Research Of Electrochemical Biosensor Based On Graphene Composite Modified Carbon Ionic Liquid Electrode

Recently, electroanalytical technique has drawn wide attention because of it’s advantages such as simple operation, high sensitivity, low cost and so on. As reseach continues, the working electrode of electrochemical analysis has developed from bare electrode which exhibits some disadvantages such as small signal response, low electron transfer speed and low sensitivity to chemically modified electrode. Ionic liquid (IL) has many special physical and chemical properties such as high ionic conductivity, good solvating properties, wide electrochemical window, which can be applied inelectrochemical field either as supporting electrolyte or the modifier for chemically modified electrode. In this thesis, IL1-hexylpyridinium hexafluorophosphate is used as a modifier to fabricate a kind of carbon ionic liquid electrode (CILE). Then we fabricated several kinds of chemically modified electrodes through coalting or electrodepositing, and the electrochemical behaviors of several medical molecules are studied in details. The thesis can be summaried as follows:1. We report on a carbon ionic liquid electrode modified with a composite made from Nafion, graphene oxide and ionic liquid, and its application to the sensitive determination of rutin. The modified electrode was characterized by cyclic voltammetry and electrochemical impedances pectroscopy. It shows excellent cyclicvoltammetric and differential pulse voltammetric performance due to the presence of nanoscale graphene oxide and ionic liquid, and their interaction. A pair of well defined redox peaks of rutin appears at pH3.0, and the anodic peak current is linearly related to its concentration in the range from0.08μM to0.1mM with a detection limit of0.016μM (at3σ). The modified electrode displays excellent selectivity and good stability, and was successfully applied to the determination of rutin in tablets with good recovery.2. Two kinds of chemically modified electrodes donated as DNA/GR/CILE and DNA/Au/GR/CILE were fabricated by electrodeposition process. The electrochemical behaviors of dopamine were studied on the two modified electrodes respectively. The electrochemical parameters of DA on the two electrodes were calculated with the electron transfer coefficient (a), the electron transfer number (n), the apparent heterogeneous electron transfer rate constant (ks). Under the optical conditions, the oxidation peak current was in linear with their concentration and the detection limit was calculated by differential pulse voltammetry. The results have shown that the signal response is bigger and the detection limit is lower on the DNA/Au/GR/CILE than on DNA/GR/CILE, which maybe attribute to the useage of Au nanoparticles with signal amplification effect. These two modified electrodes display excellent selectivity and good stability and can be further used to detect DA content in the real drug samples.3. The graphene (GR) film modified carbon ionic liquid electrode (CILE) was fabricated by directly electroreduction in a graphene oxide colloidal solution by one-step potentiostatic electrodeposition. Then the nanogold was electrodeposited on the surface of GR/CILE to get a modified electrode as Au/GR/CILE. The electrode was further characterized by different methods including electrochemical impedance spectroscopy, cyclic voltammetry and scanning electron microscope(SEM). The results showed better electrochemical performances compared with CILE. The modified electrode was further applied to the determination of folic acid and y-L-glutamyl-cysteinyl-glycine (GSH) with satisfactory results.