The Application Research Of Graphene Modified Electrodes In The Glucose Bisensor

The aim of the present work is to study the activity of glucose oxidase in graphene (GN) and muti-wall carbon nantubes (MWCNTs) modified on glass carbon electrode, and to establish highliy sensitivity the glucose biosensor based the direct electron transfer of the glucose enzyme for the detection of glucose. Research work in this thesis is financially supported by the National Natural Science Foundation of China (No.21005003). This paper consists of three chapters:Chapter 1 is general introduction. In this paper, the principle of the glucose sensor, the methods of enzyme immobilization, and the synthetic method of GN and MWCNTs was simply introduced. The recent development of nanomaterial in electrochemical glucose biosensor was mainly reviewed. Finally, the purpose and main content of this research work were simply presented.Chapter 2 Construction of the glucose biosensor based of the direct electron transfer of the glucose oxidase using the GN modified on glass carbon electrode. GN was prepared by chemical reduction method using graphite oxide obtained by modified Hummers method. The chemical composition, crystalline structure and morphology of GN were studied by all kinds of methods. The electrochemical behavior, H2O2 å'Œ O2, two signal moledcules of the electrochemical glucose biosensor, was studied on surface of the graphene modified on electrode. Studies have shown that the GN obtained have good electrochemical properties, and can be used to build a good performance glucose bisensor. The high sensitive glucose biosensor was fabricated by immobilized glucose oxidase onto the surface of the GN modified the glass carbon electrode. The reduction peak current using cyclic voltammetry (CV) is decreased with the increase of glucose concentration and the linear range was 0.5-7.0 mM for glucose with a detection limit of 0.38 mM (S/N=3), and the detection sensitivity is 49.6μA mM-1 cm-2. The fabricated glucose biosensor shows a high sensitivity, good selectivity, satisfactory stability and reproducibility. The glucose biosensor has been applied to determination of glucose in human serum sample with a satisfactory result.Chapter 3 The research of activity of glucose oxidase on the surfaces of GN and MWCNTs. By comparing the electrochemical behaviors of glucose oxidase and glucose bisensor in nitrogen, air and oxygen saturated PBS, the activity of glucose oxidase on the surfaces of GN and MWCNTs was preliminary studied. This wok demonstrates two questions. Firstly, the direct electron transfer of the glucose enzyme is only affected by FAD, and has no relationship with the activity of glucose enzyme. Secondly, the glucose enzyme of the direct contanct with GN and GN-SWCNTs may be killed by GN and GN-SWCNTs. But for the glucose enzyme of the away from GN and GN-SWCNTs, the activity of the enzyme is kept. So, the glucose biosensor has the reponse to its substrate glucose because the active glucose enzyme can finish the direct electron transfer of enzyme due to the oxygen entry. Because of the limitation of experimental conditions and theoretical knowledge, the conjecture and hypothesis of the chapter are obtained by the electrochemical method, and shouled be proved by other methods to obtained more credible proof.