Real time tracking of the propagation of phase-transition front induced by potential control for organic thin films on electrode surfaces

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The 2-dimensional (2D) phase transition of viologens was investigated. In the case of heptyl viologen (HV), the first-order phase transition between gas-like adsorption layer of oxidized form and 2D condensed phase of reduced form produces a spike-like voltammetric response. Measurements of UV visible light reflectance transitions in response to double potential step enabled us to establish 1:1 coexistence of the two phases even within the bi-stable potential region of the first order transition. It was found that the width of the bi-stable potential region can be regulated by intermolecular interaction in the condensed film. We newly made it possible to track the phase transition front using the interfacial potential difference measurements with a row of micro-probe electrodes, though the potential change was too small to catch the movement of the front. We also **ed to see the front using a fluorescence microscope and the local reflection measurements, but it was difficult to see the … More front.The phase change of amphiphilic molecules with terminal adsorption-desorption active groups, such as 4-pyridyl or imidazo-1-yl, was investigated at a Au(111) single crystal electrode. All these molecules showed dynamic phase changes ranging from compact monolayer to desorbed aggregated structure. The changes are sensitive to the molecular structures. The effects of the existence of the amide linkage, position of the linkage, pH, the presence of bicarbonate ion, and number of the touching procedures upon the phase change were explored. The potential dependent phase change was clearly tracked using the spectroelectrochemical techniques.The pontential-induced reversible phase change of the adsorption layer of a dendrimer was realized for the first time. A PAMAM dendrimer, the periphery of which, was totally modified with 4-pyridyl groups, exhibited reversible partial desorption-readsorption behavior as well as orientational change of peripheral groups on a Au(111) electrode surface in an unbuffered KClO_4 aqueous solution. Less