Electrochemical Biosensor Based On Carbon Nanomaterials And Its Catalysis

Since nanomaterials possess special structures and a series of fantastic physical and chemical properties, they have got wide applications in various kinds of fields including biosensor, photocatalysis or electrocatalysis, materials engineering, bio medicine, energy storage and conversion and environmental protection and have shown their unique advantages. In recently years, carbon-based nanomateirals have received wide attentions of the scientific community especially the electrochemical community due to their unique properties of high surface area, good conductivity and chemical stability. Moreover, many breakthroughs have been made on these carbon-based nanomaterials. In this thesis, we combine the research of materials science, analytical chemistry and electrochemistry and developed carbon-based nanocomposite for the application of biosensor and elctrocatalysis.In Chapter1, we introduced the research and development of nanomaterials, electrochemical sensors and fuel cells, respectively and reviewed the application of nanomaterials in electrochemical sensor and energy-related electrocatalysis including in the fuel cells. Then we proposed a scheme of nanomaterials-based biosensor and electrocatalysis study.In Chapter2, a Cytc-based hydrogen peroxide biosensor was fabricated via layer-by-layer (LBL) assemble of ordered mesoporous carbon and poly(diallyldimethylammonium) on the surface of an indium tin oxide (ITO) glass electrode. UV-vis absorption spectroscopy was applied to characterize the process of forming the assembled layers. Cyclic voltammetry revealed a direct and quasi-reversible electron transfer between cytochrome c and the surface of the modified ITO electrode. The surface-controlled electron transfer has an apparent heterogeneous electron-transfer rate constant (ks) of5.9±0.2s-1in case of the5-layer electrode. The biosensor displays good electrocatalytic response to the reduction of H2O2, and the amperometric signal increase steadily with the concentration of H2O2in the range from5μM to1.5mM. The detection limit is1μM at pH7.4.In Chapter3, Palladium nanoparticles were loaded in situ on novel mesoporous carbon nanospheres (MCNs), which possess high specific surface area and large pore volume. The resulting Pd/MCNs hybrid nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). By using Pd/MCNs as the catalyst matrices to modify the surface of glassy carbon electrode. a nonenzymatic sensor was developed for the determination of hydrogen peroxide (H2O2). Cyclic voltammetry (CV) and amperometry (at an applied potential of-0.30V versus SCE) were used to study and optimize the performance of the electrochemical sensor. It was demonstrated that the sensor not only exhibits good electrocatalytic activity toward the reduction of H2O2but also has high sensitivity偶of307.5μA mM-1cm-2, low detection limit of1.0μM, and wide linear response range from7.5μM to10mM. Moreover, the sensor shows excellent stability and anti-interference capability for the detection of H2O2.In Chapter4, a new carbon foam material (MCF) with hierarchical structure was synthesized using ordered macroporous silica foam as the template. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen sorption characterizations show that the MCF has typical foam-like morphology with well-developed porosity (i.e. micro-, meso-, and macropores), large specific surface area and pore volume. Afterwards, Pt nanoparticles with good dispersion and uniform size were in-situ loaded on the MCF using polyol reducing method. The as-obtained Pt/MCF nanocomposite was developed as an electrocatalyst for methanol oxidation. Cyclic voltammograms show that the Pt/MCF has much larger electrochemical surface area than Pt supported on Vulcan XC-72carbon black (Pt/C) as the catalyst. Consequently, Pt/MCF catalyst exhibits more superior MOR electrocatalytic activity with higher current density than Pt/C.In Chapter5, MoS2nanoparticles were in-situ reduced on ordered mesoporous carbon nanospheres via hydrothermal route with (NH4)2MoS4as the precursor. SEM, TEM, XPS and ICP-AES techniques was used to characterize the morphology, component and content of the supported MoS2nanoparticles. The results show that the supported MoS2has typical layered structure with good dispersion. Furthermore, an electrocaltyst for hydrogen evolution was developed based on the MoS2/MCNs nanocomposite. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were used to study the electrocatalytic activity of the MoS2/MCNS for hydrogen evolution. The MoS2/MCNs exhibit high catalytic activity for hydrogen evolution with a low overpotential of about100mV (vs. RHE) and a very high current density of about34mA cm-2at the overpotential of200mV. A theory outlining the origins of the Tafel slope for a Volmer-Heyrovsky (rate determining step) mechanism of hydrogen evolution at MoS2catalytic edge sites is presented. In Chapter6, we summarized and proposed the objects and schemes for further research.