Fabrication Of Electrochemical Sensor And Immunosensor Based On Functionalized Graphene

Different methods have been used to improve the solvency of GR by functionalization or electrodeposition to prepare GR modified electrode. The main contents can be summarized as follows:1. The gold nanoparticles appear to adhere to GR that act as spacers to inhibit aggregation of GR sheets. The obtained GR/Au nanocomposites modified glassy carbon electrode exhibited high sensitivity in the detection of epinephrine (EP). It has been found that oxidation of EP at this modified electrode occurred at less positive potentials than on bare GCE. The anodic peak current observed were directly proportional to EP concentration between the range of5.0×10--8.0×10mol L-1(LOD=7.0×10-9mol L-1). At the same time, this electrode also showed favorable electrocatalytic activity toward some other small biomolecules (such as dopamine, β-nicotinamide adenine dinucleotide, uric acid et al.), suggesting the potential applications of GR/Au nanocomposites for constructing biosensors.2. A solution-based method was used to prepare GR/Au nanocomposites via a chemical co-reduction. The obtained GR/Au nanocomposites were easily dispersed homogeneously into N,N-dimethylformamide (DMF) in the presence of ionic liquids (ILs)1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]). First, GR/Au/ILs composites modified electrode (GR/Au/ILs/GCE) was fabricated. Second, thionine (Thi) was chemisorbed onto GR/Au/ILs films through the electrostatic force with the nano-Au. Then the result electrode was applied for the sensitive determination of hydrogen peroxide (H2O2). The results indicated that presence of ILs not only disperse the GR/Au nanocomposites but also increase the sensitivity for H2O2. The sensor displayed a linear range range from4.0×-6to2.9×10-3mol L-1. The detection limit was4.3×10-7mol L-1(S/N=3).3. A simple and rapid electrochemical method was developed for the determination of theophylline (TP), based on the excellent properties of ED-GO film. The result indicated that ED-GO film modified GCE exhibited efficiently electrocatalytic oxidation for TP with relatively high sensitivity and stability. The electrochemical behavior of TP at ED-GO/GCE was investigated in detail. Under the optimized conditions, the oxidation peak current was proportional to TP concentration in the range of8.0×10-7to6.0×10-5mol L-1with the detection limit of6.0×10-7mol L-1(S/N=3). The proposed method was successfully applied to green tea samples with satisfactory results.4. The fuctionalized graphene with poly(diallyldimethylammonium chloride)(PDDA-GR) was modifed on the glassy carbon electrode, which can increase the surface area to combine more negtive-charged prepared silica nanoparticles. Nano-gold was coated on silica nanoparticles through thionine linking, which was used to immobilize antibodies. Interlayer thionine was not only a bridging but also an excellent electron mediator. The proposed immunosensor exhibited simple fabrication, good reproducibility and a broad linear range.