Developing a rapid fabrication of colloidal crystal film is one of the technical issues to apply to wide and various fields. We have been investigating a drying process of colloidal aqueous ethanol (EtOH) suspension formed by electrophoretic deposition (EPD). Here, the detailed formation mechanism of the colloidal crystal films with the closest packing structure was investigated by optical microscope and spectroscopy. The growth mechanism from the colloidal suspension to the colloidal crystal film was found to consist of four stages. In the first stage, concentrated colloidal suspension changed to order structure, i.e., nonclosely packed colloidal crystal by Alder phase transition. After this crystallization, we observed Bragg’s diffraction peak and structural color. In the second stage, the diffraction peak shifts toward the shorter-wavelength direction (blue shift) due to the reduction of the interparticle distance of the nonclosely packed colloidal crystal. Finally, this peak shift continued until the closely packed colloidal crystal film was formed. In the third stage, the diffraction peak kept almost a similar wavelength due to the liquid film of aqueous EtOH covering on the colloidal crystal film. In the fourth stage, the colloidal crystal film changed from wet to dry condition. The structural color changes from green to blue by the evaporation of the solvent from the interspace of the colloidal crystal film. This color change is explained by the change in the refractive index of the interparticle medium from solvent to air. One of the key findings in our process is a rapid crystal growth using concentrated colloid aqueous EtOH suspension. Drying the concentrated suspension formed a closely packed colloidal crystal film within 55 s. This process has the potential for high-speed deposition of the colloidal crystalline thin films.

中文翻译：

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从浓乙醇悬浮液快速生长胶体晶体薄膜。

发展胶体晶体膜的快速制造是适用于广泛的各种领域的技术问题之一。我们一直在研究通过电泳沉积（EPD）形成的胶体乙醇水溶液（EtOH）悬浮液的干燥过程。在此，通过光学显微镜和光谱学研究了具有最紧密堆积结构的胶体晶体膜的详细形成机理。发现从胶体悬浮液到胶体晶体膜的生长机理包括四个阶段。在第一阶段，浓缩的胶体悬浮液改变为有序结构，即通过Alder相变非紧密堆积的胶体晶体。结晶后，我们观察到布拉格的衍射峰和结构颜色。在第二阶段 由于不紧密堆积的胶体晶体的粒子间距离的减小，衍射峰向短波长方向移动（蓝移）。最后，该峰移动一直持续到形成紧密堆积的胶体晶体膜为止。在第三阶段，由于EtOH水溶液的液膜覆盖在胶体晶体膜上，衍射峰保持几乎相似的波长。在第四阶段，胶体晶体膜从湿状态变为干状态。通过从胶态晶体膜的间隙中蒸发掉溶剂，结构颜色从绿色变为蓝色。这种颜色变化是通过粒子间介质的折射率从溶剂到空气的变化来解释的。我们过程中的主要发现之一是使用浓缩胶体EtOH水性悬浮液的快速晶体生长。干燥浓缩的悬浮液，在55 s内形成紧密堆积的胶体晶体膜。该工艺具有高速沉积胶态晶体薄膜的潜力。