| With improved understanding of structure and function of human gene, and the development of the Human Genome Project, DNA diagnostics has become an important area of molecular biology and biotechnology. The detection of specific base sequences in human, viral and bacterial nucleic acids is becoming increasingly important in several areas such as the detection of disease-causing, food-contaminating organisms to forensic and environmental research. The study on the electrochemical behavior of base is of important theoretical and practical significance in life science. Room temperature ionic liquids (RTILs) have excellent physical and chemical properties, such as good solvating properties, high conductivity, non-volatility, low toxicity, large electrochemical window and good electrochemical stability. In this thesis the direct electrochemical investigations on bases were performed with electroanalytical method. The paper can be summarized as follows:1. A Ni/Al layered double hydroxide (LDH) was synthesized and further immobilized on a carbon ionic liquid electrode (CILE), which was prepared by using 1-(3-chlorine-2-hydroxypropyl)-3-methylimidazolium acetate as the modifier. The characteristics of LDH/CILE were investigated by scanning electron microscopy and cyclic voltammetry. Under the selected conditions the LDH/CILE showed better electrochemical response towards the detection of dopamine (DA) than the CILE. The parameters of DA electro-oxidation on the LDH/CILE were calculated with the values of electron transfer coefficient (α), the number of electrons transferred (n), the apparent heterogeneous electron transfer rate constant (ks) and the diffusion coefficient (D) as 0.426, 2.25, 1.66 s-1 and 7.06×10-5 cm2/s, respectively. This modified electrode can be further used to detect DA content in the real drug samples.2. A voltammetric sensor was fabricated by applying a Nafion and multi-walled carbon nanotubes (MWCNTs) composite film on the surface of a carbon ionic liquid electrodes (CILE). The CILE was prepared by mixing 1-butyl-3-methylimidazolium hexa?uorophosphate ([BMIM]PF6) with graphite powder. The electrochemical behaviors of adenine on the Nafion-MWCNTs/CILE were investigated in pH 5.5 Britton-Robinson (B-R) buffer solution. Adenine showed an irreversible adsorption-controlled oxidation reaction with enhanced electrochemical response on the modified electrode, which was due to the presence of high conductive MWCNTs on the CILE surface. The electrochemical parameters of adenine electro-oxidation reaction were calculated and the experimental conditions such as the accumulation time and potential, solution pH were optimized. Under the optimal conditions, the oxidation peak current was linear to adenine concentration over the range from 1.0×10-7 to 7.0×10-5 mol/L with the detection limit estimated to be 3.3×10-8 mol/L (3σ). The modified electrode showed good stability and selectivity without the interferences from various foreign substances. The milk powder samples were detected by the proposed method with satisfactorily results.3. Three kinds of carbon ionic liquid electrodes (CILE) were constructed by mixing graphite powder with ionic liquids 1-carboxyl-methyl-3-methylimidazolium hexafluorophosphate ([CMMIM]PF6), 1-(3-chloro-2-hydroxy-propyl)-pyridinium acetate (PPCH3COO) or 1-(3-chloro-2-hydroxy-propyl)-3-methylimidazole acetate (PMIMCH3COO). The electrochemical behaviors of adenosine-5′-triphosphate (5′-ATP),adenosine-5′-monophosphate (5′-AMP) or thymine was studied on the CILE, respectively, and the results were compared with that of CPE. The electrochemical parameters of 5′-ATP, 5′-AMP or thymine on the CILE was calculated with the electron transfer coefficient (α), the electron transfer number (n), the apparent heterogeneous electron transfer rate constant (ks) and the value of surface coverage (ГT). Under the selected conditions the oxidation peak current was in linear with their concentration and the detection limit (3σ) was calculated by differential pulse voltammetry. |
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