The Applications Of Graphene And Graphene Composite Materials In Biological Electrochemical Sensing

Graphene (GE) has elusive two-dimensional structure and possesses high mechanicalcapacity, perfect electrical properties and selectivity. Graphene and its derivatives haveattracted interests of chemistry scientists since single-layer graphene is striped first time in2004. Dopamine (DA), ascorbic acid (AA) and uric acid (UA) are requisite biologicalcomponent in human life and play important roles in the life activities. Abnormal levels ofthem are symptoms of several diseases such as Parkinson’s disease and hyperuricaemia etal. Therefore, it is of utmost importance to detect these species with desired sensitivity andaccuracy. Electrochemical techniques currently appear to be suitable for the determinationof these species due to its high sensitivity, easily operable, cost effective and fast response.In our experiment, graphene and its composite materials are used to modify electrodes, andthen used to detect UA, AA and DA. The main contents of this thesis are as follows：(1) A facile and cost effective approach has been developed towards electrochemicalfabrication of graphene-modified carbon fiber electrode (GE/CFE) to determine the contentof UA and the oxidation graphene is reduced by electrochemical method. According toSEM images, CFE is uniformly and wholly wrapped by GE layers. The advantages of thusobtained GE/CFE for UA detection are supported by its higher peak current intensity andlower oxidation potential compared with those of bare glassy carbon electrode (GCE), barecarbon fiber electrode (CFE), and graphene-modified glassy carbon electrode (GE/GCE).The combined merits of GE and CFE endow the modified electrode with large specificsurface area, high electrical conductivity and increased electron transfer rate. Thisexperiment provides a feasible way for the development of new type and environmentalprotection material biological molecules.(2) A novel layer-by-layer assembly of graphene sheets and gold nanoparticlesmodified carbon fiber electrode (GE/Au/GE/CFE) is successfully fabricated and applied to simultaneous determination of DA and UA. The structure of GE/Au/GE/CFE ischaracterized by scanning electron microscope (SEM). It is observed that goldnanoparticles are homogeneously assembled between two layers of GE sheets.GE/Au/GE/CFE has higher electrocatalytic activity for the oxidation of DA and UA andpossesses two well-defined and fully resolved anodic oxidation peaks when compared withgraphene modified carbon fiber electrode (GE/CFE) and graphene and gold nanoparticlesmodified carbon fiber electrode (Au/GE/CFE). Moreover, the composite electrode displayshigh reproducibility and selectivity for the determination of UA and DA.(3) A novel and sensitive carbon fiber electrode (CFE) modified by graphene flowers,a new3D graphene structure, is prepared and used to simultaneously determine AA, DAand UA. SEM images show that beautiful and layer–petals graphene flowershomogeneously bloom on the surface of CFE. Moreover, It can be believed that thegraphene flowers and ripples of graphene increase the surface area of electrode, electrontransfer and electrode response. In addition, the obtained electrode shows satisfactoryresults when applied to the determination of AA, DA and UA in urine and serum samples.This work may provide a valuable clue for the use of graphene to detect electroactivebiomolecules.