Fabrication And Application Of Electrochemical Sensors Based On Graphene Nanocomposite Materials

Graphene is a two-dimensional nanomaterial composed of a single layer of carbon atoms with special structure,which has a variety of excellent performance,and has become a hot topic with greatly attention in the current research,such as electronic,catalytic,battery,chemistry and biosnesor.However,GR reunion and stack occur easily,three-dimensional graphene(3DGR)not only overcome this phenomenon,itself also has the unique porous structure,while maintaining the inherent properties of graphene piece,all sorts of 3D graphene application performance is also improved.In recent years 3D graphene composites has attracted a lot of attention,because of its synergistic effect that make two comprehensive performance is better than that of the original composition of composite material meet the requirements of different,these features make 3D graphene composites are applied in the construction of the sensor.Electrochemical biosensors are devices that can identify the specific target material based on biological molecules as the main functional components and according to certain rules to convert this perception.A modified electrode is the current research focus that often used as a transducer in chemical and biological sensor.In this paper different nanomaterial are used as modifiers with graphene to fabricate four kinds of composite materials and a kind of carbon nanomaterial,further used for the preparation of modified electrodes and immobilization of biological activity material on the electrode that investigated in details and the thesis can be summarized as follows:1.A nanocomposite composed of graphene(GR)and zinc oxide(ZnO)nanorods was synthesized by a hydrothermal method,which has excellent properties of high conductivity,large specific surface area and excellent biocompatibility that attribute to the synergistic effect of GR and ZnO.Then myoglobin(Mb)was immobilized on the electrode surface with as chitosan the film forming material.Spectroscopic results confirmed that Mb retained its native structure within the composite.Cyclic voltammetric investigation of CTS/Mb/GR-ZnO/CILE in pH 3.0 buffer solutionindicated that direct electron transfer of Mb in the composite with the CILE was realized with a pair of quasi-reversible redox waves appeared.A kind of the third generation electrochemical biosensor was fabricated with CTS/Mb/GR-ZnO/CILE used as working electrode,which was applicated to the detection of trichloroacetic acid(TCA).The fabricated biosensor displayed the advantages such as high sensitivity,good reproducibility and long-term stability.2.An electrochemical biosensor was fabricated by using myoglobin(Mb)and single-walled carbon nanohorns(SWCNHs)modified carbon ionic liquid electrode(CILE).By using chitosan(CTS)as the film forming material,the modified electrode was constructed and demonstrated as CTS/Mb/SWCNHs/CILE.Spectroscopic results indicated that Mb remained its secondary structure within the composite.The modified electrode exhibited excellent electrocatalytic behaviors to the reduction of different substrates including TCA and NaNO2.The result indicated that the catalytic reduction peak current of tricholoacetric acid(TCA)increased linearly with the tricholoacetric acid(TCA)concentration from 0.9 to 51.0 mmol/L;the catalytic reduction peak currents of sodium nitrite(NaNO2)were in proportional to the concentration in range of 0.04 to 0.74 mmol/L.3.A nanocomposite of three-dimensional graphene(3DGR)and dendritic gold(Au)was obtained by electrochemical deposition,which was modified on the surface of carbon ionic liquid electrode(CILE)and further mercaptoacetic acid(MAA)was self-assembled on the surface of Au/3DGR/CILE.It was used for the immobilization of probe ssDNA this fabricated biosensor was used to the detection of PCR amplification sample of Listeria monocytogenes hly gene sequence.The presence of wrinkled 3DGR on the electrode surface mightbe benefit to the formation of the special dendritic structure nanogold,which could supply more sites for the immobilization of DNA sequence on the electrode surface.Under the optimal conditions the specific Listeria monocytogenes hly gene sequence could be detected in the linear concentration range from 1.0×10-14 to 1.0×10-6 mol/L with the detection limit as 3.3×10-15 mol/L(3?).Furthermore,this biosensor was used to the detection of PCR amplification sample of Listeria monocytogenes that extracted from deterioratedfish.4.A kind of electrochemical DNA biosensor was preparation based on gold nanoparticles(Au)and thiol graphene(TGR)nanocomposites modified ionic liquid carbon electrode for sensitive detection of specific nuc gene of Staphylococcus aureus and this biosensor was used to the detection of PCR amplification sample of Staphylococcus aureus.The electrochemical behavious of different modified electrodes were studied by using cyclic voltammograms and electrochemical impedance electrochemical technique,showed that the presence of Au and TGR increases the effective area of electrode,thus increasing the probe sequence in the load on the electrode.Based on the method of differential pulse voltammetric,indicated that the constructed electrochemical DNA biosensor has good selectivity,sensitivity,wide detection range and low detection limit.5.A nanocomposite composed of platinum(Pt)gold(Au)and three-dimensional graphene(3DGR)was synthesized by a hydrothermal method,which was modified on the surface of carbon ionic liquid electrode(CILE)as film forming material and used for the immobilization of probe ssDNA.Scanning electron microscope technology showed the morphology of film forming material,further the electrochemical characterization of the modified electrodes were tested by using cyclic voltammetry technique.Differential pulse voltammetric results showed that linear concentration of target gene sequence was achieved from 1.0×10-13 mol/L to 1.0×10-6 mol/L with the detection limit as 2.9×10-14 mol/L.Experimental results showed that Pt-Au-3DGR has good electrical conductivity,and can increase the effective area of electrode,which could act as a platform for the loading of more probe ssDNA could be further fixed on the surface of modified electrode.The proposed electrochemical DNA sensor could be used to identify the target ssDNA sequence with good selectivity,stability and reproducibility,low detection limit and wide detection range.