Synthesis And Analytical Application Of Novel Functional Conducting Mateirals

With the development of biotechnology, electrochemical biosensor has been widelyapplied, which has advantages of simple design and preparation, good stability, highsensitivity, good selectivity. However, it is important that biological material is immobilizedstably and actively to the surface of sensing transducer in the whole preparation process ofbiosensor construction. The stability and activity of biomolecules decline when fixingmolecules by traditional dispensing, which has influence on sensor performance. Thus, westudied the preparation of functional conducting material and its application for biomoleculesimmobilization which activity protected by ionic liquid. We also studied the application ofconducting materials in the field of chemical and biological sensors.The monomers of novel functional conducting polymers which have–COOH functionalgroup:2,5-di-（2-thienyl）-1H-pyrrole-1-（p-benzoic acid）（DPB） and2,5-di-（2-thienyl）-1H-pyrrole-1-（p-phenylacetic acid）（DPP） were synthesized through friedel-crafts acylation,Paal-Knorr condensation and nitrile hydrolysis reaction. The products were characterized andanalyzed by IR, NMR, UV, fluorescence and electrochemical method. The experimentalresults show that maximum absorption wavelength of DPB and DPP are344nm and346nm,respectively, the maximum excitation lights are500nm and508nm, respectively. Monomerswere oxidized irreversibly at0.95V, the polymer film formed on the electrode surfacereversible redox which anodic peak and cathodic peak are0.65V and0.58V for the PolyDPB,and0.65V and0.59V for the PolyDPP respectively. With scanning speed increasing thecurrent response increased, which indicated novel functional conducting polymers have agood conductivity.The effect of covalent immobilization and ionic liquids on the properties of biomoleculeswere studied with biological micro-reactor which built by functional conductive polymerfixing lipase. The conducting polymer films were electropolymerized on carrier, and thelipase were immobilized on the films by covalent binding with carboxyl groups of filmswhich activated by EDC/NHS as a activator to fabricate micro-reactor. The esterificationreaction of phenyl ethyl acetate catalyzed by lipase was used as a model reaction toinvestigate optimized reaction conditions. Under the optimal reaction conditions:[D（2-mb）Im][PF6] as solvent,35℃and reaction for24hours, the conversion was about82%.[D（2-mb）Im][PF6] is temperature ionic liquids which can separation from product withoutfurther extraction at low temperature and avoiding using organic solvents. The effect ofcovalent immobilization and ionic liquids on the activity and stability of lipase were studiedby fluorescence spectroscopy, scanning electron microscopy and circular dichroism spectrumrevealed. The experimental results show that characteristic peaks at350nm of lipase were changed in different ionic liquids; the strength of peaks is consistent with the productconversion. Meanwhile it also revealed that the structure of the enzyme is more stable in ionicliquid, while covalent could lead to a change of enzyme orderly structure content and theeffect on enzyme activity still need further research. The activity of lipase was notsignificantly reduced in repetitive experiments.The immunusensor built by functional conductive polymer fixing antibody and itsproperties were studied. Graphene oxide, DPB and chloroauric acid were electrodeposited onthe surface of gold electrode, then AFB₁antibody was then connected covalently to polyDPBfilm with EDC/NHS as activator and the mixture of ionic liquid with chitosan was finallycoated on surface of the film. In this work, electrochemical performances of the sensor wereinvestigating by cyclic voltammetry and electrochemical impedance spectroscopy,respectively. The experimental results indicated that graphene and gold nanocompositeobviously improve electron transfer of the film, and apparent electro-active surface areas ofG/GE （0.2188cm2） and AuNPs/PolyDPB/G/GE （0.2640cm2） was much bigger than baregold electrode （0.1772cm2）. Electron transfer impedance responses of the sensor increaselinearly when aflatoxin B₁concentration is the range from3.2×10-15mol/L to3.2×10-13mol/L.Detection limit was found to be1.1×10-15mol/L （S/N=3）. Due to covalently connection ofantibody on the electrode and excellent biocompatibility of the ionic liquid, the sensor offersgood stability. The electrochemical response of the senor can keep almost constant afterstored at4℃for20weeks at least. Proposed method has been successfully applied todetermine AFB₁in peanut.