Application Of Nitrogen - Doped Graphene - Gold Nanoparticle Composites In Electrochemical DNA Sensor

As a unique two-dimensional (2D) monolayer carbon material consisted of sp2 carbon atoms, graphene showed varieties of exceptional performances compared with other traditional carbon materials, such as high conductivity, good biocompatibility, large specific surface area and other excellent properties. However, as the unique zero bandgap energy properties of graphene, it restrictedits use in some fields. Graphene can be modified and changed the properties to expand its applications in relevant fields. DNA testing play an important role in the fields of gene sequencing, clinical diagnostics, environmental monitoring, bio-pharmaceuticals and protein research, owing to the high sensitivity and good selectivity of the DNA biosensors, they have already used to detect DNA sequences, which causing the researchers’attentions. Gold nanoparticles (AuNPs) has good biocompatibility, high conductivity and have the capable of self-assembly with DNA, so theyhas been widely used in the biosensorand electrochemical analysis fields.In this paper, GO was prepared using a modified Hummers’ method and nitrogen-doped graphene (N-G) was synthesized using (NH4)2CO3 as nitrogen source by co-reduction and doping. The difference of nitrogen content of the doped graphene at different conditions were discussed to get the optimal conditions of prepared nitrogen-doped graphene.At the same time, the synthesized nitrogen doped graphene as supporting materials of AuNPsto prepared hybrid nano-composites nitrogen-doped graphene supported gold nanoparticles (Au/N-G) by the reduction of HAuCl4 using sodium citrate as the reducing agent via microwave irradiation.Themorphology of the nano-composites measured with various techniques such as TEM, XRD, EDX, Element mappingand XPS indicated that AuNPs were effectively loaded on the surface of N-G.The cyclic voltammetry(CV) andelectrochemical impedance spectroscopy (EIS) analysis suggested that Au/N-G was an excellent electrode material, which possessing outstanding electrochemical features for electron transfer.Next, the Au/N-G was modified onto glassy carbon electrode, then a certain sequence probes ssDNA was fixed on the electrode surface according to the principle of self-assembled, and the electrochemical properties of the DNA biosensor were studied. The methylene blue was used as indicator, the electrochemical properties of the different chemically modified electrodes were disscussed using electrochemical methods, we discuss changes in the electrode surface electrochemical properties of different stages of modification, and assembly time for the effect of different concentrations of different indicators of electrochemical sensors were discussed, we tested the selectivity and detection limit of the electrochemical DNA sensors in the preferred assembly conditions.