Studies On The Electrochemical Behavior Of Small Biomolecules On Graphene Modified Electrodes Containing Various Content Of Oxygen-functional Groups.

(1) In this paper, firstly graphene sheets were successfully stripped out from bulk graphite utilizing modified Hummers method, and their morphology were observed by SEM. Graphene prepared here contained large amounts of oxygen-containing functional groups (C=O, C-O-C,-OH and -COOH etc.) without further treatment by reducing atmosphere. For the restoration of the special two-dimensional hexagonal crystal structure of graphene to obtain its excellent electrical and electrochemical properties, at first graphene oxide solution was dropped on the surface of pre-treated glassy carbon electrode so as to acquire graphene oxide modified electrode, and then the modified electrode was electrochemically reduced by introducing cyclic voltammetry technology in an acidic phosphate buffer solution. By controlling the negative switching potential and reduction time of cyclic voltammetry, graphene oxide modified electrodes of different reduction degree were obtained.(2) Then three kinds of electroactive molecules,Fe(CN)63-/Fe(CN)64-, AA, DA and UA, were utilized as probes to study their electrochemical behavior of the modified electrode. The results indicated that the difference of graphene oxide reduction degree directly influenced the type and quantity of oxygen-containing groups on graphene oxide, consequently it had a significant impact on electrochemical behavior of Fe(CN)63-/Fe(CN)64-, AA, DA and UA, mainly presented as the peak potential and peak current changes in cyclic voltammetry and differential pulse voltammetry curves. Then we further carefully observed the relation between the peak potential and peak current of AA and DA in differential pulse voltammetry and the reduction degree of graphene oxide, and found out that various oxygen-containing functional groups in graphene oxide played different roles in the electron transfer between AA or DA and the electrode surface:C-O-C,-OH and-COOH on the edge of graphene oxide were very likely to be the catalytic active sites of AA and DA oxidation and reduced their electron transfer active energy to some extent; on the contrary C=O on the basic plane seriously hindered their electrode reaction.(3) Finally, to have an optimum detection response of AA and DA, the best reduction conditions of graphene oxide modified electrodes were explored, and then the current-time response and differential pulse voltammetry methods were utilized to detect AA and DA concentration separately and simultaneously and satisfactory results were obtained.