Construction Of Functional Membrane Electrodes Based On Nano-interface And The Applications

Modification on the suface of electrodes affects the electrochemical reaction enormously.Controlling the exterior structure of the electrode surface chemically and exploring new functional electrode interface by molecular design are the key to the study of electrochemical analysis.On the functional electrode interface electrochemical reaction can conduct according to human intention. In recent years, the nanotechnology has received considerable attention in the field of electrochemistry. Because of the size in the boundary of atom cluster and macroscopical objects, the nanometer-sized materials have special properties, such as large surface-to-volume ratio, increased surface activity, quantum size effect, catalysis, etc.. They have been used to fabricate chemically modified electrode, which exhibits an excellent electrochemical characteristic toward some analytes. So, constructing functional membrane of nanoelectrode interface and exploring new methods of simultaneous determination of multi-analyte and dertermination of biology sample can extend the application area of electrochemistry and electroanalytic chemistry.In this thesis, we developed our work focusing on the conctructing and application of functional membrane on the nanoelectrode interface.The paper is divided into the following three parts.1. Fabrication of the single-wall carbon nanotube compound polymer film electrode and the simultaneous electrochemical behavior ofaminophenol isomersThe electrode was constructed by electropolymerization of 4-aminopyridine at single-wall carbon nanotubes modified glassy carbon electrode (SWNTs/POAPE).The configuration and electrochemical properties of SWNTs/POAPE were characterized by scanning electronic micrographs (SEM) and voltammetry. The SWNTs/POAPE showed an excellent electrocatalytic activity to the oxidation of aminophenol isomers and capability of determining three aminophenol isomers simultaneously. The oxidation peak potential difference between m-aminophenol and o-aminophenol was 416 mV, o-aminophenol and p-aminophenol 119 mV, indicating that the o-, m- and paminophenol could be identified entirely at the SWNTs/POAPE. The proposed electrode has been applied to the simultaneous voltammetric determination of aminophenol isomers in mixture without previous chemical or physical separations. 2. Direct electrochemistry and electrocatalysis of hemoglobin immobilized onto carbon nanotubes modified ultra-thin carbon paste electrodeIn this paper, a novel amperometric third-generation hydrogen peroxide biosensor was fabricated by immobilization of hemoglobin (Hb) on single-wall carbon nanotube (SWNTs) and sol-gel modified inlaying ultra-thin carbon paste electrode (IUTCPE). IUTCPE film was formed by inlaying carbon paste onto the surface of nickel-chromium substrate. Hb compound SWNTs and sol-gel film was dripped in the IUTCPE. Scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS) were employed to characterize the modified electrodes. Results showed that the Hb+SWNT+Sol-gel/IUTCPE not only greatly promoted directly electron transfer of Hb but also exhibited good electrocatalytic activity towards the reduction of hydrogen peroxide (H₂O₂). Moreover, the cost of the substrate electrode was greatly decreased. A potential application of this excellent electrode is to be used as the third-generation biosensors.3. Electrochemical study of the interactions of dsDNA with redox-active molecules based on the immobilization of dsDNA on the nano porous chitosan modified inlaying ultra-thin carbon paste electrodeA single wall carbon nanotubes (SWNTs) compound chitosan modified inlaying ultra-thin carbon paste electrode (SWNTs+Chi/IUTCPE) based DNA biosensor for the interactions of double stranded DNA (dsDNA) with redox-active molecules were explored by using voltammetric methods.Ds-DNA were electrostatically attached by using nano porous chitosan onto inlaying ultra-thin carbon paste electrode.The surface characterization of the modified electrodes were investigated by scaning electronic microscopy ( SEM ) and electrochemiscal impedence spectroscopy (EIS).The results indicated that dsDNA can be immobilized effectively.1. The study of interactions between dsDNA and methylene blue (MB).The electrochemistry of MB was investigated at different modified electrodes by means of cyclic voltammetry (CV),the results indicated that the charge transfer (CT) between MB and the electrode surface is a DNA mediated redox process and MB deed interacted with DNA.Altering the scan rate from 20 to 220 mV s^-1,both the anodic and the cathodic peak currents of MB at the dsDNA/ SWNTs+Chi/IUTCPE have linear relationships with the scan rate (v),as expected for a adsorption-controlled process.The peak potentials of MB shifted in the negative direction linearly to the pH value from 6.0 to 7.4. 2. The study of interactions between dsDNA and acridine orange (AO). Differential Pulse Voltammetry was utilized to study the interactions between dsDNA and AO.On the surface of dsDNA /SWNTs+Chi/IUTCPE, the reaction process was a adsorption-controlled process between the scan rate of 20 and 400. There is not only electrostatic attraction but also intercalations between dsDNA and AO.