Photofunctional Characteristics at Interfaces

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Irradiation of a focused 1064 nm laser beam to an aqueous butanol solution under an optical microscope gives rise to formation of a single butanol microdroplet through photo-thermal phase separation of the solution. Simultaneously, the butanol microdroplet produced can be manipulated in space by the 1064 nm laser beam and studied by fluorescence/Raman microspectroscopies. The particular technique was also combined successfully with a microchip as well as with a capillary electrophoresis. On the basis of such a new developed technique, an ultra-race amount of an analyte in an aqueous butanol solution can be extracted into a single picoliter butanol droplet by laser irradiation and the liquid/liquid extraction processes of the analyte have been studied in detail on the basis of fluorescence microspectroscopy. In the case of the use of a microchip, in particular, consecutive and automatic liquid/liquid extraction of an analyte into a single droplet has been achieved by a laser beam. Furth … More ermore, the analyte separated by a capillary electrophoresis has been extracted and analyzed by the present methodology, which has high potential as a novel technique for microanalytical chemistry.On the other hand, gold electrodes modified with a ferrocene-terminated alkanethiol self-assembled monolayer (SAM) have been successfully integrated into a polymer microchannel chip. On the basis of oxidation-reduction reactions of the ferrocenyl groups in the SAM, electrochemical flow control of the solution in a microchannel has been demonstrated. The fundamental mechanisms of the electrochemical flow control in the microchannel chip have been also elucidated on the basis of contact angle measurements and surface-enhanced infrared absorption spectroscopy. The study has demonstrated that a perchlorate anion as a counter ion of the ferrocenium cation adsorbed simultaneously onto the SAM surface upon the electrochemical oxidation of the ferrocenyl group in the SAM and this accompanies adsorption of water molecules on the SAM surface, giving rise to the increase in the wettability of the SAM/electrode surface. Upon reduction of the ferrocenyl group, a perchlorate ion and water molecules distribute to the water phase. Through adsorption/desorption of a perchlorate ion and water molecule, the surface wettability can be controlled electrochemically. Less