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The Electrochemical Characterization Of Ferrocene Derivatives And Their Application In Biosensor

Posted on:2009-09-24Degree:MasterType:Thesis
Country:ChinaCandidate:R WangFull Text:PDF
GTID:2178360278471223Subject:Analytical Chemistry
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Biosensors,which were a new field based on biology,iatrology,physics, chemistry and electronic technology,have become the main analytical methods in clinical and biochemical analyses and in other areas such as environmental control, food quality control etc.With their potential utility as specific,simple and direct detection techniques and reductions in size,cost and time of analysis,biosensors continue to be a very active area of research.The name biosensor is a device composed of a biological recognition element and a transducer.It has been reported that the crucial aspect in the fabrication of a biosensor is the deposition of biorecognition molecule,such as an enzyme,antibody(antigen),sequence of DNA, etc,in high amounts with retention of their specific activity.For these reasons an increasing number of diferent immobilization procedures have been investigated. Therefore the selection of the electronic mediator,the modification of the mediator onto the electrode surface,the methods of the biorecognition moleculeim mobilization and the construction of a novel biosensor had been developed in this thesis and describled as follows:1.In this article,a detailed electrochemical study of a novel 6-ferrocenylhexanethiol(HS(CH2)6Fc) self-assembled multiwalled carbon nanotubes-Au nanoparticles(MWNTs/Au NPs) composite film was demonstrated. MWNTs/Au NPs were prepared by one-step in situ synthesis using linear polyethyleneimine(PEI) as bifunctionalizing agent.HS(CH2)6Fc,which acted as the redox mediator,was self-assembled to MWNTs/Au NPs via Au-S bond. Transmission electron microscopy(TEM),energy-dispersive X-ray analysis(EDX), Fourier transformed infrared absorption spectroscopy(FT-IR),UV-visible absorption spectroscopy,and cyclic voltammetry were used to characterize the properties of the MWNTs/Au NPs/HS(CH2)6Fc nanocomposite.The preparation of the nanocomposite was very simple and effectively prevented the leakage of the HS(CH2)6Fc mediator during measurements.The electrooxidation of AA could be catalyzed by Fc/Fct couple as a mediator and had a higher electrochemical response due to the unique performance of MWNTs/Au NPs.The nanocomposite modified electrode exhibited excellent catalytic efficiency,high sensitivity,good stability,fast response(within 3s) and low detection limit toward the oxidation of AA at a lower potential.2.A novel amperometric biosensor for glucose was developed by entrapping glucose oxidase(GOx) in a chitosan composite doped with ferrocene monocarboxylic acid-aminated gold nanoparticles/multiwall carbon nanotubes nanocomposite (MWNTs/Au NPs/FMC/GOx/CS).The entrapped ferrocene mediator performed excellent redox electrochemistry and the presence of MWNTs/Au NPs improved the conductivity of the composite film.This matrix showed a biocompatible microenvironment for retaining the native activity of the entrapped GOx and was in favor of the accessibility of substrate to the active site of GOx,thus the affinity to substrates was improved greatly.The resulting glucose biosensor showed high sensitivity,long-term operational stability,fast response time.The line range of the biosensor was from 0.01 to 2.5 mM with a detection limit of 3.6μM(S/N=3).The apparent Michaelis-Menten constant(Km) for the biosensor was 1.21 mM.3.A simple and controllable electrodeposition method is described to fabricate a homogeneous chitosan-ferrocene/Au nanoparticles/glucose oxidase(CS-Fc/Au NPs/GOx) nanocomposite film with porous structure.The morphologies and electrochemistry of the nanocomposite film were investigated by using scanning electron microscopy(SEM) and electrochemical techniques including electrochemical impedance spectroscopy(EIS) and cyclic voltammetry(CV), respectively.The ferrocene group(Fc) covalently bounded chitosan hybrid(CS-Fc) can effectively avoid the leakage of Fc and retain its electrochemical activity.Further immobilization of Au NPs into the porous structure of the CS matrix enhances both the charge-transport properties of the composite and bioaffinity to enzyme.Biosensor based on this CS-Fc/Au NPs/GOx film has advantages of fast response,excellent reproducibility and high stability.This sensor shows a linear response to glucose in the concentration range from 0.02 mM to 8.66 mM with a detection limit of 5.6μM at a signal-to-noise ratio of 3.The detection sensitivity is as high as 14.3μA·mM-1·cm-2. The present method offers a facile way to fabricate biosensors and bioelectronic devices. 4.A novel amperometric immunosensor for the detection of hepatitis B surface antigen(HBsAg) has been developed by means of electrodeposition and self-assembling techniques.Firstly,a porous nano-structure CS-Fc film was formed by electrodeposition,then Au NPs were chemisorbed onto the amino-groups of the porous CS-Fc composites,and finally HBsAb was adsorbed onto the surface of the bilayer Au NPs to construct an HBsAb/Au NPs/CS-Fc immunosensor.The characteristics of the modified electrode at different stages of modification were studied by cyclic voltammetry(CV) and electrochemical impedance spectroscopy (EIS).In addition,the performances of the resulting immunosensor were studied in detail.The present immunosensor exhibits a wide linear range from 0.05~305.05 ng·mL-1 with a low detection limit of 0.016 ng·mL-1 at signal-to-noise ratio of 3. Moreover,the studied biosensor exhibited high sensitivity,good reproducibility and long-term stability.
Keywords/Search Tags:multiwalled carbon nanotubes, nanocomposite, gold nanoparticle, ferrocene, biosensor
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