Controllable Polymerization Of Dopamine On Electrode Surface And Studies On Several Electrochemical Sensors

Modified electrode is of most importance in energy, environment, material and life science research. Interface research using chemically modified electrodes has been developed as one of the important directions in the field of electrochemical research. In this paper, electrodes were obtained through surface modification, and it is divided into two parts. On the one hand, the interface structure of the material modified electrode was studied. The homogeneous polydopamine film was prepared by a controllable interfacial polymerization on the stainless steel electrodes. Meanwhile, the morphology of polymer film, hydrophilic, chemical composition, mechanism of film forming and corrosion resistance were also studied. On the other hand, sensing property of matrixs modified electrode was studied. Preparation of several new matrix electrochemical biosensors which were successfully applied to detect the substrates. The contents are as follows.1. In the introduction, the superior performance, research progress and application aspects of electrochemical polymerization and polydopamine film are summarized. Furthermore, the classification of biosensors, the methods of immobilization enzyme and prospect and application of nanomaterials in biosensors are also discussed. Finally, a review of the methods used in this experiment is presented in this paper.2. The morphology, chemical composition, mechanism of film forming and corrosion resistance of polydopamine film prepared by electrochemical polymerization on the 316 stainless steel electrodes were studied. We prepared polydopamine films with different thickness by changing different scan cycle number of cyclic voltammetry, which were characterized by ellipsometry, Contact angle measurement (CA), FTIR, SEM and XPS. The polymer hydrophilicity, chemical composition, and surface morphology were also studied. It was found that the polymer is hydrophilic and lipophilic material with round or oval shaped particles. The formation of "island" distributed in the surface of the substrate. Then we investigated the electropolymerization mechanism that the intramolecular cyclization of amino group takes place during oxidative polymerization of dopamine and the cyclic product can be oxidized and reduced. Finally, we investigated and verified the excellent corrosion resistance of the prepared film in simulated seawater (3.5% NaCl) solution using electrochemical method. And it can keep long term stability.3. A sensitive electrochemical molecularly imprinted sensor was developed for the detection of aflatoxin B1 (AFB1), by electropolymerization of p-aminothiophenol functionalized gold nanoparticles in the presence of AFB1 as template molecule. The extraction of the template leads to the formation molecular imprinting that is able to specifically recognize AFB1 through π-π interactions between AFB1 molecules and aniline moieties. The performance of the developed sensor for the detection of AFB1 was investigated by linear sweep voltammetry using a hexacyanoferrate/hexacyanoferrite solution as redox probe. Due to the p-doping effect, the electron transfer rate increases when concentration of AFB1 increases. The molecularly imprinted sensor exhibits a broad linear range, between 3.2 fM and 3.2 μM and a quantification limit of 3 fM. Selectivity studies were also performed use other aflatoxins and ochratoxin A. This sensor exhibited good selectivity towards other aflatoxins and ochratoxin A.4. A new conductometric biosensor based on interdigitated electrodes (IDEs) was developed for the detection of urea using new type of fluorinated functional ization Au nanoparticles (PF-HEG-Au NPs). Gold nanoparticles (AuNPs) were first synthesized following the citrate process, with an average diameter of 14 nm. AuNPs were then functionalized with 11-mercaptoundecyl-hexaethyleneglycol (HEG) and then with 1H,1H,2H,2H-perfluorodecanethiol (PF). The fluorinated functionalization AuNPs were characterized using TEM, UV-Vis spectrophotometry and FTIR spectroscopy. Urease mixed with these fluorinated functionalization AuNPs, was then cross-linked with glutaraldhedyde vapor on the IDE surface. In the presence of urea, the conductometric response was measured. The best sensitivity of 198 μS/mM and the best detection limit of 0.5 μM for urea detection were obtained with PF-HEG-Au nanoparticles modified electrodes in comparison with the performance of bare Au NPs modified electrodes (91 μS/mM and 2 μM,respectively) and of urease directly coupled electrodes (3μS/mM and 100 μM, respectively).This fully demonstrated the superiority of the new electrode. When stored in phosphate buffer (5 mM, pH 6.7) at 4℃, the new biosensor with PF-HEG-Au nanoparticles showed good stability for more than 12 days.5. A new conductometric biosensor (ETS-10) based on new kinds of zeolite was developed for the immobilization of urease and detection of urea using new type of ETS-10, Ag-ETS-10 zeolite as matrix substrate. The ETS-10 and Ag-ETS-10 were synthesized, characterized by XRD and SEM to exam the structure characteristics and performance. The zeolite material dropwise on the electrode by heating to 200℃.Urease was then cross-linked with glutaraldhedyde vapor on the zeolite electrodes to detect urea. The biosensor based on ETS-10 zeolite exhibited best sensitivities. The sensitivity is almost 20 times as much as that the no zeolite. Linear range is 0 to 0.85 mM, showing good stability and repeatability. The performance is superior to the general zeolite materials.