Molecular analysis of adsorbed layers on electrode surfaces by in-situ gravimetric methods

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Objectives of this project are(1)to develop in-situ gravimetric methods in an electrochemical system and(2)to clarify the fine structure of adsorbed layers and electrochemical reactions on electrode surfaces. An outline of the results is described below.1. Development of in-situ gravimetric methodsThe highly sensitive electrochemical quartz crystal microbalancc(EQCM)was constructed. Sensitivity of the EQCM is 0.1 Hz in frequency(2 ng/cm^2 in mass)for 0.1 sec sampling time so that the frequency change much below a monolayer level can be measured accurately. A data acquisition and analysis system was also constructed, to which frequency change was stored with simultaneously measured potential and current.2. Fine structure of adsorbed layers and electrochemical reactions on cieclrode surfaces(1) Adsorption of water molecules on a platinum electrode was demonstrated clearly by frequency decrease in so-called hydrogen and double-layer regions. Formation mechanism of adsorbed oxygen laycr wa … More s proposed based on potential-dependence of the amount of adsorbed water molecules and the charge consumed during the oxidation of Pt surface.(2) In-situ and dynamic monitoring of self-assembling process of alkancthiols revealed that well - oriented monolayers were constructed through two successive adsorption steps differcnt in adsorption rate. fast initially and slow subsequently. Redox of this monolayer causes ion-pairing between the oxidized monolayer and anions in solution. Formalion of THE ion-pair and the amount of solvent in the monolayer are strongly dependent on the structure of the monolayer.(3) It is clarified that the identity of ion participating in ion transport accompanying redox switching of polypyrrole films is a function of cleclrolyte anion used in the polymerization and the redox reaction, cleclrode potential, and film thickness.The present new findings give the fundamental but extremely useful informations concerning the structure of double-laser. and the structure and the cleetrochemical reaction of adsorbed layer which provides specific functions on the cleclrode surface. Less