The Studies Of Mangetic Nanocomposite Molecularly Imprinted Electrochemical Sensors Based On Magnetic Field Directed Self-assembly

As an emerging self-assembly method,magnetic field directed self-assembly has widely potential application in electrochemical and biological sensors.It could fast direct and immobilize magnetic nanoparticles for controlling the three-dimensional structure of the modified film of electrodes.At present,the potential food safety problems,such as food additives and harmful substances were striking.Due to the composition complex of sample in food analysis,the determination of target objects often were disturbed by coexistence contents.Thus,it was necessary to establish new technologies and methods for the determination of analytes.In this work,two electrochemical sensors were successfully established and employed for the selective detection of amaranth and estradiol in samples which were based on magnetic field directed self-assembly technique,molecularly imprinted technology,nanotechnology and electrochemical sensing technology.Section 1.The study of Fe3O4@rGO doped amaranth molecularly imprinted electrochemical sensing film based magnetic field directed self-assembly:In molecular imprinting,the complex including the function monomer of aniline,the template of amaranth and Fe3O4@rGO was pre-assembled through ?-? stacking and hydrogen bonding interactions,and then were self-assembled on the surface of magnetic glassy carbon electrode(MGCE)with the help of magnetic field induction.After that,molecularly imprinted sensing film was constructed by one-step electropolymerization.The doping of Fe3Oa@rGO in imprinting sensing film greatly simplified the modifying process of the electrodes and made the membrane uniform and controlled based on the magnetic characteristics.On the other hand,the magnetic nanocomposite owned abundant ?-? conjugated structure,which suppied enough ?-? binding sites for amaranth in aqueous solution.Moreover,Fe3O4@rGO nanocomposite enhanced the specific surface area,resulting in the increase of the current response of imprinting film due to the large specific surface area.In this method,the fabricated molecularly imprinted electrochemical sensor(MIES)with the help of magnetic field directed self-assembly exhibited good sensitivity,selectivity,reproducibility and efficiency for the determination of amaranth in fruit drinks.The average recoveries were 93.6-100.8%with RSD lower than 2.7%.Section 2.The study of Fe304@Au estradiol molecularly imprinted polymers magnetic sensing film:glutathione(GSH)functionalized Fe3O4@Au was chosen as magnetic nano-functional monomer and aniline was chosen as cross-linking agent.Polymerization was completed by in situ in the acidic ethanol solution and the magnetic molecularly imprinted polymers(MMIPs)were synthesized after removing the template molecule.The E2-MMIPs were obtained by using MMIPs as dispersive solid-phase extraction material for recognizing E2 from sample,and the magnetic sensing "soft" film was constructed after E2-MMlPs were assembled onto the surface of electrodes evenly and orderly based on magnetic field directed assembly.The research was the first combination of dispersive solid-phase extraction technique and magnetic field directed self-assembly for the preparation of estradiol electrochemical magnetic sensing film which was simple and easy for operation avioding the complex modification of electrodes.And the "soft" sensing film was peeled off from the electrode by removing the magnet in MGCE,which could obtain the effect of self-cleaning and greatly simplified the refresh process of modified electrodes.Furthermore,MMIPs could be synthesized abundantly,and the used MMIPs nanoparticles could be enriched,recycled and reused after eluting targets based on external magnetic field.In addition,the use of Fe3O4@Au and PANI in MMIPs could improve the conductivity and electrocatalytic activity of sensing "soft"film which could dramatically increase the sensitivity of the imprinting sensing film.The linear range of the magnetic sensing "soft" film for detecting E2 was from 0.025-10.0 ?mol L-1 with the limit of detection(LOD)was 2.76 nmol L-1(S/N= 3).