Reaserch And Application Of Electrochemical Sensor Based On Carbon Molecular Wire Electrode

Molecular wire is a molecule or an assembly of molecules that able to conduct electricity, It is the key component that allows electron deliver from one device to another device or a functional groups to another function. Phenyleneacetylene oligomers which have wire-like properties are promising materials for a wide variety of applications in molecular electronic devices due to their ideal conductivity. Diphenylacetylene (DPA) is the smallest conjugated oligomer and can be used as a conducting binder in carbon paste electrode (CPE), it is conductive and rigid, the two benzenes are connected by rigid ethinyl so that conjugation effect being the principal component. The new type of carbon molecular wire electrode (CMWE) was constructed by mixing graphite powder and Diphenylacetylene (DPA) rather than paraffin oil. In this thesis different electrochemical sensors were fabricated and used to investigate the behaviors of nucleotide molecules. The thesis can be summarized as follows:1. A new electrochemical sensor was fabricated by applying gold nanoparticles film on the surface of CMWE. The electrochemical behaviors of metol on the Au/CMWE were investigated in pH5Britton-Roinson (B-R) buffer solution. Due to the presence of high conductive gold nanoparticles on the surface of CMWE, modified electrode exhibited excellent electrocatalytic ability to metol. The parameters of metol electro-oxidation on Au/CMWE were calculated with the values of electron transfer coefficient (a), the apparent heterogeneous electron transfer coefficient (ks), the number of electrons transferred (n) and the diffusion coefficient (D) as0.48,3.7s-1,2.2and1.24×10-5cm2/s, respectively. The detection limit was calculated as6.37×10-7mol/L (3σ) for metol by differential pulse voltammetry. 2. Another new electrochemical sensor (GR/CMWE) was fabricated by applying graphene on the surface of CMWE. The characteristics of GR/CMWE were investigated by scanning electron microscopy (SEM) and cyclic voltammetry. The electrochemical bahaviors of DA on the GR/CMWE were investigated. DA showed an reversible diffusion-controlled reaction with enhanced electrochemical response on the modified electrode, which was due to the presence of highly conductive graphene on the CMWE surface. The electrochemical parameters of DA electro-oxidation reaction were calculated and the experimental conditions were optimized. Under the optimal conditions, the oxidation peak current showed good relationship with the DA concentration over the range from8×10-7mol/L to2×10-3mol/L with the detection limit estimated to be2.55×10-7mol/L(3σ).3. Two kind of modified electrodes were fabricated by using graphene (GR), bismuth nanoparticles or pyronin B composite materials modified carbon molecular wire electrode (CMWE). And the modified electrodes were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical behaviors of p-nitrophenol and quercetinon were studied on the Bi/GR/CMWE and Poly(PyB)-GR/CMWE with the electrochemical parameters caculated respectively. The detection limit were caculated as6.37×10-7mol/L for p-nitrophenol and6.37×10-8mol/L for quercetinon by differential pulse voltammetry.