| The analysis and detection of biomolecule is of great significance to obtaining chemical and biological information and understanding the relationship between the structure and function of biomolecule.In recent years,the electrochemical analysis towards biomolecules obtained more and more attention.Two kinds of composite films with vanadium-substituted polyoxometalate were fabricated by layer-by-layer self-assembly method.The growth process of composite film was monitored by UVvis spectroscopy.Scanning electron microscope?SEM?and X-ray photoelectron spectroscopy?XPS?were applied to characterize the surface morphology and the elemental composition of the composite films.In addition,cyclic voltammetry?CV?,electrochemical impedance spectroscopy?EIS?and differential pulse voltammetry?DPV?were used to investigate the sensing properties of two composite films,and explore the application in real samples.The results were shown as followed:1.The composite film(PEI/P2Mo16V2/PEI/CNTs@Au)2 was constructed based on polyoxometalate,carbon nanotubes and Au nanoparticles.The result showed that the incorporation of the three kinds of active components would improve the electrocatalytic activity to the oxidation of FA and electron transfer rate greatly.In 0.2 M phosphate buffer solution?pH = 7.35?,the composite film(PEI/P2Mo16V2/PEI/CNTs@Au)2 had a linear range of FA from 4.99 × 10-7 M to 1.29 × 10-5 M and 1.29 × 10-5 M to 1.21 × 10-3 M,and a limit of detection to be 3.96 × 10-8 M?S/N = 3?.In addition,the composite film has an excellent anti-interference property to potential co-exist interfering species like inorganic ions and biomolecules?including NaCl,K2CO3,NH4 Cl,Na2NO2,NaSO4,fructose,L-glutamate and glucose?.The developed sensor has a good working and long-term stability as well.Besides,the sensor was applied in detecting FA in vitamin b tablet,the recoveries were all in the allowable error range.2.Graphene oxide?GO?nanosheets and polyoxometalate,H8P2Mo16V2O62(P2Mo16V2),were co-assembled into composite film(PEI/P2Mo16V2-rGO)4.Under UV irradiation,a photoreduction reaction took place in the film which converted GO to reduced GO?rGO?due to the photocatalytic activity of P2Mo16V2.The(PEI/P2Mo16V2-rGO)4 composite film was investigated to have a good catalytic activity for the oxidation of FA and optimized experimental conditions like the best pH and number of layers by cyclic voltammetry?CV?.Electrochemical impedance spectroscopy?EIS?proved that the composite film owned the higher electron transfer rate and smaller resistance.The composite film was used to selective determination of FA in the presence of important interferents,which include dopamine?DA?and uric acid?UA?at physiological pH.The current response was increased linearly with increasing FA concentration in the range of 9.99 × 10-9-7.96 × 10-4 M,the detection limit was found to be 2.84 × 10-10 M.Furthermore,the developed sensor was successfully applied in human serum samples analysis. |
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