摘要/Abstract
对α-磷酸锆（α-ZrP）/H2O分散体系利用离心沉淀–再分散的方法，进行溶剂置换制备α-ZrP的有机溶剂分散体系.意外发现，使用这个方法可以容易地得到具有结构色的α-ZrP/有机溶剂分散体系.以丙酮为溶剂，当α-ZrP质量分数在0.76%～1.86%之间时，分散体系可以反射426～635 nm范围内的可见光，表现出相对应的结构色.增加体系中离子浓度，呈现红色结构色的α-ZrP/丙酮分散体系（α-ZrP质量分数0.87%）的紫外–可见光反射光谱曲线发生蓝移，表明体系中周期结构的形成主要依赖于α-ZrP纳米片层之间的静电排斥力.结构色的形成还存在一定的尺寸依赖性，大尺寸的α-ZrP纳米片相对于小尺寸样品（1.10 μm vs.0.48 μm）更容易形成表现出结构色的长程有序结构.利用此方法，还得到了以乙腈和丁腈为溶剂，具有明显结构色的分散体系.目前，研究中使用的许多片状无机粒子都具有与α-ZrP晶体相似的层间表面电荷结构，因此本工作所报道的方法对制备这类粒子的长程有序分散体系具有普遍借鉴意义.
关键词: α-磷酸锆, 纳米片状粒子, 分散体系, 液晶相, 结构色
α-zirconium phosphate (α-ZrP) crystals with high-crystallinity were synthesized via hydrothermal method and exfoliated with tetrabutylammonium hydroxide (TBAOH) in aqueous dispersion maintained at 0℃ in an ice bath. The exfoliated α-ZrP nano-sheets were then transferred into selected organic solvents, such as acetone, via centrifugal precipitation and re-dispersion process. This process was repeated 3 to 5 times to replace the water with the desired organic solvents. During the solvent-replacing process, most of the free TBAOH in α-ZrP/H2O dispersion was also removed, which was confirmed by characterizing the organic contents via thermo-gravimetric analysis for the solids obtained from both the water dispersion and the resulted acetone dispersion. Serendipitously, the dispersions of α-ZrP/organic solvent with structural colors could be easily obtained using this solvent-replacement method. After the solvent-replacing process was repeated for 5 times, the resulted α-ZrP/acetone dispersions could reflect visible light in the range of 426 nm to 635 nm when the mass fraction of α-ZrP was between 0.76% and 1.86%, thus showing the corresponding structural colors. Increasing the concentration of TBA+ ions in α-ZrP/acetone dispersion (α-ZrP mass fraction 0.87%), its UV-Vis reflection spectrum showed a blue-shift, indicating that the formation of periodic structures mainly depended on the electrostatic repulsion between α-ZrP nano-sheets. The formation of structural color also showed a size-dependence on the exfoliated α-ZrP nano-sheets. The nano-sheets with large-size was more likely to form the long-range ordered structure showing structural color compared with the relatively small ones (1.10 μm vs. 0.48 μm). The dispersions with acetonitrile or butyronitrile as solvent, which exhibited obvious structural colors, could also be obtained using this solvent-replacement method. At present, many plate-like inorganic particles used in the research have intrinsic charges on their gallery faces that similar to the microstructure of α-ZrP crystals, so the method reported here can give general guidance for the preparation of the dispersions with long-range periodic structures for these particles.
Key words: α-zirconium phosphate, nano-sheets, dispersion, liquid crystal phase, structural color
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