| Using new materials,including hybrid composites,nanomaterials and biomolecular materials,in construction of chemically modified electrode in order to broaden the application range of analysis technology has already been active area of modern electroanalytical chemistry and biosensing study.In this thesis,chemically modified electrodes based on polyaniline(PANI),cationic surfactants and other materials were fabricated.Cyclic voltammetry,differential pulse voltammetry and chronoamperometry were used in the investigation of electrochemical and electorcatalytic behaviors of glucose,glucose oxidase(GOD),dopamine(DA)and ascorbic acid(AA)on these modified electrodes.Biosensing study was also progressed.The thesis may provide theoretical and practical basis for developing new modified electrodes,enriching the content of electroanalytical chemistry and biosensing research.There are three chapters in this thesis.The main contributes of author are summarized as follows,1.Modified electrode based on polyvinylpyrrolidone(PVP)protected Prussian blue nanoparticles(PBNPs)-FANI/multi-walled carbon nanotubes(MWNTs)hybrid composites was fabricated by electrochemical method.And a new type of amperometric glucose biosensor was prepared by immobilizing GOD in crosslinked CS network on the modified electrode.SEM technique was used to characterize the morphologies of modified electrodes and PB was found nanoscaled.Effects of applied parameters on the analytical performance of the biosensor were also investigated.The results show that this biosensor exhibits fast current response(＜6s)and a good linearity in the range of 6.7×10-6to 1.9×10-3mol·L-1with a high sensitivity of 6.28μA·(mmol·L-1))(-1)and a detection limit of 2.0×10-6mol·L-1(S/N=3)for the detection of glucose.The apparent activation energy of enzyme-catalyzed reaction and apparent Michaelis-Menten constant arc evaluated as 23.9 kJ.mol-1and 1.9 mmol.L-1 respectively,which suggests a high affinity of the enzyme-substrate.The biosensor was successfully applied to determine the glucose concentration in human serum samples.Compared to other biosensors reported previously,this glucose biosensor exhibits high sensitivity,good stability,fast response and good stability.2.Inteffacial polymerization method was used to prepare the PANI-Au nannocomposites.SEM,FTIR and EDX techniques were used to characterize the morphologies and chemical composition of PANI-Au nanocomposites and proved this synthesis method.Enzyme electrode was constructed by coating with the CS solution containing GOD/PANI-Au/MWNTs,and the direct electrochemistry of immobilized GOD was investigated.The voltammetric results indicated that the GOD immobilized in CS/PANI-Au/MWNTs composites exhibited a pair of well-defined and nearly symmetrical redox peaks,which resulted from the direct electron transfer between GOD and the underlying electrode.The formal redox potential of GOD was -0.462 V (vs.SCE).The electron transfer rate constant of the immobilized GOD at the modified electrode was 10.9 s-1.Further experiments demonstrate that the immobilized GOD retained its bioelectrocatalytic activity for the oxidation of glucose.The enzyme electrode can be used as a glucose biosensor.In the presence of glucose,the enzyme electrode showed fast(＜7 s)and sensitive response and the catalytic peak current was linear to glucose concentration in the range of 0.5 to 7.4 mmol·L-1with a sensitivity of 0.922μA·(mmol.L-1)-1.The resulted CS/PANI-Au/MWNTs composites can help GOD retain its activity,and facilitate the electron transfer between the enzyme and the electrode.The combination of PANI-Au nanocomposites with redox active enzymes would appear to offer an excellent and convenient way for a fundamental understanding of biological redox reactions as well as the development of reagentless biosensors 3.MWNTs/cetyl pyridine bromide(CPB)composites modified electrode was fabricated simply.Electrochemical behavior of dopamine(DA)and ascorbic acid(AA) was investigated at the modified electrode and bare electrode,a differential pulse voltammetry method for simultaneous determination of DA and AA was set up. According to results of cyclic volatmmetry,the oxidation over potential of AA was lowered owing to the electrostatic interaction of CPB and negatively charged AA,and the potential difference of DA and AA was about 380 mV,indicating the common overlapped oxidation peaks of AA and DA can be separated completely.Shown by the results of differential pulse voltammetry,it has a good linearity of 1.0×10-5～8.0×10-4mol·L-1and 5.0×10-6～1.8×10-4mol·L-1for DA and AA,respectively.4.Cetyl trimethyl ammonium bromide(CTAB)/CS composites film modified electrode was fabricated simply.Electrochemical behavior of DA and AA was investigated at the modified electrode and bare electrode,a differential pulse voltammetry method for simultaneous determination of DA and AA was set up. According to results of cyclic voltammetry,the oxidation over potential of AA was lowered owing to the electrostatic interaction of CTAB and negatively charged AA, and the potential difference of DA and AA was about 360 mV,indicating the common overlapped oxidation peaks of AA and DA can be separated completely.Shown by the results of differential pulse voltammetry,it has a good linearity of 1.0×10-5～2.8×10-3mol·L-1and 5.0×10-6～6.0×10-4mol·L-1for DA and AA,respectively.
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