Recrystallization and Zone Melting of Charged Colloids by Thermally Induced Crystallization
Recrystallization and Zone Melting of Charged Colloids by Thermally Induced Crystallization
复制标题
热诱导结晶带电胶体的重结晶和区域熔融
DOI：
10.1021/la401410g
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发表时间：
2013
期刊：
影响因子：
3.9
通讯作者：
and Junpei Yamanaka
中科院分区：
文献类型：
--
作者：
Mariko Shinohara;Akiko Toyotama;Misaki Suzuki;Yukihiro Sugao;Tohru Okuzono;Fumio Uchida;and Junpei Yamanaka
我们研究了重结晶和区熔结晶方法的应用，这已被广泛用于制造大，高纯度的原子和分子系统的晶体，带电胶体晶体。我们的样品是含有弱碱性吡啶的胶体二氧化硅的水分散体（粒径d = 108或121 nm，颗粒体积分数λ = 0.035-0.05）。由于粒子电荷数的增加，样品在加热时结晶，并且它们在冷却时可逆地熔化。在重结晶实验期间，多晶胶体在Peltier冷却装置中部分熔融，然后通过停止冷却并使系统返回到环境温度来结晶。通过熔化多晶胶体样品的窄区域（宽度为毫米级），然后将样品缓慢移动到冷却装置上以使熔融区域再结晶来进行区熔结晶。使用这两种方法，我们制造了几厘米大小的晶体，从毫米大小的原始多晶开始时，结晶速率足够慢（33 μm/s）。此外，胶体晶体的光学质量，如衍射峰的半带宽，显着改善。这些方法，对炼器也有帮助。当结晶速率足够慢（≤ 0.1 μm/s）时，少量杂质颗粒（荧光聚苯乙烯颗粒，d= 333 nm，λ = 5 × 10-5）被排除在胶体晶体之外。我们期望本研究结果将有助于制备大的，高纯度的胶体晶体。
We examined the application of recrystallization and zone-melting crystallization methods, which have been used widely to fabricate large, high-purity crystals of atomic and molecular systems, to charged colloidal crystals. Our samples were aqueous dispersions of colloidal silica (with particle diameters ofd= 108 or 121 nm and particle volume fractions of ϕ = 0.035–0.05) containing the weak base pyridine. The samples crystallized upon heating because of increases in the particle charge numbers, and they melted reversibly on cooling. During the recrystallization experiments, the polycrystalline colloids were partially melted in a Peltier cooling device and then were crystallized by stopping the cooling and allowing the system to return to ambient temperature. The zone-melting crystallization was carried out by melting a narrow zone (millimeter-sized in width) of the polycrystalline colloid samples and then moving the sample slowly over a cooling device to recrystallize the molten region. Using both methods, we fabricated a few centimeter-sized crystals, starting from millimeter-sized original polycrystals when the crystallization rates were sufficiently slow (33 μm/s). Furthermore, the optical quality of the colloidal crystals, such as the half-band widths of the diffraction peaks, was significantly improved. These methods were also useful for refining. Small amounts of impurity particles (fluorescent polystyrene particles,d= 333 nm, ϕ = 5 × 10–5), added to the colloidal crystals, were excluded from the crystals when the crystallization rates were sufficiently slow (∼0.1 μm/s). We expect that the present findings will be useful for fabricating large, high-purity colloidal crystals.