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

金属纳米颗粒的形状控制很重要，因为纳米颗粒与大块金属不同的许多特性强烈地依赖于它们的形状。光照射对胶体粒子的形状控制是一种方便的方法。本研究的目的是：(1)更精确地阐明光诱导形状转换的机制；(2)建立一个合适的系统来研究微尺寸系统。研究结果表明：本研究的目的是：1)更精确地阐明光诱导形状转换的机制；2)建立一个合适的系统来研究微尺度系统。研究结果表明：1)银纳米粒子被卤素离子氧化刻蚀。在光致形状转换过程中。纳米粒子被卤素离子蚀刻形成银离子，溶液中agcl_2的存在证实了这一点。2)银离子形成纳米晶体。波长依赖性研究结果表明，光照射不会引起光还原，而是通过等离子激元激发控制晶体生长。3)利用微芯片进行了光辐射实验。然而，纳米颗粒在微通道壁上的沉降明显发生。

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.