Preparation Of Four Kinds Of Modified Electrode Based On Ionic Liquid And Direct Elecctrochemistry

Direct electron transfer of metalloproteins with electrodes has aroused great interest in recent years due to the potential applications in the study of the redox properties of the biomolecules. The investigations can also provide useful information on the electron transfer mechanism and establish the foundation for the preparation of biosensors and bioreactors. Different methods have been proposed to realize the direct electron transfer process. Among them the protein film modified electrodes have been widely studied because the presence of biocompatible film on the electrode surface can provide suitable microenvironments to keep the native structure of protein and accelerate the direct electron transfer rate between protein and electrodes. Many composite films including biopolymers, sol-gel, nanomaterials and polyelectrolytes have been used in the film fabrication. In this thesis IL and nano-materials are used as modifiers to fabricate several kinds of modified electrodes and the direct electrochemical behaviors of biomolecules were studied in details. The thesis can be summarized as follows:1. Hemoglobin (Hb) and horseradish peroxidase (HRP) were immobilized on the surface of carbon ionic liquid electrode (CILE) by drop-coating method and the direct electrochemistry of Hb or HRP was further studied. CILE was constructed based on the substitute of paraffin with 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM]EtOSO3) to mix with graphite powder. Hb and HRP were immobilized on the surface of CILE with different substances such as Nafion, hyaluronic acid (HA), ionic liquid (IL), chitosan (CTS), CdS nanorod and CoO nanoflower to fabricate the modified electrodes such as HRP-HA-CdS-IL/CILE and Hb-Nafion-CoO-IL/CILE. The characteristics of Hb and HRP in these modified films were investigated by UV-Vis spectrum, scan electron microscopy (SEM), 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, which indicated that the direct electrochemistry of heme proteins were realized. The electrochemical behaviors of Hb and HRP in the modified electrode were carefully investigated and the electrochemical parameters were calculated. The modified electrodes showed excellent electrocatalytic behaviors to the reduction of trichloroacetic acid (TCA) and H2O2 with the apparent Michaelis-Menten constants(KMapp) calculated, respectively.2. CILE was prepared by mixing graphite powder with 1-ethyl-3-methylimidazolium ethylsulphate ([EMIM]EtOSO3) and liquid paraffin. A stable ordered mesoporous carbon (OMC) film was formed on the surface of carbon ionic liquid electrode (CILE) with the help of Nafion to get a modified electrode denoted as Nafion-OMC/CILE. Direct electrochemistry of double-stranded DNA (dsDNA) was investigated on OMC modified CILE. Brilliant cresyl blue (BCB) was electropolymerized on the surface of a CILE by cyclic voltammetric sweep in the potential range from -0.5 to 1.0 V. A stable polymer film of BCB was obtained on the CILE and a pair of redox peaks appeared. This modified electrode showed excellent electrocatalytic response to ascorbic acid with the increase of the electrochemical responses.