Enzyme Electrochemical Sensors Based On Composites Of Graphene Research

Amperometric enzyme-based biosensors have received considerable interest due to the convenient manipulation, the high sensitivity, and the high selectivity. It has been widely applied in the determination of H2O2 and glucose, playing an important role in the areas of food determination, medicine and environmental analysis. Immobilization of biological molecules is the key step to fabricate biosensors and is the key factor that may have an effect on the stability, sensitivity and selectivity. On the other hand, the electron transfer between the redox activity center of enzyme and the electrode is the fundament to fabricate enzyme-based biosensors. The electron transfer can be achieved through two different pathways. One involves electron-shuttling mediators to establish an electrical communication between redox proteins and the underlying electrodes. In this scheme, there are still several challenges to keep mediators from diffusing away from the electrode surface into the bulk solution. The other pathway involves direct electron transfer between redox proteins and the electrode. Herein, the method and material used to immobilize biomolecules are the crucial factors. In this paper, we firstly design and prepare a novel graphene/polyaniline composite with high specific area and good biocompatibility. Then the mixture of graphene/PANI and ionic liquids are chosen to modify the carbon-glass electrode. In this way, we have successfully achieved direct electron transfer between redox proteins and the modified electrode. The established directly electrochemical enzyme electrodes have a fine performance. This paper mainly completes the following research.(1) Graphene is obtained by reducing graphene oxide with hydrazine hydrate. And then its composite with polyaniline is prepared via in-suit polymerization. The structure and morphology of the prepared materials were investigated using Fourier transform infrared spectrometer, Raman spectra, transmission electron microscope, and scanning electron microscope. The results indicate that graphene and polyaniline are compounded successfully; the large surface area facilitates the immobilization of enzymes.(2) The electrochemical performances of the electrodes modified by the prepared graphene-based materials are studied by cyclic voltammogram. The results indicate the modified electrodes show better conductivity compared with the bare electrode. The addition of ionic liquid further elevates the conductivity of decorated electrodes. The conductivity can be improved to a best level when a volume of 4μL of the mixture solution is adopted on a 3 mm carbon-glass electrode. (3) On the basis of the previous research work, three kinds of enzyme electrochemical biosensors have been constructed. The graphene-based materials exhibit excellent electrochemical properties. It can realize the direct electron transfer between the active sites of the immobilized enzymes (catalase,horse radish peroxidase,glucose oxidase) and the modified electrodes. The performances of the biosensors are investigated by using of cyclic voltammetry and chronoamperometry. Each biosensor is proved to own a good linear relationship, low detection limit, good repeatability, and stability. In addition, the preparation conditions such as the amount of enzyme, pH of the buffer, etc., are also studied systematically. Meanwhile, dynamic process is also explored.