The Construction Of Functionalized Polyoxometalate Modified Electrode And Its Application In The Determination Of NADH And L-tryptophan

The chemically modified electrode means that a substance having excellent properties is purposefully fixed to the surface of the electrode by a appropriate method to obtain an electrode which having certain specified functionalities.And it has been widely used in the field of electroanalysis due to their excellent selectivity,good stability and high sensitivity.Therefore,a novel type of chemically modified electrode built by different materials and different modification methods will provide a theoretical and experimental basis for its development and application in catalysis,electrochemical sensors and other areas.Polyoxometalates(POMs)are widely used in catalysis and electrochemical sensors owing to their excellent chemical stability,reversible redox activities,and special electrocatalytic properties.Thus,it is of great significance to design and develop functionalized polyoxometalate modified electrodes and to extend their applications in electrocatalysis.In this paper,polyoxometalates were used as active components in combination with other active materials.Some novel functionalized polyoxometalates-based modified electrodes were constructed by layer-by-layer self-assembly technique(LBL)and electrochemical deposition technique,and were investigated its application in detecting the biological activity molecular.The details are as follow:1.The polyelectrolyte(PAH)and Keggin-type POMs(PMo11V)were modified onto the glassy carbon electrode by alternating electrodeposition and self-assembly technique.A novel multilayer composite film(PAH/PMo11V)4 was developed for the determination of nicotinamide adenine dinucleotide(NADH).The electrochemical behavior and stability of the electrode was investigated by cyclic voltammetry.The results show that the electrode exhibited good catalytic activity for NADH oxidation.Amperometric studies show that the electrode has a wide linear range,a fast response and a low detection limit for detection of NADH.The proposed sensor has potential application in practical samples.2.A novel multilayer composite film PEI/(P2Mo17V-AuAg/PDDA-rGO]4 was constructed using the LBL method based on the P2Mo17V-AuAg/rGO due to the high specific surface area and good electron conductivity of AuAg nanoparticles and graphene,then it used to detect L-tryptophan.The growth of multilayer composite films was observed by UV spectra.The electrocatalytic performance and sensing properties of the multilayer composite film modified electrode were investigated by cyclic voltammetry and amperometric.The results show that the modified electrode can effectively fix the POMs/Au-Ag NPs on the surface of graphene.The modified electrode has good reproducibility and stability,and can be applied to the determination of L-tryptophan in human serum.3.A multilayer composite film PEI/(PMo9V3/PDDA-Fe3O4)6 was constructed by layer-by-layer self-assembly method based on vanadium substituted POMs(PMo9V3)and PDDA functionalized Fe3O4 nanoparticles.The electrocatalytic performance and sensing properties of the multilayer composite film towards NADH and L-tryptophan were measured by electrochemical impedance spectroscopy,differential pulse voltammetry,cyclic voltammetry and amperometric,respectively.The results show that the multilayer composite films had good sensitivity,anti-interference,reproducibility,and excellent work stability and long-term stability.Furthermore,it can be used for the detection of NADH and L-tryptophan in human serum.