The Study On Fabrication Of Functionalized Graphene-based Nanostructures And Electrochemical Sensing

Graphene, a two-dimension(2D) honeycomb monolayer of graphite, has attracted tremendous interest in the field of physics, chemistry and materials in recent years due to its unique structural, electrical, thermal, optical and mechanical properties. Graphene is considered attractive material for preparation of nanocomposites, electrochemical sensors, and nano devices, which is acknowledged as a rising star after fullrence and carbon nanomaterials since it was discovered in 2004. Therefore, in this thesis, studies on graphene’s property, functionalization, construction of graphene-based nanostructures and electrochemical applications were carried out. The main points of this thesis are summarized as follows:(1) In most graphene-based electrochemical applications, graphene nanoplatelets(GNPs) have been applied. Now, electrochemical properties of GNPs are compared with those of carbon nanotubes(CNTs) and glass carbon. GCE, CNT- and GNP-coated electrodes were then applied for electrochemical oxidation of endocrine-disrupting chemicals. The GNP-coated electrode was characterized by scanning electron microscope, atomic force microscopy and electrochemical techniques. Compared with the GCE and CNT-coated electrode, higher peak current for the oxidation of 4-nonylphenol is achieved on the GNP-coated electrode, together with lower capacitive current; and the calculated detection limit can be as low as 30 nmol/L. Electrochemical oxidation of 2,4-dichlorophenol, bisphenol A, and octylphenol in the absence or presence of 4-nonylphenol was studied on the GNP-coated electrode. The results suggest that GNPs have better electrochemical performance than CNTs and are thus more promising for electrochemical applications, for example, electrochemical detection and removal of endocrine-disrupting chemicals.(2) Graphene nanoplatelets have been applied as the support to electrodeposit monometallic Au and Pd nanoparticles as well as bimetallic Au-Pd nanoparticles. These nanoparticles have been characterized with scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and electrochemical techniques. They are further utilized as the catalysts for electrochemical oxidation of hydrazine. Compared with monometallic Pd and Au nanoparticle, when bimetallic nanoparticles are applied as the catalyst, their composition affects the peak potential and peak current for the oxidation of hydrazine. Higher oxidation current is achieved when bimetallic Au-Pd nanoparticles with an atomic ratio of 3:1 are deposited on graphene nanoplatelets. Au Pd/GNP/GCE shows good linear to the oxidation of hydrazine in the range 0.02~166.6 μmol/L and the calculated detection limit can be as low as 5 nmol/L. Metal nanoparticle-loaded graphene nanoplatelets are thus novel platforms for electrocatalytic, electroanalytical, environmental, and related applications.(3) Porous Pd Cu nanoparticle-loaded graphene nanoplatelets are fabricated by electrodeposition, then the composite membrane was applied to support glucose oxidase. Scanning electron microscope, energy dispersive X-ray spectroscopy, and electrochemical techniques are applied to characterize the film. The prepared modified sensor(GOD/Pd Cu/GNP/GCE) exhibits enhanced catalytic activity and stability towards the sensing of glucose. The detection limit of amperometric response is 20 nmol/L. The proposed method is thus a novel platform for sensing, enzyme immobilization, electroanalysis and related applications.