The Electrochemical Behavior Of Thiol / Lecithin Mixed Bilayers

Biomembrane is the barrier of cell surface and exchange channels of substance between inside and outside circumstance. Lecithin is the important ingredient of biomembrane and is connected with the metabolism of life. Due to the complexity of biomembrane, now it is impossible to observe and investigate the original biomembrane. People all along search one good model system of biomembrane to study the transmembrane electron transfer mechanism. HBM has both the stability of SAM and the resemblance of biomembrane. So it is generally considered that HBM is now the best system of transmembrane electron transfer. Ca2+ interaction with has long been reported. The base and premise of the experiments is to prepare the model system of biomembrane. HBM is chosen as the experiment model in this thesis. The substrate of HBM is SAMs of octadecanethiol. Then it is used to assemble the lecithin. The influence of Ca2+ ions on the electron transfer of Fe(CN)63-/4- couple on Au supported HBM is investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The main contents are as follows: Several models system of biomembrane has been summarized. Physiologicalfunction and application have been introduced briefly. Token technology of membrane has been reviewed. Effects of over potential to electrochemical behaviors of the octadecanethiol/lecithin HBM on gold has been measured by EIS. The complex plane capacitance plot and Nyquist plot reflect mutually. The results of EIS indicate that polar potential could augment apparent interface capacitance and decrease the electrochemical reaction resistance and accelerate the electron tunneling. The electrochemical behavior of HBM combined Ca2+ has been tested by CV. In the 0.2 M KC1 solution, interface capacitance becomes larger when increasing the concentration of Ca2+ ions. Then the membrane thickness becomes lower. In 0.2 M KC1 solution containing Fe(CN)63-/4- couple, the inverse sigmoid CV curves become broader. The interaction Ca2+ with the HBM may be a complexation of Ca2+ with lecithin head groups, which lowers the interactions between lecithin head group and octadecanethiol, making the HBM looselypacked. With the increase of Ca2+ concentration, the membrane capacitance is accelerated; With the increase of Ca2+ concentration and the immersed time of the electrode in the CaCl2, the electrochemical reaction is decreased. This is consistent with the conclusion drawn from CV experiments. It is concluded that ion-channels generated by Ca2+ ions play the role similar to micro defects. First, calcium ions can bind with lecithin head group and then increase the membrane capacitance. Second, the relative dielectric constant is greatly increased as the result of the permeation of ions and water molecules into HBM through Ca2+ induced micropores. Third, micropores in Au-HBM enlarge the area of the HBM/electrolyte interface. Cu particles have been prepared by chronoamperometry(C A) on not well-assembled thiol monolayers on gold for the first time, the study of electrodeposited Cu by SAM has been little reportded. The final aim is to provide a novel way to prepare nanoparticles.