Preparation Of Graphene Composite Film Modified Electrode And Its Application

Single layered graphene, emerging as a true two-dimensional nanomaterial, has tremendous potential for electrochemical catalysis and biosensing as a novel electrode material. In general, graphene has a large surface area, excellent conductivity, and strong mechanical strength. The functionalized and defective graphene sheets are more hydrophilic and can be easily dispersed in solvents with long-term stability. Moreover, they are more easily produced in mass quantities as compared with the carbon nanotubes. In this work, we give a general view of recent advances in electrochemical sensors based on graphene.The primary research work is as follows:1. Electrochemical reduction of oriented graphene oxide-nafion films and its application in determination of dopamineGraphene oxide (GO)-Nafion is assembled on a glassy carbon electrode (GCE). Subsequently, it is shown that the GO can be reduced electrochemical ly by scanning the potential from -1.2 to 1.0 V vs the Ag/AgCl electrode in PBS (pH=7.0). The GO-Nafion and reduced graphene oxide (rGO)-Nafion are characterized by Raman spectroscopy and scanning electron microscopy (SEM). The electrochemical method of reducing GO-Nafion may open up another way of controlling the reduction of GO and the extent of reduction to obtain highly conducting graphene on electrode materials. The electrochemical behavior of dopamine on the electrochemical reduction of Graphene oxide (rGO) and Nafion composite film modified glassy carbon electrode was investigated by differential pulse voltammetry (DPV) with a linear range from 0.8μM to 40μM. The results indicated that this new electrochemical sensor exhibited an excellent electrochemistry activity towards the oxidation of dopamine. The detection limits for DA was 74 nM. With good selectivity and sensitivity, the method has been applied to determination of DA in DA hydrochloride injection solution with satisfactory results. 2. A glassy carbon electrode modified with graphene and poly(acridine red) for sensing uric acidThe surface of a glassy carbon electrode (GCE) was modified by electropolymerization of acridine red onto its surface and then covering it with graphene dropped. The morphology was characterized by scanning electron microscopy. Uric acid (UA) is effectively adsorbed on the surface of the modified electrode and generates a sensitive anodic peak in solutions of pH 6.5. Differential pulse voltammetry was used to evaluate the electrochemical response of the modified GCE to UA. Compared to the bare GCE, the GCE modified with acridine red, and to the graphene modified electrode, the new GCE displays high electrochemical activity in giving an oxidation peak current that is proportional to the concentration of UA in the range from 0.8 to 150μM, with a detection limit of 0.3μM (at an S/N of 3). The modified electrode displays excellent selectivity, sensitivity, and a wide linear range. It has been applied to the determination of UA in real samples with satisfactory results.3. Simultaneous determination of dopamine and serotonin using graphene/poly(p-aminobenzene sulfonic acid) film-coated glassy carbon electrodeA promising electrochemical biosensor was developed by dropping graphene on the surface of glassy carbon electrode electropolymerized with poly(p-aminobenzene sulfonic acid) film. The graphene/poly(p-aminobenzene sulfonic acid) composite was used to determine dopamine (DA) and serotonin (5-HT), exhibiting stable and sensitive current responses toward DA and 5-HT oxidation. The linear response was obtained in the range of 0.3 to 15.0μM with a detection limit of 9.0×10-8 M for DA, and in the range of 0.8 to 15.0μM with a detection limit of 6.4×10-7 M for 5-HT (s/n = 3), respectively. The oxidation of DA and 5-HT were controlled by the adsorption surface process, as well as the competitive adsorption between DA and 5-HT were investigated at the graphene/poly(p-aminobenzene sulfonic acid)/glassy carbon electrode. The designed sensor had been successfully applied for the determination of DA and 5-HT in DA hydrochloride injection solution and obtained satisfactory results.4. Electrophoretic deposition of Ni/graphene oxide nanocomposite and its application for catalytic oxidation of ethanol in alkaline solutionNanocomposite films of nickel nanoparticle-deposited expandable graphene oxide sheet (Ni/GO) are fabricated directly by electrophoretic deposition (EPD) method. The microstructure and morphology of the prepared film samples are characterized by scanning electron microscope (SEM). At the same time, the catalytic activity and stability of the Ni/GO film for the oxidation of methanol are evaluated through cyclic voltammetry and chronoamperometry tests. A linear dependence of response current vs. ethanol concentration with a detection limit of 0.58 nM was obtained. The as-synthesized Ni/GO nanocomposite exhibits high catalytic activity and good stability for the oxidation of methanol, which may be attributed to its high specific surface area of the graphene oxide catalyst support.