Fabrication Of Carbon Nanocomposites And Their Applications In Electrochemical Sensor

Carbon nanomaterials which possess special properties in a variety of ways,such as high specific surface area,high strength and toughness,good chemical stability and excellent electrical conductivity,have been applied in many fields.However,in the research and practical utilization,carbon nanomaterials are often doped to improve the specific surface area,accelerate the electron transfer and enhance the electrocatalytic properties of the materials.The improvement of these properties is of great significance to the construction of new electrochemical sensors.In this thesis,we have explored the preparation of carbon nanocomposites and their applications in electrochemical sensors,which are based on one dimensional carbonnanotubes and two dimensional graphene.First,the spherical silver nanoparticles and Ag/CNT nanocomposites were synthesized by a simple chemical reduction method at room temperature.The morphology and composition were characterized by scanning electron microscopy（SEM）and energy dispersive spectroscopy（EDS）.The prepared material is fixed on the surface of a glassy carbon electrode to form a modified electrode.L-cysteine was detected with chronoamperometry method and the result showed that the electrode modified by Ag/CNT possessed a low detection limit（0.4μM）and a wider detection range（1-86μM）to L-cysteine.Secondly,the multi-walled carbon nanotube（MWCNT）decorated by copper nanoparticles was prepared by microwave-assisted method,which was constructed an electrochemical sensor to determinate hydroquinone（HQ）.The morphology and crystalline phase of Cu/CNT nanocomposite was characterized by SEM and X-ray diffraction（XRD）,respectively.Cyclic voltammetry（CV）and electrochemical impedance spectroscopy（EIS）were utilized to characterize the electrochemical properties and surface properties of the Cu/CNT modified electrode.Due to the synergistic effect of Cu NPs and CNT,the modifiedelectrodeshowedgoodelectrochemicalactivityandincreasedthe electrochemical signal of HQ detection.Under the optimized conditions,the linear response range of HQ is 0.10¹00μM,and the detection limit is 0.04μM.In addition,the modified electrode has good reproducibility and excellent anti-interference performance.Satisfactory results were obtained by the modified electrode for the determination of the actual samples.Thirdly,nanocomposite of gold nanoparticles loaded on reduced graphene oxide（Au NPs@RGO）nanosheets was prepared via a simple reduction method.The as-prepared nanocomposite was characterized by SEM,energy dispersive X-ray spectroscopy（EDX）and ultraviolet visible absorption spectroscopy.An electrochemical sensor based on Au NPs@RGO was developed for simultaneous detection of Cu²⁺and Hg²⁺.The electrochemical behavior of two kinds of metal ions on the modified electrode was examined by cyclic voltammetry.Cu²⁺and Hg²⁺were measured by differential pulse voltammetry（DPV）with modified electrode.The detection limit of Cu²⁺was 0.02μM,the detection range was from 0.05¹0μM,and the detection limit of Hg²⁺was 1.8 nM,and the detection range was 5²000 nM.The sensor was applied to detecte heavy metal ions in water samples.Fourthly,a new electrochemical sensor based on Ag-Cu/RGO nanocomposite was constructed.The prepared Ag-Cu/RGO nanocomposite was characterized by SEM,EDX,X-ray photoelectron spectroscopy（XPS）and Transmission electron microscope（TEM）.Ag-Cu/RGO nanocomposite was explored to modify glassy carbon electrode for determination of Susan I and the electrochemical behavior of the modified electrode was inquired.The result displayed that the detection range was 1 nM¹.0×10⁴nM,the detection limit was as low as 0.4 nM.The method was successfully applied to the determination of Sudan I in ketchup and chili powder.Last but not least,the different components of Ag,Cu bimetallic nanoparticles were carried out to attach on graphene nanosheets in the work.Silver,copper bimetallic nanoparticles with different stoichiometric ratios were successfully dispersed on the surface of reduced graphene oxidation.The obtained composites were characterized by SEM,EDX,XRD,XPS and TEM.The results show that the components and morphology of the bimetal can be controlled by changing the proportion of the precursor.The mechanism of synthesis was discussed;it provides a new idea for the controllable synthesis of bimetallic nanoparticles.Ag_0.5Cu_0.5/RGO nanocomposite modified electrode showed superior electrocatalytic performance for H₂O₂.