Shape control of metal nanonarticles using light irradiation and a micro-sized reaction system

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Shape control of metal nanoparticles is important because many properties of nanoparticles differing from those of bulk metal strongly depend on their shape. Photoirradiation for colloidal particles is interested as a convenient method for the shape control.The aims of the present study are 1) clarifying the mechanism of the photo-induced shape conversions more precisely, and 2) developing a proper system for the investigation using micro-sized systems. As results of the investigation, we have revealed that:The aims of the present study are 1) clarifying the mechanism of the photo-induced shape conversions more precisely, and 2) developing a proper system for the investigation using micro-sized systems. As results of the investigation, we have revealed that:1) Oxidative etching of silver nanoparticles by halogen ions is involved. in the photoinduced shape conversion process. Nanoparticles are etched by halogen ions to form silver ions, which were confirmed by the presence of AgCl_2-in the solutions.2) The nanocrystals are formed from the silver ions. The results of a wavelength dependence study suggested that photoirradiation does not cause photoreduction but control crystal growth via plasmon excitation.3) We have carried out photoirradiation experiments by using microchips. However, sedimentation of nanoparticles on the wall of micro channels significantly occurred.