Studies On The Application Of Graphene In Electrochemical Glucose Sensors And Supercapacitors

In this thesis, the main research is concentrate upon graphene which is a newtwo-dimensional sheet of sp2-bonded carbon material. This paper includes two parts:one-step synthesis of Pd/graphene nanocomposites for the application inNonenzymatic amperometric glucose biosensors; Carbonaceous debris contained ingraphene oxide/graphene greatly impact on their electrochemical capacitances.Detailed contents are as follows:(1) The Pd nanoparticle (PdNPs)–graphene (GR) nanocomposite weresynthesized using a facile one step reduction of graphene oxide (GO) prepared bymodified Hummers method and PdCl2. Such a PdNPs–GR nanocomposite can be usedfor the electrocatalytic oxidation of glucose in alkaline medium. GO possess so manyabundant surface oxygenic functional groups which is benefit for the binding of noblemetal ions. When reduction with hydrazine, it is easy to nucleation, not only canprevent agglomeration of GR but also critical for the formation of small particle sizeof PdNPs. This PdNPs/GR/GCE electrode shows good electrochemical performancefor the detection of glucose, such as short response time (4s), low detection limit of9M, wide linear range which up to5.8mM and good testing stability.(2) Rourke et al. have demonstrated that the graphene oxide (GO), as preparedby the modified Hummers method, is composed of functionalized graphene sheetsdecorated by carbonaceous debris. The debris can strongly adhere to the surface ofgraphene sheets via noncovalently and hydrogen bonds. But this interaction becomesrepulsive under basic conditions because of the negative charge on the deprotonateddebris thus easy to be eliminated. We demonstrated that the carbonaceous debris alsopresent in grapheme (GR) and exhibit significant different influence on theelectrochemical capacitances of GO and GR. In this paper, a systematic comparativestudy of materials with the absence and presence of debris, such as graphene oxide(GO), electrochemically reduced graphene oxide (EGR) and chemically reducedgrapheme oxide (CGR) is presented. The specific capacitance of GO significantlyincreased after the removal of debris probably due to the restoration of theconjugated π network and thus enhances the electronic conductivity. However,the removal of debris might reduce the wettabilities of the GR and increase therisk of restacking of graphene sheets so that reduce the surface area of graphene thusdecrease the specific capacitance of GR.