Investigation Of Charge Transfer Reactions At Liquid/liquid Interfaces

Studies of charge (electron and ion) transfer across a liquid/liquid interface (L/L interface) by scanning electrochemical microscopy (SECM) is one of the novel areas in electrochemistry and electroanalytical chemistry. In my Ph. D. dissertation, the progress and historical background of this area is briefly reviewed, The main results are as follows:A L/L interface supported on a metallic electrode has been used to study electron ET reactions by SECM. The system is composed of an aqueous droplet adhered on a platinum disc electrode and immersed into an organic electrolyte solution. The ET reactions between 7,7,8,8-tetracyanoquinodimenthane radical anion (TCNQ.-) in organic solution and ferricyanide in aqueous solution have been investigated on SECM controlled by the externally polarized potential. The apparent heterogeneous rate constants for the ET reactions extracted by fitting the SECM experimental approach curves to the theoretical values obey the Butler-Volume formula in some ranges, and they are found to be potential dependent. This method enables a fast and convenient method to measure ET and IT reactions kinetic parameter.The modification of the water/1,2-dichloroethane interface with a new typeβzeolite membrane is studied. As a means of investigating the analytical potential of this interface the facilitated transfer of various alkali and alkaline earth metal ions have been investigated using voltammetric methods. This work allows the observation of the transfer of extremely hydrophilic ions, due to the size-exclusion of organic ions from the interior of the zeolitic framework. Additionally. volume exclusion effects are shown to affect facilitated ion transfer processes involving alkali metal cations. It is hoped to extend this study to investigate the diffusion of ions within the zeolite pores with electrochemical methods, and to apply these properties to size selective sensors.A kind of didodecyldimethylammonium bromide (a synthetic lipid) layer membranes was supported on a glassy carbon electrode. We studied the ion channel behavior of the supported bilayer lipid membrane by scanning electrochemical microscopy (SCEM) in Tris (2,2'-bipyridine) ruthenium (II) solution. Perchlorate anion was used as presence of stimulus and ruthenium (II) complex cations as the probing ions of SECM measuring, the lipid membrane channel was open and exhibited distinct SECM positive feedback curve. The channel was in a closed state in the absence of perchlorate anions while reflected SECM negative feedback curve. The rates of electron transfer reaction at the lipid membranes surface were detected depended on the potential by SECM.In this section,n-Si(1 1 1) crystalline electrode was modified by carboxyl acid groups and sulfonic groups. The flat band potential (U_fb), relation between flat band potential and the carbon numbers to the modified samples and relation between photocurrent density and potential of the modified electrodes were studied. ATR–IR spectra and XPS analysis show that the organic compounds were connected to n-Si(1 1 1) wafer by Si-C bond. Calculation indicates that the surface modification ratio increased with the carbon number of organic groups decreased. Mott–Schottky plots gives the flat band potential of the samples to shift to negative positions with the carbon number decreased in both of the two different systems and the flat band potential of the sample with the group of -(CH₂)₃SO₃H reaches to -0.82V, which is more negative than reported, and the flat band potential of all the samples in this paper are more negative than the sample with methyl group. The photocurrent and photovoltage of the modifications are stable enough under solar illumination for a long time. Another work,by combining the self-assembly of initiator, ATRP and coordination to metal ions, Pb²⁺ and Cd²⁺, PAAM homopolymer brushes and the functional MMC brushes of PAAM were prepared on the surface of silicon wafers.The samples were confirmed by XPS and contact angle measurement. AFM was used to characterize the surface of silicon. these polymers should have interesting properties for many applications, such as electrochemical materials, optimized sensory, modified electrode and interface electrochemistry.