Studies On The Electrochemical Sensor Based On The Graphene Modified Electrodes

In this thesis, great efforts have been devoted to the fabrication of graphene (GP)and functionalized graphene electrodes and their practical application inelectrochemical sensors and electrochemical biosensors. It has two parts: thepreparation of the iodate sensor based on the graphene electrode modified by mediator9,10-phenanthrenequinone (PQ) and its adhibition in determination of iodate in realsamples; the preparation of NADH biosensor utilizing dopamine derived grapheneelectrode.(1) The graphene was prepared by the chemical reduction of graphite oxidewhich was obtained through the modified Hummer`s method. The graphenenanocomposite modified electrode was achieved simply and conveniently by theadsorption of PQ molecules. The raw material (graphite), intermediate product(graphite oxide), end product (graphene) in the process of graphene manufacture andthe nanocomposite were well characterized by X-ray diffraction (XRD), Fouriertransform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Wefully studied the electrochemical behavior and kinetic characteristics of the modifiedelectrode which showed good electrochemical catalytic activity towards the reductionof iodate. The iodate sensor displays high sensitivity (1.04μA μM-1), low detectionlimit (1.0×10~8M), rapid response (less than2s), and broad linear range (from5.0×10~8to6.0×10~3M)，all of them are superior to the similar iodate sensor.(2)The graphite oxide was prepared in the same way as mentioned earlier. Afteractivation of the carboxyl groups on the surface of GO by addition of EDC andsulfo-NHS, dopamine was put in and then firmly covalently bonding to graphite oxide.The expected functionalized graphene electrode was successfully fabricated after theelectrochemical reduction of graphite oxide which was monitored under the cyclicvoltammetry. It appeared that the electrode showed excellent electrocataltyic activitytowards NADH in the presence of other interferences such as uric acid,acetaminophen, and ascorbic acid. The NADH sensor exhibited a wide linear rangewith a lower detection limit as well as a high sensitivity.