Fabrication Of Graphene-modified Electrode And Its Analytical Applications

The single-atom thick material graphene is a new type of carbon nanomaterials, which is comprised of a monolayer of carbon atoms packed into a two-dimensional honeycomb lattice. It shows excellent electrical, mechanical and thermodynamic properties. Because of the unique structure and performance, grapheme, as one of the research focuses, draw great attention of investigators. It has been widely applied in many different field, such as nanocomposites, sensors, transparent conductive films, biomedicine. Moreover, the chemically modified electode is an important research direction of electroanalytical chemistry. Graphene-modified electrode also has aroused extensive concern. In this work on the thesis, graphite nanosheets were prepared via a two-step method, including oxidation reduction reaction. Then, the graphene-modified electrode were fabricated by immobilizing graphite nanosheets on the surface of a pretreated glassy carbon electrode. Combing the characteristics of material graphene and analytical techniques, the applications of the modified electode in the field of analytical chemistry were studied.The modified electode developed by immobilizing graphene on the surface of glassy carbon electrode showed excellent electro-catalytic activity for reduction and oxidation of vitamin B12. It can be used for sensitive detection of vitamin B12. A sensitive linear response for vitamin B12was obtained in the concentration range of1.6×10-7-9.5×10-6mol/L, and the detection limit is5.9×10-8mol/L using differential pulse voltammetry. The electrochemical sensor has been applied to determining vitamin B12in tablets, human serum and urine.The modified electrode prepared showed an excellent electrochemical response to adenine. Based on that, a high-sensitivity detection of adenine was established. The electrochemical behavior and detection of adenine was investigated by cyclic voltammetry and differential pulse voltammetry, respectively. Under the optimum conditions, it was found that the peak current was linear with the concentration of adenine between5.O×10-7to1.48×10-5mol/L, the linear regression equation was iP(μA)=0.00139+0.2019c (μmol/L), the correlation coefficient r=0.9986, and the detection limit was9.4×10-8mol/L. The electrochemical sensor has been applied to determining adenine in tablets, human serum and urine. The modified electrode was constructed by casting grapheme-nafion composite on the pretreated glassy carbon electrode surface. A new electroanalytical chemistry system of pyridoxine detection was developed. The electrochemical sensor greatly improves the response to adenine. Under the optimum conditions, there is a linear relationship between the peak current and the pyridoxine concentration in the range of3.5×10-7to1.2×10-5mol/L, the linear regression equation was ip (μA)=0.08315+1.9501c (μmol/L), the correlation coefficient r=0.9989, and the limit of detection was8.2×10-8mol/L. The proposed method has been applied to assay merchandise tablets, human serum and urine satisfactorily.