Preparation Of Functionalized Graphene Modified Electrode And Its Application For Biosensing

Recently, graphene has been a research hotspot because of its unique two-dimensionalstructure and advantages. The functionalization of graphene to prepare grphene-basednanocomposite can extend the potential application of graphene and the electrochemicalproperties of graphene can be improved because of the synergy effect of differentconstituents. Graphene nonacomposites has been used in direct electrochemical reseachand preparation of the third-generation electrochemical biosensors, which showedexcellent sensitivity and good selectivity towards the detection of glucose, DNA, H2O2,dopamine and other small biomolecules.Biosensor has been widely used in many fields because of its high sensitivity,excellent selectivity, fast response, low cost and easy manipulation. The introduction ofgraphene nanocomposite into the electrochemical biosensor can improve its properties,which have been widely used in environmental monitoring, life science, food productionand pharmacy industries.In this study, the functionalization of graphene was investigated systematically, andthe graphene nanocomposite modified electrodes were prepared and applied in biosensingfor some small molecules. The details of my work as follows:1. Preparation of PDDA functionalized graphene modified electrode and itsapplication for uric acid sensingIn this work, graphite oxide was synthesized chemically by Hummers method andreduced by hydrazine hydrate to synthesize graphene (G) functionalized with PDDA(PDDA-G). The characterizations of the PDDA-G were performed by UV-vis absorptionspectra, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fouriertransform-infrared (FTIR) spectra. The experimental results showed that the compositematerial was successfully synthesized and the prepared PDDA functionalized graphene hadgood flake-like shapes. The modified glassy electrode based on PDDA-G composite filmwas prepared (PDDA-G/GCE), and the electrochemical behaviors of uric acid at this modified electrode were studied by cyclic voltammetry (CV). The result suggested that themodified electrode had the better electrochemical response to uric acid (UA) oxidationthan that at the the bare glassy carbon electrode. The PDDA-G/GCE showed sensitiveresponse to UA oxidation with a wide linear range of0.1-60μM, and the detection limitwas to be0.03μM (S/N=3). The modified electrode could eliminate the interference ofascorbic acid (AA) and could be used as UA sensor for its fast detection.2. Preparation and application of a sensitive enzymeless sensor for hydrogen peroxidebased on poly(sodium4-styrenesulfonate-graphene modified electrodeIn this work, poly (sodium4-styrenesulfonate) functionalized graphene (PSS-G) wassynthesized via π-π interaction. Characterization was performed by TEM, FTIR andUV-vis. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) wereused to characterize the performance of the PSS-G modified electrode. The resultsindicated that the modified electrode had good electrocatalytic ablitily toward hydrogenperoxide (H2O2), which could be used as a enzymeless sensor for H2O2. The result alsosuggested that, at an applied potential of-0.7V, the sensor had a sensitive response to thereduction of H2O2with a wide linear range of10μM-21.88mM, and the detection limitwas to be3.0μM (S/N=3).3. Preparation and application of sensitive enzymeless sensor for hydrogen peroxidebased on Prussian blue/PDDA-graphene modified electrodA novel, sensitive and enzymeless electrochemical sensor based on Prussian blue/poly(diallyldimethylammonium chloride) functionalized graphene composite film wasfabricated for the detection of hydrogen peroxide. Graphite oxide was synthesizedchemically by Hummers method and then was reduced by hydrazine hydrate in thepresence of PDDA. Prussian blue (PB) was deposited on PDDA-G matrix byelectrochemical method. With the synergistic effect of PDDA-G and PB, the PB/PDDA-Gcomposite film modified electrode (PB/PDDA-G/GCE) shows good electrocatalyticablitily toward the reduction of H2O2, at an applied potential of-0.3V, which can be usedas an H2O2enzymeless sensor. The sensor showed good response to the reduction of H2O2in a wide linear range of3.0-2061μM, and the detection limit was1.0μM (S/N=3). This sensor will be promising for the fast detection of H2O2in real sample.4. Preparation of PEI-G composite film modified electrode and its application fordetection of8-hydroxy-2’-deoxyguanosineIn this work, polyethyleneimine (PEI) functionalized graphene (PEI-G) compositeswere prepared through covalently functionalizing graphene (G) with PEI. Thecharacterizations of the PEI-G composite were performed by TEM, FTIR, UV–visabsorption spectra and XRD. Cyclic voltammetry was used to study the electrochemicalperformance of8-hydroxy-2′-deoxyguanosine (8-OH-dG) at the PEI-G modified eletrode.The experimental results indicated that graphene was well dispersed and the composite wassuccessfully synthesized. This PEI-G modified eletrode exhibited a good current responseof8-OH-dG and could effectively diminish the interference of uric acid. In0.1M pH8.0PBS, the oxidation peak current of8-OH-dG was linear with its concentration in the rangeof7×10-9-7.56×10-7M and7.56×10-7-3.556×10-6M with the detection limit of2.3nM(S/N=3). The standard addition recovery of healthy people’s urine was also studied withsatisfactory results. Furthermore, the modified electrode had good reproducibility andstability and could be used for the determination of8-OH-dG in the real sample.