Development of preparation of core-shell particles and their ordering

为了防止颗粒的聚集和损坏，已经提出了二氧化硅涂层。采用改进的Stober法成功地在粒径为10 nm的Ag纳米粒子、粒径为15 nm的Au纳米粒子和粒径为20 nm的Co纳米粒子表面包覆了SiO2。二氧化硅壳厚度随浓度条件的变化而变化。二氧化硅包覆的Ag和Au纳米颗粒的光性能可以用Mie理论解释。二氧化硅包覆的钴纳米粒子表现出不同于块体材料的磁性。该方法也可以推广到二氧化硅包覆的碘化银纳米颗粒和荧光微球。通过浸涂技术在玻璃基底上实现了亚微米级聚苯乙烯和二氧化硅球的单层化。为了在基底上单层的六方密堆积结构的球，有必要降低分散的胶体悬浮液的离子强度。通过重复浸涂过程实现了球体的多层。对于大球体在小球体上分层的情况，大球体在小球体的单层上单层，就像球体在平面上单层一样。对于小球层叠在大球上的情况，小球沿着大球的外围位于空隙中。

For preventing aggregation and damage of particles, silica-coating has been proposed. Ag nanoparticles with a size of 10 nm, Au nanoparticles with a size of 15 nm and Co nanoprticles with a size of 20 nm were successfully coated with silica with a modified Stober method. Silica shell thickness was varied with varying concentration conditions. Photo-properties for the silica-coated Ag and Au nanoparticles could be explained with a Mie theory. The silica-coated Co nanoparticles showed magnetic properties different from bulk materials. The proposed method could be also extended to silica -coating AgI nanopartides and fluorescent microspheres.Mono-layering of sub-micron-sized polystyrene and silica spheres on glass substrates by a dip-coating technique has been demonstrated. For the mono-layering the spheres in a hexagonal close-packed structure on the substrates, it was necessary to reduce ionic strength of dispersion of the colloidal suspension. Multi-layering of the spheres was achieved by repeating the dip-coating process. For the case of large spheres layered on small ones, the large spheres were mono-layered on the mono-layer of the small spheres just as spheres were mono-layered on a flat surface. For the case of small spheres layered on large ones, the small spheres were located in void along periphery of the large spheres.