二氧化硅纳米粒子薄膜的制备及光学性能

Self-assembly and Optical Properties of Silica Nanoparticulate Thin Films

以二氧化硅胶体和聚二烯丙基二甲基氯化铝（ＰＤＤＡ）为原料，利用静电自组装技术制备了ＰＤＤＡ／ＳｉＯ_２复合薄膜．ＴＥＭ图象显示．薄膜中的ＳｉＯ_２纳米粒子为密堆积，薄膜均匀、致密；电子衍射实验结果显示，所组装的薄膜为非晶态膜．载玻片表面组装ＳｉＯ_２纳米粒子薄膜后，透射率随薄膜双层数增加呈现周期变化．薄膜具有增透作用，载玻片双面组装薄膜后在一定波长范围内的透射率可提高５％以上．ＰＤＤＡ／ＳｉＯ_２复合薄膜的光学性质主要由ＳｉＯ_２纳米粒子决定，每一双层的平均物理厚度小于ＳｉＯ_２纳米粒于的粒径，薄膜中存在层间穿插现象。

Silica nanoparticle thin films were built up from SiO2 colloid and poly(diallyldimethylammonium chloride) (PDDA) by using the electrostatic self-assembly technique. The TEM image(to see Fig. 3) of a 40-bilayer thin film revealed that SiO2 nanoparticles were closely packed and that the coverage of the SiO2 nanoparticles over the thin film was uniform. The electron diffraction pattern showed that the self-assembled thin film was amorphous. The transmissivity of a glass slide coated with PDDA/SiO2 multilayers exhibited periodical oscillation as the bilayer number of the thin film was increased (to see Fig. 4). The composite thin films under some bilayers were antireflection coatings. A net increment of more than 5% in the transmissivity of a glass slide could be yielded over the same wavelength range after PDDA/SiO2 composite thin films were assembled onto both sides of the slide (to see Fig. 5). Within the composite thin films, the average physical thickness of one PDDA/SiO2 bilayer was less than the average diameter of the SiO2 particles, which implied substantial overlap between the adjacent SiO2 nanoparticle layers. Although the PDDA/SiO2 multilayer thin films were prepared in the alternating layer-by-layer assembly fashion, the optical properties of the composite thin films were determined mainly by the SiO2 nanoparticles, and the composite thin films served the function of single-layer coatings.