaction with amino groups.Fenton reaction between Fe(?)and hydrogen peroxide induced the increase of the cathodic peak current of PTH during the cyclic voltammetric scan.Fluoride ions could react with the Fe(?),which was the product of Fenton reaction,by complexation reaction.It was favorable to the generation of OH and resulted in the further enhancement of the cathodic peak current of PTH.An indirect and sensitive electrochemical method for the F-detection was developed.The proposed sensor showed a good linear response to F-in the concentration range of 10 nM-10 mM and the detection limit was 0.31 nM at a signal-to-noise ratio of 3.This sensor exhibited some advantages,such as high sensitivity,wide detection range and good selectivity.3.A glassy carbon electrode modified with PAA was prepared by using a two-step cyclic voltammetric scan.Copper ions and glutaraldehyde were immobilized simultaneously on the dye-polymer modified electrode surface through an adsorption step based on the chemical bonding.The Bcl-2 antibodies were captured on the electrode surface owing to the crosslinking reaction in the presence of glutaraldehyde.The different modified electrode surfaces were characterized by electrochemical technologies.The specific reaction between Bcl-2 antigens and the antibodies led to a strong steric effect,which had a significant inhibition for the Fenton-type reaction between Cu2+ and H2O2.As a result,the quantitative detection of Bcl-2 antigen was realized.The detection range of Bcl-2 antigen concentration changed from to 100 ?g mL-1 and the detection limit was 0.72 ng mL-1 at a signal-to-noise ratio of 3.