Study On The Preparation Of Nanoparticle/Molecularly Imprinted Polymer Electrochemical Sensor And Its Application

Molecularly imprinted polymers (MIPs) have a lot of advantages, such as specific recognition function, good stability, resistance to severe environment, long service life and can be recycled, and so on. In theory, MIPs of any molecular can be synthesized. The use of biosensor has difficulties in preservation, proper conditions and limited object, and MIPs sensor overcomes the aforementioned drawbacks, so it becomes one of the research hotspots in electrochemical sensor. Comparing with other techniques, the advantage of electropolymerization is that the thickness and the density of the polymer layer can be monitored and regulated easily. In recent years, nanoparticles have attracted great attention in the electrochemical research as a modified material, because they can improve the detection sensitibity of electrochemical reaction by enhancing electron transfer. In this paper, two types of MIPs/nanoparticles electrodes were developed by integrating electropolymerization with nanoparticles modified electrodes via taking analeptic and aniline compounds as template molecule and functional monomer, respectively. The imprinted sensors showed high recognition ability and affinity, and were successfully applied to the determination of analeptic in real samples.In addition, the direct electron transfer between redox proteins and electrode surface are of great importance for not only studying the electron transfer between biomolecules in biological system, but also investigating the novel enzyme biosensors. A novel material was used to investigate the direct electrochemistry of hemoglobin in this thesis.The main contents of this thesis are summarized as follow:(1) Fabrication and analytical application of voltammetric sensor for brucine based on molecularly imprinted poly-o-phenylenediamine/SWNTs modified electrodeA molecularly imprinted poly-o-phenylenediamine/SWNTs modified electrode was developed by electropolymerization via taking brucine as template molecule, and o-phenylenediamine as functional monomer. The characterization of electrochemically synthesized molecularly imprinted poly-o-phenylenediamine/SWNTs electrode was investigated via scanning electron microscope (SEM) and atomic force microscope (AFM). The electrochemical behaviors of brucine at the molecularly imprinted poly-o-phenylenediamine/SWNTs electrode, the optimal experimental conditions, incubation time, selectivity, stability and repeatability were investigated. Under the optimal experimental conditions, the current response of the imprinted sensor was linear to the concentration of brucine in the range of6.2×10-7～1.2×10-5M, and a detection limit of2.1×10-7M was obtained. And the imprinted electrochemical sensor was successfully applied to the determination of brucine in human serum samples.(2) Fabrication and analytical application of impedimetric sensor for salbutamol based on and molecularly imprinted poly-p-aminothiophenol/AuNPs modified electrodeA molecularly imprinted poly-p-aminothiophenol/AuNPs modified electrode was fabricated via electropolymerization by taking salbutamol and p-aminothiophenol as template molecule and functional monomer, respectively. Scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS) were employed to investigate the surface morphologies and electrochemiacal properties of the imprinted layer. The presence of some analogues (clenbuterol and terbutaline) didn’t interrupt the determination of salbutamol, the imprinted electrode exhibited excellent selectivity, low detection limit and good long-time storage stability for the determination of SAL. Ferricyanide was used as oxidation-reduction probe, and the determination was carried out by measuring the variation of impedimetric response. Fast response can be achived within12min covering a linear range of6.2×10-9～2.4×10-7M, and a detection limit of3.1×10-9M was obtained. The imprinted electrochemical sensor was successfully applied to the determination of salbutamol in finely swine feed samples.(3) Fabrication and analytical application of electrochemical biosensor based on immobilization of Hb in CS-DMF/GR composite film.Hb-CS-DMF/GR/GCE was developed by intergrating graphene nanosheet with chitosan-N, N-Dimethylformamide (CS-DMF) hydrogel. The surface morphologies of the modified electrode were characterized by SEM, and direct electrochemistry of Hb on the graphene nanosheet-based electrode were investigated by cyclic voltammetry; the effects of phosphate buffer pH, scan rate, and temperature on the biosensor were investigated to provide optimum analytical performance. Moreover, several electrochemical parameters, e.g., the heterogeneous electron transfer rate constant (ks), were calculated in detail. The results indicated that Hb immobilized on the surface of the graphene modified electrode could keep its bioactivity, and showed excellent electrocatalytic activities toward nitrite reduction with a low detection limit of1.8×10-7M. The apparent Michaelis-Menten constant (km) was down to0.16μM, indicating that the biosensor possessed high affinity to NaNO2. The good performance of the proposed sensor is attributed to excellent conductivity and electron mobility of grapheme and good biocompatibility of chitosan, which enhances the Hb content by electrostatic interaction between GR and CS, and promotes direct electron transfer between redox Hb and the surface of electrodes.