King / Schiff Base, The Electrochemical Behavior Of Self-assembled Monolayer

Self-assembled monolayer (SAM) is more regular and more stable than LB membrane and it has a high stability, we can investigate it easily by means of physical and chemical techniques. Thus, this new kind of super-thin organic film studied widely and quickly became a hot-topic in many fields, such as chemistry of interface, chemistry of material, et al. Schiff bases belong to a class of compounds that contain an imine or azomethine group (-RC=N-). Schiff bases are useful in many fields. However, there has no research being taken on schiff base SAM in and outside of the country-. In this report, a certain schiff base SAM was successfully prepared for the first time and its electrochemical behavior was investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), which may develop a new w ay for the study of SAM and schiff base as well.Firstly, the schiff base SAM was investigated by means of EIS and CV7. The conclusions are as follows:1. The schiff base SAM was successfully prepared and the self-assembly process w as investigated by means of EIS. Results from CV7 and EIS experiments show that the membrane is somewhat loose when compared to the alkanethiol SAM.2. The electrochemical behavior of the schiff base monolayer in solutions with different pH value was also investigated. We concludedthat the membrane capacitance varied little when it was in neutral or basic solutions, while it become larger when the acidity of the solutions was enforced, implying that the structure of the schiff base SAM changed with the acidity of the solutions.3. Inserting ODT molecule in the schiff base SAM can improve the packness of the schiff base SAM's structure and increase its blocking property.4. Electrochemical reaction resistance is greatly enhanced when over-potential was applied. We proposed that this phenomenon probably is due to the existence of some molecular force among schiff bases.The combination between schiff base and Cu2+ was also observed. The results are as follows:1. The reaction between schiff base and Cu + was investigated by means of EIS, which lead to the decrease of the electrochemical reaction resistance of the SAM and its combining process could be divided into two: a rapid step followed by a slow one.2. We concluded that certain space is necessary for the combination of Cu2+ with schiff base SAM during the reaction, while in the case of schiff base membrane fabricated by ODT, no variation was found.3. A good linear relationship between the concentration of Cu2+and the electrochemical charge resistance was obtained when the schiff base act with different concentration of Cu +.As the C=N was introduced into the schiff base, so it is necessaryfor us to probe the reduction behavior of schiff base SAM, the results are shown below:1. The CV and EIS experiments convinced us that the C=N can be reduced, and we knew from experiments that this reaction is almost irreversible. With the decrease of the number of C=N in the membrane, the current of reduction peak decreased.2. The influence of over-potential on the the membrane which may lead to the reduction of C=N group in schiff base SAM was also investigated by exerting an over-potential on the monolayer in the EIS experiments, which is consistent with the results from CV experiments.