Photocontrolled aggregation of colloidal silica
Photocontrolled aggregation of colloidal silica
复制标题
胶体二氧化硅的光控聚集
DOI：
10.1039/jm9940400883
复制
发表时间：
1994
期刊：
影响因子：
--
通讯作者：
K. Ichimura
中科院分区：
文献类型：
--
作者：
M. Ueda;Haeng;K. Ichimura
具有十亚甲基间隔基的螺苯并吡喃已被化学吸附在直径为150 nm的胶体二氧化硅颗粒的表面上。当被光致变色单元覆盖的二氧化硅颗粒分散在折射率与二氧化硅匹配的有机溶剂中时，它们表现出正常的光致变色性。正常的光致变色，即使在高极性的乙二醇，其中低分子量的螺吡喃显示反转的光致变色，这一事实表明，二氧化硅表面的高度亲水性的字符被转换为一个相对疏水的，由于长的烃链。当光致变色颗粒分散在四氯化碳中时，UV照射诱导絮凝，引起胶体二氧化硅的沉降。随后的可见光照射恢复了分散状态，显示了光控制的光响应系统，并提供了一个新的。
Spirobenzopyran having a decamethylene spacer has been chemisorbed on the surface of colloidal silica particles of diameter 150 nm. The silica particles covered with the photochromic units displayed normal photochromism when they were dispersed in organic solvents having refractive indices matched with that of the silica. The fact that normal photochromism was observed even in highly polar ethylene glycol, in which a low-molecular-weight spiropyran shows reversed photochromism, indicates that the highly hydrophilic character of the silica surface is converted to a relatively hydrophobic one owing to the long hydrocarbon chain. When the photochromic particles were dispersed in carbon tetrachloride, the UV irradiation induced flocculation, causing sedimentation of the colloidal silica. Subsequent visible light irradiation recovered the dispersed state, showing the photocontrol of the dispersibility and offering a novel photoresponsive system.