Preparation And Sensing Properties Of Polyaniline Modified Enzyme Electrode

Conductive polymers,as molecular wires connecting the active sites of biological molecules and electrodes,can significantly improve the electrochemical performance of the biosensors.Polyaniline(PANI)is used to construct the glucose biosensor due to its low cost in synthesis,high conductivity,and good environmental stability.However,PANI shows complexity in its doped composition,degree of oxidation and aggregation structures.In order to explore the relationship between its electrochemical performance and the hierarchical structure and charge transportation properties,glucose biosensors have been constructed which are made of PANI with different chain architecture(linear and branched),and different enzyme embedding matrix(PANI,composite or grafted PANI with chitosan).The compositions and structures of the electrodes,and the amount of the adsorbed enzyme are quantitatively or semi-quantitatively characterized by Fourier transform infrared spectrometer(IR),UV-visible spectroscopy(UV-vis),X-ray diffraction(XRD),thermogravimetry/differential thermal analysis(TG/DTA),etc.The electrochemical performance is also investigated.The results show that those glucose sensors made of linear-chain PANI and chitosan(CS)and the electrostatic assembly of GOx show a better response for the glucose detection with broad linearity and high sensitivity.The main contents are presented as follows:PANIs doped with hydrochloric acid and camphor sulfonic acid are synthesized by chemical oxidation and ultrasonic treatment respectively.FTIR,UV and XRD are used to determine the single chain and aggregate structures of the PANI synthesized.Electrochemical performances of the glucose oxidase electrodes have been compared which are made of PANI with linear and branched chains,it shows an obvious redox peaks for the electrode made of branched PANI,and its oxidation current is higher than that of linear PANI.They are assumed to be attributed to more adsorption of GOx in the branched PANI.The composite of PANI and CS have been used as matrix of the enzyme electrode,and the electrostatic assembly of GOx is adopted to construct the glucose biosensors.The influences of the scan rate and pH on the electrochemical performances of the biosensors have been studied.At optimal experimental conditions the linear range and sensitivity of glucose detection of the PANI decorated biosensors have been evaluated,whose dependence on the ratio of PANI and CS is also investigated.The CS grafted PANIs(PANI-g-CS)are synthesized.FTIR,UV-vis,TG/DTA are used to characterize the compositions and structures of the product.The glucose biosensors are constructed by electrostatic assembly of GOx on PANI-g-CS.cyclic voltammetry(CV)results show that the electrode with PANI-g-CS is of similar linearity with that of the composite of PANI-CS,but its sensitivity is lower,due to its low conductivity of grafted PANI.It has been proved by the dielectric relaxation spectroscopy that the conjugated structure of PANI is damaged in grafting.