Its Performance And Build Bio-based Sensing Electrode Laponite- Graphene Composite Membrane

1. Characterization and application to the design of amperometric phenol biosensor based on laponite/graphene composite filmLaponite, a colloidal suspension of negatively charged elementary platelets, presents all the advantages of clay such as high porosity, good adsorption properties and good biological compatibility.2D material graphene with an atomic thickness,has unique mechanical properties and good electrical conductivity. Combining with the advantages of two kinds of materials, the laponite-graphene composite material was used to immobilize polyphenol oxidase for the construction of a biosensor for phenolic compounds. The isothermal titration microcalorimetry (ITC), contact angle (CA), electrochemical impedance spectroscopy (EIS), fourier transform infrared (FT-IR) and scanning electron microscope (SEM) were used to investigate the materials. The laponite-G/PPO bio-electrode had a good and fast of the electrochemical response for catechol, providing a wide linear range and a high sensitivity of5072.2mA M-1cm-2as well as the activation energy of17.79kJ mol-1. The apparent Michaelis-Menten constant was0.082mM. At S/N=3, the detection limit was20nM. In addition, effects of electrode construction, pH value, applied potential and temperature were investigated and discussed.2. Amperometric detection of glouse with glucose oxidase immobilized in the laponite/graphene composite filmThe material laponite-graphene was used to co-immobilize the glucose oxidase(GOD) as complex matrix for the construction of enzyme-based bioelectrode. Due to the good adsorption properties of laponite-graphene composite material, more enzyme could be fixed on the bio-electrode. In addition, the good electrical conductivity promoted a fast of the electrochemical response and high sensitivity. Besides the influence factors such as the ratio of laponite and graphene, the ratio of fixed materials and enzyme, the quantity of the enzyme, we also explored the experimental parameters such as pH, the applied potential and temperature for the best analytical performance of the electrode. Amperometric detection of glucose with an unmediated sensor at0.6V (vs.SCE) resulted in a rapid respose, a wide linear of0.2μM-3mM with a sensitivity of124.84mA M-1cm-2, the apparent Michaelis-Menten constant (KMapp) of0.39mM, and the activation energy for enzymatic reaction of17.21kJ mol-1. Furthermore, the biosensor exhibited good anti-interference and satisfactory stability.3. Development of a high analytical performance-xanthine biosensor based on laponite/graphene modified-electrodeA novel xanthine biosensor based on immobilization of xanthine oxidase (XnOx) by composite materials laponite-graphene was developed. The composite films have been described by SEM, FT-IR and EIS. The results displayed that PPO kept the essential feature of its native structure in the porous film. And the porous films were beneficial to the electron transfer between the substrate and the electrode interface. Therefore biosensors construction and experimental conditions paraments were optimized. In the best conditions, the bio-electrode had an excellent electrochemical response with a sensitivity of139mA M-1cm-2and a linear response to xanthine of a concentration range of0.49nM-0.02μM. Furthermore, laponite-G/XnOx bio-electrode showed good reproducibility. It retained72%of the original activity after30days.