Development Of Electrochemical Biosensor Based On Functional Graphene Composite Materials

Electrochemical biosensor is an analytical device for the detection of an analyte that combines a biological component with a electrochemical detector. A modified electrode is the current research focus that often used as a transducer in chemical and biological sensor. Nanomaterials are often used in the fields of chemical for modified electrodes because of its unique optical, electrical, catalytic properties and good biocompatibility. Owing to the unique and outstanding physical and chemical properties, graphene has been widely investigated in different fields of chemistry. By integrating 2D graphene sheets into a desired three-dimensional(3D) macroscopic assemblies is an effective way for tuning and controlling their electrical, optical, chemical, mechanical or catalytical properties. Recent researches reveal that 3D graphene macromaterials exhibit enhanced performance in the applications of energy storage, environment, sensing and biological analysis. In this paper different nanomaterial are used as modifiers with graphene to fabricate several kinds of composite materials, and furthur used for the preparation of modified electrodes and immobilization of redox protein on the electrode are investigated in details and the thesis can be summarized as follows:1. In this paper a graphene(GR) and copper sulfide(Cu S) nanocomposite was synthesized by hydrothermal method and used for the electrode modification with a N-butylpyridinium hexafluorophosphate based carbon ionic liquid electrode(CILE) as the substrate electrode. Hemoglobin(Hb) was immobilized on the modified electrode to get a biocompatible sensing platform. UV-Vis and FT-IR spectroscopic results confirmed that Hb retained its native secondary structure in the composite. Direct electron transfer of Hb incorporated into the nanocomposite was investigated with a pair of well-defined redox waves appeared on cyclic voltammogram, indicating the realization of direct electrochemistry of Hb on the modified electrode. The results can be ascribed to the presence of GR-Cu S nanocomposite on the electrode surface that facilitates the electron transfer rate between the electroactive center of Hb and the electrode. The Hb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acidin the concentration range from 3.0 to 64.0 mmol/Lwith the detection limit of 0.20 mmol/L(3σ). The fabricated biosensor displayed the advantages such as high sensitivity, good reproducibility and long-term stability.2. A three-dimensional graphene(3D GR) and gold(Au) composite was synthesized by electrodeposition and used for the electrode modification with a 1-hexylpyridinium hexafluorophosphate(HPPF6) based carbon ionic liquid electrode(CILE) as the substrate electrode. Myoglobin(Mb) was further immobilized on the surface of 3D GR-Au/CILE to obtain an electrochemical sensing platform. Direct electrochemistry of Mb on the modified electrode was investigated with a pair of well-defined redox waves appeared on cyclic voltammogram, indicating the realization of direct electron transfer of Mb with the underlying electrode. The results can be ascribed to the presence of highly conductive 3D GR-Au composite on the electrode surface that accelerate the electron transfer rate between the electroactive center of Mb and the electrode. The Mb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid in the concentration range from 0.2 to 36.0 mmol/Lwith the detection limit of 0.06 mmol/L(3σ).3. A three-dimensional electroreducted graphene oxide(3DGR) and silver(Ag) nanostructure was synthesized by electrodeposition method and used for the electrode modification with a N-butylpyridinium hexafluorophosphate(BPPF6) based carbon ionic liquid electrode(CILE) as the substrate electrode. Hemoglobin(Hb) was immobilized on the modified electrode to get a biocompatible siensing platform CS/Hb/Ag/3DGR/CILE. Direct electron transfer of Hb incorporated into the composite was investigated with a pair of well-defined redox waves appeared on cyclic voltammogram, indicating the realization of direct electrochemistry of Hb on the modified electrode. The results can be ascribed to the presence of Ag/3DGR composite on the electrode surface that facilitates the electron transfer rate between the electroactive center of Hb and the electrode.4. A carbon microsphere(CMS) was synthesized by hydrothermal method and used for the electrode modification with a 1-butylpyridinium hexafluorophosphate based carbon ionic liquid electrode(CILE) as the substrate electrode. The characteristics of CMS were investigated by different methods including Scanning electron microscopy, Transmission electron microscopic, X Ray Diffraction, Raman spectrum and FT-IR spectrum. Hemoglobin(Hb) was further immobilized on the modified electrode with a layer of chitosan film to get a biocompatible sensing platform. UV-Vis absorption and FT-IRspectra confirmed that Hb remained its native secondary structure in the composite. Electrochemical performances of the modified electrode were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Direct electron transfer of Hb on the modified electrode was acheived with a pair of well-defined redox waves appeared on cyclic voltammogram, indicating the realization of direct electrochemistry of Hb with the working electrode. The results could be ascribed to the presence of CMS on the electrode surface with large surface area and good conductivity that facilitated the electron transfer rate between the electroactive center of Hb and the electrode. The Hb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid in the linear concentration range from 2.0 to 70.0 mmol/L with the detection limit of 0.30 mmol/L(3σ). The fabricated electrode displayed the advantages such as high sensitivity, good reproducibility and long-term stability, which implied that CMS was promising for fabricating the third-generation bioelectrochemical sensor.