Preparation And Analytical Application Of Electrochemical Biosensors Based On Three Dimensions Carbon Materials

Carbon Materials possess some distinguished characteristics, such as good electrical conductivities, strong corrosion resistance, low density, high chemical stability and more readily available. Furthermore, carbon materials have a wide potential window (from -1.0V to 1.0V vs. SCE) in most electrolytical solution. These special characteristics endow carbon materials with wide applications in electrochemical and electroanalytical chemistry. Otherwise, there are few functional groups on surface of the pristine carbon materials, which constrict them in the application of electroanalytical chemistry. Therefore, we make use of dopamine self-polymerizing to realize the functional surface of carbon materials. Because of many reductive groups existing on the surface of polydopamine (Pdop), some noble metal reduced and loaded on the surface of materials, resulting wide application in the electroanalytical chemistry.In this paper, electroanalytical studies on three dimensions carbon materials (carbon nanosphere, carbon nanotube and graphene) were carried out systematically, and two kinds of carbon materials were further functionalized with polydopamine. The exact work is summarized as follows:(1) Monodisperse colloidal carbon nanospheres were prepared from aqueous glucose solutions by hydrothermal synthesis. We coated the CNPs with Pdop, and further loaded by Ag nanoparticles. At the same time, we investigated the prepared material properties and basic structure before coating or loading by XRD, FT-IR, SEM, TEM and so on. We also studied systemically the direct electron transfer of Haemoglobin immobilized on the prepared materials, and prepared the Nafion/Hb/Ag-Pdop@CNPs GCE, and constructed the electrochemical biosensor for H₂O₂.(2)The polymerization of dopamine, which was developed to functionalize the MWCNTs. The method has trait of facility, mildness, controllable compared with other regular ones. Ag nanoparticles on the surface of as-prepared composite materials, Ag-Pdop@MWCNTs, were dispersed well. And we characterized the materials by many manners.The prepared Ag-Pdop@MWCNTs modified Au electrode has a favorable catalytic ability for reduction of H₂O₂. The resulted sensor could detect H₂O₂ in a linear range of 20?30000μM at a signal-to-noise ratio of 3. And the sensitivity was calculated as 2.134μA/mM. Additionally, it selectively detected H₂O₂ and exhibited negligible interference of many coexisting materials.At the same time, Ag-Pdop@MWCNTs composite materials were used to modify the GC electrode for the direct electron transfer of GOD, and glucose was successfully detected indirectly by sensing of H₂O₂ with satisfying results.(3) Graphitic oxide was prepared according to Hummer method, then the graphene was synthesized by a chemical method to reduce graphitic oxide. Thanks to the excellent conductivity and biocompatibility of graphene, Nafion/HRP/graphene modified GCE was fabricated, and the direct electrochemisty of HRP was realized. Based on the above, we constructed an electrochemical biosensor for H₂O₂. The results show that the biosensor exhibits both good biocompatibility and storage stability. The new sensor shows a linear range of 0.33-14.0μM, with a calculated limit of 0.11μM(S/N=3).