Study On Chemically Modified Electrodes And Immunosensor Based On Nanomaterials

Nanomaterials have been regarded as "the most futurest materials in the century of 21",when the structure of matter added to nanometer,it would bnng special surface effect,small size effect,macroscopic quantum tunnel effect and quantum size effect,so,its characteristic of light,electricity,heat,machine and chemical would appear obvious changes and take on superior performance.because of the special surface effect and quantum size effect of nanomaterials,it's surface and electron state are different to that of interior.The increase of surface active sites will produce special catalytic effect towards the electrochemical characteristic of some matter.So the sensitivity and selectivity of the electrode modified by nanomaterial would increase.Chemically modified electrodes and electrochemical biosensors are one of the important aspects in modern analytical chemistry,and it applied in many research fields,such as,chemistry,biotechnology, medicine and environmental.Biosensor is a sensor device combine with sense organ which was used to immobilize biomolecule and energy conversion device to determine one or several substance.The interuption of nanomaterial provide a new stage for the development of biosensor.The catalytic active of biomolecule and the response current of electrode can be improved after immobilizing biomolecule by nanomaterial.Compared with traditional sensors,novel biosensor based on nanomaterial have higher sensitivity and selectivity,moreover,the response rate also can be improved and realized monitor at time. This paper described several electrochemical biosensors based on nanomaterial.The works and conclusions are included as follows:The first part:A Novel Nonenzymatic Hydrogen Peroxide Sensor Based On Polypyrrole Nanowires-Copper Nanocomposite Modified Gold ElectrodeIn recent years,the appearance of one dimension nanomaterials(nanowires nanotube nanostick) provide new ideas for the development of sensors.Polypyrrole nanowires was came in to being during the process of polymerize pyrrole.It's special surface structure is beneficial to the embed of nanoparticles.In this paper,Ppy nanowires was fabricated by electrochemical methods,copper nanoparticles was modified on the electrode by electropolymerized.So the PPy-copper nanocomposite modified electrode was obtained and exhibited good electroeatalytic for the reduction of hydrogen peroxide(H₂O₂).Under the optimal experiment condition,the linear range of this sensor is 7.0×10^-6～4.3×10^-3mol/L with a detection limit of 2.3×10^-6 mol/L(S/N=3).More over,the system described in this paper is not only a simple and effective method but also overcame disadvantages of enzyme based biosensor.The second part:Study on immunosensor based on polypyrrole,MWNT and nano-CaCO₃ nano-gold modified electrode1.Calcium carbonate,a natural mineral with great biocompatibility,also attracted great attention in industry,technology,medicine,and many other bio-related fields.Nano-sized CaCO₃ particles show greater advantages than that of regular sized particles,such as the much larger specific surface area.It has already proved that it can be used in immobilizing biomolecular,for example,enzyme and so on.In this paper,we simultaneously took advantages of two kinds of nanomaterials(nano-gold and nano-CaCO₃) with good biocompatibility provide good microenvironment to immobilize and keep activity of the protein molecular.So,the negatively charged Prussian blue was deposited on the electrode firstly,nano-CaCO₃ was adsorbed on the surface of PB through electrostatic interaction,then nano-gold was modified on the modified electrode through electrochemical method to immobilize carcinoembryonic antigen(CEA). Under optimal condition,the immunosensor was electrochemically monitored by cyclic voltammetry(CV) and it exhibited a electrochemical behavior to CEA in a concentration range of 0.3 to 20 ng/mLå'Œ20 to100 ng/mL,with a detection limit of 0.1 ng/mL.2.In order to avoid the drop of mediator immobilize on immunosensor,an amperometric immunosensor without mediator was fabricated for detection of prostate-specific antigen(PSA).Negativly charged MWNT dispersed by sodium dodecyl sulfate(SDS) was droped on the electrode,conductive polymer polypyrrole was coated on MWNT modified electrode by electrochemical method.Ppy is positively charged when it was electropolymerized under proper condition.The electrostatic interaction increase the stability of modified electrode.Moreover,The appear of good oxireduce peak of Ppy after polymerized on MWNT modified electrode avoid the using of mediator.Nano-gold was modified on the modified electrode through electrodepositing to immobilize anti-PSA.Under optimal condition,the proposed immunosensor exhibited a good electrochemical behavior to PSA in a concentration range of 0.1 to 4 ng/mL and 4 to 50 ng/mL,with a detection limit of 0.04 ng/mL.Moreover,it showed good stability and selectivity.