In Situ Infrared Spectroscopic Study On The Electrooxidation Mechanisms Of Several Organic Molecules And The Adsorption Process Of Protein

In situ infrared reflection spectroelectrochemisty, which is the combination of infrared spectroscopy and electrochemistry, can provide infrared spectral and electrochemical information at the same time. It has become a powerful tool for in situ determining the intermediate, adsorbed species and products of electrode reaction. And it has been widely used to study electrocatalytic oxidation mechanism and adsorption/desorption process. This information gives valuable data for a molecular picture of solid/liquid interface and contributes to the study of electrochemical process at a molecular level.Attenuated total reflection infrared spectroscopy (ATR) is a useful tool for surface analysis providing structural and chemical information about the sample. Compared with the traditional transmission IR techniques, the method has several advantages including non-destruction, aqueous sample analysis, and convenience. ATR spectroscopy can yield valuable surface-chemical data with reduced interferences from solvent, which allows exploring solid/liquid interfacial phenomena and monitoring chemical or biological reaction in situ. The studies in this thesis are summarized as follows:1. The principle, method and the recent progress of in situ infrared reflection spectroelectrochemisty and attenuated total reflection infrared spectroscopy technique is reviewed.2. The electrochemical redox reaction of p-methylaminophenol on platinum electrode in 0.2 mol L^-1 KC1 solution was investigated by cyclic voltammetry and in situ reflection absorption Fourier transform infrared spectroscopy (FTIRS).The results show that two electrons and protons were transferred during the redox process of p-methylaminophenol. The electrochemical oxidation of p-methylaminophenol yields /?-N-methylobenzoquinoeimin intermediate at first. And the resulted p-N-methylobenzoquinoeimin further undergoes irreversible hydrolysis to yield /?-benzoquinone and methylamine.3. The electrochemical oxidation of pyridoxol (PN) on a poly crystal line gold electrode was investigated by cyclic voltammetry and in situ Fourier transform infrared spectroscopy (FTIRS). In 0.1 M aqueous NaOH, the gold electrode showed a high catalytic activity for the irreversible oxidation of PN via an approximate first-order kinetic process. The individual ionic species and the major tautomeric equilibria of PN molecules in aqueous solutions were evidenced well from the pH-dependent attenuated total internal reflection (ATR) spectra, and the results were in good agreement with the voltammetric observations. In situ single potential alteration reflectance spectroscopy (SPAIRS) demonstrated that a lactone form of PN, rather than pyridoxal aldehyde, was likely formed, which was subsequently diffused into thin layer solution and underwent hydrolysis slowly to pyridoxic acid (PA) as the final product. In addition, the adsorption of PN at Au electrode was characterized by in situ subtractively normalized interfacial Fourier transform spectroscopy (SNIFTIR) method, which revealed that the adsorption of deprotonated PN, via nitrogen atom in vertical configuration on electrode surface, occurred from -0.5 V vs Ag|AgCl|KCl(sat), which was much lower than the potential of PN electrooxidation observed from ca. 0 V.