Application Of Ionic Liquid Modified Electrode In Electrochemical Biosensor

The electrochemical biosensor has attracted a wide range of research and application in the fields of analysis and detection due to its ease of use, high sensitivity, good selectivity. Currently, the third generation enzyme electrochemical biosensor is developed rapidly, but there are great limitations to the scope of its application because of the lack of easy ways to immobilize enzyme and the deep burying of the electroactive prosthetic group. Ionic liquids (ILs) have been utilized in the fields of electrochemistry and electroanalysis due to their higher ionic conductivity, wider electrochemical windows, non-volatile and non-toxic. The special characteristics of nanomaterials such as high surface area and high activity, also make them the most promising candidates used in electrochemical sensor. Introduction of ionic liquids and nanomaterials provide an opportunity for the construction of a sutable bio-sensor system. In this paper, a varitey of third generation enzyme electrochemical biosensors were constructed based on the synergy of multiple composit and were used to study the direct electrochemical and electrocatalytic behavior of heme proteins. The main points of the thesis are as follows:1. Hydrophobic Ionic liquids (ILs)1-butylpyridinium hexafluorophosphate (BPPF6) and1-hexylpyridinium hexafluorophosphate (HPPF6) were used as adhesive and modifier to prepare ionic liquid modified carbon paste electrode (CILE). Hemoglobin (Hb) and myoglobin (Mb) were immobilized on the surface of CILE with chitosan (CTS), NMoO4and CoMoO4nanorods composite material, respectively, to construct CTS/Hb-NiMoO4/CILE and CTS/Mb-CoMoO4/CILE. The characteristics of Hb and Mb in these modified films were investigated by scan electron microscopy, FT-IR spectrum, UV-Vis spectrum and electrochemical methods. The results showed that Hb and Mb retained its native structure in these composites. A pair of quasi-reversible, stable and well-defined cyclic voltammetric peaks appeared, and the synergistic effects between IL and multicomposite can greatly promote the electron transfer rate. The electrochemical behaviors of Hb and Mb in the modified electrode were carefully investigated with the electrochemical parameters calculated. The Mb and Hb modified electrode showed excellent electrocatalytic behaviors to the reduction of trichloroacetic acid (TCA) and hydrogen peroxide (H2O2).2. Two kinds of hemoglobin (Hb) biosensors were constructed by using graphene (GR), multi-walled carbon nanotubes (MWCNT), graphene oxide (GO) and ionic liquid1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) composite as modifier. The modified electrodes were prepared by coating Hb, Nafion, GR-MWCNT and GO-IL composite on ionic liquid1-hexylpyridinium hexafluorophosphate (HPPF6) modified electrode (CILE) and were denoted as Nafion/Hb-GR-MWCNT/CILE and Nafion/Hb-GO-IL/CILE, respectively. The electrochemical behaviors of Hb on the modified electrode were carefully investigated with the electrochemical parameters calculated. UV-Vis and FT-IR results showed that Hb in these films retained its native structure. Electrochemical behavior of Hb on Nafion/Hb-GR-MWCNT/CILE and Nafion/Hb-GO-IL/CILE was investigated with a pair of well-defined redox peak appeared in pH3.0PBS buffer. The modified electrodes showed excellent electrocatalytic behaviors and low detection limit to the reduction of TCA, H2O2and NaNO2with the apparent Michaelis-Menten constants(KMapp) calculated.3. By using ionic liquid1-butylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) as the working electrode, graphene (GR) nanosheets and silver nanoparticle (AgNP) were electrodeposited on the surface of CILE with a potentiostatic method step by step. The fabricated Ag/GR/CILE was used as a new platform for the protein electrochemistry and hemoglobin (Hb) was immobilized on its surface with chitosan (CTS) as the film forming material. The electrochemical behaviors of Hb were carefully investigated with the electrochemical parameters calculated. The characteristics of these modified electrodes were investigated by UV-Vis spectrum, scan electron microscopy (SEM) and electrochemical methods. The fabricated CTS/Hb/Ag/GR/CILE showed good electrocatalytic ability to the reduction of trichloroacetic acid (TCA) with a linear range from0.8to22.0mmol/L, and the detection limit (3σ) as0.42mmol/L.