Structural Changes in Acetophenone Fluid Films as a Function of Nanoscale Thickness.
Structural Changes in Acetophenone Fluid Films as a Function of Nanoscale Thickness.
复制标题
苯乙酮液膜的结构变化作为纳米级厚度的函数。
作者：
Samantha L. Nania;S. Shaw
我们报告了通过检查在固体银衬底上支持的不同厚度的苯乙酮膜的发展流体/固体界面的实验观察。动态润湿技术提供了流体膜厚度作为转速函数的实验控制。对椭偏仪和红外反射吸收光谱数据进行了分析，提供了绝对膜厚和不同膜厚下化学环境变化的细节。这些数据与基于苯乙酮/银对的物理化学性质预测流体膜厚度的理论模型进行了比较。当衬底的速度从0.003 cm s-1变化到1.872 cm s-1时，流体膜的厚度从约200 nm变化到2 μm。随着速度的增加，膜厚的增加遵循朗道趋势，该趋势与速度2/3成线性关系。我们的数据还显示了分子取向变化的明确证据，作为膜厚度的函数，当在受限的界面环境中，较薄的膜越来越多地由苯乙酮分子组成时，就会发生这种变化。最薄的流体薄膜（<100 nm）的光谱变化显示出与冷冻苯乙酮的透射傅里叶变换红外（FTIR）数据相似的特征，表明这些薄膜由于其纳米尺度的限制而高度有序。
We report experimental observations of a developing fluid/solid interface by examining acetophenone films of varying thicknesses, supported on solid silver substrates. A dynamic wetting technique provides experimental control of fluid film thickness, as a function of rotational velocity. Ellipsometry and infrared reflection absorption spectroscopy data are analyzed to provide absolute film thickness and details of the changing chemical environment for varying film thickness. These data are compared to theoretical models that predict fluid film thicknesses, based on physical-chemical properties of the acetophenone/silver pair. As the velocity of the substrate is varied from 0.003 cm s-1 to 1.872 cm s-1, the fluid film's thickness changes from a ca. 200 nm to 2 μm. This increase in film thickness with increasing velocity follows a Landau trend, which is linear with respect to velocity2/3. Our data also show clear evidence of molecular orientation changes, as a function of film thickness, which occur as the thinner films are increasingly comprised of acetophenone molecules within a confined, interfacial environment. The spectral changes for the thinnest fluid films (<100 nm) are shown to exhibit features similar to transmission Fourier transform infrared (FTIR) data of frozen acetophenone, suggesting that these films are highly ordered, as a result of their nanometer-scale confinement.