| This thesis summarizes the research status and progress on nanoelectrode ensembles, electrochemical immunosensor for aflatoxins and self-assembly modified electrodes. The gold three dimensional nanotube electrode ensembles(3DTNEs) has been fabricated by using polycarbonate membrane as the template, and its properties are characteried. In addition, a two-dimensional model is established to discuss the diffusion of 3DTNEs. Two impedimetric immunosensors with high sensitivity for AFB1 have been prepared respectively based on protein A(SPA) self-assembled film and p-aminothiophenol(4-ATP) self-assembled membrane modified 3DTNEs.The morphology and composition of 3DTNEs are evaluated by SEM, EDX, and XRD. 3DTNEs is confirmed not only with consistent orientation and uniform distribution, but also with high purity. The assembled process of 3DTNEs is optimized, which proves that it can effectively avoid leakage and other electrochemical signals after adding gold film between 3DTNEs and conductive collector. The active area of 3DTNEs has been respectively calculated by the methods of redox capacity, cyclic voltammetry and electrochemical impedance spectroscopy. The results prove that the method of redox capacity can reflect more accurately the real area of 3DTNEs. Moreover, the cyclic vol tammetric behavior of 3DTNEs is simulated by Comsol Simulation Software at different pipe diameters. Simulative results indicate that the diffusion layer is great overlap within the parameters of this study, and mainly controlls by linear diffusion.Based on SPA self-assembling on conventional gold electrode and 3DTNEs, the AFB1 immunosensors have been constructed. The parameters of concentration of protein A, the modified time of each substance, test systems, polarization potential of impedance measurement and immunological reaction time are optimized. Then the equivalent circuit is built to simulate the impedance spectra. The detection limits of the two immunosensors by EIS are 2.2×10-9 g/m L(S/N=3) and 1.0×10-12 g/m L(S/N=3) respectively. The immunosensor prepared by SPA/3DTNEs is used to detect AFB1 concentration in corn samples, and the average recovery is 97.1%.The AFB1 immunosensor of BSA/anti-AFB1/SPA/GA/4-ATP/3DTNEs has been fabricated by self-assembling 4-ATP monolayers on 3DTNEs. The performances of 4-ATP modified electrode are characterized, and the polarization potential measurement and test system are optimized. The immunosensor for AFB1 determination exhibits a linear range from 4.0×10-12 g/m L to 2.0×10-9 g/m L with a detection limit of 2.1×10-12 g/m L(S/N=3), and the average recovery for AFB1 in corn samples is 95.3%. |
