| Carbon materials with high electrical conductivity and great stability have been widely used in both analytical and material science. Graphene （GP）, a novel two-dimensional carbon nanomaterial, composed of monolayers of carbon atoms arranged in a honeycombed network with six-membered rings. Due to its large specific surface area, excellent conductivity properties and other outstanding properties, graphene has sparked more attentions in various applications. Recently, it has also been found that graphene exhibited the ability to promote electron transfer reaction between the redox center of proteins or enzymes and the surface of electrode when used as electrode material. Graphene based nanocomposites could act as effective supports to immobilize electroactive enzymes on electrode and fabricate mediator–free electrochemical biosensors, which not only maintained the native bioactivity of immobilized enzymes, but also promote electron transfer between enzyme and electrode.The main contents of the thesis are summarized as follows:1. Poly（1-vinyl-3-butylimidazolium） bromide (poly（ViBuIm+Br-） was firstly applied to functionalize the graphene viaπ-πinteraction to prepare Poly（ViEtIm+Br-）-GP nanocomposite. The composite was positively charged and used for enzyme immobilization. Glucose oxidase （GOD） was immobilized onto the Poly（ViEtIm+Br-）-GP modified glassy carbon （GC） electrode by electrostatic interaction. The GOD/Poly（ViEtIm+Br-）-GP/GC modified electrode was succeeded in realizing direct electron transfer between GOD and the electrode. The GOD/Poly（ViEtIm+Br-）-GP/GC electrode showed a wide linear range for glucose determination from 0.8 to 20 mM, low detection limit of 0.267 mM and excellent sensitivity of 0.767 A·cm-2·mM-1. The nanocomposite offered an efficient platform for the development mediator-free enzymatic electrochemical biosensors.2. A novel electrochemical was prepared by combining sodium dodecylbenzenesulfonate （SDBS）, a surfactant, and excellent conductivity of graphene via hydrophobic-hydrophobic interaction. The nanocomposite （SDBS/GP） was firstly used as electrode material for immobilizing redox enzyme. Based on electrostatic interaction, horseradish peroxidase （HRP） was self-assembled with SDBS/GP on the surface of electrode to form HRP/SDBS/GP/GC electrode. UV–Vis and FT-IR spectra were used to monitor the assembly process and indicated the immobilized HRP on the SDBS/GP matrix well retained its native structure and bioactivity. A pair of stable and well-defined redox peaks of HRP with a formal potential of about -0.249 V in a pH 5.7 phosphate buffer solution （PBS） were obtained at HRP/SDBS/GP/GC electrode, demonstrating direct electron transfer between the immobilized HRP and electrode was achieved. In addition, the immobilized HRP possessed good electrocatalytic activity for H2O2, NaNO2 and O2.3. 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-（1’-rac-glycerol） （sodium salt） （POPG） was one of lipids with eximious biocompatibility. POPG/GP nanocomposite was prepared by non covalent interaction. The nanocomposite was endowed with excellent properties of the two independent components, such as biocompatiblity of the POPG and the outstanding electric properties of graphene. Moreover, the existence of POPG on graphene could not only assist dispersion of graphene in aqueous solution, but also make it negatively charged, which was favorable for immobilization of enzyme （such as HRP） via self-assembly. The HRP/POPG/GP/GC modified electrode commendably realized direct electron transfer and exhibited good electrochemical performance,execellent stability and reproducibility. Moreover, the modified electrode showed good electrocatalytic performance to H2O2 with high sensitivity, wide linear range and good stability. Therefore, such biocompatible nanocomposite had potential applications in direct electrochemistry and fabrication of electrochemical biosensors. |
