Budapest University of Technology and Economics, Department of Physical Chemistry and Materials Science, Centre for Colloid Chemistry, H-1521 Budapest, Hungary.
Langmuir. 2010 Feb 16;26(4):2694-9. doi: 10.1021/la9027207.
We present the studies on the structure and optical properties of bidisperse Stöber silica nanoparticulate Langmuir films prepared at the air/water interface in a Wilhelmy film balance and transferred onto glass slides using the Langmuir-Blodgett technique. Three different compositions (covered area ratios: 4:1; 1:1, and 1:4) of two bidisperse systems were used in the experiments. Bidisperse samples (B1 and B2) were prepared by mixing the appropriate amount of monodisperse sols of particles with 61 and 100 nm diameters (B1) and those with 37 and 100 nm diameters (B2). By surface pressure-area isotherms and (transmission and scanning) electron microscopy images we provide information about the structure of the films. Optical properties of the supported films were measured with UV-vis spectroscopy and the transmittance spectra were evaluated in terms of an optical model which allows monotonous in-depth variation of the refractive index across the film. (1) We have found that the refractive index decreased from the substrate-layer interface toward the air-layer interface when the smaller particles were in majority, and increased otherwise. That would suggest that the smaller particles of each bidisperse system can be positioned at the air side of the film if they are in minority in the sample and they can be situated on the substrate if they are in majority. The scanning electron microscope images of bidisperse films supported the in-depth film structure suggested by optical studies.
我们介绍了在威比尔膜天平上制备的具有双分散斯托伯二氧化硅纳米颗粒的朗缪尔膜在空气/水界面上的结构和光学性质的研究，并使用 Langmuir-Blodgett 技术将其转移到载玻片上。在实验中使用了两种双分散体系的三个不同组成（覆盖面积比：4:1；1:1 和 1:4）。双分散样品（B1 和 B2）是通过混合适量的单分散胶体颗粒（直径为 61 和 100nm 的 B1 和直径为 37 和 100nm 的 B2）制备的。通过表面压-面积等温线和（透射和扫描）电子显微镜图像，我们提供了有关膜结构的信息。用紫外-可见光谱测量了支撑膜的光学性质，并根据允许折射率在膜中单调变化的光学模型评估了透过率光谱。（1）我们发现，当较小的颗粒占多数时，折射率从基底层界面向空气层界面减小，反之则增加。这表明，如果每个双分散体系中的较小颗粒在样品中占少数，则可以将其定位在膜的空气侧，如果它们占多数，则可以将其定位在基底上。支撑双分散膜的扫描电子显微镜图像支持了由光学研究建议的深入膜结构。
