Direct Electrochemistry Of Redox Proteins In Ionic Liquid And Nanoparticles Material Composite Films

In this dissertation, the third-generation electrochemical biosensors based on direct electron transfer between the proteins and the underlying electrodes were fabricated and developed. Heme proteins are a kind of redox proteins. Studies on the direct electrochemistry of redox proteins can be used for the understanding of the mechanisms of electron transfer reactions and oxidation/reduction in life processe, which can also be proposed as a sensitive method for proteins determination. Due to the unique optical, electrical and catalytic characters of nanoparicles, nanoparticles have attracted much attention for their novel applications in the modified electrodes. Room temperature ionic liquids (RTILs) have excellent physical and chemical properties. The main points of the thesis are summarized as follows:1. Three room temperature ionic liquids (RTILs) modified carbon paste electrodes (CPE) were constructed based on the substitute of paraffin with 1-butyl-3-methylimidazolium hexafluorophate (BMIMPF₆), N-butylpyrifinium hexafluorophosphate (BPPF₆) or 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) to mix with graphite power.2. The direct electrochemistry of hemoglobin (Hb) and myoglobin (Mb) on the carbon ionic liquid electrode (CILE) were carefully studied. Hb and Mb were immobilized on the surface of CILE with Nafion and polyvinyl alcohol (PVA) film or Nafion/MWCNTs film by step-by-step method. The characteristics of Hb and Mb in these modified films were investigated by scan electron microscopy, UV-Vis spectrum, FT-IR spectrum and electrochemical methods. The results showed that Hb and Mb in these films retained its native structure. A pair of well-defined and quasi-reversible cyclic voltammetric peaks appeared. Nanoparticles and room temperature ionic liuqids could provide a favorable microenvironment and enhance direct electron transfer rate. The electrochemical behaviors of Hb and Mb in the modified electrode were carefully investigated with the electrochemical parameters calculated. The Hb and Mb modified electrode showed excellent electrocatalytic behaviors to the reduction of hydrogen peroxide (H₂O₂), trichloroacetic acid (TCA) and sodium nitrite (NaNO₂), The apparent Michaelis-Menten constants (KMapp) of the sensors were calculated.3. The direct electrochemistry of Hb with TiO₂ nanoparticle was carefully studied on the carbon ionic liquid electrode (CILE), which was fabricated by using N-butylpyridinium hexafluorophosphate (BPPF₆). Hb was immobilized on the surface of CILE with TiO₂ nanoparticle by adsorption method. The direct electrochemistry and electrocatalysis of Hb in modified film was investigated. The results showed that Hb in the film retained its native structure. A pair of well-defined and quasi-reversible cyclic voltammetric peaks appeared and the electrochemical parameters were furthur calculated.