Application Of Graphene Composite Materials In Electrochemical Biosensor

Electrochemical biosensor is a kind of biosensor which combines the electrochemical sensor with the specific identification of biological molecules. Nanomaterials have special effects such as surface effect, volume effect, quantum size effect and macroscopic quantum tunneling effect. Graphene has a larger specific surface area and higher conductivity. Because of the synergy between the two kinds of substances, it is widely used in the filed of electrochemical biosensors to make up the deficiency of single material in practical application. The main content of this paper includes the following parts:1. Graphene（GR） and bismuth（Bi） film were directly electrodeposited on carbon ionic liquid electrode（CILE） surface. Myoglobin（Mb） was fixed on the Bi/GR/CILE surface with a thin Nafion membrane to get a Nafion/Mb/Bi/GR/CILE. Cyclic voltammetric results showed that a couple of well-defined redox peaks was present on the voltammograms, exhibiting the achievement of direct electron transfer of Mb on the electrode. This Mb modified electrode reveals fine electrocatalytic activity to the reduction and detection of trichloroacetic acid（TCA） in the linear range from 0.50 to 46.0 mmol/L with the detection limit of 0.167 mmol/L（3σ）.2. A three-dimensional graphene（3D GR） was directly electrodeposited on the surface of carbon ionic liquid electrode（CILE） and further modified by electrodeposited zinc oxide（ZnO） to get a ZnO@3D GR hybrid composite. Then Mb was immobilized on the surface of composite modified electrode with a Nafion film to get the biosensor named as Nafion/Mb/ZnO@3D GR/CILE. On cyclic voltammetric a pair of well-defined redox peaks appeared, indicating the realization of direct electron transfer of Mb with the underlying electrode. The modified electrode displayed good electrocatalytic activity to the reduction of trichloroacetic acid（TCA）, and the catalytic reduction peak current had a good linear relationship to TCA concentration in the range from 0.50 to 30.0 mmol/L with the detection limit of 0.167 mmol/L（3σ）.3. An electrochemical DNA biosensor was prepared using electroreduced graphene oxide（ERGO）, titanium dioxide（TiO₂） nanowires and chitosan（CS） modified carbon ionic liquid electrode as the substrate electrode. The presence of nanocomposite on the electrode surface can increase the surface area and fix the ssDNA probe sequence by electrostatic attraction. After the hybridization with the target ssDNA sequence under the selected conditions, methylene blue（MB） was used as the electrochemical indicator for monitoring the hybridization reaction. This electrochemical DNA sensor exhibited good ability to discriminate between one-base and three-base mismatched ssDNA sequences, and the polymerase chain reaction amplification product of the tlh gene from oyster samples was further detected with satisfactory results.4. Using three-dimensional graphene（3D GR） modified ionic liquid carbon paste electrode（CILE） as the substrate electrode. The constant potential adsorption in the surface of a fixed probe ssDNA, methylene blue（MB） as indicator to detect hybridization reaction of MB was detected by differential pulse voltammetry（DPV）, and the sequence of nuc gene of staphylococcus aureus was detected quantitatively. The PCR amplification products of the nuc gene of staphylococcus aureus were detected by the electrochemical DNA sensor.