DNA Immobilization/Hybridization On Plasma Graphene-based Composites

As a kind of two-dimensional carbon material, graphene has been widely research andapplication in sensors and biotechnology. The graphene surface modified, functional groups,such as amino, hydroxyl, carboxyl groups can enhance its biocompatibility. In this study, theself-assembling approach and plasma polymerization method were used to modify thegraphene surface, and formed amino functional graphene (G-NH2) and nanocomposites ofgraphene and plasma polymerization. On the basis of the understranding on its chemical,surface and electrochemical performances, the application of the resultant nanomaterials assensitive layer for DNAbiosensors were systemly investivated.Firstly, the self-assembling approach was used to prepare G-NH2nanosheets viamodifying its surface by amino groups. Additionally, plasma polymerization process wasapplied to synthetize graphene/polyallylamine (G-PPAA) and graphene/poly propargylamine(G-PpPG). The chemical structures and surface morphologies of the as-preparedgraphene-based nanocomposites were characterized by Fourier Transform InfraredSpectrometer, X-ray photoelectron spectroscopy and Atomic force microscopy, respectively.It shown that G-NH2surface is smooth, in which the amino group content is relative high. Forgraphene-based nanocomposites, their surface appeared to be rough; the amino group contentof graphene-based nanocomposites deposited at the low plasma input power was higher.Their electrochemical properties were investigated by electrochemical impedancespectroscopy. It demonstrated that the electrochemical properties of G-NH2do not reduceobviously. For graphene-based nanocomposites, their electrochemical properties werereduced with the plasma input power.Based on the understanding of basic properties of G-NH2and graphene-basednanocomposites, electrochemical workstation and Quartz crystal microbalances (QCM) wereused to investigate the electrochemical behavior and dynamics behavior of single-strandedDNA immobilized onto their suirface. The results shown the electrochemical change of theDNA immobilization/hybridization processes, and received the detection limit of the targetDNA, it is0.8nM.Finally, graphene-based nanocomposites were used as biosensors for Hg2+detection. In which, two test methods were applied. For G-PPAA nanocomposites, single-stranded DNAwas immobilized following by the hybridization of targrt DNA in the environment of Hg2+,where T-Hg2+-T base pairs were form by coordinative interaction between Hg2+and thymine.The detection of Hg2+was analysis by Quartz crystal microbalances and Differential PulseVoltammetry, and achieved different detection limit, the detection limits are1.0nM and0.07nM, respectively. In case of G-PpPG, it was used as sensitive membrane for single-strandedDNA immobilization, which the single-stranded DNA contains thymine, so thesingle-stranded DNA can hybridize to double-stranded DNA by itself in the environment ofmercury ions. Electrochemical differential pulse voltammetry was used to measure thedetection limit of Hg2+, and the detection limit is0.02nM. The thesis supplys aminofunctionalized graphene could be used as a candicate material for biosensors.