Studies On The Electrochemical Sensor Based On The Graphene-graphene Oxide

Graphene is a two-dimensional nanomaterial with an atomically thick honeycomblattice and it is a rapidly rising star of carbon nanomaterial after the discoveries offullerenes and carbonnanotube. Graphene has attracted great interest in the field ofmaterials in the past several years because of its unusual mechanical, electronic andquantum properties. However, the applications of graphene have been greatlyhindered by its poor solubilities, because graphene with integrity structure has highchemical stability, and its strong tendency to form aggregates because of the strong?-? stacking interactions between graphene nanosheets. Thus, improving watersolubility and biocompatibility of graphene is very important to the directelectrochemistry of proteins, the detection of environmental pollutants and thedevelopment of electrochemical sensors. Graphene oxide, the product of chemicalexfoliation of graphite, is essentially a graphene sheet derivatized by some oxygenfunctionalities, such as phenol hydroxyl, epoxide groups, ketonic and carboxylicfunctional groups, and should be viewed as an amphiphile with a largelyhydrophobic basal plane and hydrophilic edges. Graphene oxide can act as asurfactant sheet to disperse graphite and carbon nanotubes in water.In this study, a novel graphene-graphene oxide (GR-GO) nanocomposite wasfabricated by using the strong ?-? stacking interactions between graphene andgraphene oxide nanosheets with the help of ultrasonication. The application ofGR-GO nanocomposite in electrochemical sensors was investigated. The maincontents were summarized as follows:1. Simultaneous determination of dihydroxybenzene isomers based on graphene-graphene oxide nanocomposite modified glassy carbon electrodeGraphene-graphene oxide (GR-GO) nanocomposite was fabricated by mixinggraphene and graphene oxide together with the help of ultrasonication. The preparedmaterial was characterized by the scanning electron microscopy, transmission electronmicroscopy, Raman spectroscopy and electrochemical impedance spectra. The resultsindicated that graphene-graphene oxide nanocomposite has good conductivity, largesurface area and could be dispersed well in water. Then the nanocomposite was usedto fabricate a sensitive dihydroxybenzene isomers sensor and the simultaneous determination of dihydroxybenzene isomers based on graphene-graphene oxidenanocomposite modified glassy carbon electrode was achieved owing to the goodconductivity and large surface area of graphene-graphene oxide. Under the optimalconditions, the oxidation peak currents of hydroquinone (HQ) and catechol (CC) werelinear over the range of0.5–300?M with the detection limits of0.16?M (S/N=3)for HQ and0.2?M for CC, respectively. In addition, the GR-GO modified electrodeshowed excellent stability, reproducibility and anti-interference ability.2. Direct electrochemistry and of glucose oxidase based on graphene-graphene oxidenanocomposite and glucose determinationOn the basis of the last work, we found that GR-GO with oxygen functionalities onsurface is much helpful for cross-linking and/or entrapping the glucose oxidase(GOD). Herein, GOD was immobilized onto the surface of GR-GO without any fixingmaterials and the electrochemical method was used to characterize it. A pair ofwell-defined redox peaks was observed at the GOD/GR-GO/GCE in the potentialrange form0.7to0.1V, indicating that GOD assembled on GR-GO retained itsnative structure and bioactivity and underwent effective direct electron transfer (DET)reaction. The voltammetric results indicated that the direct electrochemistry of GODwas a two proton and two electron transfer electrochemical process. Under theoptimal conditions, a wider linearity range from0.1mM to11mM with a detectionlimit of20?M was achieved. The proposed method will potentially be applied to thethird generation of glucose biosensor.